The objective of this master thesis is to design, implement, and evaluate sliding mode control (SMC) applied to stabilize slugging using only the downhole pressure as measurement. The pros and cons of the resulting output-feedback sliding mode controller are to be evaluated against the conventional PI controller. The thesis is based on, and a continuation of the work and conclusions of my project thesis, where the conclusion was that the SMC might have a significant potential for increased oil production and recovery. The clear limitation was however the uncertainty regarding the validity of the van Der Pol model used, and the fact that the SMC was provided the real time-derivative states. Therefore the original main tasks of this thesis was to implement a high fidelity simulation model of severe riser slugging, and to design (and test) differentiators with the purpose of evaluating the output-feedback performance of the SMC. As it turn out that I was not able to achieve the task of stabilizing the pressure with SMC on the chosen OLGA model, the focus of this thesis has in agreement with my supervisors been changed quite a lot from the task requested in the project description. Possible reasons for the lack of results, and the chosen focus of the thesis is presented in the introduction chapter. The thereby chosen focus became the task of designing testing differentiators for the SMC, but with testing on the van Der Pol model. Before presenting and arguing for this change of focus in the section about task and limitation, the introduction chapter starts by giving a brief overview of the environment or setting the controlling challenge is a part of, and follows up by presenting the work and conclusion of that project thesis. In the end of the chapter, the structure of the thesis is shortly listed. The introduction is followed up by giving a further insight to the slug problematic. An overview of the historical development, and a description of some research within the field are provided. The last part of the chapter gives a quite thorough description on the riser slugging phenomenon. Thereby the sliding mode controller (SMC) is presented in chapter 3. The challenge concerning chattering is also discussed, and the approach of using boundary layer to suppress the chattering is introduced. In chapter 4, the empirical van der Pol based model is derived, and the model is augmented to use the valve rate as control input. Chapter 6 gives a discussion on why the SMC should be performed on the choke rate and not directly on the choke opening. This section also designs the SMC that will be used for testing, and the needed time-derivatives for testing the SMC are derived. The chosen main focus of this thesis is to evaluate if there is possible to design observers (differentiators) that meets the requirements for the designed SMC to stabilize slugging. The tests are performed on the van Der Pol model. This task is introduced through chapter 7, that present general observer theory, theory about using observers combined with SMC, and finally the two observers chosen for further testing; the high gain observer (HGO) and the robust high-order sliding mode differentiator (RHOSMD). The first stage in evaluating the HGO and RHOSMD is open loop testing, and is described in chapter 8. The observers perform well for the ideal case of no disturbance, but in the presence of measurement noise the conclusion is that estimations of the higher order time-derivatives do likely not meet the very demanding requirements of the SMC. The biggest problem is probably the time-delay of the estimation, but the correctness of the amplitude might also be a problem. In chapter 9 the observers was tested further in a SMC controlled closed loop system to get a more precise indication on how well the observers are fitted for their intended task of providing the SMC with the required estimations. As for the open loop tests, the 'isolated' estimation performance of the required states was considered, but the main focus was the performance of the output-feedback SMC compared to the performance of manual choking, the PI controller, and the performance of the state-feedback SMC. This chapter confirmed the assumption from the open loop testing that in presence of measurement noise, the observers is not able to meet the demanding requirements of the designed SMC. For the theoretical ideal case of no disturbance the results is very good, especially for the HGO. In the case of measurement noise, the RHOSMD perform slightly better. In both chapter 8 and 9, tuning is considered and discussed. However, since the conclusions of the observer testing is negative, the SMC is not tested further. The results will be negative for output-feedback testing, and a quite extensive state-feedback testing of the SMC is performed in the project thesis. The main results and conclusions throughout the thesis, are presented in chapter 10. The chapter also contain a short discussion where it is concluded that the alternative designs, SMC with direct choke rate control and SMC of the choke acceleration, will not be a solution on the state-feedback SMC problems described in this thesis. There is also a short discussion regarding CPU and system requirements for the observers and the controller. At the very end, further work is discussed.

