Dissertations / Theses on the topic 'Guidance'

Emergence of mobile technologies, with their ever increasing computing power, embedded sensors, and connectivity to the Internet has created many new applications such as navigational guidance systems. Unfortunately, these devices can become problematic by inappropriate usage or overloading of the audiovisual channels. Wearable haptics has come to the rescue with the promise of offloading some of the communication from the audiovisual channels. The main goal of our research is to develop a spatiotemporal guidance system based on the potentials and limitations of the sense of touch. Our proposed guidance method, Periodic Vibrotactile Guidance (PVG), guides movement frequency through periodic vibrations to help the user achieve a desired speed and/or finish a task in a desired time. We identify three requirements for a successful PVG system: accurate measurement of the user's movement frequency, successful delivery of vibrotactile cues, and the user's ability to follow the cues at different rates and during auditory multitasking. In Phase 1, we study the sensitivity of different body locations to vibrotactile cues with/without visual workload and under different movement conditions and examine the effect of expectation of location and gender differences. We create a set of design guidelines for wearable haptics. In Phase 2, we develop Robust Realtime Algorithm for Cadence Estimation (RRACE) which measures momentary step frequency/interval via frequency-domain analysis of accelerometer signals available in smartphones. Our results show that, with a 95% accuracy, RRACE is more accurate than the published state-of-the-art time-based algorithm. In Phase 3, we use the guidelines from Phase 1 and the RRACE algorithm to study PVG. First we examine walkers' susceptibility to PVG which shows most walkers can follow the cues with 95% accuracy. Then we examine the effect of auditory multitasking on users' performance and workload, which shows that PVG can successfully guide the walker's speed during multitasking. Our research expands the reach of wearable haptics and guidance technologies by providing design guidelines, a robust cadence detection algorithm, and Periodic Vibrotactile Guidance -- an intuitive method of communicating spatiotemporal information in a continuous manner -- which can successfully guide movement speed with little to no learning required.
Science, Faculty of
Computer Science, Department of
Graduate

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2000.
Includes bibliographical references (p. 241-251).
Anticipatory route guidance consists of messages, based on traffic network forecasts, that assist drivers' path choice decisions. Guidance is consistent when the forecasts on which it is based are verified after drivers react to it. This thesis addresses the formulation and development of solution algorithms for the consistent anticipatory route guidance generation (RGG) problem. The thesis proposes a framework for the problem, involving a set of time-dependent variables and their relationships. Variables are network conditions, path splits and guidance messages. Relationships are the network loading map, transforming path splits into network conditions; the guidance map, transforming network conditions into guidance messages; and the routing map, transforming guidance messages into path splits. The basic relationships can be combined into three alternative composite maps that model a guidance problem. Consistent guidance corresponds to a fixed point of a composite map. With stochastic maps, RGG model outputs are stochastic process realizations. In this case, the consistency fixed point corresponds to stationarity of the RGG solution process. Numerical methods for fixed point computation were examined, focusing on approaches that are rigorous and applicable to large-scale problems. Methods included Gibbs sampling for highly stochastic maps; generalizations of functional iteration for deterministic maps; and the MSA and Polyak iterate averaging method for "noisy" (deterministic plus disturbance) maps. A guidance-oriented dynamic traffic simulator was developed to experiment with RGG solution methods. Computational tests using the simulator investigated the use of Gibbs sampling to compute general stochastic process outputs; and examined the performance of the averaging methods under different model formulations, problem settings and degrees of stochasticity. Gibbs sampling successfully generated realizations from the stationary solution process of a fully stochastic model, but entails considerable computational effort. For noisy problems, the MSA found fixed points in all cases considered. Polyak averaging converged between two and four times faster than the MSA in low or moderate stochasticity problems, and performed comparably to the MSA in other problems. Formulations involving path-level variables converged more quickly than those involving link-level variables.
by Jon Alan Bottom.
Ph.D.

Mestrado em Engenharia Electrónica e de Telecomunicações
Com os avan cos tecnol ogicos que se têm registado nos ultimos anos torna-se, cada vez mais, necess ario desenvolver solu cões que permitam facilitar o dia-a-dia das pessoas que sofrem de alguma impossibilidade f sica. E de facto crucial come car a aplicar a tecnologia no desenvolvimento de sistemas que permita a essas pessoas tornarem-se independentes e capazes de responder a todas as tarefas di arias. Assim, inspirado pelo Instrument Landing System (ILS), que e um sistema que permite aos pilotos aterrarem os aviões em seguran ca quando as condi cões metereol ogicas e visuais não são as mais favor aveis, pretende-se desenvolver um mecanismo que permita aos invisuais identi carem a aproxima cão de uma porta, e consequemente ajud a-los a entrar ou sair da divisão. De um modo geral, este trabalho foca-se no desenvolvimento de uma antena que permita fazer a identificação da porta. Pretende-se que a antena apresente um diagrama de radia ção com a forma de uma bolacha, pois a detecçãco do m aximo ir a levar a entrada ou sa da correcta da porta. Para atingir este objectivo, a antena a ser desenvolvida e um agregado linear e uniforme de dipolos, cujo o diagrama de radia c~ao cumpre as especi ca cões pretendidas. Outro aspecto importante acerca do agregado de dipolos diz respeito a sua constru cão, pretende-se que a antena a desenvolver seja impressa. Esta op cão prende-se com a sua rela cão simplicidade e baixo custo com e ciência e desempenho.
With all the technological developments that have happened during the past few years, it has become necessary to come up with systems that are capable of improving everyday tasks of people who have physical disabilities. Actually, it is important to improve the living conditions of these people by providing them mechanisms that would make them stop relying on the others. Bearing this in mind, the idea for this dissertation was inspired by the ILS, which is a landing system that allows pilots to land with safety in poor visibility and weather conditions. It is aimed to design an antenna for a system that helps the visually impaired or the blind to guide themselves indoor. In fact, it is intended to develop a system that helps them to identify a door, and at the same time guide them to enter or exit the room correctly. In general, this work is focussed in the design of a suitable antenna for door identi cation. The main speci cation that the antenna has to meet is having an extremely narrow radiation pattern. The reason behind this speci cation is due to the way that the receiver would know when to tell the user that a door entrance is approaching, in other words, the identi cation of a door is made through maximum search of the radiation pattern. When this maximum value is found, the person knows that he or she is correctly positioned to enter or exit the room. The antenna would be a linear array of uniform amplitudes and spacing of dipoles with a radiation pattern similar to a cookie. Another aspect concerning the antenna is what materials it would be made of. Considering the relation between simplicity and low-cost with e ciency and performance, a printed antenna would be the ideal solution for the project's system.

