Fault detection method and device and vehicle

Abstract

The invention relates to a fault detection method and device and a vehicle, and relates to the technical field of vehicles. The fault detection method comprises the steps that under the condition that the operation duty ratio of an electromagnetic valve is larger than a duty ratio threshold value, a pressure time domain signal of an intake manifold is obtained; a target frequency domain signal with a preset frequency is extracted from the pressure time domain signal, and the preset frequency is the control frequency of the electromagnetic valve; and determining whether the to-be-detected pipeline in the at least one desorption pipeline is in a desorption flow fault state or not according to the signal amplitude of the target frequency domain signal. According to the invention, the problems of increased hardware cost and increased installation and maintenance difficulty caused by installation of a special flow sensor are avoided, and the hardware cost and maintenance cost are reduced on the premise of ensuring the timeliness and reliability of desorption flow fault detection.

Description

Technical Field

[0001] This application relates to the field of vehicle technology, and in particular to a fault detection method, device and vehicle. Background Technology

[0002] With increasingly stringent global emission regulations, hybrid vehicles have become an important technological path to achieve energy conservation and emission reduction. Their fuel evaporative emission control systems must ensure that fuel vapors captured by the carbon canister are reliably introduced into the engine for combustion, preventing leakage and pollution. Therefore, effective monitoring of the carbon canister desorption flow rate is a crucial step in meeting mandatory regulatory diagnostic requirements.

[0003] Currently, the industry primarily relies on installing direct flow sensors in the desorption pipeline to monitor the desorption flow of the carbon canister. However, directly installing sensors not only increases hardware costs but also subsequent maintenance costs, making it difficult to widely apply in mass-produced vehicles. How to reliably detect engine desorption flow faults without adding sensors that directly collect flow data has become a pressing issue. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a fault detection method, apparatus, and vehicle that can improve the timeliness and reliability of desorption flow fault detection without increasing hardware and maintenance costs.

[0005] In a first aspect, this application provides a fault detection method applied to a vehicle, the vehicle including an engine and a carbon canister, the carbon canister being connected to the engine's intake manifold via at least one desorption line, and a solenoid valve being installed between the carbon canister's outlet and the at least one desorption line. The fault detection method includes: acquiring a pressure time-domain signal of the intake manifold when the solenoid valve's operating duty cycle is greater than a duty cycle threshold; extracting a target frequency-domain signal of a preset frequency from the pressure time-domain signal, wherein the preset frequency is the control frequency of the solenoid valve; and determining whether the pipeline under test in the at least one desorption line is in a desorption flow fault state based on the signal amplitude of the target frequency-domain signal.

[0006] In some technical solutions of this application, at least one desorption pipeline includes a low-pressure pipeline and a high-pressure pipeline. The low-pressure pipeline is connected between the carbon canister and the intake manifold, and the high-pressure pipeline is connected between the carbon canister and the intake end of the turbocharger. The exhaust end of the turbocharger is connected to the intake manifold. Before acquiring the pressure time-domain signal of the intake manifold, the fault detection method further includes: acquiring the ambient pressure and the intake pressure of the intake manifold; if the intake pressure is less than the ambient pressure, determining the low-pressure pipeline as the pipeline to be tested; if the intake pressure is greater than or equal to the ambient pressure and less than a preset pressure, determining the high-pressure pipeline as the pipeline to be tested.

[0007] In some technical solutions of this application, extracting a target frequency domain signal with a preset frequency from a pressure time domain signal includes: performing discrete sine function counting based on a preset frequency and a preset period to determine a sine phase angle, wherein the preset period is the update period of the sine function counter of the discrete Fourier transform; determining a cosine phase angle by performing phase shift processing on the sine phase angle; and determining the real and imaginary components in the complex expression of the target frequency domain signal based on the pressure time domain signal, the sine phase angle, and the cosine phase angle.

[0008] In some technical solutions of this application, determining the real and imaginary components in a complex number expression based on the pressure time-domain signal, the sine phase angle, and the cosine phase angle includes: determining the instantaneous value of the imaginary part based on the pressure time-domain signal and the sine function value, and determining the instantaneous value of the real part based on the pressure time-domain signal and the cosine function value, wherein the sine function value is a function value determined based on the sine phase angle, and the cosine function value is a function value determined based on the cosine phase angle; integrating the instantaneous values ​​of the imaginary part and the instantaneous values ​​of the real part yields the imaginary and real components.

[0009] In some technical solutions of this application, before determining whether the pipeline to be detected is in a desorption flow fault state based on the signal amplitude of the target frequency domain signal, the fault detection method further includes: determining the initial amplitude of the target frequency domain signal based on the imaginary component, the real component, and a preset integration time window; compensating the initial amplitude based on the environmental pressure compensation coefficient and / or the duty cycle compensation coefficient to determine the signal amplitude; wherein, the environmental pressure compensation coefficient is a coefficient determined based on the environmental pressure within a preset period, and the duty cycle compensation coefficient is a coefficient determined based on the operating duty cycle of the solenoid valve within a preset period.

[0010] In some technical solutions of this application, determining whether the pipeline under test is in a desorption flow fault state based on the signal amplitude of the target frequency domain signal includes: obtaining the average amplitude of at least two signal amplitudes within a preset time period; determining that the pipeline under test is not in a desorption flow fault state if the average amplitude is greater than or equal to an average value threshold; and determining that the pipeline under test is in a desorption flow fault state if the average amplitude is less than an average value threshold. The average value threshold corresponds to the pipeline under test.

[0011] In some technical solutions of this application, determining whether the pipeline under test is in a desorption flow fault state based on the signal amplitude of the target frequency domain signal includes: acquiring at least two signal amplitudes within a preset time period; determining a target number of target amplitudes among the at least two signal amplitudes, wherein the target amplitude is the amplitude among the at least two signal amplitudes that is greater than an amplitude threshold; determining that the pipeline under test is not in a desorption flow fault state if the target number is greater than or equal to the quantity threshold; and determining that the pipeline under test is in a desorption flow fault state if the target number is less than the quantity threshold; wherein the amplitude threshold corresponds to the pipeline under test, and / or the quantity threshold corresponds to the pipeline under test.

[0012] In some technical solutions of this application, before extracting the target frequency domain signal of the preset frequency from the pressure time domain signal, the fault detection method further includes: obtaining the pressure value of the pressure time domain signal of the intake manifold; if the pressure value is less than the pressure threshold, determining that at least one desorption pipeline is in a desorption flow fault state, and stopping the step of extracting the target frequency domain signal of the preset frequency from the pressure time domain signal; if the pressure value is greater than or equal to the pressure threshold, continuing the step of extracting the target frequency domain signal of the preset frequency from the pressure time domain signal.

[0013] Secondly, embodiments of this application provide a fault detection device applied to a vehicle. The vehicle includes an engine and a carbon canister. The carbon canister is connected to the engine's intake manifold via at least one desorption line. A solenoid valve is provided between the carbon canister's outlet and the at least one desorption line. The fault detection device includes: The acquisition module is used to acquire the pressure time-domain signal of the intake manifold when the operating duty cycle of the solenoid valve is greater than the duty cycle threshold; the extraction module is used to extract the target frequency domain signal of the preset frequency from the pressure time-domain signal, wherein the preset frequency is the control frequency of the solenoid valve; the determination module is used to determine whether the pipeline to be tested in at least one desorption pipeline is in a desorption flow fault state based on the signal amplitude of the target frequency domain signal.

[0014] Thirdly, embodiments of this application provide a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method provided in the first aspect.

[0015] Fourthly, embodiments of this application provide a vehicle, including: a memory; a processor; and a computer program; wherein the computer program is stored in the memory and configured to be executed by the processor to implement the method provided in the first aspect.

