Mechanical diode based, high-torque piezoelectric rotary motor

A compact high-torque rotary motor was developed for use in large-displacement structural shape control applications. The main principle underlying its operation is rectification and accumulation of small resonant displacements of piezoelectric bimorphs using roller clutches as mechanical diodes. On the driving half of each cycle, the forward motion of the bimorph is converted to rotation of the shaft when the hub torque exceeds that of the load. On the recovery half of each cycle, a second, fixed, roller clutch prevents the load from backdriving the shaft. This approach substantially increased the output mechanical power relative to that of previous inchworm-type motor designs. Experiments to date have demonstrated a stall torque of about 0.6 N-m, a no-load speed of about 720 RPM, and peak power output greater than 5 W. The use of commercial roller clutches, piezoelectric bimorphs, single frequency drive signals also resulted in a simpler, cheaper design.