Re: Motion Controllers

A. Paul Montgomery wrote:
In article <XJidnXgoLYDuVe7eRVn-qw@xxxxxxxxxxxx>, tim@xxxxxxxxxxxxxxxx says...

I'd like to think that I could buy such a controller off the shelf, but I'm coming up with a whole bunch of near-misses. There seem to be any number of controllers that will accept encoder feedback from a motor and drive it to a set point given a digital command -- I need a controller that will take the command and feedback as voltages, incorporate the summing junction in hardware, and implement a PID on the result.

Is there such a thing I can buy off the shelf, or should I be unlimbering the old schematic package?

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Tim Wescott
Wescott Design Services
http://www.wescottdesign.com



First I decided to change my Nic, but this is the poster formerly know as HoPpeR. Several reasons which I will not go into unless someone wants to know. I would have done this from the beginning but was not for sure if I was going to stick around. Sorry for the inconvenience.

I'm having problems with the ASCII drawing for some reason I try fixed font and get the same. Got any suggestions? You might just send me the thing via email in html or pdf.

From your description I do not understand the need for the controller. The amp has a controller and the boards I used accept voltage inputs. The board I was thinking about takes a scaled or unscaled speed control signal and produces a proportional motor speed. The PID and voltage or encoder feedback is built in. It should be a complete control/amp package. I looked at Peter's company and his stuff does the same thing. His product line is more high end and I suspect more expensive but will do the same thing. If they truly have up to speed tech support 24/7 and the price is not too much higher, I suspect that I will be buying my boards from him. He seems to have evolved in the logging industry. Peter, if you are listening in maybe some input would be good here.

If you are trying to control the gyro application is something like synchronous application you might need to think about some sort of more sophisticated controls, but I don't think this is the case if the input is by a joystick directly. I used these boards on a web system with about 10 motors all sharing the pull load. The product was thin rubber sheeting and the operators trimmed the speed by had while the master speed was simply a single voltage source. I think that this is an example of one or both us use misunderstand some fundamental things because of different terms like I posted about earlier.

If it seems that someone is being dense just assume that it's me. I looked for indications of PID compensators and didn't find anything. Could you give me some specific part numbers as examples, or do all of their drives include PID compensation?

I had my head up my assumptions in another way that may prove troublesome, however. In production at least the system has to run off of 12 or 24VDC -- in hindsight it's obvious that I should have mentioned this. This doesn't mean that I can't use AC powered stuff to help the guy out for a prototype/demo system, however (assuming I can limit the voltage to the motors, of course).

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
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