Design And Reliability Study Of Battery Management System For Hybrid Electric Vehicles Based On Functional Safety

As the energy crisis and environmental pollution problems are increasing,energy saving and environmental protection become a new goal of the automobile industry development.New energy vehicles,which can be driven by diversified configuration of energy,has attracted widespread attention and has been greatly developed with its low emissions and low noise advantages.For new energy vehicles,regardless of electric vehicles or hybrid vehicles,power battery and its application technology is still very critical technology.Battery management system,short for BMS,is of great significance for improving the battery charge and discharge performance,extending battery life and improving the reliability of the system.At present,the application of the electrical devices,electronic devices and programmable electronic devices in the field of automotive control area is becoming more and more widely used,but some new safety issues in automotive electronic continue to occur.As dangerous incidents happens frequently,functional safety has attracted worldwide attentions from the government,customers and major car companies.At the end of 2011,the automotive industry officially released ISO26262 road vehicle functional safety standards for the automotive electrical and electronic system risks,which plays an important role in ensuring the safety of automotive functional safety-related electronic system.ISO26262 international standard provides a set of clear process for the battery management system development based on functional safety to ensure that the battery management system is reliable and safe.The battery management system directly monitors and manages the entire process of battery operation,including battery charge and discharge process,battery safety protection,battery fault diagnosis and other parts.Based on ISO26262,the hazard analysis and risk assessment of the battery management system is carried out.The functional safety goals and functional safety requirements of the battery management system are analyzed and the corresponding automotive safety integrity level(ASIL)is obtained.According to the functional safety allocation and decomposition principle,the functional safety goals and functional safety requirements are assigned to the hardware and software design.The development of battery management system is guided by modularization.The hardware design uses Freescale's 16-bit embedded single-chip MC9S12GA192 as the core process unit.After the relevant modules are expanded,the functional safety related parameters in BMS are accurately detected,including the voltage,current,temperature and insulation resistance.The hardware circuit is designed redundantly combined with the functional safety mechanism.Based on the functional safety standard,the software design is completed on the basis of hardware,and the V development process is designed forwardly.The system architecture design,software module design and software unit design are completed,including voltage and current sampling software design,high voltage power supply software design and fault diagnosis module design and so on.According to the ISO26262 requirements on hardware and software design,the hardware-in-the-loop(HIL)testing platform is built.The reliability of the BMS is verified by testing the data acquisition accuracy and fault diagnosis corresponding test on the bench.