<p>This paper describes development of an optimal 3D path planner with collision avoidance for a 9 DOF robot manipulator. The application of the robot manipulator will be on an unmanned oil platform where it will be used for inspection. Most of the time the robot manipulator will follow a pre-programmed collision-free path specified by an operator. Situations where it is desirable to move the end effector from the current position to a new position without specifying the path in advance might occur. To make this possible a 3D path planner with collision avoidance is needed. The path planner presented in this paper is based on the well known Probabilistic Roadmap method (PRM). One of the main challenges using the PRM is to make a roadmap covering the entire collision free Configuration space, Cfree, and connect it into one connected component. It is shown by empirical testing that using a combination of the Bridge Sampling technique and a simple Random sampling technique gives best Coverage of the Cfree space and highest Connectivity in the roadmap for the given environment. An algorithm that increases the Connectivity and sometimes provide Maximal Connection is also described. A backup procedure that can be executed on-line if a query fails is also presented. The backup procedure is slow, but it increases the chances of succeeding a query if the goal is in a difficult area. It is also investigated if the coverage and connectivity can be further improved by using the potential field planner when connecting the waypoints. Empirical testing showed that the improvements of Coverage and Connectivity were limited and the sampling and query time increased. The query time for a roadmap containing 400 nodes and one containing 1000 nodes was compared. It turned out that a large roadmap did not necessarily affect the query time negative because it made it easier to connect the start and goal nodes. Three existing path smoothing algorithms and a new algorithm, called Deterministic Shortcut, were implemented and tested. Empirical testing showed that the Deterministic Shortcut algorithm outperformed the others when it came to path smoothing versus time.</p>

<p>This thesis discusses the theoretical aspects of the unscented Kalman filter (UKF) and nonlinear model predictive control (NMPC) and try to evaluate their practical value in a dynamic positioning (DP) system. A nonlinear horizontal vessel model is used as the basis for performing state, disturbance, and parameter estimation, and attempts at controling the vessel using NMPC are made. It is shown that the extended Kalman filter (EKF), which is much used in various navigation applications including DP, is outperformed both theoretically and practically in simulations by the UKF. Much of which is due to the UKF's improved approximation of the estimated system's true stochastic properties. An attempt to estimate the current from the hydrodynamical damping forces have been applied and shown to be working when the vessel is not subjected to other slowly-varying drift forces. It is implemented a dual estimation approach to try to estimate hydrodynamic damping, which is a very real problem for actual vessels and DP systems. A theoretical evaluation of NMPC is performed and it is concluded that NMPC schemes could fulfill a need in vessel control and DP. Its combination of model based control, optimization approach to achieving performance and predictive properties are indeed useful also for DP. It is found that NMPC could be a step towards a unified control approach combining low and high speed reference tracking, station-keeping and several other control operations which today are handled by separate control approaches. NMPC provides the control designer with an exceptional amount of freedom when quantifying the performance, that it is impossible not to find some use for NMPC.</p>

<p>Wave Power is a technology that was founded in the 70's, but which still not has reached full industrial recognition as a energy source. In this thesis there is a literature study on different concepts of Wave Energy Converters(WEC) which has been build in full scale, and there is a great variety in the concepts. There is a theory chapter where ocean waves theory, mass-spring-damper dynamics, hydrodynamics and maximum power capture are presented. The modeling work was done on a axisymmetric point absorber WEC, which can be said to have the greatest potential for energy absorption because it is small relative to the wavelength of the incident waves. To be able to simulate on the model, a control strategy must be included, and I have included PID control and Model Predictive Control as strategies to be able to capture maximum power with Phase Latching. I believe that Model Predictive Control will be the best choice for control system, although it is not as robust as PID control, but because of its predictive behavior. At last there is a chapter where further work and some concluding remarks are given.</p>

