JP2016118439A - Position detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a position detection device capable of enhancing both high precision and high speed of a position detection device.SOLUTION: Two signals differing in phase by 90° changing in a sine wave shape at a pitch of a wavelength λ relative to measurement displacement are outputted from detection coils 2, 3. Storage devices 6,7 are stored with the amplitude ratio/phase-difference with respect to the two signals, and the amplitude ratio/phase-difference are removed from the two signals respectively in multipliers 8, 10 and a subtracting device 9. The two signals after removing the amplitude ratio/phase-difference are converted into position data in an interpolation computing device 12. A radius computing device 11 calculates radius values of the two signals after removing the amplitude ratio/phase-difference. Multipliers 22, 23 and operators 26, 27 calculates variation of the amplitude ratio/phase-difference based on a double angle sinewave table 20, a double angle cosine wave table 21, the position data, and the radius value, and updates the amplitude ratio/phase-difference stored in the storage devices 6. 7.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a position detection device that converts an output signal from a position sensor that outputs two signals that change in a sinusoidal shape corresponding to a measured displacement and that are 90 degrees out of phase with each other into position information.

  The amplitude ratio / phase difference component of the two signals included in the output signal from the position sensor that outputs two signals that change in a sinusoidal shape corresponding to the measured displacement and that are 90 degrees out of phase with each other is obtained. Patent Document 1 discloses a position detection device that uses a radius calculation means for calculating the square root of the sum of squares, automatically removes an offset component, and converts it into highly accurate position information. FIG. 2 is a diagram quoted from Patent Document 1 and omits devices and the like that are not necessary for the present invention.

  The rotor 1 in FIG. 2 is made of a magnetic material having 36 irregularities in one rotation at a pitch of a wavelength λ = 10 degrees on the outer peripheral portion, and is fixed to a rotating shaft. When the rotating shaft rotates, the two types of detection coils 2 and 3 generate a cosine wave analog signal AC and a sine wave analog signal AS of the rotational displacement θ / 36 due to reluctance change due to the unevenness of the outer periphery of the rotor. These signals are converted into digital signals DC and DS by AD converters 4 and 5, respectively.

  When the power is turned on, the storage devices 6 and 7 store the amplitude ratio / phase difference component with respect to the signals DC and DS measured at the time of manufacturing the position detection device. The multiplier 8 multiplies the phase difference component PJ from the storage 6 and the signal DC. The subtracter 9 subtracts the output signal from the multiplier 8 and the signal DS to remove a phase difference component with respect to the signal DC included in the signal DS. The multiplier 10 multiplies the amplitude ratio component BJ from the storage device 7 and the signal DS after the phase difference component removal output from the subtractor 9 to remove the amplitude ratio component for the signal DC included in the signal DS. As a result, the multiplier 10 outputs a signal DSC from which the amplitude ratio / phase difference component with respect to the signal DC included in the signal DS is removed.

In the interpolation calculator 12, the signals DC and DSC are subjected to arc tangent calculation with two variables as inputs, and converted into a position signal IP indicating the amount of rotation within 1/36 of the rotation axis. Further, the signals DC and DSC are calculated by the radius calculator 11 according to Equation 1, and the radius amount RD of the Lissajous circle, which is the square root of the square sum of the signals DC and DSC, is output. SQRT represents the square root and ^ 2 represents the square.
RD = SQRT (DC ^ 2 + DSC ^ 2) (Formula 1)

  Regarding the change in radius when there is a component that deteriorates the interpolation accuracy such as offset, phase difference, amplitude ratio, etc., if numerical analysis is performed with a spreadsheet tool etc., it is the same as the amount of the component that deteriorates, or at least It has been found that a change of about ½ can be obtained. Also, if one of the two signals has an offset error, the radius amount changes in a cosine wave shape at the wavelength of λ, and if the other has an offset error, the radius amount changes in a sine wave shape at the wavelength of λ. doing. It has also been found that if there is an amplitude difference between the two signals, the radius amount changes in a cosine wave shape at a wavelength of λ / 2. Further, it has been found that if there is a phase difference between the two signals, the radius amount changes sinusoidally at a wavelength of λ / 2. In addition, if there is a second-order harmonic distortion in one of the two signals, the radius will change to two sinusoidal waves of the same amplitude having wavelengths of λ and λ / 3, and the second harmonic distortion will be in the other It has been found that the radius varies into two cosine waves of the same amplitude having wavelengths of λ and λ / 3. In addition, it is clear that the change in the radius amount is very small compared to the change amount of the two signals that change at the pitch of the wavelength λ. From the above, the technique disclosed in Patent Document 1 quantitatively obtains a component that deteriorates the interpolation accuracy such as offset, phase difference, amplitude ratio, and the like based on a radius amount with small fluctuation.

