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Technical Paper

Integration of SEA Tire Model with Vehicle Model

1999-05-17
1999-01-1700
Statistical energy analysis (SEA) has recently emerged as an effective tool for design assessment in the automotive industry. Automotive OEM companies develop vehicle models to aid design of body and chassis systems. The tire and wheel suppliers develop and supply component models to OEM companies in the engineering stage. In the model development process, some information on the vehicle side or component side is necessary for model development and correlation. A suitable termination representation of the vehicle characteristics on the tire/wheel model is required. This termination should account for the dissipation of energy on vehicle body and chassis side, otherwise the component model will overestimate the vibration responses and energy levels. On the vehicle model side, a representative simplified tire/wheel model may be sufficient for full vehicle road noise simulation.
Technical Paper

Experimental Determination of the Noise Emitting Parts of a Rotating Tire in the European Research Project TINO

1999-05-17
1999-01-1732
One of the objectives in the European Research project TINO is to identify, in detail, the surfaces of a rotating tire which actually generate the radiated noise. The approach is completely experimental and is based upon the ASQ (Airborne Sound Quantification) technique. The quantification of the contribution of the different tire surfaces to the sound pressure measured under defined conditions is carried out through a process of near-field measurements during rotation of the tire and static acoustic transfer function measurements. The ASQ method is further developed and tested when focussing at the applications. In first instance, the procedure has been validated and fine-tuned under well-controlled boundary conditions at a tire chassis dynamometer. The results of this first investigation served also as a “reference” set of data which has been used for verification and validation of numerical tire models.
Technical Paper

Tire/Road Interface Airborne Noise Characteristics Generation

1999-05-17
1999-01-1731
In recent years there has been much interest in problems involving the noise prediction and reduction inside and outside the vehicle. Tire/road exterior noise has been considered to be the major vehicle exterior noise source. However, this paper describes an investigation into the characteristics of the air pumping noise mechanism in terms of source locations and directionality. Some rubber tire/road air pumping noise measurements are presented, whereas some predicted results are computed based on the boundary element method (BEM) to display some parameters which are found to be difficult to be obtained experimentally.
Technical Paper

Tire/Pavement Interaction Noise Source Identification Using Multi-Planar Nearfield Acoustical Holography

1999-05-17
1999-01-1733
In this study, multi-planar Nearfield Acoustical Holography (NAH) is used to investigate noise radiated from the front, side and rear areas of single tires on a two-wheel trailer. Contributions to the radiated noise from the leading edge, trailing edge, and sidewall of the tire are identified. Two tires - an experimental monopitch tire and a production passenger car tire - are evaluated on a smooth asphalt pavement at 58 km/hr. From the measured complex pressure, acoustic intensity is reconstructed on three planes surrounding the tire using modified NAH procedures. Additionally, sound power levels are presented in tabulated and spectra forms. Tire noise generating mechanisms are inferred based on the results.
Technical Paper

A Non-Averaging Method of Determining the Rheological Properties of Traction Fluids

1999-05-03
1999-01-1518
Traction machines have been frequently used to study the rheological properties of lubricants in elasto-hydrodynamic lubrication (EHL) contacts. Fundamental properties are inferred from EHL traction measurements based on the average pressures and temperatures in the contact. This average approach leads to uncertainty in the accuracy of the results due to the highly nonlinear response of fluid rheological behavior to both pressure and temperature. A non-averaging method is developed in this paper to determine the elastic and plastic properties of traction fluids operating in EHL contacts at small slide-to-roll ratios. A precision line-contact traction rig is used to measure the EHL traction at a given oil temperature and Hertz pressure. By choosing a sensible pressure-property expression, the parameters of the expression can be determined through the initial slope and peak traction coefficient of the traction measurements.
Technical Paper

The Effect of Tire Stiffness Parameters on Medium-Duty Truck Handling

2000-05-01
2000-01-1645
This paper presents the results of a sensitivity study on the effect of tire stiffness parameters on selected handling performance metrics of a medium-duty truck. The tire stiffness parameters considered in the study are radial stiffness, longitudinal or braking stiffness, and cornering stiffness. An ADAMS model of a medium-duty truck was developed to simulate vehicle handling maneuvers. Two handling scenarios were considered: a combined braking and cornering scenario and a split-μ, straight-line braking scenario. The results of the study indicate that all three tire stiffness parameters are important in accurately predicting vehicle handling performance. Furthermore, when conducting design studies on suspension and steering system design variables other than tire stiffness parameters, the choice of specific values used for the tire stiffness parameters can significantly influence the results of the design studies.
Technical Paper

