Test method of transmission resistance of new energy vehicle

Abstract

The present application relates to the technical field of automobile transmission resistance test, and provides a kind of new energy vehicle transmission resistance test method, comprising: the new energy vehicle to be tested is stationary, and its braking system is placed in the state of no braking resistance;Based on the gear to be tested and the target speed corresponding to the gear to be tested, the motor control is carried out on the vehicle, and in the case where the time of stable operation of the motor reaches the preset time threshold, the motor torque data is collected, and stable operation refers to the fluctuation value of motor speed within the preset error range, and the preset time threshold is selected according to the working temperature of transmission system lubricating oil, the gear to be tested includes neutral gear and at least one non-neutral gear;Based on the motor torque data, the average output torque of the motor is calculated;Based on the average output torque of the motor corresponding to the non-neutral gear and the neutral gear, the transmission resistance torque and the transmission resistance of the non-neutral gear at the corresponding target speed are calculated. To solve the problem that the test of new energy vehicle transmission resistance cannot consider high precision and low cost.

Description

Technical Field

[0001] This invention relates to the field of automotive transmission resistance testing technology, and in particular to a method for testing the transmission resistance of new energy vehicles. Background Technology

[0002] Although the operating resistance of the transmission system in new energy vehicles is small, it directly affects the vehicle's energy efficiency and driving range. Therefore, it is necessary to conduct high-precision testing on this resistance.

[0003] The relevant transmission resistance testing technologies have the following problems: the indirect derivation method requires modeling and reverse calculation of resistance based on dozens of parameters, and the large number of parameters can easily lead to error accumulation and the testing process is cumbersome; the disassembly bench test requires disassembling components such as the transmission and rear axle, which breaks the vehicle assembly constraints, cannot reflect the real resistance coupling characteristics in the integrated state, and has high operating costs; the real vehicle test is easily affected by external environmental interference such as road surface and wind resistance, and it is difficult to separate pure transmission resistance.

[0004] There is currently no effective solution to the problem that testing the transmission resistance of new energy vehicles cannot simultaneously achieve high precision and low cost in related technologies. Summary of the Invention

[0005] The present invention provides a method for testing the transmission resistance of new energy vehicles, which at least solves the problem in related technologies that testing the transmission resistance of new energy vehicles cannot simultaneously achieve high precision and low cost.

[0006] This invention provides a method for testing the transmission resistance of a new energy vehicle, comprising: placing the new energy vehicle to be tested at rest and placing the braking system of the new energy vehicle in a state with no braking resistance; controlling the motor of the new energy vehicle based on the gear to be tested and the target speed corresponding to the gear to be tested; and collecting motor torque data when the motor of the new energy vehicle has been running stably for a preset time threshold, wherein stable operation means that the fluctuation value of the motor speed is within a preset error range, and the preset time threshold is selected based on the working temperature of the transmission system lubricating oil; the gear to be tested includes neutral gear and at least one non-neutral gear; calculating the average output torque of the motor based on the motor torque data; and calculating the transmission resistance torque and transmission resistance of the non-neutral gear at the corresponding target speed based on the average output torque of the motor corresponding to the non-neutral gear and the average output torque of the motor corresponding to the neutral gear.

[0007] Preferably, multiple target speeds are set for the same gear position to be tested; after calculating the transmission resistance torque and transmission resistance of the non-neutral gear at the corresponding target speed based on the average output torque of the motor corresponding to the non-neutral gear and the average output torque of the motor corresponding to the neutral gear, the method further includes: based on the transmission resistance of each of the multiple target speeds corresponding to the non-neutral gear, outputting the resistance characteristic curve of the transmission system corresponding to the non-neutral gear in the entire speed range, which is used to characterize the change of transmission resistance of the new energy vehicle under different operating conditions.

[0008] Preferably, calculating the average output torque of the motor based on the motor torque data includes: performing abnormal peak removal processing on the motor torque data based on a moving average filtering algorithm to obtain valid data; and determining the average output torque of the motor based on the arithmetic mean of the valid data.

