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Technical Paper

A Computer Model Based Sensitivity Analysis of Parameters of an Automotive Air Conditioning System

2004-03-08
2004-01-1564
The objective of this work is to perform a computer model based sensitivity analysis of parameters of an automotive air conditioning system to identify the critical parameters. Design of Experiment (DOE) and Analysis of Variance (ANOVA) techniques have been used to identify the critical parameters and their relative effects on the air conditioning system performance. The sensitivity analysis has been verified by running similar tests on an air conditioning system test stand (AC Test Stand).
Technical Paper

A Computerized Optimization Method Of Engine Mounting System

2003-05-05
2003-01-1461
This paper presents a method for optimization design of an engine mounting system subjected to some constraints. The engine center of gravity, the mount stiffness rates, the mount locations and/or their orientations with respect to the vehicle can be chosen as design variables, but some of them are given in advance or have limitations because of the packaging constraints on the mount locations, as well as the individual mount rate ratio limitations imposed by manufacturability. A computer program, called DynaMount, has been developed that identifies the optimum design variables for the engine mounting system, including decoupling mode, natural frequency placement, etc.. The degree of decoupling achieved is quantified by kinetic energy distributions calculated for each of the modes. Several application examples are presented to illustrate the validity of this method and the computer program.
Technical Paper

A Fully Variable Mechanical Valvetrain with a Simple Moving Pivot

2005-04-11
2005-01-0770
A continuously variable lift, duration and phase mechanical lift mechanism is described, as applied to the intake valvetrain of a SOHC, 4-valve per cylinder, four-cylinder production engine. Improvements in fuel economy were sought by reduction of pumping losses and improved charge preparation, and optimization of WOT torque was attempted by variation of intake valve closing angle. Adjustment of the mechanism is achieved by movement of the pivot shaft for the rocker arms. The relationship between lift, duration and phase is predetermined at the design stage, and is fixed during operation. There is considerable design flexibility to achieve the envelope of lift curves deemed desirable. The operation of the mechanism is described, as are the development procedure, testing with fixed cams, some cycle simulation, friction testing on a separate rig and dyno testing results for idle, part load and WOT.
Technical Paper

A Graphical Representation of Road Profile Characteristics

2004-03-08
2004-01-0769
Load data representing severe customer usage is required during the chassis development process. One area of current research is the use of road profiles for predicting chassis loads. The most direct method of predicting these loads is to run dynamic simulations of the vehicle using numerous road profiles as the excitation. This onerous task may be avoided, and a greatly reduced number of simulations would be required, if roads having similar characteristics can be grouped. Currently, road profiles are characterized by their spectral content. It has been noted by several researches, however, that road profiles are generally nonstationary signals that contain significant transient events and are not well described in the spectral domain. The objective of this work, then, is to develop a method by which the characteristics of the road can be captured by describing these constitutive transient events.
Technical Paper

A Hybrid Method for Vehicle Axle Noise Simulation with Experimental Validation

2003-05-05
2003-01-1707
Recently, many authors have attempted to represent an automobile body in terms of experimentally derived frequency response functions (FRFs), and to couple the FRFs with a FEA model of chassis for performing a total system dynamic analysis. This method is called Hybrid FEA-Experimental FRF method, or briefly HYFEX. However, in cases where the chassis model does not include the bushing models, one can not directly connect the FRFs of the auto body to the chassis model for performing a total system dynamic analysis. In other cases when the chassis model includes the bushings, the bushing dynamic rates are modeled as constant stiffness rather than frequency dependent stiffness, the direct use of the HYFEX method will yield unsatisfactory results. This paper describes how the FRF's of the auto body and the frequency dependent stiffness data of the bushings can be combined with an appropriate mathematical formulation to better represent the dynamic characteristics of a full vehicle.
Technical Paper

