ALBERT

Description: A new efficient heuristic algorithm has been developed for the dynamic facility layout problem with budget constraint (DFLPB) using optimization via simulation technique. The heuristic integrates integer programming and discrete event simulation to address DFLPB. In the proposed algorithm, the nonlinear model of the DFLP has been changed to a pure integer programming (PIP) model. Then, the optimal solution of the PIP model has been used in a simulation model that has been designed in a similar manner as the DFLP for determining the probability of assigning a facility to a location. After a sufficient number of runs, the simulation model obtains near optimum solutions. Finally, to test the performance of the algorithm, several test problems have been taken from the literature and solved. The results show that the proposed algorithm is more efficient in terms of speed and accuracy than other heuristic algorithms presented in previous works.

Description: Flickermeter is a common name for a system that measures the obnoxiousness of flicker caused by voltage fluctuations. The output of flickermeter is a value of short-term flicker severity indicator, . This paper presents the results of the numerical simulations that reconstruct the processing of flickermeter in frequency domain. With the use of standard test signals, the characteristics of flickermeter were determined for the case of amplitude modulation of input signal, frequency modulation of input signal, and for input signal with interharmonic component. For the needs of simulative research, elements of standard IEC flickermeter signal chain as well as test signal source and tools for acquisition, archiving, and presentation of the obtained results were modeled. The results were presented with a set of charts, and the specific fragments of the charts were pointed out and commented on. Some examples of the influence of input signal’s bandwidth limitation on the flickermeter measurement result were presented for the case of AM and FM modulation. In addition, the diagrams that enable the evaluation of flickermeter’s linearity were also presented.

Description: The design, implementation, and characterization of a microelectromechanical systems (MEMS) capacitive accelerometer-based middle ear microphone are presented in this paper. The microphone is intended for middle ear hearing aids as well as future fully implantable cochlear prosthesis. Human temporal bones acoustic response characterization results are used to derive the accelerometer design requirements. The prototype accelerometer is fabricated in a commercial silicon-on-insulator (SOI) MEMS process. The sensor occupies a sensing area of 1 mm × 1 mm with a chip area of 2 mm × 2.4 mm and is interfaced with a custom-designed low-noise electronic IC chip over a flexible substrate. The packaged sensor unit occupies an area of 2.5 mm × 6.2 mm with a weight of 25 mg. The sensor unit attached to umbo can detect a sound pressure level (SPL) of 60 dB at 500 Hz, 35 dB at 2 kHz, and 57 dB at 8 kHz. An improved sound detection limit of 34-dB SPL at 150 Hz and 24-dB SPL at 500 Hz can be expected by employing start-of-the-art MEMS fabrication technology, which results in an articulation index of approximately 0.76. Further micro/nanofabrication technology advancement is needed to enhance the microphone sensitivity for improved understanding of normal conversational speech.

Description: Breathwalk is a science of combining specific patterns of footsteps synchronized with the breathing. In this study, we developed a multimedia-assisted Breathwalk-aware system which detects user's walking and breathing conditions and provides appropriate multimedia guidance on the smartphone. Through the mobile device, the system enhances user's awareness of walking and breathing behaviors. As an example application in slow technology, the system could help meditator beginners learn “walking meditation,” a type of meditation which aims to be as slow as possible in taking pace, to synchronize footstep with breathing, and to land every footstep with toes first. In the pilot study, we developed a walking-aware system and evaluated whether multimedia-assisted mechanism is capable of enhancing beginner's walking awareness while walking meditation. Experimental results show that it could effectively assist beginners in slowing down the walking speed and decreasing incorrect footsteps. In the second experiment, we evaluated the Breathwalk-aware system to find a better feedback mechanism for learning the techniques of Breathwalk while walking meditation. The experimental results show that the visual-auditory mechanism is a better multimedia-assisted mechanism while walking meditation than visual mechanism and auditory mechanism.

Description: We have acquired 2-D and 3-D microwave tomographic images of the calcaneus bones of two patients to assess correlation of the microwave properties with X-ray density measures. The two volunteers were selected because each had one leg immobilized for at least six weeks during recovery from a lower leg injury. A soft-prior regularization technique was incorporated with the microwave imaging to quantitatively assess the bulk dielectric properties within the bone region. Good correlation was observed between both permittivity and conductivity and the computed tomography-derived density measures. These results represent the first clinical examples of microwave images of the calcaneus and some of the first 3-D tomographic images of any anatomical site in the living human.

Description: Diagnostic confirmation of cancer in solid organs is based on biopsy findings. In a standard 12-core prostate biopsy protocol, conventional biopsy needles sample only 0.95% (∼0.228 cm $^{3}$ ) of a typical 24-cm $^{3}$ prostate gland. The primary objective of this study was to enhance the sensitivity of standard biopsy protocol by gauging electrical properties of tissue simultaneously with tissue extraction for histopathology analysis. A conventional biopsy (Bx) needle was instrumented with an electrical impedance spectroscopy (EIS) sensor to interrogate the tissue volume surrounding the needle tip. The EIS-Bx device was evaluated in a series of saline bath and ex vivo porcine experiments. It was found to sense a volume of 0.286 cm $^{3}$ of tissue around the needle tip. EIS measurements were recorded from three ex vivo human prostates using the device, and the extracted biopsy cores were histologically assessed. Prostate conductivity σ ranged from 0.179 to 0.3310 S/m for benign tissues and 0.0746 to 0.0837 S/m for malignant tissues at frequencies ranging from 1 to 100 kHz. Relative permittivity ϵ $_{r}$ ranged from 2.10×10 $^{6}$ to 2.9 × 10 $^{4}$ for benign and 6.63×10 $^{5}$ to 5.3 × 10 $^{3}$ for cancer tissues over the same frequency range. Both are found to be significantly higher in normal prostate tissues than in malignant tissue $(p$ 〈 0.00001).

Description: Due to the growing shortage of donor livers, more patients are waiting for transplantation. Living donor liver transplantation may help expanding the donor pool, but is often confronted with the small-for-size syndrome. Since the hemodynamic effects of partial hepatectomy are not fully understood, we developed an electrical rat liver model to compare normal with resected liver hemodynamics. Detailed geometrical data and 3-D reconstructions of the liver vasculature of two rats were gathered by combining vascular corrosion casting, micro-CT scanning, and image processing. Data extrapolations allowed obtaining a total liver pressure- and flow-driven electrical analog. Subsequently, virtual resections led to 70%, 80%, or 90% partial hepatectomy models. Results demonstrated hyperperfusion effects such as portal hypertension and elevated lobe-specific portal venous flows (11, 12, and 24 mmHg, and 1.0–3.0, 1.8–3.5, and 7.4 ml/min for 70%, 80%, and 90% hepatectomy, respectively). Comparison of two 90% resection techniques demonstrated different total arterial flows (0.28 ml/min versus 0.61 ml/min), portal (24 mmHg versus 21 mmHg), and sinusoidal pressures (14 mmHg versus 9.5–12 mmHg), probably leading to better survival for lower portal and sinusoidal pressures. Toward the future, the models may be extrapolated to human livers and help us to optimize hepatectomy planning.

Description: This paper presents a useful technique for totally automatic detection of myocardial infarction from patients’ ECGs. Due to the large number of heartbeats constituting an ECG and the high cost of having all the heartbeats manually labeled, supervised learning techniques have achieved limited success in ECG classification. In this paper, we first discuss the rationale for applying multiple instance learning (MIL) to automated ECG classification and then propose a new MIL strategy called latent topic MIL, by which ECGs are mapped into a topic space defined by a number of topics identified over all the unlabeled training heartbeats and support vector machine is directly applied to the ECG-level topic vectors. Our experimental results on real ECG datasets from the PTB diagnostic database demonstrate that, compared with existing MIL and supervised learning algorithms, the proposed algorithm is able to automatically detect ECGs with myocardial ischemia without labeling any heartbeats. Moreover, it improves classification quality in terms of both sensitivity and specificity.

Description: In high-field magnetic resonance imaging (MRI) systems, $B_0$ fields of 7 and 9.4 T, the RF field shows greater inhomogeneity compared to clinical MRI systems with $B_0$ fields of 1.5 and 3.0 T. In multichannel RF coils, the magnitude and phase of the input to each coil element can be controlled independently to reduce the nonuniformity of the RF field. The convex optimization technique has been used to obtain the optimum excitation parameters with iterative solutions for homogeneity in a selected region of interest. The pseudoinverse method has also been used to find a solution. The simulation results for 9.4- and 7-T MRI systems are discussed in detail for the head model. Variation of the simulation results in a 9.4-T system with the number of RF coil elements for different positions of the regions of interest in a spherical phantom are also discussed. Experimental results were obtained in a phantom in the 9.4-T system and are compared to the simulation results and the specific absorption rate has been evaluated.

Description: Motivated by the goals of automatically extracting vessel segments and constructing retinal vascular trees with anatomical realism, this paper presents and analyses an algorithm that combines vessel segmentation and grouping of the extracted vessel segments. The proposed method aims to restore the topology of the vascular trees with anatomical realism for clinical studies and diagnosis of retinal vascular diseases, which manifest abnormalities in either venous and/or arterial vascular systems. Vessel segments are grouped using extended Kalman filter which takes into account continuities in curvature, width, and intensity changes at the bifurcation or crossover point. At a junction, the proposed method applies the minimum-cost matching algorithm to resolve the conflict in grouping due to error in tracing. The system was trained with 20 images from the DRIVE dataset, and tested using the remaining 20 images. The dataset contained a mixture of normal and pathological images. In addition, six pathological fluorescein angiogram sequences were also included in this study. The results were compared against the groundtruth images provided by a physician, achieving average success rates of 88.79% and 90.09%, respectively.

