A MEMS-based Adaptive AHRS for Marine Satellite Tracking Antenna∗

Satellite tracking is a challenging task for marine applications. An attitude determination system should estimate the wave disturbances on the ship body accurately. To achieve this, an Attitude Heading Reference System (AHRS) based on Micro-Electro-Mechanical Systems (MEMS) sensors, composed of three-axis gyroscope, accelerometer and magnetometer, is developed for Marine Satellite Tracking Antenna (MSTA). In this paper, the attitude determination algorithm is improved using an adaptive mechanism that tunes the attitude estimator parameters based on an estimation of ship motion frequency. In order to get fast running cycle frequency of attitude estimator, Kalman filter is simplified to reduce calculation burden together with other improvemetns. An Immersion and Invariance (I&I) frequency estimator is designed using Lyapunov theory to estimate the ship motion frequency. The estimated frequency is then used to adjust the gain matrix in Kalman filter. The designed algorithms are implemented in ARM processor and the attitude obtained is compared to a high-precision commercial Inertial Measurement Unit (IMU) to validate the performance of designed AHRS.