A NO x Method and system for synchronous measurement of NH3 concentration

Abstract

This invention relates to a method and system for simultaneous measurement of NOx and NH3 concentrations. The method includes: introducing NOx into a nitrogen dioxide atmosphere, and then into a nitrogen dioxide atmosphere. x The sensor's first oxygen pump applies an excitation voltage; simultaneously, NO is collected. x The sensor's output signal; Fourier transforms are performed on the excitation voltage signal sequence and the output signal sequence respectively to obtain the frequency domain feature vectors of the excitation voltage and the output signal; Based on the frequency domain feature vectors of the excitation voltage and the output signal obtained under different excitation voltages, an overdetermined system of equations is constructed and solved to obtain NO. x Concentration and NH3 concentration. Compared with the prior art, the present invention solves the problem of NH3 affecting NO concentration. x The cross-sensitivity issue of measurements was addressed by providing NO synchronously. x The measured value of NH3 concentration was compared with that of NO. x The accuracy of concentration and NH3 concentration measurement.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of automobile exhaust aftertreatment, and in particular to a NO x concentration synchronous measurement method and system. BACKGROUND

[0002] With the increasingly stringent global emission regulations, selective catalytic reduction technology (SCR) has become one of the core technologies of diesel vehicle exhaust aftertreatment systems. The SCR system reduces nitrogen oxides (NO x ) in exhaust gas by injecting urea (decomposed into ammonia NH3). To achieve efficient closed-loop control of the SCR system, it is necessary to accurately measure the NO x concentration downstream of the catalyst.

[0003] The widely used NO x sensor is a double-chamber flow-limited amperometric sensor based on zirconia solid electrolyte. Its basic principle is: the first chamber pumps the oxygen partial pressure in the chamber to a stable value through the first oxygen pump, and the Pt electrode catalyzes the oxidation of some easily oxidizable gases; the second chamber decomposes the NO x diffused from the first chamber into N2 and O2 through the second oxygen pump, and the limiting current corresponding to the amount of oxygen generated by the decomposition is measured to calculate the NO x concentration.

[0004] However, the existing NO x sensor has a serious technical defect: cross-sensitivity to NH3. When NH3 leakage occurs in the SCR system, unreacted NH3 will enter the NO x sensor. On the high-temperature Pt electrode in the first chamber, NH3 will be oxidized into NO or N2 (for example: 4NH3+5O2→4NO+6H2O). If it is oxidized into NO, it will cause the sensor reading to be too high, resulting in measurement errors of NO x concentration, which in turn affects the closed-loop control accuracy of the SCR system, leading to NO x , NH3 emission exceeding the standard or waste of urea. Existing solutions include: 1) a NH3 sensor is connected in series before the NO x sensor, increasing the cost and complexity of the system; 2) a NH3 leakage model based on engine operating conditions is established for software compensation, which is complex and has limited accuracy; 3) improve the sensor structure or material, which has high research and development costs.

[0005] The traditional NO x sensor drives the first oxygen pump with a constant voltage, and the NO xConcentration. However, in practical applications, sensor output is easily affected by temperature fluctuations, airflow changes, NH3 cross interference and sensor aging, etc., resulting in measurement deviation. In addition, when NO x and NH3 exist simultaneously in the tail gas, the reactions of the two on the sensor electrode are competitive and coupled, and a single steady-state response cannot distinguish the contributions of the two, forming an underdetermined problem, which cannot achieve simultaneous measurement. Patent application CN109312655A discloses a method for detecting NH3 leakage using a NOX sensor. The method compares the NO x The deviation between the actual measured signal and the estimated value is set as a threshold value under high or low temperature working conditions. If the deviation value or NO x The average value of the actual measured signal is continuously higher than the threshold value, and it is determined that there is NH3 leakage and a flag is set. This method only relies on NO x The original defect of the sensor (cross-sensitivity to NH3) indirectly judges NH3 leakage, which neither eliminates NH3 cross interference nor synchronously obtains NH3 concentration.

