A method for obtaining dynamic stiffness and load of commercial vehicle engine mount

Abstract

The present invention relates to a method for obtaining the dynamic stiffness and load of a commercial vehicle engine mount, which mainly includes the following steps: (1) in the complete vehicle state, three-directional acceleration sensors are arranged at the active end and passive end of the engine's power mount; (2) in the complete vehicle state, the active end and passive end of the engine's power mount are excited with a hammer respectively, and the transmission coefficients in the X, Y, and Z directions are measured and obtained; (3) the dynamic stiffness of the four mounts are calculated respectively; (4) in the vehicle uniform acceleration state, the acceleration response of the active end and the acceleration response of the passive end of the four power mounts are measured and obtained; (5) the deformation of the active end and the passive end of the engine are calculated; and (6) the internal force load of the power mount under a set working condition is calculated. The present invention avoids modal testing and comprehensive solution of sub-structural components, has high calculation efficiency, low error, and is easy to use.

Description

Technical Field

[0001] The present invention belongs to the technical field of automobile dynamics, and in particular relates to a method for obtaining the dynamic stiffness and load of a commercial vehicle engine mount. Background Art

[0002] Traditional substructure analysis theory, based on classical structural dynamics, can be easily applied to the analysis of structural kinematic characteristics, but presents certain difficulties in analyzing system kinematic characteristics. This theory requires various assumptions regarding coupling stiffness and contact distances between substructures in complex systems. Simulation analysis and calculations require parameter identification, such as dynamic load identification and structural damping identification. In engineering applications, different standards exist for demarcating coupling interfaces, and the complex process of dynamic parameter identification leads to insufficient identification accuracy, a current drawback of substructure analysis technology. Summary of the Invention

[0003] In response to the technical problems existing in the above-mentioned background technology, the present invention proposes a method for obtaining the dynamic stiffness and load of a commercial vehicle engine mount. The method directly obtains the dynamic structural transfer characteristics of the system through testing in the complete vehicle state, and then solves the dynamic stiffness and force load of the engine mount, avoiding modal testing and comprehensive solution of sub-structural components. The method has high computational efficiency, low error, and is easy to apply. It also has high accuracy in the medium and low frequency ranges, making it suitable for evaluating the dynamic characteristics, parameter identification, and diagnosis of automotive systems.

[0004] The technical solutions of the present invention are as follows:

[0005] The above-mentioned method for obtaining the dynamic stiffness and load of a commercial vehicle engine mount mainly includes the following steps: (1) in the whole vehicle state, three-directional acceleration sensors are arranged at the active end and passive end of the engine's power mount; (2) in the whole vehicle state, the active end and passive end of the engine's power mount are excited with a hammer respectively, and the transmission coefficients in the X, Y, and Z directions are measured and obtained; (3) the dynamic stiffness of the four mounts are calculated respectively; (4) in the state of uniform acceleration of the vehicle, the acceleration response of the active end of the four power mounts and the acceleration response of the passive end of the four power mounts are measured and obtained; (5) the deformation of the active end and the passive end of the engine are calculated; (6) the internal force load of the power mount under the set working conditions is calculated.

[0006] The commercial vehicle engine mount dynamic stiffness and load acquisition method, wherein: the transmission functions in the X, Y, and Z directions obtained in step (2) are respectively

[0007]

[0008]

[0009]

[0010] Among them, in the above formulas (1-10), (1-11) and (1-12), (b) indicates that the excitation or response is generated on the substructure B, c indicates coupling, S indicates the system level or the assembly state of the whole vehicle, the active end measurement point is c(b1), the passive end measurement point is c(a1), and the transfer function matrix is The first letter in the subscript represents the response end, and the second letter represents the stimulus end.

[0011] The commercial vehicle engine mount dynamic stiffness and load acquisition method, wherein the dynamic stiffness of the four mounts is expressed as The calculation formula is as follows:

[0012]

[0013] The diagonal matrix is:

[0014]

[0015] The commercial vehicle engine mount dynamic stiffness and load acquisition method, wherein: the four mount dynamic stiffness It is calculated by the following formula (1-9);

[0016]

[0017] Among them, in formula (1-9) represents the transfer matrix from point c(a) to point c(a), represents the transfer matrix from point c(b) to point c(b), represents the transfer matrix from point c(b) to point c(a), Represents the transfer matrix from point c(a) to point c(b).

[0018] The commercial vehicle engine mount dynamic stiffness and load acquisition method, wherein: the deformation in step (5) is expressed as X i (ω) is calculated by the following formula (1-15);

[0019]

[0020] Among them, u in formula (1-15) c ( bi )(ω) represents the acceleration response of point bi, u c ( ai )(ω) represents the acceleration response of point ai, where i = 1.2.3.4 and ω is the natural circular frequency.

