Control Engineering's Motors, Drives, and Motion Control Newsletter for April 2001


In this issue:




Web-based expert system help for motors, motion control

Need an 'expert' to help analyze a motion axis, size electric motors, and select various mechanical components that make up a motion control system?

Web-based VirtualSizer, a new productivity enhancement tool may be your answer. Available from Motion Tech Trends (MTT, Inglewood, Calif.), this expert system software is intended for individual supplier companies serving the motors, drives, and motion control markets. VirtualSizer allows applications engineers, sales staff, and channel partners to more efficiently define and specify the company's best products for a specific application-based on customer data input.

The software operates at a company's web site, and is customized around its products, database, and operator interface needs. 'Being on the web offers unlimited communication with customers and their instant access to your product database,' says MTT president George Gulalo.

VirtualSizer software specifies motors, drives, linear translators, etc., providing a list of potential part numbers and highlighting the optimal product. System analysis and expert advice are part of the capabilities. For more information, contact MTT at Tel: 310/674-3445 . See a longer version of this item in April 20, 2001, Daily News .


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Rockwell Science Center's new business direction, power device developments

Rockwell Science Center (RSC, Thousand Oaks, Calif.)-a world-class research and development facility for Rockwell Automation, Rockwell Collins, industry partners, and the U.S. Government-heads toward independence. Later in 2001, RSC will be established as an independent company, jointly owned by Rockwell Automation and Rockwell Collins. While retaining R&D capabilities for the above clients, the goal is to change RSC's 'laboratory image' to a business-oriented facility able to develop high-tech industrial products. See CE , Feb. 2001, p 114 for one product example.

Among its wide-ranging technology coverage, RSC has traditionally strong ties to electric drives. Power semiconductor devices make up a particularly active area. On a recent visit to the Science Center, I was shown leading-edge developments in silicon carbide (SiC) power-switching devices. SiC technology is seen as the future of power electronics, because of capabilities such as 100X power dissipation, high-temperature operation (400 °C), higher power density, etc., compared to present generation semiconductors. Commercial products are two to three years away, but prototypes such as Schottky diodes have been successfully demonstrated.

Other RSC developments related to motors and drives include adaptive motion control that will correct system inertia mismatch and improve controller bandwidth/stability, and modular ac-ac converters that will enable direct, one-stage power conversion for compact regenerative drives.


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Simplify your torque measurements

Embedded Magnetic Domain (EMD) torque sensors, developed by FAST Technology (Livonia, Mich.; Ottobrunn, Germany, near Munich), promise to ease torque measurement in shafts compared to complex strain-gage methods or those requiring specialized instrumentation. EMD technology is a non-contact method that combines magnetic induction and electronic processing to obtain direct torque readings in real time, says the manufacturer.

FAST Technology's EMD torque sensing technique contains only three main elements. The torque-carrying shaft is conditioned with a permanent magnetic pattern and actually becomes part of the measurement system. (Shaft material must be magnetizable.) A detection head (sensor) measures changes in the shaft's magnetic field caused by the applied torque. Completing the system are proprietary electronic circuits that condition the sensor's signals to indicate magnitude and direction of torque transmitted by the shaft.

Standard EMD torque sensors measure torque up to 1,000 Nm (737 lb-ft) on shafts rotating as fast as 100,000 rpm (or stationary shafts). EMD works with shaft to detection head gaps of 0.5-10 mm (0.02-0.4 in.). Custom sensors with higher torque capacity are available. Typical torque measurement accuracy is given as 0.5% of full-scale reading. Target applications include automotive and power tool manufacturers.


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Two robust encoder signals from one output

A motor drive and a machine sequencer in your control system each need a position signal, but only one output is available from a distant encoder that's subject to signal interference.

Here's one possible remedy. Signal Splitter, a digital encoder signal splitting device from NorthStar Technologies Inc. (Westerville, O.), is designed to route one encoder signal to multiple isolated devices. In a sense, one encoder can function as two units. Signal Splitter also acts as a signal booster and repeater for fading encoder signals. This capability is useful in cases where electrical interference is present or the encoder and drive/machine are widely separated. Signal Splitter outputs two clean, independent, and isolated 5-26 V dc square wave signals. The device is compatible with any incremental digital encoder, according to the manufacturer. .


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Get a handle on harmonic distortion

A first step is a way to assess harmonics conditions at your site. Wavemaker harmonic distortion simulation software, developed by Reliable Power Meters (Los Gatos, Calif.), is a teaching tool for that purpose. Using graphs and charts created by Wavemaker, plant and utility engineers can learn more about how switch-mode power supplies, motor drives, and other nonlinear loads affect their electrical distribution system. The software demonstrates input current waveform changes due to various preset levels of harmonics. Wavemaker is available free of charge on a business-card-sized CD-ROM. .

To reduce excessive harmonics, Acme Electric Corp., Power Distribution Div. (Lumberton, N.C.), offers I-Trap neutral current reducer, with maximum current ratings of 100-450 A, NEMA 2 housing, and built-in amp meter for continuous reading of neutral current. High neutral currents come from unbalanced and harmonic loads. I-Trap is said to cut three-phase neutral current at least by 50%. Degree of reduction depends on where the device is placed in a distribution system-the closer to the load the better.


