Self-adaptive compensation method for quadrature error of magnetic encoder

Abstract

The invention belongs to the technical field of motor control, and discloses a magnetic encoder quadrature error adaptive compensation method, which comprises the following steps of: judging whether a correction coefficient is empty or not, and if so, executing a correction coefficient calibration process; otherwise, entering a single sampling point correction coefficient verification process. According to the invention, a hardware feedback circuit does not need to be designed, digital processing can be directly carried out on sine and cosine signals collected by the magnetic encoder, quadrature error adaptive compensation under the condition of unknown signal frequency is realized, the detection precision and reliability of the magnetic encoder can be improved, the production test efficiency is effectively improved, and the time cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of motor control, and in particular relates to a magnetic encoder quadrature error adaptive compensation method, 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 the influence of manufacturing process, installation accuracy and environmental factors, magnetic encoders often have orthogonal errors, that is, there is a certain deviation between the signals (sine and cosine) in two orthogonal directions, resulting in inaccurate measurement results.

[0003] Commonly used magnetic encoder sine and cosine signal compensation methods include: (1) using the known frequency of the generated single-frequency signal as a reference, and then solving the amplitude and phase imbalance factors of the sine and cosine signals; (2) ellipse fitting with higher complexity. Of the two compensation methods, 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, phase shifting, etc. require the design of hardware circuits to achieve adaptive compensation of sine and cosine signals, but this is not friendly to 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 the time cost.

[0005] To achieve the above object, the technical solution adopted by the present invention is: A magnetic encoder quadrature error adaptive compensation method is applied to a production test stage, and 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 cosine signal , the DC component of the sinusoidal signal The DC component of the 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 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, and 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 and cosine signal ; The sinusoidal signal of a single sampling point is corrected by using the first correction matrix M and the second correction matrix P. and cosine signal Performing orthogonal compensation, and performing normalization processing using a normalization matrix F after the 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 re-perform the single sampling point correction coefficient verification process until all sampling points are verified; otherwise, execute the correction coefficient calibration process.

[0006] Several optional methods are also provided below, but they are not intended to be additional limitations on the above-mentioned overall solution, but are merely further supplements or preferences. Under the premise that there are no technical or logical contradictions, each optional method can be combined with the above-mentioned overall solution separately, and multiple optional methods can also be combined.

[0007] Preferably, the N sinusoidal signals and N cosine signals Solve for the DC component of the sinusoidal signal separately The DC component of the cosine signal ,include: In the formula, Indicates sampling points, Indicates The sampling voltage value corresponding to the sinusoidal signal of the sampling point is Indicates The sampling voltage value corresponding to the cosine signal of the sampling point.

[0008] As a preferred method, the method of establishing 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 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: In the formula, 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: In the formula, is the amplitude mismatch factor, is the phase mismatch factor.

[0009] Preferably, the amplitude mismatch factor and phase mismatch factor The calculation process is as follows: Calibrate based on the statistical characteristics of the signal itself, let: Then, calculate the amplitude mismatch factor and phase mismatch factor for: In the formula, Express expectations.

[0010] Preferably, the multi-sampling point correction coefficient verification process includes: The sinusoidal signal of N sampling points is corrected by using the first correction matrix M and the second correction matrix P. and cosine signal Perform orthogonal compensation respectively, and perform normalization processing using a normalization matrix F after orthogonal compensation; Calculate the errors between the N normalized sine signals and the normalized cosine signals and the unit circle to obtain an average error value. If the average error value is less than or equal to the error threshold, the verification passes; otherwise, the verification fails.

[0011] Preferably, the average error value calculation formula is as follows: In the formula, is the average error value, Indicates sampling points, For the The normalized sinusoidal signal of sampling points, For the The normalized cosine signal of sampling points.

[0012] Preferably, the sinusoidal signal of a single sampling point is corrected by using the first correction matrix M and the second correction matrix P. and cosine signal Perform quadrature compensation, including: In the formula, represents the sinusoidal signal after orthogonal compensation, Represents the cosine signal after orthogonal compensation.

[0013] Preferably, the calculation formula of the single point error value is as follows: In the formula, 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.

[0014] Preferably, the number of sampling points N in the calibration process of the correction coefficient covers n sine and cosine signal cycles, and .

