JP2002054923A - Angle measuring instrument of surveying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and quickly obtain an interpolating amount and to keep its accuracy for a long period. SOLUTION: In this angle measuring instrument of a surveying device comprising a control part 4 for calculating an interpolating amount on the basis of an output signal from a light receiving part 3 receiving the transmitted light or reflected light from an outer peripheral edge part having the graduation of a rotary encoder 1, and accurately measuring an angle on the basis of the interpolating amount, multiplier parts α, β to be multiplied by a function f [n] of a position equivalent to an output signal (an) from CCD of a cosine wave component C and a tangent wave component S of space frequency ωin an interpolation arithmetic expression θI are expanded in advance, and triangular functions included in each expanded term are respectively calculated in the control part 4. A constant of the multiplier part composed of each calculated term is obtained as a coefficient of each output signal and stored in a storing part 5 with a period T.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angle measuring device of a surveying instrument that performs an arithmetic process from an output signal from a light receiving unit based on a predetermined interpolation arithmetic expression, calculates an interpolation amount, and measures an angle.

[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. As the absolute type rotary encoder, for example, there is known a configuration in which two types of scales, which are widely and narrowly varied over the entire circumference, are all provided at equal intervals, but are provided in mutually different unique patterns.

Normally, in this absolute type angle measuring device, for example, as shown in FIG.
A light emitting unit 2 such as an LED that emits reading light toward the scale of the rotary encoder 1; and scales 1A and 1B of the rotary encoder 1 of the light from the light emitting unit 2.
Reflected or reflected (reflective type) at a part (transmissive type)
A light receiving unit 3 such as a CCD for receiving light, and a calculating unit (not shown) for calculating an interpolation amount from a predetermined interpolation calculation expression based on signal data output from the light receiving unit 3 and interpolating a measurement angle. When,
A display unit (not shown) for displaying angle measurement data based on the calculation result is provided.

Here, a description will be given of an angle measuring method in the angle measuring device using an interpolation operation formula with reference to FIG.
For example, the rotary encoder 1 is provided with M scales 1A and 1B provided at equal intervals but with two different widths of a wide width and a narrow width, and is provided at a peripheral portion thereof, of which k continuous scales 1A and 1B are provided. The position J (however, J
Is a positive number). That is, as the angle θc to be measured, θc = 360 ° × (J / M) (1) However, (360 ° / M) steps (scale pitch) are obtained.

Here, in order to measure the angle between the graduations and the interpolation amount θI, a phase angle ψ when the pitch of the graduations is 2π is calculated. Thereby, the interpolation amount θI is as follows: θI = (360 ° / M) × (ψ / 2π) (2) Therefore, the angle θ obtained from the output signal output from the CCD once read is as follows: θ = θc + θI (3)

Next, the interpolation amount θI between the scales will be described. If you expand the expression by Fourier transform, Here, if the position x is made to correspond to a discretized one with respect to n, Here, the range of n is changed from the interval [−∞, + ∞] to the interval [−
N, + N], multiply by the weight Wn, Becomes

By the way, at the spatial frequency ω0 obtained from a certain period T0, the equation (6) is Becomes However, ω0 = (1 / T0) × 2π (8) Further, when the equation (7) is expanded, Becomes

Then, substituting equation (8) into equation (9),
When expanded, here, In other words, the expression (10) is as follows: F (ω0) = C−jS (13)

Next, this expansion formula (10) or (13)
The relationship between the above and the configuration of the angle measuring device will be described with reference to FIG. F [n] in equations (5) to (12)
Is a function (position function) using the position as a variable. The projected image Z of the scale projected by the light emitting unit 2 on the CCD as the light receiving unit 3 is output signal data of the output signal data output from the pixel position of the CCD. It is equivalent to the sequence an. Here, an indicates 2N + 1 pieces of data which contribute to the angle calculation among the CCD output signals, and a0 indicates C
This is the coordinate origin on the CD.

