ADRC-Based Tube MPC Approach for Trajectory Tracking of Four-Mecanum-Wheel Mobile Vehicle

This article proposes a novel composite control approach based on an inner-outer-loop framework to tackle the trajectory tracking problem for the four-mecanum-wheel mobile vehicle (FMWMV) in the presence of disturbances and system constraints. To tackle the constraints of FMWMV, the modified tube model predictive control (MPC) is utilized in the outer loop. The constraints are implicitly satisfied by solving the optimal control problem. The disturbance rejection ability of MPC is enhanced with the help of the inner loop controller. The size of the tube can be contracted by adjusting the parameters of the inner loop controller rather than being determined by the upper bound of disturbance. It makes FMWMV more close to the optimal trajectory. To counteract the influence of disturbance, the variable-gain active disturbance rejection control method is adopted in the inner loop. The error-based variable gains are incorporated both in the tracking differentiator (TD) and the extended state observer (ESO) to improve the transient and steady-state performance. The ranges of variable-gain functions are explicitly given for the TD and ESO, respectively. Finally, the effectiveness of the proposed control approach is validated through the simulation and experimental results.