Numerical control device with speed override control

• US 5,309,074 A
• Filed: 02/24/1993
• Issued: 05/03/1994
• Est. Priority Date: 05/18/1992
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Mizukami, Yuji
• Primary Examiner(s): Ip, Paul
• Application Number:
  US08/021,961
• Time in Patent Office: 433 Days
• Field of Search: 318/560-646, 364/674.01-674.33
• US Class Current: 318/571
• CPC Class Codes: G05B 19/416 characterised by control of velocity, acceleration or deceleration G05B19/19 takes precedence
• CPC Class Codes: G05B 2219/34157 Synchronize interpolation of different axis boards, simultaneous start
• CPC Class Codes: G05B 2219/43101 Change time constants acceleration, deceleration as function of feed rate override
• CPC Class Codes: G05B 2219/43156 Feed rate
• CPC Class Codes: G05B 2219/50015 Multi cutting, twin tools contact at same time workpiece, balance cutting

Abstract

A multi-system numerical control device which receives input commands for each system and is operative to control the speed and acceleration/deceleration of corresponding moveable objects, such as a motors. Each system has an interpolation unit and an acceleration/deceleration unit that is responsive to a corresponding time constant. A speed override device is operative to generate a speed reduction control signal that is applied to the interpolation unit to reduce the speed and to the acceleration/deceleration unit to reduce the time constant, thereby ensuring that the position relationship between the systems will not be lost even when override is applied.

Claims

1. A numerical control device for a machine tool comprising:

a plurality of controlled systems, the operation of at least a first and second of said systems being synchronized and being represented by respective acceleration/deceleration time constants;

a speed override input for inputting a speed override command;

an interpolation processor for reading a machining program and outputting resultant drive signals;

a time-constant processor that modifies said respective acceleration/deceleration time constants for said first and second systems in response to said speed override command and in accordance with a predetermined functional relationship, and that outputs acceleration and deceleration control signals based on the modified time constants and the drive signals;

wherein said functional relationship substantially maintains the synchronized operation of said first and second systems.

2. A numerical control device for a machine tool as set forth in claim 1, wherein said time-constant processor calculates said respective modified time constants for said first and second systems in proportion to said speed override.

3. A numerical control device for a machine tool as set forth in claim 2, wherein said time constant processor calculates said respective modified time constants in response to the same speed override factor.

4. A numerical control device for a machine tool as set forth in claim 1, wherein said respective modified time constants are different.

5. A numerical control device for a machine tool comprising:

at least a first and a second controlled system, each comprising a moveable part and being responsive to input commands;

means for providing a speed override to at least said first and said second controlled systems;

speed calculating means, responsive to said speed override means, for producing a speed signal for controlling the speed of each said moveable part; and

acceleration/deceleration means for providing acceleration and deceleration control signals for said first and second controlled systems for respective prescribed periods of time, said acceleration/deceleration means being responsive to said speed override means for modifying said prescribed periods of time in predetermined functional relationship to said provided speed override;

wherein said functional relationship substantially maintains a positional relationship between said movable parts.

6. The numerical control device as set forth in claim 5, further comprising time constant calculating means responsive to said speed override means for modifying original time constants representative of said prescribed periods of time.

7. A numerical control device as set forth in claim 6, wherein said functional relationship is defined by:

space="preserve" listing-type="equation">JN=JO/R

where

JO is one of said original time constants,

R is said speed override, and

JN is a modified time constant.

8. The numerical control device as set forth in claim 6, wherein said time constant calculating means outputs said modified time constants, and

said acceleration/deceleration means inputs said modified time constants in order to modify said prescribed period of time.

9. The numerical control device as set forth in claim 5, wherein a respective acceleration/deceleration time constant is predetermined for each said system.

10. The numerical control device as set forth in claim 5, wherein said acceleration/deceleration means is operative according to a linear function.

11. The numerical control device as set forth in claim 5, wherein said acceleration/deceleration means is operative according to an exponential function.

12. The numerical control device as set forth in claim 5, wherein said provided speed override slows the speed of each said moveable part.

13. The numerical control device as set forth in claim 5, wherein said acceleration/deceleration means comprises:

a shift register having a plurality of buffer registers;

a selector for selecting among said plurality of buffer registers to provide a shift-register output, wherein the selection is determined by said provided speed override; and

processing means responsive to a drive signal, to said shift register output and to said provided speed override for providing said acceleration and deceleration control signals.

14. The method of controlling a plurality of systems in a numeral control device, each said system having a corresponding acceleration/deceleration time constant, in response to input control signals, comprising:

generating respective speed control signals for each said system in response to said input control signals and at least one speed override command; and

modifying each said time constant, in response to said speed override command, according to a predetermined functional relationship which substantially maintains a positional relationship between controlled portions of said systems.

15. The method of controlling a plurality of systems in a numerical control device, as set forth in claim 14, further comprising detecting said override command within said input control signals.

16. The method of controlling a plurality of systems in a numerical control device, as set forth in claim 14, wherein said modifying step comprises re-calculating said acceleration/deceleration time constants in proportion to the speed override factor determined in response to said speed override command.

17. The method of controlling a plurality of systems in a numerical control device, as set forth in claim 16, wherein said functional relationship is defined by:

space="preserve" listing-type="equation">JN=JO/R

where

JO is one of said acceleration/deceleration time constant,

R is said speed override factor, and

JN is a modified time constant.

18. A multi-line numerical control method for numerically controlling independent lines individually under control of independent machining programs, each said line having a respective acceleration/deceleration time constant and being operative to operate a motor, comprising the steps of:

(a) analyzing each of said machining programs to identify a commanded feedrate for a corresponding line;

(b) in response to said analysis, overriding each feedrate commanded by said each machining program analyzed at step (a) to provide respective override values;

(c) calculating a modified corresponding acceleration/deceleration time constant to maintain positional relationships between the lines according to each override value at step (b); and

(d) exercising acceleration/deceleration control of the motor on each line using each modified acceleration/deceleration time constant calculated at step (c).

19. A multi-line numerical control apparatus for numerically controlling independent lines individually under control of independent machining programs, each said line having a respective acceleration/deceleration time constant and being operative to operate a motor, comprising:

(a) program analyzing means for analyzing each of said machining programs to identify a commanded feedrate for each said motor;

(b) an overriding device for overriding each feedrate commanded by said each machining program analyzed by said program analyzing means;

(c) acceleration/deceleration time constant calculating means for calculating a modified acceleration/deceleration time constant for each said line in order to maintain positional relationships between the lines according to each override value of said overriding device; and

(d) accelerating/deceleration means for exercising the acceleration/deceleration control of a motor on each line using each modified acceleration/deceleration time constant calculated by said acceleration/deceleration time constant calculating means.