Custom controllers provide flexibility

After spending four years in the U.S. Air Force and graduating from Minnesota State University Mankato with a B.S. in Physics, Math, and Chemistry and Minor in Psychology and Art, Peter Pemrick went on to do graduate work in Solid State Electronics at the University of Minnesota. His past work includes stints at Sheldahl Co in 1966 where he worked on the Apollo spacecraft thermal control and at Kiowa Corp. (Emerson Electronic Motion Control), which he co-founded in 1979. In 1989, Pemrick founded Quantum Controls Inc, which custom designs and manufactures electronic controls for the O.E.M. market.

The more functions motion controllers perform, the higher the speed needed. Customized devices provide the flexibility required for multi-functional applications, and digital signal processor (DSP) speeds will double every 18 months, much like the CPU chips of the computer industry.

DESIGN NEWS: DSP-based motion control is gaining in popularity. What are its specific strengths over other solutions?

PEMRICK: The big thing with DSPs is that they can typically do multi-functions and at greater speeds. Engineers can do a lot more in a shorter period of time. I most definitely think they will grow in popularity. There are a lot of applications out there that need to be multi-functional, requiring fast mathematical calculations at greater speed than micro controllers, and a DSP is the solution.

Q: Many standard motor controllers are available. What application requirements would create a need for a custom solution?

A: If the application involves more than just running the motor, then you might want a custom device that can run the other functions. For example, one of our biggest customers produces a control for handicapped door openers. With all of the functions they want it to do (motor control, clutch control, functionality control) organizing it onto one circuit board saves space, wires, and cost.

Q: If there is such a thing, what does a typical "custom" solution consist of?

A: Typically, you have to have some sort of controlling device such as hand-wired logic, a microcontroller, or a DSP with inputs and outputs. The outputs are typically power output devices to run motors, valves, etc. Input devices may be encoders for position or speed sensing, proximity sensors, limit switches, an external bus to talk to the outside world, and probably an operator's interface. Such interfaces can be as simple as a few buttons and a numeric or alphanumeric display. Then, finally, there is the packaging to consider. Environmental, safety, and aesthetic considerations dictate the packaging.

Q: What do engineers need to know about their application requirements in order to select the most appropriate motion control solution?

A: A lot of companies out there have an application. A great deal of them do not have a written specs of what its functionality should be. The design engineers have to learn about the application as well as how it works. They have to put themselves in the customer and end user's perspective. Also they have to consider future requirements, and design in the required flexibility. If you turn the clock back 25 years, you didn't have this kind of flexibility with microcontrollers. Even further back, there was one controller per application and if you wanted a different application then you would have to change it all over again.

Q: Can you give us a sneak preview of what's beyond 80 MHz DSP for motion control?

A: I don't see 80 MHz as a breakthrough. I think in general, that these types of products grow in speed and performance like the Intel products for PCs. About every 18 months, they double in speed and capability but for the same price. You're talking about 2 GHz processors now. I think the DSP is going to keep on growing in speed and performance, probably doubling every two years.