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  • 1
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    Attitude control with realization of linear error dynamics (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: An attitude control law is derived to realize linear unforced error dynamics with the attitude error defined in terms of rotation group algebra (rather than vector algebra). Euler parameters are used in the rotational dynamics model because they are globally nonsingular, but only the minimal three Euler parameters are used in the error dynamics model because they have no nonlinear mathematical constraints to prevent the realization of linear error dynamics. The control law is singular only when the attitude error angle is exactly pi rad about any eigenaxis, and a simple intuitive modification at the singularity allows the control law to be used globally. The forced error dynamics are nonlinear but stable. Numerical simulation tests show that the control law performs robustly for both initial attitude acquisition and attitude control.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Journal of Guidance, Control, and Dynamics (ISSN 0731-5090); 16; 1; p. 182-189.
    Format: text
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  • 2
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    Global transformation of rotation matrices to Euler parameters (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A global algorithm for transforming rotation matrices to Euler parameters is presented. Although it has no apparent computational or numerical advantage over the known algorithms, it elucidates the relationship between the rotation matrix form and the Euler parameter form. It employs the singular-value decomposition, a numerically ideal algorithm involving orthogonal transformations. Attitude parameterization is reviewed and an analytical framework is provided.
    Keywords: NUMERICAL ANALYSIS
    Type: Journal of Guidance, Control, and Dynamics (ISSN 0731-5090); 15; 5, Se
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  • 3
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    Direct inversion of rigid-body rotational dynamics (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The global linearization (inversion) of rigid-body rotational dynamics is reviewed, and representations in terms of quaternions and direction cosines are compared. Certain properties common to quaternions and direction cosines that make their use preferable to Euler angles and that simplify the inversion procedure are described. Applications of the inversion procedure for state estimation and attitude control are discussed. To avoid complexities caused by aerodynamics, an example of direct inversion for linear feedback control of spacecraft attitude is given.
    Keywords: CYBERNETICS
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  • 4
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    Flight evaluation of differential GPS aided inertial navigation systems (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: Algorithms are described for integration of Differential Global Positioning System (DGPS) data with Inertial Navigation System (INS) data to provide an integrated DGPS/INS navigation system. The objective is to establish the benefits that can be achieved through various levels of integration of DGPS with INS for precision navigation. An eight state Kalman filter integration was implemented in real-time on a twin turbo-prop transport aircraft to evaluate system performance during terminal approach and landing operations. A fully integrated DGPS/INS system is also presented which models accelerometer and rate-gyro measurement errors plus position, velocity, and attitude errors. The fully integrated system was implemented off-line using range-domain (seventeen-state) and position domain (fifteen-state) Kalman filters. Both filter integration approaches were evaluated using data collected during the flight test. Flight-test data consisted of measurements from a 5 channel Precision Code GPS receiver, a strap-down Inertial Navigation Unit (INU), and GPS satellite differential range corrections from a ground reference station. The aircraft was laser tracked to determine its true position. Results indicate that there is no significant improvement in positioning accuracy with the higher levels of DGPS/INS integration. All three systems provided high-frequency (e.g., 20 Hz) estimates of position and velocity. The fully integrated system provided estimates of inertial sensor errors which may be used to improve INS navigation accuracy should GPS become unavailable, and improved estimates of acceleration, attitude, and body rates which can be used for guidance and control. Precision Code DGPS/INS positioning accuracy (root-mean-square) was 1.0 m cross-track and 3.0 m vertical. (This AGARDograph was sponsored by the Guidance and Control Panel.)
    Keywords: AIRCRAFT COMMUNICATIONS AND NAVIGATION
    Type: AGARD, Integrated and Multi-Function Navigation; 17 p
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  • 5
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    Conflict Probability Estimation for Free Flight (1996)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: The safety and efficiency of free flight will benefit from automated conflict prediction and resolution advisories. Conflict prediction is based on trajectory prediction and is less certain the farther in advance the prediction, however. An estimate is therefore needed of the probability that a conflict will occur, given a pair of predicted trajectories and their levels of uncertainty. A method is developed in this paper to estimate that conflict probability. The trajectory prediction errors are modeled as normally distributed, and the two error covariances for an aircraft pair are combined into a single equivalent covariance of the relative position. A coordinate transformation is then used to derive an analytical solution. Numerical examples and Monte Carlo validation are presented.
