JPS58127208A - Positioning control system for machine tool - Google Patents

Abstract

PURPOSE:To improve the operability, by correcting mistake in count pulse automatically and avoiding the restoration to the home position, based on the level of two-phase output of an encoder at past power supply interruption and re-application. CONSTITUTION:When a paper supply is applied, position information of a control variable is fetched to a CPU20 from a counter 16 via the 2nd input port 26, and the CPU20 recognizes the present position. When the power supply is interrupted from this state, the CPU20 recognizes the interruption of power supply with a power supply interruption detecting circuit 30, opens the 1st input port 24 to fetch two-phase outputs (A, B) of the encoder at the power supply interruption, introduces the position information at the same point of time the 2nd port 26 and stores it in a data memory 23. When the power is applied again, the level of two-phase outputs (A', B') of the encoder 10 at the re-application is fetched for the comparison with the level of the two-phase output (A, B) in the memory 23. if there is a difference between the levels, whether or not the presence of the count pulse is discriminated and correction is made at the presence of pulses.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to detecting the position of a table, tool, etc. in a machine tool, and in particular, accurately detects the position information of the object (table, tool, etc.) whose position was being controlled at the time of the previous power cut-off when the power is turned on again. The present invention relates to a positioning control system for detecting.

Conventional position detection in this type of machine tool uses an incremental type pulse encoder (incremental encoder) that is related to the movement of the position controlled object, and the contents of a reversible counter are determined by count pulses generated based on the output of the encoder. This is generally done by controlling the increase or decrease.

FIG. 1 is an explanatory diagram of position detection by an incremental encoder, and shows the processing process of the output signal of the encoder in a time chart.

In the figure, signals (A) and (B) are the A-phase and 8-phase output waveforms of the incremental encoder, respectively, and a phase difference of π/2 is given between them. Therefore, by determining the phase leading or lagging relationship of the signal (A>-(B)all),
It becomes possible to detect movement of the control pair 9 of the table, tool, etc. in the forward or reverse direction. Shin@(C1・D
, E, F, G) indicate processed signals for the detection in item 1. First, by differentiating the signal (A>, the signal (C)
A differential pulse train is created by a short-width positive pulse at the rising edge of the signal (A) and a negative pulse of the same width at the falling edge of the signal (A), as shown in FIG. The differential pulse train (C) is extracted separately into a positive pulse train (D) and a negative pulse train (E), and the inverted value of the signal @ (B) is extracted in order to determine the phase relationship between the two-phase outputs (A, B) of the encoder. B) AND is performed between each of the two. As a result, a count-up pulse (F) representing the amount of movement of the controlled object in the forward direction is generated by the positive pulse train (O) and the inverted value (B), and a count-up pulse (F) is generated in the direction of one rotation by the negative pulse train (E) and the inverted value (B). A countdown pulse representing the amount of movement of <G
) are obtained, and by driving a reversible counter with these signals (F, G), the position information of the control Iλ→elephant is detected.

Although it is widely used today because of its advantages, it has the disadvantage that when the power is turned off and then turned on again and restarted according to the position information at the time of the previous power cut, an error occurs in the information. In other words, in the time chart of Figure 1, if the power is cut off at point (A) of signal (A), there is a risk that point (A) will shift due to mechanical changes and/or characteristics of the encoder when the power is turned on again. There is. If this state occurs and point (0) is detected when the power is turned on again, the count-up pulse (x) will become uncounted, as is clear from the figure, and an error of <-) 1 pulse will occur in the position information. .

Conversely, when the power is turned off, it is the point (0) and when it is turned on again, it is the point (0).
If (a), it is clear that an error of (+)1 pulse will occur. Further, the same can be said about points (c) and (d) with respect to the countdown pulse (V).

Because of these drawbacks, systems using incremental encoders have the inconvenience of having to return to the home position every time the machine starts O''+1.・This can be solved by using an encoder (scale for detecting absolute values), but absolute encoders not only increase the cost of the system but also
It has drawbacks such as being unsuitable for long-distance detection.

The present invention is intended to improve the above-mentioned drawbacks of the conventional technology.The purpose of the present invention is to use an incremental encoder that has been widely used in the past to provide positional information when the power is turned on again when the power is cut off 211M. An object of the present invention is to provide a positioning control system that can automatically correct errors in the positioning control system.

A feature of the present invention for achieving the above purpose is that it has an increase-5) type pulse 1 encoder, and controls the content of the counter to increase or decrease according to the count pulses for the two phases of the encoder. A process for detecting position information of a position controlled ill object f\:' In a machine positioning control system, when the power is cut off, the phase output level state of the engine 1- and the position information of the position controlled object are memorized, 5. Compare the stored two-phase output level state with the output level state of the encoder when the power is turned on again, and if the result does not match, the encoder is limited between when the power is cut off and when the power is turned on again. By determining the presence or absence of a count pulse in the output time width and increasing or decreasing the content of the counter by 1 count pulse according to the presence of the count pulse, the error in position information when the power is turned on again compared to when the power is 1nlIi is automatically corrected. It is found in the positioning control system of machine tools such as

The present invention will be explained in detail below with reference to the drawings.

