Uncertain moving obstacles avoiding method in 3D arbitrary path planning for a spherical underwater robot

In order to avoid the risk of obstacles collision during the spherical underwater robot (SUR) move to target points in 3D arbitrary path planning, an underwater obstacle avoiding method was studied. Considering the uncertainty of the movement of obstacles in the actual environment, we present an uncertain moving obstacle avoiding method based on the improved velocity obstacle method. In addition, to reduce the distance and time of obstacle avoidance, the concept of the time of obstacle avoiding was designed. First, the size and velocity information of obstacles are obtained through the camera, which can provide an accurate decision basis for obstacles avoidance in the next step. Then, according to the time when the robot collides with the obstacle, the time of start and end of the obstacle avoidance is determined. The movement direction and velocity of the robot are obtained based on the improved velocity obstacle method and the movement characteristics of SUR. Finally, a detailed 3D arbitrary path planning analysis based on an improved ant colony algorithm was conducted. A series of experiments were carried out in the pool that validates the proposed methods are also presented. •Present an uncertain moving obstacle avoiding method based on the improved velocity obstacle method.•Determining the time of start and end the obstacle avoidance.•Design a 3D arbitrary path planning system in complex environment for fourth-generation Spherical Underwater Robot (SUR IV).•Establish a stability system based on PID control to realize the SUR IV anti-interference motion.