MOTION CONTROL & LINEAR MOTION FEATURE Operating under flight conditions
Nanomotion’s autofocussing stage, which has been designed to position an optronic device to within 2.5 microns under ‘flight-condition’ vibration levels of more than
12g, demonstrates many of the advantages that the company’s piezo-ceramic motor technology can offer. Here Jon Howard, general manager for UK distributor Heason Technology, covers some of the plus-points the application conveys
D
eveloped by Nanomotion, the autofocussing stage is capable of
directly driving a lens system with a mass of 25 to 35g to a precise location over a travel range of 20mm, with a positioning resolution of 0.25 microns – with the need to position rapidly and repeatably hold exact position without drift. All this whilst subjected to shock loading of 35 to 45g, temperature variations from -40˚C to +50˚C and the fast changing aircraft orientation. The assembly was used to replace a
rotary DC motor and lead screw, which weighed more, was larger, and could not handle the vibration of the aircraft. So, the new assembly uses two Nanomotion Edge 4X motors, each of which produces 1.2N force but only weighs 2g. The stage mechanics fit into a footprint of less than 65 x 45mm and, including a 0.25 micron linear encoder for servo feedback and drive electronics, the total mass is less than 50g. When it comes to airborne equipment
and optronic applications in general, minimal SWaP (Size, Weight, and Power) is essential. Nanomotion’s patented ultrasonic standing wave piezo motors provide the highest power density (force per volume occupied) over other motor technologies such as DC motors, stepper motors and solenoids. Power- to-size ratio is clearly key in avionics but can also be applied to ground based
typical in practically all defence and aero applications, it is also necessary for high throughput production machines. Whilst control algorithms for traditional servo motors can manipulate and help correct servo errors that larger mechanical systems can experience, overall mass is a key factor. Of benefit here, Nanomotion solutions do not have to rely upon elaborate motion control which has an impact on system costs and complexity. Optimal performance under
high shock conditions is also essential in applications such as weapon mounted systems or withstanding high g-forces (acceleration) for equipment used on missile platforms. The excellent shock resistance is probably less important in industrial use but the high resilience contributes to the reliability that all applications demand. In operation, once the autofocussing stage position has been set it needs to be held without drift over comparatively long time periods. The piezo ceramic stages actually hold position without consuming power which is a huge advantage here. A DC servo motor or a stepper motor would need to remain powered and, while consuming power, it heats up. This heat is ultimately
Another significant advantage for
piezo ceramic motors is non-magnetic operation. For avionics, traditional motors with magnetic fields operating near a compass could be a problem. The non-magnetic qualities also benefit applications in test equipment and research where proximity to sensors and highly sensitive measurement systems must
Nanomotion’s single-axis linear focussing stage - available from Heason Technology
be avoided. Proven Nanomotion solutions include X-Ray imaging, magnetometers, semiconductor production and test equipment, and use in synchrotron radiation facilities. Positioning stages for many of these processes often require extremely low or no magnetic materials to be present. The same motors are often required to be used in high-vacuum. The company designs and
“When it comes to airborne equipment and optronic applications in general, minimal SWaP (size, weight and power) is essential”
defence or commercial systems, as well as industrial and research applications where miniaturisation and precise motion is essential.
MOTION SOLUTIONS The autofocussing stage application calls for servomotor and motion mechanics that have a very high natural frequency and a fast response time. While vibration-resistant motion is
transmitted to the positioning structure and, due to thermal expansion, can change the actual position. This advantage can also be applied to energy critical applications – such as portable equipment where power may be sourced from a battery. Motion actuated systems requiring high stiffness, where leadscrews or gearboxes may have hysteresis or back-drive, can also gain benefit from this aspect of the technology.
/ DESIGNSOLUTIONS
manufactures linear and rotary stages with non-magnetic materials for bearings, encoders and stage mechanics for applications that are sensitive to magnetic fields and suit UHV environments. In addition, Nanomotion integrates its piezo ceramic technology into separate linear and rotary motors as well as complete positioning stages and motion modules, with a comprehensive range of drives and controllers also available, along with other ancillary components.
Heason Technology T: 01403 792300
www.heason.com
DESIGN SOLUTIONS | NOVEMBER 2015 23
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