JP2008304249A - Encoder signal processing device and its signal processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an encoder position calculation device and a correction method capable of removing an error of a harmonic distortion even if each component of a harmonic included in a two-phase input signal is different in each phase, and acquiring a highly-accurate position signal. <P>SOLUTION: The two-phase input signal digitized by an A/D converter 1, and two or more pieces of position data calculated by a position data calculation part 3 based on the two-phase input signal are acquired, and a third harmonic amplitude superimposed on each input signal is calculated by a third harmonic amplitude calculation part 4. A third harmonic is removed from the input signal based on the third harmonic amplitude by a third harmonic correction part 5. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a signal processing apparatus and a signal processing method for an encoder such as a rotary encoder that detects a rotation angle of a rotating body such as a motor and a linear encoder that detects displacement of a linear stage and the like.

Conventionally, there has been disclosed a position signal calibration device that removes the third harmonic superimposed on the two-phase analog signal obtained from the sensor signal detection means (see, for example, Patent Document 1).
FIG. 6 is a block diagram showing a configuration of a conventional encoder signal processing apparatus.
In the figure, reference numerals 21 and 22 denote normalizing means for adjusting the zero points and amplitudes of two-phase input signals X and Y obtained from a sensor signal detecting means (not shown), and 23 is an arctangent calculation of the normalized two-phase signals. The arc tangent calculating means for using the position data as a position data, 24 is a correcting means for correcting an error due to the third harmonic from the arc tangent calculation result, 25 is a zero point parameter calculating means for calculating the zero point parameter of the two-phase input signal, 26 is an amplitude correction parameter calculation means for calculating the amplitude correction parameter of the two-phase input signal, 27 is a third harmonic error correction parameter calculation means for calculating the third harmonic error of the two-phase input signal, and 28 is It is a peak value detecting means for detecting a peak value of a two-phase input signal.

Next, the operation will be described.
For the two-phase input signal, the peak detecting means 28 detects the respective maximum and minimum values of the maximum and minimum values of the two-phase input signals X and Y and the sum and difference of the two-phase signals. Using the detected peak value, the zero point parameter calculating means 25 uses the zero point correction parameter, the amplitude correction parameter calculating means 26 uses the amplitude correction parameter, and the third harmonic error correction parameter calculating means 27 uses the detected peak value. Calculate the third harmonic error. After normalizing the zero point and the amplitude by the normalizing means 21 and 22 using the zero point correction parameter and the amplitude correction parameter, the position data is obtained by the arc tangent calculating means 23 based on these normalized data. calculate. Furthermore, the corrected position data is obtained by deleting the error amount due to the third harmonic from the position data using the third harmonic error correction parameter.

As described above, the conventional encoder signal processing apparatus detects the maximum and minimum values of the two-phase input signal, and the maximum and minimum values of the sum and difference, and uses them to superimpose the third harmonic on the input signal. The amount of error due to was calculated, and the position data was corrected accordingly.
Japanese Patent No. 2839340

However, the conventional encoder signal processing apparatus detects the maximum and minimum values of the two-phase input signals, and the maximum and minimum values of the sum and difference, and uses them to superimpose the third harmonic on the input signal. As a result, the third harmonic component included in the two-phase input signal is assumed to be equal. However, in reality, each input signal has different characteristics due to the design and assembly accuracy of the sensor and individual differences, and the amplitude amount of the harmonic component relative to the fundamental wave is also different. Even if normalization is performed, the amplitudes of the harmonics included in the two signals are not equal.
For this reason, there has been a problem that the error of the third harmonic distortion cannot be completely eliminated and a highly accurate position signal cannot be obtained.

  Therefore, the present invention has been made in view of such problems, and even if the harmonic components contained in the two-phase input signal are different in each phase, it is possible to eliminate the harmonic distortion error and achieve high accuracy. It is an object of the present invention to provide an encoder position calculation apparatus and a correction method capable of obtaining a position signal of.

In order to solve the above problems, the present invention is configured as follows.
According to the first aspect of the present invention, the periodic A-phase and B-phase two-phase sinusoidal analog signals obtained from the sensor signal detection unit according to the positions of two relatively displaced objects are converted into digital signals, respectively. In the encoder signal processing method for calculating position data from the digital signal and obtaining the position of the object from the position data, the position data at any two positions and the A-phase digital signal at the two positions The A phase third harmonic amplitude is calculated from the obtained A phase digital data α ₁ , α ₂ , and the B phase obtained from the position data at any two positions and the B phase digital signal at the two positions digital data beta _1, beta ₂ from calculating the third harmonic amplitude phase B, the a-phase third harmonic amplitude and phase B the third harmonic amplitude a phase digital signal and B-phase digital signal Each corrected, it is characterized in that to calculate the position data from the corrected A-phase digital signal and the B-phase digital signal.

