Analysis and integration of One Pedal Drive strategy in a Mild-Hybrid vehicle.

Vehicle hybridization allows for better performances and reduced tailpipe emissions at the cost of a more complex architecture, this is the starting point of the thesis work that analyses the software impact transitioning from a conventional Internal Combustion Engine (ICE) vehicle to a hybrid vehicle with a focus on the new torque path structure, which represents the flow of signals connecting the driver’s demand, in terms of accelerator pedal engagement, to the final torque quantity delivered by the ICE and Electric Motor (EM). Mild Hybrid Electric Vehicles (MHEV) operate in Charge Sustaining (CS) mode to keep the State of Charge (SoC) of the High-Voltage battery between two threshold values in every operating condition thanks to the regenerative braking feature that allows for battery recharging by means of conversion of kinetic energy in electrical energy using the bi-directional possibilities of the EM. The mechanism allowing for regenerative braking in the P0 hybrid architecture with automatic transmission under study is the “One Pedal Drive” strategy that enables the driver to request both positive torque, for traction, and negative torque, for regeneration, by modulation of the accelerator pedal depending on the driving condition, the brake pedal is used just for friction braking. The pedal-based regeneration mechanism is studied starting from a mathematical description of the control strategy, highlighting problems and proposed solutions to allow for correct regeneration while avoiding the degradation of the mechanical components in the powertrain and engine stall. After the strategy description, analysis of the software implementation in the Engine Control Unit (ECU) is carried out at a functional level, providing a description of every subsystem composing the One Pedal Drive software module with analysis of real ECU signals involved during test maneuvers. Finally, the virtual validation activity is carried out using a co-simulation environment, in which the hybrid powertrain plant is defined in GT-Suite and the One Pedal Drive control strategy is defined in MATLAB/Simulink, to assess the effectiveness of the strategy under WLTC and NEDC driving cycles and foot-pedal activity of the driver for both conventional vehicle and Mild Hybrid vehicle. The co-simulation environment is modified and improved for correct integration of the embedded control strategy under study, leading to fast and cheap assessment of the performance of the One Pedal Drive using different calibration datasets and under different driving cycles with enhanced possibility of assessing control choice impact on emissions with a reduced dependency on vehicle or HIL laboratories, allowing for reduced costs and time for development.