Current research has focused on developing robots that can imitate the musculoskeletal structure of human body to achieve skillful movements similar to those of a human. Several studies have investigated the end-point trajectory of musculoskeletal systems, but a sensor is essential for trajectory tracking. The previously proposed muscular internal force feedforward control method achieves point-to-point convergence to a desired position without any sensor; however, it lacks explicit control over the specific end-point trajectory from the initial to the desired position. Given that the end-point trajectory depends on the shape of the potential field generated by the control input, the trajectory sometimes takes a detour depending on how the desired position is set. To resolve this limitation, in this study, a novel shaping method is proposed for the end-point trajectory of musculoskeletal systems using the muscle redundancy. The end-point trajectory is shaped by optimizing a control input that cannot be uniquely determined due to the muscle redundancy based on the objective function of joint torques. As an advantage in the proposed method, the end-point trajectory can be shaped without sensors. Furthermore, the control input can be prevented from saturating the output limit by formulating the problem as a constrained minimization problem. The effectiveness of the proposed method is presented using simulation results. The proposed method definitely converges at the desired position without depending on the shaping result of the end-point trajectory because the target is a musculoskeletal system with muscular arrangements that converge to the desired position.
Matsutani et al. (Fri,) studied this question.