Usually the offset occured in the servo control system is eliminated by integral action. However incorrectly tuned integral action often causes overshoot and deley the convergence. Here is the alternative method to eliminate the offset. It doesn't require the calculation of integral gain and converges to the set point faster than that using integral action. In the following webpage I explained the method and showed the comparison with integral action based on the simulation.

http://139.134.5.123/tiddler2/digital3/digital3.htm (Please use InternetExplore on Windows 98/2000. After clicking, some pop-up windows will open for averting spammers, but please don't mind them.)

-- Harry Yosh (tiddler2@bigpond.com), December 06, 2003