Abstract

With the popularization and wide application of drones in military and civilian fields, the safety of drones must be considered. At present, the failure and drop rates of drones are still much higher than those of manned aircraft. Therefore, it is imperative to improve the research on the safe landing and recovery of drones. However, most drone navigation methods rely on global positioning system (GPS) signals. When GPS signals are missing, these drones cannot land or recover properly. In fact, with the help of optical equipment and image recognition technology, the position and posture of the drone in three dimensions can be obtained, and the environment where the drone is located can be perceived. This paper proposes and implements a monocular vision-based drone autonomous landing system in emergencies and in unstructured environments. In this system, a novel map representation approach is proposed that combines three-dimensional features and a mid-pass filter to remove noise and construct a grid map with different heights. In addition, a region segmentation is presented to detect the edges of different-height grid areas for the sake of improving the speed and accuracy of the subsequent landing area selection. As a visual landing technology, this paper evaluates the proposed algorithm in two tasks: scene reconstruction integrity and landing location security. In these tasks, firstly, a drone scans the scene and acquires key frames in the monocular visual simultaneous localization and mapping (SLAM) system in order to estimate the pose of the drone and to create a three-dimensional point cloud map. Then, the filtered three-dimensional point cloud map is converted into a grid map. The grid map is further divided into different regions to select the appropriate landing zone. Thus, it can carry out autonomous route planning. Finally, when it stops upon the landing field, it will start the descent mode near the landing area. Experiments in multiple sets of real scenes show that the environmental awareness and the landing area selection have high robustness and real-time performance.

Highlights

  • Unmanned aerial vehicles (UAVs) are non-manned aircraft that are operated by radio remote control equipment or a self-contained program control device

  • The appropriate landing height H is selected from the previous grid height categories and the appropriate landing area S is set according to the size of the UAV

  • In order to reduce the error of the pose information and the 3D point cloud data estimated by the simultaneous localization and mapping (SLAM) system, after completing the initialization, the UAV started the closed-loop flight, followed by some closed loops of smaller radius

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Summary

Introduction

Unmanned aerial vehicles (UAVs) are non-manned aircraft that are operated by radio remote control equipment or a self-contained program control device. Based on the previous paper, authors in [2] describes the tracking guidance for autonomous drone landing and the vision-based detection of the marker on a moving vehicle with a real-time image processing system. An anti-collision algorithm that takes both safety and economy into consideration will automatically re-plan the route after the UAV has implemented collision avoidance maneuvers to continue the task This method can be applied to the passive landing of drones in complex scenarios or in emergency situations and the active landing of drones, and to many areas such as the automatic driving of unmanned vehicles, augmented reality, and the autonomous positioning of robots. Based on a grid map and region segmentation, we present a visual landing technology to explore a suitable landing area for drones in emergencies and unknown environments.

The Approach
Sparse Depth Measurement
Grid Map Creation
Pose and Map Optimization
Region Segmentation-Based Landing Area Detection
Experimental Platform
Real-Time Control Experiments
Landing Area Detection in Multi-Scenario
Findings
Conclusions
Full Text
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