Attitude estimation using modified rodrigues parameters and UKF

An all-attitude estimation algorithm is proposed using unscented Kalman filter (UKF) with the modified Rodrigues parameter representing the attitude. The modified Rodrigues parameters are simple and efficient in the problem of attitude estimation, but they can not be used in all-attitude motions, because they will be singular. It is possible to describe any rotations without encountering singularity by switching between the modified Rodrigues parameter and their shadow parameters. UKF uses nonlinear models directly and is suitable for precise attitude estimation. In this paper, an attitude estimator for the typical attitude determination mode composed of gyros and vector observations is designed by using the UKF, in which the attitude is presented by the way of switching between the modified Rodrigues parameters and their shadow parameters. There will be a jump of covariance matrix of state at the switching point, which brings the disturbance for the estimator. Therefore, a modification for the estimator is introduced at the switching point. Simulation results demonstrate the efficacy of the presented algorithm.