Simulation and Control of Auxiliary Devices in Heavy-Duty Vehicles

Abstract: For modern heavy-duty vehicles, improved fuel consumption is a necessity in order to cope with governmental demands and to stay ahead of competitors. This thesis examines how the fuel consumption can be reduced by controlling the auxiliary systems, such as the cooling system. All auxiliary systems are powered by the combustion engine and therefore reducing the power consumption of the auxiliaries would decrease the fuel consumption of the vehicle. The power consumption of the auxiliary devices is evaluated using recorded driving data for various vehicles and routes. It is shown that the consumption of the auxiliary systems depends on both vehicle and ambient variables, such as temperature and road topology. It is also concluded that controlled auxiliaries are beneficial for improved fuel consumption, but the drawback is decreased robustness. When the energy consumption of the auxiliaries is known, an optimal control problem for reducing the energy consumption of the cooling system is presented. With the road topology assumed to be known, the optimal velocity, the optimal gear choice with the possibility to use neutral gear with idling engine, as well as the optimal fan control are decided. Finally, the optimal control problem is solved for different scenarios and it is concluded that the cooling system influences both the optimal velocity and the optimal gear choice.