Anti-cheating method and system for automobile emission detection

Abstract

The invention relates to an anti-cheating method and system for vehicle emission detection, and relates to the technical field of vehicle emission detection.The method comprises the steps that when a vehicle is in an implicit state, terminal resistance and a first waveform of a CAN bus are collected; injecting a micro-current into the CAN bus, and collecting the voltage to ground of an H pin, the voltage to ground of an L pin and a second waveform of the CAN bus; a bus terminal resistor is disconnected, a pulse signal is injected into the CAN bus, and a reflection waveform is collected; respectively comparing the terminal resistance, the H voltage to ground, the L voltage to ground and the reflection waveform with respective set standards, and comparing the first waveform with the second waveform; and if the terminal resistance, the H voltage to ground, the L voltage to ground and the reflection waveform do not conform to respective set standards and the second waveform has signal attenuation and distortion compared with the first waveform, judging that a cheating device module exists. By measuring and comparing relevant parameters, the difference between the to-be-measured vehicle data and the normal vehicle data is observed, the operation is simple, convenient and rapid, and the time cost is saved.

Description

Technical Field

[0001] This application relates to the field of vehicle emission testing technology, and in particular to an anti-cheating method and system for automobile emission testing. Background Technology

[0002] CAN, or Controller Area Network, is one of the most widely used fieldbuses internationally. Designed for microcontroller communication in automotive environments, CAN facilitates information exchange between various ECUs (Electronic Control Units) to form a network of automotive electronic control units. For example, CAN control devices are embedded in engine management systems, transmission controllers, instrument clusters, and electronic backbone systems. During vehicle emissions testing, an OBD diagnostic tool connects to the vehicle's CAN network to collect emissions data. To pass emissions tests, some vehicles add a cheating module to the CAN network entry point to intercept vehicle data and generate specific data to send back to the OBD diagnostic tool. Therefore, a method is needed to detect and accurately measure the presence of such cheating modules in a vehicle.

[0003] Chinese patent application CN202310288076.8, published on July 11, 2023, discloses a method for determining SCR cheating in diesel vehicles based on remote OBD data, including: Step S1, data acquisition operation: for each model of diesel engine to be detected, remote OBD data streams of normal vehicles and cheating vehicles equipped with that model of diesel engine are acquired in advance; Step S2, extraction of associated data items operation: for the remote OBD data streams of normal vehicles and cheating vehicles acquired in Step S1, associated data items of nitrogen oxide (NOx) emissions are extracted from them respectively; Step S3, construction of vector machine sub-model operation: first, the associated data items extracted from the remote OBD data streams of normal vehicles and cheating vehicles in Step S2 are merged and then a vehicle status label data item is added to form a training data set; then... The support vector machine (SVM) model is trained using the training data set to obtain a SVM training model for the specific diesel engine model used for SCR cheating detection in diesel vehicles. Then, using this SVM training model, a sub-model is constructed that can return the proportion of normal data rows in a data stream that is unknown whether it belongs to a normal or cheating vehicle. Step S4, cheating vehicle detection operation: For a diesel vehicle to be detected equipped with a certain model of diesel engine, the remote OBD data stream of the diesel vehicle to be detected is obtained. Then, based on the associated data items obtained in step S2, corresponding data items are selected from the remote OBD data stream of the diesel vehicle to be detected and merged to form a judgment data set. Then, the judgment data set is fed into the SVM sub-model corresponding to the diesel engine model of the diesel vehicle to be detected, and the vehicle status is judged through this SVM sub-model to obtain the vehicle status judgment result.

[0004] In implementing the above method, the inventors discovered the following problem: When training a model using normal data and then inputting the data to be tested into the model for judgment, the emission test data will differ depending on the vehicle, its age, etc. Therefore, it is necessary to train the model individually for different vehicles and their ages before inputting the corresponding data into the model. This process requires training a large number of models and measuring a large amount of data, is cumbersome, and takes a long time, increasing the time cost for staff. Summary of the Invention

[0005] Therefore, it is necessary to provide an anti-cheating method for vehicle emissions testing that is simple, convenient, and quick to evaluate, addressing the aforementioned technical problems.