In the invention according to claim 2, the A-phase third-order harmonic amplitude a ₃ is defined as A phase with a ₁ as the A-phase fundamental wave amplitude and θ ₁ and θ ₂ as position data at arbitrary two positions. In the case of simultaneous equations a ₁ Cosθ ₁ + a ₃ Cos3θ ₁ = α ₁
a ₁ Cosθ ₂ + a ₃ Cos3θ ₂ = α ₂
The B-phase third harmonic amplitude b ₃ is a simultaneous equation in the case of the B-phase where b ₁ is the B-phase fundamental wave amplitude and θ ₁ and θ ₂ are the position data at any two positions. b ₁ Sinθ ₁ -b ₃ Sin3θ ₁ = β ₁
b ₁ Sinθ ₂ -b ₃ Sin3θ ₂ = β ₂
It is characterized by calculating by solving.

The invention according to claim 3, wherein the A-phase third harmonic amplitude a ₃ calculates the third harmonic amplitude for the location of the plurality of sets of two arbitrary points, calculated the third harmonic The B-phase third-harmonic amplitude b ₃ is an average of the amplitudes, and the third-harmonic amplitude is calculated for any two positions of a plurality of sets, and the calculated third-harmonic amplitudes are averaged. It is characterized by that.

  The invention described in claim 4 is a harmonic amplitude calculating operation for calculating the A phase third harmonic amplitude and the B phase third harmonic amplitude, and the harmonics for correcting the A phase digital signal and the B phase digital signal, respectively. A correction operation and a position data calculation operation for calculating position data are repeatedly performed in sequence.

  The invention according to claim 5 is characterized in that the A-phase third-order harmonic amplitude and the B-phase third-order harmonic amplitude are stored and used as initial data when the power is turned on.

According to a sixth aspect of the present invention, the periodic A-phase and B-phase two-phase sinusoidal analog signals obtained from the sensor signal detection unit in accordance with the positions of two relatively displaced objects are respectively digital signals. In the signal processing method of the encoder for calculating the position data from the digital signal and obtaining the position of the object from the position data, the amplitude of the fifth harmonic of the A phase is 0 and the amplitude of the third harmonic is The A-phase third-order harmonic amplitude a ₃ is calculated from the position data θ ₁ , θ ₂ at the two non-zero positions and the A-phase digital signals α ₁ , α _{2 at the} two point positions to obtain the third-order A-phase. From the position data θ ₃ , θ _{4 at} the positions of the two points where the amplitudes of the harmonics are not 0, the A phase digital signals α ₃ , α _{4 at} the positions of the two points, and the A phase third harmonic amplitude a ₃ to A calculating a phase fifth harmonic amplitude a _5, the B phase Position data theta ₁ at the position of the amplitude of the amplitude of harmonics is 0 third harmonic two points not at _0, theta A phase digital signal beta ₁ in ₂ and the two points located, beta ₂ from B-phase 3 The second harmonic amplitude b ₃ is calculated, the position data θ ₃ , θ ₄ at two positions where the amplitude of the third harmonic of the B phase is not 0, and the B phase digital signal β _{3 at} the two positions, B-phase fifth harmonic amplitude b ₅ is calculated from β ₄ and B-phase third harmonic amplitude b ₃ , and A-phase third-harmonic amplitude a ₃ and A-phase fifth-harmonic amplitude a ₅ are used as A-phase. The digital signal is corrected, the B phase digital signal is corrected with the B phase third harmonic amplitude b ₃ and the B phase fifth harmonic amplitude b ₅ , and the corrected A phase digital signal and the B phase digital signal are corrected. It is characterized by calculating position data.

In the invention according to claim 7, the A-phase third harmonic amplitude a ₃ is a simultaneous equation in the case of A phase where a ₁ is the A-phase fundamental amplitude. A ₁ Cosθ ₁ + a ₃ Cos3θ ₁ = α ₁
a ₁ Cosθ ₂ + a ₃ Cos3θ ₂ = α ₂
The A-phase fifth harmonic amplitude a ₅ is calculated by solving the following equation: In the case of the A-phase, the simultaneous equations a ₁ Cosθ ₃ + a ₃ Cos3θ ₃ −a ₅ Cos5θ ₅ = α ₃
a ₁ Cosθ ₄ + a ₃ Cos3θ ₄ −a ₅ Cos5θ ₄ = α ₄
Calculated by solving, the B-phase third harmonic amplitude _{a 3,} if the phase B _{b 1} as B-phase fundamental wave amplitude equations _{b 1 Sinθ 1 -b 3 Sin3θ 1} = β 1
b ₁ Sinθ ₂ -b ₃ Sin3θ ₂ = β ₂
Calculated by solving the B-phase fifth harmonic amplitude _{a 5} in the case of B-phase simultaneous equations _{b 1 Sinθ 3 -b 3 Sin3θ 3} -b 5 Sin5θ 3 = β 3
b ₁ Sinθ ₄ -b ₃ Sin3θ ₄ -b ₅ Sin5θ ₄ = β ₄
It is characterized by calculating by solving.

