Precise motion measurements are essential for Anti-heeling systems that depends on accurate heel input to function correctly. In dynamic sea conditions, a standard inclinometer cannot distinguish between true heel and vessel acceleration, leading to false readings and unstable ballast corrections. A Motion Reference Unit (MRU) solves this by using sensor fusion to deliver dynamic roll measurements that remain accurate regardless of vessel motions.
With accurate real-time data on roll, pitch, and all six degrees of freedom, Norwegian Subsea MRUs give anti-heeling system operators the insight needed to understand how dynamic vessel motions from waves, turning, and cargo shifts, interact with true heel angle, and how to separate them reliably. This data is the foundation for stable ballast control, protecting both the vessel and its cargo, and ensuring the anti-heeling system performs accurately in real sea conditions.
Anti-heeling systems operate in a dynamic environment, yet most are still controlled by a sensor designed for static conditions. An inclinometer measures the angle of inclination relative to gravity, which works well when a vessel is stationary. At sea, it cannot tell the difference between a true heel angle and a lateral acceleration caused by waves or turning. The result is false heel readings, incorrect ballast corrections, and a control system that works against itself.
When a vessel turns or takes a wave, lateral accelerations act on the inclinometer in exactly the same way as gravity. The sensor has no way to separate the two. This leads directly to incorrect input to the anti-heeling control loop, triggering ballast corrections that are unnecessary, mistimed, or in the wrong direction. In harsh sea states, this can cause the system to oscillate rather than stabilise, increasing wear on pumps and valves and reducing the safety margin of the vessel.
A Motion Reference Unit uses sensor fusion, combining high-end gyroscopes and accelerometers — to calculate true roll angle independently of dynamic accelerations. Where an inclinometer sees only a combined signal, an MRU separates true gravitational heel from wave-induced and motion-induced accelerations, delivering a clean, stable, and accurate roll measurement in real sea conditions.
The result for the anti-heeling control system is a fundamentally better input signal, faster response, stable control loop, reduced pump cycling, and a significantly improved safety margin.
50 m depth, IP 68
5 cm or 5.0%
Lemo or SubConn 8 or SubConn 16
IP 65
5 cm or 5.0%
RJ45 or RJ50
"Norwegian Subsea MRUs had the accuracy, the temperature range, and the enterprise-level quality we required"
"They are rock solid. Many Norwegian Subsea MRUs have been running 24/7 inside Miros products for up to eight years without issue, producing real-time data every second."
