KR102619849B1 - System and method for monitoring the purging process of a urea solution injection system - Google Patents

Abstract

The present invention discloses a system and method for monitoring the return process of a urea solution injection system, wherein the urea solution injection system includes a storage tank, a nozzle, and a pump connected between the storage tank and the nozzle through a fluid pipe, and a return process monitoring system. It includes a sensor module that detects the fluid pressure in the fluid pipe and a control module that controls the pump. After the return mode of the urea solution injection system starts, the sensor module has n (an integer of n≥2) data collection sections ( Pressure values within the fluid pipe are continuously collected at Δt), and digital signal processing is performed on the pressure values collected at each data collection section (Δt) to obtain frequency component data corresponding to the natural frequency of the pump, and the control module is n It is configured to determine whether the frequency component data and standard data obtained from the th data collection interval (Δt) follow the same distribution in terms of small sample statistics, and the return mode stop time is associated with the small sample statistical method analysis results.

Description

System and method for monitoring the return process of the urea solution injection system {SYSTEM AND METHOD FOR MONITORING THE PURGING PROCESS OF A UREA SOLUTION INJECTION SYSTEM}

The present invention relates to a system and method for monitoring the return process of a urea solution injection system used in diesel vehicles.

Currently, selective catalytic reduction (SCR) systems are widely used in diesel vehicles to treat engine exhaust gases due to environmental concerns. The SCR system mainly includes a urea solution injection system, and when necessary, the urea solution is sprayed into the engine exhaust pipe to treat nitrogen oxides in the engine exhaust gas in a non-polluting manner and discharge them to the outside.

Generally, each time the urea solution is sprayed, in order to prevent clogging due to urea solution crystals remaining in the fluid pipe and/or nozzle of the urea solution injection system, the urea solution injection system is sprayed with the remaining urea solution solution. The urea solution enters a return mode allowing it to be pumped into the storage tank of the injection system. In the prior art, regardless of whether the remaining urea solution was pumped cleanly, most return modes are set to run for a long time, such as 90 seconds.

However, sometimes the suction mode is still in operation even when the residual urea solution is less and the suction is faster (compared to the above time period), which not only results in wastage of diesel fuel but also increases the emission of pollutants. In addition, pumping The process does not need to last for a long time, as it causes unnecessary noise and at the same time affects the service life of the diesel engine.

The purpose of the present invention is to provide a system and method that can accurately determine the return mode end point of a urea solution injection system.

According to one aspect of the present invention, it is used in a urea solution injection system that passes through a storage tank, a nozzle, and a fluid pipe and includes a pump connected between the storage tank and the nozzle, and a sensor module that detects the fluid pressure in the fluid pipe. And a return process monitoring system including a control module for controlling the pump, wherein after the return mode of the urea solution injection system starts, the sensor module monitors the fluid in n (n is an integer of ≥2) data collection sections. Pressure values within the pipe are continuously collected, digital signal processing is performed on the pressure values collected in each data collection section to obtain frequency component data corresponding to the natural frequency of the pump, and the control module operates in the nth data collection section. A return process monitoring system for a urea solution injection system is provided that determines whether the obtained frequency component data and standard data follow the same distribution in terms of small sample statistics, and determines the return mode stop time according to the analysis results.

Additionally, the control module is configured to stop the return mode after the time or duration from starting the return mode.

Additionally, the small sample statistic is the T distribution statistic, i.e. the T test.

In addition, the standard data is collected after the return mode of the urea solution injection system starts, the sensor module collects the pressure value in the fluid pipe in the first data collection section, and digital signal processing is performed on the collected pressure value to Obtain frequency component data corresponding to the natural frequency of the pump.

In addition, the control module calculates the T value and the P value according to the T distribution statistical method for the frequency component data obtained from the nth data collection section and the standard data, and the T value is greater than a predetermined first threshold value, and P If the value is less than a predetermined second threshold, the time at which the return mode should be stopped is determined to be at or after the end of the nth data collection section.

