Directional stability of road vehicles
Abstract
The driver of a vehicle has a significant influence on handling and stability of the vehicle. Due to the complex behavior of a human pilot, a driver model is usually neglected when dealing with the problem of vehicle stability. This research focuses on the interaction between the vehicle and the human pilot. Three classes of vehicles, a flexible vehicle, a simple car and a car-trailer combination, are considered. A model characterizing human operator behavior in a regulation task is employed to study directional stability. Linear stability is analyzed by the application of the Routh-Hurwitz criteria and stability boundaries separating the stable domain of operation of the driver from the unstable one are constructed. The effect of driver as well as vehicle parameters on stable domain of operation of the system is then investigated. It is shown that the only possible type of transition in stability in driver/vehicle systems studied is due to at least a pair of purely imaginary roots of the characteristic polynomial moving into the right half of the s-plane. The linear analysis then predicts an oscillatory instability with increasing amplitude. The addition of kinematic as well as slip angle nonlinearities in the vehicle model can have a stabilizing effect on these oscillations. They may also be responsible for the opposite, namely a stable linear motion may become unstable to finite size disturbances. These nonlinear motions are predicted by a bifurcation analysis and are verified by direct numerical simulation.
Degree
Ph.D.
Advisors
Soedel, Purdue University.
Subject Area
Mechanical engineering|Automotive materials
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