Automatic real-time offset calibration of gyroscopes

This paper reports on real-time offset calibration of a three-axis gyroscope whereby the angular rate sensor is part of an IMU in the field. If the IMU is in motion, the orientation changes of the gyroscope can be compared with those from other calibrated attitude sensors to identify the offset of the gyroscope. However, the acceleration sensor of an IMU in the field is typically uncalibrated and thus prevents an exact offset calibration during motion. In this paper, a new multi-model error state Kalman filter is proposed in order to determine the gyroscope’s offset. This filter exclusively uses an uncalibrated accelerometer for determining the gyroscope's offset. Consequently, the resulting calibration system is only partially observable which in turn influences the observability of the requested offset parameters. However, the latter conditions are the typical situation encountered in an IMU in the field. Therefore, the observability conditions as well as the stability of the multi model error state Kalman filter will be analyzed in the second part of this paper.