[0006] Therefore, there is an urgent need for a low-cost, high-precision and high-response-speed method to eliminate the NH3 cross-sensitivity of the existing NO x sensor and simultaneously obtain the concentration information of NH3. SUMMARY

[0007] The purpose of the present application is to overcome the defects of the prior art and provide a NOx and NH3 concentration synchronous measurement method and system.

[0008] The purpose of the present application can be achieved by the following technical solutions:

[0009] A NO x and NH3 concentration synchronous measurement method, comprising the following steps:

[0010] Applying an excitation voltage to the first oxygen pump of the NO x sensor;

[0011] Synchronously collecting the output signal of the NO x sensor while applying the excitation voltage;

[0012] Performing Fourier transform on the signal sequence of the excitation voltage and the signal sequence of the output signal respectively to obtain the frequency domain feature vector of the excitation voltage and the frequency domain feature vector of the output signal;

[0013] According to the frequency domain feature vectors of the excitation voltage and the output signal obtained under different excitation voltages, an overdetermined equation set is constructed and solved to obtain the NO x concentration and the NH3 concentration.

[0014] Further, the NO x The sensor is a double-chamber current-limited amperometric sensor based on zirconium oxide solid electrolyte, comprising a first chamber and a second chamber, wherein a first oxygen pump is arranged in the first chamber, and a second oxygen pump and a measurement pump are arranged in the second chamber.

[0015] Further, the excitation voltage dynamically changes over time, which is obtained by superimposing a periodic alternating current signal on a direct current bias voltage, and the excitation voltage is:

[0016]

[0017] wherein, is the excitation voltage, is time, is the direct current bias voltage, is the periodic alternating current signal.

[0018] Further, the frequency of the periodic alternating current signal is set in the range of 0.1 Hz to 10 kHz, preferably 1 Hz to 5 kHz, and more preferably 1 kHz to 2 kHz. x The electrochemical system of the sensor can respond normally and can cause a change in the oxidation rate of NH3 on the Pt electrode within a range.

[0019] Further, the NO x The output signal of the sensor is the pump current of the measurement pump, and the calculation formula is:

[0020]

[0021]

[0022] wherein, is the output signal, is the sensitivity of the NO x sensor, is the NO x concentration, is the NH3 concentration, is the conversion rate of NH3 to NO x , is the surface area of the Pt electrode surface in the first chamber for NH3 oxidation reaction, is a natural exponential function, is the theoretical maximum rate that can be reached by the NH3→NO x reaction when all active sites on the Pt electrode surface are completely covered by NH3, is the energy barrier that needs to be overcome for the N–H bond of the NH3 molecule to break on the Pt electrode surface and form a N–O bond, is the gas constant, is the working temperature, is the adsorption equilibrium constant of NH3 on the Pt electrode surface, is the competitive adsorption term, is the adsorption equilibrium constant of O2 on the Pt electrode surface, is the oxygen partial pressure in the first chamber, is the theoretical maximum rate of NH3→N2 reaction when all active sites on the Pt electrode surface are completely covered by O2, is the energy barrier for the N–H bond breaking and N–N bond forming of NH3 molecule on the Pt electrode surface, is the desorption rate constant.

[0023] Further, the oxygen partial pressure in the first chamber is:

[0024]

[0025] wherein, is the oxygen partial pressure in the first chamber, is the reference oxygen partial pressure, is the natural exponential function, is the Faraday constant, is the gas constant, is the working temperature, is the excitation voltage;

[0026] The competitive adsorption term is:

[0027]

[0028] wherein, is the competitive adsorption term, is the adsorption equilibrium constant of NH3 on the Pt electrode surface, is the NH3 concentration.

[0029] Further, the frequency domain feature vector comprises the amplitude and phase information of the signal sequence at the fundamental frequency and harmonic frequencies.

