Shuhao Chen

Brief An adaptive control scheme for systems with unknown actuator failures

A state feedback output tracking adaptive control scheme is developed for plants with actuator failures characterized by the failure pattern that some inputs are stuck at some unknown fixed values at unknown time instants. New controller parametrization and adaptive law are developed under some relaxed system conditions. All closed-loop signals are bounded and the plant output tracks a given reference output asymptotically, despite the uncertainties in actuator failures and plant parameters. Simulation results verify the desired adaptive control system performance in the presence of actuator failures.

An adaptive actuator failure compensation controller using output feedback

An adaptive control scheme using output feedback for output tracking is developed for systems with unknown actuator failures that some unknown inputs are stuck at some unknown fixed values at unknown time instants. An effective controller structure is proposed which achieves desired plant-model output matching when implemented with matching parameters and asymptotic output tracking when implemented with adaptive parameter estimates. A completely parametrized linear error equation is obtained based on which a stable adaptive law is derived for parameter adaptation in the presence of parameter uncertainties. All dosed-loop signals are bounded and the plant output tracks a given reference output asymptotically, despite the uncertainties in actuator failures and plant parameters, as shown analytically and by simulation results from a case study of yaw rate control of Boeing 747 lateral dynamics.

An adaptive actuator failure compensation scheme for controlling a morphing aircraft model

An adaptive compensation control scheme is developed for a morphing aircraft model with actuator failures. Morphing actuators are special in the sense that they operate only at two states: on or off, and that they are used in large numbers to fulfill certain actuation function. We derive a failure model for morphing actuators and develop an adaptive scheme to estimate the actuation effectiveness and to update the number of actuators to be activated. A feedback control scheme is redesigned for adaptive actuator failure compensation, which ensures desired closed-loop stability and tracking properties. A simulation study with a linearized lateral dynamics model of the ICE aircraft is presented to demonstrate the system performance in the presence of uncertain actuator failures.

Brief paper: A stable block model predictive control with variable implementation horizon

In this paper, we present a stable receding horizon model predictive control for discrete-time nonlinear systems. The standard MPC scheme is modified to incorporate (1) a block implementation scheme where a string of the optimized input is applied instead of a single value; (2) an additional constraint which guarantees that a Lyapunov function decreases over time; (3) a variable implementation window that facilitates the constraints enforcement. Stability of the closed-loop system with the proposed algorithm is established. Examples and simulation results are given to illustrate the effectiveness of the control scheme. The impacts of several key design parameters on the overall performance are also analyzed and discussed.

An adaptive actuator failure compensation controller for MIMO systems

Two adaptive control schemes based on MRAC are developed for a class of MIMO systems with unknown actuator failures. An effective controller structure is proposed to achieve the desired plant-model output matching when implemented with matching parameters. Based on design conditions on the controlled plant, which are needed for nominal plant-model output matching for a chosen controller structure, two adaptive versions of the nominal controller are proposed and adaptive laws are derived for updating the controller parameters when plant and failure parameters are unknown. All closed-loop signals are bounded and the plant outputs track the given reference outputs asymptotically, despite the uncertainties in failures and plant parameters. Simulation results are presented to show the desired performance of the adaptive control system in the presence of unknown rudder and aileron failures in an aircraft lateral dynamic model.

State Feedback Designs for State Tracking

In this chapter, we solve the adaptive actuator failure compensation problems for linear time-invariant systems with unknown actuator failures and unknown dynamics, using state feedback for state tracking. In Section 2.1, the plant-model state matching conditions, controller structure, and adaptive designs are presented for a linear time-invariant system with up to m − 1 (where m is the total number of actuators) actuator failures characterized by some of the plant inputs being stuck at some unknown fixed or varying values that cannot be influenced by control action, for example, the “lock-inplace” type of actuator failures. Adaptive actuator failure designs for systems with up to m − 1 parametrizable time-varying failures and up to m − 1 unparametrizable time-varying failures are developed in Section 2.2 and Section 2.3, respectively. In Section 2.4, parametrization and design results such as plant-model matching and adaptive controller structure are extended to the case when the state reference model system has multiple inputs, which allows more freedom in characterizing desired system behavior. In Section 2.5, necessary and sufficient plant-model matching conditions, and adaptive control designs for systems with up to m − q, 1 ≤ q ≤ m − 1, lock-in-place actuator failures are derived and the effectiveness of adaptive compensation is verified by simulation results from Boeing 747 lateral control.

An adaptive control scheme for systems with unknown actuator failures

A state feedback output tracking adaptive control scheme is developed for plants with actuator failures characterized by the failure pattern that some inputs are stuck at some unknown fixed values at unknown time instants. This scheme relaxes the conditions on the controlled plant for desired plant-model output matching in the presence of actuator failures. New controller parametrization and adaptive law are developed under less restrictive conditions. All closed-loop signals are bounded and the plant output tracks a given reference output asymptotically, despite the uncertainties in actuator failures and plant parameters. Simulation results verify the desired adaptive control system performance.

Adaptive actuator failure compensation control for MIMO systems

Two adaptive failure compensation control schemes based on MRAC are developed for a class of MIMO LTI systems with unknown actuator failures. An effective controller structure is proposed to achieve the desired plant-model output matching when implemented with matching parameters. Design conditions are specified for such nominal plant-model output matching. Two adaptive versions of the nominal controller are proposed and stable adaptive laws are derived for updating the controller parameters when plant parameters and failure parameters are unknown. All closed-loop signals are bounded and the plant outputs track the given reference outputs asymptotically, despite the uncertainties in actuator failures and plant parameters. Simulation results for an aircraft lateral dynamic model verify the desired adaptive control system performance in the presence of unknown rudder and aileron failures.

A stable block model predictive control with variable implementation horizon

In this paper, we present a stable receding horizon model predictive control for discrete-time nonlinear systems. The standard MPC scheme is modified to incorporate (1) a block implementation scheme where a string of the optimized input is applied instead of a single value; (2) an additional constraint which guarantees that a Lyapunov function decreases over time; (3) a variable implementation window that facilitates the constraints enforcement. Stability of the closed-loop system with the proposed algorithm is established. Examples and simulation results are given to illustrate the effectiveness of the control scheme. The impacts of several key design parameters on the overall performance are also analyzed and discussed.

Adaptive actuator failure compensation for a transport aircraft model

Adaptive actuator failure compensation schemes are developed for a class of multi-input and single-output plants with actuator failures characterized by certain inputs stuck at some unknown fixed value at unknown time instants. Conditions and controller structures for achieving state tracking and output tracking in the presence of actuator failures are derived. Adaptive laws are designed for updating some of the controller parameters when the actuator failure parameters are unknown. Simulation results for a linearized transport aircraft model with actuator failure show the desired system performance with adaptive failure compensation.