A method and device for diagnosing faults in an internal combustion engine based on instantaneous rotational speed

Abstract

The present application relates to the field of internal combustion engine diagnosis, and particularly relates to an internal combustion engine fault diagnosis method and device based on instantaneous speed. The present application discloses an internal combustion engine fault diagnosis method based on instantaneous speed, comprising the following steps: 1) collecting the speed signal of the internal combustion engine to be tested; 2) calculating the speed parameter of the internal combustion engine to be tested by using the speed signal of the internal combustion engine to be tested; 3) obtaining the fault interval data of the internal combustion engine; 4) comparing the speed parameter of the internal combustion engine to be tested with the fault interval data; and 5) outputting the comparison result. The present application uses the time domain and frequency domain waveforms of instantaneous speed and instantaneous speed fluctuation rate to jointly diagnose the running state of the internal combustion engine, thereby improving the accuracy of the diagnosis result.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of internal combustion engine diagnosis, in particular to an internal combustion engine fault diagnosis method and device based on instantaneous speed. BACKGROUND

[0002] In the development of industrial production, mechanical equipment occupies an important position, its running state affects the production efficiency and product quality of enterprises, and some important equipment is related to the fate of enterprises, which will bring huge economic losses and social influence if it fails. With the continuous development of economic society, the function of mechanical equipment is constantly improved, the structure of equipment is more and more complicated and automated, the number of parts is increasing, and the possibility and type of mechanical failure are more. There are many phenomena of serious consequences caused by mechanical equipment failure. For modern equipment, through the improvement of structure design and the improvement of process technology, the quality of the whole mechanical product is improved, and at the same time, the operation state of the equipment needs to be detected by modern scientific technology to prevent failure, so as to ensure the normal operation of the equipment. There are problems such as inconvenient installation and high price in the common diagnosis method, the instantaneous speed of internal combustion engine can reflect the smoothness of mechanical equipment, the torque of internal combustion engine, etc., which has important significance in actual research.

[0003] As early as the late 1970s and early 1980s, scholars have studied the method of diagnosing internal combustion engine failure by using instantaneous speed, which can detect internal combustion engine failures including misfire, cylinder combustion difference, piston ring gas leakage, etc. With the development of computer technology and signal analysis and processing technology, the use of instantaneous speed for internal combustion engine fault diagnosis and condition monitoring technology is becoming mature and practical, and the fault diagnosis device based on instantaneous speed diagnosis principle and related analysis system and instrument are also gradually developed. At present, the existing fault diagnosis device based on instantaneous speed of internal combustion engine in China needs to be matched with computer and sensor, and the instantaneous speed is analyzed and processed in real time through the software of computer terminal. The installation cost is high and almost no portability. With the development of the times, the computing power and function of MCU are rapidly improved, making it possible to use MCU for data analysis and calculation. Therefore, advanced MCU and diagnosis method should be used to design a fault diagnosis device based on instantaneous speed, which takes MCU as the control core, has fault diagnosis and speed measurement functions, and has high portability. SUMMARY

[0004] In order to overcome the above problems, the purpose of the present application is to provide an internal combustion engine fault diagnosis method and device based on instantaneous speed, which uses the time domain and frequency domain waveform of instantaneous speed and instantaneous speed fluctuation rate to diagnose the running state of internal combustion engine, and improves the accuracy of diagnosis results.

[0005] In order to achieve the above purpose, the internal combustion engine fault diagnosis method based on instantaneous speed designed by the present application is characterized by comprising the following steps:

[0006] 1) Acquire the speed signal of the internal combustion engine under test;

[0007] 2) Calculate the speed parameters of the internal combustion engine under test using the speed signal of the internal combustion engine under test: instantaneous speed difference a, instantaneous speed fluctuation rate difference b, speed harmonic order c, fluctuation rate harmonic order d, and amplitude e;

