Motorcycle dynamic vibration absorber optimization method and dynamic vibration absorber

Abstract

The invention discloses a motorcycle vibration absorber optimization method based on a multi-dimensional dynamic vibration absorber design and a dynamic vibration absorber, and the method comprises the steps: calculating the vibration characteristics of a motorcycle under a working condition, and building a whole vehicle dynamics simulation model; the accuracy of the obtained simulation model is verified through modal analysis, unit load excitation is applied to the fixed position of an engine, the vibration acceleration of the cushion mounting point position is calculated, and the VTF is calculated based on the vibration acceleration; analyzing the VTF from the engine to the fixed position of the cushion, and calculating modal contribution degrees of different frequency peak values to identify main influence modals influencing the VTF; constructing a finite element mesh model of the dynamic vibration absorber according to the space structure size of the battery; constraint conditions are applied to bottom nodes of the elastic mechanism located at the bottom of the power battery, and the mode of the dynamic vibration absorber is calculated; and with the volume minimization of the elastic mechanism as a target and the modal frequency as a constraint condition, topological optimization is carried out, so that the optimized dynamic vibration absorber is obtained.

Description

Technical Field

[0001] The present invention relates to the field of motorcycle vibration absorption performance control, and in particular to a motorcycle dynamic vibration absorber optimization method based on multi-dimensional dynamic vibration absorber design and a dynamic vibration absorber. Background Art

[0002] With the development of motorcycle design, the vibration comfort performance of motorcycles, especially NVH, a key factor that can be intuitively felt by consumers, has become increasingly important. Compared with other modes of transportation, the vibration comfort problem of motorcycles is more significant. Vibration is mainly transmitted to the human body through the handlebars, footrests, and seat, which are the three parts that come into direct contact with the human body. Human exposure to vibration is divided into two types: whole-body vibration (WBV) and hand-arm vibration (HAV). For motorcycles, WBV is mainly transmitted through the seat and footrests, while HAV is mainly transmitted through the handlebars.

[0003] In order to suppress the vibrations of the road excitations that are transmitted through the tires, front forks / rear shock absorbers to the frame and riding interfaces such as handlebars, seat, and pedals, thereby improving riding comfort, the two main strategies currently adopted are vibration isolation and vibration avoidance. In terms of vibration isolation, the vibration energy can be attenuated by optimizing the spring stiffness and damping of the passive suspension, or by using semi-active / active suspension systems with electronically controlled valves or electromagnetic actuators; in terms of vibration avoidance, the focus is on optimizing the natural frequency of the frame to avoid the risk of resonance with road excitations. However, in actual products, it is almost impossible to completely avoid all excitation frequencies, and the superposition of power system operation and multi-source road vibrations often accidentally excites local modes, generating resonance peaks, which in turn pose a potential threat to comfort and safety.

[0004] Therefore, effectively reducing vehicle vibration and improving ride comfort without incurring additional costs is a technical problem that urgently needs to be solved. This invention proposes a motorcycle vibration absorption system based on a multi-dimensional dynamic vibration absorber design that can meet the needs of multi-directional and multi-frequency vibration suppression, thus potentially resolving the problems existing in the existing technology. Summary of the Invention

[0005] In order to overcome the defects of the prior art, the present invention provides a motorcycle dynamic vibration absorber optimization method and a dynamic vibration absorber based on a battery-based multi-dimensional dynamic vibration absorber design.

[0006] A motorcycle vibration absorber optimization method based on multi-dimensional dynamic vibration absorber design, comprising:

[0007] Step 1: Calculate the vibration characteristics of the motorcycle under operating conditions, construct a multi-degree-of-freedom three-dimensional model of the vehicle, establish a finite element model of the frame, and thus build a vehicle dynamics simulation model; in the simulation model, a dynamic vibration absorber is installed below the fixed bracket of the motorcycle seat; the finite element model of the frame considers the first-order vertical bending, first-order lateral bending, and first-order torsional modal frequencies of the frame;

[0008] Step 2: Verify the accuracy of the simulation model obtained in step 1 through modal analysis. If the error between the vibration response trend of the simulation model and the test results is within the preset value, the model is considered accurate. Otherwise, return to step 1 to analyze the differences between the simulation model and the actual vehicle, reconsider the welding position, length, material thickness, and treatment of stress concentration areas of the frame, and re-simulate.

