Adaptive Second Order Recursive Terminal Sliding Mode Control for a Four-Wheel Independent Steer-by-Wire System

An adaptive second order recursive terminal sliding mode (SO-RTSM) is developed for the steering angle control of a four-wheel independent steer-by-wire (4WI-SbW) system. A recursive sliding mode structure is presented based on which the reaching phase is eliminated. Moreover, the finite time convergence of the tracking error is guaranteed compared to common integral sliding mode control (ISMC). Furthermore, to suppress chattering, instead of a first-order sliding mode used in a conventional ARTSM controller, a second order nonsingular terminal sliding mode is adopted such that reaching control input is obtained in an integral form. The advantage of the proposed controller is that the chattering can be effectively reduced without decreasing the control accuracy. Experiments are carried out on a real 4WI-SbW vehicle to demonstrate the fast convergence rate and small chattering of the proposed controller.