Y. P. Chang

Robustness of mount systems for idle NVH, Part I: Centre of Gravity (CG) mounts

A key parameter for frequency or modal separation of the powertrain is the basic mount design. For East-West engine configurations, there are two fundamental arrangements of mounts: the CG and pendulum arrangements. This paper discusses the variability of the modal separation of the powertrain rigid body modes as a function of the variability of the mount geometry and property parameters as well as sub-frame mount stiffness values. Six and 12 Degrees of Freedom (DOF) models are used in the analysis. Detailed Design of Experiment (DOE) studies are conducted.

LITERATURE SURVEY OF TRANSIENT DYNAMIC RESPONSE TYRE MODELS

This paper presents a literature review of simulation models that focus on transient dynamic tyre response. Such response largely arises from road roughness, tyre/wheel assembly nonuniformities, and different contact interfaces, and it is directly related to vehicle handling, control, and ride comfort. Generally speaking, three primary approaches have been used to model this kind of response: lumped parameter models, semi-analytical approaches, and full finite element method (FEM) analysis. These three approaches represent three different areas, viewpoints and major interests separately. Advantages, disadvantages, and motivations for use of these different models are discussed. As computational speeds increase at a rapid pace, FEM models continue to gain recognition and prominence as a major analytical tool for tyre design and development in tyre dynamics studies. This survey pays special attention to FEM tyre dynamics models and to studies that relate tyre parameters such as stiffness and damping to tyre design and performance.

FEA Rotating Tire Modeling for Transient Response Simulations

A full nonlinear finite element P185/70R14 passenger car radial-ply tire model was developed and run on a 1.7-meter-diameter spinning test drum. The virtual tire/drum/cleat finite element model was constructed and tested using the nonlinear finite element analysis software, PAM-SHOCK. The tire model was constructed in extreme detail with three-dimensional solid, layered membrane, and beam finite elements, incorporating over 18,000 nodes and 24 different types of materials. In addition to the tire model itself, the rim was also included and rotated with the tire, with proper mass and rotational inertial effects. The FFT algorithm was applied to examine the transient response information in the frequency domain. The result showed that this P185/70R14 tire has clear peaks of 84 and 45 Hz transmissibility in the vertical and longitudinal directions. Also the paper presents the prediction of tire standing waves phenomenon, and computer animations of the standing waves phenomenon were carried out for the first time. The effects of different tire inflation pressures and tire axle loadings were investigated with respect to their influences on the formation of standing waves. The parameters adopted in this FEA tire model were validated against experimental work and showed excellent agreement.Copyright

Robustness of mount systems for idle NVH, Part II: pendulum mounts

The pendulum mounting strategy in east-west powerplant configurations is based on two major mounts, one at the engine side and the other at the transmission side and one or two roll-restrictors. This system is used in many of todays vehicles, particularly those with lighter powertrains. This paper discusses the variability of the modal decoupling strategy as a function of variations of the powertrain pendulum mount stiffness, location and inertia properties. In addition, this paper discusses impact of mass and inertia variations. A six degrees of freedom model is used in the analysis. Detailed design of experiment studies are described.

Optimisation of frequencies of a two-span shaft system joined with a hinge

A driveshaft with discontinuities (i.e. joints) is a major component in various industries. A multi-piece driveshaft in automotive applications is joined using constant velocity or universal joints or a combination of both. This article presents an exact solution for the vibration of a two-piece driveshaft with an intermediate single joint. The joint is modelled as a frictionless internal hinge. The Euler-Bernoulli beam theory is used. Lumped masses are placed on each side of the joint to represent the joint mass. Equations of motion are developed using the appropriate boundary conditions and then solved using exact solutions. Natural frequencies and modes shapes are obtained. Numerical results obtained here are compared with those obtained using experimental and analytical tools (e.g. finite elements). Parametric studies are performed and optimisation studies are conducted to maximise bending frequencies. Effects of many parameters are examined.

