MCRLS for On-line Spacecraft Mass- and Thruster-Property Identification

E. Wilson, D.W. Sutter, and R.W. Mah (USA)


identification; spacecraft; mass; thruster; on-line;parameter estimation


Spacecraft control, state estimation, and fault-detection-and-isolation systems are affected by unknown variations in the vehicle mass and thruster properties. It is often difficult to accurately measure inertia terms on the ground, and mass properties can change on-orbit as fuel is expended, the configuration changes, or payloads are added or removed. Multiple concurrent recursive least squares identification (MCRLS ID) algorithms using gyros and accelerometers to monitor vehicle motions are used here to identify on-line the vehicle inertia, inverse-inertia, center of mass, thruster force, and total mass. Originally developed for application to the X-38 v.201 spacecraft, the algorithms have been extended and implemented on the MIT SPHERES experimental spacecraft, which are now awaiting launch to the ISS for space-based testing. The MCRLS ID algorithm is summarized briefly, and advances in the specific ID algorithms are presented. An accurate and efficient filtering method for estimating angular acceleration from raw gyro signals is presented.

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