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For indoor close-range high-accuracy attitude measurement using inertial and vision sensors, the major challenge is to achieve a reliable attitude in various scenarios, specifically in the absence of vision information. To address this challenge, we present a fusion strategy for reliable attitude measurement using a micro electro mechanical system (MEMS) gyroscope and camera, particularly during discontinuous vision observations. The proposed algorithm consecutively executes update and prediction modes. In the update mode, when both inertial and visual data are available, the complete Kalman Filter (KF) conducts the entire filtering process and updates residual and state errors. In the absence of visual data, the partial KF operates only when the time update and filtering state vectors are compensated by the transfer residual, which is estimated through self-propagating state error. The parameters of least-squares support vector machine (LSSVM-NARX) continuously update until the next discontinuous vision observation occurs, with the desired outputs and inner inputs being the error angles and the exogenous inputs being the gyroscope values and time. In the prediction mode, without visual data, LSSVM-NARX can provide estimated angle errors between the complete and partial KFs, which are used to eliminate errors from partial KF output vectors to obtain a reliable and accurate attitude solution. Comparisons and extensive semi-physical simulation experiments under various motion trajectories were performed to validate the effectiveness and superiority of the proposed scheme in an accurate and reliable attitude measurement capability associated with discontinuous observations. [ABSTRACT FROM AUTHOR]

• The mechanism of nonreciprocal errors under the magnetic field-variable temperature field is proposed. • Based on dual-polarization interferometric fiber optic gyroscope (IFOG). • The nonreciprocal errors under the magnetic field, variable temperature field and magnetic field-variable temperature field are compared. A dual-polarization fiber optic gyroscope system is built to systematically analyze the nonreciprocal errors of the system under the magnetic field-variable temperature field. Under the magnetic field-variable temperature field, the nonreciprocal errors are caused by magnetic-thermal coupling birefringence nonreciprocal error, linear birefringence nonreciprocal error and Shupe effect error. The nonreciprocal errors of dual-polarization fiber optic gyroscope system are related to temperature and temperature gradient. In X and Y polarization states, the signs of magnetic-thermal coupling birefringence nonreciprocal error and linear birefringence nonreciprocal error are opposite, and these two errors can be suppressed in the dual-polarization system. But the Shupe effect errors are the same in X and Y polarization states, which can not be suppressed in the dual-polarization system. The experimental results are consistent with the theoretical analysis, which verifies the correctness of the nonreciprocal error model under the magnetic field-variable temperature field. The research results provide a theoretical and experimental basis for the study of the environmental adaptability of the fiber optic gyroscope and other common-path fiber sensing systems based on dual-polarization. [ABSTRACT FROM AUTHOR]