In addition, the standard data collects the pressure value in the fluid pipe in one data collection section after the return mode of the urea solution injection system starts when there is only air in the fluid pipe and/or the nozzle. Then, digital signal processing is performed on the collected pressure values to obtain frequency component data corresponding to the natural frequency of the pump.

In addition, the control module calculates the T value and the P value according to the T distribution statistical method for the frequency component data obtained from the nth data collection section and the standard data, and the T value is less than a predetermined third threshold value, and P If the value is less than a predetermined second threshold, the time at which the return mode should be stopped is determined to be at or after the end point of the nth data collection section.

Additionally, the digital signal processing is DFT.

Additionally, the natural frequency of the pump is 8.33Hz; and/or the data collection period is 6 seconds.

Additionally, the duration is 90 seconds.

According to another aspect of the present invention, a return process monitoring method used in a urea solution injection system comprising a storage tank, a nozzle, and a pump connected between the storage tank and the nozzle via a fluid plate, comprising:

After the return mode of the urea solution injection system starts, continuously collecting pressure values in the fluid pipe in n (an integer of n≥2) data collection sections;

Obtaining frequency component data corresponding to the natural frequency of the pump by performing digital signal processing on the pressure values collected in each data collection section; and

It includes determining whether the frequency component data and standard data obtained from the nth data collection section follow the same distribution in terms of small sample statistics, and determining the return mode stop time according to the analysis results.

By adopting the above-described technical means of the present invention, the end time of the return mode of the urea solution injection system can be accurately determined, reducing the waste of fuel in diesel vehicles, reducing the emission of exhaust gas pollutants and noise in the return mode. The duration can be shortened.

The above and other contents of the present invention will be more fully understood through the detailed description below with reference to the drawings. It should be noted that the proportions of each drawing may be different for accurate description, but this does not affect the understanding of the present invention. In the drawing:
Figure 1 schematically shows a system block diagram of a urea solution injection system used in diesel vehicles.
Figure 2 shows the frequency at the natural operating frequency of the pump of the urea solution injection system obtained through Fourier transformation of the pressure signal in the fluid pipe measured respectively in a state filled with liquid and in a state with only air. Signal components are schematically represented.
Figure 3 schematically shows the results of analysis of pressure data in the fluid pipe detected in the return mode of the urea solution injection system through the T test.
Figure 4 schematically shows a method for monitoring the return process of the urea solution injection system according to an embodiment of the present invention.

In each drawing of the present invention, features that have the same structure or similar functions are denoted by the same reference numerals.

Figure 1 schematically shows a system block diagram of a urea solution injection system used in a diesel vehicle. The urea solution injection system generally includes a storage tank 100 for storing the urea solution, a nozzle 300, and a pump 200 connected through a fluid pipe between the storage tank 100 and the nozzle 300. Includes. The pump 200 is used to pump the urea solution from the storage tank 100 through a fluid pipe to the nozzle 300 to selectively and controllably inject the urea solution into the engine exhaust pipe of a diesel vehicle (not shown).

Each time the nozzle 300 completes the urea solution injection process, the pump 200 operates in the reverse direction so that the urea solution remaining in the fluid plate and/or the nozzle 300 is returned to the storage tank 100. . Finally, the nozzle 300 communicates with the atmosphere.

The urea solution injection system further includes a sensor module 400 and a control module 500. For example, the sensor module 400 may be any type of fluid pressure sensor known to those skilled in the art, and as shown in FIG. 1, is installed in the fluid pipe of the urea solution injection system to detect the fluid. Detects the fluid pressure state in the pipe. The control module 500 is connected to data from the pump 200 and the sensor module 400, controls the operation of the pump 200, and receives pressure measurement data in the fluid pipe from the sensor module 400. Control module 500 includes a computer. For example, the control module 500 may be an electronic control unit (ECU) of a diesel vehicle.

