Measurement method, device, circuit and encoder based on an eddy current encoder

Abstract

The application relates to the technical field of eddy current encoders, and discloses an eddy current encoder-based measurement method, device, circuit and encoder. The eddy current encoder-based measurement method comprises the following steps: in a starting stage of the eddy current encoder, a main frequency, an amplitude corresponding to the main frequency and an initial phase value are determined from a first quadrature signal group output by the eddy current encoder, and a second quadrature signal group is generated according to the main frequency, the amplitude corresponding to the main frequency and the initial phase value; in the case of a running stage of the eddy current encoder, the second quadrature signal group is taken as reference signals of a third quadrature signal group output by the eddy current encoder, and digital signal processing is performed to obtain a physical quantity measurement value. At least, the method is beneficial to realizing more accurate measurement by constructing reference signals with better phase error compensation effects.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of eddy current encoders, and in particular relates to an eddy current encoder-based measurement method, device, circuit and encoder. BACKGROUND

[0002] Eddy current encoders are widely used in rotary position measurement scenarios, and are particularly suitable for non-contact high-precision angle detection in harsh environments. Such encoders usually form phase-orthogonal sensing signals (sin / cos waveforms) through excitation and sensing coils, and send the signals to a real-time angle calculation chip after front-end sampling and conditioning.

[0003] In actual systems, the amplitude, frequency, phase and other parameters of the original signals output by the eddy current encoder may be non-ideal due to factors such as coil structure, noise interference, sampling drift, etc., which may affect the angle calculation accuracy. Therefore, the eddy current encoder usually has a self-calibration mechanism to construct a reference signal to compensate for the phase error caused by the above factors to improve the measurement effect.

[0004] However, the current scheme of compensating for phase error by reference signal still cannot satisfy the improvement effect of measurement. SUMMARY

[0005] The present application provides an eddy current encoder-based measurement method, device, circuit and encoder, which at least has the advantage of constructing a reference signal with better phase error compensation effect to achieve more accurate measurement.

[0006] According to some embodiments of the present application, the first aspect of the present application provides an eddy current encoder-based measurement method, comprising: in the startup phase of the eddy current encoder, determining the main frequency and the amplitude and initial phase value corresponding to the main frequency from a first set of quadrature signals output by the eddy current encoder, and generating a second set of quadrature signals according to the main frequency and the amplitude and initial phase value corresponding to the main frequency; in the running phase of the eddy current encoder, taking the second set of quadrature signals as a reference signal of a third set of quadrature signals output by the eddy current encoder, and performing digital signal processing to obtain a physical quantity measurement value.

[0007] According to some embodiments of the present application, the second aspect of the embodiments of the present application further provides a measurement device based on an eddy current encoder, comprising: a first processing module, configured to determine a main frequency and an amplitude and an initial phase value corresponding to the main frequency from a first quadrature signal group output by the eddy current encoder in a starting stage of the eddy current encoder, and generate a second quadrature signal group according to the main frequency and the amplitude and the initial phase value corresponding to the main frequency; and a second processing module, configured to take the second quadrature signal group as a reference signal of a third quadrature signal group output by the eddy current encoder in a running stage of the eddy current encoder, and perform digital signal processing to obtain a physical quantity measurement value.

[0008] According to some embodiments of the present application, the third aspect of the embodiments of the present application further provides an integrated circuit, comprising: a receiving module, an analog signal processing module and a digital signal processing module connected in sequence; wherein the receiving module is configured to obtain a signal generated on a receiving coil in an eddy current encoder and output to the analog signal processing module; the analog signal processing module is configured to sample the received signal to obtain a first quadrature signal group or a third quadrature signal group and output to the digital signal processing module, wherein the first quadrature signal group is a sampling result in a starting stage, and the third quadrature signal group is a sampling result in a running stage; and the digital signal processing module is configured to determine a main frequency and an amplitude and an initial phase value corresponding to the main frequency from the received first quadrature signal group, generate a second quadrature signal group according to the main frequency and the amplitude and the initial phase value corresponding to the main frequency, take the second quadrature signal group as a reference signal of the received third quadrature signal group, and perform digital signal processing to obtain a physical quantity measurement value.

[0009] According to some embodiments of the present application, the fourth aspect of the embodiments of the present application further provides an eddy current encoder, comprising: a carrier; an excitation coil and a receiving coil arranged on the carrier; and an integrated circuit arranged on the carrier and connected with an output end of the receiving coil, wherein the integrated circuit is the integrated circuit of the third aspect.

