Aircraft Rotor Damage Detection via Actuator Control Signatures
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Solution Overview
Problem
Active vibration reduction systems in aircraft mask changes in rotor harmonic vibrations, making it difficult for existing Health and Usage Monitoring Systems to detect damage to main and/or tail rotors, as they reduce vibrations to low amplitudes and eliminate characteristic phases, complicating the detection of manufacturing tolerances and environmental influences.
Innovation Solution
A method involving actuator control variables determined during reference flight operations to create a reference signature, which is compared to flight-specific signatures to detect deviations indicative of rotor damage, using adjustable trim tabs and control rods to reduce vibrations and record manipulated variables in a coordinate system for data analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active vibration reduction systems are used to reduce rotor vibrations, then vibration amplitudes are reduced and comfort is improved, but damage detection capability deteriorates because the systems mask vibration changes caused by rotor damage
Solution Approach 1:
The patent uses actuator control variables as an intermediary parameter to detect rotor damage. Instead of directly measuring vibrations (which are masked by active reduction systems), the method monitors the control signals sent to actuators, which must work harder to maintain vibration reduction when damage occurs. This intermediary measurement approach allows damage detection while the active vibration reduction system remains operational.
Solution Approach 2:
The method implements feedback by continuously comparing actual actuator control variables against reference values obtained during undamaged flight operations. When deviations exceed thresholds, the system generates damage warnings. This feedback mechanism enables real-time damage detection without requiring the active vibration reduction system to be disabled.
2Measurement precision
If active vibration reduction systems operate to eliminate characteristic vibration phases, then vibration comfort is improved, but measurement precision for damage detection deteriorates because characteristic phases are no longer present
Solution Approach 1:
The patent inverts the measurement approach by not measuring vibrations directly, but rather measuring the control effort required to maintain vibration reduction. When rotor damage occurs, the actuators must adjust their control variables to compensate for changed vibration characteristics, and these control adjustments serve as the detection signal, effectively detecting damage through the 'other way round'.
Solution Approach 2:
The method replaces mechanical vibration measurement with electrical signal analysis. Instead of analyzing mechanical vibration phases with sensors, the system analyzes electrical control signals sent to actuators, substituting a mechanical measurement problem with an electrical signal processing solution that is not affected by the active vibration reduction system's masking effect.
3Measurement precision
If reference patterns are created for damage detection, then damage detection accuracy is improved, but device complexity increases due to the need to store and compare multiple reference patterns for different flight conditions
Solution Approach 1:
The patent implements dynamic reference pattern selection based on current flight conditions. Instead of storing and comparing against all possible reference patterns simultaneously, the system dynamically selects the appropriate reference pattern matching the current flight state (hover, forward flight, backward flight, etc.). This dynamic approach maintains high detection accuracy while reducing the active comparison workload and system complexity.
Solution Approach 2:
The method changes the parameter space by using normalized actuator control variables and grouping flight conditions into discrete categories. This parameter transformation allows the system to manage reference pattern complexity by organizing data into manageable flight condition groups, reducing the computational burden of comparison while maintaining detection accuracy across diverse operating conditions.
Data Source
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AI summary
The invention relates to a method for detecting damage to a rotor of an aircraft, wherein the aircraft has actuators for actively reducing vibration, the method comprising the steps: determining actuator manipulated variables in a reference flight mode of the aircraft; presenting the determined actuator manipulated variables in the reference flight mode of the aircraft in the form of coordinates of a coordinate system, wherein the coordinate system has a multiplicity of data range tiles; acquiring the number of actuator manipulated variables in the reference flight mode of the aircraft which are arranged in each data range tile; eliminating the data range tiles whose number of actuator manipulated variables in the reference flight mode of the aircraft is below a limiting value, as result of which a reference flight signature is produced; determining actuator manipulated variables for a flight-specific signature; presenting the determined actuator manipulated variables in the flight mode of the aircraft in the form of coordinates of a coordinate system, wherein the coordinate system has a multiplicity of data range tiles, wherein the data range tiles of the flight-specific signature are formed so as to be identical to the data range tiles of the reference flight signature; acquiring the number of actuator manipulated variables in the flight mode of the aircraft which are arranged in each data range tile; eliminating the data range tiles whose number of actuator manipulated variables in the flight mode of the aircraft is below a limiting value, as a result of which a flight-specific signature is produced; comparing the respective data range tiles of the flight-specific signature and of the reference flight signature, wherein, when a limiting value for the number of deviating data range tiles between the flight specific signature and the reference flight signature is exceeded, a warning signal for detection of damage is output.