Product Short Description
Product Series
KONGSBERG MRU Marine Motion Reference Unit Platform
Product Brief
Marine certified compact inertial motion reference unit integrating MEMS accelerometers and gyroscopes to measure vessel heave, surge, sway, roll, pitch and yaw six-degree-of-freedom motion for offshore dynamic positioning, crane compensation and marine navigation systems.
Description
Technical Specifications
- Measured Motion Axes: 6 DOF (Heave, Surge, Sway, Roll, Pitch, Yaw)
- Angular Measurement Range Roll / Pitch: ±45°
- Heave Vertical Displacement Range: ±10 m
- Static Angular Accuracy Roll/Pitch: ±0.02°
- Heave Measurement Accuracy: ±2 cm
- Gyro Angular Rate Bandwidth: 0–100 Hz
- Internal Sensor Core: Triaxial MEMS accelerometer + triaxial MEMS gyroscope array
- Supply Voltage: DC 12 V to DC 24 V marine wide power range
- Digital Interfaces: RS485 Modbus RTU, NMEA 0183, CANopen
- Operating Temperature: -40 °C to +70 °C
- Enclosure Protection Rating: IP67 fully sealed aluminum housing
- Marine Approvals: DNV GL, ABS, LR marine safety certification
Functional Features
- Real-time heave filtering algorithm to eliminate wave frequency noise for crane compensation systems
- Internal temperature self-calibration loop to eliminate inertial drift under vessel ambient temperature fluctuation
- Built-in static levelling auto-compensation for tilted mounting installation
- Simultaneous multi-protocol data output to connect DP controller, survey sonar and crane PLC simultaneously
- Permanent non-volatile memory stores mounting offset calibration parameters without external power retention
- Continuous internal hardware self-test with fault flag output for vessel monitoring alarm systems
Structural Characteristics
- Main housing: Machined marine-grade AISI 5052 aluminum alloy with hard anodized anti-saltwater corrosion coating
- Internal sensor assembly: Shock-isolated MEMS PCB stack with silicone vibration damping potting
- Cable connector: M12 8-pin marine sealed brass nickel-plated circular connector
- Mounting base: Integral flat flange with four standard mounting threaded holes for deck/control cabinet fixation
- Internal wiring: Teflon insulated low-noise signal conductors resistant to salt fog corrosion
Working Principle
Triaxial MEMS gyroscopes continuously measure vessel angular velocity; triaxial accelerometers capture linear acceleration vectors. Onboard DSP executes strapdown inertial navigation algorithm to integrate raw inertial data, separate gravitational static tilt from wave-induced dynamic motion, and output compensated roll, pitch, yaw, heave, surge, sway motion values via digital communication buses.
Advantage Highlights
- Full marine third-party classification society certification for offshore dynamic positioning safety critical systems
- Optimized heave filtering function reduces crane load swing during offshore lifting operations
- IP67 saltwater resistant enclosure tolerates open deck splash and high-humidity engine room environments
- Wide DC input range compatible with standard vessel 12V/24V marine power distribution systems
- Shock-damped internal sensor construction withstands vessel wave impact mechanical vibration
Applicable Industries
Offshore oil & gas dynamic positioning vessels, marine hydrographic survey ships, offshore construction crane heave compensation, passenger ship stabilizer control, underwater ROV navigation reference
Installation Requirements
- Mount unit on rigid flat vessel structural bulkhead or deck beam; avoid thin flexible panel mounting causing vibration resonance
- Perform static levelling calibration post-installation to correct mounting angular offset
- Separate MRU signal cables from high-power thruster variable frequency drive wiring with minimum 40 cm clearance
- Connect equipment protective earth terminal to vessel main hull grounding bus bar for lightning surge protection
Operation Precautions
- Avoid installation adjacent to heavy magnetic equipment (winch motors, transformers) which distort MEMS inertial vector measurement
- Execute full internal self-test routine monthly during vessel port maintenance cycles
- Do not disassemble sealed aluminum housing; factory seal breakage voids marine classification certification
- Replace connector sealing gaskets every 2 years for open-deck mounted units exposed to salt fog
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