Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1990-05-02
1992-10-13
Shoop, Jr., William M.
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
G05B 1918
Patent
active
051554240
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a numerical control method and, more particularly, to a numerical control method in an NC apparatus having a C-axis control function for positionally controlling a spindle in the direction of rotation.
2. Description of the Related Art
In a machine tool having a spindle motor, there are cases where a blank is subjected to predetermined machining while positional control is performed by a spindle motor in the same manner as with a servomotor. In a lathe, for example, a blank is subjected to drilling or grooving by positionally controlling a spindle, namely the blank, in the direction of rotation (C-axis direction), or the blank is subjected to machining such as helical grooving by simultaneously transporting a cutter while the blank is being rotated in the C-axis direction by numerical control.
It is difficult to make the servo-loop gain or acceleration/deceleration time constant in the spindle motor control system agree with the servo-loop gain or acceleration/deceleration time constant in the servomotor (feed motor) control system, and these values usually are different. Consequently, in a case where the amounts of delay in the motors differ from each other and C-axis control is performed at the same time as control along the other feed axis, the actual path of movement becomes displaced from the command path of movement owing to the disparity in the amounts of delay.
Accordingly, it has been contemplated, solely for cases where a changeover is made from velocity control in which a spindle is rotated at a fixed velocity to C-axis control, to manually set the characteristic values (acceleration/deceleration constant, servo-loop gain, etc.) of feed-motor axis control so as to agree with those of the spindle motor, and restore the characteristic values of spindle control to their original values at the end of C-axis control. However, this approach is troublesome since the manual changeover must be made manually whenever control is changed over.
Accordingly, an object of the present invention is to provide a numerical control method in which axis control characteristic values of a spindle motor and servomotor can be made to agree and then be restored to original values automatically.
SUMMARY OF THE INVENTION
In the present invention, the foregoing object is attained by preparing a first G-code word for achieving agreement between axis control characteristic values of a C-axis motor control system and axis control characteristic values of a feed-axis motor control system, as well as a second G-code for restoring axis control characteristic values changed by the first G-code wor to original values, commanding the first G-code word before performing simultaneous control of the C axis and feed axis, causing the axis control characteristic values of the feed motor control system to agree with the axis control characteristic values of the C-axis motor control system by the first G-code word, commanding the second G-code word after simultaneous control of the C axis and feed axis ends, and restoring the axis control characteristic values of the feed motor control system to original values by the second G-code word.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a numerical control apparatus according to the present invention;
FIG. 2 is a block diagram of an axis controller;
FIG. 3 is an acceleration/deceleration characteristic diagram;
FIG. 4 is a primary delay characteristic of a servo-circuit; and
FIG. 5 is a flowchart of processing according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 is a block diagram of an NC apparatus according to the present invention, in which numeral 11 denotes a processor, 12 a program memory (ROM) storing a control program, 13 a RAM for storing results of processing as well as an NC program being executed, 14 a RAM (non-volatile memory), backed up by a battery, for storing axis control characteristic values, described below, 15 a CRT/MDI unit having a di
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Fujibayashi Kentaro
Miyake Masahiko
Sasaki Tako
Fanuc Ltd.
Shoop Jr. William M.
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