Aerodynamic forces that act on a vehicle play a critical role in impacting the vehicle longitudinal dynamics, particularly stopping distance and time during vehicle braking. Currently, many vehicles use a rear spoiler to enhance the vehicle aerodynamic performance. In vehicles equipped with an active rear spoiler, a mechanism is used to control the spoiler angle of attack, based on various inputs and parameters. This article investigates the impact of an active rear spoiler, with a variable angle of attack, on both the vehicle aerodynamic forces and longitudinal braking dynamics, such as braking stopping distance and time. A two-dimensional (2D) computational fluid dynamics (CFD) model, using ANSYS-Fluent®, is employed to estimate the impact of the angle of attack of the rear spoiler on the vehicle aerodynamic forces (lift and drag forces) for comparison with a vehicle lacking a spoiler. Furthermore, the CFD results are used as inputs in a realistic vehicle braking mathematical model to estimate the vehicle stopping distance and time at different spoiler angles of attack, and the obtained results are compared to the case of the vehicle that is not equipped with a spoiler. The proposed vehicle model, which includes the vehicle aerodynamic forces, is simulated using MATLAB/Simulink®. The simulation results demonstrate that the vehicle rear spoiler has a clear impact on the vehicle braking distance and time, especially at high vehicle speeds. Based on the simulation results, novel 2D maps, which relate the vehicle stopping distance and time to the angle of attack of the vehicle rear spoiler, are presented. These maps can be used as a good basis for estimating the optimal spoiler angle of attack for vehicle braking at different initial speeds and, hence, can provide significant help in the design of an optimal braking system controller for the vehicle.
Longitudinal Dynamics of a Vehicle Equipped with an Active Rear Spoiler
Sae Int. J. Passeng. Veh. Syst
Sae International Journal of Passenger Vehicle Systems ; 15 , 3 ; 183-194
01.07.2022
12 pages
Aufsatz (Konferenz)
Englisch
Impact of Rear Spoiler on Vehicle Braking Longitudinal Dynamics
SAE Technical Papers | 2021
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