By the way, when the rotary encoder 1 rotates to change the positional relationship between the CCD and the rotary encoder 1, the projected image Z of the scale on the CCD is changed.
Changes from FIG. 6 to FIG. 7, for example. As a result, the position function f [n] also changes, but the spatial frequency ω and the period T do not change.

Since data relating to the scale from the rotary encoder is sampled at regular intervals as an output signal from the CCD, the output signal an is output every time this data is sampled.
Is updated. Then, the latest angle θ (= θc + θI) is sequentially calculated from the updated data, and the equations (11) and (12) are used in this calculation.

For example, considering the cosine wave component (11), Similarly, for the sine wave component (12), Becomes

By the way, the rotary encoder 1 is provided with graduations of equal pitch, and the interval between the graduations corresponds to the period T0. Further, the cycle of the projected image Z on the CCD varies depending on the installation state of the sensor, but the spatial frequency ω0 corresponding to the scale cycle T0 becomes dominant. Therefore, the absolute value of the right side of the equation (7) is calculated by changing ω0, and the maximum ω0 at this time is the spatial frequency corresponding to the period of the scale. Note that the relationship between the spatial frequency ω and the period T is related by equation (8).

As described above, the operation formula (2) for obtaining the interpolation amount θI is calculated by using the phase angle 、, and this phase angle ψ is calculated as follows: ψ = tan ⁻¹ (S / C) In other words, using (15), it is calculated from a trigonometric function consisting of a sine component S and a cosine component C, and a period T is included in this trigonometric function.

As a result, the interpolation amount θI is given by (2),
From equations (11), (12), and (15), the following interpolation equation θI = (360 ° / M) · (1 / 2π) · tan ⁻¹ (S / C) (16) , The arctangent function is expanded into, for example, 2N + 1 number of terms, and a trigonometric function is calculated for each term. In other words, in the arc tangent function, the output signal an and the sine wave component or the cosine wave component are multiplied for each element of each CCD, and their sums are obtained. A tangent function value is obtained.

As described above, the interpolation formula includes a trigonometric function for each term. However, the calculation of the trigonometric function is particularly troublesome and time-consuming, causing inconvenience.

In such an interpolation formula, the period T enters the trigonometric function in the sine wave component and the cosine wave component of the spatial frequency ω, and this period T is determined once. After that, the period T is not invariable, and the period T may fluctuate due to, for example, aging.

Therefore, when trying to measure the angle with high precision,
It is conceivable that the cycle T is calculated every time the angle measurement is performed, and the angle measurement is performed by the interpolation formula every time according to the calculated cycle T. In this manner, the calculation of the cycle T is performed by calculating the interpolation amount. If it is performed every time, it takes more time and cannot be put to practical use.

[0019]

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to make it possible to easily, quickly and maintain the accuracy for a long period of time.

[0020]

SUMMARY OF THE INVENTION An angle measuring device for a surveying instrument according to the present invention is provided with a rotary encoder that is provided with scales at a peripheral edge thereof at equal pitches and rotates along a measuring direction, and is directed toward the peripheral edge provided with the scales of the rotary encoder. A light emitting unit that emits reading light and a light receiving unit that receives transmitted light or reflected light at the scale portion of the outer peripheral edge of the reading light, and an interpolation operation expression based on an output signal from the light receiving unit, A measurement unit for calculating an interpolation amount, and a storage unit for storing a cycle of the projection image of the slit and a program for the calculation process performed by the calculation unit, and calculating an interpolation amount to measure an angle. An angle measuring device for the machine, wherein the arithmetic unit previously calculates a trigonometric function included in the interpolation arithmetic expression as an array of constants and stores it in a storage unit, and the arithmetic unit always performs Calculate the interpolation amount from the interpolation formula When handles trigonometric function part as a constant, and characterized by being configured to perform only the product-sum operation.

When the control unit calculates the interpolation amount and performs the angle measurement, the control unit calculates the difference between the cycle T stored in the storage unit and the actually calculated cycle every time or at a constant frequency. If the difference exceeds a predetermined value, it is preferable to perform a self-diagnosis in which the newly calculated cycle is stored in the storage unit.

