Hybrid Analog-Digital Control for Aircraft Engine Stability
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Solution Overview
Problem
Power control systems in aircraft, particularly those using microprocessors, are susceptible to event upsets such as voltage spikes and power failures due to high energy cosmic particle impacts at high altitudes, which can damage components and disrupt control functions.
Innovation Solution
A hybrid control system combining a primary analog control loop with a digital controller connected via a digital-to-analog converter, allowing the analog loop to continue operating with the last value received from the digital controller in case of signal unavailability, ensuring continuous control of electric machines coupled to gas turbine engines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a digital controller is used to control the electric machine, then control precision and programmability are improved, but susceptibility to event upsets and reliability deteriorate
Solution Approach 1:
The control system is segmented into two independent parts: a digital controller for supervisory functions and parameter adjustment, and a separate analog control loop for primary control execution. This segmentation allows the analog loop to operate independently without being affected by digital controller failures, thus resolving the contradiction between digital control precision and reliability.
Solution Approach 2:
A digital-to-analog converter serves as an intermediary between the digital controller and the analog control loop. The converter includes a hold circuit that maintains the last valid control signal even when the digital controller fails, allowing the analog loop to continue operating with stale but valid commands, thereby preventing complete system failure.
2Adaptability or versatility
If a microprocessor is used in the primary control loop, then control flexibility and adaptability are improved, but vulnerability to cosmic particle impacts and reliability worsen
Solution Approach 1:
The patent replaces the vulnerable microprocessor-based primary control with an analog control loop that uses continuous electrical signals and analog computing elements (operational amplifiers, integrators, proportional controllers). This substitution eliminates the digital electronics that are susceptible to cosmic ray-induced bit flips and latch-up, providing inherent radiation hardness while maintaining control flexibility through analog parameter adjustment.
3Measurement precision
If signal processing is performed digitally, then measurement accuracy and control precision are improved, but system complexity and susceptibility to faults increase
Solution Approach 1:
The patent extracts the complex digital signal processing functions from the primary control path and relocates them to a separate digital supervisory controller. The analog control loop retains only the essential proportional-integral control functions, which are inherently more reliable and simpler. This extraction reduces the complexity of the critical control path while preserving digital processing capabilities for non-critical functions.
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 hybrid control system provides a stable and reliable control architecture that is immune to faults and event upsets, maintaining control until the digital controller restarts and preventing damage to power system components.
Implementation Method 1
the digital-to-analog converter being configured to hold a last value received from the digital controller
Data Source
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AI summary
A hybrid control system (26) for controlling an electric machine (20) coupled to a gas turbine engine (10) is provided. The control system comprises: a primary analog control loop (28) including an analog controller (32) for controlling the electric machine based on a set point and a measured output of the electric machine; and a digital controller (30) of the turbine engine operationally connected to the primary analog control loop to adjust at least one control parameter associated with the analog controller.