Encoder instantaneous angular velocity estimation method and system based on multi-frequency modulation scale decomposition and reconstruction

Abstract

The present invention proposes a method and system for estimating the instantaneous angular velocity of an encoder based on multi-frequency modulation scale decomposition and reconstruction. The method is as follows: firstly, the encoder pulse signal under multi-scale modulation is obtained by analyzing and modeling the encoder signal components, and the pulse signal spectrum is obtained after fast Fourier transform; secondly, the pulse signal spectrum is decomposed by multi-scale frequency domain filtering to obtain analytical signals under different modulation scales; then, the frequency domain frequency reduction and modulation characteristic component sensitivity of the multi-scale modulation analytical signal components are evaluated; then, the analytical signal spectrum is obtained by weighted reconstruction of the frequency domain multi-scale modulation analytical signal components, and the analytical signal is obtained by time domain conversion of the multi-scale reconstructed analytical spectrum; finally, according to the properties of the analytical signal, the instantaneous angular velocity of the encoder multi-scale reconstructed signal can be obtained. This method realizes the high-precision calculation of the encoder angular velocity.

Description

Technical Field

[0001] The present invention relates to the technical field of rotating machinery fault diagnosis, and in particular to an encoder instantaneous angular velocity estimation method and system based on multi-frequency modulation scale splitting and reconstruction. Background Art

[0002] Encoders are mainly used for speed measurement and positioning, and are widely used in precision manufacturing, automotive engineering, railways and ships. The instantaneous angular velocity of rotating machinery contains information about its operating status and characteristic frequency, and has the advantages of being unaffected by the transmission path and having no transmission attenuation. It is one of the important means of mechanical equipment status monitoring and fault diagnosis. However, how to obtain accurate instantaneous angular velocity signals and improve the signal-to-noise ratio of the instantaneous angular velocity signals of rotating machinery is an important challenge faced by rotating machinery status monitoring and fault diagnosis based on instantaneous angular velocity signals. The square wave and pulse signals output by the encoder as the shaft rotates can be split into a series of odd-frequency modulation signals, and the rotating machinery information modulated on each modulation frequency scale is different. The instantaneous angular velocity obtained by the traditional M method, T method and frequency demodulation method only uses the modulation information on the 1-fold frequency, while ignoring the effective information on the higher modulation frequency scale, resulting in a waste of sampling bandwidth and effective modulation information. Summary of the invention

[0003] In order to overcome the defects in the prior art, the object of the present invention is to provide an encoder instantaneous angular velocity estimation method and system based on multi-frequency modulation scale decomposition and reconstruction.

[0004] In order to achieve the above-mentioned object of the present invention, the present invention provides an encoder instantaneous angular velocity estimation method based on multi-frequency modulation scale decomposition and reconstruction, comprising the following steps:

[0005] Get the rotary mechanical encoder signal ω(t);

[0006] Perform component analysis and modeling on the encoder signal ω(t) to obtain the encoder pulse signal under multi-scale modulation;

[0007] Perform fast Fourier transform on the encoder pulse signal under multi-scale modulation to obtain the encoder pulse signal spectrum FT(f);

[0008] Perform multi-scale frequency domain filtering and decomposition on the encoder pulse signal spectrum FT(f) to obtain the analytical signal AS under different modulation scales m (f);

[0009] Analytical signals AS under different modulation scales m (f) Down-convert the components in the frequency domain to shift the analytical signals of different modulation scales to the same modulation frequency band, and obtain the analytical signals AS under different modulation scales after down-conversion m'(f);

[0010] Evaluate the sensitivity of the modulation characteristic components of the analytical signal at different modulation scales, and weight the sensitivity of each characteristic event at different modulation scales;

[0011] Perform frequency domain weighted reconstruction on analytical signals of different modulation scales that are translated to the same modulation frequency band to obtain a frequency domain multi-scale reconstructed analytical signal ASz(f);

[0012] Performing time domain transformation on the frequency domain multi-scale reconstructed analytical signal ASz(f) to obtain the time domain multi-scale reconstructed analytical signal y(t);

[0013] Calculate the instantaneous angular velocity of the time domain multi-scale reconstructed analytical signal y(t) to obtain the instantaneous angular velocity of the encoder.