Fundamental Physics Behind New Suspension Concept for Automobiles

2000-05-01
2000-01-1647
The Transverse Leaf suspension with Superior Roll Axis is a new suspension concept for automobiles. It enables the load transfer during a turn to be more evenly redistributed between the two wheels on the same axle thus optimizing its tires lateral force capabilities. The TLSRA concept is made up of a single transverse leaf spring linking the middle of the sprung mass to the outer end of 2 transverse suspension arms per axle. Those transverse arms are mounted close to the middle of the sprung mass with their attachment points located above the mass centroïd. Each wheel assembly is mounted directly onto the free end of its respective suspension arm. Because body roll is now counteracting vertical load transfer during transient and permanent operating conditions, this suspension enables designers to keep spring stiffness low without compromising road handling.
Technical Paper

Using μ Feedforward for Vehicle Stability Enhancement

2000-05-01
2000-01-1634
Vehicle stability augmentation has been refined over many years, and currently there are commercial systems that control right/left braking and throttle to create vehicles that remain controlled when road conditions are very poor. These systems typically use yaw rate and lateral acceleration in their control philosophy. The tire/road friction coefficient, μ, has a significant role in vehicle longitudinal and lateral control, and there has been associated efforts to measure or estimate the road surface condition to provide additional information for the stability augmentation system. In this paper, a differential braking control strategy using yaw rate feedback, coupled with μ feedforward is introduced for a vehicle cornering on different μ roads. A nonlinear 4-wheel car model is developed. A desired yaw rate is calculated from the reference model based on the driver steering input.
Technical Paper

A New Method for Determining Tire Traction on Ice

2000-05-01
2000-01-1640
The development of tires traction models is very important for tire mechanics and automobile dynamics. Based on principle of thermal balance and theory of frictional melting, a new method for determining tire traction on an iced highway was presented. It was shown that the computed results could compare with the available test results. The advantages of a car with CTI-DS travelling on ice or compact snow were demonstrated in theory and in experiment. It was recommended that an automobile be operating at lower inflation pressures to increase tire traction force on the above highways.
Technical Paper

MRA Vehicle Dynamics Simulation-Matlab®/Simulink®

2000-05-01
2000-01-1624
Milliken Research Associates has developed a new simulation tool, named Vehicle Dynamics Simulation-Matlab/Simulink (VD-M/S). Produced for the government's Variable Dynamic Testbed Vehicle (VDTV), VD-M/S is an 18 degree-of-freedom simulation programmed in the Matlab/Simulink environment. It contains a detailed non-linear tire model, kinematic and compliance effects, aerodynamic loadings, etc. as do MRA's other simulation programs. Unique to VD-M/S is its development from Day One as a simulation catered to the inclusion and exploration of active systems within the vehicle.
Technical Paper

Vehicle and Tire Modeling for DynamicAnalysis and Real-Time Simulation

2000-05-01
2000-01-1620
This paper reviews the development and application of a computer simulation for simulating ground vehicle dynamics including steady state tire behavior. The models have been developed over the last decade, and include treatment of sprung and unsprung masses, suspension characteristics and composite road plane tire forces. The models have been applied to single unit passenger cars, trucks and buses, and articulated tractor/trailer vehicles. The vehicle model uses composite parameters that are relatively easy to measure. The tire model responds to normal load, camber angle and composite tire patch slip, and its longitudinal and lateral forces interact with an equivalent friction ellipse formulation. The tire model can represent behavior on both paved and off-road surfaces. Tire model parameters can be automatically identified given tire force and moment test data.
Technical Paper

Analysis of Automotive Handling Based on Tire Cornering Properties in Non-Steady State Conditions

1999-11-15
1999-01-3758
Non-steady state (NSS) tire cornering properties show obvious differences from steady state (SS) tire cornering properties. A two-DOF automobile model with steer angle as an input is established based on the known NSS tire model considering complex carcass deformation. The tire model can certainly be applied to modelling of a multi-DOF automobile system. The frequency responses of lateral acceleration and yaw rate are then derived. An evaluation index, amplitude-frequency characteristic of relative error (AFCRE), is used to analyze the influences of NSS front wheels (FW) and/or rear wheels (RW) on automotive handling. The influences of NSS FW are much greater than those of NSS RW only on automotive handling. The established automobile model can also be applied to other similar studies of vehicle dynamics.
Technical Paper

Optimal Mass and Geometric Parameters in Multi-Wheel Drive Trucks for Improved Transport and Fuel Efficiency

1999-11-15
1999-01-3733
To develop better performing vehicles, for ground transportation, it is necessary to improve the theory in vehicle dynamics for choosing suitable mass and geometric parameters for highway as well as for off road trucks. A new approach is required for choosing such optimal mass and geometric parameters. The present paper is devoted to this problem. A new method for synthesis of mass and geometric parameters is introduced here. The method allows us to synthesize the parameters in such way as to provide a vehicle with the best transport efficiency under various road surface conditions. Constraints such as limitations on these parameters, vehicle running modes, mass and geometric parameters are included in the model. Furthermore other constraints for vehicle running abilities which are dependent on mass and geometric parameters, as well as an algorithm for synthesizing mass and geometric parameters are also included in the paper for pre-optimization process.
Technical Paper

Optimal Suspension Damping for Improved Driver- and Road- Friendliness of Urban Buses

