JP2002022491A - Surveying equipment with absolute encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide surveying equipment with an absolute encoder capable of displacing two sensors from each other by an predetermined angle and most accurately installing them to a rotary encoder. SOLUTION: Any one sensor S1 among the sensors S1 and S2 is fixed to any given location α on graduations provided in the circumferential edge of the rotary encoder 1, and the other sensor S2 is temporarily placed in the vicinity of a location displaced by the predetermined angle. The locations of the sensors S1 and S2 are computed by a code pattern, and it is verified whether the computed locations are displaced from each other by the predetermined number of codes or not and the relationship between both phase angles from the parity of the number of all the graduations. By appropriately displacing the other sensor S2 and repeating the same operations in the case that it is determined that the sensor locations are not displaced from each other by the predetermined angle, it is possible to position the sensors accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surveying instrument for performing angle measurement using a rotary encoder and a sensor, and more particularly to a surveying instrument having an absolute type rotary encoder, that is, an absolute encoder.

[0002]

2. Description of the Related Art As a rotary encoder used in an angle measuring device of a surveying instrument, there is an incremental type having scales of the same pattern at equal intervals, and a rotary encoder corresponding to an azimuth angle and an altitude angle. Absolute type is known in which the scale patterns are different from each other, and the azimuth angle and the altitude angle are associated with the scale positions in a 1: 1 relationship.

Usually, in this absolute type rotary encoder, two kinds of scales which are widely and narrowly varied over the entire outer peripheral edge are all at equal pitch intervals (that is, the same period), but have different unique patterns. Is provided.

Further, in an angle measuring apparatus having such an absolute type rotary encoder, for example, as shown in FIG. A light emitting unit 2 such as an LED for emitting reading light, and graduations 1A and 1B of the rotary encoder 1 of the light from the light emitting unit 2
A light receiving unit 3 such as a CCD that receives light reflected (reflection type) or transmitted (transmission type) at a part, and an interpolation amount based on a signal data output from the light receiving unit 3 and a predetermined interpolation operation formula A calculation unit (not shown) for calculating and interpolating the measurement angle,
A display unit (not shown) for displaying angle measurement data based on the calculation result is provided.

[0005] Of these sensors, in particular, regarding the sensor composed of the light emitting section 2 and the light receiving section 3, these sensors are connected to each other.
By disposing the two pairs at an angle shifted by 80 degrees,
There is known a so-called opposite reading type having a feature that occurrence of an eccentricity error can be prevented.

Therefore, in this sensor of the facing reading system,
In order to detect the interpolation amount as accurate as possible,
It is necessary to dispose the two sensors facing each other at an angle different by 0 degrees. However, no effective means or method for accurately assembling and arranging these sensors has been developed so far, and is a subject to be solved in the future.

[0007]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention has an absolute encoder in which two sensors can be installed as accurately as possible by shifting the position by a required angle with respect to an absolute type rotary encoder. The purpose is to provide a surveying instrument.

[0008]

SUMMARY OF THE INVENTION In a surveying instrument having an absolute encoder according to the present invention, a scale at a peripheral portion of an absolute type rotary encoder is read by two sensors provided at a predetermined phase angle shifted from each other, and an altitude angle and a horizontal angle are read. In a surveying instrument having an absolute encoder for measuring, when any one of the two sensors is fixed at an arbitrary position on the periphery of the rotary encoder, a scale position corresponding to a code of one of the two sensors From the vicinity of a code that differs by the number of codes corresponding to the predetermined angle difference, and from the code, a constant angular relationship to the phase angle of one sensor due to the evenness of the total number of graduations And the other sensor is provided.

In the present invention, when the total number of the scales is an even number, the codes differ from the code corresponding to a certain scale of one of the sensors in a clockwise or counterclockwise direction by half of the total number of codes. And the other sensor is provided at a position shifted by the same phase angle as that of one sensor, and when the total number of graduations is odd, from the graduation corresponding to a code of one sensor In the vicinity of the middle position between the scale corresponding to the code that differs from the half value of the total number of codes in the clockwise or counterclockwise direction by an integer excluding the decimal part and the scale corresponding to the code next to the scale. The other sensor is provided at a position where the phase angle of the other sensor is shifted by π from the phase angle of one sensor.

The position of the rotary encoder in the radial direction is adjusted with respect to at least one of the sensor positions so that the period between the scales measured by each sensor is equal to or less than a predetermined allowable value. It can be carried out.

[0011]

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a surveying instrument having an absolute encoder according to the present invention, in which a rotary encoder 1, a sensor including a light emitting unit 2 and a light receiving unit 3, and a control unit 4 partially constituting an arithmetic unit,
A storage unit 5 and a display unit 6 are provided.

