INTRODUCTION

The term vehicle motion refers to its translation along and rotation about all three axes (i.e., longitudinal, lateral, and vertical). By the term longitudinal axis, we mean the axis that is parallel to the ground (vehicle at rest) along the length of the car. The lateral axis is orthogonal to the longitudinal axis and is also parallel to the ground (vehicle at rest). The vertical axis is orthogonal to both the longitudinal and lateral axes.

Electronic controls can automate some driver functions that were previously performed manually.

Rotations of the vehicle around these three axes correspond to angular displacement of the car body in roll, yaw, and pitch. Roll refers to angular displacement about the longitudinal axis; yaw refers to angular displacement about the vertical axis; and pitch refers to angular displacement about the lateral axis.

Electronic controls have been recently developed with the capability to regulate the motion along and about all three axes. Individual car models employ various selected combinations of these controls. This chapter discusses motion control electronics beginning with control of motion along the longitudinal axis in the form of a cruise control system.

The forces that influence vehicle motion along the longitudinal axis include the powertrain (including, in selected models, traction control), the brakes, the aerodynamic drag, and tire-rolling resistance, as well as the influence of gravity when the car is moving on a road with a nonzero inclination (or grade). In a traditional cruise control system, the tractive...