A signal determination method for an ultrasonic urea concentration sensor

Abstract

This invention provides a signal determination method for an ultrasonic urea concentration sensor, comprising: acquiring the echo signal of the ultrasonic urea concentration sensor and converting the echo signal into a current voltage energy value; determining whether the current voltage energy value is higher than a threshold line; when the current voltage energy value is higher than the threshold line, comparing it with energy line A and energy line B; when energy line A < current voltage energy value ≤ energy line B, outputting the current detection value of the sensor; when the threshold line < current voltage energy value ≤ energy line A, comparing the current voltage energy value with previously continuously received historical voltage energy values, and if the values ​​are stable, outputting the current detection value of the sensor; if a threshold jump occurs, maintaining the previous detection value. This invention, through the joint determination of the threshold line, energy line, and historical energy stability, can reduce the risk of urea concentration misjudgment caused by bubble interference and improve the reliability of the sensor output.

Description

Technical Field

[0001] This invention relates to the field of sensor signal processing technology for vehicle after-treatment systems, and in particular to a signal determination method for an ultrasonic urea concentration sensor. Background Technology

[0002] In diesel vehicle exhaust aftertreatment systems, urea solution concentration is one of the key parameters affecting the normal operation of the selective catalytic reduction (SCR) system. To detect urea solution concentration, ultrasonic urea concentration sensors are widely used in the industry. These sensors typically emit ultrasonic waves and receive the echo signals, calculating the urea concentration based on the propagation characteristics of the waves in the urea solution. These sensors offer advantages such as strong anti-interference capabilities, high detection accuracy, and low cost, making them widely used in vehicle urea concentration detection scenarios.

[0003] However, ultrasonic urea concentration sensors are susceptible to air bubbles during practical use. When ultrasonic waves encounter air bubbles in their propagation path, the bubbles alter the propagation path and echo waveform, distorting the echo signal received by the sensor and resulting in abnormal voltage energy values. If the sensor still treats this abnormal echo signal as a valid signal, it may output an incorrect urea concentration value, further causing the vehicle's guidance system to falsely issue a malfunction indicator lamp, impacting the user's driving experience. The technical briefing also clearly states that air bubbles affect the ultrasonic waveform, causing the sensor to output incorrect values.

[0004] In existing technologies, the reliability of ultrasonic urea concentration sensors is typically determined using a single threshold line. This involves converting the ultrasonic echo signal into a voltage energy signal and then determining whether the voltage energy value exceeds a preset threshold. Generally, signals above the threshold are considered reliable, while signals below the threshold are considered unreliable. The main difference between manufacturers lies in the varying threshold values ​​they set.

[0005] However, when the sensor is affected by bubble interference, the energy value of the invalid echo signal may also exceed the threshold. In this case, if a single threshold is still used for judgment, the invalid echo signal is easily misjudged as a valid signal, causing the sensor to output an incorrect urea concentration value. Therefore, the method of judging signal reliability solely by a single threshold has insufficient robustness, and a signal determination method that can distinguish between valid echo signals and abnormal echo signals affected by bubble interference is needed. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a signal determination method for an ultrasonic urea concentration sensor. By setting energy lines A and B above a threshold line and combining the stability comparison between the current echo energy value and historical continuous energy values, the echo signal of the ultrasonic urea concentration sensor is divided into zones for determination, thereby reducing the risk of sensor erroneous output caused by bubble interference.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a signal determination method for an ultrasonic urea concentration sensor, comprising the following steps:

[0008] S1: Acquire the echo signal from the ultrasonic urea concentration sensor and convert the echo signal into the current voltage energy value;

[0009] S2: Set the threshold line, energy line A, and energy line B;

[0010] S3: Determine whether the current voltage energy value is higher than the threshold line;

[0011] S31: If the current voltage energy value is not higher than the threshold line, it is determined that the current echo signal does not meet the requirements of a valid signal, and the current detected value is not used as a valid output value, or the previous detected value is maintained for output.