[0009] Preferably, the motor control of the new energy vehicle is performed based on the gear to be tested and the target speed corresponding to the gear to be tested, including: based on an adaptive PID closed-loop control algorithm, the motor control of the new energy vehicle is performed by adjusting the motor drive torque.

[0010] Preferably, the motor control of the new energy vehicle is based on the gear to be tested and the target speed corresponding to the gear to be tested, including: sending a control command to the motor controller and controlling the motor of the new energy vehicle by adjusting the motor speed.

[0011] Preferably, before controlling the motor of the new energy vehicle based on the gear to be tested and the target speed corresponding to the gear to be tested, the method further includes: determining the gear to be tested and the target speed corresponding to the gear to be tested based on the transmission gear range and speed range corresponding to the actual driving of the vehicle, taking into account both low-speed break-in and medium-to-high-speed operating conditions.

[0012] Preferably, before controlling the motor of the new energy vehicle based on the gear to be tested and the target speed corresponding to the gear to be tested, the method further includes: driving the new energy vehicle by means of an external motor when the motor is not directly or indirectly mounted on the input shaft end of the new energy vehicle assembly.

[0013] Preferably, after placing the braking system of the new energy vehicle in a state of no braking resistance, the method further includes: if the new energy vehicle is a four-wheel drive vehicle, adjusting the driving mode of the new energy vehicle to a rear-wheel drive mode and disconnecting the front axle power connection; if the new energy vehicle is a hybrid vehicle, controlling the clutch disengagement of the new energy vehicle so that the engine does not participate in transmission.

[0014] Preferably, the method further includes: when the new energy vehicle is a hybrid vehicle, after the new energy vehicle to be tested is left stationary, removing the drive shaft of the new energy vehicle to measure the gearbox resistance in the transmission system of the new energy vehicle.

[0015] Preferably, the new energy vehicle to be tested is placed at rest, which includes: lifting the new energy vehicle to be tested off the ground so that the rear wheels of the new energy vehicle do not contact the ground.

[0016] This invention provides a method for testing the transmission resistance of new energy vehicles. The method involves placing the new energy vehicle under test at rest and assuming its braking system is in a state with no braking resistance. Based on the gear to be tested and its corresponding target speed, the vehicle's motor is controlled. When the motor operates stably for a preset time threshold, motor torque data is collected. Stable operation means that the fluctuation value of the motor speed is within a preset error range. The preset time threshold is selected based on the working temperature of the transmission system lubricating oil. The gear to be tested includes neutral and at least one non-neutral gear. The average output torque of the motor is calculated based on the motor torque data. Based on the average output torque of the motor corresponding to the non-neutral gear and neutral, the transmission resistance torque and transmission resistance of the non-neutral gear at the corresponding target speed are calculated. By measuring the transmission resistance, the original vehicle assembly state is preserved, eliminating the need for multi-parameter modeling. The obtained data more closely reflects actual operating conditions, and the operation is simple and low-cost. This method solves the problem in related technologies where testing the transmission resistance of new energy vehicles cannot simultaneously achieve high precision and low cost. Attached Figure Description

[0017] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other embodiments based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart illustrating the steps of a method for testing the transmission resistance of a new energy vehicle in an embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram of the structure of an electronic device according to an embodiment of the present invention. Detailed Implementation

[0020] Embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. While some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0021] Although the operating resistance of the transmission system in new energy vehicles is small, it directly affects the vehicle's energy efficiency and driving range. Therefore, it is necessary to conduct high-precision testing on this resistance.

[0022] The relevant transmission resistance testing technologies have the following problems: the indirect derivation method requires modeling and reverse calculation of resistance based on dozens of parameters, and the large number of parameters can easily lead to error accumulation and the testing process is cumbersome; the disassembly bench test requires disassembling components such as the transmission and rear axle, which breaks the vehicle assembly constraints, cannot reflect the real resistance coupling characteristics in the integrated state, and has high operating costs; the real vehicle test is easily affected by external environmental interference such as road surface and wind resistance, and it is difficult to separate pure transmission resistance.