[0014] This method provides an effective means for estimating the encoder angular velocity considering mechanical failures. It uses the effective rotating mechanical information at a higher modulation frequency scale to accurately reconstruct the instantaneous angular velocity at multiple modulation scales, thereby achieving high-precision calculation of the encoder angular velocity.

[0015] In a preferred embodiment of the method, the steps of performing component analysis and modeling on the encoder signal ω(t) to obtain the encoder pulse signal under multi-scale modulation are:

[0016] Component analysis: The encoder signal ω(t) is divided into a constant speed part and a fluctuating speed part, that is, Where ω0 is the constant speed, ω k (t) is the instantaneous angular velocity fluctuation caused by the kth characteristic event, and n is the total number of characteristic events;

[0017] Modeling: The continuous Fourier series expansion of the encoder pulse signal is Get the encoder pulse signal under multi-scale modulation, where is the modulation angle phase information in the pulse signal, Where t refers to time, m is a positive integer, m represents the mth order modulation scale, and N is the number of encoder lines. is the initial rotation angle of the encoder;

[0018] Pulse signal modulation frequency f c The relationship with the constant speed component is: where f r is the shaft rotation frequency, f mc is the mth order modulation frequency.

[0019] In a preferred embodiment of the method, the encoder pulse signal spectrum

[0020]

[0021] In a preferred embodiment of the method, analytical signals AS under different modulation scales are obtained. m The steps of (f) are:

[0022] In the frequency domain, a rectangular window is added to the positive spectrum of the modulated signal centered on different modulation scale frequencies to obtain the analytical signals of different modulation scales:

[0023] Where N is the number of encoder lines, m is a positive integer, m = 1, 2, 3, ..., representing the mth order modulation scale, f r is the shaft rotation frequency.

[0024] In a preferred embodiment of the method, the down-converted analytical signal AS under different modulation scales m The calculation formula of '(f) is:

[0025]

[0026] This preferred solution performs frequency reduction operations on modulation information of different scales, takes previously ignored information into consideration, obtains rotating mechanical information at higher modulation frequency scales that has been previously neglected, and makes the final encoding smooth instantaneous angular velocity more accurate.

[0027] In a preferred embodiment of the method, the steps of evaluating the sensitivity of the modulation characteristic components of the analytical signal at different modulation scales and weighting the sensitivity of each characteristic event at different modulation scales are as follows:

[0028] The calculation formula of the sensitivity evaluation index of the modulation characteristic components of the analytical signal with different modulation scales is:

[0029] Among them, Mean() refers to the average value of the function value within a given frequency range, ind m_k is the sensitivity index to the characteristic event k within the mth order modulation scale, f k is the frequency of the characteristic event k of interest, f mc is the modulation frequency of the m-order pulse signal;

[0030] The sensitivity of each characteristic event in different modulation scales is weighted, and the formula is: Among them, W m_k It represents the weighting coefficient of the characteristic event k based on the mth order modulation scale of sensitivity, and M represents the total order of the modulation scale.

[0031] In a preferred embodiment of the method, the signal spectrum is analyzed Among them, W m_kIt represents the weighting coefficient of the characteristic event k based on the mth order modulation scale of sensitivity, and M represents the total order of the modulation scale.

[0032] In a preferred embodiment of the method, the instantaneous angular velocity of the encoder Among them, Im is the imaginary part, To reconstruct the differential signal of the analytical signal.

[0033] The present invention also proposes an encoder instantaneous angular velocity estimation system, including a data acquisition module, a processor and a memory, wherein the data acquisition module acquires a rotating mechanical encoder signal and transmits it to the processor, the processor is communicatively connected to the memory, and the memory is used to store at least one executable instruction, wherein the executable instruction enables the processor to execute operations corresponding to the encoder instantaneous angular velocity estimation method based on multi-frequency modulation scale splitting and reconstruction of the present invention to obtain the encoder instantaneous angular velocity.

[0034] The beneficial effects of the present invention are as follows: the present invention provides an effective means for estimating the encoder angular velocity taking into account mechanical faults, can obtain the neglected rotating machinery information at a higher modulation frequency scale, and utilizes this effective information to accurately reconstruct the instantaneous angular velocity at multiple modulation scales, thereby achieving high-precision calculation of the encoder angular velocity, and has good application prospects in rotating machinery fault diagnosis.