Description: Model averaging is a widely used technique in biomedical applications. Two established model averaging methods, iterative shape averaging (ISA) method and virtual insect brain (VIB) method, have been applied to several organisms to generate average representations of their brain surfaces. However, without sufficient samples, some features of the average Drosophila brain surface obtained using the above methods may disappear or become distorted. To overcome this problem, we propose a Bézier-tube-based surface model averaging strategy. The proposed method first compensates for disparities in position, orientation, and dimension of input surfaces, and then evaluates the average surface by performing shape-based interpolation. Structural features with larger individual disparities are simplified with half-ellipse-shaped Bézier tubes, and are unified according to these tubes to avoid distortion during the averaging process. Experimental results show that the average model yielded by our method could preserve fine features and avoid structural distortions even if only a limit amount of input samples are used. Finally, we qualitatively compare our results with those obtained by ISA and VIB methods by measuring the surface-to-surface distances between input surfaces and the averaged ones. The comparisons show that the proposed method could generate a more representative average surface than both ISA and VIB methods.

Description: The aim of this study is to investigate muscular fatigue and to propose a new fatigue index based on the continuous wavelet transform (CWT) which is compared to the standard fatigue indexes from literature. Fatigue indexes are all based on the electrical activity of muscles [electromyogram (EMG)] acquired during an electrically stimulated contraction thanks to two modules (electromyostimulation + electromyography recording) that can analyze EMG signals in real time during electromyostimulation. The extracted parameters are compared with each other and their sensitivity to noise is studied. The effect of truncation of M waves is then investigated, enlightening the robustness of the index obtained using CWT.

Description: Patient-specific mathematical models of respiratory mechanics can offer substantial insight into patient state and pulmonary dynamics that are not directly measurable. Thus, they offer significant potential to evaluate and guide patient-specific lung protective ventilator strategies for acute respiratory distress syndrome (ARDS) patients. To assure bedside applicability, the model must be computationally efficient and identifiable from the limited available data, while also capturing dominant dynamics and trends observed in ARDS patients. In this study, an existing static recruitment model is enhanced by considering alveolar distension and implemented in a novel time-continuous dynamic respiratory mechanics model. The model was tested for structural identifiability and a hierarchical gradient descent approach was used to fit the model to low-flow test responses of 12 ARDS patients. Finally, a comprehensive practical identifiability analysis was performed to evaluate the impact of data quality on the model parameters. Identified parameter values were physiologically plausible and very accurately reproduced the measured pressure responses. Structural identifiability of the model was proven, but practical identifiability analysis of the results showed a lack of convexity on the error surface indicating that successful parameter identification is currently not assured in all test sets. Overall, the model presented is physiologically and clinically relevant, captures ARDS dynamics, and uses clinically descriptive parameters. The patient-specific models show the ability to capture pulmonary dynamics directly relevant to patient condition and clinical guidance. These characteristics currently cannot be directly measured or established without such a validated model.

Description: In this paper, a new conductive polymer foam-surfaced electrode was proposed for use as a capacitive EEG electrode for nonintrusive EEG measurements in out-of-hospital environments. The current capacitive electrode has a rigid surface that produces an undefined contact area due to its stiffness, which renders it unable to conform to head curvature and locally isolates hairs between the electrode surface and scalp skin, making EEG measurement through hair difficult. In order to overcome this issue, a conductive polymer foam was applied to the capacitive electrode surface to provide a cushioning effect. This enabled EEG measurement through hair without any conductive contact with bare scalp skin. Experimental results showed that the new electrode provided lower electrode–skin impedance and higher voltage gains, signal-to-noise ratios, signal-to-error ratios, and correlation coefficients between EEGs measured by capacitive and conventional resistive methods compared to a conventional capacitive electrode. In addition, the new electrode could measure EEG signals, while the conventional capacitive electrode could not. We expect that the new electrode presented here can be easily installed in a hat or helmet to create a nonintrusive wearable EEG apparatus that does not make users look strange for real-world EEG applications.

Description: Understanding the skin's material properties and natural motion is critical to a myriad of applications from tissue engineering to spacesuits. While there is an extensive understanding of human skin properties based on active tensile testing, both in vitro and in vivo, there is a little current knowledge of the strains experienced by skin during natural movements. Using a motion capture system, we have developed a new technique to measure skin movement and strain around the knee during a squatting motion. With these new data, we are also able to calculate the local direction of lines of nonextension, or contours of the skin that remain a constant length during motion, lines of minimum extension, and lines of minimum compression.

Description: A partially perturbed particle swarm optimization (PPSO) has been proposed for identifying the parameters of the Beeler–Reuter (BR) equation from action potential data. In the PPSO algorithm, the 63 BR equation parameters are divided into groups, and parameter patterns are made from the combination of the groups. PPSO enhances the capability of conventional particle swarm optimization (CPSO) by partially perturbing the coordinates of the globally best particle with the patterns when the searching process is locally confined. “Experimental data” were produced for cardiac myocytes simulated by the BR equation and the equation of Luo and Rudy (1991), and were used to test the algorithm of PPSO. The test results show that PPSO was able to identify the parameters of the BR equation effectively for different cardiac myocytes, while still retaining the conceptual simplicity and easy implementation of CPSO.

Description: Accurate glycemic control (AGC) is difficult due to excessive hypoglycemia risk. Stochastic TARgeted (STAR) glycemic control forecasts changes in insulin sensitivity to calculate a range of glycemic outcomes for an insulin intervention, creating a risk framework to improve safety and performance. An improved, simplified STAR framework was developed to reduce light hypoglycemia and clinical effort, while improving nutrition rates and performance. Blood glucose (BG) levels are targeted to 80–145 mg/dL, using insulin and nutrition control for 1–3 h interventions. Insulin changes are limited to +3U/h and nutrition to ±30% of goal rate (minimum 30%). All targets and rate change limits are clinically specified and generalizable. Clinically validated virtual trials were run on using clinical data from 371 patients (39841 h) from the Specialized Relative Insulin and Nutrition Tables (SPRINT) cohort. Cohort and per-patient results are compared to clinical SPRINT data, and virtual trials of three published protocols. Performance was measured as time within glycemic bands, and safety by patients with severe (BG 〈 40 mg/dL) and mild (%BG 〈 72 mg/dL) hypoglycemia. Pilot trial results from the first ten patients (1486 h) are included to support the in-silico findings. In both virtual and clinical trials, mild hypoglycemia was below 2% versus 4% for SPRINT. Severe hypoglycemia was reduced from 14 (SPRINT) to 6 (STAR), and 0 in the pilot trial. AGC was tighter than both SPRINT clinical data and in-silico comparison protocols, with 91% BG within the specified target (80–145 mg/dL) in virtual trials and 89.4% in pilot trials. Clinical effort (measurements) was reduced from 16.2/day to 11.8/day (13.5/day in pilot trials). This STAR framework provides safe AGC with significant reductions in hypoglycemia and clinical effort due - o stochastic forecasting of patient variation—a unique risk-based approach. Initial pilot trials validate the in-silico design methods and resulting protocol, all of which can be generalized to suit any given clinical environment.

Description: Epilepsy is a neurological disorder characterized by sudden, often unexpected transitions from normal to pathological behavioral states called epileptic seizures. Some of these seizures are accompanied by uncontrolled, often rhythmic movements of body parts when seizure activity propagates to brain areas responsible for the initiation and control of movement. The dynamics of these transitions is, in general, unknown. As a consequence, individuals have to be monitored for long periods in order to obtain sufficient data for adequate diagnosis and to plan therapeutic strategy. Some people may require long-term care in special units to allow for timely intervention in case seizures get out of control. Our goal is to present a method by which a subset of motor seizures can be detected using only remote sensing devices (i.e., not in contact with the subject) such as video cameras. These major motor seizures (MMS) consist of clonic movements and are often precursors of generalized tonic–clonic (convulsive) seizures, sometimes leading to a condition known as status epilepticus, which is an acute life-threatening event. We propose an algorithm based on optical flow, extraction of global group transformation velocities, and band-pass temporal filtering to identify occurrence of clonic movements in video sequences. We show that for a validation set of 72 prerecorded epileptic seizures in 50 people, our method is highly sensitive and specific in detecting video segments containing MMS with clonic movements.

Description: Face plastic surgery (PS) plays a major role in today medicine. Both for reconstructive and cosmetic surgery, achieving harmony of facial features is an important, if not the major goal. Several systems have been proposed for presenting to patient and surgeon possible outcomes of the surgical procedure. In this paper, we present a new 3-D system able to automatically suggest, for selected facial features as nose, chin, etc., shapes that aesthetically match the patient's face. The basic idea is suggesting shape changes aimed to approach similar but more harmonious faces. To this goal, our system compares the 3-D scan of the patient with a database of scans of harmonious faces, excluding the feature to be corrected. Then, the corresponding features of the $k$ most similar harmonious faces, as well as their average, are suitably pasted onto the patient's face, producing k+1 aesthetically effective surgery simulations. The system has been fully implemented and tested. To demonstrate the system, a 3-D database of harmonious faces has been collected and a number of PS treatments have been simulated. The ratings of the outcomes of the simulations, provided by panels of human judges, show that the system and the underlying idea are effective.

Description: Recently, sparse representation has attracted a lot of interest in various areas. However, the standard sparse representation does not consider the intrinsic structure, i.e., the nonzero elements occur in clusters, called group sparsity. Furthermore, there is no dictionary learning method for group sparse representation considering the geometrical structure of space spanned by atoms. In this paper, we propose a novel dictionary learning method, called Dictionary Learning with Group Sparsity and Graph Regularization (DL-GSGR). First, the geometrical structure of atoms is modeled as the graph regularization. Then, combining group sparsity and graph regularization, the DL-GSGR is presented, which is solved by alternating the group sparse coding and dictionary updating. In this way, the group coherence of learned dictionary can be enforced small enough such that any signal can be group sparse coded effectively. Finally, group sparse representation with DL-GSGR is applied to 3-D medical image denoising and image fusion. Specifically, in 3-D medical image denoising, a 3-D processing mechanism (using the similarity among nearby slices) and temporal regularization (to perverse the correlations across nearby slices) are exploited. The experimental results on 3-D image denoising and image fusion demonstrate the superiority of our proposed denoising and fusion approaches.

