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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.
1

Intelligent autopilots for ships

Zirilli, Antonio January 2000 (has links)
The design of automatic systems for steering a ship presents difficult challenges because of their dynamic properties which vary considerably within the range of sailing conditions. Automatic steering of ships has its origin at the beginning of the century and was prompted by the introduction of the gyrocompass. Until the earlier 70s almost all autopilots for a ship were based on the proportional-derivative-integral (PID) controller. The main disadvantage with PID controllers is that the optimal parameters setting can be achieved only for a particular sailing condition. This shortcoming was and is still dealt with in the framework of adaptive theory where the controller parameters are adjusted in the attempt to seek the optimum of a pre-set performance function. Despite such a potential advantage, at present adaptive control theory is limited to linear plants and requires a certain amount of a-priori information for a successful application. This thesis is concerned with the applicability of intelligent control techniques to the problem of designing course-keeping and course-changing autopilots for ships. For this reason the framework of intelligent control theory is introduced and a pragmatic definition of intelligent controllers is stated. The learning and adaptive features of neural networks and fuzzy logic systems are exploited and used to solve advantageously the control design problem. Adaptive networks are used as a unifying structure where different kinds of neural networks and fuzzy logic paradigms can be described. In this framework, comparisons between neural networks and fuzzy logic systems are made and results from one field can be easily extended to the other. Although the use of such systems for the design of autopilots is in its early stage, the majority of the contributions which have appeared in literature have focused on the use of feedforward networks trained with the back-propagation algorithm. The main contributions of this thesis are the critical analysis of the feedforward network controller trained with the back-propagation algorithm, the proposition of an alternative controller architecture based on the use of radial basis function networks and to give conditions under which the stability analysis of the intelligent controllers so designed can be evaluated.
2

Identifikace pohybů na letištní ploše / Movements Identification on Aerodrome Ground

Burián, Petr January 2008 (has links)
The diploma thesis is concerning the A-SMGCS, surveillance technolgies, data fusion technologies and complex system providing identification of mobiles and aircraft on aerodrome ground. Describing architecture of A-SMGCS on Praha-Ruzyne airport and giving information about ANS procedures with A-SMGCS. Including Cost-Benefit analysis about instalation of automatic systems for localization and identification of mobiles and aircraft on aerodrome ground.
3

Effektivisering av materialflödet i inlagringsprocessen i ett distributionslager : Genom exkludering av begränsningar / A study about how a distributioncenter´ inbound process can get more efficient.

Ramde, Sara, Qadir, Lana January 2018 (has links)
Syfte – Syftet med studien är att identifiera kritiska begränsningar i inlagringsprocessen i ett distributionslager för att därmed kunna effektivisera materialflödet. Studiens syfte uppnås genom att följande forskningsfrågor har formulerats: Vilka kritiska begränsningar kan förekomma i materialflödet i en inlagringsprocess i ett distributionslager? Hur kan de identifierade begränsningarna exkluderas i en inlagringsprocess? Metod – Studien hade en induktiv ansats och datainsamling skedde genom intervjuer, observationer, dokumentstudier och litteraturstudier. En fallstudie genomfördes på ett distributionslager och empiri och teori har jämförts för att kunna uppfylla studiens syfte. Resultat – Studiens resultat påvisar att de förekommande kritiska begränsningarna i ett distributionslager är brist på yta, materialhantering, automatiska system samt lagerlayout. Studiens slutsats är att begränsningarna är sammankopplade och påverkar varandra eftersom de ingår i samma process. För att exkludera begränsningarna bör distributionslager implementera diverse standarder i sin inlagringsprocess och arbeta med ständiga förbättringar. Implikationer – Studien bidrar inte med nya teorier men bidrar med praktisk nytta för distributionslager med liknande kriterier som studiens fallföretag. Begränsningar – Studien riktar enbart in sig på distributionslager och var en fallstudie av enfallsdesign. Genom att utföra flera liknande undersökningar på företag med liknande kriterier hade generaliserbarheten kunnat stärkas. / Purpose – The purpose of the study is to identify critical constraints in the inbound process at a distribution warehouse. To accomplish the purpose two research questions were formulated: Which critical constraints can occur in the material flow in the inbound process at a distribution warehouse? How can the identified constraints be excluded in the inbound process? Method – The study was performed inductively, and the data collection techniques were interviews, observations, document studies and literature studies. A single case study was performed at a distribution warehouse and the empirical data and theories were compared to accomplish the purpose of the study. Findings – The result of the study demonstrates that the critical constraints in the inbound process at a distribution warehouse are space, material handling, automatic systems and warehouse layout. The conclusion of the study is that the constraints are connected and affect each other since they are all included in the same process. To exclude the constraints different types of standards should be implemented in the inbound process, and distribution warehouses should work with continuous improvements. Implications – The study does not contribute to new theories but can be practically beneficial for distribution warehouses similar to the studies case study. Limitations – The study only focuses on one distribution warehouse and is therefore a single case study. The generalizability could have been higher if the study had been conducted at multiple distribution warehouses.

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