FAQs
Find the answer to your question here, or contact us at sales@norwegian-subsea.no.
Find the answer to your question here, or contact us at sales@norwegian-subsea.no.
A motion Reference Unit (MRU) is a device that measures motion in all six degrees of freedom (DoF): roll, pitch, yaw & surge, sway and heave. The six DoF positions, velocities and accelerations are measured by the MRU using high-end gyroscopes and accelerometers (and sometimes magnetometers) and processed by advanced sensor fusion algorithms.
When navigating the complexities of motion sensing and navigation systems, it is essential to understand the distinctions between devices and systems like Inertial Measurement Units (IMUs), Inclinometers, Roll & Pitch sensors, Vertical Reference Units (VRU), Attitude and Heading Reference Systems (AHRS), Motion Reference Units (MRUs), Gyrocompasses, and GNSS-Aided Inertial Navigation Systems (GNSS/INS). Each serves specific purposes and offers different levels of functionality, accuracy, and application scope.
Gyrocompass
The MRU (Motion Reference Unit) monitors vessel motions to evaluate risks related to sloshing and structural fatigue in cargo containment systems. It supports a condition-based inspection regime under DNV’s Alternative Survey Programme (ASP).
When navigating the complexities of motion sensing and navigation systems, it is essential to understand the distinctions between devices and systems like Inertial Measurement Units (IMUs), Inclinometers, Roll & Pitch sensors, Vertical Reference Units (VRU), Attitude and Heading Reference Systems (AHRS), Motion Reference Units (MRUs), Gyrocompasses, and GNSS-Aided Inertial Navigation Systems (GNSS/INS). Each serves specific purposes and offers different levels of functionality, accuracy, and application scope.
Inclinometer
The HS / commodity code for Norwegian Subsea MRUs is 9015.80.0000
A commodity code, also known as a Harmonized System (HS) code or tariff code, is a standardized numerical method used to classify traded products for customs purposes. It's crucial for calculating import duties, taxes, and identifying potential trade restrictions. These codes are globally recognized and consist of a specific number of digits, typically eight for exports and ten for imports.
When navigating the complexities of motion sensing and navigation systems, it is essential to understand the distinctions between devices and systems like Inertial Measurement Units (IMUs), Inclinometers, Roll & Pitch sensors, Vertical Reference Units (VRU), Attitude and Heading Reference Systems (AHRS), Motion Reference Units (MRUs), Gyrocompasses, and GNSS-Aided Inertial Navigation Systems (GNSS/INS). Each serves specific purposes and offers different levels of functionality, accuracy, and application scope.
When navigating the complexities of motion sensing and navigation systems, it is essential to understand the distinctions between devices and systems like Inertial Measurement Units (IMUs), Inclinometers, Roll & Pitch sensors, Vertical Reference Units (VRU), Attitude and Heading Reference Systems (AHRS), Motion Reference Units (MRUs), Gyrocompasses, and GNSS-Aided Inertial Navigation Systems (GNSS/INS). Each serves specific purposes and offers different levels of functionality, accuracy, and application scope.
Inertial Measurement Unit (IMU)
Yes. An MRU provides high-resolution measurements of roll angles, which makes it an effective tool for inclining tests (stability verification / "krengeprøve"). Unlike traditional pendulums, an MRU can deliver accurate data even when the test is carried out at sea under less-than-ideal conditions. By filtering out wave-induced motions and recording precise responses to applied test weights, the MRU improves both accuracy and efficiency of the inclining test.
A VRU is an advanced device that measures the attitude (roll and pitch) of an object using high-end accelerometers and gyroscopes, combined with advanced sensor fusion algorithms. VRUs provide very accurate roll and pitch measurements, even in dynamic environments.
In applications requiring real-time, high-accuracy roll and pitch data the VRU's precise Roll and Pitch data allows control systems to react effectively. For example, motion compensation of GNSS antenna for dynamic positioning (DP-systems), stabilizing fins on vessels or advanced Instrument compensation - Used in monitoring and control systems where only roll and pitch data is needed.
When navigating the complexities of motion sensing and navigation systems, it is essential to understand the distinctions between devices and systems like Inertial Measurement Units (IMUs), Inclinometers, Roll & Pitch sensors, Vertical Reference Units (VRU), Attitude and Heading Reference Systems (AHRS), Motion Reference Units (MRUs), Gyrocompasses, and GNSS-Aided Inertial Navigation Systems (GNSS/INS). Each serves specific purposes and offers different levels of functionality, accuracy, and application scope.
