Non-Contact Impedance Control for Manipulators

Impedance control is one of the most effective control method for a manipulator in contact with its environment. In this method, however, the end-effector of the manipulator does not move until an external force is exerted. Therefore an impact force from the environment cannot be avoided. The present paper proposes a concept of a non-contact impedance control for a manipulator, which can regulate virtual impedance between the end-effector and external objects using visual information. First, a virtual force exerted from the object that is not contact with the manipulator is introduced. The virtual force is computed from the non-contact impedance and the motion of the object, so that the manipulator can respond the approaching object without any contact. Then the proposed method applies to an object avoidance problem and a contact task. Validity of the proposed method is verified through computer simulations. Finally, the proposed method is implemented using a direct-drive robot and a PSD camera system in the planar task space. Experimental results show that the non-contact impedance control is realized with a high sampling rate and a sufficient accuracy.