Tailsitter VTOL Transition Control for Precise Target Alignment
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Solution Overview
Problem
VTOL aircraft face challenges in accurately transitioning from forward flight to VTOL orientation near a target ground location, often resulting in overshooting or undershooting due to reliance on user estimates and unreliable airspeed measurements, leading to increased hover time and aggressive maneuvers.
Innovation Solution
An adaptive transition system that monitors ground speed and distance to the target using a flight control system, adjusting the conversion rate to ensure the aircraft is vertically aligned with the target in the VTOL orientation, reducing reliance on user estimates and airspeed measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed conversion rate per fixed transition schedule is used, then the transition process is simple to execute, but the aircraft may overshoot or undershoot the target ground location due to unreliable airspeed measurements and user estimates
Solution Approach 1:
The system continuously monitors actual ground speed and distance to target during the transition phase, comparing these values against scheduled values. The conversion rate is dynamically adjusted based on the difference between actual and scheduled ground speed, creating a closed-loop feedback system that ensures accurate target alignment while maintaining simple operation
Solution Approach 2:
The transition system evolves from a static fixed conversion rate schedule to a dynamic adaptive schedule. The conversion rate becomes a variable parameter that automatically adjusts during the transition based on real-time ground speed measurements, allowing the system to adapt to changing conditions while maintaining operational simplicity
2Device complexity
If user estimates based on ground-level winds and payload are used to determine transition start point, then the system requires minimal equipment, but the transition accuracy deteriorates due to unreliable estimates
Solution Approach 1:
The system replaces manual user estimation with an automated electronic control system that uses ground speed sensors and position data. This substitution eliminates the need for complex wind and payload calculations by the user, providing accurate transition start point determination through automated sensing and processing
3Reliability
If hovering sideways is used to reach the target ground location after transition, then the aircraft can compensate for position errors, but additional power is consumed that reduces overall range
Solution Approach 1:
The system performs preliminary positioning during the transition phase itself by dynamically adjusting the conversion rate to account for ground speed variations. This preliminary action ensures the aircraft is correctly positioned above the target before transitioning to hover, eliminating the need for subsequent corrective hovering maneuvers and reducing power consumption
Data Source
AI summary
A tailsitter aircraft includes an airframe, a thrust array attached to the airframe and a flight control system. The thrust array includes propulsion assemblies configured to transition the airframe from a forward flight orientation to a VTOL orientation at a conversion rate for an approach to a target ground location in a forward flight-to-VTOL transition phase. The flight control system implements an adaptive transition system including a transition parameter monitoring module configured to monitor parameters including a ground speed and a distance to the target ground location. The adaptive transition system includes a transition adjustment determination module configured to adjust the conversion rate of the airframe from the forward flight orientation to the VTOL orientation based on the ground speed and the distance to the target ground location such that the airframe is vertically aligned with the target ground location in the VTOL orientation of the forward flight-to-VTOL transition phase.