[0010] The technical solutions provided in the embodiments of the present application have at least the following advantages:

[0011] In the starting stage of the eddy current encoder, the main frequency and the amplitude and initial phase value corresponding to the main frequency of the encoder are determined from the first quadrature signal group output from the encoder eddy current encoder to generate the second quadrature signal group as the reference signal in the starting stage, instead of extracting the main frequency in advance and then constructing the reference signal when needed, so that the main frequency and the reference signal are obtained under the same state of the eddy current encoder, especially the reference signal is obtained in the starting stage before the starting of the running stage, which can accurately describe the state of the eddy current encoder in the running stage, thereby providing better phase error compensation effect for the running stage, and can more accurately and reliably provide a reference for digital signal processing based on the third quadrature signal group, and obtain more accurate physical quantity measurement values. BRIEF DESCRIPTION OF DRAWINGS

[0012] One or more embodiments are illustrated by way of example in the figures that form a part of this disclosure and which are shown by way of example, not limitation, in which like references indicate similar elements, and in which:

[0013] Figure 1 is a flowchart of the measurement method based on the eddy current encoder provided in an embodiment of the present application;

[0014] Figure 2 is a signal comparison diagram related to the measurement method based on the eddy current encoder provided in another embodiment of the present application;

[0015] Figure 3 is the amplitude spectrum of the signal in the first quadrature signal group related to the measurement method based on the eddy current encoder provided in another embodiment of the present application;

[0016] Figure 4 is the phase spectrum of the signal in the first quadrature signal group related to the measurement method based on the eddy current encoder provided in another embodiment of the present application;

[0017] Figure 5 is the amplitude spectrum of the signal in the second quadrature signal group related to the measurement method based on the eddy current encoder provided in another embodiment of the present application;

[0018] Figure 6 is the phase spectrum of the signal in the second quadrature signal group related to the measurement method based on the eddy current encoder provided in another embodiment of the present application;

[0019] Figure 7 is a flowchart of the main frequency determination related to the measurement method based on the eddy current encoder provided in another embodiment of the present application;

[0020] Figure 8 is a flowchart of the measurement method based on the eddy current encoder provided in another embodiment of the present application;

[0021] Figure 9 is a structural schematic diagram of a reference signal construction device of an eddy current encoder provided in another embodiment of the present application;

[0022] Figure 10 is a structural schematic diagram of an integrated circuit provided in another embodiment of the present application. DETAILED DESCRIPTION

[0023] As known from the background, the existing scheme of compensating phase error by using a reference signal still cannot satisfy the improvement effect on measurement.

[0024] It is found through analysis that the above problem is caused at least by the following reason: in order to construct a reference signal in time when needed, the existing scheme usually completes the main frequency estimation before using the eddy current encoder to measure, and then constructs the reference signal based on the estimated main frequency when using the eddy current encoder to measure, so as to reduce the overhead of main frequency estimation when using the eddy current encoder to measure, and to construct the reference signal faster, to process the digital signal, and to realize the measurement. That is, the main frequency estimation and the use of the main frequency are in different stages, and the influencing factors of the phase error of the eddy current encoder may be different between the two stages, and the influence degree of the same influencing factor on the phase error may also be different, so that the pre-estimated main frequency may not accurately reflect the current phase error, resulting in poor compensation effect, and further, the improvement effect on measurement does not reach the expectation.

[0025] Based on this, the embodiments of the present application provide a measurement method, device, circuit and encoder based on an eddy current encoder, by placing the determination of the main frequency and the generation of the second orthogonal signal group used as the reference signal in the starting stage before the running stage when the reference signal is needed, so that the time difference between the construction and the use of the reference signal is small, the influencing factors and the influence degree of the phase error during the construction and the use of the reference signal are basically consistent, so that the phase compensation effect realized by the reference signal is better, and a more accurate physical quantity measurement value is obtained.

[0026] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the embodiments of the present application will be described in detail below with reference to the drawings. However, those skilled in the art can understand that in the embodiments of the present application, many technical details are proposed in order to make the readers better understand the present application. However, the technical solutions claimed by the present application can be realized even without these technical details and various changes and modifications based on the following embodiments.

[0027] The division of the following embodiments is for the convenience of description, and should not constitute any limitation on the specific implementation modes of the present application. The various embodiments can be combined with each other and referenced to each other without contradiction.

[0028] The embodiment of the present application provides a measurement method based on an eddy current encoder, which is applied to the eddy current encoder, or a module (or circuit, chip, etc.) related to signal processing in the eddy current encoder, or a host computer of the eddy current encoder. The following will be described in combination with different embodiments.

[0029] In some embodiments, as shown in the flow of the measurement method based on the eddy current encoder, the following steps are included. Figure 1

[0030] Step 101, in the starting stage of the eddy current encoder, the main frequency and the amplitude and initial phase value corresponding to the main frequency are determined from the first quadrature signal group output by the eddy current encoder, and the second quadrature signal group is generated according to the main frequency and the amplitude and initial phase value corresponding to the main frequency.

[0031] Step 102, in the running stage of the eddy current encoder, the second quadrature signal group is taken as the reference signal of the third quadrature signal group output by the eddy current encoder, and the digital signal processing is performed to obtain the physical quantity measurement value.

[0032] In the embodiment shown in Figure 1 In the starting stage of the eddy current encoder, the main frequency and the amplitude and initial phase value corresponding to the main frequency of the encoder are determined from the first quadrature signal group output by the eddy current encoder, to generate the second quadrature signal group as the reference signal in the starting stage, instead of extracting the main frequency in advance and then constructing the reference signal when needed, so that the main frequency and the reference signal are obtained in the consistent state of the eddy current encoder, especially the reference signal is obtained in the starting stage before the running stage, which can accurately describe the state of the eddy current encoder in the running stage, thereby providing better phase error compensation effect for the running stage, and can more accurately and reliably provide reference for the digital signal processing based on the third quadrature signal group, to obtain more accurate physical quantity measurement value.

