Adaptive Multi-design Integration Based Failure Compensation Techniques And Its Application

Actuator failures have damaging effect on the performance of control systems, leading to undesired system behavior or even instability. For system safety and reliability, such actuator failures must be properly accommodated, actuator failures compensation is an important topic of both theoretical and practical significance.Actuator failures are uncertain in nature. Very often it is impossible to predict in advance which actuators may fail during system operation, when the failures occur, what types and what values of the failures are. It may also be impractical to determine the failure parameters after a failure occurs. Moreover, the whole closed-loop control system will become underactuated due to some uncertain actuator failures. In this case, the actuator failure compensation control design will be more difficult and complex.This dissertation is to develop new adaptive actuator failure compensation control schemes for nonlinear systems with system parameter and actuator failure uncertainties. The proposed adaptive failure compensation schemes are capable of handling unknown actuator failures, guaranteeing system stability and tracking performance without explicit knowledge of the occurances of actuator failures and the failure values. The contributions of this dissertation are the development of new adaptive nonlinear control schemes, which provid a guideline for applications and system designs and extend the adaptive nonlinear systems.This dissertation addresses several adaptive actuator failure compensation problems to obtain systematic results, which are presented as follows:(1) The output tracking problem for multivariable parametric strict-feedback systems with unknown actuator failures is investigated and a backstepping based adaptive actuator failure compensation scheme is developed.(2) The output tracking problem for multi-input multi-output feedback linearizable systems with unknown actuator failures is studied and a feedback linearization based adaptive actuator failure compensation scheme is developed.(3) Two multiple-controller integration based adaptive actuator failure compensation schemes are developed for the rigid-body systems with known and unknown plant parameters, moreover, the robustness of our scheme with respect to unmodeled dynamics is analyzed.(4) Furthermore, the adaptive fault-tolerant control problem of uncertain underactuated systems due to unknown actuator failures is considered. Such problem has never been studied and solved in the literature. An effective adaptive fault-tolerant control scheme is developed for underactuated rigid-body systems with unknown parameters based on multiple-model design.For each design, a parameterized controller structure for each considered compensable failure pattern is obtained by solving actuation equation derived from nonlinear control design, then a composite controller to cover all possible failure patterns is developed based on the defined failure indicator functions. For adaptive design with plant parameter and actuator failure uncertainties, we first derive the error equations. Based on the error equations, adaptive laws updating the unknown controller parameters are derived. It is shown in detailed analysis that, for all the developed adaptive actuator failure compensation schemes, all closed-loop signals are bounded and asymptotic tracking is guaranteed, despite the uncertainties in actuator failures and plant parameters. In all the developed schemes, a fault detection and diagnosis procedure is not needed.To verify the effectiveness of the proposed adaptive actuator compensation schemes, a variety of applications including near space vehicle, rigid spacecraft with different kinds of actuators and 3D rigid-body system are addressed. The simulation results showing the proposed adaptive actuator compensation schemes can compensate the unknown actuator failure and guarante system stability and tracking performance.