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Inflation Pressure Effects in the Nondimensional Tire Model

Milliken Research Associates, Inc.-Douglas L. Milliken
University at Buffalo-Edward M. Kasprzak, Kemper E. Lewis
Published 2006-12-05 by SAE International in United States
Inflation pressure affects every aspect of tire performance. Most tire models, including the Radt/Milliken Nondimensional Tire Model, are restricted to modeling a single inflation pressure at a time. This is a reasonable limitation, in that the Nondimensional model forms an input/output relationship between tire operating conditions and force & moment outputs. Traditional operating conditions are normal load, slip angle, inclination angle, slip ratio and road surface friction coefficient.Tire pressure is more like a tire parameter than a tire operating condition. Since the Nondimensional Tire Model is semi-empirical it does not specifically deal with tire parameters like sidewall height or tread compound. Still, tire pressure is the easiest tire parameter to change, and as the air temperature within the tire varies during use so does the inflation pressure. Thus, it is desirable to incorporate inflation pressure into the Nondimensional Tire Model as an input.This paper discusses the effects of tire pressure on tire force and moment output. Effects on lateral force and aligning torque are investigated in detail. Additionally, the effects on cornering stiffness, friction coefficients,…
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Tire Asymmetries and Pressure Variations in the Radt/Milliken Nondimensional Tire Model

Milliken Research Associates, Inc.-Douglas L. Milliken
University at Buffalo, State University at New York-Edward M. Kasprzak, Kemper E. Lewis
Published 2006-02-14 by SAE International in United States
The Nondimensional Tire Model is based on the idea of data compression to load-independent curves. Through the use of appropriate transforms, tire data can be manipulated such that, when plotted in nondimensional coordinates, all data falls on a single curve. This leads to a highly efficient and mathematically consistent tire model.In the past, data for slip angle and slip ratio has been averaged across positive and negative values for use with the transforms. In this paper, techniques to handle tire asymmetries in lateral and longitudinal force are presented. This is an important advance, since in passenger cars driving/braking data is almost always asymmetric and, depending on tire construction, lateral force data may follow likewise.In addition, this paper is the first to explore the inclusion of inflation pressure as an operating variable in the Nondimensional Tire Theory. Inflation pressure affects the shape of the tire curves, notably the linear range stiffness and peak force friction coefficient. With this new variable, the operating conditions addressed by Nondimensional Tire Theory now include slip angle, slip ratio, inclination angle,…
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Elementary Analysis of Race Circuit Barrier Placement

Milliken Research Associates, Inc.-Edward M. Kasprzak
Published 2000-11-13 by SAE International in United States
Some fundamentals of barrier placement are derived in this paper and the results are analyzed. While no ideal barrier distance from the racing line can be found for every scenario, each case has a single, worst distance which maximizes impact severity as measured by the vehicle's velocity component normal to the barrier. The ramifications of placing a barrier beyond this critical distance or between the critical distance and the racing groove are examined. Ideas for extending this research are also provided.
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Racecar Optimization and Tradeoff Analysis in a Parallel Computing Environment

Milliken Research Associates, Inc.-Edward M. Kasprzak
State University of New York at Buffalo-Kurt Hacker, Kemper Lewis
Published 2000-11-13 by SAE International in United States
In this paper, we present an approach to the optimization of a racecar using vehicle dynamics simulation in a parallel-computing environment. The use of vehicle dynamics simulations in the automotive and auto racing industries is widespread. Complex vehicle simulations can include hundreds of parameters and be very computationally expensive to perform. This limits the number of design configurations that can be considered within a reasonable time, preventing thorough exploration of the design space. It also limits the usefulness of these simulations during the course of a race weekend when time is of the essence. In this paper, we present results from work to overcome this problem. Our results focus on determining the Pareto optimal designs for a vehicle model with three design variables running simulated races around corners of different radii.
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MRA Vehicle Dynamics Simulation-Matlab®/Simulink®