[0033] For the convenience of understanding the embodiment shown in Figure 1 The steps of the embodiment will be explained and described as follows.

[0034] ​In step 101, in a start-up phase of the eddy current encoder, a main frequency and an amplitude and an initial phase value corresponding to the main frequency are determined from a first quadrature signal group output by the eddy current encoder, and a second quadrature signal group is generated according to the main frequency and the amplitude and the initial phase value corresponding to the main frequency. The first quadrature signal group is the original signal output by the eddy current encoder. For example, in some embodiments, the first quadrature signal group is an electrical signal output by a receiving coil in the eddy current encoder after different sampling.

[0035] It should be noted that the number of signals included in the first quadrature signal group is not limited by the embodiments of the present application, which is related to the output of the receiving coil of the eddy current encoder, and can be 2, 3, 6, etc. Here, it will not be listed one by one. For ease of understanding, the following will mainly take an example of a first quadrature signal group including 2 quadrature signals for description.

[0036] It should be further noted that the determination of the main frequency and the amplitude and the initial phase value corresponding to the main frequency, and the generation of the second quadrature signal group are not limited by the embodiments of the present application.

[0037] In some embodiments, the determination of the main frequency and the amplitude and the initial phase value corresponding to the main frequency from the first quadrature signal group output by the eddy current encoder can be realized by the following manner: determining the main frequency from the first quadrature signal group; converting the first quadrature signal group to the frequency domain to obtain a complex spectrum; and determining the amplitude and the initial phase value of the spectrum component corresponding to the main frequency in the complex spectrum as the amplitude and the initial phase value corresponding to the main frequency.

[0038] In some embodiments, the generation of the second quadrature signal group according to the main frequency and the amplitude and the initial phase value corresponding to the main frequency can be realized by the following expression:

[0039] ;

[0040] ;

[0041] wherein, and is the second quadrature signal group, is the amplitude, is the main frequency, is the initial phase value.

[0042] It should be noted that the above is only an example of a first quadrature signal group and a second quadrature signal group including 2 signals. In some embodiments, the first quadrature signal group and the second quadrature signal group can also include 3 signals, 6 signals, etc. Moreover, the above is only an example of constructing quadrature signals taking the cos function and the sin function as an example. In some embodiments, other ways of constructing quadrature signals can also be used. Here, it will not be listed one by one.

[0043] In some embodiments, in order to obtain more accurate amplitude and initial phase values, the first group of quadrature signals is combined before frequency domain conversion to obtain a complex signal, i.e., complex signal , wherein, is the imaginary unit, , The first group of quadrature signals includes two quadrature signals. Further, the frequency spectrum of the complex signal is obtained; the main frequency corresponding to the complex spectrum value is obtained on the frequency spectrum; and the amplitude and the initial phase value are extracted from the spectrum component according to the following expression:

[0044] ;

[0045] ;

[0046] wherein, represents a modulo operation, represents an angle operation.

[0047] Of course, the above is only an example, and various methods for determining the amplitude and initial phase value of the signal component corresponding to the specified frequency in the signal have been provided in the related art, which are also applicable to the implementation of the present step, and will not be described one by one here.

[0048] In addition, regarding the determination of the main frequency mentioned in the above embodiments, different embodiments will be described below.

[0049] In some embodiments, the main frequency can be determined by zero-crossing detection, wherein the zero-crossing detection is an algorithm for determining the frequency by the time interval between the zero-crossing points (adjacent time domain symbol change points) of the signal in the time domain. It does not require the number of periods contained in the signal, and allows the duration of the signal to cover only a few waveform periods (for example, less than 5 periods), so that when the sampling time is short in the starting stage of the eddy current encoder, the main frequency can be accurately and reliably determined in real time and efficiently.

[0050] In some embodiments, the main frequency is determined from the first set of quadrature signals by using a zero-crossing detection method, which can be implemented by: selecting a signal from the first set of quadrature signals as a to-be-processed signal; determining an average time interval between adjacent time-domain symbol change points of the to-be-processed signal; determining a signal period of the to-be-processed signal according to the average time interval, and determining a frequency corresponding to the signal period as the main frequency. Thus, when multiple time-domain symbol change points (i.e., multiple sets of zero-crossing points) are involved, the time interval between the zero-crossing points is determined by taking an average value, and then the main frequency is determined, which is more accurate and reliable, can reduce the interference degree of burst factors, extreme values, and the like, and obtain a more accurate main frequency.

[0051] For example, in some embodiments, the first set of quadrature signals includes signals and signals .

[0052] 1. Selecting or as the to-be-processed signal .

[0053] 2. Calculating the symbol change points of the to-be-processed signal , i.e., finding points that satisfy , where represents a sign operation. Thus, a zero time sequence is obtained, where is the total number of data contained in the zero time sequence .

[0054] 3. Calculating the average time interval between adjacent time-domain symbol change points in the zero time sequence , which can be implemented by the following expression:

[0055] .

