+ KrcT;] rD

Ideally, we want the actual speed to be exactly equal to the desired speed. This requires a closed-loop speed gain of exactly I .0, which requires an impossible loop gain of infinity; however, perfect accuracy is never required in practical systems, so

large, but finite loop gain is always acceptable. Actually, as long as the closed-loop speed gain is constant, we can get the actual speed equal to what we want without having infinite loop gain, by using the following simple trick. If the closed-loop speed gain were, say, 0.90, and we wanted an actual speed of 100 radjsec, we would just set wo.des to 100/0.90 = 111.1. That is, we ask for a larger speed than we actually want, because we know we get only 90% of what we ask for.