Generally, in the return mode of the urea solution injection system, the fluid pressure value in the fluid pipe measured by the sensor module 400 is the initial return (there is still a large amount of urea solution in the fluid pipe and/or nozzle 300). remain) and the return phase (there is only air in the fluid pipe and/or nozzle 300, and almost no urea solution exists) are different from each other.

The sensor module 400 samples 250 data points within each time zone at a sampling time interval of 20 milliseconds, and returns mode when there is only a urea solution in the fluid pipe and/or nozzle 300, and the fluid pipe and /or collect pressure data for the return mode when there is only air in the nozzle 300, and perform a discrete Fourier transform (DFT) on the collected pressure data to remove the influence of other background noise on the collected data. Calculations are made, and the frequency component of the natural frequency of the pump 200 (8.33 Hz in the present invention) is obtained and displayed in FIG. 2.

The abscissa (T) in Figure 2 represents time, and the ordinate (A) represents the amplitude of the 8.33 Hz harmonic at each time (corresponding to each black dot). As shown, the return mode of the urea solution injection system lasted 90 seconds from start to finish. Line (1) represents data processing results obtained when there is only a urea solution in the fluid pipe and/or nozzle 300, and line (2) represents data processing results obtained when there is only air in the fluid pipe and/or nozzle 300. Shows the results. Although it is impossible to distinguish between the two frequency components of line (1) and line (2) by directly observing them, in the present invention, the two data (1) and data (2) were processed using a small sample statistical method. .

In the present invention, the small sample statistical method is preferably T distribution statistics or T test. For specific technical information related to statistics, please refer to Wikipedia (https://en.wikipedia.org/Student%27s_t-test).

The data (line) 1 and data (line 2) of FIG. 2 are processed according to the T test, especially the 2-sample-T test. Here, the premise of conducting a T test, especially a 2-sample T test, on two data sets is that the "null hypothesis" of the T test is that the mean values of the distributions of the two data are the same, that is, the two data conform to the same distribution. It will happen. The “alternative hypothesis” is that the difference in the mean values of the distributions of the two data is large, that is, the two data do not conform to the same distribution. Calculating on this premise, the T value of the T test is 7.12, and the P value is 0.000. In the present invention, the T value indicates that there is a slight standard deviation difference between the mean values of the two data distributions, and the P value indicates the probability of rejecting the “null hypothesis” if the “null hypothesis” is true.

Therefore, the main concept of the present invention is as follows. In the return mode of the urea solution injection system, a small sample statistical analysis was performed on the specific frequency component of the pressure data detected in the fluid pipe in real time, and the distribution of pressure data measured in real time in the fluid pipe and the distribution of pressure data when only the urea solution was present were performed. If the pressure data distribution difference is too large or the pressure data distribution difference when only air is too small, it is determined that the remaining urea solution in the fluid pipe of the urea solution injection system has already been returned cleanly, and the urea solution injection system's Return mode must be exited.

Figure 3 schematically shows the analysis results of pressure data in the fluid pipe measured in the return mode of the urea solution injection system through the T test, where the pressure data is continuously collected through multiple data collection sections with each data collection section being 6 seconds. Measure. All collected pressure data were obtained through DFT processing. The data processed for the first 6 seconds after the return mode measurement started was taken as standard data by the frequency component of 8.33Hz, and the data obtained by processing every subsequent 6 seconds and the above standard data were used. By comparing and calculating through the T test, the T value (T _lim ) and P value (P _lim ) are determined correspondingly. In the T test calculation mentioned here, the "null hypothesis" is that the mean value of the data distribution obtained by processing every 6 seconds following the standard data is the same, and the "alternative hypothesis" is the data obtained by processing every 6 seconds following the standard data. The difference in the mean values of the distributions is very large.