[0021] The commercial vehicle engine mount dynamic stiffness and load acquisition method, wherein: the internal force load in step (6) is expressed as F i (ω) is calculated by the following formula (1-16);

[0022] F i (ω)=K i (ω)x i (ω)(1-16);

[0023] Among them, X in formula (1-16) i (ω) is the deformation of the passive end, K i (ω) is the suspension point dynamic stiffness.

[0024] Beneficial effects:

[0025] The method for obtaining the dynamic stiffness and load of a commercial vehicle engine mount of the present invention is rationally conceived. The dynamic structural transfer characteristics of the system are directly obtained by testing in the complete vehicle state, and the dynamic stiffness and force load of the engine mount are then solved, thus avoiding modal testing and comprehensive solution of sub-structural components.

[0026] The present invention directly obtains the dynamic structural transfer characteristics of the system through measurement without disassembling the engine (powertrain), and calculates the suspension dynamic stiffness and load under set working conditions through formulas (1-15) and (1-16). The calculation efficiency is high, the error is low, and the application is convenient. The accuracy is high in the medium and low frequency ranges, so it is suitable for the evaluation, parameter identification and diagnosis of the dynamic characteristics of automobile systems.

[0027] The present invention calculates the dynamic stiffness by using the frequency response functions between coupling points at multiple system levels, thus avoiding complicated decoupling work and achieving good recognition accuracy. The invention can be extended to engines with three-point and five-point mounts. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the excitation and response relationship of substructure A in the commercial vehicle engine mount dynamic stiffness and load acquisition method of the present invention;

[0029] Figure 2 Schematic diagram of the excitation and response relationship of substructure B in the commercial vehicle engine mount dynamic stiffness and load acquisition method of the present invention;

[0030] Figure 3 This is the excitation and response relationship diagram of the coupled assembly of substructure A and substructure B in the commercial vehicle engine mount dynamic stiffness and load acquisition method of the present invention;

[0031] Figure 4 This is a diagram showing the measurement point positions of a four-point suspension coupling system in the commercial vehicle engine mount dynamic stiffness and load acquisition method of the present invention;

[0032] Figure 5 Schematic diagram of the engine assembly position in the commercial vehicle engine mount dynamic stiffness and load acquisition method of the present invention. DETAILED DESCRIPTION

[0033] The commercial vehicle engine mount dynamic stiffness and load acquisition method of the present invention regards the entire vehicle as a system and the responding body other than the powertrain (engine, gearbox) as a substructure A, such as Figure 1 As shown; the excitation source powertrain (engine plus gearbox part) is combined into a substructure B, as shown Figure 2 As shown; substructures A and B are connected together through a vibration reduction system, as shown Figure 3 shown.

[0034] The excitation and response relationship of substructures A and B in the free state is as follows: Figure 1 and Figure 2 As shown, if there is coupling between substructures A and B, the relationship between the excitation and response of the coupled assembly is as follows: Figure 3 As shown. The relationship between substructures A and B is expressed as follows:

[0035]

[0036] in

[0037]

[0038]

[0039]

[0040] Combine the coupled terms into one term, and the basic formula is:

[0041]

[0042]

[0043] [C]=([H A ] c(a)c(a) +[H B ] c(b)c(b) +[K c ] -1 ) -1 (1-7)

[0044]

[0045] is the dynamic stiffness matrix of the coupled assembly

[0046]

[0047] In the system assembly state, the measured Substituting the three sets of transfer functions into equations 1-9, we can obtain

[0048] The above is the principle of inverse substructure analysis, which is based on the modal synthesis method. According to the above principle, the following steps are tested to obtain the system transfer matrix

[0049] S100, vehicle status, three-directional acceleration sensors are arranged at the active and passive ends of the engine's power mount. Taking the four-point mount as an example, the test point positions are as follows: Figure 4 shown.

[0050] S200, in the vehicle state, the active and passive ends of the engine power mount are stimulated by hammers, and the transmission coefficients in the X, Y, and Z directions are measured.

[0051]

[0052]

[0053]

[0054] Among them, in the above equations (1-10), (1-11) and (1-12), (b) indicates that the excitation or response is generated on the substructure B, c indicates coupling, S indicates the system level or the assembly state of the whole vehicle, the active end measurement point is c(b1), and the passive end measurement point is c(a1); the transfer function matrix The first element of the subscript represents the response end, and the last element represents the stimulus end (i.e., the transmission function The letters in front of the matrix subscript represent the response end, and the letters in the back represent the excitation end, such as c(b2)c(b1) represents the transmission function from point b1 to point b2 at the coupling point).

