Moving on underwater soft floor is a difficult task to mobile robots. Legged robots are suitable to move on soft and sandy surface. However, waterflow may easily turn the robot over, and many legged robots cannot recover from upside down posture. Sensors and actuators rich robot may find proper actions to recover. But they may suffer from frequent malfunctions in severe underwater environment.
We have designed a simple and strong mechanism to walk on underwater floor. The deign consists of legs at all side faces. These legs are driven by a central worm gear. The gear drives a bevel gear and a linkage at each leg, which generates pseudo leg movement. By choosing phases of legs as a solution of four-color problem (map coloring), all the gaits formed by landing legs drive the robot moving forward to the same direction. This ensures the robot to keep moving the same direction after rolling over by waterflow.