[0023] Therefore, the present invention provides a method for testing the transmission resistance of a new energy vehicle, including steps S101 to S104.

[0024] Step S101: Place the new energy vehicle to be tested at rest and put the braking system of the new energy vehicle into a state of no braking resistance.

[0025] Step S102: Based on the gear to be tested and the target speed corresponding to the gear to be tested, the motor of the new energy vehicle is controlled. When the motor of the new energy vehicle runs stably for a time that reaches a preset time threshold, the motor torque data is collected. Stable operation means that the fluctuation value of the motor speed is within a preset error range. The preset time threshold is selected according to the working temperature of the transmission system lubricating oil. The gear to be tested includes neutral gear and at least one non-neutral gear.

[0026] Step S103: Calculate the average output torque of the motor based on the motor torque data.

[0027] Step S104: Based on the average output torque of the motor corresponding to the non-neutral gear and the average output torque of the motor corresponding to the neutral gear, calculate the transmission resistance torque and transmission resistance of the non-neutral gear at the corresponding target speed.

[0028] Placing the braking system of a new energy vehicle in a state without braking resistance means releasing the braking system lock to avoid interference from braking resistance. For example, releasing the electronic parking brake.

[0029] The resistance of the transmission system is mainly composed of bearing friction, gear meshing loss, seal clamping force and lubricating oil viscous resistance, and the values ​​are usually from a few Newton-meters to tens of Newton-meters.

[0030] Those skilled in the art can determine the preset error range for motor speed fluctuations by comprehensively considering industry testing practices, motor control accuracy, and testing accuracy requirements. For example, the preset error range could be ±5 r / min or ±10 r / min.

[0031] Determining a preset time threshold based on the operating temperature of the transmission system lubricating oil is to ensure that the lubricating oil reaches a stable operating temperature after the motor has been running stably for the preset time threshold, thus eliminating the impact of temperature fluctuations on viscous resistance. Taking existing transmission lubricating oils for new energy vehicles / vehicle gearboxes as an example, and considering the oil temperature rise characteristics after a cold start at room temperature, 60 seconds is selected as the preset time threshold. Furthermore, those skilled in the art can determine the specific value of the above-mentioned preset time threshold based on the specific transmission system lubricating oil used and through a limited number of experiments.

[0032] The methods for controlling the motor of a new energy vehicle can be, but are not limited to, torque control and speed control, which will be further explained in this embodiment.

[0033] Motor torque data (motor output torque data) can be continuously collected through motor controller messages.

[0034] The method provided in this invention employs in-situ testing, preserving the vehicle's assembly state; it requires no external sensors or dynamometers, resulting in low cost and simple operation; it eliminates motor losses and external interference, ensuring high testing accuracy. It is suitable for vehicles with motors directly or indirectly mounted on the input shaft end of the vehicle assembly, and can be applied to factory inspection, component optimization, fault diagnosis, and other scenarios. Resistance testing is performed directly using the original vehicle motor, eliminating the need for an external dynamometer and simplifying operation.

[0035] Specifically, compared to deriving resistance by calculating efficiency, the method provided by the embodiments of the present invention does not require modeling based on dozens of parameters such as engine output torque, transmission slip ratio, and hydraulic system losses. The process is relatively simple, and the resistance measurement accuracy will not be low due to the accumulation of errors in multiple stages. It can directly output the comprehensive resistance value.

[0036] Compared to disassembling components such as the transmission and rear axle one by one and installing them individually on a high-precision dynamometer for segmented testing, the method provided by the embodiments of the present invention has lower operating costs, does not disrupt the assembly constraints of the various components of the transmission system, and can reflect the true resistance coupling characteristics of the vehicle in its integrated state.

[0037] Compared to the actual vehicle coasting method, which is subject to external interferences such as road friction, wind resistance, and tire rolling resistance, the method provided by the embodiments of the present invention can separate external interferences from the pure resistance of the transmission system, which helps to improve the test accuracy.

