| The inertial navigation systems are generally formed by gyroscopes and accelerometers. Gyroscopes are used for measuring the angular motion parameters and accelerometers for the linear acceleration. The application technology of MEMS 1MU has been widely thought much of. At present, the gyroscope free micro inertial measurement unit (GF-IMU) is one of the important research direction, because of the simple principle of the accelerometer the more potential to improve the performance of the accelerometer than that of the gyro. The specific force and angular rate are simultaneously calculated by outputs of the accelerometers forming the GF-MIMU. Using linear accelerometers instead of gyroscope in GF-MIMU not only can make the inertial navigation system cost, but also overcome the demerit of which gyroscope is incapable of the great angle motion and the strong shock. In this paper, the main research work is on the suitable configuration modes of GF-MIMU.Fist, the work is how to calculate the angular velocity from the accelerometer outputs in GF-MIMU. The way to calculate the angular velocity is subject to the positions and sensitive directions of the accelerometers. A new six accelerometers configuration mode is presented based on investigating the six accelerometers and nine accelerometers configuration modes presented by others, furthermore, it is derived theoretically and simulated for the method on calculating angular velocity and acceleration; Next, an extended Kalman filter designed and applied to the angular velocity estimate of the six accelerometers configuration mode and its improved one presented in this paper, the results show that the extended Kalman filter can reduce the angular velocity errors resulted from the accelerometer bias. Last, the angular rate is analyzed in the case of installation error which brings the larger calculating error, and the gray predict method is used to get the estimate equation of accelerometer output, and then get exacter angular velocity. |
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