Accommodation of unknown actuator faults using output feedback‐based adaptive robust control

Abstract

In this paper, we solve the problem of output tracking for linear uncertain systems in the presence of unknown actuator failures using discontinuous projection-based output feedback adaptive robust control (ARC). The faulty actuators are characterized as unknown inputs stuck at unknown values experiencing bounded disturbance and actuators losing effectiveness at unknown instants of time. Many existing techniques to solve this problem use model reference adaptive control (MRAC), which may not be well suited for handling various disturbances and modeling errors inherent to any realistic system model. Robust control-based fault-tolerant schemes have guaranteed transient performance and are capable of dealing with modeling errors to certain degrees. But, the steady-state tracking accuracy of robust controllers, e.g. sliding mode controller, is limited. In comparison, the backstepping-based output feedback adaptive robust fault-tolerant control (ARFTC) strategy presented here can effectively deal with such uncertainties and overcome the drawbacks of individual adaptive and robust controls. Comparative simulation studies are performed on a linearized Boeing 747 model, which shows the effectiveness of the proposed scheme.

Design of L1 adaptive controllers for human patient anesthesia

“…We note here that our focus is specifically on the use and evaluation of L 1 adaptive methods. However have been other robust and adaptive techniques, providing for example fault tolerance to actuator faults and allowing for system delays (Gayako & Yao, 2011;Wu & Yang, 2014), which will be considered in future designs.…”

Robust fault-tolerant control based on sliding mode method for uncertain linear systems

“…Assume the closed-loop FTC system (6) satisfying Assumptions 1-4, and linear matrix inequality (LMI) (11) is feasible. Then the sliding mode FTC law described in equations (12) and (13) with adaptive laws (15) and (16) can ensure that the closed-loop system (6) is asymptotically stable and the H ' performance bound is no larger than g 0 despite actuator failures, unmatched uncertainties, and disturbance effects.…”

“…Since Theorem 1 implies that Q . 0, a(t) = x T (t)P À1 B 2v = 0, and outputs of the adaptive mechanisms (15) and (16) are all zero, one can see that…”

“…Considering the adaptive laws given in equation (15), we have À2hml Nm0 k a k + 2g À1 mm 0 _ m 0 = 0 Furthermore, the adaptive laws (16) are adopted, and we can obtain the inequality as follows…”

“…It is worth noting that adaptive actuator failure compensation control schemes, as one of the effective active methods, have been recently studied to compensate for unknown actuator failures. [9][10][11][12][13][14][15][16][17] On another research front, parameter uncertainties and external disturbances are two further challenges to be addressed in the design of FTC systems. [18][19][20][21][22] Fortunately, the insensitivity and robustness properties of sliding modes to certain types of disturbance and uncertainty 23,24 make it very attractive for FTC design especially in the area of flight control.…”