Comparative study of motion reference sensors (Offshore)

Staff Mentor:

prof. J. Hellendoorn

Other Mentor(s):

Ir. Maarten Vaandrager, JB Systems


System identification; Identification and estimation; Learning and adaptive control


The offshore industry is continuously trying to improve efficiency and safety. Especially with current low oil prices it is more relevant than ever to reduce downtime and improve the workability in rough weather.

Reducing downtime and improving workability and safety is typically achieved by compensating hoisting, drilling or pipe laying operations for the motions of the vessel. The motions are measured by a sensor called a ‘motion reference unit’ or MRU. The measured motion is transformed to motion at a relevant point such as a crane tip, pipe tensioner or drill string compensator. These signals are send to a controller that drives a winch or hydraulic cylinders that compensate the vessel motions and stabilize the process.

The MRU sensor is a crucial part in the compensation of the motions. Since it is very hard to accurately measure translational motions these sensors are very costly, varying in price from 10-60 thousand euros. MEMS technology has greatly improved the performance of the lower end of the MRU market over the last several years.

It is not easily concluded from the sensor specifications what the real life performance is in a typical offshore application and choosing the right sensor for your application is not trivial. Most companies have invested time and money in researching which sensor is the right sensor for them but tend to keep this knowledge to themselves as a ‘company secret’. There are no publicly available comparative studies that quantitatively compare the most common sensors.

An openly available comparative study based on real life experiments would benefit the offshore industry by providing insight in the performance of the sensors in specific real life applications. The suppliers of the most commonly used MRU’s (Kongsberg, SBG, SMC, Octans) have agreed to provide a sensor for this experiment.

- Research literature on MRU technology and offshore motion compensation applications.

- Define typical offshore motion compensation applications as test cases.

- Define a definition of ‘sensor performance’.

- Conduct experiments that simulate the test cases on a motion platform and collect motion data.

- Publish the result in an openly available white paper.

Desription from JB Systems

© Copyright Delft Center for Systems and Control, Delft University of Technology, 2017.