A time-varying intermodulation torsional vibration signal generator

Abstract

The application discloses a time-varying inter-harmonic torsional vibration signal generator, which comprises a main controller, an input end of the main controller is electrically connected with an output end of a first filter, a second filter and an analog-digital module, an input end of the analog-digital module is electrically connected with an output end of a third filter, the main controller is bidirectionally electrically connected with an SRAM module, a FLASH module, a network card chip, a USB chip and an RS232 module, and an output end of the main controller is electrically connected with an input end of a level module, an optical coupler and an analog-digital module. Compared with a mechanical torsional vibration test bench, the time-varying inter-harmonic torsional vibration signal generator has simple structure, can comprehensively cover test working conditions, can fully test the precision of a torsional vibration analysis device, can provide various linear signals or multi-frequency signals, and can evaluate the time-varying inter-harmonic signal processing situation of the torsional vibration analysis device.

Description

Technical Field

[0001] This invention relates to the field of signal generator technology, specifically to a torsional vibration signal generator containing time-varying interharmonics. Background Technology

[0002] The measurement, application, and research of torsional vibration signals in various rotating shaft systems are becoming increasingly widespread. Mechanical inertial torsional vibration meters can measure lower-frequency shaft torsional vibrations, but because this measurement is contact-based, the system structure is complex, installation is cumbersome, and data recording is difficult, making it unsuitable for high-speed shaft measurement. Currently, digital electrical signal torsional vibration measurement devices are mainly replacing them. Digital torsional vibration meters generally use non-contact sensors to acquire real-time rotational speed data at a high sampling rate, and then use time-frequency algorithms for processing and analysis. They offer advantages such as easy installation, the ability to measure torsional vibrations over a wide speed range, and real-time analysis. The non-contact sensors in this system mainly include Hall effect gear speed sensors, magnetoelectric gear speed sensors, photoelectric encoders, laser sensors, photoelectric reflective sensors, and photoelectric through-beam sensors. The main characteristic of these sensors is that after the shaft system rotates with a characteristic code disk, a pulse signal modulated by the real-time rotational speed is generated through a corresponding device. The measuring instrument obtains the torsional vibration signal by demodulating and analyzing this pulse signal. Demodulation methods for this pulse signal can be divided into two categories: analog processing and digital processing. Analog processing mainly uses a series of narrowband filter circuits and integrator circuits to demodulate the signal. Digital processing, after filtering and shaping, uses algorithms to analyze and obtain torsional vibration information. Different processing methods result in significantly different levels of accuracy, making it necessary to quickly and conveniently verify the accuracy of the torsional vibration acquisition device. A torsional vibration signal generator is used to generate relatively standard and definite torsional vibration signals to measure the accuracy of the torsional vibration acquisition device. Mechanical bench-type torsional vibration calibration systems can not only calibrate the torsional vibration acquisition device but also evaluate the sensor signal to some extent. However, bench systems are complex and expensive. Pure digital torsional vibration calibrators do not have bench systems; they only simulate the signal from the sensor in the torsional vibration measurement system, making it easier to evaluate the accuracy of signal processing in the torsional vibration acquisition device. However, existing pure digital torsional vibration calibrators only provide relatively simple linear or single-frequency signals and cannot evaluate the torsional vibration analysis device's processing of non-time-varying interharmonic signals. Summary of the Invention

[0003] (a) Technical problems to be solved

[0004] To address the shortcomings of existing technologies, this invention provides a torsional vibration signal generator containing time-varying interharmonics, which solves the problem that existing torsional vibration signal calibrators cannot evaluate the torsional vibration analysis device's processing of non-time-varying interharmonic signals.

[0005] (II) Technical Solution

[0006] To achieve the above objectives, the present invention provides the following technical solution: a time-varying interharmonic torsional vibration signal generator, comprising a main controller, wherein the input terminal of the main controller is electrically connected to the output terminals of a first filter, a second filter, and an analog-to-digital module; the input terminal of the analog-to-digital module is electrically connected to the output terminal of a third filter; the main controller is bidirectionally electrically connected to an SRAM module, a FLASH module, a network card chip, a USB chip, and an RS232 module; and the output terminal of the main controller is electrically connected to the input terminals of a level module, an optocoupler, and a digital-to-analog module.

