JPS6048686B2 - position detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for detecting the position of an object by generating signals as the object moves and counting the number of waveforms.

An incremental rotary encoder has been known as a position detection device that detects the position of an object by generating signals as the object moves and counting the number of waveforms. There is.

The principle is as shown in FIG. 1, in which a rotating slit plate 1 has a pattern in which light transmitting parts 1a and light blocking parts 1b are arranged consecutively at a predetermined pitch and on the same circumference concentrically with the rotating shaft 5. A light emitting diode 3 and a photodiode 4 are arranged across the rotating slit plate 1 and the fixed slit 2 with a pattern carved at the same pitch, and the position of the rotating slit plate 1 is detected via the rotating shaft 5. By rotating the object (for example, a machine tool) as it moves, the light entering the photodiode 4 from the light emitting diode 3 is blocked a number of times corresponding to the amount of movement of the object, thereby blocking the light from the photodiode 4. The position of the object is detected by counting the number of waveforms (number of pulses) of the signal obtained from 4. In such a position detection device, the resolution of position detection is determined by the number of pulses obtained per rotation of the rotary slit plate 1.

Conventionally, resolution has been improved by increasing the number of light and dark patterns on the rotating slit plate 1 (increasing the density) to increase the number of pulses per rotation. but,
In this method, as the number of bright and dark patterns increases, the width of each bright and dark pattern must be narrowed, but since there is a limit to the precision of cutting the bright and dark patterns, the diameter of the rotating slit plate 1 is increased. It was necessary to ensure a wide range of light and shade. This has resulted in the disadvantage that the detection device becomes larger and heavier. This invention solves the above-mentioned deficiencies in the conventional ones. It is an object of the present invention to provide a position detection device that can improve resolution without increasing the size of the device by removing points. According to this invention, a plurality of signals, each of which corresponds to the amount of movement of the position detection target, are positive and whose phases are shifted by a predetermined angle from each other by a combination of a light-dark pattern and a plurality of photocouplers. The position of the object (linear position or angular position
position). That is, by using a plurality of signals whose phases are shifted by a predetermined angle, information obtained by dividing the signal into each phase angle can be obtained, so that high resolution can be obtained even if the density of the bright and dark patterns remains low. There is. Moreover, in the present invention, it is possible to obtain not only a resolution equal to the number of signals but also a resolution higher than the number of signals. Furthermore, in the present invention, the signal bundle as described above is used as one gnoloop, and a plurality of groups of signal bundles are created in which the groups are out of phase with each other by a predetermined angle shorter than the phase angle between the signals, and the signal bundles in each group are similarly A higher resolution is obtained by extracting cross points and summing the cross points in all groups.

That is, this invention divides one wavelength of the signal by the phase angles of the plurality of signals in each group, and further divides one section thus divided into smaller sections by the phase angles of the groups. Ensures resolution. In this way, when dividing originally obtained information to improve resolution, it is necessary that each division width be equal.

To achieve this, it is necessary to make sure that the width of each division made by using the phase shift between the signals is equal, and that the width of each division that is further divided into narrower sections using the phase shift between the groups is equal. Both are necessary. To achieve the former, it is necessary to set the phase angle between the signals in each group to a value that corresponds to the number of signals, and to achieve the latter, it is necessary to set the phase angle between the groups to a value that corresponds to the number of groups and the number of signals. It is necessary to set the value according to the phase angle between them. Specifically, if the phase angles are set according to the number of signals in one group and the number of groups as shown in Table 1, the final division widths will be equal.
According to Table 1, if the number of signals in one group is n) and the number of groups is m, a resolution of 2m(n-1) can be obtained.

The coefficient ``2'' is added when comparing two signals with different phases, as shown in Figure 2, when the signals Sl and S2 (
Since it crosses every H8O゜, this cross point
l,X2,. This is because the present invention, which counts X3, X4, X5, X6, . . . , can obtain twice the resolution compared to counting the number of waveforms of each signal S1 or S2. Note that n-1 is a set of n signals in which ±2 signals with the same phase are adjacent to each other. The combination is n
This is due to -1. Also, in the case of n=2, the number of signals and resolution are exceptionally equal, which goes against the purpose of this invention to obtain resolution greater than the number of signals, so n≧
3 is a condition of this invention. Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 3 schematically shows an example of the internal configuration of an incremental rotary encoder to which the present invention is applied.

