Foldable Multi-Rotor UAV Arms for Compact Storage and Flight Lift

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Solution Overview

Problem

Existing aerial vehicles, such as UAVs, face challenges in optimizing form factor and portability due to the outward extension of arms and rotor blades, which increase volume and reduce portability, and existing locking mechanisms are cumbersome, unreliable, and weight-increasing.

Innovation Solution

The UAV includes foldable sections that can transform between flight and compact configurations using elastic elements and actuation, allowing arms and rotor blades to be automatically or semi-automatically retracted and extended, with minimal manual intervention, and optimizing internal space usage without widening the airframe.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the arms and rotor blades are extended outward for flight operation, then the lift force and flight performance are improved, but the volume occupied by the aerial vehicle increases and portability deteriorates

Engineering Contradiction:
Improvelift forceVSAvoidvolume occupied
Core Design Contradiction:
StrengthVSVolume of moving object

Solution Approach 1:

The arms are designed to be movable between extended and retracted positions relative to the central body. During flight operation, the arms extend outward to provide sufficient lift force. When not in use, the arms retract to minimize the volume occupied, thereby improving portability while maintaining flight performance when needed.

Inventive Principle:
Principle #15Dynamics

2Stability of the object's composition

If manual locking mechanisms are used to secure folded arms, then the structural stability is improved, but the device complexity and weight increase

Engineering Contradiction:
Improvestructural stabilityVSAvoidlocking mechanism complexity
Core Design Contradiction:
Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The arm folding and locking system operates automatically without requiring manual intervention. The propulsion units or dedicated actuators drive the arms between folded and extended states, and locking mechanisms engage automatically at predetermined positions, reducing mechanical complexity and eliminating the need for manual operation while maintaining structural stability.

Inventive Principle:
Principle #25Self-service

3Ease of operation

If the airframe is widened to accommodate rotatable joints of foldable sections, then the ease of operation is improved, but the form factor deteriorates and internal space optimization is reduced

Engineering Contradiction:
Improvefolding operation easeVSAvoidairframe shape
Core Design Contradiction:
Ease of operationVSShape

Solution Approach 1:

The rotatable joints for the foldable arms are positioned along the longitudinal axis of the central body rather than requiring lateral space. This allows the arms to rotate and fold without widening the airframe, maintaining a streamlined form factor while enabling smooth folding operations through longitudinal positioning of the joint mechanisms.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

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 design improves the form factor and portability of UAVs by reducing dimensions when not in use, minimizing manual effort, and enhancing reliability and weight efficiency.

Implementation Method 1

The joints may comprise one or more elastic elements. Each elastic element may be configured to cause the arm connected thereto to automatically retract when the arm is reversibly folded to a predetermined state. Each elastic element may also be configured to cause the arm connected thereto to automatically extend when the arm is reversibly extended to a predetermined state.

Methodology Applied
Scientific EffectElasticity: Elasticity

Data Source

PatentEP3971084B1AÉronef multi-rotor pliable
Publication Date: 2026.04.22 SZ DJI TECH CO LTD
  • EP3971084B1 patent drawingFigure 1
  • EP3971084B1 patent drawingFigure 2
  • EP3971084B1 patent drawingFigure 3

AI summary

An unmanned aerial vehicle (UAV) is described, comprising: a central body; and a plurality of arms extendable from the central body, wherein each arm of said plurality of arms is configured to support one or more propulsion units, wherein each of the plurality of arms is configured to transform between (1) a flight configuration wherein the arm is extending away from the central body, and (2) a compact configuration wherein the arm is folded against the central body, and wherein at least one of the plurality of arms is configured to be rotated about a first rotational axis that causes a distal end of the at least one of the plurality of arms to move both horizontally and vertically relative to the central body when transforming between the flight configuration and compact configuration.