Experimental evaluation of the importance of compliance for robotic impact control

We present experimental results for impact control of a 2DOF DD manipulator against a stiff and compliant environment. The manipulator is commanded to approach the stiff environment at a specified velocity, and, once in contact with it, to exert a specified force on it. We present a simple understanding of the three stages of impact control, the pre-contact stage, the impact stage and the post contact stage; we adopt such a basic approach due to the ambiguous nature of results presented in the literature. Besides, in doing so, we take into cognizance the state-of-the art in robotic hardware, which have important implications in any implementation of impact control strategies. The emphasis of the paper is on experimental implementation; a clear cut distinction between what works and what does not. Our results indicate that for very stiff environments, stable impact control may be achieved at low velocities only, and that for a compliant system, there is a trade-off between approach velocity, compliance, sampling time and the bandwidth of the robotic system.<>