[0056] 4. Calculating the main frequency , which can be implemented by the following expression:

[0057] .

[0058] It should be noted that the above example is only an example of taking an arithmetic average, and in some embodiments, other average methods can also be used, which will not be listed one by one here. In addition, the above example is only an example of taking the average time interval between any two adjacent time-domain symbol change points, and in some embodiments, the average time interval between two adjacent time-domain symbol change points that satisfy and the like can also be taken, which will not be listed one by one here.

[0059] Of course, the above is only an example of the zero-crossing detection method, and in some embodiments, the median of the time interval between adjacent time domain symbol change points can also be used to determine the fundamental frequency, and the like, which will not be listed one by one here.

[0060] In some embodiments, the determination of the fundamental frequency can be realized by a frequency domain analysis method, which is a method of converting a signal from a time domain to a frequency domain, and then analyzing the frequency components of the signal in the frequency domain. It is more accurate and efficient on the basis of the number of cycles contained in the signal, so the fundamental frequency will be accurate and reliable, real-time and efficient.

[0061] In some embodiments, the frequency domain analysis method is used to determine the fundamental frequency from the first orthogonal signal group, which can be realized by the following way: combining the first orthogonal signal group into a complex signal; according to the frequency domain analysis method, determining the frequency corresponding to the maximum amplitude from the complex signal as the fundamental frequency. At this time, by combining the first orthogonal signal group and then processing, the analysis can combine more comprehensive content, so that the fundamental frequency is more accurate and reliable.

[0062] For ease of understanding, the following will take an example of the first orthogonal signal group including two signals to provide an explanation, but this does not mean that the first orthogonal signal group can only include two signals.

[0063] Taking the first orthogonal signal group including signal and signal as an example, in some embodiments, there are:

[0064] 1. Merge the first orthogonal signal group to obtain a complex signal , which can be realized by the following expression:

[0065] , where is the imaginary unit.

[0066] 2. Discrete Fourier Transform (DFT) is performed on the complex signal to obtain a frequency spectrum point sequence , that is:

[0067] , where N is the number of sampling points contained in the signal.

[0068] 3. According to the frequency spectrum point sequence , the fundamental frequency is calculated, which can be realized by the following expression:

[0069] ;

[0070] , where dt is the sampling time interval, is at the maximum value .

[0071] It should be noted that the above is only a frequency domain analysis method provided by taking a complex signal as an example, and in some embodiments, a frequency domain analysis can also be performed on each signal in the first orthogonal signal group, and the like, which will not be listed one by one here.

[0072] On the basis of the above embodiments, on the basis of frequency domain analysis, a periodic truncation and a second frequency domain analysis (i.e., a method of determining the main frequency by using the frequency domain analysis method + periodic truncation + the second frequency domain analysis method) can be further combined, so that the periodic truncation makes the signal content contained in the first orthogonal signal group include an integer number of periods, so that the main frequency is not affected by the frequency spectrum leakage problem that occurs when the first orthogonal signal group contains a non-integer period, thereby further improving the accuracy of the main frequency and further optimizing the compensation effect of the reference signal constructed based on the main frequency. Still taking the case of merging the first orthogonal signal group into a complex signal as an example, in some embodiments, the frequency domain analysis method and the periodic stage are used to determine the main frequency from the first orthogonal signal group, which can be implemented in the following manner: the first orthogonal signal group is merged into a complex signal; according to the frequency domain analysis method, the frequency corresponding to the maximum amplitude in the complex signal is determined as an initial main frequency; according to the signal period corresponding to the initial main frequency, the complex signal is periodically truncated to obtain a truncated signal; and according to the frequency domain analysis method, the frequency corresponding to the maximum amplitude in the truncated signal is determined as the main frequency.

[0073] It should be noted that the number of periods of the truncated signal is not limited in the embodiments of the present application, and it can be set according to requirements. In some embodiments, according to the signal period corresponding to the initial main frequency, the complex signal is periodically truncated to obtain a truncated signal, which can be implemented in the following manner: according to the signal period corresponding to the initial main frequency, a truncation position is determined; the signal part of the complex signal in the interval [0, ] is retained to obtain a truncated signal. Wherein, the truncation position is obtained by the following expression:

[0074] ;

[0075] Wherein, is the truncated signal, is the signal period corresponding to the initial main frequency, which satisfies: , is the main frequency, is the floor operation, is the signal length of the complex signal.

[0076] That is, more complete signal fragments in a period are preserved as much as possible to form a closed period window, so that the signal can be analyzed based on more comprehensive information, and the main frequency obtained will be more accurate.

[0077] Based on the above embodiment, simulation experiments are performed on the reference signal reconstruction in the starting state and the running state, and results as shown in Figures 2 to 6 are obtained.

[0078] In the running state, a waveform comparison diagram of a first orthogonal signal group and a second orthogonal signal group (i.e., a reference signal) as shown in Figure 2 is obtained, where the horizontal axis represents time, the vertical axis represents amplitude, the blue solid line is the waveform of the signal (which will be obtained after sampling ) in the first orthogonal signal group of the above embodiment, the yellow solid line is the waveform of the signal (which will be obtained after sampling ) in the first orthogonal signal group of the above embodiment, the blue dashed line is the waveform of in the second orthogonal signal group, and the yellow dashed line is the waveform of in the second orthogonal signal group.

