Blending of Series-Parallel Compliant Actuation With Field Weakening Control for Explosive Motion Generation

In this work, we investigate and validate two methods that can extend the explosive motion capabilities of series elastic actuated robots during standing jumps. First, field weakening control is exploited on multiple joints of a monoped to boost their peak velocities. However, field weakening operation reduces actuation torque capacity at those velocities, due to consuming current reserves. To address this torque reduction, we leverage energy-efficient parallel elastic actuators, in biarticulated knee-ankle and monoarticulated knee configuration. The proposed concept therefore combines the torque and inter-joint power transfer benefits of parallel and biarticulated articulation with the velocity increase permitted by field weakening to amplify the explosive power output in a monoped robot prototype. A substantial performance increase of up to 54% in jump height is achieved after experimentally tuning the motion for each configuration. This validates the efficacy of the approach for improving the explosive capabilities of series elastic actuated robots.