Propeller Hydraulic Actuator Load Feedback Control
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Solution Overview
Problem
Existing propeller pitch change hydraulic actuation systems experience position loop instabilities due to interactions with other control loops in aircraft powerplant systems, particularly when operating frequencies shift over time, leading to inefficiencies and stress on the system.
Innovation Solution
A propeller pitch change hydraulic actuation system with a double-acting dual chamber actuator, equipped with pressure sensors to measure load differentials and a closed-loop controller that includes an inner load loop, stabilizes the position loop and increases its bandwidth, thereby decoupling interactions with other control loops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the position loop operates at a specific bandwidth to minimize interactions with other powerplant systems, then decoupling from engine power and rotational speed control loops is achieved, but position loop instabilities occur when operating frequencies shift over time due to hardware ageing, manufacturing tolerances, and changing operating conditions
Solution Approach 1:
The patent introduces a load feedback loop that measures the actual load on the pitch actuator and feeds this information back to the controller. This allows the position loop to dynamically adjust to load variations caused by frequency shifts, maintaining stability despite changes in operating conditions, hardware ageing, or manufacturing tolerances.
Solution Approach 2:
The patent implements a dynamic control approach where the position loop bandwidth is not fixed but can adapt to changing operating conditions. By incorporating load sensing and feedback, the system dynamically adjusts its response characteristics to maintain optimal performance across varying frequencies and conditions, rather than relying on a static bandwidth setting.
2Productivity
If the position loop bandwidth is increased to improve response time and control performance, then actuator position control performance is enhanced, but interactions with other control loops (engine power regulation, rotational speed regulation, synchrophasing loops) increase
Solution Approach 1:
The load feedback mechanism provides real-time information about actual actuator loading conditions, allowing the control system to compensate for interactions with other loops. By sensing the load and adjusting the control signal accordingly, the system can maintain fast response without amplifying unwanted interactions with engine power regulation, rotational speed regulation, or synchrophasing loops.
Solution Approach 2:
The load sensing system acts as an intermediary between the position loop and other control loops. By measuring and feeding back the actual load conditions, it provides a mediating signal that allows the position loop to respond quickly while automatically compensating for interactions with other systems, effectively decoupling them through load-based feedback.
3Device complexity
If a single pressure sensor is used to measure differential pressure between chambers, then device complexity is reduced, but measurement precision of load differential may be insufficient for optimal control
Solution Approach 1:
The patent uses pressure sensors as intermediaries to indirectly measure the load differential on the actuator. By measuring the hydraulic pressure in the actuator chambers and calculating the load from these pressure readings, the system achieves precise load measurement without requiring direct force sensors, balancing measurement precision with device simplicity.
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
The solution stabilizes the pitch control, enhances actuator position control performance, and widens the position loop bandwidth, making the system more robust against frequency shifts and interactions, allowing for better decoupling and improved operational stability.
Implementation Method 1
hydraulic fluid pressure is applied from a chamber on each side of a piston, and the pressure differential between the two chambers moves the piston one way or the other. The movement of the piston provides an actuation force.
Implementation Method 2
at least one pressure sensor for obtaining pressure measurements from which a load differential applied to the piston by the circuits can be calculated
Data Source
AI summary
A propeller hydraulic actuation system, includes a double-acting dual chamber hydraulic pitch change actuator. The pitch change actuator includes a first pressure circuit having first fluid supply lines and a first hydraulic chamber and a second pressure circuit having second fluid supply lines and a second hydraulic chamber. A piston separates the first and second chambers. At least one pressure sensor is provided for obtaining pressure measurements from which a load differential (F) applied to the piston by the circuits can be calculated. A closed loop controller is arranged to control the fluid supplied to the first and second pressure circuits, wherein the closed loop controller includes an actuator position loop arranged to utilise feedback on the actuator position to control the actuator position.