Adaptive Fault-Tolerant Tracking Control of Direct-Drive Servo Systems With Actuator Faults and Saturation

Direct-drive servo systems are widely used in the field of transportation, but the existence of actuator failures and saturation will threaten system safety and cause serious traffic accidents. In this article, an adaptive fault-tolerant tracking control (AFTTC) method for direct-drive servo systems is proposed to address the complex constraint problems in traffic tasks. The system dynamics model with actuator failures and asymmetric saturation is first constructed, and an estimation algorithm with convergence characteristics is comprehensively adopted to deal with actuator failures and parameter uncertainties. In particular, a smooth function is cleverly introduced to achieve a smooth transition of the saturation inflection point output. To minimize the influence of various nonlinearities and uncertainties, a finite-time neural network observer is designed. It is worth mentioning that the designed controller is suitable for the above-mentioned complex multiconstraint conditions and can achieve asymptotically stable tracking of the closed-loop system. Experimental results show that compared with traditional adaptive fault-tolerant control (FTC), the proposed AFTTC method improves the steady-state performance of the system by 26.5% and 28.2%, which further improves the safety of transportation industry tasks.