The purpose of the project is the development and study of guidance algorithms of missiles in the particular configuration of the simultaneous use of two pursuers to intercept one evader. The profits of this configuration are applied to allocation in a three missiles – two targets scenario. The implemented techniques deal with optimal control theory, more particularly with differential game theory, mainly the linear and linear quadratics, which are commonly used in guidance law. Differential game theory allows determining the optimal commands of the players of one pursuer - one evader game with the minimization of the miss distance for the pursuer and maximization of the same miss distance for the evader as criteria of this optimal problem. A new optimal command law for the evader is developed in the two pursuers against one evader game (called 2x1 games) with the same time-to-go as well as with different time-togo. These new optimal commands are implemented and validates in two 2D simulations: a linear one, developed in Matlab script, and a non linear one, based on a Simulink model. An extension of the capture zones of each missile is demonstrated and tested in simulations. The 2x1 game and the induced no-escape-zone extension are finally integrated and verified in realistic simulation with a 6 d.o.f missile Simulink model. The 2x1 configuration’s use is applied to allocation on 3 pursuers - 2 evaders scenarios based on the same 3D missile model and the benefits are analysed.
Le but de ce rapport et le développement et l'étude d'un algorithme de guidage missile dans le cas particulier de l'utilisation simultanée de deux missiles pour intercepter une cible. L'avantage de cette configuration est utilisé pour l'allocation des missiles dans un scenario de trois missiles contre deux cibles. Les techniques mises en oeuvre sont issues de la théorie du control optimal et plus particulièrement de la théorie des jeux différentiels linéaire et quadratique linéaire, qui sont couramment utilisés dans les lois de guidage. La théorie des jeux différentiels permet de déterminer les commandes optimales des joueurs d'un jeu un missile-une cible avec comme critère optimal la minimisation de la distance de passage finale pour le missile et la maximisation de cette même distance pour la cible. Une nouvelle loi de commande optimale pour la cible est établie pour le jeu de deux missiles – une cible (appelé jeu 2x1) avec aussi bien des time-to-go identiques que des time-to-go différents. Ces lois de commande optimales sont implémentées et validées dans deux simulations en 2D: une linéaire, développé en script Matlab, et une non-linéaire, développé sous Simulink. Une extension des zones de captures (no-escape-zone) de chacun des missiles est démontrée et testée avec les simulations. Le jeu 2x1 et l'extension des no-escape-zone qui en découle est finalement intégré et vérifié dans une simulation 3D sous Simulink plus réaliste, basé sur un modèle de missile à six degrés de libertés. L'utilisation d'une configuration 2x1 pour de l'allocation est appliqué à un scenario de trois missiles contre deux cibles basé sur les même modèle de missile à six degrés de libertés.

Future robots are expected to cooperate with humans in daily activities. Efficient cooperation requires new techniques for transferring human skills to robots. This thesis presents an approach on how a robot can extract and replicate a motion by observing how a human instructor conducts it. In this way, the robot can be taught without any explicit instructions and the human instructor does not need any expertise in robot programming. A system has been implemented which consists of two main parts. The first part is data acquisition and motion extraction. Vision is the most important sensor with which a human can interact with the surrounding world. Therefore two cameras are used to capture the image sequences of a moving rigid object. In order to compress the incoming images from the cameras and extract 3D motion information of the rigid object, feature detection and tracking are applied to the images. Corners are chosen as the main features because they are more stable under perspective projection and during motion. A reliable corner detector is implemented and a new corner tracking algorithm is proposed based on smooth motion constraints. With both spatial and temporal constraints, 3D trajectories of a set of points on the object can be obtained and the 3D motion parameters of the object can be reliably calculated by the algorithm proposed in this thesis. Once the 3D motion parameters are available through the vision system, the robot should be programmed to replicate this motion. Since we are interested in smooth motion and the similarity between two motions, the task of the second part of our system is therefore to extract motion characteristics and to transfer these to the robot. It can be proven that the characteristics of a parametric cubic B-spline curve are completely determined by its control points, which can be obtained by the least-squares fitting method, given some data points on the curve. Therefore a parametric cubic B–spline curve is fitted to the motion data and its control points are calculated. Given the robot configuration the obtained control points can be scaled, translated, and rotated so that a motion trajectory can be generated for the robot to replicate the given motion in its own workspace with the required smoothness and similarity, although the absolute motion trajectories of the robot and the instructor can be different. All the above modules have been integrated and results of an experiment with the whole system show that the approach proposed in this thesis can extract motion characteristics and transfer these to a robot. A robot arm has successfully replicated a human arm movement with similar shape characteristics by our approach. In conclusion, such a system collects human skills and intelligence through vision and transfers them to the robot. Therefore, a robot with such a system can interact with its environment and learn by observation.

We propose an augmented reality system to automatically identify lumbar vertebral levels and the lamina region in ultrasound-guided epidural anesthesia. Spinal needle insertion procedures require careful placement of a needle, both to ensure effective therapy delivery and to avoid damaging sensitive tissue such as the spinal cord. An important step in such procedures is the accurate identification of the vertebral levels, which is currently performed using manual palpation with a reported success rate of only 30%. In this thesis, we propose a system using a trinocular camera which tracks an ultrasound transducer during the acquisition of a sequence of B-mode images. The system generates a panorama ultrasound image of the lumbar spine, automatically identifies the lumbar levels in the panorama image, and overlays the identified levels on a live camera view of the patient’s back. Several experiments were performed to test the accuracy of vertebral height in panorama images, the accuracy of vertebral levels identification in panorama images, the accuracy of vertebral levels identification on the skin, and the impact on accuracy with spine arching. The results from 17 subjects demonstrate the feasibility of the approach and capability of achieving an error within a clinically acceptable range for epidural anesthesia. The overlaid marks on the screen are used to assist locating needle puncture site. Then, an automated slice selection algorithm is used to guide the operator positioning a 3D transducer such that the best view of the target anatomy is visible in a predefined re-slice of the 3D ultrasound volume. This re-slice is used to observe, in real time, the trajectory of a needle attached to the 3D transducer, towards the target. The method is based on Haar-like features and AdaBoost learning algorithm. We have evaluated the method on a set of 32 volumes acquired from volunteer subjects by placing the 3D transducer on L1-L2, L2-L3, L3-L4 and L4- L5 interspinous gaps on each side of the lumbar spine. Results show that the needle insertion plane can be identified with a root mean square error of 5.4 mm, accuracy of 99.6%, and precision of 78.7%.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2005.
Includes bibliographical references (p. 223-228).
This thesis proposes a hybrid route guidance system in which predictive guidance is generated in a centralized layer and revised in a reactive, decentralized layer that resides on-board the vehicle. This hybrid approach is intended to improve guidance quality by balancing the ability of the centralized layer to generate consistent guidance with the ability of the decentralized layer to respond rapidly to incidents. Centralized guidance is computed using a rolling-horizon Dynamic Traffic Assignment routine based on the Method of Successive Averages. This guidance is disseminated to equipped vehicles in the form of prescribed paths, which may be subsequently revised by an on-board decentralized layer. This decentralized layer revises only the local portion of the vehicle's path in order to limit the potential negative impact of its myopic reactive algorithm. The layer uses a simple splitting algorithm in order to heuristically balance demand on alternate paths. Both layers utilize data collected by guided vehicles. The centralized layer uses position data from guided vehicles. The decentralized layer uses local arc travel time data which is shared among guided vehicles.
(cont.) This approach follows the vision of a vehicle-centric route guidance system whose design is focused on the vehicle, rather than on stationary components. In order to test the performance of the proposed system, a small test network is simulated in a simple network simulator. The primary experimental questions are: whether the hybrid system provides higher quality route guidance than either a fully centralized or fully decentralized system; and how hybrid guidance quality is affected by various parameters of the system and the testing environment. Results of testing confirm that the hybrid system provides higher quality guidance than either centralized or decentralized systems in most scenarios; in no scenario is the hybrid system found to perform measurably worse than the centralized or decentralized system. The greatest benefits of the hybrid system are found to be in incident scenarios, supporting the hypothesis that the decentralized layer may aid incident response.
by Jennifer Margaret Farver.
Ph.D.

