• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 558
  • 236
  • 181
  • 106
  • 75
  • 41
  • 32
  • 14
  • 12
  • 10
  • 7
  • 5
  • 5
  • 4
  • 4
  • Tagged with
  • 1453
  • 394
  • 297
  • 211
  • 171
  • 164
  • 152
  • 150
  • 140
  • 136
  • 120
  • 115
  • 110
  • 96
  • 95
  • 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.
101

Modelling and control of a light-duty hybrid electric truck

Park, Jong-Kyu 09 1900 (has links)
This study is concentrated on modelling and developing the controller for the light-duty hybrid electric truck. The hybrid electric vehicle has advantages in fuel economy. However, there have been relatively few studies on commercial HEVs, whilst a considerable number of studies on the hybrid electric system have been conducted in the field of passenger cars. So the current status and the methodologies to develop the LD hybrid electric truck model have been studied through the literature review. The modelling process used in this study is divided into three major stages. The first stage is to determine the structure of the hybrid electric truck and define the hardware. The second is the component modelling using the AMESim simulation tool to develop a forward facing model. In order to complete the component modelling, the information and data were collected from various sources including references and ADVISOR. The third stage is concerned with the controller which was written in Simulink. This was run in a co-simulation with the AMESim vehicle model. Through the initial simulation, the charge-sustaining performance of this controller was verified and improved. Finally, the simulations for the complete model were carried out over a number of drive cycles, such as CBDTRUCK, JE05, and TRL LGV drive cycle, to evaluate and analyse the effect on the fuel economy and the vehicle performance by the engine operating zone and the EM power capacity. The report presents a comparison of the fuel efficiency of the conventional vehicle and the LD hybrid electric truck. The results obtained by the simulation show the feasibility to build the complete vehicle with the designed controller.
102

Design of Controller board for a Lunar Rover

Rejas, Marcos January 2010 (has links)
The Lunar Rover (Roony) is a robotic project group at Mälardalens University composed by students. The objective of this group is to design and build an autonomous robot that has to be able to move by itself through the moon terrain. The Lunar Rover is divided in several sub-projects from different knowledge areas; the objective of this electronic thesis is to design a controller board.   The designed board will be able to connect the robot to an external dispositive (via JTAG, or WIFI), and also it will control and connect the different robot’s peripherals. The main component of the controller board is the microcontroller AT90CAN128. The peripherals are a steeper motor, a LIDAR system (Light Detection And Ranging), a WIFI chip(WIPORT™), a bus can driver, an accelerometer, a LIPO( Lithium-Ion Polymer) battery charger, a Solar photovoltaic cell handler, and sixteen DC motors(four in each leg of the robot). Once the logic design has finished, the PCB design is done attending the size limitations of the robot. Once the design has finished, a prototype has been built and tested using ATMEL software.
103

Passive Control for a Human Power Amplifier,providing Force Amplification, Guidance and Obstacle Avoidance

Eskilsson, Fredrik January 2011 (has links)
In this master thesis a control strategy for a Human Power Amplifier (HPA) ispresented. An HPA can be described as a machine that amplifies a force exertedby a human operator. The HPA in this thesis can best be described as a mechanicalore with two degrees of freedom.The approach for the control strategy presented here is to look at the controlproblem not directly as a force amplifying problem, but as coordination problembetween the real system and a virtual system, where the virtual system is used asa reference. If the systems are synchronized then desired force amplification willnaturally follow from that.Furthermore is the possibility to implement guidance and obstacle avoidanceon the machine investigated. The guidance is performed by using velocity fields,i.e., vector fields where a vector represents the desired velocity for each point inthe plane. For the obstacle avoidance potential fields are used, where the idea isthat a high potential should repel the machine from restricted areas.
104

Controllerarbete på Scania : En studie kring controllerns dagliga arbete

Eriksson, Niclas, Larruy, Ludvig January 2011 (has links)
Vi studerar controllers dagliga arbete inom FoU-enheten på ett stort svenskt företag. Därtill jämförs det dagliga arbetet i praktiken med controllerns egen samt chefens åsikter om vad tid bör läggas på, samt med den bild av den moderna controllerrollen som presenteras i litteraturen. För att åstadkomma denna jämförelse har intervjuer utförts med tio controllers och enkätsvar har erhållits från fem avdelningschefer. De avdelningar som har studerats är de största konstruerande avdelningarna på Scanias FoU enhet lokaliserad i Södertälje. Studien visar att viss tidsbrist förekommer och att controllers lägger en betydande del av sin arbetstid på rutinartade uppgifter. Detta begränsar tiden controllers kan spendera på uppgifter av utbildande karraktär. Detta är olyckligt eftersom utbildning är något som både chefer och controllers önskar att det kunde läggas mer tid på. Även mer omfattande analytiskt arbete efterlyses av såväl controllers som chefer. Sammanfattningsvis kan det konstateras att chefernas och controllernas önskebilder stämmer bättre överrens med de egenskaper som i litteraturen sägs vara utmärkande för den moderna controllern än vad det dagliga arbetet gör.
105

