Comparative Study of Passive and Active Attitude Control of a Microsatellite

Paper number

IAC-07-C1.I.02

Author

Mr. Harijono Djojodihardjo, Universitas Al Azhar Indonesia, Indonesia

Coauthor

Setyamartana Parman, Malaysia

Coauthor

Md Azlin Md Said, Malaysia

Year

2007

Abstract

A comparative study to be carried out on the  passive and active control of a flexible microsatellite, which is here assumed to consist of rigid main body and symmetrical and flexible solar panels equipped by on-off thrusters. For passive control gravity-gradient stabilization will be considered, while for active control,  thrusters, momentum wheels or control moment gyros can be considered. As passive control, the use of a long tail boom will be selected, while for active control we study the application of shaped torque inputs resulted by on-off electric thrusters. In this study, the satellite considered has no control and no damping properties on the flexible solar panels. In the analysis, the equations of motion of the satellite developed earlier by the first author is utilized. Rest-to-rest maneuver is considered . 
A time-optimal input is an input given to a certain maneuver in the shortest time duration. The input to slew the system in rest-to-rest maneuver is a bang-bang in maximum amplitude. The dynamics of the satellite is simulated numerically using the unconditionally stable Newmark method. To reduce the satellite oscillation after maneuver by using thruster, time-optimal input shaping method is selected. The main purpose of the input shap¬ing is to limit the amount of residual vibration that oc¬curs when the system reaches its desired setting point. Whenever possible, the bang-bang input is used as the standard for commands that slew from rest to rest.
As a passive control, the long rigid boom is attached to the main body of satellite in Zb-direction in order to reduce the attitude angle oscillations. To reduce the roll oscillation, as in the active control, the roll and yaw torque inputs then to be shaped. Under time-optimal roll and yaw shaped torques and by combining with the bang-bang pitch torque, the roll angle oscillation can be reduced sharply. 
The study shows that input shaping method and rigid long boom can be used to control the attitude maneuver of the microsatellite. Both input shaping and long boom attachment can successfully reduce residual oscillations of attitude angles into the accepted levels. To reduce roll angle oscillation,  the use of rigid long boom has a better capability than the input shaping, but the duration of torques needed is about 2.5 times. Besides of torques, thruster forces are also needed to maneuver the satellite with rigid long boom attached to the main body. In summary, Results indicate that both rigid long boom attaching and input shaping can successfully satisfy the pointing accuracy.

Abstract document

IAC-07-C1.I.02.pdf

Manuscript document

IAC-07-C1.I.02.pdf (🔒 authorized access only).

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