Fractional-order adaptive fuzzy decentralized tracking control for steer-by-wire system.

The steer-by-wire (SbW) system, as the core component of vehicle steering, needs to track the front wheel angle accurately. To mitigate the angle tracking accuracy degradation caused by D-Q axes coupling, time-varying motor electrical parameters, and load disturbance, a fractional-order adaptive fuzzy decentralized tracking control (FAFDTC) strategy is proposed in this paper. First, considering time-varying motor parameters, D-Q axes coupling, and fractional-order characteristics of components, a fractional-order SbW interconnected system is constructed to enhance its ability to characterize nonlinearities, time-varying dynamics, and system coupling. Subsequently, considering time-varying parameters, D-Q axes coupling, and disturbances that include load changes, second-order paradigm squared-value adaptive FLSs with auxiliary functions are designed to estimate nonlinear functions and compensate for approximation errors and external disturbances. Finally, a fractional-order command-filtered adaptive backstepping controller integrating the adaptive parameters of FLSs and auxiliary functions is proposed to ensure front wheel angle tracking accuracy and robustness. Experiment results demonstrate that the proposed FAFDTC reduces the front wheel angle tracking error by 48.58 % and 59.78 % compared to the comparison controllers, verifying the effectiveness and superiority of the proposed controller.