  In the Fourier analyzer (FFT) 13, every time the rotational position changes by λ, the interpolation value IP output from the interpolation calculator 12 and the radius amount for each position change of λ / 2n (n is an integer of 3 or more). A Fourier analysis is performed based on a value corresponding to RD.

In the calculator 14, the calculation of Expression 2 is performed on the signal S2 that is the sine component of the wavelength λ / 2 of the radius RD calculated by the FFT 13 and the signal RDA that is the average radius, and the signal DP is output. .
DP = 2 * S2 / RDA (Formula 2)

  In the subtracter 16, the signal DP output from the calculator 14 is subtracted from the signal PJ for removing the phase difference component of the signal DS stored in the storage device 6. The signal subtracted by the subtracter 16 is stored in the storage 6 by the storage command signal SET from the FFT 13 and used as a phase difference correction value of the signal DS.

  With the above configuration, it is possible to detect how much the phase difference of the signal DS with respect to the signal DC is shifted from 90 degrees by only the rotation change of the wavelength λ, and to remove the phase difference component from the signal DS.

In the calculator 15, the calculation of Expression 3 is performed on the signal C 2 that is the cosine component of the wavelength λ / 2 of the radius RD calculated by the FFT 13 and the signal RDA that is the average radius, and the signal DB is output. .
DB = (RDA + C2) / (RDA-C2) (Formula 3)

  In the multiplier 17, the signal BJ for removing the amplitude ratio component of the signal DS stored in the storage device 7 is multiplied by the signal DB output from the arithmetic unit 15. The signal multiplied by the multiplier 17 is stored in the storage 7 by the storage command signal SET from the FFT 13 and used as an amplitude ratio correction value of the signal DS.

  With the above configuration, it is possible to accurately identify and remove from the signal DS an amount in which the amplitude ratio of the signal DS to the signal DC is different from 1, only by the rotational change of the wavelength λ.

JP 2008-232649 A

  In the method of calculating the amplitude ratio / phase difference component from the radius amount RD described in Patent Document 1, in order to perform Fourier analysis, the radius amount for each position change of 1 / n 2 within the wavelength λ pitch. A value corresponding to RD must be calculated. However, there is a problem that the amplitude ratio / phase difference component cannot be extracted because Fourier analysis cannot be performed at a speed at which the position changes by more than λ corresponding to 2 n power per AD sample period.

  The position detection device of the present invention is a position detection device that outputs position information corresponding to a measured displacement, a position sensor that outputs two signals that are 90 degrees out of phase that change sinusoidally, and Amplitude ratio component removing means for removing the amplitude ratio component of the two output signals, an interpolation calculating means for converting the two signals after removal of the amplitude ratio component into position information, and the square of the two signals from the position sensor Radius calculating means for calculating the square root of the sum, and correlation calculating means for multiplying the fluctuation component of the output of the radius calculating means and a cosine wave having a double frequency based on position information from the interpolation calculating means, respectively. And DC component extraction means for extracting the DC component of the output value of the correlation calculation means, wherein the amplitude ratio component removal means removes the amplitude ratio component based on the output value of the DC component extraction means Special To.

  The position detection device of the present invention is a position detection device that outputs position information corresponding to a measured displacement, a position sensor that outputs two signals that are 90 degrees out of phase that change sinusoidally, and Phase difference component removal means for removing the phase difference component of the two output signals, interpolation calculation means for converting the two signals after the phase difference component removal into position information, and the square of the two signals from the position sensor Radius calculation means for calculating the square root of the sum, and correlation calculation means for multiplying the fluctuation component of the output of the radius calculation means and a sine wave having a double frequency based on the position information from the interpolation calculation means, respectively. And DC component extracting means for extracting a DC component of the output value of the correlation calculating means, wherein the phase difference component removing means removes the phase difference component based on the output value of the DC component extracting means. Special To.

