Method of tuning a vibration absorber
View Patent ↗A method of tuning a vibration absorber on a driving frequency, in which the absorber includes a damper block secured to a support having one end fixedly mounted in an orifice, includes the steps of: a measurement step for estimating the offset between the tuned frequency of the absorber and the driving frequency in order to produce a reference value; and an adjustment step of adjusting at least one adjustment value of the absorber to the reference value.
1. A method of tuning a vibration absorber to a reference driving frequency, said absorber comprising a damper block secured to a support having one end mounted in fixed manner in a structure, the method comprising:
a measurement step for estimating the offset between the tuned frequency of said absorber and the driving frequency so as to produce a reference value; and
an adjustment step for adjusting at least one adjustment value of said absorber to said reference value;
wherein said measurement step comprises:
establishing an estimated transfer function for said absorber over a frequency band extending on either side of said driving frequency, on the basis of a first series of measurements of the acceleration at the mount in the structure, and on the basis of a second series of measurements of acceleration at said damper block;
defining a theoretical transfer function for said absorber, which function is parameterized by said tuned frequency;
minimizing the difference between said estimated transfer function and theoretical transfer function in order to obtain said tuned frequency; and
defining said reference value by means of said tuned frequency.
2. A method according to claim 1 , wherein the definition of said reference value by means of said tuned frequency is performed by means of a model having one degree of freedom.
3. A method according to claim 1 , in which the structure is the structure of a helicopter.
4. A method according to claim 1 , in which, in order to calculate the estimated transfer function on the basis of the acceleration measurements, use is made of Hanning weighting.
5. A method according to claim 1 , in which, in order to adjust the resonant absorber, the block is moved along the blade to a required position corresponding to the reference value, and the block is locked in said position.
6. A method according to claim 1 , in which, in order to adjust the absorber, the mass of the block is modified.
7. A method according to claim 6 , in which, in order to modify the mass of block, the number of washers secured to the block is increased or decreased.
8. A device for adjusting a vibration absorber, the device comprising means for implementing the method according to claim 1 .