JPH0147052B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to an absolute type encoder that outputs a signal related to an absolute position such as a displacement position or a rotation angle. More specifically, the present invention provides a code board having two types of lattice patterns in which information of "1" and "0" is arranged periodically;
The present invention relates to an encoder equipped with two sets of sensors arranged oppositely in two types of lattice patterns.

[Description of Prior Art] Conventionally, a linear motor is equipped with a code plate having a code made up of a grid pattern in which information of "1" and "0" is arranged periodically, and a plurality of sensors for detecting the grid pattern. Encoders or rotary encoders are known.

However, in conventionally known encoders, the minimum measurement limit for displacement position or angle measurement is determined by the subdivision limit of the grid pattern.
There were limits to achieving high precision and high resolution.

[Object of the present invention]

Here, the present invention is an absolute type encoder and aims to realize a high-precision, high-resolution encoder.

[Summary of the invention]

The device according to the present invention includes a first grid pattern in which information of “1” and “0” is arranged periodically;
a second lattice pattern in which "1" and "0" information are periodically arranged at a slightly different pitch from the arrangement pitch of "1" and "0" information in the lattice pattern; A first sensor array that detects the first lattice pattern, a second sensor array that detects the second lattice pattern, and a drive that drives the first and second sensor arrays to obtain alternating signals from each of these sensor arrays. and a calculation circuit that receives alternating signals from each sensor array and reference signals from the drive means, performs predetermined calculations, and outputs an absolute position signal.

[Description of Embodiments] FIG. 1 is a configuration explanatory diagram showing an example of a code plate used in an apparatus according to the present invention, in which A is a perspective view and B is a side view. Here, a linear encoder with an optical grating pattern will be exemplified.

In these figures, the code plate 1 includes transparent,
A first grid pattern 11 in which opaque "1" and "0" information is arranged periodically at pitch P ₁ , and transparent and opaque "1" and "0" information is arranged periodically at pitch P _1.
A second grating pattern 12 is provided which is arranged periodically with a pitch _P2 slightly different from that of the second grating pattern 12. In this example, in the range of length L, the first lattice pattern has N information of "1" and "0" with pitch P ₁ , and the second
The lattice pattern is such that the information of “1” and “0” is pitched.
The case where N+1 pieces are arranged with P ₂ (P ₁ > P ₂ ) is shown. A first sensor array 21 is installed close to the first grating pattern 11 and detects the first grating pattern. 22 is a second sensor array;
It is installed close to the second grating pattern 12 and detects the second grating pattern. These first and second
The sensor arrays 21 and 22 each have a pitch
It is composed of a plurality of photodiodes (five in this example) arranged in P ₃ and P ₄ .

The code plate 1 is irradiated with parallel light from the front.
Light (striped light pattern) passing through the transparent portion of the lattice pattern is irradiated onto the light receiving surface of each sensor array 21, 22. Here, for example, the code plate 1 is given a displacement to be measured, and each sensor array 21,
22 in the direction of arrow a or arrow b, and along with this movement, the striped light pattern irradiated onto each sensor array 21, 22 moves.

