Software Design Of Lithium-ion Battery Management System In Electric Vehicles

The development of vehicles bring not only convenience to our life, but also avariety of problems. The environment and energy problems put forward newrequirements for the development of automobile industry. New energy vehicles due toits advantages in many aspects has drawn much attentions, and as a field of newenergy vehicles, electric vehicles has achieved much progress in many aspects. Butthere are still many key technical issues need to be solved, battery managementsystem is one of them. This paper from the view of battery management systemsoftware design, builded the software framework of battery management system, andcarried some rearch on the battery SOC estimation. The main research work includesthe following aspects:(1) This paper puts forward using RC equivalent circuit model to simulate thevoltage response characteristics of lithium-ion battery. Using multiple linearregression method processing the experimental data of pulse discharge experimentsidentified the model parameters of RC equivalent circuit model. Considering thecharacteristic parameters of battery need to calculate with other variables, this articledefined the parameters and data formats used in the battery management system.(2) This paper applied the μC/OS II real-time operating system in the design ofupper computer software and completed the transplantation of it in the uppercomputer microcontroller MC9S12XS256. The code of transplantation was given.Based on the μC/OS II real-time operating system, the functionality of uppercomputer are diveded into different tasks, and their priority and cycle time weredefined respectively.(3) After defining the functionality of the battery management system, thebattery management system is structurally divided into upper computer and lowercomputer. And then the software design flow of upper computer and lower computerwere described. The upper computer software design is based on μC/OS II operatingsystem, the lower computer software design is based on the sequence of allfunctionality completed in a cycle. The upper computer and lower computer adoptCAN bus communicate. The data frame format of single cell battery voltage andtemperature communicated between upper computer and lower computer is definedreference the DeviceNet communication protocols. (4) Considering the adaptive kalman filter method adopts index weightingmethod calibrating noise statistical properties may easily result in sudden disturbancedivergent, this paper proposed using the fuzzy adaptive kalman filter method toimprove it. Applying the UDDS driving cycles to compare the simulation precision ofdifferent methods, the results show that the fuzzy adaptive kalman filtering methodcompared with the traditional kalman filtering method has higher SOC estimationaccuracy.