[0079] As can be seen from Figure 2 , the second orthogonal signal group is corrected in the amplitude dimension relative to the original waveform.

[0080] In the starting state, the amplitude spectrum and the phase spectrum in the first frequency spectrum analysis are as shown in Figure 3 and Figure 4 respectively, and the amplitude spectrum and the phase spectrum in the second frequency spectrum analysis are as shown in Figure 5 and Figure 6 respectively. Wherein, Figures 3 to 6 the horizontal axis of Figure 3 and Figure 5 represents the frequency of the corresponding signal, Figure 4 and Figure 6 the vertical axis represents the amplitude of the corresponding signal, and the vertical axis represents the phase of the corresponding signal.

[0081] Figures 3 to 6 As can be seen from , the main frequency concentration degree in the amplitude spectrum of the second frequency spectrum analysis is improved compared with the main frequency concentration degree in the amplitude spectrum of the first frequency spectrum analysis. It means that after the second clipping, the main frequency estimation accuracy is improved.

[0082] Therefore, the measurement method based on the eddy current encoder provided in the embodiments of the present application can have the following effects:

[0083] 1. It can be applied to high-precision inductive sensor systems and can be widely used in I / Q output type sensors such as eddy current encoders and rotary transformers. Combined with the algorithm for frequency estimation and reference waveform reconstruction, the measurement accuracy of physical quantities such as angle and displacement can be effectively improved, and system self-calibration can be realized.

[0084] 2. The algorithm structure is clear and adaptable. The core process includes DFT transformation, period truncation, window function weighting and spectral line interpolation, with small operation amount and closed structure, which is suitable for deployment on low-power MCU (Microcontroller Unit), FPGA (Field Programmable Gate Array) or SoC (System on Chip) platform, and is convenient for software and hardware integration.

[0085] 3. Multi-strategy main frequency extraction mechanism, precision controllable. According to the state of the eddy current encoder, the frequency estimation precision can reach the order of magnitude of one thousandth of the sampling frequency when needed (the current simulation experiment only shows the implementation effect of the frequency domain analysis method, but still can be combined with the zero-crossing detection method and other main frequency extraction schemes provided in the embodiments of the present application).

[0086] 4. Without high sampling rate or complex hardware resources, frequency and phase recovery can be completed only by relying on a certain length of sampling data (covering multiple periods), without the need for high-order filters or phase-locked loops, reducing system cost and suitable for low-cost integration in domestic sensor chips.

[0087] 5. It has clear industrial landing scenarios and is suitable for industrial servo, motor control, rail transportation, automation equipment and other application scenarios. It can be deployed cooperatively with inductive sensor chips and has clear engineering direction and commercialization path.

[0088] Of course, the above is only an example, and the signal in one or a preset number of periods can also be reserved as a truncated signal. For example, when one period is reserved, the signal can be found from any position (as long as the signal length is greater than one period length) to the front or back as a truncated signal, and so on. Here, it will not be repeated.

[0089] In some embodiments, the determination of the main frequency can also be realized by a scheme in which the DFT analysis method is combined with other processing. For example, from the first set of quadrature signals, the determination of the main frequency can be realized by the following manner: combining the first set of quadrature signals into a complex signal; applying a Hanning window to the complex signal to obtain a windowed signal; determining, according to the frequency domain analysis method, a frequency corresponding to a maximum amplitude from the windowed signal as an initial main frequency; performing interpolation on a domain of a position where the initial main frequency is located in a sequence of spectral points of the windowed signal to obtain a sub-index offset; and determining the main frequency according to the initial main frequency and the sub-index offset. At this time, after the main frequency is obtained by the frequency domain analysis, the main frequency scheme under the target state is further introduced, the search accuracy of the main frequency is further improved by windowing and interpolation (i.e., the main frequency is determined by the frequency domain analysis method + windowing + interpolation), a higher-precision main frequency can be obtained, and thus a higher-precision reference signal can be generated to support a better compensation effect.

[0090] It should be noted that the target state is not limited by the embodiments of the present application. It can be understood that the processing under the target state obtains a higher-precision main frequency, and therefore the target state can be a state in which high-precision is required, for example, a state entered when the user instructs high-precision output, or a state entered in a high-precision detection scenario, and the like, which will not be enumerated here.

[0091] In addition, the acquisition of the complex signal has been described above, and will not be enumerated here.

[0092] It should be further noted that the parameters of the Hanning window are not limited by the embodiments of the present application, and can be set according to application scenarios and requirements. In some embodiments, the window signal of the Hanning window can be:

[0093] ;

[0094] wherein N is the length of the window signal.

[0095] Of course, the above is only an example, and in some embodiments, other Hanning windows can also be used, which will not be enumerated here.

[0096] Furthermore, the embodiments of the present application do not limit the interpolation method, for example, it can be parabolic interpolation, or polynomial interpolation, and the like, which will not be enumerated here.

[0097] For the convenience of understanding, the following will take parabolic three-point interpolation as an example to provide an explanation of the processing under the target state.

