Actuator Failure Compensation Scheme Research Articles

A switching-free multiple-model approach for adaptive FTC of non-Lipschitz nonlinear uncertain systems under persistent actuator failures

A novel actuator failure compensation scheme is proposed for affine nonlinear uncertain systems (not necessarily Lipschitz) subject to persistent/intermittent actuator faults/failures unknown in time, magnitude and pattern. The proposed control methodology satisfies the nonlinear separation principle through a modular backstepping control. The controller is then augmented with multiple estimation models to estimate failure induced parametric uncertainties and unknown system parameters. The output transient performance at start up and post-failure instances, is improved on account of a two layer adaptation which enhances the convergence speed and accuracy of parameter estimates. The proposed fault tolerant control (FTC) method yields a faithful accommodation of uncertain finite as well as infinite/intermittent/persistent actuator failures while ensuring satisfactory output transient and steady state performances. Further, compared to existing multiple model based adaptive fault tolerant control design for nonlinear systems, the proposed methodology circumvents the issues of stability due to switching between different models and utilizes a minimum number of estimation models for parameter estimation without compromising on the output performance. Consequently, the computational burden is also reduced. Compared to multiple model adaptive control based FTC strategies proposed earlier which assume finite actuator failures and Lipschitz nonlinear system, the proposed method is applicable to both Lipschitz and non-Lipschitz nonlinear systems affected by intermittent actuator failures. Using the concepts from stability analysis in random nonlinear impulsive systems, the L∞ and L2 bounds on tracking error for all future time are derived in the case of intermittent/persistent actuator failures obtained using the proposed fault-tolerant controller. The improvement of output transient performance in the proposed control scheme in comparison with controller with single identifier, is theoretically proved and quantified.

Adaptive Actuator Fault Compensation and Disturbance Rejection Scheme for Spacecraft

An adaptive actuator failure compensation scheme is proposed for attitude tracking control of spacecraft with unknown disturbances and uncertain actuator failures. A new feature of this adaptive control scheme is the adaptation of the failure pattern parameter estimates, as well as the failure signal parameter estimates, for direct adaptive actuator failure compensation. Based on an adaptive backstepping control design, the estimates of the disturbance parameters are used to solve the disturbance rejection problem. Without the requirement of additional fault detection mechanism, the switching function is designed to automatically locate and turn off the unknown faulty actuators by observing a control performance index. The asymptotic stability of the system output in the presence of actuator failures is rigidly proved through standard Lyapunov approach, while the other signals of the closed-loop system are guaranteed to be bounded. Simulation results verify the desired adaptive actuator failure compensation performance.

A novel adaptive actuator failure compensation scheme based on multi-design integration for half-car active suspension system

A new actuator failure compensation scheme in the presence of actuator failures with multi-uncertainties is proposed for half-car active suspension systems based on multi-design integration. A parameterized function has been introduced to denote the multiple failures occurred in the front and rear actuators. An effective feedback controller is designed to obtain asymptotic tracking and closed-loop system stability by employing backstepping technique. Based on the desired controller, multiple adaptive control signals are designed corresponding to each possible failure case. By introducing failure indicator functions and integrating these control signals, a composite controller is constructed to handle all failure patterns, which ensures both pitch and vertical motions of car body to stabilize and track the desired signals. Finally, simulation is conducted to verify the effectiveness of the controller proposed in this study.

Actuator failure compensation for two linked 2WD mobile robots based on multiple-model control

Abstract This paper develops a new actuator failure compensation scheme for two linked two-wheel drive (2WD) mobile robots based on multiple-model control. First, a configuration of two linked 2WD robots is described, and their kinematics and dynamics are modeled. Then, a multiple-model based failure compensation scheme is developed to compensate for actuator failures, consisting of a kinematic controller, multiple dynamic controllers and a control switching mechanism, which ensures system stability and asymptotic tracking properties. Finally, simulation results verify the effectiveness of the proposed failure compensation control system.

Multidesign Integration Based Adaptive Actuator Failure Compensation Control for Two Linked 2WD Mobile Robots

This paper develops an actuator failure compensation control scheme for two linked mobile robots. The kinematic and dynamic models of two robots with a physical link that is employed to deal with actuator failures for two-wheel drive mobile robots are proposed. Then, a kinematic controller is designed, which is a virtual one. Based on this controller, multiple adaptive dynamic control signals are designed to cover all possible failure cases. By combining these dynamic control signals, the dynamic controller is designed, which ensures desired system stability and asymptotic tracking properties. Finally, simulation results verify the effectiveness of the proposed adaptive actuator failure compensation scheme.

