Optimal muscular arrangement using genetic algorithm for musculoskeletal potential method with muscle viscosity

Muscle contractions (or equivalent mechanical ele-ments) are responsible for joint movement in systems with musculoskeletal structure. Because muscles can only transmit force in the tensile direction in such sys-tems, the internal force exists between the muscles. By utilizing the potential field generated by the internal force, the musculoskeletal potential method makes it possible to control the position without complex real-time calculations or sensory feedback by entering step-inputs of the balanced internal force at the target pos-ture. However, the conditions of convergence to the target posture strongly depend on muscular arrange-ment. Previous studies have elucidated the mathemati-cal conditions of the muscular arrangement; however, they provide sufficient conditions that must be satis-fied by the muscular arrangement to converge to the target posture, which do not necessarily lead to optimal muscular arrangement conditions. This study proposes a method to determine the optimal muscular arrangement of a two-joint six-muscle system, wherein muscle viscosity is considered, that uses a genetic algorithm and an evaluation function considering the motion response time. The effect of the obtained muscular arrangement is verified in a simulation.