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1、毕业设计(论文) 外文翻译 英文翻译题目一： New analytical method to evaluate the powerplant and chassis coupling in the improvement vehicle NVH英文翻译题目二： 学 院 名 称： 机械工程 专 业： 汽车服务工程 班 级： 汽车 071 姓 名： 陈晔 学 号 07405050104 指 导 教 师： 李发宗 定稿日期： 2011 年2月18日外文翻译：评估改进车辆振动噪音中发动机和底盘耦合的全新分析法英文题目一New analytical method to evaluate the pow
2、erplant and chassis coupling in the improvement vehicle NVH翻译内容第929-934页指导教师评语外文翻译与毕业选题相关，译文质量较好，字数达标，符合本科毕业论文外文翻译要求。指导教师签字年 月 日英文题目二翻译内容指导教师评语指导教师签字 年 月 日 New analytical method to evaluate the powerplant and chassis coupling in the improvement vehicle NVHE. Courteille a,b, L. Lotoing b, F. Mortier
3、a, E. Ragneau bAbstractThe design of an automotive powerplant mounting system is an essential part in vehicle safety and improving the vehicle noise, vibration and harshness (NVH) characteristics. One of the main problems encountered in the automotive design is isolating low frequency vibrations of
4、the powerplant from the rest of the vehicle. The significant powerplant mass makes the choice of frequency and mode arrangements a critical design decision. Several powerplant mounting schemes have been developed to improve NVH properties concentrating on the positioning and design of resilient supp
5、orts. However these methods are based on decoupling rigid body modes from a grounded powerplant model which ignores chassis and suspension system interactions.But it cannot be stated that decoupling the grounded rigid body modes of the powerplant will systematically reduce chassis vibrations. In thi
6、s paper, a new analytical method is proposed to examine the mechanisms of coupling between the powerplant and the vehicle chassis and subsystems. The analytical procedure expands the equation of motion of the vehicle components to such that a domain of boundary conditions used in the 6 degrees-of-fr
7、eedom powerplant mounting model can be defined. An example of this new procedure is given for improving NVH chassis response at idle speed using the torque roll axis decoupling strategy.Keywords: Powerplant mounting system; Optimization; Dynamic isolation; Coupled systems1. IntroductionIn vehicles,
8、the engine mounts play an essential role for the noise, vibration and harshness (NVH) comfort. The main functions of these mounts (rubber or hydraulic) are to provide static supports for the powerplant and to isolate the vibrations of the powerplant from the rest of the vehicle. To provide design ch
9、aracteristics necessary for the NVH improvement in terms of rigidity and damping it is essential to simulate the responses of the powerplant mounting system to low frequency vibrations. Is is essential that the model includes the primary interactions between the powerplant mounting system and each o
10、f the vehicle subsystems. In the early stages of the vehicle design most of the necessary data needed from the subsystems are not yet fully described. Thus, to begin a theoretical layout of the powerplant mounting system, some reasonable assumptions of the vehicle components must be made. Specifical
11、ly, the model includes rigid body representations of the powerplant and the chassis; with appropriate values for the location of the centers of gravity, masses, and moments of inertia. This simulation model enables the assessment of the rigid body modes of the powerplant in the vehicle. As well, the
12、 motions of the powerplant and the chassis under various engine operating conditions (idle, full load speed sweep) and road/wheel inputs can be analyzed.Equations of motion for the powerplant mounting system include parameters for a rigid chassis. On the contrary, the chassis flexibility may have a
13、significant effect on powerplant vibrations and mounting forces transmitted from the powerplant to the structure, especially when flexible vibration modes of the chassis are excited. The dominant vibration modes of body structure at idle speed should be the first longitudinal bending mode and the fi
14、rst torsional mode, normally above 3035 Hz. Experimental verification of the simulation models assumptions through measurements of the vibration modes of the chassis should be included in future work.The current industrial strategies use a model approach to analyze the harmonic response of the power
15、plant on resilient supports attached to ground (Brach, 1997; Khajepour and Geisberger, 2002). The 6 degrees-of-freedom model used in the modal analysis is interesting insofar as the response to an excitation is calculated and interpreted according to the position in frequency and to the form of the
