dynamic mode for optimal control

Hi All,
I am working on a dyamic control of a mobile robot. I have developed a nonlinear dynamic model. What I am not sure is how accurate the dynamic
model is needed in order to have a stable optimal control output?
Any suggestions are welcome.
Everett
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On Fri, 07 Dec 2007 22:58:48 +0000, Everett X. Wang wrote:

If the robot is stable by itself, set all your gains to zero.
If you want more than just a stable robot you may need to use more information than what you've shared with us.
I've got a pretty jaundiced view of "optimal control". It works great, as long as you jigger the process by putting a cost on the control variables. This is almost never done because the control variables are expensive -- it's done to fake the algorithm into making a 'safer' controller, and the margins are hard to figure out.
I suggest you try the high-control-variable-cost approach, but go back and check your system for stability as you vary the parameters of of your plant. If you want to do this in a formal manner, study up on robust control.
--
Tim Wescott
Control systems and communications consulting
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Hi Tim,
Thanks for your suggestions. Yes, I have picked a control cost and control variable and obtained a two point boundary value problem, which is solved by using relaxtion method. The process requires iteration. But it is not too bad for a P3 machine. What is the high-control-variable-cost approach? I have not studied robust control. What is the main difference between optimal control and robust control? Can you tell me the pros and cons of the two methods?
Thanks a lot and have a nice weekend,
Everett ps. You have given me quite a few suggestions already on the selection of brushless vs. step motor, optimal control etc before. Thanks a lot.
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It is a matter of means that you use. The following refers to linear and nonlinear systems:
1. The transfer function should be as accurate as possible. 2. Then you can find best feedforward use. 3. In addition disturbances should also be best compensated.
What I mean can be seen in an example with 2 disturbances:
Page 1: Definitions Page 2: PID control Page 3: PID and feedforward Page 4: PID and feedforward and disturbance compensations
http://home.arcor.de/janch/janch/_control/20071208-controlcomparison /
The examples are based on a linear system. The linear ODEs can be replaced by nonlinear ODEs if known. The process transfer function can be preferably found via measurements.
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Regards/Gre http://home.arcor.de/janch/janch/menue.htm
Jan C. Hoffmann eMail aktuell: snipped-for-privacy@nospam.arcornews.de
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