The Test Design And System Identification For SMA Structure Vibration In Spacecraft

In this paper,the shape memory alloy cantilever beam structure used in spacecraft is taken as the research object.The sine sweep test and random vibration test are designed under the different thermal environment based on "GJB 5020-2003: temperature,humidity,vibration test equipment calibration method".The acceleration data of the sample are collected by the sensor and transform to displacement response by using the Simpson formula.The sample resonance frequency peak shifts to low frequency and amplitude decreases with the increase of the excitation magnitude,which reflects the nonlinear dynamics system.Based on the Hilbert-Huang algorithm,the low-frequency modal function of the sample under the algorithm is drawn through numerical calculations by MATLAB.The change of resonant frequency near 16 Hz with time is analyzed.Getting conclusion of the resonant frequency decreases with the increase of temperature by comparing the different temperature of sample amplitude-frequency curve.Based on the theory of one-dimensional continuous wavelet transform based on Complex Morlet wavelet basis,the real time-frequency chromatogram is drawn through MATLAB numerical calculation,which to analysis the variation of unstable frequency band with time and temperature.The conclusion that the frequency of resonant peak decreases with the increase of temperature is obtained.The comparisons of the first three order resonance frequency in different temperature using Hilbert-Huang and wavelet transform theory are made.It shows that the unstable zone tends to be uniform,and get the conclusion: the shape memory alloy cantilever resonant frequency decreases with the increase of temperature.This conclusion can be used to guide the design of shape memory alloy components.It is of great significance to avoid the failure as resonance when taking full consideration of the influence: resonant frequency of the components changes with the working temperature.