Tension-Adaptive Body Shape Control of a Snake Robot for Rope Climbing by Current Feedback

In this paper, we propose a control method for the snake robot to adapt its body shape to the rope tension while climbing a rope, which is a flexible environment, in response to the joints’ current. The frictional force and the robot joint load vary depending on the amount of rope tension. A large tension may overload the robot joints, but a small tension may cause the robot slip and fall. Therefore, it is important for the robot to be able to change its body shape and adapt appropriately to the tension in rope climbing. In order to achieve this, we focused on the fact that joint loads and motor current values are related and devised a control system to change the robot’s body shape according to the motor current values. The concept is to change the robot’s body shape in order to obtain the maximum twisting angle at a constant current value. It should be noted that this control cannot guarantee that the robot will not slip and fall, but it can avoid excessive joint loading. The efficacy of this control for tension adaptation was validated through experiment.