[0009] After confirming the accuracy of the model, a unit load excitation is applied to the fixed position of the engine to calculate the vibration acceleration at the seat cushion mounting point, and based on this, the vibration transfer function (VTF) is calculated;

[0010] Step 3: Based on the vibration transfer function obtained in Step 2, analyze the VTF from the engine to the seat cushion mounting position. Select multiple frequencies with high peak values ​​and calculate the modal contributions of different frequency peaks to identify the main influencing modes of the VTF, thereby obtaining the design parameters of the dynamic vibration absorber. Also, extract the modal frequencies whose contributions to the seat cushion mounting bracket are higher than the preset value.

[0011] Step 4: Construct a finite element mesh model of the dynamic vibration absorber based on the motorcycle's power battery based on the battery's spatial structural dimensions. Apply constraints to the bottom nodes of the elastic mechanism located at the bottom of the power battery to calculate the dynamic vibration absorber's modes.

[0012] Step 5: With the goal of minimizing the volume of the elastic mechanism, topology optimization is performed based on the modal frequencies obtained in step 3 as constraints to obtain the optimized dynamic vibration absorber.

[0013] The optimized dynamic vibration absorber can meet the needs of multi-directional and multi-frequency vibration suppression.

[0014] Furthermore, establishing a finite element model of the frame includes: using solid elements and shell elements with an average size of 3±0.5 mm to perform finite element meshing on key structures such as the motorcycle frame and handlebars.

[0015] Furthermore, in step three, the modal contributions of the seat cushion fixing bracket position in the X and Z directions are analyzed; based on the modal contribution analysis, the modes that contribute more than 30% to the vibration of the seat cushion fixing bracket position are extracted; further, based on the relationship between excitation and response, the main resonant modes are extracted, and combined with the vibration mode characteristics of the whole vehicle mode, the vibration mode with a greater impact on the vibration is obtained, and the design parameters of the dynamic vibration absorber are obtained, including the absorbed frequency and vibration mode.

[0016] A battery-based power vibration absorber includes a power battery and an elastic mechanism. The elastic mechanism is installed at the bottom of the power battery of a motorcycle, and the structure of the elastic mechanism is obtained by topological optimization design using the motorcycle power vibration absorber optimization method.

[0017] The beneficial effects of the present invention are:

[0018] 1. By constructing a finite element model of the vehicle frame and performing modal analysis to verify the model's accuracy, a full vehicle simulation model is established. The model's effectiveness is verified through VTF comparison, which accurately reflects the vehicle's dynamic characteristics under actual operating conditions and provides reliable basic data for subsequent optimization design.

[0019] 2. A dynamic vibration absorber is constructed based on the battery size, with the goal of minimizing the volume of the elastic mechanism located at the bottom of the battery. The modal frequencies obtained through VTF identification are then used to perform topological optimization to design a multi-dimensional dynamic vibration absorber. This design can meet the requirements of multi-directional and multi-frequency vibration suppression, effectively reducing vehicle vibration and improving driving comfort without any additional cost, making it highly economical.