Thesis (M. Eng.)--Harvard-MIT Division of Health Sciences and Technology, 2006.
MIT Institute Archives copy: Pages 101-130 bound in reverse order.
Includes bibliographical references (p. 123-130).
Cardiac arrhythmias are characterized by a disruption or abnormal conduction of electrical signals within the heart. Treatment of arrhythmias has dramatically evolved over the past half-century, and today, minimally-invasive catheter-based therapy is the preferred method of eliminating arrhythmias. Using an electroanatomical (EA) mapping system, which precisely tracks the position of catheters inside the patient's body, it is possible to construct three-dimensional maps of the ventricular and atrial chambers of the heart. Each point of these maps is annotated based on bioelectrical signals recorded from the electrodes located at the tip of the catheter. These maps are then used to guide catheter ablation within the heart. However, the electroanatomical mapping procedure results in relatively sparse sampling of the heart and a significant amount of time and skill are require to generate these maps. In this thesis, we present our software system for the integration of pre-operative, patient-specific magnetic resonance (MR) or computed tomography (CT) imaging data with real-time electroanatomical mapping (EAM) information.
(cont.) Following registration between the EAM and imaging data, the system allows for real-time catheter navigation within patient-specific anatomy. We then evaluate candidate registration strategies to rapidly and accurately align the pre-operative imaging data with the intra-operative mapping data using simulated electroanatomical mapping data using the great cardiac vessels including the aorta, superior vena cava, and coronary sinus. Based on these in vitro results, we focus on a registration strategy which is constrained by the ascending and descending aorta. In vivo prospective evaluation of the resulting image integration was then performed (n>200) in both experimental and clinical electrophysiology procedure. To compensate for residual error following registration or patient movement during a procedure, we present and evaluate warping strategies for deforming the pre-operative imaging data into agreement with the intra-operative mapping information.
by Zachary John Malchano.
M.Eng.

The space industry and the technological developments regarding space exploration hasn’t been this popular since the first moon landing. The privatization of space exploration and the vertical landing rockets made rocket science mainstream again. While being able to reuse rockets is efficient both in terms of profitability and popularity, these developments are still in their early stages. Vertical landing has challenges that, if neglected, can cause disastrous consequences. The existing studies on the matter usually don’t account for aerodynamics forces and corresponding controls, which results in higher fuel consumption thus lessening the economical benefits of vertical landing. Similar problems have been tackled in studies not regarding booster landings but regarding planetary landings. And while multiple solutions have been proposed for these problems regarding planetary landings, the fact that the reinforcement learning concepts work well and provide robustness made them a valid candidate for applying to booster landings. In this study, we focus on developing a vertical booster descent guidance and control law that’s robust by applying reinforcement learning concept. Since reinforcement learning method that is chosen requires solving Optimal Control Problems (OCP), we also designed and developed an OCP solver software. The robustness of resulting hybrid guidance and control policy will be examined against various different uncertainties including but not limited to wind, delay and aerodynamic uncertainty.
Rymdindustrin och den tekniska utvecklingen av rymdutforskningen har inte varit så populär sedan den första månlandningen. Privatiseringen av utforskningen av rymden och de vertikala landningsraketerna medförde att raketvetenskapen återkom som en viktig huvudfråga igen. Även om det är effektivt att återanvända raketer i form av lönsamhet och popularitet, är denna utveckling fortfarande i sina tidiga stadier. Vertikal landning har utmaningar som, om de försummas, kan orsaka katastrofala konsekvenser. De befintliga studierna i frågan redovisar vanligtvis inte aerodynamikkrafter och motsvarande regulatorer, vilket resulterar i högre bränsleförbrukning som minskar de ekonomiska fördelarna med vertikal landning. Liknande problem har hanterats i studier som inte avsåg boosterlandningar utan om planetariska landningar. Även om flera lösningar har föreslagits för dessa problem beträffande planetariska landningar, det faktum att förstärkningsinlärningskonceptet fungerar bra och ger robusthet gjorde dem till en giltig kandidat för att ansöka om boosterlandningar. I den här studien fokuserar vi på att utveckla en lagstiftning för styrning av vertikala booster-nedstigningar som är robust genom att tillämpa koncepten inom förstärkningsinlärning. Ef- tersom förstärkt inlärningsmetod som väljs kräver lösning av optimala kontrollproblem (OCP), designade och utvecklade vi också en OCP-lösningsmjukvara. Robustheten för resulterande hybridstyrning och kontrollpolicy kommer att undersökas mot olika osäkerheter inklusive, men inte begränsat till vind, fördröjning och aerodynamisk osäkerhet.

Linear drives provide many new attractive solutions for the material transportation and processing in the manufacturing industry. With no mechanical transmission elements, they enable high dynamics and rigidity as well as low installation- and low maintenance-costs. That performance can give the linear motor system a better precision, a higher acceleration and a higher speed of the moving part. Therefore, the material transportation and processing using linear motors is studied and applied increasingly in manufacturing industry. For these applications, the linear motor is typically with stationary long primary and a short moving secondary. As the secondary part is passive, no energy transmission is required between the moving and stationary part, avoiding the use of brushes or inductive transmission. The motor type best suited for the mentioned applications is the synchronous one with permanent magnets, because of its higher efficiency, compactness, but most important because it allows a higher air-gap. In the usual approach, the linear motor is only used for thrust force production. The guidance is usually implemented by a mechanical assembly. The guidance constrains the movement to the longitudinal displacement, fixing the lateral and vertical displacement: yaw, roll and pitch. To achieve the necessary precision of the movement, accurate mechanical guidance is required. Such the mechanical assembly can be complex and source of high friction. In this dissertation, a research of an active guiding system is presented. The purpose of this research is finding out a solution for the material transportation and processing applications. The target is a linear drive system, which can reduce the complicated mechanical structure. In additions, the passive vehicle is also necessary. The result of the research is PM-synchronous linear motors with long and double-sided primaries. In the system, the lateral displacement and the yaw angle are controlled while a simple wheel-rail system fixes the vertical displacement. This combination of the magnetic and mechanical guidance offers a good trade-off among the complexity of the control, actuators and mechanics, when considering industrial applications. To allow multiple vehicles traveling simultaneously and independently on the guide-way (each vehicle is controlled by an individual part of the guide-way), the double side primary is separated into segments. With that structure, flexible-operating methods can be implemented. That is very useful in process-integrated material handling where different speeds of material carriers in each processing station are necessary. Another advantage of segmented structure is the energy saving. The power is supplied only to the segment or the two consecutive segments in which the vehicle runs over. In one segment, each side of the primary is supplied by its own inverter, allowing the necessary degree of freedom to control the lateral position and the yaw angle in addition to the thrust control. In order to make the vehicle completely passive, a capacitive sensor is proposed and implemented to measure the lateral position and the yaw angle. The sensor has active parts installed on the guide-way and passive parts on the vehicle. The mathematical analysis and the finite element method (FEM) are used to analysis the proposed system. With the analysed results, the control for the system is investigated in detail. Hardware and software for the experimental system is developed and implemented. The analysed results and the experimental results validate the proposed system. That gives a new solution for the material transportation and processing application using linear synchronous motors.

