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Embedded Systems October 2000 Vol13_11

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1.5 , , , . . , i ..... . , , : :8 c: ·iii o o o 4 II: ! . II.. 0.5 1 :, 1 !!~: ------~------~~~~==----------~ , , , , - - Command Position - - • Drive __ • Control too much overshoot then reduce the gain by a factor of two or four. Once you are close, fin e tune the propor- tional gain by factors of two until you like what you see. Once you have your proportional gain set, start increasing integral gain . Your starting values wi ll probably be from 0.0001 to 0.01. Here again, you want to find the range of in tegral gain that gives you reasonably fast perfor- mance without LOO much overshoot and without being too close to oscillation. ~: .",,: -0.5 ,!--...,~:-::-.- ~. ---.--.....,.."" .. "'"...,:=::.---::..:..~--,...- 2 6 Time ...... ., _~_._ i.. _ ... __ _ : 8 10 Other issues Unless you are working on a proj ect with very critical performance para- meters you can often get by with con- trol gains that are within a factor of two of the "correct" value. This means that you can do all your "multiplies" with shifts. This can be very handy when you' re wo rking with a slow processor.

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