Non-Inductive Actuation Mechanisms to Reduce Interference with Magnetometer-Based Navigation

A non-inductive rotary actuator system is proposed to move canards in miniature guided munitions without magnetic interference. This new actuator is a piezoelectric ceramic motor that uses ultrasonic vibrations to directly rotate a shaft with high torque and speed and without gears or other mechanical linkages. Multiple vibrating piezoelectric beams generate tangential forces on the rotating shaft. The forces from the individual piezo elements are optimized in frequency, amplitude and preload and driven by advanced electronic circuits which maximize power density and efficiency. The tangential forces from individual piezo elements are designed to add together and produce 0.2 N-m of torque, 0.13 m/sec speed, using approximately 30 W and fitting in a volume of one inch cubed The system is designed to be simple, low mass and strong enough withstand high launch accelerations. The piezoelectric devices operate directly from less than 24 volts which eliminates the need for a voltage boost and associated inductors. Two-phase ultrasonic drive signals are generated using high-efficiency full-bridge switching integrated circuits. The drive and control electronics, including the driver IC’s, position sensor, and microprocessor fit inside the actuator volume.