<p>The need for spectrally efficient transmission on mobile and wireless channels is prevalent. A promising scheme for such transmission is adaptive coded modulation. In this thesis, techniques for assessing the performance of such systems are presented. One of the vulnerable points of such systems is the need for a reliable feedback channel. Channel prediction is proposed as a technique to combat the harmful effects of feedback delay.</p><p>The Nakagami distribution is often employed in a model for the fading envelope of a wireless channel; this leads to a gamma-distributed signaltonoise ratio. Nakagami (1960) provides expressions for the probability density function (PDF) of the product, sum, and ratio of two correlated gamma-distributed random variables (RVs). However, such an expression for the difference between two such RVs has not been provided by Nakagami.</p><p>A new expression for this PDF is provided in this dissertation, and it is shown that it is closely related to a distribution first described by McKay (1932). Applications of the new PDF include outage probability calculation in an environment with self-interference and assessment of the quality of certain channel estimation techniques.</p>

The need for spectrally efficient transmission on mobile and wireless channels is prevalent. A promising scheme for such transmission is adaptive coded modulation. In this thesis, techniques for assessing the performance of such systems are presented. One of the vulnerable points of such systems is the need for a reliable feedback channel. Channel prediction is proposed as a technique to combat the harmful effects of feedback delay. The Nakagami distribution is often employed in a model for the fading envelope of a wireless channel; this leads to a gamma-distributed signaltonoise ratio. Nakagami (1960) provides expressions for the probability density function (PDF) of the product, sum, and ratio of two correlated gamma-distributed random variables (RVs). However, such an expression for the difference between two such RVs has not been provided by Nakagami. A new expression for this PDF is provided in this dissertation, and it is shown that it is closely related to a distribution first described by McKay (1932). Applications of the new PDF include outage probability calculation in an environment with self-interference and assessment of the quality of certain channel estimation techniques.

<p>Updating the model parameters of the control system of an oil and gas production system for the reasons of cost-effectiveness and production optimization, requires a data set of input and output values for the system identification procedure. A requirement for the system identification to provide a well performing model is for this data set to be informative. Traditionally, the way of obtaining an informative data set has normally been to take the production system out of normal operational order, in the interest of performing experiments specificially designed to produce informative data. It is however desirable to use segments of process data from normal operation in the system identification procedure, as this eliminates the costs connected with a halt of operation. The challenge is to identify segments of the process data that give an informative data set. Dynamic Identifiability Analysis (DYNIA) is an approach to locating periods of high information content and parameter identifiability in a data set. An introduction to the concepts of data mining, system identification and parameter identifiability lay the foundation for an extensive review of the DYNIA method in this context. An implementation of the DYNIA method is presented. Examples and a case study show promising results for the practical functionality of the method, but also raise awareness to elements that should be improved. A discussion on the industrial applicability of DYNIA is presented, as well as suggestions towards modifications that may improve the method.</p>

