Servos: Overkill? Or simplicity?

I've frequently heard equipment builders or end users say that their packaging application is too simple for using servos, or conversely, servos are too complex for their application. Therefore, I am intrigued when I find what appears to be a very simple application implemented with servos. A couple of years ago, a grocery store meat department shrink wrap machine with multi-axis servos caught my eye. Recently at Promat, the Material Handling Industry of America show, servos on smart chain hoists piqued my interest.

"Servos on a chain hoist! How ridiculous," you might say. But, this application has been around for a few years now. At least three vendors were showing this at Promat: Knight, Stanley and Gorbel. All had single axis systems and Knight had a coordinated motion 3 axis system that allowed working in X, Y and Z coordinates. The "chain hoists" are actually lift assist devices used to improve the ergonomics of lifting and moving materials. For example, one might be lifting a role of packaging material to place it on an unwind stand, or lifting a highly machined mechanical part and placing it into an assembly--without banging the pieces together.

One supplier told me that they developed their technology in conjunction with a Cal Tech professor who was designing exoskeletons for soldiers. The idea was to create a 'superman' and make the exoskeleton move just like the soldier would move. By applying this advanced military technology, these lift assist devices can create motion that emulates human behavior. This is accomplished through the intelligent application of load cells for feedback, absolute encoders for measuring position and servos for precision and programmability.

If you've ever tried to use an electric hoist and trolley to move a load, you know that oscillations, swinging and overcoming momentum can be problematic. The system prevents oscillations and swinging, senses the operator's intentions and emulates his intended movements. Dead zones can be programmed to prevent the part from hitting permanent obstructions. The speed and acceleration of movement can be programmed based upon where in free space the part is actually located.

So, the next time that you need to implement some sort of powered motion on a packaging machine or line, think about the servo-enabled programmable chain hoist. It adds considerable value by adding intelligence to something that is fundamentally quite simple. Maybe you can do the same in your application and create competitive advantage where you least expected it.

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