Vision Guided Drone Flight for Entering Confined Spaces for Inspection

Unmanned aerial vehicle (UAV) flight in confined spaces is an emerging area of interest because solutions can create opportunities for developing drone-based inspections for societal benefits, military and other applications. This article describes new work in the area of UAV flight in confined spaces. To develop the UAVs' ability to operate in small space environments, the task of identifying an opening to the confined space and determine its center was solved, with the goal being to autonomously minimize the distance between the UAV's position and the gate's center. There were three main approaches for gate detection, each involving placing an object in the four corners of the gateway. The first approach to gate detection was grayscale and HSV filtering of LED lights. Using a combination of both HSV and grayscale filtering caused glare from the LED lights to skew center detection of each light. The second strategy was to train YOLOv5 using over 200 annotated images of LED lights, but it still produced an issue of identifying false positives which caused the center to skew. The third detection strategy utilized april tags instead of LED lights. The specific patterns solve the issue of false positives entirely, for each april tag has a unique recognizable pattern. The new issue was visibility as a result of lighting. However, the positives of size manipulation and accuracy overshadowed this. The maximum resolutions and distances at which the April tags could be detected were tested with the picamera V1. Based on algorithms for the RaspberryPi, the UAV was able to adjust it's flight with the center of the april tag gateway achieving the project goal.