<p>The topic of this paper is to control and synchronize sphere-shaped spacecrafts in a leader-follower synchronization scheme. In order to achieve this objective, a nonlinear mathematical model of the vehicles has been developed. The design is based on rigid body dynamics where the vessel is actuated by means of three orthogonally mounted reaction wheels. The attitude dynamics is derived using Euler parameters. In the pursuit of reaching the main goal of controlling and synchronizing the satellites, it is natural to rst develop control algorithms for single vehicle control. A sliding mode controller and a backstepping controller have been derived for this matter, and are compared for optimality. Both controllers are based on nonlinear control theory and are designed to control the angular velocity of the satellite. The system in combination with both the controllers is proven to be asymptotically stable. Due to cases where the spacecraft does not have angular velocity measurements, an estimator for the angular velocity is derived. Using LaSalle's theorem, asymptotic stability is proven for the observer in the time-invariant case, while Matrosov's theorem is utilized for system explicitly dependent on time. For operational assignments where it is not sufficient with only one satellite, a synchronizing scheme for several satellites has been proposed. The scheme is based on a leader-follower synchronization design, and is derived assuming that none of the satellites are equipped with angular velocity measurements. It is therefore possible to implement and utilize the nonlinear observer for angular velocity estimation in each vehicle. The controllers are designed in a similar manner for both the leader and the follower using backstepping control. The leader is set to follow an arbitrarily smooth trajectory, while the follower's objective is to track the leader's attitude, given by measurements and estimations. The various systems are tested in a lab setup with the AUVSAT. The AUVSAT is a sphere shaped, autonomous underwater satellite actuated by means of three orthogonally reaction wheels. The experiments are performed when the AUVSAT is submerged in a water tank, making it possible to emulate a gravity free environment equal to what a satellite traveling in space is experiencing. The AUVSAT build up is presented where hardware and software components are chosen with respect to simplicity, cost and space restrictions. Several experiments are carried out using the AUVSAT to evaluate the performance of the controllers, observer and the synchronization scheme. For all cases, the system tracks a time-varying sinusoidal reference signal in addition to a squareshaped sequence. In this way, one can truly validate transient responses, steady-state and tracking maneuvers to determine the performance of the various systems. The experiments show that the sliding mode controller and backstepping controller works quite similar and with a satisfactorily behavior throughout the experiments. However, there are some lack of performance of the combined observer and controller system when tracking the sinusoidal time-varying reference. In the synchronization scheme, the leader follows the desired trajectory and the follower tracks the leader's attitude to some extent. Comments on the results are presented in addition to proposed strategies and thoughts on how to improve the overall performance of the various systems.</p>

<p>Natural gas from organic rich shales has become an important part of the supply of natural gas in the United States. Modern drilling and stimulation techniques have increased the potential and profitability of shale gas reserves that earlier were regarded as unprofitable resources of natural gas. The most prominent property of shale gas reservoirs is the low permeability. This is also the reason why recovery from shale gas wells is challenging and clarifies the need for stimulation with hydraulic fracturing. Shale gas wells typically exhibit a high initial peak in the production rate with a successive rapid decline followed by low production rates. Liquid accumulation is common in shale wells and is detrimental on the production rates. Shut-ins of shale gas wells is used as a means to prevent liquid loading and boost the production. This strategy is used in a model-based production optimization of one and multiple shale gas well with the objective of maximizing the production and long-term recovery. The optimization problem is formulated using a simultaneous implementation of the reservoir model and the optimization problem, with binary variables to model on/off valves and an imposed minimal production rate to prevent liquid loading. A reformulation of the nonlinear well model is applied to transform the problem from a mixed integer nonlinear program to a mixed integer linear program. Four numerical examples are presented to review the potential of using model-based optimization on shale gas wells. The use of shut-ins with variable duration is observed to result in minimal loss of cumulative production on the long term recovery. For short term production planning, a set of optimal production settings are solved for multiple wells with global constraints on the production rate and on the switching capacity. The reformulation to a mixed integer linear program is shown to be effective on the formulated optimization problems and allows for assessment of the error bounds of the solution.</p>

<p>The problem of performing accurate path maneuvering tasks in planar space is investigated in thesis. The purpose is to utilize limited knowledge about the vehicle's maneuverability constraints to output feasible reference signals. Acceleration limitations of the vehicle have been used in an algorithm that determines forward speeds in such way that a predefined path can be followed at high speeds. The algorithm ensures that the speed is reduced before acute turns. Furthermore, an existing steering law has been modified to dynamically take the limitations of the vehicle into consideration when determining the desired course. This modified steering law exhibits desirable convergence characteristics toward the desired path. A complete guidance system, which combines the path convergence algorithm with the path speed algorithm, has been proposed. This system is able to rapidly converge to the desired path and follow this path, even for paths where the curvature is large. The modified steering law has been combined with a path-tracking speed controller. The path-tracking speed controller makes sure the vehicle can track a target on a predefined path. The resulting path-tracking system is able to follow a leader vehicle's path by creating accurate paths online from periodically sampled positions. A method for creating feasible U-turns in a lawn-mower pattern has been proposed. For a given vehicle speed, the resulting path obeys angular speed and angular acceleration constraints. Finally, the proposed algorithms are tested in simulations to illustrate their behavior and usefulness.</p>

<p>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.</p>

<p>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.</p>

<p>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.</p>

<p>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.</p>