基于CAN总线的高精度程控电阻器设计

Design of High Precision Programmable Resistor Based on CAN Bus

在电动汽车电池管理系统(BMS)的开发设计过程中,硬件在环(HIL)测试是基于开发和测试的V模式流程中必不可少的环节。通常情况下,在HIL环境中,为了准确模拟实际电池的温度变化,BMS需要高精度的电阻器模拟实际负温度系数(NTC)温度传感器的输出阻抗变换。针对这一问题,设计了一种基于CAN总线的高精度程控电阻器。为提升程控电阻阻值输出精度,给出了一种基于开关网络的程控电阻器改进拓扑结构。介绍了各电阻阻值的选取原则,并提出了基于称重比较算法的开关网络选择方法。借助飞思卡尔单片机及CAN总线接口,设计了基于LabVIEW的程控电阻实时控制上位机软件。试验测试数据表明:该电阻器可在6 MΩ内连续可调,当阻值小于100Ω,将绝对误差控制在1Ω以内;当阻值大于100Ω,相对误差可控制在0.05%以内,满足测试需求。该电阻器可以实现电阻并行控制输出以及在大量程内连续高精度输出,且为硬件在环测试提供了高效的工具设备。该系统可满足电动汽车自动化测试的要求。

In development and design of the battery management system（ BMS） of electric vehicle,the hardware in the loop（ HIL） test is an essential part of the V mode process based on development and test. Normally,in the HIL test environment,for accurately simulating the actual temperature change of the battery,the high-precision resistor is needed to simulate the resistance-temperature characteristics of the NTC temperature sensor. Aiming at this issue,the high precision programmable resistor based on CAN bus is designed. In order to enhance the accuracy of the output resistance of programmable resistor,an improved topological structure based on switching network for programmable resistor is proposed,and the selection principle of the resistance value of each resistor is given,and the switching network selection method based on weighing comparison algorithm is put forward. With help of Freescale single chip computer and CAN bus interface,the host computer software based on Lab VIEW for controlling the programmable resistor in real time is designed. Experimental data show that the resistor can be continuously adjusted in 6 MΩ,and the absolute error can be controlled in 1 Ω within 100 Ω,and the relative error can be controlled in 0. 05% above 100 Ω,which meets the test requirements. The resistor can implement parallel control output and continuous high precision output in large range,it provides an efficient tool and equipment for HIL test. This system can meet the requirements of automatic test for electric vehicle.