Analysis and Improvement of Attitude Output Accuracy in Rotation Inertial Navigation System

Inertial navigation system (INS) measures vehicle’s angular rate and acceleration by orthogonally mounted tri-axis gyroscopes and accelerometers and then calculates the vehicle’s real-time attitude, velocity, and position. Gyroscope drifts and accelerometer biases are the key factors that affect the navigation accuracy. Theoretical analysis and experimental results show that the influence of gyroscope drifts and accelerometer biases can be restrained greatly in rotation INS (RINS) by driving the inertial measurement unit (IMU) rotating regularly, thus improving navigation accuracy significantly. High accuracy in position and velocity should be matched with that in attitude theoretically since INS is based on dead reckoning. However, the marine and vehicle experiments show that short-term attitude output accuracy of RINS is even worse compared with that of nonrotation INS. The loss of attitude accuracy has serious impacts on many task systems where high attitude accuracy is required. This paper researched the principle of attitude output accuracy loss in RINS and then proposed a new attitude output accuracy improvement algorithm for RINS. Experiment results show that the proposed attitude compensation method can improve short-term pitch and roll output accuracy from 20~30 arc seconds to less than 5 arc seconds and azimuth output accuracy improved from 2~3 arc minutes to less than 0.5 arc minutes in RINS.

Thermal Modeling and Compensation of MEMS Accelerometer

As for MEMS Micro machined accelerometer, biases characteristic always varies with temperature fluctuations. Through establishing the error model between the MEMS accelerometer biases and the temperature variation in the temperature range of-20 °C ~ 60 °C, studying on the bias changed with thermal variation of MEMS accelerometer, and the test results show that MEMS accelerometer bias caused by temperature change have decreased from more than 5mg to lessen than 1mg before and after compensation. Also based on the temperature error model of the MEMS accelerometer bias in static and dynamic condition, the whole temperature characteristics have been improved to some extent, which would improve the precision in the inertial navigation systems.