Influence of a reconfigurable wheelbase on lateral vehicle dynamics

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Abstract

This thesis describes the concept of a reconfigurable wheelbase for a car as a way to improve agility at higher velocities. Altering the longitudinal position of each wheel with respect to the centre of gravity, leads to a change in lateral wheel forces. This affects the car's yaw rate, therefore making it possible to influence its agility. Available literature has shown that this subject is still quite weakly investigated, which makes it an interesting topic of research. To investigate this influence of actively reconfiguring the wheelbase, simulations were done using IPG Carmaker together with MATLAB/Simulink, during which a simplified vehicle model of a Toyota Camry was used. A proportional derivative controller combined with control allocation was designed to regulate the reconfigurable wheelbase system. It features a reference generator that returns a desired yaw rate and activation logic which ensures that the controller is only activated in a velocity range of 60 km/h to 110 km/h and when a steering input is given. Furthermore, a benchmark study is designed, using a fuzzy logic controller that is based on a simplified version of one presented by Soltani et al. (2017). This controller uses the same reference generator and activation logic for consistency. The rules and membership functions of the fuzzy logic block are adopted from the mentioned paper. The performance of both these controllers and a baseline vehicle without any control, are evaluated for a step steer manoeuvre, an increasing circle manoeuvre and a double lane change, at different velocities and/or steering amplitudes. Based on the results of these tests, it is shown that both controllers are able to influence the lateral dynamics positively during most of these manoeuvres and are therefore able to improve the vehicle's agility in the velocity range in which the controller is active.

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