阅读说明：本技术 基于汽车动力悬置系统的半主动阻尼拉杆的设计方法 (Design method of semi-active damping pull rod based on automobile power suspension system ) 是由 王道勇 蒋勉 何宽芳 李学军 李纪雄 于 2019-09-06 设计创作，主要内容包括：本发明公开基于汽车动力悬置系统的半主动阻尼拉杆的设计方法,当发动机在启停、自动启停和原地换挡时,电磁阀通电,外通道被关闭,油液主要从运动活塞上的阻尼孔在复原腔和压缩腔来回流动,产生大阻尼衰减动力总成的振动,以快速衰减动力总成的振动。在发动机怠速和汽车高速巡航时,电磁阀断电,外通道打开,油液开始从外通道流动,产生较小的阻尼隔离发动机的高频振动,进而在发动机悬置、变速箱悬置和防扭拉杆安装位置和刚度不变的前提下,通过对半主动阻尼拉杆的合理设计,可以减小汽车在启停、自动启停和原地换挡时整车的冲击与振动。(The invention discloses a design method of a semi-active damping pull rod based on an automobile power suspension system. When the engine is in idle speed and the automobile is in high-speed cruising, the electromagnetic valve is powered off, the outer channel is opened, oil begins to flow from the outer channel, high-frequency vibration of the engine is isolated by smaller damping, and then impact and vibration of the whole automobile can be reduced when the automobile is started and stopped, automatically started and stopped and the automobile is shifted in situ through reasonable design of the semi-active damping pull rod on the premise that the mounting positions and rigidity of the engine suspension, the gearbox suspension and the torsion-proof pull rod are unchanged.)

1. The design method of the semi-active damping pull rod based on the automobile dynamic suspension system is characterized in that:

the semi-active damping pull rod comprises a cylinder barrel (100), a moving piston (110) and a floating piston (120) which are slidably sleeved in the cylinder barrel (100), and a damping rod (130) coaxially connected with the moving piston (110), wherein the moving piston (110) and the floating piston (120) divide the inside of the cylinder barrel (100) into a recovery cavity (140), a compression cavity (150) and a nitrogen cavity (160) which are arranged on the left and right, an outer channel (170) is arranged on the outer side of the cylinder barrel (100), the outer channel (170) is respectively communicated with the recovery cavity (140) and the compression cavity (150), an electromagnetic valve (180) is installed on the outer channel (170), and a plurality of damping holes (111) are uniformly distributed on the moving piston (110);

the design steps of the semi-active damping pull rod are as follows:

step 1: the semi-active damping pull rod is arranged on one side of the torsion-proof pull rod, and the semi-active damping pull rod is respectively connected with an engine and an auxiliary frame to establish a complete vehicle three-degree-of-freedom model;

step 2: testing the acceleration and the dynamic reaction of an engine suspension, a gearbox suspension and an anti-torsion pull rod in a power assembly suspension system in each direction when an engine is started, stopped and automatically started and stopped through experiments, and obtaining the excitation force of the power assembly through an excitation force identification method;

and step 3: taking the semi-active damping pull rod as a fourth point suspension, and calculating and optimizing the mounting position of the semi-active damping pull rod and the dynamic stiffness of the semi-active damping pull rod in idling by using a complete vehicle three-degree-of-freedom model;

and 4, step 4: obtaining longitudinal dynamic reaction force of each suspension through experiments and performing Fourier transform to obtain vibration frequency of each suspension when an engine is started and stopped, namely obtaining vibration frequency of the semi-active damping pull rod;

and 5: calculating dynamic stiffness and damping coefficient of the semi-active damping pull rod when the semi-active damping pull rod shares different forces according to a force sharing principle;

step 6: the dynamic response evaluation index of the vibration of the power assembly and the whole vehicle when the engine is started and stopped is provided, and the following evaluation indexes are mainly adopted aiming at the vibration of the power assembly and the whole vehicle when the engine is started and stopped:

(1) the degree of impact of the powertrain;

(2) longitudinal acceleration of powertrain/body mass center;

and 7: respectively bringing dynamic stiffness and damping coefficients of the semi-active damping pull rod sharing different forces into a complete vehicle dynamic model with thirteen degrees of freedom, calculating a dynamic response evaluation index, and selecting a group of minimum values according to the calculation results of the longitudinal acceleration and the impact degree of the power assembly;

and 8: and calculating the force shared by the semi-active damping pull rod corresponding to the minimum dynamic response evaluation index, and calculating the aperture of the outer channel (170), the diameter of the moving piston (110), the diameter, the number and the length of the damping holes (111).

