热膜式空气质量流量传感器动态非线性建模

Nonlinear Dynamic Modeling of Hot Film Type Mass Air Flow Sensor

热膜式空气质量流量传感器响应速度较快,测量范围宽,可靠性高,广泛应用于发动机空燃比的测量。但是,这种传感器的动态非线性问题影响了进气量测量的精度。采用基于多幅值阶跃信号的Hammerstein模型和两步辨识方法描述了传感器的特性。通过动态标定实验,得到不同幅值的阶跃输入、输出数据。根据幅值,用最小二乘拟合方法确定非线性系数,由输入数据和非线性系数得到静态非线性环节的输出。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,有利于传感器动态非线性的校正。建模结果表明,动态非线性模型比线性模型可更准确地描述传感器的特性。

The hot Film type mass air flow sensor is widely used to measure the air fuel ratio of engines due to its quick response, wide range and high reliability. However the nonlinear dynamic characteristics of the sensor influence the measuring accuracy of the air flow entering engines. In order to describe the sensor characteristics the Hammerstein model which is based on the multi-amplitude step response is adopted and the two-step identifying method is used. Through the dynamic calibration experiments, the step input and output data with different amplitudes are collected. Using these amplitudes, the nonlinear static coefficients are determined by the least square method. And based on input data and nonlinear static coefficient, the output of nonlinear static subsystem is calculated. According to output data, the transfer function of linear dynamic subsystem is identified by the linear regression method. The sensor＇s nonlinear dynamic models in the block format are set up, and are suited for nonlinear dynamic correction of thesensor. The modeling results show that the nonlinear dynamic models are more accurate than the linear dynamic models to describe the characteristics of the sensor.