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For the applications of sensitive to the friction moment of aerospace instrument bearing, the model of the crown style cage with six degree-of-freedom is built. The conventional fourth-order Runge-Kutta method with variable time steps is used to perform the numerical integration. The cage motion is obtained and the proportion of friction moment caused by cage in the beating's total friction moment can be known. The cage axial motion can be measured by using a non-contact laser linear displacement sensor, and the bearing's total friction moment can be measured by YZC-II tester. Comparing these experimental results to calculated results, an acceptable consistent is achieved, which can help to verify of feasibility of the program. The analysis shows that for the aerospace instrument bearings working at ultra-low speeds and under low loads, the friction moment caused by cage cannot be neglected, and especially it occupies a large proportion in the bearing's total friction moment at the startup time. [ABSTRACT FROM AUTHOR]

A new satellite attitude estimation method named cubature quaternion estimator (CQE) based on cubature Kalman filter(CKF) is proposed for better estimation performance in terms of numerical accuracy and filtering stability. Attitude is propagated by using quaternion while generalized Rodrigues parameters are employed to express angular errors for avoiding singularity of the new method. The cubature information quaternion estimator (CIQE) is proposed by combining CQE and information filtering paradigm to overcome low efficiency on account of multiple sensor fusion. Simulations demonstrate that the new method achieves desired performance under the condition of large initial errors. [ABSTRACT FROM AUTHOR]