Calibration method and system of nitrogen and oxygen sensor

Abstract

The present invention discloses a nitrogen oxygen sensor calibration method and a calibration system. The nitrogen oxygen sensor calibration method according to an embodiment of the present invention comprises obtaining a plurality of calibration values; establishing a first equation under a first oxygen concentration according to calibration parameters of the calibration values; establishing a second equation under a second oxygen concentration according to calibration parameters of the calibration values; establishing a calibration equation according to the first equation and the second equation, and the calibration equation is used for calibration of the nitrogen oxygen sensor. The nitrogen oxygen sensor calibration method and the calibration system according to the embodiment of the present invention are simple and easy to implement, and the calibration result is accurate.

Description

Technical Field

[0001] The present invention relates to the technical field of sensor calibration, and in particular to a nitrogen oxygen sensor calibration method and a calibration system. Background Art

[0002] With the development of economy and society, the number of motor vehicles is also increasing year by year, but the harmful components contained in the exhaust gas emitted by motor vehicles will cause serious pollution to the atmosphere, such as carbon monoxide, nitrogen oxides (nitrogen monoxide and nitrogen dioxide, collectively referred to as NOx), sulfides, fine particles, etc. These harmful components greatly affect the environment and the survival of animals and plants.

[0003] In the prior art, nitrogen oxide sensors are of great significance to the exhaust gas treatment system of motor vehicles. Nitrogen oxides produced by motor vehicles undergo catalytic reactions to generate harmless nitrogen, and the catalytic reaction of nitrogen oxides requires ammonia. Since ammonia is toxic, urea is usually provided in the catalytic reaction. In order to control the amount of urea added in the catalytic reaction, it is necessary to accurately obtain the amount of urea added through a nitrogen oxide sensor, and the premise for achieving accurate measurement is that the nitrogen oxide sensor is accurately calibrated. However, the current calibration methods often have problems such as complex calibration methods and poor accuracy.

[0004] Therefore, it is hoped that there will be a new nitrogen oxide sensor calibration method and calibration system that can overcome the above problems. Summary of the invention

[0005] In view of the above problems, an object of the present invention is to provide a nitrogen oxide sensor calibration method and a calibration system, so as to reduce the difficulty of calibration and improve the accuracy of the calibration results.

[0006] According to one aspect of the present invention, a method for calibrating a nitrogen oxygen sensor is provided, comprising acquiring a plurality of calibration values; establishing a first equation at a first oxygen concentration according to calibration parameters of the calibration values; establishing a second equation at a second oxygen concentration according to the calibration parameters of the calibration values; and establishing a calibration equation according to the first equation and the second equation, wherein the calibration equation is used for calibrating the nitrogen oxygen sensor.

[0007] Optionally, the calibration parameters include at least one of oxygen concentration, nitrogen oxide concentration, first pump current and third pump current.

[0008] Optionally, the calibration method also includes establishing a third equation based on the calibration parameters of the first calibration value and the calibration parameters of the second calibration value, wherein the third equation is a linear equation about the first pump current; establishing the calibration equation based on the first equation, the second equation and the third equation, wherein the nitrogen oxide concentration corresponding to the first calibration value is zero; and the nitrogen oxide concentration corresponding to the second calibration value is zero.

[0009] Optionally, the calibration equation is a surface function related to the first pump current and the third pump current.

[0010] Optionally, the calibration method also includes establishing a fourth equation based on calibration parameters of the calibration value, wherein when the third pump current is greater than a first threshold, the nitrogen oxide sensor is calibrated according to the fourth equation; when the third pump current is less than or equal to the first threshold, the nitrogen oxide sensor is calibrated according to the calibration equation.

[0011] Optionally, the fourth equation is a linear equation about the third pump current established according to a third calibration value and a fourth calibration value, wherein the fourth calibration value is determined according to a maximum nitrogen oxide measurement value.

