Time‐optimal trajectory planning of a redundantly actuated planar parallel robot driven with series elastic actuators

Abstract

This paper addresses the time‐optimal trajectory planning of a redundantly actuated parallel robot driven by series elastic actuators. Here, the actuation redundancy allows prestressing the elastic components of the drives and enables more degrees of freedom in the trajectory planning. To this end, a time‐optimal control problem is formulated that takes also the physical constraints into account, that is actuation torques, task and joint space limits and self‐collisions. A flatness‐based parametrization of the dynamics is used in the nonlinear optimization problem and solved with the multiple shooting technique within the CasADi framework using IPOPT as a solver. Results are shown and compared to time‐optimal trajectories, both redundantly and non‐redundantly actuated with rigid drives.