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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
831

Next Generation Helm : Improving the user experience inside a boat helm

Thyni, Emil January 2022 (has links)
The design and functionality of the controls inside a boat helm are a big part of the user experience for operators. This master thesis focuses on the boat helm and the equipment from Volvo Penta placed in it. The aim is to present solutions to user’s problems revealed from interviews and look at future technology that will change the helm station. This project has been conducted in cooperation with Volvo Penta vehicle controls department. The project was conducted following a four-phase project plan with the phases learn, ideate, build, and launch. The learn phase focused on gaining state of practice information about today’s situation, using interviews to understand the stakeholders and benchmarking to understand the current marine market. The learn phase also focused on state of the art research to learn about future technologies. The ideate phase consisted of creative workshops to ideate around the findings from the learn phase. These ideas or concepts were then prototyped using a 3D printer and evaluated at a prototype evaluation during the build phase. The launch phase finalized the project by implementing the feedback from the prototype evaluation and visualizing the final concepts, highlighting the problems that were found and presenting design opportunities. The outcome of this project is several concepts presenting design opportunities for Volvo Penta when creating the next generation helm. Such as a scroll wheel joystick placed on the throttle, a driving-oriented joystick, and a modular button panel with both visual and haptic buttons. The outcome also presents information about handling increased automation/autonomy gathered from the theoretical framework and the prototype evaluation. / Designen på kontrollerna och instrumenten i förarmiljön för båtar spelar en stor roll för användarupplevelsen. Detta examensarbete fokuserar på förarmiljön i båtar och de instrument av Volvo Penta som finns inom den. Målet är att presentera lösningar till användarproblem som funnits genom intervjuer och undersöka framtida teknologi som kan förändra förarmiljön. Projektet har gjorts i samarbete med Volvo Penta vehicle controls. Projektet följde en projektplan på fyra delar; learn, ideate, build and launch. Learn fasen fokuserar på att samla information kring dagens situation genom användarintervjuer och analysera framtida teknik som måste tas i åtanke. Ideate fasen innehöll kreativa workshops för att skapa idéer kring de problem som hittats i learn fasen. I build fasen användes en 3D printer för att skapa prototyper och dessa testades på en prototyp utvärdering. Projektet avslutades med launch fasen som implementerade feedback från prototyp utvärderingen och visualiserade det slutgiltiga koncepten. Dessa koncept visar på det problem som funnits och på design möjligheter för hur dessa kan förbättras. Projektet resulterade i konceptuella instrument som visar de problem och möjligheter som kommer finnas i nästa generations förarmiljö. Dessa resultat var joystick vinkelgivare placerad på gasreglaget, en joystick inriktad för körning och en modulär knappanel med visuella och haptiska knappar. Information gällande hantering av automatisering och mer autonom körning från den teoretiska referensramen och prototyp utvärderingen presenteras även.
832

BRAIN-COMPUTER INTERFACE FOR SUPERVISORY CONTROLS OF UNMANNED AERIAL VEHICLES

Abdelrahman Osama Gad (17965229) 15 February 2024 (has links)
<p dir="ltr">This research explored a solution to a high accident rate in remotely operating Unmanned Aerial Vehicles (UAVs) in a complex environment; it presented a new Brain-Computer Interface (BCI) enabled supervisory control system to fuse human and machine intelligence seamlessly. This study was highly motivated by the critical need to enhance the safety and reliability of UAV operations, where accidents often stemmed from human errors during manual controls. Existing BCIs confronted the challenge of trading off a fully remote control by humans and an automated control by computers. This study met such a challenge with the proposed supervisory control system to optimize human-machine collaboration, prioritizing safety, adaptability, and precision in operation.</p><p dir="ltr">The research work included designing, training, and testing BCI and the BCI-enabled control system. It was customized to control a UAV where the user’s motion intents and cognitive states were monitored to implement hybrid human and machine controls. The DJI Tello drone was used as an intelligent machine to illustrate the application of the proposed control system and evaluate its effectiveness through two case studies. The first case study was designed to train a subject and assess the confidence level for BCI in capturing and classifying the subject’s motion intents. The second case study illustrated the application of BCI in controlling the drone to fulfill its missions.</p><p dir="ltr">The proposed supervisory control system was at the forefront of cognitive state monitoring to leverage the power of an ML model. This model was innovative compared to conventional methods in that it could capture complicated patterns within raw EEG data and make decisions to adopt an ensemble learning strategy with the XGBoost. One of the key innovations was capturing the user’s intents and interpreting these into control commands using the EmotivBCI app. Despite the headset's predefined set of detectable features, the system could train the user’s mind to generate control commands for all six degrees of freedom of adapting to the quadcopter by creatively combining and extending mental commands, particularly in the context of the Yaw rotation. This strategic manipulation of commands showcased the system's flexibility in accommodating the intricate control requirements of an automated machine.</p><p dir="ltr">Another innovation of the proposed system was its real-time adaptability. The supervisory control system continuously monitors the user's cognitive state, allowing instantaneous adjustments in response to changing conditions. This innovation ensured that the control system was responsive to the user’s intent and adept at prioritizing safety through the arbitrating mechanism when necessary.</p>
833

