Vehicle Handling Qualities

Abstract

The paper is concerned in general with quantitative methods of analysis for the general steady-state motion of an automobile and, in particular, for methods that are able to assess the non-linear characteristics of vehicles. In this context it is observed that any quantity used must satisfy three requirements; it must have a physical significance and be capable of prediction and measurement. For this purpose three basic handling concepts are considered, understeer, static margin and slip/steer gradient. Following the analysis of the perturbation motion about steady circular motion, the concepts are rationalized and related to the theoretical vehicle behaviour. In a discussion of this analysis the relationship between the three concepts are investigated and subsidiary vehicle parameters highlighted. The final stage of the quantitative method outlined is dealt with in a section on experimental procedures. Three procedures, response mapping, tethered testing and steering pad tests, are examined, and the required measurements and analysis processes needed to obtain measurements of the handling qualities are derived. Finally a typical set of experimental results from a response mapping experiment is included as an example of processes described. It is concluded that the concepts of understeer, static margin and slip/steer gradient can be successfully applied theoretically to the general non-linear cornering motion of an automobile, and that experimental techniques exist that yield measurements from which quantities defined by the theoretical analysis can be obtained, with the exception that measurement of static margin in the general non-linear motion condition is not satisfactory because of experimental problems. The tethered test technique and the steering pad test are also able to provide measures of the most important associated vehicle stability parameter.