Dr Roger Skjetne

Professor Roger Skjetne is part of the Marine Cybernetics research group at the Department of Marine Technology at NTNU. In 2000 he received his M.Sc. degree in control engineering at the Univ. of California at Santa Barbara and his Ph.D. degree in 2005 at NTNU, for which he was awarded the Exxon Mobil prize for best Ph.D. thesis in applied research. Prior to his studies, he worked as an electrician for Aker Elektro AS on numerous oil installations for the North Sea. In 2004-2009, he was employed in the company Marine Cybernetics AS, which offered services for independent verification by HIL simulation on safety-critical marine control systems. From August 2009 he has held the position of Professor in marine control engineering at the Dept. of Marine Technology at NTNU. His research interests are within nonlinear control theory for motion control of single and groups of marine vessels, dynamic positioning systems for ships and rigs, particularly for arctic operations, and environmentally robust control of electric power systems on ships and rigs.

Arctic DP: Safe and green dynamic positioning operations of offshore vessels in an arctic environment.
It is estimated that one fourth of the world's known and not yet exploited oil and gas reserves are in the Arctic. As the easy accessible hydrocarbon resources are getting scarcer, this provides an incentive for offshore technology to approach arctic regions. However, operation in arctic regions pose new challenges related to vulnerable ecosystems and substantially different behavior of vessels due to the presence of ice. It is an expressed need to strengthen the competences of the Norwegian maritime industry in arctic marine operations with special focus on dynamic positioning. For these reasons, this research project targets development of dynamic positioning control systems and supporting ice management systems for acceptable commercial operations in an arctic ice-infested environment.

D2V: Design and verification of control systems for safe and energy-efficient vessels with hybrid power plants.
Dynamically positioned vessels with electric power plants in the range of 10-80 MW are used in the offshore industry in several safety-critical operations including drilling, supply, offloading, construction, anchor handling, and production. This project targets development of knowledge and competence in the design and qualification of safe and environmentally robust power and energy management systems for safer and greener offshore vessels. In a power production system consisting of unconventional and mixed types of producers, onboard an offshore vessel, it is likely on the load-sharing level that these may be coordinated more robustly and more optimally by applying new methods in nonlinear control theory on synchronization and coordination. On a high level, new methods within optimal control theory should be applied to ensure optimization regarding safety, energy efficiency, and emissions. These topics are addressed in this research project.

DyCoF: Dynamics and Control of Formations.
Dynamical processes or systems interacting in a coordinated and cooperative manner exist around us everywhere. In nature such dynamic coordinated groups exist naturally, and can be observed for instance in schooling fish, flocking birds, or swarming insects. Industrial applications are for example naval formations, offshore towing operations, formation flying of manned and unmanned airplanes, groups of underwater vehicles, and other formations of robotic vehicles. Typically, a coordinated group of systems can be able to multiply the production capacity, perform tasks with higher efficiency, execute complex tasks that any single system cannot perform alone, make the overall group of systems more redundant and fault-tolerant, or perform spatially distributed and time-synchronized sensing. In a coordinated group of systems, each individual system or dynamic process is called an agent, while the aggregated and coordinated group of agents is called a formation. The motion of a formation typically involves a transient phase - denoted the group coordination phase - where the agents respond to take their place in the formation, and an operational phase - denoted the formation mission phase - where the formation as a whole performs a coordinated collective mission task.

At all times, the agents of the formation must adhere to rules ensuring anti-collision and obstacle avoidance. In general this means that the formation cannot behave like an aggregated rigid structure, but rather as a flexible entity where the topology of the formation changes continuously.

When controlling a formation, the challenges targeted in this research are to understand the interconnection mechanisms between the agents and to develop elegant formation control methods accordingly. The latter means ensuring group coordination with a "natural" transient performance, and then carrying out the formation mission, taking into account formation guidance, sensing, and communication between the agents, obstacle avoidance, anti-collision, and autonomous reconfiguration according to changing tasks, environmental conditions, and faults.

Extensive list of publications

Other publications:

Journal and Magazine Articles

  • Skjetne, R. and Egeland O., "Hardware-in-the-loop testing of marine control systems." Modeling, Identification and Control (MIC), 27(4), pp. 239-258, 2006.
  • Skjetne, R., Fossen, T. I., and Kokotovic, P. V., "Adaptive Maneuvering, with Experiments, for a Model Ship in a Marine Control Laboratory." Automatica, 41(2), pp. 289-298, 2005.
  • Skjetne, R., Smogeli, Ø. N., and Fossen, T. I., "A nonlinear ship maneuvering model: Identification and adaptive control with experiments for a model ship." Modeling, Identification and Control (MIC), 25(1), pp. 3-27, 2004.
  • Skjetne, R., Fossen, T. I., and Kokotovic, P. V., "Robust Output Maneuvering for a Class of Nonlinear Systems." Automatica, 40(3), pp. 373-383, 2004.

International Conference Papers

  • Skjetne, R., Jørgensen, U., and Teel, A.R. (2011), "Line-of-sight path-following along regularly parametrized curves solved as a generic maneuvering problem," in Proc. IEEE Conf. Decision & Control, IEEE, Orlando, USA, Dec. 2011.
  • Thorvaldsen, C. and Skjetne, R. (2011), "Formation control of fully-actuated marine vessels using group agreement protocols," in Proc. IEEE Conf. Decision & Control, IEEE, Orlando, USA, Dec. 2011.
  • Kjerstad, Ø. K., Skjetne, R., and Jenssen, N. A. (2011), "Disturbance rejection in dynamic systems by use of acceleration feedforward: Application to dynamic positioning," in Proc. 18th IFAC World Congress, Milano, Italy, Aug.-Sept. 2011.
  • Skjetne, R. and Teel, A. R. (2004), "Maneuvering dynamical systems by sliding-mode control," in Proc. American Control Conf., AACC, Boston, USA, June 2004. (Best student speaker award at conference session).
  • Skjetne, R., Ihle, I.-A. F., and Fossen, T. I. (2003), "Formation Control by Synchronizing Multiple Maneuvering Systems," in Proc. 6th IFAC Conf. Manoeuvering and Control of Marine Crafts, Girona, Spain, Sept. 2003.
    Skjetne, R., Teel, A. R., and Kokotovic, P. V. (2002), "Nonlinear Maneuvering with Gradient Optimization," in Proc. 41st IEEE Conf. Decision and Control, pp. 3926-3931, Las Vegas, NV, USA, Dec. 2002.