Gear Shifting Optimization Strategy for CO2 Reduction in 48 V Hybrid P0 Architecture

The battle against global warming and air pollution drive the legislation framework to push on more strict regulations. Nevertheless, OEMs must not refrain from facing those challenges, following increasingly ambitious targets in terms of efficiency, performances and costs. What is proposed in this work is the set-up of a gear shifting strategy that allow to fulfill the driver request, also in real driving conditions, and at the same time obtain a fuel economy improvement. As a matter of fact, with a gear shifting it is possible to operate a load point shifting, both for combustion engine and electric machine, and let the machines work in more efficient load points. After a brief survey of the state of art of the 48 V hybrid features and of the driving regulations, an outline on the simulation environment is supplied. The forward model of the vehicle and driver behavior is implemented in AMEsim while the control model has been developed with MATLAB Simulink. Hence, the control model will be presented and the gear shifting optimization strategy is explained. It consists of the implementation of two main set of laws: one for traction phase and one for breaking phase. While in traction phase, it is possible to perform a gear shifting, for a given power demand at the wheels, in a point where the combustion engine is more efficient, and so decreasing the fuel consumption. While in braking phase, enhancing the regenerative braking reducing all the losses sources will lead to a greater value of the electrical energy recovered. Thereby, a set of analysis and results is provided, checking the effectiveness of the strategy and the drivability both in the WLTP cycle and in the real driving conditions. In the end, and outlook of the possible applications, which are not limited only on the CO2 reduction, is provided. Significant results are obtained, considering that the model can be implemented in real time for serial production.