JP4202098B2  Phase difference error detection device and interpolation error estimation device using the same  Google Patents
Phase difference error detection device and interpolation error estimation device using the same Download PDFInfo
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 JP4202098B2 JP4202098B2 JP2002338343A JP2002338343A JP4202098B2 JP 4202098 B2 JP4202098 B2 JP 4202098B2 JP 2002338343 A JP2002338343 A JP 2002338343A JP 2002338343 A JP2002338343 A JP 2002338343A JP 4202098 B2 JP4202098 B2 JP 4202098B2
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 phase difference
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Description
[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a phase difference error detection apparatus and an interpolation error estimation apparatus using the same, and more particularly to an improvement in a phase difference error detection mechanism of an encoder signal that originally has a phase difference of 90 degrees.
[0002]
[Prior art]
Conventionally, an encoder output signal processing device is used to obtain highresolution phase angle data by digitally interpolating a twophase sine wave signal of an encoder that detects, for example, position, angular velocity, angular velocity, etc. .
Since there is a processing limit on the interval of the grating formed on the encoder scale, in order to measure an interval finer than the scale grating, the spatial period of the phase change of the sinusoidal signal output from the encoder is further subdivided and interpolated. There is a need.
[0003]
For this reason, various interpolation circuits are conventionally used. For example, an interpolation circuit based on digital processing is based on digital data obtained by sampling a twophase sine wave signal that has a phase difference of 90 degrees and is output from an encoder at a predetermined frequency, at each sampling point. The phase angle data is obtained and the position information of the encoder is obtained.
[0004]
By the way, in the interpolation of the twophase sine wave signal, the signal is assumed to be a sine wave signal that does not include an error. However, in reality, there are errors such as an offset, a difference in amplitude between two phases, and an error in phase difference. Therefore, this causes an interpolation error. In order to avoid this, manual or automatic signal adjustment is performed to calibrate the interpolation error.
[0005]
[Problems to be solved by the invention]
By the way, there has conventionally been a technique for obtaining the difference between the offset and the amplitude, but there is no appropriate technique capable of automatically and autonomously detecting the phase difference error, and the interpolation based on the phase difference error is present. In order to calibrate the error, adjustment by an expert or a separate device is required.
For this reason, it is difficult for the user to easily calibrate the interpolation error due to the phase difference error, and it has been strongly desired to develop a technique capable of easily and accurately detecting the phase difference error. There was no suitable technology that could solve this.
[0006]
The present invention has been made in view of the abovedescribed problems of the prior art, and an object of the present invention is to provide a phase difference error detection device capable of easily and accurately detecting a phase difference error of a twophase sine wave signal of an encoder, and It is to provide an interpolation error estimation device used.
[0007]
[Means for Solving the Problems]
As a result of intensive studies on the detection of the phase difference error, the inventor succeeded in formulating the phase difference error. By obtaining the phase difference error using this phase difference error expression, the phase difference error of the twophase sine wave signal can be detected easily and accurately. As a result, it has been found that the interpolation error due to the phase difference error can be estimated and calibrated easily and accurately without adjustment by a skilled person or using a separate device, and the present invention has been completed.
[0008]
That is, in order to achieve the abovementioned object, claim 1 of the present invention is provided.AffectThe phase difference error detecting device originally has a twophase sine wave A output from an encoder with a phase difference of 90 degrees._{1}, B_{1}A phase difference error detection device for detecting an error of the phase difference ofTwophase sine wave A _{ 1 } , B _{ 1 } Includes substantially only a phase difference error and can be expressed by the following equation (5). _{ 1 } , B _{ 1 } Coordinate axis rotation unit, switching point detection unit, and axis length calculation to detect the position of the major axis and minor axis of the Lissajous waveform created by combining And a long / short axis ratio calculating means for obtaining a length ratio k from the length of the long axis and the length of the short axis obtained by the long / short axis detecting means..
[0009]
[Number 5]
Sine wave A1 = sin (u)
Sine wave B1 = cos (u + ε) (5)
Where u: 2πx / λ
x: position of the encoder
λ: of the sine wavewavelength
ε: Phase difference error
[0010]
Then, the major axis / minor axis of the Lissajous waveform and the ratio k of the lengths of a and b are obtained by the major / minor axis ratio calculating means to obtain the phase difference error ε..
[0011]
The long / short axis detection means rotates the XY coordinate axis on which the Lissajous waveform is created by 45 degrees so that the axis of the Lissajous waveform is parallel or orthogonal. _{ 2 } Y _{ 2 } Coordinate axis rotation part to convert to coordinate axis and X of Lissajous waveform _{ 2 } Y _{ 2 } X of four quadrant switching points divided by coordinate axes _{ 2 } Y _{ 2 } Switching point detection unit for detecting coordinate values, and X of the switching point of the Lissajous waveform obtained by the switching point detection unit _{ 2 } Y _{ 2 } The X from the coordinate value _{ 2 } Y _{ 2 } A long axis and a short axis of the Lissajous waveform on the coordinate axis, and an axis length calculation unit for obtaining the lengths of a and b.
[0012]
Say hereTwophase sine wave A_{1}, B_{1}The Lissajous waveform created by synthesizing is a perfect circle if there is no phase difference error. If there is a phase difference error, it becomes an ellipse with a major axis and a minor axis in a direction inclined 45 degrees with respect to the XY coordinate axis regardless of the magnitude, and the ratio of the major axis length to the minor axis length depends on the magnitude of the error. Things that change.
[0013]
In the present invention,The long / short axis detecting means preferably includes an absolute value equal point detecting unit and an axis length calculating unit.
[0014]
Here, the absolute value equal point detector is configured to output a twophase sine wave A on the Lissajous waveform._{1}, B_{1}Are detected from the four quadrants divided by the XY coordinate axes.
