Hydraulic Actuator Position Locking for Last-Command Hold
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Solution Overview
Problem
Conventional hydraulic actuators in helicopters tend to revert to a fail-safe position during electrical failures, making it difficult to maintain the last commanded position, which is undesirable for flight control parameters.
Innovation Solution
The hydraulic actuator system includes a position-lock controller along the hydraulic lines that hydraulically decouples the actuator controller from the retract or extend cavities in response to a failure, maintaining the hydraulic lines in an open state to lock the actuator in the last commanded position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional hydraulic actuators are used in helicopters, then the actuator automatically positions to a fail-safe position during electrical failures, but this causes unintended movement that compromises flight control parameters
Solution Approach 1:
A position lock controller is introduced as an intermediary component in the hydraulic line between the actuator controller and the actuator. This intermediary device includes a solenoid that, when de-energized during electrical failures, closes a valve to lock hydraulic pressure and prevent unintended actuator movement, thereby resolving the conflict between automatic fail-safe positioning and maintaining last-commanded position for flight control reliability
2Adaptability or versatility
If the actuator controller maintains hydraulic connection during failures, then the actuator can be repositioned, but this allows unintended movement to fail-safe position
Solution Approach 1:
The position lock controller transitions from a static always-connected state to a dynamic state where it can be selectively activated. The solenoid-driven valve dynamically switches between open (allowing repositioning) and closed (locking position) states based on operational needs, enabling the system to adapt between repositioning capability and position stability as required
3Reliability
If a position lock controller with solenoid is added to the hydraulic line, then the actuator can be locked in last commanded position during failures, but this increases device complexity
Solution Approach 1:
The position lock controller utilizes the existing electrical failure condition to its advantage - when power is lost, the solenoid automatically de-energizes and the valve closes to lock the actuator position. This self-activating feature during failures reduces the need for additional complex control logic and monitoring systems, as the locking action occurs automatically based on the failure condition itself
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution allows the actuator to remain in the last commanded position during failures, preventing unintended movement and maintaining control under load, even in low-pressure conditions, thus enhancing the reliability of flight control systems.
Implementation Method 1
the position-lock controller is configured to close the valve to lock hydraulic pressure between the piston head and the piston in response to a failure of the hydraulic actuator system
Implementation Method 2
the position-lock controller comprises a solenoid
Data Source
AI summary
Hydraulic actuator systems of aircraft are described. The hydraulic actuator systems include a hydraulic actuator having a housing and piston therein. The piston includes a piston head separating the housing into a retract cavity and an extend cavity. An actuator controller is hydraulically coupled to the retract cavity by a first hydraulic line and hydraulically coupled to the extend cavity by a second hydraulic line and configured to control a hydraulic pressure within each of the retract cavity and the extend cavity to control actuation of the hydraulic actuator. A position-lock controller is arranged along at least one of the first hydraulic line and the second hydraulic line, the position-lock controller is configured to hydraulically decouple the actuator controller from at least one of the retract cavity and the extend cavity.