A two-dimensional calibration method for a nitrogen oxide sensor output

Abstract

The application belongs to the field of automobile exhaust aftertreatment, and particularly relates to a two-dimensional calibration method for output results of a nitrogen oxide sensor, comprising the following steps: constructing a ratio table between accurate nitrogen oxide concentration values and corresponding nitrogen oxide concentration test values under different oxygen concentration and nitrogen oxide concentration environments, taking the oxygen concentration and the nitrogen oxide concentration test values as indexes of oxygen concentration and nitrogen oxide concentration in the ratio table respectively, determining the ratio, and correcting the nitrogen oxide concentration test values; constructing a ratio table between accurate oxygen concentration values and corresponding oxygen concentration test values under different second chamber pump currents Ip1 and different oxygen concentration environments, taking the current Ip1 corresponding to the oxygen concentration test value and the oxygen concentration test value as indexes of Ip1 and oxygen concentration in the ratio table respectively, determining the ratio, and correcting the oxygen concentration test values; and finally setting a control target parameter of Ip1 in dynamic control of the nitrogen oxide sensor, and applying the ratio table to the output of the nitrogen oxide sensor. The application can improve the measurement accuracy of the sensor and accelerate dynamic response tracking.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of automobile exhaust aftertreatment, and more particularly relates to a two-dimensional calibration method for output results of a nitrogen oxide sensor. BACKGROUND

[0002] With the continuous upgrading of emission standards, the internal combustion engine industry has been unable to meet the requirements of energy saving and emission reduction in the technical route. In order to save energy, it is necessary to improve fuel utilization, and nitrogen oxide NOx is generated under high-temperature oxygen-rich conditions, which is more and more paid attention to by people due to its environmental pollution and harm to human health. The concentration detection and emission control technology is the most advanced and popular research field in the world at present. Nitrogen oxide NOx sensor is mainly divided into two categories based on zirconia solid electrolyte and metal oxide semiconductor from the material, and the metal oxide semiconductor material is not suitable for use in complex vehicle environment due to poor stability and short service life.

[0003] The only mature and commercialized vehicle nitrogen oxide sensor at present is a current type nitrogen oxide sensor based on the limiting current working principle of zirconia solid electrolyte material, which is composed of a nitrogen oxide sensor measuring probe and a controller, and can simultaneously complete oxygen concentration and nitrogen oxide concentration detection by relying on three pump cells.

[0004] The upgrading of emission regulations puts forward higher requirements for the purification efficiency of the aftertreatment system, thereby putting forward higher requirements for the measurement accuracy of the nitrogen oxide sensor, so that its accuracy requirement reaches within 10 ppm. The measurement accuracy of the nitrogen oxide sensor is influenced by many factors such as the output characteristics of the core ceramic sensing chip, the activity of the sensing electrode, the cross-sensitivity, the calibration process, and the dynamic control effect of the matching controller. Firstly, the oxygen concentration and nitrogen oxide concentration measurement output electric signals and atmosphere concentration signals of the nitrogen oxide sensor are theoretically linear characteristics, but are influenced by factors such as temperature, sensitive atmosphere, and zero point bias in the application process, and have certain nonlinear characteristics. In addition, due to the complexity of the material and process of the core ceramic sensing chip of the nitrogen oxide sensor, the actual product cannot achieve 100% consistency. In actual application, the one-dimensional linear calibration alone cannot meet the measurement accuracy requirements of the nitrogen oxide sensor in the full amount of 0-3000 ppm. In addition, in the actual vehicle application, the working conditions are complex, and higher requirements are put forward for the dynamic control measurement response speed and anti-interference ability of the sensor

[0005] Therefore, it is necessary to adopt a suitable calibration method to improve the calibration accuracy and optimize the dynamic control of the nitrogen oxide sensor. SUMMARY

[0006] In view of the defects and improvement needs of the prior art, the present application provides a two-dimensional calibration method for output results of a nitrogen oxide sensor, which aims to improve the calibration accuracy of the nitrogen oxide sensor.

[0007] To achieve the above object, according to one aspect of the present application, a two-dimensional calibration method for nitrogen oxide sensor output results is provided, comprising:

[0008] S1, collecting oxygen concentration test values and nitrogen oxygen concentration test values output by a nitrogen oxide sensor;

[0009] S2, taking the oxygen concentration test values and the nitrogen oxygen concentration test values as indexes of oxygen concentration and nitrogen oxygen concentration in a first two-dimensional ratio table respectively, and determining a ratio by using a bilinear two-dimensional interpolation calculation method; calculating the product between the ratio and the nitrogen oxygen concentration test values to obtain corrected nitrogen oxygen concentration test values, thereby completing calibration of nitrogen oxide sensor output results;

[0010] The first two-dimensional ratio table is obtained by using the following construction method: setting a first oxygen concentration in an atmosphere table environment, changing the nitrogen oxygen concentration in the environment under the oxygen concentration, collecting nitrogen oxygen concentration test values output by the nitrogen oxide sensor based on a first reference linear relationship under different nitrogen oxygen concentrations, the first reference linear relationship is constructed under a second oxygen concentration environment different from the first oxygen concentration, and represents a linear relationship between a third chamber pump current and nitrogen oxygen concentration test output; obtaining the nitrogen oxygen concentration values calculated by the first reference linear relationship under the second oxygen concentration environment corresponding to the different nitrogen oxygen concentrations as nitrogen oxygen concentration accurate values; calculating the ratio of each nitrogen oxygen concentration accurate value to the corresponding nitrogen oxygen concentration test value; changing the first oxygen concentration in the atmosphere table environment, repeating the step, and thereby constructing a two-dimensional ratio table of the ratio between the nitrogen oxygen concentration accurate values and the corresponding nitrogen oxygen concentration test values under different first oxygen concentrations and different nitrogen oxygen concentrations.