[0016] The technical solution provided in this application has the following advantages compared with the prior art: The fault detection method, apparatus, readable storage medium, and vehicle provided in this application compare the operating duty cycle of a solenoid valve with a duty cycle threshold to determine whether the solenoid valve is in normal working condition, and acquire the intake manifold pressure time-domain signal when the solenoid valve is in normal working condition. Then, a target frequency domain signal corresponding to a preset frequency controlling the solenoid valve is extracted from the pressure time-domain signal, thereby converting the detection of desorption flow into the detection of a target frequency domain signal at a preset frequency. Next, the presence of desorption flow in the pipeline to be detected is detected based on the signal amplitude of the target frequency domain signal. This application utilizes the physical phenomenon that the periodic operation of the solenoid valve in the carbon canister inevitably generates pressure disturbances at the same frequency in the intake manifold. By monitoring the target frequency domain signal corresponding to these pressure disturbances, the desorption flow rate can be inferred and detected in reverse. The pressure time domain signal relies solely on the existing intake manifold pressure sensor on the vehicle, and the extraction of the target frequency domain signal relies solely on the known preset frequency controlled by the solenoid valve. There is no need to install a physical sensor to measure the fluid flow rate in the desorption pipeline, thus avoiding the increased hardware costs and installation and maintenance difficulties caused by installing a dedicated flow sensor. While ensuring the timeliness and reliability of desorption flow fault detection, it reduces hardware and maintenance costs. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A schematic diagram of a fuel evaporation control system in some embodiments of this application is shown; Figure 2 A schematic diagram of the structure of the Venturi tube in an embodiment of this application is shown; Figure 3 Schematic diagrams of the carbon canisters in some embodiments of this application are shown; Figure 4 Schematic diagrams of a fuel evaporation control system in some other embodiments of this application are shown; Figure 5 This is a flowchart of a fault detection method according to some embodiments of this application; Figure 6 This is a schematic block diagram of a fault detection device according to some embodiments of this application.

[0020] Figure label: 100 Evaporation control system, 101 Engine, 102 Carbon canister, 1021 Buffer chamber, 1022 Mixing chamber, 1023 Fuel evaporation chamber, 1024 Intake port, 1025 Exit port, 1026 Breather, 103 Desorption line, 1031 High-pressure line, 1032 Low-pressure line, 104 Intake manifold, 105 Venturi tube, 106 Solenoid valve, 107 Check valve, 108 Turbocharger. Detailed Implementation

[0021] To better understand the above-mentioned objectives, features, and advantages of this application, the solution of this application will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0022] Many specific details are set forth in the following description to provide a thorough understanding of this application, but this application may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only a part of the embodiments of this application, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0023] Before describing the embodiments of this application in detail, the technical background involved in this application is described here so that those skilled in the art can have a clearer understanding of the embodiments of this application.

[0024] Figure 1 Schematic diagrams of a fuel evaporation control system in some embodiments of this application are shown. Figure 2 A schematic diagram of the structure of the Venturi tube in an embodiment of this application is shown. Figure 3 Schematic diagrams of the carbon canisters in some embodiments of this application are shown. Figure 4 Schematic diagrams of fuel evaporation control systems in other embodiments of this application are shown, such as... Figures 1 to 4 As shown, the vehicle's fuel evaporation control system 100 includes an engine 101, a carbon canister 102, a desorption line 103, and an intake manifold 104. The carbon canister 102 is connected to the intake manifold 104 of the engine 101 via the desorption line 103. When the fuel evaporation control system 100 is running, under the vacuum of the intake manifold 104, outside air enters from the vent of the carbon canister 102, flows through the activated carbon inside the canister, and desorbs the fuel vapor it adsorbs. This mixture is then drawn into the intake manifold 104 via the desorption line 103 and finally enters the cylinder of the engine 101 to participate in combustion.

[0025] Specifically, when the pressure in the intake manifold 104 is greater than the ambient pressure, the flushing line of the carbon canister 102 is a high-pressure desorption line 103. The flushing power comes from the pressure difference between the outlet pressure of the carbon canister 102 valve and the pressure of the intake pipe after the air filter. Since the pressure difference between the two is very small, the flow rate is also very small. In order to increase the flow rate of this line, a Venturi tube three-way valve is added to this section of the line. The Venturi effect of the Venturi tube 105 is used to increase the desorption flow rate.

[0026] like Figure 2 As shown, the Venturi tube 105 is a pipe that initially contracts and then gradually expands. When gas or liquid flows through the Venturi tube 105, the dynamic pressure reaches its maximum value at the narrowest point of the pipe, while the corresponding static pressure reaches its minimum value. The velocity of the gas or liquid increases due to the change in the cross-sectional area of ​​the flow. The entire flow must pass through the narrowing opening of the pipe simultaneously, thus the pressure decreases at the same time, creating a pressure difference. This pressure difference can be used to calculate the gas or liquid flow rate using Bernoulli's theorem. Because the Venturi tube 105 generates low pressure at high flow rates, a strong adsorption force is generated near the high flow rate region.

[0027] For example, when the engine 101 of the vehicle is a naturally aspirated engine, there is one desorption line 103, that is, the carbon canister 102 is connected to the intake manifold 104 of the engine 101 through a desorption line 103.

[0028] For example, when the vehicle's engine 101 is a turbocharged engine 101, the carbon canister 102 is connected to two desorption lines 103, forming a dual path, one of which is a low-pressure line 1032 and the other is a high-pressure line 1031. The low-pressure line 1032 is connected to the intake pipe at the front end of the compressor of the turbocharger 108, and the high-pressure line 1031 is connected to the intake manifold 104. The fuel evaporation control system 100 switches according to the operating conditions of the engine 101. When the turbocharger 108 is not working and the intake manifold 104 is under negative pressure, the air-fuel mixture is drawn into the intake manifold 104 through the high-pressure line 1031, similar to the process of the naturally aspirated engine 101. When the turbocharger 108 is working and the intake manifold 104 is under positive pressure, the system switches to the low-pressure line 1032. The vacuum at the compressor inlet is used to draw in the air-fuel mixture, which is then delivered to the intake manifold 104 and the cylinders of the engine 101 after passing through the compressor and intercooler.

[0029] like Figure 3As shown, the carbon canister 102 includes a buffer chamber 1021, a mixing chamber 1022, and a fuel evaporation chamber 1023. The air intake port 1024 of the carbon canister 102 is connected to the fuel evaporation chamber 1023, the air outlet port 1025 of the carbon canister 102 is connected to the mixing chamber 1022, and the breather port 1026 of the carbon canister 102 is connected to the buffer chamber 1021. Since gasoline is a volatile liquid, the fuel tank is often filled with vapor at room temperature. The fuel evaporation control system 100 can introduce fuel vapor into the carbon canister 102. The activated carbon in the carbon canister 102 can first adsorb and then desorb the fuel vapor, and then introduce the desorbed fuel into the engine 101 for combustion and prevent it from evaporating into the atmosphere.

[0030] like Figure 4 As shown, the fuel evaporation control system 100 also includes a solenoid valve 106, which is disposed between the outlet of the carbon canister 102 and at least one desorption line 103. Each desorption line 103 is also provided with a one-way valve 107, which enables the desorption line 103 to be unidirectionally connected from the carbon canister 102 to the engine 101.

[0031] Specifically, the solenoid valve 106 of the activated carbon canister 102 is an on / off control valve used to control the flow of regenerated fuel vapor within the canister 102. By controlling the opening and closing of the solenoid valve 106, the amount of fuel vapor entering the cylinder can be effectively controlled, minimizing interference with the air-fuel ratio control of the engine 101 and ensuring stable operation of the engine 101. This solenoid valve 106 is primarily controlled by a PWM (Pulse-Width Modulation) signal. When the opening conditions of the solenoid valve 106 are met, the sealing element is pulled down by the electromagnetic force generated by the solenoid coil, forming an opening between the sealing element and the armature. The fuel vapor stored in the activated carbon canister 102 is reduced, and the gasoline vapor within the activated carbon canister 102 is carried into the cylinder by clean air under the vacuum of the intake manifold 104 to participate in combustion. This not only reduces emissions but also reduces fuel consumption.

[0032] In related technologies, a fault needs to be reported when the desorption flow cannot be detected entering the engine, i.e., a desorption flow fault is reported. This fault indicates that the flow rate in the desorption line is too low or there is no flow. The industry primarily monitors the carbon canister desorption flow by installing a direct flow sensor in the desorption line. However, turbocharged engines have two desorption lines, requiring separate flow sensors for each. This not only increases hardware costs but also necessitates reserving operating space for the flow sensors for ease of subsequent inspection and maintenance. This results in high hardware costs and occupies engine compartment space, making widespread application in mass-produced vehicles difficult.

