Real-time on-board obstacle avoidance for UAVs based on embedded stereo vision

TL;DR

This paper presents a lightweight, real-time obstacle avoidance system for UAVs using embedded stereo vision, optimized disparity map computation on FPGA, and reactive navigation, enhancing safety and reducing development costs.

Contribution

It introduces an FPGA-optimized disparity estimation method using semi-global matching and high-level synthesis, enabling real-time obstacle avoidance on lightweight UAVs.

Findings

Achieved real-time obstacle detection and avoidance in UAVs.

Validated system performance with Hardware-in-the-Loop and flight simulators.

Demonstrated effective obstacle avoidance with optimized FPGA implementation.

Abstract

In order to improve usability and safety, modern unmanned aerial vehicles (UAVs) are equipped with sensors to monitor the environment, such as laser-scanners and cameras. One important aspect in this monitoring process is to detect obstacles in the flight path in order to avoid collisions. Since a large number of consumer UAVs suffer from tight weight and power constraints, our work focuses on obstacle avoidance based on a lightweight stereo camera setup. We use disparity maps, which are computed from the camera images, to locate obstacles and to automatically steer the UAV around them. For disparity map computation we optimize the well-known semi-global matching (SGM) approach for the deployment on an embedded FPGA. The disparity maps are then converted into simpler representations, the so called U-/V-Maps, which are used for obstacle detection. Obstacle avoidance is based on a reactive approach which finds the shortest path around the obstacles as soon as they have a critical distance to the UAV. One of the fundamental goals of our work was the reduction of development costs by closing the gap between application development and hardware optimization. Hence, we aimed at using high-level synthesis (HLS) for porting our algorithms, which are written in C/C++, to the embedded FPGA. We evaluated our implementation of the disparity estimation on the KITTI Stereo 2015 benchmark. The integrity of the overall realtime reactive obstacle avoidance algorithm has been evaluated by using Hardware-in-the-Loop testing in conjunction with two flight simulators.