Uncertain Actuator Failures Research Articles

Fault-tolerant Control of High-speed Trains with Uncertain Parameters and Actuator Failures Using Control Reallocation and Adaptive Control

Because of increased requirements on the reliability, maneuverability and survivability of modern highspeed trains, more and more advanced control theory is applied against actuator failures. The control reallocation and adaptive control have long been attracting research interest in the field of fault-tolerant control, which is reflected in the design and development of powerful and complex control systems against actuator failures. In this paper we investigate the velocity tracking control problem of high-speed trains with multiple vehicles connected through couplers in the case of actuator failures. First, the multiple point-mass model is built and the common actuator failures of the train operation control system are divided into two types: stuck in a fixed value and loss of effectiveness. When plant inputs are stuck in a fixed value, a novel approach based on the control reallocation theory is implemented to ensure the system stability and performance. Meanwhile when the loss of the actuator effectiveness occurs, a robust adaptive fault-tolerant control method is applied. Then, the effectiveness of the proposed approach is also confirmed through numerical simulations based on a train similar to China Railways High-speed 5 (CRH5).

A discrete-time parameter estimation based adaptive actuator failure compensation control scheme

This article studies discrete-time adaptive failure compensation control of systems with uncertain actuator failures, using an indirect adaptive control method. A discrete-time model of a continuous-time linear system with actuator failures is derived and its key features are clarified. A new discrete-time adaptive actuator failure compensation control scheme is developed, which consists of a total parametrisation of the system with parameter and failure uncertainties, a stable adaptive parameter estimation algorithm, and an on-line design procedure for feedback control. This work provides a new design of direct adaptive compensation of uncertain actuator failures, using an indirect adaptive control method. Such an adaptive design ensures desired closed-loop system stability and tracking properties despite uncertain actuator failures. Simulation results are presented to show the desired adaptive actuator failure compensation performance.

Adaptive Fault Detection and Fault-Tolerant Control of NASA Generic Transport Aircraft Model

In this paper, adaptive fault detection and fault-tolerant control schemes for aircraft flight systems are investigated and evaluated on a high-fidelity aircraft model–the nonlinear NASA generic transport model. State feedback for output tracking and output feedback for output tracking multivariable model reference adaptive control schemes are developed, where plant-model matching conditions are much less restrictive than that of the state feedback for state tracking design, to ensure stability and asymptotic output tracking for the aircraft in the presence of uncertain actuator failures and structural damage. Based on an aircraft system dynamic coupling feature and different actuator failure patterns, adaptive detectors are constructed to detect damage and actuator failures. Our adaptive detection schemes are equipped with feedback fault-tolerant control to ensure signal boundedness requirement. Desired performance of the developed schemes is demonstrated by extensive simulation studies on the nonlinear NASA generic transport model.

A Multiple-Model Based Adaptive Actuator Failure Compensation Scheme for Control of Near-Space Vehicles

This paper presents a new adaptive actuator failure compensation control scheme for nonlinear systems motivated from a near space vehicle control application, using a multiple-model failure estimation and control approach. Such a design employs multiple controllers, each of which is designed for each failure pattern in the failure pattern set of interest and is constructed with parameters from adaptive estimates of the failure parameters of a specific actuator failure. Each estimator is based on a complete parametrization of the corresponding actuator failure. A switching mechanism is set up, based on finding the minimal performance cost index from the estimation errors, to select the most appropriate controller to generate the current control signal. Simulation results from the attitude control of a near space vehicle dynamic model in the presence of uncertain actuator failures are presented to show the desired adaptive actuator failure compensation performance.

Adaptive Failure Compensation Control with Redundant Actuators⋆

AbstractRedundant actuators are commonly used for actuator failure compensation but bring new challenges for feedback control design as uncertain failures can introduce large structural, parametric and actuation uncertainties. Two key technical issues are associated with using redundant actuators: how to coordinate redundant actuators for effective feedback control, and how to adaptively compensate uncertain actuator failures. In this paper, we present a systematic overview of direct adaptive failure compensation based solutions to these issues for different types of control systems: state tracking and output tracking, using state feedback or output feedback, for linear and nonlinear systems.

Adaptive actuator failure compensation control of uncertain nonlinear systems with guaranteed transient performance

In order to accommodate actuator failures which are uncertain in time, pattern and value, we propose two adaptive backstepping control schemes for parametric strict feedback systems. Firstly a basic design scheme on the basis of existing approaches is considered. It is analyzed that, when actuator failures occur, transient performance of the adaptive system cannot be adjusted through changing controller design parameters. Then we propose a new controller design scheme based on a prescribed performance bound (PPB) which characterizes the convergence rate and maximum overshoot of the tracking error. It is shown that the tracking error satisfies the prescribed performance bound all the time. Simulation studies also verify the established theoretical results that the PPB based scheme can improve transient performance compared with the basic scheme, while both ensure stability and asymptotic tracking with zero steady state error in the presence of uncertain actuator failures.