<p>Cargo transfer between two vessels at sea requires the ramp connection between the vessels to be as stable as possible. The complex nature of the system makes employing control methods difficult. This thesis explores two ideas for improving performance of the interconnected system. First idea examines the possibility of actuating the smaller of the vessels with fins, so as to reduce the relative movement between the two points where the ramp is connected to the ships. The second idea using the larger ship to shield the smaller one from incoming waves. It is assumed that the total disturbance is minimized at a certain angle to the waves, and an Extremum-Seeking based controller is used to find this angle. To allow ship models to change dynamically as cargo offloads, the technique of extremum seeking is extended in this thesis to allow a certain type of model uncertainties.</p>

<p>New offshore oil recourses that are developed are more difficult to drill and increase the requirements to the technology in the offshore industry. A relatively new technology is Managed Pressure Drilling where a choke topside is used to control the bottom hole pressure. The bottom hole pressure measurement is unreliable, which motivates the need for an observer. Different methods for estimation will be presented and compared in this thesis. Proofs of convergence are outlined for the Stamnes observer, derived for the Grip observer and some stepping stones for further work are presented for the Optimal Polynomial Filter. Each observer is simulated with a simple step in the mud pump to verify the estimation laws. The results show that all observes estimated the bottom hole pressure correctly for this simple case. A more realistic case, a pipe connection, is also simulated for each observer. The case includes zero flow from the mud pump, which reveals that all observers miss the estimation convergence in this case, but that the estimate converges when there is flow from the mud pump. One of the states that affects the bottom hole pressure is the pressure loss due to friction in drill string and annulus. Earlier work modeled these losses as quadratic with respect to the flow through the bit, which are simplifications. To improve the estimate of the bottom hole pressure, new and better friction models are needed. Measurement data from Gullfaks C are analyzed to get new knowledge of friction loss in the drilling string and annulus. For the drill string the quadratic friction model is found to be good enough, catching the main behavior. On the other hand, the friction loss in the annulus is a more complicated function of flow. The annulus friction is approximated with sets of basis functions and the weighted sum of these functions gives an approximation to the friction curve. Each weight is estimated to get the friction loss estimate. The use of the weighted sum of four 1st-order b-spline functions give a good approximation to the real friction curve, and the weight for each basis function is estimated. This is tested in simulations both with a simple case and the pipe connection case. The simulations show that the annulus friction loss and the bit pressure are estimated correctly.</p>

<p>Valve stiction is one of the largest stand-alone reasons for oscillatory behavior in process industry. It is reported by Siemens Oil and Gas that valve stiction is a problem that is hard and time consuming to detect at offshore production plants for oil and gas. As a result, Siemens Oil and Gas wants to develop an algorithm that detects stiction. The algorithm is thought to be a feature of the logging system of Siemens in the future. To better understand the problem and scope of stiction at a offshore oil and gas production plant, the effects of stiction is studied on a model of such a plant. The study shows that oscillations from stiction in the control valves of a first stage separator easily spread to downstream components such as the connected gas compressor. An algorithm that detects stiction from routine operating data is developed in this thesis. The method in base for the algorithm is chosen from a variety of methods for stiction detection. To choose a suitable method in base for the algorithm a brief survey of methods for detecting stiction is given. The algorithm output is a stiction index that indicate the presence of stiction in the data analyzed. The algorithm detects stiction in data from non-integrating processes with constant inputs and can be applied on data with a varying sample rate. Proper testing on real data from an offshore production plant remains to be done. The algorithm should also be improved to handle data containing noise. Two new ideas of detecting stiction in integrating processes are presented in the end of the thesis. The new ideas try to regain the hidden ellipses in the PV-OP plots from data with stiction from integrating processes. The first idea is to plot the OP data against time shifted PV data, while the second idea is to plot the OP data against high-pass filtered PV data. Both the ideas show promising results but need to be further developed and tested before they can be applied in a future application for stiction detection.</p>

