JPH02303721A - Control method for electrode feeding of discharging machine - Google Patents

Abstract

PURPOSE:To perform a high electrode control and to increase a working speed and working accuracy by controlling the feeding speed of the electrode of a discharging machine by a fuzzy control. CONSTITUTION:A waveform feature detection means 19 detects the maximum value Vn of a gap voltage and the value of a discharging delay time Tn and a smoothing means 20 produces Vi and Ti which are smoothed by taking the averaged value of these values, etc., inputting it to a fuzzy control part 12. At this control part 12 a fuzzy inference is executed at a fuzzy inference part 12a based thereon, a moving command (a feeding command pulse Pn) is output with its fuzzing at an interpretation part 12b and the feeding of the electrode 34 of a discharging machine is controlled. A high electrode 34 control can thus be realized and the working speed and working accuracy can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrode feed control system for an electric discharge machine, and more particularly to an electrode feed control system for an electric discharge machine that uses fuzzy control to control electrode feed.

[Conventional technology]

The electrode feed control method for die-sinking electrical discharge machines detects the average voltage of the discharge voltage waveform, the delay time until the start of discharge, etc., and adjusts these detected values to the reference target voltage and reference target delay time. A method is used to control the distance between poles using a servo motor.

This control is generally performed as follows.

(a) Detecting the average voltage of the discharge voltage waveform, the delay time until the start of discharge, etc.

(b) Find the difference between this detected value and a preset reference target voltage, reference target delay time, etc. (C) The value obtained by multiplying this difference by a certain gain is used as a movement command to the servo motor.

(d) Repeat (a) to (c) at regular intervals.

As a result, the electrode is constantly controlled to maintain the reference target distance.

[Problem to be solved by the invention]

However, detected values such as the average voltage of the discharge voltage waveform and the delay time until the start of discharge generally differ for each discharge. In other words, these detected values are determined not only by the gap distance between the electrode and the workpiece, but also by the sludge (processing debris) between the electrodes.
It changes depending on complex factors such as the state of the ions and the state of the ions.

Therefore, with conventional control methods, machining speed decreases,
Alternatively, there was a problem that the discharge became unstable.

The present invention has been made in view of these points, and an object of the present invention is to provide an electrode feed control system for an electric discharge machine that uses fuzzy control to control the electrode feed speed.

[Failure to solve the problem]

In order to solve the above-mentioned problems, the present invention provides an electrode feed control method for an electric discharge machine that controls the feed of an electrode of an electric discharge machine, in which the feed speed of the electrode is controlled by fuzzy control. An electrode feeding control method is provided.

[Effect]

Characteristic elements of the gap voltage waveform, such as gap voltage and discharge delay time, are detected, fuzzy inference is performed based on these values, and the electrode feeding speed is controlled using the defuzzified output.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

Figure 1 shows CNC die-carving electrical discharge machining 2 for carrying out the present invention.
FIG. 2 is a block diagram showing the configuration of the machine. The machining condition/machining process setting means 13 manually inputs the required data from the CRT/MDI unit 11, and sends machining power supply parameters related to machining voltage or machining current to the machining power supply 40, and control parameters regarding oscillation to the electrode oscillation control means 14. Next, control parameters regarding the jump period and jump distance are manually input to the jump control means 15. The servo control means 16 manually receives commands output from the electrode swing control means 14, the jump control means 15, and the fuzzy control section 12, which will be described later.
The X-axis peripheral servo motor 31, the Y-axis layer servo motor 32, and the ZM servo motor 33 are driven.

A high-frequency pulse voltage is output from the machining power source 40 and applied between the electrode 34 and the workpiece 35 fixed on the table, and the table 36 is moved on the X-Y plane according to the instructions of the machining process. The electrode 34 moves on two axes, and the workpiece 34 is subjected to electrical discharge machining.

The gap voltage waveform detection means 17 detects the electrode 34 and the workpiece 3.
5 is detected and sent to the AD converter 18. The AD converter 18 digitizes this voltage waveform,
It is sent to the waveform feature extraction means 19.

FIG. 2 shows an example of the gap voltage waveform input to the waveform feature extraction means 19. The gap voltage waveform 50 has Vn as the maximum value, and after a predetermined discharge delay time Tn, a discharge occurs and becomes a low voltage, and this cycle is repeated at high frequency.The maximum value Vn and the discharge delay time TnO value are respectively set at the time of a normal spark. A waveform that is within a predetermined range but changes depending on the state of discharge; for example, when completely open, the maximum value Vn remains constant from the beginning to the end of one cycle,
That is, the discharge delay time Tn matches the period of one cycle. Conversely, when a short circuit occurs, the voltage becomes low from the beginning, and the discharge delay time Tn becomes zero.

Returning to FIG. 1 again, explanation will be given. The waveform feature detection means 19 detects the maximum value Vn of the gap voltage and the values of the discharge delay time Tn and sends them to the smoothing means 20.

The smoothing means 20 generates smoothed Vi and Ti by taking the average value of these values, and inputs them to the fuzzy control section 12.

