And that probably means a good deal of friction too, right? BTW what do you
mean by 'fairly large' inertia? Got a number?

The better control strategy is of course closed loop. But since you're
asking open loop, i guess that's not an option. Disclaimer: I'm not a
control systems expert. But there is a limit as to how accurate you're going
to be able to get with an open-loop system. And if you have external
disturbances of any sort (one of the main reason people use control
systems), open loop isn't going to get you there.

Do you have a model of the system? Have you done any experimental
determination of the system's behavior, such as time-domain or frequency
domain response? Do you need to move the load over a wide range of speeds
(as in a profile), or just a constant speed? How often do you have to move
the load? All of these things will play a role, especially with open-loop
control. Motor characteristics tend to change as the motor warms up.
Sometimes it makes a difference, sometimes not.


-----Original Message-----
From: Karl Skinner [mailto:karl@SKIN-NER.FREESERVE.CO.UK]
Sent: Monday, April 02, 2001 7:06 AM
To: PICLIST@MITVMA.MIT.EDU
Subject: [PIC]: DC Motor open-loop control stategy


Hi Piccers, can anyone help please with getting a better control strategy
for open-loop control of a DC motor driving a fairly large inertia. I'm
thinking along lines of "rate-lag" to improve response, but have been in
Piclist and Google to no avail.

Looking forward to your replies
Karl Skinner

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