A system for simply obtaining the frequency deviation of a balanced suspension commercial vehicle

Abstract

The present application relates to a kind of simple acquisition balanced suspension commercial vehicle frequency deviation system, can guarantee in the early stage of whole vehicle design without sample car state, still can obtain reliable frequency deviation result, high efficiency fast and do not need stronger professional ability;After inputting whole vehicle design parameter, it can be completed automatic calculation, then directly obtains suspension frequency deviation, and there is no professional requirement to calculation personnel;And theoretical calculation model considers the influence of cab suspension and power assembly suspension vertical stiffness on suspension frequency deviation, can obtain accurate frequency deviation result to support product development;The system provided by the present application has no requirement to the simulation ability and professional knowledge of operator, input design parameter directly outputs suspension frequency deviation result, without analyzing and judging each order modal shape;The system does not need to purchase professional software;For different vehicle modification design parameter, no need to repeatedly build model and so on.

Description

Technical Field

[0001] This invention relates to the field of automotive performance testing technology, and in particular to a simple system for obtaining the off-frequency of a balanced suspension commercial vehicle. Background Technology

[0002] The NVH performance of a vehicle significantly impacts passenger comfort. During the early stages of vehicle development and later NVH performance improvement phases, it's crucial to determine the vehicle's modal distribution. A key aspect of this is determining the suspension frequency. The suspension frequency is the natural frequency of the vertical movement of the sprung and unsprung masses in the front and rear suspensions. There are front suspension sprung mass frequency, front suspension unsprung mass frequency, rear suspension sprung mass frequency, and rear suspension unsprung mass frequency. Obtaining a reliable suspension frequency is extremely important. Methods for obtaining the suspension frequency mainly include experimental testing, theoretical calculation, and simulation analysis. For balanced suspension commercial vehicles, current methods for obtaining the suspension frequency suffer from the following problems:

[0003] 1. Experimental testing is currently the primary method for obtaining suspension frequency deviation in vehicles with balanced suspensions. Experimental testing requires the following steps: after preparing a prototype vehicle, sensors are deployed; then, the actual vehicle is tested; and finally, the test data is processed to output the frequency deviation result. Obtaining suspension frequency deviation through experimentation requires a prototype vehicle, so it's impossible to rely on experiments to obtain suspension frequency deviation in the early stages of vehicle development. Furthermore, experimental methods are inefficient and consume significant human and material resources.

[0004] 2. For theoretical calculation methods, establishing mathematical models requires calculation personnel to have a solid professional foundation and theoretical literacy; moreover, existing theoretical models in the industry are overly simplified, such as ignoring balance shafts and cab suspensions, making it difficult to obtain accurate off-frequency results to support product development.

[0005] 3. Simulation analysis requires analysts to have certain simulation analysis capabilities; after the analysis is completed, the mode shapes of each order need to be analyzed before the suspension off-frequency results can be determined, requiring analysts to have a solid professional foundation; simulation analysis requires the purchase of professional software, which is costly; and the adaptability to different vehicle models is poor, requiring repeated modeling and simulation to obtain the suspension off-frequency. Summary of the Invention

[0006] This invention proposes a simple system for obtaining the offset frequency of a balanced suspension commercial vehicle. It can ensure reliable offset frequency results even in the early stages of vehicle design when there is no prototype vehicle. It is efficient, fast, and does not require strong professional skills.

[0007] To address the problems mentioned above in the background section, the present invention is achieved through the following technical solution:

[0008] A simple system for obtaining the offset frequency of a balanced suspension commercial vehicle includes the following steps:

[0009] Step 1: Obtain the vehicle design parameters. After converting the design parameters into the parameters required for the calculation model by establishing static equilibrium equations, input them into the theoretical calculation model.

[0010] Step 2: Solve the theoretical calculation model to obtain the eighth natural frequency of the model. Then, substitute the natural frequency into the vibration equation and solve the linear homogeneous equation system to obtain the mode shape corresponding to the natural frequency.

[0011] Step 3: Establish the relationship between the mode shape and the suspension off-frequency by using the vehicle design parameters, and then determine the suspension off-frequency corresponding to the mode shape.

[0012] Step 4: Output the front suspension spring load frequency, the front suspension unsprung load frequency, the rear suspension spring load frequency, and the rear suspension unsprung load frequency.

