A power battery service working condition simulation test platform and a regulation and control method thereof

Abstract

The application discloses a kind of power battery service condition simulation test platform and base modulation method, test platform includes five steel plates of parallel interval arrangement, column shaft is through middle three steel plates and is fixedly connected with head and tail;Screw rod cooperates disc spring to realize pre-tightening force application and release.To-be-measured battery is arranged between second, third steel plate, displacement sensor gathers expansion displacement, load sensor is placed between third, fourth steel plate, double-acting cylinder adjusts support stiffness, and parallel six-axis motion platform applies six degrees of freedom vibration excitation.Control and data acquisition system connects each sensor, cylinder and motion platform.Control system determines target stiffness according to displacement signal, from pre-set displacement-stiffness relationship library, combined with load feedback, cylinder pressure is adjusted by PID controller and electrical proportional valve, to realize constraint stiffness closed loop continuous regulation and control.The application can simulate the real service condition of battery under the coupling of charge and discharge and vibration, realize pre-tightening force independent application, constraint stiffness continuously adjustable and dynamic mechanical load reproduction.

Description

Technical Field

[0001] This invention relates to the field of performance testing technology under battery mechanical operating conditions control, specifically to a power battery service condition simulation test platform and its control method. Background Technology

[0002] With the rapid development of the new energy vehicle industry, the safety, cycle life, and service reliability of power batteries, as the core energy storage component of electric vehicles, have received widespread attention. During charging and discharging, power batteries undergo volume expansion and contraction, accompanied by material structure evolution, stress accumulation, and performance degradation. In actual vehicle operation, power batteries are typically not in a free state but are installed in battery modules or battery packs, operating under specific preload and constraint stiffness conditions, and continuously subjected to vibrations and impacts from the vehicle body. These mechanical boundary conditions are coupled with the battery's own charging and discharging expansion behavior, leading to dynamic changes in the internal stress state and its distribution within the battery, thereby affecting the battery's aging process, cycle life, and safety performance.

[0003] However, current research on the mechanical behavior and charge / discharge performance of power batteries largely focuses on testing individual battery cells under static compression, constant clamping, unidirectional vibration, or specific charge / discharge conditions, typically emphasizing the impact of a single factor on battery performance. While some studies consider the constrained state of the battery within modules or battery packs, they often employ fixed boundaries or discrete stiffness conditions, making it difficult to reflect the changes in battery constraint stiffness with structural response in real-world applications. Although some vibration testing devices can apply external mechanical excitation, they lack the ability to coordinate and independently control the initial preload and installation stiffness of the battery, thus failing to realistically simulate the comprehensive mechanical conditions under a vehicle environment. Existing technologies generally lack a testing method capable of simultaneously simulating preload, constraint stiffness, and vehicle vibration loads, and characterizing the internal stress changes under their coupled effects.

[0004] Preload determines the initial stress state of the battery, constraint stiffness affects the degree of restriction on battery expansion and deformation, and vehicle vibration introduces additional loads. These three factors together constitute the key mechanical boundary conditions for the practical application of power batteries. Accurately simulating these conditions and their coupling effects during the testing phase helps to more realistically evaluate the battery's deformation response, stress evolution, lifespan degradation, and safety risks in practical applications. It can also provide a reliable basis for power battery structural design, constraint strategy optimization, and charge / discharge performance prediction.

[0005] Therefore, it is particularly important to develop a test platform capable of simulating the dynamic mechanical loads experienced by batteries under real driving conditions. This platform should be able to apply independently set preload to the battery, achieve continuous adjustment of constraint stiffness, and reproduce multi-degree-of-freedom vibration excitation during vehicle operation. This would allow for a more realistic simulation of the actual installation and operating environment of power batteries in automobiles, providing a testing method for studying their internal stress variation patterns and lifespan evolution mechanisms. Summary of the Invention

[0006] The main objective of this invention is to overcome the shortcomings and deficiencies of the prior art and provide a power battery service condition simulation test platform and its control method, which realizes the coupled loading of charging and discharging, constraint stiffness, preload and six-degree-of-freedom vibration, and provides a reliable test means for the study of multi-field coupling characteristics and service performance evaluation of power batteries.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a power battery service condition simulation test platform, comprising:

