<p>Handling slug flow is a matter of necessity in the oil and gas industry. Large slugs cause problems at the production platform by overfilling the first stage separator leading to poor separation and pressure increase, which again could lead to more flaring or even complete process shut-down. Using the riser base pressure as the controlled variable has been shown in several academic papers to have a stabilizing effect on the slug flow. In this thesis it has been concentrated on designing robust anti-slug controllers using this variable as the controlled variable. Experience from Hydro's multiphase rig at their Research Centre in Porsgrunn shows that re-tuning of anti-slug controllers during experiments is necessary to be able to keep the flow stabilized. This is caused by the change in process gain, which is large for operation around small valve openings and low for operation around large valve openings. An OLGA model was developed for this multiphase rig. This model was shown to predict the amplitude of the slugs and their frequencies fairly well, however, the transition point from stable flow to slug flow differed to a larger extent. Several gain scheduling controllers were designed and tested on this model. The best gain scheduling approach which was found was based on a gain scheduling regime controlling the riser base pressure in a secondary loop without integral action, with a slow primary loop controlling the valve opening (with integral action). The scheduling variable was a low-pass filtered measurement of the valve opening. This approach was also robust with respect to noise and lowered inlet rates.</p>

<p>This report treats modelling, simulation and control of a fixed-wing aircraft, including implementation of a Aircraft Flight Control System (AFCS). The design and construction of a suitable airframe (design og konstruksjon av ubemannet fly for visuell overvåkning) by Jon Bernhard Hsøtmark is continued in this work. This system was designed to be suitable for surveillance purposes, using electrical propulsion and being low cost. Preferable characteristics considering stability and control to ease control, implementation and tuning of controllers were built into the airframe. The work done here confirms that the goal in cite{bib:bernhard} was met, and compleating the autonomous system using feedback regulation.newline The work finished this spring were divided in to three reports. Design and implementation of sensor and computer system for fixed-wing UAV, by Edgar Bjørntvedt Modelling, simulation and control of fixed-wing UAV, Jon Bernhard Høstmark Ground Station and hardware peripherals for fixed-wing UAV, Mikael K. Eriksen Each task was assigned to one person. This report includes the work done with respect to modeling, simulation, control and testflights. The main focus was building a working prototype. In addition to the technical work, the author of this report has ensured that the project stayed on track. The conclusion in the end of the report discuss this further. June 2007 the three subsystems was integrated for flight testing. Video supplied with this work show stable autonomous flight confirming a working AFCS. Having a working system is thought to be of great value for further work. The working system can also be used for verifying the analytical models obtained thought this work. Adding more sensors to the computer system enable further and tighter controllers, such as height control and waypoint navigation. With these features the UAV system should be ready for surveillance purposes in the commercial market.</p>

<p>The increasing need for more energy in the world is making the oil companies search for hydrocarbons in deeper water and with longer distances between the well and platform(step-out) never experienced before. Current systems are designed to operate in deepwater with relatively short step-outs. Since the search now is starting to exceed this, the operational conditions are changed and the electro-hydraulic system is closing in on its operational limits. Hence, the increasing need for a system that supports the long step-outs and the deeper water. Aker Kvaerner has started looking into the development for an All Electric Subsea Production system. In co-operation with Aker Kvaerner Subsea, a functional design specification for an electric subsea gate valve actuator has been developed and included in this thesis. This functional design specification will include all the requirements that a subsea electric actuator must conform to. This includes the operational requirements, size limitations, failsafe needs etc. Based on this specification, a design for a electric actuator and including motor driver control system layout on the all electric x-mas tree is proposed as a part of the All Electric Subsea Production system. The actuator will be used to operate the gate valves on a x-mas tree which controls the flow of hydrocarbons through the valves into the pipelines. Most of the existing subsea gate valve actuators are currently using hydraulic oil to operate the valves linearly. Here a concept is being suggested in replacement of the hydraulic fluid, while still complying with the necessary design specification. A number of electrical machines for potential use in this application are presented and evaluated. A Permanent Magnet Synchronous Machine is being investigated further. These machines can be custom made, and can also be made with built in redundancy. Calculation of size for the Permanent Magnet Synchronous Machine has been done, to determine suitability within the space limitation of the apparatus. Two layouts for controlling the actuators on the all electric x-mas tree are proposed. These two are also evaluated against the standards made for subsea production systems and the no 'single point failure' requirement made by the industry. The chosen solution proposed for controlling the electrical actuators is an integrated design, where all actuators have their own motor driver inside. This thesis conclude that an electrical actuator will be technically and mechanically possible to build(from an electrical perspective), using the design and control layout proposed.</p>