[0013] Preferably, the theoretical calculation model in step two is as follows:

[0014] A×[Z c Z p Z f Z m Z r Z b φ j φ b ] T ·sin(ω pt +ψ)=0 (1)

[0015] In equation (1) ω p Let ψ be the natural frequency of the vibration model, and ψ be the phase angle of the vibration model.

[0016] The Z c Z p Z f Z m Z r Z b φ j φ b These are the amplitudes;

[0017] In the formula:

[0018]

[0019] If equation (1) holds at all times, and Z c Z p Z f Z m Z r Z bφ j φ b If there is a non-zero solution, then we must have:

[0020] |A|=0 (3)

[0021] After solving, ω is obtained p The eight non-zero solutions are the eighth natural frequencies of the eight-degree-of-freedom model; substituting the natural frequencies into matrix A yields the adjoint matrix A. * A * Each column can be regarded as the mode shape of the model at that natural frequency;

[0022] Wherein, the Z c The Z-axis represents the vertical translation of the driver's cab; pt The Z-axis represents the vertical translation of the powertrain. f The Z-axis represents the vertical translation of the front axle; m The Z-axis represents the vertical translation of the bridge. r The Z-axis represents the vertical translation of the rear axle; b The φ represents the vertical translation of the mass on the spring; j To balance the pitch of the suspension; the φ b For the pitch of the frame; m c For the cab mass; m p For powertrain mass; m f The unsprung mass is m. m The unsprung mass of the middle bridge; m r The unsprung mass of the rear axle; m j1 For the mass of the rear leaf spring; K c For cab suspension stiffness; K p For powertrain mounting stiffness; K ft1 K represents the front axle tire stiffness. fs1 K represents the front suspension stiffness. mt1 For rear axle tire stiffness; K ms1 For rear suspension stiffness; L c1 L is the X-coordinate of the cab's center of mass in the vehicle coordinate system; p1 L represents the X-coordinate of the powertrain's center of mass in the vehicle coordinate system. fmr L is the horizontal distance from the front axle to the balance shaft. m1 M is the distance between the middle and rear axles; j The sum of the masses of the two rear suspensions; M b L is the sprung mass. f L is the distance in the X direction from the front axle to the center of mass of the sprung mass; c L is the distance in the X direction from the cab to the center of mass of the sprung mass; p L is the distance in the X direction from the center of mass of the powertrain to the sprung mass; jL is the distance in the X direction from the cab to the center of mass of the sprung mass; m It is half the distance between the middle and rear axles, and L r Equal; I j I is the moment of inertia of the rear suspension along the center of the balance axis. b Let f1 be the moment of inertia of the sprung mass along the center of mass in the pitch direction; where f1 is the front axle load and f2 is the middle and rear axle load.

[0023] Preferably, the suspension deflection frequency corresponding to the mode is determined by combining the mode shape and the associated spring stiffness;

[0024] B1 is the amplitude of the combined mode shape of the front suspension spring load and the associated spring stiffness, as shown in the following formula:

[0025]

[0026] B2 is the amplitude of the front axle mode shape and associated spring stiffness, as shown in the following formula:

[0027] B2 = z f ×K ft -(l f ×φ b +z b -z f )×K fs (5)

[0028] B3 is the amplitude of the combined mode shape of the rear suspension spring load and the associated spring stiffness, as shown in the following formula:

[0029]

[0030] B4 is the amplitude of the combined modal vibration of the middle bridge and the associated spring stiffness, as shown in the following formula:

[0031] B4 = z m ×K mt -K ms ×(l m ×φ j -l j ×φ b +z b -z m (7)

[0032] B5 is the amplitude of the rear axle mode shape and associated spring stiffness, as shown in the following formula:

[0033] B5 = z r ×K rt -K ms ×(-l r ×φ j -l j ×φ b+z b -z r (8)

[0034] B6 is the amplitude of the cab mode shape and associated spring stiffness combined, as shown in the following formula:

[0035] B6=(z c -(l c ×φ b +z b ))×K c (9)

[0036] B7 is the amplitude of the combined powertrain mode shape and associated spring stiffness, as shown in the following formula:

[0037] B7=(z p -(l p ×φ b +z b ))×K p (10)

[0038] Then, the mode shapes corresponding to the first seven natural frequencies are substituted into equations (4) to (10), and the suspension offset frequency is obtained by comparing the amplitudes.

[0039] If B1 is the largest, then the natural frequency of this order corresponds to the front suspension spring load mass offset frequency;

[0040] If B2 is the largest, then the natural frequency of this order corresponds to the unsprung mass offset frequency of the front suspension.