INTEGRATION OF CONTROL SYSTEMS INTO INTERLOCKING MATERIALS

Ethan West Guenther (13163403) 28 July 2022 (has links)
<p>  </p> <p>Architectured materials offer engineers more options for choosing materials with their desired properties. Segmenting materials to create topological interlocking materials (TIMs) creates materials, which can deform in greater amounts without failure and absorb more strain energy. Previous research on TIMs has shown that the stiffness and reaction force of these materials can be directly controlled by controlling the boundary forces offered by the frame which constrains these materials.</p> <p>The research presented in this paper investigated a TIM made into a 1-Dimension beam like structure called a lintel. This research investigated not only the mechanics of this structure, but also developed a method of directly controlling the reaction force at a given displacement using shape memory alloy (SMA) wires. These wires would actuate the boundary pieces used to constrain the system. These actuation wires coupled with force sensors imbedded into the lintel allowed a feedback control loop to be established, which would control the reaction force. The reaction force was then controlled to create a smart structure which could optimize the strain energy absorption under the constraint of a maximum allowable load, similar to cellular solids used in packaging and padding materials.</p> <p>To develop this smart structure, four separate investigations occurred. The first was finite element analysis (FEA) performed to model the loading response of the lintel. This experiment demonstrated that the Mises Truss Model was effective at modelling the lintel. The second was an experimental validation of the FEA model performed in the first investigation. This experiment validated the Mises Truss Model for the lintel. The third investigation simulated the active lintel using computational software and the model of the lintel established in the first two investigations. This experiment demonstrated computationally the ability of SMA wires to control the reaction force as desired in an idealized case. The fourth and final investigation experimentally validated the ability to create and active lintel and created a functioning prototype. This demonstrated experimentally the ability of the active lintel to control reaction force as desired.</p> <p>This project has demonstrated the viability to create smart structures using segmented materials, which in the future may be used in a variety of applications including robotics and adaptive structures in harsh environments. </p>
834

Energy optimization tool for mild hybrid vehicles with thermal constraints / Energioptimeringsverktyg för milda hybridfordon med termiska begränsningar

