JPH021617B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrical discharge machining control device, particularly an electrical discharge machining control device that controls the position of an electrode according to the state of the electrical discharge between an electrode and a workpiece. Regarding improvements.

[Prior Art] In an electric discharge machining control device, the position of the machining electrode must be controlled according to the state of the electric discharge gap between the electrode and the workpiece. In this case, the response of the control system is required to be fast.

For this reason, this type of electrical discharge machining control device uses a control device in which a speed servo system is incorporated into a position servo system, as shown in FIG. 1st
An example of a conventional electric discharge machining control device is shown in the figure, in which the electrical quantity representing the state of electric discharge between the electrode 10 and the workpiece 12 is sampled, arithmetic processed, and held. An electrode position command signal generator 14 that updates and outputs the position command Zc of the electrode 10 at regular intervals, and a position detector 4 that outputs the detected position value Zf of the electrode 10.
0, and an error counter 16 that outputs the difference (Zε) between the detected position value Zf and the position command value Zc, and drives the electrode 10 using the output value Zε of the error counter 16 as a speed command value. A speed servo system 18 is shown.

A current-controlled pulse voltage is applied between the electrode 10 and the workpiece 12 from a power supply device 20 for electrical discharge machining. Also, the state during the discharge is A/D
The data is updated via the (analog/digital) converter 22 at predetermined time intervals and input to the electrode position command signal generator 14 .

The electrode position command signal generating device 14 is composed of an input latch circuit 24, a logic operation circuit 26, and a zero-order hold output latch circuit 28.

The state of 〓 during discharge input from the A/D converter 22 at predetermined time intervals is determined by the logic operation circuit 26.
The output value Zε of the error counter 16 is added to the electrode position basic data in this logic operation circuit 26, and the electrode position command value Zc is calculated as electrode position basic data ZE, which is the basis of the electrode position command value. It is preset into the error counter 16 via the zero-order hold output latch circuit 28.

In other words, the logic operation circuit 26 shown in FIG.
The following is an explanation using the timing chart of the electrode position command value Zc output at .

The electrode position command value Zc for the basic data ZE at time t1 is first obtained by adding the error Zε' of the electrode position command value Zc' obtained from the basic data ZE' at time Δt before to the basic data ZE. The relationship between these values is as shown in Figure 7,
The output value Z〓, which is a tracking error, is the value (difference) obtained by subtracting Z _f from Z _c before adding the electrode position command basic data ZE. Z _c is the error counter 16 with period △t
The value _Zf set to is a pulse sent from the electrode position detector 40, and is sent in a time-division manner in units of counts of the error counter 16, and the positive and negative directions of each of these values are as follows. As shown in FIG. 7, the direction approaching the workpiece 12 is positive.

Then, as shown in the figure, the electrode position command value is
The output of Zc is latched by the zero-order hold and is performed at time t2 after a time Δt, and the electrode position command value Zc is preset in the error counter 16.

The speed servo system 18 includes a D/A (digital/analog) converter 30 and a differential amplifier 32.
, a DC servo motor 34, and a command generator 36, and the electrode 10 is driven by the servo system 18 and the feed mechanism 38 (see arrow).

The position of the electrode 10 is detected by a position detector 40 such as a differential transformer, and the detected position value is
Zf is sent to the input side of the error counter 16.
As a result, a position servo type is configured, and the output value Zε of the error counter 16, that is, the tracking error Zε
The position of the electrode 10 where the voltage becomes zero becomes a control target position (hereinafter referred to as the origin), and the motor 34 rotates in a direction toward this origin to perform the control during the discharge.

[Problems to be Solved by the Invention] Now, in the conventional device configured as described above, the electrode position command value Zc or the electrode position command data ZE in the positive direction with respect to the origin is given as shown in FIG. As illustrated in FIG. The difference of the same sign as the electrode position command value Zc is the position detection value from the electrode position command value Zc′.
If Zf is large, take the difference with the opposite sign from the electrode position command value Zc, and this difference is sent as the following error Zε to the speed servo system 18 as the speed command value, while The data is sent as addition data to the logic operation circuit 26 in the electrode position command signal generator 14.

