Super-twisting algorithm with fast super-twisting disturbance observer for steer-by-wire vehicles

Abstract

The control performance of a vehicle steer-by-wire (SBW) system can be seriously affected by vagaries of tyre-road conditions and external disturbance. Aiming at the problem of fast estimating and compensating the time-varying disturbance torque acting on the front wheels under different working conditions, this article presents a super-twisting algorithm (STA) combined with fast super-twisting disturbance observer (FSTDO) control scheme. At first the SBW system is modelled according to the experiment plant. Secondly, the FSTDO is designed according to SBW system model. A fast reaching law is adopted to accelerate the sliding variable convergence rate and enhance the response speed of the observer. The FSTDO-STA controller adopts STA control in closed-loop system. The control signal is continuous, so that, the chattering could be inhibited. The stability of FSTDO error dynamics and closed-loop dynamics is proved in the sense of Lyapunov. Finally, comparative verification experiments are carried out to demonstrate the validity of FSTDO-STA. The FSTDO-STA controller can quickly estimate and compensate disturbance torque under various operating conditions. Compared with other comparative algorithms, the proposed controller has some advantages in response speed, control accuracy and robustness. And it was corroborated by the experimental results.