[0030] Further, the overdetermined equations are:

[0031]

[0032] wherein, is the frequency domain feature vector of the output signal obtained under the application of the 1st excitation voltage, is the model function of the support vector machine, is the frequency domain feature vector of the 1st excitation voltage, is the NO x concentration, is the NH3 concentration, To obtain the frequency domain eigenvector of the output signal under the second excitation voltage, For the frequency domain eigenvector of the second excitation voltage, To obtain the frequency domain eigenvector of the output signal under the application of the Mth excitation voltage, Let be the frequency domain eigenvector of the Mth excitation voltage;

[0033] The NO x The concentration estimates of NH3 and NH4+ were obtained by fitting the solution using the least squares method, where the objective function of the least squares method is:

[0034]

[0035] In the formula, Let the objective function be the least squares method. The number of different excitation voltages, In the first The frequency domain eigenvector of the output signal is obtained under the application of an excitation voltage. In the first The frequency domain eigenvector of the excitation voltage, It is the vector norm.

[0036] Furthermore, based on various known NO... x The combined concentration of NH3 and the frequency domain eigenvectors of the excitation voltage and output signal collected under different operating conditions, along with their corresponding NO concentrations. x The actual concentration of NH3 was used to train the support vector machine through offline calibration.

[0037] According to another aspect of the invention, a NO is provided. x The system for simultaneous measurement of NH3 concentration includes:

[0038] Excitation voltage application module, used to apply excitation voltage to NO x The sensor's first oxygen pump applies an excitation voltage;

[0039] The output signal acquisition module is used to simultaneously acquire NO while the excitation voltage is applied. x The sensor's output signal;

[0040] The frequency domain feature vector acquisition module is used to perform Fourier transform on the signal sequence of the excitation voltage and the signal sequence of the output signal respectively to obtain the frequency domain feature vector of the excitation voltage and the frequency domain feature vector of the output signal.

[0041] The synchronous measurement module is used to construct and solve an overdetermined system of equations based on the frequency domain eigenvectors of the excitation voltage and the frequency domain eigenvectors of the output signal obtained under different excitation voltages, to obtain NO.x concentration of NH3.

[0042] Compared with the prior art, the present application has the following beneficial effects:

[0043] 1. The present application is based on the existing commercially available NO x sensor hardware, by applying an excitation voltage to the first oxygen pump of the NO x sensor and synchronously collecting the output signal of the NO x sensor, and solving the excitation voltage frequency domain feature vector and the output signal frequency domain feature vector obtained under different excitation voltage applications to obtain the NO x concentration and NH3 concentration, solving the cross-sensitivity problem of NH3 on the NO x measurement, and synchronously providing the measurement values of NO x and NH3 concentration, providing more abundant control inputs for the SCR system.

[0044] 2. The present application is based on frequency domain analysis and support vector machine, by the excitation voltage frequency domain feature vector and the output signal frequency domain feature vector obtained under different excitation voltage applications, fully mining the deep information in the dynamic response of the NO x sensor, constructing a more accurate concentration solving overdetermined equation set, and then solving the NO x concentration and NH3 concentration, improving the measurement accuracy of NO x concentration and NH3 concentration. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 A flowchart of a NO x and NH3 concentration synchronous measurement method according to the present application is shown in the figure.

[0046] Figure 2 A schematic diagram of the relationship between the excitation voltage signal and the output signal is shown in the figure. DETAILED DESCRIPTION

[0047] The present application will be described in detail below in combination with the drawings and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present application, and detailed implementation and specific operation processes are given, but the protection scope of the present application is not limited to the following embodiments.

[0048] English abbreviations involved:

[0049] Selective Catalytic Reduction, SCR

[0050] Support Vector Machine, SVM

[0051] Embodiment 1

[0052] The embodiment provides a NO x synchronous measurement method, as shown in the following steps: Figure 1

[0053] S1, applying an excitation voltage to a first oxygen pump of a NO x sensor.