Virtual Detection of a Radial-Ply Tire’s Three-Dimensional Free Vibration Modes Transmissibility

A full nonlinear finite element P205/70R14 passenger car-radial-ply tire model was developed and run on a 1.7-meter-diameter spinning test drum model at a constant speed of 50 km/h in order to investigate the tire transient response characteristics, i.e. the tire three-dimensional free vibration modes transmissibility in X, Y and Z directions. The tire model was constructed in extreme detail with three-dimensional solid, layered membrane, and beam elements. The reactions forces of the tire axle in longitudinal (X axis), lateral (Y axis) and vertical (Z axis) directions were recorded when the tire rolled over a cleat on the test drum, and then the FFT algorithm was applied to examine the transient response information in the frequency domain. The result showed that this tire has clear peaks of 45, 40, and 84 Hz transmissibility in the longitudinal, lateral and vertical directions. This result was validated against previous studies by analytical, experimental, and FEA model approaches and showed excellent agreement. The parameters adopted in this FEA tire model were also compared with experimental work and the extraordinary agreement was also confirmed. The tire three dimensional free vibration modes transmissibility was successfully detected virtually.Copyright

Dynamic analysis and simulation of driveability and control of a double transition shifting system

“Double Transition Shift” refers to the shift process in a special structured automatic transmission which employs more than one pair of clutches and brakes to perform a gear shift. Since more elements are involved during the shift process, the double transition shift algorithm is much more complicated than the traditional gearbox. Therefore, the development of the control strategy to accomplish the optimal driveability becomes a challenge for automotive control engineers.

A Virtual Cam Method for Locating Instant Centers of Kinematically Indeterminate Linkages

Kinematically indeterminate linkages are those whose complete set of instant centers cannot be obtained by Kennedys theorem. A linkage of this kind is often characterized as having no four-bar loop, or even if one exists, it does not lead to the finding of all other instant centers in the multiple-loop chain. This paper presents a simple graphical method for dealing with many of these linkages. While not altering the total degrees of freedom of the linkage, a virtual cam is introduced to help locate some key instant centers. This method also lends itself to applications along with Pennocks method to achieve greater usability.

Tyre vertical transmissibility transient response analysis

A finite element radial-ply passenger car P205/70R14 tyre model was developed and numerically ran on the road with-a-cleat to examine the tyre transient response characteristics. The tyre vertical reaction force was recorded when the tyre encountered the cleat, and then the FFT algorithm was applied to extract the information from the frequency domain. The simulation results showed that this tyre has a clear transmissibility peak at 84 Hz. Five important tyre model parameters were investigated to validate the reliability and accuracy of the simulation algorithm. The results were compared to previous studies by analytical, computational, and experimental approaches and showed excellent agreement.

A Simple Proof of the Existence of the Collinearity Circle for a Force-Input Coupler-Driven Four-Bar

This research investigates analytical analysis and synthesis problems of force-input and coupler-driven four-bar linkages. Very little bibliography can be found of this type of mechanism in contrast to the conventional torque-input crank-driven four-bars. Traditional four-bar mechanisms use the adjacent links jointed to the ground as input/output links; whereas a coupler-driven four-bar mechanism is actuated by applying the force or torque directly to the coupler link, the member has no direct connection to the base. In this paper, the transmission performance indices, TI (Transmissibility Index) and MI (Manipulability Index) are reviewed, Collinearity Points are defined, where both the MI and TI are unity and therefore the optimal motion transmission performance can be achieved. The Collinearity Circle, which is the locus of all Collinearity Points, is proposed, a novel performance indicator which is used to monitor the effectiveness of the transmission in a force-input coupler-driven four-bar. The beauty of this Collinearity Circle lies not only in its convenient shape, which is a circle, but also in its derivation that can be shown to be merely geometry-dependent. Just like the famous Instant Center, which is also only geometry-dependent, this new Collinearity Circle will prove to be a handy addition to the kinematics toolbox for its power to enable speedy construction and ballpark estimations on the transmission properties of force-input coupler-driven mechanisms. Observations and applications are presented.Copyright