Abstract:
Unmanned aerial vehicles (UAVs), also known as drones, have gained popularity and
significant attention in different disciplines of military and civilian services due to their
versatility, lower cost and ease of deployment. Just like any other fixed wing aircraft, landing
phase of fixed wing UAV is the most critical and challenging phase of flying. GPS has been
widely used as the primary navigation sensor for UAVs but the accuracy of GPS, without any
form of augmentation, is not enough for autonomous landing where precise height estimation
is mandatory for safe landing. Although, most of the fixed wing UAVs are equipped with
autonomous landing system, still it is recommended to put a human pilot in the loop for a safer
landing. In addition to GNSS and INS, state of the art fixed wing military UAVs are aided by
ground-based landing radars for safe autonomous landing. Ground based landing radars are
expensive as well as restrict operation of UAVs to specific runways equipped with radars.
Now a days, RTK GPS receivers are getting cheaper and more accurate. Cheaper laser distance
measuring sensor like LIDAR can also be used for precise altitude measurement. In this
research work, altitude estimating performances of GPS, RTK GPS and LIDAR have been
compared using Software in The Loop (SITL) simulation to find out which sensor works best
as reliable flare altitude estimating sensor for fixed wing UAV. The findings of simulation
were further consolidated by developing a test setup and carrying out test flights. Simulation
and test flight results show the potentials of using cost effective sensors like LIDAR sensor
and RTK GPS as landing aid during the flare phase of landing for fixed wing UAV.
