Turbopropeller Engine Control System Priority Selection
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Solution Overview
Problem
Existing turbopropeller engine control systems face challenges in smoothly transitioning between Alpha and Beta modes, require complex alignment algorithms, and are unreliable if the pitch angle sensor fails, leading to hazardous propeller overspeed and inefficient ground operations.
Innovation Solution
A combined control system that manages propeller speed and pitch using a priority selection scheme, allowing for simultaneous control of propeller speed and pitch, with a scheduler and regulators to adjust pitch to a minimum Ground Pitch value during ground operations, and relying on a hydraulic lock for flight safety, eliminating the need for continuous pitch angle measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate control loops for propeller speed and pitch are used with complex alignment algorithms, then mode transitions can be managed, but the device complexity increases and reliability decreases if pitch angle sensor fails
Solution Approach 1:
The patent combines separate control loops for propeller speed and pitch into a single integrated control loop that simultaneously controls both parameters. This merging eliminates the need for complex alignment algorithms between separate loops and removes dependence on pitch angle sensors, thereby improving reliability while reducing device complexity
Solution Approach 2:
The invention extracts and eliminates the pitch angle sensor from the control system by using alternative sensing methods (propeller speed sensor and power lever position sensor) to derive pitch information. This removal of the unreliable sensor component directly addresses the reliability issue while simplifying the overall system
2Reliability
If minimum pitch is limited to MFP value during flight operations, then propeller overspeed is prevented, but ground operation efficiency decreases due to excessive thrust and increased fuel consumption
Solution Approach 1:
The patent implements dynamic adjustment of the minimum pitch limit based on operational context. During flight operations, the system maintains the conservative MFP limit to prevent overspeed, while during ground operations it dynamically lowers the minimum pitch limit to enable more efficient propeller angles. This dynamic adaptation resolves the contradiction by applying different safety margins appropriate to each operational phase
Solution Approach 2:
The invention changes the minimum pitch parameter value based on detected operational conditions (flight vs. ground). By monitoring parameters such as aircraft weight on wheels or pitch rate, the system adjusts the minimum pitch constraint to optimize fuel efficiency during ground operations while maintaining safety during flight
3Measurement precision
If pitch angle sensor is used for continuous measurement, then control precision is improved, but system reliability decreases when sensor fails
Solution Approach 1:
The patent introduces intermediary calculations that derive pitch angle information from other reliable sensors (propeller speed sensor and power lever position sensor) rather than directly relying on the pitch angle sensor. This intermediary approach maintains measurement precision through mathematical relationships while eliminating the single point of failure
Solution Approach 2:
The invention replaces the mechanical/electrical pitch angle sensor with a computational approach using software algorithms that calculate pitch angle from propeller speed and power lever position data. This substitution eliminates the physical sensor component that can fail while maintaining the necessary measurement precision through mathematical modeling
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
Ensures safe and efficient operation by allowing smooth transitions between modes, reducing pilot workload, and maintaining control even if the pitch angle sensor fails, with improved fuel efficiency and reduced risk of propeller overspeed.
Implementation Method 1
the propeller actuation assembly is provided with a safety passive device called 'hydraulic lock', the aim of which is to limit the propeller pitch to a minimum idle position
Data Source
AI summary
An electronic control system (30) for a turbopropeller engine (12) having a gas turbine (20) and a propeller assembly (13) coupled to the gas turbine (20), controls propeller operation based on a pilot input request, via generation of a driving quantity (Ip) for an actuation assembly (29) designed to adjust a pitch angle (β) of propeller blades (2) of the propeller assembly (13). The control system (30) envisages: a propeller speed regulator (39), receiving at its input a propeller speed error (ep), indicative of a difference between a propeller speed measure (Nr) and a propeller speed demand (Nrref), and generating at its output, based on the propeller speed error (ep), a first control quantity (Outi); a propeller pitch regulator (42), receiving at its input a propeller pitch error (ep), indicative of a difference between a propeller pitch demand ( ) and a pitch position measure (β), and generating at its output, based on the propeller pitch error (ep), a first control quantity (Out2); and a priority selection stage (45), configured to implement a priority selection between the first and the second control quantities, for providing at the output the driving quantity (IP), based on the priority selection between the first and the second control quantities.