Kongsberg MRU H Motion Reference Unit

The versatile heave compensator

This 5th generation MRU is specially designed for heave compensation

applications.

Typical applications

The MRU H is specially designed for motion measurements in marine

applications requiring highly accurate heave measurements in

environments with extreme horizontal accelerations. This MRU is an

ideal sensor for roll, pitch and heave compensation of offshore cranes

and echo sounders. The MRU H can also be used for typical ship

motion monitoring applications such as helideck motion monitoring,

hydroacoustic positioning systems, as well as hull stress monitoring.

Function

The MRU H incorporates three highly accurate accelerometers and

three Micro-Electro-Mechanical-Structures (MEMS) angular rate

gyros. This unit achieves high reliability by using solid-state sensors

with no rotational or mechanical wear-out parts.

The unit is delivered with Windows based configuration and data

presentation software. In this software vector arms from where

the MRU is mounted to center of gravity (CG) and two individually

configurable monitoring points (MPs), can be defined. The heave

measurements can be output in four different locations (the MRU

itself, CG, MP1 and MP2) simultaneously on serial lines or Ethernet

port. A typical monitoring point is the transducer head or the crane

tip.

Output variables

The MRU H outputs roll, pitch and heave together with linear

acceleration in 3-axes. The MRU H outputs heave position, velocity

and accelerations in adjustable frames. In addition, roll and pitch

angles and corresponding angular rate vectors are output.

PFreeHeave® algorithm

The PFreeHeave algorithm uses past measurements to output

a correct and phase-free heave from the MRU. PFreeHeave has an

advantage in long swell conditions and for applications that can

utilize a heave signal that is delayed some minutes, typically seabed

mapping applications.

External inputs

The MRU H accepts input of external speed and heading information

on separate serial lines or Ethernet for improved accuracy in

heave, roll and pitch during turns and accelerations. For time

synchronization the MRU accepts a 1-second time pulse (1PPS) input

on a TTL line (XIN) or as RS-232/422 signal.

Digital I/O protocols

For this 5th generation MRU data is available through both Ethernet

interface and serial lines enabling easy distribution of MRU data to

multiple users on board the vessel. Output protocols for commonly

used survey equipment are available on two individually configurable

serial lines and Ethernet/UDP.

FEATURES

• 0.010° roll and pitch dynamic accuracy

• High accuracy heave measurements even in dynamic environments

• Outputs on RS-232. RS-422 and Ethernet

• High output data rate (200 Hz)

• Precise heave at long wave periods by use of PFreeHeave®

algorithms

• Lever arm compensation to two individually configurable

monitoring points

• Small size, light weight and low power consumption

• No limitation to mounting orientation

• Each MRU delivered with Calibration Certificate

• Selectable communication protocols in the Windows based

MRU configuration software

• 2-year warranty