【作者】 张进；

【导师】 徐科军；

【作者基本信息】 合肥工业大学 ， 控制理论与控制工程， 2007， 硕士

【摘要】 为了提高发动机空燃比控制的质量,必须研究空燃比控制相关传感器的动态性能,建立准确的动态模型。本论文主要研究空燃比控制中的两种关键传感器:热膜式空气质量流量传感器和宽带型废气氧传感器的动态性能。热膜式空气质量流量传感器存在动态非线性问题,必须建立动态非线性模型。为此,进行了传感器静、动态实验,采用静动态分离的方法建立了Hammerstein和Wiener两种动态非线性块联模型,以准确地描述热膜式空气质量流量传感器的动态非线性特性。热膜式空气质量流量传感器的响应速度在某些工况下不能满足控制要求,自身的非线性也会影响控制精度。为此,设计了Hammerstein和Wiener形式的动态校正器,并采用dSPACE系统实现,取得了较好的仿真和实验结果。为了研究宽带型氧传感器的动态特性,设计了基于发动机台架的易于实现的宽带型氧传感器阶跃响应实验方案,并进行了多种排气温度、多输入幅值情况下的动态实验。通过对实验数据的分析和处理,得出了辨识模型所需的输入和输出数据,采用基于预测误差的方法,建立了适合各种工作情况的氧传感器动态模型,得出了时域性能指标。宽带型废气氧传感器必需配有相应的控制器才能使用,控制器的性能直接影响传感器的性能。设计了基于dSPACE平台的宽带型废气氧传感器控制器,用ControlDesk软件开发了测量和控制单元,整定了控制单元的参数。更多还原

【Abstract】 It is necessary to study the dynamic characteristics of sensors related to engines and establish their accurate dynamic models so as to improve the quality of the engine air-fuel ratio (AFR) control. Two kinds of key sensors, hot-film mass air flow (MAF) sensor and universal exhaust oxygen gas sensor, for the AFR control are fully studied in this paper.The non-linear dynamic model of the hot film MAF sensor must be built because the sensor possesses the nonlinear dynamic characteristics. The sensor static and dynamic experiments were conducted, and two kinds of nonlinear dynamic block-oriented models are built in Hammerstein and Wiener forms with the method of static-dynamic characteristic separation. The models can describe the non-linear dynamic characteristics of the sensor accurately.The response time of the hot-film MAF sensor can not meet the control requirements under certain conditions, and the nonlinearity will affect the control precision. In order to solve the problems the dynamic correctors were designed in Hammerstein and Wiener forms. A dynamic corrector was developed with dSPACE system, and its validity was verified by the results of simulation and experiment.A step response experimental scheme of the universal exhaust oxygen gas sensor was designed based on an automobile engine testing bench in order to identify the dynamic performance. The dynamic experiments were carried out in different exhaust temperatures and lambda values. Through analyzing and processing the experiment data, the proper input-output data were obtained for modeling. The prediction error method (PEM) was adopted to build the sensor dynamic model that adapts different operating conditions, and the performance indexes were obtained in time domain.The universal exhaust oxygen gas sensor cannot operate without a special controller. The controller will affect the performance of the sensor to a great extent. A controller was designed based on dSPACE system. Its measuring and controlling modules were developed by the software - ControlDesk. The parameters of the controlling module were tuned.更多还原