Backstepping experimentally applied to an antagonistically driven finger with flexible tendons

The Hand Arm System of DLR is a complex mechatronic system built to approach the human in terms of dynamics and dexterity. Its fingers are antagonistically actuated by flexible tendons, resulting in a nonlinear flexible joint. The advantages of such a design are the high dynamics but more importantly the enhanced robustness. Nonlinear control methods have been developed in the community that are, at least in principle, applicable to such systems. However, because of the complexity of some methods, most works are focusing on simulations and do not consider the practical issues arising with hardware. Such issues are, for example, the need for derivatives or the use of large matrix inversions. In this paper, we adapt the backstepping method to the specific case of an antagonistic actuation. The modeling of the mechanism is followed by the design of the controller and the work is concluded by a set of experimental results on the hand of the Hand Arm System, the ”Awiwi hand”