[0012] Optionally, establishing the first equation at the first oxygen concentration according to the calibration parameters of the calibration value includes establishing the first equation according to the calibration parameters of the fifth calibration value, the calibration parameters of the sixth calibration value and the calibration parameters of the seventh calibration value, and the first equation is a quadratic equation about the third pump current.

[0013] Optionally, establishing the second equation at the second oxygen concentration according to the calibration parameters of the calibration value includes establishing the second equation according to the calibration parameters of the eighth calibration value, the calibration parameters of the ninth calibration value and the calibration parameters of the tenth calibration value, and the second equation is a quadratic equation about the third pump current.

[0014] Optionally, the air pressures corresponding to the multiple calibration values ​​are the same; the calibration method also includes obtaining a first verification value and a second verification value; obtaining a pressure correction coefficient according to the first verification value, the second verification value and the calibration equation, wherein the oxygen concentration corresponding to the first verification value is the same as the oxygen concentration corresponding to the second verification value; the nitrogen oxide concentration corresponding to the first verification value is the same as the nitrogen oxide concentration corresponding to the second verification value; the air pressure corresponding to the first verification value is the same as the air pressure corresponding to the calibration value, and the air pressure corresponding to the first verification value is less than the air pressure corresponding to the second verification value.

[0015] According to another aspect of the present invention, a nitrogen oxide sensor calibration system is provided, which is calibrated by the calibration method as described above, and the calibration system comprises a mixed gas source module and a host computer control module; the mixed gas source module comprises a plurality of gas sources, a plurality of controllable flow meters and a mixer; the plurality of controllable flow meters are connected to the plurality of gas sources in a one-to-one correspondence, and the gases from the plurality of gas sources flow out through the corresponding controllable flow meters and are mixed in the mixer to form a mixed gas, wherein the gases from the plurality of gas sources comprise nitrogen oxides and oxygen; the host computer control module comprises a host computer and an industrial control card; the host computer is connected to the plurality of controllable flow meters to control the concentrations of nitrogen oxides and oxygen in the mixed gas; the industrial control card is used to obtain test data of the nitrogen oxide sensor on the mixed gas to calibrate the mixed gas.

[0016] According to the nitrogen oxygen sensor calibration method and calibration system of the embodiment of the present invention, equations under different oxygen concentrations are established according to calibration parameters, and then a calibration equation is established. The calibration method is simple and easy, and the calibration result is accurate.

[0017] Furthermore, the calibration equation is segmented according to the third pump current, and different calibration equations correspond to calibrations in different nitrogen oxide concentration ranges, thereby ensuring the accuracy of the calibration.

[0018] Furthermore, after obtaining the calibration equation, different verification values ​​are substituted into the pressure correction coefficient, and then a corrected calibration equation corresponding to the pressure correction coefficient is obtained to calibrate gases with different pressures, which has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0020] Figure 1 A schematic diagram of the structure of a nitrogen oxygen sensor is shown.

[0021] Figure 2 Shows Figure 1 Schematic diagram of the chemical reactions occurring in each test chamber in the nitrogen oxygen sensor shown.

[0022] Figure 3 A schematic diagram according to an embodiment of the present invention is shown.

[0023] Figure 4 A method flow chart of a nitrogen oxygen sensor calibration method according to an embodiment of the present invention is shown.

[0024] Figure 5 A schematic diagram of a method for calibrating a nitrogen oxygen sensor according to a first embodiment of the present invention is shown.

[0025] Figure 6A schematic diagram of a method for calibrating a nitrogen oxygen sensor according to a second embodiment of the present invention is shown.

[0026] Figure 7 A comparative schematic diagram of the calibration method before optimization is shown.

[0027] Figure 8 A comparative schematic diagram of the optimized calibration method is shown.

[0028] Fig. 9 A schematic diagram of calibration test results according to an embodiment of the present invention is shown.

[0029] Fig.10 A structural schematic diagram of a nitrogen oxygen sensor calibration system according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0030] Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. In each of the accompanying drawings, identical elements are represented by identical or similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not drawn to scale. In addition, some well-known parts may not be shown in the drawings.

