一种基于比例反馈控制原理的动载荷时域反演方法

通过借鉴系统控制论中的比例反馈控制原理,提出了一种新的结构动载荷时域反演方法.该方法在原开环系统的输出与结构模型之间连接一个虚拟的比例反馈增益,使得原来的开环系统成为一个虚拟的闭环反馈控制系统,系统控制信号为实测的结构加速度响应.反馈控制器将系统输出与控制信号之闻的差值进行放大后作为反馈不断输入到结构模型中,直到差值趋于稳定,此时该差值与反馈增益的乘积经过高通滤波后即得到所反演的动态载荷.该方法将载荷反演问题的求解转化为正问题中的结构瞬态响应求解,采用一般的数值解法如New-mark法即可实现,因此计算比较简便迅速.该方法仅需要测量结构的加速度响应即可进行反演,便于实际应用,而且并不十分依赖于真实的初始条件,由于不存在误差累积的现象,反演结果具有较好的稳定性.最后,通过海洋平台结构冰载荷反演的模型实验和数值仿真证明了该方法的有效性.

A dynamic load identification method in time domain based on proportional feedback control principle

A new dynamic load identification method in time domain is proposed based on proportional feedback control principle.In the approach the original open-loop dynamic system is changed into a virtual closed-loop feedback control system by connecting a virtual proportional feedback gain between the output and the structural model.The measured structural acceleration response is selected as the control signal of the virtual closed-loop system,and it is always compared with the output in the controller.The control error is amplified by the feedback gain and input into the control system as feedback until it converges or runs stable.Then the product of the error and the feedback gain that goes through high pass filter is the dynamic load signal to be identified.The method changes the inverse problem into the corresponding direct problem,namely solving structural transient response,for which many widely-used numerical algorithms can be employed,e.g.Newmark method,so its calculation is simple and fast.Moreover,the method is quite convenient for engineering application in that only structural acceleration response is necessary and the exact initial condition is no longer indispensable in the calculation.Because the identification error does not cumulate during the calculation,the stability of the identified result can also be strong.Finally,the effectiveness of the method is proved by the model test and numerical simulation of ice load identification of an offshore platform structure.