A magnetic encoder quadrature error adaptive compensation method

Abstract

The application belongs to the technical field of motor control, and discloses a magnetic encoder quadrature error adaptive compensation method, whether the correction coefficient is empty is judged, if empty, a correction coefficient calibration process is executed, otherwise a single sampling point correction coefficient verification process is entered. The application does not need to design a hardware feedback circuit, can directly carry out digital processing on the sine and cosine signals collected by the magnetic encoder, realizes adaptive compensation of the quadrature error in the case of unknown signal frequency, can improve the detection precision and reliability of the magnetic encoder, effectively improves the production test efficiency, and reduces the time cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of motor control, and in particular relates to a method for adaptively compensating for quadrature errors of a magnetic encoder, aiming to improve the detection accuracy and reliability of the magnetic encoder. Background Art

[0002] As an important angle detection device, magnetic encoders are widely used in industrial automation, robotics, aerospace, and other fields. However, in practical applications, due to factors such as manufacturing process, installation accuracy, and environmental factors, magnetic encoders often suffer from quadrature error. This refers to a certain deviation between the two orthogonal signals (sin and cosine), resulting in inaccurate measurement results.

[0003] Common methods for compensating the sine and cosine signals of magnetic encoders include: (1) using the known frequency of a single-frequency signal as a reference to calculate the amplitude and phase imbalance factors of the sine and cosine signals; and (2) using elliptical fitting, which is more complex. The former requires the known frequency of the sine and cosine signals, while the latter is not suitable for systems with high-speed processing requirements. In addition, feedback and phase shifting can be used to achieve adaptive compensation of the sine and cosine signals through hardware circuit design, but this is not suitable for systems with unknown center frequencies. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for adaptive compensation of the orthogonal error of a magnetic encoder. The method is mainly applicable to the production test of the encoder. It can realize adaptive compensation of the orthogonal error of the magnetic encoder when the frequency of the sine and cosine signals is unknown, thereby improving the detection accuracy and reliability of the magnetic encoder, effectively improving the production test efficiency, and reducing time costs.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A magnetic encoder quadrature error adaptive compensation method is applied in the production test stage, and the magnetic encoder quadrature error adaptive compensation method includes:

[0007] Determine whether the correction coefficient is empty. If it is empty, execute the correction coefficient calibration process; otherwise, enter the single sampling point correction coefficient verification process;

[0008] The calibration process of the correction coefficient is as follows:

[0009] Get N sinusoidal signals obtained by continuous sampling of the magnetic encoder at N sampling points and N cosine signals ;

[0010] According to N sinusoidal signals and N cosine signals Solve for the DC component of the sinusoidal signal separately a direct current component of the sine signal a direct current component of the sine signal a direct current component of the sine signal save to the first correction matrix M;

[0011] according to the sine signal a direct current component of the sine signal get N sine signals after removing direct current components , according to the cosine signal a direct current component of the cosine signal get N cosine signals after removing direct current components , respectively take the maximum and minimum values of the sine signals after removing direct current components and the cosine signals after removing direct current components save to the normalization matrix F;

[0012] establish a conversion model of the ideal orthogonal signal and the sine signals after removing direct current components and the cosine signals after removing direct current components take the conversion coefficients in the conversion model and save to the second correction matrix P;

[0013] take the first correction matrix M, the normalization matrix F and the second correction matrix P as correction coefficients, execute a multi-sampling point correction coefficient verification process based on the correction coefficients, if the verification is passed, save the correction coefficients, and enter a single-sampling point correction coefficient verification process; otherwise, clear the correction coefficients and re-execute the correction coefficient calibration process;

[0014] The single-sampling point correction coefficient verification process is as follows:

[0015] get the sine signal and the cosine signal of the magnetic encoder at a single sampling point;

[0016] compensate the sine signal and the cosine signal of the single sampling point using the first correction matrix M and the second correction matrix P, and perform normalization processing using the normalization matrix F after the orthogonal compensation;

[0017] calculate the error of the normalized sine signal and the normalized cosine signal after normalization processing and the unit circle to get a single-point error value, if the single-point error value is less than or equal to the error threshold, take the next sampling point to re-perform the single-sampling point correction coefficient verification process, until the verification of all sampling points is completed and the process is ended; otherwise, execute the correction coefficient calibration process.

