CLF-CBF Based Quadratic Programs for Safe Motion Control of Nonholonomic Mobile Robots in Presence of Moving Obstacles

摘要

A control Lyapunov function and control barrier function-based quadratic program (CLF-CBF-QP) is proposed to safely navigate a nonholonomic mobile robot (NMR) facing a moving obstacle. The conventional CLF-CBF-QP realizes safety and stability conditions using distance-based CLF and CBF without considering the practical limitations of the steering angle. Hence, the NMR may execute undesirable avoidance maneuvers such as u-turns. This work introduces a safety condition on the steering angle to maintain efficient, smooth avoidance maneuvers. The safe steering condition keeps the NMR steering angle within a predefined envelope of the reference steering angle. Moreover, one can improve the response time of the control system by enforcing exponential decay rates on the CLF and CBF. However, fixed decay rates lead to aggressive maneuvers around moving obstacles, where the CLF and CBF may produce conflicting conditions. Hence, this work proposes to optimize the decay rates of the CBF and CLF in real-time to improve the NMR performance during obstacle avoidance maneuvers. Lastly, the effectiveness of the proposed control method is verified by simulating two case studies where an NMR i) overtakes and ii) avoids head-on collision with a moving obstacle.