VTOL Propulsion Unit Transition Through Unstable Flow Zones
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Solution Overview
Problem
The transition between hover and cruise flight in VTOL aircraft, particularly eVTOL aircraft, is challenging due to complex aerodynamic interactions causing excessive energy consumption, uncertainties in airflow conditions, and potential structural damage from limit cycle oscillations, leading to reduced controllability and efficiency.
Innovation Solution
A method involving individually controllable propulsion units with flaps and engines that maneuver through unstable flow conditions by consecutively pushing units through a forbidden zone of uncertain airflow, avoiding steady operation within this zone by dynamically adjusting flap angles and engine speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If propulsion units operate within the unstable flow condition zone during transition, then the transition process can be completed, but the controllability is reduced and limit cycle oscillations may occur causing structural damage
Solution Approach 1:
The patent applies the skipping principle by commanding the propulsion units to rapidly traverse the unstable flow condition zone rather than operating within it. The control system detects when a propulsion unit approaches the unstable zone boundaries and initiates a rapid transition through the zone, minimizing the time spent in the dangerous flow regime where attached and separated flow conditions are uncertain and can cause limit cycle oscillations.
2Productivity
If propulsion units operate within the unstable flow condition zone during transition, then the transition process can be completed, but limit cycle oscillations may occur causing structural damage
Solution Approach 1:
The patent applies the skipping principle by commanding the propulsion units to rapidly traverse the unstable flow condition zone rather than operating within it. The control system detects when a propulsion unit approaches the unstable zone boundaries and initiates a rapid transition through the zone, minimizing the time spent in the dangerous flow regime where attached and separated flow conditions are uncertain and can cause limit cycle oscillations.
3Reliability
If traditional flight control law tuning is used to account for flow condition uncertainties, then safety margins are maintained, but control effectiveness is compromised
Solution Approach 1:
The patent extracts the problematic uncertainty factor by removing the propulsion units from operation within the unstable flow condition zone entirely. Instead of tuning control laws to compensate for uncertain flow conditions, the system actively avoids the zone by detecting its boundaries and commanding rapid transitions through it, thereby eliminating the source of control effectiveness compromise while maintaining safety.
4Reliability
If propulsion units transition slowly through the unstable flow condition zone, then control authority is maintained, but energy consumption increases dramatically reducing battery life
Solution Approach 1:
The patent applies the skipping principle by commanding the propulsion units to rapidly traverse the unstable flow condition zone rather than operating within it. The control system detects when a propulsion unit approaches the unstable zone boundaries and initiates a rapid transition through the zone, minimizing the time spent in the dangerous flow regime where attached and separated flow conditions are uncertain and can cause limit cycle oscillations.
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 stable flight throughout the transition phase by maintaining airflow in either attached or separated regimes, improving controllability and reducing energy consumption without imposing operational limitations.
Implementation Method 1
each propulsion unit generates a thrust force and/or a lift force
Implementation Method 2
each propulsion unit generates a thrust force and/or a lift force
Implementation Method 3
the state of the airflow may be either attached to or separated from the control effector surface
Data Source
AI summary
During the transition of a vertical take-off and landing aircraft from hover flight to cruise flight and vice versa, a method for controlling this transition is configured to push propulsion units of the VTOL aircraft through an unstable flow condition zone within a predetermined time period. Each propulsion unit is mounted to a mounting portion of the aircraft in a movable manner about at least one degree of freedom and comprises a flap serving as a lifting and control surface and at least one engine connected with the flap, and each propulsion unit receives command signals for flap angle and engine speed or speeds so that each propulsion unit generates a thrust force and/or a lift force.