[0038] In summary, the method provided by the embodiments of the present invention can solve the problem in the related art that testing the transmission resistance of new energy vehicles cannot simultaneously achieve high precision and low cost.

[0039] Preferably, the new energy vehicle to be tested is placed at rest, which includes: lifting the new energy vehicle to be tested off the ground so that the rear wheels of the new energy vehicle do not contact the ground.

[0040] Preferably, after placing the braking system of the new energy vehicle in a state with no braking resistance, the above method further includes: when the new energy vehicle is a four-wheel drive vehicle, adjusting the driving mode of the new energy vehicle to rear-wheel drive mode and disconnecting the front axle power connection. If the power connection of the front axle and front drive system of a four-wheel drive vehicle is not disconnected, additional transmission resistance will be generated as the wheels spin freely, causing the test results to be mixed with the front axle resistance, making it impossible to accurately reflect the true resistance value of the target drive system (rear wheel system). By cutting off the front axle power and eliminating the interference of the front drive system, it helps to ensure that the test data focuses only on the target drive components.

[0041] When the new energy vehicle is a hybrid vehicle, the clutch disengagement is controlled to prevent the engine from participating in transmission. The engine itself and the coupling components between the engine and transmission in a hybrid vehicle have inherent transmission resistance. If the engine participates in transmission, its own resistance will be included in the test results, deviating from the goal of testing only the transmission system. By completely isolating the engine-side resistance through clutch disengagement, it is ensured that the test resistance comes solely from the transmission system components.

[0042] Preferably, before controlling the motor of the new energy vehicle based on the gear to be tested and the target speed corresponding to the gear to be tested, the above method further includes: determining the gear to be tested and the target speed corresponding to the gear to be tested based on the transmission gear range and speed range corresponding to the actual driving of the vehicle, taking into account both low-speed break-in and medium-to-high-speed operating conditions.

[0043] Low-speed break-in refers to entering a low-speed range to allow the transmission system lubricating oil to heat up to the operating temperature and the transmission components to fully break in, eliminating the interference of temperature and break-in status on resistance.

[0044] Medium- and high-speed operating conditions refer to the medium- and high-speed speed range covering daily driving, and the transmission resistance measured under actual driving conditions.

[0045] Preferably, the motor control of the new energy vehicle is performed based on the gear to be tested and the target speed corresponding to the gear to be tested, including: the motor control of the new energy vehicle is performed by adjusting the motor drive torque based on an adaptive PID closed-loop control algorithm.

[0046] The adaptive PID closed-loop control algorithm adjusts the motor drive torque and dynamically optimizes the control parameters (proportional coefficient Kp, integral coefficient Ki, and derivative coefficient Kd) to address the resistance fluctuations caused by the coupling of multiple components in the transmission system, enabling the motor speed to quickly reach the target value and maintain stability.

[0047] Preferably, the motor control of the new energy vehicle is based on the gear to be tested and the target speed corresponding to the gear to be tested, including: sending control commands to the motor controller and controlling the motor of the new energy vehicle by adjusting the motor speed.

[0048] The motor speed control command is sent to the motor controller, which executes the control command to make the motor speed quickly reach the target value and maintain stability.

[0049] Preferably, calculating the average output torque of the motor based on the motor torque data includes: performing abnormal peak removal processing on the motor torque data using a moving average filtering algorithm to obtain valid data; and determining the average output torque of the motor based on the arithmetic mean of the valid data. This helps to eliminate test errors caused by signal interference and instantaneous fluctuations, ensuring the accuracy and reliability of the average output torque of the motor, and providing data support for the accurate calculation of subsequent transmission resistance.

[0050] Preferably, multiple target speeds are set for the same gear to be tested.