[0055] S300, calculate the dynamic stiffness of the four mounts according to formula (1-9)

[0056]

[0057] The diagonal matrix is:

[0058]

[0059] S400: Under the vehicle uniform acceleration state, measure and obtain the acceleration response u of the active end of the four power mounts. c(b1) (ω),u c(b2) (ω),u c(b3) (ω),uc(b4) (ω) and the passive end acceleration responses u of the four dynamic mounts c(a1) (ω),u c(a2) (ω),u c(a3) (ω),u c(a4) (ω), as shown in Table 1 below.

[0060] Table 1 Description of measurement point layout

[0061]

[0062]

[0063] S500, calculate the deformation of the active and passive ends of the engine:

[0064]

[0065] Among them, u in formula (1-15) c(bi) (ω) represents the acceleration response of point bi, u c(ai) (ω) represents the acceleration response of point ai, where i = 1.2.3.4 and ω is the natural circular frequency.

[0066] S600. Calculate the internal force load of the power mount under the set working conditions:

[0067] F i (ω)=K i (ω)x i (ω)(1-16)

[0068] Among them, X in formula (1-16) i (ω) is the deformation of the passive end, K i (ω) is the suspension point dynamic stiffness.

[0069] The present invention directly obtains the dynamic structural transfer characteristics of the system through testing in the whole vehicle state, and then solves the dynamic stiffness and force load of the engine mount, avoiding modal testing and comprehensive solution of sub-structural components. It has high calculation efficiency, low error, easy application, and high accuracy in the medium and low frequency ranges. Therefore, it is suitable for evaluation, parameter identification and diagnosis of the dynamic characteristics of automobile systems.

Claims

1. A method for obtaining the dynamic stiffness and load of a commercial vehicle engine mount, characterized in that: The acquisition method mainly includes the following steps: (1) In the vehicle state, three-directional acceleration sensors are arranged at the active and passive ends of the engine power mount; (2) In the vehicle state, the active and passive ends of the engine power mount are excited with a hammer, and the transmission coefficients in the X, Y, and Z directions are measured; (3) Calculate the dynamic stiffness of the four mounts respectively; The dynamic stiffness of the four mounts is expressed as [K c ], the calculation formula is as follows: [K c ]The diagonal matrix is: The four suspension dynamic stiffnesses [K c ] is calculated by the following formula (1-9); Among them, in formula (1-9), [H S ] c(a)c(a) represents the transfer matrix from point c(a) to point c(a), [H S ] c(b)c(b) represents the transfer matrix from point c(b) to point c(b), [H S ] c(a)c(b) represents the transfer matrix from point c(b) to point c(a), [H S ] c(b)c(a) Represents the transfer matrix from point c(a) to point c(b); (4) Under uniform acceleration of the vehicle, measure and obtain the acceleration responses of the active ends of the four dynamic mounts and the acceleration responses of the passive ends of the four dynamic mounts; (5) Calculate the deformation of the active and passive ends of the engine; (6) Calculate the internal force load of the dynamic mount under the set working conditions.

2. The commercial vehicle engine mount dynamic stiffness and load acquisition method according to claim 1, characterized in that: The transmission functions in the X, Y, and Z directions obtained in step (2) are [H S ] c(a)c(a) 、[H S ] c(b)c(b) 、[H S ] c(a)c(b) : Among them, in the above formulas (1-10), (1-11) and (1-12), (b) indicates that the excitation or response is generated on the substructure B, c indicates coupling, S indicates the system level or the assembly state of the whole vehicle, the active end measurement point is c(b1), the passive end measurement point is c(a1), and the transfer function matrix [H S The letters in front of the subscript of ] represent the response end, and the letters in the back represent the stimulus end.

3. The commercial vehicle engine mount dynamic stiffness and load acquisition method according to claim 1, characterized in that: The deformation amount in step (5) is expressed as X i (ω) is calculated by the following formula (1-15); Among them, u in formula (1-15) c(bi) (ω) represents the acceleration response of point bi, u c(ai) (ω) represents the acceleration response of point ai, where i = 1.2.3.4 and ω is the natural circular frequency.

4. The commercial vehicle engine mount dynamic stiffness and load acquisition method according to claim 1, wherein: The internal force load in step (6) is expressed as F i (ω) is calculated by the following formula (1-16); F i (ω)=K i (ω)x i (oh) (1-16)； Among them, X in formula (1-16) i (ω) is the deformation of the passive end, K i (ω) is the suspension point dynamic stiffness.

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