[0035] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0037] Figure 1 It is a schematic diagram of multi-scale modulation of rotary mechanical encoder signals;

[0038] Figure 2 is a schematic diagram of the process of this method;

[0039] Figure 3 It is a schematic diagram of frequency domain filtering and decomposition of multi-scale modulated signals;

[0040] Figure 4 It is a schematic diagram of frequency domain downconversion of multi-scale modulation analysis signal components;

[0041] Figure 5 It is a schematic diagram of frequency domain weighted reconstruction of multi-scale modulated signals;

[0042] Figure 6 It is a flowchart of the weighted reconstruction operation of frequency domain multi-scale modulation signal. DETAILED DESCRIPTION

[0043] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0044] In the description of the present invention, unless otherwise specified and limited, it should be noted that the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the internal connection between two components. It can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances.

[0045] like Figures 1 to 6 As shown, the present invention provides an encoder instantaneous angular velocity estimation method based on multi-frequency modulation scale decomposition and reconstruction, the method first obtains the encoder pulse signal under multi-scale modulation by analyzing and modeling the encoder signal components, and obtains the pulse signal spectrum after fast Fourier transform; secondly, the pulse signal spectrum is subjected to multi-scale frequency domain filtering decomposition to obtain analytical signals under different modulation scales; then, the multi-scale modulation analytical signal components are frequency domain down-converted and the sensitivity of the modulation characteristic components is evaluated; then, the analytical signal spectrum is obtained by weighted reconstruction of the frequency domain multi-scale modulation analytical signal components, and the analytical signal is obtained by time domain conversion of the multi-scale reconstructed analytical spectrum; finally, according to the properties of the analytical signal, the instantaneous angular velocity of the encoder multi-scale reconstructed signal can be obtained.

[0046] The specific steps are as follows:

[0047] Get the rotary machine encoder signal ω(t).

[0048] The encoder signal ω(t) is subjected to component analysis and modeling to obtain the encoder pulse signal under multi-scale modulation.

[0049] The components here refer to characteristic components, which can be understood as the amplitude, steepness, etc. of the signal. The characteristic components used in this paper are the ratio of the modulation frequency domain amplitude of the characteristic frequency to the mean value near the characteristic frequency. In layman's terms, the split analytical signal is a single-peak signal in the frequency domain, and this method considers the ratio of the peak amplitude to the average value of the amplitude near the peak frequency.

[0050] Specifically, component analysis: The schematic diagram of multi-scale modulation of rotary mechanical encoder signals is as follows Figure 1 As shown in the figure, ω is the actual shaft speed, which consists of a constant speed part and a fluctuating speed part, and can be expressed as: encoder signal Where ω0 is the constant speed, ωk (t) is the instantaneous angular velocity fluctuation caused by the kth characteristic event, and n is the total number of characteristic events.

[0051] Modeling: The original signal measured by the encoder is a continuous signal. Taking the encoder pulse signal as an example, its continuous Fourier series expansion is: in is the rotation angle phase information modulated in the pulse signal, Where t refers to time, m is a positive integer, m represents the mth order modulation scale, N is the number of encoder lines, and one circle of the code disk. is the initial rotation angle of the encoder.

[0052] Pulse signal modulation frequency f c The relationship with the constant speed component is: where f r is the shaft rotation frequency, the subscript m represents the mth order modulation scale, f mc is the mth order modulation frequency.

[0053] In actual measurement, the encoder output signal is a continuous pulse signal and meets the Direheli convergence condition. Therefore, the encoder pulse signal under multi-scale modulation is subjected to fast Fourier transform to obtain the encoder pulse signal spectrum FT(f):

[0054] Encoder pulse signal spectrum

[0055] Perform multi-scale frequency domain filtering and decomposition on the encoder pulse signal spectrum FT(f) to obtain the analytical signal AS under different modulation scales m (f).

[0056] Specifically, a rectangular window is added to the positive spectrum of the modulated signal centered on the frequency of different modulation scales in the frequency domain to obtain the analytical signals of different modulation scales:

[0057] Where N is the number of encoder lines, m is a positive integer, m = 1, 2, 3, ..., representing the mth order modulation scale, f r is the shaft rotation frequency, such as Figure 3 and Figure 6 As shown, analytical signals of the 1st to mth order modulation scales are obtained.

[0058] Based on the Fourier transform properties, the analytical signal AS under different modulation scales m (f) Down-convert the components in the frequency domain to shift the analytical signals of different modulation scales to the same modulation frequency band, and obtain the analytical signals AS under different modulation scales after down-conversion m '(f).