In the storage unit, the period of the projected image of the slit is stored, and when the change of the period is detected, the period stored in the storage unit is stored again as a new period after the change. It is preferable that the control unit recalculates each constant part of the trigonometric function including the cycle and stores the calculated constant part again in the storage unit.

[0023]

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows an angle measuring device of a surveying instrument according to the present invention.
, A light emitting unit 2 and a light receiving unit 3, a control unit 4, a part of which constitutes an arithmetic unit, a storage unit 5, and a display unit 6.

The rotary encoder 1 is a disc-shaped one that rotates in accordance with the rotation angle along the direction of measurement, and has a light-transmitting portion (or light-shielding portion) along the entire outer peripheral edge.
Graduations having two types of widths, wide and narrow, are provided.

The light emitting section 2 emits light toward the outer peripheral edge provided with the scale of the rotary encoder. 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
A CCD (Charge Coupled Device) that receives light transmitted through a light-transmitting portion, which is a scale on the outer peripheral edge, is used so as to face the light-emitting portion 2 opposite to the light-emitting portion 2. . 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 the A / D conversion section 3.
The analog signal output from the CCD is converted into a digital signal and output to the control unit 4. In addition, as this light receiving part 3,
In addition to the one in this embodiment, for example, the optical path may be changed by an appropriate reflecting member, so that the rotary encoder 1 is arranged on the same side as the light emitting unit 2.

The control unit 4 based on the output signal data a _n from the A / D converter 32, the output signal data a _n a position equivalent function f [n] and later "natural period" T0
The interpolation operation expression (16) described using , An interpolation amount θI is calculated and angle measurement is performed.

In particular, in this embodiment, after assembling the CCD, the period T in the interpolation equation (16), which is slightly different depending on the state of assembling of the CCD, is calculated, and this is calculated in advance as the "natural period" T0. The following constant parts α and β in the interpolation operation formula (16) are calculated using the “natural period” T0, and are stored in the storage unit 5 in advance.

That is, in the above-mentioned interpolation formula (16), the cosine component of the spatial frequency is Similarly, for the sine component (12), It is.

Of these, the output signals a _-N from the CCD are as follows:
a ₀ ,..., a _N For each multiplier part to be multiplied, ie, each cosine coefficient: α _−N = W− _N · cos [(2π / T0) · (−N)] ······ α ₀ = W ₀ · cos [(2π / T0) · (0)] · · · · · · α _N = W _N · cos [(2π / T0) · (N)] (where α _-N , ..., α ₀ ,..., Α _N are constants) (17 ′) and each sine coefficient: β _−N = W− _N · sin [(2π / T0) · (−N)] ······· β ₀ = W ₀ · sin [(2π / T0) · (0)] β _N = W _N · sin [(2π / T0) · (N)] (where β _-N ,..., Β _0, ..., beta _N is a constant) (18 ') previously calculated by the calculated numerically and stored in a storage unit 5 the value of the calculation result as a constant.

Therefore, the following simplified interpolation equation (hereinafter, referred to as a real interpolation equation), that is, the following equation that does not require the operation of a trigonometric function, is given by: θI = (1 / 2π) · ( 360 ° / M) tan ^-1 [[(α- _N -(-N)) + ... + (Α ₀ · (0)) +... + (Α _N · (N))] / [(β _-N · (-N)) + ... + (β ₀ · (0)) +… + (Β _N · (N))]] (16 ′), the interpolation amount θI can be calculated.

The storage unit 5 stores the "natural period" T0 as well as the coefficients α and β shown in (17) and (18) as constants together with the "natural period" T0. I have.

Therefore, according to the angle measuring apparatus according to this embodiment, the stored "natural period" T0, and the trigonometric function part α and the constant calculated and converted using the "natural period" T0. β is stored in the storage unit in advance. As a result, thereafter, the interpolation amount θI is calculated each time based on the real interpolation calculation expression (16 ′), so that it is not necessary to perform the cumbersome and time-consuming calculation of the trigonometric function every time.

