The Cobotic Hand Controller: Design, Control and Performance of a Novel Haptic Display

Abstract

The design, control and performance of the Cobotic Hand Controller, a novel, six-degree-of-freedom, admittance controlled haptic display is examined. A highly geared admittance architecture is often used to render high impedances with reasonable sized actuators for a haptic display. The Cobotic Hand Controller is an extremely faithful realization of an admittance display, since it is capable of obtaining an infinite gear ratio and can render infinite impedances (up to its own structural stiffness). The incorporation of continuously variable transmissions utilizing hardened steel elements in dry-friction rolling contact provide the Cobotic Hand Controller with high bandwidth, low power requirements, and an extremely wide stable dynamic range. Here, an admittance based control algorithm for powered cobots, a novel solution to the actuation redundancy of this device, and a heuristic to avoid slip in the transmissions are described. The performance of the Cobotic Hand Controller is measured in terms of dynamic range.