Static Stability and Control of the Automobile Utilizing the Moment Method

Some three and a half years ago the present authors described a new method for analyzing automobile stability and control (see SAE Paper No. 760712, “The Static Directional Stability and Control of the Automobile,” October 1976). The present paper is an extension of the earlier work with particular emphasis upon its application, interpretation, and general utility for evaluating automobile stability and controllability. Specific applications of the technique to production vehicles will be used for illustration. The usefulness of the method for mapping out the total maneuvering performance in the nonlinear and limit handling as well as in the linear range will be examined. Such items as off-trim operation, a maneuvering diagram, tangent speed, and the determination of the transient response from the Moment Method diagrams will be discussed, as will the possibility of developing a universal diagram based on a force/moment presentation for the vehicle. A conclusion that this method offers distinct advantages in analyzing car stability and control, including front drive problems, is reached.