2. The design method of the semi-active damping pull rod based on the automobile dynamic suspension system according to claim 1, is characterized in that:

in step 1, the complete vehicle thirteen-degree-of-freedom model is as follows:

establishing a complete vehicle three-freedom-degree vibration model consisting of tires, unsprung masses, suspensions, a vehicle body and a power assembly, wherein the power assembly is transversely arranged and driven by a front wheel of the vehicle, and establishing coordinate systems O at the mass centers of the power assembly and the vehicle body respectively_p-X_pY_pZ_pAnd O_b-X_bY_bZ_bWherein X is_pPointing to the rear of the vehicle, Y_pParallel to the engine crankshaft axis and directed from the gearbox towards the engine end, Z_pDetermined by the right-hand rule, X_b，Y_b，Z_bAre each independently of X_p，Y_p，Z_pParallel, power assembly including six degrees of freedom, vehicleThe body comprises three degrees of freedom of vertical direction, lateral inclination and pitching, and unsprung mass m_u1，m_u2，m_u3And m_u4With vertical freedom.

3. The design method of the semi-active damping pull rod based on the automobile dynamic suspension system according to claim 2, is characterized in that:

in step 3, q is applied to the drive train under the action of the excitation force_pIs the displacement of the center of mass of the powertrain, q_p ^T＝(x_p，y_p，z_p，α_p，β_p，γ_p) Wherein x is_p，y_p，z_pRespectively the translational displacement of the center of mass of the power assembly along the X, Y and Z axes, alpha_p，β_p，γ_pIs the rotational displacement of the center of mass of the power assembly around the X, Y and Z axes, q_bIs the displacement of the center of mass of the vehicle body, q_b ^T＝(z_b，α_b，β_b)，z_b，α_b，β_bDisplacement of the center of mass of the car body in the vertical direction, the side-tipping direction and the pitching direction, q_uFor the displacement of the four unsprung masses of the vehicle in the vertical direction, q_u ^T＝(q_u1，q_u2，q_u3，q_u4)。

4. The design method of the semi-active damping pull rod based on the automobile dynamic suspension system according to claim 1, is characterized in that:

in step 8, in the calculation analysis of the damping force of the damping pull rod, the following assumptions are defined:

(1) the working temperature and the working environment of the damping pull rod can change in the working process, and the viscosity value is constant;

(2) the damping pull rod structure is a rigid element and cannot be deformed;

(3) tiny damping change generated by oil gravity is not considered;

(4) within a certain enclosed space, the pressure is a constant value.

Technical Field

The invention relates to the field of automobiles, in particular to a design method of a semi-active damping pull rod based on an automobile power suspension system.

Background

Automobile power assembly suspension system can effectual isolation power assembly transmit vibration and the noise in the car, improves the vehicle and takes the travelling comfort, consequently through suspension system's reasonable design, for reducing the impact and the vibration of car when opening and stopping, automatic opening and stopping and shift gears in situ, can take 3 different methods: (1) reducing the torque loading rate at engine start, i.e. increasing the time for the engine speed to reach idle speed, by an Engine Management System (EMS); (2) increasing the stiffness of the suspension system; (3) temporary damping is added to the suspension system. In the three methods, increasing the engine start time reduces the vibration of the powertrain, but increases fuel consumption; the rigidity of the suspension is increased, the dynamic reaction force of the suspension is reduced, the vibration transmitted to a vehicle body by the suspension element is reduced, but the vibration isolation performance of the suspension system in idling is reduced by increasing the rigidity of the suspension; the torsion-proof pull rod (rubber suspension) in the suspension system mainly plays a role in large torque and large impact, but the torsion-proof pull rod has a small damping coefficient and cannot quickly attenuate torque impact.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the design method of the semi-active damping pull rod based on the automobile power suspension system is provided, and under the premise that the installation positions and rigidity of an engine suspension, a gearbox suspension and an anti-torsion pull rod are not changed, impact and vibration of the whole automobile during starting and stopping, automatic starting and stopping and in-situ gear shifting of the automobile can be reduced through reasonable design of the semi-active damping pull rod.

