Elastic string are added on both sides of the robot snake to realize the function of biological tendons

In animals, coupled joint articulation by tendons over two or more joints is common and is an effective structure to save and transfer energy by connecting a joint with positive power and another joint with negative power. In undulatory swimming, the torque required on the middle of body is significantly greater than that of the front and posterior part. Robot are designed by adding motors to the joints to input internal torques for body deformation. The distribution of torques required for body deformation means that there is a large load on intermediate joint. Elastic string are attached to both sides of the robot snake to balance the load on each joint.

In experiment, the effect of string on balance moment is realized by adjusting the movement of tail joint. A small amplitude motion in phase with the middle joint moment is added to the tail joint. The load of the intermediate joint decreased in robot snake.