Langevin Flexural Piezoelectric Motor Based on Stator Precessional Motion

In this work, a new piezoelectric motor is described wherein the stator is a bolted Langevin structure excited in flexural vibration. Two piezoelectric disks are sandwiched by two cylindrical inertial masses and their metallization is divided in four sectors. By applying suitable electrical signals to the four sectors, a traveling rotating thickness deformation is excited, and if the structure is excited at its natural flexural frequency, a well-sustained traveling rotating flexural deformation takes place in the Langevin vibrator. The bolt exceeds in length the inertial masses of the Langevin vibrator, acting as a central axle animated by a wide precessional motion. The rotor is a cylindrical permanent magnet pressed in contact with the top surface of the axle by means of a little nylon axle. A slipping takes place between the stator and the rotor and a torque is generated. The motor is able to give relatively high speed (≈2800 rpm) and torque (15 N m). The very robust structure of the stator makes this motor easy scalable in size and suitable for high power applications. A simple mathematical model to design the working frequency of the stator is described; theoretical results and experimental measurements were compared.