[0033] To address the problems existing in the aforementioned related technologies, this application provides a fault detection method applied to a vehicle. The vehicle includes an engine and a carbon canister. The carbon canister is connected to the engine's intake manifold via at least one desorption line, and a solenoid valve is installed between the carbon canister's outlet and the at least one desorption line. The following detailed description of the fault detection method in this application uses a vehicle controller as the executing entity: Figure 5 This is a flowchart of a fault detection method according to some embodiments of this application, such as... Figure 5 As shown, the method includes: S501 acquires the intake manifold pressure time-domain signal when the solenoid valve's operating duty cycle is greater than the duty cycle threshold.

[0034] In this embodiment, the operating duty cycle of the solenoid valve is continuously monitored. When the operating duty cycle is detected to be greater than a preset duty cycle threshold, it is determined that the solenoid valve has started working. At this time, real-time measurement values ​​from the intake manifold pressure sensor are collected and recorded, forming a continuous pressure time-domain signal. This enables the acquisition of raw physical signals, including potential fault information, under normal operating conditions of the solenoid valve during the data acquisition phase. This pressure time-domain signal serves as the data foundation for subsequent analysis.

[0035] Specifically, an operating duty cycle greater than a duty cycle threshold serves as the starting condition for desorption flow fault diagnosis, ensuring that the solenoid valve is in an active, non-closed state. In this state, theoretically, desorption flow should be generated. If the solenoid valve is completely closed, there is no desorption flow, therefore, desorption flow fault diagnosis is unnecessary.

[0036] It should be noted that while a duty cycle greater than the duty cycle threshold is one of the activation conditions for desorption flow fault diagnosis, the vehicle controller also sets several additional activation conditions. These other activation conditions are used to determine whether there are other faults in the vehicle, thus avoiding the reduction in the accuracy of desorption flow fault diagnosis due to other faults.

[0037] For example, the duty cycle threshold includes a first duty cycle threshold, which can be set to 0, ensuring the solenoid valve is in normal working condition. Specific starting conditions include: the solenoid valve's operating duty cycle is greater than 0 to ensure normal operation; the fuel evaporation control system voltage is stable and does not exceed the limit of 16V; the engine speed is greater than the limit of 1250 rpm to ensure normal engine start-up; the ambient temperature is greater than -40 degrees Celsius, otherwise it will affect fuel evaporation; and the solenoid valve's operating frequency is stable.

[0038] S502 extracts the target frequency domain signal of the preset frequency from the pressure time domain signal.

[0039] The preset frequency is the control frequency of the solenoid valve.

[0040] In this embodiment, the acquired pressure time-domain signal is processed by using a frequency domain analysis algorithm to decompose the time-domain pressure signal into the sum of sinusoidal components of different frequencies. Then, the frequency component of the preset frequency of the solenoid valve is extracted from the obtained spectrum, and this frequency component is the target frequency domain signal.

[0041] It should be noted that the frequency of the solenoid valve of the carbon canister is a fixed frequency. The signal controlled by the carbon canister is similar to a signal of preset frequency acting on the pressure signal of the intake manifold. By extracting the signal of preset frequency from the intake manifold pressure, the target frequency domain signal is obtained. This target frequency domain signal can characterize the desorption flow at the solenoid valve.

[0042] In this embodiment, the preset frequency is the operating frequency of the solenoid valve of the carbon canister during its periodic opening and closing. Due to the periodic operation of the solenoid valve, changes in the desorption flow rate and the resulting pressure fluctuations in the intake manifold can occur. Therefore, the pressure fluctuations in the intake manifold will exhibit energy concentration at this frequency. By using this preset frequency as a key, the frequency component related to the desorption flow rate, i.e., the target frequency domain signal, can be separated from the pressure time domain signal.

[0043] For example, the preset frequency is 10Hz, meaning the control frequency of the solenoid valve is a fixed 10Hz. This preset frequency is merely an example; it is understood that designers can set the preset frequency value according to actual needs.

[0044] In this embodiment, the pressure time domain signal is mixed with various interference signals such as engine intake noise and combustion fluctuations. By setting a preset frequency, the corresponding target frequency domain signal can be extracted from it, thereby stripping away and highlighting the frequency component of the periodic disturbance caused by the carbon canister desorption flow at a specific time, and further transforming the detection of desorption flow into the detection of a specific frequency signal.

[0045] S503, based on the signal amplitude of the target frequency domain signal, determine whether the pipeline to be tested in at least one desorption pipeline is in a desorption flow fault state.

[0046] In this embodiment, the pipeline to be tested is the pipeline that theoretically has desorption flow when the solenoid valve is working normally. Specifically, when the vehicle engine is a naturally aspirated engine, there is only one desorption pipeline, and the pipeline to be tested is this single desorption pipeline. When the vehicle engine is a turbocharged engine, there are two desorption pipelines, and the pipeline to be tested is the desorption pipeline with desorption flow. Specifically, the high-pressure pipeline is the pipeline to be tested when the turbocharger is running, and the low-pressure pipeline is the pipeline to be tested when the turbocharger is not running.

[0047] In this embodiment, the signal amplitude of the target frequency domain signal is calculated. This signal amplitude can characterize the intensity of the pressure fluctuation caused by the desorption flow, and thus the normality of the desorption flow can be inferred from the signal amplitude.

[0048] Specifically, a high signal amplitude indicates that the pressure fluctuation caused by the desorption flow is sufficient, thus inferring that the desorption flow is normal and there is no desorption flow fault in the pipeline under test. A low signal amplitude indicates that the pressure fluctuation caused by the desorption flow is weak or absent, thus inferring that the desorption flow is insufficient or interrupted, and there is a desorption flow fault in the pipeline under test.

[0049] In this embodiment, the solenoid valve's operating duty cycle is compared with a duty cycle threshold to determine whether the solenoid valve is in normal operating condition. When the solenoid valve is in normal operating condition, the intake manifold pressure time-domain signal is acquired. Then, a target frequency domain signal corresponding to a preset frequency controlling the solenoid valve is extracted from the pressure time-domain signal, thereby converting the detection of desorption flow into the detection of a target frequency domain signal at a preset frequency. Next, the presence of desorption flow in the pipeline to be detected is detected based on the signal amplitude of the target frequency domain signal. This application utilizes the physical phenomenon that the periodic operation of the solenoid valve in the carbon canister inevitably generates pressure disturbances at the same frequency in the intake manifold. By monitoring the target frequency domain signal corresponding to these pressure disturbances, the desorption flow rate can be inferred and detected in reverse. The pressure time domain signal relies solely on the existing intake manifold pressure sensor on the vehicle, and the extraction of the target frequency domain signal relies solely on the known preset frequency controlled by the solenoid valve. There is no need to install a physical sensor to measure the fluid flow rate in the desorption pipeline, thus avoiding the increased hardware costs and installation and maintenance difficulties caused by installing a dedicated flow sensor. While ensuring the timeliness and reliability of desorption flow fault detection, it reduces hardware and maintenance costs.

[0050] In some embodiments of this application, at least one desorption line includes a low-pressure line and a high-pressure line, wherein the low-pressure line is connected between the carbon canister and the intake manifold, the high-pressure line is connected between the carbon canister and the intake end of the turbocharger, and the exhaust end of the turbocharger is connected to the intake manifold. Before acquiring the intake manifold pressure time-domain signal, the fault detection method also includes: Obtain the ambient pressure and the intake pressure of the intake manifold; if the intake pressure is less than the ambient pressure, identify the low-pressure pipeline as the pipeline to be tested; if the intake pressure is greater than or equal to the ambient pressure and less than the preset pressure, identify the high-pressure pipeline as the pipeline to be tested.

[0051] In this embodiment, when the vehicle's engine is a turbocharged engine, at least one desorption line includes a low-pressure line and a high-pressure line. The low-pressure line connects the carbon canister and the engine's intake manifold. When the intake pressure in the intake manifold is lower than the ambient pressure, a vacuum exists in the intake manifold, and the low-pressure line utilizes this pressure difference to draw fuel vapor from the carbon canister into the engine. The high-pressure line connects the carbon canister and the turbocharger's intake end, which is the inlet side of its internal compressor. When the intake pressure in the intake manifold is greater than or equal to the ambient pressure, the turbocharger pressurizes the fuel vapor in the carbon canister and drives it into the engine.