[0018] Several optional methods are also provided below, but they are not intended to be additional limitations on the above-mentioned overall solution. They are merely further supplements or optimizations. Under the premise that there are no technical or logical contradictions, each optional method can be combined separately for the above-mentioned overall solution, or multiple optional methods can be combined.

[0019] As an advantage, the method according to N sinusoidal signals and N cosine signals Solve for the DC component of the sinusoidal signal separately The DC component of the sum cosine signal ,include:

[0020]

[0021] Where, Indicates the sampling points, Indicates the The sampling voltage value corresponding to the sinusoidal signal of the sampling point is Indicates the The sampling voltage value corresponding to the cosine signal of the sampling point.

[0022] As a preference, the creation of an ideal orthogonal signal and a sinusoidal signal after removing the DC component And the cosine signal after removing the DC component The conversion model is used to obtain the conversion coefficients in the conversion model and save them to the second correction matrix P, including:

[0023] Create an ideal orthogonal signal and a sinusoidal signal after removing the DC component And the cosine signal after removing the DC component The conversion model is as follows:

[0024]

[0025] Where, is the ideal amplitude of the ideal quadrature signal, is the angle value of the ideal orthogonal signal, 、 、 and is the conversion factor;

[0026] Take the sinusoidal signal after removing the DC component And the cosine signal after removing the DC component The model is as follows:

[0027]

[0028] Then we get:

[0029]

[0030]

[0031]

[0032]

[0033] Therefore, the second correction matrix P is obtained as:

[0034]

[0035] Where, is the amplitude mismatch factor, is the phase mismatch factor.

[0036] Preferably, the amplitude mismatch factor and phase mismatch factor The calculation process is as follows:

[0037] Calibration is performed based on the statistical characteristics of the signal itself, so:

[0038]

[0039] Then, calculate the amplitude mismatch factor and phase mismatch factor for:

[0040]

[0041] Where, Express expectations.

[0042] Preferably, the multi-sampling point correction coefficient verification process includes:

[0043] The sinusoidal signal of N sampling points is corrected by the first correction matrix M and the second correction matrix P. Sum and cosine signals Perform orthogonal compensation respectively, and use the normalization matrix F to perform normalization processing after orthogonal compensation;

[0044] Calculate the error between the N normalized sine and cosine signals and the unit circle to obtain the average error value. If the average error value is less than or equal to the error threshold, the verification passes; otherwise, the verification fails.

[0045] Preferably, the average error value is calculated as follows:

[0046]

[0047] Where, is the average error value, Indicates the sampling points, For the The normalized sinusoidal signal of sampling points, For the The normalized cosine signal of the sampling points.

[0048] As an advantage, the sinusoidal signal of a single sampling point is corrected by using the first correction matrix M and the second correction matrix P. Sum and cosine signals Perform quadrature compensation, including:

[0049]

[0050] Where, represents the sinusoidal signal after quadrature compensation, Represents the cosine signal after quadrature compensation.

[0051] Preferably, the calculation formula of the single point error value is as follows:

[0052]

[0053] Where, is the single point error value, is the normalized sinusoidal signal of a single sampling point, is the normalized cosine signal of a single sampling point.

[0054] Preferably, the number of sampling points N in the calibration process of the correction coefficient covers n periods of sine and cosine signals, and .