Development of a low level autonomous machine

Griffith, Jason Carl 05 September 2008 (has links)
An autonomous machine is a machine that can navigate through its environment without human interactions. These machines use sensors to sense the environment and have computing abilities for receiving and interpreting the sensory data as well as for controlling their displacement. At the University of Saskatchewan (Saskatoon, Canada), a low level autonomous machine was developed. This low level machine was the sensor system for an autonomous machine. The machine was capable of sensing the environment and carrying out actions based on commands sent to it. This machine provided a sensing and control layer, but the path planning (decision making) part of the autonomous machine was not developed.<p>This autonomous machine was developed on a Case IH DX 34H tractor with the purpose of providing a machine for testing software and sensors in a true agricultural environment. The tractor was equipped with sensors capable of sensing the speed and heading of the tractor. A control architecture was developed that received input commands from a human or computer in the form of a target heading and speed. The control architecture then adjusted controls on the tractor to make the tractor reach and maintain the target heading and speed until a new command was provided. The tractor was capable of being used in all kinds of weather, although some minor issues arose when testing in rain and snow. The sensor platform developed was found to be insufficient for proper control. The control structure appeared to work correctly, but was hindered by the poor sensor platform performance.
106

Research and Development of General Purpose Controller for Underwater Vehicle

Chang, Wen-li 21 July 2010 (has links)
During the underwater vehicle R&D process, a crucial task in the beginning phase is to decide the specifications of sensors and actuators. The designers need to make decisions if an off-the-shelf product will meet the requirement, or more efforts should be devoted to the development of a component. The communication format undertaken between the controller and the subsystems is another important design issue worth of close attention. Once these specifications are settled, it will be very troublesome to change them afterwards in case a design flaw is discovered. It will be even worse if the problems are found after the prototype vehicle is constructed. In order to ensure the flexibility and shorten the development time, this paper proposes an architecture for general-purpose low level controller suitable for underwater vehicles. We suggest using the idea of ¡§tiers¡¨ to construct a vehicle controller with multiple layers. Generally speaking, there are many different paths of information flow in a vehicle control system. It can be high-level tier and abstractive intention of the human operator interpreted by the man-machine interface; or the mid-level tier control commands to maneuver the vehicle to a specific direction; down to the low -level tier as the raw commands fed to the thrusters. The performance and the reliability of the system deeply depend on the flow of these information and commands. High- and mid-level tiers information can be modeled mathematically, but the low-level tier is product-dependent. In other words, once a new sensor or actuator is installed, the control software related to these components need to be revised accordingly. The modification of the software might exist at multiple places if the structure is not organized as tiers. In order to maintain full flexibility of the vehicle controller structure throughout the R&D period, the high- and mid-level will be implemented in the man-machine interface for ROV case, and in the mission planner in the AUV case. The low-level tier is implemented in the onboard computer. The onboard low-level controller covers a variety of communication format of physical ports, such as serial line, D/A, A/D, D/IO and PWM. Port setting parameters, such baud-rate or DA range, can be specified remotely on the surface. The physical connecting ports of the sensors can be changed freely without rewiring or reprogramming. Taking the stability of the controller as the top priority, we used DOS operating system as the platform to implement our concepts. DOS has been in the market for more than two decades, but it has the merits of fast in booting, highly stable, efficient in computation. We use its timer interrupt service INT 0X1C to construct a realtime thread to poll the readiness of sensory channels, and uploads the data to the surface via a channel-driven packet. The packets delivered to the surface are split into channels and reconstructed back to their original raw data format. The other necessary service routines, such as DA, AD and DIO, are also embedded inside this thread for its promptitude. We constructed an experimental platform with this low-level controller to verify if the vehicle alitude control can be accurate enough as the carrier of the Seafloor Laser Scanner developed by our lab. Prior to the experiments, issues, such as whether the bouyancy of the system is pro or con for driving the vechile, were studied with Simulink. The poorness of altitude control caused by the deadzone effect of the thruster failed to be duplicated as in the simulation, while the alitude control gave a tracking error within ¡Ó 5cm.
107

