Abstract: We proposed and developed a small bionic amphibious spherical robot system for tasks such as coastal environment monitoring and offshore autonomous search and rescue. Our third-generation bionic small amphibious spherical robots have many disadvantages, such as the lack of maneuverability and a small operating range. It is difficult to accomplish underwater autonomous motion control with these robots. Therefore, we proposed a fourth-generation amphibious spherical robot. However, the amphibious spherical robot developed in this project has a small and compact design, with limited sensors and external sensing options. This means that the robot has weak external information collection capabilities. We need to make the real time operation of the robot’s underwater motion control system more reliable. In this paper, we mainly used a fuzzy Proportional-Integral-Derivative (PID) control algorithm to design an underwater motion control system for a novel robot. Moreover, we compared PID with fuzzy PID control methods by carrying out experiments on heading and turning bow motions to verify that the fuzzy PID is more robust and exhibits good dynamic performance. We also carried out experiments on the three-dimensional (3D) motion control to validate the design of the underwater motion control system.

Key words: bionic amphibious spherical robot, fuzzy PID control, underwater motion control system, underwater three-dimensional motion, water-jet thruster