[0012] S32: If the current voltage energy value is higher than the threshold line, then compare the current voltage energy value with energy line A and energy line B;

[0013] S321: When energy line A < current voltage energy value ≤ energy line B, output the current detection value of the sensor;

[0014] S322: When the threshold line < current voltage energy value ≤ energy line A, compare the current voltage energy value with the N previously received historical voltage energy values.

[0015] S3221: If the current voltage energy value is stable relative to N historical voltage energy values, then output the current sensor detection value; if the current voltage energy value changes by a threshold relative to N historical voltage energy values, then maintain the previous detection value output.

[0016] Preferably, the energy line A is used to characterize the upper limit of the waveform signal energy value above a preset proportion after the sensor is subjected to bubble interference, and the energy line B is used to characterize the upper limit of the theoretical energy value of the output waveform of the sensor body.

[0017] Preferably, the energy line A is obtained based on statistical analysis of bubble resistance test data, and is the upper limit of the energy value of the waveform signal covering more than 90% of bubble interference.

[0018] Preferably, the energy line B is determined based on the hardware capabilities of the sensor waveform transmitter.

[0019] Preferably, N is an integer greater than or equal to 2.

[0020] Preferably, the stable state includes: the deviation between the current voltage energy value and N historical voltage energy values ​​is less than a preset deviation threshold; or, the current voltage energy value and N historical voltage energy values ​​form a continuous, smooth, and abrupt energy change trend.

[0021] Preferably, the threshold jump is when the deviation of the current voltage energy value from the average of historical voltage energy values ​​exceeds a preset deviation threshold, or when the rate of change of the current voltage energy value from the previous historical voltage energy value exceeds a preset rate of change threshold.

[0022] Preferably, step S32 further includes step S322: when the current voltage energy value is greater than the energy line B, it is determined that the current echo signal exceeds the theoretical energy range of the sensor, and the previous detection value is maintained, or the current detection value is not updated.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. This invention no longer relies solely on a single threshold line to determine the reliability of the echo signal. Instead, it further sets up energy lines A and B above the threshold line to perform partitioned judgment of the echo signal, thereby improving the precision of signal reliability judgment.

[0025] 2. The present invention sets up a historical continuous energy value comparison logic between the threshold line and the energy line A, which can identify energy mutations caused by bubble interference and avoid invalid echo signals being misjudged as valid signals because they are higher than the threshold line.

[0026] 3. When the energy value is between energy line A and energy line B, the present invention directly outputs the current detection value. When the energy value is between the threshold line and energy line A, it combines stability judgment to output or maintain the previous detection value, thereby taking into account both signal response speed and anti-bubble interference capability.

[0027] 4. By maintaining the detected value before the output when a significant change occurs, this invention can reduce the risk of the urea concentration sensor outputting incorrect values, reduce the probability of the vehicle guidance system falsely reporting a fault light, and improve the user's driving experience.

[0028] 5. This invention does not require changes to the hardware structure of the ultrasonic urea concentration sensor. It can improve the reliability of the sensor output simply by optimizing the signal judgment logic. It has the advantages of low implementation cost and strong applicability. Attached Figure Description

[0029] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0030] Figure 1 This is a flowchart illustrating the ultrasonic urea concentration sensor signal determination method in an embodiment of the present invention.

[0031] Figure 2 This is a schematic diagram of the voltage energy signal generated by the conversion of ultrasonic echo signal in an embodiment of the invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0033] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0034] It should be noted that similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, all directional indications (such as up, down, left, right, front, back, bottom, etc.) in this application are only used to explain the relative positional relationships and movements between components in a specific orientation (as shown in the figures). If the specific orientation changes, the directional indication will also change accordingly.

[0035] like Figure 1 and Figure 2 As shown, this embodiment provides a signal determination method for an ultrasonic urea concentration sensor to reduce the influence of air bubbles on the detection results of the ultrasonic urea concentration sensor, comprising the following steps:

[0036] In step S1, the echo signal from the ultrasonic urea concentration sensor is acquired, and the echo signal is converted into the current voltage energy value.