The abscissa in Figure 3 represents time, the unit is seconds, and the left ordinate and right ordinate are T obtained through a T test for two data (i.e. standard data and subsequent data obtained by processing every 6 seconds), respectively. Indicates the value (T _lim ) and the P value (P _lim ). As shown in the figure, T=O at time 6 seconds, which is equivalent to a simultaneous comparison with the data processed during the first 6 seconds. As time passes, the P value gradually decreases and the T value gradually increases. Therefore, if we determine that the T value exceeds a certain limit value and the P value is less than a certain limit value, the data processed for the current 6 seconds is already the data processed for the first 6 seconds (i.e., the pressure when only the urea solution is in the fluid pipe). It can be judged that there is a very large distribution difference with the data). In other words, it can be determined that only air has already passed through the fluid pipe in the current 6 second section.

For Figure 3, the limit value of the T value is set to 3, and the limit value of the P value is set to 0.005. Therefore, at time t0=24 seconds, if the T value exceeds 3 and the P value is less than 0.005, it is determined that there is only air in the fluid pipe, that is, the return mode should be stopped. According to experimental observations, the time when only air actually exists in the fluid pipe is t1 = 21 seconds. Therefore, it was demonstrated that the stop time of the return mode can be determined more accurately by processing the pressure data using a small sample statistical method. Additionally, it is clear to those skilled in the art that by changing the data collection period (e.g., reducing it to 5 seconds, 4 seconds, or less), the accuracy of the determined return mode stop time can be further improved.

In one embodiment, the return process monitoring system of the urea solution injection system of the present invention may include a sensor module 400 and a control module 500 to realize the above-mentioned concept. In the present invention, the term "return" refers to generating negative pressure in the fluid pipe by the action of the pump 200 so that the fluid in the nozzle 300 and/or the fluid pipe flows from the nozzle 300 through the fluid pipe to the storage tank 100. ) refers to ensuring that there is no choice but to return to the direction.

Figure 4 schematically shows a method for monitoring the return process of the urea solution injection system according to an embodiment of the present invention. In step S10, the data collection period (Δt) used in the return mode of the urea solution injection system and the duration of the return mode (td) are determined. For example, Δt=6 seconds, td=90 seconds. In step S20, the return mode of the urea solution injection system is operated. In step S30, the pressure value in the fluid pipe is collected in the first data collection section Δt using the sensor module 400, and DFT technology is used. The collected pressure values are processed to obtain frequency component data corresponding to the natural frequency (e.g., 8.33 Hz) of the pump 200, and the frequency component data is maintained as standard data. For those skilled in the art, it is clear that within each data collection interval Δt, the sampling rate of data is determined by the detection device actually used.

In step S40, the pressure value in the fluid pipe at the nth data collection section (ΔT) is collected using the sensor module 400, and the collected pressure value is processed using DFT technology to obtain a unique value of the pump 200. Obtain the nth frequency component data corresponding to the frequency (e.g., 8.33Hz), where n is an integer equal to 2. In step S50, it is analyzed whether the nth frequency component data and the standard data obtained in step S30 follow the same distribution in terms of small sample statistics, and the T value and P value are calculated. In step S60, it is determined whether the T value obtained in step S50 is greater than the first limit value (T _lim ), and at the same time, it is determined whether the P value obtained in step S50 is less than the second limit value (P _lim ). For example, in Figure 4, T _lim =3 and P _lim =0.005. If the determination result in step S60 is “Yes,” the process proceeds to step S90, and the return mode is immediately stopped. If the determination result of step S60 is “No”, the process proceeds to step S70. In step S70, it is determined whether the return mode has been performed beyond the duration (td) of the return mode determined in step S10. If the determination result of step S70 is “Yes,” the process proceeds to step S90, and the return mode is immediately stopped. If the determination result of step S70 is “No”, the process proceeds to step S80. In step S80, n=n+1, and the process goes back to step S40.

