时变可展开结构的时频域系统辨识理论和方法研究

As the development of space technology, deployable structure has increasingly widened the practical range of spatial structure. It is of great significance to carry on the research on the dynamics of the deployable structure in both the theoretical study and engineering application of the spatial structure. In both the operation and deploy process of the deployable structure, its mass, stiffness and damping are usually time-varying. Besides, it is consisted of many components and connections which could cause strong nonlinear dynamic behavior. For such multi-degree-of-freedom time-varying nonlinear system, it is difficult to establish the accurate dynamic model. This project applies the parameterized time-frequency analysis to obtain the accurate instantaneous mode parameters from the output of the system. Through analytical signal method, the relationship between the obtained instantaneous mode parameters and the time-varying nonlinear characteristics of the system is established. The former includes the instantaneous mode nature frequency, mode shape and instantaneous amplitude, and the latter contains time-varying nonlinear damping and stiffness. Based on such relationship, we can reconstruct the time-varying nonlinear characteristic models for the system, such as damping ratio, backbone, restoring/damping force curve and so on. In addition, given the fact that the deployable structure is of multi-degree-of-freedom, its coupling features are identified through separating the each vibration modes. Therefore, the time-frequency domain based system identification can be realized by analyzing the above characteristic models based on the instantaneous mode parameters extracted from the system input and output. The identification performance of the proposed methods will be verified through the experiment on a test rig of the deployable structure. Through the project, the time-frequency domain system identification could provide an alternative theory and approaches for the dynamic modelling of the deployable structure. Moreover, it has great practical potential in modelling and optimization design for the complex structure.

随着宇航科技的发展，可展开结构大大拓宽了大型空间结构的应用领域，其动力学问题是大型空间技术理论研究和向工程应用转化的关键环节之一。可展开结构是典型的时变系统，连接构件多，非线性特征表现突出。对于这类多自由度时变非线性系统，为其建立准确的动力学模型较为复杂和困难。本项目采用参数化时频分析提取瞬时模态特征，并通过解析信号法获得时变非线性系统特征参数与瞬时模态特征的关系。然后，基于提取的瞬时模态特征重构系统特性表征模型，如骨架线、弹性力/阻尼力曲线等，并结合瞬时模态特征分离方法辨识多自由度系统的耦合特征，最终实现对可展开结构这一类多自由度时变非线性系统特征及参数的辨识。在理论和方法研究基础上，本项目将通过实验验证该时频域系统辨识方法的有效性。研究成果将为复杂时变系统的时频域辨识提供理论依据和方法基础，在基于实验方法的复杂结构动力学建模问题和参数优化设计等方面具有较好的应用前景。

可展开结构是典型的时变系统，连接构件多，且非线性特征表现突出。时变非线性系统应用广泛，本课题将基于参数化时频分析方法对多自由度非线性时变振动系统的时域响应进行研究分析：利用非线性与时变系统的非平稳时域响应特征与其系统时变非线性特征的量化关系，为系统响应信号的时频特征与系统模态特征建立联系，从而利用响应的时频域信息估计系统的时变非平稳特征；通过研究参数化时频分析对复杂非平稳信号的分析技术，为多自由度时变非平稳系统响应信号的时频域分析提供有效的信号描述、分量分解和特征提取方法，为复杂时变系统的时频域辨识提供理论依据和方法基础；基于提取的瞬时模态特征重构系统特性表征模型，如骨架线、弹性力/阻尼力曲线等，并结合瞬时模态特征分离方法辨识多自由度系统的耦合特征，为复杂结构动力学建模问题和参数优化设计等方面提供技术思路；通过实验验证提出的参数化时频分析方法，有效地分析复杂系统的时域响应信号，并准确地估计复杂系统的非线性特征或非线性激励，为基于实测数据的时频域分析估计系统时变非线性特征提供研究基础。