[0009] A first steel plate, a second steel plate, a third steel plate, a fourth steel plate, and a fifth steel plate arranged in parallel and at intervals;

[0010] A plurality of column shafts, the two ends of which are fixedly connected to the first steel plate and the fifth steel plate respectively, and pass through the second steel plate, the third steel plate and the fourth steel plate in sequence;

[0011] A pre-tensioning assembly, comprising a lead screw threadedly connected to the first steel plate and a disc spring sleeved on the lead screw, for making the force applied to the battery more evenly distributed;

[0012] The lithium battery to be tested is placed between the second and third steel plates during the test;

[0013] A displacement detection component, wherein the displacement detection component is used to detect the thickness direction displacement of the lithium battery under test;

[0014] A load detection component is disposed between the third steel plate and the fourth steel plate, and is used to detect the load applied to the lithium battery under test;

[0015] A pneumatic stiffness adjustment assembly is disposed between the fourth steel plate and the fifth steel plate and is used to adjust the constraint stiffness of the test platform for the lithium battery under test.

[0016] A parallel six-axis motion platform is set below the fifth steel plate to apply six-degree-of-freedom vibration excitation;

[0017] The control and data acquisition system is connected to the displacement detection component, load detection component, pneumatic stiffness adjustment component, and parallel six-axis motion platform, respectively.

[0018] As a preferred technical solution, the lead screw and the disc spring are respectively provided with corresponding pin holes. When the pin holes are aligned, the lead screw and the disc spring are rigidly connected by inserting a crossbar to lock the preload.

[0019] As a preferred technical solution, linear bearings are respectively provided at the positions where the second steel plate, the third steel plate, and the fourth steel plate are penetrated by the column axis, so that the second steel plate, the third steel plate, and the fourth steel plate can move linearly along the column axis.

[0020] As a preferred technical solution, the displacement detection assembly includes an upper L-shaped plate, a lower L-shaped plate, and a displacement sensor. The upper L-shaped plate is fixedly connected to the second steel plate, the lower L-shaped plate is fixedly connected to the third steel plate, and the displacement sensor is mounted on the upper L-shaped plate with its measuring probe in contact with the lower L-shaped plate.

[0021] As a preferred technical solution, the displacement sensor is a micrometer-level capacitive micrometer, and two of them are arranged diagonally; the load sensor in the load detection assembly is a resistance strain gauge load sensor.

[0022] As a preferred technical solution, the pneumatic stiffness adjustment assembly includes a cylinder, which is a double-acting cylinder structure, including a high-pressure cylinder and a low-pressure cylinder. The high-pressure cylinder and the low-pressure cylinder are arranged differentially to achieve continuous adjustment of the constraint stiffness through intake pressure adjustment.

[0023] As a preferred technical solution, the parallel six-axis motion platform includes six servo actuators. The host computer in the control and data acquisition system is used to analyze the road spectrum information to generate the target vibration signal, and output the extension and contraction commands to drive the six servo actuators to move in coordination based on the inverse kinematics model, so as to reproduce the six-degree-of-freedom vibration waveform.

[0024] As a preferred technical solution, it also includes a displacement-stiffness relation library and a PID controller to achieve continuous and precise control of the stiffness of the battery module;

[0025] The displacement-stiffness relation library pre-stores the correspondence between displacement and target stiffness constructed based on experimental data; during the control process, the displacement signal collected in real time by the displacement sensor is transmitted to the displacement-stiffness relation library, which outputs the corresponding target stiffness command to the PID controller according to the current displacement value; at the same time, the load signal collected in real time by the load sensor is fed back to the PID controller.

[0026] The PID controller generates control commands based on the deviation between the expected pressure value corresponding to the target stiffness command and the actual load signal, using a proportional-integral-derivative control algorithm, and outputs them to the electric proportional valve.

[0027] The electric proportional valve adjusts its opening according to the command, thereby precisely controlling the gas pressure entering the high-pressure cylinder and the low-pressure cylinder, driving the fourth steel plate to produce corresponding actions, and realizing continuous adjustment of the stiffness of the fourth steel plate.