<p>In this thesis, a closed-loop control algorithm for regulating the blood glucose concentration in type 1 diabetic patients is developed. Two control criteria are imposed on the system, namely: -Avoidance of hypoglycemia. (blood glucose concentrations should always be above $3 frac{mmol}{L}$) -Reduction in the average blood glucose concentration compared to what is achieved with manual control. (average blood glucose concentrations should preferably be less than $7.0 frac{mmol}{L}$). The developed control algorithm manages to fulfill both these control criteria. Hypoglycemia is avoided, and average blood glucose concentrations is reduced by $20%$ and $22%$ to a level of $7.0 frac{mmol}{L}$ and $6.9 frac{mmol}{L}$ in the two test subjects. However, further experiments should be carried out to test the robustness of the control algorithm, and a thorough investigation of safety issues for the user needs to performed. As a basis for the implementation of closed-loop blood glucose control, data from three diabetic patients is used to identify the parameters of a proposed mathematical model of the human insulin-glucose regulatory system. The identification process reveals that there is large variations between individual patient's parameter values, and the difference in insulin sensitivity is found to be specially high, both between and within patients.</p>

<p>The purpose of this thesis has been to develop methods for identification of nonlinear models to be used in ship autopilots. An accurate model is essential when developing autopilot systems. Although a number of identification methods are available, only a few ship maneuvers are described in the literature. During this report a literary study on nonlinear identification methods has been carried out and an overview over several methods is presented. A new maneuvering model derived by Andrew Ross is simulated to generate measurement data. Based on the measurements during several predefined maneuvers, an iterative prediction error method is applied to identify the parameters of two different autopilot models. Secondly, a new ship maneuver is suggested for identification of ship steering dynamics. Compared to the classic turning circle and zig-zag maneuver the new maneuver shows better convergence properties and perform good adaptation of the dynamics. At last the identified autopilot models are verified by simulating the ship in closed-loop using a model-based autopilot controller.</p>

<p>This thesis contains a steady state simulation model of a multistage crude oil production plant. The unstable reservoir fluid is separated into crude oil and gas in a three stage gas oil separation plant. Peng Robinson Equation of State and successive substitution is used to model the separators. The liquid output for the third stage separators is stable crude oil and the crude oil is sold on the international market. The gas liberated in the separators is compressed by centrifugal compressors and injected into the reservoir. Several methods for modelling centrifugal compressors are discussed. The discussion concludes that Dimensionless Parameters is the best suited method for this case and this method is therefore used. The plant studied has three separation stages at decreasing pressure and the standard control method is to use fixed separator pressure. This is not optimal and brute force optimization is used to find the optimal pressure set-points. Adaptive pressure set-points will improve product separation and therefore increase the profit. The profit is calculated as the income from crude oil sale minus the energy cost. Using this new method, the optimum separator pressures for Snorre A are determined. As a result, the profit is increased with 0.17, 0.11 and 0.07 present for three different inlet conditions. For one year this small increase in profit gives an extra two million dollars in income. The adaptive pressure set-points give an extension of the plant’s maximum capacity for a reservoir fluid with a high gas oil ratio.</p>

<p>The control solution is a crucial part of Managed Pressure Drilling. Existing solutions are often based on Proportional plus Integral (PI) control and have several drawbacks, mainly poor performance for some common drilling operations and a large need for retuning. Better control solutions will reduce costs and improve safety. This thesis presents a comparison of two adaptive control solutions versus a PI benchmark. Both complexity, tuning, performance and robustness will be compared. The two adaptive solutions considered are the well-known Model-Reference Adaptive Control method, and the recently developed $Lone$ adaptive control method. The control solutions are tested on a wide range of common drilling operations, some common controller issues, changing parameters and for two different control setpoints. The adaptive control solutions are shown to give better performance and to have less need for retuning, but not without costs. The main issues of the $mathcal{L}_1$ adaptive controller is low time-delay margins and high computational demands, but the performance is much better than for the benchmark controller. The most important recommendation for future work is evaluation of higher order filter designs for the $mathcal{L}_1$ adaptive controller, because of the potential to both reduce computational needs and to optimize time-delay margins.</p>