The axis length calculation unit obtains the length of the major axis and the length of the minor axis of the Lissajous waveform on the XY coordinate axis from the XY coordinate value of each point obtained by the absolute value equal point detection unit.
[0015]
In the present invention, it is preferable to include a phase difference error calculation means.
Here, the phase difference error calculating means substitutes the length ratio k obtained by the long / short axis ratio calculating means into the following equation 6 to obtain the twophase sine wave A_{1}, B_{1}Is obtained.
[0016]
[Formula 6]
Phase difference error ε = sin^{1}((1k^{2}) / (1 + k^{2})) ... (6)
[0017]
Moreover, in this invention, it is suitable to provide a program storage means and a calculating means.
Here, the program storage means calculates the Lissajous waveform to be corrected based on the following equation 7 including the ratio k of the major axis length to the minor axis length of the Lissajous waveform obtained by the major / minor axis ratio calculating means. An arithmetic program for performing phase correction of the upper coordinate value and obtaining a coordinate value on the Lissajous waveform in which the phase difference error is corrected is stored in advance.
Further, the calculation means obtains coordinate values on the Lissajous waveform in which the phase difference error is corrected based on the calculation program stored in the calculation program storage means.
[0018]
[Expression 7]
Where X and Y are coordinate values on the Lissajous waveform before correction
X ′ and Y ′ are coordinate values on the Lissajous waveform in which the phase difference error is corrected
[0019]
In the present invention, it is preferable that a program creation means for creating an arithmetic program stored in the program storage means is provided.
[0020]
In the present invention, it is preferable that the program creation means includes an input unit and a processing unit.
Here, the input unit inputs the calculation program.
The processing unit stores the arithmetic program input from the input unit in the program storage unit.
Examples of the input unit include an input device such as a keyboard and a mouse. Moreover, as a processing part, CPU etc. are mentioned as an example, for example.
[0021]
In the present invention, it is preferable that the program creation unit includes an output unit that outputs a previously created calculation program to the program storage unit.
An example of the output unit mentioned here is an external program creation device including an external computer, for example.
The creation of a program here includes the case where a new computation program is created and the case where a change is made to an existing computation program.
[0022]
In order to achieve the above object, an interpolation error estimating apparatus according to the present invention is a twophase sine wave A obtained from the phase difference error detecting apparatus according to the present invention._{1}, B_{1}The phase difference error [epsilon] is substituted into the following equation (8), and interpolation error calculation means for obtaining an interpolation error E due to the phase difference error [epsilon] is provided.
[0023]
[Equation 8]
Interpolation error E = (λ / 2π) (− εsin^{2}u) ... (8)
Where λ: the sine wavewavelength
ε: In the present inventionAffectPhase difference error obtained from phase difference error detector
u: 2πx / λ
x: position of the encoder
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic configuration of an encoder output signal processing apparatus using an interpolation error estimating apparatus according to an embodiment of the present invention.
[0025]
The output signal processing device 10 shown in FIG. 1 includes an encoder 12, an interpolation circuit 14, an interpolation error estimation device 16, and an interpolation error correction device 18.
The interpolation circuit 14 is, for example, a twophase sine wave A output from the encoder 12._{1}, B_{1}Is interpolated to obtain highresolution phase angle data C_{1}, D_{1}Is output to the interpolation error correction device 18.
[0026]
The interpolation error estimation device 16 first has a twophase sine wave A input from the encoder 12 to the interpolation circuit 14._{1}, B_{1}For example, errors in offset, amplitude ratio and phase difference are detected. Sine wave A_{1}, B_{1}Includes an offset, an amplitude ratio, and a phase difference error, and can be expressed by the following equation (9), the interpolation error estimation device 16 sets the detected offset, amplitude ratio, and phase difference error values to the following equation (10). By substituting, the interpolation error E due to the offset, amplitude ratio and phase difference errors is estimated.
[0027]
[Equation 9]
Sine wave A_{1}= As_{1}sin (2πx / λ) + Vs
Sine wave B_{1}= Ac_{1}cos (2πx / λ + ε) + Vc (9)
[0028]
[Expression 10]
Interpolation error E = (λ / 2π) {(− Vs / As_{1}) Cosu + (Vc / Ac_{1}) Sinu
+ (Ac_{1}/ As_{1}1) sinucosuεsin^{2}u} (10)
Where λ: the sine wave A_{1}, B_{1}ofwavelength
u: 2πx / λ
x: position of the encoder 12
As_{1}, Ac_{1}: Sine wave A_{1}, B_{1}Each amplitude of
Vs, Vc: Twophase sine wave A obtained by the device 16_{1}, B_{1}Each offset error of
Ac_{1}/ As_{1}: Twophase sine wave A obtained by the device 16_{1}, B_{1}Amplitude ratio error
ε: Twophase sine wave A obtained by the device 16_{1}, B_{1}Phase difference error
[0029]
The interpolation error E obtained by the interpolation error estimation device 16 is sent to the interpolation error correction device 18. In the interpolation error correction device 18, the output C of the interpolation circuit 14 is output._{1}, D_{1}Is adjusted by the interpolation error E obtained by the interpolation error estimating device 16, and the position information X of the encoder 12 from which the influence of the offset, the amplitude ratio and the phase difference error is removed is output.
By configuring the output signal processing apparatus 10 in this way, it is possible to correct the interpolation error of the encoder signal.
[0030]
By the way, in order to easily and accurately correct the interpolation error of the encoder signal, it is necessary to easily and accurately estimate the interpolation error. In order to easily and accurately estimate the interpolation error, detection of the error parameter is very important. These error parameters include offset, amplitude ratio, and phase difference errors. For this offset and amplitude ratio, detection methods have been established in the past, but phase difference errors are automatic and autonomous. However, there is no appropriate technique that can be detected, and adjustment by an expert or a separate device is required. For this reason, it is difficult for the user to easily calibrate the interpolation error.
