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Enhanced Characteristic Vibration Signal Detection of Generator Based on Time-Wavelet Energy Spectrum and Multipoint Optimal Minimum Entropy Deconvolution Adjusted Method (2020)

He, Yu-Ling ; Wang, Tao ; Sun, Kai ; [et al.]

Hindawi

In: Mathematical Problems in Engineering. 2020; 2020: 1-11. Published 2020 Apr 20. doi: 10.1155/2020/6916289.

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Publication Date: 2020-04-20

Description: To overcome the shortage of low SNR (signal to noise ratio) of the multipole generator vibration signal which brings rigid difficulty to the fault diagnosis, a new method which combines the Time-Wavelet Energy Spectrum (TWES) with the Multipoint Optimal Minimum Entropy Deconvolution Adjusted (MOMEDA) algorithm is proposed. This method uses TWES to extract and enhance the characteristic signal, while employing MOMEDA to optimize the spectrum structure and filter the noise. The application of this method to the simulating signal as well as the test stator vibration signal in a 6-pole generator before and after rotor interturn short circuit fault validates the effectiveness of the method. Moreover, the comparison among the proposed method and some other general methods such as the Empirical Mode Decomposition (EMD) and the maximum correlative kurtosis deconvolution (MCKD) suggests that the proposed method is superior to these methods.

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Restoration Methods Selection for Wood Components of Chinese Ancient Architectures Based on TODIM with Single-Valued Neutrosophic Sets (2020)

Long, Xiaolu. ; Liu, Lizhi. ; Xiao, Can. ; [et al.]

Hindawi

In: Mathematical Problems in Engineering. 2020; 2020: 1-14. Published 2020 May 13. doi: 10.1155/2020/5049360.

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Publication Date: 2020-05-13

Description: The selection of restoration methods for ancient architectures is of great significance for the protection of human cultural heritage. This paper proposes a novel restoration methods selection approach for wood components of Chinese ancient architectures, in which a multicriteria group decision-making (MCGDM) method with decision-making information is in the form of single-valued neutrosophic sets (SNNSs). Firstly, it establishes an index system by comprehensively considering subjective and objective criteria. In addition, the best-worst method (BWM) and the entropy weight method are combined to produce index weights. Furthermore, the TODIM method is utilized by the single-valued neutrosophic sets to prioritize restoration methods. Finally, a specific case of wood component restoration is conducted to demonstrate the practicability of the proposed model. The robustness and effectiveness of the proposed method is verified by sensitivity analysis and comparison analysis.

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Robust Adaptive Output Feedback Control for a Class of Underactuated Aerial Vehicles with Input and Output Constraints (2020)

Tran, Trong-Toan ; Nguyen, Tan-No ; Nguyen, Duc-Duy ; [et al.]

Hindawi

In: Mathematical Problems in Engineering. 2020; 2020: 1-18. Published 2020 May 16. doi: 10.1155/2020/7193136.

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Publication Date: 2020-05-16

Description: This paper addresses the problem of nonlinear robust adaptive output feedback controller for a class of underactuated aerial vehicles with input and output constraints. To solve the problem, the modular design strategy is proposed for the control design. By using the neural networks (NNs) to approximate system uncertainties and observers to reconstruct system states, robust adaptive output feedback controllers are developed. By using a combination of saturation functions and barrier functions, input and output constraints are simultaneously dealt with. The design methodology shows that a cascaded system of an input-to-state stable (ISS) subsystem driven by an ultimate bounded (UB) subsystem enjoys ultimate boundedness property. In addition, the tracking error converges to adjustable neighbourhoods of the origin.

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A Discrete-Space Train Movement Model for a High-Speed Train under Temporary Speed Restriction (2020)

Long, Sihui ; Meng, Lingyun ; Wang, Yihui ; [et al.]

Hindawi

In: Mathematical Problems in Engineering. 2020; 2020: 1-11. Published 2020 May 19. doi: 10.1155/2020/5386406.

