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Spotlight on Motors and Motion Control

Bob Michaels

February 15, 2012

6 Min Read
Spotlight on Motors and Motion Control

Stepper motors for medical equipment
Suitable for use in medical equipment applications, the STM24 series of high-torque integrated stepper motors from Applied Motion Products Inc. features built-in CANopen communication. Offered in a NEMA 24 frame size, these hybrid motors consist of a NEMA stepper motor, a microstepping drive, and a controller, providing holding torque rated to 340 oz-in. One version of the motors accepts step and direction, analog input, joystick control, and streaming host commands via the SCL language, while the other adds stand-alone programmable operation by means of the Q programming language. Both versions offer a choice of either RS-232 or RS-485 communication. Adhering to the CAN in Automation specifications DS301 and DSP402, these integrated motors support profile position, profile velocity, and homing modes at data rates up to 1 Mbps. An optional integrated 4000-count encoder provides stall detection and prevention.
Applied Motion Products Inc.

Space-saving linear actuator
Haydon Kerk Motion Solutions Inc. offers the 36-mm-OD G4 linear actuator in an alternative configuration that includes a special adapter plate to allow the smaller unit to substitute for 42- and 46-mm actuators in existing applications. Employed in medical equipment, the space-saving actuator model is available in captive, noncaptive, and external linear configurations and uses the same bolt pattern and pilot surface as the larger devices it can replace. Featuring a force output range of 16 to 58 lbf, the actuator employs optimized tooth geometry and high-energy neodymium magnets, resulting in high continuous force output. Custom-engineered plastics and large bearings provide rotor support and high axial load capability.
Haydon Kerk Motion Solutions Inc.

Servomotors for fluid-metering systems
Value-Line (VLM) limited-feature-set servomotors from Kollmorgen are designed to offer peak torque in the range of 0.5 to 16 Nom. Used in such medical device applications as fluid-metering systems, the servomotors feature cost-efficient feedback options and flying leads that remove the need for intermediate cables, according to their manufacturer. The motors are available in the most commonly used sizes with 12 standard windings; in NEMA 23, NEMA 34, and metric mounting standards; and with multiple shaft configurations to facilitate integration into nearly any system. Operating at 120/240 V ac or 160/320 V dc, they can deliver rated speeds up to 6000 rpm while providing maximum continuous torque of nearly 5 Nom to accommodate the 16-Nom peak capability. Multiple feedback and cable options provide configuration flexibility.

Medical-grade brushless dc motor
The EC8 8-mm brushless dc motor from Maxon Precision Motors offers continuous torque as great as 0.95 mNom, a nominal maximum speed of 80,000 rpm, and an efficiency rating of 70%. Available with or without Hall sensors and with 6-, 12-, and 24-V windings, this motor can be combined with a specified planetary gearhead. One-quadrant amplifiers serve as controllers, and users can choose between an amplifier directly connected via flexprint and a miniature plug-in module. Manufactured to ISO 13485 standards, the miniature motor is suited for a variety of medical device applications, including portable analyzers, metering systems, and analytical instrumentation.
Maxon Precision Motors

Dc micromotors
The Faulhaber 3272 CR dc micromotor offers graphite commutation and torque as high as 120 mNom in higher-power medical micromotor applications, such as blood pumps, catheter drive systems, and processing equipment. Measuring 32 mm in diameter and 72 mm in length and weighing 312 g, this motor, supplied by MicroMo Electronics Inc., is based on an ironless stator coil that supports high performance. At a nominal voltage between 12 and 48 V, it maintains a very flat n/M curve. In addition, the modularly designed microdrive can be equipped with a three-channel encoder or combined with a range of custom precision gearheads. A speed controller and motion controller from the same manufacturer are available to control the micromotor's speed or manage the device when it is deployed as a positioning drive.
MicroMo Electronics Inc.

Fiber-optic rotary encoders
MR320-series incremental encoders and MR330-series absolute position sensors from Micronor Inc. afford medical equipment designers a range of fiber optics-based options for resolving medical device motion control design issues. The encoders can solve problems that conventional electronics-based encoders and resolvers cannot, including issues associated with electromagnetic interference (EMI), electrical isolation, or high-intensity electromagnetic fields, according to their manufacturer. The latter series is suited for applications requiring high-resolution position feedback and offers 13-bit positioning accuracy over 0° to 360°. The fiber-optic rotary encoders utilize a 100%-passive optical sensor with a duplex fiber link to a remote active controller. They are also immune to EMI, generate no electromagnetic emissions, and involve no ground loops. Operative over distances as great as 2500 m, the encoders' fiber-optic link ensures that the patient is fully isolated from electrical equipment. Nonmetallic models can also be supplied for MRI and other applications involving extreme electromagnetic fields.
Micronor Inc.

Low-voltage servo drive
Suitable for use in surgical hand tools, medical pumps, and ventilation equipment, Portescap's LVD is a low-voltage servo drive that is designed to support small and large brushed dc motors, brushless motors, and low-inductance motors. Housed in a high-power-density package, the servo drive features a 12- to 48-V-dc power supply and is capable of 7-A RMS continuous and 12-A RMS peak current. It also features multiple I/O inputs and can be operated in current, velocity, or position modes. In addition, the drive provides high sampling rates for the velocity and position loops, allowing wide bandwidth and accuracy. Measuring 117 × 83.5 × 21.5 mm and weighing 250 g, the LVD is one of the smallest low-voltage drives available, according to its manufacturer. It operates in conjunction with Axis Manager, drive-commissioning software that features user-friendly windows for motor and feedback configuration, various control-loop tuning functions, an I/O setup window, and comprehensive monitoring and recording features. The software communicates with the drive via RS-232 or CANopen.

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