[0006] This application provides a method for preventing cheating in vehicle emissions testing, comprising: acquiring the terminating resistance and a first waveform of the CAN bus while the vehicle is in a concealed state; injecting a microcurrent into the CAN bus and acquiring the voltage of the H pin to ground, the voltage of the L pin to ground, and a second waveform of the CAN bus; disconnecting the bus terminating resistance, injecting a pulse signal into the CAN bus, and acquiring the reflected waveform; comparing the terminating resistance, the H pin to ground voltage, the L pin to ground voltage, and the reflected waveform with their respective set standards, and comparing the first waveform with the second waveform; if the terminating resistance, the H pin to ground voltage, the L pin to ground voltage, and the reflected waveform all fail to meet their respective set standards, and the second waveform exhibits signal attenuation and distortion compared to the first waveform, then it is determined that a cheating module exists.

[0007] In one embodiment, when acquiring the voltage to ground of pin H, the voltage to ground of pin L, and the second reflected waveform of the CAN bus, a microcurrent is repeatedly injected and a set number of acquisitions are performed, and the average value is taken.

[0008] In one embodiment, the setting standard for the terminating resistor, the voltage of H pin to ground, and the voltage of L pin to ground is the corresponding setting range.

[0009] In one embodiment, the reflected waveform is set as total reflection with no attenuation.

[0010] In one embodiment, the attenuation of the second waveform compared to the first waveform includes a slower rising or falling edge and a differential voltage absolute value greater than a set voltage value.

[0011] In one embodiment, the distortion of the second waveform compared to the first waveform includes signal ringing and waveform asynchrony or amplitude deviation between the H pin and the L pin, as well as a set amplitude value.

[0012] In one embodiment, signal ringing includes high-frequency oscillations with a frequency greater than a set frequency value after the signal edge.

[0013] This application also provides an anti-cheating system for vehicle emissions testing, comprising: a signal generator module, a circuit measurement module, an oscilloscope module, and a data processing module. The circuit measurement module actively acquires the terminating resistance of the vehicle's CAN bus and then inputs a start signal to the signal generator. Upon receiving the start signal, the signal generator injects a micro-current into the vehicle's CAN bus input. The circuit measurement module acquires the H-to-ground voltage and L-to-ground voltage of the vehicle's CAN bus. With the bus terminating resistance disconnected, the oscilloscope module injects a pulse signal into the CAN bus and acquires the reflected waveform. With the bus terminating resistance continuously connected, the oscilloscope module... After actively acquiring the first waveform at the vehicle's CAN bus input, the module sends a start signal to the signal generator. Upon receiving the start signal, the signal generator injects a micro-current into the vehicle's CAN bus input, and the oscilloscope module acquires the second waveform at the vehicle's CAN bus input. The data processing module compares the terminating resistance, H-to-ground voltage, L-to-ground voltage, and reflected waveform with their respective set standards, and compares the first waveform with the second waveform. If the terminating resistance, H-to-ground voltage, L-to-ground voltage, and reflected waveform do not meet their respective set standards, and the second waveform shows signal attenuation and distortion compared to the first waveform, then it is determined that a cheating module exists.

[0014] The anti-cheating method for vehicle emissions testing provided in this application has the following beneficial effects: 1. In the latent state, the circuit measurement module measures the terminal resistance, H-to-ground voltage, and L-to-ground voltage, while the oscilloscope module measures the reflected waveform, the first waveform, and the second waveform. The above parameters are then compared, allowing for a simple and clear observation of the differences between the data of the vehicle under test and the data of a normal vehicle. The operation is simple and fast, helping to save time and costs.