1999-11-15
1999-01-3728
Dynamic interactions of urban buses with urban roads are investigated in view of the vibration environment for the driver and dynamic tire forces transmitted to the roads. The static and dynamic properties of suspension component and tires are characterized in the laboratory over a wide range of operating conditions. The measured data is used to derive nonlinear models of the suspension component, and a tire model as a function of the normal load and inflation pressure. The component models are integrated to study the vertical and roll dynamics of front and rear axles of the conventional and modern low floor designs of urban buses. The resulting nonlinear vehicle models are thoroughly validated using the fieldmeasured data on the ride vibration and tire force response of the buses.
Technical Paper

Life Cycle Activity Analysis Applied to the Portuguese Used Tire Market

2000-04-26
2000-01-1507
A mathematical programming decision model - Life Cycle Activity Analysis (LCAA), integrating economics and environment in the optimization of the life cycle of products is presented. LCAA is based on the integration of “activity analysis” with the “life cycle assessment” framework. An illustrative application taken from the Portuguese used tire market is described. The model features two scenarios for tire end-of-life recovery technologies, where the environmental consequences of the prohibition of tire landfill are analyzed, namely in terms of energy use. Alternative end of life strategies such as tire remanufacture (retreading), recycling, heat generation in cement plants is considered in the model. The model shows that, provided the Portuguese constraints on the capacity of the alternative solutions, the prohibition of tire landfill result in a 5% decrease of energy consumption over the total tire life cycle.
Technical Paper

SMASH – Program for Car Accident Simulation

2000-03-06
2000-01-0848
In the paper SMASH - a computer program for road accident simulation is presented. Besides the logic of the program the models of vehicle, tire and crash itself are analyzed briefly. Data and diagrams showing the comparison between SMASH results and actual tests data are presented.
Technical Paper

The Durability and Reliability of Variators for a Dual-cavity Full-toroidal CVT

2000-03-06
2000-01-0826
A full-toroidal CVT has been expected as a new generation of transmission. However, high contact pressure is needed to generate traction force and temperature due to shear in contact areas becomes very high. Therefore, the fatigue life of variator is insufficient. This paper describes the application of developed bearing steel to improve the fatigue life of the varitator. Failure due to pitting depends on a film parameter Λ so that the limitation of Λ to prevent failure has been determined by a two roller test machine. Durability test of the variator made of developed bearing steel with the larger Λ than the limitation has been carried out to confirm the prevention of pitting by a dual-cavity full-toroidal CVT's variator test rig. The thickness of EHD (Elastohydrodynamic) fluid film has also been calculated by isothermal Newtonian EHD analysis with spin motion to confirm whether adequate film thickness is provided to avoid failure.
Technical Paper

A New EPS Control Strategy to Improve Steering Wheel Returnability

2000-03-06
2000-01-0815
This paper proposes a new Electric Power Steering (EPS) control strategy that enables improvement to steering-wheel returnability. Using a conventional EPS controller, frictional loss torque in the steering mechanism reduces steering-wheel returnability, which drivers occasionally perceive as unpleasant. This phenomena occurs in any EPS system regardless of motor type or mounting location. To improve steering-wheel returnability for EPS-equipped vehicles, we developed a new control strategy based on estimation of alignment torque generated by tires and road surfaces. This proposed control strategy requires no supplemental sensors like steering-wheel angle or motor-angle sensors. We experimented with this proposed control algorithm using a test vehicle and confirmed that it enables improved steering wheel returnability and also better on-center feeling.
Technical Paper

Optimization of the Tractive Performance of Four-Wheel-Drive Tractors - Correlation between Analytical Predictions and Experimental Data

2000-09-11
2000-01-2596
Analytical studies reveal that for a four-wheel-drive tractor with rigidly coupled drive axles to achieve the optimum tractive performance under a given operating condition, the theoretical speed (the product of angular speed and free rolling radius) of the front tires must be equal to that of the rear tires, or the theoretical speed ratio must be one. This paper presents tractive performance test data obtained using an instrumented four-wheel-drive tractor with seven different sets of tires at various theoretical speed ratios. Field data confirm the analytical findings that when the theoretical speed ratio is equal to one, the slip efficiency and tractive efficiency reach their respective peaks, the fuel efficiency (the ratio of drawbar power to fuel consumed per hour) reaches a maximum, and the overall tractive performance is at an optimum.
Technical Paper

Gravity as an Environmental System

2000-07-10
2000-01-2244
This paper examines gravity as a controllable environmental parameter. In long-duration orbital habitats and interplanetary vessels, designers face difficult decisions as to whether to provide artificial gravity, and if so, how much. Habitats on the moon and minor planets pose other issues. Partial gravity offers greater freedom of movement on the vertical axis, but may hinder floor traction and horizontal mobility. The minimum gravity required to preserve health remains unknown. Supplementing significant but insufficient natural gravity with artificial gravity is problematic. However, the presence of at least some natural gravity may offer other alternatives that are not available in orbit.
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