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A Complementary High Precision Acoustic Positioning System for Dynamic Positioning Vessels

Morten Berntsen View Supplier Profile

Originally printed in: Exploration & Production: The Oil & Gas Review - 2005

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The HAIN can be used on any vessel equipped with a hydroacoustic positioning reference (HPR) or HiPAP acoustic positioning system and consists of three main units:

• Inertial measurement unit (IMU) – the IMU contains three accelerometers and three fibre optic gyros that measure the vessel’s accelerations and rotation in three axes very accurately.
  
• HAIN computer – the HAIN computer executes the navigation algorithm, which consists of strap- down navigation equations and a Kalman filter. The unit is interfaced to an IMU and an acoustic positioning operator station (such as that of the HiPAP). The HAIN computer receives the aiding positions (latitude and longitude) from the acoustic positioning operator station and will limit the position drift inherent in inertial navigation systems. Vessel position, attitude, speed and expected accuracy of the data are sent back to the operator station at a 1Hz update rate.
  
• Operator station – The HAIN system is operated from an acoustic positioning operator station. The information received from the HAIN computer is displayed and sent to external computer(s). The operator station can request status information from the HAIN computer to be displayed, which helps the operator to check the system in realtime.
  
• The HAIN accuracy is derived from Kongsberg’s two to three years of experience combining acoustic measurements and the readings from inertial sensors onboard a remotely controlled vehicle (ROV) in an optimum manner. The navigation equations updating the vessel position, velocity, attitude and depth is almost continuously based on the readings from the IMU. A Kalman filter corrects these values when new acoustic positions and readings are available.

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