CONTROLLER FOR SEWING MACHINE

摘要

A digital speed control system for a sewing machine comprises a digital speed setting device which responds to manual depression of a foot pedal by generating a digital position signal. A variable frequency divider divides the frequency of speed related pulses so that its output frequency is an integral submultiple of the input frequency, which is variable as a function of the digital position signal. A period detector senses the interval between pulses that occur successively at the output of the frequency divider and generates binary data representing the sensed interval. The interval-representing data is translated into a second period data in an arithmetic unit according to a predetermined transfer function. The arithmetic unit provides correction of the most recently sensed pulse interval according to the direction and amount of the deviation of the most recent pulse interval with respect to the preceding pulse interval, whereby the second period data is accordingly modified by an amount proportional to the rate of sewing speed variation. A pulse generator translates the second period data into pulse for activating a magnetic clutch or a magnetic brake depending on a sign of the second period data to accelerate or decelerate the sewing machine.