Hybrid position/force control, velocity projection, and passivity

Hybrid position/force control is an approach to robot manipulator control to deal with tasks involving mechanical interaction between the robot and its environment. It consists in controlling simultaneously some position parameters, and some interaction force parameters. The main challenge associated with this approach is to guarantee the controlled system stability for any choice of the position- and force-controlled parameters. This is all the more difficult as the robot interacts dynamically with an environment whose dynamics are usually poorly known. In this paper, we propose solutions regarding the position control loop. They are based on passivity theory.