The Influences of Structure Parameters on BKX-IPKM’s Modal
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After FEA models of BKX -Ⅰparallel kinematic machine and its substructures are constructed ,whichbased on ANSYS, detailed modal analysis of them are made. Via processing detailed modal analysis re-sults, the disciplinarian influences of structure parameters on the modal of PKM are confirmed and thekey parts and unsubstantial components which influence the PKM'modal are got. So, it affords reliablereferences and supports for the 6 -UPS PKMstructure design and farther dynamical analysis.Cite
Based on synthesis modal technique,a method of extracting modal parameters of constrained structure from free modal test data is researched on.A steel plate experiment is conducted in ordor to prove the extracting method.The normal mode spectrum matrix constituted of low order frequencies of the structure can be derived from the free test data,while the normal mode shapes and the extra high order modes can be obtained through FEM analysis.The boundary constrains are equivalent as a kind of sub-structure,and the modal synthesis is used to extract the constrained modal parameters.Experiment results are consistent with numeric calculation results,so the extracting method is feasible.
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Matrix (chemical analysis)
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The substructural modal parameters of NF 125 motor are successfully obtained by employing transfer function modal analysis in frequency domain,based on real and complex modal test results.Furthermore,the whole structural dynamic equations are established.
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The FEA model of body-in-white of an independent development passenger car is established,and the body's structure is simplified with ensuring mechanics characteristics of body structure. Modal frequency and modal characteristics of each steps of body-in-white are obtained through the free modal analysis of this FEA model,and they are compared with the result of the experimental result to evaluate the body's dynamic characteristic.
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Taking car's body-in-white as subject,this paper analyzes the vibration of the body-in-white based on the experimental modal analysis method.The modal parameters such as the mode frequency,damp and shape of the frame are identified by using random signal.The results of the finite element modal analysis are compared with that of test,then comments are offered on the dynamic characteristics of the car's body-in-white.
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The lower orders natural frequencies, modes of vibration and damper rates can be obtained, and the unsubstantial parts of the machine are made sure, based on the experimental modal and sensitivity analysis of the 6-DOF Parallel platform. This paper takes the parallel kinematic machine BKX-I as an example, the methods about the experimental modal analysis and sensitivity analysis are studied, some measures about how to improve the dynamic characteristics of the machine are put forward, which provides useful methods for the dynamical design and the optimal dynamic design of the machine structure.
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In this paper,the FEM model of a car's body-in-white is created with Hypermesh FEM software.Through the free modal analysis of this FEA model,different-order modal frequency and modal characteristics of body-in-white is computed.The modal analysis results and frequency characteristics of vehicle's excitation are compared and analyzed,and will supply the reference standard for dynamic design and revision.
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Modal Analysis has become a well known tool to derive the mode shapes of existing machine structures. In this paper, it will be shown that modal parameters derived from modal testing can be used to investigate the effect of potential design changes on a test structure. The method described here uses the fact that transfer functions given by the modal parameters can be written as rational functions. Considering a desired modification we can build the rational transfer functions of the modified structure. Then, the modal parameters are calculated again by partial fraction expansion, that means without processing the frequency responses numerically. The method is realized for mass, stiffness and damping modifications. It can be extended to coupling of substructures. Furthermore, an example of a mass modification of an existing structure is presented in the paper.
Mode (computer interface)
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This study explores the method of extracting modal parameters of constrained structure from test data. The normal mode spectrum matrix constituted of low order frequencies of the structure can be derived from the free test data, while the normal mode shapes and the extra high order modes can be obtained through FEM analysis; The boundary constrains are equivalent as a kind of sub-structure, and the modal synthesis is used to extract the constrained modal parameters. Experiment and simulation are conducted and the results show that the extraction method based on the modal synthesis and which combines the experiment model and the analytical model is feasible.
Modal matrix
Mode (computer interface)
Matrix (chemical analysis)
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The dynamic characteristics of light-weighted structure are more important due to its flexible property. In this paper, the experiment of modal analysis for Motorman-HP20 robot is carried out. The method of one location for response and multi-locations for excitation are applied in the experiment. The orthogonal polynomials curve fitting method is used for modal parameters identification. The first six order modal parameters are obtained. The results show that the structure of L-shape arm may be re-designed due to the modal shapes due to severe vibration of L-shape arm in modal frequencies of some prior orders and the poor base frequency.
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