The purpose of this thesis was to study the use of adjoint methods for gradient calculations in Model Predictive Control (MPC) applications. The goal was to find and test efficient optimization methods to use in MPC on oil reservoir models. Handling output constraints in the optimization problem has been studied closer since they deteriorate the efficiency of the MPC applications greatly. Adjoint- and finite difference approaches for gradient calculations was tested on reservoir models to determine there efficiency on this particular type of problem. Techniques for reducing the number of output constraints was also utilized to decrease the computation time further. The results of this study shows us that adjoint methods can decrease the computation time for reservoir simulations greatly. Combining the adjoint methods with techniques that reduces the number of output constraints can reduce the computation time even more. Adjoint methods require some more work in the modeling process, but the simulation time can be greatly reduced. The principal conclusion is that more specialized optimization algorithms can reduce the simulation time for reservoir models.

The topic of this thesis is modeling and simulation of anchor handling vessels. Computer simulations of anchor handling vessels can be used to evaluate the forces acting on them, and to gain valuable insight into their operational limitations. Introductorily, an overview containing important aspects of anchor handling operations is presented. The objective is to highlight important subjects that must be considered before a simulator is developed. A simulator of an anchor handling vessel is successfully implemented in Matlab and Simulink. The simulator contains modules for ballast tanks, anti-roll tanks, cables, seabed and anchor interaction, winch systems and guide pins. The vessel model is matched up against a real anchor handling vessel to give realistic thrust characteristics. The simulator is capable of simulating both anchor deployment and anchor recovery operations in real time. Catenary equations are used to model cables. A quasi-static polynomial approach with look-up tables is used for implementation. The method allows the use of different catenary models to simulate different phases of the anchor handling operation. A catenary model of two cables with a point load, imitating the effect of an anchor, is developed based on existing catenary models in the literature. The simulator is verified through simulations. A set of case studies is used to evaluate the vessel performance during anchor deployment and recovery. The case studies consider operation in ideal and rough weather conditions, and it is shown how equipment failures and poor vessel configuration can lead to decreased vessel stability and loss of maneuvering capabilities.

Real-world stock markets exhibit periods of increased volatility and bursts in stock prices. This thesis is about creating similar dynamics in a model to gain insight into these potentially dangerous phenomena. A transaction tax able to stabilize the markets is briefly discussed. The relationship between rational and speculative traders is found to be crucial. If the speculative mindsets are allowed to dominate the markets, chaos is inevitable. Simulations show a direct relation between speculation and violent price movements. The discussed transaction tax is found to make the market more robust by targeting the most destabilizing form of trading - short-term speculation.