[0055] The present invention provides a method for adaptively compensating for quadrature errors of magnetic encoders. This method can directly digitize the sine and cosine signals collected by the magnetic encoder without designing a hardware feedback circuit, thereby achieving adaptive quadrature error compensation in the case of unknown signal frequencies. This method can improve the detection accuracy and reliability of the magnetic encoder, effectively increase production test efficiency, and reduce time costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 This is a flow chart of a method for adaptively compensating for quadrature errors of a magnetic encoder according to the present invention;

[0057] Figure 2 The AD of the present invention collects the original sine and cosine signal waveforms;

[0058] Figure 3 Schematic diagram showing the comparison of Lissajous diagrams before and after the orthogonal compensation of the present invention;

[0059] Figure 4Schematic diagram comparing the Lissajous figure and the unit circle after the orthogonal signal is normalized in the present invention. DETAILED DESCRIPTION

[0060] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0061] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0062] To overcome the problems of the prior art, this embodiment provides a method for adaptively compensating for quadrature errors of a magnetic encoder, which performs adaptive quadrature error compensation on the sine and cosine signals obtained by AD sampling through an error threshold to eliminate the encoder measurement error caused by non-orthogonality.

[0063] This embodiment provides a method for adaptively compensating for quadrature errors in magnetic encoders, primarily for use during the production testing phase. It is used to set the correction coefficients of a calibration device so that the device can perform real-time calibration based on the correction coefficients during user use. It should be noted that the method can also be applied during user use. For example, a calibration button can be provided on the calibration device to trigger the execution of the method. This can be configured based on actual needs. Triggering can be understood as executing the method based on a specified signal (e.g., a calibration instruction).

[0064] like Figure 1 As shown, the magnetic encoder quadrature error adaptive compensation method of this embodiment includes:

[0065] Step S1, determine whether the correction coefficient is empty, if it is empty, execute the correction coefficient calibration process of step S2; otherwise enter the single sampling point correction coefficient verification process of step S3.

[0066] Step S2, the calibration process of the correction coefficient is as follows:

[0067] Step S2.1: Obtain N sinusoidal signals obtained by continuous sampling of the magnetic encoder at N sampling points and N cosine signals The number of sampling points N needs to cover n sine and cosine signal cycles, and , which can generally be determined based on the maximum operating frequency of the system. For example, in this embodiment, the sampling length N is 3000, covering 15 sine and cosine signal cycles.

[0068] N sinusoidal signals obtained by continuous sampling and N cosine signals The waveform diagram is as follows Figure 2 As shown in the figure, it can be observed that due to the non-orthogonal errors in amplitude and phase, the orthogonal imbalance of the two signals is quite obvious. Sum and cosine signals The general model of is expressed as:

[0069]

[0070] Where, 、 Represent the sinusoidal signals in the conventional model Sum and cosine signals The amplitude, 、 Represent the sinusoidal signals in the conventional model Sum and cosine signals The phase, 、 Represent the sinusoidal signals in the conventional model Sum and cosine signals The DC component of .

[0071] Based on the conventional model, the sinusoidal signal is transformed into Sum and cosine signals The conventional model of is rewritten as the error model:

[0072]

[0073] Where, is the ideal amplitude of the ideal quadrature signal, is the angle value of the ideal orthogonal signal, is the amplitude mismatch factor (amplitude difference) in the error model, is the phase mismatch factor (phase difference) in the error model, is the DC component of the sinusoidal signal in the positive error model, is the DC component of the cosine signal in the error model.

[0074] Step S2.2: According to N sinusoidal signals and N cosine signals Solve for the DC component of the sinusoidal signal separately The DC component of the sum cosine signal , the DC component of the sinusoidal signal The direct current component of the cosine signal Save to the first correction matrix M.

[0075] The direct current component is obtained by solving the signal mean value With and store it as the mean coefficient in the correction matrix , where is the signal sampling length of the positive cosine, , are the output values of the encoder corresponding to each sampling point:

[0076]

[0077] In the formula, represents the th sampling point, represents the th sampling point of the sampling voltage value corresponding to the sine signal, represents the th sampling point of the sampling voltage value corresponding to the cosine signal.

[0078] Step S2.3, according to the sine signal and the direct current component of the sine signal N sine signals after removing the direct current component , according to the cosine signal and the direct current component of the cosine signal N cosine signals after removing the direct current component , respectively take the maximum and minimum values of the sine signal after removing the direct current component and the cosine signal after removing the direct current component , save to the normalization matrix F.

