基于模糊PID的UEGO传感器控制方法研究

Research on Control Method of UEGO Sensor Based on Fuzzy PID

摘要:

宽域废气氧传感器具有较宽的空燃比测量范围,广泛地应用于稀燃发动机空燃比控制系统;UEGO传感器需要配套控制器才能正常工作,通过控制传感器的温度和泵电流,实现空燃比的测量；然而,UEGO传感器温度具有非线性,泵电流参数存在摄动,给其控制带来了困难;为了缩短冷启动时间,采用斜坡加热与模糊PI相结合的分段温度控制策略,以克服温度的非线性和冷启动的加热限制；采用基于OE模型的系统辨识法,建立不同工况下的泵电流模型,据此采用模糊PID的控制方法提高泵电流的控制精度与响应速度,克服泵电流参数不确定性的影响,从而提高传感器的动态性能;在空气环境和混合气配气平台上进行实验,结果表明:UEGO传感器冷启动时间少于20 s,温度控制精度较高,泵电流调节时间为191 ms,动态响应速度快、抗干扰能力强。

Abstract:

Universal Exhaust Gas Oxygen (UEGO) sensor has a wide range of air-fuel ratio measurement, is widely used in air-fuel ratio control system of the lean burn engine. The UEGO sensor should work with the controller. The air-fuel ratio can be measured by controlling temperature and pump current.However, the temperature of the UEGO sensor is nonlinear and the pump current parameter is perturbed, which bring difficulties to the control. In order to shorten the start-up time, segmented temperature control strategy combining slope heating with fuzzy PI is adopted to overcome the temperature non-linearity and the heating limitation during the start-up.OE model based system identification method is used for establishing the pump current model under different operating conditions, and the fuzzy PID control method is used to improve the control accuracy and response speed of the pump current, so as to overcome the influence of the uncertainty of the pump current parameters and thus improve the dynamic performance of the sensor.The results show that the start-up time of UEGO sensor is less than 20 s, and the temperature control precision is high. The pump current regulation time is 191 ms, and the dynamic response is fast with strong anti-interference ability.