Method for in-flight assessment of freedom from flutter of an airplane

摘要

A computer-implemented method for in-flight assessment of freedom from flutter of an airplane, involving analyzing the airplane structure vibrations based on signals indicated by sensors located on the airplane structure. The computations are performed in real-time based on current measurement data collected from the sensors. For measurement data from individual sensors there are determined mode shapes of vibrations. The relevancy of modes of vibrations is determined by subtracting from the vibrations signal the particular mode of vibrations and calculating the value of decrease in the rest sum of squares.

主权项

1. A measurement system for in-flight assessment of freedom from flutter of an airplane, the system comprising:
a plurality of vibration sensors located on a wing of the airplane, with two vibration sensors per selected wing chord, the vibration sensors for measuring finite duration non-stationary flutter vibrations signals; and signal processing circuits for processing the finite duration non-stationary flutter vibrations signals from the plurality of vibration sensors, the signal processing circuits configured to:
analyze airplane structure vibrations based on the finite duration non-stationary flutter vibrations signals measured by the vibration sensors;perform computations of the airplane structure vibrations in real-time based on current measurements from the vibration sensors;determine, for a plurality of mode shapes of each of the finite duration non-stationary flutter vibrations signals, a natural frequency (f), a damping coefficient (ζ), a phase (φ) and an amplitude (A) for each mode shape by using a method of least squares of errors of time signals based on measurements from the vibration sensors;determine a significance of the determined mock shapes of each of the finite duration non-stationary flutter vibrations signals by subtracting from the finite duration non-stationary flutter vibrations signal the determined mode shapes, and calculating a value of decrease in a residual sum of squares; andevaluate the airplane structure vibrations by analyzing estimates of an autocorrelation function Ryy(l) for operational finite duration non-stationary flutter vibrations signals, by computing the autocorrelation function Ryy(l) by multiplying a constant number of samples of the finite duration non-stationary flutter vibrations signal (yn) by successive segments of the finite duration non-stationary flutter vibrations signal (yn), the finite duration non-stationary flutter vibrations signal having a size of N samples, and by summing results according to an equation:Ryy⁡(l)=1N/2⁢∑n=1N/2⁢yn·yn+ln=1,2,3,…⁢,Nl=0,1,2,…⁢,N/2 to obtain the autocorrelation function Ryy(l) having a length of a half of the evaluated segment of the finite duration non-stationary flutter vibrations signal (yn) while maintaining the values of the damping coefficients (ζ) of the finite duration non-stationary flutter vibrations signals.