According to the eighth aspect of the present invention, the periodic A-phase and B-phase two-phase sinusoidal analog signals obtained from the sensor signal detection unit in accordance with the positions of two relatively displaced objects are respectively digital signals. In an encoder signal processing apparatus that obtains the position of the object from the position data, an A / D converter that converts the data into an A / D converter and a calculation unit that calculates position data from the digital signal. The A-phase harmonic signal amplitude is calculated from the position data at the position of A and the A-phase digital signals α ₁ and α _{2 at} the positions of the two points. signal beta _1, and harmonic amplitude calculating unit for calculating a B-phase harmonic amplitude from beta _2, a-phase digital signal and B-phase digital signal by the a-phase harmonic amplitudes and the B-phase harmonic amplitudes It is characterized by a comprising: a harmonic correction unit which corrects each of the position data calculation unit which calculates position data from the corrected A-phase digital signal and the B-phase digital signal.

In the invention according to claim 9, the harmonic amplitude calculation unit is configured as a simultaneous equation in the case of the A phase, where a ₁ is the A phase fundamental wave amplitude, θ ₁ and θ ₂ are position data at two arbitrary positions. a ₁ Cosθ ₁ + a ₃ Cos3θ ₁ = α ₁
a ₁ Cosθ ₂ + a ₃ Cos3θ ₂ = α ₂
To calculate the A-phase third harmonic amplitude a ₃ , b ₁ as the B-phase fundamental wave amplitude, θ ₁ and θ ₂ as the position data at any two positions, and simultaneous equations b for the B-phase ₁ Cosθ ₁ + b ₃ Cos3θ ₁ = β ₁
b ₁ Cosθ ₂ + b ₃ Cos3θ ₂ = β ₂
The B-phase third harmonic amplitude b ₃ is calculated by solving the above.

Further, in the invention described in claim 10, the harmonic amplitude calculation unit is configured so that the simultaneous equation a ₁ Cosθ ₁ + a ₃ Cos3θ ₁ = α _{1 in} the case of the A phase where a ₁ is the A phase fundamental wave amplitude.
a ₁ Cosθ ₂ + a ₃ Cos3θ ₂ = α ₂
By solving
Calculating the A-phase third harmonic amplitude _{a 3,}
In the case of phase A, simultaneous equations a ₁ Cosθ ₃ + a ₃ Cos3θ ₃ −a ₅ Cos5θ ₅ = α ₃
a ₁ Cosθ ₄ + a ₃ Cos3θ ₄ −a ₅ Cos5θ ₄ = α ₄
By solving
Calculating the A-phase fifth harmonic amplitude _{a 5,}
For Phase B b ₁ as B-phase fundamental wave amplitude equations _{b 1 Sinθ 1 -b 3 Sin3θ 1} = β 1
b ₁ Sinθ ₂ -b ₃ Sin3θ ₂ = β ₂
By solving
B phase 3rd harmonic amplitude b ₃ is calculated,
For B-phase simultaneous equations _{b 1 Sinθ 3 -b 3 Sin3θ 3} -b 5 Sin5θ 3 = β 3
b ₁ Sinθ ₄ -b ₃ Sin3θ ₄ -b ₅ Sin5θ ₄ = β ₄
It is characterized by calculating a B-phase fifth harmonic amplitudes b ₅ by solving.

According to the first aspect of the present invention, since the third harmonic amplitude of each of the A phase and the B phase is calculated and the third harmonic distortion is corrected using these information, highly accurate position data. Is obtained.
According to the second aspect of the invention, if the third harmonic amplitudes of the A phase and the B phase are obtained by solving two simple simultaneous equations, high-accuracy position data can be obtained by simple processing. .
According to the third aspect of the present invention, if the third-order harmonic amplitude is calculated for any two positions of a plurality of sets, and the calculated third-order harmonic amplitude is averaged, a highly accurate third-order harmonic is obtained. Amplitude is obtained.
According to the fourth aspect of the present invention, if the harmonic amplitude calculation operation, the harmonic correction operation, and the position data calculation operation are repeatedly performed in sequence, the third harmonic amplitude is updated, and the third harmonic distortion due to environmental changes. It is possible to obtain position data that is resistant to environmental changes that can respond to changes in the environment.
According to the fifth aspect of the present invention, if the A-phase third harmonic amplitude and the B-phase third harmonic amplitude are stored in a nonvolatile memory and used as initial data at power-on, etc. Highly accurate position data can be obtained immediately.
According to the invention described in claim 6, the third and fifth harmonic amplitudes of the A phase and the B phase are calculated, and the third and fifth harmonic distortions are corrected using these information. Therefore, highly accurate position data can be obtained.
According to the seventh aspect of the invention, if the third and fifth harmonic amplitudes of the A phase and the B phase are obtained by solving simple four simultaneous equations, the position data with high accuracy can be obtained by simple processing. Is obtained.
According to the invention described in claim 8, the calculation unit includes a harmonic amplitude calculation unit that calculates the A phase harmonic amplitude and the B phase harmonic amplitude, and the A phase harmonic amplitude and the B phase harmonic amplitude. High-accuracy because it includes a harmonic correction unit that corrects the phase digital signal and the B phase digital signal, and a position data calculation unit that calculates position data from the corrected A phase digital signal and the B phase digital signal, respectively. Encoder signal processing apparatus can be realized.
According to the ninth aspect of the present invention, if the third harmonic amplitudes of the A phase and the B phase are obtained by solving two simple simultaneous equations, high-precision position data can be obtained by simple processing. An accurate encoder signal processing apparatus can be realized.
According to the tenth aspect of the invention, if the third and fifth harmonic amplitudes of the A phase and the B phase are obtained by solving four simple simultaneous equations, high-precision position data can be obtained by simple processing. The resulting highly accurate encoder signal processing apparatus can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of an encoder signal processing apparatus according to a first embodiment of the present invention.
In FIG. 1, 1 is an A / D converter that converts two-phase periodic analog signals Sa and Sb obtained from a sensor signal detector (not shown) into digital signals α and β, and 3 is position data for calculating position data. The calculation unit 4 is a harmonic amplitude calculation unit that detects the _third harmonic amplitudes a ₃ and b ₃ , and 5 is a harmonic correction unit that corrects the two-phase digital signal based on the third harmonic amplitude information. Reference numeral 6 denotes a calculation unit, which includes a position data calculation unit 3, a harmonic amplitude calculation unit 4, and a harmonic correction unit 5.