[0052] In this embodiment, the vehicle is equipped with an ambient pressure sensor and an intake pressure sensor. The intake pressure sensor is located on the intake manifold, and the current ambient pressure value is read from the ambient pressure sensor. Simultaneously, the current absolute intake manifold pressure value is read from the intake manifold pressure sensor. The ambient pressure serves as a reference pressure, representing external atmospheric conditions. The intake pressure, the pressure value within the intake manifold, is acquired by the intake pressure sensor at the intake manifold and represents the real-time pressure value indicating the current state of the engine's intake system. The acquired ambient and intake pressures can be used as a basis for subsequent determination of the engine's intake state.

[0053] It should be noted that the sampling points for the obtained ambient pressure and intake pressure are the same, that is, a set of ambient pressure and intake pressure are pressure values ​​collected at the same sampling time.

[0054] In this embodiment, after obtaining the intake pressure and ambient pressure, the intake pressure and ambient pressure are compared to determine the intake state of the engine, and the determined intake state of the engine can characterize the pipeline to be detected where the current desorption flow should be present.

[0055] Specifically, if the intake pressure is lower than the ambient pressure, the engine's intake is determined to rely on the negative pressure within the intake manifold. This means the system internally sets a flag to "low-pressure line diagnostic mode," identifying the low-pressure line as the line to be tested. Intake pressure lower than ambient pressure is a key physical criterion for determining whether the engine is operating under naturally aspirated conditions. Under this condition, a vacuum is formed within the intake manifold, and the low-pressure line operates with a pressure differential, while the high-pressure line is typically inactive due to the lack of positive pressure in the intake manifold. Therefore, the low-pressure line is identified as the line to be tested in this situation.

[0056] For example, an intake pressure lower than ambient pressure is one of the activation conditions for the "low-pressure pipeline diagnostic mode." The specific activation conditions for the "low-pressure pipeline diagnostic mode" include: intake pressure less than or equal to ambient pressure; engine speed less than the maximum limit of 3000 rpm; small intake pressure fluctuations within a controllable range; fuel cut-off indicator not activated; intake pressure greater than the minimum limit of 15 kPa; and the solenoid valve's duty cycle greater than the minimum limit of 0.3 and less than or equal to the maximum limit of 0.75. Other activation conditions are used to determine whether the vehicle is in a normal operating state with detectable desorption flow. For example, a solenoid valve duty cycle less than or equal to the maximum limit of 0.75 can prevent an increase in the fuel vapor mixture entering the intake manifold, which could adversely affect the air-fuel ratio of the in-cylinder mixture.

[0057] In some possible implementations, if the low-pressure pipeline is determined to be the pipeline to be tested, the operating duty cycle of the control solenoid valve is adjusted to the low-pressure detection duty cycle, the expression (1) of which is as follows: (1) in, The duty cycle for low-pressure detection is set, and min() is used to calculate the minimum value. The duty cycle at the current moment. The duty cycle for the calibrated low-pressure diagnostics.

[0058] Specifically, if the intake pressure is greater than or equal to the ambient pressure, it is determined that the current engine intake does not rely on the negative pressure in the intake manifold and requires turbocharger intervention for boosting. This means the system internally sets a flag to "high-pressure line diagnostic mode," identifying the high-pressure line as the line to be monitored. Intake pressure greater than or equal to ambient pressure is a key physical criterion for determining whether the engine is in boost mode. Under this condition, the intake manifold is under positive pressure or its pressure is balanced with the external environment. The line that should be activated and perform desorption functions is the high-pressure line, ensuring that the system can automatically switch the monitoring target to the backup high-pressure line when the low-pressure line cannot function, achieving full-condition diagnostic coverage.

[0059] For example, an intake pressure greater than or equal to ambient pressure is one of the activation conditions for the "high-pressure pipeline diagnostic mode." The specific activation conditions for the "high-pressure pipeline diagnostic mode" include: intake pressure higher than ambient pressure but less than the maximum pressure limit; engine speed less than the maximum limit of 6000 rpm; stable intake pressure changes; fuel cut-off indicator not activated; and solenoid valve duty cycle greater than the minimum limit of 0.3 and less than or equal to the maximum limit of 0.75. Other activation conditions are used to determine whether the vehicle is in a normal operating state with detectable desorption flow. For example, a solenoid valve duty cycle less than or equal to the maximum limit of 0.75 can prevent an increase in the fuel vapor mixture entering the intake manifold, which could adversely affect the air-fuel ratio of the in-cylinder mixture.

[0060] In some possible implementations, if the high-pressure pipeline is determined to be the pipeline to be tested, the operating duty cycle of the control solenoid valve is adjusted to the high-pressure detection duty cycle, and the expression (2) for the high-pressure detection duty cycle is as follows: (2) in, For high-voltage detection duty cycle, min() is used to calculate the minimum value. The duty cycle at the current moment. The duty cycle for high-voltage diagnostics is calibrated.

[0061] In this embodiment, ambient pressure and intake pressure are used as the basis for identifying engine operating conditions. By comparing intake pressure and ambient pressure in real time, the system automatically identifies whether the engine is in a naturally aspirated state or a turbocharged state. It accurately identifies the desorption pipeline that should be activated in this state as the object to be tested, thereby pinpointing the desorption flow fault detection to a specific faulty pipeline. That is, it determines whether the pipeline to be tested is a low-pressure pipeline or a high-pressure pipeline, making the fault diagnosis output information more targeted. When it is determined that the desorption pipeline to be tested is in a faulty state, it can output specific fault alarm information for different desorption pipelines, enabling maintenance personnel to determine the source of the fault based on the fault prompt information. Maintenance personnel do not need to perform tedious troubleshooting and can directly determine whether the components on the low-pressure pipeline or the high-pressure desorption pipeline need to be checked, thereby improving maintenance efficiency and accuracy.

[0062] In some embodiments of this application, extracting a target frequency domain signal of a preset frequency from a pressure time domain signal includes: Discrete sine function counting is performed based on a preset frequency and a preset period to determine the sine phase angle, where the preset period is the update period of the sine function counter of the discrete Fourier transform; the cosine phase angle is determined by performing phase shift processing on the sine phase angle; based on the pressure time domain signal, the sine phase angle and the cosine phase angle, the real and imaginary components in the complex expression of the target frequency domain signal are determined.

[0063] In this embodiment, the target frequency domain signal corresponding to the preset frequency is extracted from the pressure time domain signal by means of discrete Fourier transform.

[0064] Specifically, the intake pressure signal collected by the intake pressure sensor, after low-pass and high-pass filtering, yields a carbon canister desorption flow signal that is a pressure time-domain signal. This pressure time-domain signal changes continuously over time, making it difficult to accurately describe its time-domain transfer function. Fourier transform can convert the time-domain signal into a frequency signal for processing, allowing for accurate estimation of the signal's amplitude and phase changes. Fourier transform represents the ability to express a time-domain function that meets certain conditions as a sine function, cosine function, or a linear combination of their integrals. The discrete Fourier transform formula (3) is as follows:

[0065] The discrete Fourier transform formula is transformed based on Euler's formula (4) as follows: (4) Based on the above formulas (3) and (4), the expressions for the real components (5) and imaginary components (6) of the discrete Fourier transform can be determined as follows:

[0066]

[0067] In formulas (3) to (6) above, X k For Fourier amplitude, k For Fourier frequency, N Let be the length of the discrete Fourier transform interval. i The imaginary unit, n is the number of sampling points, is the real component of the Discrete Fourier Transform, and is the imaginary component of the Discrete Fourier Transform.

[0068] In this embodiment, the preset period is the update period of the sine function counter used to generate the reference signal within the Discrete Fourier Transform algorithm. The preset period is a fixed software task execution cycle or a counter accumulation step time. Discrete sine function counting is a software counting method where the discrete sine function discretizes and accumulates time according to the preset period, generating a linearly increasing count value. This count value is used to calculate the instantaneous phase of the sinusoidal reference signal. The sinusoidal phase angle is an angle value calculated based on the discrete sine function count value and a preset frequency. Determining the sinusoidal phase angle is the first step in generating a reference signal synchronized with the desorption flow of the solenoid valve. This generates an instantaneous phase angle of a sinusoidal reference signal with the same frequency as the periodic opening and closing of the solenoid valve. This sinusoidal phase angle provides the computational basis for subsequently constructing orthogonal reference signal pairs.

