Enhanced attitude control structure for small satellites with reaction wheels

Attitude accuracies of a three-axis satellite are highly influenced by space environment disturbances and uncertainties. Similar to actuators, an attitude controller also plays an important role and must be robust enough to cope with any disturbances and uncertainties. Various controllers have be...

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Main Author:	Ismail, Zuliana
Format:	Thesis
Language:	English
Published:	2019
Subjects:	Attitude control systems (Astronautics) Microspacecraft
Online Access:	http://psasir.upm.edu.my/id/eprint/98227/1/FK%202019%20159%20-%20IR.pdf
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id	my-upm-ir.98227
record_format	uketd_dc
spelling	my-upm-ir.982272022-08-02T01:46:40Z Enhanced attitude control structure for small satellites with reaction wheels 2019-08 Ismail, Zuliana Attitude accuracies of a three-axis satellite are highly influenced by space environment disturbances and uncertainties. Similar to actuators, an attitude controller also plays an important role and must be robust enough to cope with any disturbances and uncertainties. Various controllers have been used for satellite attitude controls either linear or nonlinear control theories. This thesis presents an enhanced attitude control structure for a small satellite with reaction wheels (RWs) and the wheel angular momentum unloading control using magnetic torquers (MTQs). In order to improve the attitude control performances, a proportional derivative-active force control (PDAFC), and a Fuzzy PD-AFC are developed. For the momentum unloading control, a Fuzzy-proportional integral (Fuzzy-PI) is developed to remove the excess wheel momentum. Using the PD-AFC and Fuzzy PD-AFC, the actual disturbances torques are considered totally rejected by the system without having to have any direct prior knowledge on the actual disturbances itself. These days, however, satellites have become increasingly more complex, with many additional components, such as antennas, cameras, solar panels and mechanical manipulators. These components introduce flexible mode which results in a satellite dynamic system becoming highly nonlinear. Therefore, a robust nonlinear controller such as sliding mode control (SMC) is highly desirable. Besides, a number of studies have shown that, fractional order controller (FOC) could enhance the control system performance due to its extra degrees of freedom. In this thesis, a fractional order sliding mode control (FOSMC) is developed. In fact, this current work will be one of the maiden works on FOSMC for small satellites. All the proposed controllers were also tested for a satellite with only two functional RWs, in which the control allocation technique is proposed to solve the underactuated satellite attitude control problem. All the relevant attitude control architectures are developed together with their governing equations. Eventually, all control algorithms are numerically treated and analysed. The research results obtained proved that the PD-AFC, Fuzzy PD-AFC and FOSMC to be successful in achieving the overall stability attitude control system in the presence of external disturbances and uncertainties, i.e., PD-AFC (±0.0040° - 0.0055°) ; Fuzzy PD-AFC (±0.0010° - 0.0015°); FOSMC (±0.00020), and with the Fuzzy-PI for momentum unloading control whereby, the wheel momentum can be well maintained. Finally, the research for underactuated satellite attitude control performances using two RWs have been also successfully demonstrated and the research results proved that the control allocation technique provides a good performance in controlling the satellite attitude. Attitude control systems (Astronautics) Microspacecraft 2019-08 Thesis http://psasir.upm.edu.my/id/eprint/98227/ http://psasir.upm.edu.my/id/eprint/98227/1/FK%202019%20159%20-%20IR.pdf text en public doctoral Universiti Putra Malaysia Attitude control systems (Astronautics) Microspacecraft Varatharajoo, Renuganth
institution	Universiti Putra Malaysia
collection	PSAS Institutional Repository
language	English
advisor	Varatharajoo, Renuganth
topic	Attitude control systems (Astronautics) Microspacecraft
spellingShingle	Attitude control systems (Astronautics) Microspacecraft Ismail, Zuliana Enhanced attitude control structure for small satellites with reaction wheels
description	Attitude accuracies of a three-axis satellite are highly influenced by space environment disturbances and uncertainties. Similar to actuators, an attitude controller also plays an important role and must be robust enough to cope with any disturbances and uncertainties. Various controllers have been used for satellite attitude controls either linear or nonlinear control theories. This thesis presents an enhanced attitude control structure for a small satellite with reaction wheels (RWs) and the wheel angular momentum unloading control using magnetic torquers (MTQs). In order to improve the attitude control performances, a proportional derivative-active force control (PDAFC), and a Fuzzy PD-AFC are developed. For the momentum unloading control, a Fuzzy-proportional integral (Fuzzy-PI) is developed to remove the excess wheel momentum. Using the PD-AFC and Fuzzy PD-AFC, the actual disturbances torques are considered totally rejected by the system without having to have any direct prior knowledge on the actual disturbances itself. These days, however, satellites have become increasingly more complex, with many additional components, such as antennas, cameras, solar panels and mechanical manipulators. These components introduce flexible mode which results in a satellite dynamic system becoming highly nonlinear. Therefore, a robust nonlinear controller such as sliding mode control (SMC) is highly desirable. Besides, a number of studies have shown that, fractional order controller (FOC) could enhance the control system performance due to its extra degrees of freedom. In this thesis, a fractional order sliding mode control (FOSMC) is developed. In fact, this current work will be one of the maiden works on FOSMC for small satellites. All the proposed controllers were also tested for a satellite with only two functional RWs, in which the control allocation technique is proposed to solve the underactuated satellite attitude control problem. All the relevant attitude control architectures are developed together with their governing equations. Eventually, all control algorithms are numerically treated and analysed. The research results obtained proved that the PD-AFC, Fuzzy PD-AFC and FOSMC to be successful in achieving the overall stability attitude control system in the presence of external disturbances and uncertainties, i.e., PD-AFC (±0.0040° - 0.0055°) ; Fuzzy PD-AFC (±0.0010° - 0.0015°); FOSMC (±0.00020), and with the Fuzzy-PI for momentum unloading control whereby, the wheel momentum can be well maintained. Finally, the research for underactuated satellite attitude control performances using two RWs have been also successfully demonstrated and the research results proved that the control allocation technique provides a good performance in controlling the satellite attitude.
format	Thesis
qualification_level	Doctorate
author	Ismail, Zuliana
author_facet	Ismail, Zuliana
author_sort	Ismail, Zuliana
title	Enhanced attitude control structure for small satellites with reaction wheels
title_short	Enhanced attitude control structure for small satellites with reaction wheels
title_full	Enhanced attitude control structure for small satellites with reaction wheels
title_fullStr	Enhanced attitude control structure for small satellites with reaction wheels
title_full_unstemmed	Enhanced attitude control structure for small satellites with reaction wheels
title_sort	enhanced attitude control structure for small satellites with reaction wheels
granting_institution	Universiti Putra Malaysia
publishDate	2019
url	http://psasir.upm.edu.my/id/eprint/98227/1/FK%202019%20159%20-%20IR.pdf
_version_	1747813849406373888

Enhanced attitude control structure for small satellites with reaction wheels

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