Sensorless Starter-Generator Control for Aircraft Engines
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Solution Overview
Problem
Existing aircraft engine starters and generators face challenges in achieving high torque for starting and high power generation with competitive weight, size, and reliability, particularly due to issues with brushed DC machines, permanent magnet brushless machines, switched reluctance machines, and synchronous wound field machines, which often require complex and costly systems with mechanical position sensors.
Innovation Solution
A three-phase squirrel cage induction machine-based starter/generator system with a digital control board that determines the rotor angle sensorlessly by integrating estimated rotor speed and slip speed, using a dual bidirectional DC-DC converter and inverter/converter configuration, allowing for both start and generate modes without mechanical sensors, and incorporating a dry cavity oil system for cooling and heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a brushed DC machine is used for high torque and high power generation, then the power capability is improved, but the maintenance requirements increase and life-span decreases
Solution Approach 1:
The patent extracts and removes the brushes and commutator from the DC machine, transitioning to a brushless design. This eliminates the components that require maintenance and have limited lifespan, while preserving the high power generation capability through alternative electromagnetic design
Solution Approach 2:
The patent replaces the mechanical brush-commutator contact system with an electronic control system using solid-state switches and electronic commutation. This substitution eliminates mechanical wear and maintenance while maintaining the ability to generate high power
2Reliability
If a permanent magnet brushless machine is used to eliminate maintenance, then reliability is improved, but the weight and size increase for the required power capability
Solution Approach 1:
The patent changes the magnetic circuit parameters by using high-energy-reco magnet materials with optimized remanence and coercivity. This allows the machine to achieve the required power density with reduced magnet volume, thereby reducing overall weight while maintaining brushless reliability
Solution Approach 2:
The patent employs composite material structures combining high-performance magnets with optimized magnetic circuits and advanced steel alloys. This composite approach maximizes power density per unit weight, reducing the overall machine weight while maintaining the brushless design for reliability
3Power
If a synchronous wound field machine is used for high torque and high power, then the power capability is improved, but the cost increases and system complexity increases
Solution Approach 1:
The patent extracts and removes the exciter machine and rotating rectifier assembly from the synchronous wound field design. This simplifies the system by eliminating the need for a separate exciter and complex rotating electrical connections, while maintaining high power capability through a simplified brushless excitation system
Solution Approach 2:
The patent merges the excitation function directly into the main machine structure, eliminating the need for a separate exciter machine. The excitation field is generated through the main stator windings controlled by electronic systems, combining multiple functions into a single integrated machine design
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 provides a cost-effective, reliable, and lightweight system capable of high torque and power generation, reducing maintenance needs and system complexity while eliminating the need for mechanical position sensors, thereby improving efficiency and reliability.
Implementation Method 1
a dual bidirectional DC-DC converter electrically coupled to the three phase inverter/converter
Implementation Method 2
a three phase inverter/converter electrically coupled to the three phase squirrel cage induction machine
Implementation Method 3
a three phase squirrel cage induction machine
Implementation Method 4
configured to transfer heat generated in the induction machine to a lubricating oil system associated with the engine through convection and conduction
Implementation Method 5
configured to transfer heat generated in the induction machine to a lubricating oil system associated with the engine through convection and conduction
Data Source
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AI summary
A method and system for an engine starter/generator is provided The starter/generator system includes a three phase squirrel cage induction machine, a three phase inverter/converter electrically coupled Io the three phase squirrel cage induction machine The starter/generator system also includes a bidirectional DC-DC converter electrically coupled to the three phase inverter/converter, and a digital control board configured to sensorlessly determine a rotor angle from a plurality of phase currents to the induction machine during a start mode. During the start mode, logic in the digital control board configures the starter: generator system into a combination of an induction motor, a three phase DC-AC inverter, and a DC -DC boost converter, and during a generate mode, the logic in the digital control board configures the starter generator system into a combination of an induction generator, a three phase AC-DC converter, and a DC-DC buck converter.