[0031]
Therefore, what is characteristic in the present invention is that the phase difference error is formulated in order to easily and accurately detect the phase difference error of the twophase sine wave of the encoder signal without adjustment by a skilled person or using a separate device. It is that.
Therefore, in this embodiment, the interpolation error estimation device 16 includes a phase difference error detection device 20.
[0032]
First embodiment
FIG. 2 shows a phase difference error detection device used in the interpolation error estimation device 16 shown in FIG.20The schematic structure of is shown.
In the present embodiment, the twophase sine wave A_{1}, B_{1}It is assumed that the coordinate axis is rotated 45 degrees so as to be parallel or orthogonal to the axis of the substantially elliptical Lissajous waveform to obtain the phase difference error. Further, the interpolation error estimation device shown in FIG.16In this example, errors of offset, amplitude ratio, and phase difference are assumed as parameters. However, hereinafter, it is assumed that the error of the offset and amplitude ratio is adjusted by an arbitrary method._{1}, B_{1}Is substantially including only the phase difference error, and can be expressed by the following formula 11._{1}, B_{1}An example in which a Lissajous waveform is created by combining
[0033]
[Expression 11]
Sine wave A1 = sin (u)
Sine wave B1 = cos (u + ε) (11)
Where u: 2πx / λ
x: position of the encoder
λ: of the sine wavewavelength
[0034]
FIG.A phase difference error detection device 20 shown in FIG.FIG.A coordinate axis rotating part (long / short axis detecting means) 22 as shown in FIG.
The coordinate axis rotating unit 22 is connected to an encoder, and a twophase sine wave A output from the encoder._{1}, B_{1}Are added and subtracted to rotate the XY coordinate axis on which the elliptical Lissajous waveform is created by 45 degrees so that the axis of the elliptical Lissajous waveform is parallel or orthogonal._{2}Y_{2}Convert to coordinate axes, 2 phase sine wave A_{2}, B_{2}And
[0035]
The coordinate axis rotating unit 22 shown in FIG. 9A is connected to a switching point detecting unit (long / short axis detecting means) 24 as shown in FIG. For this reason, the twophase sine waves A <b> 2 and B <b> 2 from the coordinate rotation unit 22 are input to the switching point detection unit (long / short axis detection means) 24.
[0036]
The switching point detector 24 is configured to generate the X of the elliptical Lissajous waveform._{2}Y_{2}X of the switching point of each of the four quadrants (first quadrant to fourth quadrant) divided by the coordinate axes_{2}Y_{2}Detect coordinate values.
The switching point detection unit 24 includes coordinate quadrant detection elements 26, 28, 30, 32, nearzero detection elements 34, 36, sampling elements 38, 40, 42, 44, and the like.
[0037]
The coordinate quadrant detection elements 26, 28, 30, and 32 are made of, for example, a comparator and the like,_{2}, B_{2}The coordinate quadrant of is detected.
The zero vicinity detecting elements 34 and 36 are made of, for example, a window comparator or the like, and include a sine wave A_{2}, B_{2}Is in the vicinity of 0.
The sampling elements 38, 40, 42, 44 are formed of, for example, a latch, and the sine wave A when the coordinate quadrant and the vicinity of 0 are simultaneously satisfied._{2}Or B_{2}Is sampled.
[0038]
The phase difference error detection apparatus according to the present embodiment includes averaging units 46, 48, 50, 52, axis length calculation units 54, 56, long / short axis ratio calculation means 58, and phase difference error calculation means 60. .
[0039]
The averaging units 46 to 52 include, for example, a divider or a bit shift, and average the sample point values.
The axial length calculation units 54 and 56 are composed of, for example, a subtracter, and calculate the difference between the values obtained by the averaging units 46 to 52._{2}Y_{2}The major axis length a and minor axis length b of the elliptical Lissajous waveform on the coordinate axis are obtained.
[0040]
The long / short axis ratio calculating means 58 is composed of, for example, a divider, etc._{2}Y_{2}Of the Lissajous waveform on the coordinate axesMajor axis minor axis length, a and bThe ratio k is obtained.
The phase difference error calculating means 60 is composed of, for example, a productsum calculator, etc._{2}Y_{2}A twophase sine wave A is obtained by substituting the ratio k of the major axis and minor axis length of the Lissajous waveform on the coordinate axis into the following equation (12)._{1}, B_{1}Is obtained.
[0041]
[Expression 12]
Phase difference error ε = sin^{1}((1k^{2}) / (1 + k^{2})) ... (12)
[0042]
The phase difference error detection apparatus according to this embodiment is configured as described above, and the operation thereof will be described below.
First, sine wave A_{1}Sine wave B on the X axis_{1}When the Lissajous waveform is plotted on the Y axis, the Lissajous waveform becomes a perfect circle when the phase difference error ε = 0. On the other hand, when the phase difference error ε ≠ 0, an ellipse having an axis in a direction inclined by 45 degrees with respect to the XY coordinate axis is used regardless of the size. The ratio changes.
[0043]
For this purpose, first, the coordinate axis rotating unit 22 rotates the XY axes as shown in FIG. 3A by π / 4 (45 degrees) as shown in FIG._{2}Y_{2}When converted to coordinates, the major and minor axes of the ellipse are X_{2}Y_{2}Parallel or perpendicular to the axis.
That is, the XY coordinate axis as shown in FIG. 6A is rotated by π / 4 (45 degrees) from the following coordinate rotation formula, and the X as shown in FIG._{2}Y_{2}Get the coordinate axes.
