Constraints and Model Predictive control of wheeled mobile robot in the presence of obstacles

This work considers the problem of formation control for a team of nonholonomic wheeled mobile robots in an obstacle environment. Virtual structure formation approach and APF method are obtained to determine the reference trajectories of the robots. The virtual structure formation control strategy is obtained here to compute each individual robot trajectory whereas the reference path of the virtual center of the formation is generated by artificial potential fields. Many control strategies are discussed here. Next, a new control algorithm based on model predictive control and the nonlinear dynamics of the system is presented here. The control algorithm is applied to the nonlinear system using three different controllers traditional Model Predictive Control (MPC), Laguerre based MPC and nonlinear MPC. Using model predictive control, the dynamic model of the wheeled mobile robot is used to calculate the torques required to track the trajectory. The optimal solution of both formation and tracking problems is derived using a proposed control law. The control law could use the information from other robots to maintain the formation shape which can be guaranteed by using a new cost function. Simulations were accomplished using Matlab. The results demonstrate that the proposed controllers can achieve the trajectory tracking and formation keeping objectives also in the present of disturbance.