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In this paper, a real time simulator of the engine-generator for a series hybrid electric bus is designed which can be used for hardware in the loop testing of the hybrid bus control unit. As an important step for designing a hardware in the loop simulator, messages that the engine and generator receive from the vehicle control unit are identified. Design of the simulator is based on these received messages and dynamic behavior of the components. Since the engine and generator receive speed or torque commands from the vehicle control unit, two PID controllers are designed to bring the engine or generator to the desired speed. By applying appropriate inputs, different modes of operation of the diesel-generator is simulated including the soft start process and steady state operation. For a simulator, the ability to interface with a real hardware requires a real time simulation. To do so, the design process is implemented in LabVIEW environment and results show that the designed simulator gives responses close to real test results and it is suitable for developing the hybrid vehicle control unit.

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Due to the complexity in the control system of hybrid vehicles, the electronic control units should go through extensive testing before getting installed in a prototype vehicle. In the first stages of the development process, Hardware-in-the-Loop (HiL) simulation can not be performed because the hardware components of the vehicle are not yet available. In this case, Model-in-the-loop (MiL) simulation is used which couples the designed control software with an environment simulation with no need for a special hardware. In this paper, the MiL simulation is introduced for verification of the vehicle control software in a series hybrid electric bus. To do so, considering the dynamic behavior of various components of the vehicle, a simulator of the hybrid bus is designed by going through with the input/outputs of the vehicle control software. Using the designed test bench, the user can act as a real driver and experience different driving regimes and analyze the control software commands. In the designed simulator, all subsystems are simulated separately in LabVIEW environment and real-time simulation is achieved with an acceptable error. Therefore, it can be used in a HiL test bench for testing each of the vehicle components. The designed simulation model has been validated using real test results. Using that, results show that all control functions in the vehicle control software can be tested and verified with no cost and in the shortest possible time.