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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.
501

The Development of a Miniature Flexible Flapping Wing Mechanism for use in a Robotic Air Vehicle

Jadhav, Gautam 14 March 2007 (has links)
In this study a mechanism which produced flapping and pitching motions was designed and fabricated. These motions were produced by using a single electric motor and by exploiting flexible structures. The aerodynamic forces generated by flexible membrane wings were measured using a two degree of freedom force balance. This force balance measured the aerodynamic forces of lift and thrust. Two sets of wings with varying flexibility were made. Lift and thrust measurements were acquired as the mechanism flapped the wings in a total of thirteen cases. These thirteen cases consisted of zero velocity free stream conditions as well as forward flight conditions of five meters per second. In addition, flapping frequency was varied from two Hertz to four Hertz, while angle of attack offsets varied from zero degrees to fifteen degrees. The four most interesting conditions for both sets of wings were explored in more detail. For each of these conditions, high-speed video of the flapping wing was taken. The images from the video were also correlated with cycle averaged aerodynamic forces produced by the mechanism. Several observations were made regarding the behavior of flexible flapping wings that should aid in the design of future flexible flapping wing vehicles.
502

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.
503

Advanced Driving Environment and Intelligent Vehicle Control by Visual Rhythm Analysis

Hsu, Cheng-Jie 05 September 2010 (has links)
The motivation of this paper is to propose a simple and reliable method to identify on-road vehicle events, particularly in the driving situations. A content rhythm is extracted by applying a virtual line lies on the same position of each frame. Thereupon a simplified representation of a continuous video is to record the temporal information of vehicle status. Thus, vehicle situations such as changing lane, safe distance and speed display can be detected instantly by analyzing the statistical characteristics of content rhythm. The proposed method can not only prevent accidents but also improve the traffic safety by monitoring the on-road vehicle status. Experimental results show the proposed method is reliable for vehicle event detection.
504

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.
505

Assessing Benefits in Vehicle Speed and Lateral Position when Chevrons with Full Retroreflective Sign Posts are Implemented on Rural Horizontal Curves

Re, Jonathan M. 16 January 2010 (has links)
Driving a horizontal roadway curve requires a change in vehicle alignment and a potential reduction in speed. Curves may present a challenging situation during adverse conditions or to inattentive drivers. Chevron signs provide advanced warning and positive guidance throughout the curve. Some agencies place supplemental retroreflective material on sign posts to enhance the signs? conspicuity and visibility. The objective of this study was to determine any incremental benefits in vehicle speed and lateral lane position when retroreflective material was applied to Chevron sign posts (ChevFull). This study analyzed three separate evaluation scenarios in a before, after, and after-after experimental design. There was an existing Baseline evaluation with no vertical delineation, a standard Chevron evaluation, and an experimental ChevFull treatment evaluation. Data collection measured vehicle speed and lateral position data at the point of curvature and mid-point on two separate curves. Findings showed that both Chevrons and the ChevFull treatment moved vehicles away from oncoming traffic by about 15 inches. Overall, there was little difference between the lateral position findings of the two Chevron treatment scenarios. Chevrons achieved a 1.28 MPH reduction in mean vehicle speed from the Baseline evaluation and the ChevFull treatment obtained a 2.20 MPH reduction. The findings determined that the benefits of the ChevFull treatment were not substantial. The author recommends that the MUTCD should continue to present the ChevFull treatment as an optional delineation tool. Based on this research, the author does not recommend any changes to the MUTCD.
506

Influence of barrier separated HOV lane access locations on Houston HOV lane utilization

Lipnicky, Kevin David 15 May 2009 (has links)
High Occupancy Vehicle (HOV) lanes are employed in many cities as a traffic congestion mitigation technique. These lanes are intended to provide a travel time benefit to carpools and buses, thus providing an incentive to form carpools or take transit. The time and frustration involved in finding and using HOV lane access points may act as a deterrent to HOV lane use. Thus, proper planning of HOV lane access may be able to improve convenience for potential users, increasing HOV lane utilization. By optimizing HOV lane volumes, high levels of service and trip reliability are ensured for those who carpool. Congestion is also reduced on General Purpose Lanes (GPLs) due to the diverted traffic. Public approval is tied to HOV lane utilization, which may be affected by access. Thus, HOV lane success may be determined in part by accessibility. This research investigated the possible relationship between the time required to access the HOV lane and travelers' choice of HOV lane as their mode. Additionally, the distance to HOV lane access points and the type of access point used were examined for their influence on HOV lane use rates. It was concluded that neither the type of HOV lane access point, nor the added time necessary to access the HOV lane were significant factors in HOV lane use rates. Instead, the convenience of carpool formation and the convenience of HOV lane access to traveler's origins and destinations were found to be the most important factors in HOV lane use rates. Specifically, the HOV lane use rate for the area 5 to 7 miles from the nearest HOV lane exit, which includes Downtown Houston, was much higher than the use rates for any other area.
507