[0051] Based on the average output torque of the motor corresponding to the non-neutral gear and the average output torque of the motor corresponding to the neutral gear, after calculating the transmission resistance torque and transmission resistance of the non-neutral gear at the corresponding target speed, the above method also includes: based on the transmission resistance of each of the multiple target speeds corresponding to the non-neutral gear, outputting the resistance characteristic curve of the transmission system corresponding to the non-neutral gear in the entire speed range, which is used to characterize the change of transmission resistance of new energy vehicles under different operating conditions.

[0052] For example, the non-neutral gear is selected as needed. k is the number of the selected non-neutral gear.

[0053] The target speed is selected according to the requirements. , where m is the number of the selected target rotational speed.

[0054] During the speed stabilization phase, motor output torque data is continuously collected via motor controller messages. Taking the non-neutral gear numbered k as an example, the motor torque data at different target speeds is collected. An outlier peak was removed using a moving average filtering algorithm, and the effective data in the stable segment was selected. The arithmetic mean of the effective data was then calculated to obtain the average output torque of the motor. .

[0055] The average output torque of the motor from the first non-neutral gear to the kth non-neutral gear can be expressed as: ; The average output torque of the motor in neutral gear is It is used to characterize the no-load resistance of a motor.

[0056] Since external interference has been shielded before testing, the output torque of the motor during stable operation is only used to overcome the running resistance of the transmission system and the motor's own no-load resistance. Therefore, after deducting the no-load resistance, the remaining torque is completely equivalent to the running resistance torque of the transmission system.

[0057] Taking a non-neutral gear (numbered k) and a target speed (numbered m) as an example, the corresponding transmission resistance torque (comprehensive transmission system resistance torque) is: .

[0058] Next, combining the wheel rolling radius of the aforementioned new energy vehicle with the speed ratio from motor torque to the wheel end, we can obtain the transmission resistance corresponding to the non-neutral gear (numbered k) at the target speed (numbered m). Wherein, transmission resistance = (transmission resistance torque × speed ratio from motor torque to the wheel end) Wheel rolling radius.

[0059] Based on the transmission resistance corresponding to different non-neutral gears at different target speeds, the resistance characteristic curve of the output transmission system in the entire speed range can intuitively reflect the resistance change law under different working conditions.

[0060] Preferably, before controlling the motor of the new energy vehicle based on the gear to be tested and the target speed corresponding to the gear to be tested, the above method further includes: driving the new energy vehicle by means of an external motor when the input shaft end of the new energy vehicle assembly is not directly or indirectly equipped with a motor.

[0061] The external motor can perform the same speed stabilization control and torque data acquisition functions as the original vehicle motor. The entire test control logic, data processing, and resistance calculation process require no modification. This breaks the limitation of relying solely on the original vehicle motor for testing, expanding the range of applicable vehicle models. It maintains the in-situ testing characteristics throughout the process, without disassembling the transmission system or damaging the vehicle's assembly state, continuing the advantages of low cost, high precision, and ease of operation. This helps improve the versatility of the aforementioned method.

[0062] Preferably, the above method further includes: when the new energy vehicle is a hybrid vehicle, after the new energy vehicle to be tested is left stationary, the drive shaft of the new energy vehicle is removed in order to measure the gearbox resistance in the transmission system of the new energy vehicle.

[0063] The aforementioned hybrid vehicles may be, but are not limited to, plug-in hybrid vehicles and hybrid electric vehicles using the P2 structure.

[0064] In addition to testing the overall resistance of the transmission system, the method provided in this embodiment can also test the resistance of a specific part of the transmission system of a hybrid vehicle, such as the gearbox resistance, by removing the drive shaft.

[0065] In summary, the method provided by the embodiments of this invention lifts the rear wheels of the vehicle off the ground while maintaining the original vehicle assembly state of the transmission system. Through power coupling between the drive motor and the original vehicle transmission system, adaptive PID control or speed self-control is used to maintain a stable motor speed. Motor torque data during the stable phase is collected to obtain the average output torque of the motor, which can be equivalent to the transmission system resistance. Alternatively, the transmission system resistance can be calculated based on the average output torque of the motor. This method avoids the accumulation of multi-parameter modeling errors, preserves the original vehicle assembly state, provides data that more closely reflects actual working conditions, is simple to operate, and has low cost. It can cover all scenarios including factory quality inspection, component optimization, energy efficiency calibration, and fault diagnosis. It can be used for batch testing on the production line as well as for transmission system optimization and fault diagnosis during the R&D stage.