[0008] The instantaneous speed time-domain waveform, instantaneous speed fluctuation rate time-domain waveform, instantaneous speed frequency domain waveform, and instantaneous speed fluctuation rate frequency domain waveform of the internal combustion engine under test are obtained using the digital speed signal. The compression top dead center is then calculated using the instantaneous speed time-domain waveform of the internal combustion engine under test. to The instantaneous speed difference 'a' is calculated using the time-domain waveform of the instantaneous speed fluctuation rate of the internal combustion engine under test. to b) is the instantaneous speed fluctuation rate difference; c) is the speed harmonic order calculated from the instantaneous speed frequency domain diagram of the internal combustion engine under test; d) is the fluctuation rate harmonic order calculated from the instantaneous fluctuation rate frequency domain diagram of the internal combustion engine under test; e) is the amplitude calculated from the instantaneous speed frequency domain diagram of the internal combustion engine under test.

[0009] 3) Obtain internal combustion engine fault range data:

[0010] 3.1) Acquiring typical speed signals: Typical speed signals of internal combustion engines under normal conditions and single-cylinder fuel cut-off conditions are acquired using magnetoelectric sensors;

[0011] 3.2) Calculate typical speed parameters of an internal combustion engine using typical speed signals: A) Sum of instantaneous speed differences; B) Sum of instantaneous speed fluctuation rate differences; C) Harmonic order of typical speed; D) Harmonic order of typical fluctuation rate.

[0012] Using typical internal combustion engine speed signals, the following waveforms were calculated: instantaneous speed time-domain waveform, instantaneous speed fluctuation rate time-domain waveform, instantaneous speed frequency domain waveform, and instantaneous speed fluctuation rate frequency domain waveform under normal operating conditions; instantaneous speed time-domain waveform, instantaneous speed fluctuation rate time-domain waveform, instantaneous speed frequency domain waveform, and instantaneous speed fluctuation rate frequency domain waveform under single-cylinder fuel cut-off conditions; and the instantaneous speed time-domain waveforms under normal operating conditions and single-cylinder fuel cut-off conditions were used to calculate... to The sum of instantaneous speed differences A; calculated using the time-domain waveform diagrams of instantaneous speed fluctuation rate under single-cylinder fuel cut-off conditions of the internal combustion engine. to B; C; D; Calculate the typical speed harmonic order from the instantaneous speed fluctuation rate difference of the internal combustion engine under normal operating conditions using the instantaneous speed frequency domain diagram;

[0013] 3.3) Frequency Domain Analysis:

[0014] If c > C, d > D, and e > 0.1, the processor output frequency domain is abnormal; otherwise, the processor output frequency domain is normal.

[0015] 3.4) Set the internal combustion engine fault range data:

[0016] If a ≤ 25% * A, output: Normal;

[0017] If: 25%*A<a≤75%*A,b≥115%*B,output: Low fault alarm;

[0018] If 25%*A < a ≤ 75%*A, b < 115%*B, and the frequency domain is abnormal, output: low fault alarm;

[0019] If 25%*A < a ≤ 75%*A and b < 115%*B, and the frequency domain is normal, output: potential risk;

[0020] If: 75%*A<a≤105%*A,b≥108%*B,output: Low fault alarm;

[0021] If 75%*A < a ≤ 105%*A, b < 108%*B, and the frequency domain is abnormal, output: low fault alarm;

[0022] 75%*A < a ≤ 105%*A, b < 108%*B, and the frequency domain is normal, output: high potential risk;

[0023] If a > 105% * A; the processor outputs: High fault alarm;

[0024] 4) Compare the engine speed parameters to be tested with the data in the fault range;

[0025] 5) Output the comparison results.

[0026] As a preferred embodiment, the speed signal in step (1) is obtained by installing a gear disk on the internal combustion engine shaft and using a sensor to sense the change in magnetic gap between the tooth tip and tooth root of the gear disk to obtain a sinusoidal speed signal.

