Trajectory Tracking Control for Differential-Drive Mobile Robot by a Variable Parameter PID Controller

— Differential-drive mobile robots are most commonly used in industrial applications among wheeled mobile robots. Therefore, this paper presents a method to design a variable parameter PID controller for a differential-drive mobile robot following NURBS trajectory with a desired time-varying velocity. First, the robot's nonlinear kinematic error model is established, from which linearized around the desired angular velocity to obtain a linear error equation. Then, the variable parameter PID controller is designed to control the robot to follow the NURBS trajectory with minor error under the condition of time-varying velocity. The controller coefficients are selected through simulation and experiment to achieve the minor kinematic error. A platform robot is designed and built to demonstrate the proposed controller. Simulation and experimental results are presented to illustrate the effectiveness of the proposed controller. Therefore, it is possible to apply this result to control mobile robots in industrial applications.