CN102997867A - Absolute angle measurement device and angle measurement method thereof - Google Patents

Abstract

The invention discloses an absolute angle measurement device and an angle measurement method thereof. The absolute angle measurement device comprises a signal disc, a plurality of sensors and a processor, wherein the sensors are uniformly mounted at the positions close to the edge of the signal disc. When the signal disc rotates for a circle, and characteristics of signals scanned by the sensors are presented as a complete cosine cycle. The processor is electrically connected with the sensors. The peripheral light transmittance of a light transmission disc varies in a cycle of cosine functions, and since signals on the light transmission disc are continuous, an accurate angle value can be obtained at an optional position, and errors of the sensors can be eliminated effectively.

Description

A kind of absolute type angle measurement device and the method that takes measurement of an angle thereof

Technical field

The method that the present invention relates to a kind of absolute type angle measurement device and take measurement of an angle.

Background technology

At present, the most frequently used method that takes measurement of an angle is to rely on the disc type optical encoder to measure, the disc type optical encoder belongs to the absolute value angular encoder, to utilize digitally coded mode to represent the addendum modification of lighting from former, that is engrave the yardstick mark at rule, after secondary chi stops to move, survey the position of ordering scale with reading symbol.Traditional photoelectric encoder is to read coding at radial direction, but affected by the code-disc radius size, and the closer to the center, scale is less, so code is wide and code length all is affected, code bit number can not be done very high, and code bit number directly has influence on measuring accuracy.In addition, traditional code-wheel, measuring accuracy is limited by partition size, and the angle that obtains within lattice all is same value.

Summary of the invention

It is high that technical matters to be solved by this invention provides a kind of degree of accuracy, can both obtain at an arbitrary position the absolute type angle measurement device of accurate angle value and the method that takes measurement of an angle thereof.

In order to solve the problems of the technologies described above, technical scheme provided by the present invention is: a kind of absolute type angle measurement device comprises signal panels, sensor and processor; Described sensor is provided with a plurality of, and evenly is installed in the position near the edge of signal panels; Described signal panels rotate a circle, and the signal characteristic of sensor scan is a complete cosine cycle; Described processor is connected with sensor electrical.

Described signal panels are toroidal.

Described signal panels are transparent plate, and sensor is optical sensor; Transmittance around the described transparent plate becomes the cosine function of one-period to change.

The method that a kind of absolute type angle measurement device takes measurement of an angle adopts aforementioned angle-measuring equipment, and concrete steps are:

1. throw light in a side of transparent plate;

2. optical sensor gathers optical signal data at the opposite side of transparent plate, and the data that collect send to processor;

3. draw the anglec of rotation of transparent plate after processor is processed data.

Described step 3. in processor concrete grammar that data are processed be: n the optical sensor that is installed in around the transparent plate collects a discrete cosine sequences x (0), x (1) ... x (n-1), then utilize Fourier transform to calculate and try to achieve X (1), then calculate its imaginary part and the arc tangent of the real part ratio phase place that just can obtain this discrete series, this phase value is exactly the accurate angle value at current disk place.

Describedly utilize Fourier transform to calculate to try to achieve the concrete formula of X (1) to be:

$X\left(1\right)=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(n\right)(\mathrm{COS}\frac{2\mathrm{\π}}{N}n-\mathrm{jSIN}\frac{2\mathrm{\π}}{N}n).$

After having adopted technique scheme, the present invention has positive effect: the transmittance around the transparent plate of the present invention becomes the cosine function of one-period to change, because the signal on the transparent plate is continuous, therefore accurate angle value can both be obtained at an arbitrary position, and sensor error can be effectively got rid of.

Description of drawings

Content of the present invention is easier to be expressly understood in order to make, and the below is according to specific embodiment and by reference to the accompanying drawings, and the present invention is further detailed explanation, wherein

Fig. 1 is the structural representation of embodiments of the invention 1.

Label in the accompanying drawing is:

Signal panels 1, sensor 2.

Embodiment

(embodiment 1)

Present embodiment comprises signal panels 1, sensor 2 and processor.

Signal panels 1 are toroidal.Sensor 2 is provided with a plurality of, and evenly is installed in the position near the edge of signal panels 1.Signal panels 1 rotate a circle, and the signal characteristic of sensor 2 scannings is a complete cosine cycle.Processor is electrically connected with sensor 2.