[0027] As a preferred embodiment, in step (1), after acquiring the speed signal of the internal combustion engine under test, a window function is used to filter the speed signal of the internal combustion engine under test; in step (3.1), a typical speed signal of the internal combustion engine is acquired and a window function is used to filter the typical speed signal.

[0028] As a preferred embodiment, the instantaneous rotational speed time-domain waveform diagram in step (2) is calculated as shown in formula (1):

[0029]

[0030] In the formula f s Let p be the sampling frequency, z be the number of teeth on the gear disk, and tooth averaging is used to reduce the influence of gear disk mechanical tolerances on instantaneous speed. i+2 -p i Equivalent to m is the number of teeth to be averaged, and the instantaneous rotational speed n is obtained. i The instantaneous rotational speed time-domain waveform is stored in the form of a linked list.

[0031] As a preferred embodiment, the calculation of the instantaneous speed fluctuation rate time-domain waveform in step (2) is as follows:

[0032] By querying the linked list to retrieve two consecutive instantaneous speed detection values ​​n[k] and n[k+1], with a time interval t = (p[k+1] - p[k]) / fs, the instantaneous speed fluctuation rate ε can be obtained. i :

[0033]

[0034] The instantaneous rotational speed fluctuation rate ε was obtained i The data is stored in a linked list to form a time-domain waveform diagram of instantaneous speed fluctuation rate.

[0035] As a preferred option, in step (2), the instantaneous speed frequency domain diagram and the instantaneous speed fluctuation frequency domain diagram are obtained by performing Fourier transform on the instantaneous speed and the instantaneous speed fluctuation, respectively.

[0036] An internal combustion engine fault diagnosis device based on instantaneous rotational speed, characterized in that it includes a gear disk, a sensor, a mounting bracket, and a monitoring module; the gear disk is mounted on the internal combustion engine shaft, the mounting bracket is fixed to the internal combustion engine housing, a magnetoelectric probe for sensing the rotation signal of the gear disk is fixed at one end of the mounting bracket, and the monitoring module is fixed at the other end of the mounting bracket; the monitoring module is connected to the magnetoelectric probe via a signal line; the monitoring module includes a signal receiving unit, a data processing unit, a fault range data storage unit, a comparison unit, and a diagnostic result output unit;

[0037] The signal receiving unit is used to receive the rotational speed signal of the internal combustion engine shaft;

[0038] The data processing unit is used to calculate the speed signal to obtain the speed parameters of the internal combustion engine under test;

[0039] The fault zone data storage unit is used to store fault zone data;

[0040] The comparison unit is used to compare the speed parameters of the internal combustion engine under test with the fault range data in the fault range data storage unit;

[0041] The diagnostic result output unit is used to output the comparison results.

[0042] As a preferred embodiment, the signal receiving unit obtains a sinusoidal speed signal by installing a gear disk on the internal combustion engine shaft and using a sensor to sense the change in magnetic gap between the tooth tip and tooth root of the gear disk.

[0043] As a preferred embodiment, the gear disk is provided with missing teeth for calibrating the waveform and ignition timing.

[0044] As a preferred embodiment, the monitoring module is a microcontroller.

[0045] The advantages of this invention are:

[0046] (1) This invention uses the time-domain and frequency-domain waveforms of instantaneous speed and instantaneous speed fluctuation rate to diagnose the operating status of internal combustion engines, thereby improving the accuracy of the diagnostic results.

[0047] (2) This invention uses MCU as the computing core, which reduces installation costs and has portability.

[0048] (3) In traditional equipment, the top dead center sensor is installed on the camshaft to detect the ignition timing of the cylinder. However, since a four-stroke internal combustion engine has a cycle of 720 degrees, and both its ignition point and scavenging point are located at top dead center, it is impossible to determine the ignition timing by missing teeth. In the internal combustion engine fault diagnosis device based on instantaneous speed of the present invention, a tooth is set on the gear disk to calibrate the waveform and the missing ignition timing. After receiving the speed signal, the signal is compared with the recorded standard signal. If the waveform and the position of the missing tooth do not match the standard signal, the waveform will be shifted by a specific angle according to the recorded internal combustion engine parameters to achieve calibration of the waveform and the ignition timing.