[0007] To further optimize this technical solution, the network card chip, USB chip, and RS232 module are bidirectionally electrically connected to the PC display screen.

[0008] To further optimize this technical solution, the output terminal of the optocoupler is electrically connected to the input terminal of the relay.

[0009] To further optimize this technical solution, the first filter and the second filter are electrically connected to the main controller via the eQEP bus and the eCAP bus, respectively.

[0010] To further optimize this technical solution, the main controller is electrically connected to the level module and the optocoupler via the ePMW bus and the GPIO bus, respectively.

[0011] To further optimize this technical solution, the main controller is electrically connected to the network card chip and the USB chip via the XINTF bus.

[0012] (III) Beneficial Effects

[0013] Compared with the prior art, the present invention provides a torsional vibration signal generator containing time-varying interharmonics, which has the following advantages:

[0014] Compared with mechanical torsional vibration test benches, this time-varying interharmonic torsional vibration signal generator has a simple structure and complex test conditions. It can fully verify the accuracy of the torsional vibration analysis device, provide complex linear or multi-frequency signals, and evaluate the torsional vibration analysis device's processing of non-time-varying interharmonic signals. Attached Figure Description

[0015] Figure 1 This is a schematic diagram illustrating the system principle of the present invention.

[0016] In the diagram: 1. Main controller; 2. SPAM; 3. FLASH module; 4. First filter; 5. Second filter; 6. Third filter; 7. Analog-to-digital module; 8. Network card chip; 9. USB chip; 10. RS232 module; 11. PC display screen; 12. Level module; 13. Optocoupler; 14. Digital-to-analog module; 15. Relay. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1:

[0019] Please see Figure 1 This invention provides a technical solution: a torsional vibration signal generator with time-varying interharmonics, including a main controller 1, model TMS320F28335, with a main frequency of 150MHz, 12 PWM channels and 6 CAP channels, capable of simultaneously providing multiple torsional vibration speed pulse signals, and able to capture pulse signals through CAP for self-calibration. The input terminal of the main controller 1 is electrically connected to the output terminals of the first filter 4, the second filter 5, and the analog-to-digital module 7, model AD7606. To ensure accuracy, the main controller 1 is electrically connected to the analog-to-digital module 7 via an XINTF bus, which can be used to acquire analog signals of torsional vibration. The input terminal of the analog-to-digital module 7 is electrically connected to the output terminal of the third filter 6. The main controller 1 is bidirectionally electrically connected to the SRAM module 2, FLASH module 3, network card chip 8, USB chip 9, and RS232 module 10. The SRAM module 2 is model IS61LV51216AL, the FLASH module 3 is model 39VF800A, the network card chip 8 is model W5300, the USB chip 9 is model FT2232H, and the RS232 module 10 is model MAX3232. The output terminal of the main controller 1 is electrically connected to the input terminals of the level module 12, the optocoupler 13, and the digital-to-analog module 14. The level module 12 is model 74LVC245, the optocoupler 13 is model PC817, and the digital-to-analog module 14 is model DAC8552. The main controller 1 is electrically connected to the digital-to-analog module 14 via the SPI bus to generate analog signals. Compared with the mechanical torsional vibration test bench, it has a simple structure and complex test conditions. It can fully verify the accuracy of the torsional vibration analysis device, and can provide complex linear signals or multi-frequency signals. It can also evaluate the torsional vibration analysis device's processing of non-time-varying interharmonic signals.

[0020] Specifically, the network card chip 8, USB chip 9, and RS232 module 10 are bidirectionally electrically connected to the PC display screen 11.

[0021] Specifically, the output terminal of optocoupler 13 is electrically connected to the input terminal of relay 15.

[0022] Specifically, the first filter 4 and the second filter 5 are electrically connected to the main controller 1 via the eQEP bus and the eCAP bus, respectively.

