EFFECTS OF VEHICLE PARAMETERS ON VEHICLE HANDLING

SAID WAHID ZEWARI, Purdue University

Abstract

A mathematical model of a four wheeled pneumatic tire passenger car is established in order to study the effects of vehicle parameters on its steady-state and transient responses. Of special interest are those parameters which are easily and frequently changed by the driver. This investigation deals with maneuvering (executing a turn or a lane change) and severe braking (any combination of locked wheels) in order to determine the relative importance of various vehicle parameters such as tire stiffness, vehicle loading and vehicle velocity. This study provides an understanding of the safety problems and the precautionary measures that should be taken in order to avoid handling difficulties. The model is nonlinear and consists of a sprung mass and two unsprung masses. The sprung mass is free to roll, pitch and bounce relative to the unsprung masses and the overall model is allowed to yaw and to maneuver on a horizontal plane. Tire lateral forces and self aligning torques are treated as nonlinear and are obtained from tire carpet plots. The effects of speed on lateral force and self aligning torque are assumed to be negligible, but the effect of traction is taken into account. The derivation of the mathematical model which is based on Euler's equations of motion is discussed in detail and numerical techniques are used to obtain solutions for selected inputs. This investigation shows that the average car as it leaves the factory is safe as far as braking and normal maneuvering are concerned. There are factors that do affect the safe handling of the vehicle that are at the discretion of the operator such as the velocity at which the vehicle is operated, the manner in which the vehicle is loaded, and the quality of the replacement tires. Since these factors can greatly affect vehicle safety, there is a need to educate the public in these matters.

Degree

Ph.D.

Subject Area

Automotive materials

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