Subjective and Objective Assessment Of Vehicle Handling Performance

The results of a research programme involving a three pronged approach to vehicle handling - involving a series of experimental measurements, subjective assessments and modelling predictions (1) - were presented at FISITA 98 in Paris. From the analysis of this extensive range of results it was concluded that although some significant areas of correlation e.g. transient step steer responses, were identified, there was still some way to go before the confidence levels such as those associated with aircraft practice could be achieved. Consequently, a subset of the results - in particular those associated with the results frequency response measurements - have been analysed using a technique proposed originally in 1990 at Mitsubishi (2). This approach is called the “Four Parameter Evaluation Method” and uses a rhombus pattern graph to plot out steady state yaw velocity gain, natural frequency of yaw velocity, damping of yaw velocity response and phase delay at 1 Hz lateral acceleration. A selection of the driver subjective ratings based on the 49 questions posed in the original work is compared with the objective results as expressed in the Four Parameter metrics. The paper identifies several areas in which subjective questions are significantly linked to each of the metrics and again highlights the potential value of frequency response data in correlating subjective and objective results.