基于虚拟变形法的移动质量识别方法研究

Moving mass identification based on virtual distortion method

在车-桥耦合系统的移动质量(荷载)识别反问题中,识别移动质量会面临重构系统、优化缓慢的问题;而若直接识别移动荷载常常会遇到病态问题且对噪音敏感。针对这些缺陷,根据虚拟变形法(VDM)的结构快速重分析思想,提出移动动态影响矩阵,实现利用较少的传感器即可快速而准确地识别移动质量(荷载)。以移动质量为优化变量,避免了识别荷载常遇到的病态问题,对噪音鲁棒性强;且需要传感器信息少。每步优化中,利用移动动态影响矩阵,无需时时重构车-桥耦合系统的时变系统参数矩阵,优化效率高。VDM方法的思想是将实际结构的响应计算转化为初始结构模型在相同外荷载作用下的响应,与在结构模型发生改变的位置施加相关的虚拟变形或虚拟力引起的响应的线性叠加。通过简支梁模型和框架梁模型验证了该方法的可行性和有效性,即使在5%的噪声影响下,利用一个传感器就可以很好地识别多个移动质量。

In the inverse analysis of vehicle-bridge coupled system,moving mass（load） identification is a crucial problem.However it is difficult to perform because that moving mass identification usually needs the construction of the variant system matrix which causes the huge computational work and makes the optimization rather slow,and that moving load identification is a well known ill-conditioned problem,which is very sensitivity to noise.Aiming at improving these deficiencies,this paper presents a fast and accurate method to identify moving mass based on Virtual Distortion Method（VDM）,of which the basic concept is： the response of the modified structure equals to the response of an intact structure subjected to the same external load and to certain virtual distortions which model the changes of the actual structure.The measured structural response is used to identify the moving mass;unknown mass are taken as the optimization variables instead of the usually chosen moving mass-equivalent force.In this way well-conditioning of the identification is ensured and the number of the necessary sensors is decreased.The numerical costs are considerably reduced by using the introduced concept of the moving dynamic influence matrix.Numerical experiments of a beam and a frame with 5% measurement error demonstrate that moving masses can be identified using fewer sensors.