Method of diagnosing a servomotor control circuit

A method of diagnosing a servomotor control circuit, before executing numerical processing, including a servomotor, a control unit for providing a numerical value, a pulse distributor, operatively connected to the control unit, for carrying out arithmetic operations for pulse distribution based on the numerical value provided by the control unit, a position detector, operatively connected to the servomotor, for generating a positional pulse each time the servomotor rotates through a predetermined angular interval, an error storage unit, operatively connected to the position detector and the pulse distributor, for computing and storing the difference between the number of positional pulse generated by the position detector and the number of distributed pulses generated by the pulse distributor, and a D/A converter, operatively connected to the error storage unit, for converting the difference into an analog output, the servomotor being controlled by the analog output from the D/A converter, said method comprising the steps of:

• (a) supplying the numerical value from the control unit to the pulse distributor to enable the pulse distributor to effect the arithmetic operations while the servomotor is in a de-energized state;
• (b) reading a stored content of the error storage unit, supplied with the distributed pulses from the pulse distributor, into the control unit;
• and
• (c) checking the servomotor control circuit for normal and malfunctioning conditions by comparing the stored content, read into the control unit, with the numerical value.