Rotorcraft Propeller Sensing for Drift-Free Indoor Positioning

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Solution Overview

Problem

Existing rotorcraft systems lack accurate and cost-effective navigational sensing, with current solutions being limited in accuracy, restricted to outdoor or indoor use, expensive, and power-intensive.

Innovation Solution

The system embeds simple sensors into the rotating propellers of a rotorcraft to provide low-cost sensing of bearing, elevation, and distance, enabling communication with base stations, other rotorcraft, and robots.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If existing navigational sensing systems are used, then positioning capability is provided, but cost and power consumption increase significantly

Engineering Contradiction:

Improvepositioning accuracyVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent replaces complex mechanical/electronic navigation systems (GPS, inertial sensors, cameras) with a magnetic field-based sensing system. The rotor blades act as antennas that detect magnetic field signatures from transmission sources, substituting power-intensive mechanical and electronic systems with a simpler electromagnetic field interaction approach that consumes less power while providing positioning capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system uses magnetic field signatures as a simplified copy or representation of position information, rather than directly using complex sensor data from multiple navigation systems. The magnetic field patterns serve as a lightweight informational copy that enables positioning without requiring the full complexity of traditional navigation stacks.

Inventive Principle:

Principle #26Copying

2Measurement precision

If existing navigational sensing systems are used, then positioning capability is provided, but system cost increases

Engineering Contradiction:

Improvepositioning accuracyVSAvoidsystem cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent replaces expensive mechanical and electronic navigation systems with a magnetic field-based approach. Instead of using costly GPS receivers, inertial measurement units, and camera systems, the invention uses the rotor blades themselves as magnetic field sensors, dramatically reducing component costs while maintaining positioning functionality.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The rotor blades serve multiple functions: they generate lift/thrust for flight and simultaneously act as antennas for magnetic field detection. This multi-functionality eliminates the need for separate navigation hardware, reducing overall system cost while providing both propulsion and positioning capabilities.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If existing navigational sensing systems are used, then outdoor navigation is enabled, but indoor navigation capability is lost

Engineering Contradiction:

Improveenvironmental adaptabilityVSAvoidnavigation reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent replaces GPS-dependent navigation systems with magnetic field-based sensing that works independently of satellite signals. By using the Earth's magnetic field and local magnetic signatures from transmission sources, the system provides continuous navigation capability both outdoors and indoors, eliminating the outdoor/indoor limitation of GPS-based systems.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Ease of manufacture

If simple sensor systems are used, then cost and power consumption are reduced, but measurement accuracy deteriorates

Engineering Contradiction:

Improvesystem costVSAvoidpositioning accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The system uses the dynamic rotation of rotor blades to sweep the magnetic field sensing capability in multiple directions. As the blades rotate, they detect magnetic field signatures from different angles and positions, dynamically gathering information that enhances positioning accuracy despite using simple sensor components. The motion itself becomes part of the sensing mechanism.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The rotating rotor blades perform periodic sensing sweeps of the magnetic field environment. Each rotation provides a complete 360-degree scan of magnetic signatures, and by analyzing the periodic pattern of detected fields over multiple rotations, the system can accurately determine position and orientation using simple sensors.

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS12326725B2Sensing and communication system for rotorcraft

Publication Date: 2025.06.10 NORTHWESTERN UNIV

AI summary

A system for determining positional information of a rotorcraft includes a central controller and a first sensor unit. The first sensor unit is mounted to a first rotating portion of the rotorcraft and is in communication with the central controller. The first sensor unit includes one or more first receivers configured to receive signals from a remote transmission source. The first sensor unit also includes a processor configured to determine a bearing of the rotorcraft relative to the remote transmission source based in part on the signals received from the remote transmission source. The first sensor unit further includes a transmitter configured to transmit the bearing of the rotorcraft to a central controller of the rotorcraft.