[0069] Specifically, after the desorption flow diagnosis algorithm is started, a software counter is established and its initial value is set to 0. This counter is incremented once at the arrival of each preset period ts. Then, using the current counter value, along with the known preset frequency of the carbon canister control valve and the constant of pi, the cosine phase angle at the current moment is calculated, typically using a modulo operation. The expression for the count of the discrete Fourier transform cosine function (7) is as follows:

[0070] in, Counting the cosine functions of the discrete Fourier transform. Counting the sine functions in the Discrete Fourier Transform. This refers to the control frequency of the solenoid valve, i.e., the preset frequency.

[0071] It should be noted that the counting condition for the Discrete Fourier Transform cosine function is to satisfy the starting condition of the high-pressure pipeline or low-pressure pipeline as the pipeline to be detected in the above embodiment. When the Discrete Fourier Transform sine function count is greater than the sine count limit, the counter is set and the counting is restarted. The expression (8) for the Discrete Fourier Transform sine function count is as follows:

[0072] in, Counting the cosine functions of the discrete Fourier transform. Counting the sine functions in the Discrete Fourier Transform. This is the preset cycle.

[0073] Specifically, the expression for the sinusoidal phase angle (9) is as follows: .

[0074] in, The phase angle is sinusoidal. Counting the cosine functions of the discrete Fourier transform. Counting the sine functions in the Discrete Fourier Transform. This refers to the control frequency of the solenoid valve, i.e., the preset frequency.

[0075] In this embodiment, after obtaining the sinusoidal phase angle, a phase shifting process is performed on it, i.e., a fixed numerical addition operation is performed to obtain the cosine phase angle. By shifting the sinusoidal phase angle by a fixed amount, it is ensured that the signal generated based on the cosine phase angle has the same frequency as the signal generated based on the sinusoidal phase angle and is orthogonal to it, thus completely representing the real and imaginary components of the target frequency domain signal after the discrete Fourier transform.

[0076] Specifically, substituting the expression for the sine phase angle (9) into formula (7) yields the expression for the cosine phase angle. The expression for the cosine phase angle (10) is as follows:

[0077] Among them, among them, The phase angle is sinusoidal. Counting the cosine functions of the discrete Fourier transform. Counting the sine functions in the Discrete Fourier Transform. This refers to the control frequency of the solenoid valve, i.e., the preset frequency.

[0078] In this embodiment, the pressure time-domain signal is the original physical quantity to be analyzed. The sine phase angle and cosine phase angle provide a direction template that is synchronized with and orthogonal to the interference signal. By performing correlation operation between the pressure signal in the time domain and a pair of orthogonal reference signals of known frequency, the pressure fluctuation component caused by the periodic operation of the solenoid valve is effectively separated and enhanced from the noisy pressure signal. The pressure fluctuation component is then quantized with real and imaginary components.

[0079] Specifically, the real component expression (11) and imaginary component expression (12) for generating the discrete Fourier transform of the sinusoidal signal are as follows:

[0080] (12) in, For the real part, This is the imaginary part. Counting the cosine functions of the discrete Fourier transform. Counting the sine functions in the Discrete Fourier Transform. is the control frequency of the solenoid valve, i.e., the preset frequency, and p is the instantaneous value in the pressure time domain signal.

[0081] In this embodiment, a sinusoidal phase angle is generated by a preset frequency and a preset period. Then, a cosine phase angle matching the sinusoidal phase angle is generated by phase offset processing. Then, based on this orthogonal reference signal phase that is completely synchronized with the operation of the solenoid valve, a single-frequency discrete Fourier transform is performed on the pressure time domain signal at a preset frequency. In this way, a periodic component with the same frequency as the carbon canister desorption action is extracted from the complex engine intake pressure signal. It resists the influence of interference noise of other frequencies and has a strong suppression capability for signals of other frequencies, further improving the accuracy of indirect detection of desorption flow through pressure signal.

[0082] In some embodiments of this application, the real and imaginary components in a complex number expression are determined based on the pressure time-domain signal, the sine phase angle, and the cosine phase angle, including: The instantaneous values ​​of the imaginary part and the real part are determined based on the pressure time-domain signal and the sine function value, respectively. The sine function value is a function value determined based on the sine phase angle, and the cosine function value is a function value determined based on the cosine phase angle. The imaginary and real instantaneous values ​​are integrated to obtain the imaginary and real components.

[0083] In this embodiment, the imaginary instantaneous value is an intermediate calculation result obtained by calculating the instantaneous value of the pressure time-domain signal with the corresponding sine function at the calculation time. This imaginary instantaneous value is used to characterize the magnitude of the component in the pressure time-domain signal that is in phase with the sinusoidal parameter signal at that moment. The real instantaneous value is an intermediate calculation result obtained by calculating the instantaneous value of the pressure time-domain signal with the corresponding cosine function at the calculation time. This real instantaneous value is used to characterize the magnitude of the component in the pressure time-domain signal that is in phase with the cosine parameter signal at that moment.

[0084] Specifically, in each algorithm calculation cycle, the imaginary and real instantaneous values ​​are calculated, with the algorithm calculation cycle synchronized with a preset cycle. By calculating the imaginary and real instantaneous values, the pressure time-domain signal can be demodulated, allowing the wideband pressure time-domain signal to be compared with a pair of orthogonal reference signals. The calculation transforms the frequency component information hidden in the pressure time-domain signal, which is in sync with the solenoid valve's operating frequency, into an instantaneous signal that can characterize its amplitude and phase.

[0085] Please refer to expressions (11) and (12) for details, where, p The instantaneous value in the pressure time-domain signal. The value of the sine function. This is the value of the cosine function.

[0086] In this embodiment, the imaginary and real instantaneous values ​​are integrated within a preset integration time window to obtain the imaginary and real components within the integration time window. This integration time window includes at least one calculation cycle, i.e., at least one preset cycle for synchronization. An integration time window is set. When integration begins, the imaginary and real instantaneous values ​​of the two accumulator variables are initialized to 0. In each subsequent calculation cycle, after calculating new imaginary and real instantaneous values, they are immediately added to the corresponding accumulators. This accumulation process continues until the accumulation time reaches the integration time window. At this point, the integrated value is the imaginary component, and the integrated value is the real component. Since the demodulated imaginary and real instantaneous values ​​still contain some noise, integration processing can significantly enhance the effective signal components generated by the target desorption flow, while greatly attenuating other irrelevant noise such as engine combustion fluctuations and airflow disturbances. The output imaginary and real components can more reliably characterize the two scalar values ​​of the target frequency signal strength and phase.

[0087] In this embodiment, the imaginary and real instantaneous values ​​are determined by the pressure time-domain signal and the sine and cosine phase angles, respectively. Then, by integrating multiple imaginary and real instantaneous values ​​within the integration time window, the real and imaginary components are obtained. The real and imaginary components obtained through integration have fewer interference signals, further improving the accuracy of subsequent desorption flow detection based on the target frequency domain signal including both real and imaginary components.

[0088] In some embodiments of this application, before determining whether the pipeline to be detected is in a desorption flow fault state based on the signal amplitude of the target frequency domain signal, the fault detection method further includes: The initial amplitude of the target frequency domain signal is determined based on the imaginary component, the real component, and the preset integration time window; the initial amplitude is compensated based on the environmental pressure compensation coefficient and / or the duty cycle compensation coefficient to determine the signal amplitude; wherein, the environmental pressure compensation coefficient is a coefficient determined based on the environmental pressure within a preset period, and the duty cycle compensation coefficient is a coefficient determined based on the operating duty cycle of the solenoid valve within a preset period.

[0089] In this embodiment, the imaginary and real components are orthogonal projection values ​​extracted through integration. The imaginary and real components together define the vector of the target frequency signal in the complex plane. The preset integration time window is a pre-defined time window for integrating the imaginary and real components, and this preset time window includes at least one preset period. The frequency information of the imaginary and real components extracted from the pressure time-domain signal is converted into an initial amplitude of a scalar. This initial amplitude can effectively characterize the original intensity of the pressure fluctuation caused by the carbon canister desorption flow at the solenoid valve.