Description: Tetrapolar bioimpedance measurements on subjects have long been suspected of being affected by stray capacitance between the subjects’ body and ground. This paper provides a circuit model to analyze that effect in the frequency range from 100 Hz to 1 MHz in order to identify the relevant parameters when impedance is measured by applying a voltage and measuring both the resulting current and the potential difference between two points on the surface of the volume conductor. The proposed model includes the impedance of each electrode and the input impedance of the differential voltage amplifier. When common values for the circuit parameters are assumed, the simplified model predicts: 1) a frequency-independent gain (scale factor) error; 2) inductive artifacts, that is, the measured impedance increases with increasing frequency and may include positive angle phases; and 3) resonance that can affect well below 1 MHz. In addition to the stray capacitance to ground, relevant parameters that determine those errors are the capacitance of the “low-current” electrode and the input capacitance of the differential voltage amplifier. Experimental results confirm those theoretical predictions and show effects from several additional resonances above 1 MHz that also depend on body capacitance to ground.

Description: We introduce a method to automatically extract spike features of the AIDS virus imaged through an electron microscope. The AIDS virus spike is the primary target of drug design as it is directly involved in infecting host cells. Our method detects the location of these spikes and extracts a subvolume enclosing the spike. We have achieved a sensitivity of 80% for our best operating range. The extracted spikes are further aligned and combined to build a 4-D statistical shape model, where each voxel in the shape model is assigned a probability density function. Our method is the first fully automated technique that can extract subvolumes of the AIDS virus spike and be used to build a statistical model without the need for any user supervision. We envision that this new tool will significantly enhance the overall process of shape analysis of the AIDS virus spike imaged through the electron microscope. Accurate models of the virus spike will help in the development of better drug design strategies.

Description: Electromagnetic absorption and subsequent heating of nanoparticle solutions and simple NaCl ionic solutions is examined for biomedical applications in the radiofrequency range at 13.56 MHz. It is shown via both theory and experiment that for in vitro measurements the shape of the solution container plays a major role in absorption and heating.

Description: Image-guided needle placement, including ultrasound (US)-guided techniques, have become commonplace in modern medical diagnosis and therapy. To ensure that the next generations of physicians are competent using this technology, efficient and effective educational programs need to be developed. This paper presents the Perk Tutor: a configurable, open-source training platform for US-guided needle insertions. The Perk Tutor was successfully tested in three different configurations to demonstrate its adaptability to different procedures and learning objectives. 1) The Targeting Tutor, designed to develop US-guided needle targeting skills, 2) the Lumbar Tutor, designed for practicing US-guided lumbar spinal procedures, and (3) the Prostate Biopsy Tutor, configured for US-guided prostate biopsies. The Perk Tutor provides the trainee with quantitative feedback on progress toward the specific learning objectives of each configuration. Configurations were implemented through simple rearrangement of hardware and software components, attesting to the modularity and ease of configuration. The Perk Tutor is provided as a free resource to enable research and development of educational programs for US-guided intervention.

Description: Histological tissue sections provide rich information and continue to be the gold standard for the assessment of tissue neoplasm. However, there are a significant amount of technical and biological variations that impede analysis of large histological datasets. In this paper, we have proposed a novel approach for nuclear segmentation in tumor histology sections, which addresses the problem of technical and biological variations by incorporating information from both manually annotated reference patches and the original image. Subsequently, the solution is formulated within a multireference level set framework. This approach has been validated on manually annotated samples and then applied to the TCGA glioblastoma multiforme (GBM) dataset consisting of 440 whole mount tissue sections scanned with either a 20 $times$ or 40 $times$ objective, in which, each tissue section varies in size from 40k $times$ 40k pixels to 100k $times$ 100k pixels. Experimental results show a superior performance of the proposed method in comparison with present state of art techniques.

Description: Regulation of intracranial pressure (ICP) is vital to proper brain function. Pathologic conditions such as traumatic brain injury and hydrocephalus can cause lethal changes in ICP through an imbalance of fluid passage into and out of the craniospinal space. The relationship between craniospinal volume and pressure determines to a large extent whether such imbalance can be compensated or if it will lead to neuronal damage. Phantom models are predisposed for the evaluation of medical procedures and devices that alter volume in the spinal or cranial space. However, current phantoms have substantial limitations in the reproduction of craniospinal pressure–volume relationships, which need to be overcome prior to their deployment outside the basic research setting. We present herein a novel feedback controlled phantom for the reproduction of any physiologic or pathologic pressure–volume relation. We compare its performance to those of existing passive methods, showing that it follows reference curves more precisely during both infusion of large volumes and fast oscillatory volume changes.

Description: With proper source spacing, low loss left-handed metamaterial (LHM) lens should be useful for hyperthermia treatment of large area tumors. With a flat LHM lens applicator, conformal hyperthermia can be performed by joint heating of multiple microwave sources (antennas). In the hyperthermia, we restrict distance of two neighboring sources within a critical source interval, arrange the sources in a specific array of general shape in accord with the tumor, and adjust the source-to-lens distance to acquire desired inclination of the heating zone for better fit to tumor region. It is shown that inclination can also be adjusted by the phases of microwave sources. A maneuverable LHM-based hyperthermia scheme is thus proposed to generate a relatively large and even tilted heating pattern in tissue.

Description: Magnetic resonance images of the tongue have been used in both clinical studies and scientific research to reveal tongue structure. In order to extract different features of the tongue and its relation to the vocal tract, it is beneficial to acquire three orthogonal image volumes—e.g., axial, sagittal, and coronal volumes. In order to maintain both low noise and high visual detail and minimize the blurred effect due to involuntary motion artifacts, each set of images is acquired with an in-plane resolution that is much better than the through-plane resolution. As a result, any one dataset, by itself, is not ideal for automatic volumetric analyses such as segmentation, registration, and atlas building or even for visualization when oblique slices are required. This paper presents a method of superresolution volume reconstruction of the tongue that generates an isotropic image volume using the three orthogonal image volumes. The method uses preprocessing steps that include registration and intensity matching and a data combination approach with the edge-preserving property carried out by Markov random field optimization. The performance of the proposed method was demonstrated on 15 clinical datasets, preserving anatomical details and yielding superior results when compared with different reconstruction methods as visually and quantitatively assessed.

Description: Brain source localization accuracy in magnetoencephalography (MEG) requires accuracy in both digitizing anatomical landmarks and coregistering to anatomical magnetic resonance images (MRI). We compared the source localization accuracy and MEG-MRI coregistration accuracy of two head digitization systems—a laser scanner and the current standard electromagnetic digitization system (Polhemus)—using a calibrated phantom and human data. When compared using the calibrated phantom, surface and source localization accuracy for data acquired with the laser scanner improved over the Polhemus by 141% and 132%, respectively. Laser scan digitization reduced MEG source localization error by 1.38 mm on average. In human participants, a laser scan of the face generated a 1000-fold more points per unit time than the Polhemus head digitization. An automated surface-matching algorithm improved the accuracy of MEG-MRI coregistration over the equivalent manual procedure. Simulations showed that the laser scan coverage could be reduced to an area around the eyes only while maintaining coregistration accuracy, suggesting that acquisition time can be substantially reduced. Our results show that the laser scanner can both reduce setup time and improve localization accuracy, in comparison to the Polhemus digitization system.

Description: The ability to accurately locate a polyp found on computed tomographic colonography (CTC) at subsequent optical colonoscopy (OC) is an important task in colorectal cancer screening. We present a method to more accurately match polyp locations at CTC and OC. A colonoscope was modeled as a flexible tube with negligible stretch and minimal strain. The path of the colonoscope was estimated using a minimal-energy curve method. The energy function was defined and optimized by a subdivision scheme. The prediction of polyp locations at OC from CTC was converted to an optimization problem. The prediction performance was evaluated on 134 polyps by comparing the predicted with the true polyp locations at OC. The method can accurately predict polyp locations at OC to within ±0.5 colonoscope mark (5 cm) for more than 58% of polyps and to within ±1 colonoscope mark (10 cm) for more than 96% of polyps, significantly improving upon previously published methods. This method can be easily incorporated into routine OC practice and allow the colonoscopist to begin the examination by targeting locations of potential polyps found at CTC.

Description: System identification of physiological systems poses unique challenges, especially when the structure of the system under study is uncertain. Nonparametric techniques can be useful for identifying system structure, but these typically assume stationarity and require large amounts of data. Both of these requirements are often not easily obtained in the study of physiological systems. Ensemble methods for time-varying nonparametric estimation have been developed to address the issue of stationarity, but these require an amount of data that can be prohibitive for many experimental systems. To address this issue, we developed a novel algorithm that uses multiple short data segments. Using simulation studies, we showed that this algorithm produces system estimates with lower variability than previous methods when limited data are present. Furthermore, we showed that the new algorithm generates time-varying system estimates with lower total error than an ensemble method. Thus, this algorithm is well suited for the identification of physiological systems that vary with time or from which only short segments of stationary data can be collected.

Description: Affective phenomena, as reflected through brain activity, could constitute an effective index for the detection of music preference. In this vein, this paper focuses on the discrimination between subjects’ electroencephalogram (EEG) responses to self-assessed liked or disliked music, acquired during an experimental procedure, by evaluating different feature extraction approaches and classifiers to this end. Feature extraction is based on time–frequency (TF) analysis by implementing three TF techniques, i.e., spectrogram, Zhao–Atlas–Marks distribution and Hilbert–Huang spectrum (HHS). Feature estimation also accounts for physiological parameters that relate to EEG frequency bands, reference states, time intervals, and hemispheric asymmetries. Classification is performed by employing four classifiers, i.e., support vector machines, $k$ -nearest neighbors $(k$ -NN), quadratic and Mahalanobis distance-based discriminant analyses. According to the experimental results across nine subjects, best classification accuracy {86.52 (±0.76)%} was achieved using $k$ -NN and HHS-based feature vectors ( FVs) representing a bilateral average activity, referred to a resting period, in $beta$ (13–30 Hz) and $gamma$ (30–49 Hz) bands. Activity in these bands may point to a connection between music preference and emotional arousal phenomena. Furthermore, HHS-based FVs were found to be robust against noise corruption. The outcomes of this study provide early evidence and pave the way for the development of a generalized brain computer interface for music preference recognition.

