Fiber optic gyros (FOGs) are sensitive to the environment fields where they are mounted, and their drifts are easily affected when surrounding temperature field or magnetic field changes. In FOG strapdown inertial navigation system (INS), gyro drifts caused by environmental fields are stable mostly, thus they could be calibrated and compensated beforehand and would not cause obvious alignment and navigation errors. However, in rotation INS (RINS), although navigation errors caused by the constant components of FOG drifts could be well attenuated, the gyro sensing axes are changing relative to the environmental fields in the RINS, which would lead to periodically changing gyro drift components when inertial measurement unit is pointing to different headings, thus producing serious alignment and navigation errors in FOG RINS. To solve this problem, a four-position heading effect calibration algorithm was proposed, and its effectiveness and validity were verified through a dual-axis FOG RINS by turntable experiments. The experimental results show that the azimuth alignment accuracy of the FOG RINS improves from 0.2 deg to about 0.04 deg, increasing five times approximately, which illustrates that the proposed heading effect calibration algorithm could further improve the navigation performance of FOG RINS significantly.
A rotary inertial navigation system requires higher calibration accuracy of some error parameters owing to rotation. Conventional multiposition and rotation calibration methods are limited, for they do not consider sensors’ actual operating condition. In order to achieve these parameters’ values as closely as possible to their true values in application, their influence on navigation is analyzed, and a relevant new calibration method based on a system’s velocity output during navigation is designed for the vital error parameters, including inertial sensors’ installation errors and the scale factor error of fiber optic gyro. Most importantly, this approach requires no additional devices compared to the conventional method and costs merely several minutes. Experimental results from a real dual-axis rotary fiber optic gyro inertial navigation system demonstrate the practicability and higher precision of the suggested approach.