[0090] It should be noted that the low-pressure pipeline diagnostic mode and the high-pressure pipeline diagnostic mode use the same method to calculate the initial amplitude. The following explanation will use the low-pressure pipeline diagnostic mode as an example. The calculation formula (13) for the initial amplitude is as follows:

[0091] in, The initial amplitude, For the real part, This is the imaginary part. This is the time integral value.

[0092] In this embodiment, ambient pressure affects the intake air density and the engine's pumping characteristics, thereby influencing the signal amplitude of pressure fluctuations caused by the desorption flow rate. The duty cycle of the solenoid valve directly dictates the magnitude of the desorption flow rate. Under normal, fault-free conditions, a larger duty cycle results in a larger desorption flow rate and consequently, a larger pressure fluctuation amplitude. In other words, the solenoid valve's operating duty cycle directly affects the signal amplitude of pressure fluctuations caused by the desorption flow rate. Therefore, by determining the duty cycle compensation coefficient using the current operating duty cycle of the solenoid valve and the ambient pressure compensation coefficient using the current ambient pressure, and then compensating the initial amplitude using the duty cycle compensation coefficient and / or the ambient pressure compensation coefficient, the compensated signal amplitude is obtained.

[0093] Specifically, the expression for the environmental pressure compensation coefficient (14) is as follows:

[0094] in, This is the environmental pressure compensation coefficient. This is the integral value of environmental pressure. The integral value over time. , All are compensation constants, where, The value is 6.5. The value is 0.5. The value is 1.

[0095] The expression for the duty cycle coefficient (15) is as follows:

[0096] in, This is the duty cycle compensation coefficient. The integral value of the duty cycle. The integral value over time. , All are compensation constants, where, The value is 6.5. The value is 0.5. The value is 1.

[0097] For example, when compensating the initial amplitude using the duty cycle compensation coefficient, the initial amplitude is multiplied by the duty cycle compensation coefficient to obtain the compensated signal amplitude.

[0098] For example, when compensating the initial amplitude using an environmental pressure compensation coefficient, the initial amplitude is multiplied by the environmental pressure compensation coefficient to obtain the compensated signal amplitude.

[0099] For example, when compensating the initial amplitude using the environmental pressure compensation coefficient and the duty cycle compensation coefficient, the initial amplitude is multiplied by the environmental pressure compensation coefficient and the duty cycle compensation coefficient to obtain the compensated signal amplitude.

[0100] In this embodiment, the frequency information of the imaginary and real components extracted from the pressure time-domain signal is converted into an initial amplitude that can effectively characterize the pressure fluctuation intensity caused by the carbon canister desorption flow at the solenoid valve. Then, an environmental pressure compensation coefficient is determined based on the environmental pressure, and a duty cycle compensation coefficient is determined based on the solenoid valve's operating duty cycle. The initial amplitude is then compensated using the environmental pressure compensation coefficient, making the desorption flow fault detection applicable to vehicles operating in different environments. Furthermore, the initial amplitude is compensated using the duty cycle compensation coefficient, making the desorption flow fault detection applicable to vehicles operating under different conditions, thereby further improving the accuracy of desorption flow fault detection.

[0101] In some embodiments of this application, determining whether the pipeline to be detected is in a desorption flow fault state based on the signal amplitude of the target frequency domain signal includes: Obtain the average amplitude of at least two signal amplitudes within a preset time period; if the average amplitude is greater than or equal to the average threshold, determine that the pipeline under test is not in a desorption flow fault state; if the average amplitude is less than the average threshold, determine that the pipeline under test is in a desorption flow fault state; wherein, the average threshold corresponds to the pipeline under test.

[0102] In this embodiment, the preset duration is a period of time used to collect multiple signal amplitudes and perform statistical analysis during the fault determination phase. It should be noted that the preset duration can be set according to actual needs.

[0103] For example, the preset duration can be a diagnostic test cycle that is completed in one go, and the preset duration covers multiple consecutive preset integration time windows.

[0104] In this embodiment, at least two signal amplitudes are multiple amplitudes calculated within a preset time period. These multiple signal amplitudes provide multiple independent detection samples. While a single signal amplitude may be affected by random noise such as instantaneous airflow disturbances, multiple detection samples can more stably reflect the trend of the detection samples. By calculating the average of multiple signal amplitudes, random fluctuations and high-frequency noise in the data can be effectively smoothed out, resulting in more stable and reliable detection data.

[0105] In this embodiment, the average threshold is a critical value determined based on numerous calibration tests. This average threshold characterizes the lowest expected level of signal amplitude that the corresponding test pipeline can achieve under normal operating conditions. When the signal amplitude is greater than or equal to the average threshold, it indicates that the desorption flow signal is strong and meets expectations, and there is no desorption flow fault. When the signal amplitude is less than or equal to the average threshold, it indicates that the desorption flow signal is weak, and there is a desorption flow fault.

[0106] For example, the expression (16) for determining that there is no desorption flow fault is as follows:

[0107] in, The average value is the amplitude. To diagnose normal count values, To diagnose fault count values, The average threshold, It is the sum of the amplitudes of multiple signals.

[0108] In this embodiment, random interference is suppressed by averaging the amplitudes of at least two signals. Using the average amplitude as a detection indicator improves the stability and reliability of the detection indicator. By comparing the average amplitude with an average threshold that matches the pipeline type, the accuracy of detecting different types of pipelines can be improved.

[0109] In some embodiments of this application, determining whether the pipeline to be detected is in a desorption flow fault state based on the signal amplitude of the target frequency domain signal includes: Acquire at least two signal amplitudes within a preset time period; determine the target number of target amplitudes among the at least two signal amplitudes, wherein the target amplitude is the amplitude among the at least two signal amplitudes that is greater than an amplitude threshold; if the target number is greater than or equal to the quantity threshold, determine that the pipeline under test is not in a desorption flow fault state; if the target number is less than the quantity threshold, determine that the pipeline under test is in a desorption flow fault state; wherein the amplitude threshold corresponds to the pipeline under test, and / or the quantity threshold corresponds to the pipeline under test.

[0110] In this embodiment, at least two signal amplitudes are multiple amplitudes calculated within a preset time period, providing multiple independent detection samples. Each signal amplitude is compared to a common amplitude threshold to determine if it belongs to a target amplitude, which is the amplitude detected as a non-detachment flow fault. The number of target amplitudes among the at least two signal amplitudes is counted to obtain the target quantity.

[0111] It should be noted that the amplitude threshold is matched with the pipeline to be tested, that is, low-pressure pipelines and high-pressure pipelines correspond to different amplitude thresholds.

[0112] In this embodiment, after obtaining the target quantity, the target quantity is compared with a quantity threshold. If the target quantity is greater than or equal to the quantity threshold, it is determined that there are enough qualified test samples within a detection cycle, and therefore, the pipeline under test is determined not to be in a desorption flow fault. If the target quantity is less than the quantity threshold, it is determined that there are not enough qualified test samples within a detection cycle, and therefore, the pipeline under test is determined to be in a desorption flow fault.

[0113] It should be noted that the quantity threshold is matched with the pipeline to be tested, that is, low-pressure pipelines and high-pressure pipelines correspond to different quantity thresholds.

[0114] In this embodiment, an amplitude threshold is set to establish a clear pass / fail benchmark for each observation, and the pass / fail status of each signal amplitude is judged. Then, a quantity threshold is used to perform a secondary judgment on the comparison results of multiple signal amplitudes, thereby determining the frequency of pass / fail occurrences among multiple detection results. This counting-based judgment method is insensitive to occasional interference signals because the judgment is based on the number of pass / fail occurrences. Simultaneously, it allows a few observations to slightly fall below the threshold due to momentary interference, as long as the majority of observations are pass / fail. This enhances the fault tolerance of the diagnosis, thereby improving accuracy. Furthermore, different amplitude thresholds and / or quantity thresholds for different pipelines ensure that the judgment criteria most suitable for the respective signal characteristics of the two systems with different characteristics (low-pressure and high-pressure) are adopted. Appropriate single amplitude pass / fail lines and overall pass rate requirements are set for low-pressure and high-pressure pipelines respectively, thus achieving the goal of improving accuracy when diagnosing both pipelines.

