mohammad javad esfandyari

The battery pack is one of the main components in electric vehicles which is usually composed of many cells connected in series. Battery state of charge estimation is one of the most important functions of the battery management system in electric vehicles. Due to the different manufacturing and operational conditions, all of the cells in a battery pack do not have the same states of charge and therefore, the cell and pack states of charge are not the same. This paper presents a method for battery pack state of charge estimation which benefits rather low computational cost as well as the high precision. First, the coulomb counting method and the open circuit voltage graph, which is obtained from the experimental results, are used simultaneously to estimate the pack average state of charge. Then, the extended Kalman filter method is used to estimate the difference between the pack average state of charge with those of the cells. The proposed method has been evaluated and verified using an experimental test bench for three series-connected lithium cells. Experimental test results indicate good performance of the proposed method in estimating the lithium battery pack state of charge.

This paper presents a method for maintaining the battery safe operating voltage region in a hybrid electric vehicle. Using the instantaneous value for the battery voltage in the proposed method, the traction motor maximum torque is limited through an interaction between the BMS and vehicle control unit. Unlike the methods based on battery State of Power (SoP) estimation in which the battery safe operation cannot be guaranteed because of the model-based nature, performance of the proposed method does not rely on the precision of battery modelling and can be used in different life conditions for the battery. In addition, due to low computational costs, the proposed algorithm can be easily implemented on the BMS. Performance of the designed algorithm has been evaluated in a Hardware-in-the-Loop (HiL) test bench for a series hybrid electric bus and compared with the results of SoP estimation based methods. Results indicate the improvement towards maintaining the safe operating voltage region in various life conditions for the battery.

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.

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.