Use of vehicle dynamics modeling to quantify race car handling behavior

The objective of this research is to compute quantitative measures of racing vehicle behavior and relate them to qualitative driver assessments. Road racing vehicle “development” has relied on driver's verbally telling their engineers how the car “feels”. Modern race cars are equipped with numerous sensors and data acquisition systems. However, raw sensor data often does not show the engineer what the driver is trying to explain. This research has extended the utility of the available data by applying Extended Kalman Filtering (EKF) to the measured sensor data to estimate the tire and aerodynamic forces acting on the vehicle along with vehicle and tire sideslip angles. It is shown that this new information relates to the driver's comments about vehicle understeer/oversteer. Developing the procedures for computing this objective measure of the vehicle behavior that correlates with the driver's subjective assessment is a necessary first step before racing vehicle handling and performance problems can be analyzed and corrected scientifically.; A model of the longitudinal and vertical dynamics of a race car is used in an EKF to estimate the aerodynamic forces acting on the vehicle. It is shown that the EKF can accurately predict the aerodynamic forces while rejecting some of the unmeasured roadway disturbances and is a significant improvement over estimating the aerodynamic downforce from the suspension force measurements alone.; A vehicle yaw/roll plane model is used in an EKF to estimate unknown tire lateral forces and chassis and tire sideslip angles. Tire lateral forces and slip angles are fundamental quantities in the study of vehicle handling dynamics, yet are not available to the race engineer using the sensor data alone. A computed value called Balance, the difference between the front and rear tire slip angles, is defined and shown to correlate with driver comments about vehicle understeer and oversteer. This allows the engineer to “see” in the data what the driver is describing. It is proposed that the Balance calculation can provide part of a common language between the driver and engineer, allowing them to discuss in a quantitative way how the vehicle should be improved.