[0115] In some embodiments of this application, before extracting the target frequency domain signal of a preset frequency from the pressure time domain signal, the fault detection method further includes: Obtain the pressure value of the pressure time domain signal of the intake manifold; if the pressure value is less than the pressure threshold, determine that at least one desorption line is in a desorption flow fault state, and stop the step of extracting the target frequency domain signal of the preset frequency from the pressure time domain signal; if the pressure value is less than or equal to the pressure threshold, continue the step of extracting the target frequency domain signal of the preset frequency from the pressure time domain signal.

[0116] In this embodiment, upon acquiring the time-domain pressure signal of the intake manifold, the pressure value is directly extracted. This pressure value is the instantaneous pressure, and it is compared with a pressure threshold. If the pressure value is greater than or equal to the pressure threshold, it is determined that at least one desorption line may or may not have a desorption flow fault. Therefore, the subsequent detection process based on the amplitude of the target frequency domain signal continues. If the pressure value is less than the pressure threshold, it is determined that the flow in at least one desorption line is low, or even close to zero. Therefore, at least one desorption line is directly determined to be faulty.

[0117] For example, the pressure threshold ranges from 10 kPa to 20 kPa, and can be specifically selected as 15 kPa.

[0118] For example, when it is determined by the pressure value and the pressure threshold that the signal amplitude detection based on the target frequency domain signal needs to continue, the operating duty cycle of the solenoid valve is adjusted to the diagnostic duty cycle, and the expression (17) of the diagnostic duty cycle is as follows: (17) in, To diagnose the duty cycle, The duty cycle of the previous operation. This is the preset adjustment value.

[0119] In this embodiment of the application, before extracting the target frequency domain signal from the pressure time domain signal, a quick judgment is made by comparing the pressure value with the pressure threshold, which further improves the efficiency of judging whether there is a desorption flow fault in the desorption pipeline.

[0120] In some specific implementations, the fuel vapor flow rate assessment process for low-pressure pipelines is similar to that for high-pressure pipelines. Therefore, the fuel vapor flow rate assessment process for low-pressure pipelines will be used as an example for explanation. The assessment process includes: Fourier transform control, Fourier transform integration, calculation of low-pressure pipeline monitoring values, and evaluation and counting of test values.

[0121] The Fourier transform control is governed by a state machine. The 10Hz carbon canister control signal undergoes a Fourier transform controlled by a Fourier transform flag. When this flag is activated, the low-pressure pipeline steam flow signal monitoring begins. The state machine's computational architecture mainly includes initialization, waiting to enter, initialization delay, Fourier transform initiation, evaluation of prepared test values, final diagnostic evaluation, carbon canister clearing mode, and resetting the Fourier transform. The initialization action includes setting the test value count, carbon canister clearing completion flag, and carbon canister clearing activation flag to initial values ​​of 0. The waiting to enter action involves entering the monitoring state when low-pressure pipeline monitoring is triggered. In the waiting to enter state, the time, Fourier transform trigger flag, and prepared test flag are set to 0. The initialization delay action involves entering the diagnostic calculation state when the flag is activated. Before diagnosing the test signal, a delay time of 1.6 seconds is set to ensure the stability of the incoming signal processing. After the delay time is exceeded, the carbon canister signal Fourier transform is initiated. The Fourier transform initiation process includes: activating the Fourier transform trigger flag, which initiates amplitude-frequency conversion of the 10Hz solenoid valve control signal, and determining the sampling period of the 10Hz raw intake pressure signal using the time in the state machine. When the execution time exceeds the set 0.6s, the next action is initiated. The evaluation of the prepared test values ​​includes entering the diagnostic test mode upon entering this state, with the diagnostic test flag set to 1. The model evaluates the canister signal processed by the Fourier transform in the previous state. It primarily evaluates the signal amplitude of the 10Hz solenoid valve control signal and analyzes whether canister flow is passing through the low-pressure pipeline. Simultaneously, the test count begins, counting the number of test values ​​that meet the requirements. When the test count exceeds the set 5 times, the canister control signal diagnosis for one sampling period is completed, and the diagnosis completion flag is set to 1. When the canister clearing diagnostic mode flag is activated, the test count TvCnt exceeds the set threshold, or the canister clearing diagnostic mode is incomplete and the test count is less than the final test count value by 5 times, the canister clearing diagnostic mode is initiated, clearing the canister diagnostic buffer. When the duty cycle of the carbon canister control valve is greater than that of the carbon canister clearing mode, it enters the Fourier transform reset state. Upon entering the Fourier transform reset state, the Fourier transform trigger flag is reset to 0. Structural simulation is performed at a preset period of 0.1 seconds. When the diagnostic test is completed, the test completion flag is set to 1. When the test count value is greater than the final evaluation count, the final evaluation flag is set to 1.

[0122] The Fourier transform integral primarily calculates the real and imaginary integral values ​​of the 10Hz intake manifold pressure signal after Fourier transform within the sampling period. Additionally, the integral values ​​of ambient pressure and the solenoid valve's operating duty cycle are calculated within the sampling time. This is mainly to compensate for the 10Hz intake manifold pressure signal (i.e., the solenoid valve's control signal) by calculating the average values ​​of these two parameters during the Fourier transform execution time. Integral calculation begins after a flag is activated.

[0123] The low-pressure pipeline monitoring value is used to determine the signal amplitude of the 10Hz intake manifold, corresponding to the low-pressure pipeline flow. This signal is affected by the ambient pressure and the duty cycle of the carbon canister valve. Therefore, after obtaining the initial amplitude based on integration, the initial amplitude is compensated by the ambient temperature and the operating duty cycle of the solenoid valve to obtain the final signal amplitude.

[0124] The process of calculating and evaluating test values ​​for low-pressure pipeline monitoring is based on signal amplitude. When there are multiple signal amplitudes, the average amplitude of these multiple amplitudes can be compared to an average threshold. If the average amplitude is greater than or equal to the average threshold, it is determined that there is no desorption flow fault; otherwise, it is determined that there is a desorption flow fault. Alternatively, the number of signal amplitudes exceeding the amplitude threshold can be counted. If the target number obtained from the count is greater than or equal to the number threshold, it is determined that there is no desorption flow fault; otherwise, it is determined that there is a desorption flow fault.

[0125] After completing the desorption flow diagnosis step, the fault diagnosis code rate is output. The fault codes output for low-pressure and high-pressure desorption lines are similar except for the line identifier. The following explanation uses the low-pressure line as an example: The main outputs of the low-pressure pipeline carbon canister flow diagnosis include a low-pressure pipeline monitoring request suppression flag, a quick test completion flag, a low-pressure pipeline desorption flow monitoring normal flag, and a low-pressure pipeline desorption flow monitoring fault flag.

[0126] Suppress the low-pressure pipeline monitoring request flag. This flag is activated only when the final evaluation of the low-pressure pipeline desorption flow signal is completed and the rapid monitoring status is stopped.

[0127] The quick monitoring completion flag is used to indicate that quick monitoring is complete. This flag is activated when the final evaluation completion flag is activated and the quick monitoring status is selected to run.

[0128] The low-pressure pipeline monitoring normal indicator is used to indicate that the final diagnosis is normal. When both the final assessment normal indicator and the final assessment indicator are activated, the low-pressure pipeline monitoring normal indicator is at position 1. The low-pressure pipeline monitoring fault flag is used to characterize the final fault monitoring. When the final assessment normal flag is not activated and the final assessment flag is activated, the low-pressure pipeline monitoring fault flag is set to 1.

[0129] Figure 6 Here are some structural block diagrams of fault detection devices according to embodiments of this application, such as... Figure 5 As shown, the fault detection device 600 is applied to a vehicle, which includes an engine and a carbon canister. The carbon canister is connected to the engine's intake manifold via at least one desorption line. A solenoid valve is installed between the carbon canister's outlet and the at least one desorption line. The fault detection device 600 includes: The acquisition module 601 is used to acquire the pressure time-domain signal of the intake manifold when the operating duty cycle of the solenoid valve is greater than the duty cycle threshold. Extraction module 602 is used to extract a target frequency domain signal of a preset frequency from the pressure time domain signal, wherein the preset frequency is the control frequency of the solenoid valve; The determination module 603 is used to determine whether the pipeline to be tested in at least one desorption pipeline is in a desorption flow fault state based on the signal amplitude of the target frequency domain signal.