[0020] 3. This multi-dimensional dynamic vibration absorber design fully considers the vibration transfer function of the entire frame. Even if the frame mode is close to the excitation frequency, it can effectively suppress the vibration excited by the road surface, thus solving the risks existing in the existing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the energy curve of the vibration along the X, Y, and Z directions of the seat cushion as the engine speed changes;

[0022] Figure 2 It is a force diagram of the dual dynamic vibration absorber in the motorcycle dynamic vibration absorber optimization method;

[0023] Figure 3a : This is a comparison of the VTF results calculated under X-direction excitation before and after the dynamic absorber is added to the simulation in step 5, where "dynamic absorber" is the VTF result with the dynamic absorber added. A represents the response acceleration, F represents the excitation force, and X and Z represent the directions. The blue line (Ax / Fx absorber) is the ratio of the x-direction acceleration to the x-direction excitation force after adding the dynamic absorber of the present invention. The green line (Ax / Fx) is the ratio of the x-direction acceleration to the x-direction excitation force without adding the dynamic absorber of the present invention. The orange line (Az / Fx absorber) is the ratio of the z-direction acceleration to the x-direction excitation force after adding the dynamic absorber of the present invention. The red line (Az / Fx) is the ratio of the z-direction acceleration to the x-direction excitation force without adding the dynamic absorber of the present invention.

[0024] Figure 3b: This is a comparison of the VTF results calculated under Z-direction excitation before and after the dynamic vibration absorber was added in the simulation in step 5. The blue line (Ax / Fz absorber) is the ratio of the x-direction acceleration to the z-direction excitation force after adding the dynamic vibration absorber of the present invention; the green line (Ax / Fz) is the ratio of the x-direction acceleration to the z-direction excitation force without adding the dynamic vibration absorber of the present invention; the orange line (Az / Fz absorber) is the ratio of the z-direction acceleration to the z-direction excitation force after adding the dynamic vibration absorber of the present invention; and the red line (Az / Fx) is the ratio of the z-direction acceleration to the z-direction excitation force without adding the dynamic vibration absorber of the present invention.

[0025] Figure 4a The optimization method of the dynamic vibration absorber is shown for the torsional vibration with a third-order modal frequency of 448 Hz. Figure 4b It shows the floating and sinking vibration with the 4th order modal frequency of 683 Hz;

[0026] Figure 5 A schematic diagram showing a rubber solid element after topology optimization in the optimization method of a dynamic vibration absorber;

[0027] Figure 6 Flowchart of a motorcycle vibration absorber optimization method designed for the multi-dimensional dynamic vibration absorber. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions, beneficial effects and significant improvements of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the drawings provided in the examples of the present invention. Obviously, all the described embodiments are only partial embodiments of the present invention, rather than all embodiments; based on the demonstrations made in the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field based on the content, implementation methods and drawings of the present invention without making any creative work shall fall within the scope of protection of the present invention.

[0029] It should be noted that the terms "first", "second", "third", etc. in the description and claims of the present invention are only used to distinguish different objects, rather than to describe a specific order.

[0030] It should also be noted that the following specific embodiments may be combined with each other, and the same or similar concepts or processes therein may not be repeated in some embodiments.

[0031] like Figure 1As shown, by arranging vibration three-axis acceleration sensors at the motorcycle engine suspension position point A, the seat position point B, and the seat fixing bracket position point C, an O-XYZ Cartesian coordinate system is established, wherein the X-axis points horizontally in the direction of the motorcycle's forward movement and is parallel to the motorcycle's longitudinal plane, the Y-axis is the intersection of the motorcycle's transverse plane and the road plane and points to the right, and the Z-axis is vertically upward; the vibration characteristics of the motorcycle under third gear acceleration in the WOT working condition are tested on the rotating hub chassis. Figure 1 As shown in the figure, an analysis of the energy curves of the seat cushion's vibration in the X, Y, and Z directions as a function of engine speed reveals a significant increase in X-direction vibration at 4500 RPM, while the Z-direction vibration energy suddenly increases at 7000 RPM. This phenomenon is consistent with subjective perception: at low speeds, the seat cushion's fore-and-aft vibration (X-direction) is more pronounced, while as engine speed increases, the up-and-down vibration (Z-direction) becomes more pronounced. By converting the excitation frequency obtained by speed conversion and analyzing it in conjunction with the characteristics of a two-cylinder engine, it is found that its second-order excitation energy is relatively high. Specifically, X-direction vibration begins to increase at 150 Hz, while Z-direction vibration begins to significantly increase at 230 Hz.