[0037] When the ultrasonic urea concentration sensor is working, it emits ultrasonic signals into the urea solution. These ultrasonic signals propagate through the urea solution and generate echo signals. The sensor receives these echo signals and converts them into voltage energy signals. The energy value of these voltage energy signals characterizes the intensity of the echo signals and serves as a basis for determining the reliability of the current detection value.

[0038] In step S2, the threshold line, energy line A, and energy line B are set.

[0039] In this embodiment, a threshold line, energy line A, and energy line B are pre-set. The threshold line is used for preliminary validity determination of the echo signal; energy line A characterizes the upper limit of waveform signal energy value above a predetermined percentage after the sensor is subjected to bubble interference, and energy line A is obtained through statistical analysis of a large amount of bubble resistance test data; energy line B characterizes the theoretical upper limit of the output waveform of the sensor body, and energy line B is related to the hardware capability of the sensor's waveform transmitter. In this embodiment, energy line A represents the upper limit of waveform signal energy value above 90% after bubble interference, energy line B represents the theoretical upper limit of the output waveform of the sensor body, and energy line A cannot replace the threshold line.

[0040] Furthermore, in some embodiments, the order of steps S1 and S2 can be interchanged.

[0041] In step 3, it is determined whether the current voltage energy value is higher than the threshold line.

[0042] S31: If the current voltage energy value is not higher than the threshold line, it is determined that the current echo signal does not meet the requirements of a valid signal, and the current detected value is not used as a valid output value, or the previous detected value is maintained.

[0043] In this embodiment, after the sensor acquires the current voltage energy value corresponding to the current echo signal, it first determines whether the current voltage energy value is higher than the threshold line. If the current voltage energy value is not higher than the threshold line, it indicates that the current echo signal energy is low and does not meet the basic requirements of a valid signal. The sensor does not use the current detected value as a valid output value, or maintains the previous detected value for output.

[0044] S32: If the current voltage energy value is higher than the threshold line, then compare the current voltage energy value with energy line A and energy line B.

[0045] S321: When energy line A < current voltage energy value ≤ energy line B, output the current detection value of the sensor.

[0046] When the current voltage energy value is greater than energy line A but not greater than energy line B, i.e., when "A < current voltage energy value ≤ B" is satisfied, it indicates that the current echo signal energy is within a relatively high and reasonable energy range, and the sensor directly outputs the current detected value. The current detected value can be the urea concentration value calculated based on the current echo signal.

[0047] S322: When the threshold line < current voltage energy value ≤ energy line A, compare the current voltage energy value with the N previously received historical voltage energy values.

[0048] When the current voltage energy value is greater than the threshold line but not greater than the energy line A, i.e., when the condition "threshold line < current voltage energy value ≤ A" is met, it indicates that although the current echo signal exceeds the threshold line, it is in an energy range with a high risk of bubble interference. At this time, the sensor does not directly output the current detected value, but instead compares the current voltage energy value with the N previously continuously received historical voltage energy values.

[0049] S3221: If the current voltage energy value is stable relative to N historical voltage energy values, output the current sensor detection value; if the current voltage energy value experiences a threshold jump relative to N historical voltage energy values, maintain the previous detection value output.

[0050] When the energy value is between A and B, the current judgment value is output directly; when the energy value is between the threshold line and A, it needs to be compared with the N energy values ​​received previously. If it is stable, the current detection value is output; if there is a significant jump, the previous detection value is maintained.

[0051] Specifically, the sensor can buffer N consecutive historical voltage energy values ​​received before the current voltage energy value, where N is an integer greater than or equal to 2. The sensor can calculate the average, variance, range, rate of change, or trend fit value based on the N historical voltage energy values, and determine whether the current voltage energy value is in a stable distribution state based on the above statistical parameters.

[0052] If the deviation between the current voltage energy value and the N historical voltage energy values ​​is within a preset allowable range, or if the current voltage energy value and the historical voltage energy values ​​form a continuous, smooth, and abrupt energy change trend, then it is determined that the distribution of the current voltage energy value compared with the previously received energy value is stable, and the sensor directly outputs the current detection value.