Adaptive Compensation of Actuator Failures using Multiple Models

In this paper, a novel actuator failure compensation scheme is proposed for affine nonlinear uncertain systems subject to actuator faults/failures unknown in time, magnitude and pattern. The proposed control methodology utilizes a backstepping procedure integrated with multiple estimation models to estimate failure induced parametric uncertainties and unknown system parameters. Relative to existing direct adaptive backstepping based fault compensation strategies, the proposed fault tolerant control (FTC) method yields a faithful accommodation of uncertain actuator failures while ensuring satisfactory output transient and steady state performances. Further, compared to multiple model based adaptive FTC design, the proposed methodology circumvents the issues of stability due to switching between different models and utilizes a minimum number of estimation models for parameter estimation without sacrificing the output performance and thereby reducing the computational burden. Simulation results illustrate the effectiveness and applicability of the proposed method to FTC design problem for longitudinal pitch control of Boeing 747-100/200 aircraft.

An adaptive actuator failure compensation scheme for two linked 2WD mobile robots

This paper develops a new adaptive compensation control scheme for two linked mobile robots with actuator failurs. A configuration with two linked two-wheel drive (2WD) mobile robots is proposed, and the modelling of its kinematics and dynamics are given. An adaptive failure compensation scheme is developed to compensate actuator failures, consisting of a kinematic controller and a multi-design integration based dynamic controller. The kinematic controller is a virtual one, and based on which, multiple adaptive dynamic control signals are designed which covers all possible failure cases. By combing these dynamic control signals, the dynamic controller is designed, which ensures system stability and asymptotic tracking properties. Simulation results verify the effectiveness of the proposed adaptive failure compensation scheme.

Adaptive control of uncertain nonlinear time delay systems in the presence of actuator failures and applications to chemical reactor systems

This paper presents an adaptive actuator failure compensation scheme for a class of uncertain nonlinear systems with unknown nonlinearities, unknown time varying delays and in the presence of time varying actuator failures. The considered actuator failure is modeled to cover both loss of effectiveness and stuck at some time varying values where the values, times and patterns of the failures are unknown. With the help of Neural Networks to approximate the unknown nonlinear functions, a novel adaptive actuator failure compensation controller is developed based on the backstepping design method. The appropriate Lyapunov–Krasovskii functionals are introduced to design new adaptive laws to compensate the unknown time varying actuator failures as well as uncertainties from unknown nonlinearities and time varying delays. The proposed design method does not require a priori knowledge of the bounds of the unknown time delays and actuator failures. The boundedness of all the closed-loop signals is guaranteed and the tracking error is proved to converge to a small neighborhood of the origin. Finally, the developed approach is applied to the control design of a chemical reactor with delayed recycle streams. The simulation results are provided to show the effectiveness of the proposed approach.

An adaptive actuator failure compensation scheme for a cooperative manipulator system

SUMMARYThis paper develops a new adaptive actuator failure compensation algorithm for the control of a cooperative robotic system subject to uncertain actuator failures. The benchmark robotic system has two manipulators to balance a rigid platform, and the right-side manipulator contains one actuator and the left-side manipulator has two actuators (one of which may fail during system operation, but it is uncertain how much, when and which actuator may fail). The developed adaptive actuator failure compensation scheme, based on adaptive integration of three individual failure compensators and direct adaptation of controller parameters, is capable of ensuring desired closed-loop stability and asymptotic output tracking, despite the failure uncertainties. Such an adaptive actuator failure compensation method is extended to control of a general cooperative robotic system. Simulation results are shown to verify the desired adaptive failure compensation control performance.

Adaptive actuator failure compensation for a class of MIMO nonlinear time delay systems

In this paper, an adaptive actuator failure compensation scheme is proposed for a class of parametric-strict-feedback multi- input multi-output nonlinear systems with unknown time- varying state delays. The considered actuator failures are types of loss of effectiveness, in which unknown system inputs may lose unknown fraction of their effectiveness. The adaptive compensation controller is constructed by utilizing a backstepping design method. The appropriate Lyapunov–Krasovskii functionals are introduced to design new adaptive laws to compensate the unknown actuator failures as well as uncertainties from unknown parameters and state delays. The boundedness of all the closed-loop signals is guaranteed, and the tracking errors are proved to converge to a small neighborhood of the origin. Simulation results are provided to show the effectiveness of the proposed approach.

Adaptive actuator failure compensation and disturbance rejection scheme for spacecraft

An adaptive actuator failure compensation scheme is proposed for attitude tracking control of spacecraft with unknown disturbances and uncertain actuator failures. A new feature of this adaptive control scheme is the adaptation of the failure pattern parameter estimates, as well as the failure signal parameter estimates, for direct adaptive actuator failure compensation. Based on an adaptive backstepping control design, the estimates of the disturbance parameters are used to solve the disturbance rejection problem. The unknown disturbances are compensated completely with the stability of the whole closed-loop system. The scheme is not only able to accommodate uncertain actuator failures, but also robust against unknown external disturbances. Simulation results verify the desired adaptive actuator failure compensation performance.