[0011] The present application proposes to further correct the nitrogen oxygen concentration test values detected and output by the nitrogen oxide sensor, and the correction method is as follows: taking the oxygen concentration test values and the nitrogen oxygen concentration test values obtained by the sensor as indexes of oxygen concentration and nitrogen oxygen concentration in a two-dimensional ratio table respectively, determining a ratio by using a bilinear two-dimensional interpolation calculation method; calculating the product between the ratio and the nitrogen oxygen concentration test values to obtain corrected nitrogen oxygen concentration test values. In the construction of the two-dimensional ratio table, the calibration method including calibration atmosphere oxygen concentration and calibration atmosphere nitrogen oxide concentration is designed based on the linear output characteristics of the oxygen concentration and the nitrogen oxide concentration measured by the nitrogen oxide sensor. Considering that the basic principle of the nitrogen oxide sensor is based on the oxygen ion conduction function of high-temperature zirconia solid electrolyte and the limiting current principle, and the electrode characteristics of the ceramic chip affect the calibration output linear characteristics, the present application uses a two-dimensional linear interpolation calibration algorithm to eliminate the influence of oxygen concentration dependence on real-time measurement of nitrogen oxygen concentration, and can solve the problem that the measurement accuracy of the nitrogen oxygen sensor is affected by the calibration accuracy.

[0012] Further, before performing S2, the method further comprises: correcting the oxygen concentration test value, and the specific implementation is:

[0013] corresponding to the second chamber pump current and the oxygen concentration test value in the second two-dimensional ratio table, and adopting a bilinear two-dimensional interpolation calculation mode to determine a ratio; calculating the product between the ratio and the oxygen concentration test value obtained in S1 to obtain the corrected oxygen concentration test value;

[0014] The second two-dimensional ratio table is obtained by the following construction method: setting the second chamber pump current with a first current value, changing the oxygen concentration in the atmosphere table environment under the second chamber pump current with the first current value, collecting the oxygen concentration test value output by the nitrogen oxide sensor based on the second reference linear relationship under different oxygen concentrations, the second reference linear relationship is constructed under the second chamber pump current with a second current value different from the first current value, and represents the linear relationship between the first chamber pump current and the oxygen concentration test output; obtaining the oxygen concentration value calculated by the second reference linear relationship under the detection process control target parameter second chamber pump current with the second current value in the different oxygen concentration environment, as the oxygen concentration accurate value; calculating the ratio between each oxygen concentration accurate value and its corresponding oxygen concentration test value; changing the first current value, repeating the step, and thus constructing a two-dimensional ratio table of the oxygen concentration accurate value and its corresponding oxygen concentration test value under different second chamber pump currents and different oxygen concentration environments.

[0015] A further beneficial effect of the present application is that the present application also corrects the influence of the different second chamber pump currents as process control target parameters on oxygen concentration measurement. According to the differences between batches of nitrogen oxide sensor core ceramic sensing chips during static calibration, differentially setting the second chamber pump current as the process control target parameter helps to reduce the oxygen concentration dependency of the nitrogen oxide sensor, so that the oxygen concentration dependency remains consistent, thereby improving the problem of low calibration efficiency caused by insufficient sensor consistency.

[0016] The present application also provides a two-dimensional calibration method for the output results of a nitrogen oxide sensor, comprising:

[0017] S1, collecting the oxygen concentration test value output by the nitrogen oxide sensor under the detection process control, wherein the second chamber pump current is one of the process control target parameters;

[0018] S2, the current second chamber pump current corresponding to the oxygen concentration test value and the oxygen concentration test value corresponding to the oxygen concentration test value are respectively taken as the indexes of the second chamber pump current and the oxygen concentration in the two-dimensional ratio table, and a ratio is determined by using a bilinear two-dimensional interpolation calculation method; the product of the ratio and the oxygen concentration test value is calculated to obtain a corrected oxygen concentration test value, and the calibration of the output result of the nitrogen oxide sensor is completed;

[0019] Wherein, the two-dimensional ratio table is obtained by the following construction method: setting the second chamber pump current with the first current value, changing the oxygen concentration in the atmosphere table environment under the second chamber pump current with the first current value, collecting the oxygen concentration test value output by the nitrogen oxide sensor based on the reference linear relationship under different oxygen concentrations, the reference linear relationship is constructed under the second chamber pump current with the second current value different from the first current value, which represents the linear relationship between the first chamber pump current and the oxygen concentration test output; the oxygen concentration value calculated by the reference linear relationship under the detection process control target parameter second chamber pump current with the second current value in the different oxygen concentration environment is obtained as the oxygen concentration accurate value; the ratio between each oxygen concentration accurate value and its corresponding oxygen concentration test value is calculated; change the first current value, repeat the step, and thus the two-dimensional ratio table of the oxygen concentration accurate value and its corresponding oxygen concentration test value under different second chamber pump currents and different oxygen concentration environments is constructed.

