Method for testing and detecting reliability of whole plug-in hybrid electric automobile

Abstract

The invention relates to the field of automobiles, in particular to a method for testing and detecting the reliability of a whole plug-in hybrid electric automobile. According to verification key points and test purposes, the whole vehicle reliability verification working condition can be divided into a whole vehicle structure test detection part, a power and transmission test detection part and an environment test detection part. Based on user condition analysis and confirmation, PHEV automobile structure reliability verification uses a structure reliability part of a same-platform fuel oil automobile reliability specification; pHEV power and transmission system reliability working condition design is further set; and according to the characteristic that after-sales insulation faults of the PHEV are frequent and according to the environment boundary of an after-sales scene, an environment simulation verification working condition is designed, synchronous input of a vibration load and an environment load is realized, insulation design defects can be quickly found, and the escape probability of the design defects is greatly reduced.

Description

Technical Field

[0001] The present invention relates to the field of automobiles, and in particular to a reliability testing method for a plug-in hybrid electric vehicle. Background Art

[0002] Under the dual pressure of environmental protection and energy conservation, new energy vehicles have become a major trend in the development of the automotive industry in the future. Due to the many problems of automotive batteries such as "long charging time", "low energy density, range anxiety", and "high manufacturing cost", the development of pure electric vehicles (EV) is subject to certain restrictions. Plug-in Hybrid Electric Vehicles (PHEV) take into account the advantages of pure electric vehicles and traditional energy vehicles and are an important development direction for some time to come. From 2017 to 2022, the sales share of new energy models has increased year by year, and exceeded 2.3 million in 2023. As a new form of power drive, it is very important to verify the whole vehicle with high quality and efficiency.

[0003] A plug-in hybrid electric vehicle (PHEV) is a hybrid vehicle that combines pure electric power with internal combustion engine power. It was created mainly to solve the problems of pure electric vehicles such as range anxiety and charging convenience. By being equipped with an internal combustion engine generator, PHEVs can continue to drive after the battery is exhausted, alleviating users' range anxiety while also improving charging convenience. In addition, PHEVs can also reduce emissions, improve performance, and enhance flexibility, giving them advantages in terms of environmental protection, power output, and driving experience. There are significant differences between PHEVs and traditional fuel vehicles:

[0004] There are some significant differences in the physical structure between fuel vehicles and PHEVs. The system structure of PHEV vehicles is relatively complex, mainly consisting of components such as internal combustion engines, electric motors, battery packs and controllers. The internal combustion engine can directly drive the wheels or charge the battery; the electric motor can drive the vehicle alone or work in conjunction with the internal combustion engine; the battery pack is used to store electrical energy and can be charged by an external power source or the internal combustion engine; the controller is responsible for managing the operation of the power system and optimizing power distribution. This dual-power source structure allows PHEV vehicles to flexibly switch between internal combustion engines and electric motors as needed to achieve optimal fuel economy and performance. In contrast, the system structure of fuel vehicles is relatively simple, mainly including internal combustion engines, transmission systems, fuel tanks and exhaust systems. The internal combustion engine generates power by burning fuel, the transmission system transmits power to the wheels, the fuel tank stores fuel for the engine, and the exhaust system emits exhaust gas.

[0005] There are significant differences between PHEV and fuel vehicles in terms of energy flow, which are mainly reflected in energy sources, energy conversion and utilization efficiency. First of all, the energy flow of PHEV vehicles is relatively complex, involving two forms of energy: electrical energy and fuel energy. In PHEV vehicles, electrical energy can be charged by external power supply batteries, or by internal combustion engine power generation or kinetic energy recovery; while fuel energy is generated by internal combustion engine combustion of fuel. This dual-energy structure enables PHEV vehicles to flexibly choose to use electric drive or internal combustion engine drive according to different driving conditions and needs, maximize energy utilization and improve energy utilization efficiency. In contrast, the energy flow of fuel vehicles is relatively simple and direct, mainly relying on the conversion of fuel energy. Fuel vehicles generate power by burning fuel through internal combustion engines, and then transmit the power to the wheels through the transmission system to achieve vehicle driving. Fuel vehicles have a single energy source, mainly relying on fossil fuels such as petroleum, and PHEV vehicles are relatively superior to fuel vehicles. PHEV vehicles can directly drive the vehicle through electric motors, with high efficiency in electrical energy conversion. At the same time, the internal combustion engine can also achieve high fuel utilization efficiency when working, and the overall energy utilization efficiency is high. In addition, PHEV vehicles can also convert braking energy into electrical energy storage through kinetic energy recovery technology, further improving energy utilization efficiency. The energy conversion efficiency of fuel vehicles is relatively low, and a certain amount of heat loss will be generated when the internal combustion engine burns fuel, and the energy utilization efficiency is relatively limited. In summary, the differences in energy flow between PHEV vehicles and fuel vehicles are mainly reflected in energy sources, energy conversion and utilization efficiency. PHEV vehicles, with their dual energy structure and efficient energy utilization characteristics, have more superior energy-saving and environmental protection performance, which is in line with the trend of future automobile development. With the continuous improvement of energy utilization efficiency and environmental protection requirements, PHEV vehicles are expected to become an important development direction of the future automobile market.