A Minimum-Effort Motion Algorithm for Digital Human Models

2003-06-17
2003-01-2228
A new realistic motion control algorithm for digital human models is presented in this paper based on the principle of effort minimization. The proposed algorithm is developed through an innovative mathematical model to make the applications more flexible and more global, especially for the visualization of human motions in automotive assembly operations. The central idea of this unique model is to interpret the solution of the homogeneous Lagrange equation for a mannequin as the origin of dynamic motion. Furthermore, a digital human possesses about 42 joints over the main body except the head, fingers and toes, and offers a large room of kinematic redundancy. We have found 14 new 3-D independent motion markers assigned over the human body to constitute a Cartesian coordinate system, under which a minimum-effort based dynamic control scheme is developed using a state-feedback linearization procedure.
Technical Paper

A Multiple Order Conformability Model for Uniform Cross-Section Piston Rings

2005-04-11
2005-01-1643
This paper examines the conformability of elastic piston rings to a distorted cylinder bore. Several bounds are available in the literature to help estimate the maximum allowable Fourier coefficient in a Fourier expansion of bore distortion: the analytically derived bounds in [7] and [8], and the semi-empirically derived bounds discussed in [9]. The underlying assumptions for each set of analytic bounds are examined and a multiple order algorithm is derived. The proposed algorithm takes account of multiple orders of distortion at once. It is tested with finite element (FE) data and compared to the classical bound approach. The results indicate that the bounds in [7] are compatible with linear elasticity theory (LET), whereas the bounds in [8] are not. Furthermore, numerical evidence indicates that the present multiple order algorithm can predict seal breaches more accurately than either of the other analytic bounds.
Technical Paper

A Study on Vehicle Elastomer Mount Preloading and Impact Response with Test Validation

2005-04-11
2005-01-1415
A variety of elastomer mounts are being used for vehicles as isolators/dampers between body and frame, on the engine cradle, etc. These vehicle flexible mounts, made of mainly rubber materials and housed in a metallic tube, are indispensable components affecting the quality of the vehicle ride, noise and vibration. In the auto industry, the usual practice when designing vehicle flexible mounts is to minimally reflect impact considerations in the mount design features. However, in most high-speed vehicle crash events where the mounts fail, the crash responses, including occupant injury severity, are known to be very different from the responses of non-failure cases. Even in low-speed vehicle impact cases, excessive deformation of the flexible mounts could cause significant variance in the compliance of the vehicle acceleration level to the air-bag firing and timing threshold requirements.
Technical Paper

An Approach to Torque-Based Engine Management Systems

2001-03-05
2001-01-0269
The ever-growing number of interacting electronic vehicle control systems requires new control algorithms to manage the increasing system complexity. The paper describes a torque-based engine control architecture which uses a central torque demand variable to control the regulating qualities. This torque demand variable is the result of the coordination of all torque requests throughout the vehicle. Therefore, the system manages the whole process of prioritizing the torque demands of the different subsystems such as electronic stability or transmission control. If further vehicle subsystems have to be integrated, the structure can be easily extended as the torque demand variable is the only interface between the engine control algorithms and other vehicle control systems.
Technical Paper

An Automated Head Impact Development for Automobile Instrument Panel Application

2016-04-05
2016-01-1370
During the course of automobile Instrument Panel (IP) design development, the occupant head impact CAE simulation on IP are routinely performed to validate FMVSS201 requirements. Based on FMVSS201 requirements, the potential head impact zones on the IP are first identified. Then, the head impact zones are used to locate the various target points that must be impacted on IP. Once the critical target locations on IP are chosen, there are several computational steps that are required to calculate impact angles and head form (HF) center of rotation in reference to target points. Then, CAE engineer performs a repetitive process that involves positioning each individual HF with proper impact angle, assigning initial velocity to HF, and defining surface contacts within the finite element model (FEM). To simplify these lengthy manual steps, a commercially available software HyperMesh® CAE software tool is used to automate these steps. The automation scripting tool is based on TCL programming.
Technical Paper

