Motors and Drives
Most of its Squiggle products are micro linear motors, but it recently supplied a custom rotary actuator for the NASA Jet Propulsion Laboratory’s Cobra fibre positioner, which is part of the Wide-Field Multi Object Spectrometer (WFMOS) that is due to be commissioned on the Subaru Telescope on Mauna Kea, Hawaii, in 2013.
compact dimensions, a high peak torque at sustained speeds, high holding torque, and high precision without wind-up or backlash. In the Cobra application there was a restriction on motor diameter but length was not as important. For some applications, however, space in the axial direction is limited, which calls for ‘flat’ motors. Faulhaber offers an extensive range of miniature and micro-motors and accessories, and has recently extended its portfolio of flat DC micro- motors. Supplementing the existing range of precious metal commutated DC micro-motors, the two new micro-motor Series 15… and 26… are more powerful, with electronic commutation based on three digital Hall-effect sensors. With nominal voltages of 6 or 12V, the 15mm diameter flat motors provide a continuous output torque of 0.6mNm, while the 26mm diameter models provide 3.8mNm. In addition, gearmotor versions of these offer output torques of up to 30 or 100mNm (Fig. 2). According to Faulhaber, the motors are free of cogging
Fig. 2. Faulhaber has extended its portfolio of flat DC micro-motors to include 15 mm and 26 mm diameter units with continuous output torques of 0.6 mNm and 3.8 mNm.
Working to JPL’s specifications, New Scale developed two custom miniature rotary motors that were optimised for high torque and precision. These two piezoelectric motors, measuring only 2.4 x 2.4mm and 4.6 x 4.6mm in size, offer a resolution of better than 0.1 degree step, and torque levels that are said to be twice those of DC micro-motors of a similar size (stall torques are 0.6mNm for the SQR-2.4 and 3.0 mNm for the SQR-4.6). Each Cobra fibre positioner comprises one SQR-2.4 and one SQR-4.6 rotary piezo motor in a two-stage theta-phi configuration. Overall dimensions are 8mm diameter x 85mm long (Fig. 1). The WFMOS will have a total of 2400 Cobra positioners in a hexagonal array with 8mm between centres. New Scale says that eliminating the need for gear reduction mechanisms means direct-drive rotary motors can be built with characteristics such as very
and deliver smooth motion, high efficiency and long operational lifetimes. Gearmotor versions are available with reduction ratios of 6:1 to 324:1 (Series 15…) or 8:1 to 1257:1 (Series 26…) within the same overall length. Both motor series can be used in conjunction with the Faulhaber Series SC 1801S speed controller, though the Series 26… motors are optionally available with an integrated speed controller. Applications for these durable, flat DC micro-motors include portable devices and continuous-duty equipment such as pumps and fans. Other recent developments from Faulhaber include the Series AES-4096 high-resolution, single-turn absolute encoders that can used with the company’s high-power, 2mm diameter, BX4 Series four-pole brushless DC servomotors for precision commutation and optimised position and speed control down to 20 RPM. Incorporating innovative single- chip magnetic encoder technology, the encoders help to reduce torque ripple, improve motor efficiency and reduce electrical noise. In addition, Faulhaber’s Series IE3 incremental encoders
are now available in higher resolutions. Also benefiting from the single-chip magnetic encoder technology, these devices are now offered with resolutions of 32, 64, 128, 256, 512, and 1024 pulses per channel per rotation. Other resolutions are available on request, and there is an optional line driver that includes differential signal outputs. The Series IE3 incremental encoders can be mounted on Faulhaber CR and CXR series graphite commutated motors or integrated in the BX4 high-power brushless servomotors (Fig. 3). Speed and position control are provided using Faulhaber’s versatile SC2804 speed controllers or MCDC/BL 3006 motion controllers.
Medical devices
Fig. 3. Faulhaber’s Series IE3 incremental encoders may be mounted on CR and CXR series graphite commutated motors or integrated in the BX4 high-power brushless servomotors.
Maxon Motor, the Swiss manufacturer of high-precision drive systems, has recently extended its range of brushless micro-motors with the addition of the EC 8 series, which are 8mm in diameter and 22mm long. These high-quality motors are manufactured to meet the requirements of ISO 13485, Medical devices - Quality management systems - Requirements for regulatory purposes, so are suitable for use in medical sampling robots, portable analysers and
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