A HIGH TORQUE TO WEIGHT RATIO ROBOT ACTUATOR

A light-weight, high-torque actuator with accurate torque control capa bility is described. The actuator uses a small hydrostatic transmissio n to achieve the advantage of large gear reduction from a high speed D C motor, and retains accurate joint torque sensing and control capabil ities with no backlash. A disadvantage of the actuator is that is intr oduces extra dynamics which must be accounted for in robot control sys tems. It is shown that state feedback enables closed loop control of j oint torque, with full back drivability, through an effective gear rat io of 485:1 for the experimental system. The actuator can therefore be used for both position control and output force control, which is ess ential for modern robot control algorithms. A mathematical model of th e system is presented in this paper along with experimental results.