Piezoelectric direct drive three axis high precision gimbal (Hierax)

This paper presents a novel three axis gimbal (Hierax) actuated by linear piezoelectric motors. The Hierax will be used as part of a ground-based tracking system which compensates for innate unmanned aerial vehicle (UAV) sensor error and enables UAVs to land completely and reliably autonomously. The use of the piezoelectric motors gives the Hierax characteristics and performance unattainable with traditional electromagnetic motors such as no backlash or servo dither, extremely quick response, high torque at low speeds, minimal EMI/RFI noise and the ability to hold a position without heat generation or power as long as the external torque on the axis does not exceed the holding torque of the piezoelectric motor. The linear motion from the linear piezoelectric motors is converted into rotary motion by driving a disk around an axis of rotation. Linear motors are used because the output torque can be easily tailored to the application by either increasing the number of motors or the moment arm. The Hierax is a three axis man portable gimbal with travel of 30, 90 and 360 (continuous) degrees in the respective axes. The Hierax has achieved angular accelerations of 15,498, 19,151 and 11,159 degs/s2 and angular velocities of 554, 827 and 62 degs/s, respectively.