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  • 1
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    Adaptive control: Stability, convergence, and robustness (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The deterministic theory of adaptive control (AC) is presented in an introduction for graduate students and practicing engineers. Chapters are devoted to basic AC approaches, notation and fundamental theorems, the identification problem, model-reference AC, parameter convergence using averaging techniques, and AC robustness. Consideration is given to the use of prior information, the global stability of indirect AC schemes, multivariable AC, linearizing AC for a class of nonlinear systems, AC of linearizable minimum-phase systems, and MIMO systems decouplable by static state feedback.
    Keywords: CYBERNETICS
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  • 2
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    A Framework for Optimal Control Allocation with Structural Load Constraints (2010)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Conventional aircraft generally employ mixing algorithms or lookup tables to determine control surface deflections needed to achieve moments commanded by the flight control system. Control allocation is the problem of converting desired moments into control effector commands. Next generation aircraft may have many multipurpose, redundant control surfaces, adding considerable complexity to the control allocation problem. These issues can be addressed with optimal control allocation. Most optimal control allocation algorithms have control surface position and rate constraints. However, these constraints are insufficient to ensure that the aircraft's structural load limits will not be exceeded by commanded surface deflections. In this paper, a framework is proposed to enable a flight control system with optimal control allocation to incorporate real-time structural load feedback and structural load constraints. A proof of concept simulation that demonstrates the framework in a simulation of a generic transport aircraft is presented.
    Keywords: Aircraft Stability and Control
    Type: ARC-E-DAA-TN1503 , AIAA Atmospheric Flight Mechanics Conference; Aug 02, 2010 - Aug 05, 2010; Toronto, Ontario; Canada
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  • 3
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    Sensitivity Analysis of Linear Programming and Quadratic Programming Algorithms for Control Allocation (2009)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The Next Generation (NextGen) transport aircraft configurations being investigated as part of the NASA Aeronautics Subsonic Fixed Wing Project have more control surfaces, or control effectors, than existing transport aircraft configurations. Conventional flight control is achieved through two symmetric elevators, two antisymmetric ailerons, and a rudder. The five effectors, reduced to three command variables, produce moments along the three main axes of the aircraft and enable the pilot to control the attitude and flight path of the aircraft. The NextGen aircraft will have additional redundant control effectors to control the three moments, creating a situation where the aircraft is over-actuated and where a simple relationship does not exist anymore between the required effector deflections and the desired moments. NextGen flight controllers will incorporate control allocation algorithms to determine the optimal effector commands and attain the desired moments, taking into account the effector limits. Approaches to solving the problem using linear programming and quadratic programming algorithms have been proposed and tested. It is of great interest to understand their relative advantages and disadvantages and how design parameters may affect their properties. In this paper, we investigate the sensitivity of the effector commands with respect to the desired moments and show on some examples that the solutions provided using the l2 norm of quadratic programming are less sensitive than those using the l1 norm of linear programming.
    Keywords: Aircraft Stability and Control
    Type: ARC-E-DAA-TN-369 , AIAA Infotech@Aerospace Conference and Exhibit; Apr 06, 2009 - Apr 09, 2009; Seattle, WA; United States
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  • 4
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    Investigation of Optimal Control Allocation for Gust Load Alleviation in Flight Control (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Advances in sensors and avionics computation power suggest real-time structural load measurements could be used in flight control systems for improved safety and performance. A conventional transport flight control system determines the moments necessary to meet the pilot's command, while rejecting disturbances and maintaining stability of the aircraft. Control allocation is the problem of converting these desired moments into control effector commands. In this paper, a framework is proposed to incorporate real-time structural load feedback and structural load constraints in the control allocator. Constrained optimal control allocation can be used to achieve desired moments without exceeding specified limits on monitored load points. Minimization of structural loads by the control allocator is used to alleviate gust loads. The framework to incorporate structural loads in the flight control system and an optimal control allocation algorithm will be described and then demonstrated on a nonlinear simulation of a generic transport aircraft with flight dynamics and static structural loads.
    Keywords: Aircraft Stability and Control
    Type: ARC-E-DAA-TN5507 , AIAA Modeling and Simulation Technologies Conference; Aug 13, 2012 - Aug 16, 2012; Minneapolis, MN; United States
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  • 5
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    Resource Balancing Control Allocation (2010)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Next generation aircraft with a large number of actuators will require advanced control allocation methods to compute the actuator commands needed to follow desired trajectories while respecting system constraints. Previously, algorithms were proposed to minimize the l1 or l2 norms of the tracking error and of the control effort. The paper discusses the alternative choice of using the l1 norm for minimization of the tracking error and a normalized l(infinity) norm, or sup norm, for minimization of the control effort. The algorithm computes the norm of the actuator deflections scaled by the actuator limits. Minimization of the control effort then translates into the minimization of the maximum actuator deflection as a percentage of its range of motion. The paper shows how the problem can be solved effectively by converting it into a linear program and solving it using a simplex algorithm. Properties of the algorithm are investigated through examples. In particular, the min-max criterion results in a type of resource balancing, where the resources are the control surfaces and the algorithm balances these resources to achieve the desired command. A study of the sensitivity of the algorithms to the data is presented, which shows that the normalized l(infinity) algorithm has the lowest sensitivity, although high sensitivities are observed whenever the limits of performance are reached.