Previous studies of physical guidance (PG - physically constraining error during practice of a motor task) have found it to be ineffective in enhancing motor learning. However, most studies have used a highly constraining form of physical guidance that may have encouraged undue dependency. In addition, previous research has not fully considered the interaction between visual feedback and PG, and many of the studies have failed to use standard delayed retention tests with knowledge of results unavailable (no-KR). The current experiment examine the effects of varying levels of constraint in PG, as well as the interaction of PG and visual guidance (VG), using no-KR retention tests. This study involved 99 subjects divided into nine acquisition trial condition groups, forming from a 3 x 3 factorial design with factors of PG x VG, each presented at levels designated as tight, bandwidth, or none. Subjects undertook a two-dimensional pattern drawing task with no KR, PG, or VG as a pre-test, before completing 100 practice trials under one of the nine conditions. The same test was given as a retention test (immediately after practice) and as a delayed retention test (two days later). A transfer test, using a different pattern, was also administered on the second day. Almost all groups performed better on the immediate transfer test than they had on the pre-test. However, after two days only three groups (PG bandwidth-VG tight, PG none-VG bandwidth, and PG none-VG none) retained this improvement and only two groups (PG bandwidth-VG bandwidth and PG none-VG none) performed significantly better on the transfer task than their pre-test. It is proposed that bandwidth guidance generally promotes learning and that bandwidth physical guidance may enhance proprioceptive cues. Independent of PG and VG effects, KR (an overall error score) also facilitated learning.

Previous studies of physical guidance (PG - physically constraining error during practice of a motor task) have found it to be ineffective in enhancing motor learning. However, most studies have used a highly constraining form of physical guidance that may have encouraged undue dependency. In addition, previous research has not fully considered the interaction between visual feedback and PG, and many of the studies have failed to use standard delayed retention tests with knowledge of results unavailable (no-KR). The current experiment examine the effects of varying levels of constraint in PG, as well as the interaction of PG and visual guidance (VG), using no-KR retention tests. This study involved 99 subjects divided into nine acquisition trial condition groups, forming from a 3 x 3 factorial design with factors of PG x VG, each presented at levels designated as tight, bandwidth, or none. Subjects undertook a two-dimensional pattern drawing task with no KR, PG, or VG as a pre-test, before completing 100 practice trials under one of the nine conditions. The same test was given as a retention test (immediately after practice) and as a delayed retention test (two days later). A transfer test, using a different pattern, was also administered on the second day. Almost all groups performed better on the immediate transfer test than they had on the pre-test. However, after two days only three groups (PG bandwidth-VG tight, PG none-VG bandwidth, and PG none-VG none) retained this improvement and only two groups (PG bandwidth-VG bandwidth and PG none-VG none) performed significantly better on the transfer task than their pre-test. It is proposed that bandwidth guidance generally promotes learning and that bandwidth physical guidance may enhance proprioceptive cues. Independent of PG and VG effects, KR (an overall error score) also facilitated learning.

Syftet med denna studie är att undersöka vägledningssamtalet och vägledares yrkesroll på högskolan. Undersökningen utgår från rollteorier som genomgående ställs mot det empiriska materialet där vägledarrollen på olika sätt kommer in. Studien tydliggör även begreppet projekt som beskriver hur ett vägledningssamtal kan analyserar beroende på vilka förväntningar och syften de olika deltagarna i samtalet har. Metoden som har använts är kvalitativ och studien utgår ifrån sammanlagt sex informanter, varav fyra med vägledningssökande och två med vägledare.Studien visar på att samtliga vägledningssökande har rollförväntningar som till stor del handlar om att få information, och det är just informationsbiten som de ser som viktigast när det handlar om vägledningssamtalen. Båda vägledarna berättar även att de huvudsakligen arbetar med just informationsbiten. Studien visar också att samtliga av de vägledningssökande är relativt nöjda efter vägledningssamtalet och att deras rollförväntningar har uppfyllts. I analysen och diskussionen presenteras våra reflektioner kring studiens resultat, och hur man skulle kunna arbeta för att ge en tydligare bild av studie- och yrkesvägledares yrkesroll.

The ability to fly has greatly expanded the possibilities for robots to perform surveillance, inspection or map generation tasks. Yet it was only in recent years that research in aerial robotics was mature enough to allow active interactions with the environment. The robots responsible for these interactions are called aerial manipulators and usually combine a multirotor platform and one or more robotic arms. The main objective of this thesis is to formalize the concept of aerial manipulator and present guidance methods, using visual information, to provide them with autonomous functionalities. A key competence to control an aerial manipulator is the ability to localize it in the environment. Traditionally, this localization has required external infrastructure of sensors (e.g., GPS or IR cameras), restricting the real applications. Furthermore, localization methods with on-board sensors, exported from other robotics fields such as simultaneous localization and mapping (SLAM), require large computational units becoming a handicap in vehicles where size, load, and power consumption are important restrictions. In this regard, this thesis proposes a method to estimate the state of the vehicle (i.e., position, orientation, velocity and acceleration) by means of on-board, low-cost, light-weight and high-rate sensors. With the physical complexity of these robots, it is required to use advanced control techniques during navigation. Thanks to their redundancy on degrees-of-freedom, they offer the possibility to accomplish not only with mobility requirements but with other tasks simultaneously and hierarchically, prioritizing them depending on their impact to the overall mission success. In this work we present such control laws and define a number of these tasks to drive the vehicle using visual information, guarantee the robot integrity during flight, and improve the platform stability or increase arm operability. The main contributions of this research work are threefold: (1) Present a localization technique to allow autonomous navigation, this method is specifically designed for aerial platforms with size, load and computational burden restrictions. (2) Obtain control commands to drive the vehicle using visual information (visual servo). (3) Integrate the visual servo commands into a hierarchical control law by exploiting the redundancy of the robot to accomplish secondary tasks during flight. These tasks are specific for aerial manipulators and they are also provided. All the techniques presented in this document have been validated throughout extensive experimentation with real robotic platforms.
La capacitat de volar ha incrementat molt les possibilitats dels robots per a realitzar tasques de vigilància, inspecció o generació de mapes. Tot i això, no és fins fa pocs anys que la recerca en robòtica aèria ha estat prou madura com per començar a permetre interaccions amb l’entorn d’una manera activa. Els robots per a fer-ho s’anomenen manipuladors aeris i habitualment combinen una plataforma multirotor i un braç robòtic. L’objectiu d’aquesta tesi és formalitzar el concepte de manipulador aeri i presentar mètodes de guiatge, utilitzant informació visual, per dotar d’autonomia aquest tipus de vehicles. Una competència clau per controlar un manipulador aeri és la capacitat de localitzar-se en l’entorn. Tradicionalment aquesta localització ha requerit d’infraestructura sensorial externa (GPS, càmeres IR, etc.), limitant així les aplicacions reals. Pel contrari, sistemes de localització exportats d’altres camps de la robòtica basats en sensors a bord, com per exemple mètodes de localització i mapejat simultànis (SLAM), requereixen de gran capacitat de còmput, característica que penalitza molt en vehicles on la mida, pes i consum elèctric son grans restriccions. En aquest sentit, aquesta tesi proposa un mètode d’estimació d’estat del robot (posició, velocitat, orientació i acceleració) a partir de sensors instal·lats a bord, de baix cost, baix consum computacional i que proporcionen mesures a alta freqüència. Degut a la complexitat física d’aquests robots, és necessari l’ús de tècniques de control avançades. Gràcies a la seva redundància de graus de llibertat, aquests robots ens ofereixen la possibilitat de complir amb els requeriments de mobilitat i, simultàniament, realitzar tasques de manera jeràrquica, ordenant-les segons l’impacte en l’acompliment de la missió. En aquest treball es presenten aquestes lleis de control, juntament amb la descripció de tasques per tal de guiar visualment el vehicle, garantir la integritat del robot durant el vol, millorar de l’estabilitat del vehicle o augmentar la manipulabilitat del braç. Aquesta tesi es centra en tres aspectes fonamentals: (1) Presentar una tècnica de localització per dotar d’autonomia el robot. Aquest mètode està especialment dissenyat per a plataformes amb restriccions de capacitat computacional, mida i pes. (2) Obtenir les comandes de control necessàries per guiar el vehicle a partir d’informació visual. (3) Integrar aquestes accions dins una estructura de control jeràrquica utilitzant la redundància del robot per complir altres tasques durant el vol. Aquestes tasques son específiques per a manipuladors aeris i també es defineixen en aquest document. Totes les tècniques presentades en aquesta tesi han estat avaluades de manera experimental amb plataformes robòtiques reals