[0020] The beneficial effects of the present application are: the present application corrects the influence of the different second chamber pump currents as process control target parameters on oxygen concentration measurement, on the one hand, according to the differences between batches of nitrogen oxide sensor core ceramic sensing chips, the second chamber pump current as the process control target parameter is set differently, which helps to reduce the oxygen concentration dependence of the nitrogen oxide sensor, so that the oxygen concentration dependence is consistent, thereby improving the problem of low calibration efficiency caused by insufficient sensor consistency; on the other hand, the setting value of the second chamber pump current as the process control target parameter is set dynamically according to the working condition, so that the oxygen concentration of the first chamber is in a reasonable range, thereby improving the dynamic control performance of the nitrogen oxide sensor, including the measurement response speed and the anti-interference ability.

[0021] Further, the second chamber pump current as the process control target parameter has a value range of (x1*Ip0, x2*Ip0), Ip1>0; in the formula, Ip0 represents the pump current of the first chamber; x1 represents the lower limit coefficient of the value, and x2 represents the upper limit coefficient of the value, both of which are positively related to the size of the first diffusion channel.

[0022] The application also provides a control method of a nitrogen oxide sensor, which adjusts the second chamber pump current Ip1 as a process control target parameter in real time based on the dynamic change of the atmosphere in the real vehicle sensing detection process, wherein the Ip1 set value is increased when the vehicle load increases, the Ip1 set value is reduced when the vehicle load decreases, and the oxygen concentration test value output by the nitrogen oxide sensor is calibrated and corrected by using the two-dimensional calibration method.

[0023] The application has the following beneficial effects: in the application process, the setting of the calibration process parameter Ip1 has a great influence on the dynamic anti-interference ability and dynamic measurement precision of the three-chamber closed-loop control under the standard WLTC working condition, in order to improve the dynamic response speed, anti-interference ability and dynamic precision, it is necessary to optimize the multi-chamber closed-loop control strategy, that is, the application increases the Ip1 set value when the vehicle load increases, increases the first chamber steady-state oxygen concentration, and enhances the dynamic control response speed of the first pump unit. When the vehicle load decreases, the Ip1 set value is reduced, the first chamber steady-state oxygen concentration is reduced, and the oxygen concentration-dependent transient influence is reduced. The value of the second pump unit closed-loop control target parameter Ip2 is set dynamically according to the actual working condition. p1

[0024] Further, the nitrogen oxide concentration test value output by the nitrogen oxide sensor is calibrated and corrected by using the two-dimensional calibration method.

[0025] The application also provides a computer readable storage medium, which comprises a stored computer program, wherein the computer program controls the device where the storage medium is located to perform the two-dimensional calibration method of the nitrogen oxide sensor output result, the two-dimensional calibration method of the nitrogen oxide sensor output result and / or the control method of the nitrogen oxide sensor when the computer program is run by a processor.

[0026] Overall, the above technical solutions conceived by the application can achieve the following beneficial effects:

[0027] The two-dimensional calibration method provided by the application introduces the process control target parameter Ip1 in the calibration process of the main pump current Ip0 and the oxygen concentration output, takes the oxygen concentration output calibration as the basis in the calibration of the measurement pump current Ip2 and the nitrogen oxide concentration output, and dynamically sets the process control target parameter Ip1 when the nitrogen oxide sensor is controlled in the multi-chamber mode. This method can improve the measurement precision of the nitrogen oxide sensor, improve the dynamic response tracking and measurement precision performance of the sensor, and reduce the requirement for the consistency of the core ceramic chip of the nitrogen oxide sensor. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 ​A two-dimensional calibration method flow chart of nitrogen oxide sensor output results provided by the embodiment of the present application is shown in the figure;

[0029] Figure 2 A structure diagram of the nitrogen oxide sensor provided by the embodiment of the present application is shown in the figure;

[0030] Figure 3 Another two-dimensional calibration method flow chart of nitrogen oxide sensor output results provided by the embodiment of the present application is shown in the figure;

[0031] Figure 4 An oxygen concentration calibration output result schematic diagram provided by the embodiment of the present application is shown in the figure;

[0032] Figure 5 An oxygen concentration calibration output result schematic diagram provided by the embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0034] Embodiment one

[0035] A two-dimensional calibration method of nitrogen oxide sensor output results, as shown in the figure, comprises: Figure 1

[0036] S1, collecting oxygen concentration test values and nitrogen oxide concentration test values output by the nitrogen oxide sensor;

[0037] S2, taking the oxygen concentration test values and the nitrogen oxide concentration test values as indexes of oxygen concentration and nitrogen oxide concentration in the first two-dimensional ratio table respectively, and using a bilinear two-dimensional interpolation calculation method to determine a ratio; calculating the product between the ratio and the nitrogen oxide concentration test value to obtain a corrected nitrogen oxide concentration test value, and completing the calibration of the nitrogen oxide sensor output results;

