Motion control: The past 10 years

One of Control Design’s earliest editions, February ’98, took a shot at identifying emerging trends in machine controls. Conspicuous by its absence among the eight trends was any real mention of drive technology. However, the article saw something coming. In its “What About These?” sidebar, it noted that “Integrated drives, the combination of controller and motor as one unit, are becoming popular where variable-speed functionality has to fit in small spaces. For open-loop vector control, the miniaturization of inverter components and new feedback algorithms are bringing small-footprint drives up to 10 hp into practical use.” It clearly didn’t stop there.

All of us were accustomed to finding a rectifier diode, power transistor, thyristor, gate-turnoff thyristor (GTO), and the insulated gate bipolar transistor (IGBT) in electronic drive technology descriptions. However, in the June 1998 issue, we examined a technology that “claims to be the world’s smallest, standard medium-voltage AC drive system—in terms of power and voltage compared to size—is now on the market. The compact size is achieved by using an integrated gate commutated thyristor (IGCT) semiconductor switch. The IGCT consists of a power-handling device known as a gate commutated thyristor (GCT) integrated with the device control circuitry. Uniform switching eliminates the need for a snubber.” We reported claims that IGCTs deliver extremely fast switching and high yields suitable for power conversion from 400-6,500 hp at up to 4.16 kV. IGCT technology, developed by ABB Industrial Systems was touted to operate at up to 1,000 Hz, which was four times faster than previous power devices at full rating.

Electric Power and Efficiency
In the June 2001 issue, we got a sense of what electric drives and motors were becoming capable of when we reported on Milacron’s all-electric injection molding machine, which the company claimed to be two to four times more energy-efficient than conventional machines and could save 8.9 million MWh of electricity.

“Some of the largest global companies have already mandated across-the-board energy reductions in their operations because they realize the cost savings go straight to the bottom line,” said Barr Klaus, vice president of technology for Ferromatik Milacron North America. “At three times the efficiency of conventional machines, all-electric injection-molding technology can be a strong component in those reductions, and our resource center will serve as an important, time-saving means to accelerate validation of the process.”

Though it sounded contradictory, “all-electric injection molding machines actually are three times more efficient than conventional hydraulic machines,” claimed Klaus. “That’s because the all-electric machine motors use energy only when actually doing work, unlike conventional hydraulically powered machines, where motors consume energy while idling.” A switch to new all-electric injection machines was expected to save an estimated 700,000 MW of power and $42 million in energy annually in California.

With all the emphasis on drive electronics, Control Design didn’t forget about motors. A September 2001 Editor’s Page aimed at those machine builders who relied on big motors and drives with heavy-duty cycles, argued they could do their customers a big favor by encouraging use of motors meeting high-efficiency standards.

Earlier that summer, CEE, a consortium of motor manufacturers, trade associations, electric utilities, and government agencies, kicked off the “Motor Decisions Matter” campaign to encourage more motor management to cut energy costs.

The editorial stated: “Motor standards based on the 1992 Energy Policy Act set the efficiency of a new NEMA Premium 30 hp motor to about 92-93% versus the 88% installed average. NEMA Premium defines motors that are single-speed, polyphase, 1-500 hp, two, four and six-pole, squirrel-cage induction motors NEMA Design A or AB, continuous rated.”

It was clear that promoting more expensive, efficient motors is a tricky spot for machine builders, who really would have to sell a customer on more upfront costs. However, “the CEE reports that energy represents as much as 97% of a motor’s total lifecycle operating costs,” stated the column. “The Department of Energy says a typical 30 hp motor in service today will gobble up about $22,000 worth of electricity per year at $0.10/kWh in continuous-duty service.”

Baldor Electric’s president, John McFarland, had visited our offices a month earlier to emphasize that Baldor was a sponsor of the CEE campaign, and reported that, depending on the duty cycle, the payback on its 30-hp unit from energy savings could be less than 18 months.

Regarding mechanical components, the magazine noted in a 2003 issue that vendors were crediting improvement in ball screw design and manufacturing as a key to improving machine performance and accuracy. “Advances in ball screw design and manufacturing have greater influence on improved machine performance, but given the increased number of mating and moving parts, matching part tolerances is far more critical for maintaining accuracies over a long distance. Ball screws are well suited for applications with high acceleration and deceleration needs.” These improvements have resulted in simpler, more accurate machines. Now, even on many of the more precise machines, linear encoders that were once a necessity to verify machine accuracy (duplicating feedback with a motor-mounted encoder) no longer are required.

Growth and More Transition
Control Design looked for innovation with articles such as “Motor Drives Hunt for Success.” This  November 2004 product roundup reported, “Machine builders seeking new and advanced drives and motion control systems that conform to some—any!—sort of standard might be frustrated by the lack of new products available.” The article pointed to the push by each supplier to create its own proprietary architecture and networking scheme. That situation continues today.

In 2005, things looked pretty good. The November drives roundup noted a new ARC Advisory Group study that showed the market for motors, drives, and motion control technologies was poised to grow at an annual rate of 6.1% worldwide over the next five years. “However, suppliers will be challenged over the next few years to differentiate themselves and offer better value propositions to industrial OEMs,” said ARC’s senior analyst, Himanshu Shah “This is critical in the face of an expanding market where user requirements differ significantly.”

A February 2006 article noted that AC motors performing tasks once relegated to DC motors becomes more obvious to machine builders as they see how motor manufacturers adjust product lines. Emerson Industrial Motors had dropped its DC business a couple of years earlier due to declining interest and sales of DC motors. “With NEMA-standardized AC motor products, the customer buys off-the-shelf and plugs into the drive to get the performance the application requires,” said Rob Boteler, Emerson’s industrial motors marketing director.

From my own recent experience in the field, I’ve seen how Axis New England, an automation solution center in the Boston area, makes innovative use of new motion control technology to manipulate 300-mm wafers for Axcelic Technologies. This application, completed in six months, provides kinematic adaptation to as many as 14 robotic axes, plus 10 additional axes. Using older technology required as many as five controllers. That’s a big change from where we were 10 years ago.

About the Author

Loren Shaumis principal at Comtec, Syracuse, Ind., which provides research in the machine and general factory automation markets. You can reach him at [email protected].