Extended Smooth Orthogonal Decomposition for Modal Analysis

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Zhi-Xiang Hu ◽  
Xiao Huang ◽  
Yixian Wang ◽  
Feiyu Wang
Keyword(s):  
Modal Analysis ◽  
Degrees Of Freedom ◽  
Eigenvalue Problems ◽  
Search Algorithm ◽  
Damping Ratio ◽  
Orthogonal Decomposition ◽  
Vibration System ◽  
Output Only ◽  
Damped Systems ◽  
Smooth Orthogonal Decomposition

The smooth orthogonal decomposition (SOD) is an output-only modal analysis method, which has simple structure and gives good results for undamped or lightly damped vibration systems. In the present study, the SOD method is extended to incorporate various measurements that contain the displacement, the velocity, the acceleration, and even the jerk (derivation of the acceleration). Several generalized eigenvalue problems (EVPs) are put forward considering different measurement combinations, and it is proved that all these EVPs can reduce to the eigenvalue problems of the undamped vibration system. These different methods are called extended smooth orthogonal decomposition (ESOD) methods in this paper. For the damped vibration system, the frequencies obtained by different ESOD methods are different from each other. Thus, a cost function is defined and a search algorithm is proposed to find the optimal frequency and damping ratio that can explain these differences. Although the search algorithm is derived for the single-degree-of-freedom (SDOF) vibration systems, it is effective for the multi-degrees-of-freedom (MDOF) vibration system after assuming that the smooth orthogonal coordinates (SOCs) computed by the ESOD methods are approximate to the modal coordinate responses. In order to verify the ESOD methods and the search algorithm, simulations are carried out and the results indicate that all ESOD methods reach correct results for undamped vibration systems and the search algorithm can give accurate frequency and damping ratio for damped systems. In addition, the effects of measurement noises are considered and the results show that the proposed method has anti-noise property to some extent.

Output-Only Modal Analysis of an Internal Unreachable Module Embedded in a Space Electronic Equipment

2012 ◽  
Author(s):  
Lassaad Ben Fekih ◽  
Georges Kouroussis ◽  
David Wattiaux ◽  
Olivier Verlinden ◽  
Christophe De Fruytier
Keyword(s):  
Finite Element ◽  
Modal Analysis ◽  
Degrees Of Freedom ◽  
Transverse Direction ◽  
Mode Shapes ◽  
Fe Model ◽  
Fe Method ◽  
Numeric Model ◽  
Stiffness Matrices ◽  
Output Only

An approach is proposed to identify the modal properties of a subsystem made up of an arbitrary chosen inner module of embedded space equipment. An experimental modal analysis was carried out along the equipment transverse direction with references taken onto its outer housing. In parallel, a numerical model using the finite element (FE) method was developed to correlate with the measured results. A static Guyan reduction has led to a set of master degrees of freedom in which the experimental mode shapes were expanded. An updating technique consisting in minimizing the dynamic residual induced by the FE model and the measurements has been investigated. A last verification has consisted in solving the numeric model composed of the new mass and stiffness matrices obtained by means of a minimization of the error in the constitutive equation method.

scholarly journals ESTIMATION OF STRUCTURAL DYNAMICS OF A MODEL BOOM OF DRAGLINE DRE-23 BY OUTPUT-ONLY SYSTEM IDENTIFICATION METHODS

2011 ◽  
Author(s):  
Zakir Faruquee ◽  
Hal Gurgenci
Keyword(s):  
System Identification ◽  
Modal Analysis ◽  
Damping Ratio ◽  
Canonical Variate ◽  
Identification Methods ◽  
Analysis Methods ◽  
Electrodynamic Shaker ◽  
Simulated Field ◽  
Output Only ◽  
Frequency Domain Decomposition

Two output -only system identification methods namely Canonical Variate Analysis (CVA) and Frequency Domain Decomposition (FDD) were used to estimate the dynamics (Mode shape, natural frequency and damping ratio) of the model boom of the dragline DRE 23. The boom was excited separately with an impulse hammer and with an electrodynamic shaker with chirp, random and simulated field excitations. In all cases, the excitations as well as the responses of the model boom were measured. The dynamics were obtained from the response measurements using Output-Only methods as well as from both the excitations and responses using conventional modal analysis methods. In all cases, the estimations of the dynamics by Output-Only methods were comparable if not better than those estimates obtained by the convention modal analysis methods.

