Gary Kirckof, P.E. finds servomotors exciting. So much so that he wrote a book on the topic called Servomotor Sizing and Application. “What’s exciting,” says Kirckof, “is servomotors can do more than just move an object from point A to point B. Collectively the motors can move linkages, such as robots, but they do so much more. Once the logic for controlling the motors is figured out, it provides a level of abstraction. We are now no longer burdened by how each motor moves, so we can concentrate on the motion of the object carried by the robot. This level of abstraction helps us accomplish our goal faster on each successive application of the robot.”

“I always associate servomotors with industrial machinery but they are used everywhere,” Kirckof said. “I know one application where servomotors and cables give actors and actresses the ability to fly around on stages like Peter Pan.”

“Servomotors are also used on solar collectors,” said Kirckof, “but they are useless without the algorithm that tells them where the sun is. The application of servomotors is thus the combination of motors and electronics with the electronics being the brains.”

According to Kirckof, applying servomotors on industrial equipment came into being because of the need for higher throughput. He explains: “Using servomotors at the point of application reduces the mechanical mass and inertia that allows the higher acceleration rates needed to increase throughput. The use of multiple motors requires the need for tight coordination between the motors and this is achieved through the processor driving the machinery. The processors I use are great in that the logic in them provides me a level of abstraction so I can coordinate motion easily. I can concentrate on what I want to achieve instead of how to achieve it. Of course, the motors can only do what you want them to do when they are sized appropriately.”

Early career days
Influenced in part by his father, who was a mechanical contractor, Kirckof went to the University of Minnesota to study mechanical engineering. “I grew up around pipes and refrigeration equipment, and I felt at the time it would be a good line of work. My father recognized my interest in electronics early. On one occasion, when I was in high school, I helped his crew troubleshoot a boiler feed-water system. Not much, but it was a start.”

A degreed mechanical engineer, Kirckof is also registered as both a mechanical and electrical engineer. He spent the bulk of his 30-plus year career working with automated equipment and assembly lines. More than half of this time, he worked for Remmele Engineering (they are now Aspect Automation). Kirckof stated this was his dream job “because the machinery was large, a mixture of mechanical and electrical components, and best of all it required tons of programming.” Currently, he works for Beckhoff Automation and says he has fun with motors almost every day.

In the early days, he commented how difficult it was to find the right collection of hardware to accomplish his goal. “One piece would bring in an extra encoder but it wasn’t fast enough while another one was but didn’t have enough I/O and so forth. I don’t have that problem anymore, and I feel I’m only limited by my own imagination.”

Kirckof recalls an incident early in his career, where he was in an automotive plant and the car manufacturer needed an array of sensors to count the automobiles as they passed from one department to another.

“I was stumped on how to do this because my training and background up to this point was basically piping and fluid flow. The founder of the electronics I was using happens to be in the plant so I asked him how he would count the cars. He explained how to use multiple sensors, how to condition the sensors with timers, and how to construct the logic. After I comprehended what he was telling me, I was struck with a revelation that I can use programmable logic to accomplish almost anything. More so it showed me a field of practice that was a lot more interesting than dirty old pipes.”

Based on this recollection, Kirckof emphasized how a little guidance can really help and for this reason has included examples of applications in his book. “I want to show readers there are a lot of possibilities; possibilities that they may not be aware of.”

Writing the book
Kirckof describes a time when servomotors first appeared on machinery. “There wasn’t much information on how to apply servomotors or to figure out how big of a motor to use,” he explained. In searching for literature, he would gather whatever information he came across. “Incidentally,” he said, “my best source of information was in the back of manufacturer’s catalogs. Unfortunately, this source of information is disappearing now that manufacturers are relying more on the Internet to publish their catalogs.”

Although he credits the University of Minnesota for providing him with a good education in mechanical engineering, he emphasized there were no classes specifically on sizing motors. Currently, however, he is happy to see vocational schools starting to teach his field of practice of control engineering.

Thus seeing a need for a comprehensive manual on sizing motors, Kirckof took his pile of notes, articles, and other material available and then applied his more than 30 years’ worth of experience sizing and applying motors to write the book.

“I suppose the real desire to write the book was to rid myself of the burden of having to explain the sizing process over and over. Plus you can never do the subject justice in a few hours. Now I can just direct people to ISA’s web site.”

Kirckof hopes the book not only helps readers understand how to use servomotors but also helps them select and size them as well. He emphasizes the importance of the examples in his book, especially the ones on camming. For more information, go to

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