  When two objects are relatively displaced in a linear direction, the sensor signal detection unit (not shown) may use a linear encoder detection unit as the sensor signal detection unit, and the two objects are relatively rotated. In the case of displacement, the detection unit of the rotary encoder may be used. The sensor signal detection unit (not shown) may be of any type such as a magnetic type, an optical type, a capacitance type, or a resolver type as long as the analog signal changes according to the relative displacement. It doesn't matter. Further, a signal amplifier circuit such as an operational amplifier may be provided in the previous stage of the A / D converter 1. Moreover, the calculating part 6 can be comprised using one or more various devices which have digital calculation functions, such as a microcomputer and DSP.

Next, the harmonic amplitude calculation operation in the present embodiment will be described.
FIG. 2 is a signal waveform diagram for explaining the calculation principle of the harmonic amplitude in the present embodiment, and shows the relationship between the fundamental wave and the third harmonic included in the sensor signal. (A) shows the relationship between the fundamental wave and the third harmonic in the A phase signal, and (B) shows the relationship between the fundamental wave and the third harmonic in the B phase signal.

When the third harmonic is superimposed on the sensor signals Sa (Cos signal) and Sb (Sin signal), the fundamental wave and the third harmonic have a phase relationship as shown in FIG. The digital signals α and β are expressed as follows: α = a ₁ Cosθ + a ₃ Cos3θ where the amplitude of the fundamental wave is a ₁ , b ₁ , and the amplitude of the third harmonic is a ₃ , b ₃
β = b ₁ Sinθ-b ₃ Sin3θ
It is represented by
However, (theta) is a position.
The position data calculation unit 3 calculates position data θ _i from a two-phase digital signal using an arc tangent calculation (tan-1).

The harmonic amplitude calculation unit 4 calculates the position data θ _i for two or more positions of the A-phase and B-phase digital signals, and acquires the digital data α _i and β _i at these positions (i = 1-n).
These relations are
For phase A,
a ₁ Cosθ ₁ + a ₃ Cos3θ ₁ = α ₁
a ₁ Cosθ ₂ + a ₃ Cos3θ ₂ = α ₂
...
a ₁ Cosθ _n + a ₃ Cos3θ _n = α _n
For phase B,
b ₁ Sinθ ₁ -b ₃ Sin3θ ₁ = β ₁
b ₁ Sinθ ₂ -b ₃ Sin3θ ₂ = β ₂
...
b ₁ Sinθ _n -b ₃ Sin3θ _n = β _n
It is represented by
The unknown number of relational expressions for phase A is a ₁ , a ₃ , the relational expression for phase B is b ₁ , b ₃ , and there are two unknowns for both the relational expression for phase A and the relational expression for phase B. If the minute data is acquired, a ₁ , a ₃ and b ₁ , b ₃ can be obtained.

When calculating the 3rd harmonic amplitude from a set of 2 points of data,
a ₃ = (α ₁ Cosθ ₂ -α ₂ Cosθ ₁ ) / (Cos3θ ₁ · Cosθ ₂ -Cos3θ ₂ · Cosθ ₁ )
_{b 3 = (β 1 Sinθ 2} - β 2 Sinθ 1) / (Sin3θ 2 · Sinθ 1 - Sin3θ 1 · Sinθ 2)
Ask for.
The calculation accuracy can be improved by calculating the third harmonic amplitude using two or more sets of data and averaging the calculated third harmonic amplitudes. In addition, the calculation accuracy can be improved by using the least square approximation method.
Note that the A phase and the B phase may acquire data at different positions. In addition, as a condition of acquired data, points where the amplitudes of the fundamental wave and the third harmonic are both 0, that is, points of θ = π / 2, 3π / 2 in the A phase and 0, π in the B phase are not used. Further, when the calculation is performed with only two points, a pair of two points with symmetric θ = 0 and π in the A phase and two points with symmetric θ = π / 2 and 3π / 2 are not used with the B phase.

