A lot of electric components have been installed in a vehicle today for comfort, safety and environment. This tendency is said to be continued in the future. Therefore, additional power supplies such as exhaust gas electricity generation system and thermal electricity generation system have been developed in the world to supply additional electricity as well as an enlargement of an alternator. However, if these new electricity supply systems are installed in a present electric power system that is controlled based on a voltage feedback, each supply system cannot be controlled effectively, because it is difficult to control output power of each system independently. An electric power based control system, Vehicle Electric power Flow management system (VEF), has been developed to avoid this problem.
Sum of required electric power is calculated based on electric loads power and battery charging power. This required power is allocated to each power supply system. This assignment is performed according to an index, a running cost of electricity. This index is called DENPI (Design of Electric Network with Power Index). For example, DENPI of the alternator changes according to an engine torque, a rotational speed and efficiency. Therefore, electric power system can supply electricity more effectively by selecting power system according to DENP. VEF automatically allocates each power supply system according to DENPI of each power supply system. As this function has a unique structure, it can be extensively applied to new electricity generation systems in various categories of vehicles.
VEF has been evaluated with a test vehicle, and the results show that this structure is applicable to a real vehicle and the running cost of electricity is improved 30% compared to a conventional system.