[0028] The displacement and load changes of the fourth steel plate are collected and fed back by the sensor again, forming a closed-loop control circuit.

[0029] Secondly, this invention provides a method for continuous adjustment of the stiffness of a power battery under service conditions, based on the aforementioned power battery service condition simulation test platform, comprising the following steps:

[0030] S1: The displacement signal in the thickness direction of the lithium battery under test is acquired in real time through the displacement detection component.

[0031] S2: The control and data acquisition system determines the target stiffness based on the displacement signal using a preset displacement-stiffness correspondence library;

[0032] S3: The load signal is acquired in real time through the load detection component, and the load signal is fed back to the PID controller;

[0033] S4: The PID controller generates adjustment commands based on the target stiffness and the load signal;

[0034] S5: Control the pneumatic stiffening assembly to adjust the gas pressure of the cylinder according to the adjustment command, so as to drive the fourth steel plate to move;

[0035] S6: Repeat steps S1 to S5 to form a closed-loop control to achieve continuous adjustment of the constraint stiffness of the lithium battery under test.

[0036] 10. A method for continuous adjustment of the stiffness of a power battery under service conditions according to claim 9, characterized in that, in step S2, the displacement-stiffness correspondence library is constructed based on battery charge-discharge cycle experimental data under different initial compression amounts and different constraint stiffnesses, with real-time displacement as input and target stiffness as output.

[0037] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0038] 1. This invention integrates continuous stiffness control, preload preset, and measured load spectrum reproduction functions to achieve comprehensive testing under the coupling effect of multiple physical fields. It overcomes the shortcomings of existing equipment with single function and limited testing dimensions, and can comprehensively reflect the complex physical environment and variable working conditions faced by the battery in actual use, significantly improving the accuracy and comprehensiveness of battery performance evaluation.

[0039] 2. The present invention adopts a cylinder design with a double-acting cylinder structure, which achieves bidirectional adjustment of stiffness through cooperative work, thereby enhancing the stability and controllability of the system and effectively solving the problems of complex structure and high cost of existing equipment;

[0040] 3. This invention, through the design of a parallel six-axis motion platform, achieves accurate reproduction of excitations on complex road surfaces, breaking through the limitation of existing equipment that can only simulate a single working condition, and improving the flexibility and adaptability of testing. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is the main view of the battery service condition simulation platform in this embodiment.

[0043] Figure 2 This is a top view of the battery service condition simulation platform in this embodiment.

[0044] Figure 3 This is a time-domain waveform diagram of the Y-axis acceleration of the parallel six-axis motion platform in this embodiment.

[0045] Figure 4 This is a time-domain waveform diagram of the pitch angular velocity of the parallel six-axis motion platform in this embodiment.

[0046] Figure 5 This example illustrates the effect of module stiffness and initial compression on displacement.

[0047] Figure 6 This is a schematic diagram of the control principle of the battery service condition simulation platform in this embodiment.

[0048] Explanation of reference numerals in the attached figures:

[0049] 1-Screw 1; 2-First steel plate; 3-Second steel plate; 4-Upper linear bearing; 5-Third steel plate; 6-Load sensor; 7-Fourth steel plate; 8-Cylinder; 9-Fifth steel plate; 10-Parallel six-axis motion platform; 11-Column shaft; 12-Load sensor base; 13-Lower linear bearing; 14-Middle linear bearing; 15-Lower L-shaped plate; 16-Upper L-shaped plate; 17-Shim; 18-Lithium battery; 19-Displacement sensor; 20-Disc spring. Detailed Implementation

[0050] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative effort are within the scope of protection of the present application.

[0051] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0052] like Figure 1 , Figure 2 As shown in the figure, the power battery service condition simulation test platform provided in this embodiment adopts a stiffness continuous adjustment-preload preset and measured load spectrum reproduction device, including a first steel plate 2, a second steel plate 3, a third steel plate 5, a fourth steel plate 7 and a fifth steel plate 9 arranged in parallel, multiple cooperating column shafts 11, a lead screw 1, a disc spring 20, a displacement sensor 19, a load sensor 6, a cylinder 8 and a parallel six-axis motion platform 10.

