34689588.rar_michael_时频

The package includes two main Matlab programs for non-linear vibration SDOF system identification: FREEVIB and FORCEVIB. It also includes simulation examples and the demo program RUN. The identification method is based on the Hilbert transform analysis I have developed in recent years. Run the program RUN.M and use the cursor (with a mouse) for choosing "start" and "stop" points for the chosen time fragment. ***************************************************** Function FREEVIB (Free Vibration Analysis) Function FREEVIB is a signal processing M-File for Matlab 6.x It determines the instantaneous modal parameters of a linear and non-linear vibration SDOF system. [y,A,f,f0,h]=freevib(y,Fs,N,stype) Inputs: y is the vibration signal in time domain, Fs is the sampling frequency [Hz], N is the Hilbert filter order (100<=N<=240), stype is the signal type, e.g. displacement, velocity, or acceleration. Outputs: y - chosen time fragment of the initial signal, A - the signal envelope, f - the signal instantaneous frequency [Hz], f0 - the system natural frequency [Hz], h - the system damping coefficient [1/sec] y'' + 2*h*y' +(2*pi*f0)^2*y = 0 EXAMPLE: [y,A,f,f0,h]=freevib(y,1000,200,'d'); ****************************************************** Function FORCEVIB (Forced Vibration Analysis) Function FORCEVIB is signal processing M-File for Matlab 6.x and Optimization Toolbox. It determines instantaneous modal parameters of linear and non-linear vibration SDOF system under foced excitation. [y,A,f,f0,h,ph,m]=forcevib(x,y,Fs,N,stype) Inputs: x is the forced excitation, y is the vibration signal in time domain, Fs is the sampling frequency [Hz] N is the Hilbert filter order (100<=N<=240) stype is a signal type, e.g. displacement, velocity, or acceleration. Outputs: y - chosen time fragment of the initial signal, A - the signal envelope, f - the signal instantaneous frequency [Hz], f0 - the system natural frequency [Hz], h - the damping coefficient [1/sec], ph - the phase shift, m - massa. m*y'' + 2*m*h*y' + m*(2*pi*f0)^2*y = x EXAMPLE: [y,A,f,f0,h,ph,m]=forcevib(x,y,1000,200,'d'); ****************************************************** LIMITATIONS: The sampling frequency Fs has to be in the range Fs=(10-100)*f0. The length of the vector y must be more than three times the filter order N Display Resolution: 1024 x 768 � 2003 - Michael Feldman, PhD