[0066] The present invention also provides an electronic device, including: at least one processor; and a memory communicatively connected to the at least one processor. The memory stores a computer program executable by the at least one processor, which, when executed by the at least one processor, causes the electronic device to perform steps S103 and S104 of the method described above.

[0067] like Figure 2 As shown, the electronic device includes a computing unit 201, which can perform various appropriate actions and processes based on a computer program stored in a read-only memory (ROM) 202 or a computer program loaded from a storage unit 208 into a random access memory (RAM) 203. The RAM 203 may also store various programs and data required for the operation of the electronic device. The computing unit 201, the ROM 202, and the RAM 203 are interconnected via a bus 204. An input / output (I / O) interface 205 is also connected to the bus 204.

[0068] Multiple components in the electronic device are connected to I / O interface 205, including: input unit 206, output unit 207, storage unit 208, and communication unit 209. Input unit 206 can be any type of device capable of inputting information into the electronic device. Input unit 206 can receive input digital or character information and generate key signal inputs related to user settings and / or function control of the electronic device. Output unit 207 can be any type of device capable of presenting information and may include, but is not limited to, a display, speaker, video / audio output terminal, vibrator, and / or printer. Storage unit 208 may include, but is not limited to, disks and optical discs. Communication unit 209 allows the electronic device to exchange information / data with other devices through computer networks such as the Internet and / or various telecommunications networks, and may include, but is not limited to, modems, network cards, infrared communication devices, and / or wireless communication transceivers, such as Bluetooth devices, WiFi devices, WiMax devices, cellular communication devices, and / or the like.

[0069] The computing unit 201 can be a variety of general-purpose and / or special-purpose processing components with processing and computing capabilities. Some examples of computing units 201 include, but are not limited to, CPUs, graphics processing units (GPUs), various special-purpose artificial intelligence (AI) computing units, various computing units that run machine learning model algorithms, digital signal processors (DSPs), and any suitable processors, controllers, microcontrollers, etc.

[0070] It should be noted that the term "comprising" and its variations used in the embodiments of this invention are open-ended, meaning "including but not limited to". The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". The modifications of "one" and "a plurality" mentioned in the embodiments of this invention are illustrative and not restrictive, and those skilled in the art should understand that unless explicitly indicated otherwise in the context, they should be understood as "one or more". The descriptions of terms such as "first", "second", etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of indicated technical features.

[0071] The user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in the embodiments of this invention are subject to strict compliance with relevant laws, regulations, and regulatory requirements in their collection, storage, use, processing, transmission, provision, and disclosure, and adhere to the principles of legality, legitimacy, necessity, and good faith. The acquisition of relevant information and data is premised on the user's explicit consent or other legitimate reasons, and a clear and convenient authorization management approach is provided to the user, allowing the user to independently choose to consent, withdraw consent, or refuse to provide relevant information. For functions that rely on user information, if the user does not authorize or withdraws authorization, the corresponding technical function cannot be implemented, and the technical solution of this invention is not applicable in this scenario.

[0072] The steps described in the method embodiments provided by the present invention can be performed in different orders and / or in parallel. Furthermore, the method embodiments may include additional steps and / or omit the steps shown. The scope of protection of the present invention is not limited in this respect.

[0073] The term "embodiment" in this specification refers to a specific feature, structure, or characteristic described in connection with an embodiment that may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily imply the same embodiment, nor does it imply independence or alternativeity from other embodiments. The various embodiments in this specification are described in a related manner, with reference to each other for similar or identical parts. In particular, for apparatus, device, and system embodiments, since they are substantially similar to method embodiments, the description is relatively simple, and relevant details are referred to in the description of the method embodiments.

