Additional Drive Circuitry for Piezoelectric Screw Motors

Modules of additional drive circuitry have been developed to enhance the functionality of a family of commercially available positioning motors (Picomotor™ or equivalent) that provide linear motion controllable, in principle, to within increments ≤30 nm. A motor of this type includes a piezoelectric actuator that turns a screw. Unlike traditional piezoelectrically actuated mechanisms, a motor of this type does not rely on the piezoelectric transducer to hold position: the screw does not turn except when the drive signal is applied to the actuator. In the original application for which these modules were developed, a clockwise-vs.-counterclockwise asymmetry in the pulses generated by a driver module that operates at a rate of ≤1 kHz made it impossible to reliably command the advertised ≤30-nm steps in either direction. In addition, the original application involved low-duty-cycle operation, which offered the opportunity to reduce cost by using a single driver module with multiplexing circuitry to drive several motors. There was an additional desire to modify the motors by integrating limit switches into them to provide calibration and position-reference signals.