A Proposition of Overlap Speed Detection Method and Improvement of Characteristics of Speed Observer

In a speed control system used a low resolution rotary encoder, the unstable phenomena is caused by the long pulse period in extremely low speed region. Currently, a speed estimation method utilizing the disturbance observer is applied to suppress it. But this method required highly precise speed detection. So, in order to improve the speed detection characteristics, the speed measurement circuit is increased to four circuits, which number is same as the pulse edge types. And the measurement periods are overlapped each others.Furthermore, the fluctuation of a static friction at zero speed region cannot be estimated. So there is a problem of the speed hunting phenomena. Therefore, by applying the upper limit information in place of speed detection and continually operating the observer, the torque and speed estimation are corrected more accurately.It was confirmed through experiments that by applying the above mentioned technology, it is possible to obtain a stable and high speed response characteristic from zero speed to high speed regions.