Internal and external excitation coupled electrically-driven durability test bench

Abstract

The invention relates to the technical field of durability tests, and discloses an internal and external excitation coupled electric drive durability test bench, which comprises a test platform, two oppositely arranged internal excitation simulation units are arranged on the test platform, and the internal excitation simulation units are used for simulating internal power input of an electric drive system; a portal frame is arranged on the test platform between the two internal excitation simulation units, an external excitation simulation unit is arranged on the portal frame, an electric driving system is mounted on the external excitation simulation unit, and the external excitation simulation unit is used for simulating that the electric driving system is subjected to external excitation from a road surface; a decoupling mechanism is arranged between each internal excitation simulation unit and the electric driving system, and the decoupling mechanisms can realize decoupling control of the internal excitation simulation units and the external excitation simulation units. According to the technical scheme, the problems that an existing test bench is poor in durability test simulation performance and insufficient in accuracy and equivalence are solved, and an effective basis is provided for reliability evaluation of electric driving systems such as new energy automobiles.

Description

Technical Field

[0001] The present invention relates to the technical field of durability testing, and particularly to an electric drive durability test bench with coupled internal and external excitations. Background Art

[0002] With the rapid development of electric devices such as electric vehicles, the electric drive system, as a core power component, its reliability and lifespan directly affect the overall performance, user experience, and safety of electric devices. The durability test of the electric drive system is a key means to evaluate its reliability and lifespan. By simulating the actual operating conditions, the performance of the electric drive system under long-term operation can be detected.

[0003] However, the existing electric drive durability test benches on the market currently have obvious limitations. During actual service, the electric drive system is in a complex working condition where internal and external excitations are coupled for a long time. The internal excitation and external excitation interact with each other and jointly act on the system performance and lifespan. However, some test benches adopt a single internal excitation method, only inputting torque and speed under typical working conditions through a work machine to simulate the service state of the electric drive system, but ignoring the influence of external environmental changes on the electric drive system; some other test benches only focus on external excitation, using a vibration table to apply PSD (Power Spectral Density) to carry out durability tests, without considering the complexity of the internal power input of the electric drive system. Most of the existing test benches only focus on one type of excitation method, resulting in poor simulation of durability tests, seriously affecting the accuracy and equivalence of the tests, and it is difficult to meet the requirements for reliability assessment of electric drive systems such as new energy vehicles. Summary of the Invention

[0004] The present invention aims to provide an electric drive durability test bench with coupled internal and external excitations to solve the problems of poor simulation, insufficient accuracy, and equivalence of durability tests of existing test benches, and to provide an effective basis for the reliability assessment of electric drive systems such as new energy vehicles.

[0005] To achieve the above object, the present invention adopts the following technical solution: An electric drive durability test bench with coupled internal and external excitations, including a test platform. There are two relatively arranged internal excitation simulation units on the test platform, and the internal excitation simulation units are used to simulate the internal power input of the electric drive system; a gantry is arranged on the test platform between the two internal excitation simulation units, and an external excitation simulation unit is arranged on the gantry. An electric drive system is installed on the external excitation simulation unit, and the external excitation simulation unit is used to simulate the external excitation received by the electric drive system from the road surface; a decoupling mechanism is arranged between each internal excitation simulation unit and the electric drive system, and the decoupling mechanism can achieve decoupling control between the internal excitation simulation unit and the external excitation simulation unit.

[0006] The beneficial effects of this solution are as follows: Different from the traditional test bench with single excitation, this solution accurately simulates the torque and speed output of the electric drive system under different working conditions through the internal excitation simulation unit, and the external excitation simulation unit truly restores the external environment such as road surface bumps and vibrations, realizing a high degree of simulation of the coupled working conditions of internal and external excitations, making the test process closer to the actual operation state, greatly improving the test accuracy, and providing scientific and accurate data support for system reliability evaluation. At the same time, the decoupling mechanism effectively isolates the internal and external excitations, avoiding mutual interference between factors such as torque and speed changes and vibrations and impacts, ensuring that each excitation unit acts stably and accurately on the electric drive system, improving the stability and reliability of the test data, and providing a reliable basis for product R & D optimization. In addition, this test bench also has good versatility. It is not only applicable to the durability test of the electric drive system of electric vehicles, but also can be widely used in many fields such as electric ships and electric construction machinery, effectively meeting diverse test requirements and providing strong support for the technological development of the electric equipment industry.

