| 摘要 |
PURPOSE:To allow highly accurate rotational speed control by reading the number of revolutions of a DC motor from the current waveform thereby eliminating the tachometer. CONSTITUTION:Current to be fed to a DC motor is detected, and the frequency of AC component representative of r.p.m. of the DC motor is counted. The number of revolutions N thus obtained may be integer times as high as true number of revolutions because of noise. At steps S5-S10, a decision is made whether the number of revolutions N is integer times as high as true value using upper and lower limits M, L of the number of revolutions N estimated from the current value T and the number revolutions N is divided by an integer and the quotient is determined as a current number of revolutions so long as it comes within the upper and lower limits M and L. Duty ratio is then regulated depending on the current number of revolutions such that a target number of revolutions N is reached. This constitution eliminate the need of tachometer and realizes highly accurate rotational speed control. |