[0053] The multiple column shafts 11 are fixedly connected at both ends to the first steel plate 2 and the fifth steel plate 9, respectively, and pass through the second steel plate 3, the third steel plate 5, and the fourth steel plate 7 in sequence. At the points where the second steel plate 3, the third steel plate 5, and the fourth steel plate 7 pass through, linear bearings 4 (upper), 14 (middle), and 13 (lower) are respectively installed to ensure that each steel plate can move smoothly and linearly along the column shafts 11.

[0054] Furthermore, the lead screw 1 is threadedly connected to the center of the first steel plate 2, and a preload can be applied to or released to the second steel plate 3 by turning the lead screw 1. The lead screw 1 and the disc spring 20 are respectively provided with pin holes. When the pin holes coincide, a crossbar can be inserted to rigidly connect the two, thereby locking the preload. Preferably, the disc spring 20 has an elastic constant of 200 N / mm and a natural length of 100 mm, used to store and release the preload, reducing vibration transmission.

[0055] During testing, the lithium battery 18 to be tested (preferably 95.5×40×4 mm) is wrapped with a polyimide film pad 17 and placed between the second steel plate 3 and the third steel plate 5. The upper L-shaped plate 16 is fixedly connected to the side of the second steel plate 3, and two diagonally arranged displacement sensors 19 are mounted on it. These displacement sensors 19 (preferably Keyence GT2-H12K micrometer-level capacitive grating micrometers) employ micrometer-level resolution capacitive grating micrometers to monitor real-time changes in battery thickness. The lower L-shaped plate 15 is fixedly connected to the side of the third steel plate 5, serving as the measurement reference for the displacement sensors 19.

[0056] Furthermore, the load sensor 6 (preferably an Omega LCM305-500N resistance strain gauge sensor) is a resistance strain gauge load sensor used to monitor the preload value on the first steel plate in real time. It is installed inside the load sensor base 12, which is fixedly connected to the fourth steel plate 7, so that the load sensor 6 is located between the fourth steel plate 7 and the third steel plate 5.

[0057] Furthermore, the cylinder 8 (preferably an SMC_JP_CQ2B6310DZ type double-acting cylinder) is positioned between the fourth steel plate 7 and the fifth steel plate 9. It includes a high-pressure cylinder and a low-pressure cylinder, arranged differentially, to achieve bidirectional stiffness adjustment through coordinated operation. The cylinder's exhaust port has an adjustable structure, used to adjust the opening of the exhaust valve, thereby controlling the cylinder's extension and retraction speed. Both the high-pressure and low-pressure cylinders have a stroke of 10 mm and a maximum working pressure of 0.9 MPa. The adjustable exhaust port of cylinder 8 is controlled by a solenoid valve, which in turn adjusts the cylinder's extension and retraction speed.

[0058] Furthermore, the entire testing device composed of the aforementioned components is fixedly positioned directly above a parallel six-axis motion platform 10. The parallel six-axis motion platform includes six servo actuators, each with a drive unit connected to a host computer system. The host computer system is used to analyze real road spectrum information and generate a target vibration signal containing multiple degrees of freedom. The control system of the parallel six-axis motion platform receives this target signal and, based on an inverse kinematics model, calculates and outputs extension / retraction commands in real time to drive the six servo actuators to move in tandem. Each servo actuator precisely executes push-pull actions according to the commands. Through high-precision servo closed-loop control and dynamic decoupling algorithms, the platform accurately reproduces the six-degree-of-freedom vibration waveform of the target road spectrum, thereby simulating the operating conditions of the power battery during the driving of a new energy vehicle.