16、modes.Typical design strategies move input source frequencies away from the rigid body natural frequencies of the powerplant in order to avoid resonances (Gray et al., 1990; Kano and Hayashi, 1994). Vibrations are minimized within this design approach by manipulating the rigid body modes of the grou
17、nded powerplant and shaping the response through the torque roll axis decoupling and the elastic axis decoupling methods attempt. The background theory of these techniques is widely described in literature (Patton and Geck, 1984; Singh and Jeong, 2000; Brach, 1997). However, by considering the power
18、plant to be grounded these design strategies neglect the influences of the chassis, exhaust subsystem, drive-shaft, wheel suspension . . . .Lately, researches have focused on the significance of the rigid body modes alignment for grounded powerplant to its invehicle behavior (Sirafi and Qatu, 2003;
19、Hadi and Sachdeva, 2003). These studies deal with the accuracy of NVH vehicle models and raise the problem of interactions between the different subsystems. Various powertrain models have been studied and their accuracy was discussed through a full vehicle model. By the evaluation of actual cases, t
20、he existence of these interactions have been clearly demonstrated. Nevertheless, no general formalism have been introduced to evaluate the limits of the modeling assumptions made during the development of the classical 6 degrees-of-freedom powerplant mounting schemes.The aim of the proposed method i
21、s to highlight and identify, through an analytical procedure, the relationships between the powerplant mounting schemes and the vehicle response characteristics. In the second section, the general equations of motion are reformulated using an original matrix, the coupling matrix introduced for coupl
22、ed plates (Bessac and Guyader, 1996). With the characteristics of the coupling matrix, acceptable boundary conditions used in the traditional 6 degrees-of-freedom mounting strategies can be defined for different engine operating conditions. As an example in Section 3, these parameters are defined fo
23、r engine models in the idle state. In the last section of the paper, the issue of the torque roll axis decoupling strategy is analyzed using the coupling parameters in terms of improvement of the dynamic chassis responses at idle speed.2. Formulation of the coupling problem2.1. Modelling of the vehi
24、cle systemDerivation of the equations of motion to simulate dynamic behaviors of powerplant mounting systems with supporting structures, a good modelling of the total vehicle system can consist of four subsystems: the powerplant which includes engine and transmission, the engine mounts, the chassis
25、and the suspension. Since small displacements can be assumed, the powerplant is modelled as rigid body of time-invariant inertial matrix of 6 dimensions. The powerplant is supported by an arbitrary number of mounts on the vehicle chassis, that is modelled as an elastically suspended rigid body as sh
26、own in Fig. 1.The mounts classically used in powerplant mounting application are bonded metal-rubber construction. It is possible to get better isolation effects than conventional rubber mount systems with hydraulic engine mount. Hydraulic engine mount control the damping characteristics by using th
27、e fluid viscosity. Elastomeric materials behave visco-elastically, thus engine mounts are represented by three sets of .mutually perpendicular of linear springs and viscous dampers in parallel. No rotational stiffness of the mounts has been considered. The stiffness matrix Kmi and damping matrix Cmi
28、 of a mount i can be written in the local coordinate system as: ，and (1)Fig. 1. Powerplant mounting modelFig. 2. Translational u and rotational displacements of the powerplant center of gravity.The subscript mi corresponds to the mount frame coordinates Rmi (Fig. 1) of the ith mount. The stiffness a
29、nd damping matrices must be transformed from the local mount coordinate system Rmi to the global coordinate system R by the following linear transformation: ,and (2)The element mi is the transformation matrix from the local coordinate system Rmi to the global one R. The elements of mi consist of dir
30、ectional cosines of the local frame with respect to R defined from Euler angles.2.2. Equations of motionAnother transformation is necessary to express the equations of motion of the powerplant and chassis centers of gravity in terms of displacements and rotations. This transformation relates the dis
31、placements of each mount with respect to the displacements and rotations of the powerplant and chassis centers of gravity. The superscripts (e) and (c) stands for powerplant and chassis respectively. The superscript (b) may refer to either the powerplant or the chassis. A generalized vector q (Eq. (