[0006] Currently, most reliability tests in the industry are conducted using the same reliability specifications as for fuel vehicles, and no scientific reliability specifications are designed to verify the key systems of PHEVs based on their characteristics.

[0007] According to market research results, since there is no range anxiety, the overall usage scenarios of fuel vehicles and PHEVs on the same platform are very similar, so many companies directly use the same platform fuel vehicle verification specifications to verify the reliability of PHEV models as shown in the following table. The total mileage and distribution differences are relatively small, but the mileage proportion of the engine starting in different scenarios is quite different.

[0008] Table 1 Comparative analysis of user scenarios between fuel vehicles and PHEV vehicles on the same platform

[0009]

[0010] As shown in Table 1, the mileage of fuel vehicles and PHEVs on the same platform on highways, national and provincial highways, suburban areas, and cities is relatively close. According to the evaluation principles of specification development, the two scenarios can be regarded as the same. Unlike fuel vehicles that rely on the engine throughout the entire process, the energy of PHEVs can come from engine power generation or from the power grid. According to the survey and analysis results in Table 1, the proportion of engine starts varies greatly in different scenarios. This requires special consideration in the reliability verification specifications. Otherwise, there may be a misalignment between assessment and user needs, with users with high mileage receiving less verification and users with low mileage receiving more verification. This may eventually lead to an increase in the frequency of after-sales failures, causing customer complaints and damaging the brand.

[0011] Secondly, from the driving dimension, PHEV has three driving modes: "pure electric drive", "engine drive" and "motor and engine co-drive", which are quite different from engine-driven cars. PHEV also has energy recovery during braking and gliding. If the above characteristics are not considered during the standard operation design, it may lead to insecure verification.

[0012] Third, from the after-sales perspective, fuel vehicle failures are mainly concentrated in the engine and control, and exhaust after-treatment system, while PHEV failures are mainly concentrated in insulation protection, charging adaptability, battery packs, etc. Therefore, it is necessary to strengthen special verification related to waterproofing, charging adaptability, battery pack protection, etc. Summary of the invention

[0013] In view of the above problems and the user scenario characteristics of the PHEV automobile market, a dedicated reliability test method is designed to better match user needs and make design verification more reasonable and efficient.

[0014] The vehicle reliability test is divided into a vehicle structure test, a power and transmission test, and an environmental test; the vehicle structure test includes verifying the reliability of the vehicle body, interior and exterior trim, and chassis components; the power and transmission test includes verifying the reliability of the powertrain and transmission system; the environmental test includes verifying the reliability of electronic and electrical related parts.

[0015] Furthermore, under the vehicle structure test, the vehicle will be subjected to different vibration, impact and torsion tests to evaluate the strength and stability of the body structure; body components: doors, windows, and roof undergo opening and closing operation tests to evaluate their durability in long-term use; chassis components: suspension system, braking system and steering system are tested under different road conditions to ensure their reliability and stability under various working conditions.

[0016] Furthermore, under the power and transmission test, the powertrain components: engine, gearbox, reduction box, battery pack are subjected to long-term, high-load operation tests to evaluate their reliability and durability under various working conditions; the components of the transmission system: clutch and drive shaft are also tested under different road conditions to ensure the stability of the vehicle in terms of power output and transmission.

[0017] Furthermore, under environmental testing, the vehicle is tested under environmental conditions of different temperatures and humidity to evaluate the performance of the electronic system, body electrical system, power battery system, and ADAS system in different environments and to verify the reliability and stability of the vehicle under extreme climatic conditions.

