Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1989-09-07
1991-06-25
Ip, Paul
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
318567, 3185681, 318603, 36447428, G05B 1929
Patent
active
050270451
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS
This application is cross-referenced to U.S. application Ser. No. 07/342,533 and U.S. application Ser. No. 07/342,534.
BACKGROUND OF THE INVENTION
The present invention relates to a high-precision pulse interpolation method, and more particularly, to a high-precision pulse interpolation method for controlling a piston lathe and the like.
Due to the increasing speed of microprocessors and increased integration of memory circuits, etc., numerical control apparatuses must carry out more complex controls and process greater quantities of data. Accordingly, a time allowed for carrying out pulse interpolation is very limited. Particularly, when using an increased number of axes, it is difficult to shorten the task period for a pulse interpolation, which is about 5 to 10 ms.
Nevertheless, to carry out machining by using a piston lathe, a cam grinder or the like, or the equivalent to a conventional machining using a cam, a task period of about 1 ms is required.
Such a task period can be achieved if a faster microprocessor or more microprocessors are used. This, however, greatly increases costs and thus is not practical.
SUMMARY OF THE INVENTION
In view of the foregoing, the object of the present invention is to provide a high-precision pulse interpolation method of controlling a piston lathe and the like.
To achieve the above object, the present invention provides a high-precision pulse interpolation method wherein an amount of movement of individual axes of a numerical control apparatus is interpolated with a high precision. The ; and method comprises outputting an interpolation pulse twice or more during one task, the interpolation pulse being output at regular intervals by a servo control circuit to thereby carry out a pulse interpolation with a high precision.
That is, a plurality of interpolations are carried out during one task. Each interpolation pulse is delivered to the servo control circuit, which then outputs the interpolation pulse at regular intervals for processing, whereby a result equivalent to a pulse interpolation in a shorter task period can be obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram illustrating a numerical control apparatus according to one embodiment of the present invention;
FIG. 2 is a flowchart of a process executed in the numerical control apparatus (CNC);
FIG. 3 is a schematic diagram of a piston lathe to which the present invention is applied; and
FIG. 4 is a diagram illustrating the relationship between an interpolation and a task time.
DESCRIPTION OF THE PREFERRED EMBODIMENT
An embodiment of the present invention will now be described with reference to the drawings.
FIG. 3 is an example of a piston lathe to which the present invention is applied. In FIG. 3, a piston 11 is fixed to and rotated by a chuck, not shown, and a tool 14 for turning is moved in the X-axis and Z-axis directions. The X axis comprises an X1 axis 13 and an X2 axis 12. The X2 axis 12 is designed to move at a high speed. The movement of the X axis is normally controlled by the X1 axis 13.
To machine the piston 11 at a high speed with the arrangement of FIG. 3, the X2 axis 12 must quickly respond in synchronism with the rotation of the piston 11, and therefore, a task time for the necessary interpolation should be approximately 1 ms.
FIG. 4 is a diagram illustrating the relationship between the interpolation and the task time. Assuming that an interpolation is carried out between points P0 and P8, if the task period is 8 ms, then the interpolation is carried out linearly from point P0 to point P8, and accordingly, a deviation from the intended curve occurs. In contrast, if the task period is 1 ms, an interpolation is carried out for points P1, P2, P3, . . . and P8, whereby a curve closer to the intended curve is obtained. The present invention is capable of carrying out such an interpolation regardless of the performance of the microprocessor and without increasing the number of microprocessors used.
FIG. 1 is a block diagram of a nume
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Fanuc Ltd.
Ip Paul
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