Certainly, signal panels 1 also can be other shapes.

Signal panels 1 can be transparent plate, and sensor 2 is the optical sensor that cooperates with it.Transmittance around the transparent plate becomes the cosine function of one-period to change.

The method that adopts aforementioned angle-measuring equipment to take measurement of an angle, concrete steps are:

1. throw light in a side of transparent plate;

2. optical sensor gathers optical signal data at the opposite side of transparent plate, and the data that collect send to processor;

3. draw the anglec of rotation of transparent plate 1 after processor is processed data, concrete grammar is: be installed in transparent plate n optical sensor on every side and collect discrete cosine sequences a: x (0), x (1) ..., x (n-1); Then utilize Fourier transform to calculate and try to achieve X (1), formula is:

$X\left(1\right)=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(n\right)(\mathrm{COS}\frac{2\mathrm{\π}}{N}n-\mathrm{jSIN}\frac{2\mathrm{\π}}{N}n),$ Then calculate its imaginary part and the arc tangent of the real part ratio phase place that just can obtain this discrete series, this phase value is exactly the accurate angle value at current disk place.

Obtain the derivation of above-mentioned formula, and utilize Fourier transform to calculate that the principle of angle is:

To the spectrum analysis of discrete-time signal, can use discrete time Fourier transform, i.e. DTFT.DTFT makes us can be in the frequency spectrum of numeric field frequency analysis signal and the frequency response characteristic of discrete system, but still has two practical problemss for DTFT: 1, numeric field frequencies omega=Ω T is a continuous variable, is unfavorable for calculating with computing machine.For the ease of carrying out frequency-domain analysis and the processing of discrete-time signal and system with the method for numeral, only carry out discretize not enough in time domain, also must carry out discretize at frequency spectrum.2, the sequence processed of digitizing solution can only be for time-limited, so, the spectrum analysis problem of finite length sequence is discussed specially.

According to such requirement, drawn the concept of the discrete Fourier transformation of finite length sequence.The discrete Fourier transformation of finite length sequence, referred to as discrete Fourier transformation, i.e. DFT (Discrete Fourier Transform).DFT is defined as follows.

Be provided with limit for length's sequence x (n), n=0,1,2, Λ, N1-, its discrete Fourier transformation DFT is defined as:

$X\left(k\right)=\mathrm{DFT}\left[x\left(n\right)\right]=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(n\right)e^{-j\frac{2\mathrm{\π}}{N}\mathrm{kn}},$ 0≤k≤N-1

Can release according to above-mentioned formula:

$x\left(n\right)=\mathrm{IDFT}\left[X\left(k\right)\right]=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}X\left(k\right)e^{j\frac{2\mathrm{\π}}{N}\mathrm{kn}},$ 0≤n≤N-1

Second formula is called discrete fourier inverse transformation (IDFT).First formula and second formula consist of a DFT transfer pair.DFT is the discrete Fourier transformation to finite length sequence, and the characteristics of DFT all disperse in time domain or at frequency spectrum, and all is time-limited.

DFT provides the fast algorithm FFT that comes a kind of method, the especially DFT of analytic signal and system with computing machine or dsp chip, is widely used in many science and technology, and has promoted developing rapidly of Digital Signal Processing and related discipline.

X (k) is generally plural number, and the form that can be write as real part and imaginary part is:

X(k)＝X _R(k)+jX _I(k)

Or the form of amplitude and phase place:

Amplitude wherein | X (k) is called the amplitude spectrum of sequence x (n), phase place

Be called the phase spectrum of sequence x (n), they are respectively:

$\left|X\left(k\right)\right|=\sqrt{X_R^2\left(k\right)+X_I^2\left(k\right)}$

For the transparent plate 1 of present embodiment, at a time all periodic sampling N point then can be thought with N times of circular frequency sampling one-period cosine signal.According to nyquist sampling theorem, N＞=2.

After the sampling, we just obtain the finite length sequence x (n) in a certain moment like this, n=0, and 1,2, Λ, N-1, its discrete Fourier transformation is:

$X\left(k\right)=\mathrm{DFT}\left[x\left(n\right)\right]=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(n\right)e^{-j\frac{2\mathrm{\π}}{N}\mathrm{kn}},$ 0≤k≤N-1

For the standard cosine signal of transparent plate 1, its frequency the point on the corresponding frequency domain be k=1.