Description: This paper studies the design of a robust discrete-time sliding-mode control (DT–SMC) for a high precision electrohydraulic actuator (EHA) system. Nonlinear friction in the hydraulic actuator can greatly influence the performance and accuracy of the hydraulic actuators, and it is difficult to accurately model the nonlinear friction characteristics. In this paper, it is proposed to characterize the frictions as an uncertainty in the system matrices. Indeed, the effects of variations of the nonlinear friction coefficients are considered as norm-bounded uncertainties that span a bounded region to cover a wide range of the real actuator friction. For such a discrete-time dynamic model, for the EHA system with system uncertainty matrices and a nonlinear term, a sufficient condition for existence of stable sliding surfaces is proposed by using the linear matrix inequality approach. Based on this existence condition, a DT–SMC is developed such that the reaching motion satisfies the discrete-time sliding mode reaching condition for uncertain systems. Simulation and experimental studies on the EHA system illustrate the effectiveness and applicability of the proposed method.

Description: This paper focuses on the integration of inertial measurement unit (IMU) with two real-time kinematic global positioning system (GPS) units in an adaptive Kalman filter (KF) for driftless estimation of a vehicle’s attitude and position in 3-D. The observability analysis reveals that 1) integration of a single GPS with IMU does not constitute an observable system; and 2) integration of two GPS units with IMU results in a locally observable system provided that the line connecting two GPS antennas is not parallel with the vector of the measured acceleration, i.e., the sum of inertial and gravitational accelerations. The latter case makes it possible to compensate the error in the estimated orientation due to gyro drift and its bias without needing additional instrument for absolute orientation measurements, e.g., magnetic compass. Moreover, in order to cope with the fact that GPS systems sometimes lose their signal and receive inaccurate position data, the self-tuning filter estimates the covariance matrix associated with the GPS measurement noise. This allows the KF to incorporate GPS measurements in the data fusion process heavily only when the information received by GPS becomes reliably available. Finally, test results obtained from a mobile robot moving across uneven terrain demonstrate driftless 3-D pose estimation.

Description: This paper presents a novel active body weight support (BWS) method, which is capable of virtually offloading full or partial body mass for a potential application of enhancing treadmill-based locomotion rehabilitation. The mass-offloading capability is realized by actively compensating a desired amount of body weight and inertia force using an acceleration-feedback scheme. The method has been studied by dynamics simulations and a specially designed nonhuman experiment. In the simulation study, the human and the BWS device were modeled as a multibody dynamical system interacting dynamically with the treadmill. The ground reaction forces were recorded as the dynamic load on the person. A cam-slider-based experiment was designed and conducted to test the engineering feasibility of the mass-offloading capability. Both the simulation and experiment results demonstrated that the BWS system can compensate any desired amount of gravity force and inertia force and, therefore, has the effect of virtually reducing the mass of a person attached to the system.

Description: This paper describes a magnetic levitation system that uses a planar array of 16 cylindrical coils to levitate a platform containing two permanent disk magnets. Position and orientation feedback for closed-loop levitation control is provided by an optical rigid-body motion tracker and wireless LED markers. The actuation model for the levitation system across the full translation and rotation ranges was calculated using electromagnetic finite element analysis and validated with force and torque measurements between a single magnet and coil using motion stages and a six-axis force sensor. The transformation from the set of coil currents to the force and torque generated on the levitated body is recalculated in real time at each update of the levitated platform position and orientation obtained from the motion tracker using a precomputed single magnet and coil actuation model, and redundant kinematic control methods are used to find the least squares set of coil currents to generate the forces and torques needed to stabilize the levitated platform by proportional-derivative feedback control. The approximately $80 times 80 times 25$ mm translation range of the implemented levitation system is comparable to the dimensions of the levitated magnet platform. The rotation ranges are $pm 40^circ$ in roll and $pm 15^circ$ in pitch, with unlimited yaw. The horizontal translation ranges can be extended by adding coils to the array, and the vertical translation and tilt rotation ranges are limited by heat dissipation in the coils. Analysis and control methods of the system are described, and large range translation and rotation trajectory following experimental results are given.

Description: This paper discusses the use of voice coil actuators to enhance the performance of shift-by-wire systems. This innovative purely electric actuation approach was implemented and applied to a Formula SAE race car. The result was more compact and faster than conventional solutions, which usually employ pneumatic actuators. The designed shift-by-wire system incorporates a control unit based on a digital signal processor, which runs the control algorithms developed for both gear shifting and launching the car. The system was successfully validated through laboratory and on-track tests. In addition, a comparative test with an equivalent pneumatic counterpart was carried out. This showed that an effective use of voice coil actuators enabled the upshift time to be almost halved, thus proving that these actuators are a viable solution to improving shift-by-wire system performance.

Description: This paper explores a robust $mu$ -synthesis control scheme for structural resonance vibration suppression of high-speed rotor systems supported by active magnetic bearings (AMBs) in the magnetically suspended double-gimbal control moment gyro (MSDGCMG). The derivation of a nominal linearized model about an operating point was presented. Sine sweep test was conducted on each component of AMB control system to obtain parameter variations and high-frequency unmodeled dynamics, including the structural resonance modes. A fictitious uncertainty block was introduced to represent the performance requirements for the augmented system. Finally, D-K iteration procedure was employed to solve the robust $mu$ -controller. Rotor run-up experiments on the originally developed MSDGCMG prototype show that the designed $mu$ -controller has a good performance for vibration rejection of structural resonance mode with the excitation of coupling torques. Further investigations indicate that the proposed method can also ensure the robust stability and performance of high-speed rotor system subject to the reaction of a large gyro torque.

Description: Many minimally invasive surgical procedures are now performed using teleoperated robotic systems. However, such commercially available systems do not provide significant force feedback to the surgeon. This reduces surgeon's dexterity and increases tissue trauma when performing the operation. In this paper, a compact and lightweight forceps’ manipulator using pneumatic artificial muscles (PAMs) for minimally invasive surgery is presented, which allows for the perception of manipulation force without the usage of the force sensor. The main advantage of this concept is that no force sensor has to be integrated into surgical instruments and inserted into the patient's body. Rather, a disturbance observer is integrated into the slave-side controller for the estimation of the external force acting at the forcep's tip. This approach reduces costs and stabilizability demands for forceps’ manipulator while enables haptic feedback to the surgeons. Results of force perception experiments and comparison with forceps’ manipulator driven by pneumatic cylinders are presented to validate the concepts.

Description: Active disturbance rejection control method that can actively compensate nonlinear model uncertainties and unpredictable external disturbances is proposed for an accurate position tracking of an ionic polymer–metal composite actuator. An empirical model of the electroactive polymer actuator is constructed by fitting the step response of the actuator. Experimental results show that the present active disturbance rejection control scheme can substantially improve the control performance in the tracking of various reference motions including step, sinusoidal, trapezoidal, and sawtooth wave profiles. The proposed scheme offers an innovative solution for the position tracking of an ionic polymer–metal composite actuator with highly nonlinear dynamics.

Description: This paper explores the design methodology and effectiveness of small-scale magnetorheological dampers (MRDs) in applications that require variable damping. Previously, applications of MRD have been chiefly limited to vehicle shock absorbers and seismic vibration attenuators. There has been recent biomedical interest in active-damping technology, however, particularly in the field of rehabilitation robotics. The topic at hand is the feasibility of developing MRDs that would be functionally and cosmetically adequate for actuation of an upper limb tremor suppression orthosis. A Bingham plastic model is used to determine MRD's functional characteristics, and experimental data are presented to validate the mathematical model. The feasibility of applying the developed small-scale MRDs to attenuation of tremorous motion is explored.

Description: In order to fulfill the requirements of low energy consumption and two sensing directions, a novel bidirectional acceleration switch is proposed by utilizing the magnetic-fields-based tristable mechanism that can maintain the three stable states without input power and with high position accuracy and repeatability. The bidirectional acceleration switch mainly consists of an inertial mass supported by two parallel elastic beams, two metal contact points, and four permanent magnets with one imbedded in the inertial mass and the other three fixed in the case along the vertical direction. Based on the magnetic charge model, the nonlinear magnetic force is analyzed, and then, a static design model of the bidirectional switch is established by considering the elastic force, the magnetic force, the contact force, and the inertial force. To validate the feasibility of the design method, a miniature sample of the switch is fabricated. The results of the centrifugal experiment show that the threshold accelerations in two directions are 53.0 and -52.0 g, respectively, which are close to the design values of 55.0 and -50.0 g, correspondingly. In addition, the threshold values can be adjusted by changing the relative distances among the four magnets.

Description: In this paper, we report on the design, modeling, and experimental testing of a piezoelectric-driven microgripper making use of both an integrated gripping force sensor and an integrated tip displacement sensor. In the developed microgripper, a stack piezoelectric ceramic actuator is used to simultaneously obtain the tip displacement and the gripping force. A novel monolithic compliant mechanism is proposed to act as the microdisplacement transmission mechanism to obtain the large tip displacement and to provide the possibility of integrating both the gripping force sensor and the tip displacement sensor into the microgripper. The relationship between the gripping force, tip displacement, input force, and input displacement of the piezoelectric-driven microgripper and the dynamic model are established using the pseudorigid-body-model method. The characteristics of the developed microgripper are tested and the case of gripping an optical fiber is presented. The experimental results indicate that: 1) the theoretical model for the developed microgripper matched well with the measured results; 2) the integrated gripping force sensor and tip displacement sensor could accurately measure the gripping force and tip displacement; 3) the developed microgripper could achieve a displacement magnification of $16.0 times$ with respect to the stack piezoelectric ceramic actuator to realize the large tip displacement with high resolution but is also able to possess the parallel movement of its gripping jaws and the constant displacement magnification.