[0098] Suppose the windowed signal satisfies: , ​is a window function of the Hanning window, then a sequence of spectral points will be obtained after the discrete Fourier transform , that is,

[0099] .

[0100] Thus, the position of the initial main frequency will be obtained satisfies: .

[0101] Therefore, based on the spectral points at frequencies k-1, k, and k+1, parabolic interpolation can be performed on the interval [k-1, k+1] to obtain the sub-index offset of the frequency position , that is,

[0102] .

[0103] Further, the index of the main frequency is obtained , where, in some examples, the index of the main frequency satisfies: .

[0104] Finally, the main frequency is obtained satisfies: .

[0105] wherein, is a sampling time interval.

[0106] It should be noted that, for the main frequency obtained by the above-mentioned manner, in addition to the examples provided above, the initial phase value thereof can also be obtained by the following expression:

[0107] .

[0108] .

[0109] .

[0110] At this time, since the processing is based on the interpolated spectral point sequence, the initial phase value also has higher precision.

[0111] Through simulation experiments, it is found that the above-mentioned manner can improve the precision to 10 times of the original, is suitable for the built-in high-precision calibration logic of the eddy current encoder chip, and can be used to determine the main frequency when high-precision measurement or high-phase compensation effect needs to be achieved.

[0112] Of course, the above is only an example of the determination manner of the main frequency, and in some embodiments, other manners can also be used to achieve, for example, Figure 7As shown, the above zero-crossing detection method, the frequency domain analysis method + period truncation + the second frequency domain analysis method, and the frequency domain analysis method + windowing can be deployed in the eddy current encoder. In use, one of the methods is selected to determine the dominant frequency according to the actual measurement scene. Here, it will not be listed one by one.

[0113] In step 102, in the case of the running phase of the eddy current encoder, the second orthogonal signal group is used as the reference signal of the third orthogonal signal group output by the eddy current encoder, and digital signal processing is performed to obtain the physical quantity measurement value. In the related art, there are schemes for performing digital signal processing based on the reference signal and the current signal output by the eddy current encoder to obtain the physical quantity measurement value (such as the measurement value, the displacement measurement value, etc.). These schemes are also applicable to the implementation of step 102. The main difference is that the reference signal used in step 102 is obtained through step 101. Here, it will not be listed one by one.

[0114] In some embodiments, as shown in the flow of the eddy current encoder measurement method, the following steps are included: Figure 8

[0115] Step 801, in the starting phase of the eddy current encoder, the dominant frequency and the amplitude and initial phase value corresponding to the dominant frequency are determined from the first orthogonal signal group output by the eddy current encoder, and the second orthogonal signal group is generated according to the dominant frequency and the amplitude and initial phase value corresponding to the dominant frequency.

[0116] Step 802, fitting the error between the first orthogonal signal group and the second orthogonal signal group to obtain an error fitting time sequence signal. The fitting includes piecewise linear fitting, polynomial fitting or orthogonal basis projection fitting.

[0117] Step 803, updating the second orthogonal signal group according to the error fitting signal.

[0118] Step 804, in the case of the running phase of the eddy current encoder, the second orthogonal signal group is used as the reference signal of the third orthogonal signal group output by the eddy current encoder, and digital signal processing is performed to obtain the physical quantity measurement value.

[0119] In Figure 8 In the embodiments shown above, the fitting of the error between the first orthogonal signal group and the second orthogonal signal group is further introduced, so that the phase error is further compensated by the error fitting signal obtained through the fitting processing, thereby further improving the accuracy of the reference signal, further improving the compensation effect, and obtaining more accurate measurement effect.

[0120] For ease of understanding Figure 8 ​The steps of the embodiment will be explained below. Among them, steps 801 and 804 are the same as steps 801 and 804 Figure 1 The steps 101 and 102 in the embodiment are basically the same, and will not be repeated here.

[0121] In step 802, the error between the first and second quadrature signal groups is fitted to obtain an error fitting time sequence signal. The fitting includes piecewise linear fitting, polynomial fitting or orthogonal basis projection fitting. The embodiments of the present application do not limit the fitting method.

[0122] In some embodiments, the first quadrature signal group includes signals and signals For example, the error signal between the reference signal and the measured reference signal is:

[0123] ;

[0124] ;

[0125] wherein, and are error signals, and are measured reference signals.

[0126] The error usually includes system gain offset, phase drift, nonlinear response, DC bias, amplitude-frequency distortion and other characteristics.

[0127] Therefore, the above error signal can be fitted by using a corresponding fitting method:

[0128] If piecewise linear fitting is used, the error signal is divided into several segments according to equal time intervals or signal amplitude distribution, and a linear model is used for fitting within each segment:

[0129] ;

[0130] wherein, is the fitting result, , are linear fitting parameters, is the fitting interval.

[0131] This method can capture slow gain drift, time drift, integral bias and other phenomena, and has fewer model parameters, which is convenient for real-time estimation and online deployment. The fitting residual can be used to judge the error abnormality or the degree of misadjustment accumulation.

