JP2839341B2 - Calibration device for position signal - Google Patents

Description

The present invention relates to an apparatus that removes a distortion component from a signal approximated by sin θ and cos θ, and accurately obtains the value of θ.
In particular, the present invention relates to a signal calibration device which can measure a fine position with high accuracy by applying to an apparatus for electrically processing an analog output such as an encoder and a resolver.

[Conventional technology]

Devices that output cosine and sine signals, such as encoders and resolvers, are widely used as position measurement means used for automatic control and the like. A signal representing a position is obtained by inputting the signal to a device for counting a Luth sequence obtained by binarizing these signals or a device for performing an arc tangent operation.

[Problems to be solved by the invention]

The former method is widely used for encoders that can obtain signals of hundreds to thousands of cycles per rotation, and the latter method is generally used for resolvers that can obtain signals of one to several cycles per rotation. In recent years, when the resolution of the position measuring device has been required to be improved, an arc tangent operation process is performed on an encoder signal having a large number of cycles per rotation to measure a fine angle.

Incidentally, the measurement of the position by the arc tangent operation has a problem that an error occurs when the cosine and sine signals output from the encoder include distortion.

These devices include analog circuits such as amplifiers, and include sources of errors such as drift of zero point, fluctuation of gain, and non-linearity.

The present invention has been made to solve the above problems, and has as its object to provide a signal calibrator that digitally processes a signal containing distortion to remove the distortion.

[Means for solving the problem]

The invention according to claim (1) according to the present invention is a COS
cosine signal x including θ and sine signal y including Sin θ
A position signal calibration apparatus for removing a second harmonic, which is a distortion component included in the two signals, from the position measurement signal consisting of the consine signal x and the sine signal y, and the sum and sum of these signals. peak value detecting means for detecting the respective maximum and minimum values of the differences as follows d ₀ to _{d 7, d 0 = max (} x), d 1 = max (x + y), d 2 = max (y), d 3
= Min (x-y), d 4 = min (x), d 5 = min (x + y), d 6 = min (y), d 7
= Max (x-y), a parameter _{g x, g y, z x} , z y, b x, parameter calculating means for calculating by the following formula the values of _{b y, g x = (d} 0 + d 4) / 2 g _y = (d ₂ + d ₆ ) / 2 z _x = (d ₁ −d ₃ −d ₅ + d ₇ ) / 4 z _y = (d ₁ + d ₃ −d ₅ −d ₇ ) / 4 b _x = z _x − Using (d ₀ −d ₄ ) / 2 b _y = z _y − (d ₂ −d ₆ ) / 2 and the calculated parameter value, the following equation x = g _x {cos θ−b _x cos (2θ)} by + z _x ...... (1) that a correction means for obtaining a _{y = g y {sinθ-b} y cos (2θ)} + z y ...... (2) position signal cosθ and sin [theta is the removal of distortion solve is there.

Further, in the invention described in claim (2), the d ₀ = max
(X), d ₁ = max (x + y), d ₂ = max (y), d ₃ = min (x
−y), d ₄ = min (x), d ₅ = min (x + y), d ₆ = min
(Y), the peak value detecting means for detecting the _{d 7 = max (x-y} ) is, theta is when close to the i [pi] / 4, claims, characterized in that taking the following values as d _i (1), wherein Position signal calibration device.

Here, i is an integer from 0 to 7, and p is a positive constant smaller than 1.

d ₀ = d ₀ + p (x−d ₀ ) d ₁ = d ₁ + p (x + y−d ₁ ) d ₂ = d ₂ + p (y−d ₂ ) d ₃ = d ₃ + p (−x + y−d ₃ ) d _{4 = d 4 + p (-x} -d 4) d 5 = d 5 + p (-x-y-d 5) d 6 = d 6 + p (-y-d 6) d 7 = d 7 + p (x-y −d ₇ ).

[Action]

In the invention according to claim 1 of the present invention, the peak value detecting means uses d ₀ = max (x), d ₁ = max (x + y),
d ₂ = max (y), d ₃ = min (xy), d ₄ = min (x), d ₅ =
min (x + y), d ₆ = min (y), d ₇ = max (x−y) are detected, and the detected value (peak value) is used by the correcting means using the formula (1), The correction of the original signal of the expression 2) is performed.

Further, when the peak value detecting means for detecting the peak value used for the correction, when θ is close to iπ / 4, each peak value d ₀ to
sequentially captures d _7, the correction of the original signal is performed based on this.

〔Example〕

 First, the operation principle of the present invention will be described.

As deviation from the cosine and sine functions in the original signal,
There are mainly a zero point and an amplitude deviation and recording caused by an amplifier circuit, and a crosstalk and harmonics caused by a detection unit.

