An attitude determination algorithm for a spacecraft using nonlinear filter

In this paper, the algorithm for a real time attitude estimation of a space craft motion is investigated. The proposed algorithm for attitude estimatio n is the second order nonlinear filter form not containing truncation error in estimation values. The proposed second order nonlinear filter has impro ved performance compared with the EKF (extended Kalman filter), because the algorithm does not contain any truncation bias and covariance of the estim ator is compensated by the nonlinear terms of the system. Therefore, the pr oposed second order nonlinear filter is a suboptimal estimator. However, th e proposed estimator requires a lot of computation because of an inherent n onlinearity and complexity of the system model. For more efficient computat ion, this paper introduces a new attitude estimation algorithm using the st ate divided technique for a real time processing which is developed to prov ide an accurate attitude determination capability under a highly maneuverab le dynamic environment. To compare the performance of the proposed algorithm with the EKF, simulati ons have been performed with various initial values and measurement covaria nces. Simulation results show that the proposed second order nonlinear algo rithm outperforms the EKF. The proposed algorithm is useful for a real time attitude estimation since it has better accuracy compared with the EKF and requires less computing time compared with any existing nonlinear filters.