Rotary Piezo Micro Motor

New Scale Technologies announced that it has developed new rotary piezoelectric motors using its patented SQUIGGLE micro motor technology. The custom rotary micro motors were developed for NASA Jet Propulsion Laboratory's ''Cobra'' fiber positioner, part of the Wide-Field Multi Object Spectrometer (WFMOS) to be commissioned on the Subaru Telescope on Mauna Kea, Hawaii in 2013.

Working with JPL's design requirements, New Scale developed two custom miniature rotary motors optimized for high torque and precision. The two piezoelectric motors, measuring only 2.4 x 2.4 mm and 4.6 x 4.6 mm in size, offer better than 0.1 degree step resolution and twice the torque of similar-sized DC micromotors.

SQR custom rotary piezo motor performance

- Custom Model SQR-2.4 SQR-4.6
- Size 2.4 x 2.4 mm 4.6 x 4.6 mm
- Step Resolution 0.10° 0.06°
- Speed >=60 rpm >=60 rpm
- Stall Torque 0.6 mN-m 3.0 mN-m

Each Cobra fiber positioner comprises one SQR-2.4 and one SQR-4.6 rotary piezo motor in a two-stage theta-phi configuration. Overall positioner dimensions are 8 mm diameter x 85 mm length. The WFMOS will have 2400 Cobra positioners in a close-packed hex array pattern on 8-mm centers.

Additional applications envisioned
In addition to the fiber positioning application for spectrometry, New Scale can design and integrate custom rotary piezoelectric motors for use anywhere that miniature rotary motors are used, including electronic locks, micro pumps, and scanning systems. New Scale rotary piezo motorscan be optimized for other design parameters including smaller size or higher speeds.

The SQUIGGLE motor design consists of piezoelectric plates that are activated to generate ultrasonic vibrations in a hollow metal stator tube. These vibrations directly drive a rotor in the tube using friction as the driving force. Eliminating the need for gear reduction mechanisms, this design enables direct-drive rotary motors with very small size, high peak torque at sustained speeds, high holding torque, and high precision without windup or backlash.

About the Cobra fiber positioner
The Cobra is a two-degree-of-freedom mechanism that can position an optical fiber in the prime focus of the telescope to a precision of 5 µm. The theta-phi style positioner contains two custom rotary SQUIGGLE motors with one offset from the other, enabling the optic fiber to be placed anywhere in a 9.5 mm diameter patrol region. The patrol diameter of the actuator is large enough to obtain 100% sky coverage with the close-packed hex array pattern of 2400 positioners on 8-mm centers. The Cobra, named because it resembles a snake ready to strike, allows red shift observations of 2400 cosmological targets simultaneously. It allows, for the first time, large scale Galactic Archeology and Dark Energy surveys, helping to unlock the secrets of the universe. For more information, refer to IEEE Aerospace Conference paper #1185, Version 5; ''Cobra - a Two-Degree of Freedom Fiber Optic Positioning Mechanism,'' by C. Fisher, D. Braun and J. Kaluzny of JPL and T. Haran of New Scale Technologies, March 2009, ISBN 978-1-4244-2622-5/09 - posted with permission the New Scale Technologies website. Download at www.newscaletech.com/app__notes/Cobra-JPL-article.html