Traction Control System development for an AWD hybrid vehicle

The purpose of this thesis work is to design a Traction Control System algorithm for an all-wheel-drive hybrid vehicle. Generally, the control aim is to prevent the driven wheels from spinning, in order to guarantee vehicle stability, especially on slippery roads. In this specific case, the control logic has to be also adapted for three vehicle driving modes: Comfort, Wet and Sport. First of all, the 14-degrees-of-freedom vehicle model is implemented on the VI-CarRealTime software and its overall dynamic performances are evaluated. The vehicle object of this study is a high performance one, equipped with two independent electric motors on front wheels and an internal combustion engine on rear axle. The control structure is developed on MATLAB-Simulink environment: starting from setting general control aims, the differences among the three driving modes are established. The controller acts on the vehicle powertrain, reducing motors and engine output torques in case of wheels excessive rotation. Proportional-Integral (PI) controllers are adopted for torques regulation. The three Traction Control modes performances are at first assessed through off-line tests, which consist in co-simulations of VI-CarRealTime and MATLAB-Simulink environments. The passive vehicle and the controlled one are compared on different scenarios to verify the effectiveness of control action: a straight-line maximum acceleration manoeuvre is performed on different road conditions, including constant mu-split, variable mu-split, low friction surfaces. The same set of scenarios is used also to analyse the differences between the proposed control and an internal VI-CarRealTime one. Tests’ results show how all the designed control achieves its task, enhancing vehicle stability and acceleration performance. Finally, on-line tests of acceleration manoeuvres are performed: vehicle model and control are implemented on a dynamic driving simulator. During tests executions the subjective feedbacks of the driver are collected, in order to evaluate how the control activation affects driver perception of the vehicle dynamic behaviour.