Performance Evaluation of AHRS based MEMS for Unmanned Underwater Vehicle

Generally, underwater unmanned vehicle (UUV) have adopted an inertial navigation system (INS), dead reckoning (DR), acoustic navigation and geophysical navigation techniques as the navigation method because GPS does not work in deep underwater environment. Although the tactical inertial sensor has been usually used at UUV for precise control during long operation time because the sensor can provide very detail measurement, it is not suitable to use the tactical inertial sensor for small size and low cost UUV. A cost effective and small size attitude heading reference system (AHRS) which incorporates measurements from 3-axis micro-machined electro mechanical system (MEMS) gyroscopes, accelerometers, and 3-axis fluxgate magnetometers has been developed to provide a complete attitude solution for UUV. The MEMS-based AHRS overcome many problems that have inhibited the adoption of inertial system for small UUV such as cost, size and power consumption. Since distortions of the earth's magnetic field are a result of external magnetic influences generally classified as either a hard or soft iron effect, AHRS provides calibrated angular rate, calibrated acceleration, calibrated magnetometer measurements, and the estimated body attitude. Test and assessment of developed MEMS-based AHRS for UUV are demonstrated through dynamic test on the 3-axis Rate Table, and hardware in the loop simulation (HILS) test.