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ABSTRACT: This paper studies the discrete-time multivariable model reference adaptive control (MRAC) design for discrete time linearized aircraft systems under damage conditions. A discrete-time sequential linear system with uncertain parameters and an unknown dynamics offset is used to model the large uncertain system parametric and structural changes caused by damage. The invariance properties of the two important design conditions, the interactor matrix and the signs of the high frequency gain matrix, of the discrete-time systems are studied. A discrete-time state feedback MRAC scheme is developed to ensure closed-loop signal boundedness and asymptotic output tracking in the presence of damage. Simulation study of the linearized NASA Generic Transport Model (GTM) shows the desired system performance under uncertain damage.
American Control Conference (ACC), 2011; 08/2011
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ABSTRACT: This paper studies the multivariable model reference adaptive control (MRAC) design for aircraft systems under simultaneous actuator failures and airframe damage. A modeling study of the aircraft under failure and damage conditions is conducted, which captures the key characteristics of the aircraft dynamics under such hazardous conditions. The key design conditions for the multivariable MRAC design are studied for nominal and post-hazard aircraft systems, and the invariance of these essential conditions is concluded under realistic failure and damage conditions. A multivariable MRAC scheme is developed to ensure stability and asymptotic output tracking for the aircraft in the presence of uncertain actuator failures and airframe damage. Simulation results are presented to demonstrate the application of the proposed adaptive control scheme to the NASA Generic Transport Model (GTM).
American Control Conference (ACC), 2011; 08/2011
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Automatica. 01/2011; 47:804-812.
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ABSTRACT: Direct model reference adaptive control is considered when the plant-model matching conditions are violated due to large changes in the plant or incorrect knowledge of the plant's mathematical structure. Because of the mismatch, the plant can no longer track the original reference model, but may be able to track a modified reference model that still provides satisfactory performance. The proposed approach uses a time-varying ‘adaptive’ reference model that reflects the achievable performance of the changed plant. The approach consists of direct adaptation of state feedback gains for state tracking and simultaneous estimation of the plant-model mismatch. The reference model adapts to the changed plant, and is redesigned if the estimated plant-model mismatch exceeds a bound determined via robust stability and/or performance criteria. The resulting controller offers asymptotic state tracking in the presence of plant-model mismatch as well as matched parameter deviations.
International Journal of Control 01/2011; 84(1):180-196. · 0.98 Impact Factor
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ABSTRACT: Aircraft damage causes large uncertain system parametric and structural changes which lead to unknown deviations of the aircraft equilibrium points and unknown coupling of the aircraft dynamics. To deal with such unknown changes, we use a sequential linear model with a dynamics offset to represent a linearized aircraft system before and after damage. A state feedback multivariable model reference adaptive control (MRAC) scheme is developed for such a linear model, with adaptive compensation of the uncertain dynamics offset as well as system parametric uncertainties. Desired closed-loop signal boundedness and asymptotic output tracking are established. Numerical values of linearized models from the NASA GTM were used in the simulation study and its results verified the desired system performance despite uncertain damage.
American Control Conference (ACC), 2010; 08/2010
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ABSTRACT: This paper revisits the multivariable MRAC problem, by studying adaptive state feedback control for output tracking of multi-input and multi-output (MIMO) systems. With such a control scheme, the plant-model matching condition is much less restrictive than those for state tracking, while the controller enjoys a simpler structure than that of an output feedback design with the guarantee of the asymptotic tracking of multiple outputs. Such a control scheme is useful for applications when the plant-model matching condition for state tracking cannot be satisfied. A stable adaptive control scheme is developed based on LDS decomposition of high frequency gain matrix, which ensures closed-loop stability and asymptotic output tracking. A simulation study is conducted for an aircraft model, with desired simulation results presented.