An Efficient Procedure for Vehicle Thermal Protection Development

2005-04-11
2005-01-1904
Vehicle thermal protection is an important aspect of the overall vehicle development process. It involves optimizing the exhaust system routing and designing heat shields to protect various components that are in near proximity to the exhaust system. Reduced time to market necessitates an efficient process for thermal protection development. A robust procedure that utilizes state of the art CFD simulation techniques proactively during the design phase is described. Simulation allows for early detection of thermal issues and development of countermeasures several months before prototype vehicles are built. Physical testing is only used to verify the thermal protection package rather than to develop heat shields. The new procedure reduces the number of physical tests and results in a robust, efficient methodology.
Technical Paper

Anti-Shudder Property of Automatic Transmission Fluids - A Study by the International Lubricants Standardization and Approval Committee (ILSAC) ATF Subcommittee

2000-06-19
2000-01-1870
In recent years, the slip lock-up mechanism has been adopted widely, because of its fuel efficiency and its ability to improve NVH. This necessitates that the automatic transmission fluid (ATF) used in automatic transmissions with slip lock-up clutches requires anti-shudder performance characteristics. The test methods used to evaluate the anti-shudder performance of an ATF can be classified roughly into two types. One is specified to measure whether a μ-V slope of the ATF is positive or negative, the other is the evaluation of the shudder occurrence in the practical vehicle. The former are μ-V property tests from MERCON® V, ATF+4®, and JASO M349-98, the latter is the vehicle test from DEXRON®-III. Additionally, in the evaluation of the μ-V property, there are two tests using the modified SAE No.2 friction machine and the modified low velocity friction apparatus (LVFA).
Technical Paper

Application of Multi-Parameter and Boundary Mannequin Techniques in Automotive Assembly Process

2003-06-17
2003-01-2198
This paper deals with the multi-parameter and boundary mannequin techniques in creating human models in automotive applications. The concepts and applications of single-parameter, multiple parameter and boundary mannequin method are discussed respectively to clarify certain confusion. Emphasis is put on how to create boundary mannequins for a specific application, which may have been puzzling many engineers in practical applications. The authors would like to share their experience in using the digital human modeling software and make discussions on some common issues. A number of case studies from typical automotive manufacturing assembly operations are also presented to demonstrate the usage of the multi-parameter and boundary mannequin techniques.
Technical Paper

Application of Simplified Load Path Models for BIW Development

2019-04-02
2019-01-0614
Simplified load path models (SLMs) of the body in white (BIW) are an important tool in the body structure design process providing a highly flexible, idealized concept model to explore the design space through load path evaluation, material selection, and section optimization with rapid turnaround. In partnership with Altair Engineering, the C123 process was used to create and optimize SLMs for BIW models at FCA US LLC. These models help structures engineers to develop efficient load paths, sections, and joints for improved NVH as ultra-high-strength steels enable thinner gauges throughout the body structure. A few key differences in the SLM modeling method are contrasted to previous simplified BIW modeling methods. One such example is the parameterization of cross sections through response surface models rather than using contemporary finite element descriptions of arbitrary cross sections.
Technical Paper

Attempts for Reduction of Rear Window Buffeting Using CFD

2005-04-11
2005-01-0603
This paper summarizes the major activities of CFD study on rear window buffeting of production vehicles during the past two years at DaimlerChrysler. The focus of the paper is the attempt to find suitable solutions for buffeting suppression using a developed procedure of CFD simulation with commercial software plus FFT acoustic post-processing. The analysis procedure has been validated using three representative production vehicles and good correlation with wind tunnel tests has been attained which has gained the confidence in solving the buffeting problem. Several attempts have been proposed and tried to find solution for buffeting reduction. Some of them are promising, but feasibility and manufacturability still need discussion. In order to find suitable solution for buffeting reduction, more basic research is necessary, more ideas should be collected, and more joint efforts of CFD and testing are imperative.
Technical Paper

