The singular value decomposition of the measured frequency response function matrix, as a very effective tool of experimental modal analysis is used over the last twenty-five years. The complex mode indication functio...
详细信息
The singular value decomposition of the measured frequency response function matrix, as a very effective tool of experimental modal analysis is used over the last twenty-five years. The complex mode indication function has become a common numerical tool in processing experimental data. There are many references on the development of complex mode indication function including the enhanced mode indication function and its use together with the enhanced frequencyresponsefunction to form spatial domain modal parameter estimation methods. Another amendment of the enhanced mode indicator function method is the extension of the single degree-of-freedom aspects of the complex mode indication function method to include a limited number of modes. In the paper, methods for estimation of damped eigen frequencies, modal damping and mode shapes are presented that are based on singular value decomposition of frequency response function matrix. It is shown how to obtain phase information for the complex mode indication function, in order to use the standard single degree-of-freedom modal parameter estimation methods. New aggregated frequencyresponsefunction is introduced. A least-squares approximation will be presented for eliminating the error caused by frequency discretization. Analytical models and examples taken from vehicle industry are also used to demonstrate applications of the aggregated frequencyresponsefunction method and estimation of modal damping.
Traditional control strategy study of the multi-axial electro-hydraulic shaking table(MAEHST) is based on linear model,ignoring the coupling and nonlinearity factors,which results in the waveform distortion and the co...
详细信息
Traditional control strategy study of the multi-axial electro-hydraulic shaking table(MAEHST) is based on linear model,ignoring the coupling and nonlinearity factors,which results in the waveform distortion and the control *** overcome these limitations,a model considering the hydraulic system nonlinearity and mechanical coupling using the software Simulink/Sim Mechanics is built.A vibration decoupling control strategy based on multiple input multiple output(MIMO) system identification is proposed to improve the waveform replication *** proposed control method applies the MIMO H1 estimator to identify frequency response function matrix(FRFM) of the system,not only considering the diagonal element,but the off-diagonal element to acquire the coupling characteristics of six degrees of freedom(DOFs) of *** then the inverse frequency response function matrix(IFRFM) is calculated using the singular value decomposition technique to obtain the drive signal combined with the reference *** experiments are carried out,and the results indicate that the MIMO vibration decoupling control strategy successfully minimizes the coupling and improve the waveform replication precision of the shaking table.
Electronic equipments in flexible slender aerospace structures are subjected to severe vibration environments during the course of flight. In order to qualify the equipment for real life environment, they are subjecte...
详细信息
Electronic equipments in flexible slender aerospace structures are subjected to severe vibration environments during the course of flight. In order to qualify the equipment for real life environment, they are subjected to vibrations levels using electrodynamic shaker tables on ground. Control sensors are placed at the critical locations and desired spectra are achieved on the electronic packages at the section level testing. During this testing, the flexible modes of the structure are ignored. In this present study, a methodology of vibration testing is described to achieve the desired spectra at the specified locations on the structure. The article discusses a frequency domain identification of the required input forces to achieve desired acceleration spectra at the specified control locations on the structure. A generalized formulation of input force identification for multiple input multiple output is presented for the vibration testing methodology. Three different configurations like single input single output, multiple input single output, and multiple input multiple output are simulated and verified with the experiments at collocated and non-collocated control sensor-exciter combinations. From the experiments, it has been observed that the desired acceleration spectra at the specified locations are achieved to a good degree of accuracy. Moreover, the efficacy of the proposed method is experimentally verified for the structure with closely spaced modes. Apart from the acceleration control, velocity control approach is also presented in this article.
暂无评论