[0049] (4) This invention does not require a specific internal combustion engine model. It can automatically generate fault ranges by inputting external parameters and typical signals. It can be used for a variety of different devices and has universality. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the internal combustion engine fault diagnosis device based on instantaneous rotational speed according to the present invention;

[0051] 1. Gear disk; 2. Sensor; 3. Mounting bracket; 4. Monitoring module; 5. CANopen 4.1; 6. ModBus TCP 4.2;

[0052] Figure 2 This is a schematic diagram of the signal conditioning circuit of the present invention;

[0053] Figure 3 The instantaneous speed time-domain waveforms of the internal combustion engine under normal operating conditions and single-cylinder fuel cut-off conditions are shown.

[0054] Figure 4 The instantaneous speed fluctuation rate time-domain waveform diagram of an internal combustion engine under normal operating conditions and single-cylinder fuel cut-off conditions;

[0055] Figure 5 This is a frequency domain diagram of the instantaneous speed of an internal combustion engine under normal operating conditions.

[0056] Figure 6 This is a frequency domain diagram of the instantaneous speed fluctuation rate of an internal combustion engine under normal operating conditions.

[0057] Figure 7 This is a frequency domain diagram of the instantaneous speed of the internal combustion engine under test.

[0058] Figure 8 This is a frequency domain plot of the instantaneous speed fluctuation rate of the internal combustion engine under test. Detailed Implementation

[0059] To better understand the present invention, the invention will be described in detail below with reference to the accompanying drawings and specific examples.

[0060] Combination Figure 1 As shown, an internal combustion engine fault diagnosis device based on instantaneous rotational speed includes a gear disk 1, a sensor 2, a mounting bracket 3, and a monitoring module 4. The gear disk 1 is mounted on the internal combustion engine shaft, and the mounting bracket 2 is fixed to the internal combustion engine housing. A sensor 2 for sensing the rotation signal of the gear disk is fixed to one end of the mounting bracket 2; in this embodiment, the sensor 2 is a magnetoelectric probe. The monitoring module 4 is fixed to the other end of the mounting bracket 2; in this embodiment, the monitoring module 4 is a microcontroller (MCU). The MCU includes a signal receiving unit, a data processing unit, a fault range data storage unit, a comparison unit, and a diagnostic result output unit.

[0061] (1) The signal receiving unit is used to receive the rotational speed signal of the internal combustion engine shaft under test. The signal receiving unit first uses an industrial bus to receive the analog signal transmitted by the magnetoelectric probe. The industrial bus includes CANopen (4.1) and ModBus TCP (4.2), which are connected to the CAN peripheral and Ethernet peripheral of the microcontroller, respectively. In addition, a signal conditioning circuit is connected between the magnetoelectric probe and the signal receiving unit. The signal conditioning circuit combines... Figure 2As shown in the figure, the magnetoelectric probe is connected to a voltage follower and a decoupling capacitor to reduce shunt and prevent parasitic oscillation. The output of the voltage follower is connected to a proportional operational amplifier circuit to amplify the sine signal to a suitable amplitude and output it to the signal receiving unit of the single-chip microcomputer. A voltage stabilizing diode and a decoupling capacitor are connected in front of the signal receiving unit of the single-chip microcomputer to achieve overvoltage protection and prevent parasitic oscillation. The MCU uses the AD acquisition peripheral to convert the analog signal of the magnetoelectric sensor into a digital signal, and uses DMA to transfer the value of the AD acquisition register to the continuous memory space of the signal receiving unit that has been opened up. The DMA and data processing unit in the MCU are independent of each other and each has a separate data bus. Using DMA to transfer data can maximize the computing power of the MCU.