The embodiment shown in FIG. 3 is an example in which the number of detection signals in one group is three and the number of groups is two, that is, the resolution is increased eight times. In FIG. 3, on the rotating slit plate 10, a pattern consisting of light transmitting portions 10a and light blocking portions 10b is formed continuously at a predetermined pitch, concentrically with the shaft 11, and on the same circumference. The rotation shaft 11 of the rotary slit plate 10 is rotated according to the movement of a position detection target (shown in the figure). Two photocoupler groups Gl and G2 are arranged to sandwich the rotating slit plate 10. Each of these photocoupler groups Gl and G2 is composed of three photocouplers. The photocoupler group G1 includes photocouplers Pl, P2, P3 (light emitting diodes (which may be filament lamps, discharge tubes, laser diodes, etc.)) Dl, D2, D3 and photodiodes (phototransistors, photocells, etc.). ) Dl, d2
, d3), and the light from the light emitting diodes Dl, D2, D3 is incident on the photodiodes Dl, d2, d3 through the transparent portion 10a of the rotating slit plate 10, respectively.

From the photodiodes Dl, d2, and d3, signals whose phases are shifted by 90° are taken out according to Table 1. For this purpose, photocouplers Pl, P2, and P3 are rotated to determine the brightness and darkness pattern of the slit plate 10. = 1 pitch at a time in the continuous direction (circumferential direction of the rotation plate 10 at 360 degrees).

Of course, one pitch is an extremely short distance, and during that time there are 11 pitches.
Since it is difficult to arrange the photocouplers Pl, P2, and P3 so that they are shifted by 4 pitches, they are arranged so that they are relatively shifted by 114 pitches at every few pitches, and as a result, they are arranged by 114 pitches. What is necessary is to obtain signals whose phases are shifted. Photocoupler group G
2 are photocouplers Pll, Pl2, Pl3 (light emitting diodes Dll, Dl2, Dl3 and photodiodes D
ll, dl2, dl3), the mutual positional relationship of which is set in the same manner as the photocouplers Pl, P2, P3, and signals whose phases are shifted by 90 degrees are extracted.

According to Table 1, the photocoupler group G1 and the photocoupler group G2 are arranged with a phase shift of 45° (that is, one pitch of the bright/dark pattern). 360°8 As a result, the total of 6 signals, 3 signals from photocoupler group G1 and 3 signals from photocoupler group G2, is 45
The relationship is such that the phase is shifted by degrees (see Figure 5).

In FIG. 3, there are slit groups 12-1, 12 between the rotating slit plate 10 and the photodiodes Dl, d2, d3.
A light-receiving fixed slit plate 12 having numbers -2 and 12-3 formed therein is arranged.

This fixed slit plate 12 has photodiodes Dl, d2.
, d3 from oblique directions, and the light emitting diodes Dl, D2, The light from D3 is transmitted to photodiodes Dl, d2, d. 3. Therefore, the slit groups 12-1, 12-
2 and 12-3 are formed on the optical axes of photocouplers Pl, P2, and P3, respectively. In addition, each slit group 12-1
, 12-2, 12-3 are composed of a plurality of slits formed at the same pitch as the pattern of the rotating slit plate 1-0, and a large amount of light is transmitted to the photodiodes Dl, d2, d3.
The signal-to-noise ratio is improved by making the light incident on the ground.
The light-receiving fixed slit plate 13 performs the same function for the photocoupler group G2, and each photocoupler Pll,
Slit groups 13-1 and 13- correspond to Pl2 and Pl3.
2 and 13-3 are formed, respectively. Figure 4 is the third
The transparent portion (slit) 10a of the rotating slit plate 10 and the slit 12- of the fixed slit plate 12 in the illustrated embodiment
1, 12-2, 12-3 and the positional relationship between the fixed slit plate 13 and the slits 13-1, 13-2, 13-3.

