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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.
31

Heterogeneous MBS forwarder modeling and co-simulation / Metodik för samsimulering av pendelarmsskotare

Yang, Liunan January 2015 (has links)
The forwarder acts as an important role in mechanized Cut-to-Length timber harvesting system. But the majority of forwarder products on the market are not suspended or simply suspended by bogies which limit the riding quality of forwarder and result in soil damage due to large tireground interaction force. The Forestry Research Institute of Sweden is developing an active controlled pendulum arm suspension system actuated by hydraulic cylinders on the forwarder prototype named XT28. The aim of this active suspension system is to compensate the inherent shortcomings of the current suspension solutions. The thesis project focuses on implementing a heterogeneous simulation methodology which integrates the Multi-Body System model of XT28 built in MSC ADAMS/View with active suspension control model developed in MATLAB/Simulink. Thus, the co-simulation process is visualized in ADAMS/View. The results show that the active controlled pendulum arm suspension could improve the riding quality in a large extend and reduce the force between tire and ground at the same time. The cosimulation between ADAMS and Simulink is proved as a feasible and efficient approach to study the active control system for pendulum arm suspension on XT28 forwarder. / Skotaren har tillsammans med skördaren en central roll i den fullt mekaniserade kortvirkesmetoden för skogsavverkning. Majoriteten av dagens skotare på marknaden har sex eller åtta hjul, som är monterade parvis på boggilådor. Det innebär att de saknar chassidämpning, vilket begränsar operatörens komfort och orsakar även stora markskador på mjuk mark. Skogforsk koordinerar realiseringen av en fullskaleprototyp, som går under arbetsnamnet XT28, med sex hjul monterade på varsin pendelarm. Pendelarmarna har varsin hydraulcylinder som möjliggör aktiv helmaskinsdämpning. Detta examensarbete är inriktat på att skapa, demonstrera och verifiera en heterogen simuleringsmetodik, som integrerar och möjliggör samsimulering av en dynamisk mekanikmodell utvecklad i MSC Adams/View med en reglermodell för aktiv styrning av pendelarmarna. Reglermodellen har utvecklats i MATLAB / Simulink. Simuleringsresultaten, som visualiseras i Adams-miljön, visar att den aktiva pendelarmregleringen skulle kunna förbättra åkkomforten signifikant, och också kraftigt markkontaktkrafterna. Det visas att samsimulering mellan ADAMS och Simulink är en effektiv metod för att verifiera prestandan hos aktiva reglersystem för pendelarmsfjädring på prototypskotaren XT28.
32

Learning a Grasp Prediction Model for Forestry Applications

Olofsson, Elias January 2024 (has links)
Since the advent of machine learning and machine vision methods, progress has been made in tackling the long-standing research question of autonomous grasping of arbitrary objects using robotic end-effectors. Building on these efforts, we focus on a subset of the general grasping problem concerning the automation of a forwarder. This forestry vehicle collects and transports felled and cut tree logs in a forest environment to a nearby roadside landing. The forwarder must safely and energy-efficiently grip logs to minimize fuel consumption and reduce loading times. In this thesis project, we develop a data-driven model for predicting the expected outcome of grasping attempts made by the forwarder's crane. For a given pile of logs, such a model can estimate the optimal horizontal location and angle for applying the claw grapple, enabling effective grasp planning. We utilize physics-based simulations to create a ground truth dataset of 12 500 000 simulated grasps distributed across 5000 randomly generated log piles. Our semi-generative, supervised model is a fully convolutional network that inputs the orthographic depth image of a pile and returns images predicting the corresponding grasps' initial grapple angle and outcome metrics as a function of position. Over five folds of cross-validation, our model predicted the number of grasped logs and the initial grapple angle with a normalized root mean squared error of 15.77(2)% and 2.64(4)%, respectively. The grasps' energy efficiency and energy waste were similarly predicted with a relative error of 14.43(2)% and 21.06(3)%. / Sedan tillkomsten av maskininlärnings- och maskinseendebaserade metoder har betydande framsteg gjorts inom forskningsområdet för autonom greppning av godtyckliga objekt med en robotisk sluteffektor. Vi bygger vidare på dessa resultat och fokuserar på en del av det generella greppningsproblemet gällande automatisering av en skotare. Denna skogsmaskin samlar in och transporterar fällda och kapade trädstammar från avverkningsplats till upplag intill närliggande skogsbilväg. Skotaren måste greppa och lyfta stockarna på ett säkert och energieffektivt sätt för att minimera bränsleförbrukningen samt minska lastningstiderna. I detta examensarbete utvecklar vi en datadriven modell för att förutsäga det förväntade resultatet av gripförsök utförda av skotarens kran. För en given timmerstockshög kan en sådan modell uppskatta den optimala positionen och vinkeln för att applicera skotarens gripklo, vilket möjliggör effektiv planering av lastningen. Vi använder fysikbaserade simuleringar för att skapa ett dataset med 12 500 000 simulerade gripförsök fördelade över 5000 slumpmässigt genererade timmerhögar. Vår semi-generativa, övervakade modell är ett djupt faltningsnätverk utan helt sammankopplade neuronlager som tar in en ortografisk djupbild av en timmerhög och returnerar bilder som predikterar de motsvarande gripförsökens initiala gripvinkel och resultatmått som en funktion av position. Vid en femfaldig korsvalidering förutsåg vår modell antalet greppade stockar och den initiala gripvinkeln med ett normaliserat rotmedelkvadratfel på 15.77(2)% respektive 2.64(4)%. Gripförsökens energieffektivitet och energiförlust predikterades på liknande sätt med ett relativt fel på 14.43(2)% och 21.06(3)%.
33