[0031] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. Many specific details of the present invention, such as the structure, materials, dimensions, processing technology and techniques of the components are described below to provide a clearer understanding of the present invention. However, as those skilled in the art will appreciate, the present invention may be implemented without following these specific details.

[0032] It should be understood that when describing the structure of a component, when a layer or a region is referred to as being "on" or "over" another layer or another region, it may mean that it is directly on the other layer or another region, or that other layers or regions are included between it and the other layer or another region. Moreover, if the component is turned over, the layer or a region will be "below" or "beneath" another layer or another region.

[0033] Figure 1 A schematic diagram of the structure of a nitrogen oxygen sensor is shown. Figure 2 Shows Figure 1 Schematic diagram of the chemical reactions occurring in each test chamber in the nitrogen oxygen sensor shown.

[0034] like Figure 1 : is a structural diagram of a nitrogen oxygen sensor, which includes a first test chamber, a second test chamber, a third test chamber and an air reference chamber in sequence. There is a first diffusion channel between the first test chamber and the outside world, a second diffusion channel between the first test chamber and the second test chamber, and a third diffusion channel between the second test chamber and the third test chamber. A heating layer is also provided in the nitrogen oxygen sensor.

[0035] The nitrogen oxygen sensor includes a P+ common electrode, a REF reference electrode, a P- negative electrode, an M1 negative electrode and an M2 negative electrode. The P- electrode is arranged in a first test chamber, the M1 negative electrode is arranged in a second test chamber, the M2 negative electrode is arranged in a third test chamber, and the REF reference electrode is arranged in an air reference chamber.

[0036] The P+ common electrode and the P- negative electrode form a first pump unit, the P+ common electrode and the M1 negative electrode form a second pump unit, and the P+ common electrode and the M2 negative electrode form a third pump unit. The REF reference electrode and the P- negative electrode form a first Nernst sensing unit, the REF reference electrode and the M1 negative electrode form a second Nernst sensing unit, and the REF reference electrode and the M2 negative electrode form a third Nernst sensing unit.

[0037] like Figure 2 It is a schematic diagram of the working process of the nitrogen oxygen sensor. The first pump unit of the first test chamber is the main pump unit, the second pump unit of the second test chamber is the auxiliary pump unit, and the third pump unit of the third test chamber is the measuring pump unit.

[0038] First, the exhaust gas (mixed gas for calibration) passes through the first diffusion channel to the first test chamber. HC, CO, H2 and other gases will be oxidized on the electrodes of the first test chamber, and the remaining gases are mainly oxygen (O2) and nitrogen oxides (NO X ). Then set the main pump voltage V according to the oxygen concentration p0 , pumping oxygen out of or into the first test chamber, the ultimate goal is to keep the oxygen content in the first test chamber at a low and stable state. At this time, a first pump current (IP0) will be formed between the P+ and P- electrodes, which can be used to characterize the oxygen concentration in the exhaust gas. The first test chamber and the air reference chamber form an oxygen concentration difference, and according to the Nernst principle, a Nernst voltage will be formed between the REF and P- electrodes.

[0039] Subsequently, the exhaust gas will pass through the second diffusion channel to the second test chamber, which will continue to pump the remaining oxygen in the exhaust gas to the outside, and finally further reduce the oxygen content in the second test chamber. X Decomposed into NO, taking NO as an example, as O2 decreases, the balance of the reaction 2NO2→2NO+O2 is broken, thus accelerating the decomposition of NO2. By setting a suitable pump voltage V p1 , can guarantee NO X It is completely decomposed into NO, but NO will not be decomposed prematurely.

[0040] Finally, the exhaust gas will enter the third test chamber through the third diffusion channel. At this time, the remaining nitrogen oxides in the exhaust gas are mainly NO. There are two sources of NO: one is NO X The third test chamber is used to detect the concentration of NO in the exhaust gas, but it cannot be measured directly. The pump voltage V applied between P+ and M2 is p2 It will reduce NO (nitrogen oxides) and transmit them to the outside world through the electrolyte. As O2 decreases, the balance of the reaction 2NO→N2+O2 is broken, and eventually all NO will be decomposed. All the O2 pumped out comes from NO, so the third pump current (IP2) formed in the external circuit between the P+ and M2 electrodes can be used to indirectly measure the concentration of nitrogen oxides in the exhaust gas.

