Conceptual Design of a Variable Stiffness Mechanism in a Humanoid Ankle using Parallel Redundant Actuation
In IEEE-RAS International Conference on Humanoid Robots, (Humanoids-2018), 06.11.-09.11.2018, IEEE, 2018.
Future robots will rely more than today on high precision, better energy efﬁciency and safe handling (e.g. human-machine interaction). An inevitable step in the development of new robots is therefore the improvement of existing mechanisms, since better sensors and algorithms do not satisfy the demands alone. During the last three decades, Parallel Redundant Mechanisms (PRM) came more into the focus of research,astheyareadvantageousintermsofsingularityavoidance, fast movements and energy efﬁciency. Subsequently, yet another technology - the Variable Impedance Actuator (VIA) emergedwhichproposestochangeitsinherentstiffnessallowing an adaptation to its environment and to handle for example dynamic movements or shock absorptions. This work aims to create a new mechanism where a stiffness and position control for 2 degrees of freedom (DOF) is achieved by 3 actuators with ﬂexible elements. It is thus a combination of the PRM and VIA, while taking advantage of both technologies but asking for a more sophisticated mathematical description. Practical implementation is intended for a humanoid ankle mechanism. Kinetostatic and stiffness models are derived and incorporated into the simulation of the mechanism. The simulations show thatimprovementsintermsofsingularityremovalanddexterity are achieved. Furthermore, the adaptation of human like gait performances is presented.