What’s an actuator?

Discussing eddy-current actuators is hard without the word ‘actuator.’ It is clunky and reeks of jargon, but the alternatives are worse. “Tractor Beam” is evocative but misleading. “Electromagnetic force generator” is so generic it says almost nothing. “Eddy-current force generator” begins to stray into the land of sleep-inducing engineering names and “contactless eddy-current force generator” definitely does.

So what is an actuator?

According to the first entry at dictionary.com,  an actuator is

1. a person or thing that actuates.

Ah, of course. That clears everything up.

Wikipedia and the second entry at dictionary.com are both painfully specific:  

“An actuator is a type of motor for moving or controlling a mechanism or system.”

2. a servomechanism that supplies and transmits a measured amount of energy for the operation of another mechanism or system.

Both of these definitions fail to the full meaning of an actuator as well. An actuator doesn’t have to be a motor, nor does it have to measure the amount of energy it transmits to the system. Your hand is an actuator, but fails both of those tests. The similarity at the end of these definitions does get closer to answering ‘what is an actuator?’  An actuator is a system or mechanism that does *something* to another mechanism or system.

The clue to that *something* lies in the definition of an actuator’s verb form – actuate:

1. To put into action or mechanical motion

So putting it all together, an actuator is a system or mechanism that induces physical motion into another system. Or more elegantly, “something that turns energy into motion.”  This idea is everywhere in robotics, because robots are essentially computers that use actuators to interact with the real world. So, after a painstaking discussion, the implication of an eddy-current actuator is clear: a system that induces physical motion via eddy currents.

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