Roll & Pitch Sensor
When navigating the complexities of motion sensing and navigation systems, it is essential to understand the distinctions between devices and systems like Inertial Measurement Units (IMUs), Inclinometers, Roll & Pitch sensors, Vertical Reference Units (VRU), Attitude and Heading Reference Systems (AHRS), Motion Reference Units (MRUs), Gyrocompasses, and GNSS-Aided Inertial Navigation Systems (GNSS/INS). Each serves specific purposes and offers different levels of functionality, accuracy, and application scope.
GNSS-Aided Inertial Navigation System (GNSS/INS)
Yes, Norwegian Subsea Motion Reference Units (MRUs) are highly suitable for applications involving wave analysis. Our sensors provide precise measurements of motion in 6 Degrees of Freedom (6DoF), encompassing Roll, Pitch, Yaw, Surge, Sway, and crucially for wave analysis, Heave.
The high-accuracy Heave (vertical motion) data generated by our MRUs is fundamental for determining key wave characteristics such as wave height and period. Norwegian Subsea MRUs deliver a reliable Heave accuracy of 5.0 cm or 5.0%, enabling detailed analysis of sea states.
Improving the accuracy of subsea sensors fundamentally relies on selecting a high-performance unit designed specifically for the demanding underwater environment. At Norwegian Subsea, we achieve superior accuracy through a combination of state-of-the-art MEMS sensor technology, advanced sensor fusion algorithms, and robust hardware engineering, validated in real sea conditions.
Our algorithms are crucial for filtering noise and accurately calculating motion parameters like Roll, Pitch, Heave, Surge, Sway, and Yaw (6DoF), even under complex, irregular motion patterns typical of subsea operations. Furthermore, our sensors undergo rigorous testing and validation in real sea conditions, ensuring their performance specifications are met in the environments where they will be deployed.
Selecting the appropriate motion sensor for a subsea Remotely Operated Vehicle (ROV) is critical for precise navigation, positioning, and tool manipulation. Key comparison factors include accuracy (Roll, Pitch, Heave, Yaw), depth rating, physical size and weight, robustness, ease of integration with ROV control systems, reliability in harsh environments, and overall cost-effectiveness.
Norwegian Subsea offers the MRU Subsea, specifically engineered for demanding underwater applications like ROV operations. This unit features a robust, compact titanium housing depth-rated to 6000 meters, making it ideal for deep-water tasks. We provide different accuracy levels to meet specific operational needs, with Roll and Pitch accuracy options of ±0.05° (Series 3000), ±0.02° (Series 6000), or ±0.01° (Series 9000), and a standard Heave accuracy of 5.0 cm or 5.0%. Our sensors utilize advanced MEMS technology and sensor fusion algorithms, validated in real sea conditions.
A motion sensor, like the Motion Reference Units (MRUs) developed by Norwegian Subsea, functions by detecting and measuring movement. At their core, these sensors utilize state-of-the-art Micro-Electro-Mechanical Systems (MEMS) technology. MEMS accelerometers measure linear acceleration (changes in velocity along the Surge, Sway, and Heave axes), while MEMS gyroscopes measure angular velocity (rate of rotation around the Roll, Pitch, and Yaw axes).
To provide a comprehensive and accurate measurement of motion in all six degrees of freedom (6DoF) – Roll, Pitch, Yaw, Heave, Surge, and Sway – data from multiple MEMS sensors is intelligently combined. Norwegian Subsea employs advanced sensor fusion algorithms that process these raw sensor inputs, filtering out noise and compensating for external forces like gravity, to calculate precise orientation and movement data in real-time.
An IMU is an electronic device that measures and reports an object's linear acceleration and angular velocity using a combination of accelerometers and gyroscopes along three orthogonal axes (X, Y, and Z). It achieves this by utilizing a combination of sensors—primarily accelerometers and gyroscopes, and occasionally magnetometers. IMUs only provide raw data from their sensors and do not include "smart" features such as processing (e.g., Kalman Filter). The IMU cannot provide attitude (roll and pitch), velocity, or position without external processing.
This is very different from a Motion Reference Unit (MRU) which is a specialized device and self-contained sensor that measures motion in all six degrees of freedom (DoF): Roll, Pitch, Yaw, Surge, Sway and Heave. The six DoF positions, velocities and accelerations are measured by the MRU using high-end gyroscopes and accelerometers (and sometimes magnetometers) together with advanced fusion algorithms.
A Motion Reference Unit (MRU) is essential for safe and efficient offshore crane operations. Mounted on the vessel or platform, the MRU precisely measures the 6 Degrees of Freedom (6DoF) motion: Roll, Pitch, Yaw, Heave, Surge, and Sway.
