A multi-mode attitude determination and control system for small satellites

[摘要] ENGLISH ABSTRACT:New advanced control techniques for attitude determination and control of small (micro)satellites are presented. The attitude sensors and actuators on small satellites are limited inaccuracy and performance due to physical limitations, e.g. volume, mass and power. Toenhance the application of sophisticated payloads such as high resolution imagers within theseconfinements, a multi-mode control approach is proposed, whereby various optimizedcontroller functions are utilized during the orbital life of the satellite.To keep the satellite's imager and antennas earth pointing with the minimum amount of controleffort, a passive gravity gradient boom, active magnetic torquers and a magnetometer areused. A cross-product detumbling controller and a robust Kalman filter angular rateestimator are presented for the preboom deployment phase. A fuzzy controller andmagnetometer full state extended Kalman filter are presented for libration damping and Z-spinrate control during inactive imager periods.During imaging, when high performance is required, additional fine resolution earth horizon,sun and star sensors plus 3-axis reaction wheels are employed. Full state attitude, rate anddisturbance estimation is obtained from a horizon/sun extended Kalman filter. A quaternionfeedback reaction wheel controller is presented to point or track a reference attitude duringimaging. A near-minimum time, eigenaxis rotational reaction wheel controller for largeangular maneuvers.Optimal linear quadratic and minimum energy algorithms to do momentum dumping usingmagnetic torquers, are presented. A new recursive magnetometer calibration method isdesigned to enhance the magnetic in-flight measurements. Finally, a software structure isproposed for the future onboard implementation of the multi-mode attitude control system.

[发布机构] Stellenbosch University