[0041] When the inventors used the nitrogen oxygen sensor as described above for calibration, they found that the calibration was often inaccurate. Figure 3 As shown, after in-depth research, the inventors found that NO decomposition will cause the current of the third pump current (IP2) to decrease, and the third pump current (IP2) is not linearly related to the concentration of nitrogen oxides. On this basis, the inventors proposed a new nitrogen oxide sensor calibration method and calibration system.

[0042] Figure 4 FIG. 1 is a flow chart of a method for calibrating a nitrogen oxygen sensor according to an embodiment of the present invention. Figure 4 As shown, the nitrogen oxygen sensor calibration method according to an embodiment of the present invention includes the following steps:

[0043] In step S101, a plurality of calibration values ​​are obtained;

[0044] A plurality of calibration values ​​are obtained, wherein calibration parameters of the calibration values ​​include at least one of oxygen concentration, nitrogen oxide concentration, a (measured) first pump current (measured IP0), a (measured) second pump current (measured IP1), and a (measured) third pump current (IP2).

[0045] In step S102, a first equation under a first oxygen concentration is established according to the calibration parameters of the calibration value;

[0046] A first equation at a first oxygen concentration is established according to the calibration parameters of the calibration values, for example, the first equation is established according to the calibration parameters of the fifth calibration value, the calibration parameters of the sixth calibration value and the calibration parameters of the seventh calibration value, and the first equation is a quadratic equation about the third pump current.

[0047] In step S103, a second equation under a second oxygen concentration is established according to the calibration parameters of the calibration value;

[0048] A second equation at a second oxygen concentration is established according to the calibration parameters of the calibration values, for example, the second equation is established according to the calibration parameters of the eighth calibration value, the calibration parameters of the ninth calibration value and the calibration parameters of the tenth calibration value, and the second equation is a quadratic equation about the third pump current.

[0049] In step S104, a calibration equation is established according to the first equation and the second equation, and the calibration equation is used for calibration of the nitrogen oxide sensor.

[0050] A calibration equation is established according to the first equation and the second equation. The calibration equation is used for calibration of the nitrogen oxygen sensor. That is, the nitrogen oxygen sensor that needs to be calibrated can be calibrated according to the calibration equation.

[0051] In an optional embodiment of the present invention, the calibration equation is a surface function about the first pump current (IP0) and the third pump current (IP2). Optionally, a third equation is established according to the calibration parameters of the first calibration value and the calibration parameters of the second calibration value, and the third equation is a linear equation about the first pump current; the calibration equation is established according to the first equation, the second equation and the third equation. Among them, the nitrogen oxide concentration corresponding to the first calibration value is zero; the nitrogen oxide concentration corresponding to the second calibration value is zero.

[0052] In an optional embodiment of the present invention, the air pressure corresponding to the multiple calibration values ​​is the same (the calibration parameters of the calibration values ​​include, for example, air pressure, and the air pressure of each calibration value is the same). The nitrogen oxygen sensor calibration method according to the embodiment of the present invention further includes:

[0053] A first verification value and a second verification value are obtained. Optionally, the verification parameters of the first verification value and the second verification value include at least one of oxygen concentration, nitrogen oxide concentration, air pressure (value), and the like.