Singh, Chitranjan, Tamilinas, Tamas January 2020 (has links)
The current global scenario is such where impact on the environment is becoming a rising concern. Global automotive manufacturers have focused more towards hybrid and electric vehicles as both more aware customers and governmental legislation have begun demanding higher emission standards. One of the many ways that Volvo Car Group approaches this trend is by mild hybridization which is by assisting the combustion engine by a small electric motor and a battery pack. A smart energy management strategy is needed in order to get the most out of the benefits that hybrid electric vehicles offer. The main objective of this strategy is to utilize the electrical energy on-board in such a manner that the overall efficiency of the hybrid powertrain becomes as high as possible. The current implementation is such that the decision for using the on-board battery is non-predictive. This results in a sub-optimal utilization of the hybrid powertrain. In this thesis, a predictive energy optimization tool is developed to maximize the utility of hybridization and the practical implementation of this tool is investigated. The optimization considers both the capacity as well as the thermal loadconstraints of the battery. The developed optimization tool uses information about the route ahead together with convex optimization to produce optimal reference trajectories of the battery states. These trajectories are used in a real-time controller to determine the battery use by controlling the adjoint states in the Equivalent Consumption Minimization Strategy equation. This optimization tool is validated and compared with the baseline controller in a simulation environment based on Simulink. When perfect information about the road ahead is known, the average reduction in fuel consumption is 0.99% relative the baseline controller. Several issues occurring in the real implementation are explored, such as the limited computational speed and the length of the route ahead that can be predicted. For this reason the information input to the optimization tool is segmented and the resulting performance is investigated. For a 30 second segmentation of the future route information, the average saving in fuel consumption is 0.13% relative to the baseline controller. It is shown that the main factor limiting the amount of savings in fuel consumption is the introduction of the thermal load constraints on the battery. / Det nuvarande globala scenariot är sådant där miljöpåverkan håller på att bli en växande angelägenhet. Globala fordonstillverkare har fokuserat mer på hybrid- och elfordon, eftersom både mer medvetna kunder och statlig lagstiftning har börjat kräva högre emissionskrav. Ett av de många sätt som Volvo Car Group närmar sig denna trend är genom mild hybridisering genom att bistå förbränningsmotorn med en liten elmotor och ett batteripaket. En smart strategi för energihantering behövs för att få ut det mesta av de fördelar som hybrida elfordon erbjuder. Huvudsyftet med denna strategi är att utnyttja den elektriska energin ombord på ett sådant sätt att den totala effektiviteten hos hybriddrivlinan blir så hög som möjligt.Den nuvarande implementeringen är sådan att beslutet att använda det fordonsbaserade batteriet är inte-förutsägbart. Detta resulterar i en suboptimal användning av hybriddrivlinan. I denna avhandling är ett prediktivt Energioptimeringsverktyg utvecklat för att maximera nyttan av hybridisering och det praktiska implementerandet av detta verktyg undersöks. Optimeringen beaktar både kapaciteten och de termiska belastningsbegränsningarna hos batteriet. Det utvecklade optimeringsverktyg använder information om vägen framåt tillsammans medkonvex optimering för att producera optimala referenstrajektorier av batteritillståndet. Dessa trajektorier används i en realtidsstyrenhet för att bestämma batterianvändningen genom att kontrollera adjungerade tillstånden strategiekvationen för den ekvivalenta förbrukningsminimiseringen. Optimeringsverktyget verifieras och jämförs med den ursprungliga styrenheten i en simuleringsmiljö baserad på Simulink. När perfekt information om vägen framåt är känd, är den genomsnittliga minskningen av bränsleförbrukningen 0,99 % relativt den ursprungliga styrenheten. Flera frågor som uppstår i den verkliga implementeringen undersöks, såsom den begränsade beräkningshastigheten och längden på den väg framåt som kan förutses. Av denna anledning är segmenteras informationen till optimeringsverktyget och den resulterande prestandan undersöks. För en 30 sekunders segmentering av framtida väginformation är den genomsnittliga besparingen i bränsleförbrukningen 0,13 % i förhållande till den ursprungligastyrenheten. Resultaten visar att den viktigaste faktorn som begränsar bränsleförbrukningsbesparingen är införandet av de termiska belastningsbegränsningarna på batteriet.
835

Challenges and signal processing of high strain rate mechanical testing

Lamdini, Barae 13 May 2022 (has links)
Dynamic testing provides valuable insight into the behavior of materials undergoing fast deformation. During Split-Hopkinson Pressure Bar testing, stress waves are measured using strain gauges as voltage variations that are usually very small. Therefore, an amplifier is required to amplify the data and analyze it. One of the few available amplifiers designed for this purpose is provided by Vishay Micro-Measurements which limits the user’s options when it comes to research or industry. Among the challenges of implementing the Hopkinson technology in the industry are the size and cost of the amplifier. In this work, we propose a novel design of a signal conditioning amplifier that provides the following functionalities: voltage excitation for strain gauges, wide gain range (1-1000), signal balancing, shunting, and filtering. The main objective is to make a smaller and cheaper amplifier that provides equivalent or better performance allowing larger application of the Hopkinson technology in the industry.
836

Design And Implementation Of An Inverted Short Baseline Acoustic Positioning System

Frabosilio, Jakob 01 September 2024 (has links) (PDF)
This document details the design, implementation, testing, and analysis of an inverted short baseline acoustic positioning system. The system presented here is an above-water, air-based prototype for an underwater acoustic positioning system; it is designed to determine the position of remotely-operated underwater vehicles (ROVs) and autonomous underwater vehicles (AUVs) in the global frame using a method that does not drift over time. A ground-truth positioning system is constructed using a stacked hexapod platform actuator, which mimics the motion of an AUV and provides the true position of an ultrasonic microphone array. An ultrasonic transmitter sends a pulse of sound towards the array; microphones on the array record the pulse of sound and use the time shift between the microphone signals to determine the position of the transmitter relative to the receiver array. The orientation of the array, which is necessary to transform the position estimate to the global frame, is calculated using a Madgwick filter and data from a MEMS IMU. Additionally, a dead reckoning change-in-position estimate is formed using the IMU data. The acoustic position estimate is combined with the dead reckoning estimate using a Kalman filter. The accuracy of this filtered position estimate was verified to 22.1mm within a range of 3.88m in this air-based implementation. The ground-truth positioning system runs on an ESP32 microcontroller using code written in C++, and the acoustic positioning system runs on two STM32 microcontrollers using code written in C. Extrapolation of these results to the underwater regime, as well as recommendations for improving upon this work, are included at the end of the document. All code written for this thesis is available on GitHub and is open-source and well-documented.
837