The primary application in crane operations is Active Heave Compensation (AHC). The MRU provides high-accuracy, real-time heave (vertical motion) data to the crane's control system. This allows the winch system to actively compensate for the vessel's vertical movement caused by waves, keeping the crane hook and load stable relative to the seabed or a fixed structure.
A VRU is an advanced device that measures the attitude (roll and pitch) of an object using high-end accelerometers and gyroscopes, combined with advanced sensor fusion algorithms. VRUs provide very accurate roll and pitch measurements, even in dynamic environments.
In applications requiring real-time, high-accuracy roll and pitch data the VRU's precise Roll and Pitch data allows control systems to react effectively. For example, motion compensation of GNSS antenna for dynamic positioning (DP-systems), stabilizing fins on vessels or advanced Instrument compensation: Used in monitoring and control systems where only roll and pitch data is needed.
Data filtering is a critical process within Motion Reference Units (MRUs) designed to refine raw sensor measurements by removing noise and isolating the true motion components. At Norwegian Subsea, our MRUs utilize advanced sensor fusion algorithms and Kalman Filter algorithm that intelligently process data from state-of-the-art MEMS accelerometers and gyroscopes.
These sophisticated algorithms act as highly optimized filters, effectively distinguishing between vessel motion and unwanted noise or vibrations. This ensures the delivery of exceptionally accurate and stable measurements for Roll, Pitch, Heave, Yaw, Surge, and Sway in real sea conditions with irregular waves and coupled motions.
Motion monitoring is fundamental to ensuring safety, operational efficiency, and asset integrity within the offshore oil and gas industry. Accurate, real-time measurement of vessel and equipment motion, including Roll, Pitch, Heave, Yaw, Surge, and Sway (6 Degrees of Freedom - 6DoF), is essential for conducting complex operations safely and effectively in dynamic maritime environments.
Norwegian Subsea's high-performance Motion Reference Units (MRUs) provide the critical motion data required by various essential systems. This includes Dynamic Positioning (DP) systems for precise vessel station-keeping, Helideck Monitoring Systems (HMS) to ensure safe helicopter operations, Active Heave Compensation (AHC) systems for stable crane and winch performance, and Motion Compensated Gangways that allow for secure personnel transfers between vessels and installations.
Motion monitoring is fundamental to enhancing safety and operational efficiency in the demanding offshore environment. It involves the precise measurement of vessel, platform, and equipment movements across all six degrees of freedom (6DoF) – Roll, Pitch, Heave, Yaw, Surge, and Sway. High-performance sensors, such as Norwegian Subsea's Motion Reference Units (MRUs), provide the critical real-time data needed for monitoring, control or instrument compensation, ensuring safe personnel and cargo transfers, and optimizing operational windows in challenging sea states.
Our MRUs are integral components in numerous critical offshore applications:
Norwegian Subsea Motion Reference Units (MRUs) are designed to provide high-accuracy, real-time motion data crucial for monitoring, control or instrument compensation in demanding marine and subsea applications. Our MRUs utilize state-of-the-art MEMS sensors combined with advanced sensor fusion algorithms to continuously measure Roll, Pitch, Yaw, Heave, Surge, and Sway (6 Degrees of Freedom - 6DoF).
The core function enabling real-time analysis is the MRU's internal processing capability. Raw sensor readings are processed onboard using sophisticated algorithms to calculate precise orientation and motion data with minimal latency. This processed data is then immediately available for output.
Deciding whether to rent or purchase a motion reference unit depends on the project duration and frequency of use. While renting might appear suitable for very short-term, isolated projects, purchasing often presents a more cost-effective and reliable solution in the long run. Owning the sensor ensures availability when needed and eliminates recurring rental costs.
Our MRUs are engineered for reliability and longevity, often requiring no recalibration during their operational life for most applications, significantly reducing maintenance overhead and total cost of ownership compared to repeated rentals. At the moment Norwegian Subsea does not offer a rental service of our products, but in some cases we offer to sell a discounted demo-unit for potential recurring customers. Please contact us if you are interested in a testing our MRUs.
Motion sensors, specifically high-accuracy Motion Reference Units (MRUs), are crucial components in subsea monitoring operations. They provide precise measurements of motion in all six degrees of freedom (Roll, Pitch, Yaw, Heave, Surge, Sway), which is essential for the safe and efficient operation of underwater equipment and structures.