The rotary encoder 1 is an absolute type which is constituted by two disc-shaped members which respectively rotate in the horizontal and vertical measurement directions, and has two types of bars which are wide and narrow along the entire outer peripheral edge. The scales composed of the light-transmitting portions 1A and 1B (see FIG. 5) are arranged at equal pitch intervals (that is, at the same period).
Are provided.

The light emitting section 2 emits light toward the outer peripheral edge of the rotary encoder 1 provided with a scale. In this embodiment, an LED (light emitting diode) is used. The lighting operation of the light emitting unit 2 is controlled by an LED driver 21 controlled by the control unit 4.

On the other hand, the light receiving section 3 includes the rotary encoder 1
Are arranged so as to face directly opposite to the light-emitting portion 2 with the light-transmitting portion 1A,
A CCD (Charge Coupled Device) that receives the transmitted light transmitted through 1B is used. The operation of the light receiving unit 3 is controlled by a CCD driver 31 controlled by the control unit 4. The output of the light receiving section 3 is A / A
The analog signal output from the CCD is connected to the input of the D conversion unit 32, is converted into a digital signal, and is output to the control unit 4. Note that this light receiving unit 3
In addition to the configuration of this embodiment, the configuration may be such that the optical path is changed by, for example, an appropriate reflecting member so that the rotary encoder 1 is disposed on the same side as the light emitting unit 2.

The control unit 4 performs an arithmetic operation based on a predetermined interpolation operation equation from the output signal data from the A / D conversion unit 32 and the cycle T detected from the output signal data.
The angle measurement is performed by calculating the interpolation amount. Further, as shown in FIG. 2, when one of the sensors S1 is fixed at an arbitrary position α with respect to the scale of the rotary encoder 1 at the time of assembling the sensor, an angle corresponding to the position α Then, the position shifted by a required angle is confirmed according to a predetermined program, and the other sensor S2 can be accurately installed.

That is, the total number of graduations (total graduations) engraved over the entire outer peripheral edge of the rotary encoder 1 is N
When two sensors are provided in a positional relationship shifted by 180 degrees, the position obtained from the code obtained from the data taken from the CCD at one sensor position α is η, and the phase at that time is η. The angle (corresponding to the position between the CCD reference and the scale pitch (T)) is defined as θ. Further, if the position on the code obtained from the data acquired from the CCD at the other sensor position β which is 180 ° away from the other and on the code is ε, and the phase angle at that time is ψ, if the total number N of the codes is even, Ε−η = N / 2 θ = ψ (1) When the total number N of codes is an odd number, ε−η = (N−1) / 2 θ = ψ + π (1) ′ Adjust β to satisfy.

Further, the control unit 4 includes two sensors S
In order to confirm that S1 and S2 are set apart from each other by the same distance R from the rotation center O along the radial direction, the period is read by each sensor. The values are compared, and the result is displayed on the display unit 6.

The storage unit 5 stores a program for a series of sensor positioning performed on the sensor by the control unit 4 and also stores a previous cycle which is a pitch between each scale. It has become.

Next, a specific method for installing a sensor in a surveying instrument having an absolute encoder according to the present invention will be described below.

Of the two sensors S1 and S2 installed,
First, the position of one sensor S1 is fixed. That is, an arbitrary scale of the rotary encoder 1 is selected, and the sensor S1 is set at a position α (hereinafter, referred to as a reference boundary portion) corresponding thereto.
Is installed. Then, based on the output signal from the sensor S1, the position obtained from the code corresponding to the position of the sensor S1 is calculated. Next, based on the position α of the sensor S1, 180
The other sensor S2 is temporarily fixed at a position where the angle is expected to differ by degrees. Then, in the same manner as described above, the position obtained from the code corresponding to the position of the sensor S2 is calculated based on the output signal from the sensor S2 itself.

In this way, since the position obtained from the code corresponding to the position of the sensor S1 and the position of the sensor S2 is known, it is determined whether or not the position of S1−the position of S2 = 180 degrees. I do. If it is determined that the difference between these positions is different from 180 degrees, the position of the temporarily fixed sensor S2 is appropriately shifted.
Repeat the above operation to check the position. Thereby, the sensor S2 can be accurately positioned and attached to the position β that faces 180 degrees.

When the two sensors S1 and S2 are installed 180 degrees opposite to each other, the sensors S1 and S2 are moved from the rotation center position O of the rotary encoder 1 in FIG. It is checked whether or not it is installed at a position separated by an equal distance R in the radial direction. That is, in each of these sensors S1 and S2, as shown in FIG.
The length between each scale, that is, one cycle T is calculated. Then, it is determined that the periods T1 and T2 calculated by the respective sensors S1 and S2 are within a certain allowable range k of the following expression (2), that is, | T1−T2 | <k (2) If so, the sensor S1,
The installation work of S2 is completed. On the other hand, when it is determined that there is a periodic error exceeding the allowable range k, as shown in FIG. 3, the radial distances of both sensors are different (R
1 ≠ R2). In this case, for example, the sensor with the larger cycle is shifted to the center side along the radial direction of the rotary encoder 1 by an appropriate amount, or the sensor with the smaller cycle is shifted by the appropriate amount outward along the radial direction of the rotary encoder 1. Just shift it.