Description: This paper experimentally verifies that a multiple-client–server architecture based on switched Ethernet can be used as a real-time communication standard for possible applications in factory automation, by observing the effects of packet delays, network congestion, and packet loss on the performance of a networked control system (NCS). The NCS experimental setup used in this research involves real-time feedback control of multiple plants connected to one or more controllers over the network. A multiclient–multiserver (MC–MS) architecture on a local area network (LAN) was developed using user datagram protocol as the communication protocol. In the single-client–single-server (SC–SS) system, as the Ethernet link utilization increased over 82%, the average packet delays and steady-state error of a dc motor speed-control system increased by 2231% and 304%, respectively. As the link utilization increased beyond the threshold, employing an additional server in the NCS reduced average packet delays and also overcame the negative effects of Ethernet's flow control mechanism. The MC–MS architecture is tested with artificially generated random packet loss. The standard deviation of steady-state error (SSE) at 80% utilization with packet loss is found to be 70.2% less than SC–SS and 200% less than multiclient–single-server architecture. The MC–MS architecture remained stable till 70% of control or measurement packet loss.

Description: In this paper, a novel 5-degrees-of-freedom robot for performing needle-based interventions on small animal subjects is presented. The robot can realize dexterous alignment of the needle using two parallel mechanisms, and has a syringe mechanism to insert needles to subjects. Operations on small animals require high accuracy positioning during needle insertion. The kinematic calibration procedure of the robot using an optical tracker as an external sensor is presented to enhance accuracy of the system. After the kinematic calibration, the positioning accuracy of the needle tip is measured as 0.4 mm RMS. The robot design is light weight, and has a motion bandwidth of 4 Hz. The robot can track reference trajectories with a closed-loop controller.

Description: This paper describes an efficient control strategy for a piezoelectric microactuator using charge recovery. For piezoelectric actuators, as well as other actuators that behave primarily as capacitive loads, energy consumption can be reduced by minimizing the number of times an actuator is charged and by recovering stored energy when it is turned off. An integer programming-based algorithm is used to drive microrobotic legs powered by piezoelectric actuators to a specified angle in a specified time using minimum energy. Partial charge recovery is incorporated; this allows the use of a more flexible controller than a pure on–off controller, with two or more intermediate voltage levels between the minimum and maximum voltages available to improve positioning accuracy. Simulated and experimental tests show that a prototype piezoelectric robotic leg joint achieved controlled movements with one third of the energy consumed by a pure on–off controller.

Description: This paper reports the design, development, and magnetic resonance imaging (MRI) compatibility evaluation of an actuated transrectal prostate robot for MRI-guided needle intervention in the prostate. The robot performs actuated needle MRI guidance with the goals of providing $1)$ MRI compatibility; $2)$ MRI-guided needle placement with accuracy sufficient for targeting clinically significant prostate cancer foci; $3)$ reducing interventional procedure times (thus increasing patient comfort and reducing opportunity for needle targeting error due to patient motion); $4)$ enabling real-time MRI monitoring of interventional procedures; and $5)$ reducing the opportunities for error that arise in manually actuated needle placement. The design of the robot, employing piezoceramic-motor actuated needle guide positioning and manual needle insertion, is reported. Results of an MRI compatibility study show no reduction of MRI signal-to-noise ratio (SNR) with the disabled motors. Enabling the motors reduces the SNR by 80% without radio frequency (RF) shielding, but the SNR is only reduced by 40–60% with RF shielding. The addition of RF shielding is shown to significantly reduce image SNR degradation caused by the presence of the robotic device. An accuracy study of MRI-guided biopsy needle placements in a prostate phantom is reported. The study shows an average in-plane targeting error of 2.4 mm with a maximum error of 3.7 mm. These data indicate that the system’s needle targeting accuracy is similar to that obtained with a previously reported manually actuated system, and is sufficient to reliably sample clinically significant prostat- cancer foci under MRI guidance.

Description: A novel rotary nanomotor is described using two axially aligned, opposing chirality nanotube shuttles. Based on intershell screw-like motion of nanotubes, rotary motion is generated by electrostatically pulling the two cores together. Simulations using molecular dynamics show the generation of rotation from armchair nanotube pairs and their actuation properties. The simulation results point toward the use of these motors as building blocks in nanoelectromechanical systems and nanorobotic systems for sensing, actuation, and computation applications.

Description: A typical mechatronic problem (modeling, identification, and design) entails finding the best system topology as well as the associated parameter values. The solution requires concurrent and integrated methodologies and tools based on the latest theories. The experience on natural evolution of an engineering system indicates that the system topology evolves at a much slower rate than the parametric values. This paper proposes a two-loop evolutionary tool, using a hybrid of genetic algorithm (GA) and genetic programming (GP) for design optimization of a mechatronic system. Specifically, GP is used for topology optimization, while GA is responsible for finding the elite solution within each topology proposed by GP. A memory feature is incorporated with the GP process to avoid the generation of repeated topologies, a common drawback of GP topology exploration. The synergic integration of GA with GP, along with the memory feature, provides a powerful search ability, which has been integrated with bond graphs (BG) for mechatronic model exploration. The software developed using this approach provides a unified tool for concurrent, integrated, and autonomous topological realization of a mechatronic problem. It finds the best solution (topology and parameters) starting from an abstract statement of the problem. It is able to carry out the process of system configuration realization, which is normally performed by human experts. The performance of the software tool is validated by applying it to mechatronic design problems.

Description: This paper presents a nanomanipulation system for operation inside scanning electron microscopes (SEM). The system is compact, making it capable of being mounted onto and demounted from an SEM through the specimen-exchange chamber (load-lock) without breaking the high vacuum of the SEM. This advance avoids frequent opening of the high-vacuum chamber, thus, incurs less contamination to the SEM, avoids lengthy pumping, and significantly eases the exchange of end effectors (e.g., nanoprobes and nanogrippers). The system consists of two independent 3-DOF Cartesian nanomanipulators driven by piezomotors and piezoactuators. High-resolution optical encoders are integrated into the nanomanipulators to provide position feedback for closed-loop control. The system is characterized, yielding the encoders’ resolution of 2 nm and the piezoactuators’ resolution of 0.7 nm. A look-then-move control system and a contact-detection algorithm are implemented for horizontal and vertical nanopositioning.

Description: This paper presents a new method for the design of distributed controllers that achieves component swapping modularity (CSM) in control systems. Our approach, referred to as the direct method, is based on solving a bilevel optimization problem to obtain the distributed controller gains directly. In the previously proposed three-step method, the distributed controllers were obtained by matching with a precomputed centralized controller. To illustrate our approach, we consider an engine idle speed control problem, where CSM is achieved with respect to the throttle actuator. The results indicate that the direct method can significantly improve the CSM metric compared to the three-step method. In addition, for a certain distributed control structure, the direct method enables the designer to tradeoff between desired system performance and CSM.

Description: This study designs an optimal single-pulse stimulus in pacemakers to treat sudden cardiac arrest, while minimizing the pulse amplitude and reducing the delivered energy. Based on theYanagihara, Noma, and Irisawa (YNI) model that describes the potential behavior of a sinoatrial node in a heart, it develops the frequency entrainment between irregular YNI-response and optimal single-pulse. This study derives the minimum amplitude of the optimal single-pulse for successful entrainment. Simulation results confirm that the proposed optimal single pulse is effective to induce rapid response of sudden cardiac arrest for heartbeat recovery, while a reduction in delivered energy of 91%, comparing with conventional pulse. This study will be helpful not only for the treatment of sudden cardiac arrest but also for prolonging battery longevity and reducing the stimuli pain on patients with implantable medical devices.

Description: In this paper, a new actuator with adjustable stiffness (AwAS) is presented. AwAS is capable of controlling the position and stiffness of a joint, independently. The proposed actuator can regulate the joint stiffness through a wide range with minimum energy consumption by means of a small motor. This is possible due to its novel mechanical configuration that achieves the stiffness regulation not through the control of spring pretension (as in most of the existing variable stiffness joints) but by using the variable lever arm principle. The regulation of the lever arm length is achieved through the displacement of the spring elements. An important consequence of this mechanism is that the displacement needed to change the stiffness is perpendicular to the forces generated by the spring. This helps to reduce the energy/power required to regulate the stiffness. It is experimentally shown that AwAS is capable of minimizing energy consumption through exploiting the natural dynamics in real time for both fixed and variable frequency motions.

Description: This paper introduces a methodology for designing real-time controllers capable of enforcing desired trajectories on microrobotic insects in vertical flight and hovering. The main idea considered in this work is that altitude control can be translated into a problem of lift force control. Through analyses and experiments, we describe the proposed control strategy, which is fundamentally adaptive with some elements of model-based control. In order to test and explain the method for controller synthesis and tuning, a static single-wing flapping mechanism is employed in the collection of experimental data. The fundamental issues relating to the stability, performance, and stability robustness of the resulting controlled system are studied using the notion of an input-output linear time-invariant (LTI) equivalent system, which is a method for finding an internal model principle (IMP) based representation of the considered adaptive laws, using basic properties of the $z$ -transform. Empirical results validate the suitability of the approach chosen for designing controllers and for analyzing their fundamental properties.

Description: This paper presents an integrated direct/indirect adaptive robust control scheme for a class of nonlinear dynamic systems preceded by unknown nonsymmetric, nonequal slope dead-zone nonlinearity. Departing from existing approximate adaptive dead-zone compensations, this paper uses indirect parameter estimation algorithms along with on-line condition monitoring to obtain an accurate estimation of the unknown dead zone when certain relaxed persistent-excitation conditions are satisfied—a theoretical result that cannot be achieved with the existing methods. Such a result is obtained by making full use of the fact that though not being linearly parameterized globally, the unknown dead zone can still be linearly parameterized perfectly within certain known working ranges. With these accurate estimates of dead-zone parameters, perfect dead-zone compensation is then constructed and utilized in the development of a performance-oriented adaptive robust control algorithm for the overall system. Consequently, asymptotic output tracking is achieved even in the presence of unknown dead zone. In addition, the proposed algorithm achieves certain guaranteed robust transient performance and final tracking accuracy even when the entire system may be subjected to other uncertain nonlinearities and time-varying disturbances. The proposed algorithm is also experimentally tested on a linear motor drive system preceded by a simulated unknown nonsymmetric dead zone. Comparative experimental results obtained validate the effectiveness of dead-zone compensation and the high-performance nature of the proposed approach in practical implementation.