Milliken Research Associates, Inc.-Edward M. Kasprzak, Douglas L. Milliken
Published 2000-05-01 by SAE International in United States
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.
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Steady-State Vehicle Optimization Using Pareto-Minimum Analysis

Milliken Research Associates, Inc.-Douglas L. Milliken
State University of New York at Buffalo-Kemper E. Lewis
Published 1998-11-16 by SAE International in United States
Designing for optimal performance across a variety of situations involves compromise decisions. Through the investigation of a two-variable optimization of a vehicle for two different “races” the importance of this compromise design is underscored. The use of Pareto-minimal solution techniques, borrowed from game theory, aid in the design process by limiting the number of possible compromise designs, highlighting which solution applies for a given situation and providing some insight to the sensitivity of the design.
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Analysis and Correlation using Lap Time Simulation-Dodge Stratus for the North American Touring Car Championship

Milliken Research Associates, Inc.-David J. Segal, Douglas L. Milliken
Chrysler Corp.-Dan W. Thomas
Published 1996-12-01 by SAE International in United States
Simulation of race circuit performance had a significant impact on the design and development of the Dodge Stratus North American Touring Car Championship (NATCC) entry. The analysis involved utilization of the Milliken Research Associates, Inc. (MRA) Lap Time Simulation (LTS) program which predicts lap time based on data describing the vehicle, tires, and race track.Input data for the simulation was obtained from several sources. Chrysler Vehicle Engineering provided vehicle design information and engine power data. Tire characteristics were measured at Calspan Corporation. Aerodynamic coefficients were derived from scale model wind tunnel tests performed by Reynard Racing Cars Ltd. at the Houghton Wind Tunnel, Royal Military College of Science Shrivenham, Wiltshire, UK. X-Trac Ltd. provided transaxle specifications and race line data was derived from on-board measurements and circuit maps.Parametric studies of the vehicle variables were performed for various tracks. The results were used, in conjunction with more traditional race car design techniques, to specify the initial vehicle design and the range of setup adjustments required to tune the car for different tracks.The results were correlated with…
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Moment Method - A Comprehensive Tool for Race Car Development

Milliken Research Associates, Inc.-William F. Milliken, Douglas L. Milliken
Team Lotus Ltd.-Peter G. Wright
Published 1994-12-01 by SAE International in United States
The MRA Moment Method computer program automates an original approach to the analysis of race car handling. For a given speed and power/braking condition, the computer solution covers the full maneuvering envelope and presents the results graphically in one figure. The model is based on a comprehensive nonlinear vehicle representation utilizing tire, chassis, and aerodynamic input data as available to race car designers and developers. The paper will first explain and illustrate the Moment Method in general terms, with some graphical examples.The ability of the technique to model the behavior of an F.1 car traversing a small bump in mid-corner on a Grand Prix circuit is then reviewed. The results correlate well with the driver comments relative to changes in directional stability (plow/spin) as the car pitches over the bump. It also correlates well with the lateral acceleration/speed that the driver is willing to use in this corner.
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An Efficient Method for Treating Race Tire Force-Moment Data

Milliken Research Associates, Inc.-Hugo S. Radt
Published 1994-12-01 by SAE International in United States
Experience shows that raw data from tire test machines requires processing to obtain reliable results from complex vehicle models. Lateral force and self aligning torque data on a P275/40VR-17 Eagle ZR-S tire are processed, plotted and fitted in order to facilitate data smoothing and to provide a simple, accurate representation of the tire for race car simulations. The approach employs nondimensional variables for lateral force, self aligning torque and slip angle, so that data points for different loads all fall on the same normalized curve. Additional features of the method are described, based on investigations of passenger car tires. An efficient “reduced” test sequence is presented.
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Active Suspension

Milliken Research Associates, Inc.-William F. Milliken
Published 1988-04-01 by SAE International in United States
This paper defines an active suspension and gives a brief history of the development of the LOTUS system, the only successful fully-active embodiment to date. The modal approach and overall system are described. The performance and potential of active suspension relative to the conventional suspension is discussed. Off-road applications are reviewed. The paper concludes with a statement on the future of generalized active control.
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