  In a preferred aspect, the DC component extraction means comprises a low-pass filter that receives the output of the correlation calculation means, and the position detection device further performs differential calculation of position information from the interpolation calculation means. In this manner, the apparatus includes a speed conversion unit that converts the signal into a speed signal, and an amplitude ratio storage unit that stores the amplitude ratio component set based on the value of the speed signal.

  In a preferred aspect, the DC component extraction means comprises a low-pass filter that receives the output of the correlation calculation means, and the position detection device further performs differential calculation of position information from the interpolation calculation means. And a phase difference storage unit for storing the phase difference component set based on the value of the speed signal.

  In another preferred aspect, the correlation calculation means in amplitude ratio component removal has a low-pass filter that outputs a DC component of the output value of the radius calculation means, and the DC component is output from the output value of the radius calculation means. By removing, the fluctuation component of the output of the radius calculation means is input.

  In another preferred aspect, the correlation calculation means in phase difference component removal has a low-pass filter that outputs a DC component of the output value of the radius calculation means, and the DC component is output from the output value of the radius calculation means. By removing, the fluctuation component of the output of the radius calculation means is input.

  According to the present invention, a component corresponding to the amplitude ratio / phase difference component can be extracted by the correlation calculation of the output of the radius calculation means and the two signals of the position sensor without using the Fourier transform. For this reason, it is possible to identify the amplitude ratio / phase difference component with high accuracy as in Patent Document 1. Further, it is possible to identify the amplitude ratio and the phase difference with high accuracy even in the case of a rotational speed at which the position changes by λ of 2 n powers per sample period of the AD converter. Accordingly, it is possible to accurately identify the change over time in the amplitude ratio / phase difference even at high speed rotation, remove the accuracy deterioration component, and greatly improve the interpolation accuracy. That is, it is possible to achieve both high accuracy and high speed of the position detection device.

It is a block diagram of a position detection device showing an embodiment of the present invention. It is a figure which shows the conventional position detection apparatus.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1 having the same functions as those in FIG. 2 are denoted by the same reference numerals as those in FIG. 2, and redundant descriptions are omitted.

  The radius amount RD output from the radius calculator 11 is input to the low-pass filter 18, and a signal RDDC that is a DC component of the radius amount RD is output. Then, the signal RDDC is subtracted from the radius RD by the subtracter 19, and a signal RDAC that is a fluctuation component of the radius RD is output. The double angle sine wave table 20 outputs a sine wave signal 2ST having a frequency twice the rotational displacement θ / 36 based on the position signal IP within 1/36 rotation output from the interpolation calculator 12. The double angle cosine wave table 21 outputs a cosine wave signal 2CT having a frequency twice the rotational displacement θ / 36 based on the position signal IP within 1/36 rotation output from the interpolation calculator 12. The multiplier 22 correlates the signal RDAC and the double angle sine wave signal 2ST and outputs a signal RDA2S. The multiplier 23 performs a correlation operation on the signal RDAC and the double angle cosine wave signal 2CT and outputs a signal RDA2C. Signals RDA2S and RDA2C are input to low-pass filters 24 and 25, which are DC component extraction means, and DC components R2SDC and R2CDC of signals RDA2S and RDA2C are output.

The calculator 26 performs the calculation shown in Expression 4 and outputs a phase difference displacement signal DPA for the signal DC included in the signal DS.
DPA = R2SDC * 4 / RDD (Formula 4)

The calculator 27 performs the calculation shown in Equation 5 and outputs an amplitude ratio displacement signal DBA for the signal DC included in the signal DS.
DBA = (RDD + R2CDC * 2) / (RDD-R2CDC * 2) / RDD (Formula 5)

  The subtracter 16 subtracts the signal DPA output from the calculator 26 from the signal PJ for removing the phase difference component of the signal DS stored in the storage device 6 and outputs a subtraction signal PJDF. This subtraction signal PJDF becomes a phase difference component including a phase difference displacement.

