An electromechanical arm model controlled by artificial muscles

An effective and rapid response of muscle contraction and relaxation is crucial for performing appropriate body gaits, including movements of the arms and legs. Any deformation in the muscles can disrupt gait stability, making muscle movement difficult. The arm, consisting of the radius, ulna, and humerus, can be modeled as mechanically jointed pendulums, with tensions from the arm muscles varying during contraction and relaxation. In a static state, the muscles maintain constant tension and length, even when external gravitational force is applied to the hand. This study presents a system in which a pair of jointed pendulums is driven by artificial muscles, represented by flexible ropes wound around the edge of an electronic motor's wheel. Muscle movement is simulated through the adjustment of the length of the flexible ropes attached to the motor. Switching between the clockwise and counterclockwise rotation of the motor modifies the length of the flexible ropes, thereby altering the intrinsic tensions to control arm movements. Electrical signals from a simple neural circuit are used to control the rotation of the electronic motor, enabling the regulation of muscle movement in the arm model by adjustable flexible ropes. The stability criterion for the electromechanical arm is derived, and the interactions among the neural circuit, electronic motor, and jointed pendulums are examined in detail. The results and proposed scheme can contribute to the design of controllable artificial arms, providing potential assistance to disabled arms by incorporating auxiliary artificial muscles.