Next, the self-diagnosis by the control unit 4 of the angle measuring device of the surveying instrument according to the present invention, that is, the work of periodically checking the period T will be described. The angle measurement method of the surveying instrument by the control unit 4 includes steps from a first step S1 to an eighth step S8.

In a first step S1, the control unit 4 performs a self-diagnosis every time or at a constant frequency when the power is turned on.
That is, a diagnosis is started as to whether or not the period T has changed with respect to the “natural period” T0 due to a change over time.

[0036] In the second step S2, it converts the output signal a _n from the CCD to a digital signal by the A / D converter 32, and outputs the digital signal to the control unit.

In the third step S3, the control section which has received the digital signal calculates the period T in accordance with the calculation method stored in the memory provided therein.

[0038] In the fourth step S4, performs pre CCD period calculated by the control unit 4 is stored in the storage unit 5 during assembly T, i.e. the "initial setting period" T _m, prior to the angle measuring operations each time " The “relative error” dT is calculated for the “measurement cycle” _Tc . dT = | T _m− T _c |

In the fifth step S5, the fourth step S4
Whether or not the relative error dT obtained in the step satisfies the following confirmation formula, that is, the “relative error” dT is “allowable value” Tm
It is determined whether it is within ax. dT <Tmax (19) That is, when it is determined that the “relative error” dT does not satisfy the confirmation equation (19), the process proceeds to the next sixth step S6. On the other hand, when it is determined that the “relative error” dT satisfies the confirmation equation (19), the process proceeds to an eighth step S8.

In the sixth step S6, the "relative error" dT
Is determined not to satisfy the confirmation equation (19), it can be seen that a highly accurate interpolation amount θI cannot be obtained in the cycle used so far, ie, the “initial setting cycle” Tm. Therefore, the “actual measurement period” Tc newly calculated this time is used for comparison with the “actual measurement period” to be performed prior to the future angle measurement operation. Therefore, the “actual measurement cycle” Tc calculated this time
(Hereinafter, this is referred to as “late setting cycle” Tm ′) is stored in the storage unit.

In the seventh step S7, the control unit 4
Simplified implementation without the need to perform trigonometric functions every time
In the insertion equation (16 '), set in the sixth step S6
Changed "Late setting cycle" Tm 'to "Natural cycle" T0
And based on this new "natural period" T0, again
Spatial frequency ω0, cosine coefficient α in trigonometric function_-N,…,
α ₀,…, Α_N, Sine coefficient β_-N, ..., β₀, ..., β_NEtc.
calculate. Then, those stored in the storage unit 5
Exchange the data of the factor with new data and re-store
In addition, based on these new data,
New simplified real interpolation formulas that do not require arithmetic on numbers
(16 ') is recreated and updated.

In the eighth step S8, the “natural period” T
From the “initial setting cycle” _Tm to the “late setting cycle” Tm ′
Using the new real interpolation operation equation (16 ′) updated to the above, the desired altitude angle and horizontal angle are measured with high accuracy.

Meanwhile, in the fifth step S5, if the "relative error" dT is determined to satisfy the check equations (19), "initial setting period" T _m is also effective in this angle measuring measuring operation Therefore, the process proceeds to the eighth step S8, and the interpolation amount θI is calculated by the actual interpolation operation using the same period as before.

Hereinafter, the self-diagnosis work described above is performed by the same method every time (or at a constant frequency) before performing the angle measurement work every time.

[0045]

As described above, according to the present invention, the arithmetic unit calculates the trigonometric functions included in the interpolation equation in advance and stores them in the storage unit as an array of constants. Each time the unit calculates the interpolation amount from the interpolation operation expression, each constant part of the trigonometric function is incorporated as a coefficient in the interpolation operation expression. Therefore, according to the present invention, since the factor of the trigonometric function that requires a lot of time and is cumbersome is calculated in advance and converted into a constant, the amount of the trigonometric function does not need to be calculated each time the angle measurement work is performed. The calculation time of the interpolation amount can be shortened, and the highly accurate angle measurement can be performed in a short time.