[0007] Preferably, the external excitation simulation unit includes an installation platform for carrying the electric drive system and a plurality of external excitation simulation parts. Each external excitation simulation part includes a hydraulic cylinder. The hydraulic cylinder is installed on the gantry. The output shaft of the hydraulic cylinder extends downward and is fixedly connected to the installation platform. There is a spacing between the installation platform and the test platform.

[0008] The beneficial effects of this solution are as follows: In this technical solution, the setting of the hydraulic cylinder is of great significance. When simulating the external excitation working condition, the hydraulic cylinder can drive the electric drive system to descend, causing the installation platform to collide with the test platform, thereby realistically simulating complex conditions such as road surface impacts encountered by the electric drive system during actual operation. This simulation method highly conforms to the external excitation faced by the electric drive system when driving on the real road surface, and can accurately test its performance and durability when dealing with such sudden situations, making the test results highly consistent with the actual use scenario, thus providing a solid and reliable basis for the optimal design of the electric drive system.

[0009] In addition, the hydraulic cylinder can also flexibly adjust the installation height of the electric drive system. This characteristic greatly improves the versatility and adaptability of the test bench, can meet the test requirements of different types and specifications of electric drive systems, effectively reduces the time and cost losses caused by equipment adaptation problems, and significantly enhances the practicality and economy of the test bench.

[0010] Preferably, each internal excitation simulation unit includes a base and a power machine. The base is detachably connected to the test platform. The power machine is installed on the base. The output shaft of the power machine is connected to the decoupling mechanism.

[0011] The beneficial effects of this solution are as follows: In this technical solution, the working machine of the internal excitation simulation unit is installed on the base, which greatly guarantees the structural stability, reduces the shaking and displacement during the operation of the working machine, and creates a stable environment for testing. The output shaft of the working machine is connected to the decoupling mechanism, which can efficiently transmit the generated torque and rotational speed to the decoupling mechanism and then accurately transfer it to the electric drive system. This power transmission path can accurately simulate the internal power input of the electric drive system and does not interfere with the external excitation motion, enabling the test bench to more realistically restore the actual working conditions and improving the accuracy and reliability of the test results.

[0012] Preferably, each decoupling mechanism includes a coupling, a first universal adjustment unit, and a second universal adjustment unit. The first universal adjustment unit includes a guide rod and a first universal adjustment part, and the second universal adjustment unit includes a guide sleeve and a second universal adjustment part. The guide rod is fixedly connected to the first universal adjustment part, and the first universal adjustment part is detachably connected to the coupling. The output shaft of the electric drive system is installed on the coupling. The guide sleeve is fixedly connected to the second universal adjustment part, and the free end of the guide rod is slidably arranged in the guide sleeve. The output shaft of the working machine is detachably connected to the second universal adjustment part.

[0013] The beneficial effects of this solution are as follows: In this technical solution, the sliding design of the guide rod in the guide sleeve enables the decoupling mechanism to move flexibly between different input directions of torque and vertical excitation. When the internal excitation simulation unit transmits torque and the external excitation simulation unit applies vertical excitation, the interference between the two can be avoided, ensuring that the internal and external excitations can be applied to the electric drive system independently and accurately. In addition, this design can adapt to axial displacement changes. When the electric drive system undergoes axial expansion and contraction due to temperature, vibration, etc., the sliding part will adjust accordingly, preventing the structure from being damaged due to axial stress concentration, ensuring the stable operation of the test bench, and improving the accuracy and reliability of the test results.

[0014] Preferably, the second universal adjustment part includes a first fork head, a second fork head, and a cross shaft. The first fork head is fixedly connected to the end of the guide sleeve. Two opposite journal shafts of the cross shaft are rotatably arranged on the first fork head, and the other two journal shafts of the cross shaft are spherical and rotatably arranged on the second fork head. The second fork head is detachably connected to the output shaft of the working machine.

[0015] The beneficial effects of this solution are as follows: In this technical solution, the spherical journal of the cross shaft is a major technical highlight of the present invention. The spherical journal of the cross shaft is rotatably arranged in the second fork head, which can, while ensuring torque transmission, allow vertical displacement to occur, effectively achieve the decoupling of torque transmission and vertical excitation, greatly improve the system decoupling ability, and reduce stress concentration. In actual tests, when the internal excitation simulation unit outputs torque through the work machine, the cross shaft rotates flexibly to ensure the smooth transmission of torque to the electric drive system; when the external excitation simulation unit applies vertical excitation, the spherical end of the cross shaft can adaptively adjust according to the vertical displacement of the electric drive system, avoiding excessive stress accumulation caused by rigid connection and extending the service life of each component. In addition, the detachable structure greatly improves the maintainability of the system.