[0023] Specifically, the main controller 1 is electrically connected to the level module 12 and the optocoupler 13 via the ePMW bus and the GPIO bus, respectively.

[0024] Specifically, the main controller 1 is electrically connected to the network card chip 8 and the USB chip 9 via the XINTF bus.

[0025] Currently, methods for measuring shaft torsional vibration based on instantaneous rotational speed are widely used. Acquiring instantaneous rotational speed of the shaft system using gear sensors is a typical method, and its main principle is as follows: Figure 1 As shown, a gear sensor monitors evenly spaced gear encoders mounted on a shaft system. Assuming no torsional vibration, the shaft's instantaneous velocity equals its average velocity, and the encoders also rotate at a uniform speed. Therefore, the repetition period of the pulse signal per tooth output by the sensor is the same. However, when torsional vibration occurs in the shaft system, it's equivalent to adding a torsional vibration fluctuation velocity to its average velocity. At this time, the pulse sequence output by the sensor is no longer evenly spaced, but rather a frequency-modulated signal whose carrier frequency is modulated by the torsional vibration signal. The instantaneous amplitude equation of this signal is:

[0026]

[0027] Where f(t) is the original modulation signal, K PPM Let F0 be the modulation coefficient, A be the pulse amplitude (V), τ0 be the pulse width (S), and ω0 be the angular frequency of F0 (rad / s). The first term in the equation is a DC term, the second term contains the differential information of the original modulating signal f(t), and the last term represents the phase-modulated (PM) signal with Kω0 as the carrier frequency. The spectra of phase modulation (PM) and frequency modulation (FM) differ only in phase. In addition, both have the same bandwidth.

[0028] Analog torsional vibration testing uses a low-pass filter and integrator to demodulate the signal and obtain the torsion angle signal. Digital torsional vibration meters acquire pulse signals using a multi-pulse capture circuit (CAP), and the demodulation of this signal is as follows: Let the time for one rotation of the shaft be t. c From the formula The circumferential average angular velocity can be obtained as ω. c The gear has N teeth, and the time t is used to rotate n teeth. n From the formula The average velocity of the tooth can be obtained as ω, from the formula. The twist angle of the shaft can be obtained as θ. After integration, the formula can be obtained. Therefore, as long as t is measuredc , t n That's all.

[0029] The torsional vibration signal generator then uses the known torsional angle signal to inversely solve the sensor signal sequence, i.e., to solve the formula. t in n sequence. formula In the equation, if θ(n) is known, then t c The value of t can be obtained from the known twist angle signal. N is the actual number of gears in the simulation, which is also the length of the sequence and is known. Therefore, the equation can be solved to obtain t. n

[0030] Example 2:

[0031] Currently, some torsional vibration testing and analysis instruments use a torsional angle triangular wave as the torsional vibration simulation signal. This generates a 100-tooth gear output pulse signal, with a slower initial rotation and a faster rotation in the latter half, primarily consisting of 50 square wave pulses at 5000Hz and 50 square wave pulses at 5063.3Hz. Its average circumferential speed is 3018 r / min, the torsional frequency is 50.3Hz, and the peak torsional angle is 0.566. The Fourier expansion formula for the periodic function of the triangular waveform is:

[0032]

[0033] The calculated first harmonic torsion angles are 0.458°, the third harmonic torsion angle is 0.051°, and the fifth harmonic torsion angle is 0.018°. FFT is performed on the generated torsion angle signals, and the spectrum is shown in the figure. It can be seen that the amplitudes of the first, third, and fifth harmonics have certain errors compared to the theoretical amplitudes. The accuracy of amplitude calculation can be improved by improving signal processing methods, such as equal-time interpolation rearrangement or windowing. In practice, shaft systems operate at various speeds. The pulse period can be adjusted proportionally, i.e., the frequency of these 100 pulse signals can be adjusted to simulate different speeds. The number of gears in the measured signal can also be adjusted by changing the number of pulses to simulate test conditions with different numbers of gears. However, the triangular wave generator cannot completely cover all torsion angle waveforms and cannot fully validate the analysis method and instrument.

