Sliding mode-PID approach for robust low-level control of a UGV

This paper presents an efficient approach for low-level control of an unmanned ground vehicle (UGV) operating in rough terrains. In particular, it tackles with the problem of overshoot in the vehicle braking system that arises from severe nonlinearity and input time-delay. The resultant high-performance and robustness of the control system are achieved by cascading a sliding mode controller (SMC) in series with a conventional PID controller. The idea is based on modelling the system as a second order time-delay system under PID control while the SMC is incorporated to shape the control input for time-delay and nonlinearity compensation. An output predictor is also employed here to obtain the necessary information to realize the proposed controller. The validity of the proposed approach is verified through simulations for the braking system of UGVs developed at our Centre.