Transition Aircraft Control Law Blending for Safe Regime Change
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Solution Overview
Problem
Existing transition aircraft, such as eVTOLs, face challenges in safely and smoothly transitioning between vertical take-off and landing (VTOL) and horizontal flight (Aeroplane) regimes due to reliance on airspeed alone for mode transitions, which is not sufficient for achieving safe and smooth transitions.
Innovation Solution
A method for controlling transition aircraft that involves using a state machine implemented by a flight control computer to monitor and detect conditions for transition, involving airspeed and attitude measurements, and requiring confirmation from a high-level decision maker before transitioning between regimes, with gradual blending of control laws to prevent abrupt transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If transition between regimes is governed by airspeed value alone, then the control system remains simple, but the transition safety and smoothness deteriorate
Solution Approach 1:
The state machine pre-defines multiple transition conditions (airspeed thresholds, attitude angles, rate of climb/descent limits) that must be satisfied before allowing regime transition. This preliminary verification ensures that transitions only occur when the aircraft is in a safe and suitable state, preventing unsafe transitions while maintaining systematic control.
Solution Approach 2:
The control system dynamically evaluates multiple flight parameters (airspeed, attitude, vertical speed) in real-time and adapts the transition decision based on the current flight state. The state machine transitions between different control regimes (VTOL, transition, aeroplane) based on dynamic condition assessment, ensuring smooth and safe transitions.
2Reliability
If multiple conditions are checked before transition, then transition safety improves, but the control system complexity increases
Solution Approach 1:
The control system is segmented into a state machine layer and a high-level decision maker layer. The state machine handles routine condition checking and regime management, while the high-level decision maker handles exceptional cases and final approval. This segmentation distributes complexity across modular components, making the system more manageable while maintaining high safety standards.
Solution Approach 2:
The state machine acts as an intermediary between the flight parameters and the high-level decision maker. It pre-processes multiple flight conditions, consolidates the information, and presents a structured transition request to the decision maker, reducing the complexity burden on the high-level system while ensuring thorough safety checks.
3Speed
If abrupt transition between control laws occurs, then the response time is fast, but the flight comfort and stability deteriorate
Solution Approach 1:
The control laws are blended periodically over time using a transition schedule defined by the state machine. The system alternates between VTOL control law and aeroplane control law with smooth interpolation, ensuring that the transition occurs over a controlled time period rather than instantaneously, maintaining stability while achieving timely regime change.
Solution Approach 2:
The control system changes parameters gradually during transition by blending control law weights. Instead of abruptly switching from one control law to another, the system adjusts the weighting parameters of each control law continuously, ensuring smooth transitions that maintain flight stability and comfort while achieving the desired regime change.
Data Source
AI summary
A method of controlling a transition aircraft having actuators and which transitions between a first take-off/landing regime and a second horizontal flight regime, including: controlling a first actuator subset in the first regime and a second actuator subset in the second regime using the flight controller, by: a) providing measurements or estimates of flight parameters; b) depending on a current regime, checking whether a predefined set of conditions for that regime are fulfilled, by comparing flight parameters with threshold values; c) if conditions are fulfilled, signalling a decision-maker and awaiting confirmation regarding a transition to the other regime; d) instructing the flight controller to make the transition if approved; e) after transitioning in step d), commanding the aircraft according to the other regime; and f) returning to step a). Step e) includes gradually blending in a control law for the other regime over time while blending out the current regime.