Development of an Underwater Vehicle Simulation Platform

Du, Jiun-Hua 15 November 2011 (has links)
In the development of underwater vehicles, it is necessary to conduct performance test in the water tank. However, different factors need to be considered depending on different cases. The purpose of this paper is to construct a simulation platform in the air to study the scenarios like side current or constant height profiling. Although these tests are difficult to be performed in the water tank, we can get some solutions from observing the dynamics of simulation platform. The simulation platform we used consists of three links to constraint the motion in a polar coordinate system. It carries a wireless micro-camera, and two DC motor-driven propellers. At the end of the distal link and metal disk is attached on the other side of the pivot of the last link to provide counter-weight which can simulate different status of the "buoyancy" of the platform. The encoder which is uses to trace the motion of the simulation platform, is mounted at each join between two links. The control program has two parts: servo control of propellers and target tracking. In order to approach to the real-time searching, we derived image with gray scale instead of color form to increase image refreshing rate during the tracking process. For the current experiment, the target is at dot generated by an LED. The location of the bright dot is detected by a histogram-based threshold, and the actual location is further refined with intensity-weighted algorithm. The offset between of the target and the center of the image is used as the feedback to command the propellers to drive the platform. The goal is to keep the target at the center of the image as close as possible. A linear PD control (proportional - derivative) is implemented to drive the propellers. Preliminary experiments show that the simulation platform can track a target with about 15 frames per second refreshing rate under the condition that the target does not move too fast and vanishes in the image. When ROV with laser scanner syetem, seafloor away from ROV's accuracy is necessary. In this eassay, we use tracking angle and tracking bright dot to qualify and quantify the influence of buoyancy and propeller on the altitude control in different cases.
108

Maximum power tracking control scheme for wind generator systems

Mena, Hugo Eduardo 15 May 2009 (has links)
The purpose of this work is to develop a maximum power tracking control strategy for variable speed wind turbine systems. Modern wind turbine control systems are slow, and they depend on the design parameters of the turbine and use wind and/or rotor speed measurements as control variable inputs. The dependence on the accuracy of the measurement devices makes the controller less reliable. The proposed control scheme is based on the stiff system concept and provides a fast response and a dynamic solution to the complicated aerodynamic system. This control scheme provides a response to the wind changes without the knowledge of wind speed and turbine parameters. The system consists of a permanent magnet synchronous machine (PMSM), a passive rectifier, a dc/dc boost converter, a current controlled voltage source inverter, and a microcontroller that commands the dc/dc converter to control the generator for maximum power extraction. The microcontroller will also be able to control the current output of the three-phase inverter. In this work, the aerodynamic characteristics of wind turbines and the power conversion system topology are explained. The maximum power tracking control algorithm with a variable step estimator is introduced and the modeling and simulation of the wind turbine generator system using the MATLAB/SIMULINK® software is presented and its results show, at least in principle, that the maximum power tracking algorithm developed is suitable for wind turbine generation systems.
109

A Study of Real-Time Face Tracking with an Active Camera

Xie, Yao-Zhang 03 July 2005 (has links)
In this research we develop a Real-time face tracking system by single pan-tilt camera. The system includes face detection, deformable template tracking and motion control. We refer a method to search the facial features by using the genetic algorithm searching technique, the learning algorithm for face detector is based on AdaBoost. In the face tracking, we refer a tracking way to combine with detection and tracking. In the pan-tilt camera control part, two fuzzy logic controllers are designed to control the tracking and handling of moving face. We achieve a more robust tracking way than the single-template by renewing face-template continuously. Finally in our tests, the system can track the face of people in 30-frame per second under complex environment by using the personal computer.
110

A Area-Saving ROM Decoder and Design of Network Interface Controller

Chen, Ying-Pei 26 June 2000 (has links)
The thesis is composed of two different IC design projects, which are briefly introduced as follows. The first topic is an area-saving decoder structure for ROMs. In this part of work, we propose a novel 3-dimensional decoding method. The stages of address decoding are drastically shortened. Hence, the delay is reduced as well as the power consumption. The overall transistor count and the delay are thoroughly derived. A physical 256x8 ROM using the proposed decoder is fabricated by UMC 0.5 mm 2P2M CMOS technology. The second part is the NIC (Network Interface Controller) design. The NIC transfers data frames from and to transmitter and receiver buffers in the host memory, respectively. Meanwhile, the transferred data must also comply with the IEEE 802.3 standard. The design is compatible with CSMA/CD type Local Area Network, including 10/100 Mbps Ethernet.

Page generated in 0.0618 seconds