JPH0336608A - Position detecting circuit - Google Patents

Abstract

PURPOSE:To obtain the position detecting circuit which can detect a position with high precision by an inexpensive circuit by detecting a value of a free run counter by collating it with a value of a cycle counter by using a value for showing a prescribed distance in data. CONSTITUTION:The circuit is constituted so that a position detection error is detected by using a value alpha being data obtained an origin return operation executed usually and for showing a distance extending from turn-on of a power source to a first Z phase, bringing a value of a free run counter 1 brought to up or down in accordance with an A phase and a B phase signals outputted from an encoder being a position sensor to up or down in accordance with the A phase and the B phase signals, and collating it by a value of a cycle counter 3 which is reset every time by the Z phase. According to this constitution, since the counter 3 is reset every time by the Z phase, a detection error is not accumulated, and the detection error can be decided easily, and also, the circuit can be constituted at a low cost, and the detection can be executed with high precision.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a position detection circuit that detects the position of a machine tool controlled by a numerical control device, for example, and particularly to a position detection circuit that detects position detection errors caused by noise or the like. It is about detection.

[Prior Art] Fig. 3 is a block diagram showing a counter portion in a conventional position detection circuit, Fig. 4 is a timing diagram illustrating the operation of returning to the origin, and Fig. 5 is an explanatory diagram explaining the operation of returning to the origin. It is.

In the figure, (() is a free-run counter, which increases with forward rotation pulses obtained by phase discrimination of the A-phase signal and B-phase signal, which are outputs of an incremental encoder as a position sensor (not shown), and decreases with reverse rotation pulses. (2) is a data latch F that latches the data of the free run counter (1). (3) is a cycle counter, which is a counter that increases with the forward rotation pulse and decreases with the reverse rotation pulse as described above. (4) is the data latch S that latches the data of the cycle counter (3). (5) is the A-phase signal, (6) is the B-phase signal, and (7) is the Z-phase signal.
The phase signal (8) is a latch signal.

Note that since FIG. 3 is shown in a simplified manner, the circuit for performing the above-mentioned phase discrimination is not shown.

In Fig. 4, (9> indicates the timing of turning on the power. α is the distance from turning on the power to the first Z phase, RNG is the distance from the Z phase to the second phase, and N pulses per rotation. This corresponds to N if the encoder is N.

In Figure 5, ■ is the speed of the motor that drives the machine, (
]1) is the dog's operating range, (12) is the dog's ON (ON)
(13) indicates the dog-off (OFF) timing.

By the way, in numerically controlled (NC) machine tools, it is necessary to set up a coordinate system based on the machine position, so when the power is turned on, the origin return operation is always performed to move the axis to a specific position on the machine. It is necessary to preset the coordinate system.

In order to perform this return-to-origin operation, a one-rotation pulse (Z phase) of the encoder is used, and a detection means called a dog (micro switch, etc.) is installed on the machine to determine the specific position of the machine. As shown, the machine starts decelerating when it passes the dog, and after decelerating to a certain speed, it stops at the first Z phase that leaves the dog as the mechanical origin P. Using this method, the mechanical origin is determined and the coordinate system is preset.

Next, the operation will be explained.

As shown in FIG. 4, the free run counter (1) is initialized by initialization processing when the power is turned on, and from that point on, the free run counter (1) starts operating. In addition, when the cycle counter (3) is initialized, the cycle counter (3) is set to a specific value that is not normally counted by the cycle counter (3). In other words, in the case of an N pulse encoder, the cycle counter (3) keeps changing from O to N, so the cycle counter (3) continues to change from O to N. A value greater than or equal to the value is set as the v′J period value.Then, Z
Waiting for the phase to pass. The cycle counter (3) is reset when the first Z phase passes and
It starts counting the phase and B phase, and is reset every time the Z phase comes.

Here, the value of the cycle counter (3) is detected, and if it is the initial value, the counter does not latch because the Z phase has not passed. If the value is other than the initial value (0 to N), it is determined that the Z phase has passed, and the free run counter (1) and cycle counter (3) are latched simultaneously by the latch signal (81). By calculating the difference (A-B) between latch data A of data latch (2) and latch data B of data latch (4), distance α from power-on to the first Z phase can be calculated.
is detected. By being able to detect this α, it is possible to detect in advance at which position of the value of the free run counter (1) the two phases are located, and which Z phase among them is the machine origin is determined by the mechanical dog.

Further, since it is possible to detect in advance at which position of the value of the free run counter (1) the Z phase will be, the absolute position can be detected.

[9! Three problems that Akira is trying to solve: In the conventional position detection circuit as described above, if the encoder is affected by noise and the pulse count is incorrect, a position shift occurs by the amount of error, and this position shift is detected. The problem was that it could not be done.