The use of autonomously underwater vehicles (AUVs) has a great potential in scientific mission involving underwater exploration. However a major drawback with todays AUV missions is the launch and recovery process which are usually performed manually from a manned supply ship. These manned ships have a huge daily operation cost, and because AUVs can have operation times up to 70 hours these missions become extremely costly. Since the combination of an AUV together with a manned mothership is very costly the use of AUVs are very restricted. A solution here is to replace the manned mothership with an unmanned vehicle such as a unmanned surface vehicle (USV). This will reduce the cost of AUV mission drastically and therefore increase the use of AUVs on scientific missions. This motivates the need for an AUV-USV docking method which is one of the two docking scenarios treated in this master thesis. Another docking method treated here is the possibility to dock a USV together with a manned mothership without human interference. A docking method that removes the human intervention will make the USV completely unmanned, since USVs today are manually docked together with a mothership or driven back to shore by a remote control. To achieve an understanding of the field, a summary of the most relevant findings in todays literature are given. This includes the possibility to autonomously dock together an AUV with another vehicle or installation, and other related fields such as spacecraft docking and aerial refuelling. The main findings involving AUV docking, ranges from a simple fuzzy logic procedure to more advanced methods involving trajectory planning and potential field guidance. Since no extensive previous work exist on general USV docking, a short introduction is given to the most related fields, such as spacecraft docking and aerial refuelling. During air refuelling two methods are summarised which includes racetrack pattern or waypoint paths, where the receiver aircraft has two different ways of rendezvousing with the tanker, namely point parallel- or route-rendezvous. In both docking scenarios treated here, rendezvous guidance is developed since the vehicles are assumed underactuated. The docking procedure is divided into two stages, a homing stage and a docking stage. In the homing stage only rough guidance is needed which is not the case during docking stage where requirements are much tighter on positioning to avoid collisions. In the AUV to USV homing stage the USV does all the work, but during docking stage the AUV has full responsibility, since the USV only traverses along a straight path. The USV's path is here orientated against the wind direction to minimise the sideslip effect caused due to weather disturbances. Once the USV has converged to a straight path the AUV proceeds to docking from behind the USV to finalise docking. For the USV to mothership docking scenario, the USV has the full responsibility during the whole docking procedure. Here the USV is underactuated, and therefore the mothership will be in motion and only has to avoid sudden manoeuvres. In the homing stage the USV will manoeuvre towards a point given on the line of sight vector between the two vehicles. Once the USV reaches this point it will steer along a circle around the mothership to avoid collisions and to position itself in clear sight of the docking point. With clear sight achieved the USV will use its forward motion to converge sideways towards the docking point, such that docking can be completed. Finally, simulations are carried out to verify the behaviour of the developed guidance laws. During these simulations two 3DOFs underactuated USV models are being used, where both vehicles only has controllability over surge speed and yaw rate. In both docking scenarios the whole docking procedure is analysed including homing and docking stage. The simulation results shows a proper docking with a satisfying approach in both scenarios. Also the mothership's velocity is examined to understand the USV's sideway approach towards the mothership.

This master thesis treats the NTNU Rotary Wrist Device(NRWD). The wrist has been developed through several projects and assignments, all derived from Øyvind Stavdahls PhD thesis from 2002, which led to a document of functional specifications. This thesis follows from a specialization project by the writer during autumn 2009. The project looked into the error-prone circuit board that was made to control the NRWD, and came to the conclusion that it could not be used, and that a different approach was necessary. Based on the experience achieved by previous assignments a suggestion for the complete hardware circuitry has been designed. In September 09 the first revision of a protocol for communication in electrical prosthesis were released. The protocol was developed at University of New Brunswick (from here referred to as the UNB-protocol), and is presented as a proposal for a standard communication protocol in the world of electrical prosthesis. This thesis suggests an expansion to this protocol. The expansion is about device profiles, meaning that a device (e.g., a wrist prosthesis, elbow prosthesis, sensory or the like) connecting to an electrical prosthesis system will let the system know what functions it can provide, without the need of updating of the system. A complete functional specification for the NRWD has been written. The specifications are based on those from the originals made by Stavdahl, with revisions in the requirements involving communication. This to make them comply with the UNB-protocol. The protocol is build on a CAN-bus, so in practice this means that all digital communication interfaces except CAN has been removed. In addition there have been added a requirement to prevent the motor from overheating. During the assignment a complete circuit diagram for a new control system has been developed. The circuitry is ready for testing and construction. It has been emphasized to use small components and making the NRWD hardware compatible with the UNB-protocol. There are also suggested some guidelines for the software development.