[0074] The above-described embodiments are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of protection. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A method for testing the transmission resistance of new energy vehicles, characterized in that, include: For a new energy vehicle that is stationary and awaiting testing, the braking system of the new energy vehicle is placed in a state with no braking resistance. Based on the gear to be tested and the target speed corresponding to the gear to be tested, the motor of the new energy vehicle is controlled. When the motor of the new energy vehicle runs stably for a time that reaches a preset time threshold, motor torque data is collected. Stable operation means that the fluctuation value of the motor speed is within a preset error range. The preset time threshold is selected according to the working temperature of the transmission system lubricating oil. The gear to be tested includes neutral gear and at least one non-neutral gear. The average output torque of the motor is calculated based on the motor torque data. Based on the average output torque of the motor corresponding to the non-neutral gear and the average output torque of the motor corresponding to the neutral gear, the transmission resistance torque and transmission resistance of the non-neutral gear at the corresponding target speed are calculated.

2. The method according to claim 1, characterized in that, Multiple target speeds are set for the same gear to be tested; Based on the average motor output torque corresponding to the non-neutral gear and the average motor output torque corresponding to the neutral gear, after calculating the transmission resistance torque and transmission resistance of the non-neutral gear at the corresponding target speed, the method further includes: Based on the transmission resistance of each of the multiple target speeds corresponding to the non-neutral gear, the resistance characteristic curve of the transmission system corresponding to the non-neutral gear in the full speed range is output to characterize the change of transmission resistance of the new energy vehicle under different operating conditions.

3. The method according to claim 1, characterized in that, The average output torque of the motor is calculated based on the motor torque data, including: The abnormal peak values ​​of the motor torque data are removed using a moving average filtering algorithm to obtain valid data. The average output torque of the motor is determined based on the arithmetic mean of the valid data.

4. The method according to claim 1, characterized in that, Based on the gear to be tested and the target speed corresponding to the gear to be tested, the motor control of the new energy vehicle is performed, including: Based on the adaptive PID closed-loop control algorithm, the motor of the new energy vehicle is controlled by adjusting the motor drive torque.

5. The method according to claim 1, characterized in that, Based on the gear to be tested and the target speed corresponding to the gear to be tested, the motor control of the new energy vehicle is performed, including: Control commands are sent to the motor controller to control the motor of the new energy vehicle by adjusting the motor speed.

6. The method according to claim 1, characterized in that, Before controlling the motor of the new energy vehicle based on the gear to be tested and the target speed corresponding to the gear to be tested, the method further includes: Based on the transmission gear range and speed range corresponding to the actual driving of the vehicle, taking into account both low-speed break-in and medium-to-high-speed operating conditions, the gear to be tested and the target speed corresponding to the gear to be tested are determined.

7. The method according to claim 1, characterized in that, Before controlling the motor of the new energy vehicle based on the gear to be tested and the target speed corresponding to the gear to be tested, the method further includes: In the case where no motor is directly or indirectly mounted on the input shaft end of the new energy vehicle assembly, an external motor is used to drive the new energy vehicle.

8. The method according to claim 1, characterized in that, After placing the braking system of the new energy vehicle into a state with no braking resistance, the method further includes: When the new energy vehicle is a four-wheel drive vehicle, the driving mode of the new energy vehicle is adjusted to rear-wheel drive mode, and the front axle power connection is disconnected. When the new energy vehicle is a hybrid vehicle, the clutch of the new energy vehicle is disengaged so that the engine does not participate in the transmission.

9. The method according to claim 1, characterized in that, The method further includes: When the new energy vehicle is a hybrid vehicle, after the new energy vehicle to be tested is left stationary, the drive shaft of the new energy vehicle is removed in order to measure the gearbox resistance in the transmission system of the new energy vehicle.

10. The method according to claim 1, characterized in that, The method for placing a new energy vehicle under test at rest includes: lifting the new energy vehicle off the ground so that the rear wheels of the new energy vehicle do not contact the ground.

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