[0079] Subtract the direct current component of the sine signal and the direct current component of the cosine signal from the sine signal and the cosine signal respectively, to obtain the sine signal after removing the direct current component and the cosine signal after removing the direct current component :

[0080]

[0081] The normalization matrix F obtained is as follows:

[0082]

[0083] In the formula, represents the N sine signals after removing the direct current component The maximum value in represents N sinusoidal signals after removing the DC component The minimum value in Represents N cosine signals after removing the DC component The maximum value in Represents N cosine signals after removing the DC component The minimum value in .

[0084] Step S2.4: Create an ideal quadrature signal and a sinusoidal signal after removing the DC component And the cosine signal after removing the DC component The conversion model is obtained, and the conversion coefficients in the conversion model are saved to the second correction matrix P.

[0085] Create an ideal orthogonal signal and a sinusoidal signal after removing the DC component And the cosine signal after removing the DC component The conversion model is as follows:

[0086]

[0087] Where, is the ideal amplitude of the ideal quadrature signal, is the angle value of the ideal orthogonal signal, 、 、 and is the conversion factor.

[0088] According to the sinusoidal signal after removing the DC component And the cosine signal after removing the DC component The model gets 、 , further according to the trigonometric formula we can get:

[0089]

[0090]

[0091] Therefore, the second correction matrix P is obtained as:

[0092]

[0093] Where, is the amplitude mismatch factor, is the phase mismatch factor.

[0094] Calibration is performed based on the statistical characteristics of the signal itself, so:

[0095]

[0096] Then, calculate the amplitude mismatch factor and phase mismatch factor for:

[0097]

[0098] Where, Represents expectation. The correction coefficient matrix can be solved based on the amplitude error and phase error values. , and the correction coefficient matrix 、 , the normalized matrix Write to non-volatile memory (such as Flash) and use it as the correction coefficient of the system.

[0099] Step S2.5: Use the first correction matrix M, the normalized matrix F, and the second correction matrix P as correction coefficients, and execute the multi-sampling point correction coefficient verification process based on the correction coefficients. If the verification passes, save the correction coefficients (for example, write the correction coefficients into the Flash), and enter the single sampling point correction coefficient verification process of step S3 (equivalent to entering step S1 to re-determine whether the correction coefficient is empty); otherwise, clear the correction coefficients and re-execute the correction coefficient calibration process of step S2.

[0100] The multi-sampling point correction coefficient verification process includes:

[0101] Step S2.5.1: Use the first correction matrix M and the second correction matrix P to correct the sinusoidal signal of N sampling points. Sum and cosine signals Orthogonal compensation is performed respectively, and normalization processing is performed using the normalization matrix F after the orthogonal compensation.

[0102] The orthogonal compensation and normalization processing are performed on each of the N sampling points. This embodiment takes a single sampling point as an example for explanation:

[0103] 、 For the signal that has completed the orthogonal compensation, please refer to the Lissajous-Figure for comparison with the signal before calibration. Figure 3 As shown in the figure, the signal before calibration has amplitude and phase non-orthogonality errors, so its Lissajous figure is elliptical and deviates from the origin. The Lissajous figure of the signal after calibration is close to a standard circle, and the center of the circle is at the origin. 、 Expressed as:

[0104]

[0105] Then the two signals are normalized by the matrix F , Normalized sine signal , normalized cosine signal The normalization operation in the embodiment is a conventional normalization operation, and the normalization operation is calculated by taking the maximum value and the minimum value of the normalization matrix F.

[0106] Step S2.5.2, calculate the error of the N normalized sine signals and normalized cosine signals after normalization processing and the unit circle to obtain an average error value.

[0107] For N sampling points, each sampling point performs the orthogonal compensation and normalization processing operation in step S2.5.1, and the normalized sine signal obtained for the first sampling point is denoted as , and the normalized cosine signal obtained for the first sampling point is denoted as . The normalized sine and cosine signals are compared with the Lissajous figure of the unit circle, please refer to . Then, using the property that the Lissajous figure of the orthogonal signal is a standard circle, the compensation effect is evaluated, and the error value represents the average error of the radius and 1, and the average error value is calculated as: Figure 4

[0108]

[0109] Step S2.5.3, if the average error value is less than or equal to the error threshold value, the verification is passed; otherwise, the verification is failed. The error threshold value X refers to the error of the signal after normalization compensation and the unit circle. It is generally set to be between 0.01 and 0.025 (for example, it can be set to 0.02), and the specific case can be determined according to the system state and the accuracy index.

