A High-Accuracy Method for Calibration of Nonorthogonal Angles in Dual-Axis Rotational Inertial Navigation System

The dual-axis rotational inertial navigation system (RINS) can compensate the errors of inertial sensors by rotating the inertial measurement unit (IMU), thereby improving the accuracy of the inertial navigation system. However, in practical applications, nonorthogonal angles exist between the rotating axes, resulting in a decrease in navigation accuracy. In this paper, the error model of dual-axis RINS is established, which includes all nonorthogonal angles. Based on the nonorthogonal angle error model, the transformation matrix between the frames is derived, and the necessity of nonorthogonal angle calibration is discussed. The observability of the system is analyzed, and the degree of observability obtained indicates that the proposed nonorthogonal angles are observable. Then, a new nonorthogonal angle calibration method is proposed, which uses the dual-axis rotation mechanism. The proposed calibration method can calibrate all nonorthogonal angles with high accuracy, and the minimum estimation error is less than 10%. Simulations and experiments prove the effectiveness of the proposed error model and the calibration method, and demonstrate that the navigation accuracy can be significantly improved compared with the previous method.