[0059] The analytical signal AS under different modulation scales after frequency reductionm The calculation formula of '(f) is:

[0060] like Figure 4 and Figure 6 As shown, the analytical signal under the 1st to mth order modulation scale after frequency reduction is obtained.

[0061] Since the sensitivity of the characteristic frequency of instantaneous angular velocity is different at different modulation scales, for example, in a planetary gear transmission system, the rotation frequency and fault characteristics of the sun gear, planet gear, planet carrier, etc. are different. Therefore, the sensitivity of the modulation characteristic components of the analytical signal at different modulation scales is evaluated, and the sensitivity of each characteristic event at different modulation scales is weighted.

[0062] The specific steps are as follows: First, evaluate the sensitivity of characteristic signals at different modulation scales. This embodiment takes the ratio of the modulation frequency domain amplitude to the mean value near the characteristic component, such as the gear and bearing fault frequency component, as an example to calculate the sensitivity evaluation index. The calculation method is as follows:

[0063] The calculation formula of the sensitivity evaluation index of the modulation characteristic components of the analytical signal with different modulation scales is:

[0064] Among them, Mean() refers to the average value of the function value within a given frequency range, ind m_k is the sensitivity index to the characteristic event k within the mth order modulation scale, f k is the frequency of the characteristic event k of interest, such as rotation frequency, meshing frequency, bearing passing frequency, fault characteristic frequency, etc., f mc is the modulation frequency of the m-order pulse signal.

[0065] ind m_k The higher the value, the higher the energy distribution of feature event k in modulation scale m is than that of other scales, and the signal-to-noise ratio of feature event k in this modulation scale is high. When multi-scale demodulation and reconstruction is performed, the weight of the modulation scale information with higher sensitivity of feature events should be increased. Taking the simple normalization calculation of weighting coefficients as an example, the weighting coefficient of the sensitivity of each feature event in different modulation scales is Among them, W m_k It represents the weighting coefficient of the characteristic event k based on the mth order modulation scale of sensitivity, and M represents the total order of the modulation scale.

[0066] The frequency domain weighted reconstruction is performed on the analytical signals of different modulation scales that are translated to the same modulation frequency band, such as Figure 5 and Figure 6 As shown, the frequency domain multi-scale reconstruction analytical signal ASz(f) is obtained; the calculation formula is

[0067]

[0068] In order to obtain the instantaneous angular velocity signal in the time domain, the frequency domain multi-scale weighted reconstruction signal ASz(f) is converted into the time domain to obtain the time domain multi-scale reconstruction analytical signal y(t), and provide a more accurate frequency domain multi-scale reconstruction of the reconstructed time domain signal for the subsequent instantaneous angular velocity calculation.

[0069] Time domain multi-scale reconstruction analytical signal y(t) = FT -1 (AS Z (f)), where FT -1 () is the inverse Fourier transform.

[0070] Calculate the instantaneous angular velocity of the time domain multi-scale reconstructed analytical signal y(t) to obtain the instantaneous angular velocity of the encoder. Among them, Im is the imaginary part, To reconstruct the differential signal of the analytical signal.

[0071] The present invention also proposes an embodiment of an encoder instantaneous angular velocity estimation system, which includes a data acquisition module, a processor and a memory. The data acquisition module acquires a rotating mechanical encoder signal and transmits it to the processor. The processor is communicatively connected to the memory. The memory is used to store at least one executable instruction. The executable instruction enables the processor to execute operations corresponding to the encoder instantaneous angular velocity estimation method based on multi-frequency modulation scale splitting and reconstruction of the present invention to obtain the encoder instantaneous angular velocity.