[0038] ​The aforementioned first two-dimensional ratio table is constructed as follows: A first oxygen concentration is set in the atmosphere stage environment. Under this oxygen concentration environment, the nitrogen and oxygen concentration is changed, and nitrogen and oxygen concentration test values ​​output by the nitrogen oxide sensor based on a first reference linear relationship are collected at different nitrogen and oxygen concentrations. The first reference linear relationship is constructed under a second oxygen concentration environment different from the first oxygen concentration, representing the linear relationship between the third chamber pump current and the nitrogen and oxygen concentration test output. The nitrogen and oxygen concentration values ​​calculated one-to-one with the first reference linear relationship under the aforementioned different nitrogen and oxygen concentrations in the second oxygen concentration environment are obtained as the accurate nitrogen and oxygen concentration values. The ratio of each accurate nitrogen and oxygen concentration value to its corresponding nitrogen and oxygen concentration test value is calculated. The first oxygen concentration in the atmosphere stage environment is changed, and this step is repeated to construct a two-dimensional ratio table between the accurate nitrogen and oxygen concentration values ​​and their corresponding nitrogen and oxygen concentration test values ​​under different first oxygen concentrations and nitrogen and oxygen concentration environments.

[0039] The structural diagram of the nitrogen oxide sensor is shown below. Figure 2 As shown, the two-dimensional ratio table in this embodiment can be specifically constructed and implemented as follows:

[0040] If the oxygen concentration calibration point is set to 12.5%, then u nitrogen and oxygen concentration calibration points are set, denoted as C. NO-k Let represent the k-th nitrogen and oxygen concentration calibration point. Establish a linear relationship between the third chamber pump current Ip2 and the nitrogen and oxygen concentration test output, denoted as . The subscript 0 indicates that the two-dimensional linear relationship is the two-dimensional linear relationship under the condition of the reference oxygen concentration point, and it is written into the controller. Then, any oxygen concentration point is selected from w oxygen concentration calibration points. Let C represent the l-th oxygen concentration calibration point, and arbitrarily select a point C from the u nitrogen and oxygen concentration calibration points. NO-k The output C of the nitrogen and oxygen concentration at this time was tested. NO-kl ; Obtain the linear relationship from the baseline The nitrogen oxygen concentration value calculated one-to-one within the environment corresponding to the k-th nitrogen oxygen concentration calibration point under the baseline oxygen concentration condition is taken as the accurate nitrogen oxygen concentration value and denoted as . calculate With C NO-kl The ratio q kl Where u and w represent the number of elements in one row and one column of the two-dimensional ratio table, respectively, a two-dimensional linear interpolation table for nitrogen and oxygen concentration calibration under different oxygen and nitrogen-oxygen concentrations is established, and its form can be shown in Table 1 below:

[0041] Table 1. Two-dimensional linear interpolation table for nitrogen and oxygen concentration calibration.

[0042]

[0043] The two-dimensional linear interpolation table of nitrogen oxide concentration calibration is written into the controller, and the corrected calibrated nitrogen oxide concentration is output in real time during actual measurement application:

[0044] C NO-Cal = f(p (k)(l) , p (k+1)(l) , p (k)(l+1), p (k+1)(l+1) )*C NO-NCal

[0045] Wherein f(p (k)(l) , p (k+1)(l) , p (k)(l+1) , p (k+1)(l+1) ) is a general bilinear two-dimensional interpolation calculation formula, C NO-NCal is the uncalibrated real-time nitrogen oxide concentration output of the nitrogen oxide sensor under different oxygen concentration conditions in actual application. C NO-k <C NO-NCal <C NO-(k+1) , represents the real-time measurement output result of the nitrogen oxide sensor.

[0046] It should be noted that the construction steps of the above two-dimensional ratio table can be realized by automatic calibration software on the automatic atmosphere matching table. The ratio table constructed in this embodiment corrects the influence of oxygen concentration dependence on real-time measurement of nitrogen oxide concentration, and improves the dynamic measurement precision performance of the nitrogen oxide sensor.

[0047] The nitrogen oxide sensor detection output nitrogen oxide concentration test value is further corrected in this embodiment, and the correction method is: the oxygen concentration test value and the nitrogen oxide concentration test value obtained by the sensor are respectively taken as the indexes of oxygen concentration and nitrogen oxide concentration in the two-dimensional ratio table, a ratio is determined by using bilinear two-dimensional interpolation calculation method, and the product between the ratio and the above nitrogen oxide concentration test value is calculated to obtain the corrected nitrogen oxide concentration test value. When constructing the two-dimensional ratio table, the oxygen concentration and nitrogen oxide concentration measurement linear output characteristics of the nitrogen oxide sensor are used as the basis to design a calibration method including calibration atmosphere oxygen concentration and calibration atmosphere nitrogen oxide concentration. Considering that the basic principle of the nitrogen oxide sensor is based on the oxygen ion conduction function of high-temperature zirconia solid electrolyte and the limiting current principle, the electrode characteristics of the ceramic chip affect the calibration output linear characteristics, the two-dimensional linear interpolation calibration algorithm is used in this embodiment to eliminate the influence of oxygen concentration dependence on real-time measurement of nitrogen oxide concentration, and the problem that the measurement precision of the nitrogen oxide sensor is affected by the calibration precision can be solved.

