Variable-Pitch Propeller Speed Control Across the Flight Envelope
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Solution Overview
Problem
Existing propeller speed control systems in turboprop aircraft engines do not operate at the most desirable performance level over the entire flight envelope.
Innovation Solution
A method and system for controlling a variable-pitch propeller using a feedback controller that schedules gains based on power coefficient and advance ratio, without requiring knowledge of the pitch angle, to adjust the propeller pitch and improve speed control performance across different flight conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a digital speed control system is used to control oil flow to a hydraulic actuator, then operational advantages are provided, but the system does not operate at the most desirable performance level over the entire flight envelope
Solution Approach 1:
The control system dynamically adjusts the gain parameter based on real-time operating conditions (rotational speed, air density, advance ratio) rather than using fixed gain values. This allows the system to adapt to changing flight envelope conditions and maintain optimal performance across all operating regimes.
Solution Approach 2:
The system changes the control parameter (gain) based on operating conditions such as rotational speed, air density, and advance ratio. By scheduling the gain as a function of these parameters, the system achieves desirable performance levels across the entire flight envelope rather than being optimized for a single operating point.
2Device complexity
If a feedback controller with fixed gain is used, then the control system is simple to implement, but it cannot provide optimal control performance across multiple regions of the flight envelope
Solution Approach 1:
The gain is made dynamic by scheduling it as a function of operating parameters (rotational speed, air density, advance ratio). This allows the control system to adapt to different flight conditions while maintaining a relatively simple implementation structure based on standard feedback control principles.
Solution Approach 2:
The scheduled gain approach provides a universal control strategy that works across multiple regions of the flight envelope. A single control algorithm can handle various operating conditions (different speeds, densities, advance ratios) by adjusting the gain parameter, eliminating the need for multiple separate control systems.
3Reliability
If the gain is scheduled based on power coefficient and advance ratio, then closed-loop control performance is improved over multiple regions of the flight envelope, but the calculation complexity increases
Solution Approach 1:
The required derivatives (dCp/dβ, dJ/dβ, dβ/dx, dNP/dJ) are pre-calculated and stored as functions of the operating parameters. This allows the gain to be scheduled in real-time using simple look-up or interpolation operations rather than performing complex real-time differentiation and calculation, thus improving performance without excessive computational burden.
Solution Approach 2:
Instead of performing complex real-time calculations of derivatives and gain scheduling, the system uses pre-computed models and relationships that capture the essential behavior. The control algorithm copies the essential dynamics through pre-established mathematical relationships, reducing online computational complexity while maintaining accuracy.
Data Source
AI summary
Systems and methods for controlling a variable-pitch propeller of an aircraft are provided. A method for controlling the variable-pitch propeller includes using a feedback controller, operating the variable-pitch propeller at a current operating condition including a current rotational speed, determining a speed error between the current rotational speed of the variable-pitch propeller and a set point rotational speed for the variable-pitch propeller, determining a gain for the feedback controller based on a power coefficient and an advance ratio of the variable-pitch propeller. Using the feedback controller, a propeller pitch command is determined based on the speed error and using the gain. The pitch of the variable-pitch propeller is adjusted according to the propeller pitch command to reduce the speed error.