A_{2}= Cos (π / 4) × A_{1}Sin (π / 4) × B_{1}= (A_{1}B_{1}) / √2
B_{2}= Cos (π / 4) × A_{1}+ Sin (π / 4) × B_{1}= (A_{1}+ B_{1}) / √2
[0044]
Next, the position and length of the major axis / minor axis are detected by the major / minor axis detection means according to Table 1 below.
First X_{2}Y_{2}Extract values near the axis.
For example, sine wave B_{2}A coordinate quadrant detection element 30 for detecting> 0;_{2} <R (A_{2}X near the zero detection element 34 for detecting ≈0)_{2}Y_{2}Switching point P between the first and second quadrants on the axis_{21}(Boundary between first quadrant and second quadrant) is detected.
This R is an arbitrary value, for example, 5% (= 0.05 × a) of the amplitude a or the amplitude b.
[0045]
Detected sine wave B_{2}In the sampling elements 38 and 40, the value of_{21}Add to (initial value = 0)Integrated value S Ask for. In addition, in order to obtain the added number N, N_{21}= N_{21}+1 and N_{21}Is incremented.
By the long / short axis detecting means, the switching point P between the first quadrant and the second quadrant._{21}In the same way, the switching point P between the second quadrant and the third quadrant_{32}, Switching point P between the third and fourth quadrants_{43}, Switching point P between the fourth quadrant and the first quadrant_{14}Is detected.
[0046]
[Table 1]
[0047]
Next, the averaging points 46 to 52 perform sampling points P._{21}~ P_{14}The sample values of are averaged.
P_{21} B_{max}= S_{21}/ N_{21}
P_{32} A_{min}= S_{32}/ N_{32}
P_{43} B_{min}= S_{43}/ N_{43}
P_{14} A_{max}= S_{14}/ N_{14}
[0048]
Next, the axial length calculation units 54 and 56Major axis minor axis, length of a and bAsk for.
a = Amax−Amin
b = Bmax−Bmin
Next, the Lissajous waveform as shown in (B) of FIG.Ratio of length of major axis to minor axis k (= b / a)
Next, the phase difference error calculating means 60 substitutes the ratio k obtained by the long / short axis ratio calculating means 58 into the above equation 12 to obtain the phase difference error ε.
[0049]
In the present embodiment, the phase difference error calculating means 60 has the above number.1The phase difference error ε can be obtained easily and accurately using 2 as it is. However, in order to easily and rapidly calculate the phase difference error ε, the abovementioned number1It is particularly preferable to use the result of Taylor expansion of 2 to the ratio k, for example, to the 11th order as shown in the following Expression 13.
As a result, the above number1Compared with the one using 2 as it is, the calculation of the phase difference error ε can be performed easily and at high speed. At this time, by increasing / decreasing the order of Taylor expansion according to the required accuracy, it is possible to trade off the calculation time and current consumption.
[0050]
[Formula 13]
[0051]
As described above, according to the phase difference error detecting apparatus according to the present embodiment, the phase difference error was first successfully formulated. Then, the sine wave A is generated by the coordinate axis rotating part._{1}, B_{1}XY coordinate axes are rotated 45 degrees so as to be parallel or orthogonal to the axis of the substantially elliptical Lissajous waveform, and the X2Y is detected by the long and short axis detecting means._{2}The ratio of the major axis length to the minor axis length of the approximate Lissajous waveform on the coordinate axis is obtained. Then, the abovementioned number for deriving the characteristic phase difference error ε in the present embodiment by the phase difference error calculating means.1Substituting into 2 to 13, the phase difference error ε is obtained.
[0052]
As a result, in this embodiment, the phase difference error ε of the twophase sine wave can be automatically detected. Moreover, in the present embodiment, the abovedescribed number for deriving the phase difference error ε characteristic in the present embodiment.1Since 2 to 13 are used, the phase difference error ε of the twophase sine wave can be accurately detected even if noise is superimposed on the signal. Also, no external position reference is required.
[0053]
In this embodiment, the sine wave A_{2}Or B_{2}It is also possible to perform only one of the averaging processes by the averaging unit, so that the sine wave A_{2}, B_{2}The process for obtaining is simplified. Thereby, the phase difference error of the twophase sine wave of the encoder signal can be detected more easily and accurately.
[0054]
Moreover, according to the interpolation error estimation apparatus according to the present embodiment, since the phase difference error detection apparatus according to the present embodiment is used, the interpolation error E can be accurately and easily obtained. Then, according to the output signal processing apparatus of the encoder according to the present embodiment, the interpolation error E obtained by the interpolation error estimation apparatus according to the present embodiment is adjusted, and the output of the interpolation circuit is adjusted by the interpolation error correction apparatus. Thus, the interpolation error of the encoder can be corrected more easily and accurately.
[0055]
Further, in the present embodiment, the interpolation error estimation device is, for example, a sine wave A input from an encoder to an interpolation circuit._{1}, B_{1}The maximum and minimum values are detected, and the DC offset V_{s}, V_{c}Can be requested.
[0056]
Further, in the present embodiment, the interpolation error estimation device is configured to output a sine wave A input from the encoder to an interpolation circuit._{1}, B_{1}The difference between the maximum value and the minimum value of_{1}, B_{1}2 times the amplitude (2 As_{1}, 2Ac_{1}). For this reason, the sine wave A_{1}, B_{1}From the difference between the maximum and minimum values of the sine wave A_{1}, B_{1}Each amplitude (As_{1}, Ac_{1}) For each amplitude (As_{1}, Ac_{1}), The twophase sine wave A_{1}, B_{1}Amplitude ratio (As_{1}, Ac_{1}).
[0057]
Second embodiment
FIG. 4 shows a schematic configuration of a phase difference error detection apparatus according to the second embodiment of the present invention. Note that portions corresponding to the phase difference error detection apparatus according to the first embodiment shown in FIG.