The solution of the invention for solving the technical problem is as follows:

based on the design method of the semi-active damping pull rod of the automobile dynamic suspension system,

the semi-active damping pull rod comprises a cylinder barrel, a moving piston and a floating piston which are slidably sleeved in the cylinder barrel, and a damping rod which is coaxially connected with the moving piston, wherein the moving piston and the floating piston divide the cylinder barrel into a recovery cavity, a compression cavity and a nitrogen cavity which are arranged from left to right;

the design steps of the semi-active damping pull rod are as follows:

step 1: the semi-active damping pull rod is arranged on one side of the torsion-proof pull rod, and the semi-active damping pull rod is respectively connected with an engine and an auxiliary frame to establish a complete vehicle three-degree-of-freedom model;

step 2: testing the acceleration and the dynamic reaction of an engine suspension, a gearbox suspension and an anti-torsion pull rod in a power assembly suspension system in each direction when an engine is started, stopped and automatically started and stopped through experiments, and obtaining the excitation force of the power assembly through an excitation force identification method;

and step 3: taking the semi-active damping pull rod as a fourth point suspension, and calculating and optimizing the mounting position of the semi-active damping pull rod and the dynamic stiffness of the semi-active damping pull rod in idling by using a complete vehicle three-degree-of-freedom model;

and 4, step 4: obtaining longitudinal dynamic reaction force of each suspension through experiments and performing Fourier transform to obtain vibration frequency of each suspension when an engine is started and stopped, namely obtaining vibration frequency of the semi-active damping pull rod;

and 5: calculating dynamic stiffness and damping coefficient of the semi-active damping pull rod when the semi-active damping pull rod shares different forces according to a force sharing principle;

step 6: the dynamic response evaluation index of the vibration of the power assembly and the whole vehicle when the engine is started and stopped is provided, and the following evaluation indexes are mainly adopted aiming at the vibration of the power assembly and the whole vehicle when the engine is started and stopped:

the degree of impact of the powertrain;

longitudinal acceleration of powertrain/body mass center;

and 7: respectively bringing dynamic stiffness and damping coefficients of the semi-active damping pull rod sharing different forces into a complete vehicle dynamic model with thirteen degrees of freedom, calculating a dynamic response evaluation index, and selecting a group of minimum values according to the calculation results of the longitudinal acceleration and the impact degree of the power assembly;

and 8: and calculating the aperture of the outer channel, the diameter of the moving piston, the diameter, the number and the length of the damping holes according to the force shared by the semi-active damping pull rod corresponding to the minimum dynamic response evaluation index calculation value.

As a further improvement of the above scheme, in step 1, the complete vehicle thirteen-degree-of-freedom model is as follows:

establishing a complete vehicle three-freedom-degree vibration model consisting of tires, unsprung masses, suspensions, a vehicle body and a power assembly, wherein the power assembly is transversely arranged and driven by a front wheel of the vehicle, and establishing coordinate systems O at the mass centers of the power assembly and the vehicle body respectively_p-X_pY_pZ_pAnd O_b-X_bY_bZ_bWherein X is_pPointing to the rear of the vehicle, Y_pParallel to the engine crankshaft axis and directed from the gearbox towards the engine end, Z_pDetermined by the right hand rule. X_b，Y_b，Z_bAre each independently of X_p，Y_p，Z_pThe power assembly comprises six degrees of freedom, the vehicle body comprises three degrees of freedom of vertical direction, lateral inclination and pitching, and unsprung mass m_u1， m_u2，m_u3And m_u4With vertical freedom.