[0059] Furthermore, the platform also includes a displacement-stiffness relation library and a PID controller for continuous and precise control of the battery module stiffness. The displacement-stiffness relation library pre-stores the correspondence between displacement and target stiffness based on experimental data. During control, the displacement signal collected in real time by the displacement sensor is transmitted to the displacement-stiffness relation library, which outputs the corresponding target stiffness command to the PID controller based on the current displacement value. Simultaneously, the load signal collected in real time by the load sensor is fed back to the PID controller. The PID controller generates a control command based on the deviation between the expected pressure value corresponding to the target stiffness command and the actual load signal using a proportional-integral-derivative control algorithm, and outputs it to the electro-proportional valve. The electro-proportional valve adjusts its opening according to the command, thereby precisely controlling the gas pressure entering the high-pressure cylinder and the low-pressure cylinder, driving the fourth steel plate to produce corresponding actions, and achieving continuous adjustment of the stiffness of the fourth steel plate. The displacement and load changes of the fourth steel plate are again collected and fed back by the sensor, forming a closed-loop control circuit.

[0060] In another embodiment, based on the aforementioned power battery service condition simulation test platform, the road spectrum reproduction accuracy and multi-degree-of-freedom coupled loading capability of the parallel six-axis motion platform 10 are verified. The platform includes six servo actuators, whose drive devices are connected to a host computer system. Random vibration road spectrum data of a typical urban road is selected as the input target, and the power battery pack under test is installed at the center of the platform surface. The platform is run to vibrate according to the target road spectrum, and the Y-axis acceleration data representing the translational degree of freedom and the pitch angular velocity data representing the rotational degree of freedom are continuously and synchronously collected at a sampling frequency of 100 Hz for 100 seconds.

[0061] Figure 3 This is the acquired Y-axis acceleration-time domain waveform. (From...) Figure 3As can be seen, the Y-axis acceleration signal exhibits high-frequency, violent random fluctuations within the set range, with no obvious periodicity in the waveform. This is highly consistent with the randomness and wideband characteristics of real road surface excitation, effectively reproducing the lateral translation load generated by the random lateral impact on the tires during vehicle operation on the battery pack.

[0062] Figure 4 This is a time-domain waveform diagram of the pitch angular velocity obtained through synchronous acquisition. Figure 4 As can be seen, the angular velocity signal also exhibits continuous and complex random dynamic changes. The accurate reproduction of this rotational degree of freedom data indicates that this test platform can realistically simulate the pitching motion of a car body when accelerating, braking, or driving over undulating road surfaces, thereby applying longitudinal bending and dynamic torsional stresses to the battery pack that cannot be achieved by traditional single-axis vibration equipment.

[0063] Test results combining translational and rotational data show that, compared with conventional single-dimensional mechanical testing equipment, the parallel six-axis motion platform of this invention can reproduce the six-degree-of-freedom coupled vibration of real complex road spectra with high fidelity, breaking through the limitations of single mechanical loads, and can be used very effectively for high-precision mechanical simulation and safety performance evaluation of power batteries under real service conditions.

[0064] In another specific embodiment, based on the aforementioned power battery service condition simulation test platform, a displacement-stiffness relationship library for continuous stiffness control is experimentally constructed. This relationship library is the core basis for subsequent implementation of closed-loop control of constraint stiffness.

[0065] The experimental subjects were a batch of soft-pack graphite / NMC 622 lithium-ion batteries with a rated capacity of 60 Ah. Before the experiment, the lithium battery to be tested 18 was placed between the second steel plate 3 and the third steel plate 5, and the initial compression was set by turning the lead screw 1. At the same time, the gas pressure of the cylinder 8 in the pneumatic stiffness adjustment assembly was adjusted by the control and data acquisition system to set different module stiffnesses.

[0066] In the experiment, multiple different module stiffness values ​​(achieved by adjusting cylinder pressure) and multiple different initial compression values ​​(achieved by lead screw preload) were set. Under the above different parameter combinations, the battery was subjected to 1000 charge-discharge cycle aging experiments, and the expansion displacement of the battery in the thickness direction was monitored and recorded in real time by displacement sensor 19.

[0067] Figure 5This study demonstrates the influence of different module stiffness and initial compression on battery expansion displacement after 200 charge-discharge cycles. Experimental results show that, under the same initial compression, a higher module stiffness results in a smaller battery expansion displacement, indicating that higher constraint stiffness effectively suppresses battery expansion deformation during cycling. Furthermore, under the same module stiffness, an increase in initial compression leads to a corresponding decrease in battery expansion displacement, demonstrating that the magnitude of the initial preload directly affects the battery's mechanical response during cycling.