In the fuzzy control unit 12, based on these, a fuzzy inference unit 12a executes fuzzy inference, an interpretation unit 12b performs defuzzification 2, and outputs a movement command (feeding command pulse Pn). 3(a) and 3(b) are explanatory diagrams of fuzzy rules provided in the fuzzy inference section 12a.

In the figure, 60 is a fuzzy rule composed of R'-R5, AIl to A14 are membership functions showing the relationship between the maximum voltage Vi and the degree of conformity, and A22 to A25 are the relationships between the discharge delay time Ti and the degree of conformity. Membership functions showing 81-B51;! This is a membership function showing the relationship between the sending command pulse Pi and the degree of conformity.

Here, the fuzzy rule R' is the membership function Al
Based on l and B1, R1: This is a rule that infers that if Vi is small, Pi should be a large positive value.

Similarly, fuzzy rule R2 is membership function A12, A22, and B2, fuzzy rule R3 is membership function A13, A23, and B3, fuzzy rule R4 is membership function A14, A24, and B4, and fuzzy rule R5 is membership function A25 and B5
R2: If Vi is medium and Ti is small, set Pi to a positive and slightly large value R3゜If Vi is large and Ti is small, set Pi to 0 R4 = Vi If R5° is large and Ti is medium, then Pi should be set to a slightly small negative value, or if R5°Ti is large, Pi should be set to a large negative value.

The fuzzy inference unit 12a calculates the maximum value Vi of the input gap voltage and the discharge delay time Ti using the above fuzzy rule R'.
-Membership functions 31 to B5 in comparison with R'
, the degree of conformity of each sending command pulse Pi is determined, and these are superimposed to generate an inference result (not shown) into a table t membership function, which is sent to the interpreter 12b.

The interpreter 12b performs defuzzification on this membership function using, for example, the centroid method to determine the value of the feed command pulse Pn and outputs it. 1 is a block diagram showing the configuration of a CNC die-sinking electrical discharge machine.

The difference from FIG. 1 is that the smoothing means 20 is replaced with interpole distance estimating means 21, an arithmetic unit 22a, and a differentiator 22b. That is, the gap distance estimation means 20 calculates the gap distance between the electrode 34 and the workpiece 35 based on the maximum voltage Vn and the discharge delay time Tn output from the waveform feature extraction means 19, and inputs it to the calculator 22. The calculator 22 calculates the difference between this gap distance and the target reference value from the machining condition/process setting means 13, and inputs the difference to the fuzzy inference section 23a of the fuzzy control section 23. The differentiator 2gb calculates a variation δε of the difference ε between the gap distance and the target reference value and inputs the calculated value to the fuzzy inference unit 23a of the fuzzy control unit 23. The fuzzy inference section 23a executes fuzzy inference based on the input data, and the interpretation section 23b performs defuzzification and outputs a feed command pulse Pn.

Other elements with the same numbers as in FIG. 1 have the same functions, and their explanations will be omitted.

In addition, multiple fuzzy rules and membership functions for the fuzzy controller that controls electrode feeding are registered, and selected according to the processing method and material of the workpiece, etc., and fuzzy control is performed using the selected fuzzy rules and seven membership functions. You can also do this.

Although the explanation has been made by controlling the feed of the wire, the distance between the poles and the like of a wire-cut electrical discharge machining machine can also be controlled with a similar configuration.

〔Effect of the invention〕

As explained above, in the present invention, the maximum value of the gap voltage and the discharge delay time are detected, fuzzy inference is executed based on these, and the electrode feeding speed is controlled by the output, so that the advanced electrode It becomes possible to realize control, and it is possible to improve machining speed and machining accuracy including clearance.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the configuration of a CNC die-sinking electrical discharge machine for implementing the present invention, Figure 2 is an example of a gap voltage waveform, and Figures 3 (a) and (b) are explanations of fuzzy rules. FIG. 4 is a block diagram showing the configuration of another CNC die-sinking electrical discharge machine for carrying out the present invention. 12.23 Fuzzy control unit 12a, 23a ” Fuzzy inference unit 12b, 23
b Interpretation section 16 - Servo control means 19 -- Waveform feature extraction means 20 Smoothing means 21 Inter-electrode distance estimating means 22 Arithmetic unit 34 Electrode 35 Workpiece 40 Machining power source 60 Fuzzy rule Vi Maximum value of gap voltage Ti Discharge delay time

Claims (4)

[Claims] (1) An electrode feed control method for an electric discharge machine that controls the feed of an electrode of an electric discharge machine, characterized in that the feed of the electrode is controlled by fuzzy control. (2) The electrical discharge machine according to claim 1, wherein a plurality of fuzzy rules and membership functions for the fuzzy control are stored as a database and can be selected depending on the type of machining. electrode feed control method. (3) The discharge according to claim 1, wherein the maximum value of the gap voltage and the discharge delay time are input, the electrode sending command pulse is output, and the control between these is performed by fuzzy reasoning. Electrode feed control method for processing machines. (4) The difference between the gap distance and the target distance detected by the inter-electrode distance estimating means and the amount of change in this difference are input, the electrode feed command pulse is output, and the control between these is performed by fuzzy inference. An electrode feed control system for an electrical discharge machine according to claim 1, characterized in that: