Design of An Autonomous fault Tolerant Attitude Determination System for a Three Axis Satellite Based on Derivation of Different Rotation Matrices and Computation of Variance Measures

A fault tolerant attitude determination system for a three axis satellite has been suggested in this paper. For this purpose, the sun sensor and magnetometer data are only available. Using the designed algorithm, it is expected to have a reliable and continues process for computing the Euler angles. In other words, the faulty sensors should be determined and their faulty data are corrected automatically. The solution presented in this paper is a non-model based method that is based on on derivation of all possible rotations between reference and body frames. Using the Euler angles provided by these rotations, some variance measures are computed which utilized as an analytical tool for fault detection. With the development of this idea, it is shown that not only the faulty sensors but also their fault sources could be isolated. These sources are categorized into four levels that each level shows the fault extent. This paper also suggests some solutions for correcting the fault effects. So, the proposed approach is a non-model based methodology for fault management that is not affected by the dynamic variations or the uncorrect performance of the actuators. This suggestion also does not impose any additional hardware. Finally, the presented algorithms are validated using the simulations in different scenarios. The numerical results verify the expected outputs.