Tracking control of snake-like robot with rotational elastic actuators

The long-term goal of this study is to realize a locomotion control for snake-like robots on various environments. Key points for robots to adapt to various environments are measurement of stress applied to robots, and to realize locomotion control utilizing the stress. The observation leads to utilize a spring because a spring twists by the applied stress and generates energy by being twisted. We suggest a rotational elastic actuator (REA) consisting of a motor and a spring, and have developed a snake-like robot installing this mechanism at each joint. However, an effective locomotion control of the snake-like robot with REAs has not realized yet. In this paper, a controller tracking a serpenoid curve formulated from snake´s kinematics is suggested based on a dynamic model with REAs. To realize such controller, the dynamic model of the snake-like robot with REAs is derived by the Projection Method. The derived dynamic model is linearized by an input-output linearization technique. A servo controller is also designed by utilizing the linearized system with its state space representation. A smooth locomotion of the snake-like robot with REAs tracking a serpenoid curve utilizing the designed servo controller is verified through numerical simulations.