Abstract

Limited navigation capabilities of many current robots and UAVs restricts their applications in GPS denied areas. Large aircraft with complex navigation systems rely on a variety of sensors including radio frequency aids and high performance inertial systems rendering them somewhat resistant to GPS denial. The rapid development of computer vision has seen cameras incorporated into small drones. Vision-based systems, consisting of one or more cameras, could arguably satisfy both size and weight constraints faced by UAVs. A new generation of thermal sensors is available that are lighter, smaller and widely available. Thermal sensors are a solution to enable navigation in difficult environments, including in low-light, dust or smoke. The purpose of this paper is to present a comprehensive literature review of thermal sensors integrated into navigation systems. Furthermore, the physics and characteristics of thermal sensors will also be presented to provide insight into challenges when integrating thermal sensors in place of conventional visual spectrum sensors.

Highlights

  • Research on unmanned aerial vehicles (UAVs) has grown rapidly in the past decade

  • Considering the observations above, we provide a review with a focus on the integration of thermal sensors for navigation applications within the last decade, from 2010 to the present period

  • This section will discuss the specifications of different thermal sensors that are suitable for navigation application, including cooled and uncooled sensor technologies, dimensions, weights, power consumptions, resolutions and effective frame rates

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Summary

Introduction

Research on unmanned aerial vehicles (UAVs) has grown rapidly in the past decade. First, initially developed for military purposes [1], UAVs have been widely used in many applications including industrial inspection [2,3], remote sensing for mapping and surveying [4,5], rescue missions [6,7,8,9,10,11], border control [12] and for other emerging civil applications. UAVs rely heavily on an array of sensors for its navigation. IMUs provide a limited period of accurate positioning after external aiding is lost, as they drift without bound from integrating cumulative errors over time [15]. Vision-based navigation systems are a promising research direction in the field of autonomous navigation. Vision sensors can provide real-time information about a dynamic surrounding environment that is resistant to conventional jamming. Vision sensors detect reflected photons or radiated photons in specific bands across the electromagnetic spectrum. The predominance of research to date considers optical sensors that require some form of illumination of the scene. There is a substantial gap in the ability to navigate at night given that it has the potential to increase the operational period of vision systems

Navigation Problems with Thermal Sensors
Aims and Search Methodology
Structure of the Paper
Thermal Sensor System Considerations for Navigation Applications
Cooled and Uncooled Sensor
Sensor Specification Constraints for Unmanned Platforms
Platform Considerations
Physics of Thermal Sensors
Black Body Radiation
Electromagnetic Spectrum
Emissivity
Thermal Sensor Configurations
Sensor Calibration
Re-Scaling and Correction Techniques
Automatic Gain Control
Flat Field and Non-Uniformity Corrections
Combined Spectrum Techniques
Re-Scaled Data
Optical Flow
Thermal Flow
Deep Learning
Thermal Image Enhancement
Deep Learning Neural Network Based Odometry
10. Roles of Thermal Sensors in Navigation Systems and Applications
11. Navigation Approaches with Respect to System Configuration
11.2. Odometry
11.3. Other Applications
Findings
12. Discussion
13. Conclusions
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