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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

Development of Vision Payload for the Nanosatellite VELOX-I

Kumar Kadarla, Vineel January 2012 (has links)
In the recent years, CubeSat’s are evolving from purely educational tools to a standard platform for technology demonstration and miniaturized scientific instrumentation. The use of COTS (Commercial-Off-The-Shelf) components aided the ongoing miniaturiza- tion of several technologies and demonstrated successfully. Furthermore advantages in this small satellite approach are due to their lesser development times and smaller sizes suitable for multiple CubeSat launches on a single launcher into their respective desig- nated orbits which is cost effective for Universities. These architectures not only promise the combination of both temporal resolution of GEO missions with spatial resolution of LEO missions, but also breaks the trade off in conventional Earth observation satel- lite designs. A thorough implementation of the firmware of vision payload of the Nano Satellite VELOX-I for the Earth observation and remote sensing purposes, in the near future with high scientific payoff is presented here. In course of implementation various case studies have been learned, current date CCSDS recommendations for image com- pression have been considered. Effect of key components such as power, memory and data transmission capability for small satellite remote sensing applications are discussed. Implementation of the core firmware of the payload and serial interface development in Java on Linux platform of Payload Processing Unit shall be able to inherit into the future VELOX missions. / <p>Validerat; 20121128 (global_studentproject_submitter)</p>
2

Ancillary Scientific Instrument Attachment (ASIA):  A Distributed Hitchhiker Payload Carrier

Scheid, Robert Jon 18 May 2018 (has links)
As more spacecraft reach more locations in the solar system, and with increasing residual capability of those spacecraft, an opportunity exists to improve scientific return at low cost to the satellite operator and minimal effect on its primary mission, regardless of the nature of that mission. The practicality of permanently attaching a small, mass-produced, non-deployable hitchhiker payload to modern spacecraft buses is investigated, and a case study of one such payload is presented. The Ancillary Scientific Instrument Attachment (ASIA) is a modified CubeSat bus that can be mass produced, independently tested, and delivered to spacecraft manufacturers with the design, analysis, integration, test, and software development already complete. All it requires are single-string power and data connections, and a location to mount the bus structure. The unit includes power regulation; data collection and storage; command processing; thermal control; and structural support. As many as five small scientific instruments can be included, all of which increase scientific value of the host spacecraft's primary mission without significantly interfering with that mission. Generally, ASIA would operate independently, with a minimum of interaction from the host spacecraft operations team; only routine data dumps for scientific return need be executed. Scientific data processing, distribution, and bus subsystem troubleshooting are offloaded to an independent facility. One possible scientific instrument loadout is described, designed to collect data about the space environment at any location in the solar system. Recommended forward steps for designing, testing, demonstrating, and implementing such a space-based system and its ground elements are presented. / Master of Science
3

Performance analysis of satellite payload architectures for mobile services

Wyatt-Millington, Rosemary A., Sheriff, Ray E., Hu, Yim Fun 01 1900 (has links)
Yes / This paper is concerned with the effects on the network performance of moving parts of what is considered traditionally to belong to the ground segment to on board the satellite. Initially, an overview of geostationary satellite communication systems and payload technology is presented, followed by a description of the network architecture and protocols that are the basis of the simulation models. The results obtained from this testbed are presented before concluding with a discussion of the results obtained.
4

LESSONS LEARNED AND PROCESS IMPROVEMENT FOR PAYLOAD OPERATIONS AT THE LAUNCH SITE

Catena, John, Gates, Donald, Jr., Blaney, Kermit, Jr. 10 1900 (has links)
International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada / For every space mission, there are challenges with the launch site/field operations process that are addressed too late in the development cycle. This potentially causes schedule delays, cost overruns, and adds risk to the mission success. This paper will discuss how a single interface, representing the payload at the launch site in all phases of development, will mitigate risk, and minimize or even alleviate potential problems later on. Experience has shown that a single interface between the project and the launch site allows for issues to be worked in a timely manner and bridges the gap between two diverse cultures.
5