[0015] The invention provides a method for adaptively compensating the orthogonal errors of a magnetic encoder. The method can directly perform digital processing on the sine and cosine signals collected by the magnetic encoder without designing a hardware feedback circuit, thereby realizing adaptive compensation of the orthogonal errors in the case of unknown signal frequencies. The method can improve the detection accuracy and reliability of the magnetic encoder, effectively improve the production test efficiency, and reduce time costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a flow chart of a method for adaptively compensating quadrature errors of a magnetic encoder according to the present invention; Figure 2 The AD of the present invention collects the original sine and cosine signal waveform diagram; Figure 3 A schematic diagram showing the comparison of the Lissajous figure before and after the orthogonal compensation of the present invention; Figure 4 It is a schematic diagram comparing the Lissajous figure and the unit circle after the orthogonal signal is normalized in the present invention. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] 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.

[0019] 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 sine and cosine signals obtained by AD sampling through an error threshold to eliminate encoder measurement errors caused by non-orthogonality.

[0020] The magnetic encoder quadrature error adaptive compensation method provided in this embodiment is mainly used in the production test stage, and is used to set the correction coefficient of the correction device so that the correction device can perform real-time correction based on the correction coefficient when the user uses it. It should be noted that the method of the present invention can also be applied in the user use stage, for example, a correction button is provided on the correction device, and the execution of the method of the present invention is triggered by the correction button, which can be set according to actual needs. The trigger can be understood as running the method of the present invention according to a specified signal (such as a correction instruction).

[0021] like Figure 1 As shown, the magnetic encoder quadrature error adaptive compensation method of this embodiment includes: 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.

[0022] Step S2, the calibration process of the correction coefficient is as follows: 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 according to the highest operating frequency of the system. For example, in this embodiment, the sampling length N is 3000, covering 15 sine and cosine signal cycles.

[0023] 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. and cosine signal The general model of is expressed as:

[0024] In the formula, , Represent the sinusoidal signals in the conventional model and cosine signal The amplitude, , Represent the sinusoidal signals in the conventional model and cosine signal The phase of , Represent the sinusoidal signals in the conventional model and cosine signal The DC component of .

[0025] Based on the conventional model, the sinusoidal signal is transformed into and cosine signal The conventional model of is rewritten as the error model: In the formula, 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.

[0026] 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 cosine signal , the DC component of the sinusoidal signal The DC component of the cosine signal Save to the first correction matrix M.

[0027] In this embodiment, the DC component is obtained by solving the signal mean value. and , and store it as the mean coefficient in the correction matrix Among them is the signal sampling length of sine and cosine, , They are the output values ​​of the encoder corresponding to each sampling point: In the formula, Indicates sampling points, Indicates The sampling voltage value corresponding to the sinusoidal signal of the sampling point is Indicates The sampling voltage value corresponding to the cosine signal of the sampling point.

[0028] Step S2.3: 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 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.

[0029] The sinusoidal signal and cosine signal Subtract the DC component of the sinusoidal signal The DC component of the cosine signal , we can get the sinusoidal signal after removing the DC component And the cosine signal after removing the DC component : Therefore, the normalized matrix F is as follows: In the formula, Represents N sinusoidal signals after removing the DC 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 .

[0030] Step S2.4: Establish 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 taken, and the conversion coefficients in the conversion model are saved in the second correction matrix P.

[0031] 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: In the formula, is the ideal amplitude of the ideal quadrature signal, is the angle value of the ideal orthogonal signal, , , and is the conversion factor.

[0032] 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: Therefore, the second correction matrix P is obtained as: In the formula, is the amplitude mismatch factor, is the phase mismatch factor.

[0033] Calibrate based on the statistical characteristics of the signal itself, let: Then, calculate the amplitude mismatch factor and phase mismatch factor for: In the formula, Represents expectation. The correction coefficient matrix can be solved according to the amplitude error and phase error values. , and the correction coefficient matrix , , the normalized matrix Write to non-volatile memory (such as Flash) to use as the correction coefficient of the system.

[0034] Step S2.5, use the first correction matrix M, the normalization matrix F and the second correction matrix P as correction coefficients, and perform a 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.

[0035] The multi-sampling point correction coefficient verification process includes: 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. and cosine signal Orthogonal compensation is performed respectively, and after the orthogonal compensation, normalization processing is performed using a normalization matrix F.

