The main purpose of this report, is to evaluate feasibility of using The Global Positioning System as an aiding tool for vehicle state estimation based on nonlinear techniques, and to develop a potential solution to the road bank angle problem. Previous work within the CEmACS project, includes development of a general nonlinear observer for lateral and longitudinal velocity, and an augmentation in the form of road-tire friction adaptation. Because the existing solutions have been shown to lack robustness with regards to certain disturbances, such as road grade and road bank angle, it has been stated that the estimation scheme should be upgraded, so that these disturbances can be accounted for. By including GPS velocity or a or a roll rate gyro measurement in the observer feedback loop, the possibility of detecting previously inobservable quantities is gained. In simple terms, evaluation of feasibility corresponds to demonstrating improvements and limitations of new solutions, using relatively crude methods in the test procedures. Problems related to the above mentioned task, are approached by means of signal processing and control theory. Following an intuitive sequence of operations, the report presents GPS theory and results first, as this lays the foundation for all subsequent results. Methods used comprise simple differentiaton, rotational kinematics and discrete filtering. Secondly, theory and results related to nonlinear observers, with focus on GPS aiding, are examined thoroughly. Lyapunov theory, known from control engineering, is used to evaluate stability, while data from simulations and actual vehicle tests is used to show how a new observer scheme can improve existing solutions. Before the most important results are presented, something should be said about their accuracy and significance. It has already been pointed out that the methods used are not based on optimality requirements, and consequently the results are best viewed as indicators of potential, rather than absolute solutions. This is especially true for the GPS velocity calculations, which are based on differentiation of position measurements; generally not a desired approach. In this report, it is firstly shown that GPS position measurements can be used to compute receiver velocity in the body-fixed coordinate frame. While this is a crude approach, resulting in relatively poor signal to noise ratio, it is easily implemented on low-level equipment. It is also shown that it is possible to use these velocities as measurements in a nonlinear observer structure, slightly modified from previous solutions within the CEmACS project. By doing this, accurate estimates of road grade and bank v angle are achieved, so long as these vary slowly enough. Stability of the observer is not proven in the general sense, but it is shown that it can be made stable through realistic assumptions and gain selection. Stability is further demonstrated through the use of data sets from actual vehicle tests. Secondly, a mathematical model of roll dynamics is combined with a roll rate measurement to create the possibility of detecting road bank angle. This is done by the now familiar nonlinear observer approach. Usefulness is demonstrated by simulations, but no stability proof is presented. The main conclusion is that it is feasible to use GPS aiding to account for robustness problems in a vehicle state estimation scheme, and that the inclusion of a roll rate measurement opens up possibilities for “cheap” bank angle detection. A direct implementation of results presented in the report may not be ideal, but the fact that the system works for a large set of conditions, suggests that it is worthwhile to develop it further. This is especially true when it is assumed that GPS receivers will become an integral part of new vehicles in the near future. Refinements and upgrades can be made in the form of more advanced GPS technology, new parameter estimation techniques and integration with the road-tire friction adaptation scheme.

This thesis deals with the mathematical modeling of hydraulic heave compensation systems. When performing operations such as launch and recovery of remote operated vehicles and lowering subsea installation parts to the sea floor, it is important to attenuate unwanted load motion caused by elongation of the cable and heave motion of the vessel. Quite often, such operations must be put off while waiting for the weather to calm down. Extending the window of operations by developing equipment that can handle varying sea states can result in significant cost savings. There exist both electric and hydraulic heave compensation devices, but the main focus of this thesis is on the hydraulic configurations. A mathematical model is developed in Simulink, and simulations are performed for long-crested seas with values corresponding to the average sea conditions in the North Sea.

An underlying requirement for any Autonomous Underwater Vehicle (AUV) is to navigate through unknown or partly unknown environments while performing certain user specified tasks. The loss of an AUV due to collision is unjustifiable both in terms of cost and replacement time. To prevent such an unfortunate event, one requires a robust and effective Collision Avoidance System (CAS). This paper discusses the collision avoidance problem for the HUGIN AUVs. In the first part, a complete simulator for the HUGIN AUV is implemented in matlab and simulink. This includes a 6 degrees-of-freedom nonlinear AUV model, simulated environment including bottom profile and surface ice, navigation- and guidance functionality and sensor simulators. In the second part a number of well known strategies for the collision avoidance problem is presented with a short analysis of their properties. On the basis of the implemented simulator, a proposed CAS is developed and it’s performance is analyzed. This system is based on simple principles and known collision avoidance strategies, in order to provide effective and robust performance. The proposed system provides feasible solutions during all simulations and the collision avoidance maneuvers are performed in accordance with the specified user demands. The developed simulator and collision avoidance system is expected to provide a suitable framework for further development and possibly a physical implementation on the HUGIN AUVs.