Focus on safety and effectiveness in the oil and gas industry has increased the need for advanced control system for underwater vehicles. For remotely operated vehicles (ROVs) effectiveness when conducting deep sea operation is extremely critical both concerning safety and cost. For AUVs conducting survey missions, energy and collision avoidance are critical factors. A control system for ROV Minerva is being developed through the AUR-Lab at the Institute of Marine Technology at NTNU. Several guidance features have been investigated, with respect to different mission the ROV should be able to do. A guidance system has been developed, where basic functions such as a DP system with station keeping and trajectory tracking was the focus of the project thesis of the author. More advanced functionality with respect to path following has been developed, where focus have been set on different strategies to apply when the ROV is following a path. Simulations based on different strategies for following a lawnmower pattern have been simulated and evaluated with respect to time, energy and control objective. Full scale experiments with the ROV Minerva show that especially the forward speed versus arc radius is an important issue. The results show that the ROV is able to follow a path made out of straight lines and circular arcs, and particularly lawnmower patterns. For an underwater vehicle to be able to operate autonomously, stationary and dynamic obstacles have to be taken into account. A collision avoidance system based on local collision avoidance algorithms has been implemented, where focus has been on reactivity with respect to unmapped obstacles. The collision avoidance system has been through initial full scale tests with ROV Minerva, and the result are promising.

The purpose of this study is on the one hand to test the current guidance algorithm for image acquisition by the CSO satellite, and on the other hand to compare it to alternative algorithms. The latter may oer improvements to guidance precision and image quality by reducing the amount of calculation steps. The algorithms were tested in a computer environment which simulates acquisition by the satellite for a large number of cases, ensuring reliability of the results. Testing showed that image quality remains largely unchanged when using the new algorithms. This shows that the current algorithm is well-suited for use in the satellite, and that the new algorithms may be used as alternatives.

Prostate biopsy is the gold standard for cancer diagnosis. This procedure is guided using a 2D transrectal ultrasound (TRUS) probe. Unfortunately, early stage tumors are not visible in ultrasound and prostate motion/deformations make targeting challenging. This results in a high number of false negatives and patients are often required to repeat the procedure. Fusion of magnetic resonance images (MRI) into the workspace of a prostate biopsy has the potential to detect tumors invisible in TRUS. This allows the radiologist to better target early stage cancerous lesions. However, due to different body positions and imaging settings, the prostate undergoes motion and deformation between the biopsy coordinate system and the MRI. Furthermore, due to variable probe pressure, the prostate moves and deforms during biopsy as well. This introduces additional targeting errors. A biopsy system that compensates for these sources of error has the potential to improve the targeting accuracy and maintain a 3D record of biopsy locations. The goal of this thesis is to provide the necessary tools to perform freehand MR-TRUS fusion for prostate biopsy using a 3D guidance system. To this end, we have developed two novel surface-based registration methods for incorporating the MRI into the biopsy workspace. The proposed methods are the first methods that are robust to missing surface regions for MR-TRUS fusion (up to 30% missing surface points). We have validated these fusion techniques on 19 biopsy, 10 prostatectomy and 11 brachytherapy patients. In this thesis, we have also developed methods that combine intensitybased information with biomechanical constraints to compensate for prostate motion and deformations during the biopsy. To this end, we have developed a novel 2D-3D registration framework, which was validated on an additional 10 biopsy patients. Our results suggest that accurate 2D-3D registration for freehand biopsy is feasible. The results presented suggest that accurate registration of MR and TRUS data in the presence of partially missing data is feasible. Moreover, we demonstrate that in the presence of variable probe pressure during freehand biopsy, a combination of intensity-based and biomechanically constrained 2D-3D registration can enable accurate alignment of pre-procedure TRUS with 2D real time TRUS images.
Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate

Thalamotomy and pallidotomy constitute the two principal neurosurgical treatments for Parkinson's disease. Both the thalamus nuclei and the internal globus pallidus structures are found very close to the internal capsule, a critical structure that must be avoided in performing the lesion. This forces the lesion of parts of the thalamus and the globus pallidus mediale to be achieved with a spatial precision on the order of 2mm. The leukotome is a neurosurgical tool consisting of a 20cm rigid shaft with a thin metallic wire attached to its tip that can be taken in and out of the body of the shaft. It is used as a knife to perform the excision.
Some critical basal ganglia structures show no anatomical differences at all on MRI scans, even though they have different functionality. In order to provide the neurosurgeon with this missing information, we have developed a deformable volumetric atlas of the basal ganglions from the cryogenic slices atlas of Shaltenbrand and Wahren. The atlas can be non-linearly deformed to fit a patient's MRI.
We have developed a visualization platform for pre-operative and intra-operative utilization of the atlas and of the MRI datasets. Any number of datasets can be superimposed (MRI, atlases, virtual lesions...). Merging of datasets with different extents and different resolutions is supported. The platform includes 3D visualization tools as well. Graphical tools allow the neurosurgeon to see projections of the leukotome from any point of view over the MRI data and the atlas. The software is able to create models of lesions that can be compared with the MRI data and the atlas. It can also suggest an operation protocol (how to use the leukotome) if a target volume is given. This target volume can easily be drawn on the atlas by the neurosurgeon.