[0015] 2. In the explicit state, relevant data from the CAN bus is collected and compared with the actual state of the vehicle to determine whether a cheating module exists in the vehicle. This information is then corroborated with the results from the implicit state, thereby improving the accuracy of the measurement results. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of an anti-cheating method for vehicle emissions testing in one embodiment; Figure 2 This is a flowchart illustrating an anti-cheating method for vehicle emissions testing in one embodiment. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0018] ISO 15031-3 and SAE J1962 define the shape and pin positions of on-board diagnostic connectors. Emission self-diagnostic data for CAN network communication uses pins 6 (CAN H) and 14 (CAN L) of a 16-pin trapezoidal diagnostic connector as the CAN network data acquisition entry point. Therefore, OBD diagnostic tools, as data acquisition tools, also comply with this rule.

[0019] The control unit modules on the vehicle's CAN network are connected in parallel. When the OBD diagnostic tool connects to the vehicle's CAN network input and collects emission data through pins 6 / 14, the only reliable way to tamper with the vehicle's emission data is to connect a cheating module in series at the vehicle's CAN network input. This module intercepts vehicle data and generates specified data to reply to the OBD diagnostic tool. Therefore, identifying whether an illegal module is connected in series between pins 6 (CAN H) and 14 (CAN L) of the vehicle's OBD diagnostic connector can be used to determine whether an OBD cheating tool is being used for vehicle annual inspections. Furthermore, the CAN bus must comply with the ISO11898 standard (e.g., high-speed CAN requires parallel 120Ω terminating resistors at both ends). If the terminating resistors of the series modules are not configured correctly, it will cause abnormal bus impedance.

[0020] Based on the above, this application provides a monitoring terminal, including an anti-cheating system for vehicle emissions testing. The system includes a signal generator module, a circuit measurement module, an oscilloscope module, and a data processing module. The circuit measurement module actively acquires the terminating resistance of the vehicle's CAN bus and then inputs a start signal to the signal generator. Upon receiving the start signal, the signal generator injects a micro-current into the vehicle's CAN bus input. The circuit measurement module then acquires the H-to-ground voltage and L-to-ground voltage of the vehicle's CAN bus. With the bus terminating resistance disconnected, the oscilloscope module injects a pulse signal into the CAN bus and acquires the reflected waveform. With the bus terminating resistance still connected, the oscilloscope module actively acquires the first waveform at the vehicle's CAN bus input and sends a start signal to the signal generator. Upon receiving the start signal, the signal generator injects a micro-current into the vehicle's CAN bus input, and the oscilloscope module acquires the second waveform at the vehicle's CAN bus input. The data processing module compares the terminal resistance, H-to-ground voltage, L-to-ground voltage, and reflected waveform with their respective set standards, and compares the first waveform with the second waveform. If the terminal resistance, H-to-ground voltage, L-to-ground voltage, and reflected waveform do not meet their respective set standards, and the second waveform has signal attenuation and distortion compared to the first waveform, then it is determined that a cheating module exists.

[0021] The above measurements were taken in a concealed state of the vehicle, that is, when the vehicle engine is off and all other vehicle electrical appliances are turned off, generally when the vehicle key is not turned on.

[0022] Based on the above system, this application provides an anti-cheating method for vehicle emissions testing, comprising: S101, when the vehicle is in a hidden state, collects the terminating resistance and first waveform of the CAN bus.

[0023] S201 injects a micro-current into the CAN bus and acquires the voltage to ground of the H pin, the voltage to ground of the L pin, and the second waveform of the CAN bus.

[0024] S301: Disconnect the bus terminating resistor, inject a pulse signal into the CAN bus, and acquire the reflected waveform.

[0025] S401, compare the terminating resistance, H-to-ground voltage, L-to-ground voltage and reflected waveform with their respective set standards, and compare the first waveform with the second waveform; if the terminating resistance, H-to-ground voltage, L-to-ground voltage and reflected waveform do not meet their respective set standards, and the second waveform has signal attenuation and distortion compared with the first waveform, then it is determined that a cheating module exists.

[0026] Insert the monitoring terminal into the vehicle's OBD diagnostic port. During monitoring, the terminal automatically reads the voltage to ground of CAN bus H (number 6), the voltage to ground of CAN bus L (number 14), and the terminal resistance value of the CAN bus through its built-in circuit measurement module for subsequent testing. If the terminal resistance value is much greater than the set resistance, it is determined that there may be a series module.