[0110] Step S3, the single sampling point correction coefficient verification process is as follows:

[0111] Step S3.1, obtain the sine signal and the cosine signal obtained by single sampling of the magnetic encoder at a single sampling point.

[0112] Step S3.2, orthogonal compensation is performed on the sine signal and the cosine signal of the single sampling point by using the first correction matrix M and the second correction matrix P, and normalization processing is performed after orthogonal compensation by using the normalization matrix F. The orthogonal compensation and normalization processing of this step can refer to the content recorded in step S2.5.1, which will not be described here.

[0113] ​​Step S3.3, calculate the error between the normalized sine signal and the normalized cosine signal after normalization and the unit circle to obtain the single-point error value. If the single-point error value is less than or equal to the error threshold, take the next sampling point and re-perform the single sampling point correction coefficient verification process of step S3 (equivalent to entering step S1 to re-determine whether the correction coefficient is empty), until the verification of all sampling points is completed; otherwise, execute the correction coefficient calibration process of step S2.

[0114] The calculation formula for the single point error value is as follows:

[0115]

[0116] Where, is the single point error value, is the normalized sinusoidal signal of a single sampling point, It is the normalized cosine signal of a single sampling point. After obtaining the final calibration coefficient in the production test phase, the user can choose to use it only according to the calibration matrix. 、 , perform quadrature compensation on the directly acquired sine and cosine signals, or you can choose to first use the correction matrix 、 , perform orthogonal compensation on the directly collected sine and cosine signals, and after orthogonal compensation, use the normalized matrix , and obtain the normalized sine and cosine signals.

[0117] By comparison Compared with the preset error threshold X, when the error threshold condition is met, the real-time compensation of the single sampling point of the magnetic encoder orthogonal signal is completed. When the error threshold condition is not met, the self-calibration link is entered to re-update the correction matrix. 、 , the normalized matrix , in order to realize the adaptive compensation of the magnetic encoder quadrature error. It can also be determined by the roundness, and the error threshold X can be appropriately adjusted depending on the situation. In addition, the method of the present invention can also be used for other sine and cosine functions with orthogonal errors to perform error correction.

[0118] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0119] The above-described embodiments merely illustrate several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A magnetic encoder quadrature error adaptive compensation method, applied in the production test stage, characterized in that: The magnetic encoder quadrature error adaptive compensation method comprises: Determine whether the correction coefficient is empty. If it is empty, execute the correction coefficient calibration process; otherwise, enter the single sampling point correction coefficient verification process; The calibration process of the correction coefficient is as follows: Get N sinusoidal signals obtained by continuous sampling of the magnetic encoder at N sampling points and N cosine signals ; According to N sinusoidal signals and N cosine signals Solve for the DC component of the sinusoidal signal separately The DC component of the sum cosine signal , the DC component of the sinusoidal signal The DC component of the sum cosine signal Save to the first correction matrix M; According to the sinusoidal signal and the DC component of the sinusoidal signal Get N sinusoidal signals after removing the DC component , according to the cosine signal The DC component of the sum cosine signal Get N cosine signals after removing the DC component , respectively take the sinusoidal signal after removing the DC component And the cosine signal after removing the DC component The maximum and minimum values ​​of are saved in the normalized matrix F; Create an ideal orthogonal signal and a sinusoidal signal after removing the DC component And the cosine signal after removing the DC component The conversion model is obtained, and the conversion coefficients in the conversion model are saved in the second correction matrix P; The first correction matrix M, the normalization matrix F, and the second correction matrix P are used as correction coefficients. A multi-sampling point correction coefficient verification process is performed based on the correction coefficients. If the verification passes, the correction coefficients are saved and the single-sampling point correction coefficient verification process is entered; otherwise, the correction coefficients are cleared and the correction coefficient calibration process is re-executed. The single sampling point correction coefficient verification process is as follows: Get the sinusoidal signal obtained by sampling the magnetic encoder at a single sampling point Sum and cosine signals ; The sinusoidal signal of a single sampling point is corrected using the first correction matrix M and the second correction matrix P. Sum and cosine signals Perform orthogonal compensation, and perform normalization processing using a normalization matrix F after orthogonal compensation; Calculate the error between the normalized sine signal and the normalized cosine signal after normalization and the unit circle to obtain a single-point error value. If the single-point error value is less than or equal to the error threshold, take the next sampling point and repeat the single-sampling point correction coefficient verification process until all sampling points are verified; otherwise, execute the correction coefficient calibration process.