Description: We propose an application-specified integrated circuit (ASIC)-based vibration damping system implementing a semiactive controlling method called synchronized switch damping on inductor (SSDI). The ASIC integrates high-voltage switches and diodes for an “energy-extracting” passive LC shunt circuit and a controlling part for synchronous voltage inversion on the piezoelectric transducer. The controlling part has two channels, each including a range-adaptive voltage divider with protection and a peak detector with switch-control output. The system has been tested with both cantilever beam and three-side-clamped-plate structures. Cantilever beam testing shows a 15 dB damping in forced harmonic regime and a fivefold damping rate in pulsed-excitation transient response. For the three-side-clamped-plate case, wideband SSDI damping effects are observed. The damping efficiency for each mode depends on the electromechanical coupling factor and the mapping of the piezoelectric-insert damping zones. It also depends on the excitation level, and begins to increase rapidly with vibration magnitude when the piezoelectric transducer's voltage peaks exceed a certain threshold voltage $(sim 0.5$ V for the system).

Description: Dielectric elastomer actuators (DEAs) have raised interest in the field of mobile robotics. In such a field, actuator design requires a fundamental understanding of DEA energy conversion performance. To provide insight into DEA mechanical work, energy consumption, and efficiency, this paper proposes a simple thermodynamic description completed by experimental loss factors obtained over a broad range of operating conditions and modes. Extensive data gathered on cone actuators show practical efficiency limits of $sim 26%$ for acrylic actuators (VHB 4905) operating under constant charge mode and $sim 18%$ for silicone actuators operating under constant voltage mode. While charge recovery could raise these limits to $sim 60%$ , the study of a DEA rotary motor shows significant efficiency degradation caused by unconstrained electrode boundaries.

Description: The problem of perimeter detection and monitoring has a variety of applications. In this paper, a hybrid system of finite states is proposed for multiple autonomous robotic agents with the purpose of hazardous spill perimeter detection and tracking. In the system, each robotic agent is assumed to be in one of three states: searching, pursuing, and tracking. The agents are prioritized based on their states, and a potential field is constructed for agents in each state. For an agent in the tracking state, the agent’s location and velocity as well as those of its closest leading and trailing agents are utilized to control its movement. The convergence of the tracking algorithm is analyzed for multiple spills under certain conditions. Simulation and experiment results show that with the proposed method, the agents can successfully detect and track the spills of various shapes, sizes, and movements.

Description: The accuracy and resolution of metrological devices (coordinate measuring machines -CMM-, interferometers, etc.) are greatly affected by their robustness to external vibrations. This is especially important in the case of micrometric and nanometric microscopes, such as atomic force microscopes (AFM). In such cases, active vibration control strategies are frequently used, requiring actuators capable of fast and accurate responses. Piezoelectric actuators meet these requirements but they suffer from two major drawbacks, hysteresis, and rate dependence, which must be taken into consideration in the design of the control strategy. The present work proposes a novel active vibration control strategy using piezoelectric actuators for metrological devices affected by low external loads. The control strategy combines a classical sky-hook feedback with a feedforward control. The effect of hysteresis is minimized by compensating the senstivity variations of the actuator in oscillatory movements. For the design of the feedforward law, the present work demonstrates that a stack piezoelectric actuator working as a damper admits a mathematical description fulfilling differential flatness. It also proposes a formulation of the active vibration damping problem in terms of a trajectory tracking command perfectly fitted to the flatness-based control law. This strategy obtains damping improvements in the entire frequency range of operation without the instability problems derived from high feedback gains.

Description: Periodicity frequently occurs in hard disk drives (HDDs) whose servo systems with periodic phenomena can be usually modeled as linear periodically time-varying (LPTV) systems. This paper discusses optimal $H_{infty}$ control synthesis for discrete-time LPTV systems via discrete Riccati equations. First, an explicit minimum entropy $H_{infty}$ controller for general time-varying systems is obtained. Subsequently, the developed control synthesis algorithm is applied to LPTV systems and it is shown that the resulting controllers are periodic. The proposed control synthesis technique is evaluated through both single and multirate optimal $H_{infty}$ track-following control designs. The single-rate servo design shows that our proposed control synthesis technique is more numerically robust in calculating optimal $H_{infty}$ controllers for discrete-time linear time-invariant systems than the MATLAB function of “hinfsyn,” while the multirate servo design validates its ability of synthesizing multirate controllers to achieve the robust performance of a desired error-rejection function. Moreover, an experimental study—in which the developed control synthesis algorithm on a real HDD with missing position error signal sampling data is implemented—further demonstrates its effectiveness in handling LPTV systems with a large period and attaining desirable disturbance attenuation.

Description: This paper proposes a surgical manipulator with workspace-conversion ability for both minimally invasive surgery (MIS) and open surgery. The focus of the proposed surgical manipulator is on its potential use in places such as battlefields, army camps, and rural areas rather than in civilian hospitals. The proposed surgical manipulator has a workspace for MIS with a virtual remote center of motion and has a workspace for open surgery like that of an articulated manipulator. The mechanism of the surgical manipulator is proposed and implemented in this paper. A new distal rolling joint with two spiral wire ropes is also implemented. Several experiments to validate the feasibility of the surgical manipulator were carried out. Two fundamentals of laparoscopic surgery tasks were performed to compare the performance of the surgical manipulator with other MIS systems. The workspace conversion from MIS to open surgery was implemented. The workspace-conversion ability enables the surgical manipulator to attach or detach the surgical tool unit without human assistance or an assistant robot.

Description: An intelligent cane robot is designed for aiding the elderly and handicapped people's walking. The robot consists of a stick, a group of sensors, and an omnidirectional basis driven by three Swedish wheels. Recognizing the user's walking intention plays an important role in the motion control of our cane robot. To quantitatively describe the user's walking intention, a concept called “intentional direction (ITD)” is proposed. Both the state model and the observation model of ITD are obtained by enumerating the possible walking modes and analyzing the relationship between the human–robot interaction force and the walking intention. From these two models, the user's walking intention can be online inferred using the Kalman filtering technique. Based on the estimated intention, a new admittance motion control scheme is proposed for the cane robot. Walking experiments aided by the cane robot on a flat ground and slope are carried out to validate the proposed control approach. The experimental results show that the user feels more natural and comfortable when our intention-based admittance control is applied.

Description: Dynamically substructured systems (DSS) play an important role in modern testing methods. DSS enables full-size critical components of a complete system to be tested physically in real-time, while the remaining parts of the system run in parallel as a real-time simulation. The performance of DSS testing is influenced by the synchronization of the physical and numerical substructures, which necessitates the design of a DSS controller. Since the testing signal is known and can be assumed to be a perfectly measured disturbance, the DSS control can be viewed as a regulation control problem with measured disturbance attenuation. A potential problem with DSS control arises from actuator saturation, which can be encountered in DSS transfer systems and can significantly influence the testing accuracy. This paper demonstrates the application of a novel robust disturbance rejection antiwindup (AW) technique, to cope with the actuator saturation problem in DSS. Implementation results from a hydraulically-actuated DSS test rig confirm the advantage of using this novel approach over some other existing AW approaches. Furthermore, some specific practical issues are discussed for the AW compensator design, such as the tuning of parameters.

Description: We have built an anatomically correct testbed (ACT) hand with the purpose of understanding the intrinsic biomechanical and control features in human hands that are critical for achieving robust, versatile, and dexterous movements, as well as rich object and world exploration. By mimicking the underlying mechanics and controls of the human hand in a hardware platform, our goal is to achieve previously unmatched grasping and manipulation skills. In this paper, the novel constituting mechanisms, unique muscle to joint relationships, and movement demonstrations of the thumb, index finger, middle finger, and wrist of the ACT Hand are presented. The grasping and manipulation abilities of the ACT Hand are also illustrated. The fully functional ACT Hand platform allows for the possibility to design and experiment with novel control algorithms leading to a deeper understanding of human dexterity.

Description: Ankle-foot orthoses (AFOs) can be used to ameliorate the impact of impairments to the lower limb neuromuscular motor system that affect gait. Existing AFO technologies include passive devices with fixed and articulated joints, semiactive devices that modulate damping at the joint, and active devices that make use of a variety of technologies to produce power to move the foot. Emerging technologies provide a vision for fully powered, untethered AFOs. However, the stringent design requirements of light weight, small size, high efficiency, and low noise present significant engineering challenges before such devices will be realized. Once such devices appear, they will present new opportunities for clinical treatment of gait abnormalities.

Description: For the demands of surgical navigation, this paper proposes some simple 3-D point reconstruction methods. These methods regard the perpendicular feet on back-projection lines as the measurements of a 3-D point, since these feet are close to the 3-D point. And then the methods utilize the distance between 3-D point and camera and error propagation rules to adjust the weights of the feet. Finally, the weighted average of these feet is taken as the final estimation for the 3-D point. They are easy to implement, and can be used in both biocular systems and multiocular systems. Especially, as these methods have closed-form solutions, their errors can be predicted by using error propagation rules. Experiments show that they are faster and more accurate than iterative methods and their error covariance matrix can be exactly predicted.

Description: This paper presents the development and evaluation of a miniature, three-axis, fiber-optic force sensor. The sensor is manufactured using low-cost, high-resolution rapid prototyping techniques and is integrated with a catheter to enable the detection of force during MRI-guided cardiac ablation procedures. The working principle is based on reflective light-intensity modulation. A force sensitive structure (flexure) is employed to vary the distance and orientation of an integrated reflector when a force is applied at the catheter tip. In this way, the light is modulated accordingly and the force can be calculated. The sensor has a high sensitivity and an adequate linear response along all three orthogonal axes $(F_{x}, F_{y}$ , and $F_{z})$ and a working range of around 0.5 N. Low-noise, high-gain electronics provide a force resolution of less than 1 gm force. Experiments demonstrate the ability of the sensor to acquire accurate force readings in a dynamic environment. MRI-compatibility experiments are performed in a clinical 1.5-T MR scanner.