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High-speed controller CPU

New from Control Technology Corp. (CTC, Hopkinton, Mass.) is a 'significantly upgraded' CPU module for its 2700 Series automation controllers that are said to process CTC's controller programs eight to 14 times faster than the previous model. For motion-control interests, the new 2703AP module includes an enhanced on-board quadrature encoder channel for high-speed encoder counting applications. Also, two high-speed registration inputs allow users to 'trap the encoder channel's position based on machine events.'

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Motor 'briefs'

New and enhanced motor products continue to roll in from the manufacturers. Here's a recent sampling.

Animatics Corp. (Santa Clara, Calif.) has expanded its SmartMotor line-a product that integrates a controller, amplifier, and encoder into a brushless dc servomotor-to a fluid-protected design rated to IP65. New 2300 and 3400 Series SmartMotors produce 20-250 oz-in. continuous torque and run on 18-48 V dc supply. They're intended for washdown, dusty, corrosive, or outdoor applications. (Also see CE , Nov. 2000, p 104-5.)

Don't overlook voice-coil actuators for relatively long-stroke linear position control in two directions. VM Series actuators from Densitron Corp. (Santa Fe Springs, Calif.) supply up to 60 N (13.5 lb) force over a 10-mm (0.40 in.) stroke from a 36-mm (1.42 in.) long package, weighing just under 1 lb. Voice-coil actuators deliver essentially constant force over their stroke, unlike solenoid devices.

Oriental Motor USA Corp.'s (Torrance, Calif.) AlphaStep, a step motor and driver in one package, is now available in a smaller, size 11 unit (28 mm square). Two versions operating at 24 V dc input offer outputs of 7.8 and 17 oz-in. holding torque, respectively. These are Models AS34AK (1.77 in. stack length) and AS36AK (2.60 in. stack length). AlphaStep operates in both open-loop and closed-loop (as needed) to control loss of synchronism.

Thomson Airpax Mechatronics (Port Washington, N.Y.) introduced four series of 'high-torque' hybrid stepper motors: 39 mm square Series H39Y; 42 mm Series H42S; 56 mm Series H56S; and 57 mm Series H57Y. The first three series corresponds to NEMA 16, 17, and 23 sizes. These 1.8° step motors come in various stack lengths to span a holding torque range of 63 mNm to 1.47 Nm. .


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Seminars, education

Conferences, courses, and seminars offer continued education opportunities to the motion control community.

George Ellis, senior scientist at Kollmorgen (Radford, Va.), conducts one-day seminars entitled 'How to Improve Servo Systems.' Upcoming sessions will be held on May 22, 2001 (Dayton, O.), May 24 (Cleveland), and June 5 (Chicago). For information, Tel: 800/777-3786 or visit .

IEMDC 2001-International Electric Machines & Drives Conference-will run at the Massachusetts Institute of Technology (Cambridge, Mass.) on June 17-20. Engineers from both industrial and academic disciplines are expected attendees. IEMDC also includes an exhibition by manufacturing companies on June 19 and 20. Contact the IEMDC exhibits manager at Tel: 202/973-8682.

'Designing Motors & Generators for Automotive Applications' takes place on May 22-23 in Nice, France. The workshop is managed by Intertech (Portland, Me.). In the U.S., contact Tel: 207/ 781-9800.

Small Motors & Motion Association (SMMA, Sherborn, Mass.) presents various courses through its Motor & Motion College. Some related courses include 'Fundamentals of Electric Motor Design' on June 6-8 in Chicago; and 'Feedback Devices' on October 2-3 (two half days) in Durham, N.C. Contact SMMA at Tel: 508.376.5360 or .


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Control Engineering in April

Our review of product highlights seen at last month's National Manufacturing Week of shows in Chicago includes several motor and motion control items. See the News section for hardware or software offerings from Anacon Systems (Mountain View, Calif.), Baldor Electric (Fort Smith, Ark.), Danaher Motion (Simsbury, Conn.), Manufacturing Data Systems (Ann Arbor, Mich.), and Parker Hannifin (Cleveland, O.).

More related products can be found in the Products & Software section . Tubular brushless linear servo motors from California Linear Devices (Carlsbad, Calif.) provide application flexibility. They deliver forces up to 1,125 lb with stroke lengths from 2 to 18 in.

Just introduced to North America by Schneider Electric/Square D (Raleigh, N.C.) is a new generation of TeSys D Line motor starters sized for up to 20 hp at 480 V. Drastically reduced power requirements and safe, rapid installation are stressed in the TeSys D Line.

Linear Feedback Devices is the topic of this month's ' Back to Basics ' page. My short article provides an overview of some technology choices and products available to users. An Online Extra piece expands on the variety of linear feedback devices.


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Sign up for a Technology Broadcast

Be sure to catch our Technology Webcast on Distributed Control, May 1 at 1:00 p.m. CST (2:00 p.m. EST). Get more information and sign up here .


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