In this embodiment, the coordinate rotation is not performed as in the first embodiment, and the Lissajous waveform is an ellipse whose axis is inclined by 45 degrees with respect to the XY coordinate axis. Then, the points where the sine wave value is  A  ≈  B  in the first quadrant to the fourth quadrant are sampled, and the values of the XY axis components are averaged to obtain the ratio of the major axis to the minor axis.
[0058]
The long / short axis detecting means shown in the figure includes an absolute value equal point detector 170, and a twophase sine wave A on the Lissajous waveform._{1}, B_{1}Are detected from each of the four quadrants (first quadrant, second quadrant, third quadrant, and fourth quadrant) divided by the XY coordinate axes. The absolute value equal point detector 170 includes, for example, a determination element 172 and sampling elements 174, 176, 178, 180.
The absolute value equal point detector 170 is connected to an encoder, and a twophase sine wave A output from the encoder._{1}, B_{1}Is entered.
[0059]
The determination element 172 includes a sine wave A from the encoder._{1}, B_{1}The absolute values of are obtained and detected to be equal to each other.
The sampling elements 174, 176, 178, and 180 are, for example, latches and the sine wave A when the determination element 172 satisfies the condition that the absolute values are equal._{1}, B_{1}Sampling the coordinate value of.
[0060]
In the present embodiment, an averaging element 182, axial length calculation units 184 and 186, an axial length ratio calculation unit 158, and a phase difference error calculation unit 160 are provided.
The averaging element 182 includes, for example, a divider or a bit shift, and averages the values sampled by the sampling elements 174, 176, 178, 180 to obtain XY coordinate values in four quadrants.
[0061]
The axial length calculation units 184 and 186 are, for example, 4OneOf the ellipse Lissajous waveform from the XY coordinate values of the four quadrants obtained by the averaging element 182.Major axis minor axis, length of a and bAsk for.
The shaft length ratio calculating means 158 is composed of, for example, a divider, and obtains a length ratio k from the long axis length a and the short axis length b obtained by the axis length calculating units 184 and 186.
The phase difference error calculation means 160 is composed of, for example, a productsum calculation unit or the like, and substitutes the length ratio k obtained by the axis length ratio calculation means 158 into the above formulas 12 to 13 to obtain the phase difference error ε.
[0062]
The phase difference error detection apparatus according to this embodiment is configured as described above, and the operation thereof will be described below.
In the present embodiment, since the coordinate rotation is not performed, the Lissajous waveform is an ellipse inclined by 45 degrees from the XY coordinates. A point where  A  ≈  B  is sampled in the first quadrant to the fourth quadrant. That is, a point near the straight line y = x or y = −x is extracted.
[0063]
That is, sine wave A_{1}And B_{1}The absolute value of the difference is obtained from the absolute values  A  and  B 
 A  B  <R
This condition is satisfied when the Lissajous waveform is in the vicinity of a straight line y = x or y = −x as shown in FIG. The values at that time are determined based on the sign of X and Y as shown in Table 2 below, and the sample values at the sample points when the condition that the absolute values are equal in the determination element 172 are satisfied are the sampling elements 174, 176, 178, In 180, sampling and calculation are performed.
[0064]
[Table 2]
[0065]
Next, the sampling point P sampled by the sampling element by the averaging element 182._{1}~ P_{4}The sample values of are averaged.
At this time, the sample point P_{1}~ P_{4}Is on the straight line y = x or y = −x, so
X_{p1}= Y_{p1}= X_{p3}= Y_{p3}
X_{p4}= Y_{p2}= X_{p2}= Y_{p4}
Take advantage of that.
X_{p1}= S_{x1}/ N_{1}, Y_{p1}= S_{y1}/ N_{1}
X_{p2}= S_{x2}/ N_{2}, Y_{p2}= S_{y2}/ N_{2}
X_{p3}= S_{x3}/ N_{Three}, Y_{p3}= S_{y3}/ N_{Three}
X_{p4}= S_{x4}/ N_{Four}, Y_{p4}= S_{y4}/ N_{Four}
[0066]
Next, using the sample values averaged as described above by the axial length calculation units 184 and 186, an elliptical Lissajous waveform as shown in FIG.Major axis minor axis, length of a and bAsk for.
That is,aandbX_{p1}... Y_{p4}Because the angle is 45 degrees,
a= (Xp_{1}+ Yp_{1}Xp_{Three}Yp_{Three}) (√2) / 4
b= (Xp_{Four}+Y p _{ 4 }Xp_{2}Yp_{2}) (√2) / 4
Get.
[0067]
Next, the shaft length calculation units 184 and 186 obtained by the long / short axis ratio calculation means 158Major axis Minor axis lengthFrom the elliptical Lissajous waveform as shown in FIG.Major axis Minor axis lengthThe ratio k is obtained.
k= B / a
= (Xp_{Four}+Y p _{ 4 }Xp_{2}Yp_{2}) / (Xp_{1}+ Yp_{1}Xp_{Three}Yp_{Three})
Get.
[0068]
Next, the phase difference error calculating means 160 calculates the ratio k obtained as described above by the above number.1By substituting into 2 to 13, the phase difference error ε can be obtained.
Thus, in this embodimentAffectAccording to the phase difference error detection apparatus, first, the phase difference error was successfully formulated. The sampling element samples the points where the sine wave value is  A  ≈  B  in the first quadrant to the fourth quadrant, averages the values of the XY axis components by the averaging element, and calculates the long / short axis ratio calculation means. The ratio of the major axis to the minor axis is obtained.
[0069]
Then, in the present embodiment, as in the first embodiment, the abovedescribed number for deriving the characteristic phase difference error ε in the present embodiment from this ratio by the phase difference error calculating means.1Substituting into 2 to 13, the phase difference error ε is obtained.