Systém controllingu v konkrétním podniku / System Controlling in a particular Firm

Poštolková, Jana January 2009 (has links)
The thesis specialize on the logistic activities, regarding using of the controlling in the sphere of logistics. The goal is to analyze what role should subserve the controlling of the company theoretically and compare this teoretical view in the company Intersnack Inc., the logistics department and according to the following facts suggest possible improvements in the department.
34

Logistics Optimization: Application of Optimization Modeling in Inbound Logistics

Arayapan, Khanittha, Warunyuwong, Piyanut January 2009 (has links)
<p><p>To be a market leader, low cost and responsiveness are the key success factors. Logistics activities create high cost reducing competitiveness of the company, especially for the remote production base. Thus, logistics activities which are delivery planning, freight forwarder and delivery mode selection must be optimized. The focusing area of this paper is inbound logistics due to its big proportion in the total cost and involvement with several stakeholders. The optimization theory and Microsoft Excel’s Solver is used to create the standard optimization tools since it is an efficient and user friendly program. The models are developed based on the supply chain management theory in order to achieve the lowest cost, responsiveness and shared objectives. 2 delivery planning optimization models, container loading for fixed slitting and loading pattern and container loading for pallet loaded material, are formulated. Also, delivery mode selection is constructed by using optimization concept to determine the best alternative. Furthermore, freight forwarder selection process is created by extending the use of the delivery mode selection model. The results express that safety stock, loading pattern, transport mode, and minimum order quantity (MOQ) significantly affect the total logistics cost. Including hidden costs, long transit time and delay penalties, leads freight forwarder selection process to become more realistic and reliable. Shorter processing time, ensured optimal solution, transparency increase and better communication are gained by using these optimization models. However, the proper boundaries must be defined carefully to gain the feasible solution.</p></p>
35

Kinematic Control of Redundant Knuckle Booms with Automatic Path Following Functions

Löfgren, Björn January 2009 (has links)
To stay competitive internationally, the Swedish forestry sector must increase its productivity by 2 to 3% annually. There are a variety of ways in which productivity can be increased. One option is to develop remote-controlled or unmanned machines, thus reducing the need for operator intervention. Another option—and one that could be achieved sooner than full automation—would be to make some functions semi-automatic. Semi-automatic operation of the knuckle boom and felling head in particular would create “mini-breaks” for the operators, thereby reducing mental and physiological stress. It would also reduce training time and increase the productivity of a large proportion of operators. The objective of this thesis work has been to develop and evaluate algorithms for simplified boom control on forest machines. Algorithms for so called boom tip control, as well as automatic boom functions have been introduced. The algorithms solve the inverse kinematics of kinematically redundant knuckle booms while maximizing lifting capacity. The boom tip control was evaluated – first by means of a kinematic simulation and then in a dynamic forest machine simulator. The results show that boom tip control is an easier system to learn in comparison to conventional control, leading to savings in production due to shorter learning times and operators being able to reach full production sooner. Boom tip control also creates less mental strain than conventional control, which in the long run will reduce mental stress on operators of forest machines. The maximum lifting capacity algorithm was then developed further to enable TCP path-tracking, which was also implemented and evaluated in the simulator. An evaluation of the fidelity of the dynamic forest machine simulator was performed to ensure validity of the results achieved with the simplified boom control. The results from the study show that there is good fidelity between the forest machine simulator and a real forest machine, and that the results from simulations are reliable. It is also concluded that the simulator was a useful research tool for the studies performed in the context of this thesis work. The thesis had two overall objectives. The first was to provide the industry and forestry sector with usable and verified ideas and results in the area of automation. This has been accomplished with the implementation of a simplified boom control and semi-automation on a forwarder in a recently started joint venture between a hydraulic manufacturer, a forest machine manufacturer and a forest enterprise. The second objective was to strengthen the research and development links between the forestry sector and technical university research. This has been accomplished through the thesis work itself and by a number of courses, projects and Masters theses over the last three years. About 150 students in total have been studying forest machine technology in one way or the other. / QC 20100729
36

