Rotary micro drive eliminates jitter and magnetic fields -

Rotary micro drive eliminates jitter and magnetic fields

A prototype rotary piezoelectric micro drive system from New Scale Technologies, Inc., is designed to replace servo drives in UAVs (unmanned aerial vehicals) and micro-UAVs, micro assembly, and many other applications. Unlike servo drives, the new rotary drive has no measurable jitter, holds position without power, and generates no magnetic fields.

At 44 x 44 x 36 mm the prototype is also smaller than a servo drive, and offers higher position resolution. It exhibits excellent velocity, acceleration and repeatability characteristics. Measured performance includes:

  • Speed: 350 degrees/second
  • Acceleration: 3000 degrees/second2
  • Stall torque: 10 mN-m
  • No measurable jitter: reported position stable within one encoder count (0.0072 degrees)
  • Repeatability: +/- 1 encoder count everywhere (0.0072 degrees / 0.125 mradians)
  • Open loop step resolution: better than 0.5 encoder counts (0.0036 deg / 0.063 mrad)
  • Wobble in the arc-second range

This tiny rotating stage integrates several of New Scale's precision micro-motion technologies, including a high-torque direct-drive piezoelectric motor based on the patented SQUIGGLE motor, precision ball bearings with low run out and wobble, optical encoder with zero reference mark, and New Scale drive electronics and closed-loop control system. The device is PC-controlled using New Scale Pathway software for rapid evaluation and system development.

The use of the piezoelectric SQUIGGLE motor in the stage eliminates the problem of jitter. Ultrasonic vibrations of piezoelectric elements drive the motor, which locks into position and holds it even when power is off. In contrast, servo drives use an active control loop to continually seek a target position, resulting in unavoidable jitter and requiring continuous power use. Furthermore, the piezoelectric motor generates no magnetic fields when moving, eliminating a source of potential interference with sensitive instruments in the OEM system.

Applications include pan and tilt gimbals in UAVs and micro UAVs, laser stabilization systems, theta stages for micro assembly or optical inspection, and instrument testing and calibration.

Ongoing development will reduce module size 50% while integrating the breadboard electronics into the stage with New Scale's motor drive ASICs.

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