As a further improvement of the above, in step 3, q is applied to the drive train under the action of the excitation force_pIs the displacement of the center of mass of the powertrain, q_p ^T＝(x_p，y_p，z_p，α_p，β_p，γ_p) Wherein x is_p，y_p，z_pRespectively the translational displacement of the center of mass of the power assembly along the X, Y and Z axes, alpha_p，β_p，γ_pIs the rotational displacement of the center of mass of the power assembly around the X, Y and Z axes, q_bIs the displacement of the center of mass of the vehicle body, q_b ^T＝(z_b，α_b，β_b)，z_b，α_b，β_bDisplacement of the center of mass of the car body in the vertical direction, the side-tipping direction and the pitching direction, q_uFor the displacement of the four unsprung masses of the vehicle in the vertical direction, q_u ^T＝(q_u1，q_u2，q_u3，q_u4)。

As a further improvement of the above solution, in step 8, in the calculation analysis of the damping force of the damping rod, the following assumptions are defined:

(1) the working temperature and the working environment of the damping pull rod can change in the working process, and the viscosity value is constant;

(2) the damping pull rod structure is a rigid element and cannot be deformed;

(3) tiny damping change generated by oil gravity is not considered;

(4) within a certain enclosed space, the pressure is a constant value.

The invention has the beneficial effects that: the semi-active damping pull rod is arranged on one side of the torsion-proof pull rod, the semi-active damping pull rod is used as a fourth point suspension, when an engine is started and stopped, automatically started and stopped and shifted in situ, the electromagnetic valve is electrified, the outer channel is closed, oil mainly flows back and forth in the restoration cavity and the compression cavity from a damping hole in the moving piston, vibration of the large-damping attenuation power assembly is generated, and vibration of the power assembly is rapidly attenuated. When the engine is in idle speed and the automobile is in high-speed cruising, the electromagnetic valve is powered off, the outer channel is opened, oil begins to flow from the outer channel, high-frequency vibration of the engine is isolated by smaller damping, and then impact and vibration of the whole automobile can be reduced when the automobile is started and stopped, automatically started and stopped and the automobile is shifted in situ through reasonable design of the semi-active damping pull rod on the premise that the installation position and the rigidity of the engine suspension, the gearbox suspension and the anti-torsion pull rod are unchanged

The invention is used for the vibration reduction of the automobile.

Drawings

In order to more clearly illustrate the technical solution in the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly described below. It is clear that the described figures are only some embodiments of the invention, not all embodiments, and that a person skilled in the art can also derive other designs and figures from them without inventive effort.

FIG. 1 is a cross-sectional view of a semi-active damping drawbar of an embodiment of the present invention;

FIG. 2 is a thirteen-degree-of-freedom model diagram of the whole vehicle according to the embodiment of the present invention;

FIG. 3 is a schematic diagram of the operation of a semi-active damping lever of an embodiment of the present invention;

FIG. 4 is a block diagram of a semi-active damping rod motion piston of an embodiment of the present invention.

Detailed Description

The conception, the specific structure, and the technical effects produced by the present invention will be clearly and completely described below in conjunction with the embodiments and the accompanying drawings to fully understand the objects, the features, and the effects of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and those skilled in the art can obtain other embodiments without inventive effort based on the embodiments of the present invention, and all embodiments are within the protection scope of the present invention. In addition, all the coupling/connection relationships mentioned herein do not mean that the components are directly connected, but mean that a better coupling structure can be formed by adding or reducing coupling accessories according to specific implementation conditions. The technical characteristics of the invention can be combined interactively on the premise of not conflicting with each other.

Referring to fig. 1 to 4, this is an embodiment of the invention, specifically:

a design method of a semi-active damping pull rod based on an automobile power suspension system comprises the semi-active damping pull rod, wherein the semi-active damping pull rod comprises a cylinder barrel 100, a moving piston 110, a floating piston 120 and a damping rod 130, the moving piston 110 and the floating piston 120 are slidably sleeved in the cylinder barrel 100, the damping rod 130 is coaxially connected with the moving piston 110, the moving piston 110 and the floating piston 120 divide the cylinder barrel 100 into a recovery cavity 140, a compression cavity 150 and a nitrogen cavity 160 which are arranged from left to right, an outer channel 170 is arranged on the outer side of the cylinder barrel 100, the outer channel 170 is respectively communicated with the recovery cavity 140 and the compression cavity 150, oil is filled in the recovery cavity 140, the compression cavity 150 and the outer channel 170, nitrogen is filled in the nitrogen cavity 160, an electromagnetic valve 180 is installed on the outer channel 170, a plurality of damping holes 111 are uniformly distributed on the moving piston 110, and rubber bushings connected with an engine and a subframe are respectively installed at two ends of the semi-active damping, the semi-active damping pull rod is arranged on one side of the torsion-proof pull rod and is suspended as a fourth point, the electromagnetic valve 180 of the semi-active damping pull rod is connected with a vehicle-mounted power supply, and the automobile ECU controls the connection or disconnection of the electromagnetic valve 180 of the semi-active damping pull rod and the vehicle-mounted power supply. When the engine is started, stopped automatically and shifted in place, the electromagnetic valve 180 is electrified, the outer channel 170 is closed, oil mainly flows back and forth from the damping hole 111 on the moving piston 110 in the restoring cavity 140 and the compression cavity 150, vibration of the power assembly is damped by large damping, and vibration of the power assembly is damped rapidly. When the engine is in idle speed and the automobile is in high-speed cruising, the electromagnetic valve 180 is powered off, the outer channel 170 is opened, oil begins to flow from the outer channel 170, and low damping is generated to isolate high-frequency vibration of the engine.

The design steps of the semi-active damping pull rod are as follows:

step 1: establishing a complete vehicle three-DOF model, wherein the complete vehicle three-DOF model is as follows:

establishing a complete vehicle three-freedom-degree vibration model consisting of tires, unsprung masses, suspensions, a vehicle body and a power assembly, wherein the power assembly is transversely arranged and driven by a front wheel of the vehicle, and establishing coordinate systems O at the mass centers of the power assembly and the vehicle body respectively_p-X_pY_pZ_pAnd O_b-X_bY_bZ_bWherein X is_pPointing to the rear of the vehicle, Y_pParallel to the engine crankshaft axis and directed from the gearbox towards the engine end, Z_pDetermined by the right hand rule. X_b，Y_b，Z_bAre each independently of X_p，Y_p，Z_pThe power assembly comprises six degrees of freedom, the vehicle body comprises three degrees of freedom of vertical direction, lateral inclination and pitching, and unsprung mass m_u1， m_u2，m_u3And m_u4Has vertical freedom, as shown in fig. 2, and is a complete vehicle model with thirteen degrees of freedom.

Step 2: testing the acceleration and the dynamic reaction of an engine suspension, a gearbox suspension and an anti-torsion pull rod in a power assembly suspension system in each direction when an engine is started, stopped and automatically started and stopped through experiments, and obtaining the excitation force of the power assembly through an excitation force identification method;

the identification process of the excitation force comprises the following steps:

suppose that the displacement of the center of mass of the power assembly is q when the automobile is started or shifts in place_p＝(x_p,y_p,z_p,α_p,β_p,γ_p)^T，r_piFor the ith suspension in the power assembly coordinate system O_p-X_pY_pZ_pPosition (2):

r_pi＝(x_pi,y_pi,z_pi)^T(1)

defining one end of the suspension connected with the power assembly as a driving end, wherein in a power assembly suspension system, the translation displacement of the ith suspension driving end under a power assembly coordinate system is as follows:

under the power assembly mass center coordinate system, the acceleration of the ith suspension driving end is as follows:

the accelerations of the other two suspensions are supplemented in equation (3), as shown in equation (4):

the above formula is abbreviated as matrix formIn the formula a_pAnd T is a transformation matrix for the suspension active end acceleration vector obtained by experimental test. The acceleration of the powertrain center of mass may be expressed as:

the ithThe force of the suspension in three directions is defined as F_mi＝(F_mix,F_miy,F_miz)^TThen the contribution of the ith suspension to the force and moment of the powertrain's center of mass can be written as:

under the center of mass coordinate system of the power assembly, the exciting force acting on the center of mass of the power assembly is as follows:

and step 3: taking the semi-active damping pull rod as a fourth point suspension, and calculating and optimizing the mounting position of the semi-active damping pull rod and the dynamic stiffness of the semi-active damping pull rod in idling by using a complete vehicle three-degree-of-freedom model;