[0132] If polynomial fitting (also known as high order term modeling) is used, it is suitable for the case where the error signal presents periodic drift or high order non-linear response (e.g. harmonic distortion). In this case, the following linear model can be used for fitting:

[0133]

[0134] wherein, is the polynomial fitting parameter, is the fitting order, which can be selected according to the requirement, for example, based on the requirement of capturing the acceleration type drift, so that N = 2; also, based on the modeling requirement of the asymmetric jitter, the response shift caused by device aging, so that N = 3, 4, or 5.

[0135] It should be noted that some variations of polynomial fitting can be used, such as least squares, sliding window fitting, recursive least squares, and the like.

[0136] If orthogonal basis projection (also known as frequency domain compensation modeling) is used, the error signal is projected onto a plurality of orthogonal bases (such as Fourier basis, discrete cosine basis) to achieve fitting. In this case, it is suitable for the case of modeling periodic error (such as power frequency interference, systematic noise), and can identify the main interference frequency component. The following error model can be used for fitting:

[0137]

[0138] wherein, is the error signal, , , is the orthogonal basis projection fitting parameter.

[0139] In some examples, the above fitting parameters can be adjusted by a digital front-end dynamic filter, and the above algorithm can be integrated into a PLL (Phase-Locked Loop) or a synchronous shaping network for dynamic updating.

[0140] In step 803, the second quadrature signal group is updated according to the error fitting signal. In the embodiment of the present application, the update of the second quadrature signal group is realized by adding the error fitting signal to the second quadrature signal group.

[0141] The step division of the above various methods is only for the purpose of clear description, and when implemented, one step can be combined or some steps can be split and decomposed into multiple steps, as long as the same logical relationship is included, all are within the protection scope of the present application; adding irrelevant modifications or introducing irrelevant designs in the algorithm or process, but not changing the core design of the algorithm and process are within the protection scope of the present application.

[0142] ​​The second aspect of the embodiment of the present application further provides a measurement device based on an eddy current encoder, as shown in the accompanying drawings, comprising a first processing module and a second processing module. Figure 9

[0143] The first processing module is configured to determine a main frequency, a corresponding amplitude and an initial phase value of the main frequency from a first quadrature signal group output by the eddy current encoder in a starting stage of the eddy current encoder, and generate a second quadrature signal group according to the main frequency, the corresponding amplitude and the initial phase value of the main frequency.

[0144] The second processing module is configured to take the second quadrature signal group as a reference signal of a third quadrature signal group output by the eddy current encoder in a running stage of the eddy current encoder, and perform digital signal processing to obtain a physical quantity measurement value.

[0145] It can be found that the embodiment is a device embodiment corresponding to the method embodiment, and the embodiment can be implemented in cooperation with the method embodiment. The related technical details mentioned in the method embodiment are still valid in the embodiment. In order to reduce repetition, they will not be described here. Correspondingly, the related technical details mentioned in the embodiment can also be applied to the method embodiment.

[0146] It is worth mentioning that each module involved in the embodiment is a logical module. In actual application, one logical unit can be one physical unit, or a part of one physical unit, or a combination of multiple physical units. In addition, in order to highlight the innovative part of the present application, units not closely related to solving the technical problems proposed in the present application are not introduced in the embodiment, but this does not mean that there are no other units in the embodiment.

[0147] The third aspect of the embodiment of the present application further provides an integrated circuit, as shown in the accompanying drawings, comprising a receiving module, an analog signal processing module and a digital signal processing module connected in sequence. Figure 10

[0148] The receiving module is configured to obtain a signal generated on a receiving coil in the eddy current encoder and output to the analog signal processing module.

[0149] The analog signal processing module is configured to sample the received signal to obtain a first quadrature signal group or a third quadrature signal group, and output to the digital signal processing module, wherein the first quadrature signal group is a sampling result in a starting stage, and the third quadrature signal group is a sampling result in a running stage.

[0150] ​​The digital signal processing module is configured to determine a main frequency and an amplitude and an initial phase value corresponding to the main frequency from the received first quadrature signal group, and generate a second quadrature signal group according to the main frequency and the amplitude and the initial phase value corresponding to the main frequency; take the second quadrature signal group as a reference signal of a received third quadrature signal group, and perform digital signal processing to obtain a physical quantity measurement value.

[0151] It can be found that the embodiment is a circuit embodiment corresponding to the method embodiment, and the embodiment can be implemented in cooperation with the method embodiment. The related technical details mentioned in the method embodiment are still valid in the embodiment. In order to reduce repetition, they will not be described here. Accordingly, the related technical details mentioned in the embodiment can also be applied to the method embodiment.

[0152] It is worth mentioning that each module involved in the embodiment can be a physical unit, a part of a physical unit, or a combination of multiple physical units. In addition, in order to highlight the innovative part of the present application, the units not closely related to solving the technical problems proposed in the present application are not introduced in the embodiment, but this does not mean that there are no other modules or units in the embodiment.

[0153] The fourth aspect of the embodiment of the present application further provides an eddy current encoder, comprising:

[0154] A carrier body;

[0155] An excitation coil and a receiving coil arranged on the carrier body;

[0156] An integrated circuit arranged on the carrier body and connected to the output end of the receiving coil, wherein the integrated circuit is the integrated circuit as described above.

