Attitude control with FDI for an experimental satellite model

Paper number

IAC-06-C1.2.09

Author

Mr. Jøran Antonsen, NAROM - Norwegian Centre for Space-Related Education, Norway

Coauthor

Raymond Kristiansen, Narvik University College, Norway

Coauthor

Dr. Per Johan Nicklasson, Narvik University College, Norway

Year

2006

Abstract

In this paper we present some design aspects of the Attitude Determination and Control System (ADCS) for an experimental satellite model currently being built at Narvik University College (NUC), Norway. Mathematical details regarding reference frames, spacecraft dynamics and kinematics, attitude controller, actuator dynamics, actuator torque allocation and Fault Detection and Isolation (FDI) are included. The hardware model is equipped with an Inertial Measuring Unit (IMU) to provide angular velocity measurements, and four reaction wheels in a tetrahedron configuration for attitude control. It is proposed to use gimbals to make the satellite model able to rotate in all three axes. The onboard computer consists of a microcontroller from Microchip. During test procedures all data is logged and transmitted to a computer via RS232 interface where it can be analysed. The satellite model has not been finalised yet and there might be some smaller changes.

The IMU provides angular velocity measurements to the onboard ADCS. These measurements are then converted into attitude information in terms of Euler parameters. To control the attitude of the satellite model, a quaternion-based vectorial integrator backstepping controller is derived, which results in asymptotically stable equilibrium points in the closed loop system. The controller utilizes the redundancy in the Euler parameter vector to control the attitude, and gives the advantage that the closest equilibrium point with respect to rotation path is always chosen when a given attitude change is commanded.

Since the reaction wheels are electromechanical devices, they are susceptible for faults due to bearing failure, torque motor failure etc. Hence it is necessary to provide redundancy in the reaction wheel assembly. This actuator configuration provides a redundant actuator assembly, and the ADCS includes a FDI scheme to ensure proper attitude control of the satellite model in case of reaction wheel failure. When a failure is detected the control scheme is immediately changed to an alternative control scheme that isolates the failed wheel and switches to an alternate scheme such that it provides sufficient control for stabilizing the spacecraft and also compensating for disturbance torques occurring due to the malfunctioning wheel. If the error for some reason disappears, the original control scheme might be restored.

The attitude response of the system and robustness towards external disturbances and actuator failures are visualized by simulation results in Matlab. A discussion with respect to controller performance, power consumption and robustness towards external disturbances and actuator failure is given.

Abstract document

IAC-06-C1.2.09.pdf

Manuscript document

IAC-06-C1.2.09.pdf (🔒 authorized access only).

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