<p>Recent years advances within well deployment and instrumentation technology offers huge potentials for increased oil recovery from reservoir production. Wells can now be equipped with controllable valves at reservoir depth, which may possibly alter the production profitability of the field completely, if the devices are used in an intelligent manner. This thesis investigates this potential by using model predictive control to maximize reservoir production performance and total oil production. The report describes an algorithm for nonlinear model predictive control, using a single shooting, multistep, quasi-Newton method, and implements it on an existing industrial MPC platform - Statoil's in-house MPC tool SEPTIC. The method is an iterative method, solving a series of quadratic problems analogous to sequential quadratic programming, to find the optimal control settings. An interface between SEPTIC and a commercial reservoir simulator, ECLIPSE, is developed for process modelling and predictions. ECLIPSE provides highly realistic and detailed reservoir behaviour and is used by SEPTIC to obtain numerical gradients for optimization. The method is applied to two reservoir examples, Case 1 and Case 2, and develops optimal control strategies for each of these. The two examples have conceptually different model structures. Case 1 is a simple introduction model. Case 2 is a benchmark model previously used in Yeten, Durlofsky and Aziz (2002) and models a North Sea type channelized reservoir. It is described by a set of different realizations, to capture a notion of model uncertainty. The report addresses each of the available realizations and shows how the value of an optimal production strategy can vary for equally probable realizations. Improvements in reservoir production performance using the model predictive control method are shown for all cases, compared to basic controlled references cases. For the benchmark example improvements range up to as much as 68% increase in one realization, and 30% on average for all realizations. This is an increase from the results previously published for the benchmark, with a 3% average. However, the level of improvement shows significant variation, and is only marginal for example Case 1. A thorough field analysis should therefore be performed before deciding to take the extra cost of well equipment and optimal control.</p>

<p>The project includes a numerical model of heat flow in robotic welding. The modelling is done in finite element method, and afterwards exported to Matlab where the model will be linearized and model reduced. The ultimate goal is to use the model in an automated robotic welding system. In order to decide if IR-thermography may be used as a decision parameter in automated system, experimental work on temperature measurements of welding has been performed.</p>

<p>Drilling into mature, depleted fields is often difficult because of tight pressure margins. Increasing the pressure control will enable wells that previously were considered undrillable, to be drilled. Enabling drilling and increased oil recovery from depleted fields would most likely lead to a substantial increase in profit margains. A better pressure control will also increase the safety of the drilling crew, because the risk of unwanted situations such as a kick or a blow-out is decreased, also reducing the risk of unwanted environmental influence, e.g. oil spill. To compensate for the lack of a continuous measurement of the bottomhole pressure during drilling operations, an adpative observer of the bottomhole pressure is implemented. The observer implemented is tested, and shows promising results in estimating both the bottomhole pressure and the friction coefficient in the well during a pipe connection procedure. To control the pressure in the well, a low-order nonlinear model predicitve controller is developed, and it has been tested to perform well during the pipe connection procedure, where it maintains the pressure within the predefined boundaries. In this thesis both the obsever and the controller will be tested against an artificial well; simulated by a commercial software.</p>