    Keywords: Aircraft Design, Testing and Performance
    Type: ARC-E-DAA-TN1504 , American Control Conference; Jun 30, 2010 - Jul 02, 2010; Baltimore, MD; United States
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  • 6
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    Input error versus output error model reference adaptive control (1987)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Algorithms for model reference adaptive control were developed in recent years, and their stability and convergence properties have been investigated. Typical algorithms in continuous time involve strictly positive real conditions on the reference model, while similar discrete time algorithms do not require such conditions. It is shown how algorithms differ by the use of an input error versus an output error, and present a continuous time input error adaptive control algorithm which does not involve SPR conditions. The connections with other schemes are discussed. The input error scheme has general stability and ocnvergence properties that are similar to the output error scheme. However, analysis using averaging methods reveals some preferable convergence properties of the input error scheme. Several other advantages are also discussed.
    Keywords: CYBERNETICS
    Type: 1987 American Control Conference; Jun 10, 1987 - Jun 12, 1987; Minneapolis, MN; United States
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  • 7
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    Adaptive identification and control for manipulators without using joint accelerations (1987)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The authors present a new scheme for the adaptive control of mechanical manipulators along with proof of convergence. Difficulties encountered in the input-error type adaptive controller are remedied by combining an explicit identifier with discrete time updates of the parameter values along with a computed torque type control law. The new scheme requires no matrix inversion with its consequent drain on the computational power of the controller. A discussion is presented of the dynamic model of a manipulator, a computed torque adaptive scheme, an input error identifier, and a hybrid identifier.
    Keywords: CYBERNETICS
    Type: 1987 IEEE International Conference on Robotics and Automation; Mar 31, 1987 - Apr 03, 1987; Raleigh, NC; United States
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  • 8
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    Control Demonstration of Multiple Doubly-Fed Induction Motors for Hybrid Electric Propulsion (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The Convergent Aeronautics Solutions (CAS) High Voltage-Hybrid Electric Propulsion (HVHEP) task was formulated to support the move into future hybrid-electric aircraft. The goal of this project is to develop a new AC power architecture to support the needs of higher efficiency and lower emissions. This proposed architecture will adopt the use of the doubly-fed induction machine (DFIM) for propulsor drive motor application.The Convergent Aeronautics Solutions (CAS) High Voltage-Hybrid Electric Propulsion (HVHEP) task was formulated to support the move into future hybrid-electric aircraft. The goal of this project is to develop a new AC power architecture to support the needs of higher efficiency and lower emissions. This proposed architecture will adopt the use of the doubly-fed induction machine (DFIM) for propulsor drive motor application. DFIMs are attractive for several reasons, including but not limited to the ability to self-start, ability to operate sub- and super-synchronously, and requiring only fractionally rated power converters on a per-unit basis depending on the required range of operation. The focus of this paper is based specifically on the presentation and analysis of a novel strategy which allows for independent operation of each of the aforementioned doubly-fed induction motors. This strategy includes synchronization, soft-start, and closed loop speed control of each motor as a means of controlling output thrust; be it concurrently or differentially. The demonstration of this strategy has recently been proven out on a low power test bed using fractional horsepower machines. Simulation and hardware test results are presented in the paper.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN43482 , AIAA/SAE/ASEE Joint Propulsion Conference; Jul 10, 2017 - Jul 12, 2017; Atlanta, GA; United States
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  • 9
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    Control Allocation with Load Balancing (2009)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Next generation aircraft with a large number of actuators will require advanced control allocation methods to compute the actuator commands needed to follow desired trajectories while respecting system constraints. Previously, algorithms were proposed to minimize the l1 or l2 norms of the tracking error and of the actuator deflections. The paper discusses the alternative choice of the l(infinity) norm, or sup norm. Minimization of the control effort translates into the minimization of the maximum actuator deflection (min-max optimization). The paper shows how the problem can be solved effectively by converting it into a linear program and solving it using a simplex algorithm. Properties of the algorithm are also investigated through examples. In particular, the min-max criterion results in a type of load balancing, where the load is th desired command and the algorithm balances this load among various actuators. The solution using the l(infinity) norm also results in better robustness to failures and to lower sensitivity to nonlinearities in illustrative examples.
    Keywords: Aircraft Stability and Control
    Type: ARC-E-DAA-TN656 , AIAA Guidance, Navigation, and Control Conference; Aug 10, 2009 - Aug 13, 2009; Chicago, IL; United States
    Format: application/pdf
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