[0048] As a further preferred embodiment, before step S2 is performed, the method further comprises: correcting the oxygen concentration test value obtained by the sensor, and the specific implementation is:

[0049] corresponding to the second chamber pump current and the oxygen concentration test value in the second two-dimensional ratio table, and a product of the ratio and the oxygen concentration test value obtained in S1 is calculated to obtain a corrected oxygen concentration test value;

[0050] The second two-dimensional ratio table is obtained by the following method: setting the second chamber pump current at a first current value, changing the oxygen concentration in the atmosphere table environment at the second chamber pump current value, collecting the oxygen concentration test value output by the nitrogen oxide sensor based on the second reference linear relationship at different oxygen concentrations, the second reference linear relationship is constructed at the second chamber pump current value different from the first current value, and represents the linear relationship between the first chamber pump current and the oxygen concentration test output; obtaining the oxygen concentration value calculated by the second reference linear relationship in the detection process control target parameter second chamber pump current value at the second current value in the different oxygen concentration environment as the oxygen concentration accurate value; calculating the ratio between each oxygen concentration accurate value and its corresponding oxygen concentration test value; changing the first current value and repeating the step to construct a two-dimensional ratio table of the oxygen concentration accurate value and its corresponding oxygen concentration test value under different second chamber pump currents and different oxygen concentration environments.

[0051] It should be noted that the construction steps of the above second two-dimensional ratio table can be realized by automatic calibration software on the automatic atmosphere matching table. The embodiment corrects the influence of the different second chamber pump currents as process control target parameters on the oxygen concentration measurement. On the one hand, according to the differences between the batches of nitrogen oxide sensor core ceramic sensing chips, the second chamber pump current as the process control target parameter is set differently to help reduce the oxygen concentration dependence of the nitrogen oxide concentration measurement of the nitrogen oxide sensor, so that the oxygen concentration dependence is consistent, thereby the embodiment method can improve the problem of low calibration efficiency caused by insufficient sensor consistency. On the other hand, the setting value of the second chamber pump current as the process control target parameter is set dynamically according to the working condition, so that the oxygen concentration of the first chamber is in a reasonable range, thereby the embodiment method can improve the dynamic control performance of the nitrogen oxide sensor, including the measurement response speed and the anti-interference ability.

[0052] Embodiment two

[0053] A two-dimensional calibration method for the output results of a nitrogen oxide sensor, as shown in Figure 3 , comprising:

[0054] S1, collecting the oxygen concentration test value output by the nitrogen oxide sensor under the detection process control, wherein the second chamber pump current is one of the process control target parameters;

[0055] S2, the current second chamber pump current corresponding to the above oxygen concentration test value and the oxygen concentration test value corresponding to the second chamber pump current and oxygen concentration as the index of the two-dimensional ratio table, using a bilinear two-dimensional interpolation calculation method, determine a ratio; calculate the product of the ratio and the above oxygen concentration test value, get the corrected oxygen concentration test value, complete the calibration of the output results of the nitrogen oxide sensor;

[0056] Wherein, the two-dimensional ratio table is obtained by the following construction method: set the second chamber pump current value as the first current value, change the oxygen concentration in the atmosphere table environment under the second chamber pump current value, collect the oxygen concentration test value output by the nitrogen oxide sensor based on the reference linear relationship under different oxygen concentrations, the reference linear relationship is constructed under the second chamber pump current value which is different from the first current value, which represents the linear relationship between the first chamber pump current and the oxygen concentration test output; obtain the oxygen concentration value calculated by the above reference linear relationship under the detection process control target parameter second chamber pump current value as the second current value in the above different oxygen concentration environment, as the oxygen concentration accurate value; calculate the ratio between each oxygen concentration accurate value and its corresponding oxygen concentration test value; change the first current value, repeat the step, thereby constructing the two-dimensional ratio table of the oxygen concentration accurate value and its corresponding oxygen concentration test value under different second chamber pump currents and different oxygen concentration environments.

[0057] In this embodiment, the construction step of the two-dimensional ratio table can be realized automatically by the calibration software on the automatic atmosphere matching table. The correction of the second chamber pump current as the process control target parameter in this embodiment can reduce the oxygen concentration dependence of the nitrogen oxide concentration measurement of the nitrogen oxide sensor, and can improve the consistency of the sensor, thereby improving the low calibration efficiency problem caused by the insufficient consistency of the sensor. On the other hand, according to the working condition, the setting value of the second chamber pump current as the process control target parameter is set, so that the oxygen concentration of the first chamber is in a reasonable range, thereby improving the dynamic control performance of the nitrogen oxide sensor, including the measurement response speed and the anti-interference ability.

[0058] Further, as a preferred embodiment, the second chamber pump current range as the process control target parameter is (x1*Ip0, x2*Ip0), Ip1>0; wherein Ip0 represents the pump current of the first chamber; x1 represents the lower limit coefficient of the value, and x2 represents the upper limit coefficient of the value, both of which are positively correlated with the size of the first diffusion channel. The size of Ip0 is positively proportional to the diffusion of the first diffusion channel, and the larger Ip0 is, the smaller the steady-state oxygen concentration of the first chamber is. Only when the setting value of Ip1 is large can the oxygen concentration of the first chamber at the steady state be increased. The smaller Ip0 is, the higher the steady-state oxygen concentration of the first chamber is. Only when the setting value of Ip1 is small can the oxygen concentration of the first chamber at the steady state be reduced. The high and low of the oxygen concentration of the first chamber affects the oxygen concentration dependence degree, dynamic response speed and anti-interference ability of the nitrogen oxide sensor.