$X\left(1\right)=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(n\right)e^{-j\frac{2\mathrm{\π}}{N}n}$

Then have

According to Euler's formula

Calculate:

$X\left(1\right)=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(n\right)(\mathrm{COS}\frac{2\mathrm{\π}}{N}n-\mathrm{jSIN}\frac{2\mathrm{\π}}{N}n)$

Again according to the phase spectrum of DFT

Be easy to try to achieve the absolute phase values of the cosine signal of discrete signal representative, suppose that our regulation discrete series phase place is to be our angle zero-bit at 0 o'clock, the phase place of then trying to achieve is exactly the angle value that angle-measuring equipment is offset.

Illustrate as described below:

See Fig. 1, suppose to be provided with eight sensors 2, namely N=8 supposes that disk has rotated 15 degree, and then first sampled point will drop on cos15 ° of position, 2 π of each interval cosine curve of naming a person for a particular job of back/8 phase places.So disk rotary circles, 8 sensors obtain corresponding data sequence x (0) with sampling, x (1), x (2), x (3), x (4), x (5), x (6), x (7); X (0)=cos15 °+a wherein, a is arbitrary value.

The rest may be inferred, can obtain: x (0)=cos15 °+a, x (1)=cos60 °+a, x (2)=cos105 °+a, x (3)=cos150 °+a, x (4)=cos195 °+a, x (5)=cos240 °+a, x (6)=cos285 °+a, x (7)=cos330 °+a.

The substitution formula gets:

X(1)＝(0.9659x1+0.5x0.707-0.2588x0+0.866x0.707+0.9659x1+0.5x0.707+0.2588x0+0.866x0.707)-j(0.9659x0+0.5x0.707-0.2588x1-0.866x0.707-0.9659x0+0.5x0.707-0.2588x1-0.866x0.707)＝3.863324+jx1.035124。

This moment, all a can be eliminated, so a does not affect final result.

Then calculate signal phase (1)=arctg (1.035124/3.863324)=arctg0.267936=14.9993 °, 0.0007 error only is to be caused by the mantissa that previous calculations is cast out.

Because the scope of arc tangent be-90 °～90 °, add that a simple quadrant judgement just can be with the phase projection to 0 that calculates °～360 °.

Above-described specific embodiment; purpose of the present invention, technical scheme and beneficial effect are further described; institute is understood that; the above only is specific embodiments of the invention; be not limited to the present invention; within the spirit and principles in the present invention all, any modification of making, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (6)

1. an absolute type angle measurement device is characterized in that: comprise signal panels (1), sensor (2) and processor; Described sensor (2) is provided with a plurality of, and evenly is installed in the position near the edge of signal panels (1); Described signal panels (1) rotate a circle, and the signal characteristic of sensor (2) scanning is a complete cosine cycle; Described processor is electrically connected with sensor (2).

2. a kind of absolute type angle measurement device according to claim 1, it is characterized in that: described signal panels (1) are toroidal.

3. a kind of absolute type angle measurement device according to claim 1 is characterized in that: described signal panels (1) are transparent plate, and sensor (2) is optical sensor; Transmittance around the described transparent plate becomes the cosine function of one-period to change.

4. method that absolute type angle measurement device takes measurement of an angle, it is characterized in that: adopt aforementioned angle-measuring equipment, concrete steps are:

1. throw light in a side of transparent plate;

2. optical sensor gathers optical signal data at the opposite side of transparent plate, and the data that collect send to processor;

3. draw the anglec of rotation of transparent plate after processor is processed data.

5. a kind of absolute type angle measurement device according to claim 4, it is characterized in that: described step 3. in processor concrete grammar that data are processed be: n the optical sensor that is installed in around the transparent plate collects a discrete cosine sequences x (0), x (1) ... x (n-1), then utilize Fourier transform to calculate and try to achieve X (1), then calculate its imaginary part and the arc tangent of the real part ratio phase place that just can obtain this discrete series, this phase value is exactly the accurate angle value at current disk place.

6. a kind of absolute type angle measurement device according to claim 5 is characterized in that: describedly utilize Fourier transform to calculate to try to achieve the concrete formula of X (1) to be:

$X\left(1\right)=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(n\right)(\mathrm{COS}\frac{2\mathrm{\π}}{N}n-\mathrm{jSIN}\frac{2\mathrm{\π}}{N}n).$

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