Combined Pitch-Thrust Control for Stable Hybrid UAV Hover
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Solution Overview
Problem
Existing hybrid multirotor aircraft control systems face inefficiencies in maintaining stable control during hovering modes, especially in windy conditions, due to the separation of VTOL and forward propulsion systems, which leads to increased drag and reduced efficiency as they 'fight' to achieve stable position control.
Innovation Solution
Combining pitch angle and forward thrust control systems, using a controller with a splitting block to generate pitch angle and throttle commands that allow the aircraft to remain level across a wide range of airspeeds by abstracting forward thrust control into pseudo-control components fed to both propulsion systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If pitch angle control and forward thrust control are separated into independent systems, then each system can be controlled independently, but the integrators fight each other resulting in reduced control efficiency and increased energy consumption
Solution Approach 1:
The patent combines pitch angle control and forward thrust control into a unified control system where a single controller generates both pitch angle commands and forward thrust commands based on desired velocity inputs. This merging eliminates the conflicting integrators problem by coordinating both control actions through one control loop, thereby improving control efficiency while maintaining independent control capability through the coordinated output of pitch and thrust commands.
2Speed
If the aircraft pitches forward to achieve positive acceleration, then forward velocity increases, but additional VTOL thrust is required to maintain altitude and further drag is added
Solution Approach 1:
The patent merges forward thrust generation from both pitch angle adjustment and forward propulsion system thrust. The controller calculates the desired velocity and generates coordinated pitch angle and forward thrust commands, allowing the forward propulsion system to contribute to acceleration. This reduces the burden on the VTOL system to provide all forward acceleration through pitch, thereby reducing additional VTOL thrust requirements and energy consumption.
3Speed
If the aircraft pitches forward to compensate for drag, then forward velocity is maintained, but the aircraft experiences reduced efficiency and increased energy consumption
Solution Approach 1:
The patent combines drag compensation functions from both pitch angle control and forward thrust control. Instead of relying solely on pitch angle adjustment to compensate for drag, the unified control system coordinates forward thrust commands from the propulsion system to share the drag compensation burden. This reduces the energy consumption associated with excessive pitch angles while maintaining forward velocity.
4Adaptability or versatility
If separate control systems are used for VTOL and forward propulsion, then each system can operate independently, but stability during hovering in windy conditions deteriorates
Solution Approach 1:
The patent merges VTOL propulsion control and forward propulsion control into a unified control architecture. The single controller receives desired velocity inputs and generates coordinated pitch angle and forward thrust commands, enabling the systems to work cooperatively rather than independently. This coordination improves hovering stability in windy conditions by allowing the forward propulsion system to assist in counteracting disturbances while maintaining overall aircraft stability.
Data Source
AI summary
A method of controlling forward thrust of an aircraft includes receiving a first pitch angle command; generating a second pitch angle command and a forward thrust engine throttle command based on a bounded pitch angle for the aircraft; comparing a determined bounded pitch angle for the aircraft to the pitch angle corresponding to the first pitch angle command; generating a reduced pitch angle command so the resultant aircraft pitch angle does not exceed the bounded pitch angle; and generating the forward thrust engine throttle command based on the reduced pitch angle command.