[0068] Based on the experimental data above, the control and data acquisition system constructed a "displacement-stiffness" correspondence library. This library uses the real-time expansion displacement of the battery as input and the desired target constraint stiffness as output, providing a precise setting basis for subsequent stiffness closed-loop control. During actual service condition simulation, the system can quickly query and determine the currently required ideal stiffness value based on the real-time battery expansion displacement collected by displacement sensor 19, thereby driving the aerodynamic stiffness adjustment component for precise adjustment.

[0069] Another embodiment of the present invention also provides a method for continuous adjustment of the stiffness of a power battery under service conditions, such as... Figure 6 As shown, it includes the following steps:

[0070] S1. The displacement signal of the fourth steel plate 7 (whose displacement indirectly reflects the expansion of the battery) is acquired in real time by the displacement sensor 19, and the signal is transmitted to the pre-built displacement-stiffness relationship library. At the same time, the load signal applied to the fourth steel plate 7 is acquired in real time by the load sensor 6, and the signal is fed back to the PID controller.

[0071] S2. The displacement-stiffness relation library queries and determines the required ideal target stiffness value K_target based on the received current displacement signal, and sends it as an instruction to the PID controller.

[0072] S3. The PID controller converts the target stiffness K_target into a desired pressure value and compares it with the actual pressure value from load sensor 6 to calculate the pressure deviation. Based on this deviation, the PID controller generates corresponding control commands using a proportional-integral-derivative control algorithm.

[0073] S4. The control command is output to the electro-proportional valve to precisely control its opening, thereby adjusting the gas pressure entering the high-pressure cylinder and the low-pressure cylinder. The adjusted pressurized gas acts on the upper and lower chambers of the cylinder 8, driving the fourth steel plate 7 to produce corresponding actions, thus realizing continuous adjustment of the module stiffness.

[0074] The displacement and load changes of S5 and the fourth steel plate 7 are collected again by the sensors and fed back to the relational database and PID controller, forming a closed-loop control. Through this closed-loop control loop, the system can continuously and accurately adjust the stiffness of the modules according to the preset displacement-stiffness relationship to adapt to the loading requirements under different working conditions.

[0075] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0076] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A power battery service condition simulation test platform, characterized in that, include: The first steel plate (2), the second steel plate (3), the third steel plate (5), the fourth steel plate (7) and the fifth steel plate (9) are arranged in parallel and at intervals. Several column shafts (11) are fixedly connected at both ends to the first steel plate (2) and the fifth steel plate (9) respectively, and pass through the second steel plate (3), the third steel plate (5) and the fourth steel plate (7) in sequence. The pre-tightening assembly includes a lead screw (1) threadedly connected to the first steel plate (2) and a disc spring (20) sleeved on the lead screw (1) for making the force applied to the battery more evenly distributed; The lithium battery (18) to be tested is placed between the second steel plate (3) and the third steel plate (5) during the test. A displacement detection component is used to detect the thickness displacement of the lithium battery (18) under test. A load detection component is disposed between the third steel plate (5) and the fourth steel plate (7) for detecting the load applied to the lithium battery (18) to be tested; A pneumatic stiffness adjustment assembly is disposed between the fourth steel plate (7) and the fifth steel plate (9) for adjusting the constraint stiffness of the test platform on the lithium battery (18) to be tested. A parallel six-axis motion platform (10) is set below the fifth steel plate (9) for applying six-degree-of-freedom vibration excitation; The control and data acquisition system is connected to the displacement detection component, load detection component, pneumatic stiffening component and parallel six-axis motion platform (10), respectively.

2. The power battery service condition simulation test platform according to claim 1, characterized in that, The lead screw (1) and the disc spring (20) are respectively provided with corresponding pin holes. When the pin holes are aligned, the lead screw (1) and the disc spring (20) are rigidly connected by inserting a crossbar to lock the preload.