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Publication Date: 2020-05-19

Description: This paper constructs a discrete-space train movement model to evaluate the impact of a temporary speed restriction (TSR) for a high-speed railway train. The established model can demonstrate train movement under different TSR conditions. The proposed model can reveal whether a train is affected by the block section influenced by the TSR within a time duration. Moreover, the model can output detailed train trajectories and the minimal train running time between two adjacent stations to analyse the impact of the TSR. Based on the experimental results, we carry out a comprehensive analysis of the impact of several factors on the running time and train trajectories, including the length of the affected area (i.e., number of affected block sections), the location of the TSR, the limited speed value, and the stopping patterns of the train at two adjacent stations. The experiments show that the proposed discrete-space train movement model can be used to analyse the impact of the TSR on a high-speed railway train under various considered TSR conditions.

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Research on the Models of Coupling Dynamics and Damage Classification for Vehicle-Engine Vibration (2020)

Lei, Ao ; Song, Chuan-xue ; Lei, Yu-long ; [et al.]

Hindawi

In: Mathematical Problems in Engineering. 2020; 2020: 1-14. Published 2020 Mar 31. doi: 10.1155/2020/5907613.

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Publication Date: 2020-03-31

Description: Many researchers have designed the dynamic models to study the vehicle-engine vibration. However, the existing mechanical models are relatively simple, and the analysis of engine vibration damage is discussed rarely. In this paper, we proposed the models of coupling dynamics and damage classification of vehicle-engine vibration. The key advantages of these proposed models are (1) the finite elements method is adopted for the rotor and casing system, and the complex structure with multirotor and multicasing is modeled by defining support system and linking methods; (2) the hybrid numerical integral method is used to obtain the inherent frequency of the nonlinear dynamic system; and (3) the algorithms based on backpropagation (BP) neural network and radial basis function (RBF) neural network are chosen to construct the damage classification model of rotors. Experimental results based on the engine rotor tester prove that the proposed models are not only more robust than the existing works but also show that the classification algorithms can support engine damage analysis effectively.

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Shear Effects on the Anchorage Interfaces and Seismic Responses of a Rock Slope Containing a Weak Layer under Seismic Action (2020)

Long, Zhe ; Yan, Zhi-xin ; Liu, Chun-bo

Hindawi

In: Mathematical Problems in Engineering. 2020; 2020: 1-11. Published 2020 Apr 30. doi: 10.1155/2020/1424167.

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Publication Date: 2020-04-30

Description: The shear effects on the anchorage interfaces under seismic action is a key problem requiring urgent investigation in the field of rock and soil anchorages. In this paper, the model of rock slope with a weak layer was constructed by pouring, and the large-scale shaking table model test was completed. The shear strain on the anchorage interfaces and the acceleration of the slope were collected using built measurement systems. The shear effects on the two anchorage interfaces (a bolt-grout interface and a grout-rock interface) and seismic responses of the slope under seismic action were investigated. The distribution laws of the shear stress on the two anchorage interfaces along the axial direction of the bolt under seismic action were gained. The variations of the peak acceleration amplification coefficient on the slope surface, the magnitude, and the growth rate of peak shear stress on the anchorage interfaces under seismic action with different excitation directions and intensities were obtained. Furthermore, the positive relationship between the shear effect on the anchorage interfaces and the seismic response of slope was revealed. This study provides support for theoretical research, numerical simulation analysis, and aseismic design of rock and soil anchorages under dynamic conditions.

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State Synchronization for a Class of n-Dimensional Nonlinear Systems with Sector Input Nonlinearity via Adaptive Two-Stage Sliding Mode Control (2020)

Yang, Chi-Hsin ; Wang, Kun-Chieh ; Wu, Long ; [et al.]

Hindawi

In: Mathematical Problems in Engineering. 2020; 2020: 1-11. Published 2020 Jul 04. doi: 10.1155/2020/5391984.