[0054] The NO x sensor is a double-chamber current-limiting amperometric sensor based on a zirconia solid electrolyte, comprising a first chamber and a second chamber, wherein the first chamber is provided with a first oxygen pump, and the second chamber is provided with a second oxygen pump and a measurement pump.

[0055] The catalytic oxidation efficiency of the Pt electrode pair in the first chamber to NH3 is highly sensitive to the oxygen partial pressure in the chamber, and the oxygen partial pressure in the first chamber is quantitatively set by applying an excitation voltage to the first oxygen pump of the NO x sensor. The second oxygen pump voltage is adjusted according to the excitation voltage on the first oxygen pump to realize complete pumping of oxygen in the second oxygen pump. The excitation voltage dynamically changes over time and is obtained by superimposing a periodic alternating current signal on a direct current bias voltage, and the excitation voltage is:

[0056]

[0057] wherein, is the excitation voltage, is the time, is the direct current bias voltage, is the periodic alternating current signal. The periodic alternating current signal can be a sine wave, a square wave or a triangular wave, and the frequency is set to be within the range in which the electrochemical system of the NO x sensor can normally respond and can cause the oxidation rate of NH3 on the Pt electrode to change, for example, 1 Hz to 100 Hz.

[0058] S2, synchronously collecting the output signal of the NO x sensor while applying the excitation voltage.

[0059] The output signal of the NO x sensor is the result of the joint action of the real NOx concentration , the NH3 concentration and the excitation voltage . Since periodically changes, will also exhibit a corresponding periodic change. The output signal of the NO x sensor is the pump current of the measurement pump, and the calculation formula is:

[0060] ​

[0061] In the formula, For output signal, NO x Sensor sensitivity, NO x concentration, The concentration of NH3. The conversion of NH3 to NO x conversion rate

[0062] The diagram showing the relationship between the excitation voltage signal and the output signal is shown below. Figure 2 As shown, the excitation voltage signal and the output signal have the same frequency. The amplitude of the excitation voltage signal varies between 0.3 and 0.7, while the amplitude of the output signal varies between 0.5 and 1.1. The amplitude of the output signal is affected by the excitation voltage signal, and there is a phase delay between the excitation voltage signal and the output signal.

[0063] The oxygen pump in the first chamber is a solid electrolyte electrochemical cell. The relationship between its voltage and the partial pressure of oxygen in the chamber follows the Nernst equation. The partial pressure of oxygen in the first chamber is:

[0064]

[0065] In the formula, This represents the partial pressure of oxygen within the first chamber. For reference oxygen partial pressure, It is a natural exponential function. It is Faraday's constant. The gas constant is... Operating temperature The excitation voltage;

[0066] At the Pt electrode, NH3 is partially oxidized ( ) and complete oxidation ( The two molecules are in a competitive relationship and are highly sensitive to oxygen partial pressure. Therefore, NH3 is converted to NO. x The conversion rate is a function of the oxygen partial pressure, specifically expressed as:

[0067]

[0068] In the formula, The conversion of NH3 to NO x Conversion rate The concentration of NH3. The surface area of ​​the Pt electrode in the first chamber used for the NH3 oxidation reaction. It is a natural exponential function. When all active sites on the Pt electrode surface are completely covered by NH3, NH3→NOx the theoretical maximum rate that the reaction can reach, the energy barrier that needs to be overcome for an NH3 molecule to break the N-H bond and form a N-O bond on the Pt electrode surface, the gas constant, the operating temperature, the adsorption equilibrium constant of NH3 on the Pt electrode surface, the competitive adsorption term, the adsorption equilibrium constant of O2 on the Pt electrode surface, the partial pressure of oxygen in the chamber, the theoretical maximum rate that the NH3→N2 reaction can reach when all active sites on the Pt electrode surface are completely covered by O2, the energy barrier that needs to be overcome for an NH3 molecule to break the N-H bond and form a N-N bond on the Pt electrode surface, the desorption rate constant.