That is, the slits 12-1, 1 of the rotating slit plate 12
2-2 and 12-3 are patterns 1 of the rotating slit plate 10.
The phase is shifted by ι, 114 pitches from the pitch T,
11 after the slit 12-1 coincides with the transparent portion 10a.
At the 4T rotation position, the slit 12-2 becomes the transparent part 10
The slit 12 is aligned with a and further rotated by 114T.
-3 coincides with the transparent portion 10a. Slits 13-1, 13-2, 13 of fixed slit plate 13
Similarly, the phase of -3 is shifted by 114 pitches. Also, as a whole, the slits 13-1, 13-2, 13-
3, the phase is shifted by 118 pitches. Therefore, the photocoupler groups Pl, P2, P3, Pll, Pl2,
From Pl3, as shown in FIG. 5, one period corresponds to a predetermined amount of rotation of the rotating slit plate 10J), that is, a predetermined amount of movement of the position detection object) T, respectively, and signals SAI and SA2 are generated.
, SA3, SAII, SAl2, SAl3 are SAI, S
4 in the order of AII, SA2, SAl2, SA3, SAl3
They are taken out with a phase shift of 5°. Figure 6 shows the signal SA
This figure shows an example of a circuit for determining the position of a detection target based on I, SA2, SA3, SAII, SAl2, and SAl3.

In FIG. 6, the signals SAI, SA2, and SA3 output from the photodiodes Dl, d2, and d3 are in phase with each other, that is, the signal SAI, the signal SA2, and the signal S
A and signal SA3 are compared by comparison amplifiers 20-1 and 20-2, respectively. As a result, the comparison amplifiers 20-1, 20
-2 to 2? Pulse signal SB shown in figures B and c, respectively.
I2 and SB23 are output. This pulse signal SBl2
, SB23 are signals whose period is the same as the period T of the detection signals SAI, SA2, and SA3, whose duty cycle is 50%, and whose phases are shifted from each other by 114 periods. On the other hand, the signal S output from the photodiodes Dll, dl2, dl3
AII, SAl2, and SAI3 are also in phase with each other, that is, signal SAll, signal SAl2, and signal SAl2.
and signal SAl3 are compared by comparator amplifiers 30-1 and 30-2, respectively, and from comparator amplifiers 30-1 and 30-2, pulse signals SBll2 and SB shown in FIGS.
l23 is output.

These pulse signals SBII2 and SB123 are the same as the signal SB123.
The period and duty cycle are the same as l2 and SB23, the phases are shifted by 114 periods, and the signal SBl2
, SBl3 is a signal whose phase is shifted by 118 periods.
The output signals SBl2, SB23, SBl23 of the comparison amplifiers 20-1, 20-2, 30-1, 30-2 are output from the edge trigger pulse oscillators 21-1, 21-2, 31-1, 31-.
2, each rising edge and falling edge (that is, each cross point between the compared signals) is extracted.

The extracted signals are put together by the OR circuit 22, and the OR circuit 22 outputs the signal SBll+SBl2+S shown in FIG. 7f.
Bll2+SBl23 is taken out and accumulated by the up/down counter 23. Signal SBll+SBl2+SB
As is clear from FIG. 7f, ll2SBl23 is the detection signal SAI, SA2, SA3, SAII, SAl2, SA
Since the period of l3 is 118, position detection can be performed with eight times the resolution compared to the case where the number of waveforms of the detection signal is directly accumulated. Note that the accumulation by the counter 23 is switched to addition or subtraction depending on the rotational direction of the rotary slit plate 10 (that is, depending on the moving direction of the detection object).