However, in this case, this tracking error Zε tends to change from time to time due to the displacement of the electrode 10, as shown by the graph line A in FIG. Therefore, for example, at time t1, the tracking error Zε(t1) is taken into the logic operation circuit 26, added to the data ZE that will be the basis of the next electrode position command value, and sent to the zero-order hold output latch circuit 28. Let it latch, but
This latched output value, that is, the next electrode position command value Zc, is input to the error counter 16 for the first time at time t2 after a time Δt.

That is, the electrode position command signal generator 14 outputs the previous position command value Zc' and the error counter 1
After finding the tracking error Zε by 6, this tracking error
A time delay occurs until the next position command value Zc is output based on Zε. This time delay is inevitably caused by the arithmetic processing time of the logical arithmetic circuit 28, the sampling and holding time intervals, and the like. However, for this reason, the actual tracking error Zε clearly has a response delay as compared to the solid graph line A compared to the tracking error Zε when the delay time Δt is zero as imagined by the broken graph line B. I end up. As a result, smooth control is no longer performed, which may adversely affect machining accuracy, for example.

As described above, in conventional electrical discharge machining control devices, the time delay (Δt) that occurs until the next electrode position command value is actually output based on the previous tracking error
This impairs the high-speed response that should be a characteristic of this type of control device, and further increases the time delay (Δt).
There was a problem in that precise electrode position control was not possible because part of the electrode displacement information was lost due to changes during the process.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to substantially eliminate time delays in the above-mentioned devices, especially time delays inevitably caused by sampling, logical operations, holds, etc. To provide an electric discharge machining control device which can ensure high-speed response and prevent loss of part of electrode position information, thereby enabling precise electrode position control. There is a particular thing.

[Means for Solving the Problems] The present invention has been made to solve the above problems, and the electric discharge machining control device outputs basic electrode position data ZE from an electrode position signal generator,
By providing an adder between this electrode position signal generator and the error counter, the electrode position command value is
The Zc error counter is preset without any time delay.

[Function] As is clear from the above-described configuration, according to the present invention, it is possible to obtain an electric discharge machining apparatus that can perform high-speed response of the electrode position servo system and perform more precise electrode position control.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 3 shows a preferred embodiment of the electric discharge machining control device according to the present invention. The basic configuration of the device shown in the figure is similar to the conventional device described above. Therefore, the differences will be explained in particular.

The electrode position control mechanism of the electric discharge machining control device according to this embodiment uses basic electrode position data from the zero-order hold latch circuit 28 of the electrode position command signal generator 14.
An adder 42 that outputs ZE and is provided between the electrode position signal generator 14 and the error counter 16.
The above electrode position command value Zc is calculated.

That is, the generator 14 outputs the electrode position command data ZE at regular intervals. Then, the previous position command value is added to this output data ZE.
The tracking error Zε output from the error counter 16 is added based on ZE', and this added value is given to the error counter 16 as the electrode position command value Zc.

Therefore, here, the tracking error Zε output from the error counter 16 is not used as addition data for the logic operation circuit 26 in the electrode position command signal generator 14, but is used as calculation data for other control purposes. used. The tracking error Zε output from the error counter 16 is converted into an analog value by the D/A converter 30, and becomes a speed command value for the speed servo system 18. Then, based on this command value, the electrode 10 is displaced in the direction in which the tracking error Zε becomes zero. That is, tracking control is performed using a position loop servo system.

Here, FIG. 4 shows an embodiment of the adder 42 and the peripheral portion 44 of the error counter 16, and FIG. 5 shows one operational side thereof. Figures 4 and 5
In the figure, the adder 42 is the electrode position command data.
Electrode position command value Zc is obtained by adding ZE and tracking error Zε to the electrode position command value Zc.
is always output. This command value Zc is binary data and is the set input for the error counter 16, Q0 to QN.
given to. Also, at time t1, which determines the latch interval for sampling and holding in the device 14, the synchronization pulse T given to the error counter 16 causes
The data of the set input Q0~QN is the output D0~DN.
The binary data output is set to the tracking error Zε
The signal is given to the D/A converter 30 as follows.

