readme.txt

hilbert时频识别（力学领域）Michael feldman编写（自由振动、强迫振动）

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