Digital Filter Tuning for Turbine Engine Torsional Mode Attenuation
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Solution Overview
Problem
Turbine engines in aircraft face challenges with torsional modes in power transmission lines, which can lead to premature wear and damage due to excited oscillations, and existing solutions require mechanical resizing or alteration of regulation logic.
Innovation Solution
A method for parameterizing a digital filter to attenuate torsional modes in power transmission lines of aircraft turbine engines, without physically resizing the engine or modifying the regulation logic, by using a low-pass digital filter integrated into the existing monitoring loop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the mechanical design is oriented so that the torsional mode is sufficiently far from the bandwidth of the monitoring loop, then the control signals are attenuated at the torsional mode frequencies, but this requires mechanical resizing or alteration of the transmission line which increases device complexity and manufacturing cost
Solution Approach 1:
The patent replaces mechanical design modifications with a digital signal processing solution. Instead of physically resizing the transmission line or altering mechanical parameters to move the torsional mode frequency away from the control bandwidth, the invention uses a digital filter applied to the control signal in the frequency domain. This substitutes a mechanical solution with an electronic/software-based approach, maintaining the original mechanical design while achieving torsional mode attenuation.
2Productivity
If the transmission line length is increased or additional components are added to meet sizing constraints, then the power transmission capability is improved, but the torsional mode frequency moves closer to the control bandwidth increasing the risk of resonance excitation
Solution Approach 1:
The patent introduces a digital filter as an intermediary element between the control device and the transmission line. This filter acts as a mediator that modifies the control signal in the frequency domain to attenuate frequencies corresponding to the torsional mode. The intermediary allows the system to maintain increased transmission line length or additional components for power transmission capability while preventing resonance excitation through frequency-selective signal modification.
3Strength
If the stiffness of the transmission line is increased to meet sizing constraints, then the mechanical strength is improved, but the torsional mode frequency shifts closer to the control bandwidth creating resonance risks
Solution Approach 1:
The patent substitutes mechanical design changes with a digital signal processing approach. Instead of adjusting transmission line stiffness to shift the torsional mode frequency away from the control bandwidth, the invention applies a digital filter to the control signal that selectively attenuates the problematic frequency range. This allows the transmission line to maintain optimal stiffness for mechanical strength while avoiding resonance through electronic frequency filtering.
Data Source
AI summary
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.