It is clear to those skilled in the art that the method shown in FIG. 4 can be adjusted as needed, for example by changing the order of steps S10 and S20. In the method shown in FIG. 4, the pressure frequency component data collected in the first time interval (Δt) and processed correspondingly are used as standard data, which means that only the urea solution is present in the fluid pipe in the first time interval (Δt). It is conditional on doing so.

In another embodiment, the standard data is to pre-evacuate the fluid pipe and/or nozzle 300 and then continue to operate the pump 200 to allow the urea solution injection system to enter the return mode to obtain a time interval (Δt ), the pressure frequency component data can also be collected and processed accordingly to become standard data. In the above alternative embodiment, the standard data embodies the case where there is only air in the fluid pipe, that is, in the above alternative embodiment, the T value obtained in step S50 through the appropriate T test calculation is different from the first limit value. It must be determined whether it is smaller than the threshold value (T _lim ), and at the same time, it must be determined whether the P value obtained in step S50 is smaller than the second threshold value (P _lim ).

It is clear to those skilled in the art that the steps of the above-described method can be performed by the sensor module 400 and the control module 500 of the return process monitoring system of the urea solution injection system of the present invention.

In the above-described embodiment, processing the collected pressure values to obtain frequency component data corresponding to the natural frequency of the pump 200 is realized using DFT technology. It is obvious to those skilled in the art that frequency component data corresponding to the natural frequency of the pump 200 can be obtained by using other appropriate digital signal processing techniques such as wavelet transform in the present invention.

Although specific implementation methods of the present invention have been described above, these examples are provided for the purpose of interpreting the present invention and should not be construed as limiting the scope of the present invention. Additionally, it is clear to those skilled in the art that the embodiments described in this specification can be used in combination with each other. Various substitutions, changes and modifications may be considered on the premise that they do not deviate from the spirit and scope of the present invention.

Claims (20)

