Synthetic Fiber Capstan Drives for Highly Efficient, Torque Controlled, Robotic Applications

This paper describes the design and performance of a synthetic ropeon sheavedrive system. This system uses synthetic ropesinstead of steel cables to achieve low weight and a compact form factor. We demonstrate how this system is capable of 28-Hz torque control bandwidth, 95% efficiency, and quiet operation, making it ideal for use on legged robotsand other dynamic physically interactive systems. Component geometry and tailored maintenance procedures are used to achieve high endurance. Endurancetests based on walking data predict that the ropeswill survive roughly 247,000 cycles when used on large (90 kg), fully actuated bipedalrobot systems. The drive systems have been incorporated into two novel bipedalrobots capable of three-dimensional unsupported walking. Robot data illustrate effective torque tracking and nearly silent operation. Finally, comparisons with alternative transmission designs illustrate the size, weight, and enduranceadvantages of using this type of synthetic ropedrive system.