[0036] 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: , 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 non-orthogonal errors in amplitude and phase, 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. , It is expressed as:

[0037] Then the two signals are normalized by the matrix F , Normalized to the range of 1 to obtain a normalized sinusoidal signal , normalized cosine signal The normalization operation in this embodiment is a conventional normalization operation, and the maximum and minimum values ​​of the normalization matrix F are calculated during the normalization operation.

[0038] Step S2.5.2, calculate the errors between the N normalized sine signals and normalized cosine signals and the unit circle, and obtain an average error value.

[0039] For N sampling points, each sampling point performs the orthogonal compensation and normalization processing operations in step S2.5.1. The normalized sinusoidal signal obtained from the sampling points is recorded as , for the The normalized cosine signal obtained from the sampling points is recorded as For a comparison of the normalized sine and cosine signals and the Lissajous figure of the unit circle, see Figure 4 Then, the compensation effect is evaluated by using the orthogonal signal Lissajous figure as the property of the standard circle. Represents the mean error between the radius and 1. The calculated average error value is:

[0040] Step S2.5.3: If the average error value is less than or equal to the error threshold, the verification is passed; otherwise, the verification fails. The error threshold X refers to the error between the normalized compensated signal and the unit circle. It is generally set between 0.01 and 0.025 (for example, it can be set to 0.02). The specific situation can be determined according to the system status and accuracy indicators.

[0041] Step S3, single sampling point correction coefficient verification process is as follows: Step S3.1: Obtain the sinusoidal signal obtained by sampling the magnetic encoder at a single sampling point and cosine signal .

[0042] Step S3.2: Use the first correction matrix M and the second correction matrix P to correct the sinusoidal signal of a single sampling point. and cosine signal Orthogonal compensation is performed, and after the orthogonal compensation, normalization processing is performed using the normalization matrix F. The orthogonal compensation and normalization processing of this step can be referred to the content recorded in step S2.5.1, and will not be described in detail here.

[0043] 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.

[0044] The calculation formula of the single point error value is as follows: In the formula, 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. After obtaining the final calibration coefficient in the production test phase, the user can choose to use only the calibration matrix , , orthogonal compensation is performed on the directly acquired sine and cosine signals. You can also choose to first use the correction matrix , , perform orthogonal compensation on the directly acquired sine and cosine signals, and after orthogonal compensation, use the normalized matrix , and obtain the normalized sine and cosine signals.

[0045] By comparison When the error threshold condition is met, the single sampling point real-time compensation of the magnetic encoder quadrature 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 achieve the adaptive compensation of the orthogonal error of the magnetic encoder. The single point error value It can also be determined by the roundness, and the error threshold X can be appropriately adjusted according to 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.

[0046] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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.

[0047] The above-mentioned embodiments only express several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached 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 cosine signal , the DC component of the sinusoidal signal The DC component of the 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 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, and 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 and cosine signal ; The sinusoidal signal of a single sampling point is corrected by using the first correction matrix M and the second correction matrix P. and cosine signal Performing orthogonal compensation, and performing normalization processing using a normalization matrix F after the 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 re-perform 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 cosine signal ,include: In the formula, Indicates sampling points, Indicates The sampling voltage value corresponding to the sinusoidal signal of the sampling point is Indicates 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 is established and the sine signal after the DC component is removed 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, 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: In the formula, 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: In the formula, is the amplitude mismatch factor, is the phase mismatch factor.

4. The magnetic encoder quadrature error adaptive compensation method according to claim 3 is characterized in that: The amplitude mismatch factor and phase mismatch factor The calculation process is as follows: Calibrate based on the statistical characteristics of the signal itself, let: Then, calculate the amplitude mismatch factor and phase mismatch factor for: In the formula, 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 using the first correction matrix M and the second correction matrix P. and cosine signal Perform orthogonal compensation respectively, and perform normalization processing using a normalization matrix F after orthogonal compensation; Calculate the errors between the N normalized sine signals and the normalized cosine signals and the unit circle to obtain an 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 calculation formula is as follows: In the formula, is the average error value, Indicates sampling points, For the The normalized sinusoidal signal of sampling points, For the The normalized cosine signal of 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. and cosine signal Perform quadrature compensation, including: In the formula, represents the sinusoidal signal after orthogonal compensation, Represents the cosine signal after orthogonal compensation.

8. The magnetic encoder quadrature error adaptive compensation method according to claim 1, characterized in that: The calculation formula of the single point error value is as follows: In the formula, 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 sine and cosine signal cycles, and .

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