[0062] (2) The signal receiving unit outputs the rotational speed signal of the internal combustion engine shaft to the data processing unit. The data processing unit first filters the rotational speed signal of the internal combustion engine to be measured, and then calculates the rotational speed parameters of the internal combustion engine to be measured using the filtered rotational speed signal: instantaneous rotational speed difference a, instantaneous rotational speed fluctuation rate difference b, rotational speed harmonic order c, fluctuation rate harmonic order d, and amplitude e. The specific calculation process is as follows:

[0063] (2.1) Filter the rotational speed signal of the internal combustion engine to be measured:

[0064] The operation process of the FIR digital filter is as follows:

[0065] Design a type I window function FIR digital filter. The unit impulse response of the system is as follows:

[0066]

[0067] Ω is the angular frequency corresponding to the signal waveform, K is the number of AD sampling points, and M is the total sampling length. Window truncation of h d [k] gives h[k] = h d [k]W N [k]. In the formula, N = M + 1, and the value of W N [k] is 1 when K < N, and the value of W N [k] is 0 when K > N. Let the sampled data be x[K], and the filtered signal be y[k]. There is a conversion formula:

[0068] y[k] = h[k]x[k]

[0069] Using the DSP operation library in the MCU to perform the above operations on the sampled data can obtain a rotational speed signal with high signal-to-noise ratio, which is stored in the RAM for the MCU to call.

[0070] (2.2) Calculation of the instantaneous rotational speed time-domain waveform diagram:

[0071] The zero-crossing point of a sinusoidal signal is detected using interpolation. Two adjacent sample values, y[k] and y[k+1], are taken. If y[k]y[k+1] < 0, a zero-crossing point is determined to exist between k and k+1, and the point is selected. The instantaneous rotational speed n can be obtained. i as follows:

[0072]

[0073] In the formula f s Where is the MCU's AD sampling frequency, and z is the number of teeth on the gearbox. Tooth averaging is used to reduce the influence of gearbox mechanical tolerances on instantaneous rotational speed, i.e., p i+2 -p i Equivalent to m represents the number of teeth to be averaged. The obtained instantaneous rotational speed is stored in the MCU's RAM as a linked list to form the instantaneous rotational speed time-domain waveform, waiting to be modified or called.

[0074] (2.3) Calculation of the time-domain waveform of instantaneous speed fluctuation rate:

[0075] By querying the linked list to retrieve two consecutive instantaneous speed detection values ​​n[k] and n[k+1], and taking the time interval t = (p[k+1] - p[k]) / fs, the instantaneous speed fluctuation rate ε can be obtained. i :

[0076]

[0077] After performing the above transformation on the instantaneous rotational speed stored in RAM, the instantaneous rotational speed fluctuation rate and its instantaneous moment are stored in RAM again through a linked list to form the instantaneous rotational speed fluctuation rate time domain waveform, waiting to be modified or called.

[0078] (2.4) Calculation of instantaneous speed frequency domain plot and instantaneous speed fluctuation rate frequency domain plot

[0079] The radix-2 decimation-time FFT algorithm is used to perform Fourier transforms on instantaneous rotational speed and instantaneous rotational speed fluctuation rate. The formula for the Discrete Fourier Transform (DFT) is as follows: In the formula, m is the transformed frequency, N is the sampling length, and the FFT operation can decompose X[m] into:

[0080]

[0081] Further decomposition of x[2k] and x[2k+1] can further reduce the amount of computation. The program uses a structure array to store the real and imaginary parts of the signal, writes a sub-function for complex number operations, uses the bubble sort method to reorder x[k], selects the number of sampling points k as 2 to the power of n, completes n butterfly operations, and obtains the spectrum of instantaneous rotational speed and instantaneous rotational speed fluctuation rate. Let the real part of the data be a, the imaginary part be b, and the signal amplitude corresponding to frequency m be...

