Position control apparatus and method of the same, numerical control program preparation apparatus and method of the same, and methods of controlling numerical control machine tool

• US 6,097,168 A
• Filed: 08/24/1998
• Issued: 08/01/2000
• Est. Priority Date: 08/25/1997
• Status: Expired due to Fees

• Current Assignee: Toshiba Kikai Kabushiki Kaisha (Toshiba Machine Company Limited)
• Original Assignee: Toshiba Kikai Kabushiki Kaisha (Toshiba Machine Company Limited)
• Inventors: Katoh, Kooichi, Matsumoto, Michio, Sagara, Makoto
• Primary Examiner(s): Masih, Karen
• Application Number:
  US09/138,605
• Time in Patent Office: 708 Days
• Field of Search: 318/600, 318/573, 318/603, 318/560, 318/646, 318/568.11, 318/574, 318/569, 364/474.3
• US Class Current: 318/568.11
• CPC Class Codes: B25J 9/16 Programme controls programme controls in general G05B19/00, e.g. numerical pogramme controls G05B19/18; recording or playback systems G05B19/42
• CPC Class Codes: G05B 19/18 Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form G05B19/418 takes precedence
• CPC Class Codes: G05B 19/19 characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path
• CPC Class Codes: G05B 19/404 characterised by control arrangements for compensation, e.g. for backlash, overshoot, tool offset, tool wear, temperature, machine construction errors, load, inertia G05B19/19, G05B19/41 take precedence
• CPC Class Codes: G05B 2219/41 Servomotor, servo controller till figures
• CPC Class Codes: G05B 2219/49 Nc machine tool, till multiple
• CPC Class Codes: G05B 2219/50 Machine tool, machine tool null till machine tool work handling

Abstract

A position control apparatus has a target setting unit for setting a target position in a direction of the control axis of the controlled object able to be moved in directions of a plurality of control axes by moving unit; a position control unit for independently positioning the controlled object to the target position in the direction of the control axis set by the target position setting unit; and a position correcting unit for correcting the target positions in directions of other control axes by compensation amounts for correcting positioning derivation in directions of other control axes occurring when positioning the controlled object to a first target position in the direction of one control axis among the plurality of control axes and then reversing the feed direction from that first target position and positioning to a second target position.

Claims

1. A position control apparatus comprising:

a target position setting means for setting a target position of a direction of a control axis of a controlled object, the controlled object being able to move in a plurality of directions of control axes by a moving means;

a position control means for independently positioning said controlled object to a target position of the direction of the control axis, the control axis set by said target position setting means; and

a first position correcting means for correcting the target positions of the directions of other control axes, the first position correcting means compensates amounts by correcting positioning deviation in directions of other control axes occurring, when positioning the controlled object to a first target position of the direction of one control axis among the plurality of control axes, and then reversing the feed direction from that first target position and positioning to a second target position.

2. A position control apparatus as set forth in claim 1, wherein said moving means comprises:

a plurality of driving means for supplying drive power to a moving part serving as a controlled object;

a feed mechanism for linking said moving part and said driving means and transmitting the drive power from the driving means to said moving part; and

a position detecting means for detecting a position of said moving part or driving means.

3. A position control apparatus as set forth in claim 1, further comprising a second position correcting means for outputting to said position control means a compensation command for compensation of a target position of the direction of the one control axis of the controlled object when reversing the feed direction of the one control axis of the controlled object.

4. A position control apparatus as set forth in claim 1, wherein said first position correcting means comprises a reversal detecting means for detecting reversal of the feed direction of the control axis based on a first and a second target position for said one control axis.

5. A position control apparatus as set forth in claim 1, wherein said first position correcting means holds in advance compensation amounts for correcting the target positions of the directions of the other control axes.

6. A position control apparatus as set forth in claim 1, further comprising:

a program analysis and processing unit for analyzing and processing a program serving as control information for controlling the positioning in the directions of the control axes; and

a position command distribution unit for distributing position commands for each control axis obtained in said program analysis and processing unit as amounts of movement per predetermined time to the position control means.

7. A position control apparatus as set forth in claim 1, wherein:

said controlled object is a numerical control machine tool comprises a plurality of control axes able to position a workpiece and tool at target positions; and

said first position correcting means comprises a means for calculating compensation amounts for correcting target positions of other control axis directions in accordance with cutting force applied to the tool.

8. A position control apparatus as set forth in claim 1, wherein said first position correcting means holds the compensation amounts for correcting the target positions of the other control axes as functions of the position of the direction of the one control axis.

9. A position control apparatus as set forth in claim 1, wherein said first position correcting means holds compensation amounts for correcting target positions of other control axes discretely for a plurality of positions in the direction of the one control axis and interpolates the compensation amounts to calculate compensation amounts in accordance with the positions in the direction of the one control axis.

10. A position control apparatus as set forth in claim 1, wherein said first position correcting means holds cumulative values of the output compensation amounts and outputs the cumulative values as control commands to the corresponding control axes after a predetermined process is ended.

11. A position control apparatus as set forth In claim 1, wherein

said controlled object is a numerical control machine tool comprises a plurality of control axes able to move a workpiece and tool as controlled objects to any positions;

and

said first position correcting means comprises a means for changing the compensation amounts for correcting target positions in other control axes between times of machining the workpiece by the numerical control machine tool and not machining it.