[0016] Preferably, the structures of the first universal adjustment part and the second universal adjustment part are the same.

[0017] The beneficial effects of this solution are as follows: In this solution, setting the first universal adjustment part and the second universal adjustment part to have the same structure has obvious advantages. During production and manufacturing, unified molds, processes, and procedures can be used, reducing costs, simplifying management, and improving efficiency, which is conducive to large-scale production. In terms of maintenance, the parts are universal, reducing the spare parts inventory cost, and damaged parts can be replaced quickly. In terms of performance, their mechanical properties and motion laws are similar, making the decoupling mechanism more stable and reliable, improving the test accuracy and consistency of the test bench, and providing accurate data for R & D and optimization.

[0018] Preferably, the guide rod is a spline rod, and a keyway is provided inside the guide sleeve, and the spline rod is adapted to the keyway.

[0019] The beneficial effects of this solution are as follows: In this solution, designing the guide rod as a spline rod and setting a keyway adapted to it inside the guide sleeve has many remarkable advantages. The cooperation between the spline rod and the keyway ensures that the guide rod can only move axially and cannot rotate. This characteristic is extremely crucial during the test. When the internal excitation simulation unit transmits torque, it can effectively prevent the guide rod from interfering with the torque transmission path due to its own rotation, ensuring the stable and accurate transmission of torque to the electric drive system. At the same time, when the external excitation simulation unit applies vertical excitation, the guide rod only makes an axial displacement to adapt to the small position change of the electric drive system caused by the external excitation, avoiding additional forces or displacement deviations caused by the rotation of the guide rod, ensuring that the external excitation can act accurately and independently on the electric drive system, and thus greatly improving the test accuracy and reliability of the test bench, ensuring that the test results can truly reflect the performance of the electric drive system under actual complex working conditions.

[0020] Preferably, the optimization equation for the radius ratio of the output shaft of the work machine and the output shaft of the electric drive system is:

[0021] Where: is the rotation angle of the output shaft of the work machine; is the rotation angle of the output shaft of the electric drive system; is the radius ratio of the output shaft of the work machine to the output shaft of the electric drive system.

[0022] The beneficial effects of this solution are as follows: Through a specific radius ratio optimization equation, this solution can precisely regulate the power transmission relationship between the output shaft of the work machine and the output shaft of the electric drive system. By means of the quantitative correlation of the rotation angle and the radius ratio, the radius ratio of the two can be reasonably set according to different test requirements, ensuring that when the test bench simulates working conditions, the coupling effect of the internal and external excitation simulation units is more in line with the actual situation. This is conducive to presenting the response of the test system more realistically, comprehensively revealing the interaction mechanism of each component, helping researchers conduct in-depth analysis, thereby providing a scientific basis for the optimization and upgrade of the test system, and improving the accuracy and reliability of the electric drive durability test.

[0023] Preferably, a number of positioning and adjusting units are provided on the installation platform, and the electric drive system is installed on the installation platform through the positioning and adjusting units, and both the position and angle of the positioning and adjusting units can be adjusted.

[0024] The beneficial effects of this solution are as follows: In this technical solution, positioning and adjusting units are provided on the installation platform, and the electric drive system is installed on the installation platform through the positioning and adjusting units, greatly improving the convenience and flexibility of installation. Installers can quickly complete the installation and disassembly of the electric drive system without complex operations. Moreover, both the position and angle of the positioning and adjusting units can be adjusted, which can adapt to drive motors of different models and specifications, enabling the test bench to meet diverse test requirements, effectively reducing the test cost, and improving the versatility and applicability of the equipment.

[0025] Preferably, a buffer unit is installed on the test platform below the installation platform.

