A Haptic Knob with a Hybrid Ultrasonic Motor and Powder Clutch Actuator

In haptics, the forces to be displayed vary widely in terms of magnitude and bandwidth. A single actuator can hardly comply with these requirements. It has thus been proposed to combine electrical motors and passive devices in a hybrid actuator to cover a larger range of displayable forces. In this paper, different hybrid actuators are reviewed and a novel hybrid USM/clutch actuator is presented. It has been developed for haptic applications and its principle is adaptable to MR compatible robots. The complementary dynamic properties of the USM, which is a velocity source, and a torque controlled clutch, lead to a simple mechanism offering more control modes and lower power consumption than previous hybrid actuators. A haptic knob is designed and realized to test this approach. It includes a differential gear that allows the powder brake to mimic the behavior of a clutch. Haptic effects such as springs or walls have been implemented and successfully tested on the prototype.