Full Vehicle Model of a formula student car

Abstract

One of the important aspects in designing a formula-student vehicle is the understanding of the effects of different parameters on the vehicle’s behaviour. These sensitivities help the engineers to make design decisions and reach the objectives set forth by the team. Currently, the team uses a lap simulation which uses a point mass vehicle dynamics model and thus most of the effects are not covered. This lap simulation allows to map the top-level concept of the car. However, for design of different components a full-car simulation is required that is similar to the actual vehicle.

In this Master’s thesis, a full-car vehicle dynamics model is developed in the Simulink environment. The chassis model is developed using a multibody approach where the different components are modelled as rigid bodies and constrained using multibody joints. The model uses torque and steering inputs and provides outputs similar to the sensors mounted on the actual vehicle. There are two models proposed for the tyre behaviour. Firstly, the tyres are tested for steady state conditions to obtain the parameters of the basic magic formula. A thermal model for the temperature of the tyres is then proposed to obtain the tread, carcass and inflation gas temperatures. The magic formula is then extended to include the effects of temperature on the force producing capability of the tyres to achieve higher accuracy in the simulations.

A very important part of this thesis concerns the model validation. In order to ensure that the vehicle dynamics model behaves like a real car; manoeuvres performed in the dynamic events of formula student competitions were used. The skidpad and a lap of endurance event was chosen to simulate steady-state and transient behaviour of the vehicle. Moreover, the model has been tuned in an attempt to match the actual data when performing the same predefined manoeuvres. The last part of the report includes the conclusions on the model and recommendations for future work.