NARMAX模型在风洞流场建模过程中的应用

Application of NARMAX Model in Modeling Process of Wind Tunnel Flow Fields

为提高风洞的流场控制精度,建立了一种新的针对跨声速风洞流场的数学模型。采用NARMAX模型作为系统的模型结构,结合风洞运行的特点,将整个试验运行过程划分为3个阶段,然后分别对各阶段进行建模,并使用函数拟合的方式得到风洞模型。模型的关键参数阶次和采样间隔分别用伪最邻近点法和互信息法进行辨识,并将BP神经网络作为输入与输出之间的非线性映射函数,可得到稳定段总压和驻室静压的模型,最后通过马赫数的计算公式得到试验段马赫数的取值。仿真结果表明:该模型辨识精度高,能体现出风洞运行的特点。

In order to improve the control accuracy, this article proposed a new mathematical model of flow field. By using NARMAX model as system model structure, combining characteristics of the wind tunnel operation, divided the whole process into three independent steps, model of each step was established respectively, and the wind tunnel model was acquired by using function estimation. The order of the model and the sampling interval was identified by the pseudo nearest neighbor method and mutual information method respectively. BP neural network was used for mapping the network input to output as a nonlinear function, the total pressure in settling chamber and the static pressure in plenum chamber can be obtained by utilizing this model, and the Mach number was computed by using the Mach number calculation formula. The result shows that the model has high accuracy of system identification, and is able to embody characteristics of the operation of transonic wind tunnels.