2. The magnetic encoder quadrature error adaptive compensation method according to claim 1, characterized in that: According to the N sinusoidal signals and N cosine signals Solve for the DC component of the sinusoidal signal separately The DC component of the sum cosine signal ,include: Where, Indicates the sampling points, Indicates the The sampling voltage value corresponding to the sinusoidal signal of the sampling point is θ icos Indicates the The sampling voltage value corresponding to the cosine signal of the sampling point.

3. The magnetic encoder quadrature error adaptive compensation method according to claim 1, characterized in that: The ideal orthogonal signal and the sinusoidal signal after removing the DC component are established And the cosine signal after removing the DC component The conversion model is used to obtain the conversion coefficients in the conversion model and save them to the second correction matrix P, including: Create an ideal orthogonal signal and a sinusoidal signal after removing the DC component And the cosine signal after removing the DC component The conversion model is as follows: Where, is the ideal amplitude of the ideal quadrature signal, is the angle value of the ideal orthogonal signal, 、 、 and is the conversion factor; Take the sinusoidal signal after removing the DC component And the cosine signal after removing the DC component The model is as follows: Then we get: Therefore, the second correction matrix P is obtained as: Where, is the amplitude mismatch factor, is the phase mismatch factor.

4. The magnetic encoder quadrature error adaptive compensation method according to claim 3, characterized in that: The amplitude mismatch factor and phase mismatch factor The calculation process is as follows: Calibration is performed based on the statistical characteristics of the signal itself, so: Then, calculate the amplitude mismatch factor and phase mismatch factor for: Where, Express expectations.

5. The magnetic encoder quadrature error adaptive compensation method according to claim 1, characterized in that: The multi-sampling point correction coefficient verification process includes: The sinusoidal signal of N sampling points is corrected by the first correction matrix M and the second correction matrix P. Sum and cosine signals Perform orthogonal compensation respectively, and use the normalization matrix F to perform normalization processing after orthogonal compensation; Calculate the error between the N normalized sine and cosine signals and the unit circle to obtain the average error value. If the average error value is less than or equal to the error threshold, the verification passes; otherwise, the verification fails.

6. The magnetic encoder quadrature error adaptive compensation method according to claim 5, characterized in that: The average error value is calculated as follows: Where, is the average error value, Indicates the sampling points, For the The normalized sinusoidal signal of sampling points, For the The normalized cosine signal of the sampling points.

7. The magnetic encoder quadrature error adaptive compensation method according to claim 1, characterized in that: The sinusoidal signal of a single sampling point is corrected by using the first correction matrix M and the second correction matrix P. Sum and cosine signals Perform quadrature compensation, including: Where, represents the sinusoidal signal after quadrature compensation, Represents the cosine signal after quadrature compensation.

8. The method for adaptively compensating for quadrature error of a magnetic encoder according to claim 1, wherein: The calculation formula of the single point error value is as follows: Where, is the single point error value, is the normalized sinusoidal signal of a single sampling point, is the normalized cosine signal of a single sampling point.

9. The magnetic encoder quadrature error adaptive compensation method according to claim 1, characterized in that: The number of sampling points N in the calibration process of the correction coefficient covers n periods of sine and cosine signals, and .

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