An Altitude Estimation Technique for Autonomous Landing of a Quad-Rotor Using a Vision System

Abstract

This research work is to purpose a technique for autonomous landing of a quad-rotor by using the estimating of its altitude. The landing of the quad-rotor is in vertical direction. The detail about the design of a Landing Pad Target used for autonomous landing is explained. The autonomous landing procedure will include a mapping of the information on the detected landing pad to an altitude by using an altitude estimation algorithm with the Kalman filter. The information on the landing pad is in a form of graphic information which is easily to map to the estimated altitude of the quad-rotor used in the autonomous landing. The approximate errors from the estimation of the altitudes are within 1 cm. for 2 m. height. The control strategy is that the autonomous landing will start at an altitude of 10 meters while the landing target can be detected within this range. From the height between 10 m. to 3 m., the attached barometer is used for measurement of height and the vision system is used to estimate the height when the quad-rotor is lower than 3 m. From the experimental results, the effectiveness of the design of the landing pad, used with an appropriate control strategy, the approximate accuracy of 2 cm can be achieved. Most of the errors occur because during the last approach of landing, the height cannot be estimated from the vision but it is estimated from the measurement of the acceleration of the quad-rotor instead. Our purposed landing procedure is very promising for the autonomous landing of a quad-rotor and it can be implemented in real application.