A modeling method of a shock absorber in a vehicle dynamics model

Abstract

The application discloses a modeling method of a shock absorber in a whole vehicle dynamics model, and belongs to the field of vehicle dynamics modeling.The modeling method of the shock absorber in the whole vehicle dynamics model comprises the following steps: step 1, modeling each component of the shock absorber in a dynamics analysis software; step 2, connecting a bushing between a piston rod and a piston; step 3, connecting a ball pair between the piston and an oil storage outer cylinder; step 4, connecting a bushing between the oil storage outer cylinder and a guide mechanism and an oil seal; step 5, connecting a cylindrical pair between the guide mechanism and the oil seal and the piston rod; and step 6, establishing a shock absorber damping characteristic between the piston and the guide mechanism and the oil seal.The modeling method of the shock absorber in the whole vehicle dynamics model can correctly reflect the internal movement relationship of the shock absorber, can accurately analyze the static load and the dynamic load of each component, and has strong practicability and good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of automotive technology, and more specifically, relates to a method for modeling shock absorbers in a vehicle dynamics model. Background Technology

[0002] In the early stages of vehicle design, accurate multibody dynamics modeling not only accurately reflects the load magnitude of vehicle structural components but also the overall handling comfort performance and suspension K&C characteristics. Furthermore, it allows for the accurate identification of design flaws and risks related to vehicle handling and comfort, as well as structural component strength and durability design risks, during the data phase. Simultaneous optimization and rectification during this period significantly mitigates and reduces real-world risks during the prototype development stage, saving development time and costs.

[0003] As a crucial chassis component in a vehicle, the accurate modeling of the shock absorber in the vehicle's multibody dynamics model is of paramount importance. It affects both the calculation accuracy of the static loads between shock absorber components (shock absorber struts and shock absorber outer cylinders) and the simulation accuracy of the suspension's K&C characteristics.

[0004] With the continuous advancement of finite element technology and computer hardware resources, static load extraction and analysis based on multibody dynamics, as well as suspension K&C characteristic simulation and vehicle handling and stability simulation, have been widely applied in vehicle development. The detailed technical approach is as follows: 1. Use multibody dynamics software to build subsystem models such as suspension, steering, braking, and body; 2. Build corresponding front and rear suspension dynamic model assemblies, and perform static load extraction of chassis components and suspension K&C characteristic analysis; 3. Build corresponding vehicle dynamic model assemblies, and perform static load extraction of the vehicle body and vehicle handling and stability characteristic simulation analysis.

[0005] Technical Defect 1: In the suspension modeling of the first point of the above technical route, the conventional modeling method for the internal relationship of the shock absorber is to establish a cylindrical pair between the shock absorber piston rod and the outer oil reservoir (see details). Figure 1 The connection relationship between components 1 and 2 is simulated, and the vertical and axial rotational motion degrees of freedom between the piston rod and the outer oil reservoir are simply modeled. This method can effectively simulate the motion relationship between suspension components, but it cannot accurately reflect the mechanical relationship between the piston rod and the outer oil reservoir, and it cannot perform static load extraction analysis between shock absorber components.

[0006] Technical Defect 2: In the suspension modeling of point 1 of the above technical route (for MacPherson strut suspension), the conventional modeling method for the relationship between the shock absorber and the steering knuckle is to use rigid body simulation for both the shock absorber oil reservoir and the steering knuckle, and to establish a fixed joint at their connection (see details). Figure 1(The connection relationship between components 2 and 3). Although this modeling method is consistent with the actual relationship, it cannot effectively reflect the deformation relationship of the connection point attachments, which will result in a large error in the suspension K&C characteristic analysis. Summary of the Invention

[0007] The purpose of this invention is to solve the problems existing in the prior art and provide a modeling method for a shock absorber in the whole vehicle dynamics model that can accurately reflect the internal motion relationship of the shock absorber, accurately analyze the static and dynamic loads of each component, and provide load input for the strength and durability acceptance of each component of the shock absorber.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: the modeling method of this shock absorber in the whole vehicle dynamics model includes fixing the cup holder, characterized by comprising the following steps:

[0009] Step 1: In the dynamic analysis software, the components of the shock absorber are modeled separately. The components of the shock absorber include piston rod, piston, oil reservoir, guide mechanism and oil seal;

[0010] Step 2: The piston rod and the piston are connected by a bushing, and the axial direction of the bushing is consistent with the vertical movement direction of the piston rod;

[0011] Step 3: The piston and the outer oil reservoir are connected by a ball joint;

[0012] Step 4: The outer oil storage cylinder, the guide mechanism, and the oil seal are connected by a bushing, and the axial direction of the bushing is consistent with the vertical movement direction of the piston rod;

[0013] Step 5: The guide mechanism and oil seal are connected to the piston rod using a cylindrical pair.

[0014] Step 6: Establish damping characteristics between the piston, guide mechanism, and oil seal.

[0015] To make the above technical solutions more detailed and specific, the present invention also provides the following further preferred technical solutions to achieve satisfactory practical effects:

[0016] In step 2, the linear stiffness of the bushing in three directions is set to be no less than 1E+6N / mm by default. The radial torsional stiffness of the bushing is set to the radial torsional stiffness of the piston rod at the piston connection point as measured by finite element simulation or actual measurement. The axial torsional stiffness of the bushing is set to be no less than 1E+9N.mm / deg by default.

[0017] In step 3, the ball joint connection retains rotational degrees of freedom in three directions.

[0018] In step 4, the linear stiffness of the bushing in three directions is set to be no less than 1E+6N / mm by default, which is close to an immovable state. The radial torsional stiffness of the bushing is set to the radial torsional stiffness of the oil reservoir outer cylinder at the guide mechanism and oil seal connection point, which is simulated by finite element method or measured by actual measurement. The axial torsional stiffness of the bushing is set to be no less than 1E+9N.mm / deg by default.

[0019] In step 5, the axial direction of the cylindrical joint is consistent with the vertical movement direction of the piston rod, thus preserving the axial translational and rotational degrees of freedom.

[0020] The process also includes step 7: the oil reservoir outer cylinder and the steering knuckle are connected by a parallel ball joint and bushing.

[0021] The bushing's axial direction is consistent with the piston rod's vertical movement direction.

[0022] The radial torsional stiffness of the bushing is set to the radial torsional stiffness of the oil reservoir outer cylinder at the steering knuckle connection point, which is determined by finite element simulation or actual measurement. The axial torsional stiffness of the bushing is set to be no less than 1E+9N.mm / deg by default.

[0023] Compared with the prior art, the present invention has the following advantages: The modeling method of the shock absorber in the whole vehicle dynamics model of the present invention correctly establishes the connection relationship between each component according to the actual structure of the shock absorber, accurately reflects the internal motion relationship of the shock absorber, and can accurately analyze the static load and dynamic load of each component, providing load input for the strength and durability acceptance of each component of the shock absorber, which has strong practicality and good application prospects. Attached Figure Description

[0024] The following is a brief explanation of the contents depicted in the accompanying drawings and the markings therein:

[0025] Figure 1 A schematic diagram of a shock absorber model in the existing technology;

[0026] Figure 2 This is a schematic diagram of the shock absorber model in this invention;

[0027] Figure 3 This is a schematic diagram showing the modeling of the oil storage outer cylinder and the steering knuckle in this invention.

[0028] The following are marked in the diagram: 1. Piston rod; 2. Piston; 3. Oil reservoir outer cylinder; 4. Guide mechanism and oil seal; 5. Steering knuckle. Detailed Implementation

[0029] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and through the description of the examples.