[0041] If B3 is the largest, then the natural frequency of this order corresponds to the rear suspension spring load mass offset frequency;

[0042] If B4 or B5 is the largest, determine whether the product of B4 and B5 is less than zero. If it is less than zero, the natural frequency of this order corresponds to the pitch mode of the rear suspension, which is the first-order unsprung mass offset frequency of the rear suspension. If it is greater than zero, the natural frequency of this order corresponds to the vertical sway mode of the middle and rear axles, which is the second-order unsprung mass offset frequency of the rear suspension.

[0043] Preferably, the theoretical calculation model established in step two considers the influence of the pitch of the balanced suspension on the suspension frequency. In a balanced suspension vehicle, the pitch mode of the rear suspension is more easily excited than the vertical sway mode of the middle and rear axles, so it is very important to accurately identify the pitch mode of the rear suspension. The theoretical calculation model established in step two considers the influence of the vertical stiffness of the cab mount and the vertical stiffness of the powertrain mount on the suspension frequency. Both have a significant impact on the frequency of the front suspension sprung mass and the frequency of the front suspension unsprung mass.

[0044] Preferably, in step three, the relationship between the mode shape and the suspension bias frequency is to convert the amplitude of the eight degrees of freedom of the model into the amplitude corresponding to the suspension bias frequency, that is, the amplitude corresponding to the upper and lower positions of the front suspension and the upper and lower positions of the rear suspension. After considering the influence of the spring stiffness connected to the position on the amplitude, the suspension bias frequency corresponding to the natural frequency of that order is determined.

[0045] Preferably, the unsprung mass offset frequency of the rear suspension output in step four includes two orders, including the pitch mode of the rear suspension and the vertical sway mode of the middle and rear axles.

[0046] Compared with the prior art, the present invention has the following beneficial technical effects:

[0047] 1. It can ensure that reliable frequency offset results can still be obtained in the early stage of design without a prototype, thus providing a basis for subsequent design, and is efficient and fast.

[0048] 2. After inputting the vehicle design parameters, automated calculations can be completed, and the suspension off-frequency can be obtained directly without requiring professional expertise from the calculation personnel. Furthermore, the theoretical calculation model considers the influence of the vertical stiffness of the cab mount and powertrain mount on the suspension off-frequency, and can obtain accurate off-frequency results to support product development.

[0049] 3. The system provided by this invention does not require the operator to have simulation ability or professional knowledge. The input design parameters directly output the suspension off-frequency results without the need to analyze and judge the mode shapes of each order. The system does not require the purchase of professional software. The design parameters can be modified for different vehicle models without the need for repetitive model building and other work. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the balanced suspension commercial vehicle off-frequency acquisition system of the present invention;

[0051] Figure 2 This is the interface of the off-frequency calculation system of the present invention; Detailed Implementation

[0052] Example 1

[0053] like Figure 1 As shown, a simple system for obtaining the offset frequency of a balanced suspension commercial vehicle includes the following steps:

[0054] Step 1: Obtain the vehicle design parameters. After converting the design parameters into the parameters required for the calculation model by establishing static equilibrium equations, input them into the theoretical calculation model.

[0055] Step 2: Solve the theoretical calculation model to obtain the eighth natural frequency of the model. Then, substitute the natural frequency into the vibration equation and solve the linear homogeneous equation system to obtain the mode shape corresponding to the natural frequency.

[0056] Step 3: Establish the relationship between the mode shape and the suspension off-frequency by using the vehicle design parameters, and then determine the suspension off-frequency corresponding to the mode shape.

[0057] Step 4: Output the front suspension spring load frequency, the front suspension unsprung load frequency, the rear suspension spring load frequency, and the rear suspension unsprung load frequency.

[0058] The theoretical calculation model described in step two is as follows:

[0059] A×[Z c Z p Z f Z m Z r Z b φ j φ b ] T ·sin(ω pt +ψ)=0 (1)

[0060] In equation (1) ω p Let ψ be the natural frequency of the vibration model, and ψ be the phase angle of the vibration model.

