Rotor Lead-Lag Compensation via Active Control

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Solution Overview

Problem

Rotary wing aircraft rotor systems face challenges with under-damped lead-lag dynamics, leading to potential damage and instability due to ground resonance, which existing mechanical dampers attempt to address but increase cost, complexity, and maintenance requirements.

Innovation Solution

A control system utilizing sensors to detect lead-lag rates in rotor blades and a flight control computer generating compensation signals to control the blades, reducing the need for supplementary mechanical dampers by actively managing lead-lag motion through rotor blade control signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If supplementary mechanical dampers are used to provide sufficient damping for lead-lag modes, then ground resonance is prevented, but rotor system cost increases and performance decreases due to complexity, weight, hub drag, and maintenance requirements

Engineering Contradiction:

Improveprevention of ground resonanceVSAvoidcomplexity of mechanical dampers

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces mechanical lead-lag dampers with an active control system using flight control computers and actuators to provide lead-lag damping. The control system calculates lead-lag rates from sensor data and generates control signals to actuators that apply forces to dampen lead-lag motion, eliminating the need for mechanical dampers and their associated complexity, weight, and maintenance

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The control system uses the aircraft's existing flight control infrastructure and sensors to provide lead-lag damping as a self-contained function. The system monitors its own rotor blade motion through sensors and automatically adjusts blade pitch or position through actuators to maintain stable lead-lag dynamics without external mechanical components

Inventive Principle:

Principle #25Self-service

2Reliability

If supplementary mechanical dampers are used to provide sufficient damping for lead-lag modes, then ground resonance is prevented, but rotor system weight increases

Engineering Contradiction:

Improveprevention of ground resonanceVSAvoidweight of mechanical dampers

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The patent replaces physical mechanical dampers with an electronic control system that uses actuators to apply aerodynamic forces for damping. This substitution eliminates the weight of mechanical damper components while achieving the same ground resonance prevention through active control of blade pitch or position

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If supplementary mechanical dampers are used to provide sufficient damping for lead-lag modes, then ground resonance is prevented, but hub drag increases

Engineering Contradiction:

Improveprevention of ground resonanceVSAvoidhub drag

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent replaces mechanical dampers that create physical resistance and drag at the hub with an active control system that uses aerodynamic forces applied to the blades. This eliminates the mechanical friction and drag losses associated with mechanical damper operation while maintaining lead-lag stability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Reliability

If supplementary mechanical dampers are used to provide sufficient damping for lead-lag modes, then ground resonance is prevented, but maintenance requirements increase

Engineering Contradiction:

Improveprevention of ground resonanceVSAvoidmaintenance of mechanical dampers

Core Design Contradiction:

ReliabilityVSEase of repair

Solution Approach 1:

The patent replaces mechanical dampers with moving parts that require maintenance with an electronic control system. The actuators and sensors are integrated into the existing flight control system infrastructure, eliminating the need for separate mechanical damper maintenance while maintaining ground resonance prevention through active control

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentEP2976260B1Compensating for lead-lag in rotor system

Publication Date: 2018.02.14 SIKORSKY AIRCRAFT CORP

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AI summary

A control system for a rotor assembly includes a plurality of sensors configured to detect a lead-lag rate of each rotor blade of a plurality of rotor blades rotatable around a shaft and a flight control computer configured to generate lead-lag compensation signals based on the detected lead rate and lag rate of each rotor blade to control each rotor blade.