Key applications include monitoring the dynamic behavior of subsea structures like risers, subsea templates, subsea equipment, installation of bottom fixed structures and Blowout Preventers (BOPs). Accurate motion data helps ensure structural integrity and operational safety. Furthermore, MRUs are also used as navigation equipment for Remotely Operated Vehicles (ROVs) and Autonomous Underwater Vehicles (AUVs) during inspection, maintenance, repair (IMR), and survey tasks.
At Norwegian Subsea, we design all our Motion Reference Units (MRUs) for high performance, reliability, and cost-effectiveness, making the 'best' product dependent on your specific application requirements and operating environment. Our sensors utilize advanced algorithms and state-of-the-art MEMS technology, validated in real sea conditions to ensure robust and accurate 6DoF motion data (Roll, Pitch, Heave, Yaw, Surge, Sway).
Our core MRU range includes the MRU Compact (IP65, anodized aluminum, RJ45/RJ50 connectors with passive PoE) ideal for indoor or control box installations; the MRU Marine (IP68 or 50m SW option, anodized aluminum, versatile pigtail/Subconn connectors) designed for deck mounting or shallow water; the MRU Subsea (6000m depth-rated, titanium housing, Subconn connector) for deepwater applications like ROV/AUV operations and riser monitoring; and the MRU Ex (Ex d certified, stainless steel housing, pigtail cable) for hazardous area installations.
Measuring motion accurately in dynamic offshore environments presents several challenges. Error sources can generally be categorized into sensor-intrinsic factors, environmental influences, algorithmic processing limitations, and installation inaccuracies.
Intrinsic sensor errors include noise inherent in the MEMS accelerometers and gyroscopes, bias instability (drift over time), scale factor inaccuracies, and sensitivity to temperature variations. The performance of the sensor fusion algorithm, typically a Kalman filter, which combines data from multiple sensors to estimate orientation and motion (Roll, Pitch, Yaw, Heave, Surge, Sway), is also critical. Imperfections in the algorithm model or tuning can introduce errors, especially during complex or irregular motions.
Norwegian Subsea offers a range of high-performance Motion Reference Units (MRUs) designed for diverse marine, subsea, and offshore applications. All our MRUs measure 6 Degrees of Freedom (6DoF): Roll, Pitch, Heave, Yaw, Surge, and Sway. They are available in three distinct accuracy tiers based on Roll & Pitch performance: Series 3000 (±0.05°), Series 6000 (±0.02°), and Series 9000 (±0.01°). Standard Heave accuracy across the MRU range is 5.0 cm or 5.0%. For applications requiring only orientation data, Inclinometer/VRU versions are available, offering the same high Roll & Pitch accuracy without Heave/Surge/Sway output. Our sensors are designed for easy integration with broad protocol support and user-friendly web-based configuration.
The MRU Compact is designed for indoor or control box installations, featuring an IP65-rated anodized aluminum enclosure. It is exceptionally compact (12.0 x 5.7 x 5.3 cm) and lightweight (0.55 kg). Connectivity is simplified via an RJ45 or RJ50 connector supporting Ethernet communication (UDP, Modbus TCP, Ethernet/IP) with passive Power over Ethernet (PoE, 9-36V DC). The operating temperature range is -40 to +85°C.
A Motion Reference Unit (MRU) or a Vertical Reference Unit (VRU) is an important component in Dynamic Positioning (DP) systems to providing reliable and precise roll and pitch measurements. Norwegian Subsea Motion Reference Units (MRUs) are engineered for high accuracy and reliability, making them excellent choices for Dynamic Positioning (DP) systems. Our MRUs utilize advanced sensor fusion algorithms and state-of-the-art MEMS technology to provide precise 6DoF motion data (Roll, Pitch, Heave, Yaw, Surge, Sway) crucial for motion compensation of GNSS antenna and other position reference systems.
The NORSUB MRU can be configured with industry-standard protocols, enabling easy interfacing with existing DP systems or serving as a replacement for other MRUs/VRUs. The MRU/VRU can be installed in any direction. The configuration software allows for convenient setup of the remote monitoring point, specifically the GNSS antenna location.
To accommodate various installation requirements, the NORSUB MRU can be supplied with either an industrial junction box or a pigtail cable for integration into existing systems. This ensures compatibility and ease of implementation in different vessel setups.
For Remotely Operated Vehicle (ROV) operations, the Norwegian Subsea MRU Subsea is the ideal solution. Its design specifically caters to the demanding conditions of subsea environments.
The MRU Subsea features a robust titanium housing depth-rated to 6000 meters. The titanium casing is very compact and depth-rated to
6000 m. The small size and footprint make it easy to install
almost anywhere. It is equipped with a Subconn wet-mateable
connector and is easy integration onto various ROV platforms, where space and weight are often critical constraints.