[0054] A pressure correction coefficient is obtained according to the first verification value, the second verification value and the calibration equation. The pressure correction coefficient is used, for example, to correct the calibration equation to realize the calibration of the nitrogen oxide sensor at different air pressures, wherein the oxygen concentration corresponding to the first verification value is the same as the oxygen concentration corresponding to the second verification value; the nitrogen oxide concentration corresponding to the first verification value is the same as the nitrogen oxide concentration corresponding to the second verification value; the air pressure corresponding to the first verification value is the same as the air pressure corresponding to the calibration value, and the air pressure corresponding to the first verification value is less than the air pressure corresponding to the second verification value. Optionally, the verification parameter of the second verification value includes the second air pressure value, and a corrected calibration equation (corresponding to the second air pressure value) is obtained according to the second air pressure value, the air pressure corresponding to the calibration value and the calibration equation. The corrected calibration equation is used for calibration when the air pressure of the gas used for the calibration of the nitrogen oxide sensor is the second air pressure value.

[0055] It should be noted that the naming of the first to tenth calibration values ​​is for the purpose of distinguishing the overall description and has no additional limitation. In addition, when establishing different equations, the same calibration value can be used multiple times. For example, after using the first calibration value to establish the first equation, the first calibration value can also be used to establish the third equation.

[0056] The specific implementation of the present invention is further described in detail below in conjunction with the drawings and examples.

[0057] Figure 5 A method diagram of a nitrogen oxygen sensor calibration method according to a first embodiment of the present invention is shown. The following calibration points can be determined according to the most likely operating point in actual vehicle use, or according to the diesel engine type certification point, or determined by other methods.

[0058] like Figure 5 As shown, calibration point 1 ( Figure 5 The calibration parameters of the calibration point (marked with number 1 in the figure) include at least one of: 20% oxygen concentration, 0ppm (parts per million) nitric oxide, 1bar air pressure, a first pump current, a second pump current and a third pump current.

[0059] Calibration point 2 ( Figure 5 The calibration parameters of the pump (the second point marked in the figure) include at least one of: 20% oxygen concentration, 300ppm (parts per million) nitric oxide, 1bar air pressure, a first pump current, a second pump current and a third pump current.

[0060] Calibration point three ( Figure 5 The calibration parameters of the pump include: 20% oxygen concentration, 1500ppm (parts per million) nitric oxide, 1bar air pressure, at least one of the first pump current, the second pump current and the third pump current.

[0061] Calibration point 4 ( Figure 5 The calibration parameters of the calibration point (marked as point 4 in the figure) include at least one of: 4% oxygen concentration, 0ppm (parts per million) nitric oxide, 1bar air pressure, a first pump current, a second pump current and a third pump current.

[0062] Calibration point five ( Figure 5 The calibration parameters of the gas flowmeter (point 5 marked in the figure) include at least one of: 4% oxygen concentration, 300ppm (parts per million) nitric oxide, 1bar air pressure, a first pump current, a second pump current and a third pump current.

[0063] Calibration point six ( Figure 5 The calibration parameters of the gas flowmeter (the sixth point marked in the figure) include at least one of: 4% oxygen concentration, 1500ppm (parts per million) nitric oxide, 1bar air pressure, a first pump current, a second pump current and a third pump current.

[0064] Verification Point 1 Figure 5 The verification parameters of the calibration point 11 (marked in the figure) include: 4% oxygen concentration, 450ppm (parts per million) nitric oxide, 1bar air pressure, first pump current, second pump current and third pump current, etc. Optionally, the verification point 1 can not only be used to verify the calibration equation, but also can be used in conjunction with other verification points to realize the correction of the calibration equation.

[0065] Verification Point 2 Figure 5 The verification parameters of the test instrument (point 12 marked in the figure) include: 4% oxygen concentration, 450ppm (parts per million) nitric oxide, 1.5bar air pressure, at least one of the first pump current, the second pump current and the third pump current.

[0066] Optionally, IP2 is the horizontal coordinate and IP0 is the vertical coordinate. If IP1 is fixed, the graph is a curve rather than a surface.

[0067] It should be noted that the first to tenth calibration values ​​in the claims are named for the purpose of distinguishing the overall solution. Calibration points 1 to 6, verification point 1 and verification point 2 in the embodiments are for detailed description in conjunction with the drawings. The corresponding relationship between the above two can be easily and clearly obtained based on the text content.

