Multi-DOF model-based force control for telerobotic applications

For a wide range of telerobotic applications, the slave device needs to be a large, powerful, industrial type robot in order to achieve the desired tasks. Due to the large frictional forces within the gearing of such robots, a force-feedback controller is necessary to precisely control the forces the robot applies when manipulating its environment. This paper proves passivity, and therefore guarantees stability, of a model-based force controller in one degree of freedom (DOF) when subject to viscous and Coulomb friction. The controller is then expanded to muli-DOF systems. In addition to maintaining the robustness of the 1-DOF controller, the multi-DOF controller provides additional freedom to design the closed loop dynamics of the robot. This freedom allows the control designer the ability to shape and optimize how the system feels from a users perspective. The robustness of the controller is experimentally validated and the freedom to modify the closed loop dynamics is explored using a 2-DOF device.