[0034] Example 3:

[0035] In many cases, the torsional signal is not a triangular wave signal, but a sinusoidal signal related to the excitation frequency. The torsional vibration signal is simulated to test the torsional vibration device's ability to analyze this type of signal.

[0036] Let the single-frequency torsion angle signal be Where A = 1; If ω = 100π, then θ(t) = sin(100πt). Substituting the formula θ(t) = sin(100πt) into the formula... The formula is obtained as follows:

[0037]

[0038] Where t c Given the average period of rotational speed, we can obtain N represents the number of gears, here taken as 100, and n is the gear number that passes through in real time, from 1 to 100. t can be solved using a binary search method. n Sequence. Unlike the linear twisted waveform case, t n The sequence is not equally spaced, determined by t. n Time series can generate simulated pulse signals.

[0039] Example 4:

[0040] In some cases, the torsion angle is not a single-frequency signal, but a torsion angle signal that may contain interharmonics. Let the torsion angle signal be:

[0041]

[0042] Where A1 = 1; ω1 = 100π; A2 = 0.5; ω2=90π, then θ(t) n )=sin(100πt n )+0.5sin(90πt n );

[0043] achievable

[0044] Where t c The time it takes for the shaft system to rotate one revolution, that is, the time it takes to pass through 100 gears, i.e., t. c =t 100 We can obtain:

[0045] sin(100πt c )+0.5sin(90πt c ) = 0

[0046] Find the third zero of the equation, i.e., t. c . t c Once an error occurs, it accumulates over time, growing linearly. In actual time (t...), c During the test, it will also be affected by the sampling counting clock, therefore, when calculating the above signal t... c When using a time step consistent with the sampling clock during signal reconstruction (20MHz in this example), with a phase change of 2π points, the third zero-crossing point of the signal can be obtained. In this example, it is 0.02067815s.

[0047] Example 5:

[0048] The signals generated in Examples 1-4 are all stationary. In reality, the torsion angle signal may be multimodal, a time-varying interharmonic torsional vibration signal. Let the torsion angle signal be:

[0049]

[0050] Let A1 = 1; ε1 = 0.5; ω1=100π; A2=0.5; ε2=2; ω2=90π;

[0051] θ(t)=1e -0.5t sin(100πt) + 0.5e -2t sin(90πt);

[0052] Where t c 0.02066315s can be obtained by searching with a fixed step size of 20MHz;

[0053]

[0054] When N is set to 100, the tn sequence can be solved using the binary search method.

[0055] Example 6:

[0056] In practical torsion models, the influence of noise also needs to be considered. Gaussian noise is noise whose probability density function follows a normal distribution. The Gaussian distribution is denoted as N(μ) , σ 2 ), where μ is the mean (mathematical expectation) of the Gaussian distribution, σ 2 Let σ be the variance of the Gaussian distribution, when μ = 0, σ 2 When = 1, this distribution is called the standard normal distribution. The one-dimensional probability density of the Gaussian distribution can be expressed as:

[0057]

[0058] In Example 5, t is generated n Gaussian noise was added to the time series, and the amplitude of the Gaussian noise was 100dB higher than the signal-to-noise ratio of the measured sequence.

[0059] In summary, compared with mechanical torsional vibration test benches, this torsional vibration signal generator with time-varying interharmonics has a simple structure and complex test conditions. It can fully verify the accuracy of the torsional vibration analysis device, provide complex linear or multi-frequency signals, and evaluate the torsional vibration analysis device's processing of non-time-varying interharmonic signals.