[0032] Taking into account the vibration characteristics of the entire vehicle, the present invention selects the seat cushion's fixed bracket as the response point and the engine's rear upper suspension point, closest to the fixed bracket, as the excitation point. Furthermore, within the 230Hz-350Hz frequency range of the vibration transfer function (VTF), the increase in vibration amplitude is closely related to the inherent characteristics of the system. In particular, the vibration response at 150Hz shows a higher correlation with the engine's excitation. Based on these analysis results, to effectively reduce vibrations above 200Hz caused by the vehicle system's characteristic vibrations, the present invention proposes a solution using dynamic vibration absorbers to specifically suppress vibrations above 200Hz caused by the vehicle system's characteristic frequencies.

[0033] like Figure 6 As shown, a motorcycle vibration absorber optimization method based on battery-based multi-dimensional dynamic vibration absorber design includes:

[0034] Step 1: Calculate the vibration characteristics of the motorcycle under working conditions

[0035] S11: Constructing a 3D model of the vehicle with multiple degrees of freedom

[0036] According to the actual vehicle, a 3D model of the vehicle is established, and the model is modified and confirmed to complete the establishment of the 3D model. A dual dynamic shock absorber is set under the seat cushion fixing bracket. The rear upper suspension point of the engine is used as the excitation point, and the seat cushion fixing bracket is used as the response point.

[0037] Assuming that the dual-dynamic vibration absorber can achieve two-mode vibration absorption, Figure 2In the force diagram of the dual-dynamic vibration absorber shown, m0, k0, and c0 are the mass, stiffness, and damping of the frame body, respectively; m1, k1, and c1 are the mass, stiffness, and damping of the left vibration absorber, respectively; and m2, k2, and c2 are the mass, stiffness, and damping of the right vibration absorber, respectively.

[0038] S12: Constructing a finite element model of the frame

[0039] The finite element mesh of the motorcycle frame, handlebars and other key structures is divided by solid and shell elements with an average size of 3±0.5mm, and the welding connection between different structural components is realized through seam elements.

[0040] S13: Components such as the instrument panel, fuel tank, and seat are simplified using a lumped mass approach. For the larger engine, this lumped mass approach is combined with precise input of its mass and moment of inertia parameters to complete the creation of a full vehicle simulation model. The finite element model of the frame focuses on the first-order vertical bending, first-order lateral bending, and first-order torsional modal frequencies.

[0041] Step 2: Verify the accuracy of the simulation model through modal analysis and calculate the vibration transfer function (VTF)

[0042] Since motorcycles have multiple modes, meaning the system has multiple resonant frequencies, the free modes of the frame are calculated based on the finite element model obtained in step 1. The first six modes are rigid body modes, and the seventh and subsequent modes are elastic body modes.

[0043] The simulation results of the modal analysis were compared with the test data, and the error statistics are shown in Table 1. If the error between the vibration response trend of the simulation model and the test results is within a preset value of 5%, the model is considered accurate, indicating that the finite element model constructed in this invention has high precision and can accurately reflect the actual dynamic characteristics of the vehicle frame.

[0044] Table 1 Comparison of experimental and simulation modal frequencies

[0045] Serial number Test frequency / Hz Simulation frequency / Hz error / % 1 82.9 80.1 3.4 2 91.5 93.2 -1.9 3 145.2 141.1 2.8 4 162.9 168.7 -3.6 5 181.1 178.9 1.2 6 190.4 193.7 -1.7

[0046] To further verify the reliability of the vehicle model, a unit load excitation is applied to the fixed position of the engine, the vibration acceleration at the seat cushion mounting point is calculated, and the VTF is calculated based on this. If the error between the vibration response trend of the simulation model and the test results is within 5%, the model is considered accurate. Otherwise, return to step 1 to analyze the differences between the simulation model and the actual object, reconsider whether the welding position and length of the frame are consistent with the actual ones, whether the material thickness settings are the same, and whether the simplified treatment of the stress concentration area is reasonable, and then re-simulate. Figure 3a,3b shows the vibration response trend of the simulation model and the ,test results. The results show that the vibration response trend of the ,simulation model is highly consistent with the test results.,This shows that the whole vehicle simulation model established in this ,paper can accurately reflect the dynamic characteristics of the vehicle under ,actual working conditions and has high reliability.