[0027] In one embodiment, the resistance is set to 60Ω.

[0028] The monitoring terminal sends a small current (such as 1mA) to the bus through the built-in signal generator module. It analyzes the current path to detect the presence of series modules. If a series module is present, a voltage drop will occur due to the module's internal resistance when the current flows through it. If the voltage to ground of CANH 6 and CAN L 14 changes significantly compared to before the current was injected, a series module may be present.

[0029] The monitoring terminal captures the bus waveform through its built-in oscilloscope module and compares the waveform changes of the first and second waveforms before and after the monitoring terminal injects current into the CAN bus. It identifies signal attenuation or distortion caused by the impedance of the series module (such as abnormal rising / falling edges of the waveform). If signal attenuation or distortion is present, it is determined that there may be a series module.

[0030] Disconnect the bus (CAN H 6 and CAN L 14) at the CAN network entrance to put the line under test in an open circuit state. The monitoring terminal injects a pulse signal (such as a 5V square wave) into the bus entrance through the built-in signal generator module. At the same time, observe the reflected waveform through the oscilloscope module. If there is a series module, the amplitude and time delay of the reflected waveform will be abnormal due to impedance changes. If there is no series module, the reflected waveform has typical open circuit characteristics (total reflection and no attenuation).

[0031] If the above process determines that there may be a serial module, then it is determined that a cheating module exists.

[0032] Using the above method, the circuit measurement module measures the terminal resistance, H-to-ground voltage, and L-to-ground voltage, while the oscilloscope module measures the reflected waveform, the first waveform, and the second waveform. By comparing these parameters, the difference between the data of the vehicle under test and the data of a normal vehicle can be clearly observed. The operation is simple and fast, which helps to save time and costs.

[0033] In one embodiment, when acquiring the voltage to ground of pin H, the voltage to ground of pin L, and the second reflected waveform of the CAN bus, a microcurrent is repeatedly injected and a set number of acquisitions are performed, and the average value is taken.

[0034] Parallel nodes (such as terminating resistors) have a relatively small impact on the current due to their shunting effect. Therefore, high-frequency measurement and averaging can avoid interference and improve the accuracy of the measurement.

[0035] In one embodiment, the number of times can be set to 200.

[0036] In one embodiment, the setting standard for the terminating resistor, the voltage of H pin to ground, and the voltage of L pin to ground is the corresponding setting range.

[0037] Specifically, the standard setting for the terminating resistor is 60Ω±10%; the standard setting for the voltage to ground of the H pin (CAN H) is 2.5V-2.62V; and the standard setting for the voltage to ground of the L pin (CAN L) is 2.5V-2.38V.

[0038] In one embodiment, the reflected waveform is set as total reflection with no attenuation.

[0039] In one embodiment, the attenuation of the second waveform compared to the first waveform includes a slower rising or falling edge and a differential voltage absolute value greater than a set voltage value.

[0040] In one embodiment, the distortion of the second waveform compared to the first waveform includes signal ringing and waveform asynchrony or amplitude deviation between the H pin and the L pin, as well as a set amplitude value.

[0041] In one embodiment, signal ringing includes high-frequency oscillations with a frequency greater than a set frequency value after the signal edge.

[0042] In one embodiment, the frequency value is set to 10MHz.

[0043] Both the first and second waveforms include the waveforms of CAN H and CAN L. During normal vehicle data measurement, the waveforms of CAN H and CAN L are strictly complementary with no phase difference; in stealth mode, the differential voltage between CAN H and CAN L is 0V, that is, the voltage of CANH is approximately 2.5V and the voltage of CAN L is approximately 2.5V; and the rise / fall time standard CAN (ISO11898-2) is 50-150ns, depending on the bus length and load.

[0044] When determining whether attenuation exists, the following aspects can be considered: 1. Slower rising or falling edge: If the edge time is significantly prolonged (e.g., prolonged to more than 200ns), the edge time will increase by 30%-50% if the series module resistance is 100Ω.