[0018] Furthermore, for the vehicle structure test and inspection part, through market user research, it was determined that the reliability target of PHEV vehicles is to meet the needs of 95% of users and to achieve the goal of 10 years and 300,000 km without major repairs; through the collection of real user load spectrum data and statistical analysis, it was determined that the vehicle structure reliability of PHEV vehicles is consistent with that of fuel vehicles on the same platform.

[0019] Furthermore, the power and transmission test inspection part includes:

[0020] (1) Based on the working principle of the pure PHEV vehicle power system and after-sales data analysis, the power and transmission system subsystems, key components, workload types of key components, and the main influencing parameters of the workload are sorted out;

[0021] (2) Construct typical test conditions based on cluster analysis of key parameters of key systems used by users;

[0022] (3) The durability test is designed to cover total torque damage greater than or equal to the principle of "95% of users, 300,000 km cumulative torque damage"; the key categories based on user big data clustering analysis are designed to determine the operating condition types and the number of each operating condition type; based on the rotational torque damage theory, the verification method is calculated and analyzed to achieve the quality goal of "satisfying 95% of users, 300,000 km without major repairs in 10 years".

[0023] Furthermore, the power and transmission system subsystem includes a motor controller system, an electric drive assembly, a battery pack and an engine; the core components of the motor controller system are the inverter and DCDC; the electric drive assembly includes a motor, a reducer gear, and an electric drive axle; the battery pack includes a battery management system and battery cells; the engine includes the engine and its accessories.

[0024] Furthermore, the cluster analysis adopts K-means clustering, which specifically includes the following steps: (a) data preprocessing; (b) clustering analysis of data based on 16 characteristic parameters of the motor; (c) PCA method dimensionality reduction, from 16 dimensions to 5 dimensions; (d) clustering and dividing the 5-dimensional data into 5 categories based on the K-means clustering method; (e) obtaining the cluster data of each category; (f) designing the test method based on the key category; the 16 characteristic parameters are: torque standard deviation, maximum torque fluctuation when torque is reduced, average positive torque, average negative torque, acceleration standard deviation, maximum acceleration, minimum acceleration, average deceleration in the deceleration section, average acceleration in the acceleration section, speed standard deviation, maximum speed, average speed, total time, total mileage, acceleration ratio and deceleration ratio.

[0025] Furthermore, the medium operating condition types in step (3) include high-speed simulation, national and provincial highway simulation, urban simulation, mountain road simulation and suburban simulation; the cumulative torque total damage calculation method is as follows:

[0026]

[0027] Where: D is the total cumulative torque damage, N k is the torque load level; n R，i is the frequency corresponding to the i-th level torque amplitude; N f，i is the fatigue life under the i-th level torque amplitude.

[0028] Furthermore, the environmental test detection part is carried out after the road test conditions are completed. It simulates the environmental conditions of the target market. Within one day, the temperature jumps from the target market's extreme low temperature of -20°C to the target market's extreme high temperature of 50°C, and the humidity is maintained at the target market's relative highest humidity. The rapid temperature change and the vibration of the whole vehicle are used to cause the wiring harness connectors to expand and contract due to heat and cold, resulting in gaps. The high-temperature and high-humidity water vapor is fully penetrated and condensed into water droplets when cooled, causing the connectors to short-circuit and insulation failure, thereby discovering design defects.

[0029] The beneficial effects of the present invention are as follows: based on the user's on-board T-box device, no additional data acquisition equipment is required, which can save a lot of time and cost; through quantitative analysis, it is clarified that the structural reliability verification part of the PHEV vehicle borrows the structural reliability part of the reliability specification of the fuel vehicle on the same platform; using K-means clustering analysis technology, the user's driving data is automatically classified, and by analyzing the cluster center data, the user's typical "highway", "provincial road", "suburban", "urban", "mountainous" and other scenes of driving behavior information are accurately obtained. Based on the user's driving habit information in each scene, key data is extracted to achieve a strong correlation between the test condition design and the user's driving habits, and the user's use needs are superimposed with the standard design torque damage equivalence principle, which maximizes the equivalence between user needs and test verification. According to the characteristics of frequent insulation failures in PHEV vehicles after sales, according to the environmental boundaries of the after-sales scene, an environmental simulation verification condition is designed to achieve synchronous input of vibration load and environmental load, which can quickly discover insulation design defects and greatly reduce the probability of design defects escaping. An automatic monitoring and reminder system for the test process and a test result evaluation standard are designed. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 PHEV drive key systems and workload diagram;