Macromodeling Method of Fluid-Structure Interacting MEMS Based on Modal Analysis and Proper Orthogonal Decomposition

2007 ◽  
Author(s):  
Wentao Hao ◽  
Ling Tian ◽  
Bingshu Tong
Keyword(s):  
Proper Orthogonal Decomposition ◽  
Modal Analysis ◽  
Degrees Of Freedom ◽  
Orthogonal Decomposition ◽  
Mems Devices ◽  
High Complexity ◽  
Fluid Structure ◽  
Fluid Field ◽  
Speed Up ◽  
Proper Orthogonal

Because of their good performance to speed up MEMS system simulation processes, macromodels have aroused lots of attentions of scientists in the last decades. However, studies on FSI (Fluid-Structure Interaction) MEMS devices still can not satisfy the macromodeling requests because of the high complexity of fluid fields. A new method based on modal analysis and POD (Proper Orthogonal Decomposition) is tentatively put forward to reduce the order of FSI MEMS models. The structure macromodeling theory is firstly reviewed. Then the fluid field macromodeling approach is discussed in detail. At last, a 2D fixed-fixed micro-beam is analyzed and the results show that the macromodel extracted in this method can highly decrease the system degrees of freedom, while its precision is still comparable with that of detailed models.

Modal Analysis With Smooth Karhunen-Loe`ve Decomposition

2009 ◽  
Author(s):  
S. Bellizzi ◽  
Rubens Sampaio
Keyword(s):  
Random Field ◽  
Modal Analysis ◽  
Covariance Matrix ◽  
Random Fields ◽  
Time Derivative ◽  
Normal Modes ◽  
Orthogonal Decomposition ◽  
White Noise Excitation ◽  
Smooth Orthogonal Decomposition ◽  
Vibrating Systems

In this paper, the Smooth Orthogonal Decomposition is formulated in term of a Smooth Karhunen-Loe`ve Decomposition (SKLD) to analyze random fields. The SKLD is obtained solving a generalized eigenproblem defined from the covariance matrix of the random field and the covariance matrix of the associated time derivative random field. The main properties of the SKLD are described and compared to the classical Karhunen-Loe`ve decomposition. The SKLD is then applied to the responses of randomly excited vibrating systems with a view to performing modal analysis. The associated SKLD characteristics are interpreted in case of linear vibrating systems subjected to white noise excitation in terms of normal modes. Discrete and continuous mechanical systems are considered in this study.

The Model Analysis of Mobile Emergency Platform Car Frame Based on ANSYS

2012 ◽  
Vol 490-495 ◽  
pp. 2961-2965 ◽  
Author(s):  
Bo Gao ◽  
Zi Ming Kou ◽  
Juan Wu
Keyword(s):  
Modal Analysis ◽  
Natural Frequency ◽  
Optimization Design ◽  
Degrees Of Freedom ◽  
Excitation Frequency ◽  
Electrical Equipment ◽  
Elastic Vibration ◽  
Equipment Failure ◽  
Vibration System ◽  
Treatment Equipment

