Trade-offs in the implementation of rigid and intrinsically compliant actuators in biorobotic applications

Actuators with intrinsic compliant elements are more and more being adopted in the biorobotics world. However, they also have a number of unfavorable characteristics such as bulkiness and a relatively high design complexity. Meanwhile, rigid actuators that are generally more compact and simple to implement are attractive for a number of applications. Yet, their inherent limitations in achieving a particular compliance characteristic might be in conflict with other biorobots design requirements. In this paper, we present experimental results to obtain more insights about the trade-offs in using three different types of single degree-of-freedom joint actuators, namely a geared rigid motor, a direct driven rigid motor and a variable stiffness actuator for biorobotic applications. Various aspects such as impact force behavior, stiffness range and manipulability as well as power consumption of the three actuator types are further investigated and compared in this paper.