[0061] Z c Z p Z f Z m Z r Z b φ j φ b These are the amplitudes;

[0062] In the formula:

[0063]

[0064] If equation (1) holds at all times, and Z c Z p Z f Z m Z r Z b φ j φ b If there is a non-zero solution, then we must have:

[0065] |A|=0 (3)

[0066] After solving, ω is obtained p The eight non-zero solutions are the eighth natural frequencies of the eight-degree-of-freedom model; substituting the natural frequencies into matrix A yields the adjoint matrix A. * A * Each column can be regarded as the mode shape of the model at that natural frequency;

[0067] Among them, Z c Z represents the vertical translation of the driver's cab. pt Z represents the vertical translation of the powertrain. f Z represents the vertical translation of the front axle; m Z represents the vertical translation of the middle bridge. r Z represents the vertical translation of the rear axle. b φ represents the vertical translation of the mass on the spring; j To balance the pitch of the suspension; φ b For the pitch of the frame; m c For the cab mass; m p For powertrain mass; m f The unsprung mass is m. m The unsprung mass of the middle bridge; m r The unsprung mass of the rear axle; m j1 For the mass of the rear leaf spring; K c For cab suspension stiffness; K p For powertrain mounting stiffness; K ft1 Kf represents the front axle tire stiffness. s 1 represents the front suspension stiffness; K mt 1 represents the rear axle tire stiffness; K ms1 For rear suspension stiffness; L c1 L is the X-coordinate of the cab's center of mass in the vehicle coordinate system; p1 L represents the X-coordinate of the powertrain's center of mass in the vehicle coordinate system. fmr L is the horizontal distance from the front axle to the balance shaft. m1 M is the distance between the middle and rear axles; j The sum of the masses of the two rear suspensions; M b L is the sprung mass. f L is the distance in the X direction from the front axle to the center of mass of the sprung mass; c L is the distance in the X direction from the cab to the center of mass of the sprung mass; p L is the distance in the X direction from the center of mass of the powertrain to the sprung mass; j L is the distance in the X direction from the cab to the center of mass of the sprung mass; m It is half the distance between the middle and rear axles, and L r Equal; I j I is the moment of inertia of the rear suspension along the center of the balance axis. b Let be the moment of inertia of the sprung mass along the center of mass in the pitch direction.

[0068] Where f1 is the front axle load; f2 is the middle and rear axle load.

[0069] The suspension deflection frequency corresponding to a given mode is determined by combining the mode shape and the associated spring stiffness.

[0070] B1 is the amplitude of the combined mode shape of the front suspension spring load and the associated spring stiffness, as shown in the following formula:

[0071]

[0072] B2 is the amplitude of the front axle mode shape and associated spring stiffness, as shown in the following formula:

[0073] B2 = z f ×K ft -(l f ×φ b +z b -z f )×K fs (5)

[0074] B3 is the amplitude of the combined mode shape of the rear suspension spring load and the associated spring stiffness, as shown in the following formula:

[0075]

[0076] B4 is the amplitude of the combined modal vibration of the middle bridge and the associated spring stiffness, as shown in the following formula:

[0077] B4 = z m ×K mt -K ms ×(l m ×φ j -l j ×φ b +z b -z m (7)

[0078] B5 is the amplitude of the rear axle mode shape and associated spring stiffness, as shown in the following formula:

[0079] B5 = z r ×K rt -K ms ×(-l r ×φ j -l j ×φ b +z b -z r (8)

[0080] B6 is the amplitude of the cab mode shape and associated spring stiffness combined, as shown in the following formula:

[0081] B6=(z c -(l c ×φ b +z b ))×K c (9)

[0082] B7 is the amplitude of the combined powertrain mode shape and associated spring stiffness, as shown in the following formula:

[0083] B7=(z p -(l p ×φ b +z b ))×K p (10)

[0084] Then, the mode shapes corresponding to the first seven natural frequencies are substituted into equations (4) to (10), and the suspension offset frequency is obtained by comparing the amplitudes.

[0085] If B1 is the largest, then the natural frequency of this order corresponds to the front suspension spring load mass offset frequency;

[0086] If B2 is the largest, then the natural frequency of this order corresponds to the unsprung mass offset frequency of the front suspension.

[0087] If B3 is the largest, then the natural frequency of this order corresponds to the rear suspension spring load mass offset frequency;

[0088] If B4 or B5 is the largest, determine whether the product of B4 and B5 is less than zero. If it is less than zero, the natural frequency of this order corresponds to the pitch mode of the rear suspension, which is the first-order unsprung mass offset frequency of the rear suspension. If it is greater than zero, the natural frequency of this order corresponds to the vertical sway mode of the middle and rear axles, which is the second-order unsprung mass offset frequency of the rear suspension.

