Sliding-mode control of a hydrostatic drive train with uncertain actuator dynamics

A sliding-mode approach with disturbance compensation is proposed in this paper for the tracking control of a hydrostatic drive train, which is commonly used in off-road vehicles. A control-oriented modelling results in a system of four nonlinear differential equations which are subject to uncertain actuator dynamics with saturation effects and unknown disturbances — a leakage volume flow and a disturbance torque acting on the hydraulic motor. The disturbances are estimated by a nonlinear reduced-order disturbance observer and used for a disturbance compensation. Thereby, the switching part in the sliding-mode control law and chattering phenomena can be reduced. Simulation results point out that the proposed approach leads to an excellent tracking performance despite the given uncertainties in the actuator dynamics.