FIG. 2 is a block diagram showing an embodiment of the present invention, which includes a position detection means for electrically detecting the mechanical position of a position-controlled object such as a table or a tool, a microcomputer system for managing the position information, It has a detection circuit that supplies information about machine power-off to a computer system.

The position detection means includes an incremental encoder 10, a waveform shaping circuit 12, a direction discrimination circuit 14, and a counter 16. As described above, the encoder 10 extracts mechanical position information as electrical signals (A, B) having a phase difference of π/2, and supplies the electrical signals to the waveform shaping circuit 12. The circuit 12
removes high frequency components and shapes the waveform, and also
and (+1'!) to internal logic levels.

The output of the waveform shaping circuit 12 is processed in the direction discrimination circuit 14 according to the signal processing process described in connection with FIG.
Up pulse (F) and count down pulse (
G), which drives the counter 16.

The microcomputer system includes CPU20 and +JC.
Pro-Gera 11 mem (s2) connected to PU via internal bus.
2, the data memory 23, and the first and second Panonobo 1~
(24, 26> and the output port 28 are connected to the output of the waveform shaping circuit 12 through the first input port 24, and the counter 1 through the second input port 26).
6 and further provides processing information to mechanical actuator 40 via output port 28 .

Reference numeral 30 is a power failure detection circuit, which provides power failure information to the CPLI 20 and also provides power backup circuit 3.
2 to prevent the data in the data memory 23 from volatilizing.

With the above configuration, when power is being supplied, the position information of the controlled object is taken in from the counter 16 to the CPU 20 via the second input port 26, so the current position can be known. If the power is cut off in this state, the CPU
20 detects a power outage by the power outage detection circuit 30, opens the first input port 24, receives the level state of the two-phase output (A, B) of the encoder at the time of the power outage, and simultaneously receives data from the second port 26. The position information of the points is introduced and these are stored in the data memory 23.

This data is transferred to the power source 8! by the power backup circuit 32. Retained during shutdown. When the power is turned on again, the two-phase output (/M, Bi
take in the level state of through the first input port 24,
A comparison is made with the level state of the two-phase outputs (A, B) in the memory 23 at the time of power cutoff.

Figure 3 shows the distance between the two-phase outputs (A) and (B) of the encoder.
If the power is cut off at point (a), the level state of the signals (A) and (E3) when the power is cut off is lO11110''.The signal when the power is turned on again ( There is no problem if the level states of A') and (B-) match.However, if the point (b
)'s two-phase output (/M, B=) can be obtained as LJ, the level states at the time of power cut-off (a) and at the time of power-on again (b) are consistent, and at this point (a) and (b) If count pulses (F, G) exist within a limited time width, a J1 difference will occur as described above.

Therefore, if there is a level difference between the two-phase horns (A, B) and (/M, B') when the power is turned off and when it is turned on again, the encoder is limited at both times. It is determined whether or not a count pulse exists within the time width of the output, and if a count pulse exists (in this case, a count error compensation +1 for the count pulse is calculated).

The need to correct the count pulses due to the level difference between when the power is cut off and when the power is turned on again is as shown in Table 1 shown in relation to FIG.
When A, B) are at the level (1°O), (A=
, B'') takes (0°0), the count pulse in question is double counted, so a correction of 11 pulses is given, and if the signal (A, B) at the time of interruption is (0, 0). If (1, 0) is taken when the pulse is re-injected, the count pulse in question is no-count, so a correction of +1 pulse is given.

The control system described above is limited to cases where the error is within 1/4 cycle, but since machines are generally braked when the power is connected or disconnected, there is no problem in the usability of the present invention. .

In the first embodiment, a case has been described in which one count is performed for each period of the output pulse of the encoder, but it is also applicable to cases in which more counts are performed.
It can also be applied to resolvers.

As explained above, according to the present invention, when the power is turned on again,
The level state of the two-phase output of the encoder at the time of the previous power-off and the level state at the time of power-on again are different (LA).Using the C1 incremental encoder, which automatically corrects for count pulse mistakes (regardless of the origin) There is no need to perform a return operation, which not only improves operability but also makes it possible to provide an economical and inexpensive control system.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of position detection by an incremental encoder, FIG. 2 is an embodiment of the present invention, and FIG. 3 is an explanatory diagram of error correction. 10... Incremental encoder 12... Waveform shaping circuit 14... Direction discrimination circuit 16... Counter 20... CP122.23... Memory 24.26.28... Boat 30... Power failure detection circuit 32...power backup circuit

Claims (1)

[Claims] A positioning control system for a machine tool that has an incremental pulse encoder and detects position information of a position control target of a machine tool by controlling the contents of a counter to increase or decrease in accordance with the current count <)res based on the two-phase)) of the encoder. , the two-phase output level state of the above-mentioned [n]-da and the 11 information of the position IIIll object are stored in the power supply cutoff m1l18, and the stored two-phase output level state and the information are stored when the power is turned on again. The output level state of the encoder output is compared with the output level state of the encoder 1--da, and if the result does not match, the time width of the encoder output that is limited at the time of power-off and power-on again is determined. The present invention is characterized by automatically correcting the error in the position information at the time of inputting the mountain with respect to the time of power cutoff by determining the presence or absence of the current value and increasing or decreasing the contents of the counter by one count pulse according to the presence of the current number <). Positioning III control system for machine tools.