American Control Conference, 2009. ACC '09.; 07/2009
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ABSTRACT: This paper derives a stable multivariable model reference adaptive control (MRAC) scheme for systems with abrupt parameter variations (which may cause uncertain sign changes in the system¿s high frequency gain matrix), motivated by the application to in-flight aircraft systems with damages. Such sign changes are illustrated by an aircraft model with asymmetric abrupt damages, and their uncertainty is handled by a Nussbaum gain based adaptive control design to control the aircraft for both healthy and post-damage situations, by adapting controller parameters autonomously after the damages occur, for which the knowledge of time instants, structures and values of the damages is not required. A piecewise continuous Lyapunov function is utilized to prove the desired system stability and tracking properties in the presence of damages.
Decision and Control, 2008. CDC 2008. 47th IEEE Conference on; 01/2009
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Proceedings of the 48th IEEE Conference on Decision and Control, CDC 2009, combined withe the 28th Chinese Control Conference, December 16-18, 2009, Shanghai, China; 01/2009
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Robotica. 01/2009; 27:19-28.
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ABSTRACT: This paper investigates actuator failure compensation for aircraft flight control in a novel framework. A general failure compensation scheme for asymptotic tracking is developed based on a direct adaptive control approach. This control scheme is capable of utilizing the remaining control authority to achieve the desired performance in the presence of unknown and uncertain constant actuator failures occurring at unknown time instants. A nonlinear aircraft model that incorporates independently adjustable engine throttles and ailerons is employed and linearized to describe the aircraft's longitudinal and lateral motion. This model captures the key features of aircraft flight dynamics when in the engine differential mode. The proposed control scheme is applied to a transport aircraft model in the presence of three types of failures during operation: rudder failure, aileron failure, and engine malfunction. Simulation results are presented to assess the effectiveness of this adaptive failure compensation design.
IEEE Transactions on Control Systems Technology 10/2008; · 1.77 Impact Factor
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Gang Tao
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ABSTRACT: In this talk, we present some results on using adaptive control techniques to compensate unknown actuator failures in dynamic control systems.
Control and Decision Conference, 2008. CCDC 2008. Chinese; 08/2008
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ABSTRACT: In this paper, an adaptive control method is developed for the design of an artificial pancreas in the presence of patient insulin-glucose characteristic, actuation disturbance and feedback sensor uncertainties. A feedback control law is used to regulate the patientpsilas blood glucose level, and an adaptive law is derived to update the controller parameters to accommodate the system uncertainties. An adaptive estimate of the system output is employed for feedback control. Adaptive control schemes are developed and analyzed for both known and unknown insulin-glucose dynamics. A simulation study is presented to demonstrate the system performance.
Intelligent Control and Automation, 2008. WCICA 2008. 7th World Congress on; 07/2008
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ABSTRACT: In this paper, modeling and adaptive control of aircraft with synthetic jet actuators are studied. Linearized models of aircraft with synthetic jet actuators are first studied for healthy and ineffective actuators. It is shown that with loss of actuator effectiveness, independently adjustable control effectors have to be involved, and dynamic coupling is inevitable. With a specified equilibrium trajectory, parameters of aircraft models, including the dynamic coupling terms, vary continuously with time. As a demonstration of possible control techniques for such control problems, a multivariable direct adaptive control scheme is developed for such aircraft systems with some chosen operation conditions. For each operation condition, a reference system is constructed and will be switched to when under the corresponding operation condition. Such a control scheme ensures closed-loop stability and asymptotic tracking for the considered system. The robustness of such an adaptive control scheme against continuous parameter variations is also analyzed, and closed-loop stability can be guaranteed with robust adaptation.
Intelligent Control and Automation, 2008. WCICA 2008. 7th World Congress on; 07/2008
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ABSTRACT: An adaptive output feedback control scheme is developed for a class of nonlinear systems with uncertain nonlinearities, which are bounded by both static and dynamic functions of the system output, and with actuator failures whose failure time instants, patterns and values are unknown, as motivated from an aircraft flight control application. An adaptive backstepping control law using dynamic bounding is constructed to deal with unknown actuator failures as well as system parameter and dynamics uncertainties to guarantee desired system performance. Complete stability and performance analysis and illustrative simulation results of an application to aircraft flight control are presented. Copyright © 2008 John Wiley & Sons, Ltd.