A discrete‐time indirect adaptive multiple‐model actuator failure compensation scheme

SummaryA new discrete‐time actuator failure compensation control scheme is developed, using a multiple‐model adaptive control approach which has the capacity to achieve faster and more accurate compensation of failure uncertainties. An individual adaptive system, for each possible failure pattern in a failure pattern set of interest for compensation, is designed using an indirect model reference adaptive control scheme for actuator failure compensation. A multiple‐model control switching mechanism for discrete‐time systems is set up by finding the minimal performance index to select the most appropriate control law. The performance indices are based on the adaptive estimation errors of individual parameterized systems with actuator failures. Simulation results from an aircraft flight control system example are presented to show the desired closed‐loop system stability and tracking performance despite the presence of uncertain actuator failures. Copyright © 2014 John Wiley & Sons, Ltd.

Actuator failure compensation and attitude control for rigid satellite by adaptive control using quaternion feedback

The attitude control problem of a rigid satellite with actuator failure uncertainties and external disturbance is addressed using adaptive control method. A discontinuous adaptive failure compensation controller, using unit quaternion and angular velocities feedback, is designed to accommodate the external disturbance and actuator failures which are uncertain in time instants, values and patterns. A common approximate function is used to avoid system chattering caused by such discontinuous control laws. The parameters of external disturbance and failure uncertainties are estimated directly by adaptive laws, and the desired stability and output tracking properties of the adaptive control system are analyzed. Finally, simulation results of a rigid satellite with six reaction wheels are presented to illustrate the performance of the proposed adaptive actuator failure compensation scheme.

A direct adaptive actuator failure compensation scheme for satellite attitude control systems

A new direct adaptive failure compensation approach is developed for satellite attitude control systems in the presence of uncertain failures of redundant actuators. The adaptive failure compensation controller is designed via a backstepping design, which can accommodate uncertainties in actuator failure time instants, values, and patterns. The failure uncertainties are estimated directly by adaptive laws and the adaptive satellite attitude control system with actuator failures is analyzed, to show its desired stability and asymptotic tracking properties. Finally, simulation results of a satellite attitude control system with redundant reaction wheels are presented to demonstrate the effectiveness of the proposed adaptive failure compensation scheme.

An adaptive actuator failure compensation scheme for a class of nonlinear MIMO systems

This paper develops an adaptive actuator failure compensation scheme for control of a class of nonlinear multi-input–multi-output systems with redundant actuators subject to uncertain failures. The design method is to estimate the failure pattern parameters and the failure signal parameters first, and then use the parameter estimates to construct the adaptive failure compensation controller, the control law calculation is done simultaneously with parameter estimation without explicit failure detection. Closed-loop signal boundedness and asymptotic output tracking, despite the actuator failure uncertainties, are ensured analytically and verified by simulation results from its application to attitude control of a near space vehicle dynamic model.

Adaptive Control Schemes for Discrete-Time T–S Fuzzy Systems With Unknown Parameters and Actuator Failures

This paper develops a new solution framework for adaptive output feedback fuzzy control systems aimed at effectively dealing with nonlinear systems with multiple input-multiple output (MIMO) delays and in the presence of dynamics and actuator failure uncertainties. Takagi-Sugeno (T-S) fuzzy systems are employed to represent nonlinear systems, which have desired capacity for dynamic system approximation with parametric and structural properties suitable for using rigorous feedback control techniques. A multiple-delay fuzzy system prediction model is derived and its system properties are clarified. Such a prediction model enables the use of a model-based approach for fuzzy control. The design and analysis are presented for an adaptive control scheme for multiple-delay T-S fuzzy systems, as well as for an adaptive actuator failure compensation scheme for systems with redundant actuators subject to uncertain failures, for which new system parametrizations and controller structures are developed. Simulation results are presented to demonstrate the studied new concepts and to verify the desired performance of the new types of adaptive fuzzy control systems.

Adaptive actuator failure compensation with unknown control gain signs

This study deals with the problem of adaptive control for a class of non-linear systems with parameterisable time-varying actuator failures. An adaptive output-feedback actuator failure compensation scheme is proposed based on the backstepping technique and the Nussbaum gain approach. The assumption on the control gain signs is removed. The boundedness of all the closed-loop signals and the asymptotic output tracking are guaranteed in spite of the unknown actuator failures. Finally, an example is given to show the effectiveness of the proposed design method.

Adaptive output feedback control of nonlinear systems with actuator failures

In this paper, a modified adaptive actuator failure compensation scheme is proposed for a class of uncertain multi-input and single-output (MISO) nonlinear systems in the output-feedback form. We first establish a new parametric model with unknown plant parameters and actuator failure parameters, which differs from some existing results. Then, an adaptive compensation controller is constructed by utilizing the backstepping technique. The boundedness of all closed-loop signals is guaranteed. The tracking error is proved to converge to zero asymptotically. Finally, two simulation examples are provided to demonstrate the effectiveness of the proposed design scheme.