The rotation direction of the rotating slit plate 10 is determined by the comparison amplifier 20-1,
This can be determined by detecting which of them rises first using the output pulses SB12 and SB23 of 20-2. That is, as shown in the direction identification circuit 24 of FIG.
5 is driven by the signal SBl2 and the signal SB23, the cated mono multipipulator 26 is driven by the signals SBl2 and SB23, and the flip-flop circuit 27 is set by their output. When reset, a signal corresponding to the rotation direction is obtained from the flip-flop circuit 27 as shown in FIG. If the up/down counter 23 is switched to up-count or down-count by this signal, the count value will accurately correspond to the position of the object to be detected. The above example shows the case where the resolution is increased by 8 times using a two-group photocoupler equipped with three photocouplers, but the same method can be used in other cases as well.
For example, when using three groups of photocouplers each having three photocouplers, as shown in Table 1, the photocouplers in each group are shifted by 90° in phase, and the groups are arranged with a phase shift of 30° between each group. do it. At that time, as shown in FIG. 9a, the nine photocouplers output the first group of signals SCI, SC2, SC3, the second group of signals SC4, SC5, SC6, and the third group of signals SC7, SC8, SC9. is SCI, SC4, SC7
, SC2, SC5, SC8, SC3, SC6, and SC9 are extracted in this order with a phase shift of 30 degrees. If we compare the adjacent phases in each of these groups, we get the 9th
As shown in FIGS. b to g, six pulse signals having a duty cycle of 50%, the period of which is the same as that of the detection signals SCI to SC9, and whose phases are shifted by 30 degrees (that is, by 1112 periods) are obtained. By extracting the edges of these pulse signals and taking their logical sum, a pulse signal obtained by dividing the period T of the original signals SCI to SC9 by 1112 can be obtained as shown in FIG. 9h. Therefore, by counting these pulse signals, position detection can be performed with 12 times the resolution. Further, the present invention may have various variations other than those shown in the above-mentioned embodiments, such as the following. 1. Application to methods other than optical methods The transparent part of the rotating slit plate is formed as a groove, and a plurality of limit switches are arranged there at a predetermined angle and phase to mechanically generate a signal.

2 Application to Linear Scale In the above-mentioned embodiment, detection was performed by converting the linear movement of the object to be detected into the rotational movement of the rotary slit plate 1.
It is also possible to directly detect movement in a straight line.

In other words, if a linear slit plate is arranged in the direction of movement of the object to be detected, and a photocoupler is sandwiched between them so that they face each other, the positional relationship between them changes linearly as the object to be detected moves. Position detection can be performed similarly. In this case as well, the resolution can be improved by arranging a plurality of photocouplers at a predetermined angle and out of phase. )3 Use as an angular position detector In the above-described embodiment, the case of detecting a position in a linear direction was shown, but it can also be used as an angular position detecting means for a machine whose angle changes.

4 In the above-mentioned embodiment, the phase shift of the plurality of signals within each group and the phase shift between the groups were both caused by the phase shift between the photocouplers. By shifting their phases, similarly phase-shifted signals can be obtained.

For example, when obtaining two groups of signal bundles each consisting of three signals as in the embodiment described above, as shown in FIG. Three light and dark patterns 33-1 whose phases are shifted by 114 of pitch T like 32-2 and 32-3.
, 33-2, 33-3 are formed with two groups of light and dark patterns shifted in phase by 1I8T from each other, and photocouplers P23 to P23 are placed corresponding to each pattern at the same position in the continuous direction.
P28 may be placed respectively. Further, as shown in FIG. 11, three light and dark patterns 34-1, 34-2, 34-3 whose phases are shifted by 114 pitches T are used to create a phase shift of a plurality of signals in each group. , P32, P33 and photocoupler groups P4l, P4
2. By arranging P43 with a phase shift of 118T, a similar signal can be obtained by creating a mutual phase shift between the groups.

5 In the embodiment of FIG. 3, photocouplers Pl, P2, P3
were arranged independently, but one light emitting element D5l, D52 was used in each group as shown in FIG.
Three photodiodes D5l-. each constitute each group. 1, d51-2, d51-3 and photodiodes D52-1, d52-2, d52-3 are irradiated together, even if the light emitting elements D5l, D52 deteriorate over time, the detection signal in each group will be All the levels change at the same rate - the intervals between the cross points of each detection signal are constant, so there is no reduction in detection accuracy, and it is also economical because the number of elements is reduced.