An integrated audit evidence planning model to quantify the extent of audit evidence

Mentz, Marian 11 1900 (has links)
Audit evidence enables the auditor to express an opinion on the financial statements. To address the risk that the auditor may express an inappropriate opinion, the nature, timing and extent of audit procedures must be responsive to the assessed risks of material misstatement. The auditor must aggregate the levels of assurance obtained from different combinations of tests of controls, substantive analytical procedures and tests of details to respond to the assessed risks. These evidence planning decisions are complex and require professional judgement. Research has found that the extent of audit procedures is not linked to the assessed risks and that auditors may not know to aggregate evidence from different types of audit procedures. Research also supports the use of a structured audit methodology that includes decision models, to guide the application of professional judgement. This leads to the overall objective of this study: the development of an integrated audit evidence planning model to quantify the extent of audit evidence. The study employs a grounded theory model building approach, interpreting the relevant concepts and principles from the literature review into the development of the model. The integrated audit evidence planning model quantitatively relates the extent of audit evidence in a logical and structured manner with the risk assessment and three distinct overall levels of assurance needed to support the audit opinion. It uses the cumulative nature of audit evidence and the compensatory inter-relationship between tests of controls, substantive analytical procedures and tests of details to quantitatively aggregate the extent and levels of assurance from the different combinations of procedures to obtain reasonable assurance at the required overall level of assurance. The model provides a framework for influencing and guiding the exercise of professional judgement and is a practical and effective tool to benefit the users thereof when conducting an audit. Thus, the study models the extent of audit evidence with reference to the aggregation of different types and combinations of evidence and the linkage between the risk assessment and the extent of evidence that provides a flexible framework for the application of professional judgement regarding the gathering of audit evidence. / Auditing / D. Com. (Auditing)
838

A model of compelled nonuse of information

Houston, Ronald David 05 February 2010 (has links)
The philosophical and empirical study reported here developed from the observation that information science has had no comprehensive understanding of nonuse of information. Without such an understanding, information workers may use the words "nonuse of information" while referring to very different phenomena. This lack of understanding makes the job of the information professional difficult. For example, the model presented here reduces hundreds of theories of information behavior to a conceptually manageable taxonomy of six conditions that lead to nonuse of information. The six conditions include: 1) intrinsic somatic conditions, 2) socio-environmental barriers, 3) authoritarian controls, 4) threshold knowledge shortfall, 5) attention shortfall, and 6) information filtering. This dissertation explains and provides examples of each condition. The study of a novel area that had no prior theory or model required a novel methodology. Thus, for this study, I adopted the pragmatism formulated by Charles Sanders Peirce, a method of evaluating concepts by their practical consequences. This pragmatism applied in two ways to the study of nonuse of information. First, because nonuse of information is a behavior, pragmatism helped me to limit the psychologic implications of the study to behavior, rather than to expand the discussion to psychodynamics or cognition, for example. I justified this limiting on the basis that behavior reflects the use or nonuse of information, and behavior is more observable than other aspects of psychology, such as cognition. Second, Peirce's concept of pragmatism supported another of his contributions to philosophical inquiry, retroduction, sometimes referred to as abduction. To study nonuse of information through retroduction, I created a fivestep "definition heuristic," based on the writings of Spradley and McCurdy. I then created a nine-step "retroduction heuristic" based on the system of logic identified and termed "retroductive" or "abductive" by Peirce. I used this heuristic to identify examples of nonuse of information and applied the examples to a second corpus of research reports that contained examples of compelled nonuse of information. The taxonomy of this study resulted from this second application and represents a descriptive model of compelled nonuse of information. / text
839

