Extended high-gain observer-based output feedback control of underactuated quadrotor
Underactuated system is a nonlinear system having less actuators than the number of states to be controlled. The control for underactuated system is already a challenging task. It will be more difficult in the presence of external disturbances. Quadrotor is one example of an underactuated system....
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| Format: | Thesis |
| Language: | English |
| Published: |
2018
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/77274/1/FK%202018%20174%20IR.pdf |
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| Summary: | Underactuated system is a nonlinear system having less actuators than the number of
states to be controlled. The control for underactuated system is already a challenging
task. It will be more difficult in the presence of external disturbances. Quadrotor is one
example of an underactuated system. For quadrotor to overcome the external
disturbance, it needs energy. However, energy limitation is the main challenges in
quadrotor to serve the applications. An Extended High-gain Observer (EHGO) is
proposed to stabilize the underactuated system in the presence of external disturbance
with optimize energy consumption. In this study, the energy consumption is analyzed
based on the control effort represented by control signal.
EHGO has shown good potential to handle disturbances in the fully actuated system and
underactuated system. In most studies, EHGO was successfully implemented on
established board, which is of good quality but high cost. The capability of EHGO in the
low-cost off-the-shelf common board has a high interest in a wide group of practitioners,
hence it is worth investigating. Therefore, a control design framework and validation of
EHGO - output feedback control (EHGO-OFB) for quadrotor trajectory tracking under
broader flight envelope that is implementable in real-time using off-the-shelf common
quadrotor platform is presented.
A generalised closed-loop underactuated system model using EHGO-OFB in presence
of disturbances was derived. An additional dynamic state equation is obtained which
results in a closed-loop system in two-time-scale structure that is less complex.
Consequently, this thesis extended the existing theorem of EHGO-OFB from fullyactuated
to underactuated nonlinear system.
The validation was performed in simulation and experimental. In simulation, the overall
performance of EHGO-OFB in hierarchical controller (HC) improves the control effort
by 36% from the standard HC. Meanwhile, the EHGO-OFB in sliding mode control (SMC) shows 15% improvement in the control accuracy achievable using smaller control
effort compared to standard SMC. This simulation result provides an alternative to deal
with chattering problem in SMC that has become the limitation of SMC when applied to
a quadrotor.
In experiment, a 39.64% improvement in the control effort was obtained for proposed
EHGO-OFB based on existing hierarchical flight controller (HFC). The flight test was
performed in the Indoor Space flight arena in Universiti Putra Malaysia using low-cost
off-the-shelf common components with sampling rate of 0.01s. An EHGO gain of 0.01
was able to achieve a good performance for the quadrotor. The existing HFC based on
PID algorithm rejects the disturbance by physical means and consume more energy
whereas the EHGO-OFB reject the disturbance internally. The controller able to maintain
the quadrotor in a bounded area with notably smaller control effort even in the presence
of wind as external disturbance. The work in this thesis is expected to enhance the
performance of quadrotor in various fields. |
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