Mobile emergency platform is the carrier of mechanical and electrical equipment. The car frame vibration would make mechanical and electrical equipment failure even damaged. Mobile emergency platform car frame can be considered as the elastic vibration system with many degrees of freedom. Modal analysis is used to analyze the car frame. It is shown that the first natural frequency is 15.153 Hz and the second natural frequency is 19.579 Hz, which is close to20 Hz that is generated by the excitation frequency . Resonance is ocuuered. Optimization design is used to design car frame.After optimization design the natural frequency of car frame avoid the excitation frequency. Emergency mobile platform is environmental emergencies emergency treatment equipment, which video and audio monitoring equipment, wireless communications equipment , sophisticated electronic equipment and instrumentation need are carried in. When transportation or work process, these equipments, especially data-receiving treatment equipment, communications data transmission control equipment, image processing service and other equipment, will be affected inevitably even be failure for the mechanical vibration of the engine and the uneven road. If the equipment is damaged, the entire mobile platform of paralysis will be occurred. Car frame of mobile emergency platform can be considered as the elastic vibration system with many degrees of freedom and vibration led directly to the equipment failure. It is necessary to make modal analysis for the car frame.

Optimal Method for Determination of Rayleigh Damping Co-efficients for Different Materials using Modal Analysis

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
B. Rahul ◽  
J. Dharani ◽  
R. Balaji
Keyword(s):  
Boundary Conditions ◽  
Dynamic Analysis ◽  
Modal Analysis ◽  
Degrees Of Freedom ◽  
Damping Ratio ◽  
Optimal Method ◽  
Multiple Degrees Of Freedom ◽  
Rayleigh Damping ◽  
Damping Matrix

Rayleigh damping co-efficients are the essential parameters to determine the damping matrix of a system in dynamic analysis. For the systems with multiple degrees of freedom, it is difficult to arrive for suitable Rayleigh damping co-efficients. This paper represents a simple and effective method for the determination of Rayleigh co-efficients α and β for the system with multiple degrees of freedom. An unrealistic constant damping ratio for all modes is assumed to get rational value of α and β, which leads the determination of progressively varying damping ratio for all modes. By comparing the damping ratio arrived from assumed α and β with assumed unrealistic damping ratio, the suitable and most precise values are determined. This method is implemented for different materials with different boundary conditions by considering different significant modes and the effect of above parameters on α and β values are also discussed.

scholarly journals Damage Identification of Structures Based on Smooth Orthogonal Decomposition and Improved Beetle Antennae Search Algorithm

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Zhixiang Hu ◽  
Peiguan Zhang
Keyword(s):  
Damage Identification ◽  
Search Algorithm ◽  
High Reliability ◽  
Fitness Function ◽  
Damage Index ◽  
Orthogonal Decomposition ◽  
Combined Application ◽  
Polynomial Fit ◽  
Combined Algorithm ◽  
Smooth Orthogonal Decomposition

A novel damage identification method that utilizes the smooth orthogonal decomposition (SOD) combined with the improved beetle antennae search algorithm (BAS) presented by previous scholars is proposed. Firstly, the damage index which can track the curvature changing of mode shape identified by the SOD method is generated by an adaptive polynomial fit method. The locations of structure damages are determined according to the damage index. Thus, the number of possible damaged elements needed to be taken into account can be reduced when calculating the degree of damage. Then, the reduction in the stiffness at the damage location of the structure is calculated by the improved BAS in which the fitness function is constructed by calculated frequencies of the damaged structure in each iteration and the modal frequencies obtained by SOD. The BAS algorithm is improved through a fusion strategy of simulated annealing theory. Thus, the improved BAS algorithm is efficient and adaptive. The effect of this combined application in damage identification has been verified by numerical examples of a simply supported beam with single damage and a cantilever beam with double damage. The numerical results show that this combined algorithm exhibits high reliability in damage identification of beam-like structures.

The scientific bases of autocontrol with vibration phase for a resonance beating-vibration system with two degrees of freedom driven by debalances

1996 ◽  
Vol 18 (2) ◽  
pp. 43-48
Author(s):  
Tran Van Tuan ◽  
Do Sanh ◽  
Luu Duc Thach
Keyword(s):  
Degrees Of Freedom ◽  
Regulation System ◽  
Vibration System ◽  
Two Degrees Of Freedom ◽  
System Operating

In the paper it is introduced a method for studying dynamics of beating-vibrators by means of digital calculation with the help of the machine in accordance with the needs by the helps of an available auto regulation system operating with high reability.

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