3. The power battery service condition simulation test platform according to claim 1, characterized in that, Linear bearings are provided at the positions where the second steel plate (3), the third steel plate (5), and the fourth steel plate (7) are penetrated by the column shaft (11), so that the second steel plate (3), the third steel plate (5), and the fourth steel plate (7) can move linearly along the column shaft (11).

4. The power battery service condition simulation test platform according to claim 1, characterized in that, The displacement detection assembly includes an upper L-shaped plate (16), a lower L-shaped plate (15), and a displacement sensor (19). The upper L-shaped plate (16) is fixedly connected to the second steel plate (3), and the lower L-shaped plate (15) is fixedly connected to the third steel plate (5). The displacement sensor (19) is mounted on the upper L-shaped plate (16), and its measuring probe is in contact with the lower L-shaped plate (15).

5. The power battery service condition simulation test platform according to claim 4, characterized in that, The displacement sensor (19) is a micrometer-level capacitive micrometer, and two of them are arranged diagonally; the load sensor (6) in the load detection assembly is a resistance strain gauge load sensor.

6. The power battery service condition simulation test platform according to claim 1, characterized in that, The pneumatic stiffness adjustment assembly includes a cylinder (8), which is a double-acting cylinder structure, including a high-pressure cylinder and a low-pressure cylinder. The high-pressure cylinder and the low-pressure cylinder are arranged differentially to achieve continuous adjustment of the constraint stiffness through intake pressure adjustment.

7. The power battery service condition simulation test platform according to claim 1, characterized in that, The parallel six-axis motion platform (10) includes six servo actuators. The host computer in the control and data acquisition system is used to analyze the road spectrum information to generate the target vibration signal, and output the extension and contraction command to drive the six servo actuators to move in coordination based on the inverse kinematics model, so as to reproduce the six-degree-of-freedom vibration waveform.

8. The power battery service condition simulation test platform according to claim 1, characterized in that, It also includes a displacement-stiffness relation library and a PID controller for continuous and precise control of the battery module stiffness; The displacement-stiffness relation library pre-stores the correspondence between displacement and target stiffness constructed based on experimental data; During the control process, the displacement signal collected in real time by the displacement sensor is transmitted to the displacement-stiffness relation library, which outputs the corresponding target stiffness command to the PID controller based on the current displacement value; at the same time, the load signal collected in real time by the load sensor is fed back to the PID controller. The PID controller generates control commands based on the deviation between the expected pressure value corresponding to the target stiffness command and the actual load signal, using a proportional-integral-derivative control algorithm, and outputs them to the electric proportional valve. The electric proportional valve adjusts its opening according to the command, thereby precisely controlling the gas pressure entering the high-pressure cylinder and the low-pressure cylinder, driving the fourth steel plate to produce corresponding actions, and realizing continuous adjustment of the stiffness of the fourth steel plate. The displacement and load changes of the fourth steel plate are collected and fed back by the sensor again, forming a closed-loop control circuit.

9. A method for continuous adjustment of the stiffness of a power battery under service conditions, based on the power battery service condition simulation test platform described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1: The displacement signal in the thickness direction of the lithium battery (18) under test is collected in real time by the displacement detection component; S2: The control and data acquisition system determines the target stiffness based on the displacement signal using a preset displacement-stiffness correspondence database; S3: The load signal is acquired in real time through the load detection component and the load signal is fed back to the PID controller; S4: The PID controller generates adjustment commands based on the target stiffness and the load signal; S5: Control the gas pressure of the pneumatic stiffening assembly to adjust the gas pressure of the cylinder (8) according to the adjustment command, so as to push the fourth steel plate (7) to move; S6: Repeat steps S1 to S5 to form a closed-loop control to achieve continuous adjustment of the constraint stiffness of the lithium battery (18) under test.

10. The method for continuous adjustment of the stiffness of a power battery under service conditions according to claim 9, characterized in that, In step S2, the displacement-stiffness correspondence library is constructed based on battery charge-discharge cycle experimental data under different initial compression amounts and different constraint stiffnesses, with real-time displacement as input and target stiffness as output.

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