FIG. 2 is an electrical connection diagram of the device according to the invention. In this figure, 21 is a first sensor array, and 22 is a second sensor array, both of which are constructed by arranging a plurality of silicon photodiodes 1, 2, 3, . . . . 31 and 32 are the first,
first and second switch circuits connected to each photodiode of the second sensor arrays 21 and 22;
Reference numerals 1 and 42 designate first and second switch drive circuits that sequentially turn on the switches of the switch circuits 31 and 32 at regular intervals. 40 is a timing circuit that generates various timing signals; 51 is a first signal processing circuit that inputs the signal obtained through the first switch circuit 31, amplifies and filters the signal, and shapes the waveform into a square wave; 52 is a second signal processing circuit which inputs the signal obtained through the second switch circuit 32, amplifies and filters the signal, and shapes the signal into a square wave; from each of these output terminals,
Alternating signals V ₁ and V ₂ having a period corresponding to the scan period of each switch circuit 31 and 32 are generated. In other words, suppose that a light pattern passing through the transparent part of the grid pattern is illuminated, for example, on photodiodes 1, 2, 3, and 4 in the sensor array (photodiodes 5 to 8 are dark). , while the switches connected to these photodiodes are turned on, a high level signal is output, and during the period when the switches connected to the photodiodes 5, 6, 7, and 8 are turned on, a low level signal is output. A signal is output, and thereafter becomes an alternating signal in which high-level and low-level signals are repeated in accordance with the scan period of the switch. Here, since the first lattice pattern and the second lattice pattern have slightly different arrangement pitches in advance, each alternating signal V
1 and V2 have a slight phase difference. If the irradiation position of the light pattern moves, the timing at which each of these alternating signals becomes high level changes together with this. 6 is each signal processing circuit 5
1 and 52 and the reference alternating signal V _S from the timing circuit 40, the phase angle difference _{a between} the alternating signals V ₁ and V ₂ , _the reference alternating signal V _S and the alternating signal V are input. ₁ or _V2 , and 7 is an arithmetic circuit that receives the signal from _the phase measurement circuit 6 and performs a predetermined calculation to obtain a signal related to the absolute displacement position. is a display means for displaying the calculation results.

The operation of the apparatus constructed in this manner will now be described with reference to the waveform diagrams of FIGS. 3 and 4.

First, the number of transparent slits in the first lattice pattern 11 provided on the code plate 1 is na, and the number of transparent slits in the second lattice pattern 12 is nb.
(na≠nb), and assume that the code plate 1 is fixed to, for example, a table whose displacement position is to be measured, and moves together with the table. Now, code board 1
Let the displacement position of each switch circuit 31, 32 be X.
When scanned with the reference wave signal V _S =sinωt, from the first and second signal processing circuits 51 and 52, (1)
Signals V ₁ and V ₂ are obtained by using the signals V _a and V _b as square waves as shown in equation (2).

V _a = V _a0 sin (ωt + na2πX/L) (1) V _b = V _b0 sin (ωt + nb2πX/L) (2) Regarding the points where signals like equations (1) and (2) are obtained, For example, “Automation Technology” Vol. 13 No. 7 P49
This is a technique known by P54.

FIG. 3 shows the signal waveforms of the square wave shaped signals V ₁ , V ₂ and V ₃ .

The phase measurement circuit 6 receives alternating signals V ₁ (V _a ), V ₂ (V _b )
In addition to measuring the phase angles ₁ and ₂ of
Measure the difference _a between the phase angles of V ₁ and V ₂ . Here, ₁ ,
₂ and _a can be expressed by formulas (3), (4), and (5).

₁ = na2πX/L (3) ₂ = nb2πX/L (4) _a = (na-nb)・2πX/L (5) Figure 4 is a waveform diagram showing the relationship between displacement position and ₁ , ₂ , and _a . be. Note that here, na−nb=1
shall be.

As is clear from this, the difference _a between the phase angles of V ₁ and V ₂ represents the absolute position X, and
₁ or ₂ represents the position between the transparent slits.

In other words, the phase angle difference _a is 2π/na (or 2π/
nb) is equal to the sum of a certain integer j and the pitch Δ of the transparent slit within P ₁ (or P _{2 )} , as shown in equation (6).

_a /2π/na=j+Δ (6) Therefore, the displacement position X can be expressed by equation (7), and the calculation circuit 7 calculates the absolute position The signal representing the signal can be determined. This calculation result is displayed on the display 8.

X=(j·2π/na+ ₁ )L/2π (7) Here, in equation (6), if Δ is around zero, the value of the integer j may vary by +1. In this case, when ₁ > π, let j−1 be the true value, and ₁
When <π, an operation that takes j as the true value may be performed.

FIGS. 5 to 8 are explanatory diagrams showing other configuration examples of the first and second lattice patterns formed on the code plate and the sensor array used in the apparatus according to the present invention.

What is shown in FIG. 5 is the grid pattern 11, 12.
, the information of “1” and “0” is N, S, S, N
It is formed by arranging magnetized parts, and uses Hall element arrays as the sensor arrays 21 and 22 to detect magnetic flux from the magnetized parts.

