NO_(x)传感器的氧补偿及其标定策略

Oxygen compensation of the NO_(x) sensor and its calibration strategy

针对氧化锆基氮氧化物传感器信号受汽车尾气氧含量影响,导致精度不佳问题,提出一种氧补偿算法和标定策略。根据NO_(x)传感器工作原理进行模拟试验,分析不同氧含量下泵电流I_(P2)与NO_(x)浓度的关系,得出氧补偿算法,并分析了氧含量与补偿系数的关系,设计出一种实时对I_(P2)误差补偿的方案,使I_(P2)在氧含量为0%~20%,NO_(x)为0~3 000×10^(-6)范围内的误差减小到23 nA,对应NO_(x)浓度误差降低到15×10^(-6)以内。为进一步提高传感器测量的准确度,设计了一套标定方案,并与国外NO_(x)传感器进行对比测试。结果表明,该传感器在发动机瞬态工况下,NO_(x)浓度为0~2 000×10^(-6)的环境中,测量误差为0~25×10^(-6),验证了该方案的可行性,满足尾气中NO_(x)浓度的监测要求,为提高氧化锆基NO_(x)传感器精度提供了可靠的解决方法。

An oxygen compensation algorithm and calibration strategy are proposed to address the problem that the zirconia-based NO_(x) sensor signal is affected by the oxygen content of vehicle exhaust,which may result in poor accuracy.A simulation test is conducted according to the working principle of the NO_(x) sensor,the relationship between pump current I_(P2) and NO_(x) concentration at different oxygen content is analyzed.The oxygen compensation algorithm is derived,and the relationship between oxygen content and compensation coefficient is analyzed.A real-time compensation scheme for I_(P2) error is designed.Consequently,the error of I_(P2) in the range of oxygen content from 0%~20% and NO_(x) from 0~3 000×10^(-6) is reduced to 23 nA,and the Corresponding NO_(x) concentration error is reduced to within 15×10^(-6).To further improve the accuracy of the sensor measurement,a calibration scheme is designed and tested in comparison with foreign NO_(x) sensors.The results show that the sensor has a measurement error of 0~25×10^(-6) in an environment with NO_(x) concentration of 0~2 000×10^(-6) under transient engine conditions,which verifies the feasibility of the scheme and well meets the requirements for monitoring NO_(x) concentration in the exhaust gas,and provides a reliable solution for improving the accuracy of zirconia-based NO_(x) sensors.