Axons navigate long distances to their targets in the embryonic brain using a series of membrane bound and diffusible guidance cues along their pathway. This study presents an investigation of the in vitro effect of semaphorin 3A (Sema3A) on Xenopus retinal growth cones and into the role of local protein synthesis and proteasome-dependent proteolysis in mediating chemotropic responses of retinal growth cones. Growth cones acquire responsiveness to Sema3A with age and the onset of responsiveness correlates with the appearance of the Sema3A receptor component neuropilin-1(NP-1) immunoreactivity. Growth cones from "old" (stage 35/36) retinal explants collapse rapidly (5-10 minutes) in response to Sema3A and turn away from a gradient of Sema3A whereas 'young' growth cones (stage 24) are insensitive to Sema3A. Moreover, transfection of full length NP-1 into young neurones confers premature Sema3A-sensitivity. When young neurones are aged in culture they develop Sema3A-sensitivity in parallel with those in vivo suggesting that an intrinsic mechanism of NP-1 regulation mediates this age-dependent change. Sema3A-induced collapse is transient and upon recovery approximately 30% of growth cones extend new branches within 1 hour implicating Sema3A as a branching factor. Pharmacological inhibitors were used to investigate whether these three Sema3A-induced behaviours (collapse, turning and branching) use distinct second messenger signalling pathways. All three behaviours were found to be mediated via cGMP. In the presence of translation inhibitors, retinal growth cones fail to collapse in response to Sema3A and are unable to turn attractively or repulsively to Sema3A or netrin-1. Furthermore, Sema3A and netrin-1 stimulate rapid rises in phosphorylation of translation initiation proteins (eIF-4E and eIF-4EBP1) and in protein synthesis in isolated growth cones. Pharmacological inhibitors were used to determine that the effects on chemotropic responses of Sema3A and netrin-1 differ in their requirement for Phosphatidylinositol-3 kinase (PI-3 kinase) and share a common target of rapamycin (TOR) sensitive pathway leading to the initiation of translation. These effects occur within minutes suggesting that guidance molecules may steer axon growth by triggering local translation in growth cones.

Intra-cardiac procedures often involve fast-moving anatomic structures with large spatial extent and high geometrical complexity. Real-time visualization of the moving structures and instrument-tissue contact is crucial to the success of these procedures. Real-time 3D ultrasound is a promising modality for procedure guidance as it offers improved spatial orientation information relative to 2D ultrasound. Imaging rates at 30 fps enable good visualization of instrument-tissue interactions, far faster than the volumetric imaging alternatives (MR/CT). Unlike fluoroscopy, 3D ultrasound also allows better contrast of soft tissues, and avoids the use of ionizing radiation.
Engineering and Applied Sciences

The purpose of this dissertation was to establish how vibrotactile guidance cues can be used to improve marksmanship. This work originated in an effort to provide covert communication, navigation, and weapon aiming cues for infantrymen. It is predominantly an application-driven investigation rather than driven a priori by specific theoretical predictions from models of human performance. Three experiments are presented. Experiment 1 established the affect on initial response to vibrotactile guidance cues of tactor placements on the palmer versus dorsal surface of the hand, and targets appearing left versus right of center. Results suggest that tactile cues provided on the left side of the medial line of the hand afford moving the hand to the left, while tactile cues provided on the right side of the medial line afford moving the hand to the right. Experiment 2 established the affect of continuous relative distance cues and on- versus off-target vibrotactile stimuli on reaction time and accuracy for target selection. Results indicated an interaction between the pulse rate of vibrotactile stimuli and the method used to highlight an "on-target" condition; the suppressed target condition was superior to the enhanced target condition when the pulse rate increased as the cursor moved closer to a target. Experiment 3 established if there are performance differences between discrete and continuous distance information for target selection, and investigated the interaction between the near-target pulse rate and on-target cues. Results indicate that maximizing the difference between near-target guidance cues and on-target cues reduces the target selection time, particularly when the near-target pulse rates are fast (ISI = 10 msec). The results also suggest that, as with vision, the vibrotactile off-target guidance cues are not necessary during the whole target selection task. Rather, the guidance cues can be provided only during the initial pop-up condition and during the sub-movements closing on the target.
Ph.D.
Department of Psychology
Arts and Sciences
Psychology

