Research ArticleRobust model reference adaptive output feedback tracking for uncertain linear systems with actuator fault based on reinforced dead-zone modification

•Conventional approach of MRAC for SISO and MIMO systems is considered.•Two lemmas are reported for zero tracking error inside faulty conditions for SISO and MIMO systems.•Close loop stability and output tracking are ensured for both SISO and MIMO using analysis of the suitable Lyapunov candidate.•Finally, in the simulation results section the proposed fault tolerant controller approach is compared with the conventional MRAC inside faulty conditions and good performance and robustness of proposed algorithm are confirmed.

In this paper, robust model reference adaptive tracking controllers are considered for Single-Input Single-Output (SISO) and Multi-Input Multi-Output (MIMO) linear systems containing modeling uncertainties, unknown additive disturbances and actuator fault. Two new lemmas are proposed for both SISO and MIMO, under which dead-zone modification rule is improved such that the tracking error for any reference signal tends to zero in such systems. In the conventional approach, adaption of the controller parameters is ceased inside the dead-zone region which results tracking error, while preserving the system stability. In the proposed scheme, control signal is reinforced with an additive term based on tracking error inside the dead-zone which results in full reference tracking. In addition, no Fault Detection and Diagnosis (FDD) unit is needed in the proposed approach. Closed loop system stability and zero tracking error are proved by considering a suitable Lyapunov functions candidate. It is shown that the proposed control approach can assure that all the signals of the close loop system are bounded in faulty conditions. Finally, validity and performance of the new schemes have been illustrated through numerical simulations of SISO and MIMO systems in the presence of actuator faults, modeling uncertainty and output disturbance.