[0130] In this embodiment, the solenoid valve's operating duty cycle is compared with a duty cycle threshold to determine whether the solenoid valve is in normal operating condition. When the solenoid valve is in normal operating condition, the intake manifold pressure time-domain signal is acquired. Then, a target frequency domain signal corresponding to a preset frequency controlling the solenoid valve is extracted from the pressure time-domain signal, thereby converting the detection of desorption flow into the detection of a target frequency domain signal at a preset frequency. Next, the presence of desorption flow in the pipeline to be detected is detected based on the signal amplitude of the target frequency domain signal. This application utilizes the physical phenomenon that the periodic operation of the solenoid valve in the carbon canister inevitably generates pressure disturbances at the same frequency in the intake manifold. By monitoring the target frequency domain signal corresponding to these pressure disturbances, the desorption flow rate can be inferred and detected in reverse. The pressure time domain signal relies solely on the existing intake manifold pressure sensor on the vehicle, and the extraction of the target frequency domain signal relies solely on the known preset frequency controlled by the solenoid valve. There is no need to install a physical sensor to measure the fluid flow rate in the desorption pipeline, thus avoiding the increased hardware costs and installation and maintenance difficulties caused by installing a dedicated flow sensor. While ensuring the timeliness and reliability of desorption flow fault detection, it reduces hardware and maintenance costs.

[0131] It should be noted that when the vehicle is controlled by the fault detection device in the embodiments of this application, the specific implementation method is similar to the specific implementation method of the fault detection method in any of the above embodiments of the present invention. Therefore, for a detailed exemplary description of the fault detection process, please refer to the relevant description section on the fault detection method mentioned above. To reduce redundancy, it will not be repeated here.

[0132] In some embodiments of this application, a computer-readable storage medium is also provided, on which a computer program is stored, which, when executed by a processor, implements the methods provided in any of the above embodiments.

[0133] In some embodiments of this application, a vehicle is also provided, including: a memory; a processor; and a computer program; wherein the computer program is stored in the memory and configured to be executed by the processor to implement the methods provided in any of the above embodiments.

[0134] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0135] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A fault detection method, characterized in that, Applied to a vehicle, the vehicle includes an engine and a carbon canister, the carbon canister being connected to the engine's intake manifold via at least one desorption line, and a solenoid valve being installed between the carbon canister's outlet and the at least one desorption line; the fault detection method includes: When the operating duty cycle of the solenoid valve is greater than the duty cycle threshold, the pressure time-domain signal of the intake manifold is acquired. Extract a target frequency domain signal of a preset frequency from the pressure time domain signal, wherein the preset frequency is the control frequency of the solenoid valve; Based on the signal amplitude of the target frequency domain signal, determine whether the pipeline to be tested in the at least one desorption pipeline is in a desorption flow fault state.

2. The fault detection method according to claim 1, characterized in that, The at least one desorption line includes a low-pressure line and a high-pressure line, wherein the low-pressure line is connected between the carbon canister and the intake manifold, the high-pressure line is connected between the carbon canister and the intake end of the turbocharger, and the exhaust end of the turbocharger is connected to the intake manifold; Before acquiring the time-domain pressure signal of the intake manifold, the fault detection method further includes: Obtain the ambient pressure and the intake pressure of the intake manifold; If the intake pressure is less than the ambient pressure, the low-pressure pipeline is identified as the pipeline to be tested. If the intake pressure is greater than or equal to the ambient pressure and less than the preset pressure, the high-pressure pipeline is identified as the pipeline to be tested.

3. The fault detection method according to claim 1, characterized in that, Extracting a target frequency domain signal of a preset frequency from the pressure time domain signal includes: Discrete sine function counting is performed based on the preset frequency and preset period to determine the sine phase angle, wherein the preset period is the update period of the sine function counter of the discrete Fourier transform; The cosine phase angle is determined by performing phase shift processing on the sinusoidal phase angle; Based on the pressure time-domain signal, the sine phase angle, and the cosine phase angle, determine the real and imaginary components in the complex representation of the target frequency-domain signal.

4. The fault detection method according to claim 3, characterized in that, The step of determining the real component and the imaginary component in the complex number expression based on the pressure time-domain signal, the sine phase angle, and the cosine phase angle includes: The instantaneous value of the imaginary part is determined based on the pressure time-domain signal and the sine function value, and the instantaneous value of the real part is determined based on the pressure time-domain signal and the cosine function value, wherein the sine function value is a function value determined based on the sine phase angle, and the cosine function value is a function value determined based on the cosine phase angle; Integrating the instantaneous values ​​of the imaginary part and the real part yields the imaginary component and the real component.

5. The fault detection method according to claim 3, characterized in that, Before determining whether the pipeline under test is in a desorption flow fault state based on the signal amplitude of the target frequency domain signal, the fault detection method further includes: The initial amplitude of the target frequency domain signal is determined based on the imaginary component, the real component, and the preset integration time window. The initial amplitude is compensated according to the environmental pressure compensation coefficient and / or duty cycle compensation coefficient to determine the signal amplitude; The environmental pressure compensation coefficient is a coefficient determined based on the environmental pressure within the preset period, and the duty cycle compensation coefficient is a coefficient determined based on the operating duty cycle of the solenoid valve within the preset period.

6. The fault detection method according to any one of claims 1 to 5, characterized in that, The step of determining whether the pipeline under test is in a desorption flow fault state based on the signal amplitude of the target frequency domain signal includes: Obtain the average amplitude of at least two of the signal amplitudes within a preset time period; If the average amplitude is greater than or equal to the average value threshold, it is determined that the pipeline under test is not in a desorption flow fault state. If the average amplitude is less than the average value threshold, it is determined that the pipeline under test is in a desorption flow fault state; The average value threshold corresponds to the pipeline to be detected.

7. The fault detection method according to any one of claims 1 to 5, characterized in that, The step of determining whether the pipeline under test is in a desorption flow fault state based on the signal amplitude of the target frequency domain signal includes: Obtain at least two of the signal amplitudes within a preset time period; Determine a target number of target amplitudes among at least two of the signal amplitudes, wherein the target amplitude is the amplitude among at least two of the signal amplitudes that is greater than an amplitude threshold; If the target quantity is greater than or equal to the quantity threshold, it is determined that the pipeline under test is not in a desorption flow failure state; If the target quantity is less than the quantity threshold, the pipeline to be tested is determined to be in a desorption flow failure state. Wherein, the amplitude threshold corresponds to the pipeline to be detected, and / or the quantity threshold corresponds to the pipeline to be detected.

8. The fault detection method according to any one of claims 1 to 5, characterized in that, Before extracting the target frequency domain signal of the preset frequency from the pressure time domain signal, the fault detection method further includes: Obtain the pressure value of the time-domain pressure signal of the intake manifold; If the pressure value is less than the pressure threshold, it is determined that the at least one desorption pipeline is in a desorption flow failure state, and the step of extracting the target frequency domain signal of the preset frequency from the pressure time domain signal is stopped. If the pressure value is greater than or equal to the pressure threshold, the step of extracting the target frequency domain signal of the preset frequency from the pressure time domain signal continues.

9. A fault detection device, characterized in that, Applied to a vehicle, the vehicle includes an engine and a carbon canister, the carbon canister being connected to the engine's intake manifold via at least one desorption line, and a solenoid valve being installed between the carbon canister's outlet and the at least one desorption line; the fault detection device includes: The acquisition module is used to acquire the pressure time-domain signal of the intake manifold when the operating duty cycle of the solenoid valve is greater than the duty cycle threshold. An extraction module is used to extract a target frequency domain signal of a preset frequency from the pressure time domain signal, wherein the preset frequency is the control frequency of the solenoid valve; The determination module is used to determine whether the pipeline to be tested in the at least one desorption pipeline is in a desorption flow fault state based on the signal amplitude of the target frequency domain signal.

10. A vehicle, characterized in that, include: Memory; processor; as well as Computer programs; The computer program is stored in the memory and configured to be executed by the processor to implement the method as described in any one of claims 1 to 8.

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