【作者】 任好；

【导师】 徐科军；

【作者基本信息】 合肥工业大学 ， 检测与自动化装置， 2005， 硕士

【摘要】 为了提高发动机工作效率,我们需要建立发动机的模型,而传感器在发动机运行中起着极为重要的作用,因此,我们研究发动机相关传感器的动态特性。它们分别是热膜(线)式空气质量流量传感器、进气歧管绝对压力传感器和废气氧传感器。 热膜(线)式空气质量流量传感器存在动态非线性问题。本文采用基于多幅值阶跃信号的Hammerstein模型和两步辨识方法描述传感器特性。通过动态标定实验,得到不同幅值的阶跃输入、输出数据。根据其幅值,用最小二乘拟合的方法辨识出非线性系数,并由输入数据和非线性系数得到静态非线性环节的输出。再根据输出数据,运用线性自回归方法得到动态线性环节的传递函数,这样就建立起块联形式的动态非线性模型。建模结果表明,动态非线性模型比线性模型更为准确地描述了热膜(线)式空气质量流量传感器的动态特性。 进气歧管绝对压力传感器为线性传感器,所以,我们直接使用最小二乘法对输入输出数据进行辨识,建立其动态线性模型。 废气氧传感器存在系统的动态非线性问题,由于实验条件有限,我们只在一个输入点上进行了负阶跃实验。通过分析数据得到了氧传感器上升时间等参数,为下一步工作打下了基础。更多还原

【Abstract】 In order to improve the work efficiency of the engine, we need to set up the model of the engine. The sensors play a very important part in the engine operation. So we must study the dynamic characteristics of engine related sensors which are the hot film/ wire type of mass air flow sensor, the manifold absolutely pressure sensor and the exhaust gas oxygen sensor.The hot film/ wire type of mass air flow sensor has the nonlinear dynamic characteristics. In order to describe the sensor characteristics the Hammerstein model is adopted, which is based on the multi-amplitude step responses, and the two-step identifying method is utilized in this thesis. Through the dynamic calibration experiments, the step input and output signals with different amplitudes are obtained. Using the amplitudes of these data, the nonlinear static coefficients are determined by the least square method. Moreover, based on input data and nonlinear static coefficient, the output of nonlinear static subsystem is calculated. Furthermore, according to output data, the transfer function of linear dynamic subsystem is identified by the linear regression method. The sensor nonlinear dynamic models in the block format are established. The modeling results show that the nonlinear dynamic models are more accurate than the linear dynamic models to describe the sensor characteristics.As the manifold absolutely pressure sensor possessed the linear dynamic characteristics, the model coefficients are determined by the least square method directly.The nonlinear dynamic characteristics also exist in the exhaust gas oxygen sensor. We only have got the negative step response under one test condition because there are limitations in the experimental equipment. Though analyzing the output data, we have got the sensor rise time and other parameters, which lays the foundation for the further work.更多还原