[0059] Specifically, the construction of the two-dimensional ratio table in the embodiment can be as follows:

[0060] The setting range of the process control target parameter Ip1 needs to be determined according to the structural size of the first diffusion channel D0 of the nitrogen oxide sensor, wherein the diffusion capacity of D0 is positively correlated with Ip0,

[0061] Ip1∈(x1*Ip0, x2*Ip0), Ip1>0;

[0062] wherein x1 represents the lower limit coefficient of the value of Ip1, and x2 represents the upper limit coefficient of the value of Ip1, and the upper limit value of Ip1 needs to be set according to the oxygen concentration dependence degree of the nitrogen oxide sensor.

[0063] The specific steps of calibration are as follows: measuring the initial basic electrical characteristic parameter Ip0 of the nitrogen oxide sensor under normal working conditions in a room temperature calibration atmosphere environment, taking Ip1=r*Ip0, r∈(x1, x2), and establishing a two-dimensional linear relationship between Ip0 and the oxygen concentration output under the initial conditions (i.e., room temperature, Ip1=r*Ip0) The subscript 0 indicates that the two-dimensional linear relationship is the corresponding two-dimensional linear relationship under the reference condition of Ip1=r*Ip0, which is used as the reference output of the oxygen concentration. The linear relationship is written into the controller of the nitrogen oxide sensor, and any one Ip1 is taken from m Ip1 calibration points 1-i , which represents the i-th Ip1 calibration point; and any one point is taken from n oxygen concentration calibration points , which represents the j-th oxygen concentration calibration point; and the oxygen concentration test value of the nitrogen oxide sensor at this time is tested The oxygen concentration value calculated from the reference linear relationship under Ip1=r*Ip0 corresponding to the above j-th oxygen concentration calibration point in the environment is obtained as the accurate oxygen concentration value, denoted as The calculation is and The ratio P ij Therefore, a two-dimensional linear interpolation table for oxygen concentration calibration is constructed, where m and n are the number of elements in one row and one column of the two-dimensional ratio table, respectively. The form of this two-dimensional linear interpolation table for oxygen concentration calibration is shown in Table 2 below:

[0064] Table 2. Two-dimensional linear interpolation table for oxygen concentration calibration.

[0065]

[0066]

[0067] A two-dimensional linear interpolation table of m Ip1 values ​​and n oxygen concentration calibration points under each Ip1 is written into the controller. This table is output in real-time during actual measurement applications. The application method is as follows: In practical applications, the current second chamber pump current and oxygen concentration test value corresponding to the oxygen concentration test value are used as indices of the second chamber pump current and oxygen concentration in the two-dimensional ratio table, respectively. A ratio is determined using bilinear two-dimensional interpolation. The product of this ratio and the oxygen concentration test value is calculated to obtain the corrected oxygen concentration test value, thus completing the calibration of the nitrogen oxide sensor output. The corrected and calibrated oxygen concentration is expressed as:

[0068]

[0069] Where, f(p) (i)(j) ,p (i+1)(j) ,p (i)(j+1) ,p (i+1)(j+1) C is the formula for bilinear two-dimensional interpolation. O2-NCal The nitrogen and oxygen sensor is set with different I values ​​in practical applications. p1 The real-time uncalibrated oxygen concentration test output value of the sensor under the given conditions. Ip 1-i <Ip 1-set <Ip 1-(i+1) IP 1-set Indicate I p1 Real-time setting value.

[0070] Example 3

[0071] A control method for a nitrogen oxide sensor, based on the dynamic changes in atmosphere during the actual vehicle sensing and detection process, adjusts the second chamber pump current Ip1, which is a process control target parameter, in real time. When the vehicle load increases, the set value of Ip1 is increased; when the vehicle load decreases, the set value of Ip1 is decreased. The oxygen concentration test value output by the nitrogen oxide sensor is calibrated and corrected using the two-dimensional calibration method described above.

[0072] The embodiment optimizes the dynamic control algorithm of the nitrogen oxide sensor based on the calibration of embodiment two, and can optimize the dynamic tracking control strategy of the nitrogen oxide sensor based on this, thereby improving the application measurement response speed and measurement accuracy performance of the nitrogen oxide sensor.

[0073] Further, as a preferred embodiment, the nitrogen oxide sensor output nitrogen oxide concentration test value is calibrated and corrected by using the two-dimensional calibration method of embodiment one.

[0074] In the application process, under the standard WLTC working condition, the setting of the calibration process parameter Ip1 has a great influence on the dynamic anti-interference ability and dynamic measurement accuracy of the three-chamber closed-loop control. In order to improve the dynamic response speed, anti-interference ability and dynamic accuracy, it is necessary to optimize the multi-chamber closed-loop control strategy, that is, when the vehicle load increases, the Ip1 setting value is increased, the first chamber steady-state oxygen concentration is increased, and the dynamic control response speed of the first pump unit is enhanced. When the vehicle load decreases, the Ip1 setting value is reduced, the first chamber steady-state oxygen concentration is reduced, thereby reducing the oxygen concentration dependent transient influence. According to the actual working condition, the value of the second pump unit closed-loop control target parameter I p1 is dynamically set.