This invention was made to solve this problem, and uses the data obtained during the home return operation, which indicates the distance from power-on to the first Z phase, to calculate the free run counter. It is an object of the present invention to provide a position detection circuit capable of detecting a position detection error by comparing the value with the value of a cycle counter.

[Means for Solving the Problems] A position detection circuit according to the present invention detects a position sensor using data obtained during a normally performed home return operation, which is a value indicating the distance from power-on to the first Z phase. The value of a free-run counter that goes up or down according to the A-phase and B-phase signals output from the encoder, and the cycle counter that goes up or down according to the A-phase and B-phase signals and is reset every time at the Z-phase. By comparing the values, position detection errors are detected.

[Function] In this invention, since the cycle counter is reset every time in the Z phase, detection errors are not accumulated. Therefore, by comparing the value of the free run counter with the value of the cycle counter, the detection error of the free run counter is eliminated. Can be detected.

[Embodiment] FIG. 1 is a timing diagram showing an embodiment of the present invention.

In FIG. 1, parts with the same symbols as in FIG. 4 indicate the same parts, and N1. is the latch data of the free run counter, N
s is latch data of the cycle counter, and (82) is a latch signal.

Next, the operation will be explained.

When the power is turned on (9), the free run counter (1) starts operating, and the cycle counter (3) starts operating at the first z+ti.
; The operation starts from passing through y1, and at this time, the distance α to the Z phase is determined by the method described above. Further, the distance #RNG from Z phase to Z phase is input from the parameters at the time of system configuration.

After the operation starts, the free run counter (
1) and cycle counter (3) to the latch signal (82
), the respective values N,
and N8 are obtained. At this time, N.

The data of (α+N s ) should be an integral multiple of RNG. If phase A and phase B are detected incorrectly, the free run counter will try to move to the same value as the command, resulting in a positional shift.

At this time, since the cycle counter is reset every time in the Z phase, detection errors are not accumulated. Therefore, when a position detection error occurs, N.

(α+NS) is not an integral multiple of RNG.

This calculation is performed by a computer included in the NC device according to a pre-stored program. FIG. 2 is a block diagram showing an example of an arithmetic circuit. In Figure 2, (15) is a central processing unit (CPU), (l[i) is a memory that stores programs and other data, and (17) is a memory that stores programs and other data.
) is a parameter that presets machine information such as the number of pulses per revolution RNG of the encoder, the machine's pole screw pitch, and the machine's gear ratio. (18) is a bus.

The free run counter (1) and the cycle counter (3) are directly connected by a bus (18), and the value of the counter can be directly read by the CPU (15) and stored in the memory (1).
6). Using the counter value stored in this memory (16), the CPU (15) executes the following calculation.

N - (α0NS)/RNG At this time, when the position is correctly controlled, the remainder of the quotient becomes zero. When a position detection error occurs due to noise or the like, the value does not become zero, so it can be determined that there is an error.

The timing of latching the counter values should be such that both counters can be latched at the same time when you want to detect a position detection error, but since position deviations do not occur frequently, it is recommended to check them at certain intervals. do it.

[Effects of the Invention] As explained above, the present invention calculates the value of the free run counter by using the data obtained during the normal return-to-home operation and the distance from when the power is turned on until the first two phases pass. Since a position detection error is detected by comparing the value of a cycle counter that is reset each time in the Z phase, the circuit can be constructed at low cost and the detection can be performed with high precision.

[Brief explanation of drawings]

FIG. 1 is a timing diagram showing one embodiment of the present invention, and FIG.
Figure 3 is a block diagram showing an example of an arithmetic circuit, Figure 3 is a block diagram showing a counter part in a conventional position detection circuit, Figure 4 is a timing diagram explaining the operation of returning to the origin, and Figure 5 is a diagram showing the operation of returning to the origin. It is an explanatory diagram explaining operation. In the figure, (1) is a free run counter, (2) is a data latch F, (3) is a cycle counter, (4) is a data latch S, (5) is an A phase signal, (6) is a B phase signal,
(7) is the Z phase signal, (8), (81), (82) are the latch signals, α is the distance from power on to the first two phases, RN
G is the number of pulses per revolution of the encoder. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] A free-run counter that increases or decreases in response to an A-phase signal and a B-phase signal output from an encoder that is a position sensor, and outputs current position data of an operating machine; and an output from the encoder. A cycle counter that goes up or down depending on the A-phase signal and B-phase signal that is sent, and is reset each time with the Z-phase signal, and data obtained from the normal return-to-origin operation, from power-on to the first Z-phase. a position detection error detection means for detecting a position detection error by comparing the value of the free run counter with the value of the cycle counter using a value indicating a distance of the position detection circuit.