Description: This paper proposes an underactuated modular climbing robot with flat dry elastomer adhesives. This robot is designed to achieve high speed, high payload, and dexterous motions that are typical drawbacks of previous climbing robots. Each module is designed as a tread-wheeled mechanism to simultaneously realize high speed and high adhesive force. Two modules are connected by compliant joints, which induce a positive preload on the front wheels resulting in stable climbing and high payload capacity. Compliant joints also help the robot to perform various transitions. An active tail is adopted to regulate the preload of the second module. Force transfer equations are derived and stable operating conditions are verified. The stiffness coefficients of the compliant joints and the active tail force are determined optimally to satisfy the constraints of stable operation. The prototype two-module robot achieves 6- $hbox{cm}/hbox{s}$ speed and 500- $hbox{g}$ payload capacity on vertical surfaces. The abilities of flat surface locomotion, internal, external, and thin-wall transitions, and overcoming various sized obstacles are validated through experiment. The principle of joint compliance can be adopted in other climbing robots to enhance their stability and transition capability.

Description: Adaptive sliding mode and integral sliding mode grasped object slip prevention controllers are implemented for a prosthetic hand and compared to a proportional derivative shear force feedback slip prevention controller as well as a sliding mode controller without slip prevention capabilities. Slip of grasped objects is detected by band-pass filtering the shear force derivative to amplify high frequency vibrations that occur as the grasped object slides relative to the fingers. The integral sliding mode slip prevention controller provides a robust design framework for slip prevention while addressing the issue of reducing the amount of deformation that the grasped object experiences to prevent slip. Averaged results from bench top experiments show that the integral sliding mode slip prevention controller produces the least amount of deformation to the grasped object while simultaneously preventing the object from being dropped.

Description: Haptic interaction in slow virtual environments (VEs) can become unstable due to the phase lag introduced in the control loop by the slow update rate of the VE. Increasing the physical damping and/or limiting the contact stiffness rendered to users can mitigate the destabilizing effect of the low VE update rate. However, large physical damping and compliant virtual contacts decrease the sense of presence in VEs, especially during interaction with rigid virtual objects. To increase the maximum virtual contact stiffness that can be rendered to users without increasing the interface damping, this paper proposes a control strategy based on multirate wave communications between a haptic interface and a VE updated at a slow and fixed rate. The multirate wave communications are shown to be guaranteed passive only if the decrease of the wave sampling rate at the connection between the haptic interface and the VE does not cause aliasing. Therefore, an antialiasing low-pass filter is placed before the wave rate drop in the communications. The passivity condition is verified analytically and numerically for multirate haptic interaction in VEs with various contact stiffnesses and update rates. The transparency of haptic interaction in slow VEs to which users connect via passive multirate wave communications is investigated analytically in the frequency domain. Experiments validate that passive multirate wave communications can render stiffer contact in slow VEs than conventional direct coupling, and illustrate the destabilizing effect of the aliasing caused by the sampling rate drop in the communications.

Description: In this paper, we describe a method of adaptive feedforward control that can achieve zero residual vibration in rest-to-rest motion of a vibratory system. When a finite impulse response filter is used to preshape a command input, zero residual vibration is achieved for any input signal if the impulse response of the filter satisfies a condition of orthogonality with respect to the impulse response of the system under control. An equivalent condition involving sets of measured I/O data is derived that forms the basis of a direct method of adaptively tuning filter coefficients during motion. The approach requires no prior model of the system and can be applied to multimode and multiinput systems under arbitrary and nonrepetitive motions. Versions of the algorithm employing recursive least-squares techniques are developed and analyzed. As a special case of the general adaptation problem, tuning of impulse-based shapers with fixed impulse timings can also be achieved. An experimental implementation on a two-link rigid-flexible manipulator is presented. The method is thereby shown to be realizable and effective for real-world motion control problems.

Description: This paper describes a linear motor design for ultrahigh acceleration and high velocity, as well as the driving performance of the motor. First, because of its ease of control, a moving-permanent-magnet linear synchronous motor (MPM LSM) was selected. The overall structure of the motor, which consists of a table to which the permanent magnets (PMs) are attached and two fixed electromagnet (EM) lines between which the PMs move, was selected based on the simplicity of the structure and the ease of gap adjustment. The dimensions of the EMs and PMs are optimized numerically to achieve a high thrust density that can provide an acceleration of 100G or greater to the mover, which comprises PMs, spacers, and a frame. The prototype MPM LSM has a working range of 1.5 m. The mover, including the guide parts, has a length of 444 mm and a mass of 4.79 kg. The measured peak thrust was greater than $5 times 10^3$ N, and the measured average thrust was $4.03 times 10^3$ N. The prototype driven by a rectangular current command produced a maximum acceleration of greater than 100G and a velocity higher than 12 m/s for a moving distance of 0.6 m.

Description: The world production of crude oil is about 3 billion tons per year. The overall objective of the model in present study is supporting the decision makers in planning and conducting preventive and emergency interventions. The conservative equation for the slick dynamics was derived from layer-averaged Navier-Stokes (LNS) equations, averaged over the slick thickness. Eulerian approach is applied across the model, based on nonlinear shallow water Reynolds-averaged Navier-Stokes (RANS) equations. Depth-integrated standard k-ε turbulence schemes have been included in the model. Wetting and drying fronts of intertidal zone and moving boundary are treated within the numerical model. A highly accurate algorithm based on a fourth-degree accurate shape function has been used through an alternating-direction implicit (ADI) scheme which separates the operators into locally one-dimensional (LOD) components. The solution has been achieved by the application of KPENTA algorithm for the set of the flow equations which constitutes a pentadiagonal matrix. Hydrodynamic model was validated for a channel with a sudden expansion in width. For validation of oil spill model, predicted results are compared with experimental data from a physical modeling of oil spill in a laboratory wave basin under controlled conditions.

Description: Based on the DC motor speed response measurement under a step voltage input, important motor parameters such as the electrical time constant, the mechanical time constant, and the friction can be estimated. A power series expansion of the motor speed response is presented, whose coefficients are related to the motor parameters. These coefficients can be easily computed using existing curve fitting methods. Experimental results are presented to demonstrate the application of this approach. In these experiments, the approach was readily implemented and gave more accurate estimates than conventional methods.

Description: This paper presents a comparative analysis between the practical results of pig iron die-type part casting and the results reached by simulation. The insert was made of polystyrene, and the casting was downward vertical. As after the part casting and heat treatment cracks were observed in the part, it became necessary to locate and identify these fissures and to establish some measures for eliminating the casting defects and for locating them. The research method was the comparisons of defects identified through verifications, measurements, and metallographic analyses applied to the cast part with the results of some criteria specific to simulation after simulating the casting process. In order to verify the compatibility between reality and simulation, we then simulated the part casting respecting the real conditions in which it was cast. By visualising certain sections of the cast part during solidification, relevant details occur about the possible evolution of defects. The simulation software was AnyCasting, the measurements were done through nondestructive methods.

Description: The projective integration method based on the Galerkin-free framework with the assistance of proper orthogonal decomposition (POD) is presented in this paper. The present method is applied to simulate two-dimensional incompressible fluid flows past the NACA0012 airfoil problem. The approach consists of using high-accuracy direct numerical simulations over short time intervals, from which POD modes are extracted for approximating the dynamics of the primary variables. The solution is then projected with larger time steps using any standard time integrator, without the need to recompute it from the governing equations. This is called the online projective integration method. The results by the projective integration method are in good agreement with the full scale simulation with less computational needs. We also study the individual function of each POD mode used in the projective integration method. It is found that the first POD mode can capture basic flow behaviors but the overall dynamic is rather inaccurate. The second and the third POD modes assist the first mode by correcting magnitudes and phases of vorticity fields. However, adding the fifth POD mode in the model leads to some incorrect results in phase-shift forms for both drag and lift coefficients. This suggests the optimal number of POD modes to use in the projective integration method.

Description: A glazing façade subjected to blast loads has a structural behaviour that strongly differs from the typical response of a glazing system subjected to ordinary loads. Consequently, sophisticated modelling techniques are required to identify correctly its criticalities. The paper investigates the behaviour of a cable-supported façade subjected to high-level blast loading. Nonlinear dynamic analyses are performed in ABAQUS/Explicit using a sophisticated FE-model (M01), calibrated to dynamic experimental and numerical results. The structural effects of the total design blast impulse, as well as only its positive phase, are analyzed. At the same time, the possible cracking of glass panels is taken into account, since this phenomenon could modify the response of the entire façade. Finally, deep investigations are dedicated to the bearing cables, since subjecting them to elevated axial forces and their collapse could compromise the integrity of the cladding wall. Based on results of previous studies, frictional devices differently applied at their ends are presented to improve the response of the façade under the impact of a high-level explosion. Structural effects of various solutions are highlighted through dynamic simulations. Single vertical devices, if appropriately calibrated, allow reducing significantly the axial forces in cables, and lightly the tensile stresses in glass panes.

Description: This paper presents a three-fingered, eight-DOF hand, 100 N Hand II, which can exert a grasping force of 100 N. A force-magnification drive, which can maintain a large grasping force without energy consumption, allows the hand to exert such large grasping force, and a high-speed driving mechanism enables all joints to perform high-speed motions of over 400°/s. In our previous prototype (100 N Hand I), a screw and nut mechanism was used to implement force magnification. The linear motion of this mechanism was translated to rotational joint motion via a linkage mechanism, producing a relatively small motion range for each joint and with large palm dimensions. 100 N Hand II employs a worm gear instead of a screw and nut mechanism, so it can magnify the torque at an arbitrary joint angle. This improved force-magnification drive increases the motion range of each joint and reduces the palm size. The force and speed are confirmed experimentally.