The use of robotic grippers offers huge potential benefits in industrial settings. The more advanced a gripper is, the more uses it can have, thus offering large economic benefits. On the other hand, the more complex a gripper is, the more advanced its control system needs to be, in order to control it effectively and safely. This thesis will focus on controlling SCHUNK Dextrous Hand (SDH), a 3-fingered robotic gripper with 7 degrees of freedom and tactile sensors in the fingers. By creating a real-time control system the sensors in the fingers can be used to make a feedback loop that controls the fingers. This is the basis for creating an adaptive gripper that can grip objects of unknown shape, size or position. This control system in combination with a controller for a robotic manipulator arm lets the gripper attempt to grip objects even if they are out of reach. By passing requests up to an overall control system, the gripper can request a translation to a position that gives it a better chance at performing a successful grip on the targeted object. In this project, the controller for the gripper is created, and the communication to and from the manipulator control system is replaced with a simple user-interface. This user interface offers a way of testing the complete system without the use of a manipulator arm. The translations from the gripper is read out, and the target object is moved by hand, in the opposite direction. This solution offers a simple way to expand the system to include the manipulator and its control system in later editions. Initial experiments were successful, with the gripper successfully able to pick up different objects. An apple, an empty soda can (both upright and lying down) and a chocolate egg were all picked up and held firmly without damaging the object. Complications arose with regards to the sensitivity of the sensors. They were generally unable to register any pressure when the fingers came in contact with lighter objects, and had to push the objects against the other two fingers. Another problem that arose was the stability of the application created. The program was based on multi-threading, and real-time sensor analysis. The application crashing did cause some objects to be damaged in the experiments, as the application logic could not halt the fingers despite pressure being registered. Future work should focus on restructuring the application logic to improve the stability, and the control system for the manipulator arm.

Force control of robot manipulators will be needed in the future to fulfill the potential of automated solutions. For this to be possible, adequate control systems for this special purpose are required. This thesis proposes an extension to an existing force control approach found in the literature, based on direct force control, for the use of an industrial ABB robot in anode milling operations. This report presents a control system that aims to exercise force control with a robot manipulator, in order to conduct effective carbon anode milling. The control structure proposed contains both a position controller and a velocity controller, in order to enhance the final result. Because there is a gap between the theory on robot force control and the features usually available on an industrial robot, this control system is modified to be directly implementable on a standard industrial ABB robot manipulator. Simulations, and subsequent comparison, of both this control system and a control system typically found in the industry, which is based on PID control of the milling tool power consumption, are conducted. ABB’s Robot- Studio is used to perform the simulations, where models of the tool, anode and coke are used. From these simulations we see that the industrial PID controller performs very well, and that the newly proposed control approach does not quite reach the same level of performance.

Sammendrag: Hivkompensering kan deles inn i passiv, aktiv og semiaktiv kompensering utifra i hvilken grad det benyttes et aktivt pådrag for å kompensere for hivet. Hivkompenserig kan gjøres på forskjellige måter. Toppmontert sylinderkompensering og løpeblokkmontert sylinderkompensering er to vanlige kompenseringsmetoder. Denne rapporten tar blant annet for seg en forenklet modellering av RamRig heisesystem og en borestreng. Dette er gjort ved å sette opp bevegelseslikninger og kraftbalanser for de forskjellige delene av systemet, med hovedvekt på friksjonskrefter og trykktapskrefter som gjør at det passive hivkompenseringssystemet, som er en del av heisesystemet, ikke er ideelt. Rapporten beskriver deretter arbeidet med utvikling av reguleringsalgoritmer for å oppnå mest mulig konstant vekt på borekrone. Disse algoritmene danner sammen med det passive systemet et semiaktivt hivkompenseringssystem. Det ble forsøkt med PID regulator, foroverkobling av hivforstyrrelsen, kombinert foroverkobling og PD regulator, og akselerasjonstilbakekobling. Simulering viste at den av disse algoritmene som gav best kompensering var foroverkoblingsalgoritmen kombinert med PD regulator, fordi mye av tapskreftene i det passive systemet ved denne algoritmen kompenseres for før de påvirker systemet. PD regulatorens oppgave er å håndtere unøyaktigheter i modelleringen som gjør at kompenseringen til foroverkoblingsalgoritmen ikke er tilstrekkelig i seg selv. Simulering under gitte forhold viser at 95 % av hivbevegelsen blir kompensert for med denne algoritmen i kombinasjon med det passive kompenseringssystemet (mot 70 % for det rent passive systemet). Det er i denne oppgaven utviklet en modell som inneholder de mest vesentlige elementene til det reelle systemet og som er egnet som utgangspunkt for å utvikle reguleringsalgoritmer og til å simulere disse algoritmene på modellen. Det er også utviklet en egnet algoritme for regulering av vekt på borekrone for hivkompensering under boring med RamRig. Målet med oppgaven anses derfor som nådd, og oppgaven gir et godt grunnlag for videre arbeid.

