Electricity: motive power systems – Positional servo systems – With protective or reliability increasing features
Patent
1984-08-15
1986-05-27
Dobeck, B.
Electricity: motive power systems
Positional servo systems
With protective or reliability increasing features
364184, 340680, G05B 2302
Patent
active
045917701
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to improvement in a numerical controller, and more particularly to a numerical controller of improved reliability which is designed to be capable of detecting abnormalities in position sensing pulses from a position sensor.
A numerical controller generally includes a position feedback loop which drives a motor so that the difference between the number of command pulses and the number of position sensing pulses from a position sensor is reduced to zero, and causes each moving part, such as the rotary shaft of the motor or a feed table, to move to a position corresponding to the number of command pulses at a speed corresponding to the frequency of the command pulses. Accordingly, there has been such a defect that when abnormalities, such as a dropout of a pulse and mixture of noise, occur in the position sensing pulses, the moving part cannot be moved to a predetermined position. For this reason, there has been demanded a numerical controller of enhanced reliability which is adapted to be capable of detecting abnormalities in the position sensing pulses from the position sensor.
SUMMARY OF THE INVENTION
The present invention is intended to meet the abovesaid demand, and has for its object to permit the detection of abnomalities in the position sensing pulses, thereby providing for improved reliability in the numerical controller.
The present invention is provided with a counter for counting position sensing pulses which are each output from position sensing means each time a moving mechanical part moves by a fixed amount, and abnormality detecting means for detecting an abnormality in the position sensing pulses on the basis of the generation timing of a reference position sensing pulse which is output from the position sensing means upon each arrival of the moving mechanical part at a predetermined position and the count value of the counter. Since it is possible to detect abnomalities in the position sensing pulses which will cause erroneous operations such as a deviation of the actual position of the moving mechanical part a commanded position and a runaway of the motor, the reliability of the controller can be increased.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a block diagram of an embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 is a block diagram of an embodiment of the present invention, and 1 is a processing unit constituted as by a microprocessor, 2 an adder, 3 an error register, 4 a servo unit, 5 a motor, 6 a position sensor which outputs a two-phase pulse (a) each time the motor rotates through a fixed angle, and outputs a reference position sensing pulse (b) each time the rotational angular position of the motor 5 reaches a predetermined position, 7 a direction discriminating circuit which detects the direction of rotation of the motor 5 on the basis of the phase relation of the two-phase pulse a, outputs a signal c indicating the direction of rotation and outputs a position sensing pulse d each time it detects, on the basis of the two-phase pulse a, that the motor 5 has rotated through a fixed angle, 8 a reversible counter, and 9 and 10 abnormality detecting circuits. Incidentally, the direction discriminating circuit 7 produces, as its output signal c, a "1" during forward rotation of the motor 5 and a "0" during backward rotation.
The error register 3 supplies the servo unit 4 with a signal for driving the motor 5 in such a manner that the difference between the number of command pulses from the processing unit 1 and the number of position sensing pulses d from the direction discriminating circuit 7 is reduced to zero. By the output of the servo unit 4, the motor 5 is driven through an angle corresponding to the number of command pulses at a speed corresponding to the frequency of the command pulses. Incidentally, since the above-described operation is already well known, no detailed description will be given thereof.
The reversible counter 8 is initialized to a count value "0" by
REFERENCES:
patent: 3500023 (1970-03-01), Arrowood et al.
patent: 3778696 (1973-11-01), Walters et al.
patent: 4479177 (1984-10-01), Berti
patent: 4480303 (1984-10-01), Takada et al.
Isobe Shin-ichi
Sawada Kazuo
Dobeck B.
Fanuc Ltd.
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