Description: Training simulators that provide realistic visual and haptic feedback during cell indentation tasks are currently investigated. Complex cell geometry inherent to biological cells and intricate mechanical properties drive the need for precise mechanical and numerical modeling to assure accurate cell deformation and force calculations. Advances in alternative finite-element formulation, such as the mass-tensor approach, have reached a state, where they are applicable to model soft-cell deformation in real time. The geometrical characteristics and the mechanical properties of different cells are determined with atomic force microscopy (AFM) indentation. A real-time, haptics-enabled simulator for cell centered indentation has been developed, which utilizes the AFM data (mechanical and geometrical properties of embryonic stem cells) to accurately replicate the indentation task and predict the cell deformation during indentation in real time. This tool can be used as a mechanical marker to characterize the biological state of the cell. The operator is able to feel the change in the stiffness during cell deformation between fixed and live cells in real time. A comparative study with finite-element simulations using a commercial software and the experimental data demonstrate the effectiveness of the proposed physically based model.

Description: This paper considers the analysis and application of magnetic gearbox and magnetic coupling technologies and issues surrounding their use in high performance servo control systems. An analysis of a prototype magnetic coupling is used as a basis for demonstrating the underlying nonlinear torque transfer characteristics, nonlinear damping, and “pole-slipping” features when subjected to overtorque (overload) conditions. It is also shown how pole-slipping results in a consequential loss of control. A theoretical investigation into the suppression of mechanical torsional resonances in transmission systems encompassing these highly compliant magnetically coupled components is included along with experimental results from a demonstrator drive train. Automatic detection of pole slipping and a reconfigurable controller are also investigated. By addressing these issues, the proposed techniques extend the application scope of magnetic gear/coupling technologies to more demanding applications than those hitherto considered possible-specifically, for use in servo control systems and high-bandwidth mechanical drive trains.

Description: In this paper, a sliding-mode control for an offshore container crane is discussed. The offshore container crane is used to load/unload containers between a huge container ship (called the “mother ship”) and a smaller ship (called the “mobile harbor”), on which the crane is installed. The purpose of the mobile harbor is to load/unload containers in the open sea and transport them to shallower water where they can be offloaded at existing conventional ports, thereby obviating the need for expansive and expensive new facilities. The load/unload control objective is to suppress the pendulum motion (i.e., “sway”) of the load in the presence of the wave- and wind-induced movements (heave, roll, and pitch) of the mobile harbor. A new mechanism for lateral sway control, therefore, is proposed as well. A sliding surface is designed in such a way that the longitudinal sway of the load is incorporated with the trolley dynamics. The asymptotic stability of the closed-loop system is guaranteed by a control law derived for the purpose. The proposed new mechanism can suppress lateral sway, which functionality is not possible with conventional cranes. Simulation results are provided.

Description: The helical configuration represents one of the few currently available to implement contractile Dielectric Elastomer (DE) actuators. While experimental investigations have previously been reported, no model is currently available to assist design. This paper describes a simple analytical electromechanical model of helical DE actuators, applicable for relatively small strains (〈;10%), consistently with the following assumptions: the effective electrostatic pressure exerted by the compliant electrodes was considered to be constant during actuation; the elastomer was assumed to behave like a linearly elastic body. According to these assumptions, the electromechanical model was derived by means of independent electrical and mechanical analyses, the latter being based on linear elasticity. To validate the model, theoretical predictions were compared with experimental data measured from a silicone-made prototype actuator. Pros and cons of the modeling approach in the small-strain range are discussed.

Description: Numerical studies have been performed to visualize vortical flow structures emerged from jet cross-flow interactions. A single square jet issuing perpendicularly into a cross-flow was simulated first, followed by two additional scenarios, that is, inclined square jet at angles of 30° and 60° and round and elliptic jets at an angle of 90°, respectively. The simulation considers a jet to cross-flow velocity ratio of 2.5 and a Reynolds number of 225, based on the free-stream flow quantities and the jet exit width in case of square jet or minor axis length in case of elliptic jet. For the single square jet, the vortical flow structures simulated are in good qualitative agreement with the findings by other researchers. Further analysis reveals that the jet penetrates deeper into the cross-flow field for the normal jet, and the decrease of the jet inclination angle weakens the cross-flow entrainment in the near-wake region. For both noncircular and circular jet hole shapes, the flow field in the vicinity of the jet exit has been dominated by large-scale dynamic flow structures and it was found that the elliptic jet hole geometry has maximum “lifted-off” effect among three hole configurations studied. This finding is also in good qualitative agreement with existing experimental observations.

Description: This paper presents the design and development of robotic tweezers with a force- and displacement-sensing capability driven by piezoelectric stack actuators. In order to satisfy sufficient stroke and tip force for future medical operations, a rhombus strain amplification mechanism is adopted. One of the serially connected piezoelectric stack actuators nested in the end effector is used as a force sensor. The force–displacement characteristics at the outermost layer with respect to the forces of the innermost PZT actuators (i.e., forward model) is obtained from a lumped parameter model of the rhombus strain amplification mechanism and a Bernoulli–Euler beam model of the tweezer-style end effector. The end-effector tip force and displacement are measured using an inverse model of the nested multilayer structure relating these quantities to an induced voltage across the innermost PZT actuator. The prototype end effector has the size of 69 mm (length)  $times$ 14 mm (height) $times$ 13 mm (width). The performance test shows that the prototype has 1.0-N force and 8.8-mm displacement at the tip. The sensing accuracy was also evaluated through experiments. The experimental results show that the prototype has mean error of 0.086 N for force and 0.39 mm for displacement, which are equivalent to 11% of their maximum measurable values.

Description: This paper presents a precise macromodel of a signal-phase meter, which allows continuous phase measurement during simulation. It has been developed as a support tool during the design process of a signal-conditioning circuit for incremental position encoders. The development of a signal conditioning circuit requires precise measurements of small signal phases, amplitudes and offsets using the analog/digital circuit simulator. The phase measurement cannot be performed directly with a simulator, therefore an appropriate macro-model is needed for a circuit simulator. The structure of the signal-phase meter is based on the conventional signal-phase measuring method and is intended for the measuring of a cosine-signal phase with a known frequency. It recommends that the time variations of an input signal’s parameters (amplitude, phase, frequency, and offset voltage) are slow and small as possible. Rapid change of a signal’s parameters decreases the simulation result’s accuracy. A macro-model’s precision mainly depends on the chosen parameters for the macro-model and for the simulation. We show that with the proposed meter’s model, the phase angle can be measured with an accuracy of more than ±0,02%.

Description: This paper presents an optimal regulator for depth control simulation of an autonomous underwater vehicle (AUV) using a new approach of decentralized system environment called open control platform (OCP). Simulation results are presented to demonstrate performance of the proposed method.

Description: A cam-based shear force-actuated electromechanical valve drive system offering variable valve timing in internal combustion engines was previously proposed and demonstrated. To transform this concept into a competitive commercial product, several major challenges need to addressed, including the reduction of power consumption, transition time, and size. As shown in this paper, by using nonlinear system modeling, optimizing cam design, and exploring different control strategies, the power consumption has been reduced from 140 to 49 W (65%), the transition time has been decreased from 3.3 to 2.7 ms (18%), and the actuator torque requirement has been cut from 1.33 to 0.30 N·m (77%).

Description: This paper presents a three-degree-of-freedom permanent magnet (PM) spherical actuator with an iron stator. The major contribution of this paper is to study the effect of iron stator on the magnetic field and torque output of the electromagnetic spherical actuator quantitatively and qualitatively. It could be helpful for actuator design optimization. Based on the poles’ arrangement and the iron boundary, the magnetic field of the PM-pole rotor and the actuator torque are formulated analytically. The effect of iron stator on the magnetic field and torque output is analyzed with respect to structural parameters. The result shows that the iron stator can increase the radial component of the flux density and thus the actuator torque output significantly.

Description: This paper presents mechanism and controller design procedures of a new piezoactuated flexure XY stage for micro-/nanomanipulation applications. The uniqueness of the proposed stage lies in that it possesses an integrated parallel, decoupled, and stacked kinematical structure, which owns such properties as identical dynamic behaviors in X and Y axes, decoupled input and output motion, single-input-single-output (SISO) control, high accuracy, and compact size. Finite element analysis (FEA) was conducted to predict static performance of the stage. An XY stage prototype was fabricated by wire electrical discharge machining (EDM) process from the alloy material Al7075. Based on the identified plant transfer function of the micropositioning system, an $H_infty$ robust control combined with a repetitive control (RC) was adopted to compensate for the unmodeled piezoelectric nonlinearity. The necessity of using such a combined control is also investigated. Experimental results demonstrate that the $H_infty$ plus RC scheme improves the tracking response by 67% and 28% compared to the stand-alone $H_infty$ for 1-D and 2-D periodic positioning tasks, respectively. Thus, the results illustrate the effectiveness of the proposed mechanism design and control approach.

Description: It is well recognized in the automotive research community that knowledge of the real-time tire-road friction coefficient can be extremely valuable for active safety applications, including traction control, yaw stability control and rollover prevention. Previous research results in literature have focused on the estimation of average tire-road friction coefficient for the entire vehicle. This paper explores the development of algorithms for reliable estimation of independent friction coefficients at each individual wheel of the vehicle. Three different observers are developed for the estimation of slip ratios and longitudinal tire forces, based on the types of sensors available. After estimation of slip ratio and tire force, the friction coefficient is identified using a recursive least-squares parameter identification formulation. The observers include one that utilizes engine torque, brake torque, and GPS measurements, one that utilizes torque measurements and an accelerometer and one that utilizes GPS measurements and an accelerometer. The developed algorithms are first evaluated in simulation and then evaluated experimentally on a Volvo XC90 sport utility vehicle. Experimental results demonstrate the feasibility of estimating friction coefficients at the individual wheels reliably and quickly. The sensitivities of the observers to changes in vehicle parameters are evaluated and comparisons of robustness of the observers are provided.