Robust Control of High Altitude Long Endurance Unmanned Aerial Vehicles using Novel Lift Effectors
Author(s)
Cook, Robert Graham
Type
Thesis
Abstract
High-Altitude Long-Endurance Unmanned Aerial Vehicles (HALE UAVs) have been the focus
for many researchers in the past decades, and are becoming more and more attainable as
technology is improving. Recent interest into solar-powered HALE UAVs is leading the way
to achieving flight-times which are not limited by a requirement for refuelling, and could
continue for months at a time. Such aircraft have huge potential in providing reconnaissance
or communications services, and could potentially take on the usual roles of satellites as a
much cheaper alternative. One area of HALE UAV design which requires further technological
developments is automated control of trajectory, and active alleviation of gusts. The latter
concern is of particular interest to this thesis.
In this work, a coupled flight dynamics and aeroelastic methodology will be introduced.
This approach features a geometrically-exact beam model, which is required to capture the
large deformations expected in such flexible aircraft, along with unsteady aerodynamics. The
intrinsically nonlinear system is then linearised to provide an approximation to the system
dynamics which is more approachable for control synthesis. With a linearisation of the system,
robust linear control methods are applied to derive a controller which can reduce the loading
onto the system, while simultaneously stabilising it and providing some degree of robustness
which can still perform given the unmodelled dynamics that appear in the nonlinear system.
This linear control approach will be investigated on two types of HALE UAV with very
different dynamic responses to determine how well such control methods deal with nonlinearities,
and what the limitations of such an approach may be to apply in real-life. In addition,
various novel control effectors will be then considered for gust alleviation of a very flexible aircraft, using the closed-loop control as a method to fairly assess their effectiveness.
for many researchers in the past decades, and are becoming more and more attainable as
technology is improving. Recent interest into solar-powered HALE UAVs is leading the way
to achieving flight-times which are not limited by a requirement for refuelling, and could
continue for months at a time. Such aircraft have huge potential in providing reconnaissance
or communications services, and could potentially take on the usual roles of satellites as a
much cheaper alternative. One area of HALE UAV design which requires further technological
developments is automated control of trajectory, and active alleviation of gusts. The latter
concern is of particular interest to this thesis.
In this work, a coupled flight dynamics and aeroelastic methodology will be introduced.
This approach features a geometrically-exact beam model, which is required to capture the
large deformations expected in such flexible aircraft, along with unsteady aerodynamics. The
intrinsically nonlinear system is then linearised to provide an approximation to the system
dynamics which is more approachable for control synthesis. With a linearisation of the system,
robust linear control methods are applied to derive a controller which can reduce the loading
onto the system, while simultaneously stabilising it and providing some degree of robustness
which can still perform given the unmodelled dynamics that appear in the nonlinear system.
This linear control approach will be investigated on two types of HALE UAV with very
different dynamic responses to determine how well such control methods deal with nonlinearities,
and what the limitations of such an approach may be to apply in real-life. In addition,
various novel control effectors will be then considered for gust alleviation of a very flexible aircraft, using the closed-loop control as a method to fairly assess their effectiveness.
Date Issued
2012
Date Awarded
2012-08
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Palacios Nieto, Rafael
Sponsor
Engineering and Physical Sciences Research Council ; QinetiQ (Firm)
Publisher Department
Aeronautics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)