Split-Reference Force Trim Control for Smooth Re-Engagement
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Solution Overview
Problem
Modern aeronautic vehicles face challenges in smoothly reengaging force trim systems after manual adjustments, often resulting in stick jumps or oscillations due to improper implementation of rate command systems with active back-drive equipped flight control systems.
Innovation Solution
The introduction of a rapid re-trimming rate command mode that utilizes a split reference system to lock a control law detent position as a zero-rate reference, allowing pilots to command rates from this position and smoothly return to regular back-drive operation by recombining split references, preventing stick jumps and oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If force trim release is used to temporarily disengage force trim for manual adjustment, then pilot can manually change vehicle state, but stick jumps or oscillations occur when reengaging force trim
Solution Approach 1:
The system performs preliminary actions by designating the current stick position as detent position before reengaging force trim, and by pre-calculating the trim command based on the reference position. This ensures that when force trim is reengaged, the control surface is already positioned correctly, preventing stick jumps and oscillations.
Solution Approach 2:
The system uses feedback by continuously monitoring stick position and using it to generate trim commands. The reference position is established based on the stick position at the time of force trim release selection, and this reference is used to calculate the appropriate trim command when force trim is reengaged, ensuring smooth transitions.
2Extent of automation
If traditional force trim system is used, then automated flight control maintains vehicle state, but continuous pilot adjustment is required without automated trimming
Solution Approach 1:
The system dynamically switches between automated force trim mode and manual control mode. When force trim release is selected, the system transitions to manual mode where stick position commands vehicle body rate. When force trim release is deselected, the system transitions back to automated mode where the trim command is generated based on the established reference position. This dynamic switching allows the system to adapt to pilot needs while maintaining automation benefits.
Data Source
AI summary
A flight control system includes an active control inceptor, a flight control computer, and a force trim release. The active control inceptor includes a control member movable from a first position to a second position to command a vehicle-body rate and including a detent position that holds an attitude. The flight control computer generates a trim command from the second position, a reference position, and a vehicle-body state. With the force trim release selected when the control member is moved from the first position to the second position, the first position is designated as the reference position and the second position is designated as the detent position. Upon deselection of the force trim release with the control member at the second position, the second position is designated as the reference position and the trim command is designated as the detent position.