As a result, in this embodiment, the phase difference error ε of the twophase sine wave can be automatically detected. Moreover, in the present embodiment, the abovedescribed number for deriving the phase difference error ε characteristic in the present embodiment.1Since 2 to 13 are used, the error ε of the phase difference of the twophase sine wave can be accurately detected even if noise is superimposed on the signal. Also, no external position reference is required.
[0070]
Further, the phase difference error ε obtained in each of the abovedescribed configurations can be substituted into the equation 8, and the interpolation error E due to the phase difference error ε can be obtained.
Here, Equation 10 assumes an error of offset, amplitude ratio, and phase difference as parameters._{1}, B_{1}Is substantially including only a phase difference error and can be expressed by the above equation 11, the above equation 10 can be transformed into the following equation 14.
[0071]
[Expression 14]
Interpolation error E = (λ / 2π) (− εsin^{2}u) (14)
Where λ: the sine wavewavelength
ε: phase difference error obtained from the phase difference error detection device of the present invention
u: 2πx / λ
x: position of the encoder
[0072]
In this way, by substituting the phase difference error ε obtained in each configuration into the equation 14 obtained by simplifying the equation 10, the interpolation error E due to the phase difference error ε can be easily and accurately obtained. .
[0073]
In each of the above configurations, a numerical formula is used as a formula for deriving the phase difference error ε.12, that is, ε = sin−1 ((1k^{2}) / (1 + k^{2}Although the example using)) has been described, the following mathematical formula equivalent to the formula can be used.
ε = cot^{1}(K) tan^{1}(K)
Even if this equivalent equation is used, the number1The same effect as when 2 is used can be obtained.
[0074]
Note that the interpolation error estimation apparatus according to the present embodiment can perform interpolation error calculation using parameters as a factor at high speed and without any other position reference, so that interpolation correction can be performed even after interpolation calculation. Yes, it can be applied to any interpolation error correction apparatus.
[0075]
For example, in this embodiment, correction information is generated by the interpolation error correction device based on the interpolation error obtained by the interpolation error estimating unit according to this embodiment, and this is stored in a lookup table (LUT). For example, at a predetermined time such as when the apparatus is turned on, the correction information of this LUT is accessed, the output of the interpolation circuit is corrected using the correction information, and the position of the encoder from which the interpolation error is removed. It can be applied to static correction that outputs information. Alternatively, the correction information created based on the interpolation error obtained by the interpolation error estimation means is not stored in the LUT, and the interpolation error is corrected independently during normal operation such as during operation of the interpolation circuit. It can be applied to dynamic correction. Alternatively, it can be applied to a combination of the static correction and the dynamic correction. Thus, by using the correction information based on the interpolation error obtained by the interpolation error estimating apparatus according to the present embodiment, the interpolation error can be corrected easily and accurately.
[0076]
Phase correction
In phase correction, generally, a phase difference error is obtained by calculation, and correction is performed based on the phase difference error. However, since the amount of calculation is enormous, simplification of calculation has been strongly demanded, but there has conventionally been no appropriate technique that can solve this problem.
Therefore, in the present invention, in order to simplify the calculation, a method for introducing the ratio k of the major axis to the minor axis length of the Lissajous waveform is adopted as a method for calculating the phase correction, and an instruction for performing phase correction is given. It has been programmed.
[0077]
The phase correction programming will be described below.
FIG. 6 shows the arrangement of the phase correction mechanism that has been programmed to perform phase correction based on the ratio k of the major axis to the minor axis length of the Lissajous waveform. Note that portions corresponding to those in FIG.
[0078]
In the figure, the phase correction mechanism 288 is connected to the output side of the long axis / short axis ratio calculating means 258 and is connected to the output side of the averaging element 282.
Then, the ratio k from the major axis / minor axis ratio calculation means 258 and the four quadrants from the averaging element 282 (P_{1}, P_{2}, P_{3}, P_{4}) XY coordinate values are input to the phase correction mechanism 288.
As shown in FIG. 7, the phase correction mechanism 288 is made of, for example, a computer, and includes a storage unit 290 and a CPU (arithmetic unit) 292.
The storage unit 290 includes a data memory 294 and a program memory (program storage means) 296.
[0079]
The data memory 294 has a ratio k (b / a) from the major axis / minor axis ratio calculation means input via the CPU 292 and four quadrants (P) from the averaging element to be corrected._{1}, P_{2}, P_{3}, P_{4}) XY coordinate value, that is, P_{1}(X_{1}, Y_{1}), P_{2}(X_{2}, Y_{2}), P_{3}(X_{3}, Y_{3}), P_{4}(X_{4}, Y_{4}) Is memorized.
The program memory 296 stores the coordinate values (X, X, L) on the Lissajous waveform to be corrected based on the following equation 15 including the ratio k of the major axis to the minor axis length of the Lissajous waveform obtained by the major / minor axis ratio calculating means. An arithmetic program for obtaining the coordinate value (X ′, Y ′) on the Lissajous waveform in which the phase correction of Y) is performed and the phase difference error is corrected is stored in advance.
[0080]
The CPU 292 substitutes the value of the ratio k stored in the data memory 294 in Equation 15 based on the arithmetic program stored in the program memory 296, and coordinates values (X, Y on the Lissajous waveform to be corrected) ) To obtain coordinate values (X ′, Y ′) on the Lissajous waveform in which the phase difference error is corrected.
[Expression 15]
Here, X and Y are coordinate values on the Lissajous waveform to be corrected
X ′ and Y ′ are coordinate values on the Lissajous waveform in which the phase difference error is corrected
[0081]
In the present embodiment, the calculation program stored in advance in the program memory 296 is created in advance using an external program creation device when created using an internal computer that is the phase correction mechanism 288 (internal creation method). There is a case of transferring a previouslycalculated arithmetic program to an internal computer (external creation method).