[0089] The theoretical calculation model established in step two considers the influence of the pitch of the balanced suspension on the suspension frequency. In a balanced suspension vehicle, the pitch mode of the rear suspension is more easily excited than the vertical sway mode of the middle and rear axles, so it is very important to accurately identify the pitch mode of the rear suspension. The theoretical calculation model established in step two also considers the influence of the vertical stiffness of the cab mount and the vertical stiffness of the powertrain mount on the suspension frequency. Both of these factors have a significant impact on the frequency of the front suspension sprung mass and the frequency of the front suspension unsprung mass.

[0090] In step three, the relationship between the mode shape and the suspension bias frequency is to convert the amplitude of the eight degrees of freedom of the model into the amplitude corresponding to the suspension bias frequency, that is, the amplitude corresponding to the vertical position of the front suspension and the vertical position of the rear suspension. After considering the influence of the spring stiffness connected to this position on the amplitude, the suspension bias frequency corresponding to this natural frequency is determined.

[0091] The unsprung mass offset frequency output in step four includes two orders: the pitch mode of the rear suspension and the vertical sway mode of the middle and rear axles.

[0092] Example 2

[0093] like Figure 2As shown, operators can complete automated calculations by inputting the vehicle design parameters and directly obtain the suspension frequency deviation, requiring no specialized expertise from the calculation personnel. Furthermore, the theoretical calculation model considers the influence of the vertical stiffness of the cab mount and powertrain mount on the suspension frequency deviation, enabling the acquisition of accurate frequency deviation results to support product development without the need for analysis and judgment of various mode shapes. This system does not require the purchase of specialized software; design parameters can be modified for different vehicle models, eliminating the need for repetitive model building and other tasks.

[0094] explain:

[0095] Static equilibrium equations, also known as static equations, express the quantitative relationship between air pressure and altitude when forces acting on a structure in the vertical direction reach equilibrium. The law of air pressure variation with altitude reflected by the static equations is generally applicable to all atmospheric motions, except for situations with strong vertical motion where the error is larger. Its conclusions have been widely applied in meteorology. When a structure is at rest relative to its surroundings under static loads, it is said to be in static equilibrium.

[0096] Natural frequency: Natural frequency is also called natural frequency. When an object undergoes free vibration, its displacement changes with time according to a sine or cosine law. The frequency of the vibration is independent of the initial conditions and depends only on the inherent characteristics of the system (such as mass, shape, material, etc.), and its corresponding period is called the natural period. Studying natural frequency is helpful in ensuring product stability.

[0097] Modal shape: Simply put, it's the form of vibration of each mode. Mathematically, however, a modal shape is the "basis" vector of the modal space. In linear algebra, basis vectors are fundamental tools for describing and characterizing vector spaces. Any element in a vector space can be uniquely represented as a linear combination of basis vectors. In modal space, the number of these basis vectors is the order of the mode.

[0098] Phase angle: Abbreviated as "phase angle", also known as "phase", "cycle phase" or "position phase". It is a value that determines the state of a physical quantity at any given moment (or position) when the quantity varies sinusoidally or cosinely with time (or spatial position).