[0082] (2.5) Speed ​​parameters of the internal combustion engine to be tested

[0083] After calculating the compression top dead center from the instantaneous speed time-domain waveform of the internal combustion engine under test, to The instantaneous speed difference 'a' is calculated using the time-domain waveform of the instantaneous speed fluctuation rate of the internal combustion engine under test. to b) is the instantaneous speed fluctuation rate difference; c) is the speed harmonic order calculated from the instantaneous speed frequency domain diagram of the internal combustion engine under test; d) is the fluctuation rate harmonic order calculated from the instantaneous fluctuation rate frequency domain diagram of the internal combustion engine under test; e) is the amplitude calculated from the instantaneous speed frequency domain diagram of the internal combustion engine under test.

[0084] (3) Fault range data storage unit acquires internal combustion engine fault range data: The internal combustion engine fault range data is imported into the fault range data storage unit. The calculation process of the internal combustion engine fault range data is as follows:

[0085] (3.1) Acquiring typical speed signals: Typical speed signals of internal combustion engines under normal conditions and single-cylinder fuel cut-off conditions are acquired using magnetoelectric sensors.

[0086] (3.2) Calculate typical speed parameters of an internal combustion engine using typical speed signals: A) Sum of instantaneous speed differences; B) Sum of instantaneous speed fluctuation rate differences; C) Harmonic order of typical speed; D) Harmonic order of typical fluctuation rate.

[0087] First, the following waveforms are calculated using typical speed signals of an internal combustion engine: instantaneous speed time-domain waveform (wave 1), instantaneous speed fluctuation rate time-domain waveform (wave 2), instantaneous speed frequency-domain waveform (wave 3), and instantaneous speed fluctuation rate frequency-domain waveform (wave 4) under normal operating conditions; and instantaneous speed time-domain waveform (wave 5) and instantaneous speed fluctuation rate time-domain waveform (wave 6) under single-cylinder fuel cut-off conditions.

[0088] The methods for obtaining each wave are the same as in step (2) above, and will not be repeated here. Combined with... Figure 3 As shown, wave 1 and wave 5 are integrated into the crankshaft angle-speed diagram, and the calculation is performed in... to The sum of instantaneous speed differences A; combined with Figure 4 As shown, waves 2 and 6 are integrated into the crankshaft angle-instantaneous speed fluctuation rate diagram to calculate... to The sum of the instantaneous speed fluctuation rate differences B; combined with Figure 5 As shown, the typical speed harmonic order C is calculated; combined with Figure 6 As shown, the typical volatility harmonic order D is calculated;

[0089] 3.3) Frequency Domain Analysis:

[0090] If c > C, d > D, and e > 0.1, the processor output frequency domain is abnormal; otherwise, the processor output frequency domain is normal.

[0091] To illustrate frequency domain analysis, this embodiment combines... Figure 5 and Figure 7 As shown, the speed harmonic order c > the typical volatility harmonic order D; and combined with Figure 6 and Figure 8 As shown, the volatility harmonic order d > the typical volatility harmonic order D, and from Figure 7 As can be seen, the amplitude e > 0.1, therefore, the processor outputs "frequency domain anomaly".

[0092] 3.4) Set the internal combustion engine fault range data:

[0093] If a ≤ 25% * A, output: Normal;

[0094] If: 25%*A<a≤75%*A,b≥115%*B,output: Low fault alarm;

[0095] If 25%*A < a ≤ 75%*A, b < 115%*B, and the frequency domain is abnormal, output: low fault alarm;

[0096] If 25%*A < a ≤ 75%*A and b < 115%*B, and the frequency domain is normal, output: potential risk;

[0097] If: 75%*A<a≤105%*A,b≥108%*B,output: Low fault alarm;

[0098] If 75%*A < a ≤ 105%*A, b < 108%*B, and the frequency domain is abnormal, output: low fault alarm;

[0099] 75%*A < a ≤ 105%*A, b < 108%*B, and the frequency domain is normal, output: high potential risk;

[0100] If a > 105% * A; the processor outputs: High fault alarm.

[0101] (4) In the comparison unit, the speed parameters of the internal combustion engine under test are compared with the fault range data;

[0102] (5) The comparison results are output by the diagnostic result output unit.

