Hybrid electric vehicles analysis and implementation of a rule-based control strategy for a lightweight commercial vehicle

The role of environmental protection is also crucial in the automotive field and the hybridization of commercial vehicles is a current trend. The thesis is made in cooperation with AMET; its purpose is to investigate the various solutions and to define and control a model of a hybrid electric lightweight commercial vehicle. The state of the art of hybrid electric vehicles is studied, classifying them according to the hybridization factor and the powertrain structure. The potentialities of each configuration are collected, and the main pros e cons are deduced. Usually, these solutions lead to improvements in terms of fuel consumption and C02 emissions with respect to conventional vehicles, by ensuring the same performances. Therefore, a reference conventional vehicle model is implemented in TruckSim. Here the vehicle is defined at the system level and is validated over the main driving cycles. Then, it is selected a parallel P2 hybrid architecture to develop the proposed hybrid electric vehicle model. All the additional components proper of the hybrid powertrain are implemented in MATLAB/Simulink. Especially, the electric machine and the battery models are defined in Simulink, using a model-based approach. A PMSM as electric machine and a Li-ion battery, modelled with the Thevenin model (or Dual Polarization), are proposed. One of the crucial points in hybrid electric vehicles is the control strategy. An accurate control algorithm is fundamental to exploit all the hybrid powertrain potentialities. In this work, a power management strategy to optimize the power flow between the power sources is proposed. It is a rule-based control strategy implemented through Stateflow charts; based on the requested power at the wheels, four different operating modes are defined. Lastly, the hybrid electric vehicle is co-simulated between Simulink and TruckSim. Compared to the conventional vehicle model, an improvement in terms of fuel consumption in the hybrid vehicle model is achieved and discussed.