[0031] Figure 2 Cluster analysis workflow diagram;

[0032] Figure 3 Schematic diagram of clustering results;

[0033] Figure 4 Schematic diagram of low and medium speed clustering results;

[0034] Figure 5 Schematic diagram of low and medium simulation test;

[0035] Figure 6 Schematic diagram of environmental simulation conditions;

[0036] Figure 7 Schematic diagram of test process control. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] According to the verification focus and test purpose, the vehicle reliability verification conditions can be divided into vehicle structure test and inspection part, power and transmission test and inspection part, and environmental test and inspection part.

[0039] The vehicle structure test and inspection part mainly focuses on verifying the reliability of components such as the body, interior and exterior decoration, and chassis. Under such working conditions, the vehicle will be subjected to various vibration, impact, and torsion tests to evaluate the strength and stability of the body structure. Body parts such as doors, windows, and roofs will undergo opening and closing operations to verify their durability in long-term use. Chassis components such as suspension systems, braking systems, and steering systems will also be challenged under various road conditions to ensure their reliability and stability under various working conditions.

[0040] The power and transmission test and inspection part mainly focuses on verifying the reliability of the powertrain and transmission system. The powertrain components such as the engine, gearbox, reduction box, battery pack, etc. will be subjected to long-term, high-load operation tests to evaluate their reliability and durability under various working conditions. The components of the transmission system such as the clutch and drive shaft will also be verified to ensure the stability of the vehicle in terms of power output and transmission.

[0041] The environmental test section mainly focuses on verifying the reliability of electronic and electrical related parts. Under such conditions, the vehicle will be tested under different temperatures, humidity and other environmental conditions to evaluate the performance of the electronic system, body electrical system, power battery system, and ADAS system in various environments. These tests help verify the reliability and stability of the vehicle under extreme climate conditions.

[0042] Vehicle structure test and inspection part

[0043] According to the market user survey results in Table 1, the reliability target requirements of PHEV vehicles and fuel vehicles are the same, meeting the goal of 95% of users and 10 years and 300,000km without major repairs. According to the collected real user load spectrum data, after statistical analysis, the cumulative pseudo-damage that meets 95% of electric vehicle users is very close to that of fuel vehicles on the same platform, with a deviation of less than 5% control target. Table 2 is the structural load comparison data of a fuel vehicle and an electric vehicle on the same platform, so the vehicle structure reliability verification part is maintained the same as that of the fuel vehicle on the same platform.

[0044] Table 2 Comparison of nominal damage between fuel vehicle specifications and PHEV vehicle user reliability targets

[0045]

[0046] Power and transmission test and inspection part

[0047] (1) Based on the working principle of pure PHEV vehicle power system and after-sales data analysis, the power and transmission system subsystems, key components, workload types of key components, and main influencing parameters of workload are sorted out, such as Figure 1 shown.

[0048] (2) Taking the motor as an example, based on the clustering analysis of key parameters of key systems used by users, a typical test condition is constructed. This work uses K-means clustering, which is the most commonly used clustering algorithm. The technical process is shown in Figure 2 .

[0049] Its basic idea is to iteratively find a partitioning scheme for K clusters (Cluster) so that the loss function corresponding to the clustering result is minimized. The loss function is the Euclidean distance between each sample and the center point of the cluster to which it belongs. The calculation formula is as follows:

[0050]

[0051] In the formula, xi represents the i-th sample, ci is the cluster to which xi belongs, μci represents the center point corresponding to the cluster, and M is the total number of samples. The principle is shown as follows: Figure 3 As shown in the figure, the cluster center can best represent the operating habits of this type of users. Therefore, designing the test operating conditions based on the curve of the cluster center can better simulate the user's actual vehicle needs, discover potential failure modes on the user side in advance, and avoid them by design.

[0052] Taking the medium and low speed conditions as an example, the clustering results are as follows: Figure 4 As shown in Table 3, the horizontal axis is time in seconds and the vertical axis is vehicle speed in km / h. According to GPS, all roads are located in the suburbs of the city. The processing method of cluster center data is shown in Table 3.

[0053] Table 3 Cluster center processing method

[0054]

[0055] The equivalent test condition constructed based on the user's low and medium speed clustering results and the cluster center data analysis results is shown in Figure 5, where the curve is a test road trajectory, and the data next to the trajectory are the vehicle speed and braking operation, in km / h.

