Admittance Control using a Base Force/Torque Sensor.*

In this paper we investigate on the use of a base force/torque sensor for implementing position based impedance control (i.e. admittance control). By utilizing measurements of the contact force at the base of a robot manipulator, it is possible to perceive forces acting all along the robot's structure. This can be used for implementing a compliant motion control algorithm which is not limited to physical interaction at the end-effector only. We show that the use of a base force sensor instead of a sensor mounted on the end-effector poses certain limitations on the achievable closed loop dynamics. The stability and passivity properties are exemplified by an analysis for the one-degree-of-freedom case. The control performance in the multi-degrees-of-freedom case is verified by a simulation study of a Cartesian admittance controller.