It is used in a urea solution injection system including a storage tank 100, a nozzle 300, and a pump 200 connected between the storage tank 100 and the nozzle 300 through a fluid pipe, and within the fluid pipe. A return process monitoring system including a sensor module 400 that detects fluid pressure and a control module 500 that controls the pump 200,
After the return mode of the urea solution injection system starts, the sensor module 400 continuously collects pressure values in the fluid pipe in n (integers of n ≥ 2) data collection sections Δt, and each data Digital signal processing is performed on the pressure value collected in the collection section (Δt) to obtain frequency component data corresponding to the natural frequency of the pump 200,
The control module 500 determines whether the frequency component data and standard data obtained from the nth data collection period (Δt) follow the same distribution in terms of small sample statistics, and determines the return mode stop time according to the analysis result. A return process monitoring system for a urea solution injection system, characterized in that. According to claim 1,
The control module 500 is configured to stop the return mode after the time or a duration (td) from starting the return mode. The method of claim 1 or 2,
A return process monitoring system for a urea solution injection system, characterized in that the small sample statistics are T distribution statistics. The method of claim 1 or 2,
The standard data collects the pressure value in the fluid pipe in the first data collection section Δt after the return mode of the urea solution injection system starts, and the sensor module 400 provides a digital signal for the collected pressure value. A return process monitoring system for a urea solution injection system, characterized in that the frequency component data corresponding to the natural frequency of the pump 200 is obtained through processing. According to claim 4,
The control module 500 calculates the T value and the P value for the frequency component data obtained from the nth data collection section (Δt) and the standard data according to the T distribution statistical method, and the T value is a predetermined first limit value. (T _lim ), and if the value of P is less than a predetermined second limit value (P _lim ), the time at which the return mode should be stopped is configured to determine at or after the end of the nth data collection period (Δt). A return process monitoring system for a urea solution injection system, characterized in that. The method of claim 1 or 2,
The standard data is collected from the sensor module 400 in one data collection section Δt after the return mode of the urea solution injection system starts when there is only air in the fluid pipe and/or the nozzle 300. A return process monitoring system for a urea solution injection system, characterized in that it collects pressure values within the fluid pipe and performs digital signal processing on the collected pressure values to obtain frequency component data corresponding to the natural frequency of the pump 200. . According to claim 6,
The control module 500 calculates the T value and the P value for the frequency component data obtained from the nth data collection section (Δt) and the standard data according to the T distribution statistical method, and the T value is set to a predetermined third threshold. (T _lim ), and if the value of P is less than a predetermined second threshold (P _lim ), the return mode is configured to determine the time at which the return mode should be stopped at or after the end point of the nth data collection period (Δt). A return process monitoring system for a urea solution injection system. The method of claim 1 or 2,
A return process monitoring system for a urea solution injection system, characterized in that the digital signal processing is DFT. The method of claim 1 or 2,
The natural frequency of the pump 200 is 8.33Hz; And/or the data collection period (Δt) is a return process monitoring system for a urea solution injection system, characterized in that 6 seconds. According to claim 2,
The return process monitoring system for the urea solution injection system, characterized in that the duration (td) is 90 seconds. As a return process monitoring method used in a urea solution injection system including a storage tank 100, a nozzle 300, and a pump 200 connected between the storage tank 100 and the nozzle 300 through a fluid pipe, ,
After the return mode of the urea solution injection system starts, continuously collecting pressure values in the fluid pipe in n (integers of n≥2) data collection sections (Δt);
Obtaining frequency component data corresponding to the natural frequency of the pump 200 by performing digital signal processing on the pressure values collected in each data collection section Δt; and
Determining whether the frequency component data and standard data obtained from the nth data collection section (Δt) follow the same distribution in terms of small sample statistics, and determining the return mode stop time according to the analysis results; comprising; Method for monitoring the return process of a urea solution injection system. According to claim 11,
A urea solution, characterized in that the control module 500 for controlling the pump 200 is configured to stop the return mode after the return mode stop time or a duration (td) from starting the return mode. Method for monitoring the return process of an injection system. The method of claim 11 or 12,
A method for monitoring the return process of a urea solution injection system, characterized in that the small sample statistics are T distribution statistics. According to claim 13,
The standard data collects the pressure value in the fluid pipe in the first data collection section (Δt) after the return mode of the urea solution injection system starts, and digital signal processing is performed on the collected pressure value to generate the pump (200) ) A method for monitoring the return process of a urea solution injection system, characterized by obtaining the natural frequency and corresponding frequency component data. According to claim 14,
The T value and P value are calculated according to the T distribution statistical method for the frequency component data obtained from the nth data collection section (Δt) and the standard data, and the T value is greater than a predetermined first threshold (T _lim ), If the P value is less than a predetermined second limit value (P _lim ), the urea solution injection system is characterized in that the time at which the return mode should be stopped is determined at or after the end of the nth data collection period (Δt). How to monitor the return process. The method of claim 11 or 12,
The standard data collects the pressure value in the fluid pipe in one data collection section (Δt) after the return mode of the urea solution injection system starts when there is only air in the fluid pipe and/or the nozzle 300, and , A method for monitoring the return process of a urea solution injection system, characterized in that the collected pressure values are digitally processed to obtain frequency component data corresponding to the natural frequency of the pump 200. According to claim 16,
The T value and P value are calculated according to the T distribution statistical method for the frequency component data obtained from the nth data collection section (Δt) and the standard data, and the T value is less than a predetermined third threshold (T _lim ), If the P value is less than a predetermined second limit value (P _lim ), the time at which the return mode should be stopped is determined to be at or after the end point of the nth data collection period (Δt). How to monitor the return process. The method of claim 11 or 12,
A method for monitoring the return process of a urea solution injection system, wherein the digital signal processing is DFT. The method of claim 11 or 12,
A method for monitoring the return process of a urea solution injection system, characterized in that the natural frequency of the pump 200 is 8.33 Hz and/or the data collection period (Δt) is 6 seconds. According to claim 12,
The return process monitoring method of the urea solution injection system, characterized in that the duration (td) is 90 seconds.

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