Design and analysis of active aerodynamic control systems for increasing the safety of high-speed road vehicles

Abstract

The lateral stability and the safety of road vehicles is dependent on the vehicle design and operating conditions. Under operating conditions such as slippery roads, high lateral acceleration and tight cornering, the forces and torques due to the interactions between the tire and road may be saturated. Various active safety systems have been proposed and developed to mitigate these concerns but they all work based on the manipulation of tire forces. Thus, the capability of the current active safety systems cannot go beyond the performance limitation determined by the interactions between the tire and road. On the other hand, at high speeds, significant downforce can be generated by employing aerodynamic wings on the vehicle body to enhance its road holding ability. A split rear wing is proposed to control the aerodynamics of high-speed road vehicles to closely manipulate the dynamics of the vehicle. A nonlinear vehicle model is derived to simulate the vehicle’s lateral dynamics and an airfoil with a high lift to drag ratio is used to design the rear wing. A sliding mode control technique is used to design the active aerodynamic controller to achieve the objective of tracking the desired steady-state yaw rate. The selection of the control technique and the control objective is shown to be comprehensive and satisfactorily improve the handling performance. The controller design is validated using co-simulation implemented in the combined CarSim-MATLAB/Simulink simulation environment. Simulation results demonstrate that active aerodynamic control improves the lateral stability of the vehicle and that the improvement is more pronounced as the vehicle forward speed increases. The enhancement in lateral performance and road holding capability is also presented.