SIMULTANEOUS CONTROL OF ROBOT MANIPULATOR IMPEDANCE AND GENERALIZED FORCE AND POSITION

Certain industrial tasks require forces to be applied to objects durin g task execution. Of these tasks, a subset of them may be completed su ccessfully with only crude control over contact force. An open-loop me thod of force control is proposed for these applications. This method utilizes the impedance control of Hogan to achieve open-loop control o ver generalized contact forces and position. The net result is simulta neous control of manipulator mechanical impedance and the generalized position and the force of the robot. An algorithm is proposed which de termines the manipulator generalized position imputs, the only signal available to an impedance controller, in order to generate prescribed generalized forces while in contact with fixed objects. A new approach to the establishment of the stability of impedance controls during ob ject contact is given, utilizing the theory of singularly perturbed dy namic systems. Experimental results on a two degree-of-freedom robot c onfirms the validity of the approach proposed here to control contact forces in an open-loop manner. Copyright (C) 1996 Elsevier Science Ltd