Logistics Optimization: Application of Optimization Modeling in Inbound Logistics

Arayapan, Khanittha, Warunyuwong, Piyanut January 2009 (has links)
To be a market leader, low cost and responsiveness are the key success factors. Logistics activities create high cost reducing competitiveness of the company, especially for the remote production base. Thus, logistics activities which are delivery planning, freight forwarder and delivery mode selection must be optimized. The focusing area of this paper is inbound logistics due to its big proportion in the total cost and involvement with several stakeholders. The optimization theory and Microsoft Excel’s Solver is used to create the standard optimization tools since it is an efficient and user friendly program. The models are developed based on the supply chain management theory in order to achieve the lowest cost, responsiveness and shared objectives. 2 delivery planning optimization models, container loading for fixed slitting and loading pattern and container loading for pallet loaded material, are formulated. Also, delivery mode selection is constructed by using optimization concept to determine the best alternative. Furthermore, freight forwarder selection process is created by extending the use of the delivery mode selection model. The results express that safety stock, loading pattern, transport mode, and minimum order quantity (MOQ) significantly affect the total logistics cost. Including hidden costs, long transit time and delay penalties, leads freight forwarder selection process to become more realistic and reliable. Shorter processing time, ensured optimal solution, transparency increase and better communication are gained by using these optimization models. However, the proper boundaries must be defined carefully to gain the feasible solution.
37

The Evaluation of GeoNetworking Forwarding in Vehicular Ad-Hoc Networks

Rajendran, Rajapandiyan January 2013 (has links)
In Intelligent Transportation Systems (ITS), disseminating warning messages in a timely and efficient way through wireless short-range communications can save many lives and reduce traffic congestion. A geographical broadcast protocol provides data delivery to specified geographical areas, using multi-hop communications if needed. Among the main challenges for such protocols are forwarder selection and the reduction of the number of hops required to reach and cover the destination area.  In this thesis we propose an efficient geographical broadcast protocol called Preferred and Contention Based Forwarding (PCBF) and evaluate it through simulations. PCBF uses a combination of contention-based forwarding and selecting preferred forwarders also found in other protocols like Emergency Message Dissemination for Vehicular Environments (EMDV). Since the preferred forwarder is allowed to immediately forward the packet (evading contention among other potential forwarders), this approach reduces end-to-end delays. Notable extensions of PCBF compared to EMDV are the use of direct negative acknowledgements in case of unnecessary rebroadcasts and the use of forwarders outside the target region.  Our simulation results show that the PCBF protocol outperforms selected other protocols in terms of end-to-end delay, re-broadcast overhead and reliability in both sparse and dense networks.
38