[0047] Step 3: Identify the main influencing modes based on the vibration transfer function obtained in step 2

[0048] Based on the transfer function calculation results obtained in Step 2, the VTF at the engine-to-seat mount location was analyzed. Three frequencies with the highest peak values ​​were selected and the modal contributions of these peak values ​​were calculated to identify the primary influencing modes at the engine-to-seat mount location. The test results indicate that the largest vibration responses are primarily concentrated in the X and Z directions. Therefore, the modal contributions of the seat mount location in these two directions were analyzed in particular.

[0049] Based on modal contribution analysis, we extracted modes that contributed more than 30% to the vibration of the seat cushion mounting bracket. Statistical results revealed the most significant modal frequencies to be 214Hz, 247Hz, and 333Hz. We further extracted the primary resonant modes based on the excitation-response relationship and, combined with the modal shape characteristics of the entire vehicle, analyzed the modes that significantly impacted vibration.

[0050] Analysis of the results shows that the 214Hz and 247Hz modes are closely related to the dynamic characteristics of the frame. The 214Hz mode corresponds to the torsional vibration of the rear end of the frame, manifested as the torsional motion of the wheel in this mode, while the 247Hz mode corresponds to the bending vibration of the rear end of the frame, manifested as the bending deformation of the frame in this mode. The 333Hz mode mainly originates from the vibration of the rear wheel.

[0051] Step 4: Design the dynamic vibration absorber

[0052] S41: Construct a finite element mesh model of the battery according to the spatial structural dimensions of the battery; and establish four rubber entity units at the bottom thereof; the rubber entity units are respectively located at the four corners of the bottom of the battery.

[0053] S42: By applying constraints to the rubber bottom nodes (i.e., completely fixing the rubber bottom), the modal of the dynamic vibration absorber is calculated. The results are as follows: Figure 4a , as shown in Figure 4b. The third-order modal frequency is 448 Hz, a torsional vibration mode; the fourth-order modal frequency is 683 Hz, a floating vibration mode. Combining the modal characteristics of the vehicle and the dynamic vibration absorber, we determined the constraints for topology optimization, and based on this, we developed the optimized topology design for the dynamic vibration absorber.

[0054] Step 5: In the topology optimization design of the dynamic vibration absorber, the goal is to minimize the volume of the rubber block, and at the same time set the modal frequency constraints, including: the first-order modal frequency must not be lower than 200Hz, and the fourth-order modal frequency must not be higher than 250Hz. Based on the above optimization goals and constraints, the topology optimization design is carried out, and the units with a density greater than 0.5 are retained, thus obtaining the following Figure 5 The rubber solid unit shown is supported in an oblique manner. This structural layout is conducive to maintaining torsional stiffness while significantly reducing vertical stiffness. This minimizes the volume of the rubber block while meeting the modal frequency requirements, thereby optimizing the mechanical properties of the dynamic vibration absorber.

[0055] Step 6: Prepare the dynamic vibration absorber based on the optimized results, install the dynamic vibration absorber at the bottom of the battery, and install the battery with the dynamic vibration absorber on the motorcycle; apply unit load excitation at a fixed position of the engine, calculate the VTF, and keep the excitation position and response position points of the VTF consistent with the original solution without adding the dynamic vibration absorber during the calculation process.