12. A position control apparatus as set forth in claim 1, wherein

said controlled object comprises a spindle for driving a rotary tool provided in the Z-axis direction, a first moving part provided at the spindle and guided to be able to move in the Z-axis direction and the Y-axis direction, Z-axis and Y-axis lead screws provided along the Z-axis direction and the Y-axis direction and screwed into threaded portions formed in the first moving part, Z-axis and Y-axis servomotors for driving said lead screws, a second moving part for clamping the workpiece guided to be able to move in the X-axis direction, an X-axis lead screw provided along the X-axis direction and screwed into a threaded portion formed in the second moving part, an X-axis servomotor for driving said X-axis lead screw, and first to third rotational position sensors for detecting rotational amounts of said X-, Y-, and Z-axis servomotors;

said position control means sends the workpiece mounted on the second moving part in the positive direction of the X-axis to the first target position, reverses the feed direction, and positions the workpiece to the second target position; and

the first position correcting means corrects one target position among the Z-axis direction and Y-axis direction of the front end of the rotary tool when moving from the first target position to the second target position.

13. A position control method comprising:

positioning a controlled object, able to be moved in a plurality of directions of control axes to a first target position of the direction of one control axis among the plurality of control axes and then reversing the feed direction from that first target position and positioning to a second target position;

detecting a reversal of a feed direction of one control axis; and

correcting the target position of the directions of the other control axes by compensation amounts for correcting positioning deviation in directions of other control axes occurring when reversing the feed direction of one control axis.

14. A position control method as set forth in claim 13, further comprising measuring compensation amounts based on the properties of the machine.

15. A position control method as set forth in claim 13, further comprising correcting a target position in the direction of the one control axis in accordance with detection of reversal of the feed direction of the one control axis of the controlled object.

16. A method of preparation of a numerical control program for controlling a numerical control machine tool comprising a controlled object able to be moved in directions of a plurality of control axis by moving means,

said method of preparation of a numerical control program comprising

preparing a main numerical control program for controlling the driving of said controlled object;

and

inserting into a command program, contained in said main numerical control program, for driving one control axis to position said controlled object to a first target position and to reverse the feed direction and position the second target position, a compensation program for correcting the target positions in the directions of the other control axes of the controlled object to correct the main numerical control program.

17. A method of preparation of a numerical control program as set forth in claim 16, further comprising measuring in advance compensation amounts to be set in said compensation program based on mechanical properties of said numerical control machine tool.

18. A method of preparation of a numerical control program as set forth in claim 16, wherein said correcting the numerical control program further comprises inserting a compensation program for correcting a target position in the feed direction of the one control axis.

19. A numerical control program preparation apparatus comprising:

a numerical control program preparing means for preparing a numerical control program for controlling the positioning of a controlled object, able to be moved in directions of a plurality of control axes by a moving means, of a numerical control machine tool which has the controlled object;

a detecting means for detecting a command program, included in the numerical control program, for positioning said controlled object to a first target position in the direction of one control axis and then reversing the feed direction and positioning to a second target position; and

a numerical control program correcting means for inserting into the detected command program a compensation program for correcting the target positions in the directions of the other control axes of the controlled object when reversing the feed direction of the one control axis.

20. A numerical control program preparation apparatus according to claim 19, wherein said numerical control program correcting means holds said compensation amounts as values measured in advance based on the mechanical properties of said numerical control machine tool.

21. A numerical control program preparation apparatus according to claim 19, wherein said numerical control program correcting means holds compensation amounts in said compensation program as functions of a position of the feed direction of said one control axis.

22. A numerical control program preparation apparatus according to claim 19, wherein said numerical control program correcting means holds compensation amounts in said compensation program discretely for a plurality of positions in the direction of the one control axis, and interpolates the discretely held compensation amounts to calculate compensation amounts in accordance with the position in the direction of the one control axis.

23. A numerical control program preparation apparatus according to claim 19, wherein said numerical control program correcting means comprises a means for changing the compensation amounts for correcting the control commands of the other control axes between times of machining the workpiece by the numerical control machine tool and not machining it.

24. A method of control of a numerical control machine tool comprising:

preparing a numerical control program for running a numerical control console for controlling the positioning of a controlled object, able to be moved in directions of a plurality of control axes by a moving means, of a numerical control machine tool having said controlled object;

correcting the numerical control program, included in said numerical control program, by inserting into a command program for positioning said controlled object to a first target position of the direction of one control axis among a plurality of control axes and then reversing the feed direction and positioning it at a second target position, a compensation program for correcting the target positions in directions of other control axes of the controlled object;

for downloading the corrected numerical control program to the numerical control console, and

for controlling the drive of the numerical control machine tool in accordance with the numerical control program downloaded to the numerical control console.

25. A method of control of a numerical control machine tool as set forth in claim 24, wherein

said controlling the drive of the numerical control machine tool comprises correcting the positioning error in the direction of the control axis caused when reversing the feed direction of the one control axis;

and

both target positions of the one control axis direction and other control axis directions are corrected.