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Publication Date: 2020-07-04

Description: This study addresses an adaptive two-stage sliding mode control (SMC) scheme for the state synchronization between two identical systems, which belong to a kind of n-dimensional chaotic system, by considering the appearance of lumped system uncertainties and external disturbances. The controlled system is assumed to be attached to sector nonlinearity for the control input. The proposed adaptive control scheme involves time-variable state-feedback gains, which are updated in accordance with the appropriate adapted rules without foreknown the certain information of nonlinear system dynamics, bounds of lumped system uncertainties and external disturbances, and sector input nonlinearity. The derivation of the control scheme is found based on the introduced sequence of two sliding functions. The stage 1 sliding function is defined by the states of the error dynamical system, where the asymptotical stability is inherent. Then, the stage 2 sliding function is formed by the stage 1 function, where the finite-time stabilization is guaranteed. The proposed adaptive control scheme can cope with the effect of sector nonlinearity for the control to meet the control goal. The sufficient conditions of the stability of the error dynamical system are proven mathematically by means of the Lyapunov theorem. Besides, the capacity of the present scheme is carried out by the numerical studies.

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A Parameter Estimation Method of Shock Model Constructed with Phase-Type Distribution on the Condition of Interval Data (2020)

Wang, Long ; Li, Yue ; Qian, Yanling ; [et al.]

Hindawi

In: Mathematical Problems in Engineering. 2020; 2020: 1-14. Published 2020 Jun 30. doi: 10.1155/2020/1424105.

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Publication Date: 2020-06-30

Description: The phase-type distribution (also known as PH distribution) has mathematical properties of denseness and closure in calculation and is, therefore, widely used in shock model constructions describing occurrence time of a shock or its damage. However, in the case of samples with only interval data, modeling with PH distribution will cause decoupling issues in parameter estimation. Aiming at this problem, an approximate parameter estimation method based on building PH distribution with dynamic order is proposed. Firstly, the shock model established by PH distribution and the likelihood function under samples with only interval data are briefly introduced. Then, the principle and steps of the method are introduced in detail, and the derivation processes of some related formulas are also given. Finally, the performance of the algorithm is illustrated by a case with three different types of distributions.

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A Discrete Nonlinear Tracking-Differentiator and Its Application in Vibration Suppression of Maglev System (2020)

Wang, Zhiqiang ; Long, Zhiqiang ; Xie, Yunde ; [et al.]

Hindawi

In: Mathematical Problems in Engineering. 2020; 2020: 1-9. Published 2020 Jun 19. doi: 10.1155/2020/1849816.

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Publication Date: 2020-06-19

Description: Vibration of the maglev train levitation system is harmful to riding comfort and safety. The signal processing method is effective in vibration control. In this paper, a novel kind of second-order nonlinear tracking differentiator is proposed and applied to suppress the vibration phenomenon. The switching curves of the second-order discrete time optimal control system are presented by the isochronous region method. A synthetic function is acquired depending on the cases whether a point in the phase plane can reach the switching curves within one sample step. The discrete form of tracking differentiator is constructed based on the position relationship between the state point and the characteristic curves. Numerical simulation shows that this discrete tracking differentiator can quickly track an input signal without overshoot and chattering and can produce a good differential signal. A test in a maglev test bench also demonstrates the effectiveness of the tracking differentiator in the suppression of the track-train vibration.

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New Tseng-Degree Gradient Method in Variational Inequality Problem (2020)

Shan, Zhuang ; Zhu, Lijun ; He, Long ; [et al.]

Hindawi

In: Mathematical Problems in Engineering. 2020; 2020: 1-7. Published 2020 Aug 05. doi: 10.1155/2020/9832579.

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Publication Date: 2020-08-05

Description: This paper focuses on the problem of variational inequalities with monotone operators in real Hilbert space. The Tseng algorithm constructed by Thong replaced a high-precision step. Thus, a new Tseng-like gradient method is constructed, and the convergence of the algorithm is proved, and the convergence performance is higher.

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