Electromechanics of an Ocean Current Turbine

Tzelepis, Vasileios 18 December 2015 (has links)
The development of a numeric simulation for predicting the performance of an Ocean Current Energy Conversion System is presented in this thesis along with a control system development using a PID controller for the achievement of specified rotational velocity set-points. In the beginning, this numeric model is implemented in MATLAB/Simulink® and it is used to predict the performance of a three phase squirrel single-cage type induction motor/generator in two different cases. The first case is a small 3 meter rotor diameter, 20 kW ocean current turbine with fixed pitch blades, and the second case a 20 meter, 720 kW ocean current turbine with variable pitch blades. Furthermore, the second case is also used for the development of a Voltage Source Variable Frequency Drive for the induction motor/generator. Comparison among the Variable Frequency Drive and a simplified model is applied. Finally, the simulation is also used to estimate the average electric power generation from the 720 kW Ocean Current Energy Conversion System which consists of an induction generator and an ocean current turbine connected with a shaft which modeled as a mechanical vibration system.
840

Feedback Effects in Stochastic Control Problems with Liquidity Frictions

Bilarev, Todor 03 December 2018 (has links)
In dieser Arbeit untersuchen wir mathematische Modelle für Finanzmärkte mit einem großen Händler, dessen Handelsaktivitäten transienten Einfluss auf die Preise der Anlagen haben. Zuerst beschäftigen wir uns mit der Frage, wie die Handelserlöse des großen Händlers definiert werden sollen. Wir identifizieren die Erlöse zunächst für absolutstetige Strategien als nichtlineares Integral, in welchem sowohl der Integrand als der Integrator von der Strategie abhängen. Unserere Hauptbeiträge sind hier die Identifizierung der Skorokhod M1 Topologie als geeigneter Topologue auf dem Raum aller Strategien sowie die stetige Erweiterung der Definition für die Handelserlöse von absolutstetigen auf cadlag Kontrollstrategien. Weiter lösen wir ein Liquidierungsproblem in einem multiplikativen Modell mit Preiseinfluss, in dem die Liquidität stochastisch ist. Die optimale Strategie wird beschrieben durch die Lokalzeit für Reflektion einer Diffusion an einer nicht-konstanten Grenze. Um die HJB-Variationsungleichung zu lösen und Optimalität zu beweisen, wenden wir probabilistische Argumente und Methoden aus der Variationsrechnung an, darunter Laplace-Transformierte von Lokalzeiten für Reflektion an elastischen Grenzen. In der zweiten Hälfte der Arbeit untersuchen wir die Absicherung (Hedging) für Optionen. Der minimale Superhedging-Preis ist die Viskositätslösung einer semi-linearen partiellen Differenzialgleichung, deren Nichtlinearität von dem transienten Preiseinfluss abhängt. Schließlich erweitern wir unsere Analyse auf Hedging-Probleme in Märkten mit mehreren riskanten Anlagen. Stabilitätsargumente führen zu strukturellen Bedingungen, welche für ein arbitragefreies Modell mit wechselseitigem Preis-Impakt gelten müssen. Zudem ermöglichen es jene Bedingungen, die Erlöse für allgemeine Strategien unendlicher Variation in stetiger Weise zu definieren. Als Anwendung lösen wir das Superhedging-Problem in einem additiven Preis-Impakt-Modell mit mehreren Anlagen. / In this thesis we study mathematical models of financial markets with a large trader (price impact models) whose actions have transient impact on the risky asset prices. At first, we study the question of how to define the large trader's proceeds from trading. To extend the proceeds functional to general controls, we ask for stability in the following sense: nearby trading activities should lead to nearby proceeds. Our main contribution in this part is to identify a suitable topology on the space of controls, namely the Skorokhod M1 topology, and to obtain the continuous extension of the proceeds functional for general cadlag controls. Secondly, we solve the optimal liquidation problem in a multiplicative price impact model where liquidity is stochastic. The optimal control is obtained as the reflection local time of a diffusion process reflected at a non-constant free boundary. To solve the HJB variational inequality and prove optimality, we need a combination of probabilistic arguments and calculus of variations methods, involving Laplace transforms of inverse local times for diffusions reflected at elastic boundaries. In the second half of the thesis we study the hedging problem for a large trader. We solve the problem of superhedging for European contingent claims in a multiplicative impact model using techniques from the theory of stochastic target problems. The minimal superhedging price is identified as the unique viscosity solution of a semi-linear pde, whose nonlinearity is governed by the transient nature of price impact. Finally, we extend our consideration to multi-asset models. Requiring stability leads to strong structural conditions that arbitrage-free models with cross-impact should satisfy. These conditions turn out to be crucial for identifying the proceeds functional for a general class of strategies. As an application, the problem of superhedging with cross-impact in additive price impact models is solved.

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