Comparisons of adaptive fault‐tolerant insensitive control methods for a class of linear systems

Abstract

In this paper, the problem of fault-tolerant insensitive control is addressed for a class of linear time-invariant continuous-time systems against bounded time-varying actuator faults and controller gain variations. Adaptive mechanisms are developed to adjust controller gains in order to compensate for the detrimental effects of partial loss of control effectiveness and bias-actuator faults. Variations of controller gains arise from time-varying and bounded perturbations that are supposed to always exist in adaptive mechanisms. Based on the disturbed outputs of adaptive mechanisms, three different adaptive control strategies are constructed to achieve bounded stability results of the closed-loop adaptive fault-tolerant control systems in the presence of actuator faults and controller gain variations. Furthermore, comparisons of convergence boundaries of states and limits of control inputs among adaptive strategies are developed in this paper. The efficiency of the proposed adaptive control strategies and their comparisons are demonstrated by a rocket fairing structural-acoustic model. KEYWORDS actuator faults, bounded stability, disturbed adaptive mechanisms, fault-tolerant control system INTRODUCTIONIn a practical control system, it is inevitable that a component such as an actuator or a sensor is faulty at some instants because of the reason of coming from the component's quality, external working environment, internal operation conditions, etc. Under unexpected faults of components, fault-tolerant control (FTC) designs are critical to be developed to maintain stability of systems and prevent performance degradation seriously. 1,2 During the past two decades, various FTC and some relative methods have been proposed for nonlinear systems such as aircraft, 3,4 robots, 5,6 interconnected systems such as networked systems 7,8 and multiagent systems, 9-11 linear systems with time delays, 12 uncertainties and disturbances, 13 state/input saturations, 14,15 and controller gain variations. 16,17 Among those methods, active FTC has received increasing attention because of its advantages of online changing controller structure and adjusting the control parameters to accommodate actuator and sensor faults.The existing active FTC designs can be broadly classified into two categories, that is, fault detection and isolation (FDI)-based FTC and adaptive FTC designs. In the study of FDI-based FTC systems, FTC strategies are designed based on the exactly faulty information, which is obtained by FDI mechanisms. 13,18 On the other hand, an adaptive technique that can estimate the changes of system parameters in real time has been widely used to deal with many issues in Int J Adapt Control Signal Process. 2019;33: 175-195. wileyonlinelibrary.com/journal/acs

Adaptive fault‐tolerant control of mobile robots with actuator faults and unknown parameters

“…According to Tao [26], faults of an actuator can be generally classified into four types, i.e. partial loss of control effectiveness [27–29], bias‐actuator faults [30–32], outage and stuck faults [33, 34]. From the studies of the above literature, we know that the adaptive technique is always used to design fault‐tolerant control strategies for completely compensating for the effects of actuator faults.…”

Adaptive fault‐tolerant control of an axially moving system with time‐varying constraints

“…In [29], partial loss of control effectiveness, actuator amplitude and rate saturation for a linear time-invariant system are dealt with using auxiliary fault-tolerant control. [30] focuses on a robust fault-tolerant insensitive control for linear systems. To eliminate the damaging effects of faults and attenuate control gain variations from adaptive mechanisms, three adaptive control strategies are designed.…”