[0056] The detailed test operation requirements for the medium and low speed simulation test conditions are shown in Table 4 below. According to the results of user data analysis, the number of tests in which the engine is not started, that is, the number of tests relying solely on the electric power stored in the battery pack, accounts for 80%, and the number of tests in which the engine is started accounts for 20%.

[0057] Table 4 Low and medium speed operation requirements

[0058]

[0059] (3) The durability test is designed to cover the total torque damage greater than or equal to the principle of "95% of users, 300,000 km cumulative torque damage". Based on the key categories of user big data cluster analysis, the operating condition types and the number of each operating condition type are designed. Based on the rotational torque damage theory, the verification method is calculated and analyzed to achieve the quality goal of "satisfying 95% of users and 10 years 300,000 km without major repairs".

[0060]

[0061] Where: D is the total cumulative torque damage, Nk is the torque load level; nR,i is the frequency corresponding to the i-th level torque amplitude; Nf,i is the fatigue life under the i-th level torque amplitude. According to the user T-box data analysis, the total damage that meets "95% users, 300,000km cumulative torque damage" is 15.651. The constructed test condition distribution is shown in Table 5, and the test torque damage distribution is shown in Table 6.

[0062] Table 5 Test mileage distribution

[0063]

[0064] Table 6 Test torque damage distribution

[0065]

[0066] Environmental testing part

[0067] The test is carried out after the road test is completed. The purpose of the test is to simulate the target market environment. Within one day, the temperature jumps from the target market's extreme low temperature (-20°C) to the target market's extreme high temperature (50°C). The humidity is maintained at the target market's relative maximum humidity. The temperature changes rapidly and the vehicle vibrates to cause the wiring harness connector to expand and contract and produce gaps. The high-temperature and high-humidity water vapor fully intrudes and cools down to condense into water droplets, causing the connector to short-circuit and insulation failure to occur. The design of the test is shown in Table 7 and Figure 6 shown.

[0068] Table 7 Environmental simulation conditions

[0069]

[0070] Implementation of the above test

[0071] The test is mainly controlled by Beidou positioning and navigation technology and vehicle automatic control technology (automatic monitoring of accelerator pedal, automatic monitoring of steering, automatic monitoring of brakes, etc.). The principle of the method is as follows: Figure 7 shown.

[0072] Evaluation of the test results above

[0073] The overall goal of this test method is to "satisfy 95% of users and achieve the goal of 300,000 km in 10 years without major repairs." The specific goals of different systems and components will be different. The durability goals of systems directly related to safe driving, such as steering systems and braking systems, must be higher than the overall goals of the vehicle; the durability goals of important hardware, such as engines, drive motors, reduction gears, suspension systems, body sheet metal, etc., are similar to the overall goals of the vehicle; the durability goals of non-important functional components and routine maintenance parts, such as non-critical bushings, shock absorbers, tires, brake shoes, etc., are lower than the overall goals of the vehicle. Different systems have different evaluation standards. Taking a certain power battery and chassis torque attenuation control as an example, some parameter evaluation requirements are shown in Tables 8 and 9.

[0074] Table 8 Power battery requirements

[0075]

[0076]

[0077] Table 9 Chassis key torque attenuation requirements after test

[0078]

[0079] The above describes in detail the preferred implementation of this patent, but this patent is not limited to the above implementation. Various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of this patent.

Claims

1. A plug-in hybrid electric vehicle reliability test method, characterized in that: It is divided into vehicle structure test and inspection part, power and transmission test and inspection part and environmental test and inspection part; the vehicle structure test and inspection part includes verifying the reliability of the vehicle body, interior and exterior decoration and chassis components; the power and transmission test and inspection part includes verifying the reliability of the powertrain and transmission system; the environmental test and inspection part includes verifying the reliability of electronic and electrical related parts.

2. A plug-in hybrid electric vehicle reliability test detection method according to claim 1, characterized in that: In the vehicle structure test and inspection part, the vehicle will be subjected to different vibration, impact and torsion tests to evaluate the strength and stability of the body structure; body components: doors, windows, and roof will undergo opening and closing operation tests to evaluate their durability in long-term use; chassis components: the suspension system, braking system and steering system will be tested under different road conditions to ensure their reliability and stability under various working conditions.

