间隙在飞行器折叠舵面中普遍存在且不易准确描述,通过辨识方法获得间隙的真实非线性特性具有重要意义。基于直接参数估计方法建立基础激励下含间隙非线性系统辨识模型,利用相对速度和相对位移的多项式表征非线性系统的恢复力;引入显著因子剔除多项式中影响度较低的基函数,采用最小二乘求解得出恢复力多项式中各项系数,由不同自由度之间的相对关系组装出整个系统的辨识模型;通过比较基于辨识模型的系统响应和实测系统响应之间的均方误差来评价辨识精度。基础激励下含间隙三自由度结构系统数值算例的辨识结果表明:含间隙非线性系统的恢复力可通过增加刚度立方项进行准确逼近;选取折叠舵面上两处测点分别在无间隙和有间隙的工况下进行辨识,辨识所得运动方程均能较好地描述两测点的动力学特性,对含间隙折叠舵面非线性系统的离散化建模与动力学分析具有重要工程意义。
Abstract
Freeplay nonlinearity is ubiquitous in folding rudders of flight vehicles, which is difficult to be accurately described.It is necessary to obtain the real nonlinear characteristics of freeplays by using system identification methods.The identified model of the nonlinear system with freeplays under base excitation was first built using direct parameter estimation.Nonlinear restoring force was expressed by polynomials of relative velocity and displacement.A significance factor was defined to determine whether a term is an important part of the identified model, and the coefficients of the polynomials were solved by the least squares method.Finally, the completed system model can be obtained based on the relationship between different degrees of freedom, and the identification accuracy can be validated via the mean-square error between the estimated and measured responses.Identification results of a three degree of freedom numerical example demonstrate that the restoring force of a nonlinear system with freeplays can be accurately approximated by adding cubic stiffness.Furthermore, the dynamic characteristics of two measuring points on the folding rudder can be well described by the identified model, which is of importance to discretization modeling and dynamic analysis of folding rudders with freeplays.
关键词
折叠舵面 /
基础激励 /
间隙非线性 /
系统辨识
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Key words
folding rudders /
base excitation /
freeplay nonlinearity /
system identification
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脚注
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