Method for configuring a digital filter for attenuating a frequency associated with a torsion mode of a power transmission line of a turbine engine

Patent metadata

Field	Value
Publication number	US-12221984-B2
Application number	US-202017610486-A
Country	US
Kind code	B2
Filing date	Apr 6, 2020
Priority date	May 13, 2019
Publication date	Feb 11, 2025
Grant date	Feb 11, 2025

Abstract

A method for parameterizing a digital filter for attenuation of a torsional mode of a power transmission line of an aircraft turbine engine is disclosed. The mode is associated with a frequency in a confidence interval, the digital filter is low-pass and described by a transfer function equal to the quotient N(z)/D(z), integrated into a pre-existing monitoring loop of the turbine engine, to filter signals sampled at a frequency. The method includes: calculating zeros of N(z), so that the filter attenuates the frequency; updating the zeros of N(z), so that the gain of the filter satisfies, in the interval, a first gain template; and determining the poles of D(z), so that, in the bandwidth of the loop: the phase of the filter satisfies a phase template, and the gain of the filter satisfies a second gain template.

First claim

The invention claimed is:

1. A method for parameterizing a digital filter for the attenuation of a torsional mode of a power transmission line of an aircraft turbine engine, said mode being associated with a frequency F_T comprised in a confidence interval Ic,
the digital filter being of the low-pass type and:
comprising a z transfer function which is causal, stable and equal to a quotient N (z)/D (z), where N and D are polynomial functions, N being of degree strictly greater than 1,
intended to be integrated into a pre-existing monitoring loop of the turbine engine, so as to filter control signals generated by a control device of said loop and sampled at a frequency F_E, said loop being closed and associated with a bandwidth in which a gain of the loop is increased, in absolute value, by a value V,
said method being implemented by a parameterization device and including:
a step of calculating, as a function of the frequencies F_T and F_E, complex numbers forming zeros of N (z), so that the filter attenuates the frequency F_T,
a step of updating the zeros of N (z), so that a gain of the filter satisfies, in the confidence interval Ic, a first predetermined gain template as a function of an amplitude of the torsional mode, and
a step of determining real numbers forming poles of D (z), so that, in the bandwidth of the loop:
a phase of the filter satisfies a predetermined phase template as a function of the frequency F_E,
the gain of the filter satisfies a second predetermined gain template as a function of the value V.

2. The method according to claim 1 , wherein the step of updating the zeros of N (z) includes a sub-step of reducing the respective modules of the zeros at a predetermined pitch, the reduction sub-step being executed iteratively as long as the first amplitude template is not satisfied.

3. The method according to claim 1 , wherein the poles of D (z) are all considered equal to each other, the pole determination step including:
a sub-step of selecting a pole comprised strictly between −1 and 1,
a sub-step of translating the selected pole along a real axis and at a predetermined pitch, so as to obtain a translated pole,
said translation sub-step being executed iteratively as long as the phase template and the second gain template are not satisfied, the pole selected during an iteration corresponding to the translated pole obtained during the previous iteration.

4. The method according to claim 1 , wherein the first gain template corresponds to an increase, in the confidence interval Ic, of the value of the gain by an opposite of the amplitude of the torsional mode.

5. The method according to claim 1 , wherein the phase template corresponds to an increase in a phase shift introduced by the filter in the bandwidth of the closed loop.

6. The method according to claim 1 , wherein the degree of N (z) is equal to 2, so as to obtain, during the calculation step, zeros z_1 and z_2 according to the following formulation:
z _1=exp((2 ×i×π×F _ T )/ F _ E ) and z _2=exp((−2 ×i×π×F _ T )/ F _ E ).

7. The method according to claim 1 , wherein the degree of D (z) is equal to 3.

8. The method according to claim 1 , wherein the frequency F_T and the confidence interval Ic are determined beforehand during a series of tests on a test bench of dynamic behavior of the power transmission line.

9. The method according to claim 1 , said method including, following the step of determining real numbers forming poles of D (z), a step of validating temporal behavior of the digital filter, said validation step consisting in verifying that a temporal response of the filter to a step signal is monotonously increasing,
the pole D (z) determination step and the validation step being iterated as long as the behavior of the digital filter is not validated.

10. A monitoring system intended to be on board an aircraft including a turbine engine, said turbine engine comprising a power transmission line having a torsional mode associated with a frequency F_T comprised in a confidence interval Ic, said system including means for receiving a setpoint relating to a predetermined parameter, a control device configured to generate control signals sampled at a frequency F_E and means for measuring said parameter, said monitoring system forming a closed monitoring loop associated with a bandwidth in which the gain is increased, in absolute value, by a value V,
wherein the monitoring loop includes a digital filter parameterized by means of a method in accordance with claim 1 , said digital filter being integrated into said loop so as to filter the control signals.

11. An aircraft including a turbine engine, said turbine engine comprising a power transmission line having a torsional mode associated with a frequency F_T comprised in a confidence interval Ic, said aircraft further including a monitoring system according to claim 10 .

12. A non-transitory computer readable medium having stored thereon instructions which, when they are executed by a processor, configure said processor to implement a parameterization method according to claim 1 .

13. A device for parameterizing a digital filter, said filter being intended to attenuate a torsional mode of a power transmission line of an aircraft turbine engine, said mode being associated with a frequency F_T comprised in a confidence interval Ic,
the digital filter being of low-pass type and:
described by a z transfer function which is causal, stable and equal to a quotient N (z)/D (z), where N and D are polynomial functions, N being of degree strictly greater than 1,
intended to be integrated into a pre-existing monitoring loop of the turbine engine, so as to filter control signals generated by a control device of said loop and sampled at a frequency F_E, said loop being closed and associated with a bandwidth in which a gain of the loop is increased, in absolute value, by a value V,
said device including:
a processor configured to
calculate, as a function of the frequencies F_T and F_E, complex numbers forming zeros of N (z), so that the filter attenuates the frequency F_T,
update the zeros of N (z), so that the gain of the filter satisfies, in the confidence interval Ic, a first predetermined gain template as a function of the amplitude of the torsional mode, and
determine real numbers forming poles of D (z), so that, in the bandwidth of the loop:
the phase of the filter satisfies a predetermined phase template as a function of the frequency F_E,
the gain of the filter satisfies a second predetermined gain template as a function of the value V.

Assignees

• Safran Aircraft Engines

Inventors

• Raslain Typhaine

Classifications

• H04B3/542

  the information being in digital form · CPC title

• G05D19/02

  characterised by the use of electric means · CPC title

• G01H1/10

  of torsional vibrations · CPC title

• F05D2260/96

  Preventing, counteracting or reducing vibration or noise · CPC title

• F05D2220/329

  in helicopters · CPC title