[0030] In the description of this invention, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0031] The method for modeling the shock absorber in a vehicle dynamics model according to the present invention includes the following steps:

[0032] Step 1: In the dynamic analysis software, the components of the shock absorber are modeled separately. The components of the shock absorber include piston rod 1, piston 2, oil reservoir 3, guide mechanism and oil seal 4.

[0033] Step 2: A bushing is used to connect piston rod 1 and piston 2, and the axial direction of the bushing is consistent with the vertical movement direction of piston rod 1;

[0034] Step 3: The piston 2 and the oil reservoir outer cylinder 3 are connected by a ball joint;

[0035] Step 4: The outer oil reservoir 3, the guide mechanism, and the oil seal 4 are connected by a bushing, and the axial direction of the bushing is consistent with the vertical movement direction of the piston rod 1;

[0036] Step 5: The guide mechanism and oil seal 4 are connected to the piston rod 1 by a cylindrical pair;

[0037] Step 6: Establish the damping characteristics of the shock absorber between piston 2, guide mechanism, and oil seal 4;

[0038] Step 7: The oil reservoir outer cylinder 3 and the steering knuckle 5 are connected by a parallel ball joint and a bushing, with the bushing axial direction aligned with the vertical movement direction of the piston rod.

[0039] The detailed steps of this modeling method are as follows (steps 1-6 are detailed in [link]). Figure 2 As shown, step 7 Figure 3 As shown):

[0040] In step 1, the shock absorber is divided into four parts in the dynamic analysis software, and corresponding rigid body parts are created for each part, which correspond to piston rod 1, piston 2, oil reservoir 3, guide mechanism and oil seal 4 in the figure. The modeling method of the four rigid body parts is the same as the conventional modeling method.

[0041] In step 2, piston rod 1 and piston 2 are connected by a bushing. The axial direction of the bushing is consistent with the vertical movement direction of piston rod 1. The linear stiffness of the bushing in three directions is set to be no less than 1E+6 N / mm by default. In one embodiment, it is set to 10 to the power of 6 N / mm by default, which is close to an immovable state. The radial torsional stiffness of the bushing is determined according to the radial torsional stiffness of piston rod 1 at the piston 2 connection point by finite element simulation or actual measurement. The radial torsional stiffness of the bushing is the same as the radial torsional stiffness of piston rod at the piston connection point. The axial torsional stiffness of the bushing is set to be no less than 1E+9 N.mm / deg by default. In one embodiment, it can be set to 10 to the power of 9 N mm / degree, or greater than 10 to the power of 9 N mm / degree. This stiffness setting is close to an immovable state, thereby establishing a force transmission path between piston 2 and piston rod 1.

[0042] In step 3, the piston 2 and the oil storage outer cylinder 3 are connected by a ball joint, retaining rotational degrees of freedom in three directions, thereby establishing a force transmission path between the piston 2 and the oil storage outer cylinder 3;

[0043] In step 4, the outer oil reservoir 3 and the guide mechanism and oil seal 4 are connected by a bushing. The axial direction of the bushing is consistent with the vertical movement direction of the piston rod 1. The linear stiffness of the bushing in three directions is set to be no less than 1E+6N / mm by default. In one embodiment, it is set to 10 to the power of 7 N / mm by default, which is approximately immovable. The radial torsional stiffness of the bushing is determined according to the radial torsional stiffness of the outer oil reservoir 3 at the connection point of the guide mechanism based on finite element simulation or actual measurement. The radial torsional stiffness of the bushing is the same as the radial torsional stiffness of the outer oil reservoir at the connection point of the guide mechanism and oil seal. The axial torsional stiffness of the bushing is set to be no less than 1E+9N.mm / deg by default. In one embodiment, it can be set to 10 to the power of 11 Nmm / degree, which is approximately immovable (consistent with the modeling method in step 2). Thus, the force transmission path between the outer oil reservoir 3 and the guide mechanism and oil seal 4 is established.

