Patent ID: 7426447

Claim:
A method for monitoring damage to a structure having an actuator and a sensor, the method comprising: exciting the actuator across a predetermined frequency range to excite the structure; measuring a vibrational characteristic of the structure across the predetermined frequency range in response to the excitation of the actuator using the sensor; calculating a transfer function for the sensor using the measured vibrational characteristic; determining a change in the vibrational characteristic across the predetermined frequency range using the transfer function; and analyzing the determined change in the vibrational characteristic across the predetermined frequency range to facilitate determining whether the structure is damaged, wherein analyzing the determined change includes: determining an amount of nonlinearity in the determined change using: Shift(Freq)=(Coef 1 ×Freq 2 )+(Coef 2 ×Freq)+Coef 3 ; and comparing the amount of nonlinearity to a predetermined threshold.