Model Predictive Control Based Trajectory Tracking for 4WS4WD Mobile Robot

Recently, the four-wheel-steering and four-wheel- drive (4WS4WD) mobile robots have been focused on due to their flexibility and high load capacity. The traditional research for the motion control of the robots mainly realizes the smooth switching control of several fixed motion modes, which limits the platform motion performance. Considering the robots’ motion control system is highly coupled, over-actuated and nonlinear, solving the nonlinear control problem and considering the relevant constraints and coupling requirements is necessary to take full advantage of the platform’s performance. The paper uses the model predictive control (MPC) method to realize the robot’s trajectory tracking control. First, the robots build a linear error model through kinematic analysis and then obtain the state space equation of the prediction model. Next, design the objective function with multiple constraints to construct an optimization problem, and convert the optimization problem into a standard quadratic programming (QP) problem to solve. Meanwhile, receding optimization and feedback control are used for real-time optimization and correction. The simulation test indicates that the algorithm can realize the robots to track the desired trajectory stably, smoothly, and accurately.