[0026] The beneficial effects of this solution are as follows: In this technical solution, the buffer unit provided on the test platform below the installation platform plays a crucial role. During the test, whether it is the inherent vibration of the test platform due to the surrounding environment, the vibration caused by sudden external impacts, or the vibration generated during the operation of the test equipment itself, all will be significantly weakened by the buffer unit. This greatly reduces the interference of external vibrations on the test bench system, ensures the accuracy of test data, and provides a solid guarantee for the reliability of test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is the three-dimensional view of an electric drive durability test bench with internal and external excitation coupling in Embodiment 1 of the present invention; Figure 23D view of the cooperation between the external excitation simulation unit and the gantry in Embodiment 1 and Embodiment 3 of the present invention; Figure 3 3D view of the decoupling mechanism in Embodiment 1 of the present invention; Figure 4 Exploded view of the second universal adjustment unit in Embodiment 1 of the present invention; Figure 5 In Embodiment 1 of the present invention Figure 1 Partial enlarged view of location A. Detailed implementation manners

[0028] The following is a further detailed description through specific implementation manners: Reference numerals in the attached drawings of the specification include: test platform 1, base 2, power machine 3, gantry 4, electric drive system 5, installation platform 6, hydraulic cylinder 7, coupling 8, guide rod 9, guide sleeve 10, first fork head 11, second fork head 12, cross shaft 13, bearing cup 14, L-shaped connecting plate 15, waist-shaped hole 16, fixing plate 17, displacement sensor 18, load sensor 19, high-pressure accumulator 20, low-pressure accumulator 21, servo valve group 22.

[0029] Embodiment 1 As Figure 1 shown, an electric drive durability test bench with internal and external excitation coupling includes a test platform 1.

[0030] As Figure 1 shown, internal excitation simulation units are provided on both the left and right sides of the test platform 1. The internal excitation simulation units are used to simulate the internal power input of the electric drive system 5. Specifically, each internal excitation simulation unit includes a base 2 and a power machine 3. The base 2 is installed on the test platform 1 by bolts, and the power machine 3 is installed on the top of the base 2 by bolts.

[0031] As Figure 1 shown, a gantry 4 is installed on the test platform 1 between the two internal excitation simulation units by bolts. An external excitation simulation unit is provided on the gantry 4, and an electric drive system 5 is installed on the external excitation simulation unit. The external excitation simulation unit is used to simulate the external excitation received by the electric drive system 5 from the road surface.

[0032] As Figure 2As shown in the figure, the external excitation simulation unit includes an installation platform 6 for carrying the electric drive system 5 and an external excitation simulation part. The number of the external excitation simulation parts is two, and the two external excitation simulation parts are respectively arranged on the left and right sides of the top of the installation platform 6. Each external excitation simulation part includes a hydraulic cylinder 7. The hydraulic cylinder 7 is installed on the gantry 4 through bolts. The output shaft of the hydraulic cylinder 7 extends downward and is connected to the installation platform 6 through bolts, and there is a distance between the installation platform 6 and the test platform 1. In this embodiment, the hydraulic cylinder 7 adopts an MTS fatigue hydraulic cylinder 7.

[0033] As Figure 1 shown in the figure, a decoupling mechanism is provided between each internal excitation simulation unit and the electric drive system 5, and the decoupling mechanism can realize the decoupling control between the internal excitation simulation unit and the external excitation simulation unit.

[0034] As Figure 3 shown in the figure, each decoupling mechanism includes a coupling 8, a first universal adjustment unit and a second universal adjustment unit. The first universal adjustment unit includes a guide rod 9 and a first universal adjustment part. The second universal adjustment unit includes a guide sleeve 10 and a second universal adjustment part. The left end of the guide rod 9 is welded to the first universal adjustment part. The coupling 8 is connected to the first universal adjustment part through bolts. The output shaft of the electric drive system 5 is installed on the left side of the coupling 8. The right end of the guide sleeve 10 is welded to the second universal adjustment part. The right end of the guide rod 9 is slidably arranged in the guide sleeve 10. The guide rod 9 is a spline rod, and a keyway is arranged inside the guide sleeve 10. The spline rod is adapted to the keyway. The output shaft of the power machine 3 is connected to the second universal adjustment part through bolts.

[0035] As Figure 3 shown in the figure, the structures of the first universal adjustment part and the second universal adjustment part are the same. Taking the structure of the second universal adjustment part as an example for illustration, the structure of the first universal adjustment part will not be elaborated. As Figure 4 shown in the figure, the second universal adjustment part includes a first fork head 11, a second fork head 12, a cross shaft 13 and a bearing cup 14. The first fork head 11 is welded to the right end of the guide sleeve 10. The front and rear journal shafts of the cross shaft 13 are rotatably arranged on the first fork head 11 through the bearing cup 14. The upper and lower journal shafts of the cross shaft 13 are spherical and are rotatably arranged on the second fork head 12. The output shaft of the power machine 3 is connected to the right side of the second fork head 12 through bolts.

