Model predictive control-based tracking controller for hybrid-driven underwater legged robot

To address the tracking problem of the hybrid-driven underwater legged robot, a control strategy is proposed that decomposes the whole tracking control system into two subsystems: body-level and actuator-level. The body-level subsystem uses a central pattern generator (CPG)-based controller to plan suitable gaits to meet the required heading and the forward velocity, crucial for accurate tracking in underwater environments. The actuators-level subsystem employs a cooperative approach between the C-shaped legs and thrusters of the robot. To execute the intended gait while adhering to actuation constraints and the no-slip requirement, the torques of the legs are calculated by a model predictive control and feedback compensation (MPCF)-based controller. Simultaneously, the calculation of the thrusters concerns four aspects to keep the legs attached to the ground and maintain the stable locomotion of the robot. Simulations on the ROS-Gazebo platform verify the mobility of the robot and demonstrate the effectiveness of the proposed CPG-MPCF strategy.