[0069] the competitive adsorption term is:

[0070]

[0071] wherein, the competitive adsorption term, the adsorption equilibrium constant of NH3 on the Pt electrode surface, the concentration of NH3, the adsorption equilibrium constant of O2 on the Pt electrode surface, the partial pressure of oxygen in the chamber.

[0072] S3, Fourier transform the signal sequence of the excitation voltage and the signal sequence of the output signal respectively to obtain the frequency domain feature vector of the excitation voltage and the frequency domain feature vector of the output signal.

[0073] In a fixed time window, the collected signal sequence of the excitation voltage and the signal sequence of the output signal are respectively Fourier transformed to obtain their frequency domain feature vectors:

[0074]

[0075]

[0076] wherein, the frequency domain feature vector of the excitation voltage, the Fourier transform, the excitation voltage, the frequency domain feature vector of the output signal, the output signal.

[0077] Frequency domain feature vectors include the amplitude and phase information of the signal sequence at the fundamental and harmonic frequencies. The amplitude and phase information together reflect the sensor system's response to NO under specific frequency excitation. x The combined response characteristics of NH3. This step effectively overcomes the time-domain delay problem caused by gas diffusion and reaction.

[0078] S4. Based on the frequency domain eigenvectors of the excitation voltage and the frequency domain eigenvectors of the output signal obtained under different excitation voltages, construct an overdetermined system of equations and solve it to obtain NO. x Concentration and NH3 concentration.

[0079] The overdetermined system of equations is as follows:

[0080]

[0081] In the formula, To obtain the frequency domain eigenvector of the output signal under the first applied excitation voltage, For the model function of support vector machines, For the frequency domain eigenvector of the first excitation voltage, NO x concentration, The concentration of NH3. To obtain the frequency domain eigenvector of the output signal under the second excitation voltage, For the frequency domain eigenvector of the second excitation voltage, To obtain the frequency domain eigenvector of the output signal under the application of the Mth excitation voltage, Let be the frequency domain eigenvector of the Mth excitation voltage;

[0082] NO x The concentration estimates of NH3 and NH4+ were obtained by fitting the solution using the least squares method. The objective function of the least squares method is:

[0083]

[0084] In the formula, Let the objective function be the least squares method. The number of different excitation voltages, In the first The frequency domain eigenvector of the output signal is obtained under the application of an excitation voltage. In the first The frequency domain eigenvector of the excitation voltage, It is the vector norm.

[0085] During the training of SVM, based on various known NOs xand the real concentration of NH3, the SVM is trained by offline calibration. x and the real concentration of NH3, the SVM is trained by offline calibration.

[0086] Embodiment 2

[0087] This embodiment is according to the NO x and NH3 concentration synchronous measurement method, in the NO x In the case of reducing the response performance requirements of the sensor, a quasi-static measurement method is adopted, including the following steps:

[0088] At least two (preferably three or more) different, pre-set constant direct current voltage combinations are applied to the first oxygen pump and the second oxygen pump in turn, the first oxygen pump voltage is denoted as , , wherein The second oxygen pump voltage is adjusted according to the first oxygen pump voltage to realize the complete pumping of oxygen in the second oxygen pump. The first oxygen pump voltage for a period of time sufficient to make the NO x sensor output reach a steady state.

[0089] Under the action of each constant direct current voltage , the corresponding stable NO x sensor output value is collected, thereby obtaining a set containing multiple data pairs . According to the set, an over-determined equation group is constructed:

[0090]

[0091] In the formula, is the NO x sensor output value, is the model function of the support vector machine, is the NO x concentration, is the NH3 concentration, is the first oxygen pump voltage.

[0092] The over-determined equation group is solved by the least square method, and the NO x concentration and the NH3 concentration are calculated.

