An intuitive and comprehensive two-load model for Series Elastic Actuators

Actuation systems featuring inherent series compliance have over time entered more and more the focus of robotic research. The advantages are good force/torque controllability, an increased robustness against unforeseen shocks and other disturbances, and the possibility to store elastic energy. In order to fully enable Series Elastic Actuators (SEAs), a thorough understanding of the actuators internal dynamics is indispensable. Till today the vast majority of existing models for SEAs merge the moving masses within the actuator into a single mass. The two sides of the actuator are either both fixed or at most one is connected to a free moving mass. Hence this paper proposes a model in which all internal masses are kept separated and moving loads are connected to each end of the actuator. It is generalised to cover SEA implementations with the most common drive trains and arbitrary spring placement.