    Keywords: Air Transportation and Safety
    Type: NASA-TM-110411 , NAS 1.15:110411 , A-962310
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  • 6
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    Algorithms for Control of Arrival and Departure Traffic in Terminal Airspace (2016)
    In:  CASI
    Details
    Publication Date: 2019-06-06
    Description: This paper presents a design approach and basic algorithms for a future system that can perform aircraft conflict resolution, arrival scheduling and convective weather avoidance with a high level of autonomy in terminal area airspace. Such a system, located on the ground, is intended to solve autonomously the major problems currently handled manually by human controllers. It has the potential to accommodate higher traffic levels and a mix of conventional and unmanned aerial vehicles with reduced dependency on controllers. The main objective of this paper is to describe the fundamental trajectory and scheduling algorithms that provide the foundation for an autonomous system of the future. These algorithms generate trajectories that are free of conflicts with other traffic, avoid convective weather if present, and provide scheduled times for landing with specified in-trail spacings. The maneuvers the algorithms generate to resolve separation and spacing conflicts include speed, horizontal path, and altitude changes. Furthermore, a method for reassigning arrival aircraft to alternate runways in order to reduce delays is also included. The algorithms generate conflict free trajectories for terminal area traffic, comprised primarily of arrivals and departures to and from multiple airports. Examples of problems solved and performance statistics from a fast-time simulation using simulated traffic of arrivals and departures at the Dallas/Fort Worth International Airport and Dallas Love Field are described.
    Keywords: Aircraft Communications and Navigation
    Type: ARC-E-DAA-TN22021 , Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering (ISSN 0954-4100) (e-ISSN 2041-3025); 230; 9; 1762-1779
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  • 7
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    Range filtering for sequential GPS receivers with external sensor augmentation (1987)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: The filtering of the satellite range and range-rate measurements from single channel sequential Global Positioning System receivers is usually done with an extended Kalman filter which has state variables defined in terms of an orthogonal navigation reference frame. An attractive suboptimal alternative is range-domain filtering, in which the individual satellite measurements are filtered separately before they are combined for the navigation solution. The main advantages of range-domain filtering are decreased processing and storage requirements and simplified tuning. Several range filter mechanization alternatives are presented, along with an innovative approach for combining the filtered range-domain quantities to determine the navigation state estimate. In addition, a method is outlined for incorporating measurements from auxiliary sensors such as altimeters into the navigation state estimation scheme similarly to the satellite measurements. A method is also described for incorporating inertial measurements into the navigation state estimator as a process driver.
    Keywords: AIRCRAFT COMMUNICATIONS AND NAVIGATION
    Type: NASA-TM-89418 , A-87050 , NAS 1.15:89418
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  • 8
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    Simulation tests of the optimization method of Hopfield and Tank using neural networks (1988)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: The method proposed by Hopfield and Tank for using the Hopfield neural network with continuous valued neurons to solve the traveling salesman problem is tested by simulation. Several researchers have apparently been unable to successfully repeat the numerical simulation documented by Hopfield and Tank. However, as suggested to the author by Adams, it appears that the reason for those difficulties is that a key parameter value is reported erroneously (by four orders of magnitude) in the original paper. When a reasonable value is used for that parameter, the network performs generally as claimed. Additionally, a new method of using feedback to control the input bias currents to the amplifiers is proposed and successfully tested. This eliminates the need to set the input currents by trial and error.
    Keywords: CYBERNETICS
    Type: NASA-TM-101047 , A-88275 , NAS 1.15:101047
    Format: application/pdf
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  • 9
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    Inversion Of Dynamical Equations For Control Of Attitude (1995)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Method of inverting nonlinear equations of rotational dynamics of rigid body used to design feedback control of orientation of body. Applicable to both direction-cosine and quaternion formulations suitable for large-angle maneuvers. Exploiting some apparently little-known properties of direction cosine and quaternion formulations, method leads to equations for model-follower control system that exhibits exactly linear attitude-error dynamics. Quarternion system more robust in responding to large roll-angle commands.
    Keywords: MECHANICS
    Type: ARC-12769 , NASA Tech Briefs (ISSN 0145-319X); 19; 10; P. 10b
    Format: text
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  • 10
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    Trajectory Specification for Automation of Terminal Air Traffic Control (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: "Trajectory specification" is the explicit bounding and control of aircraft tra- jectories such that the position at each point in time is constrained to a precisely defined volume of space. The bounding space is defined by cross-track, along-track, and vertical tolerances relative to a reference trajectory that specifies position as a function of time. The tolerances are dynamic and will be based on the aircraft nav- igation capabilities and the current traffic situation. A standard language will be developed to represent these specifications and to communicate them by datalink. Assuming conformance, trajectory specification can guarantee safe separation for an arbitrary period of time even in the event of an air traffic control (ATC) sys- tem or datalink failure, hence it can help to achieve the high level of safety and reliability needed for ATC automation. As a more proactive form of ATC, it can also maximize airspace capacity and reduce the reliance on tactical backup systems during normal operation. It applies to both enroute airspace and the terminal area around airports, but this paper focuses on arrival spacing in the terminal area and presents ATC algorithms and software for achieving a specified delay of runway arrival time.
    Keywords: Air Transportation and Safety
    Type: ARC-E-DAA-TN28584 , AIAA SciTech 2016; Jan 04, 2016 - Jan 08, 2016; San Diego, CA; United States
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