<Internal creation method>
In the present embodiment, it is also preferable that the internal computer has a function as a program creation means for creating a calculation program stored in the program memory 296.
That is, the program creation means includes, for example, a CPU (processing unit) 292 of an internal computer, an input device (input unit) 300 that includes, for example, a keyboard and a mouse, and is connected to the CPU 292 via the interface 298, and a display 302. Is provided.
From the input device 300, the user inputs a calculation program including, for example, Formula 15 and an instruction for causing the CPU 292 to perform calculation based on Formula 15.
[0082]
The CPU 292 stores the arithmetic program input from the input device 300 in the program memory 296. The arithmetic program input from the input device 300 is displayed on the display 302.
When the user inputs a calculation program from the input device 300 while looking at the display 302, the calculation program is stored in the program memory 296 by the CPU 292.
[0083]
<External creation method>
In the present embodiment, it is also preferable to include an external program creation device (output unit) 304 that includes, for example, an external computer and has a function of creating calculation parameters and outputting them.
The external program creation device 304 is connected to the CPU 292 of the internal computer via an interface 298.
Examples of the connection method between the external program creation device 304 and the internal computer include cable connection and wireless connection using a wireless communication device. A calculation program created in advance using the external program creation device 304 is transferred from the external program creation device 304 to the program memory 296 via the interface 298 and the CPU 292.
Then, the user can display the operation program and the like transferred from the external program creation device 304 and stored in the program memory 296 on the display 302.
The display 302 can also display a measurement result before phase correction, a measurement result after phase correction, and the like.
[0084]
Next, the phase correction according to the present embodiment will be described with reference to FIG. FIG. 4A shows a Lissajous waveform including noise before phase correction displayed on the display, and FIG. 4B shows a Lissajous waveform after phase correction displayed on the display.
[0085]
As shown in FIG. 8A, the Lissajous waveform (signal) having a phase error is inclined 45 degrees, and the coordinates P at which  X  =  Y _{1}(X_{1}, Y_{1}), P_{2}(X_{2}, Y_{2}), P_{3}(X_{3}, Y_{3}), P_{4}(X_{4}, Y_{4}) Is averaged over the interval R in the figure for noise removal,Major axis minor axis, length of a and bAnd the length ratio k (b / a) is obtained.
That is, when the coordinates (X, Y) on the Lissajous waveform are X = cos (u + ε), sin (u),Major axis minor axis, length of a and bThe following number1Calculate from 6.
[0086]
[Expression 16]
When X = cos (u + ε) and Y = sin (u),
a= √2 (x_{1}+ Y_{1}X_{3}Y_{3}) / 4
b= √2 (x_{4}+ Y_{2}X_{2}Y_{4}) / 4
k = b / a
[0087]
The long / short axis ratio calculating means is obtained by the axial length calculating unit.From the length of the major axis to the minor axis, a and b, the length ratio k (= b / a)Ask for.
The CPU is the following number of ratio k17, the phase correction of the coordinate values (X, Y) on the Lissajous waveform shown in FIG. As a result, as shown in FIG. 5B, a Lissajous waveform from which the phase difference error is clearly removed is obtained, and coordinate values (X ′, Y ′) on the Lissajous waveform in which the phase difference error is corrected are obtained. be able to.
[0088]
[Expression 17]
[0089]
As described above, in this embodiment, the ratio of the length of the major axis to the minor axis of the Lissajous waveform is used for the calculation of the phase correction.1Since a simple arithmetic expression as shown in FIG. 7 is used and programmed, the calculation can be simplified in order to obtain a coordinate value in which the phase error is corrected.
[0090]
That is, the phase difference error ε is the following number1However, it is not necessary in the phase correction of this embodiment, and the calculation can be omitted. As a result, in this embodiment, the phase difference error is calculated from the ratio k of the major axis to the minor axis length of the Lissajous waveform, and compared with the one that performs phase correction based on the obtained phase difference error. Since the number can be greatly reduced, the calculation required for phase correction can be greatly simplified.
[Expression 18]
[0091]
【The invention's effect】
As described above, the present inventionAffectAccording to the phase difference error detection apparatus, first, the phase difference error was successfully formulated. And the major axis and minor axis of the Lissajous waveform created by synthesizing the twophase sine wave of the encoder, A and b lengthAsk forCoordinate axis rotation unit, switching point detection unit, axis length calculation unit forLong and short axis detection means;From the lengths of the long and short axes a and b obtained by the long and short axis detection means,A long / short axis ratio calculation means for obtaining a length ratio;With,TheSince the phase difference error information is obtained based on the length ratio k obtained by the long / short axis ratio calculation means, the phase difference error information of the encoder signal, which has been extremely difficult in the past, can be easily obtained.AndIt can be detected accurately.
In the present invention, the Lissajous waveformMajor axis minor axis, a and bBased on the length ratio k, the calculation program for performing the phase correction of the coordinate value on the Lissajous waveform to be corrected and obtaining the coordinate value on the Lissajous waveform in which the phase difference error is corrected is stored in advance. The phase correction can be easily performed by providing the program storage means and the calculation means for performing the phase correction based on the calculation program.
The present inventionThen,the aboveBy substituting the length ratio into the formula for obtaining the characteristic phase difference error in the present invention and providing the phase difference error calculating means for obtaining the phase difference error, the phase difference error of the encoder signal can be simplified. In addition,AndIt can be detected accurately.