Next, the harmonic correction operation will be described.
The harmonic correction unit 5 uses the A-phase third-order harmonic amplitude a ₃ and the B-phase third-harmonic amplitude b ₃ calculated by the harmonic amplitude calculation unit 4 to convert a two-phase digital signal into the following: Correct by calculation.
α = α'-a ₃ Cos3θ '
β = β '+ b ₃ Sin3θ'
However, α ′ and β ′ are digital signals of the sensor signals Sa and Sb before correction, and θ ′ is the previous value of the position data θ calculated by the position data calculation unit 3.
In order to improve the position calculation accuracy, the position data should be data that is a little closer to the current value than the previous value. And may be used.

As described above, in this embodiment, the third harmonic distortion superimposed on the sensor signal can be detected and the distortion can be removed, so that the position data can be calculated with high accuracy.
Further, by repeatedly executing the harmonic amplitude calculation operation and the harmonic correction operation of the present embodiment, it is possible to cope with a change in the third harmonic distortion due to an environmental change such as a temperature change.

FIG. 3 is a block diagram showing the configuration of the encoder signal processing apparatus in the second embodiment of the present invention.
In the figure, reference numeral 2 denotes a storage unit for storing harmonic amplitude. This embodiment is different from the first embodiment in that the calculation unit includes a storage unit and stores the third harmonic amplitude in advance.
The storage unit 2 may be integrated with the calculation unit 6, but is preferably a nonvolatile memory such as a ROM or a flash memory.

Next, the operation of this embodiment will be described.
In this embodiment, before actually using the encoder signal processing apparatus, the harmonic amplitude calculation operation and the harmonic correction operation shown in the first embodiment are executed to obtain the third harmonic amplitude and stored in the storage unit 2. To do. In actual use, the A-phase digital signal and the B-phase digital signal are corrected using the third-order harmonic amplitude stored in the storage unit 2.

  Thus, in this embodiment, the harmonic amplitude calculation operation and the harmonic correction operation shown in the first embodiment are executed in advance to obtain the third harmonic amplitude and stored in the storage unit. Thereafter, by correcting the A-phase digital signal and the B-phase digital signal using the stored third harmonic amplitude, a highly accurate position signal can be obtained immediately after the power is turned on.

FIG. 4 is a block diagram showing the configuration of the encoder signal processing apparatus in the third embodiment of the present invention.
In the figure, 4 'is a harmonic amplitude calculator for calculating third and fifth harmonic amplitudes to be superimposed on the sensor signal from the two-phase digital data and position data, and 5' is based on the third and fifth harmonic amplitude information. And a harmonic correction unit for correcting the two-phase digital data.
This embodiment is different from the first embodiment in that the calculation unit calculates the third-order and fifth-order harmonic amplitude and the two-phase digital data based on the third-order and fifth-order harmonic amplitude information. A harmonic correction unit for correction is provided, and harmonic distortion is removed because the sensor signal includes not only the third harmonic but also the fifth harmonic.

Next, the harmonic amplitude calculation operation in the present embodiment will be described.
FIG. 5 is a signal waveform diagram for explaining the calculation principle of the harmonic amplitude in the present embodiment, and shows the relationship when the sensor signal includes the third harmonic and the fifth harmonic. (A) shows the relationship in the A phase signal, and (B) shows the relationship in the B phase signal.

When the 3rd and 5th harmonics are superimposed on the sensor signals Sa (Cos signal) and Sb (Sin signal), the fundamental, 3rd and 5th harmonics have the phase relationship shown in the figure. The A / D converted digital signals α and β have fundamental wave amplitudes a ₁ and b ₁ , third harmonic amplitudes a ₃ and b ₃ , and fifth harmonic amplitudes a _5. , B ₅ α = a ₁ Cosθ + a ₃ Cos3θ -a ₅ Cos5θ
β = b ₁ Sinθ -b ₃ Sin3θ -b ₅ Sin5θ
It is represented by
However, (theta) is a position.
The position data calculation unit 3 calculates position data θ _i by using an arctangent calculation (tan ⁻¹ ) for a two-phase digital signal.

The harmonic amplitude calculation unit 4 first calculates the position data θ ₁ and θ ₂ at _two positions for the A phase, and acquires the digital data α ₁ and α ₂ at these positions. The positions of the two points are positions where the amplitude of the fifth harmonic is assumed to be zero, and among these, the positions of the two points having different amplitudes from which the amplitude of the third harmonic is not zero are selected. P _{1 in} FIG. 5 is the peak value of the amplitude (absolute value) of the third harmonic of the position (2n−1) π / 10 (n = 1 to 10) where the amplitude of the fifth harmonic is assumed to be zero. P ₂ is a point satisfying the above condition in that the amplitude (absolute value) of the third harmonic becomes a peak value cos (π / 10).

digital data alpha ₁ in the calculated position data theta ₁ Toko position at the location of p _1, and the relational expression for the A-phase digital data alpha ₂ in the calculated position data theta ₂ Toko position at the location of p ₂ a ₁ Cosθ ₁ + a ₃ Cos3θ ₁ = α ₁
a ₁ Cosθ ₂ + a ₃ Cos3θ ₂ = α ₂
Is obtained.
The amplitude a ₃ of the _third harmonic of the A phase is
a ₃ = (α ₁ Cosθ ₂ -α ₂ Cosθ ₁ ) / (Cos3θ ₁ · Cosθ ₂ -Cos3θ ₂ · Cosθ ₁ )
Ask for.
In order to improve the calculation accuracy, the third harmonic amplitude is calculated using data obtained by combining two other points that satisfy the above data acquisition position condition, and the calculated third harmonic amplitudes are averaged. good.

