Abstract
The robotic hand is still no match for the human hand on many skills. Manipulation of hand tools, which usually requires sophisticated finger movements and fine controls, not only poses a clear technical challenge but also carries a great potential for enabling the robot to assist humans in a wide range of tasks accomplishable using tools. This paper takes a first step to investigate how a robotic arm mounts a rigidly attached screwdriver onto a screw (pre-mounted in a tapped hole) and then tightens it using the tool. Mounting begins with sliding the screwdriver tip on the screw head along preplanned paths to search for the drive and follows with rotating the screwdriver to drop the tip into the drive. Prevention of a slip off the screw head is achieved via impedance control to install a “virtual fence” along its boundary. Turning of the screw is conducted via hybrid position/admittance control based on modeling the reaction force between the screw and the substrate. Simulation results with a KUKA Arm demonstrate the smoothness of the entire action.