Effects of the Bi-Articular Gastrocnemius Muscle of Human on the Jump Movement of the Model

Robots have one motor at each joint, but animals have bi-articular muscle driving two joints simultaneously. The bi-articular muscle characterizes animals and is predicted to have special functions. To clarify these functions, a simple human model was emploved. The model was a Jumping Jack without the guide rail. Gastrocnemius, the bi-articular muscle in the lower leg, was modeled simply by wire. The clarified bi-articular muscle functions will contribute to development of simple controlled robots. Model experiments and computer simulations were executed with and without the wire. Ground reaction force and jump movement were analyzed both in the model experiments and computer simulations. In addition, energy transformation was analyzed in computer simulations. The wire simulating the bi-articular muscle (1) controlled the direction of the ground reaction force, (2) inhibited transformation into rotational energy from the potential energy of the spring, and (3) stabilized airborne movement.