[0053] If the current voltage energy value experiences a threshold jump relative to historical voltage energy values—for example, if the deviation of the current voltage energy value from the historical average exceeds a preset deviation threshold, or if the rate of change of the current voltage energy value relative to the previous voltage energy value exceeds a preset rate of change threshold—then it is determined that the current echo signal may be affected by bubble interference. In this case, the sensor does not output the current detected value but maintains the previous detected value to avoid the urea concentration sensor erroneously outputting incorrect values ​​due to bubble interference.

[0054] Furthermore, step S32 also includes step S322: when the current voltage energy value is greater than the energy line B, it indicates that the current echo signal exceeds the theoretical energy range of the sensor. The sensor can determine that the current echo signal is abnormal and maintain the previous detection value output, or not update the current detection value.

[0055] Through the above settings, this embodiment does not simply use a single threshold line to determine the reliability of the ultrasonic urea concentration sensor signal. Instead, it further sets energy lines A and B above the threshold line and performs a secondary judgment on signals between the threshold line and energy line A by combining the stability of historical continuous energy values. This allows for the identification of energy abrupt changes caused by bubbles instantaneously passing through the ultrasonic propagation path, preventing invalid echo signals from being mistakenly identified as valid signals because they are above the threshold line. This reduces the risk of urea concentration misjudgment, decreases the probability of false alarms from vehicle guidance systems, and improves sensor output reliability and user driving experience.

[0056] The specific embodiments of the present invention have been described above. Based on the above description, those skilled in the art can make various changes and modifications without departing from the technical concept of the present invention.

Claims

1. A signal determination method for an ultrasonic urea concentration sensor, characterized in that, Includes the following steps: S1: Acquire the echo signal from the ultrasonic urea concentration sensor and convert the echo signal into the current voltage energy value; S2: Set the threshold line, energy line A, and energy line B; S3: Determine whether the current voltage energy value is higher than the threshold line; S31: If the current voltage energy value is not higher than the threshold line, it is determined that the current echo signal does not meet the requirements of a valid signal, and the current detected value is not used as a valid output value, or the previous detected value is maintained for output. S32: If the current voltage energy value is higher than the threshold line, then compare the current voltage energy value with energy line A and energy line B; S321: When energy line A < current voltage energy value ≤ energy line B, output the current detection value of the sensor; S322: When the threshold line < current voltage energy value ≤ energy line A, compare the current voltage energy value with the N previously received historical voltage energy values. S3221: If the current voltage energy value is stable relative to N historical voltage energy values, then output the current sensor detection value; if the current voltage energy value changes by a threshold value relative to N historical voltage energy values, then maintain the previous detection value output.

2. As described in claim 1, characterized in that, The energy line A is used to characterize the upper limit of the waveform signal energy value above a preset ratio after the sensor is subjected to bubble interference, and the energy line B is used to characterize the upper limit of the theoretical energy value of the output waveform of the sensor body.

3. As described in claim 1, characterized in that, The energy line A is obtained based on statistical analysis of bubble resistance test data and is the upper limit of the energy value of the waveform signal covering more than 90% of bubble interference.

4. As described in claim 1, characterized in that, The energy line B is determined based on the hardware capabilities of the sensor waveform transmitter.

5. As described in claim 1, characterized in that, N is an integer greater than or equal to 2.

6. As described in claim 1, characterized in that, The stable state includes: the deviation between the current voltage energy value and N historical voltage energy values ​​is less than a preset deviation threshold; or, the current voltage energy value and N historical voltage energy values ​​form a continuous, smooth, and abrupt energy change trend.

7. As described in claim 1, characterized in that, The threshold jump is defined as the deviation of the current voltage energy value from the average of historical voltage energy values ​​exceeding a preset deviation threshold, or the rate of change of the current voltage energy value relative to the previous historical voltage energy value exceeding a preset rate of change threshold.

8. As described in claim 1, characterized in that, Step S32 further includes step S322: when the current voltage energy value is greater than the energy line B, it is determined that the current echo signal exceeds the theoretical energy range of the sensor, and the previous detection value is maintained or the current detection value is not updated.

Images