  When rotating at a frequency lower than the cut-off frequency of the low-pass filters 18, 24, 25, the low-pass filters 18, 24, 25 cannot extract a DC component. It is necessary to stop the setting of the phase difference signal PJDF in the storage unit 6. The speed converter 28 outputs a speed signal VEL by differentiating the interpolation value IP output by the interpolation calculator 12. The speed signal VEL is compared with the set speed stored in the memory 30 by the comparator 29. When the speed signal VEL is higher than the set speed, the comparator 29 outputs a memory command signal SET. The storage device 6 stores the phase difference signal PJDF including the phase difference displacement output from the subtracter 16 when the storage command signal SET is input, and is used as a phase difference correction value of the signal DS. Therefore, the signal PJ, which is the phase difference component, is updated only when the rotational speed is sufficiently higher than the cutoff frequency of the low-pass filters 18, 24, and 25.

  The multiplier 17 multiplies the signal BJ for removing the amplitude ratio of the signal DS stored in the storage unit 7 by the signal DBA output from the computing unit 27, and outputs a multiplication signal BJDF. This multiplication signal BJDF becomes an amplitude ratio component including the amplitude ratio displacement.

  The storage device 7 stores the amplitude ratio signal BJDF including the amplitude ratio displacement output from the multiplier 17 when the storage command signal SET is input, and is used as the amplitude ratio correction value of the signal DS. Therefore, the signal BJ that is the amplitude ratio component is updated only when the rotational speed is sufficiently higher than the cutoff frequency of the low-pass filters 18, 24, and 25.

1 rotor, 2, 3 detection coil, 4, 5 AD converter, 6, 7, 30 memory, 8,
10, 17, 22, 23 Multiplier, 9, 16, 19 Subtractor, 11 Radius calculator, 12 Interpolator, 13 Fourier analyzer, 14, 15, 26, 27 Calculator, 18, 24, 25 Low Band pass filter, 20 double angle sine wave table, 21 double angle cosine wave table, 28 speed converter, 29 comparator.

Claims (6)

A position detection device that outputs position information according to measurement displacement,
A position sensor that outputs two signals that are 90 degrees out of phase that change sinusoidally;
Amplitude ratio component removing means for removing amplitude ratio components of two output signals from the position sensor;
Interpolation operation means for converting the two signals after the amplitude ratio component removal into position information;
Radius calculating means for calculating the square root of the sum of squares of two signals from the position sensor;
Correlation calculation means for multiplying a fluctuation component of the output of the radius calculation means and a cosine wave having a double frequency based on position information from the interpolation calculation means,
DC component extraction means for extracting the DC component of the output value of the correlation calculation means;
With
The amplitude ratio component removing unit removes the amplitude ratio component based on an output value of the DC component extracting unit;
A position detecting device characterized by that. A position detection device that outputs position information according to measurement displacement,
A position sensor that outputs two signals that are 90 degrees out of phase that change sinusoidally;
Phase difference component removing means for removing a phase difference component of two output signals from the position sensor;
Interpolation calculation means for converting the two signals after the phase difference component removal into position information;
Radius calculating means for calculating the square root of the sum of squares of two signals from the position sensor;
Correlation calculation means for multiplying the fluctuation component of the output of the radius calculation means and a sine wave of double frequency based on the position information from the interpolation calculation means,
DC component extraction means for extracting the DC component of the output value of the correlation calculation means;
With
The phase difference component removing unit removes the phase difference component based on an output value of the DC component extracting unit;
A position detecting device characterized by that. The DC component extraction unit is composed of a low-pass filter that receives the output of the correlation calculation unit,
The position detection device further includes:
Speed conversion means for converting the position information from the interpolation calculation means into a speed signal by performing a differential operation;
Amplitude ratio storage means for storing the amplitude ratio component set based on the value of the speed signal;
The position detection device according to claim 1, further comprising: The DC component extraction unit is composed of a low-pass filter that receives the output of the correlation calculation unit,
The position detection device further includes:
Speed conversion means for converting the position information from the interpolation calculation means into a speed signal by performing a differential operation;
Phase difference storage means for storing the phase difference component set based on the value of the speed signal;
The position detection apparatus according to claim 2, further comprising: The correlation calculation means has a low-pass filter that outputs a DC component of the output value of the radius calculation means, and removes the DC component from the output value of the radius calculation means, thereby outputting the output of the radius calculation means. Taking the fluctuation component as input,
The position detection device according to claim 1 or 3, wherein The correlation calculation means has a low-pass filter that outputs a DC component of the output value of the radius calculation means, and removes the DC component from the output value of the radius calculation means, thereby outputting the output of the radius calculation means. Taking the fluctuation component as input,
The position detection device according to claim 2 or 4, wherein

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