International Journal of Adaptive Control and Signal Processing 07/2008; 23(7):609 - 639. · 0.91 Impact Factor
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ABSTRACT: This paper addresses the compensation of aircraft damages using the direct adaptive control approach. The dynamical modeling of aircraft with damages is first introduced, which demonstrates the complex dynamics when asymmetric mass distribution occurs as the result of damages. An approximate model is proposed under certain flight conditions, and its linearization is performed, which captures the key dynamic features of the aircraft under asymmetric damages. Multivariable model reference adaptive control (MRAC) scheme is demonstrated for control of aircraft in both healthy and post-damage situations, by adapting controller parameters autonomously after the damages occur, without the knowledge of the damage time instants, nor the damage structure and values. Relaxation of design conditions is illustrated by expanding the controller structure and re-designing the adaptive law, to further reduce the need of the post-damage system knowledge.
American Control Conference, 2008; 07/2008
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ABSTRACT: In this paper, the problem of adaptively compensating sensor uncertainties is addressed in a feedback based framework. In this study, sensor characteristics are modeled as parametrizable uncertain functions and a compensator is constructed to adaptively cancel the effects of sensor uncertainties, to generate an adaptive estimate of the plant output. Such an estimated output is used for the feedback control law. Adaptive control schemes using a model reference approach with sensor uncertainty compensation are developed for LTI plants with either known or unknown plant dynamics. A new feedback controller structure is developed for the case when the plant dynamics is unknown, to handle the plant and sensor uncertainties. Simulation results are presented to show that the proposed adaptive sensor uncertainty compensation designs significantly improve system tracking performance.
American Control Conference, 2007. ACC '07; 08/2007
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ABSTRACT: In this paper, a state-space model is developed through theoretical analysis and numerical solutions to approximate the response of the human circulatory system. This system model has one critical time-varying parameter: the resistance of peripheral blood vessels. A parameter estimation scheme is derived to estimate this parameter, and the parameter estimate is used to implement an adaptive observer to estimate the aortic pressure for physiological control. An optimal adaptive controller is proposed to control the estimated aortic pressure to track a reference signal updated by a nonlinear function of the pump head to meet the physiological need. A Matlab simulation program and an experimental mock human circulatory loop are employed as test environments for the human circulatory systems with a left ventricular assist device and their physiological controllers. Different physiological conditions, such as the variation of left ventricular failures, variation of activities, and collapse of the left ventricle, are evaluated to test the designed physiological control system. Simulation and experimental results consistently show that the aortic pressure estimation error is small, and that the abnormal hemodynamic variables of a congestive heart failure patient are restored back to the normal physiological range.
IEEE Transactions on Control Systems Technology 08/2007; · 1.77 Impact Factor
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Automatica. 01/2007; 43:1869-1883.
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ABSTRACT: An aircraft model that incorporates independently adjustable engine throttles and ailerons is employed to develop an adaptive control scheme in the presence of actuator failures. This model captures the key features of aircraft flight dynamics when in the engine differential mode. Based on this model an adaptive feedback control scheme for asymptotic state tracking is developed and applied to a transport aircraft model in the presence of two types of failures during operation, rudder failure and aileron failure. Simulation results are presented to demonstrate the adaptive failure compensation scheme
American Control Conference, 2006; 07/2006
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ABSTRACT: This paper presents an adaptive scheme to adjust the gains of multiple actuating signals, as combined with an adaptive state feedback control law, for linear time-invariant single-output systems. Adaptation of multiple actuating signals makes it possible to relax some critical design conditions for desired system performance. A controller parametrization and a plant-model matching structure are derived. As an illustrative example, a simulation study is carried out for adaptive cooperative control of aircraft ailerons and rudder for desired lateral motion of tracking a reference trajectory
American Control Conference, 2006; 07/2006
