A system for non-contact measurement of mode shapes of flexible structures

Abstract

A system for non-contact measurement of the mode shape of a flexible structure, including a clamping device, an exciter, a measuring mechanism and a processor; one end of the clamping device clamping a piece to be measured is a cantilever beam; the output end of the Close to the piece to be measured; the measuring mechanism is mainly composed of a laser sensor group, a driving mechanism and a guiding mechanism; multiple laser sensors of the laser sensor group are arranged in a straight line from top to bottom along the height direction of the piece to be measured; each step of the driving mechanism, The laser sensor group moves from the current measurement point to the next measurement point; the amplitude value obtained by each laser sensor at each measurement point is input into the processor, and the processor converts the measured values ​​of each laser sensor in the laser sensor group according to the positional relationship of each measurement point. The amplitude values ​​are connected in a network to obtain the natural mode shape of the object to be measured at the excitation frequency. The invention has the advantages of high measurement accuracy and convenient use without pasting a sensor on the piece to be measured and without moving a vibration exciter.

Description

technical field [0001] The invention relates to a system for non-contact measurement of mode shapes of flexible structures. technical background [0002] Modal analysis is an important research method to study the dynamic characteristics of structures. In mechanical, automotive, aerospace, civil and other engineering fields, it is often necessary to consider the modal parameters of the structure. The dynamic parameters of the structure are determined by means of modal testing and modal analysis. A modal testing device with simple operation and high precision becomes the key to modal parameter testing. At present, the following methods are mainly used for modal testing at home and abroad: [0003] 1. Hammer impact method modal test: The energy of the hammer impact method is small, and the magnitude and direction of the impact force are not easy to control. Generally, the hammer impact method requires multiple averages to obtain more stable measurement data. There are the ...

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Problems solved by technology

[0003] 1. Hammering method modal test: The energy of the hammering method is small, and the magnitude and direction of the hammering force are not easy to control. Generally, the hammering method needs to use multiple averages to obtain more stable measurement data

There are the following difficulties in testing the modal of the structure by the hammering method: (1) It is difficult to ensure that each knocking force is the same and the knocking is at the same position

(2) The hammering method cannot directly measure the mode shape of the flexible structure

[0007] (1) The sensor is usually pasted on the structure to be tested, which brings additional mass to the structure to be tested, thereby changing the mass distribution of the structure, affecting the inherent characteristics of the structure, and causing the test results to be far from the actual;

[0008] (2) By moving the exciter, the whole process is very troublesome, and only the amplitude values ​​of a limited number of points can be measured, the measurement structure is relatively rough, and the natural mode shape of the flexible structure cannot be accurately described;

[0009] (3) It is an indirect measurement method, which cannot directly reveal the natural mode shape of the structure

[0010] In the process of shock vibration measurement, often only focus on the measurement of the bending mode, but the measurement of the torsional mode generated by the vibration cannot be detected and reflected

This poses a limitation to the modal detection, which cannot objectively and directly reflect the dynamic effect of the structure during the vibration process, and the dynamic analysis of the structure is also limited.

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