Sveinung Ohrem

• Doctor of Engineering
• Researcher at SINTEF

Aquaculture robotics is receiving increased attention and is subject to unique challenges and opportunities for research and development. Guidance, navigation and control are all important aspects for realizing aquaculture robotics solutions that can greatly benefit the industry in the future. Sensor technologies, navigation methods, motion planner...

Digital Twin technology has emerged to become a key enabling technology in the ongoing transition into Industry 4.0. A Digital Twin is in essence a digital representation of an asset that provides better insight into its dynamics by combining a priori knowledge of the system through mathematical models with online data acquired from sensors and ins...

Unmanned underwater vehicles (UUVs) have become indispensable tools for inspection, maintenance, and repair operations in the underwater domain. The major focus and novelty of this work is collision-free autonomous navigation of UUVs in dynamically changing environments. Path planning and obstacle avoidance are fundamental concepts for enabling aut...

Dynamic positioning is an important control feature for an underwater remotely operated vehicle. This paper presents a nonlinear dynamic positioning controller suited for application to vehicles with model uncertainties, operating in environments with unpredictable disturbances, such as an aquaculture net cage. The proposed controller combines the...

Aquaculture is one of the largest, and fastest growing industries in Norway. Recently, the industry has experienced significant development in the daily operations acquiring new technologies and systems that capture data and automate the different processes. These emerging technologies enable the generation of enormous amounts of data from sensors...

Aquaculture net cage inspection and maintenance is a central issue in fish farming. Inspection using autonomous underwater vehicles is a promising solution. This paper proposes laser-camera triangulation for pose estimation to enable autonomous net following for an autonomous vehicle. The laser triangulation 3D data is experimentally compared to a...

This technical note presents an output feedback controller and observer design approach for linear time-invariant systems with unknown dynamics. The presented method uses an open-loop reference model to generate the desired trajectory and a closed-loop reference model as an observer. The controller only uses the observer states. Lyapunov-based stab...

To enable more efficient production of hydrocarbons on the seabed in waters where traditional separator equipment is infeasible, the offshore oil and gas industry is leaning towards more compact separation equipment. A novel multi-pipe separator concept, designed to meet the challenges of subsea separation, has been developed at the Department of G...

Control systems are an important and increasingly complex part of most industrial and non-industrial systems. As such, identifying and handling associated risks is increasingly important. Systems- Theoretic Process Analysis (STPA) is a relatively new hazard identification method developed to analyze modern, complex control systems. While traditiona...

The design of controllers and observers often relies on first order models of the system in question. These models are often obtained either through step-response tests, through on-line or off-line identification, or through developing a mathematical model. When the system in question has unknown or uncertain parameters, the developed model also co...

Optimal control is important in the oil and gas industry, where small changes of process variables may have significant economical, environmental and safety impacts. Finding the optimal setpoint for a controlled variable may not be straight-forward for an operator, motivating the use of automatic optimization methods. A widely used optimal control...

Optimal control is important in the oil and gas industry, where small changes of process variables may have significant economical, environmental and safety impacts. Finding the optimal setpoint for a controlled variable may not be straight-forward for an operator, motivating the use of automatic optimization methods. A widely used optimal control...

In this paper we present a model of a pump station consisting of two pumps in parallel with a recycle line, and a nonlinear Model Predictive Control strategy for said pump station with suction pressure as the controlled variable. The dynamics of the flow through the pump station is described using slightly modified models previously presented for e...

As subsea production of oil and gas reaches deeper and more remote waters, the need for more compact separation equipment arises. The gas liquid cylindrical cyclone (GLCC) is a widely used separation device in topside facilities, but has yet to reach the same popularity subsea. The GLCC separates gas and liquid by inducing a swirl on the multiphase...