Rotor Vibration Reduction via Normalized Adjustment Optimization
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Solution Overview
Problem
Current methods for reducing vibrations in helicopter rotors, such as rotor trimming and mechanical balancing, face challenges in accurately determining the interdependence of adjustments and often require cumbersome optical tracking, which may not fully diagnose and correct uneven air loads and mass imbalances, leading to incomplete specification of motion and ambiguity in vibration data interpretation.
Innovation Solution
A system that determines adjustment normalization values for different types of rotor adjustments, applies coefficient of vibration data to measured vibrations, and uses FFT to select optimal adjustments in the frequency domain, minimizing the total amount of adjustment required to reduce vibrations, while considering the risks associated with each adjustment type.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If trial and error methods of rotor trimming are used, then adjustments can be made to reduce vibrations, but the interdependence of adjustments causes difficulty and may require repetitive adjustments that do not converge to an acceptable state
Solution Approach 1:
The patent transforms the adjustment process from trial-and-error to a calculated parameter optimization problem. It defines an objective function that quantifies vibration levels and uses gradient descent to systematically adjust parameters (blade pitch, hub weights, etc.) toward the optimal state, ensuring convergence rather than repetitive trial-and-error adjustments.
Solution Approach 2:
The system implements feedback by measuring actual vibration levels during flight, comparing them to the objective function, and using this information to guide subsequent adjustments. The vibration sensors provide real-time feedback that allows the system to iteratively refine adjustments until the objective function is minimized.
2Measurement precision
If optical tracking methods are used to balance rotors, then blade track can be made identical, but bulky equipment is required, considerable flight time is needed, and perfect aerodynamic trim cannot always be achieved
Solution Approach 1:
The patent replaces optical tracking systems with a mechanical vibration measurement approach. Instead of using bulky optical equipment to directly measure blade track, it uses vibration sensors to measure the effects of track deviations and infers the necessary adjustments, eliminating the need for optical systems and reducing flight time requirements.
Solution Approach 2:
The system uses vibration measurements as an intermediary to indirectly assess blade track quality. Rather than directly measuring blade position with optical systems, it measures vibration caused by track deviations and uses this intermediate data to determine the adjustments needed to achieve perfect trim.
3Ease of manufacture
If single accelerometer and shaft-phase reference sensor are used for mechanical balancing, then mass imbalance can be corrected, but uneven air loads cannot be fully diagnosed and corrected
Solution Approach 1:
The patent makes the vibration measurement system universal by designing it to detect multiple types of anomalies (mass imbalance, uneven air loads, aerodynamic faults) using the same sensor array. The multi-channel vibration sensors can distinguish between different anomaly types through signal analysis, allowing a single system to perform multiple diagnostic functions.
4Productivity
If known rotor smoothing systems process vibration data, then vibration analysis can be performed, but inherent ambiguity exists in interpreting signatures because the number of channels processed is inadequate to fully separate translational and rotational acceleration components
Solution Approach 1:
The patent resolves the ambiguity by adding dimensional capacity to the measurement system. It uses multiple vibration sensors arranged in three-dimensional space, allowing it to separately resolve translational and rotational acceleration components that single-channel systems cannot distinguish. This dimensional expansion eliminates the information loss and interpretation ambiguity.
Data Source
AI summary
Determining adjustments to decrease vibrations caused by rotating blades from a plurality of rotors includes determining a first plurality of adjustment normalization values for a plurality of possible adjustments of blades of a first one of the plurality of rotors, where the first plurality of adjustment normalization values normalizes different types of adjustments having different units, determining a second plurality of adjustment normalization values for a plurality of possible adjustments of blades of a second one of the plurality of rotors, where the second plurality of adjustment normalization values normalizes different types of adjustments having different units and where, for a particular adjustment type, an adjustment normalization value of the first plurality of adjustment normalization values is independent of a corresponding adjustment normalization value of the second plurality of adjustment normalization values for the particular adjustment type, providing coefficient of vibration data that corresponds to effects on vibration caused by adjustments to the blades, receiving a plurality of vibration values corresponding to vibrations caused by the blades, applying the coefficient of vibration data and the first and second plurality of adjustment normalization values to the vibration values to provide a set of total normalized vibration values corresponding to sets of possible adjustments to be applied to the blades, and selecting a set of adjustments having a total normalized vibration value less than a predetermined value and corresponding to a lower total amount of adjustment than other sets of adjustments having a total normalized vibration value less than the predetermined value. The predetermined value may correspond to an expected value of all errors.