Safe target-tracking algorithm with obstacle avoidance for unicycle mobile robots

A safe target-tracking and obstacle avoidance control system for unicycle mobile robots is proposed in this paper. The control system consists of two nested loops. Target-tracking law in the inner loop controls the robot to track the predetermined target by reducing the posture error to zero and its stability is analyzed by using Lyapunov function method. The tracking law also takes into account the velocity limit of the robot and tracking time efficiency. When any obstacle is detected, the external loop provides a modification on the target position based on the impedance control concept and the robot-obstacle distance measured by eight ultrasonic sensors. Simulation studies and experiments show that the tracking law is more general and practical than other methods and the control system can prevent the robot from obstacle collision.