under the action of exciting force of power assembly, q_pIs the displacement of the center of mass of the powertrain, q_p ^T＝(x_p， y_p，z_p，α_p，β_p，γ_p) Wherein x is_p，y_p，z_pRespectively the translational displacement of the center of mass of the power assembly along the X, Y and Z axes, alpha_p，β_p，γ_pThe center of mass of the power assembly is rotated and displaced around the X, Y and Z axes. q. q.s_bIs the displacement of the center of mass of the vehicle body, q_b ^T＝(z_b，α_b，β_b)，z_b，α_b，β_bThe displacement of the center of mass of the car body in the vertical direction, the side-tipping direction and the pitching direction is respectively. q. q.s_uFor the displacement of the four unsprung masses of the vehicle in the vertical direction, q_u ^T＝(q_u1，q_u2，q_u3，q_u4)。

The complex stiffness of the suspension is not adopted in the derivation of the dynamic reaction force of the suspension to the power assembly, but the dynamic reaction force of the suspension to the power assembly is written as the sum of two parts generated by the stiffness of the suspension and the damping of the suspension.

According to newton's second law, the vibration equation of the powertrain is:

in the formula, k_i＝diag(k_iu,k_iv,k_iw) For the ith suspension in its local coordinate system o_mi-u_miv_miw_miLower stiffness matrix, c_i＝diag(c_iu,c_iv,c_iw) For the ith suspension in its local coordinate system o_mi-u_miv_miw_miThe lower damping matrix. A. the_piIs from O_p-X_pY_pZ_pTo o_mi-u_miv_miw_miThe direction cosine matrix of (2). k is a radical of_piFor the ith one is suspended at O_p-X_pY_pZ_pLower stiffness matrix, c_piFor the ith one is suspended at O_p-X_pY_pZ_pThe lower damping matrix. F_p＝{F_x,F_y,F_z,M_x,M_y,M_z}^T，r_piAnd r_biFor the ith suspension in a coordinate system O_p-X_pY_pZ_pAnd O_b-X_bY_bZ_bThe position of (a).And

are respectively r_piAnd r_biIs used to generate the inverse symmetric matrix.

The vehicle body is taken as an isolated body, and the vibration equation of the vehicle body is obtained by utilizing Newton's second law:

in the formula, R_bi＝[1,y_bi,-x_bi]，R_pi＝[0,0,1,y_pi,-x_pi,0]，P_bj＝[1,y_bj,-x_bj]，k_sjStiffness in the vertical direction of the jth suspension, c_sjDamping in the vertical direction of the jth suspension, k_biFor the ith suspended at Z_bStiffness in the direction.

The vibration equations for the 4 unsprung masses are written in matrix form as:

in the formula, k_tjIs the stiffness of the jth tire in the vertical direction, q_gjFor the road displacement excitation to which the jth tire is subjected, q_gj＝{q_g1,q_g2,q_g3,q_g4}^T。

Since the wheels remain stationary and the excitation of the road surface is zero at engine start and gear shift in place, there are:

after vibration analysis is respectively carried out on the power assembly, the vehicle body and the unsprung mass, the vibration equation of the complete vehicle model with the thirteen degrees of freedom when the engine is started and stopped and the original place is obtained as follows:

since the rigidity and the installation position of the original three suspensions (an engine suspension, a gearbox suspension and an anti-torsion pull rod) are determined, the position of the fourth suspension (a semi-active damping pull rod) and the dynamic rigidity of the semi-active damping pull rod in idling are used as constraint conditions. The optimization objective function is the inherent frequency and the decoupling rate of the power assembly in the directions of six degrees of freedom, and the optimization calculation is carried out by adopting a sequential quadratic programming method (SQP).

The optimization objective function is established as follows:

in formulae (15) to (17), λ₁And λ₂Respectively, the total frequency weight coefficient and the total decoupling rate weight coefficient, alpha_iAnd beta_iThe natural frequency weight coefficient and decoupling rate weight coefficient of ith order, W_iIs the difference between the ith order natural frequency and the target frequency, J_iIs the difference between the ith order decoupling ratio and the target lower limit, f_ilAnd f_iuTarget lower and upper limits, f, of the ith order natural frequency, respectively_iIs the i (i ═ 1, 2.., 6) th order natural frequency of the suspension system, E (i, i) is the i (i) th order decoupling ratio of the suspension system, E (i, i)_lIs the target lower limit of the ith order decoupling ratio.