[0068] Establishing the first equation at the first oxygen concentration according to the calibration parameters of the calibration value includes calculating a quadratic equation of 20% oxygen concentration according to calibration point one, calibration point two and calibration point three (low ppm is preferred):

[0069] NO Xppm =a1·I 2 P2 +b1·I P2 +c1;

[0070] Among them, NO Xppm is the content of nitrogen oxides, a1 is a constant, b1 is a constant, I P2 is the third pump current, c1 is a constant.

[0071] Establishing the second equation at the second oxygen concentration according to the calibration parameters of the calibration value includes calculating a quadratic equation at 4% oxygen concentration according to calibration point four, calibration point five and calibration point six (high ppm is preferred):

[0072] NO Xppm =a2·I 2 P2 +b2·I P2 +c2;

[0073] Among them, NO Xppm is the content of nitrogen oxides, a2 is a constant, b2 is a constant, I P2 is the third pump current, and c2 is a constant.

[0074] A calibration equation for calibrating the nitrogen oxygen sensor is established based on the first equation and the second equation mentioned above.

[0075] Further, establishing a third equation according to the calibration parameters of the first calibration value and the calibration parameters of the second calibration value includes fitting a linear equation of one variable according to calibration point one and calibration point four (the fitting condition is within the range of IP1):

[0076] NO Xppm = k·I P0 +d;

[0077] Among them, NO Xppm is the content of nitrogen oxides, k is a constant, I P0 is the first pump current, and d is a constant.

[0078] The following formula (as the calibration equation) is calculated using a1, b1, c1, a2, b2, c2 in the first and second equations and k and d in the third equation:

[0079] NO X = (A0· (I P0 ·k+d)+A1)·I 2 P2 +(B0·(I P0 ·k+d)+B1)·I P2 +(C0·(I P0 ·k+d)+C1);

[0080] Among them, A0 and A1 are constants obtained according to a1 and a2; B0 and B1 are constants obtained according to b1 and b2; C0 and C1 are constants obtained according to c1 and c2.

[0081] Furthermore, after the calibration equation is obtained, the verification parameters of the verification point one are substituted into the calibration equation for verification, for example, by verifying the definition range, defining the internal control indicators, and the like.

[0082] Furthermore, after obtaining the calibration equation, the verification parameters of verification point one and the verification parameters of verification point two are respectively substituted into the calibration equation, and the pressure correction coefficient is obtained according to the verification parameters of verification point one, the verification parameters of verification point two, and the results of the two being substituted into the calibration equation respectively (the pressure correction coefficient is, for example, a constant, of course, it can also be a variable or a function, etc.). The calibration equation is corrected according to the pressure correction coefficient to obtain the pressure correction calibration equation. Specifically, the air pressure corresponding to calibration points one to six is ​​1 bar, and the obtained calibration equation also corresponds to an air pressure of 1 bar. The air pressure corresponding to verification point two is 1.5 bar, and the obtained pressure correction calibration equation corresponds to an air pressure of 1.5 bar. Optionally, pressure correction calibration equations corresponding to different air pressures are established according to the verification parameters of multiple verification points. During the calibration process, the gas pressure of the calibration gas is obtained, and the corresponding pressure correction calibration equation is selected according to the air pressure for calibration.

[0083] In an optional embodiment of the present invention, the calibration method of the nitrogen oxygen sensor further includes establishing a fourth equation according to the calibration parameters of the calibration value, wherein when the third pump current is greater than the first threshold value, the nitrogen oxygen sensor is calibrated according to the fourth equation; when the third pump current is less than or equal to the first threshold value, the nitrogen oxygen sensor is calibrated according to the calibration equation. Optionally, the fourth equation is a linear equation about the third pump current established according to the third calibration value and the fourth calibration value, wherein the fourth calibration value is determined according to the highest nitrogen oxygen measurement value.