[0044] In step 5, the guide mechanism and oil seal 4 are connected to the piston rod 1 by a cylindrical pair. The axis of the cylindrical pair is consistent with the vertical movement direction of the piston rod 1, retaining the axial movement and rotational degrees of freedom, thereby establishing the force transmission path between the piston rod 1 and the guide mechanism and oil seal 4.

[0045] In step 6, the damping characteristics of the shock absorber are established between piston 2, guide mechanism and oil seal 4. The damping force generated by the shock absorber is transmitted to piston rod 1 through piston 2. The reaction force of the damping force is transmitted to oil reservoir 3 through guide mechanism and oil seal 4, which is consistent with the damping force transmission path of solid shock absorber.

[0046] In step 7, the oil reservoir outer cylinder 3 and the steering knuckle 5 are connected by a parallel ball joint and a bushing. The axial direction of the bushing is consistent with the vertical movement direction of the piston rod 1. The linear stiffness of the bushing in the three directions can be set arbitrarily because the free movement in the three directions has been restricted by the ball joint and is in a non-movable state. The radial torsional stiffness of the bushing is determined according to the radial torsional stiffness of the oil reservoir outer cylinder 3 at the steering knuckle connection point by finite element simulation or actual measurement. The radial torsional stiffness of the bushing is the same as the radial torsional stiffness of the oil reservoir outer cylinder at the steering knuckle connection point. The axial torsional stiffness of the bushing is set by default to not less than 1E+9 N.mm / deg. In one embodiment, it can be set to 10 to the power of 11 N mm / degree, which is approximately non-rotatable. This establishes the force transmission path between the oil reservoir outer cylinder 3 and the steering knuckle rod while effectively reflecting the deformation relationship of the connection point accessories.

[0047] The above modeling method for the shock absorber incorporates the flexibility of the piston rod 1 and the outer oil reservoir 3, correctly establishing the connection relationships between the components. While accurately reflecting the internal motion relationships of the shock absorber, it can precisely analyze the static and dynamic loads of each component, providing load inputs for the strength and durability acceptance of each component. Secondly, by considering the deformation of the internal components of the shock absorber, the accuracy of the suspension K&C characteristic simulation is greatly improved.

[0048] In vehicle dynamics analysis, the conventional modeling method for the internal relationships of a shock absorber involves establishing a cylindrical pair between the shock absorber piston rod 1 and the outer oil reservoir 3, simply simulating the vertical and axial rotational degrees of freedom between them. While this method effectively simulates the motion relationships between suspension components, it fails to accurately reflect the mechanical relationship between the piston rod 1 and the outer oil reservoir 3, and cannot perform static load extraction analysis between the shock absorber components.

[0049] In conventional modeling methods, the shock absorber piston rod and oil reservoir outer cylinder only transmit force through a cylindrical pair, which cannot effectively reflect the accurate force transmission paths between the piston rod and the guide mechanism, between the guide mechanism and the oil reservoir outer cylinder, and between the piston rod and the oil reservoir outer cylinder. It also cannot accurately reflect the shock absorber damping force transmission path of the piston rod. To address the issue mentioned in technical defect 1 above—the inability to correctly reflect the mechanical relationship between the piston rod and the oil reservoir outer cylinder, and the inability to extract and analyze static loads between shock absorber components—this modeling method, based on the actual structure of the shock absorber, divides the main components into four parts: piston rod 1, piston 2, oil reservoir outer cylinder 3, guide mechanism and oil seal 4. It introduces the flexibility of piston rod 1 and oil reservoir outer cylinder 3 to correctly establish the connection relationships between each component. While accurately reflecting the internal motion relationships of the shock absorber, it can precisely analyze the static and dynamic loads of each component, providing load input for the strength and durability acceptance of each component. Furthermore, by considering the deformation of the internal components of the shock absorber, the accuracy of suspension K&C characteristic simulation is greatly improved.