[0036] To deeply analyze and efficiently optimize the coupling effect between the internal excitation simulation unit and the external excitation simulation unit, the response state of the test system, and the interaction of each component, it is necessary to carry out optimization work on the radius ratio of the output shaft of the power machine 3 to the output shaft of the electric drive system 5. The specific optimization equation used is:

[0037] Where: is the rotation angle of the output shaft of the work machine 3; is the rotation angle of the output shaft of the electric drive system 5; is the radius ratio of the output shaft of the work machine 3 to the output shaft of the electric drive system 5.

[0038] As Figure 1 and Figure 5 shown, positioning and adjusting units are provided on both the left and right sides of the top of the installation platform 6. The electric drive system 5 is installed on the installation platform 6 through the positioning and adjusting units, and the position and angle of the positioning and adjusting units can both be adjusted. Specifically, the positioning and adjusting unit includes an L-shaped connecting plate 15 and a fastener. A kidney-shaped hole 16 is provided on the installation platform 6. The L-shaped connecting plate 15 is installed on the installation platform 6 through the fastener. Due to the setting of the kidney-shaped hole 16, it is convenient to adjust the installation position and installation angle of the L-shaped connecting plate 15. Two fixing plates 17 are installed at the leftmost side of the L-shaped connecting plate 15 through bolts, and the electric drive system 5 is installed on the fixing plates 17 through bolts. In this embodiment, the fastener is a fastening bolt.

[0039] A durability test method for the electric drive system 5 of the test bench includes the following steps: S1: Install the electric drive system 5 on the installation platform 6 through the positioning and adjusting unit; S2: Connect the decoupling mechanism to the output shafts of the work machine 3 and the electric drive system 5 to ensure the decoupling of the vertical excitation and the torque input path; S3: Set the internal excitation and external excitation loading parameters; S4: Start the work machine 3 and the hydraulic cylinder 7 to achieve the simultaneous loading of the internal and external excitations; S5: Collect and analyze the test data through the data acquisition system; S6: Output a durability test report to evaluate the fatigue performance and durability of the electric drive system 5.

[0040] Embodiment 2 On the basis of Embodiment 1, a buffer unit is installed on the test platform 1 below the installation platform 6, and the buffer unit is an airbag or an air spring. Both airbags and air springs have unique advantages and can flexibly adjust the internal air pressure according to the actual situation. Through air pressure adjustment, the stiffness can be conveniently adjusted, thereby efficiently absorbing and isolating external vibrations, ensuring the stability of the installation platform 6 and even the entire test system, and reducing the interference of external vibrations on the test process and results.

[0041] Embodiment 3 On the basis of Embodiment 1 or Embodiment 2, as Figure 2As shown in the figure, it further includes a control unit. The control unit includes a controller. A displacement sensor 18 is built in the hydraulic cylinder 7. A load sensor 19, a high-pressure accumulator 20, a low-pressure accumulator 21 and a servo valve group 22 are installed on the cylinder block of the hydraulic cylinder 7. The servo valve group 22 can accurately control the flow rate of the hydraulic oil flowing into and out of the hydraulic cylinder 7 according to the input signal. The working machine 3, the hydraulic cylinder 7, the displacement sensor 18, the load sensor 19, the high-pressure accumulator 20, the low-pressure accumulator 21 and the servo valve group 22 are all electrically connected to the controller. In this embodiment, the controller selects a single-chip microcomputer of model STM32. The model of the displacement sensor 18 is Milang MTL3, and the model of the load sensor 19 is MB009.

[0042] The controller serves as the core of the control unit. The working machine 3 is connected to the controller and accepts its instructions to adjust the output power to provide power for the system. The hydraulic cylinder 7 is connected to the controller and realizes precise control through the servo valve group 22. The controller sends an input signal to the servo valve group 22 according to the system requirements, so that it can accurately regulate the flow rate of the hydraulic oil, and then control the movement of the hydraulic cylinder 7. The displacement sensor 18 monitors the position of the hydraulic cylinder 7 in real time and feeds back the signal to the controller so that it can master the operating state of the hydraulic cylinder 7. The load sensor 19 transmits the load data received by the hydraulic cylinder 7 to the controller. The high-pressure and low-pressure accumulators 21 are also electrically connected to the controller. The controller controls their charging and discharging operations according to the system pressure conditions to stabilize the system pressure. In this way, each component works together with the controller to achieve the precise control and stable operation of the entire system.