[0103] The above-described embodiments are merely one implementation of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A fault diagnosis method for internal combustion engines based on instantaneous rotational speed, characterized in that, Including the following steps: 1) Acquire the speed signal of the internal combustion engine under test; 2) Calculate the speed parameters of the internal combustion engine under test using the speed signal of the internal combustion engine under test: instantaneous speed difference a, instantaneous speed fluctuation rate difference b, speed harmonic order c, fluctuation rate harmonic order d, and amplitude e; Using the digital speed signal, the instantaneous speed time-domain waveform, instantaneous speed fluctuation rate time-domain waveform, instantaneous speed frequency domain waveform, and instantaneous speed fluctuation rate frequency domain waveform of the internal combustion engine under test are obtained through calculation. The compression top dead center is then calculated from the instantaneous speed time-domain waveform of the internal combustion engine under test. to The instantaneous speed difference 'a' is calculated using the time-domain waveform of the instantaneous speed fluctuation rate of the internal combustion engine under test. to b) is the instantaneous speed fluctuation rate difference; c) is the speed harmonic order calculated from the instantaneous speed frequency domain diagram of the internal combustion engine under test; d) is the fluctuation rate harmonic order calculated from the instantaneous fluctuation rate frequency domain diagram of the internal combustion engine under test; e) is the amplitude calculated from the instantaneous speed frequency domain diagram of the internal combustion engine under test. 3) Obtain internal combustion engine fault range data: 3.1) Acquiring typical speed signals: Typical speed signals of internal combustion engines under normal conditions and single-cylinder fuel cut-off conditions are acquired using magnetoelectric sensors; 3.2) Calculate typical speed parameters of an internal combustion engine using typical speed signals: A) Sum of instantaneous speed differences; B) Sum of instantaneous speed fluctuation rate differences; C) Harmonic order of typical speed; D) Harmonic order of typical fluctuation rate. Using typical internal combustion engine speed signals, the following waveforms were calculated: instantaneous speed time-domain waveform, instantaneous speed fluctuation rate time-domain waveform, instantaneous speed frequency domain waveform, and instantaneous speed fluctuation rate frequency domain waveform under normal operating conditions; instantaneous speed time-domain waveform, instantaneous speed fluctuation rate time-domain waveform, instantaneous speed frequency domain waveform, and instantaneous speed fluctuation rate frequency domain waveform under single-cylinder fuel cut-off conditions; and the instantaneous speed time-domain waveforms under normal operating conditions and single-cylinder fuel cut-off conditions were used to calculate... to The sum of instantaneous speed differences A; The instantaneous speed fluctuation rate of an internal combustion engine under single-cylinder fuel cut-off conditions is calculated using the time-domain waveform diagrams. to B; C; D; Calculate the typical speed harmonic order from the instantaneous speed fluctuation rate difference of the internal combustion engine under normal operating conditions using the instantaneous speed frequency domain diagram; 3.3) Frequency Domain Analysis: If c > C, d > D, and e > 0.1, the processor output frequency domain is abnormal; otherwise, the processor output frequency domain is normal. 3.4) Set the internal combustion engine fault range data: If a ≤ 25% * A, output: Normal; If: 25%*A<a≤75%*A,b≥115%*B,output: Low fault alarm; If 25%*A < a ≤ 75%*A, b < 115%*B, and the frequency domain is abnormal, output: low fault alarm; If 25%*A < a ≤ 75%*A and b < 115%*B, and the frequency domain is normal, output: potential risk; If: 75%*A<a≤105%*A,b≥108%*B,output: Low fault alarm; If 75%*A < a ≤ 105%*A, b < 108%*B, and the frequency domain is abnormal, output: low fault alarm; 75%*A < a ≤ 105%*A, b < 108%*B, and the frequency domain is normal, output: high potential risk; If a > 105% * A; the processor outputs: High fault alarm; 4) Compare the engine speed parameters to be tested with the data in the fault range; 5) Output the comparison results.