Effects of translocation and deer-vehicle collision mitigation on Florida Key deer

Parker, Israel David 02 June 2009 (has links)
Urban development and habitat fragmentation threaten recovery and management of the endangered Florida Key deer (Odocoileus virginianus clavium). Urban development has reduced deer dispersal from their core habitat resulting in deer “overabundance” and has increased deer-human interactions (mostly deer-vehicle collisions [DVCs]). Conversely, deer populations on outer islands have declined in recent years due to limited deer dispersal from source populations. In order to expand the Key deer’s range and reduce DVCs within their core habitat, wildlife managers determined translocations and DVC mitigation were needed. Thus, the objectives of my thesis were to determine (1) effects of translocation on the establishment of outer-island local populations, and (2) effects of United States 1 Highway (US 1) improvements (i.e., exclusion fencing, underpasses, deer guards, and extra lane creation) on DVCs and deer movements. I evaluated the efficacy of translocations by comparing annual survival and seasonal ranges between resident and translocated deer and by analyzing reproduction of translocated deer. Translocated females (yearlings and adults) had lower annual survival than resident deer. Conversely, males (yearlings and adults) demonstrated higher annual survival than resident males. Due to low sample sizes and large variation, these numbers are potentially less important than the high overall survival (only 4 of 38 died). Seasonal ranges were generally smaller for resident deer than translocated deer. I attribute differences in ranges to differences in habitat quality between the core habitat and destination islands and to use of soft releases. Presence of fawns and yearlings indicated successful reproduction of translocated deer. Overall, the project was successful in establishing populations on the destination islands. The US 1 Highway improvements reduced DVCs along the fenced section of US 1 (2003, n = 2; 2004, n = 1; 2005, n = 0); however, overall DVCs increased on Big Pine Key (1996–2000, x¯ = 79; 2003, n = 91; 2004, n = 84; 2005, n = 100). Data suggest DVCs shifted to the unfenced segment of US 1. However, monthly deer surveys also suggested an increase in deer numbers that may explain overall DVC increases observed in my study.
508

A Comparison of Vehicle Speed at Day and Night Rural Horizontal Curves

Quaium, Ridwan B. 2010 May 1900 (has links)
This thesis documents the linear mixed model developed for vehicle speed along two-lane two-way rural horizontal curves in the outside lane. Speed data at each curve was collected at four points along the curve including the midpoint of the curve for a minimum of 48 hours during weekdays. Vehicle speed was analyzed separately for day and night conditions. The horizontal curves were categorized into different groups using different methods using side friction demand, radius and pavement edgeline marking retroreflectivity. In the speed prediction model, radius, superelevation at the midpoint of the curve, deflection angle, posted speed limit and pavement edgeline marking retroreflectivity were used to predict the vehicle speed at the midpoint of the horizontal curve. The regression analysis indicates that all of these variables are statistically significant in predicting the vehicle speed at the midpoint of horizontal curves with a 95 percent confidence interval. The linear model determined that the vehicle speed has a positive relation with the radius of the curve, superelevation and posted speed limit but has a negative relation with the deflection angle and pavement edgeline marking retroreflectivity. Curves were categorized based on side friction demand or radius and retroreflectivity of pavement edgeline marking. ANOVA was used to compare the day and night time speed. The comparisons reveal that vehicle speed at the horizontal curves decreases as the side friction demand value of the curves increases. Another finding of this research was that even though the posted speed limit is incorporated into the calculation of side friction demand, it may be necessary to analyze the impact of posted speed limit on vehicle speed for both daytime and nighttime. Previous literature determined that drivers may drive at an unsafe speed during nighttime at high levels of retroreflectivity. The results of this study could not confirm this statement as data from this study suggests that for curves with pavement edgeline marking retroreflectivity greater than 90 mcd/m2/lx, the effects of retroreflectivity on speed was determined to be minimal. This is based on the finding that the daytime and nighttime speeda were basically the same as the daytime and nighttime speed difference was both statistically and practically insignificant.
509