[0043] The above are only embodiments of the present invention. Specific technical solutions and / or common knowledge such as characteristics well known in the art are not described in detail herein. It should be noted that for those skilled in the art, without departing from the technical solution of the present invention, several deformations and improvements can still be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicability of the patent. The protection scope required by this application shall be subject to the content of its claims, and the specific implementation manners and the like recorded in the specification can be used to interpret the content of the claims.

Claims

1. An electric drive durability test bench with internal and external excitation coupling, characterized in that: It includes a test platform, on which there are two internally excited simulation units arranged oppositely. The internally excited simulation units are used to simulate the internal power input of the electric drive system; on the test platform between the two internally excited simulation units, there is a gantry, on which there is an externally excited simulation unit, and the electric drive system is installed on the externally excited simulation unit. The externally excited simulation unit is used to simulate the external excitation received by the electric drive system from the road surface; between each internally excited simulation unit and the electric drive system, there is a decoupling mechanism, and the decoupling mechanism can realize the decoupling control between the internally excited simulation unit and the externally excited simulation unit.

2. The electric drive durability test bench with internal and external excitation coupling according to claim 1, wherein: The externally excited simulation unit includes an installation platform for carrying the electric drive system and several externally excited simulation parts. Each externally excited simulation part includes a hydraulic cylinder. The hydraulic cylinder is installed on the gantry. The output shaft of the hydraulic cylinder extends downward and is fixedly connected to the installation platform. There is a spacing between the installation platform and the test platform.

3. The electric drive durability test bench with internal and external excitation coupling according to claim 2, characterized in that: Each internally excited simulation unit includes a base and a power machine. The base is detachably connected to the test platform. The power machine is installed on the base, and the output shaft of the power machine is connected to the decoupling mechanism.

4. An electric drive durability test bench with internal and external excitation coupling according to claim 3, characterized in that: Each decoupling mechanism includes a coupling, a first universal adjustment unit and a second universal adjustment unit. The first universal adjustment unit includes a guide rod and a first universal adjustment part. The second universal adjustment unit includes a guide sleeve and a second universal adjustment part. The guide rod is fixedly connected to the first universal adjustment part. The first universal adjustment part is detachably connected to the coupling. The output shaft of the electric drive system is installed on the coupling. The guide sleeve is fixedly connected to the second universal adjustment part. The free end of the guide rod is slidably arranged in the guide sleeve. The output shaft of the power machine is detachably connected to the second universal adjustment part.

5. An electric drive durability test bench with internal and external excitation coupling according to claim 4, characterized in that: The second universal adjustment part includes a first fork head, a second fork head and a cross shaft. The first fork head is fixedly connected to the end of the guide sleeve. Two opposite journal shafts of the cross shaft are rotatably arranged on the first fork head. The other two journal shafts of the cross shaft are spherical and rotatably arranged on the second fork head. The second fork head is detachably connected to the output shaft of the power machine.

6. The electric drive durability test bench with internal and external excitation coupling according to claim 5, characterized in that: The structures of the first universal adjustment part and the second universal adjustment part are the same.

7. An electric drive durability test bench with internal and external excitation coupling according to claim 6, characterized in that: The guide rod is a spline rod, and there is a keyway inside the guide sleeve. The spline rod is adapted to the keyway.

8. An electric drive durability test bench with coupled internal and external excitation according to claim 7, characterized in that: The optimization equation for the radius ratio of the output shaft of the power machine to the output shaft of the electric drive system is: Where: is the rotation angle of the output shaft of the work machine; is the rotation angle of the output shaft of the electric drive system; is the radius ratio of the output shaft of the engine to the output shaft of the electric drive system.

9. A bench for electric drive durability test with internal and external excitation coupling, characterized in that: There are several positioning and adjustment units on the installation platform. The electric drive system is installed on the installation platform through the positioning and adjustment units, and the position and angle of the positioning and adjustment units can both be adjusted.

10. An electric drive durability test bench with internal and external excitation coupling according to claim 9, characterized in that: A buffer unit is installed on the test platform below the installation platform.

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