While both Motion Reference Units (MRUs) and Inertial Measurement Units (IMUs) measure motion, they differ significantly in their processing and output. An IMU typically consists of accelerometers and gyroscopes that provide raw acceleration and angular rate data. IMUs only provide raw data from their sensors and do not include "smart" features such as processing (e.g., Kalman Filter). The IMU cannot provide attitude (roll and pitch), velocity, or position without external processing.
A Norwegian Subsea MRU, on the other hand, is a more sophisticated system. It utilizes data from internal MEMS-based accelerometers and gyroscopes, similar to an IMU, but integrates this data using advanced sensor fusion algorithms. These algorithms process the raw sensor readings to compute and output highly accurate, real-time measurements of orientation (Roll, Pitch, Yaw) and motion (Heave, Surge, Sway) in 6 Degrees of Freedom (6DoF).
Motion Reference Units (MRUs) primarily differ based on the type of gyroscope technology they employ. Norwegian Subsea utilizes advanced Micro-Electro-Mechanical Systems (MEMS) technology in all our MRUs.
MEMS sensors are solid-state devices manufactured using techniques similar to those for integrated circuits. This results in sensors that are inherently compact, lightweight, highly robust, and significantly more cost-effective than older technologies. They offer excellent reliability and low power consumption. Our engineers combine state-of-the-art MEMS sensors with sophisticated sensor fusion algorithms to achieve high accuracy and performance, validated in real-world sea conditions.
Accurate seabed mapping using Remotely Operated Vehicles (ROVs) relies heavily on precise motion compensation of the sonar as well as sensing of the vehicle's movements. Why you need motion compensation of your sonar system?
Remotely Operated Vehicles (ROVs) rely on a suite of sophisticated sensors to navigate complex subsea environments, perform intricate tasks, and gather data. Key sensor technologies typically include imaging sonar for obstacle avoidance and mapping, cameras for visual inspection, Doppler Velocity Logs (DVLs) for measuring speed over the seabed, depth sensors, altimeters, and crucially, high-performance motion sensors.
Motion Reference Units (MRUs) are fundamental components within an ROV's sensor package. They provide precise measurements of the vehicle's orientation and motion across all six degrees of freedom (6DoF): Roll, Pitch, Heave, Yaw, Surge, and Sway. This high-fidelity motion data is essential for vehicle stability, accurate navigation when integrated with systems like DVLs or acoustic positioning (USBL/LBL), and precise control of manipulators and tooling.
Norwegian Subsea products are engineered around state-of-the-art Micro-Electro-Mechanical Systems (MEMS) sensor technology. This forms the core of our Motion Reference Units (MRUs) and motion sensors.
We combine these high-quality MEMS sensors with advanced, proprietary sensor fusion algorithms. This sophisticated processing allows us to deliver highly accurate and reliable 6 Degrees of Freedom (6DoF) motion data, including Roll, Pitch, Yaw, Heave, Surge, and Sway, even in challenging dynamic marine environments.
Norwegian Subsea specializes in high-performance motion sensors called Motion Reference Unit suitable (MRU) for demanding marine environments, including subsea applications. We offer reliable and cost-effective solutions designed and validated for real sea conditions.
For subsea use, we recommend our MRU Subsea. This unit features a robust titanium housing depth-rated to 6000 meters, making it ideal for applications such as ROV/AUV navigation and control, riser motion monitoring, Blowout Preventer (BOP) monitoring, and subsea surveys. Its compact size and ability to be mounted in any orientation allow for flexible installation.
For subsea applications, the Norwegian Subsea MRU Subsea is the ideal solution. It is specifically engineered for demanding underwater environments, featuring a robust titanium housing rated for water depths up to 6000 meters.
The MRU Subsea is exceptionally compact and lightweight, simplifying installation on various subsea equipment such as ROVs, AUVs, or monitoring structures. It comes equipped with a reliable Subconn wet-mateable connector for secure underwater connections.
Motion Reference Units (MRUs) are critically important for Helideck Monitoring Systems (HMS) because they provide precise, real-time measurements of the vessel's or platform's motion. Safe helicopter landings and takeoffs depend heavily on understanding the dynamic movement of the helideck, particularly its roll, pitch, and heave.
An MRU accurately measures these key parameters, delivering essential data to the HMS. This information allows the system, pilots, and deck crew to assess whether the helideck's motion is within the established safe operational limits. Without accurate motion data, attempting landings or takeoffs, especially in challenging sea conditions, poses significant safety risks.