[0084] Specifically, refer to Figure 6 , Figure 6 A method diagram of a nitrogen oxide sensor calibration method according to a second embodiment of the present invention is shown. In the second embodiment, the method of establishing a calibration equation through calibration points one to six is ​​the same as that of the first embodiment, but the second embodiment divides the calibration equation into applicable intervals. The concentrations of nitrogen oxides corresponding to calibration points one to six are all less than 1500ppm, and the applicable range of the calibration equation obtained according to calibration points one to six should also be that the concentration of nitrogen oxides is less than 1500ppm (when the concentration of nitrogen oxides is greater than 1500ppm, a new calibration equation is established). However, the concentration of nitrogen oxides is the object of calibration, and therefore, the third pump current value related to the concentration of nitrogen oxides is used to divide the applicable interval of the calibration range.

[0085] On the basis of the first embodiment, a calibration point 7 is added ( Figure 6 The fourth equation is established according to the calibration parameters of the calibration value, including fitting the calibration point six and calibration point seven to obtain a linear equation of one variable:

[0086] NO Xppm =A3·I P2 +C3;

[0087] Among them, NO Xppm is the content of nitrogen oxides, A3 is a constant, I P2 is the third pump current, and C3 is a constant.

[0088] When the measured third pump current is greater than the first threshold value (the first threshold value is calculated by the formula (1500-C3) / A3, or obtained by setting a constant value, etc.), calibration is performed according to the fourth equation; when the measured third pump current is less than or equal to the first threshold value, calibration is still performed using the calibration equation obtained through calibration points one to six.

[0089] Optionally, when the measured third pump current is greater than the first threshold, the oxygen concentration is not considered. Accordingly, the range of the third pump current (IP2) is changed from -1-6μA (negative one to positive six microamperes) to -1-8μA (negative one to positive eight microamperes), NO Xppm The output value is limited to 3000. The data sent by the host computer increases by two, A3 and C3.

[0090] Optionally, calibration point seven is used as the measurement point based on the highest nitrogen and oxygen measurement value of 2000PPM, and the NO+NO=N2+O2 deviation coefficient is required to be less than 16.7%.

[0091] Optionally, NO Xppm It is a surface function, input IP0, IP2, and output PPM value.

[0092] Figure 7 A comparative schematic diagram of the calibration method before optimization is shown. Figure 8 The figure shows a comparison diagram of the optimized calibration method. Figure 7 and Figure 8 It can be seen that the optimized solution (ie, the calibration method according to this embodiment) has a better and more accurate calibration effect.

[0093] Fig. 9 FIG. 2 shows a schematic diagram of calibration test results according to an embodiment of the present invention. Fig. 9 As shown, the calibration point is increased (oxygen content is 4%; NO X =2500ppm) to verify the test results, it can be seen that the calibration results are more accurate. The test results show that when the oxygen concentration is 4%, the test result is 2.2% lower; when the oxygen concentration is 10%, the test result is 6.4% lower.

[0094] According to another aspect of the present invention, a nitrogen oxygen sensor calibration system is provided, which is calibrated by the calibration method described above. The nitrogen oxygen sensor calibration system according to the present invention can be any type of existing nitrogen oxygen sensor calibration system.

[0095] Fig.10FIG. 2 shows a schematic diagram of the structure of a nitrogen oxygen sensor calibration system according to an embodiment of the present invention. Fig.10 As shown, the nitrogen oxygen sensor calibration system according to an embodiment of the present invention includes a mixed gas source module and a host computer control module. The mixed gas source module includes multiple gas sources, multiple controllable flow meters and a mixer; the multiple controllable flow meters are connected to the multiple gas sources one by one, and the gases from the multiple gas sources flow out through the corresponding controllable flow meters and are mixed in the mixer to form a mixed gas, wherein the gases from the multiple gas sources include nitrogen oxides and oxygen. The host computer control module includes a host computer and an industrial control card; the host computer is connected to multiple controllable flow meters to control the concentration of nitrogen oxides and oxygen in the mixed gas; the industrial control card is used to obtain the test data of nitrogen oxides on the mixed gas to calibrate the mixed gas.

