On hard contact force control

In this paper, we consider hard contact force control law which shows good performance as well as enhanced stability and robustness. First, we consider hard contact transition such as hammering when the manipulator's approaching velocity is high or the environment is very stiff. In hard contact, phase transition can be divided into two definitely different phases, "pre-transition phase" and "transition phase". Here we define the "pre-transition phase" and propose a novel controller named as "suppression controller" which is not only stable but also simple to implement. Based on this result, we suggest a hard contact force control scheme which is named "hybrid suppression controller". The effectiveness of these approaches are verified via experiments using POSTECH 1 DOF DD arm.