Spring-Biased Propeller Clutch Mechanism for UAV Drag Reduction
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Solution Overview
Problem
Unmanned aerial vehicles (UAVs) face challenges in efficiently managing propeller operation during take-off, landing, and transit, as excess lift is required for precision control, but this results in unwanted drag and stability issues when propellers are not in use.
Innovation Solution
A spring-biased propeller clutch mechanism that aligns propellers along a predefined axis when not in use, using feathering arms and tension springs to allow rotation at high velocities and align propellers when stationary, eliminating the need for additional electrical or mechanical components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the lift propellers are stopped to reduce electrical power consumption during transit, then energy efficiency is improved, but the stationary propellers create undesirable drag and restrict vehicle stability
Solution Approach 1:
The propeller system transitions from a static stopped state to a dynamic feathered state. The feathering mechanism allows the propeller blades to rotate to a specific angle (typically 30-45 degrees) relative to the plane of rotation, creating a dynamic configuration that reduces drag while maintaining the propeller in place. This dynamic adjustment resolves the contradiction by eliminating the harmful drag effect without requiring continuous power input.
Solution Approach 2:
The system changes the angular parameter of the propeller blades from 0 degrees (parallel to rotation plane) to a feathered angle (30-45 degrees). This parameter change transforms the aerodynamic characteristics of the stationary propeller, converting it from a drag-generating object to a low-drag configuration that aligns with the airflow during transit operations.
2Measurement precision
If excess lift capacity is provided for precision control during take-off and landing, then control precision is improved, but the vehicle experiences unwanted drag and stability issues during transit operations
Solution Approach 1:
The propeller system is segmented into multiple independently controllable units (thrust propellers and lift propellers). During transit, the lift propellers can be individually feathered while thrust propellers remain operational, allowing the vehicle to maintain stability and control precision without the drag penalty of fully operational lift propellers. This segmentation enables selective optimization of different propeller groups for different flight phases.
Solution Approach 2:
The feathering mechanism acts as an intermediary between the stopped propeller state and the full-power rotation state. By introducing this intermediate feathered position, the system can transition propellers to a state that minimizes their aerodynamic impact on vehicle stability during transit, while preserving the ability to quickly return to full operational capacity when needed for take-off or landing maneuvers.
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
This solution reduces drag and improves stability by aligning propellers when not in use, conserving energy and enhancing operational efficiency during UAV transit and landing operations.
Implementation Method 1
A spring-biased clutch mechanism having a pair of feathering arms that are rotatably mounted to the propeller and linked by tension springs or other biasing elements
Implementation Method 2
When the motor is started, and the propeller begins to rotate, the feathering arms are forced open by contact between such arms and the posts until the propeller reaches a sufficiently high angular velocity
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
Aerial vehicles may be equipped with propellers having clutch mechanisms that contract around a shaft when the propellers are not rotating, or are rotating at low angular velocities, and expand around the shaft when the propellers are rotating at sufficiently high angular velocities. The clutch mechanisms may receive one or more fixed posts within an opening or window defined therein. When the clutch mechanisms contract into a closed position, components of the clutch mechanisms come into contact with the posts, and the propellers are forced to remain in an alignment defined by the posts. When the clutch mechanisms expand into an open position, such components may rotate freely without contacting the posts. Thus, a clutch mechanism may cause a propeller to remain aligned in a desired orientation when the propeller is not required for operation, thereby reducing drag or adverse acoustic effects.