Integrated attitude determination system using a combination of magnetometer and horizon sensor data

[摘要] ENGLISH ABSTRACT:A different approach of employing attitude sensors with incomplete measurementsin an attitude determination system is investigated. The amount of available attitudesensors on small satellites are limited, and the failure of sensors can be fatalwhen accurate attitude determination is necessary. The problem with sensorswith incomplete measurements is that they must be used in combination withother sensors to obtain three dimensional attitude information. The aim is toenhance the possible number of sensor combinations that can be employed, in anattempt to improve the ability of the attitude determination system to toleratesensor failures.An alternative sensor structure consisting of a magnetometer and two horizonsensors is presented. A method to obtain vector observations of the attitudefrom a combination between magnetometer and horizon sensor measurements isderived and tested. A full state Extended Kalman Filter is used to determinethe satellite's attitude, attitude rate and disturbance torque from these vectorobservations.A second Extended Kalman Filter structure, using only magnetometer measurements,is implemented. The magnetometer Extended Kalman Filter and thehorizon/magnetometer Extended Kalman Filter are integrated to obtain a singleExtended Kalman Filter structure to determine the satellite's full attitude state.Integration is done by switching between the different pairs of vector information.A systematic analysis of the integrated filter's dynamic behaviour duringthe switching stages is done by means of a series of case studies.

[发布机构] Stellenbosch University