Next, two position data θ ₃ and θ ₄ at a position where the amplitude of the third harmonic is assumed not to be 0, and digital data α ₃ and α ₄ at this position are acquired.
These relations are
a ₁ Cosθ ₃ + a ₃ Cos3θ ₃ -a ₅ Cos5θ ₃ = α ₃
a ₁ Cosθ ₄ + a ₃ Cos3θ ₄ -a ₅ Cos5θ ₄ = α ₄
It becomes. Since the amplitude a ₃ of the _third harmonic is known,
The amplitude a ₅ of the _fifth harmonic is
_{a 5 = {(α 3 -a} 3 Cos3θ 3) Cosθ 4 - (α 4 -a 3 Cos3θ 4) Cosθ 3}
_{/ (Cos5θ 4 · Cosθ 3 -} Cos5θ 3 · Cosθ 4)
Can be obtained. The calculation accuracy can be improved by performing this process on a plurality of sets of two-point position data and digital data at these positions, and averaging the fifth-order harmonic amplitudes calculated for each set.

Similarly, regarding the B phase, the position where the amplitude of the fifth harmonic is assumed to be zero, and two different positions where the amplitude of the third harmonic does not become zero, that is, FIG. 5B. Data acquisition is performed at positions p ₁ and p ₂ . Digital Data beta ₁ and the calculated position data theta ₁ Toko position at the location of p _1, a relational expression for B-phase digital data beta ₂ at the position of the position data theta ₂ Toko calculated in the position of the p ₂ b ₁ Sinθ ₁ -b ₃ Sin3θ ₁ = β ₁
b ₁ Sinθ ₂ -b ₃ Sin3θ ₂ = β ₂
Is obtained.
The amplitude b ₃ of the B phase third harmonic is
_{b 3 = (β 1 Sinθ 2} - β 2 Sinθ 1) / (Sin3θ 2 · Sinθ 1 - Sin3θ 1 · Sinθ 2)
Can be obtained. In order to improve the calculation accuracy, similarly to the case of the A phase, the third harmonic amplitude is calculated using data obtained by combining two other points that satisfy the above data acquisition position condition, and a plurality of calculated 3 The second harmonic amplitude may be averaged.

Next, two position data θ ₃ and θ ₄ at a position where the amplitude of the third harmonic is assumed not to be 0, and digital data β ₃ and β ₄ at this position are acquired.
These relations are
b ₁ Sinθ ₃ -b ₃ Sin3θ ₃ -b ₅ Sin5θ ₃ = β ₃
b ₁ Sinθ ₄ -b ₃ Sin3θ ₄ -b ₅ Sin5θ ₄ = β ₄
It becomes. Since the amplitude b ₃ of the _third harmonic is known,
The amplitude b ₅ of the _fifth harmonic is
_{b 5 = {(β 3 +} b 3 Sin3θ 3) Sinθ 4 - (β 4 + b 3 Sin3θ 4) Sinθ 3}
_{/ (Sin5θ 4 · Sinθ 3 -} Sin5θ 3 · Sinθ 4)
Can be obtained. As in the case of the A phase, if this processing is performed on two sets of position data of two sets and digital data at this position, and the fifth harmonic amplitude calculated in each set is averaged, the calculation accuracy Can be improved.

In the harmonic correction unit 5, the A-phase third-order harmonic amplitude a ₃ , the fifth-order harmonic amplitude a ₅ calculated by the harmonic-amplitude calculation unit 4, and the B-phase third-order harmonic amplitude b ₃ , the fifth-order harmonic are calculated. using a wave amplitude b _5, a third harmonic and fifth harmonic of the 2-phase digital signal is corrected by the following equation.
α = α '-a ₃ Cos3θ' + a ₅ Cos5θ '
β = β ′ + b ₃ Sin3θ ′ + b ₅ Cos5θ ′
However, α ′ and β ′ are digital signals of the sensor signals Sa and Sb before correction, and θ ′ is the previous value of the position data θ calculated by the position data calculation unit 3.
In order to improve the position calculation accuracy, the position data should be data that is a little closer to the current value than the previous value. And may be used.

As described above, in this embodiment, the third-order harmonic distortion and the fifth-order harmonic distortion superimposed on the sensor signal can be detected and these distortions can be removed, so that highly accurate position data can be calculated.
Further, by repeatedly executing the harmonic amplitude calculation operation and the harmonic correction operation of the present embodiment, it is possible to cope with changes in third-order harmonic distortion and fifth-order harmonic distortion due to environmental changes such as temperature changes.
Further, the third-order and fifth-order harmonic amplitudes are obtained in advance by the above-described arithmetic processing, stored in the nonvolatile memory, and after turning on the power, the A-phase digital signal and the B-order harmonics are stored in the third-order and fifth-order harmonic amplitudes stored in the nonvolatile memory If the phase digital signal is corrected, a highly accurate position signal can be obtained immediately after the power is turned on.

