Actuator Servo-Control Monitoring for Selective Disengagement
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Solution Overview
Problem
Existing helicopter automatic pilot systems face increased pilot workload due to complete disengagement in response to failures, which is disadvantageous and not always economically viable, as they often require dual hydraulic circuits for redundancy.
Innovation Solution
A method and device for monitoring actuator servo-control displacement in aircraft, which differentiates between actuator blockages and divergent states, using hydraulic failure indications to selectively disable affected servo-controls, reducing unnecessary disengagement and maintaining pilot assistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complete disengagement of automatic pilot system is implemented upon failure detection, then safety is improved, but pilot workload increases significantly
Solution Approach 1:
The automatic pilot system is segmented into independent servo-controls for different flight controls (pitch, roll, yaw, throttle). When a failure is detected in one servo-control, only that specific servo-control is disengaged while others remain operational. This allows the system to maintain partial automatic assistance, reducing pilot workload compared to complete disengagement while still ensuring safety through selective failure isolation.
2Reliability
If dual hydraulic circuits are implemented for redundancy, then system reliability is improved, but device complexity and cost increase
Solution Approach 1:
A monitoring device acts as an intermediary between the hydraulic circuits and the automatic pilot system. This monitoring device detects failures in the hydraulic circuits and triggers selective disengagement of only the affected servo-control. This intermediary approach provides failure detection and isolation capabilities without requiring dual hydraulic circuits, thereby maintaining reliability while avoiding the complexity and cost of redundant hydraulic systems.
3Ease of operation
If selective disengagement of affected servo-control is implemented, then pilot assistance is maintained, but failure detection precision must be improved
Solution Approach 1:
The monitoring device continuously monitors the operation of each servo-control and hydraulic circuit, providing real-time feedback on their status. When a failure is detected, the system provides feedback information about the specific failed component, enabling precise identification and selective disengagement. This feedback mechanism ensures accurate failure detection while maintaining pilot assistance through selective rather than complete disengagement.
Data Source
AI summary
An actuator displacement servo-control for aircraft flight controls is assisted by a hydraulic circuit, configured to deliver a hydraulic failure indication. The servo-control is generated from an actuator position indication and a position set-point indication computed by a computation unit. An alarm phase is opened on detection of a servo-control operating error and is kept open as long as the error is present. During the alarm phase it is determined whether the actuator is in blocked or divergent states. If blocked, it is determined whether the duration of the alarm phase exceeds a value Tconf2; If divergent, it is determined whether the duration of the alarm phase exceeds a value Tconf1. When blocked and the duration of the alarm phase does not exceed Tconf2, it is determined whether the hydraulic circuit indicates a hydraulic failure.