Further, according to the present invention, the period of the projected image of the slit is stored in the storage unit, and when the period changes, the control unit detects the change. Is stored again in the new period, and each constant part of the trigonometric function including this period is recalculated and stored in the storage unit again. Therefore, according to the present invention, even when the cycle T fluctuates due to, for example, a change over time, when the control unit detects that the cycle T has changed by self-diagnosis or the like, a new cycle T after the change is used, Since the coefficient part corresponding to the trigonometric function part in the interpolation operation formula is newly recalculated, even when performing angle measurement over a long period of time, a constant accuracy can be maintained. It is convenient.

[Brief description of the drawings]

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

FIG. 2 is a flowchart showing an angle measuring method of the surveying instrument according to the present invention.

FIG. 3 is a schematic perspective view showing a main part of an angle measuring device that performs angle measurement by a rotary encoder.

FIG. 4 is a schematic diagram for explaining an interpolation method.

FIG. 5 is an explanatory diagram showing a relationship between a projected image by transmitted light in a rotary encoder according to the present invention and an output signal from each pixel of a light receiving unit.

FIG. 6 is an explanatory diagram showing a positional relationship between a projected image by a rotary encoder and pixels of a light receiving unit.

FIG. 7 is an explanatory diagram illustrating a change in a positional relationship between a projected image and a pixel of a light receiving unit according to rotation of a rotary encoder.

[Explanation of symbols]

Reference Signs List 1 rotary encoder 2 light emitting unit 3 light receiving unit 4 control unit 5 storage unit θI interpolation amount 量 phase angle an output signal (of CCD nth element) C cosine wave component f [n] function of position S cosine wave component N Total number of CCDs T Period Wn Weight function Z Projected image α _-N cosine coefficient α ₀ cosine coefficient α _N cosine coefficient β _-N sine coefficient β ₀ sine coefficient β _N sine coefficient ω Spatial frequency

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shinichi Suzuki 2-5-2 Higashi Oizumi, Nerima-ku, Tokyo Asahi Seimitsu Co., Ltd. (72) Inventor Tomoyuki Tajima 2-5-Higashi Oizumi, Nerima-ku, Tokyo No. 2 Asahi Seimitsu Co., Ltd.

Claims (3)

[Claims] 1. A rotary encoder provided with graduations at an equal pitch on a peripheral edge thereof and rotating along a measurement direction, a light emitting section for emitting reading light toward the peripheral rim provided with the graduation of the rotary encoder, and the reading light. A light-receiving unit that receives transmitted light or reflected light at the scale portion of the outer peripheral edge, and a calculation unit that performs a calculation process of an interpolation amount from an interpolation calculation expression based on an output signal from the light-receiving unit, A storage unit for storing a cycle of a projection image of the slit and a program for the calculation processing performed by the calculation unit, wherein the angle measurement device of a surveying instrument that calculates an interpolation amount and performs angle measurement; However, the trigonometric functions included in the interpolation formula are calculated in advance as an array of constants and stored in the storage unit.When the calculation unit calculates the interpolation amount from the interpolation formula each time, , Treats trigonometric functions as constants Angle measuring device of a surveying machine which is characterized by being configured to perform only the product-sum operation. 2. When the control unit calculates an interpolation amount and performs angle measurement, a difference between a period T stored in the storage unit and an actually calculated period is always or at a constant frequency. The self-diagnosis is performed so that when the difference is larger than a predetermined value, the newly calculated cycle is stored in the storage unit. Angle measuring device of surveying instrument. 3. A cycle of the projection image of the slit is stored in the storage section, and when it is detected that the cycle has changed, the cycle stored in the storage section is stored again as a new cycle after the change. 3. The surveying instrument according to claim 1, wherein the control unit recalculates each constant part of the trigonometric function including the cycle and stores the calculated constant part again in the storage unit. 4. Horn device.