La faute du commissionaire de transport / The freight fowarder's fault

Kioungou, Ance 18 December 2015 (has links)
Quel étrange personnage que le commissionnaire de transport ! Cet acteur majeur du monde des transports est à l’origine de nombreuses controverses doctrinales et d’un abondant contentieux judiciaire. Professionnel chargé d’organiser le transport des marchandises pour le compte d’un donneur d’ordre, il supporte une double responsabilité, de son fait personnel et du fait de tous les prestataires qu’il se substitue dans l’exécution de sa mission. Si le recours à la commission de transport est très fréquent, c’est parce qu’elle offre de garanties intéressantes aux clients, notamment la prise en charge intégrale de l’organisation du transport avec les risques qu’elle comporte. Cependant, en analysant attentivement la jurisprudence de ces dernières années, on a pu observer que la responsabilité de la plupart des commissionnaires de transport a été très lourdement appréciée. Le motif souvent retenu étant la faute personnelle, facilement assimilée à la faute lourde par les juges, avec pour conséquence la perte du bénéfice des limitations d’indemnités pour ce dernier. Que recouvre précisément la faute du commissionnaire de transport ? Sur ce point, on a assisté à une jurisprudence inflationniste notamment sur le devoir de conseil, les contours de cette notion n’étant pas clairement définis. La situation était devenue si préoccupante que les pouvoirs publics ont cru bon d’intervenir à travers deux réformes majeures. D’abord par la loi du 8 décembre 2009 avec l’introduction du nouvel article L.133-8 du Code de commerce, qui conditionne dorénavant l’exclusion des limitations d’indemnités à la preuve d’une faute dolosive ou inexcusable du commissionnaire de transport ou du transporteur. Ensuite par l’adoption du contrat type commission de transport (en vigueur depuis 2013). Ce contrat type, fruit d’une longue et laborieuse négociation entre les professionnels de ce secteur, encadre sérieusement la responsabilité personnelle du commissionnaire de transport. Comment appréhender alors la faute du commissionnaire de transport à la lumière de ces réformes ? C’est à cette question essentielle que ce travail va tenter d’apporter des éléments de réponses en s’appuyant sur les textes en vigueur et de la pratique observée dans les prétoires. / What a strange character the freight forwarder (Agent) is ! This leading player of the world of transport is the source of several doctrinal debates and implies a plentiful judicial dispute. Professional appointed to organize the transport of the goods on behalf of a contractor, he bears a double responsibility, of his personal fact and because of all the persons receiving benefits for whom he substitutes itself in the execution of his mission. If the appeal to the committee of transport is very frequent, it is due to the interesting guarantees it offers to the customers, in particular the complete coverage of the organization of the transport with the risks which it involves. However, by carefully analyzing the jurisprudence of recent years, it has been observed that the responsibility for most freight forwarders was very heavily estimated. The often held motive being the personal fault easily likened to the serious offence by the judges, involving the loss of the profit of the limitations of compensations for the latter. What does exactly the fault of the forwarder cover? On this point, we attended an inflationary jurisprudence in particular on the duty of advice, the outlines of this notion not being clearly defined. The situation had become so worrisome as public authorities saw fit to intervene through two fundamental reforms. At first by the law of December 8th, 2009 with the introduction of the new article L.133-8 of the Commercial law, which conditions from now on the exclusion of the limitations of compensations in the proof of a dolosive or unforgivable fault of the agent of transport or the carrier. And then by the adoption of the standard commission contract of transport (in force since 2013). This standard contract, fruit of a long and laborious negotiation between the professionals of this sector, frames seriously the personal liability of the forwarder. How to identify then the fault of the forwarder in the light of these reforms? It is to this essential question that this work is going to try to bring elements of answers based on the current texts and the practice observed in the courts of justice.
39

Zadní rám lesní vyvážečky L520 / Rear frame of Forwarder L520

Koumar, Martin January 2013 (has links)
This master’s thesis deals with strength analysis rear frame of forwarder LVS 520 and propose modifications of this frame. The main part of this work is strength analysis of the supporting frame of the original construction by the help of the finite elements method. Further the design of suitable structural modifications and strength analysis of the modified construction of frame. This master’s thesis has been prepared with Strojírna Novotný s.r.o. company cooperation.
40

Design přepravníku dřeva s ručním ovládáním / Design of Timber Trailer with Manual Control

Paclík, Tomáš January 2013 (has links)
Subject of this thesis is design of a timber trailer with manual control. The designed timber trailer is one of the small machines that are used for a low–volume timber production. This timber trailer operates in a rough terrain – its outstanding feature is the ability to operate on steep slopes and overcome obstacles. The concept of the control system and the safe seating of a driver are contributions to the field of ergonomics. This machine is considerate of a forest environment because it minimizes formation of soil erosion. Easy washability and maintenance are other criteria of this proposal. The functional point of the design is firmed by the purposeful and aesthetic shaping which is unique in this category. Comparison of the proposal presented in this thesis with available machines demonstrates that work of designer is indispensable part of a machine development process.

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