2. The internal combustion engine fault diagnosis method based on instantaneous rotational speed according to claim 1, characterized in that, The speed signal in step 1) is obtained by installing a gear disk on the internal combustion engine shaft and using a sensor to sense the change in magnetic gap between the tooth tip and tooth root of the gear disk to obtain a sinusoidal speed signal.

3. The internal combustion engine fault diagnosis method based on instantaneous rotational speed according to claim 2, characterized in that, In step 1), after acquiring the speed signal of the internal combustion engine under test, a window function is used to filter the speed signal of the internal combustion engine under test; in step 3.1), a typical speed signal of the internal combustion engine is acquired and a window function is used to filter the typical speed signal.

4. The internal combustion engine fault diagnosis method based on instantaneous rotational speed according to claim 3, characterized in that, The instantaneous rotational speed time-domain waveform diagram in step 2) is calculated as shown in formula (1): In the formula f s Let p be the sampling frequency, z be the number of teeth on the gear disk, and tooth averaging is used to reduce the influence of gear disk mechanical tolerances on instantaneous speed. i+2 -p i Equivalent to m is the number of teeth to be averaged, and the instantaneous rotational speed n is obtained. i The instantaneous rotational speed time-domain waveform is stored in the form of a linked list.

5. The internal combustion engine fault diagnosis method based on instantaneous rotational speed according to claim 4, characterized in that, The calculation of the instantaneous speed fluctuation rate time-domain waveform in step 2) is as shown in formula (2): By querying the linked list to retrieve two consecutive instantaneous speed detection values ​​n[k] and n[k+1], with a time interval t = (p[k+1] - p[k]) / fs, the instantaneous speed fluctuation rate ε can be obtained. i : The instantaneous rotational speed fluctuation rate ε was obtained i The data is stored in a linked list to form a time-domain waveform diagram of instantaneous speed fluctuation rate.

6. The internal combustion engine fault diagnosis method based on instantaneous rotational speed according to claim 5, characterized in that, In step 2), the instantaneous speed frequency domain diagram and the instantaneous speed fluctuation frequency domain diagram are obtained by performing Fourier transforms on the instantaneous speed and the instantaneous speed fluctuation, respectively.

7. A fault diagnosis device for internal combustion engines based on instantaneous rotational speed, characterized in that, The system includes a gear disk, a sensor, a mounting bracket, and a monitoring module. The gear disk is mounted on the internal combustion engine shaft, and the mounting bracket is fixed to the internal combustion engine housing. A magnetoelectric probe for sensing the rotation signal of the gear disk is fixed to one end of the mounting bracket, and a monitoring module is fixed to the other end of the mounting bracket. The monitoring module is connected to the magnetoelectric probe via a signal line. The monitoring module includes a signal receiving unit, a data processing unit, a fault range data storage unit, a comparison unit, and a diagnostic result output unit. The signal receiving unit is used to receive the rotational speed signal of the internal combustion engine shaft; The data processing unit is used to calculate the speed signal to obtain the speed parameters of the internal combustion engine under test; The fault zone data storage unit is used to store fault zone data; The comparison unit is used to compare the speed parameters of the internal combustion engine under test with the fault range data in the fault range data storage unit; The diagnostic result output unit is used to output the comparison results.

8. The internal combustion engine fault diagnosis device based on instantaneous rotational speed according to claim 7, characterized in that, The signal receiving unit obtains a sinusoidal speed signal by installing a gear disk on the internal combustion engine shaft and using a sensor to sense the change in magnetic gap between the tooth tip and tooth root of the gear disk.

9. The internal combustion engine fault diagnosis device based on instantaneous rotational speed according to claim 8, characterized in that, The gear disk is equipped with missing teeth for calibrating the waveform and ignition timing.

10. The internal combustion engine fault diagnosis device based on instantaneous rotational speed according to claim 7, 8, or 9, characterized in that, The monitoring module is a microcontroller.

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