Research On Functional Safety Of Battery Management System For Electrical Vehicle

With the continuous improvement of the market’s requirements for the functions of electric vehicles,the software and hardware systems of electric vehicles are increasingly developing towards a high degree of integration,which leads to an increasing number of safety accidents.Especially the spontaneous combustion,fire and explosion of electric vehicle power batteries that have been emerging in recent years makes the safety of electric vehicle widely concerned.With the continuous development of functional safety technology,the International Organization for Standardization issued the "Road Vehicle Functional Safety Standard ISO 26262: 2018" on the basis of the first edition in 2018,which proposes a set of strict development procedures and technical specifications for the hazards that may be caused by the fault behavior of electronic/electrical systems.By applying the development process and specification of ISO 26262:2018 to the functional development of the battery management system,this paper completes the software and hardware development and system integration of the battery management system.Mainly completed the following work:(1)According to the functional safety concept and the process and specifications of system design,starting from the project definition,HARA analysis is performed on typical hazardous events caused by the function failure of BMS.Based on the functional safety objectives and ASIL levels obtained by HARA analysis,the formulation and allocation of functional safety requirements is completed.Then,based on the principle of ASIL decomposition,the BMS main controller(ASIL D)is decomposed into the hardware architecture of "main control chip(ASIL C)+ monitoring chip(ASIL A)",and on this basis,the formulation and allocation of technical safety requirements are completed.Finally,referring to the currently widely used E-Gas monitoring concept,the three-layer monitoring software architecture including function layer,function monitoring layer and controller monitoring layer is designed.(2)Completed the design and safety analysis of the BMS master-slave board hardware system.By using the FMEDA analysis method to conduct a safety analysis on the designed BMS hardware,the hardware system architecture metrics are calculated,and the results show that the designed hardware system meets the requirements of functional safety goals.(3)According to the technical safety requirements of the system,the software safety requirements are derived,and the software design and verification of the BMS applicationlayer are completed.In the Simulink / Stateflow software development environment,the BMS application layer software development are completed,and the software scheduling system and the battery pack model for testing were built.Finally,Based on the established model visual closed-loop simulation platform,the test and verification of the software of BMS are completed,and the results show that the designed software system has a reliable safety monitoring function and meets the functional safety requirements of the established goals.(4)Integrating the BMS master and slave board to build a BMS test platform.According to the methods and specifications of software testing in functional safety standards,the failure injection method is used to test the functional realization of BMS controller system,and the results show that the developed BMS system has strong fault tolerance ability and can effectively guarantee the the accuracy and reliability of the system function realization.