FIGS. 3A to 3C are two-dimensional plots of the original signal when various distortion components are mixed, one of which is taken on the x-axis and the other is taken on the y-axis.

FIG. 3 (a) shows the signal x when the zero point 0 moves to 0 '. As is clear from the figure, x can detect the movement amount of the zero point by the average of the maximum value and the minimum value, and can correct the amount by subtracting this from the original signal.

FIG. 3 (b) shows a case where the amplitude of the signal x has increased. For the amplitude, x is obtained by 1/2 of the difference between the maximum value and the minimum value, and the correction can be performed by dividing the original signal by the amplitude.

When the amplifier circuit has nonlinearity, the second harmonic is mainly a problem.

FIG. 3 (c) shows the signal when the second harmonic is mixed in xy
From the plot, it can be seen that there is a large distortion with respect to the perfect circle.

If the error component is only zero point and amplitude fluctuation,
By detecting the maximum and minimum values of the signal, the zero point can be determined as their average value and the amplitude can be determined as one half of the difference. When the second harmonic derived from the non-linearity lowers the maximum value, it also lowers the minimum value. In the above method, the second harmonic is erroneously recognized as a change in the zero point. By the way, since such a second harmonic becomes zero at points separated by π / 2, a zero point can be obtained by using the values of these points without being affected by the second harmonic. Further, by calculating the difference between the zero point thus obtained and the zero point obtained from the maximum value and the minimum value, the magnitude of the second harmonic can be obtained from the following equation.

_{x 1 = (x-z x} ) / g x = cosθ-b x cos2θ y 1 = (y-z x) / g y = sinθ + b y cos2θ correction of the second harmonic, the absolute value of b _x and b _y Is smaller than 1, cos2θ can be obtained by the double angle formula using the correction signal, and can be removed as in the following equation.

of _{x 2 = x 1 + b x} (x 1 2 -y 1 2) cosθ y 2 = y 1 -b y (x 1 2 -y 1 2) sinθ Example 1 Figure 1 is the position signal according to the present invention FIG. 2 shows a block diagram of a first embodiment of the calibration device, in which actual processing is performed digitally by a microprocessor.

In this figure, 1-1 and 1-2 are normalizing means, 2-1 and 2-2 are second harmonic removing means, 3 is an arctangent calculating means, 4-1 is a zero point parameter calculating means, and 4- 2 is an amplitude correction parameter calculating means, 5 is a second harmonic error correction parameter calculating means, and 10 is a peak value detecting means.

 Next, the operation will be described.

The input signals x and y are normalized at zero point and amplitude by normalizing means 1-1 and 1-2.
The second harmonic is removed by 1,2-2.

These signals are input to the arc tangent calculation means 3 and converted into the value of θ. The arc tangent operation used here is not a general function of only the ratio of sine and cosine, but obtains θ in a range from 0 to 2π in consideration of these signs. Such a function is widely known in the C language as a standard function atan2. When this processing is performed by a microprocessor, high-speed processing is possible by having an inverse trigonometric function table in a memory and indexing the table.

On the other hand, the peak value detecting means 10 detects the peak values d _{0 to} d ₇ and, based on the peak values, the zero point parameter calculating means 4-1 and 4-1.
The zero point and the parameter for amplitude correction are calculated by the amplitude correction parameter calculation means 4-2, and the second harmonic error correction parameter is calculated by the second harmonic error correction parameter calculation means 5, respectively.

[Embodiment 2] Fig. 2 is a block diagram showing a second embodiment of the present invention, in which 6-1 to 6-8 denote angle range determining means, and 7-1 to 7-1.
Reference numeral 7-8 denotes a peak value updating means, and the rest is the same as FIG.

The angle range determining means 6-1 to 6-8 determine whether or not θ is in any peak value detection range.
Is in any range, the corresponding peak value updating means 7-1 to 7-8 operates to update the peak value. From the peak values, the zero point Z _x , Z _y , the amplitude correction parameters g _x , g _y and the second harmonic error correction are calculated by the zero point parameter calculator 4-1 and the amplitude correction parameter calculator 4-2. parameter b _x for the parameter calculation unit 5 second harmonic error correction, b _y are calculated.

In the present invention, automatic correction is performed each time a peak value is detected during operation. Therefore, even if the state of distortion of the original signal changes due to a temperature change or the like, the state of the original signal is followed, and the optimum calibration is always performed. Done. The initial value of the peak value immediately after turning on the power is
A design value (the signal generation unit is adjusted to match this) may be used, or a value actually measured for each device may be written.

