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The Effect of Normal Force Variation on the Lateral Dynamics of Automobiles
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English
Abstract
It is commonly accepted that the principal functions of an automobile suspension are to control low frequency rigid body motions, provide comfort to passengers, and to reduce tire normal force variation so that predictable handling is maintained. A good argument for reducing normal force variation is that in the extreme, if a tire is off the ground, it for certain cannot generate any lateral forces, and thus compromises lateral dynamics. The direct relationship between road holding and dynamic tire normal force variation is quantified sparsely in the literature.
In this paper a relatively simple model is proposed which exposes how normal force variation at the front and rear directly affects the vehicle yaw rate and lateral acceleration. It is shown that normal force variation at the front has potentially the same effect on lateral dynamics as does the steering input.
By proposing a 1/4 car vertical dynamic model, the tire normal force variation at the front and rear can be related to roadway unevenness. By combining the vertical and horizontal dynamic models, the lateral dynamics can be directly related to roadway unevenness. The results clearly demonstrate the effect of roadway unevenness on the lateral acceleration and yaw rate of automobiles. The model can also be used to develop control strategies to minimize tire normal force variation.
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Citation
Blank, M. and Margolis, D., "The Effect of Normal Force Variation on the Lateral Dynamics of Automobiles," SAE Technical Paper 960484, 1996, https://doi.org/10.4271/960484.Also In
Investigations and Analysis in Vehicle Dynamics and Simulation
Number: SP-1141; Published: 1996-02-01
Number: SP-1141; Published: 1996-02-01
References
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- Chalasani, R.M. “Ride Performance Potential of Active Suspension Systems - Part II: Comprehensive Analysis Based on a Full - Car Model,” ASME AMD 80 Symposium on Simulation and Control of Ground Vehicles and Transportation Systems 1987 205 234
- Karnopp, D.C. Redfeild, R.C. “Performance Sensitivity of an Actively Damped Vehicle Suspension to Feedback Variation,” Journal of Dynamic Systems, Measurement and Control March 1989 111 51 60
- Pacejka, Hans B. Bakker, Egbert Nyborg, Lars “Tyre Modeling for Use in Vehicle Dynamics Studies,” SAE 870421 1987
- Hedrick, J.K. Butsuen, T. “Invariant Properties of Automotive Suspensions,” IMechE C423 1988 35 41