Denne masteroppgaven omhandler videreutvikling av en fjernstyrt LEGO robot ved Institutt for Teknisk Kybernetikk. Roboten har tidligere gjennomgått flere utviklingssteg via prosjekter og diplom/masteroppgaver ved instituttet. Utgangspunktet for oppgaven er en robot bygget av Lego som kan fjernstyres trådløst fra PC. Roboten hadde innebygd et posisjoneringssystem og sensor for måling av avstand til omgivelsene. På PC siden ble MATLAB med tilhørende kartleggings- og navigasjonsalgoritmer brukt for å produsere kart over omgivelsene mens roboten kjørte, såkalt SLAM (Simultaneous Location And Mapping). Roboten kunne derfor under visse betingelser autonomt navigere i ukjente omgivelser. Mer konkret baserte kartbyggingen seg på å utvinne et linjebasert kart der alle objekter i robotens miljø ble redusert til linjer. Derav ble det vanskelig å produsere for eksempel runde objekter i kartet. Andre begrensinger var at posisjoneringssystemet besto kun av en dead-reckoning metode som gjorde at posisjonen til roboten etter hvert som den kjørte ble beheftet med usikkerhet som etter hvert ville gå mot uendelig. I tilegg var det svakheter i programmet når det gjaldt navigeringsstrategier i ukjente områder. I denne oppgaven gjøres det programutvikling i MATLAB for å bedre navigasjons- og kartleggingsegenskapene. Systemet baserer seg på at roboten skal kartlegge og navigere i sanntid. Det er implementert algoritmer som gjør det mulig å motta sensordata og behandle disse mens roboten kjører. Dataene presenteres grafisk i et utvidet brukergrensesnitt der både linjesegmenter og punkter tegnes i samme kart. Slik kan objekter med ulik geometrisk form representeres på en bedre måte enn før. Den innebygde simulatoren er utvidet med flere relevante labyrinter og funksjonalitet. Fra tidligere arbeid var det implementert en veggfølgingsalgoritme laget for å navigere i en linjekart. I denne oppgaven har den eksisterende veggfølgingsalgoritme blitt tilpasset til å håndtere et kombinert linje- og punktbasert kart. En ny metode for å detektere ukjente områder er laget og brukes i navigeringen. Det er foretatt en studie av en ny navigasjonsstrategi som baserer seg på et action-selected prinsipp der navigasjonsstrategier blir valgt på bakgrunn av prioriteter. Det er innført en ladestasjon som roboten kan starte og returnere til. Hensikten er å gjøre roboten mer autonom ved at den kan få ladet batteripakkene uten menneskelig påvirkning. Posisjonsestimatet til roboten kan også forbedres ved at den kan returnere til et fast punkt. Et tilpasset EKF (extended kalman filter) muliggjør oppdatering av posisjon. Tester viser at de utviklete algoritmer for kartlegging og navigering isolert fungerer tilfredsstillende. Likevel kan det ikke konkluderes med at kartleggingen har blitt mye bedre. Posisjonsestimatet er den avgjørende faktoren som begrensninger systemet. Videre arbeid er foreslått til å være forbedring av posisjonsestimatet til roboten. Dette kan gjøres ved endringer i hardware og software, samt å bruke kamera for regulering av robotposisjon. Når posisjoneringen har blitt bedre kan det være aktuelt å se på kartlegging i tre dimensjoner. Det er i rapporten henvist til artikler som beskriver en utvidelse til 3D-SLAM. En annen retning å bevege seg i er å se på samhandlede roboter, der to eller flere LEGO-roboter samarbeider om kartleggigen.