As explained above, according to the present invention, a plurality of detection signals whose phases are shifted by a predetermined angle are generated, and These signals are used to obtain signals obtained by dividing the period of the original signal, and the divided sections are further divided into thinner sections by dividing the period of the original signal into one group and shifting the phase of multiple groups by a predetermined angle. As a result, position detection can be performed with high resolution without increasing the frequency of the detection signal (that is, without increasing the density of the bright and dark pattern in the optical encoder).

In addition, these cross points, which are detected based on the comparison of two signals, are detected at two points in one period of the original signal, so high resolution can be obtained with a small number of detection signals, resulting in miniaturization, high reliability, and economy. A highly sensitive detector can be realized.
(As shown in Table 1, if m groups each consisting of n test frequency signals are used, the resolution can be increased by (n-1) times).

[Brief explanation of the drawing]

Fig. 1 is a perspective view schematically showing the internal structure of an incremental rotary encoder, Fig. 2 is a waveform diagram showing a state in which two signals with a phase difference of i cross each other, and Fig. 3 is an application of the present invention to an incremental rotary encoder. FIG. 4 is a perspective view showing an embodiment of the mechanical components in the case where the slit 1 of the rotary slit plate 10 in FIG.
0a and the fixed J fixed slits 12-1, 12-2, 12-3 and 13-1, 13-2, 13-3, FIG. 5 is a photocoupler shown in FIG. Pl, P2
, P3, and FIG. 6 is a diagram showing the signal waveforms obtained from the photocouplers Pl, P2, P3 and Pll, Pl2 in FIG.
, a block diagram showing an example of a circuit that performs position detection based on signals obtained from Pl3, FIG. 7 is an operation waveform diagram of the circuit of FIG. 6, and FIG. 8 is an operation of the direction identification circuit of FIG. 6. An explanatory diagram, Fig. 9 is an operation waveform diagram when position detection is performed based on six detection signals, and Fig. 10 is an operation waveform diagram when position detection is performed based on six detection signals. FIG. 11 is a diagram showing another embodiment of the present invention in which the signals are formed by shifting the signals in each group. FIG. 12 is a perspective view showing a modified example of the photo coupler. 10... Rotating slit plate, 11... Rotating shaft, 12, 13... Fixed slit plate, Pl,
P2, P3, Pll, Pl2, Pl3...Photo coupler (Dl, D2, D3, Dll, Dl2, Dl3
・・・・・・Light emitting diode, Dl, d2, d3, dl
l, Dl2, dl3... photodiode),
20-1, 20-2, 30-1, 30-2...
Comparison amplifier, 21-1, 21-2, 31-1, 31-2
...Edge trigger pulse oscillator, 24...
... Direction identification circuit, 32-1, 32-2, 32-3, 3
3-1, 33-2, 33-3, 34-1, 34-2, 3
4-3... Light and dark pattern row, P23 to P28,
P3l~P33...Photocoupler, D5l, D
52... Light emitting element, D5l-1, d51-2,
d51-3, d52-1, d52-2, d52-3...
····Light receiving element.

Claims (1)

[Scope of Claims] 1. A pattern in which parts that transmit light and parts that block light are continuously formed at a predetermined pitch, and [1/
{2(n-1)}] (=α) so that the light beams are received with a phase shift of each pattern, and are arranged across the pattern in the continuous direction of the pattern, and the relative position with respect to the pattern is the position of the object to be detected. n arranged to change according to movement
α/m with (n≧3) pairs of photocouplers as one group
m groups of photocouplers arranged with different phases, and circuit means for comparing n signals obtained from the photocouplers in each group with adjacent phases to detect their cross points. and circuit means for accumulating the number of cross points detected in all groups and obtaining the accumulated value as the position of the position detection object. 2. A pattern in which parts that transmit light and parts that block light are continuously formed at a predetermined pitch is formed at [1/
{2(n-1)}] (= α) m groups of pattern rows arranged with a phase shift of n columns and a light ray at the same position in the continuous direction of the pattern rows. Each group n (n
≧3) A group of photocouplers in each group, circuit means for comparing zero signals obtained from the photocouplers in each group with adjacent phases to detect their cross points, and A position detection device comprising circuit means for accumulating the number of detected cross points and obtaining the accumulated value as the position of the position detection target.