The optimization variables and constraints are:

x_min≤x≤x_max,y_min≤y≤y_max,z_min≤z≤z_max(18)

k_u>0,k_v>0，k_w>0 (19)

in the formulas (18) and (19), x, y and z are respectively the installation positions of the semi-active damping pull rods under an automobile coordinate system and have the unit of mm. k is a radical of_u,k_v,k_wThe three-dimensional rigidity of the semi-active damping pull rod under a local coordinate system is respectively expressed in the unit of N/mm.

And 4, step 4: obtaining longitudinal dynamic reaction force of each suspension through experiments and performing Fourier transform to obtain vibration frequency of each suspension when an engine is started and stopped, namely obtaining vibration frequency of the semi-active damping pull rod;

and 5: calculating dynamic stiffness and damping coefficient of the semi-active damping pull rod when the semi-active damping pull rod shares different forces according to a force sharing principle;

step 6: the dynamic response evaluation index of the vibration of the power assembly and the whole vehicle when the engine is started and stopped is provided, and the following evaluation indexes are mainly adopted aiming at the vibration of the power assembly and the whole vehicle when the engine is started and stopped:

(1) the degree of impact of the powertrain;

for an automatic transmission automobile, when an engine is started and stopped, a power assembly is regarded as a six-free rigid body because a transmission system is not connected. Thus, the jerk may be expressed as the derivative of the angular acceleration of the powertrain in the pitch direction, in rad/s³。

(2) Longitudinal acceleration of powertrain/body mass center;

the magnitude of vibration during engine starting can be generally evaluated by adopting the longitudinal acceleration of a vehicle body, namely the dynamic force of a power assembly suspension system, the advancing direction of an automobile and the inertia force of tires are balanced in the X direction of an automobile coordinate system when the engine is just started under the X direction acceleration. Namely, the method comprises the following steps:

∑F_x＝0：F_pt+F_body+F_t＝0 (21)

at the very beginning of the engine, the transmission system is not connected, the acting force of the tire is zero, and at the moment:

F_pt+F_body＝0 (22)

the body and powertrain center of mass longitudinal acceleration may be expressed as equation (25). Therefore, the acceleration of the center of mass X of the power assembly in the direction can be used as an evaluation index when the engine is started and stopped. Namely, the method comprises the following steps:

and 7: respectively bringing dynamic stiffness and damping coefficients of the semi-active damping pull rod sharing different forces into a complete vehicle dynamic model with thirteen degrees of freedom, calculating a dynamic response evaluation index, and selecting a group of minimum values according to the calculation results of the longitudinal acceleration and the impact degree of the power assembly;

and 8: and calculating the force shared by the semi-active damping pull rods corresponding to the minimum dynamic response evaluation index, and calculating the aperture of the outer channel 170, the diameter of the moving piston 110 and the diameter, number and length of the damping holes 111.

In the computational analysis of the damping force of the damping pull rod, the following assumptions are defined:

(1) the working temperature and the working environment of the damping pull rod can change in the working process, and the viscosity value is constant;

(2) the damping pull rod structure is a rigid element and cannot be deformed;

(3) tiny damping change generated by oil gravity is not considered;

(4) within a certain enclosed space, the pressure is a constant value.

Considering only the normally open orifice on the moving piston 110, the pressure variation caused by the gap of the moving piston 110, and not considering the pressure loss caused by the bypass leakage, the operation principle of the semi-active control type damping pull rod is shown in the operation principle diagram of the semi-active damping pull rod in fig. 3:

wherein Q₁And Q₂Respectively, the flow rates, V, out of the recovery chamber 140 and into the compression chamber 150₁And V₂To restore the initial volumes, P, of the chambers 140 and 150₁，P₂And P_gasThe pressures, Q, of the recovery chamber 140, the compression chamber 150 and the nitrogen chamber 160, respectively_pvFor the flow through the orifice 111, A₂To move the area of the piston 110, A₁To remove the area of the moving piston 110 after the damping rod, A_rodIs the area of the damping pull rod.