This thesis presents contributions to the Guidance, Navigation and Control (GNC) systems for multirotor vehicles by applying and developing diverse control techniques and machine learning theory with innovative results. The aim of the thesis is to obtain a GNC system able to make the vehicle follow predefined paths while avoiding obstacles in the vehicle's route. The system must be adaptable to different paths, situations and missions, reducing the tuning effort and parametrisation of the proposed approaches. The multirotor platform, formed by the Asctec Hummingbird quadrotor vehicle, is studied and described in detail. A complete mathematical model is obtained and a freely available and open simulation platform is built. Furthermore, an autopilot controller is designed and implemented in the real platform. The control part is focused on the path following problem. That is, following a predefined path in space without any time constraint. Diverse control-oriented and geometrical algorithms are studied, implemented and compared. Then, the geometrical algorithms are improved by obtaining adaptive approaches that do not need any parameter tuning. The adaptive geometrical approaches are developed by means of Neural Networks. To end up, a deep reinforcement learning approach is developed to solve the path following problem. This approach implements the Deep Deterministic Policy Gradient algorithm. The resulting approach is trained in a realistic multirotor simulator and tested in real experiments with success. The proposed approach is able to accurately follow a path while adapting the vehicle's velocity depending on the path's shape. In the navigation part, an obstacle detection system based on the use of a LIDAR sensor is implemented. A model of the sensor is derived and included in the simulator. Moreover, an approach for treating the sensor data to eliminate the possible ground detections is developed. The guidance part is focused on the reactive path planning problem. That is, a path planning algorithm that is able to re-plan the trajectory online if an unexpected event, such as detecting an obstacle in the vehicle's route, occurs. A deep reinforcement learning approach for the reactive obstacle avoidance problem is developed. This approach implements the Deep Deterministic Policy Gradient algorithm. The developed deep reinforcement learning agent is trained and tested in the realistic simulation platform. This agent is combined with the path following agent and the rest of the elements developed in the thesis obtaining a GNC system that is able to follow different types of paths while avoiding obstacle in the vehicle's route.
Aquesta tesi doctoral presenta diverses contribucions relaciones amb els sistemes de Guiat, Navegació i Control (GNC) per a vehicles multirrotor, aplicant i desenvolupant diverses tècniques de control i de machine learning amb resultats innovadors. L'objectiu principal de la tesi és obtenir un sistema de GNC capaç de dirigir el vehicle perquè segueixi una trajectòria predefinida mentre evita els obstacles que puguin aparèixer en el recorregut del vehicle. El sistema ha de ser adaptable a diferents trajectòries, situacions i missions, reduint l'esforç realitzat en l'ajust i la parametrització dels mètodes proposats. La plataforma experimental, formada pel cuadricòpter Asctec Hummingbird, s'estudia i es descriu en detall. S'obté un model matemàtic complet de la plataforma i es desenvolupa una eina de simulació, la qual és de codi lliure. A més, es dissenya un controlador autopilot i s'implementa en la plataforma real. La part de control està enfocada al problema de path following. En aquest problema, el vehicle ha de seguir una trajectòria predefinida en l'espai sense cap tipus de restricció temporal. S'estudien, s'implementen i es comparen diversos algoritmes de control i geomètrics de path following. Després, es milloren els algoritmes geomètrics usant xarxes neuronals per convertirlos en algoritmes adaptatius. Per finalitzar, es desenvolupa un mètode de path following basat en tècniques d'aprenentatge per reforç profund (deep Reinforcement learning). Aquest mètode implementa l'algoritme Deep Deterministic Policy Gradient. L'agent intel. ligent resultant és entrenat en un simulador realista de multirotors i validat en la plataforma experimental real amb èxit. Els resultats mostren que l'agent és capaç de seguir de forma precisa la trajectòria de referència adaptant la velocitat del vehicle segons la curvatura del recorregut. A la part de navegació, s'implementa un sistema de detecció d'obstacles basat en l'ús d'un sensor LIDAR. Es deriva un model del sensor i aquest s'inclou en el simulador. A més, es desenvolupa un mètode per tractar les mesures del sensor per eliminar les possibles deteccions del terra. Pel que fa a la part de guiatge, aquesta està focalitzada en el problema de reactive path planning. És a dir, un algoritme de planificació de trajectòria que és capaç de re-planejar el recorregut del vehicle a l'instant si algun esdeveniment inesperat ocorre, com ho és la detecció d'un obstacle en el recorregut del vehicle. Es desenvolupa un mètode basat en aprenentatge per reforç profund per l'evasió d'obstacles. Aquest mètode implementa l'algoritme Deep Deterministic Policy Gradient. L'agent d'aprenentatge per reforç s'entrena i valida en un simulador de multirotors realista. Aquest agent es combina amb l'agent de path following i la resta d'elements desenvolupats en la tesi per obtenir un sistema GNC capaç de seguir diferents tipus de trajectòries, evadint els obstacles que estiguin en el recorregut del vehicle.
Esta tesis doctoral presenta varias contribuciones relacionas con los sistemas de Guiado, Navegación y Control (GNC) para vehículos multirotor, aplicando y desarrollando diversas técnicas de control y de machine learning con resultados innovadores. El objetivo principal de la tesis es obtener un sistema de GNC capaz de dirigir el vehículo para que siga una trayectoria predefinida mientras evita los obstáculos que puedan aparecer en el recorrido del vehículo. El sistema debe ser adaptable a diferentes trayectorias, situaciones y misiones, reduciendo el esfuerzo realizado en el ajuste y la parametrización de los métodos propuestos. La plataforma experimental, formada por el cuadricoptero Asctec Hummingbird, se estudia y describe en detalle. Se obtiene un modelo matemático completo de la plataforma y se desarrolla una herramienta de simulación, la cual es de código libre. Además, se diseña un controlador autopilot, el cual es implementado en la plataforma real. La parte de control está enfocada en el problema de path following. En este problema, el vehículo debe seguir una trayectoria predefinida en el espacio tridimensional sin ninguna restricción temporal Se estudian, implementan y comparan varios algoritmos de control y geométricos de path following. Luego, se mejoran los algoritmos geométricos usando redes neuronales para convertirlos en algoritmos adaptativos. Para finalizar, se desarrolla un método de path following basado en técnicas de aprendizaje por refuerzo profundo (deep reinforcement learning). Este método implementa el algoritmo Deep Deterministic Policy Gradient. El agente inteligente resultante es entrenado en un simulador realista de multirotores y validado en la plataforma experimental real con éxito. Los resultados muestran que el agente es capaz de seguir de forma precisa la trayectoria de referencia adaptando la velocidad del vehículo según la curvatura del recorrido. En la parte de navegación se implementa un sistema de detección de obstáculos basado en el uso de un sensor LIDAR. Se deriva un modelo del sensor y este se incluye en el simulador. Además, se desarrolla un método para tratar las medidas del sensor para eliminar las posibles detecciones del suelo. En cuanto a la parte de guiado, está focalizada en el problema de reactive path planning. Es decir, un algoritmo de planificación de trayectoria que es capaz de re-planear el recorrido del vehículo al instante si ocurre algún evento inesperado, como lo es la detección de un obstáculo en el recorrido del vehículo. Se desarrolla un método basado en aprendizaje por refuerzo profundo para la evasión de obstáculos. Este implementa el algoritmo Deep Deterministic Policy Gradient. El agente de aprendizaje por refuerzo se entrena y valida en un simulador de multirotors realista. Este agente se combina con el agente de path following y el resto de elementos desarrollados en la tesis para obtener un sistema GNC capaz de seguir diferentes tipos de trayectorias evadiendo los obstáculos que estén en el recorrido del vehículo.

Today, parking is the main coordinator between the land use and transportation. As the urban population is increasing, more and more cars are circulating through the city in search for parking spaces, often contributing to the global problem of traffic congestion. Hence, several governments seek to improve their existing transportation systems and infrastructure. Examples of their initiatives include the launch of ‘Smart Parking’ projects in major urban areas. However, the developments to date in this area have some significant limitations lodged against them. In this dissertation, we propose 3 different smart parking systems: iParker, INDO and RFPark, to enhance the overall parking scheme. First, iParker and INDO are introduced as new parking management and reservations systems. Both change the parking behaviour from driver-side parking searching to system-side allocation. This is achieved by solving new Mixed Integer Linear Programming (MILP) optimisation problems with the objective of minimising driver's cost functions, while ensuring the maximum parking resource utilisation. Nevertheless, there are several differences between iParker and INDO. iParker is designed to operate as a country-wide system to offer drivers the optimal parking lot allocation and reservation before or at arrival to their destinations. This is based on minimising a driver's cost function that combines parking cost, reservation fees, proximity to multiple destinations and reservation type. As opposed to current reservation systems, iParker offers both static long-term reservations and dynamic short-term reservations, for both on-street and off-street parking lots. In addition, new pricing policies are proposed that allow the generation of more parking revenue and the fair distribution of parking traffic across parking lots. However, INDO is designed to operate inside individual parking lots who serve giant buildings - such as shopping malls - to offer the drivers the immediate optimal parking space allocation and the indoor guidance. A driver’s cost function here combines the times of driving inside the parking lot and walking inside the indoor destination. In addition, a Radio Frequency Identification/Near Field Communication (RFID/NFC) based navigation component is developed to provide commuters with guidance and navigation in the car park and the indoor destination. Based on simulation results, compared to the non-guided or the state-of-the-art guidance-based systems, iParker and INDO significantly reduce the average time to find a parking space and the drivers' cost, while the parking resources are more efficiently utilised. The pricing policies of iParker lead to the generation of more revenue and fair balance of traffic load across parking lots. In addition, INDO substantially reduces the commuting time indoors. On the other hand, RFPark is proposed as a new approach to parking monitoring. For the first time, Ultra High Frequency (UHF) passive RFID tags are deployed on the asphalt, and interrogated by RFID reader antennas above the parking spaces to detect the occupancy states. Most of the problems of the current cutting-edge parking occupancy detection systems are not present in this system. RFPark was analysed and implemented to show a pilot study in a real world outdoor parking environment in the University of Liverpool and has proved to have a very high detection accuracy. The innovative design and development of these 3 systems form a new ‘Smart Parking’ solution that offers to reduce the parking-related traffic congestion, enhance driver experience and improve the overall parking scheme. Although there are some challenges regarding the realisation of these smart systems, they are addressed here and solutions to them are proposed in this dissertation.

