Time-Energy Optimal Trajectory Planning for Variable Stiffness Actuated Robot

A variable stiffness actuator is inspired by the human motor control and is the most popular actuator used to exploit the human performance and human-like motion. However, these actuators are typically highly non-linear and redundant not only in their kinematics but also in their dynamics due to their capability to modulate their stiffness and positions simultaneously. It is not trivial to generate the trajectory for a strongly non-linear and redundant dynamic system equipped with variable stiffness actuators. In this paper, a trajectory planning method for a variable stiffness actuated robot via a time-energy optimal control policy is proposed. The simulation studies demonstrate the effectiveness of the trajectory planning method through the case studies of a two degree of freedom variable stiffness actuated robot. Furthermore, the results show that the proposed method could be able to generate the motion which is similar to the human arm motion strategy.