Brainy motors get real

Engineers designing motion-control systems face ongoing challenges of incorporating more features into less space with less wiring. And increasingly, they need to provide advanced machine diagnostics and communications capabilities. That's why combining motor, controller, amplifier, feedback, and communications into a single device makes a lot more sense than using discrete components-especially with today's more decentralized approach to control.

Such integrated motors reduce the number of components and subsystems that engineers must deal with. They simplify design and installation, reduce the size of the control cabinet, or eliminate it altogether. And in general, fewer discrete components means greater reliability.

Today, engineers looking for integrated motor solutions have plenty of options to choose from, but this wasn't always the case. Despite all of these benefits, integrated motor pioneer Animatics Corp. (Santa Clara, CA) had a tough sell after introducing its SmartMotor(TM)concept in late 1994. Animatics President Robert Bigler explains, "People would always ask us, if integration is the way to go, why isn't anybody else doing it? Now that we aren't the only ones doing integrated motors, and more companies are putting their toes in the water, there's a real market for intelligent motors."

That's why Animatics has recently taken advantage of its jump-start in the industry and added multi-axis-contouring capability that allows an RS-485 network of SmartMotors to perform motion profiles as complex as multi-axis splines, or as simple as circular interpolation. A popular misconception is that people think integrated motors are great for single axis applications, but not for highly coordinated motion because several motors connected over a serial network don't get serviced as fast as if they were plugged right into a PC expansion slot, explains Bigler. "We've changed all that with new firmware and host software features that allow trajectory generation to take place at both the host and at the motor. So updating and synchronization take place on an as-needed basis."

And then to really bring this to bear on a company's bottom line, Animatics has created a G-code interface that's compatible with CAD/CAM and surface generation software, so engineers can use CAD/CAM software to generate elaborate contouring codes for all kinds of manufacturing operations. Bigler says, "these host interfaces can turn a laptop computer and three SmartMotors into a complete 3-axis CNC control system."

Adding to its line of integrated servomotors, QuickSilver Controls Inc. (Covina, CA) introduces a 34-frame motor that runs at higher currents and delivers up to 1 hp at 600 rpm. "34-frame motors typically operate at speeds of 2,000 rpm to achieve this kind of output," says QuickSilver VP Dale Dalke. "This new SiverMax delivers very high power at low speed for engineers who want to eliminate gear reducers in low-speed, high-torque applications."

The SiverMax 34HC provides the same built-in features as its siblings-the 17, 23, and standard 34-frame version-with integrated controller, driver, and encoder. All operate on a 4,000-count, 1,000-line optical encoder that provides 0.09 degrees positioning resolution. "Unique to all SilverMax motors," explains Dalke, "is the ability to switch into anti-hunt mode to completely eliminate servo dithering, allowing the motor to remain motionless while maintaining position. Also unique is the ability to handle up to 100:1 inertial mismatches. Moreover, combining the patented control system with high torque "magnetic gearing" of the motor reduces or may eliminate the need for gearheads, allowing system designers to reduce overall costs."

Likewise, the 3564-BC from MicroMo Electronics Inc. (Clearwater, FL) is another integrated motion control system that combines motor, feedback, controller, drive, thermal protection, and communications into a single package (see Design News March 6, 2000, p.179). It uses a 16-bit microcomputer, program memory, peripheral capabilities in the form of a serial interface for communications, quadrature pulse for the encoder signal, and a 10-bit AD converter.

In the world of motion control and positioning, there are servos, steppers, and steppers that act like servos. Cool Muscle from MyoStat Motion Control Inc. (Aurora, ON, Canada) is the latter. MyoStat President Chris Murray explains that the company decided to use stepping motors because they are easier to mass-produce and less costly. "Combining a microstepping motor with a high quality but low cost 32-bit RISC CPU allows us to do ac servomotor control algorithms such as vector calculations, and effectively bridge the price performance gap between stepper and servomotors."

The integrated closed loop servo system combines a stepping motor, a full computer controller, amplifier, power management, and a magnetic position sensor. 128k of memory allows the inclusion of custom software directly in the motor, creating a stand-alone actuator for mechanism designers wanting to replace air cylinders, mechanical cams, or variable-speed and variable-torque controllers with a LAN-compatible intelligent motor. "Up to 128 Cool Muscles can be daisy chained together to form a synchronized motion control system," adds Murray.

Another integrated microstepping solution is MotorCube from Ann Arbor, MI-based Whedco Inc., a subsidiary of GE Fanuc Automation (Charlottesville, VA). A DeviceNet interface and the use of DSP processors differentiate it from the competition. GE Fanuc's Manager, Motion Business Walt Koetter, says, "More engineers are going to a modular controls architecture to get rid of control panels."

MotorCube is available in torque levels from 50 to 175 oz-inches, and can be used with up to 63 other industrial devices on a single network.

Colibri "intelligent" stepping motor from MESA Systems Co. decentralizes positioning and indexing operations from a central controller, like the others. But it was designed with more simple positioning operations in mind. Integrating a stepping motor, driver, controller, programmable memory, power supply, I/O, and databus into one compact device, the actuator requires only a "start" command to sequentially execute up to 20 programmed operation records.

Records include length (absolute or relative), acceleration, speed, and record repetition. "Colibri makes it very easy for engineers to design a positioning function. Programming requires only position, acceleration ramp, duration, and deceleration," explains MESA President John Kussman.

"It's interesting that the biggest benefit of integrated motors," explains Animatics Bigler, "is something we never even thought of initially. Customers fed it back to us. If an axis acts up on a machine designed with integrated motors, it's pretty obvious which motor needs to be swapped out to fix the problem. Anyone that can turn a wrench can do it."

For equipment manufacturers this means zero time troubleshooting remotely, or zero airfare to send a technician over to debug the machine's controls, drives, or wiring. And for the end user who stocks a spare integrated motor, it means essentially zero downtime.