[0093] Embodiment 3

[0094] This embodiment provides a NO x and NH3 concentration synchronous measurement system, comprising:

[0095] The excitation voltage application module is configured to apply an excitation voltage to the NO x sensor;

[0096] The output signal acquisition module is configured to synchronously acquire the output signal of the NO x sensor while the excitation voltage is applied.

[0097] The frequency domain feature vector acquisition module is configured to perform Fourier transform on the signal sequence of the excitation voltage and the signal sequence of the output signal respectively to obtain a frequency domain feature vector of the excitation voltage and a frequency domain feature vector of the output signal.

[0098] The synchronous measurement module is configured to construct an overdetermined equation set and solve the overdetermined equation set to obtain the concentration of the NO and the concentration of the NH3 according to the frequency domain feature vector of the excitation voltage and the frequency domain feature vector of the output signal obtained under different excitation voltage applications. x

[0099] The rest is the same as in Embodiment 1.

[0100] The above detailed the preferred embodiments of the present application. It should be understood that those of ordinary skill in the art can make modifications and variations without creative work based on the concept of the present application. Therefore, any technical solution obtained by logical analysis, reasoning or limited experiment based on the prior art according to the concept of the present application shall be within the protection scope defined by the claims.​

Claims

1. A NO x A method of measuring in synchronization with the NH3 concentration, characterized by, The method comprises the following steps: To NO x The first oxygen pump of the sensor applies an excitation voltage; The output signal of the sensor is synchronously collected with the application of the excitation voltage x The output signal of the sensor is synchronously collected with the application of the excitation voltage The signal sequence of the excitation voltage and the signal sequence of the output signal are respectively subjected to Fourier transform to obtain a frequency domain feature vector of the excitation voltage and a frequency domain feature vector of the output signal; Based on the frequency domain feature vectors of the excitation voltage and the output signal obtained under different excitation voltage applications, an over-determined equation set is constructed and solved to obtain NO x concentration and NH3 concentration.

2. The NOx sensor according to claim 1, wherein the NOx sensor is a sensor for measuring a concentration of NOx in exhaust gas. x A method for synchronously measuring the concentration of NH3, characterized by, The NO x The sensor is a double-chamber flow-limited amperometric sensor based on a zirconium oxide solid electrolyte, comprising a first chamber in which a first oxygen pump is arranged and a second chamber in which a second oxygen pump and a measurement pump are arranged.

3. The NOx sensor according to claim 2, wherein the NOx sensor is a sensor for measuring a concentration of NOx in exhaust gas. x A method for synchronously measuring the concentration of NH3, characterized by, The excitation voltage dynamically changes over time and is obtained by superimposing a periodic alternating current signal on a direct current bias voltage, and the excitation voltage is: wherein is the excitation voltage, is time, is the DC bias voltage, is the periodic AC signal.

4. The NOx sensor according to claim 3, wherein the NOx sensor is a sensor for measuring a concentration of NOx in exhaust gas. x A method for synchronously measuring the concentration of NH3, characterized by, The frequency of the periodic alternating signal is set in the range of 0.1 to 10 Hz x The electrochemical system of the sensor is able to respond normally and is able to cause a change in the rate of oxidation of NH3 on the Pt electrode within a range.

5. The NOx sensor according to claim 4, wherein the NOx sensor is a NOx sensor according to any one of claims 1 to 3. x A method of synchronously measuring the concentration of NH3, characterized by, The NO x The output signal of the sensor is the pump current of the measuring pump, which is calculated as wherein, is the output signal, is NO x sensitivity of the sensor, is NO x concentration, is the NH3concentration, is the conversion of NH3to NO x conversion, is the surface area of the Pt electrode surface in the first chamber available for the NH3oxidation reaction, is the natural exponential function, is the theoretical maximum rate of the NH3→ NO x reaction when all active sites of the Pt electrode surface are completely covered by NH3, is the energy barrier to be overcome for the N–H bond of a NH3molecule to break on the Pt electrode surface and form a N–O bond, is the gas constant, is the operating temperature, is the adsorption equilibrium constant of NH3on the Pt electrode surface, is the competitive adsorption term, is the adsorption equilibrium constant of O2on the Pt electrode surface, is the oxygen partial pressure in the chamber of the first chamber, is the theoretical maximum rate of the NH3→ N2reaction when all active sites of the Pt electrode surface are completely covered by O2, is the energy barrier to be overcome for the N–H bond of a NH3molecule to break on the Pt electrode surface and form a N–N bond, is the desorption rate constant.