[0075] In order to better illustrate the above embodiments, the following examples are given:

[0076] The basic output characteristic parameters of the nitrogen oxide sensor to be calibrated are tested in a room temperature air environment, as shown in Table 3. r=0.25 is selected, and Ip1=14uA is calculated according to Ip1=r*Ip0. The oxygen concentration measurement output characteristic is calibrated in a standard atmosphere table, as shown in Table 3. Figure 4

[0077] Table 3 Nitrogen oxide sensor basic characteristic parameters

[0078] Vp0 (mV) Vp1 (mV) Vp2 (mV) V0 (mV) V1 (mV) V2 (mV) Ip0 (mA) Ip1 (uA) Ip2 (uA) 322 387 397 312 425 435 3.5 14 0.08

[0079] The oxygen concentration calibration two-dimensional interpolation table is established, as shown in Table 4 below, wherein the Ip1 setting range is 1-35uA, the oxygen concentration setting range is 0%-21%, and Ip 1-m and C O2-n are set by equal division method, and are rounded after equal division. Among them, Ip1=14uA is the reference reference calibration initial value.

[0080] Table 4 Oxygen concentration calibration two-dimensional interpolation table

[0081]

[0082]

[0083] ​Ip1=14uA, oxygen concentration is 12.5%, nitrogen and oxygen concentration measurement output characteristics are calibrated in a standard atmosphere platform as shown in FIG. 5, wherein the oxygen concentration 12.5% is the normal oxygen concentration value of the nitrogen and oxygen sensor working atmosphere environment. Figure 5 The nitrogen oxide concentration calibration two-dimensional interpolation table is established as shown in Table 5.

[0084] Table 5 nitrogen oxide concentration calibration two-dimensional interpolation table

[0085]

[0086] Example Four

[0087] A computer readable storage medium comprising a stored computer program, wherein the computer program, when executed by a processor, controls a device in which the storage medium is located to perform the two-dimensional calibration method of the output result of the nitrogen oxide sensor according to the above-mentioned example one, the two-dimensional calibration method of the output result of the nitrogen oxide sensor according to the above-mentioned example two and / or the control method of the nitrogen oxide sensor according to the above-mentioned example three.

[0088] The related technical solutions are the same as those in example one, example two and example three, and will not be repeated here.

[0089] In general, the present application discloses a two-dimensional calibration method of a nitrogen oxide sensor, the main method of which is to construct a ratio table between the accurate oxygen concentration value and the corresponding oxygen concentration test value under different second chamber pump currents Ip1 and different oxygen concentration environments; at the same time, a ratio table between the accurate nitrogen and oxygen concentration value and the corresponding nitrogen and oxygen concentration test value under different oxygen concentrations and different nitrogen and oxygen concentration environments is constructed; finally, the control target parameter of Ip1 is dynamically set in the dynamic control of the nitrogen and oxygen sensor, and the ratio table is applied to the measurement output of the nitrogen and oxygen sensor. The two-dimensional calibration method proposed in the present application introduces the process control target parameter Ip1 in the process of calibrating the main pump current Ip0 and the oxygen concentration output; the oxygen concentration output calibration is used as the basis when calibrating the measurement pump current Ip2 and the nitrogen and oxygen concentration output; in the multi-chamber dynamic control of the nitrogen and oxygen sensor, the process control target parameter Ip1 can be dynamically set. This method can not only improve the measurement accuracy of the nitrogen and oxygen sensor, but also improve the dynamic response tracking and measurement accuracy performance of the sensor, and reduce the requirement for the consistency of the core ceramic chip of the nitrogen oxide sensor.

[0090] Those skilled in the art will easily understand that the above-mentioned is only the preferred embodiment of the present application, and is not used to limit the present application, any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A two-dimensional calibration method for the output of a nitrogen oxide sensor, characterized in that, include: S1. Collect the oxygen concentration test value and nitrogen oxide concentration test value output by the nitrogen oxide sensor; S2. The oxygen concentration test value and the nitrogen oxygen concentration test value are respectively used as indices of oxygen concentration and nitrogen oxygen concentration in the first two-dimensional ratio table, and a ratio is determined by bilinear two-dimensional interpolation. Calculate the product between this ratio and the nitrogen oxide concentration test value to obtain the corrected nitrogen oxide concentration test value, thus completing the calibration of the nitrogen oxide sensor output result; The first two-dimensional ratio table is constructed as follows: A first oxygen concentration is set in the atmosphere stage environment. Under this oxygen concentration environment, the nitrogen and oxygen concentration is changed, and nitrogen and oxygen concentration test values ​​output by the nitrogen oxide sensor based on a first reference linear relationship are collected at different nitrogen and oxygen concentrations. The first reference linear relationship is constructed under a second oxygen concentration environment different from the first oxygen concentration, representing the linear relationship between the third chamber pump current and the nitrogen and oxygen concentration test output. The nitrogen and oxygen concentration values ​​calculated one-to-one with the first reference linear relationship under different nitrogen and oxygen concentrations in the second oxygen concentration environment are obtained as accurate nitrogen and oxygen concentration values. The ratio of each accurate nitrogen and oxygen concentration value to its corresponding nitrogen and oxygen concentration test value is calculated. The first oxygen concentration in the atmosphere stage environment is changed, and this step is repeated to construct a two-dimensional ratio table between the accurate nitrogen and oxygen concentration values ​​and their corresponding nitrogen and oxygen concentration test values ​​under different first oxygen concentrations and nitrogen and oxygen concentration environments.

