Control strategy optimization of Toyota Mirai based fuel cell hybrid electric vehicles.

Ecological problems concerning air pollution and climate change force people to use alternative energy sources for the transportation sector. Therefore, strict limitations are set for automotive manufacturers concerning the exhaust gases, which become stringent year by year. Implementation of hydrogen instead of fossil fuels for the propulsion of vehicles is the solution to have zero noxious and greenhouse gas emissions, which provides relatively high energy density combined with the water as the only exhaust gas. This paper represents the detailed description and derivation of a Toyota Mirai (1st generation) based fuel cell hybrid vehicle model and its components for the purpose of analysis of the hydrogen consumption, change of the state of charge of battery and the variation of other parameters. In the first part, the introduction to fuel cell technology and its application in transportation sector is provided. Then, fuel cell hybrid electric vehicle mathematical model, which consist of several subsystems is derived and described. These subsystems are drive cycle, vehicle longitudinal dynamics, transmission system, electric machine, energy management system, battery, boost converter and fuel cell system model. The analysis on each subsystem is performed and the governing transfer functions are derived taking into account both traction and regeneration modes. In the second part, the model is simulated in Matlab® Simulink environment and validated using the experimental data obtained from open source ANL (Argonne National Laboratory) database. Finally, the principle of equivalent consumption minimization strategy is explained and implemented in Toyota Mirai control strategy for the purpose of investigation hydrogen consumption change depending on different control strategies. Overall 3 control strategies were used: Experimental control strategy (fuzzy logic controller), Toyota Mirai manually reconstructed control strategy for the simulation purpose (rule based controller) and equivalent consumption minimization strategy implemented control logic. Finally, all these controller are tested in Toyota Mirai (1st generation) vehicle and the values of hydrogen consumption are summarized in proper tables for comparison purposes.