Design of Transmission Systems for the Manpower-drive Vehicles

Hong, Jhou-nan 27 August 2004 (has links)
¡@¡@The transmission system of manpower-drive vehicles always plays an important role in promotion of riding performance and enjoyment. The purpose of this research is to develop a systematic methodology for the design of the transmission system of the manpower-drive vehicles. First, analyzing the patents of manpower-drive vehicles. Drawing the function structure of the transmission and concluding the basic characteristic. Second, getting several innovative ideas of transmission systems by systematic methodology and comparing with products in patents. Third, according to the requirement charts to design steering systems and frames. Fourth, all design concept variant can be created by using morphological chart method. Several design concepts can be created for new manpower-drive vehicles. Finally, using computer software to assist drawing the models and manufacturing the models. And to establish a simple systematic procedure.
510

A Study of Marketing Strategy of Native MPV

Chen, Ching-lung 24 July 2006 (has links)
¡@¡@Automobles are those highest price goods beside houses. They are a symbol of status and wealth in the past, but nowdays, almost every family can afford them. An automoble is more than a tool of travaling, but also an attribute of life style and values. Therefore, the decision factors of buying an automoble are more complicated, and the demands of consumers are more and more diversificated. For these reasons, automoble manufacturers have to develop more varied types of automobiles to fit market trends and consumer needs. ¡@¡@To conclude the trend of Taiwan automobile sales, RV(Recreation Vehicle) is increasing rapidly for the recent years because of the favor of consumers. The sales of SU(Space Utility) is about 55%, and MPV(Multi-Purpose Vehicle) is the best saler type, so MPV is one of the trand of Taiwan automobile market. ¡@¡@The beginning of Taiwan MPV history is Mazda introduced Premacy at April 2001, an obviously increasing period was after the introduce of Mitsubishi Savrin at September 2001, till September 2004, Toyota Wish introduced, the MPV segment was getting into maturity. In 2005, Mazda, Mitsubishi and Toyota contained more than 90% sales of Taiwan MPV, so the centralization and average sales of MPV is more than other segments. ¡@¡@To analize the marketing strategies of main MPVs, this research choosed the owners of Mazda Premacy, Mazda 5(which is the next type of Premacy), Mitsubishi Savrin, Mitsubishi Inspire(which is the second brand name of Savrin) and Toyota Wish to study about ¡§present car and previous car¡¨, ¡§important factors of buying¡¨, ¡§satisfication level of present car¡¨ and ¡§personal information¡¨ by questionnaires. The investigation was during April 22 to May 7 2006, and received 63 complete questionnaires. ¡@¡@According to the research, the owner of MPV is 76.2% for male, average 34.9 years old, 57.1% for colledge or more, 66.7% for marriaged and have kids, 49.2% for two generations family, average 4.4 persons per family.They are 54.0% by car-loans, 47.6% consulting their spouses, 50.8% replace-buy, because 30.2% for Ex-car was too old to use, mainly information was from magazines, and prefer allowance promotions(39.7%). They think highly of ¡§safety¡¨, ¡§exterior¡¨ and ¡§public praise¡¨ when buying a car. ¡@¡@Among main MPVs, Premacy has no superior items, but service inferior items, Mazda 5 has performance superior items, but service inferior items, Savrin has service superior items, but economy inferior items, Inspire has service superior items, but economy inferior items, Wish has service and funcation superior items, but economy and performance inferior item. ¡@¡@In the end, this research use IPA(Importancd-Performance Analysis) for a tool to analysis and suggest the future strategic actions, such as Premacy is suggested to improve ¡§after-sales service¡¨, ¡§brand image¡¨, ¡§variability of seats¡¨ and ¡§durability¡¨, Mazda 5 is suggested to improve ¡§variability of seats¡¨, Savrin 2.0 is suggested to improve ¡§discount¡¨, ¡§price¡¨ and ¡§breaks¡¨, Savrin 2.4 is suggested to improve ¡§discount¡¨, Inspire 2.0 is suggested to improve ¡§breaks¡¨, Inspire 2.4 is suggested to improve ¡§breaks¡¨ and ¡§saleman service¡¨, and Wish is suggested to improve ¡§assembling quality¡¨.

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