What is shown in FIG. 6 is the grid pattern 11, 12.
The sensor arrays 21 and 22 are coil patterns that are arranged to represent "1" and "0" depending on the presence or absence of the conductor pattern, and the sensor arrays 21 and 22 are designed to detect voltage signals caused by magnetic induction.

In the example shown in FIG. 6, the conductor pattern may be made of a magnetic material, and the inductance change may be detected by a coil pattern array.

What is shown in FIG. 7 is the grid pattern 11, 12.
Assume that slits are formed in a conductive flat plate,
The sensor arrays 21 and 22 are electrode arrays facing a flat plate, and are designed to detect changes in capacitance of the electrode arrays.

What is shown in FIG. 8 is the grid pattern 11, 12.
is formed with or without conductive electrodes, and the sensor array 2
1 and 22 are contact arrays that come into contact with this conductive electrode.

In addition, in the above embodiment, the case where the first and second switch circuits 31 and 32 are scanned with the reference signal of the same frequency was explained, but the first and second switch circuits
The switch circuits 31 and 32 are connected to different frequency signals.
It is also possible to scan using sin ωat and sinωbt. In this case, equations (1), (2), and (5) can be represented by equations (8), (9), and (10), respectively.

V _a = V _a0 sin (ωa・t+na2πX/L) (8) V _b =V _b0 sin (ωb・t+nb2πX/L) (9) _a = |ωa−ωb|t+(na−nb)2πX/L) ( 10) Furthermore, in the above embodiment, a linear encoder in which the grating pattern is arranged in a straight line is shown, but it is also possible to make the code plate disk-shaped and form the first and second grating patterns along the circumference. It may also be used for rotary encoders. In this case, absolute angular position can be measured.

In addition, in the above explanation, in the first and second sensor arrays, the relationship between the sensor arrangement pitches P ₃ and P ₄ and the "1" and "0" arrangement pitches P ₁ and P ₂ of the grid pattern is particularly described. Although not explained, any relationship may be used as long as three or more sensors are arranged, including the relationship P ₁ =P ₃ and P ₂ =P ₄ . Furthermore, as the first and second sensor arrays, sensor arrays such as those previously proposed by the inventors of the present application in Utility Model Application No. 58-31445 can also be used.

[Effects of the present invention]

As explained above, the present invention allows the phase angle difference _a to represent the absolute position even when there is no relative movement between the code plate and the sensor array, and to perform the calculation of equation (7). Therefore, the inside of the array pitch of "1" and "0" is interpolated. Therefore, according to the present invention, it is possible to realize an absolute type encoder with high precision and high resolution.

[Brief explanation of drawings]

1 is a configuration explanatory diagram showing an example of a code plate used in the device according to the present invention, A is a perspective view, B is a side view, FIG. 2 is an electrical connection diagram of the device according to the present invention, and FIG. 5 and 4 are waveform diagrams for explaining the operation, and FIGS. 5 to 8 are explanatory diagrams showing other configuration examples of the grating pattern and the sensor array. 1... Code board, 11, 12... Lattice pattern, 2
DESCRIPTION OF SYMBOLS 1, 22... Sensor array, 31, 32... Switch circuit, 41, 42... Switch drive circuit, 6... Phase measuring circuit, 7... Arithmetic circuit.

Claims (1)

[Claims] 1 The first one in which “1” and “0” information is arranged periodically
A second grid in which "1" and "0" information is periodically arranged at a pitch slightly different from that of the first grid pattern. a code plate having a pattern, first and second sensor arrays that move relative to the code plate and detect the first grating pattern and the second grating pattern, respectively;
drive circuit means for driving a second sensor array and obtaining alternating signals from each sensor array; alternating signals (V ₁ , V ₂ ) obtained from the first and second sensor arrays;
and a reference alternating signal (V _S ) from said drive circuit means.
Enter the phase angle ₁ or ₂ of V ₁ or V ₂ and V ₁ and V ₂
An encoder equipped with circuit means that measures the phase angle difference _a , performs predetermined calculations using these, and outputs an absolute position signal.