Collision avoidance for nonholonomic mobile robots among unpredictable dynamic obstacles including humans

In many service applications, mobile robots need to share their work areas with obstacles. Avoiding collisions is a fundamental requirement for these robots. In this paper a novel collision avoidance system is developed for avoiding unpredictable dynamic obstacles, including humans. The collision avoidance algorithm is based on the virtual force field (VFF) concept. The velocities of the obstacles are used in addition to their positions to improve the avoidance performance for dynamic obstacles. Unlike prior algorithms, the proposed VFF is designed to be continuous to diminish both path oscillations and the time cost for reaching the goal. To further reduce the time cost, a new virtual force (termed the detour force) is introduced. The detour force also solves the challenging avoidance problem that occurs when the centers of the robot, human/obstacle and goal are collinear; and the human/obstacle and robot are moving towards each other. In simulations and experiments with a maximum approach velocity of 1.7 m/s, the avoidance system with the new VFF algorithm generates collision-free paths with less oscillation and lower time cost.