Application And Improvement Of Rotating Modulation Technology On MEMS Strap-Down Inertial Navigation System

With the development of science and technology, inertial navigation system(INS) is indispensable in both military and civilian fields. As MEMS inertial devices are small, light and cheap, systems based on them are used more widely. However, large errors of MEMS inertial devices worsen the peformance of MEMS INS. In this paper, rotating modulation(RM) technology is applied in the MEMS strap-down inertial navigation system(SINS), which adds rotating tables into the system and periodly changes the directions of MEMS inertial measurement unit(IMU) relative to navigation coordinate. In this way, the constant errors of inertial devices, whose sensing axes are perpendicular to rotating axis, could be modulated into periodly changing errors whose average values are zero. In this case, the navigation performance of the SINS improves.Application and improvement of rotating modulation technology on MEMS strap-down inertial navigation system(SINS) are studied in this paper. Firstly, a rotating scheme for MEMS inertial devices is analyzed and designed. Then, in terms of the problem of low precision of MEMS inertial devices, self-caribration and initial alignment are studied and devised. Later, some problems of conventional attitude calculation method in rotating SINS are analyzed and the method of estimation and compensation of azimuthal angle error is proposed. In the end, the prototype of rotating MEMS SINS is established which proves the performance improvement by introducing rotating modulation technology into MEMS SINS.MEMS inertial devices are cheaper and have lower precision. In view of these, rotating schemes of Rotating SINS based on MEMS are analyzed and designed from the perspective of rotating axis number, rotating angular velocity and rotating direction. Simulation experiment with and without rotating modulation are conducted towards three primary errors of MEMS inertial devices respectively to analyze the rotating modulation effects on different errors. This provides fundamental analysis and reference for designing rotating scheme and establishing the prototype.Considering the low precision of MEMS inertial devices, this paper derives and establishes the output model of MEMS inertial devices in rotating MEMS SINS. Based on this, self-caribration is designed in the process of initial alignment, in which the biases of three gyroscopes and three accelerometers and scale factor of Z-axis gyroscope could be identificated along with the obtainment of initial attitudes. Experiments are conducted to verify the feasibility of this method.Two problems exist in the conventional attitude calculation algorithm of rotating MEMS SINS. One is that the yaw error of single-axis rotating MEMS SINS could not be modulated which affects the accuracy, the other is that high-resolution rotating angle information is required in the conventional attitude calculation algorithm. In order to solve the problems above, the method of estimation and compensation of azimuthal angle error is proposed to compensate yaw error in rotating coordinate and to estimate high-resolution rotating angle. Simulation results show that navigation performance could be improved and the rotating angle’s resolution needed could be decreased when the proposed navigation algorithm is adopted.In order to test navigation performance of rotating MEMS SINS in practical experiments, rotating MEMS SINS prototype is established. Static experiment and dynamic experiment are conducted respectively to verify the navigation performance of MEMS SINS with the aid of rotating modulation technology.This paper offers reference of design, establishment and improvement of rotating MEMS SINS and the improvement of rotating modulation technology in MEMS SINS.