Fault-tolerant control of wheeled mobile robots with prescribed trajectory tracking performance

The problem of trajectory tracking for a class of differentially driven wheeled mobile robots (WMRs) under partial loss of the effectiveness of the actuated wheels is investigated in this paper. Such actuator faults may cause the loss of strong controllability of the WMR, such that the conventional fault-tolerant control strategies unworkable. In this paper, a new mixed-gain adaption scheme is devised, which is adopted to adapt the gain of a decoupling prescribed performance controller to adaptively compensate for the loss of the effectiveness of the actuators. Different from the existing gain adaption technique which depends on both the barrier functions and their partial derivatives, ours involves only the barrier functions. This yields a lower magnitude of the resulting control signals. Our controller accomplishes trajectory tracking of the WMR with the prescribed rate and accuracy even in the faulty case, and the control design relies on neither the information of the WMR dynamics and the actuator faults nor the tools for function approximation, parameter identification, and fault detection or estimation. The comparative simulation results justify the theoretical findings.