2. The two-dimensional calibration method according to claim 1, characterized in that, Before executing S2, the method further includes: correcting the oxygen concentration test value, specifically implemented as follows: The current test values ​​of the second chamber pump current and oxygen concentration, which are used as process control target parameters, are respectively assigned as indices of the test values ​​of the second chamber pump current and oxygen concentration in the second two-dimensional ratio table. A ratio is determined by using bilinear two-dimensional interpolation. The product between this ratio and the oxygen concentration test value obtained in S1 is calculated to obtain the corrected oxygen concentration test value. The second two-dimensional ratio table is constructed as follows: A second chamber pump current is set to a first current value. The oxygen concentration in the atmosphere environment is changed under this second chamber pump current value. Oxygen concentration test values ​​output by the nitrogen oxide sensor based on a second reference linear relationship are collected under different oxygen concentrations. This second reference linear relationship is constructed under a second chamber pump current value different from the first current value, representing the linear relationship between the first chamber pump current and the oxygen concentration test output. Oxygen concentration values ​​calculated one-to-one with the second reference linear relationship under the second current value in different oxygen concentration environments are obtained as accurate oxygen concentration values. The ratio between each accurate oxygen concentration value and its corresponding oxygen concentration test value is calculated. The first current value is changed, and this step is repeated to construct a two-dimensional ratio table between different second chamber pump currents and the accurate oxygen concentration values ​​under different oxygen concentration environments, and their corresponding oxygen concentration test values.

3. A two-dimensional calibration method for the output of a nitrogen oxide sensor, characterized in that, include: S1. Collect the oxygen concentration test value output by the nitrogen oxide sensor under the detection process control, wherein the pump current of the second chamber is one of the process control target parameters; S2. The current second chamber pump current and oxygen concentration test value corresponding to the oxygen concentration test value are respectively used as indices of the second chamber pump current and oxygen concentration in the two-dimensional ratio table. A ratio is determined by using bilinear two-dimensional interpolation. The product between the ratio and the oxygen concentration test value is calculated to obtain the corrected oxygen concentration test value, thus completing the calibration of the nitrogen oxide sensor output result. The two-dimensional ratio table is constructed as follows: A second chamber pump current is set to a first current value. The oxygen concentration in the atmosphere environment is changed under this second chamber pump current value. Oxygen concentration test values ​​output by the nitrogen oxide sensor based on a reference linear relationship are collected under different oxygen concentrations. This reference linear relationship is constructed under a second chamber pump current value different from the first current value, representing the linear relationship between the first chamber pump current and the oxygen concentration test output. Oxygen concentration values ​​calculated one-to-one with the second chamber pump current value under the second current value in the detection process control target parameter are obtained as accurate oxygen concentration values. The ratio between each accurate oxygen concentration value and its corresponding oxygen concentration test value is calculated. The first current value is changed, and this step is repeated to construct a two-dimensional ratio table between different second chamber pump currents and the accurate oxygen concentration values ​​under different oxygen concentration environments, and their corresponding oxygen concentration test values.

4. The two-dimensional calibration method according to claim 3, characterized in that, The range of the second chamber pump current, which is the target parameter for process control, is the interval (x1*Ip0, x2*Ip0), where Ip1>0; where Ip0 represents the pump current of the first chamber; x1 represents the lower limit coefficient, and x2 represents the upper limit coefficient, and the values ​​are positively correlated with the size of the first diffusion channel.

5. A control method for a nitrogen oxide sensor, characterized in that, Based on the dynamic changes in atmosphere during the actual vehicle sensing and detection process, the second chamber pump current Ip1, which is a process control target parameter, is adjusted in real time. Specifically, when the vehicle load increases, the set value of Ip1 is increased; when the vehicle load decreases, the set value of Ip1 is decreased. Furthermore, the two-dimensional calibration method described in claim 3 or 4 is used to calibrate and correct the oxygen concentration test value output by the nitrogen oxide sensor. On the other hand, during static calibration, due to the inconsistency between batches of products, I... P1 The settings also need to be configured separately.

6. The control method according to claim 5, characterized in that, Also includes: The nitrogen oxide concentration test value output by the nitrogen oxide sensor is calibrated and corrected using the two-dimensional calibration method as described in claim 1.

7. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored computer program, wherein, when the computer program is executed by a processor, it controls the device where the storage medium is located to perform a two-dimensional calibration method for the output result of a nitrogen oxide sensor as described in claim 1 or 2, a two-dimensional calibration method for the output result of a nitrogen oxide sensor as described in claim 3 or 4, and / or a control method for a nitrogen oxide sensor as described in claim 5 or 6.

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