Design Of Battery Management System Architecture For Electric Vehicle Based On Function Safety

With years of development and technology accumulation,the electric vehicle battery management system(BMS)technology has matured as a whole,but the exploration and practice of function safety is relatively scarce.In November 2011,the International Organization for Standardization promulgated the Road Vehicle Function Safety Standard ISO262:2011 for passenger vehicles,which recommended a set of function safety development process,stipulated the work to be done in each development stage of the whole safety life cycle in order to achieve the corresponding automotive safety integrity level(ASIL),with the aim of minimizing the possibility of hazardous events in automotive electrical and electronic systems due to malfunctions.This thesis takes the pure electric vehicle battery management system as the research object,and designs a set of electric vehicle battery management system based on function safety according to the development process of automotive electronic system recommended by ISO26262:2011.This thesis focuses on the following four aspects:(1)Defined the functions,external interfaces,operating environment,possible hazards and failure modes of the electric vehicle battery management system;conducted hazard analysis and risk assessment on the system through FMEA and FTA,formulated and assigned system safety goals and corresponding ASIL;established the function safety requirements(FSR)of the system,and completed the function safety concept design of the system.(2)On the basis of conceptual design,the system is designed at the system level,hardware level and software level.According to function safety requirements,technical safety requirements(TSR)were established,the system architecture of "main system+safety system" was determined,and each subsystem was designed in detail to complete the system design;hardware safety requirements were derived according to technical safety requirements(HSR),determined the overall hardware architecture,detailed design of each module of the hardware circuit,specifically designed the fault diagnosis and redundancy for the safety-related hardware circuit,completed the hardware design;and exported the software safety requirements(SSR)according to the technical safety requirements,finished software architecture design and software unit design,program flow chart design of safety-related software unit,completed software design.(3)Based on the completion of the system architecture design,evaluate the safety integrity level of the designed system.The focus is on the ASIL of the system hardware by calculating the single point fault metric and the latent fault metric.The calculations show that the hardware of the designed system has reached the design goal with the safety integrity level of ASIL C.(4)System implementation and test verification of the design.The BMS prototype was produced,and the system was tested with basic functions and fault injection based on function safety.The test results show that the measurement accuracy of the system is good,the CAN communication is normal,and it has good diagnosis and recognition ability for high voltage relay adhesion,over temperature,over voltage and other faults that may cause harm,which can effectively avoid the event that violates the safety goals.