Study on Obstacle Avoidance Strategy Using Multiple Ultrasonic Sensors for Spherical Underwater Robots

During marine missions, autonomous underwater robots (AUVs) are susceptible to external disturbances, such as obstacles and ocean currents, which can easily cause mission failure or disconnection. Therefore, it is an extremely challenging task to ensure that AUVs have autonomous obstacle avoidance in the presence of multiple stationary and moving obstacles. This article focuses on developing an obstacle avoidance control strategy for the spherical underwater robot (SUR) we designed based on the ultrasonic sensor array, which considers the robot’s kinematic and dynamic model and ultrasonic sensor characteristics, simultaneously. The control law combines the guidance law and Lyapunov theory to realize real-time following and obstacle avoidance. In addition, a series of simulation and real-environment experiments are performed to validate the proposed control strategy for detecting unknown environments. Furthermore, some comparative experiments are performed and discussed to evaluate the overall performance of the control strategy in terms of the obstacle velocity, total time, and tracking error. The experimental results demonstrate the effectiveness and practicability of the proposed control strategy in underwater environment.