3. A plug-in hybrid electric vehicle reliability test detection method according to claim 1, characterized in that: In the power and transmission test and inspection part, the powertrain components: engine, gearbox, reduction box, battery pack are subjected to long-term, high-load operation tests to evaluate their reliability and durability under various working conditions; the components of the transmission system: clutch and drive shaft are also tested under different road conditions to ensure the stability of the vehicle in terms of power output and transmission.

4. A plug-in hybrid electric vehicle reliability test detection method according to claim 1, characterized in that: In the environmental testing section, the vehicle is tested under environmental conditions of different temperatures and humidity to evaluate the performance of the electronic system, body electrical system, power battery system, and ADAS system in different environments, and to verify the reliability and stability of the vehicle under extreme climatic conditions.

5. A plug-in hybrid electric vehicle reliability test detection method according to claim 2, characterized in that: In the vehicle structure test and inspection part, through market user research, it was determined that the reliability target of PHEV vehicles is to meet the needs of 95% of users and to have a 10-year and 300,000km mileage without major repairs. Through the collection of real user load spectrum data and statistical analysis, it was determined that the reliability of the PHEV vehicle structure is consistent with that of fuel vehicles on the same platform.

6. A plug-in hybrid electric vehicle reliability test detection method according to claim 3, characterized in that: The power and transmission test inspection part includes: (1) Based on the working principle of the pure PHEV vehicle power system and after-sales data analysis, the power and transmission system subsystems, key components, workload types of key components, and the main influencing parameters of the workload are sorted out; (2) Construct typical test conditions based on cluster analysis of key parameters of key systems used by users; (3) The durability test is designed to cover total torque damage greater than or equal to the principle of "95% of users, 300,000 km cumulative torque damage". The operating condition types and the number of each operating condition type are designed based on the key categories of user big data cluster analysis. Based on the rotational torque damage theory, the verification method is calculated and analyzed to achieve the quality goal of "satisfying 95% of users and achieving the goal of no major repairs in 10 years and 300,000 km".

7. A plug-in hybrid electric vehicle reliability test detection method according to claim 6, characterized in that: The power and transmission system subsystem includes a motor controller system, an electric drive assembly, a battery pack and an engine; the core components of the motor controller system are the inverter and DCDC; the electric drive assembly includes a motor, a reducer gear, and an electric drive axle; the battery pack includes a battery management system and battery cells; the engine includes the engine and its accessories.

8. A plug-in hybrid electric vehicle reliability test detection method according to claim 6, characterized in that: The cluster analysis uses K-means clustering, which includes the following steps: (a) data preprocessing; (b) data cluster analysis based on the 16 characteristic parameters of the motor; (c) PCA method dimensionality reduction from 16 dimensions to 5 dimensions; (d) Based on the K-means clustering method, the 5-dimensional data is clustered and divided into 5 categories; (e) The cluster data of each category is obtained; (f) Design test methods based on key classes; The 16 characteristic parameters are: torque standard deviation, maximum torque fluctuation when torque is reduced, average positive torque, average negative torque, acceleration standard deviation, maximum acceleration, minimum acceleration, average deceleration in the deceleration section, average acceleration in the acceleration section, speed standard deviation, maximum speed, average speed, total time, total mileage, acceleration ratio and deceleration ratio.

9. A plug-in hybrid electric vehicle reliability test detection method according to claim 6, characterized in that: The medium working condition types in step (3) include high-speed simulation, national and provincial highway simulation, urban simulation, mountain road simulation and suburban simulation; the calculation method of the cumulative torque total damage is as follows: Where: D is the total cumulative torque damage, N k is the torque load level; n R，i is the frequency corresponding to the i-th level torque amplitude; N f，i is the fatigue life under the i-th level torque amplitude.

10. A plug-in hybrid electric vehicle reliability test detection method according to claim 4, characterized in that: The environmental test detection part is carried out after the road test conditions are completed. It simulates the environmental conditions of the target market. Within one day, the temperature jumps from the target market's extreme low temperature of -20°C to the target market's extreme high temperature of 50°C, and the humidity is maintained at the target market's relative highest humidity. The rapid temperature change and the vibration of the whole vehicle are used to cause the wiring harness connectors to expand and contract due to heat and cold, resulting in gaps. The high-temperature and high-humidity water vapor is fully penetrated and condensed into water droplets when cooled, causing the connectors to short-circuit and insulation failure, thereby discovering design defects.

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