A Universal Servocontroller

Robots, milling machines, computers, printers, lawn mowers, coffee grinders and modern digital mixing desks: what do they have in common? The answer is motors: they all carry some kind of device that starts rotating when a voltage is applied to its terminals.

Have you ever tried operating one of these motors? Ever tried rotating them at just *that* speed? Ever tried holding them in just *that* position? If so, you probably got very frustrated in the process… Yet this is what all of the above appliances require. A mixing desk needs to position the pot so that the artist gets his right settings: just enough spunk, not too much noise from everybody else and, of course, outrageously loud. If your electrical lawn mover rotates its blade at too high a speed you might notice it flying off — not all that healthy I might add.

Back in ‘em good old days we had the centrifugal governor┬áto manage speed. While it is a genuine piece of art, there has been a certain evolution over the past few centuries… Quite obvious if you come to think of it really, back then the steam engine was the primer, whereas nowadays the star of electrical motors is on the rise.

One of these evolutions is the stepper motor, which is specifically designed to be able to rotate in steps. While under the right circumstances a stepper is the perfect tool, it can quickly become rather tedious when the load isn’t constant or when some bearing gets cranky. You see, there is no feedback anywhere in the system. Introducing feedback will rapidly show that the resolution of the measurement instrument is greater than that of the stepper itself.

So back to the DC motors then. You only got two wires to make it all happen. Obviously there is a need for a decent controller that can take care of all the pesky details for you. Some controller to whom you could talk to in terms of `go there’, or `keep on rotating at 15 RPS’ would come in handy.

This gets me to the bachelor thesis, which this post is actually all about, that will make just that happen: a universal servocontroller.

A dream? Perhaps, but then I must be dreaming vividly all day ;-)

-Ewald

ewal

Sensor PCB – Almost finished


3 Responses to “A Universal Servocontroller”

  1. Lieven says:

    Took the liberty of adding a picture :)
    Feel free to remove it if you don’t like it.
    -L

  2. Ewald says:

    I just updated the picture with something that won’t make people run away screaming `murder!’ ;-)

    The greenish light also looks kinda cool IMHO.

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