A block diagram of a semi-active damping rod motion piston 110 is shown in fig. 4.

Defining the direction of leftward movement of the moving piston 110 from the initial position as the positive direction, when oil flows from the orifice 111 in the moving piston 110, e.g.As shown in the upper diagram, according to the length l of the damping hole 111_hAnd the aperture d_hProportional relationship between the pressure difference Δ P between the recovery chamber 140 and the compression chamber 150_hCan be expressed as:

in the formula, Q_pvThe flow rate of the oil flowing through the orifice 111, C_dAnd C_d1Is the flow coefficient, C_dThe value range in engineering is generally 0.62-0.63, C_d10.82, A is the area of the orifice 111, ρ is the oil density, μ_tThe dynamic viscosity of the oil is shown.

When the moving piston 110 has n damping holes 111, the pressure difference Δ P between the restoring chamber 140 and the compressing chamber 150_hWith the flow rate Q of the oil through the orifice 111_pvThe relationship of (1) is:

in the formula, L_heIs the length of the equivalent orifice 111.

There is generally an annular gap between the moving piston 110 and the cylinder 100, which creates a flow rate as shown in equation (26):

where the drag link is '+' when in the return stroke and '-' when in the compression stroke.

When the relative movement speed mu₀When the value is 0:

wherein the diameter of the moving piston 110 is D, the width of the annular gap is delta, and the length of the gap is l_agLength of aperture l_hEqual, the pressure difference between two ends of the gap of the moving piston 110 is delta P, mu_tIs oilHydrodynamic viscosity. Therefore, the pressure difference formed by the gap can be written as:

the restoration and compression processes are in a symmetrical relation, and the pressure difference generated by the oil flowing in the normal through hole and the moving piston 110 gap in the restoration and compression processes can be written as follows:

the pressures of the compression chamber 150 and the nitrogen chamber 160 are substantially equal, and after determining the pressure of the compression chamber 150, the pressure of the recovery chamber 140 can be calculated,

in which gamma is equal to 1.4, A_pTo move the area of the piston 110, v₀Is the initial volume of nitrogen, P₀Is the initial pressure, X, of the nitrogen chamber 160_fIs the movement displacement of the moving piston 110;

for the movable piston 110 with a plurality of damping holes 111 connected in parallel, the length of the damping hole 111 is measured by the length of the equivalent movable piston 110, and the length L of the equivalent damping hole 111_heComprises the following steps:

in the formula, xi_h1Is a local coefficient of resistance, λ_hIs the on-way damping coefficient.

The damping force of the semi-active damping drawbar during compression can be written as:

the recovery process comprises the following steps:

in the formula, F_fM is the friction between the moving piston 110 and the cylinder 100_pIs the mass of the moving piston 110.

In the process of motion of the semi-active damping pull rod, because the mass of the motion piston 110 is small, the acceleration term is generally ignored, so the damping force of the semi-active damping pull rod mainly comprises two parts, namely the damping force of oil and the friction force of the motion piston 110, and the restoring process of the semi-active damping pull rod is taken as the positive direction, then the damping force of the semi-active damping pull rod can be written as follows:

F＝P₁(A_p-A_r)-P₂A_p+F_fsgn(V) (35)

when the automobile cruises at a high speed and the engine idles, the electromagnetic valve 180 of the semi-active control type damping pull rod is not electrified, oil mainly flows through the outer channel 170 to generate small damping, the recovery process of the semi-active damping pull rod is defined as a positive direction, and a nonlinear model of the recovery process can be expressed as follows:

wherein alpha is the bulk modulus of elasticity, C, of the oil_tThe leakage coefficient, Q, of the oil flowing in the outer passage 170₁、Q₂、V₁、V₂、P₁、P₂The physical significance of (1) is consistent with that of the working principle diagram of the semi-active damping pull rod.

Q₁＝-Q_1,2Q₂＝Q_1,2(37)

The pressures of the recuperative chamber 140 and the compression chamber 150 are solved for the semi-active damping struts as the outer channel 170 flows by equations (36) - (48). The aperture of the outer channel 170 can be calculated using equation (35).

While the preferred embodiments of the present invention have been illustrated and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims.