Asymmetric vehicle performance assessment using GG diagrams

Abstract

In closed-circuit racing such as NASCAR, vehicles often travel on highly-banked oval tracks that are dominated by left-hand corners. The aim of this paper is to study the generation and interpretation of the associated asymmetric GG diagrams and performance metrics. These include GG diagrams on inclined and/or cambered planar road surfaces, and GG diagrams on curved surfaces such as the interior face of an inverted cone. It is shown that a general fixed point on a traditional GG diagram is associated with acceleration or braking along a logarithmic spiral. Under pure acceleration and braking this spiral becomes a straight line, while under constant-speed cornering it becomes a circle. Some of these ideas are developed using a single-track car model. The paper then addresses the calculation and interpretation of GG-diagrams and performance metrics for a Generation 7 (Gen-7) NASCAR on curved road surfaces. The car's stability and performance limits under extreme lateral acceleration conditions are of particular interest. The main results come from a high-fidelity vehicle model and a representative set of parameters.