MPC motion planning-based sliding mode control for underactuated WPS vehicle via Olfati transformation

This study presents a model predictive control (MPC) motion planning-based sliding mode control (SMC) for a wheeled pendular-like suspension (WPS) vehicle by using Olfati transformation. To improve the tracking efficiency and enhance the control performance of the vehicle system, the mobile platform is required to follow the reference trajectory fast enough, while the swing of the suspension needs to be within an acceptable domain. To achieve these multi-objectives, a two-step design strategy consisting of a motion planning stage and a velocity tracking control design stage is proposed to control such an underactuated system. Specifically, a novel MPC, which satisfies various physical constraints of the WPS vehicle, is presented by which the nonholonomic constraint is dealt with as well. The SMC is then constructed in the second step to make the vehicle track the desired velocities generated by motion planning. As far as the steering subsystem is concerned, the global terminal SMC is used to ensure the fast convergence of the steering tracking; as for the forward subsystem, a composite sliding mode manifold is successfully introduced thanks to the underactuated dynamics decoupling by Olfati transformation. The numerical simulation validates the effectiveness of proposed control approaches even in the presence of sophisticated disturbance and physical limitations.