Hybrid car regenerative braking system reverse engineering and modelling from track testing analysis

Hybrid powertrains for vehicles have been widely developed in recent years and spread in the market with the double goal of reducing fuel consumption and improve performance. The integration of traditional internal combustion engine and electrical system can occur according to different layouts and control logics and may affect vehicle dynamics. The employment of a hybrid layout enables the possibility to recover energy while travelling thanks to the use of the electric motors as generators, thus increasing the energy available and enhancing the electric driving range of the vehicle. In this thesis work a parallel hybrid supercar has been analysed, investigating how the powertrains with which it is equipped cooperate. The layout of the vehicle is reported in the what follows, with the description of all the different modes in which the electric system and internal combustion engine can be combined. The study of the energy recovery active system has been the main focus of the thesis activity and is described in this report. Through a process of reverse engineering the logics behind the regenerative braking system have been explored starting from the analysis of the signals collected during track testing activities. For a better understanding of how tests have been performed, in the first part of this report the common layout of sensor positioning and the standard manoeuvres performed are described, with an eye on the electrical acquisition and elaboration. Focus of this thesis work has been the study of the electric traction’s components behaviour during braking manoeuvres, in order to identify their role in the energy recovery process and understand logics and limits occurring. Through the analysis of the dynamic response of the vehicle to the imposed input, a simplified model of the vehicle braking system has been developed and validated thanks to a process of co-simulation with a model of the whole vehicle already existing. Final part of this paper is dedicated to the comparison of the signals obtained through the simulation process with those collected during the track tests sessions. This process gave satisfactory results confirming the accuracy of the analysis and of the developed simulation model.