A High-Precision Motor Control Method for Tracking Wandering Azimuth Coordinate System Based on Tri-Axis Rotational Inertial Navigation System (RINS)

Rotating modulation technology is an effective method to improve the navigation accuracy of inertial navigation systems which modulate inertial sensor error by rotating inertial measurement unit (IMU). Benefiting from the rotational frame and high precision angle encoders, RINS could complete various rotating strategies relative to the carrier without a turntable. However, in dynamic environments, using traditional motor control methods could destroy the effect of rotation modulation easily and stimulate the errors associated with the fiber-optic gyroscopes (FOG) and accelerometers. To maintain the navigation accuracy, we propose a high-precision motor control method to track the wandering azimuth coordinate system determined by the initial heading for triaxis RINS. The innovation of the control method is that the information of FOG and absolute grating is used simultaneously to calculate motor control instructions based on the orthogonal coordinate system defined by the IMU's measuring axis direction, and the influence of non-orthogonal angles among different motor frames are considered. The correctness of the high-precision motor control method is demonstrated theoretically and experimentally. Experimental results show that this method can isolate three degrees of freedom angular motion and improve control accuracy effectively, which has important engineering value, especially for high dynamic and heavy overload applications.