〔The invention's effect〕

As described above in detail, the present invention removes the second harmonic which is a distortion component included in the two signals from the position measurement signal including the cosine signal x including COSθ and the sine signal y including Sinθ. An apparatus for calibrating a position signal, wherein a maximum value and a minimum value of the cosine signal x and the sine signal y and the sum and difference of these signals are respectively represented by the following d _0.
To the peak value detection means for detecting as _{d 7, d 0 = max (} x), d 1 = max (x + y), d 2 = max (y), d 3
= Min (x-y), d 4 = min (x), d 5 = min (x + y), d 6 = min (y), d 7
= Max (x-y), a parameter _{g x, g y, z x} , z y, b x, parameter calculating means for calculating by the following formula the values of _{b y, g x = (d} 0 + d 4) / 2 g _y = (d ₂ + d ₆ ) / 2 z _x = (d ₁ −d ₃ −d ₅ + d ₇ ) / 4 z _y = (d ₁ + d ₃ −d ₅ −d ₇ ) / 4 b _x = z _x − Using (d ₀ −d ₄ ) / 2 b _y = z _y − (d ₂ −d ₆ ) / 2 and the calculated parameter value, the following equation x = g _x {cos θ−b _x cos (2θ)} + z _x ...... (1) since to obtain the _{y = g y {sinθ-b} y cos (2θ)} + z y ...... (2) position signal cosθ and sin [theta removed strain by solving, signal processing Even if the signal includes second-order distortion due to the non-linearity of the circuit, the signal can be corrected to be a correct signal, the value of θ to be obtained can be detected with high accuracy, and the fineness of the encoder signal having many cycles per rotation can be obtained. It is possible to measure various angles.

Further, according to the present invention, when detecting the peak value, θ is iπ / 4
When near, since the respective peak value to capture as d _i, can always use the latest peak value, it has the advantage that it is possible to highly accurate correction.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a block diagram showing another embodiment of the present invention, and FIGS. 3 (a) to 3 (c) show the case where various distortion components are mixed. Original signal,
FIG. 2 is a diagram in which one is x-axis and the other is y-axis and two-dimensionally plotted. In the figure, x and y are original signals, θ is an angle to be obtained, 1-1, 1-2.
Is a normalizing means, 2-1 and 2-2 are second harmonic removing means, 3
Is an arc tangent calculation means, 4-1 is a zero point parameter calculation means, 4-2 is an amplitude correction parameter calculation means, 5 is a second harmonic error correction parameter calculation means, 6-1 to 6-8.
Denotes an angle range determining means, 7-1 to 7-8 denote peak value updating means, and 10 denotes a peak value detecting means.

Claims (2)

(57) [Claims] An apparatus for calibrating a position signal for removing a second harmonic, which is a distortion component included in two signals, from a position measurement signal including a cosine signal x including COSθ and a sine signal y including Sinθ. Peak value detecting means for detecting the maximum value and the minimum value of the cosine signal x and the sine signal y and the sum and difference of these signals as d _{0 to} d ₇ , d ₀ = max (x), d _{1 = max (x + y)} , d 2 = max (y), d 3 =
min (x-y), d 4 = min (x), d 5 = min (x + y), d 6 = min (y), d 7 =
max (xy), parameter calculating means for calculating the values of the parameters g _x , g _y , z _x , z _y , b _x , and b _y by the following formula: g _x = (d ₀ + d ₄ ) / 2 g _y = (D ₂ + d ₆ ) / 2 z _x = (d ₁ −d ₃ −d ₅ + d ₇ ) / 4 z _y = (d ₁ + d ₃ −d ₅ −d ₇ ) / 4 b _x = z _x − ( Using d ₀ −d ₄ ) / 2 b _y = z _y − (d ₂ −d ₆ ) / 2 and the calculated parameter value, the following equation is used: x = g _x ｛cos θ−b _x cos (2θ)｝ + z further comprising a correction means for obtaining an _{x ...... (1) y = g} y {sinθ-b y cos (2θ)} + z y ...... (2) position signal cosθ and sin [theta is the removal of distortion solve Calibration device for position signals. 2. The method according to claim 1, wherein d ₀ = max (x), d ₁ = max (x + y), d _{2
= Max (y), d 3} = min (x-y), d 4 = min (x), d 5 = mi
n (x + y), when d ₆ = min (y), the peak value detecting means for detecting the _{d 7 = max (x-y} ), θ is close to i [pi] / 4, the incorporation of the following values as d _i Claim (1)
Calibration device for the described position signal. Here, i is an integer from 0 to 7, and p is a positive constant smaller than 1. d ₀ = d ₀ + p (x−d ₀ ) d ₁ = d ₁ + p (x + y−d ₁ ) d ₂ = d ₂ + p (y−d ₂ ) d ₃ = d ₃ + p (−x + y−d ₃ ) d _{4 = d 4 + p (-x} -d 4) d 5 = d 5 + p (-x-y-d 5) d 6 = d 6 + p (-y-d 6) d 7 = d 7 + p (x-y −d ₇ )