<p>In coupled reservoir simulations a model of a reservoir and the production system are joined together to obtain realistic responses. One way of performing production optimization is to make use of a gas oil ratio (GOR) estimate when calculating the optimal flow rates. Today this estimate is either not accurate enough or calculating it is a time consuming process. The thesis tries on an alternative online approach for estimating the GOR. It makes use of basis functions in the form of polynomials and normalized radial basis functions together with a recursive least squares (RLS) algorithm. This yields a simple and effective optimization strategy. When using a second order polynomial together with the fast convergent recursive least squares algorithm one achieves a suitable fit to the estimated production data. The algorithm has not yet been tested together with a production optimization tool and it has not been compared to the existing methods for estimating the GOR. Still it seems to have a lot of potential and the RLS is fast, convergent and proper for the objective of this thesis.</p>

<p>Prostheses are artificial body parts that can be used by amputees. Myoelectric prostheses are controlled by so-called surface electromyograms (sEMG) that are acquired on the skin surface of the residual limb. A well-known problem in myoelectric prostheses is motion artifacts, these artifacts cause unwanted behaviour of the prosthesis. The purpose of this study is to try to cancel the effect motion artifacts have on myoelectric prosthesis control, in order to avoid unsolicited prosthesis behaviour. The subject of myoelectric prostheses and motion artifacts are outlined in this study, together with the development and characterisation of a sensor that can do simultaneous measurements of sEMG and contact forces between a surface electrode and the skin. A protocol has been developed for the recording of the different signals in a laboratory. Suitable data sets have been recorded from one test subject, and signal processing and pattern recognition methods have been applied on these data sets to generate muscle force estimates. The pattern recognition methods were linear and quadratic mapping functions, and multi-layer perceptron network. To achieve better force estimates when motion artifacts are presence, signals from FSRs are taken into consideration together with sEMG signals. A qualitative comparison reveals obvious improvements for the sEMG sensor when FSR measurement is included. The system presently undergoes quantitative assessment of static and dynamic performance. The final step will hopefully be to integrate FSRs in a real prosthesis.</p>

<p>Estimation of the annular pressure at critical locations in the well is crucial for high-precision pressure control. Certain parameters which are important in order to determine the pressure profile of the well (in particular the friction factor, bulk modulus and density in the annulus), are encumbered with high uncertainty and are besides, continuously, but slowly changing. The objective of the thesis is to employ various Kalman filter designs estimation of the bottomhole pressure and certain important parameters/slowly varying variables, during drilling. Topics that should be addressed are: 1) Literature review of the theory of Kalman filters design 2) Design and implement an Extended Kalman filter (EKF) and possibly the Unscented Kalman filter (UKF) for a) Estimation of the annulus bottom-hole pressure b) Esimation of the friction coefficient, bulk modulus and density in the annulus 3) Analyse the performance/robustness of the observer in important cases, in particular: a) Pipe connection b) Pump ramp up/down 4) Examine observer performance to unmodeled dynamics by testing the Kalman filter against data sets from Wemod 5) Evaluate performance of the observer against experimental data from Grane.</p>

<p>This thesis develops a Dynamic Positioning (DP) system for small marine craft by using the LQR controller approach. Development has been done with a 'Viknes 830' vessel in mind, which is operated by the company 'Maritime Robotics AS' and will be equipped for DP operation the during summer of 2008. A Matlab-based simulator designed for DP simulations has been developed, and is used throughout the thesis. Furthermore, a Hardware-In-the-Loop (HIL) simulator has been used in order to localize and resolve as many implementation issues as possible prior to full-scale installation. A discussion on the general use of a HIL simulator for DP is included. Three variations of a feedback LQR station-keeping controller have been implemented and compared; a simple LQR controller, an LQR controller with modeled actuator dynamics, and nally an LQR controller with actuator dynamics and integral action. A feedforward controller has been added in order to provide enhanced station-keeping performance, as well as bumpless transfer from station keeping to low-speed maneuvering. A reference model has been created for smooth transfer in-between station-keeping reference points, and as input for the feedforward controller. A passive Luenberger DP observer has been applied in order to lter out high-frequency wave loads. Simulation results reveal that the LQR controller with actuator dynamics and integral action is most likely to perform well in real-life application. The largest performance enhancement is gained from the inclusion of actuator dynamics in the controller. It is discovered that the performance turns out better if the actuator dynamics is modeled faster in the controller due to unmodeled actuator saturation limits. V</p>