[0050] The conventional modeling method for the relationship between the shock absorber and the steering knuckle 5 involves simulating both the shock absorber's outer oil reservoir 3 and the steering knuckle 5 as rigid bodies, and establishing a fixed joint at their connection point. While this modeling method is consistent with the actual relationship, it cannot effectively reflect the deformation relationship of the connection point, leading to significant errors in suspension K&C characteristic analysis. This modeling method introduces the stiffness of the steering knuckle at the shock absorber mounting point and uses a bushing for deformation modeling, greatly improving the accuracy of suspension K&C characteristic simulation.

[0051] The modeling method of the shock absorber in the whole vehicle dynamics model of the present invention correctly establishes the connection relationship between the components according to the actual structure of the shock absorber, accurately reflects the internal motion relationship of the shock absorber, and can accurately analyze the static load and dynamic load of each component. It provides load input for the strength and durability acceptance of each component of the shock absorber, and has strong practicality and good application prospects.

[0052] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0053] The present invention has been described above by way of example with reference to the accompanying drawings. However, the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution of the present invention or any direct application to other situations shall fall within the protection scope of the present invention.

Claims

1. A method for modeling a shock absorber in a vehicle dynamics model, comprising fixing a cup holder, characterized in that, Includes the following steps: Step 1: In the dynamic analysis software, the components of the shock absorber are modeled separately. The components of the shock absorber include piston rod, piston, oil reservoir, guide mechanism and oil seal. Step 2: The piston rod and the piston are connected by a bushing, and the axial direction of the bushing is consistent with the vertical movement direction of the piston rod; Step 3: The piston and the outer oil reservoir are connected by a ball joint; Step 4: The outer oil storage cylinder, the guide mechanism, and the oil seal are connected by a bushing, and the axial direction of the bushing is consistent with the vertical movement direction of the piston rod. Step 5: The guide mechanism and oil seal are connected to the piston rod by a cylindrical pair; the axial direction of the cylindrical pair is consistent with the vertical movement direction of the piston rod, thus preserving the axial movement and rotational freedom. Step 6: The piston establishes damping characteristics with the guide mechanism and the oil seal; Step 7: The oil reservoir outer cylinder and the steering knuckle are connected by a parallel ball joint and a bushing; the radial torsional stiffness of the bushing is set to the radial torsional stiffness of the oil reservoir outer cylinder at the steering knuckle connection point by finite element simulation or actual measurement, and the axial torsional stiffness of the bushing is set to the default value.

2. The method for modeling the shock absorber in the vehicle dynamics model according to claim 1, characterized in that: In step 2, the linear stiffness of the bushing in three directions is set to be no less than 1E+6N / mm by default. The radial torsional stiffness of the bushing is set to the radial torsional stiffness of the piston rod at the piston connection point as measured by finite element simulation or actual measurement. The axial torsional stiffness of the bushing is set to be no less than 1E+9N.mm / deg by default.

3. The method for modeling the shock absorber in the vehicle dynamics model according to claim 1, characterized in that: In step 3, the ball joint connection retains rotational degrees of freedom in three directions.

4. The method for modeling the shock absorber in the vehicle dynamics model according to claim 1, characterized in that: In step 4, the linear stiffness of the bushing in three directions is set to be no less than 1E+6N / mm by default. The radial torsional stiffness of the bushing is set to the radial torsional stiffness of the oil reservoir outer cylinder at the guide mechanism and oil seal connection point, as determined by finite element simulation or actual measurement. The axial torsional stiffness of the bushing is set to be no less than 1E+9N.mm / deg by default.

5. The method for modeling the shock absorber in the vehicle dynamics model according to claim 1, characterized in that: The bushing's axial direction is consistent with the piston rod's vertical movement direction.

6. The method for modeling a shock absorber in a vehicle dynamics model according to claim 5, characterized in that: The default value for the axial torsional stiffness of the bushing is set to be no less than 1E+9N.mm / deg.

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