Thereafter, the same operation is performed again, and if it is within the allowable range, the installation operation is terminated there. If the cyclic error still does not fall within the allowable range, the operation is repeated.

Therefore, according to this embodiment, as shown in FIG. 2, even if the rotary encoder 1 has, for example, even or odd scales, the angle (180 degrees) is deviated by exactly a half turn. Accurate sensor S at opposing position β
2 can be installed, and the opposing position β
Trouble, such as being erroneously installed at a position out of phase from, for example, β ′, can be prevented.

[0025]

As described above, according to the present invention, one of the two sensors is fixedly installed at an arbitrary position corresponding to the scale of this rotary encoder, and the other is installed. Are temporarily shifted by an approximate angle difference, and angles corresponding to both of these sensor positions are calculated, and whether the calculated angle difference matches a predetermined number of codes and whether both phases are equal. It is configured so that the corner is confirmed. Therefore, based on the number of codes, it is checked whether the positions of both sensors are shifted by a predetermined angle, and the phase angles are matched or shifted by π according to the evenness of the total number of scales. If it is determined whether or not the other sensor is fixed, it becomes possible to confirm whether or not the two sensors are accurately shifted by a required angle.

As a result, without using any special jigs or tools, only those provided with the angle measuring device of the surveying instrument are used.
In addition, the sensor can be accurately installed by a simple method, and a highly accurate angle measuring device can be provided at a reduced cost.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an angle measuring device of a surveying instrument to which the present invention is applied.

FIG. 2 is an explanatory diagram showing a state in which each sensor with respect to a rotary encoder is installed shifted by a half cycle.

FIG. 3 is an explanatory diagram showing an installation state of a rotary encoder in a radial direction of each sensor.

FIGS. 4A and 4B are schematic diagrams showing the installation state of each sensor with respect to the number of graduations provided on the rotary encoder, where FIG. 4A shows the installation positions for an even number and FIG.

FIG. 5 is a schematic perspective view of a main part showing a rotary encoder and a sensor installed near the rotary encoder.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotary encoder 2 Light emitting part 3 Light receiving part 4 Control part 5 Storage part α Reference boundary part β Opposite boundary part ε Position obtained from code η Position obtained from code θ Phase angle ψ Phase angle S1 (one) sensor S2 (Other) sensor T period

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) G01D 5/36 G01D 5/36 TX (72) Inventor Shinichi Suzuki 2-5-2 Higashi-Oizumi, Nerima-ku, Tokyo Asahi Seimitsu Co., Ltd. (72) Inventor Tomoyuki Tajima 2-5-2, Higashi Oizumi, Nerima-ku, Tokyo F-term inside the Asahi Seimitsu Co., Ltd. 2F065 AA39 DD19 FF17 FF19 GG07 JJ02 JJ05 JJ25 2F077 AA38 NN02 NN23 NN30 PP19 QQ02 QQ12 RR03 RR23 VV21 2F103 BA05 BA32 CA02 DA06 DA13 EA04 EA12 EB06 EB08 EB14 EB16 EB27

Claims (3)

[Claims] 1. A surveying instrument having an absolute encoder for reading a scale at a peripheral portion of an absolute type rotary encoder by two sensors provided at a predetermined phase angle and measuring an altitude angle and a horizontal angle. When any one of the two sensors is fixed at an arbitrary position on the periphery of the rotary encoder, the number of codes corresponding to a predetermined angle difference from a scale position corresponding to a certain code of the one sensor The other sensor is located in the vicinity of a different code, and from the code, at a fixed angular relationship to the phase angle of one sensor due to the evenness of the total number of graduations. A surveying instrument having an absolute encoder. 2. When the total number of scales is an even number, the code is different from the scale corresponding to a certain code of one of the sensors by half of the total number of codes in the clockwise or counterclockwise direction. If the other sensor is provided at a position shifted by the same phase angle as that of one sensor, and the total number of scales is odd, the clock starts from the position corresponding to the code of one sensor. In the vicinity of the intermediate position between the scale corresponding to the code where the code is different from the half value of the total number of codes in the direction or counterclockwise by an integer excluding the decimal part and the scale corresponding to the code adjacent thereto, The absolute sensor according to claim 1, wherein the other sensor is provided at a position where the phase angle of the other sensor is shifted by π from the phase angle of one sensor. Surveying instrument with encoder. 3. Adjusting the position of the rotary encoder along the radial direction to at least one of the sensor positions so that the period between the scales measured by each sensor is equal to or less than a predetermined allowable value. A surveying instrument having the absolute encoder according to claim 1.