  The present invention can be applied to any type of encoder position detection error correction having periodic third-order harmonic distortion with reproducible sensor signals without being limited to magnetic, optical, rotary, and linear motion types.

The block diagram which shows the structure of the signal processing apparatus of the encoder in 1st Example of this invention. Signal waveform diagram for explaining the calculation principle of the harmonic amplitude in the first embodiment The block diagram which shows the structure of the signal processing apparatus of the encoder in 2nd Example of this invention. The block diagram which shows the structure of the signal processing apparatus of the encoder in 3rd Example of this invention. Signal waveform diagram for explaining the calculation principle of the harmonic amplitude in the third embodiment The block diagram which shows the structure of the conventional encoder signal processing apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 A / D converter 2 Memory | storage part 3 Position data calculation part 4 Harmonic amplitude calculation part 5 Harmonic correction part 6 Calculation part

Claims (10)

The A-phase and B-phase two-phase sinusoidal analog signals obtained from the sensor signal detector according to the positions of the two objects that are relatively displaced are converted into digital signals, respectively, and position data is obtained from the digital signals. In the signal processing method of the encoder that calculates and obtains the position of the object from the position data,
The A-phase third harmonic amplitude is calculated from the A-phase digital data α ₁ and α _{2 at the} two points obtained from the position data at the two arbitrary points and the A-phase digital signal. B-phase third harmonic amplitude is calculated from B-phase digital data β ₁ and β _{2 at the} two points obtained from the position data at the position and the B-phase digital signal, and the A-phase third-harmonic amplitude and B A signal processing of an encoder, wherein the phase A digital signal and the phase B digital signal are respectively corrected with a phase third harmonic amplitude, and position data is calculated from the corrected phase A digital signal and the phase B digital signal Method. The A-phase third-order harmonic amplitude a ₃ is the simultaneous equation a ₁ Cos θ ₁ + a _{3 in} the case of the A phase where a ₁ is the A-phase fundamental wave amplitude, θ ₁ and θ ₂ are position data at two arbitrary positions. Cos3θ ₁ = α ₁
a ₁ Cosθ ₂ + a ₃ Cos3θ ₂ = α ₂
Is calculated by solving
The B-phase third-order harmonic amplitude b ₃ is a simultaneous equation in the case of the B phase where b ₁ is the B-phase fundamental wave amplitude, θ ₁ and θ ₂ are position data at arbitrary two positions, and b ₁ Sinθ ₁ -b ₃ Sin3θ ₁ = β ₁
b ₁ Sinθ ₂ -b ₃ Sin3θ ₂ = β ₂
The encoder signal processing method according to claim 1, wherein the calculation is performed by solving The A-phase third-harmonic amplitude a ₃ is obtained by calculating a third-order harmonic amplitude at a plurality of arbitrary two points, and averaging the calculated third-order harmonic amplitudes. third harmonic amplitude b ₃ are claims, characterized in that in which to calculate the third harmonic amplitude for the location of the plurality of sets of two arbitrary points were averaged calculated the third harmonic amplitude 3. A signal processing method for an encoder according to 2.   A harmonic amplitude calculating operation for calculating the A phase third harmonic amplitude and the B phase third harmonic amplitude, a harmonic correcting operation for correcting the A phase digital signal and the B phase digital signal, respectively, and position data for calculating position data The encoder signal processing method according to claim 1, wherein the calculation operation is repeatedly executed sequentially.   The encoder signal processing method according to claim 1, wherein the A-phase third harmonic amplitude and the B-phase third harmonic amplitude are stored and used as initial data when the power is turned on. The A-phase and B-phase two-phase sinusoidal analog signals obtained from the sensor signal detector according to the positions of the two objects that are relatively displaced are converted into digital signals, respectively, and position data is obtained from the digital signals. In the signal processing method of the encoder that calculates and obtains the position of the object from the position data,
