Analysis and Calibration of the Nonorthogonal Angle in Dual-Axis Rotational INS

Navigation errors of inertial navigation system can be effectively restrained by rotating inertial measurement units (IMU), enhancing accuracy in long-endurance navigation. However, nonorthogonal angles between rotating axes are inevitable during manufacturing. Coupled into the navigation error, nonorthogonal angles can lead to navigation accuracy, especially attitude accuracy decline during rotation. Therefore, the calibration and compensation of nonorthogonal angles will enhance the systemic reliability. In this study, we first established nonorthogonal angles model, then estimated the effect on sensitive errors of IMU using the proposed model. Based on the relationship between nonorthogonal angles and IMU attitude, an improved calibration algorithm of estimating nonorthogonal angles is presented. The results of theoretical analysis demonstrated that this method can effectively calibrate nonorthogonal angles in a simple and fast way, which is desirable for practical requirements. Simulation and comparison analysis indicated that the calibration of nonorthogonal angles is effective and practical. Finally, the feasibility of calibration and compensation is also verified by the improvement of navigation accuracy in the experiment.