Also in the present inventionAffectAccording to the interpolation error estimation device, the present inventionAffectSince the interpolation error calculation means for obtaining the interpolation error based on the phase difference error obtained from the phase difference error detection device is provided, the interpolation error due to the phase difference error can be easily determined.AndCan be estimated accurately.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a schematic configuration of an interpolation error estimating apparatus according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram of a schematic configuration of the phase difference error detection device according to the first embodiment of the present invention;
FIG. 3 is an explanatory diagram of a long / short axis detection method characteristic in the phase difference error detection apparatus shown in FIG. 2;
FIG. 4 is an explanatory diagram of a schematic configuration of a phase difference error detection device according to a second embodiment of the present invention.
5 is an explanatory diagram of a long / short axis detection method characteristic in the phase difference error detection device shown in FIG. 4; FIG.
6 is a modification of the apparatus shown in FIG.
7 is an explanatory diagram of a characteristic phase correction mechanism in the apparatus shown in FIG. 6. FIG.
8 is an explanatory diagram of a phase correction method by the phase correction mechanism shown in FIG.
[Explanation of symbols]
12 Encoder
14 Interpolation circuit
16 Interpolation error estimation device
20 Phase difference error detector
22 Coordinate axis rotating part (long / short axis detecting means)
24 cutReplacementPoint detector (long / short axis detection means)
58,158 Long / Short Axis Ratio Calculation Means
60,160 Phase difference error calculation means
172 Judgment element (absolute value equal point detection unit, long / short axis detection means)
174, 176, 178, 180 Sampling element (absolute value equal point detector, long and short axis)
Detection means)
184, 186 Axis length calculator (long / short axis detection means)
Claims (8)
 A phase difference error detection device that detects an error of a phase difference between twophase sine waves A _{1} and B _{1} that are originally output from an encoder with a phase difference of 90 degrees,
When the twophase sine waves A _{1} and B _{1} substantially include only a phase difference error and can be expressed by the following formula 1, a Lissajous waveform generated by synthesizing the twophase sine waves A _{1} and B _{1} A long / short axis detecting means comprising a coordinate axis rotating unit, a switching point detecting unit, and an axis length calculating unit for detecting the position of the long axis and the position of the short axis and obtaining the length of the long axis and the length of the short axis When,
A long / short axis ratio calculating means for obtaining a length ratio k from the length of the long axis and the length of the short axis obtained by the long / short axis detecting means;
Obtaining the ratio k between the length of the major axis and the length of the minor axis of the Lissajous waveform to determine the phase difference error ε ;
x: position of the encoder
λ: wavelength of the sine wave
ε: Phase difference error
The coordinate axis rotation unit rotates the XY coordinate axis on which the Lissajous waveform is created by 45 degrees to convert the Lissajous waveform into X _{ 2 } Y _{ 2 } coordinate axes that are parallel or orthogonal to each other , and the switching point detection unit detects the Lissajous waveform of the Lissajous waveform. The X _{ 2 } Y _{ 2 } coordinate values of the switching points in each of the four quadrants divided by the X _{ 2 } Y _{ 2 } coordinate axes are detected, and the axis length calculation unit detects the X _{ 2 } Y _{ 2 } of the switching point of the Lissajous waveform obtained by the switching point detection unit. A phase difference error detecting device for obtaining a length of a major axis and a length of a minor axis of a Lissajous waveform on the X _{ 2 } Y _{ 2 } coordinate axis from a coordinate value .  The phase difference error detection device according to claim 1 ,
The long and short axis detection means includes an absolute value equal point detection unit for detecting a point on the Lissajous waveform where the absolute values of the twophase sine waves A _{1} and B _{1} are equal from four quadrants divided by XY coordinate axes;
An axis length calculation unit that obtains the length of the major axis and the length of the minor axis of the Lissajous waveform on the XY coordinate axis from the XY coordinate value of each point obtained by the absolute value equal point detection unit; A phase difference error detection device.  In the phase difference error detection device according to claim 1 ,
The ratio k between the length of the major axis and the length of the minor axis of the Lissajous waveform obtained by the major / minor axis ratio calculating means is substituted into the following equation 2, and the phase difference error ε of the twophase sine waves A _{1} and B _{1} is calculated. A phase difference error detecting device comprising a phase difference error calculating means to be obtained.
 In the phase difference error detection device according to any one of claims 1 to 3 ,
The phase of the coordinate value on the Lissajous waveform to be corrected is corrected based on the following equation (3) including the ratio k of the major axis to the minor axis length of the Lissajous waveform obtained by the major / minor axis ratio calculating means. Program storage means for storing in advance an arithmetic program for obtaining coordinate values on the Lissajous waveform in which the phase difference error is corrected;
A phase difference error detection apparatus comprising: a calculation unit that obtains a coordinate value on a Lissajous waveform in which the phase difference error is corrected based on a calculation program stored in the program storage unit.
X ′ and Y ′ are the coordinate values on the Lissajous waveform with the phase difference error corrected  The phase difference error detection device according to claim 4 ,
A phase difference error detection apparatus comprising a program creation means for creating an arithmetic program stored in the program storage means.  In the phase difference error detection device according to claim 5 ,
The program creation means includes an input unit for inputting the arithmetic program;
A phase difference error detection apparatus, comprising: a processing unit that stores the arithmetic program input from the input unit in the program storage unit.  In the phase difference error detection device according to claim 5 or 6 ,
The phase difference error detection apparatus, wherein the program creation unit includes an output unit that outputs the arithmetic program created in advance to the program storage unit.  The phase difference error ε of the twophase sine waves A _{1} and B _{1} obtained from the phase difference error detecting device according to any one of claims 1 to 3 is substituted into the following equation 4, and an interpolation error due to the phase difference error ε An interpolation error estimating device comprising an interpolation error calculating means for obtaining E.
ε: phase difference error obtained from the phase difference error detection device of the present invention
u: 2πx / λ
x: position of the encoder
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