Patent ID: 6348795
Filing Date: 2002-02-19
Classification: G01R

Abstract:
A method for determining a resonant frequency of a mechanical device having a first mass and at least one second mass mechanically coupled to said first mass, the method comprising the steps of:calculating operating parameters related to the resonant frequency of the mechanical device, the operating parameters comprising a frequency range of operation, a final error value, and a threshold value; providing a control signal to a voltage-controlled oscillator, wherein the frequency of an output of the voltage-controlled oscillator is responsive to the control signal, and the frequency of the output of the voltage-controlled oscillator is within the calculated frequency range of operation; phase shifting the output of the voltage-controlled oscillator; translating the phase shifted output of the voltage-controlled oscillator into an oscillatory force; applying the oscillatory force to one of the masses of the mechanical device to cause the mechanical device to respond at a frequency and amplitude; measuring said response of the mechanical device and generating a response signal representative thereof in frequency and amplitude; generating an error signal proportional to the phase difference between a signal representative of the output of the voltage-controlled oscillator and said measured response signal; adjusting the control signal to the voltage-controlled oscillator to cause the oscillatory force applied to said one mass to sweep within the calculated frequency range rendering the amplitude of the response signal to approach and exceed the calculated threshold value; and when the calculated threshold is exceeded by the amplitude of the response signal, finely adjusting the control signal to the voltage-controlled oscillator until the value of the measured error signal is equal substantially to the calculated final error value, whereupon the frequency of said response signal is the resonant frequency of the mechanical device.