Navigation Functionalities for an Autonomous UAV Helicopter

Chapter 5
Sensor fusion for vision
based landing
This chapter describes the sensor fusion approach applied to a vision based
landing capability described in Paper III.
The vision based autonomous landing mode developed during the WITAS
Project has been tested on the RMAX helicopter. It allows the helicopter
to successfully complete a landing maneuver autonomously from an altitude
of about 20 meters using only a single camera and inertial sensors
(GPS is not used). An artificial landing pattern has been designed and it
is placed on the ground during the landing maneuver. An on-board video
camera, mounted on a pan-tilt mechanism, locks on the pattern while an
image processing algorithm computes the relative position of the on-board
camera and the pattern. This position is then used in the sensor fusion
filter described in this chapter in order to provide reliable helicopter state
for the autonomous landing. During the landing phase a pan-tilt controller
tracks the pattern keeping it in the middle of the image. This feature increases
the robustness of the landing approach described here, minimizing
the possibility of loosing the pattern from the camera view due to accidental,
abrupt helicopter movements.
Vision based autonomous landing is a complex problem and it requires
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