Adaptive actuator failure compensation for redundant manipulators

SUMMARYThis paper presents an adaptive actuator failure compensation method, which compensates for uncertainties due to unknown actuator failures for redundant manipulator systems. The method is first developed for manipulators whose joints are concurrently actuated. While physical realization of concurrently actuated manipulators and the advantages of their use have been understood before, in this paper failure modeling, controller structure, and adaptive update rules for handling uncertainties from the actuator failures are studied. The adaptive actuator failure compensation method is then expanded for a cooperating multiple manipulator system with uncertain actuator failures. Dynamic equations of such a multiple manipulator system in the task space are derived and the adaptive actuator failure compensation problem is formulated in the task space, for which a compensation controller structure is proposed with stable adaptive parameter update laws. The adaptive control scheme is able to compensate for the uncertainties of system parameters and actuator failures in a more general sense. For both cases, closed-loop system stability and asymptotic tracking are proved, despite uncertain system failures.

Robust Failure Compensation for a Morphing Aircraft Model Using a Probabilistic Approach

We present a probabilistic robust control design for a morphing aircraft model subject to uncertain actuator failure. The morphing aircraft model has multiple distributed arrays of shape-change devices that are used to generate moments for stabilization and low-rate maneuvering, augmenting conventional control surfaces. Each actuator operates at either on or off state; failure of each actuator could cause uncertainty in the applied control input. We characterize the morphing aircraft's actuation failure in a probabilistic way. In particular, each shape-change device within an actuator array is assumed to have certain probability to fail while devices from different arrays may have different failure probabilities. Consequently, we model the uncertain actuator failure as a random parametric uncertainty in the input matrix of the morphing aircraft model. A probabilistic robust explicit-model-following controller is then designed to stabilize the closed-loop system and to satisfy tracking performance subject to uncertain actuator failure. Simulation results are presented and evaluated for the application of this probabilistic robust failure compensation design to lateral dynamics of an Innovative Control Effector morphing aircraft model

Robust Adaptive Control Scheme for Discrete-Time System With Actuator Failures

A robust adaptive control approach using output feedback for output tracking is developed for discrete-time linear time-invariant systems with uncertain failures of redundant actuators in the presence of the unmodeled dynamics and bounded output disturbance. Such actuator failures are characterized by some unknown inputs stuck at some unknown fixed values at unknown time instants. Technical issues such as plant-model output matching, adaptive controller structure, adaptive parameter update laws, stability and tracking analysis, and robustness of system performance are solved for the discrete-time adaptive actuator failure compensation problem. A case study is conducted for adaptive compensation of rudder servomechanism failures of a Boeing 747 dynamic model presented in discrete time, verifying the desired adaptive system performance in the presence of uncertain actuator failures.

Adaptive actuator failure compensation for cooperating multiple manipulator systems

This paper presents adaptive actuator failure compensation for a cooperating multiple manipulator system with uncertain actuator failures in the task space. Advantages of designing control schemes in task spaces are emphasized, applications of task space control in robotics are discussed and a short review on control algorithms for cooperating multiple manipulator systems is given. Dynamic equations of motion of the multiple manipulator system in the task space are derived, and the adaptive actuator failure compensation problem is formulated. A compensation controller structure is proposed, for which adaptive parameter update laws are developed. The adaptive control scheme is able to compensate for the uncertainties arising from both the system parameters and the actuator failures. Based on Lyapunov stability analysis, the closed-loop signal boundedness and the convergence of the tracking error to zero are ensured.

Actuator failure compensation schemes for vibration control of a rocket fairing model

In this paper, the actuator failure compensation problem is formulated for active vibration control of a launch vehicle payload fairing. Performance of a nominal optimal control scheme for active vibration control is analyzed in light of a typical actuator failure model that certain actuator outputs are stuck at unknown fixed values at unknown time instants. Three stabilizing control schemes handling uncertain actuator failures are developed to ensure closed-loop system signal boundedness in the presence of uncertain actuator failures. Simulation results are presented to demonstrate their effectiveness.

A discrete-time robust adaptive actuator failure compensation control scheme

A robust adaptive control approach using output feedback for output tracking is developed for discrete-time linear time-invariant systems with uncertain failures of redundant actuators in the presence of the unmodeled dynamics and bounded output disturbance. Such actuator failures are characterized by some unknown inputs stuck at some unknown fixed values at unknown time instants. Technical issues such plant-model output matching, adaptive controller structure, adaptive parameter update laws, stability and tracking analysis, and robustness of system performance are solved for the discrete-time adaptive actuator failure compensation problem. A case study is conducted for adaptive compensation of rudder servomechanism failures of a Boeing 747 dynamic model presented in discrete time, verifying the desired adaptive system performance in the presence of uncertain actuator failures.