Actuator Rigging System for Force Fighting Mitigation
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Solution Overview
Problem
Conventional actuator systems with multiple actuators often experience force fighting due to differences in mounting structures, thermal variations, and aging, leading to asymmetrical movement of aircraft control surfaces, which is undesirable and critical in aircraft systems.
Innovation Solution
A three-point rigging system is implemented to determine and correct offsets between desired and actual positions of actuators, synchronizing their operation to mitigate force fighting by adjusting command signals and feedback loops, ensuring accurate and synchronized movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple actuators are used to move the same part to provide redundancy or additional strength, then reliability and actuation capability are improved, but force fighting occurs due to positioning differences between actuators
Solution Approach 1:
The system measures actual positions of multiple actuators and compares them with desired positions to determine offsets. These offset values are then used to adjust control signals sent to each actuator, creating a closed-loop feedback system that eliminates force fighting while maintaining redundant actuation capability.
2Manufacturing precision
If actuators are designed to be identical to ensure synchronized movement, then symmetry is improved, but manufacturing variations and environmental factors still cause positioning differences
Solution Approach 1:
The system determines offset values for each actuator at multiple desired positions (neutral position and at least one position on each side). These offset parameters are stored and applied to adjust control signals, compensating for manufacturing variations and environmental factors such as thermal differences and aging that cause positioning differences despite identical actuator designs.
3Measurement precision
If offset determination is performed at multiple positions including neutral and extreme strokes, then actuator accuracy across the full range is improved, but calibration time and complexity increase
Solution Approach 1:
The system determines offset values at the neutral position and at least one position on each side of neutral (such as extreme strokes). This partial multi-position calibration approach provides sufficient accuracy for most applications while reducing calibration time compared to continuous multi-point calibration, representing an optimal balance between precision and efficiency.
Data Source
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AI summary
A force fight mitigation system comprising: control means configured to provide a position command to each of two or more actuators arranged to position a surface, the position command indicative of a desired position of the actuator relative to the surface; means to detect the actual position of the actuator relative to the surface in response to the position command; and means to determine an offset between the desired position and the actual position and to store a rigging correction based on the offset; wherein, for each actuator, an offset is determined for each of three or more desired positions.