[0060] It should be noted that, in this document, terms such as "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0061] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A time-varying intermodulation torsional vibration signal generator comprising a master controller (1), characterized in that: The input end of the main controller (1) is electrically connected with the output end of the first filter (4), the second filter (5) and the analog-digital module (6), the input end of the analog-digital module (7) is electrically connected with the output end of the third filter (6), the main controller (1) is bidirectionally electrically connected with the SRAM module (2), the FLASH module (3), the network card chip (8), the USB chip (9) and the RS232 module (10), the output end of the main controller (1) is electrically connected with the input end of the level module (12), the optocoupler (13) and the digital-analog module (14); Evaluate the torsional vibration analysis device for time-varying interharmonic signal processing; In the analog torsional vibration test, the signal is demodulated using a low-pass filter and an integrator to obtain the torsional angle signal. The digital torsional vibration meter acquires the pulse signal using a multi-pulse capture circuit (CAP). The demodulation of this signal is as follows: Assume the time for one rotation of the shaft is... From the formula The circumferential average angular velocity can be obtained as follows: The number of gear teeth is The time required to rotate n teeth is measured as follows: From the formula The average speed of the tooth can be obtained as follows: From the formula The angle of twist of the shaft can be obtained as follows: The formula can be obtained after integration. Therefore, as long as it is measured , That's it; the torsional vibration signal generator then uses the known torsional angle signal to inversely solve the sensor signal sequence, that is, to solve the formula... sequence, in formula If known, It can be obtained from a known twist angle signal. The actual number of gears in the simulation, i.e., the length of the sequence, is also known, so the equation can be solved to obtain the value. , as a twist angle signal; Based on the torsional angle signal to detect the analysis capability of the torsional vibration device, wherein the torsional angle signal includes a stationary signal or a multi-modal, time-varying interharmonic torsional vibration signal, the stationary signal includes a triangular wave signal, a sinusoidal signal related to the excitation frequency, and a torsional angle signal containing interharmonics; For the sinusoidal signal related to the excitation frequency, simulate such torsional vibration signals to detect the analysis capability of the torsional vibration device for such signals; Let the single frequency torsion angle signal be where then Substitute the formula into the formula to obtain the formula: ； Where is the average period of rotation, we have , represents the number of gears, here we take 100, n is the real-time through the gear number, 1-100, can be solved by dichotomy sequence, different from the case of linear torsion angle waveform, sequence is non-equidistant, by time series can generate simulated pulse signal; For the torsional angle signal containing interharmonics, let the torsional angle signal be: ； wherein then ; Available ; wherein is the time for one revolution of the shafting, i.e. the time for passing through 100 teeth, i.e. It follows that ； The third zero point of the equation is sought, i.e. , The error is accumulated over time, and the error increases linearly. In actual testing, the sampling clock will also have an impact, so when the above signals are calculated, the time step consistent with the sampling clock in signal reconstruction is used, which is 20 MHz in this example. The phase change point can be calculated to find the third zero point of the signal, which is 0.02067815 s in this example. For the torsional angle signal that may be a multi-modal, time-varying interharmonic torsional vibration signal, let the torsional angle signal be: ； Set ; ； wherein A 20 MHz step search can yield 0.02066315 s; ； N = 100, the bisection method can be used to solve sequence, and Gaussian noise with a signal-to-noise ratio of 100 dB is added to the generated tn time sequence.

2. A time-varying intermodulation torsional vibration signal generator according to claim 1, characterized in that: The network card chip (8), the USB chip (9) and the RS232 module (10) are bidirectionally electrically connected with the PC display screen (11).

3. A time-varying intermodulation torsional vibration signal generator according to claim 1, wherein: The output end of the optocoupler (13) is electrically connected with the input end of the relay (15).

4. A time-varying intermodulation torsional vibration signal generator according to claim 1, wherein: The first filter (4) and the second filter (5) are respectively electrically connected with the main controller (1) through the eQEP bus and the eCAP bus.

5. A time-varying intermodulation torsional vibration signal generator as defined in claim 1, wherein: The main controller (1) is respectively electrically connected with the level module (12) and the optocoupler (13) through the ePMW bus and the GPIO bus.

6. A time-varying intermodulation torsional vibration signal generator as defined in claim 1, wherein: The main controller (1) is electrically connected with the network card chip (8) and the USB chip (9) through the XINTF bus. The main controller (1) is electrically connected with the network card chip (8) and the USB chip (9) through the XINTF bus.

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