Here, the tracking error Zε constantly changes with changes in the detected position value Zf of the electrode, but the detected position value Zf is created so that it is out of phase with the synchronizing pulse T, and is controlled by the control system. By synchronizing with a clock signal having a period of the minimum control time unit, the tracking error immediately before being added by the adder 42 is reduced.
The time difference between Zε' and the tracking error Zε at the time of addition can be practically eliminated. Therefore, the electrode position command data ZE from the electrode position command signal generation device 14 is added to the tracking error Zε′ before a part of the electrode displacement information changes and is lost, and the error is set as the next position command value Zc. It is applied to the counter 16, and at the same time, an accurate tracking error Zε is output.

As explained above, the adder 4 according to this embodiment
2 output (i.e., output of electrode position command value Zc)
The timing chart is shown in Figure 6b.

As shown in the figure, Zc is output simultaneously with the synchronization pulse T at time t1 without any time delay.
In comparison with the conventional example, in the conventional example shown in FIG. 6a, two pulses of the electrode position detection value Zf are input at time Δt, and the tracking error at time t2 is no longer Zε.

This makes it possible to ensure high-speed response performance and accurately control the electrode 10 before part of the electrode displacement information is lost.

In the above-described embodiment, the electrode 10 is controlled in one axis, but it is also possible to perform multi-axis control by, for example, time-division control using a multi-phase clock.

[Effects of the Invention] As described above, according to the electric discharge machining control device according to the present invention, it is possible to practically overcome the time delay that inevitably occurs due to sampling, arithmetic processing, and hold intervals. It is possible to ensure high-speed response performance of the control system, prevent part of electrode displacement information from being lost, and perform precise electrode position control.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a conventional electrical discharge machining control device, FIG. 2 is a graph diagram showing an example of the operation of the device shown in FIG. 1, and FIG. 3 is an embodiment of the electrical discharge machining control device according to the present invention. FIG. 4 is a circuit diagram showing a part of FIG. 3, FIG. 5 is a timing chart showing an example of the operation of the circuit in FIG. 4, and FIG. Output timing chart of electrode position signal generator, Figure 6b
is an output timing chart of the adder of the apparatus shown in FIG. 3, and FIG. 7 is a diagram for explaining each command value and data value of the conventional and the present invention. The same members in each figure are given the same reference numerals, 10 is an electrode, 12 is a workpiece, 14 is an electrode position command signal generator, 16 is an error counter, 18 is a speed servo system, and 20 is a power supply device for electrical discharge machining. , 22 is an A/D converter, 24 is an input latch circuit, 26 is a logic operation circuit, 28 is a zero-order hold output latch circuit, 30 is a D/A converter, 32 is a differential amplifier, 34 is a DC servo motor, 36 is a finger speed generator, 38 is an electrode feeding mechanism, 40 is an electrode position detector, 42 is an adder,
Zε is a tracking error, Zf is an electrode position detection value, Zc is an electrode position command value, and ZE is electrode position basic data.

Claims (1)

[Claims] 1. An electrode position command signal generating device that updates and outputs the position command value of the electrode at regular intervals by sampling, processing, and holding the electric quantity representing the state of the discharge gap between the electrode and the workpiece; An electric discharge machining control device having an error counter that outputs the difference between a detected position value of the electrode and the position command value, and a speed servo system that drives the electrode using the output value of the error counter as a speed command value,
means for directly adding the output value of the error counter to basic electrode position data, which is the basis of the next electrode position command value output from the electrode position command signal generator, without any time delay, and adding the result of the addition to the electrode position basic data that is the basis of the next electrode position command value output from the electrode position command signal generating device; An electrical discharge machining control device characterized by being equipped with an adder for presetting.