Vehicle Dynamics Simulation for setting up a Four-Wheel Independent Drive Electric Race Car
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This thesis covers aspects of parameterization of a four wheel independent drive electric race car, with help of the vehicle modelling tool CarMaker combined with Matlab/Simulink. Detailed descriptions of suspension, tires and brakes are introduced, and a model of the aerodynamics is developed to capture the effects of change in aerodynamic performance in dynamic situations. Two application cases are explored, namely mechanical setup of a race car and structural analysis based on vehicle dynamics simulation. By simulating typical conditions experienced with the vehicle, great insight is attained into component life, especially valuable for fatigue assessment. It is shown that numerical vehicle dynamics simulation can be used to determine the effect of highly transient and dynamic situations, which are difficult to represent by analytical means. Correlation between quasi-static calculations and dynamic simulations for steady-state maneuvers is demonstrated. But in situations which involve rapid changes in vehicle speed, as during maximum braking, the quasi-static calculations used here do not capture the large change in aerodynamic forces before load transfer fully occurs, and by that deviate from the dynamic simulation. Analysis shows that steady-state balance is affected by aerodynamic characteristics already from low speed, as aggressive aerodynamic elements are used. Overall suspension stiffness is determined to be most significant for chassis movements, while transient cornering response show little change due to overall light weight of the car and high damping levels present. It is demonstrated that a four-wheel independent drive race car will benefit from a setup which is neutral, and biased towards understeer if perfectly neutral is not achieved. An overall goal of providing a better understanding of vehicle performance and laying the groundwork for an effective testing season and successful competitions is achieved.