The design, fabrication, and characterization of millimeter scale motors for miniature direct drive robots

This paper reports on research into miniature, direct drive, high force/torque motors to support insect-sized mobile robotic platforms. The primary focus is on scalable motors based on piezoelectric transducers. The contributions of this work include: (1) the design, analysis, and characterization of a miniature mode conversion rotary ultrasonic motor based on a piezoelectric stack transducer; this produced a static torque density of 0.37 Nm/kg, (2) a millimeter scale linear piezometer, constructed with a parallel arrangement of annular stressed unimorph piezoelectric transducers and passive latches, exhibited 0.23 N of blocked force, and (3) simulation data is presented that compares these motor concepts to commercial systems in the context of scalability. Results suggest that smaller versions of the rotary ultrasonic motor would possess a static torque density seven times that of a commercial 3-mm electromagnetic system. This technology shows promise for driving the platform.