Claims

1. A simple system for obtaining the offset frequency of a balanced suspension commercial vehicle, characterized in that, Includes the following steps: Step 1: Obtain the vehicle design parameters. After converting the design parameters into the parameters required for the calculation model by establishing static equilibrium equations, input them into the theoretical calculation model. Step 2: Solve the theoretical calculation model to obtain the eighth natural frequency of the model. Then, substitute the natural frequency into the vibration equation and solve the linear homogeneous equation system to obtain the mode shape corresponding to the natural frequency. Step 3: Establish the relationship between the mode shape and the suspension off-frequency by using the vehicle design parameters, and then determine the suspension off-frequency corresponding to the mode shape. Step 4: Output the frequency offset of the front suspension spring load, the frequency offset of the front suspension unsprung load, the frequency offset of the rear suspension spring load, and the frequency offset of the rear suspension unsprung load. The theoretical calculation model in step two is as follows: A ×[Z c Z p Z f Z m Z r Z b φ j φ b ] T ·sin(ω p t+ψ)=0 (1) In equation (1) ω p Let be the natural frequency of the vibration model, t be time, and ψ be the phase angle of the vibration model. In the formula: ； For equation (1) to hold true at all times, and Z c Z p Z f Z m Z r Z b φ j φ b If there is a non-zero solution, then it is necessary to... have: ； After solving, ω is obtained p The eight non-zero solutions are the eighth natural frequencies of the eight-degree-of-freedom model. Substitute the natural frequency into the matrix A Then the adjoint matrix is ​​obtained. A * , A * Each column can be regarded as the mode shape of the model at that natural frequency; Wherein, the Z c The Z-axis represents the vertical translation of the driver's cab; p The Z-axis represents the vertical translation of the powertrain. f The Z-axis represents the vertical translation of the front axle; m The Z-axis represents the vertical translation of the bridge. r The Z-axis represents the vertical translation of the rear axle; b The φ represents the vertical translation of the mass on the spring; j To balance the pitch of the suspension; the φ b For the pitch of the chassis; m c For the weight of the cab; m p For powertrain mass; m f The unsprung mass; m m The unsprung mass of the middle bridge; m r This refers to the unsprung mass of the rear axle; m j The sum of the masses of the two rear suspensions; Kc For cab suspension stiffness; K p For powertrain mounting stiffness; K ft For front axle tire stiffness; K fs For front suspension stiffness; K rt For rear axle tire stiffness; K ms For the stiffness of the bridge suspension; K mt For the stiffness of the middle axle tires, and K rt equal; K rs For the rear axle suspension stiffness, and K ms equal; l m This is the distance between the middle bridge and the balance shaft; m b For the sprung mass; l f This is the distance in the X direction from the front axle to the center of mass of the sprung mass; l c The distance from the cab to the center of mass of the sprung mass in the X direction; l p The distance from the powertrain to the center of mass of the sprung mass in the X direction; l j This is the distance in the X direction from the balance shaft to the center of mass of the spring mass; l r The distance between the rear axle and the balance shaft, and l m equal; I j为 The moment of inertia of the rear suspension along the center of the balance axis; I b为 The moment of inertia of the sprung mass along its center of mass in the pitch direction.

2. The system for easily obtaining the offset frequency of a balanced suspension commercial vehicle according to claim 1, characterized in that, The suspension deflection frequency corresponding to the mode is determined by combining the mode shape and the associated spring stiffness. B1 is the amplitude of the combined mode shape of the front suspension spring load and the associated spring stiffness, as shown in the following formula: (4)； B2 is the amplitude of the front axle mode shape and associated spring stiffness, as shown in the following formula: （5） B3 is the amplitude of the combined mode shape of the rear suspension spring load and the associated spring stiffness, as shown in the following formula: (6) B4 is the amplitude of the combined modal vibration of the middle bridge and the associated spring stiffness, as shown in the following formula: (7) B5 is the amplitude of the rear axle mode shape and associated spring stiffness, as shown in the following formula: （8） B6 is the amplitude of the cab mode shape and associated spring stiffness combined, as shown in the following formula: (9) B7 is the amplitude of the combined powertrain mode shape and associated spring stiffness, as shown in the following formula: (10) Then, the mode shapes corresponding to the first seven natural frequencies are substituted into equations (4) to (10), and the suspension offset frequency is obtained by comparing the amplitudes. If B1 is the largest, then the natural frequency of this order corresponds to the front suspension spring load mass offset frequency; If B2 is the largest, then the natural frequency of this order corresponds to the unsprung mass offset frequency of the front suspension. If B3 is the largest, then the natural frequency of this order corresponds to the rear suspension spring load mass offset frequency; If B4 or B5 is the largest, determine whether the product of B4 and B5 is less than zero. If it is less than zero, then the natural frequency of this order corresponds to the pitch mode of the rear suspension, which is the first order unsprung mass offset frequency of the rear suspension. If it is greater than zero, then the natural frequency of this order corresponds to the vertical runout mode of the mid-rear axle, which is the second-order unsprung mass offset frequency of the rear suspension.

3. The system for easily obtaining the offset frequency of a balanced suspension commercial vehicle according to claim 1, characterized in that, In step three, the relationship between the mode shape and the suspension bias frequency is to convert the amplitude of the eight degrees of freedom of the model into the amplitude corresponding to the suspension bias frequency, that is, the amplitude corresponding to the upper and lower positions of the front suspension and the upper and lower positions of the rear suspension. After considering the influence of the spring stiffness connected to the position on the amplitude, the suspension bias frequency corresponding to the natural frequency of that order is determined.

4. The system for easily obtaining the offset frequency of a balanced suspension commercial vehicle according to claim 1, characterized in that, The unsprung mass offset frequency output in step four includes two orders: the pitch mode of the rear suspension and the vertical sway mode of the middle and rear axles.

Images