Automotive Seat Suspension Model for Ride Quality Studies

2002-03-04
2002-01-0778
A high fidelity seat suspension model, which can be used for ride quality predictions, is developed in this work. The coil-spring seat suspension model includes unique nonlinear forms for the stiffness and damping characteristics. This is the first paper to consider the nonlinear geometric effects of the suspension, derive the coil-spring suspension model from physical principles, and compare theoretical and experimental results. A simplified nonlinear form is achieved via an admissible function describing the vertical suspension deflection as a function of the lateral position. This simplified nonlinear form is compared to experimental data and demonstrated to have exceptional fidelity.
Technical Paper

CAE Fatigue Prediction of Fuel Tank Straps using Proving Ground Loads

2005-04-11
2005-01-1405
The durability of fuel tank straps is essential for vehicle safety. Extensive physical tests are conducted to verify designs for durability. Due to the complexity of the loads and the fuel-to-tank interaction, computer-aided-engineering (CAE) simulation has had limited application in this area. This paper presents a CAE method for fuel tank strap durability prediction. It discusses the analytical loads, modeling of fuel-to-tank interaction, dynamic analysis methods, and fatigue analysis methods. Analysis results are compared to physical test results. This method can be used in either a fuel-tank-system model or a full vehicle model. It can give directional design guidance for fuel tank strap durability in the early stages of product development to reduce vehicle development costs.
Technical Paper

CFD Simulation of the Flows Within Disengaged Wet Clutches of an Automatic Transmission

2003-03-03
2003-01-0320
The flow within the disengaged wet clutch packs of an automatic transmission has been simulated as a three-dimensional, steady-state, two-phase flow using the commercial computational fluid dynamics (CFD) code FLUENT. The flow within a clutch with ungrooved friction plates was first solved for validating the CFD model, followed by a simulation of the flow within a clutch with grooved friction plates. A group of dimensionless variables have been established for mathematically modeling the drag torque and power loss in clutch packs. The effects of rotating speed of friction plate, pack clearance, and flow rate on drag torque and power loss have been studied.
Technical Paper

Chassis Dynamometer Simulation of Tire Impact Response

2001-04-30
2001-01-1481
One of the major NVH concerns for automobile manufacturers is the response of a vehicle to the impact of the tire as it encounters a road discontinuity or bump. This paper describes methods for analyzing the impact response of a vehicle to such events. The test vehicle is driven on a dynamometer, on which a bump simulating cleat is mounted. The time histories of the cleat impact response of the vehicle can be classified as a transient and a repeated signal, which should be processed in a special way. This paper describes the related signal processing issues, which include converting the time data into a continous spectrum, determination of the correct scaling factor for the analyzed spectrum, and smoothing out harmonics and fluctuations in the signal. This procedure yields a smooth frequency spectrum with a correctly scaled amplitude, in which the frequency contents can be easily identified.
Technical Paper

Chrysler 45RFE a New Generation Light Truck Automatic Transmission

1999-03-01
1999-01-1260
The 45RFE is a new generation electronically controlled rear wheel drive automatic transmission. It employs real-time feedback, closed-loop modulation of shift functions to achieve outstanding shift quality and to meet demanding durability goals. It uses no shift valves; all friction element applications are effected with high-flow electro-hydraulic solenoid valves. A unique gear train arrangement of three planetary carriers allows all sun gears and annulus gears to have the same number of teeth respectively and use a common pinion gear in all carriers, resulting in significant manufacturing simplification. The three-planetary system is designed for four forward ratios of 3.00, 1.67, 1.00 and 0.75 and one reverse gear ratio equal to the low gear ratio. A fifth ratio of 1.50 is used only in certain kick-down shift sequences for highway passing. A sixth forward ratio, an additional overdrive ratio of 0.67, is available in the hardware.
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