[0056] The VTF curves before and after the installation of the dynamic vibration absorber were compared to verify the effectiveness of its improvement. Through comparison, under the action of X-direction excitation, after the introduction of the dynamic vibration absorber, the vibration acceleration response frequency of the system near 214Hz was improved, the X-direction amplitude was reduced by about 10%, and the Z-direction amplitude was reduced by about 40%. Under Z-direction excitation, after the introduction of the dynamic vibration absorber, the vibration acceleration response frequency of the system near 250Hz increased by about 10%, the X-direction amplitude was reduced by about 5%, and the Z-direction amplitude was reduced by about 20%. It can be seen that the introduction of the dynamic vibration absorber significantly reduced the vibration response of the system. In summary, the multi-dimensional dynamic vibration absorber can effectively suppress multiple resonant frequency peaks and is a feasible and effective technical means to solve WBV.

[0057] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents, and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. Non-essential improvements, adjustments or replacements made by those skilled in the art based on the contents of this specification are all within the scope of protection required by the present invention.

Claims

1. A motorcycle vibration absorber optimization method based on multi-dimensional dynamic vibration absorber design, characterized in that: include: Step 1: Calculate the vibration characteristics of the motorcycle under operating conditions, construct a multi-degree-of-freedom three-dimensional model of the vehicle, establish a finite element model of the frame, and thus build a vehicle dynamics simulation model; in the simulation model, a dynamic vibration absorber is installed below the fixed bracket of the motorcycle seat; the finite element model of the frame considers the first-order vertical bending, first-order lateral bending, and first-order torsional modal frequencies of the frame; Step 2: Verify the accuracy of the simulation model obtained in step 1 through modal analysis. If the error between the vibration response trend of the simulation model and the test results is within the preset value, the model is considered accurate. Otherwise, return to step 1 to analyze the differences between the simulation model and the actual vehicle, reconsider the welding position, length, material thickness, and treatment of stress concentration areas of the frame, and re-simulate. After confirming the accuracy of the model, a unit load excitation is applied to the fixed position of the engine, the vibration acceleration at the seat cushion mounting point is calculated, and the vibration transfer function is calculated based on this; Step 3: Based on the vibration transfer function obtained in Step 2, analyze the VTF from the engine to the seat cushion mounting position. Select multiple frequencies with high peak values ​​and calculate the modal contributions of different frequency peaks to identify the main influencing modes of the VTF, thereby obtaining the design parameters of the dynamic vibration absorber. Also, extract the modal frequencies whose contributions to the seat cushion mounting bracket are higher than the preset value. Step 4: Construct a finite element mesh model of the dynamic vibration absorber based on the motorcycle's power battery based on the battery's spatial structural dimensions. Apply constraints to the bottom nodes of the elastic mechanism located at the bottom of the power battery to calculate the dynamic vibration absorber's modes. Step 5: With the goal of minimizing the volume of the elastic mechanism, topology optimization is performed based on the modal frequencies obtained in step 3 as constraints to obtain the optimized dynamic vibration absorber.

2. The motorcycle vibration absorber optimization method based on multi-dimensional dynamic vibration absorber design according to claim 1, characterized in that: Establishing the finite element model of the frame includes: using solid elements and shell elements with an average size of 3±0.5mm to perform finite element meshing on key structures such as the motorcycle frame and handlebars.

3. The motorcycle vibration absorber optimization method based on multi-dimensional dynamic vibration absorber design according to claim 1, characterized in that: In step three, the modal contributions of the seat cushion fixing bracket position in the X and Z directions are analyzed; based on the modal contribution analysis, the modes that contribute more than 30% to the vibration of the seat cushion fixing bracket position are extracted; further, based on the relationship between excitation and response, the main resonant modes are extracted, and combined with the vibration mode characteristics of the vehicle mode, the vibration mode with the greatest impact on the vibration is obtained, and the design parameters of the dynamic vibration absorber, including the absorbed frequency and vibration mode, are obtained.

4. A battery-based power vibration absorber, comprising a power battery and an elastic mechanism, wherein the elastic mechanism is mounted on the bottom of the power battery of a motorcycle, and the structure of the elastic mechanism is obtained by topological optimization design using the motorcycle power vibration absorber optimization method according to claim 1.

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