Design of a heading autopilot and way-point navigation system an underactuated USV.

Pipelines with multiphase flow will exhibit large and highly nonlinear liquid rates during transients caused by changes in production rate. This requires either a large separator (slug catcher) downstream, capable of handling all disturbances, or, some sort of control of the rate change in order to ensure that the downstream processing equipment can cope with the disturbances. In this report, it is proposed to use smart liquid control to optimally control the production during rate changes. The term smart liquid control was coined to describe the use of nonlinear model predictive control (NMPC) and a nonlinear pipeline model to control liquid levels. The pipeline from the Snøhvit field to the Hammerfest LNG plant was used as a test case on which to implement smart liquid control. The technique was proved using a simplified OLGA pipeline model for both predictions and as process, i.e. perfect model. Good results were shown, especially when compared to manual control. Smart liquid control therefore presents a possibility to reduce separator size for new projects. Another highly interesting use of smart liquid control is to optimize the use of separator buffer capacity in order to maximize production. The NMPC method used in this report, a single shooting multistep quasi-Newton method, was elaborated on in a literature review chapter. Also an implementation of the method was made and described in the context of NMPC. The implementation of the algorithm was made in the in-house STATOIL MPC-tool, SEPTIC. In order to assess the performance of the algorithm, it was tested on a small continuously stirred tank reactor system and the results reported and discussed.

A ship scheduling problem in optimization of water-borne crude oil transportation has been investigated. The classic optimization problem the most closely related to the problem at hand is the Multi-Vehicle-Pick-up-and-Delivery Problem with Time Windows (m-PDPTW). In addition to the basic characteristics of the m-PDPTW, the studied problem has an additional degree of freedom due to having pick-ups and deliveries that are not matched. This extra freedom gives new possibilities when creating effective heuristics when dealing with transportation problems. The studied problem has been presented in relation to carefully selected background literature. On this basis a proposed heuristic has been developed, and implemented using some already existing structures in the commercial decision support system TurboRouter. The studied problem is an industrial shipping problem, an operational mode where the shipper owns the cargo to be transported. No income is therefore made directly from transporting goods. Therefore the objective function chosen was net income, which in this mode is the same as minimizing the net expenses. A multi-start local search with pre-matching of pick-ups and deliveries heuristic was chosen based on an assessment of problem size, problem type, real life applicability and existing software. This heuristic consists of three main parts. First the pick-ups and deliveries are matched and merged in a pre-matching heuristic, and then a large number of initial solutions are generated by an insertion heuristic. The best initial solutions are then improved by a local search. Two strategies were developed for pre-matching and then tested. The one with the best test results was subsequently used in the heuristic. This multi-start local search with pre-matching of pick-ups and deliveries heuristic has been subject to rigorous testing and was compared to a single-start local search and multiple initial solutions heuristic. The solutions generated by the multi-start local search heuristic were superior compared to those of the other heuristics, but the computation time necessary was high and higher than those of the heuristics which it was compared to. This high computation time is partially believed to be a result of flexible data sets resulting in broad solution spaces. In addition some computationally expensive heuristics were deployed, increasing the computation time. In real life applications, finding a solution relatively quickly is of importance. Therefore the heuristic may need to be simplified and used on "tighter" data sets than some sets used in testing to be real life applicable.

In offshore production systems for oil and gas, the wells are usually controlled manually, while the topside process is controlled using a decentralized control system. It is clear that this control structure may not be economically optimal. In the work of this thesis, one decentralized and two MPC based control systems were designed, integrating the control of the production wells and the topside process of an offshore production system. The performance of the controllers was tested in a simulation study with three different disturbance scenarios, defined in collaboration with Hydro. The simulations were also carried out using a manual control scheme, enabling a performance comparison between the designed controllers and the control conventions of today. The automatic controllers showed a significant increase in oil throughput over the manual control scheme, while performing quite similarly when compared to each other. It is however expected that the MPCs will outperform the decentralized control system in a case with a larger number of wells than was used in the simulations of this thesis. The potential of achieving additionally smoothened topside outflow rates by applying a supervisory MPC for topside setpoint manipulation was also demonstrated.

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.

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.

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.