[0045] 2. Amplitude attenuation: If the differential voltage value is greater than 0V, it is caused by signal attenuation due to the internal resistance of the series module.

[0046] When determining the presence of distortion, the following aspects can be considered: 1. Ringing: If high-frequency oscillation (frequency greater than 10MHz) occurs after the signal edge, it is due to the mismatch between the internal resistance of the series module and the bus impedance, and the reflection caused by the impedance change.

[0047] 2. Signal asymmetry: If the internal circuit of the series module is unbalanced, the CAN H and CAN L waveforms will be out of sync or the amplitude value will deviate by 10% or more.

[0048] In one embodiment, the range of modules at the entrance is determined by the distortion location. The closer to the entrance, the greater the probability of modules being connected in series, and the greater the probability of a cheating device being present.

[0049] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0050] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for preventing cheating in vehicle emissions testing, characterized in that, include: When the vehicle is in a concealed state, the CAN bus termination resistance and the first waveform are collected; Inject a microcurrent into the CAN bus and collect the voltage to ground of pin H, the voltage to ground of pin L, and the second waveform of the CAN bus. Disconnect the bus terminating resistor, inject a pulse signal into the CAN bus, and collect the reflected waveform; The terminating resistance, H-to-ground voltage, L-to-ground voltage, and reflected waveform are compared with their respective set standards. The first waveform is compared with the second waveform. If the terminating resistance, H-to-ground voltage, L-to-ground voltage, and reflected waveform do not meet their respective set standards, and the second waveform has signal attenuation and distortion compared with the first waveform, then it is determined that a cheating module exists.

2. The method according to claim 1, characterized in that, When acquiring the voltage to ground of pin H, the voltage to ground of pin L, and the second reflected waveform of the CAN bus, a microcurrent was repeatedly injected and the acquisition was repeated a set number of times, and the average value was taken.

3. The method according to claim 1, characterized in that, The setting standards for the terminating resistor, H pin voltage to ground, and L pin voltage to ground are the corresponding setting ranges.

4. The method according to claim 1, characterized in that, The standard for setting the reflected waveform is total reflection with no attenuation.

5. The method according to claim 1, characterized in that, The attenuation of the second waveform compared to the first waveform includes a slower rising or falling edge and a differential voltage absolute value greater than the set voltage value.

6. The method according to claim 1, characterized in that, The distortions in the second waveform compared to the first waveform include signal ringing and asynchrony or amplitude deviation between the waveforms corresponding to the H and L pins, as well as deviations from the set amplitude value.

7. The method according to claim 6, characterized in that, The presence of ringing in the signal includes high-frequency oscillations with a frequency greater than the set frequency value after the signal edge.

8. A cheating prevention system for vehicle emissions testing, characterized in that, include: The system comprises a signal generator module, a circuit measurement module, an oscilloscope module, and a data processing module. The circuit measurement module actively acquires the terminating resistance of the vehicle's CAN bus and then inputs a start signal to the signal generator. Upon receiving the start signal, the signal generator injects a micro-current into the vehicle's CAN bus input. The circuit measurement module also acquires the H-to-ground voltage and L-to-ground voltage of the vehicle's CAN bus. With the bus terminating resistance disconnected, the oscilloscope module injects a pulse signal into the CAN bus and acquires the reflected waveform. With the bus terminating resistance still connected, the oscilloscope module actively acquires the first waveform at the vehicle's CAN bus input and then sends a start signal to the signal generator. Upon receiving the start signal, the signal generator injects a micro-current into the vehicle's CAN bus input, and the oscilloscope module acquires the second waveform at the vehicle's CAN bus input. The data processing module compares the terminating resistance, H-to-ground voltage, L-to-ground voltage, and reflected waveform with their respective set standards, and compares the first waveform with the second waveform. If the terminating resistance, H-to-ground voltage, L-to-ground voltage, and reflected waveform all fail to meet their respective set standards, and the second waveform exhibits signal attenuation and distortion compared to the first waveform, then a cheating module is identified.

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