Autonomous Flight Control of a Nano Quadrotor Helicopter in a GPS-Denied Environment Using On-Board Vision

In this paper, a nano quadrotor helicopter which weighs about only 45 grams and has a diameter less than 0.15 m is employed for the autonomous flight control development in GPS-denied environments. Due to the very limited payload ability of the helicopter, a micro onboard vision system is designed to provide visual pose measurement. Then the attitude data obtained from a low cost micro inertial measurement unit (IMU) are fused with the visual measurement to provide accurate estimation of the helicopter´s translational position and velocity. Nonlinear flight controller is designed to hold the quadrotor in a certain position and altitude without external ground motion capture system. Moreover, trajectory tracking ability is achieved with the help of a modified visual simultaneous localization and mapping (SLAM) algorithm. Experimental results are included to demonstrate the good hovering and tracking control performance of the proposed design in GPS-denied indoor and outdoor environments. To our best knowledge, few of previous works have demonstrated autonomous control ability of a quadrotor helicopter weighs less than 50 grams without the help of external ground motion capture system in GPS-denied indoor and outdoor environments.