[0072] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0073] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for estimating instantaneous angular velocity of an encoder based on multi-frequency modulation scale decomposition and reconstruction, characterized in that: The following steps are involved: Get the rotary mechanical encoder signal ω(t); The encoder signal ω(t) is subjected to component analysis and modeling to obtain the encoder pulse signal under multi-scale modulation. The specific steps are as follows: Component analysis: The encoder signal ω(t) is divided into a constant speed part and a fluctuating speed part, that is, Where ω0 is the constant speed, ω k (t) is the instantaneous angular velocity fluctuation caused by the kth characteristic event, and n is the total number of characteristic events; Modeling: The continuous Fourier series expansion of the encoder pulse signal is Get the encoder pulse signal under multi-scale modulation, where is the rotation angle phase information modulated in the pulse signal, Where t refers to time, m is a positive integer, m represents the mth order modulation scale, and N is the number of encoder lines. is the initial rotation angle of the encoder; Pulse signal modulation frequency f c The relationship with the constant speed component is: where f r is the shaft rotation frequency, f mc is the m-th order modulation frequency; Perform fast Fourier transform on the encoder pulse signal under multi-scale modulation to obtain the encoder pulse signal spectrum FT(f); Perform multi-scale frequency domain filtering and decomposition on the encoder pulse signal spectrum FT(f) to obtain the analytical signal AS under different modulation scales m (f); Analytical signals AS under different modulation scales m (f) Down-convert the components in the frequency domain to shift the analytical signals of different modulation scales to the same modulation frequency band, and obtain the analytical signals AS under different modulation scales after down-conversion m '(f); Evaluate the sensitivity of the modulation characteristic components of the analytical signal at different modulation scales, and weight the sensitivity of each characteristic event at different modulation scales. The specific steps are as follows: The calculation formula of the sensitivity evaluation index of the modulation characteristic components of the analytical signal with different modulation scales is: Among them, Mean() refers to the average value of the function value within a given frequency range, ind m_k is the sensitivity index to the characteristic event k within the mth order modulation scale, f k is the frequency of the characteristic event k of interest, f mc is the modulation frequency of the m-order pulse signal; The sensitivity of each characteristic event in different modulation scales is weighted, and the formula is: Among them, W m_k represents the weighting coefficient of the characteristic event k based on the m-th order modulation scale of sensitivity, and M represents the total order of the modulation scale; Perform frequency domain weighted reconstruction on analytical signals of different modulation scales that are translated to the same modulation frequency band to obtain a frequency domain multi-scale reconstructed analytical signal ASz(f); Performing time domain transformation on the frequency domain multi-scale reconstructed analytical signal ASz(f) to obtain the time domain multi-scale reconstructed analytical signal y(t); Calculate the instantaneous angular velocity of the time domain multi-scale reconstructed analytical signal y(t) to obtain the instantaneous angular velocity of the encoder.

2. The encoder instantaneous angular velocity estimation method based on multi-frequency modulation scale decomposition and reconstruction according to claim 1 is characterized in that: Encoder pulse signal spectrum 3. The encoder instantaneous angular velocity estimation method based on multi-frequency modulation scale decomposition and reconstruction according to claim 1 is characterized in that: Get the analytical signal AS under different modulation scales m The steps of (f) are: In the frequency domain, a rectangular window is added to the positive spectrum of the modulated signal centered on different modulation scale frequencies to obtain the analytical signals of different modulation scales: Where N is the number of encoder lines, m is a positive integer, m = 1, 2, 3, ..., represents the mth order modulation scale, f r is the shaft rotation frequency.

4. The encoder instantaneous angular velocity estimation method based on multi-frequency modulation scale decomposition and reconstruction according to claim 3 is characterized in that: The analytical signal AS under different modulation scales after frequency reduction m The calculation formula of '(f) is:

5. The encoder instantaneous angular velocity estimation method based on multi-frequency modulation scale decomposition and reconstruction according to claim 1 is characterized in that: Analyzing the signal spectrum Among them, W m_k It represents the weighting coefficient of the characteristic event k based on the mth order modulation scale of sensitivity, and M represents the total order of the modulation scale.

6. The encoder instantaneous angular velocity estimation method based on multi-frequency modulation scale decomposition and reconstruction according to claim 1 is characterized in that: Encoder instantaneous angular velocity Among them, Im is the imaginary part, To reconstruct the differential signal of the analytical signal.

7. An encoder instantaneous angular velocity estimation system, characterized in that: The invention comprises a data acquisition module, a processor and a memory, wherein the data acquisition module acquires a rotary mechanical encoder signal and transmits it to the processor, the processor is communicatively connected with the memory, and the memory is used to store at least one executable instruction, wherein the executable instruction enables the processor to execute an operation corresponding to the encoder instantaneous angular velocity estimation method based on multi-frequency modulation scale decomposition and reconstruction as described in any one of claims 1 to 6 to obtain the encoder instantaneous angular velocity.

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