CPG-based Motion Planning of Hybrid Underwater Hexapod Robot for Wall Climbing and Transition

Most of the existing underwater legged robots are capable of moving on small-angled slopes, but few of them can climb the large-angled slope or transition from one plane to another, such as transition from horizontal plane to vertical plane. In this paper, we propose a motion planning method of a hybrid underwater hexapod robot (HUHR) driven by six C-shape legs and eight thrusters. By analyzing the relationship between rotation and displacement of the hip joint, we establish a single-leg kinematic model. By analyzing the force at the touchpoint, we propose a locomotion mechanism to ensure no slip of the C-shape leg. Based on the central pattern generator (CPG) and tripod gait, we design an aperiodic mapping between the oscillator outputs and the desired rotation angles of hip joints. Overall, a gait planning and control method for our robot is proposed to realize continuous legged locomotion from one plane to another, including directional climbing and transition between them. Furthermore, the effectiveness of the proposed method has been verified on HUHR.