Boots – shoes – and leggings
Patent
1987-12-16
1989-09-05
Ruggiero, Joseph
Boots, shoes, and leggings
318632, 364184, 36447435, G06F 1546, G05B 1918
Patent
active
048645087
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a method of restoring a commanded position and, more particularly, to a commanded position restoration method for restoring a commanded position erased by power cut-off.
BACKGROUND ART
A numerical control system is available having a counter for storing a machine position by counting pulses, which are generated by a pulse coder, in dependence upon direction of rotation, which counter continues to store the machine position even if power is cut off. In a numerical control system which includes an absolute pulse coder comprising such a pulse coder and counter, if a reference point return operation is performed just once at the time of machine installation, then automatic operation can start immediately without requiring that the reference point return operation be performed each time power is introduced to the system thereafter. In other words, in an NC system which performs numerical control using only the machine position and not a commanded position (a position conforming to commanded pulses) at the time of NC control, an absolute pulse coder is very effective since it is unnecessary to perform a reference point return operation.
However, in a numerical control system which uses a commanded position in addition to the machine position, it is necessary that the commanded position be restored. Though no difficulties are encountered if the machine position and commanded position are equal, these positions are usually different. The reason for this is that the movable machine element is moved by the commanded pulses and the position thereof is corrected by various types of correction processing, such as for a pitch error correction and straightness correction.
Accordingly, an object of the present invention is to provide a commanded position restoration method in a numerical control system, through which a commanded position which conforms to a machine position at the time power is introduced can be obtained simply and accurately.
DISCLOSURE OF THE INVENTION
The present invention provides a commanded position restoration method in a numerical control system comprising an NC unit having a path control function and machine position correction function, a motor rotated on the basis of a command from the NC unit for driving a movable machine element, a pulse coder which rotates in synchronization with rotation of the motor and which generates a pulse whenever it rotates through a prescribed angle, and a counter which counts the pulses in dependence upon the direction of rotation for storing the machine position, which counter stores the machine position even if power is cut off.
In the commanded position restoration method, a counted value C.sub.RA in the counter at the time of reference point return is set beforehand in a memory backed up by a battery. Whenever power is introduced to the system, a counted value C.sub.A in the counter is read, the reference point is hypothetically taken as the present machine position, and the machine position at introduction of power is taken as a target position. An interpolation operation is performed internally in a machine-locked state to update present machine position data C.sub.RA, the movable machine element is moved hypothetically from the reference point to the present machine position which prevailed at introduction of power (i.e. until C.sub.RA =C.sub.A holds), and a commanded position which prevailed at introduction of power is restored by using command data necessary for achieving the abovementioned movement.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a numerical control system embodying the present invention, and
FIGS. 2(A) and 2(B) is a flowchart of processing according to the invention .
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a block diagram of a numerical control system embodying the present invention, and FIG. 2 is a flowchart of processing according to the invention. In FIG. 1, components other than those constituting an NC unit are illustrated for one axis only; the compon
REFERENCES:
patent: 3691357 (1972-09-01), McIntosh
patent: 4045660 (1977-08-01), Weisgerber et al.
patent: 4107654 (1978-08-01), Nishijima
patent: 4370705 (1983-01-01), Imazeki et al.
patent: 4484287 (1984-11-01), Gamo et al.
Fanuc Ltd.
Ruggiero Joseph
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