Position data θ ₁ , θ _{2 at two} positions where the amplitude of the fifth harmonic of the A phase is 0 and the amplitude of the third harmonic is not 0, and the A phase digital data α ₁ , α _{2 at} the positions of the two points. A phase third harmonic amplitude a ₃ is calculated from the position data θ ₃ and θ ₄ at two positions where the amplitude of the third phase harmonic of the A phase is not 0 and the A phase digital at the two positions. The A phase fifth harmonic amplitude a ₅ is calculated from the data α ₃ , α ₄ and the A phase third harmonic amplitude a _3, and the amplitude of the fifth harmonic of the B phase is 0 and the amplitude of the third harmonic is The B-phase third-order harmonic amplitude b ₃ is calculated from the position data θ ₁ , θ ₂ at the two non-zero positions and the B-phase digital data β ₁ , β _{2 at the} two point positions to obtain the third-order B-phase. harmonic amplitude are both 2-point position data theta ₃ in the position of not in _0, theta ₄ and B-phase digital in position of the two points Over data beta _3, beta ₄ and calculates the B-phase fifth harmonic amplitudes b ₅ from the B-phase third harmonic amplitude b _3, the A-phase third harmonic amplitude a ₃ and A-phase fifth harmonic amplitudes a ₅ corrects the A phase digital signal, corrects the B phase digital signal with the B phase third harmonic amplitude b ₃ and the B phase fifth harmonic amplitude b ₅ , and corrects the corrected A phase digital signal and the An encoder signal processing method, wherein position data is calculated from a B-phase digital signal. The A-phase third-order harmonic amplitude a ₃ is equal to the simultaneous equation a ₁ Cosθ ₁ + a ₃ Cos3θ ₁ = α _{1 in} the case of A phase where a ₁ is the A-phase fundamental wave amplitude.
a ₁ Cosθ ₂ + a ₃ Cos3θ ₂ = α ₂
Is calculated by solving
In the case of the A phase, the A phase fifth harmonic amplitude a ₅ is equal to the simultaneous equations a ₁ Cosθ ₃ + a ₃ Cos3θ ₃ −a ₅ Cos5θ ₅ = α ₃
a ₁ Cosθ ₄ + a ₃ Cos3θ ₄ −a ₅ Cos5θ ₄ = α ₄
Is calculated by solving
The B-phase third harmonic amplitude _{a 3,} if the phase B _{b 1} as B-phase fundamental wave amplitude equations _{b 1 Sinθ 1 -b 3 Sin3θ 1} = β 1
b ₁ Sinθ ₂ -b ₃ Sin3θ ₂ = β ₂
Is calculated by solving
The B-phase fifth harmonic amplitude _{a 5} in the case of B-phase simultaneous equations _{b 1 Sinθ 3 -b 3 Sin3θ 3} -b 5 Sin5θ 3 = β 3
b ₁ Sinθ ₄ -b ₃ Sin3θ ₄ -b ₅ Sin5θ ₄ = β ₄
The encoder signal processing method according to claim 6, wherein the calculation is performed by solving An A / D converter that converts a cyclic A-phase and B-phase two-phase sinusoidal analog signal obtained from the sensor signal detector according to the positions of two relatively displaced objects into digital signals, respectively, In a signal processing apparatus of an encoder that includes a calculation unit that calculates position data from a digital signal and obtains the position of the object from the position data.
The calculation unit calculates the A-phase harmonic amplitude from the A-phase digital data α ₁ and α _{2 at the} two points obtained from the position data at the two arbitrary points and the A-phase digital signal. A harmonic amplitude calculating section for calculating a B phase harmonic amplitude from B phase digital data β ₁ and β _{2 at the} two points obtained from the position data at the two points and the B phase digital signal; A harmonic correction unit that corrects the A-phase digital signal and the B-phase digital signal with the harmonic amplitude and the B-phase harmonic amplitude, respectively, and a position where position data is calculated from the corrected A-phase digital signal and the B-phase digital signal An encoder signal processing apparatus comprising a data calculation unit. In the case of the A phase, the harmonic amplitude calculation unit a ₁ Cos θ ₁ + a ₃ Cos 3θ ₁ = α, where a ₁ is the A-phase fundamental wave amplitude, θ ₁ and θ ₂ are position data at two arbitrary positions. ₁
a ₁ Cosθ ₂ + a ₃ Cos3θ ₂ = α ₂
By solving
Calculating the A-phase third harmonic amplitude _{a 3,}
In the case of the B phase where b ₁ is the B phase fundamental wave amplitude and θ ₁ and θ ₂ are position data at arbitrary two positions, simultaneous equations b ₁ Cosθ ₁ + b ₃ Cos3θ ₁ = β ₁
b ₁ Cosθ ₂ + b ₃ Cos3θ ₂ = β ₂
The encoder processing apparatus according to claim 8, wherein the B-phase third harmonic amplitude b ₃ is calculated by solving The harmonic amplitude calculation unit calculates simultaneous equations a ₁ Cosθ ₁ + a ₃ Cos3θ ₁ = α _{1 in} the case of the A phase where a ₁ is the A phase fundamental wave amplitude.
a ₁ Cosθ ₂ + a ₃ Cos3θ ₂ = α ₂
By solving
Calculating the A-phase third harmonic amplitude _{a 3,}
In the case of phase A, simultaneous equations a ₁ Cosθ ₃ + a ₃ Cos3θ ₃ −a ₅ Cos5θ ₅ = α ₃
a ₁ Cosθ ₄ + a ₃ Cos3θ ₄ −a ₅ Cos5θ ₄ = α ₄
By solving
Calculating the A-phase fifth harmonic amplitude _{a 5,}
For Phase B b ₁ as B-phase fundamental wave amplitude equations _{b 1 Sinθ 1 -b 3 Sin3θ 1} = β 1
b ₁ Sinθ ₂ -b ₃ Sin3θ ₂ = β ₂
By solving
B phase 3rd harmonic amplitude b ₃ is calculated,
For B-phase simultaneous equations _{b 1 Sinθ 3 -b 3 Sin3θ 3} -b 5 Sin5θ 3 = β 3
b ₁ Sinθ ₄ -b ₃ Sin3θ ₄ -b ₅ Sin5θ ₄ = β ₄
The encoder processing apparatus according to claim 8, wherein the B-phase fifth harmonic amplitude b ₅ is calculated by solving

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