A master thesis from Aalborg University
Attitude Determination and Control System for AAUSAT3
Author(s)
Term
10. term
Publication year
2010
Submitted on
2010-06-02
Pages
224 pages
Abstract
This thesis describes the design and analysis of an Attitude Determination and Control System (ADCS) for CubeSats and has been motivated by the need for such a system on AAUSAT3, the next satellite from Aalborg University. Evaluation of the performance of the designed ADCS is addressed with the introduction of a simulation environment for AAUSAT3, implemented in Matlab Simulink as a library. Effort has been put in keeping the library reusable and it can therefore easily be extended for future satellites. An ADCS hardware prototype has been developed with the purpose of testing chosen sensors and actuators, which are a 3-axis magnetometer, a 3-axis gyroscope, sun sensors and magnetorquers. A quaternion implementation of an Unscented Kalman Filter for attitude estimation on CubeSats using a low cost of the shelf sensor setup, is proposed. Emphasis has been put in making the implementation accessible to other CubeSat developers via pseudo code and results indicate, that it is possible to achieve acceptable attitude estimation, even during eclipse, without high precision sensor setups, as long as bias in the sensors are estimated. It is finally shown, how reliable detumbling can be achieved by use of a B-dot control law that also provides 2-axis attitude stability relative to the local geomagnetic field by use of a permanent magnet. Additionally, ideas for a globally stabilizing attitude acquisition controller using model predictive control theory is given and problems associated with magnetic actuation and nonlinear model predictive control are outlined.
Keywords
Attitude Determination and Control System ; ADCS ; CubeSat ; AAUSAT3 ; Matlab Simulink simulation environment ; satellite ; quaternions ; Unscented Kalman Filter ; UKF ; Extended Kalman Filter ; EKF ; SVD-method ; Wahba's problem ; Detumbling ; B-dot ; 2-axis attitude stability ; globally stabilizing attitude acquisition ; Model Predictive Control ; MPC ; Nonlinear MPC ; magnetic actuation ; ADS ; ACS ; Attitude estimation ; MPC with re-linearization
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