[0096] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0097] According to the embodiments of the present invention as described above, these embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and changes can be made based on the above description. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can make good use of the present invention and the modified use based on the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for calibrating a nitrogen oxygen sensor, comprising: Get multiple calibration values; Establishing a first equation at a first oxygen concentration according to the calibration parameters of the calibration value; Establishing a second equation at a second oxygen concentration according to the calibration parameters of the calibration value; Establishing a third equation according to the calibration parameters of the first calibration value and the calibration parameters of the second calibration value, wherein the third equation is a linear equation about the first pump current; Establishing a calibration equation according to the first equation, the second equation and the third equation, wherein the calibration equation is used for calibrating the nitrogen oxygen sensor; The calibration method further comprises: A fourth equation is established according to the calibration parameters of the calibration value, When the third pump current is greater than the first threshold, the nitrogen oxide sensor is calibrated according to the fourth equation; when the third pump current is less than or equal to the first threshold, the nitrogen oxide sensor is calibrated according to the calibration equation. 2 . The nitrogen oxide sensor calibration method according to claim 1 , wherein the calibration parameter comprises at least one of oxygen concentration, nitrogen oxide concentration, a first pump current and a third pump current.

3. The nitrogen oxide sensor calibration method according to claim 1, wherein: The nitrogen oxide concentration corresponding to the first calibration value is zero; the nitrogen oxide concentration corresponding to the second calibration value is zero. 4 . The nitrogen oxide sensor calibration method according to claim 1 , wherein the calibration equation is a surface function about the first pump current and the third pump current.

5. The nitrogen oxygen sensor calibration method according to claim 1, wherein the fourth equation is a linear equation about the third pump current established according to the third calibration value and the fourth calibration value, in, The fourth calibration value is determined according to the maximum nitrogen oxide measurement value.

6. The nitrogen oxygen sensor calibration method according to claim 1, wherein the establishing of a first equation under a first oxygen concentration according to the calibration parameters of the calibration value comprises: The first equation is established according to the calibration parameters of the fifth calibration value, the calibration parameters of the sixth calibration value and the calibration parameters of the seventh calibration value. The first equation is a quadratic equation about the third pump current.

7. The nitrogen oxygen sensor calibration method according to claim 1, wherein the establishing a second equation under a second oxygen concentration according to the calibration parameters of the calibration value comprises: The second equation is established according to the calibration parameters of the eighth calibration value, the calibration parameters of the ninth calibration value and the calibration parameters of the tenth calibration value, and the second equation is a quadratic equation about the third pump current.

8. The nitrogen oxygen sensor calibration method according to claim 1, wherein the air pressures corresponding to the multiple calibration values ​​are the same; The calibration method further comprises: Obtain a first verification value and a second verification value; According to the first verification value, the second verification value and the calibration equation, a pressure correction coefficient is obtained. Among them, the oxygen concentration corresponding to the first verification value is the same as the oxygen concentration corresponding to the second verification value; the nitrogen oxide concentration corresponding to the first verification value is the same as the nitrogen oxide concentration corresponding to the second verification value; the air pressure corresponding to the first verification value is the same as the air pressure corresponding to the calibration value, and the air pressure corresponding to the first verification value is less than the air pressure corresponding to the second verification value.

9. A nitrogen oxygen sensor calibration system, calibrated by the calibration method according to any one of claims 1 to 8, the calibration system comprising a mixed gas source module and a host computer control module; The mixed gas source module includes multiple gas sources, multiple controllable flow meters and a mixer; the multiple controllable flow meters are connected to the multiple gas sources one by one, and the gases from the multiple gas sources flow out through the corresponding controllable flow meters and are mixed in the mixer to form a mixed gas, wherein: The gases from the plurality of gas sources include nitrogen oxides and oxygen; The host computer control module includes a host computer and an industrial control card; the host computer is connected to the multiple controllable flow meters to control the concentration of nitrogen oxides and oxygen in the mixed gas; the industrial control card is used to obtain test data of the nitrogen oxide sensor on the mixed gas to calibrate the mixed gas.

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