32、3) is defined by combining translational u and rotational displacements of the centers of gravity of the powerplant (Fig. 2) and of the chassis. (3)The position vector of the ith mounts center of elasticity with respect to the center of gravity of the powerplant and the chassis are given in terms of
33、 global coordinate system as: (4)and each has a corresponding skew asymmetric matrix defined as: (5)with a generalized form: (6)Let ui(b) be the translational displacement vector at the mounting point i for the rigid body (b) side. The relative translational displacement vector i for the ith mount f
34、or small motions is related to the rigid body center of gravity motions and the translational displacements at the mounting point according to Eq. (7). (7)The translational reaction force fi(e) and fi(c) and moment reactioni(e) andi(c) resulting from the application of the elastic forces of mounting
35、 i on the powerplant and the chassis centers of gravity can be expressed in the R frame as: (8) At idle speed, the connection to the ground is simply represented by four systems of linear spring and viscous damper in parallel at each wheel, characterized by their stiffness and damping coefficients f
36、ollowing the three directions of the vehicle frame coordinates R. The translational reaction force fk(c) and moment reactionk(c) from the kth suspension applied to the chassis can be expressed in the frame R with the displacement of the chassis u k(c) at the supporting point as: (9)Similarly, for th
37、e road/wheel inputs, a simple model can be used for the wheel-suspension system, with a single degree of freedom. This can be represented by a mass and a spring accounting for the wheel mass and the tires stiffness in parallel with a spring and a damper accounting for the suspension system. The dyna
38、mic interaction between the vehicle suspension and the powerplant mounting system should be included in future work.Assuming all elastic loadings from all mounts and suspension, the total elastic loadings on the powerplant and chassis centers of gravity can be expressed through a generalized square
39、stiffness matrix K of 12 dimensions (10), resulting from the assembly of the elementary stiffness matrices (mounts and suspensions).(10)The matrix K(ec) is the powerplants matrix of influence on the chassis and the reciprocal, K(ce) is the chassiss matrix of influence on the powerplant. Using a simi
40、lar assembly procedure to the elastic loadings, the total damping loadings on the powerplant and chassis centers of gravity can be expressed by a generalized square stiffness damping matrix C of 12 dimensions (11).(11)Since all component reactive forces are derived in terms of the generalized coordi
41、nates, and assuming small oscillations, the equations of motion of the powerplant and the chassis can be written as the matrix form in the frequency domain: (12)The vector F =tF(e) F(c) is the generalized external load vector. The external excitations are harmonics with known frequencies,amplitudes
42、and phases. Engine excitation forces are applied to the powerplant at the center of the crankshaft location.The response to road inputs can be studied by applying forces or displacements at the suspensions location of ground contact.The matrix M is the generalized mass matrix of the system (13).(13)
43、Withand m(b) is the mass of the rigid body (b) and M(b) its inertia matrix. C is the generalized viscous damping matrix assuming a proportionally damped system. If a structural damping matrix H is considered, viscous damping term jC may be replaced by the structural damping term jH. For the followin
44、g developments, a complex stiffness is used to model the dynamic behavior of the isolators. The bar indicates that the stiffness term is complex ().2.3. Introduction of the coupling matrixThe response of the powerplant and chassis centers of gravity can be calculated through the solving of Eq. (12).
45、 Then, the complex matrix inversion of Eq. (14) is classically used.(14)The inversion of the impedance matrix can be numerically resolved. Nevertheless, this method hinders the understanding of the coupling phenomena between the powerplant and the chassis. From the traditional equation of motion (14
46、), one can isolate a matrix presenting only terms related to the coupling from the two bodies (15).(15)For the sake of physical meaning of the coupling mechanism, the term (2M(e) 1F(e) in Eq. (15) represents the displacement of the powerplant subjected to its own excitation when the chassis is blocked (suspensions with infinite stiffnesses).This configuration