The current push from the industry for Head-Mounted Display based wearable computers to the masses for everyday use suggests that academia's goals of a tight human and computer integration is achievable. Although promising, many interaction challenges remain to achieve a deep integration. Primarily that of active cognitive support in the form of focusing user attention. This thesis investigates to what degree a system can unobtrusively, perhaps even subliminally, guide attention of a user by directing their gaze from a current point to a selected point in a virtual environment. A subjective evaluation is made regarding the characteristics of visual sensory stimuli in order to possibly achieve an unobtrusive (or even subliminal) gaze guidance. The attention guidance system developed is deployed in a controlled experiment with 30 participants. Participants are asked to fire a longbow at targets in a virtual reality environment while their point of gaze is monitored with an eye-tracker. The experiment produced interesting results, but no conclusive evidence that the system was able actively guide a user's attention nor influence their choice could be observed. The conclusion of this thesis is that further development is needed towards a system that is capable of objectively calibrating the stimuli characteristics for each individual participant.

Due to globalization and migration people and their cultures spread worldwide andcareer-guiding practitioners have to be more culturally considerate when they meetpeople. Our studies made in Fiji shows that there is a gap between thoughts regardingestimated income, education and effort in a workplace and actual labour-marketconditions. Educated and qualified Fijians look for work abroad when they can’t findemployment at home. One way to understand and describe what happens when peoplemake career decisions is to use career or decision-making theories, and a way to workwith career decisions and ideas about work is to have guidance-interviews or groupsessions. The aim of this paper is to present an example of how a recognized interviewmodel might be adapted for career guidance in a Fiji-context and what considerations that have to be made, through the explanations offered by a career theory, a decisionmaking theory and a guidance theory. Based on the life-story of a group of Fijians the result showed that the main considerations were regarding social structures and conceptions of time.

Includes abstract.
Includes bibliographical references.
This dissertation presents the design, fabrication and testing of a sounding rocket flight computer for the South African Astronomical Observatory (SAAO). Sounding rockets carry instruments with which to take measurements in the Earth’s atmosphere in sub-orbital flight. The South African Astronomical Observatory (SAAO) requires a flight computer for their sounding rockets. This flight computer is to replace the current commercial flight computer currently in use improving on its functionality and expandability.

The requirements of a modern guided weapon will be established based on the current and perceived threats at the time the design is commissioned. However the design of a modern guided weapon is a long and expensive process which can result in the weapon entering service only for the original threat to have changed or passed, inevitably inducing a capability gap. The defence budgets of the major military powers such as the UK and USA continue to shrink. As a result the emphasis of military research is being placed on adapting current legacy systems to bridge these capability gaps. One such gap is the requirement to be able to intercept small relocatable, highly manoeuvrable targets. It was demonstrated a number of years ago, that the performance of a legacy weapon against manoeuvering targets could be potentially increased by retrofitting a data link to the weapon. The data link allows commands to be sent to the weapon in flight. The commands will result in the weapon executing one or more manoeuvres which will change the shape of the trajectory. This has the potential to improve the performance of current Advanced Anti-Armour Weapons (AAAW) against manoeuvring targets. The issue which arises from data linking any weapon including an AAAW, is that the ability to shape the trajectory of the weapon will be limited due to the original design parameters of the non data linked system. Therefore in order to obtain the maximum performance increase, the trajectory shaping (retargetting) capability must be efficiently utilised over the duration of the weapon fly out. It was postulated in this thesis that this could be achieved using an integrated fire control system, which would seek to calculate an optimal shaped trajectory. The optimal trajectory should maximise the ability of the weapon to respond to target manoeuvres, thereby improving the probability of a successful intercept occurring. The potential effectiveness of an integrated fire control system was explored by considering the scenario of a generic data linked AAAW which is to intercept a small highly manoeuvrable surface vessel. A total of three integrated fire control systems were developed which calculated the optimal trajectory for different criteria. The first system optimised the weapon trajectory considering multiple predicted target trajectories. Each trajectory had an associated probability. For a given weapon trajectory, the seeker would be able to detect the target at one or more locations along certain predicted target trajectories. The sum of the probabilities associated with the detectable locations represented the total probability of intercept. The weapon trajectory was optimised by calculating the trajectory which achieved the maximum probability of intercept using simulated annealing and simple search optimisation algorithms. The second system optimised the weapon trajectory considering only the most probable trajectory (M.P.T) from a distribution of predicted target trajectories. Appropriate commands were calculated such that a location along this M.P.T trajectory was detectable at some instant in time. The third system presented in this thesis optimised the trajectory considering the maximum probability of intercept initially and then only the M.P.T trajectory later on in the engagement. The three integrated systems and a Fire and Forget system were tested against 80 random target trajectories. In each of the integrated fire control systems, the performance of the AAAW against manoeuvring targets was significantly improved when compared to the Fire and Forget results.

This research is concerned with some aspects of the counselling process within Marriage Guidance Council Counselling sessions. The first area of investigation chosen was the interaction of the counsellors image of the ideal client with her perceived image of real clients. Unfortunately, it was not possible to pursue this investigation since not all of the counsellors images of who would benefit from counselling were sufficiently stable over time. This was felt to be due to the test used (the California Q set). The second chosen area of investigation was the client counsellor verbal interaction in first counselling sessions studied using transcripts of ten female and four male clients and two couples counselled by the researcher and one woman and one couple counselled by another counsellor. The content was analysed using attribution theory. Clients made attributions from a wider range of categories than experimental studies normally allow for, the most frequently used category was emotion and attitude attributions, this is a neglected category which needs further study. The results did not support previous findings that people make Significantly more situational than personality attributions about their own behaviour. Clients have response strategies they use to reply to the counsellor, some of these are blocking strategies since they result in the counsellor dropping the subject being discussed; others are positive responses since they lead to the client· and counsellor engaging in a dialogue. All clients living with their partners who returned for a second session engaged in at least one extended dialogue with the counsellor about an attribution made by the counsellor. None of the clients who failed to return engaged in an extended dialogue with the counsellor.

Thesis (M.Sc.Eng.)
Guided airdrop systems lacking propulsion may be adversely affected by high winds. Strong winds encountered during Draper Laboratory flight testing prevented lightweight parafoil systems from landing accurately. This thesis introduces and compares multiple guidance strategies designed to address high wind scenarios in cases of differing wind knowledge fidelity. The algorithms presented significantly improve performance in high tailwind and shifting wind scenarios without compromising miss accuracy in standard wind conditions. This adds additional capability to parafoil guidance by substantially increasing the conditions under which accurate landings are possible.