Stabilization and Control of a Quad-Rotor Micro-UAV Using Vision Sensors

Abstract

Quad-rotor micro-UAVs have become an important tool in the field of indoor UAV research. Indoor flight poses problems not experienced in outdoor applications. The ability to be location- and movement-aware is paramount because of the close proximity of obstacles (walls, doorways, desks). The Helio-copter, an indoor quad-rotor platform that utilizes a compact FPGA board called Helios has been developed in the Robotic Vision Lab at Brigham Young University. Helios allows researchers to perform on-board vision processing and feature tracking without the aid of a ground station or wireless transmission. Using this on-board feature tracking system a drift stabilization control system has been developed that allows indoor flight of the Helio-copter without tethers. The Helio-copter uses an IMU to maintain level attitude while processing camera images on the FPGA. The FPGA then computes translation, scale, and rotation deviations from camera image feedback. An on-board system has been developed to control yaw, altitude and drift based solely on the vision sensors. Preliminary testing shows the Helio-copter capable of maintaining level, stable flight within a 6 foot by 6 foot area for over 40 seconds without human intervention using basic PID loop structures with minor tuning. The integration of the vision system into the control structures is explained.