[0157] Those skilled in the art can understand that the above embodiments are specific embodiments for implementing the present application, and in actual application, various changes can be made in form and details without departing from the spirit and scope of the present application.

Claims

1. A measurement method based on an eddy current encoder, characterized in that, The method comprises: In the starting phase of the eddy current encoder, a main frequency and an amplitude and an initial phase value corresponding to the main frequency are determined from a first quadrature signal group output by the eddy current encoder, and a second quadrature signal group is generated according to the main frequency and the amplitude and the initial phase value corresponding to the main frequency; In the running phase of the eddy current encoder, the second quadrature signal group is taken as a reference signal of a third quadrature signal group output by the eddy current encoder, and digital signal processing is performed to obtain a physical quantity measurement value.

2. The eddy current encoder based measurement method of claim 1, wherein, The method comprises: The main frequency is determined from the first quadrature signal group; The first quadrature signal group is converted into a frequency domain to obtain a complex frequency spectrum; In the complex frequency spectrum, an amplitude and an initial phase value of a frequency spectrum component corresponding to the main frequency are determined as the amplitude and the initial phase value corresponding to the main frequency.

3. The eddy current encoder based measurement method of claim 2, wherein, The method comprises: The first quadrature signal group is combined into a complex signal; According to a frequency domain analysis method, a frequency corresponding to a maximum amplitude is determined from the complex signal as an initial main frequency; According to a signal period corresponding to the initial main frequency, the complex signal is periodically truncated to obtain a truncated signal; According to the frequency domain analysis method, a frequency corresponding to a maximum amplitude is determined from the truncated signal as the main frequency.

4. The eddy current encoder based measurement method of claim 2, wherein, The method comprises: A signal from the first quadrature signal group is selected as a to-be-processed signal; An average time interval between adjacent time domain symbol change points of the to-be-processed signal is determined; According to the average time interval, a signal period of the to-be-processed signal is determined, and a frequency corresponding to the signal period is determined as the main frequency.

5. The eddy current encoder based measurement method of claim 2, wherein, The method comprises: The first quadrature signal group is combined into a complex signal; A Hanning window is applied to the complex signal to obtain a windowed signal; According to a frequency domain analysis method, a frequency corresponding to a maximum amplitude is determined from the windowed signal as an initial main frequency; A domain of a position where the initial main frequency is located is interpolated on a frequency spectrum point sequence of the windowed signal to obtain a sub-index offset; The main frequency is determined according to the initial main frequency and the sub-index offset.

6. The method of measurement based on an eddy current encoder according to any one of claims 1 to 5, characterized in that, After the second quadrature signal group is generated according to the main frequency and the amplitude and the initial phase value corresponding to the main frequency, the method further comprises: An error between the first quadrature signal group and the second quadrature signal group is fitted to obtain an error fitting time sequence, and the fitting comprises piecewise linear fitting, polynomial fitting or orthogonal basis projection fitting; The second quadrature signal group is updated according to the error fitting signal.

7. The method of measurement based on an eddy current encoder according to any one of claims 1 to 5, characterized in that, The second quadrature signal group is generated according to the main frequency and the amplitude and the initial phase value corresponding to the main frequency by the following expression: ； ； wherein, and is a different signal in the second orthogonal signal group, is an amplitude value corresponding to the main frequency, is the main frequency, is an initial phase value corresponding to the main frequency.

8. An eddy current encoder based measuring device, characterized in that The method comprises: The first processing module is configured to determine a main frequency, an amplitude corresponding to the main frequency, and an initial phase value from a first quadrature signal group output by the eddy current encoder during a start-up stage of the eddy current encoder, and generate a second quadrature signal group according to the main frequency, the amplitude corresponding to the main frequency, and the initial phase value. The second processing module is configured to use the second quadrature signal group as a reference signal of a third quadrature signal group output by the eddy current encoder during a running stage of the eddy current encoder, and perform digital signal processing to obtain a physical quantity measurement value.

9. An integrated circuit, characterized by The method comprises the following steps: sequentially connecting a receiving module, an analog signal processing module, and a digital signal processing module; The receiving module is configured to obtain a signal generated on a receiving coil in the eddy current encoder, and output the signal to the analog signal processing module. The analog signal processing module is configured to sample the received signal to obtain a first quadrature signal group or a third quadrature signal group, and output the first quadrature signal group or the third quadrature signal group to the digital signal processing module, wherein the first quadrature signal group is a sampling result during a start-up stage, and the third quadrature signal group is a sampling result during a running stage. The digital signal processing module is configured to determine a main frequency, an amplitude corresponding to the main frequency, and an initial phase value from the received first quadrature signal group, and generate a second quadrature signal group according to the main frequency, the amplitude corresponding to the main frequency, and the initial phase value; use the second quadrature signal group as a reference signal of the received third quadrature signal group, and perform digital signal processing to obtain a physical quantity measurement value.

10. An eddy current encoder characterized by, The method comprises the following steps: a carrier body; an excitation coil and a receiving coil arranged on the carrier body; an integrated circuit arranged on the carrier body and connected to an output end of the receiving coil, wherein the integrated circuit is the integrated circuit of claim 9.

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