| 摘要 |
PURPOSE:To reduce noise at the time of low-speed operation and to correct poor accuracy due to cogging by changing an input current waveform in the excitation according to a series of operations. CONSTITUTION:An MPU 1 outputs a duty pulse that is preliminarily determined for each excitation at a constant frequency to a PWM unit 2. Receiving this output, a current controlling transistor 6 supplies current to a stepping motor 4. By setting the duty of PWM so that it may form such a current waveform as shown in figure at a low-speed constant-speed mode, a low-duty region of PWM is eliminated and thereby the output torque of the stepping motor decreases to such a degree as is necessary and sufficient for the low-speed and constant-speed operation. By this method, noise at the time of low-speed operation is reduced and poor accuracy due to cogging is also corrected. |
