氧传感器响应变慢自适应空燃比闭环控制方法研究

Study on Adaptive Air-Fuel Ratio Close Loop Control Algorithm for Oxygen Sensor Slow Response

分析了汽油发动机空燃比闭环PI控制器的数学模型,提出了自适应空燃比闭环控制算法,研究了阶跃型氧传感器响应变慢对汽油机空燃比和排放的影响。研究结果表明:当氧传感器信号从稀到浓变慢时,过量空气系数相对于正常值会减小,同时HC和CO排放浓度会增大;当氧传感器信号从浓到稀变慢时,过量空气系数相对于正常值会增大,同时氨氧化物(NOx)排放浓度会增大。试验结果表明:设计的自适应空燃比PI控制器减小了在氧传感器响应变慢时过量空气系数偏离正常值的幅度,能够减少有害气体排放。

The impact of the oxygen sensor slow response on air-fuel ratio and emissions in SI engines was analysed, and a discrete, adaptive correction PI air-fuel ratio control algorithm for oxygen sensor slow response was presented. For the upstream oxygen sensor slow response to lean to rich mixture, the air-fuel ratio would reduce with an increase in HC and CO emissions, and for the upstream oxygen sensor slow response to rich to lean mixture, the air-fuel ratio would increase with an increase in NOx emissions. The adaptive correction PI control system is then tested, and the results show that the new designed adaptive PI controller could reduce air-fuel ratio deviation from normal value, thus reducing the harmful emissions.