Pen-based force display for precision manipulation in virtual environments

We describe the structure of a force display recently implemented for precision manipulation of scaled or virtual environments. We discuss the advantages of direct-drive parallel manipulators over geared serial manipulators for human-robot interaction application and introduce the serial-parallel structure we chose for our robot which interfaces with the human operator either at the fingertip or at the tip of a freely held pen-like instrument. We derive the statics and the dynamics, and then introduce the optimization criteria that allowed us to choose the dimensional parameters for the force display. Finally we show some of the potential application for this device.