Patent US 5,828,014

In an elevator speed control circuit that has a proportional and integral speed amp 3 responsive to the deviation between a speed command .omega.* and actual motor speed .omega..sub.M, there is provided a car motion feedback circuit that amplifies the difference between a speed command .omega.* and actual car speed .omega..sub.car (or acceleration command and actual acceleration) with amp 12, extracts car vibration characteristics through band-pass filter 14, and changes these vibration components to the optimal phase in a phase correction filter 16 for feeding back. A load torque predictor 21 estimates load torque from signals from circuits 2-19 and from actual motor speed .omega..sub.M to improve speed feedback characteristics and the effectiveness of external disturbance suppression in elevator speed control. A variety of variable circuit elements are disclosed.