6. The NOx sensor according to claim 5, wherein the NOx sensor is a sensor for measuring a concentration of NOx in exhaust gas. x A method for synchronously measuring the concentration of NH3, characterized by, The oxygen partial pressure in the cavity of the first cavity is: wherein is the oxygen partial pressure in the cavity of the first chamber, is the reference oxygen partial pressure, is the natural exponential function, is the Faraday constant, is the gas constant, is the working temperature, is the excitation voltage; The competitive adsorption term is: wherein is the competitive adsorption term, is the adsorption equilibrium constant of NH3 on the Pt electrode surface, is the NH3 concentration.

7. The NO of claim 1 x A method for measuring concentration of NH3 synchronously with the method for measuring concentration of NH3, characterized in that, The frequency domain feature vector comprises amplitude and phase information of the signal sequence at a fundamental frequency and harmonic frequencies.

8. The NO x A method for synchronously measuring the concentration of NH3, characterized by, The over-determined equation set is: wherein, is a frequency domain feature vector of the output signal obtained under application of the first excitation voltage, is a model function of the support vector machine, is a frequency domain feature vector of the first excitation voltage, is NO x concentration, is NH3 concentration, is a frequency domain feature vector of the output signal obtained under application of the second excitation voltage, is a frequency domain feature vector of the second excitation voltage, is a frequency domain feature vector of the output signal obtained under application of the Mth excitation voltage, is a frequency domain feature vector of the Mth excitation voltage; The NO x Concentration estimates of NO and NH3 are solved by least squares fitting with an objective function of: wherein is an objective function of the least square method, is the number of different excitation voltages, is the frequency domain feature vector of the output signal obtained under the application of the excitation voltage, is the frequency domain feature vector of the output signal obtained under the application of the excitation voltage, is the vector norm.

9. The NOx sensor of claim 8, wherein the NOx sensor is configured to measure the concentration of NH3. x A method of synchronously measuring the concentration of NH3, characterized by, According to various known NO x and NH3 concentrations and the frequency domain feature vectors of the excitation voltage and the output signal collected under different working conditions and their corresponding real concentrations of NO x and NH3, the support vector machine is trained through offline calibration.

10. A NO x A system for simultaneous measurement of NH3 concentration, characterized by The method comprises the following steps: The excitation voltage application module is configured to apply an excitation voltage to the NO x sensor; and the first oxygen pump of the sensor. The output signal acquisition module is used to simultaneously acquire NO while the excitation voltage is applied. x The sensor's output signal; The frequency domain feature vector acquisition module is configured to respectively subject the signal sequence of the excitation voltage and the signal sequence of the output signal to Fourier transform to obtain a frequency domain feature vector of the excitation voltage and a frequency domain feature vector of the output signal; A synchronous measurement module is configured to construct an over-determined equation set and solve the over-determined equation set to obtain the concentration of NO and the concentration of NH3 according to the frequency domain feature vectors of the excitation voltage and the frequency domain feature vectors of the output signal obtained under different excitation voltage applications. x A synchronous measurement module is configured to construct an over-determined equation set and solve the over-determined equation set to obtain the concentration of NO and the concentration of NH3 according to the frequency domain feature vectors of the excitation voltage and the frequency domain feature vectors of the output signal obtained under different excitation voltage applications. x A synchronous measurement module is configured to construct

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