Development of safety limits for load carriage in adults

Fergenbaum, Mitchell Alan 10 October 2007 (has links)
In society, personal load carriage systems (backpacks) are commonly used to transport loads by foot, however, they have also been implicated in causing injuries. The aim of this study was to develop a model for load carriage which could be used to determine safety limits in humans. To start, a number of experiments were conducted to determine the appropriateness of using pressure mapping technology to measure peak and mean pressures acting on humans during load carriage limits. Tests of accuracy and repeatability were performed using three common pressure mapping technologies: capacitance, piezoresistive and resistive ink. Pressure mapping was tested statically and dynamically on a human-like flat surface, as well as on human shoulder-shaped model. Error was found to be ≥ 20% on static flat and curved surfaces and it rose to 36-51% under dynamic conditions. Since pressure mapping would require significant modifications before it could be used to study human load carriage, a psychophysical approach was used instead. For this approach, an epidemiological study of pain was conducted based on 48 subjects who used multiple backpack designs to complete occupationally relevant tasks. As a result, pain trends and new methods of data analysis were identified that had potential use on human trials. In a final study, pain mapping, quantification of pain intensity, and physiological/motor testing were conducted on humans performing endurance exercise with light to heavy payloads. Results showed that all subjects were able to exercise with a 15-35 kg payload for 45 minutes and with a 50 kg payload for 30 minutes, without stopping. As well, pain was found to be highest in the anterior acromial (shoulder) region, particularly for the 50 kg payload (mean peak pain = 3.4/10). Based on these findings, two models were proposed: an assertive model and a conservative model to allow prediction of human load carriage limits for endurance exercise. / Thesis (Ph.D, Rehabilitation Science) -- Queen's University, 2007-10-06 15:33:31.933
6

Vertical Control of Unmanned Helicopter During Payload Drop

Raol, Divyarajsinh 27 February 2015 (has links)
Unmanned helicopters in recent years have gained much attention due to their potential in both civil as well as military applications. Helicopter is an inherently unstable system. As a result there is a growing need of developing a control structure that allows the helicopter to perform various applications while remaining stable throughout the flight. This thesis presents developments of a robust controller for the vertical channel of an unmanned helicopter while carrying and dropping a payload. In addition, a simulation platform is developed in Simulink that uses a nonlinear six degree of freedom helicopter model. Quantitative Feedback Theory, a frequency domain technique, is used to design a controller that meets specific performance criteria when uncertainties associated with different payload weights exist in the system. The controller performance is examined in simulation for an Xcell 60 helicopter for effective lifting and dropping of up to 10 lb payload. The performance is then compared with a traditional Proportional-Integral-Derivative controller. Further, the effect of actuator dynamics on the controller performance is also evaluated. Finally, a controller that is robust in minimizing the effect of actuator dynamics and the payload drop while keeping the helicopter stable in flight is designed.
7

Design of a Helicopter Slung Vehicle for Actuated Payload Placement

Collins, Robert James 29 April 2012 (has links)
Helicopters have been used in applications where they need to carry a slung load for years. More recently, unmanned (UAV) helicopters are being used to deliver supplies to military units on the ground in theaters of war. This thesis presents a helicopter slung vehicle used to carry the payload and furthermore, provide a means of actuation for the payload. This provides more control authority to the system and may ultimately allow a helicopter to fly higher with a longer tether. The vehicle designed in this thesis was designed for use with 100kg class helicopters, such as the Yamaha RMAX operated by the Virginia Tech Unmanned Systems Lab. Each system on the vehicle was custom designed — including the propulsion system, wall detection / localization system, and controller. Three shrouded propellers provided thruster actuation. A scanning laser range finder and inertial measurement unit (IMU) were used to provide localization. A first attempt at a linear full state feedback controller with a complementary filter was used to control the vehicle. All of the systems were tested individually for functionality. The shrouded propellers met their design goals and were capable of producing .7lbf of thrust each. The wall detection system was able to detect walls and windows reliably and with repeatability. Results from the controller however were less than ideal, as it was only able to control yaw in an oscillatory motion, most likely due to model deficiencies. A reaction wheel was used to control yaw of the vehicle with more success. / Master of Science
8

Payload Data Analyzer and Payload Data Generator System for Space Station Integration and Test

Werner, Jeffrey M. 10 1900 (has links)
International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, Nevada / To support the processing of International Space Station (ISS) Payloads, the Kennedy Space Center (KSC) had the need to develop specialized test and validation equipment to quickly identify interface problems between the payload or experiment under test and the communication and telemetry downlink systems. To meet this need, the Payload Data Analyzer (PDA) System was developed by the Data Systems Technology Division (DSTD) of NASA’s Goddard Space Flight Center (GSFC) to provide a suite of troubleshooting tools and data snapshot features allowing for diagnosis and validation of payload interfaces. The PDA System, in conjunction with the Payload Data Generator (PDG) System, allow for a full set of programmable payload validation tools which can quickly be deployed to solve crucial interface problems. This paper describes the architecture and tools built in the PDA which help facilitate Space Station Payload Processing.
9

Control of sound transmission into payload fairings using distributed vibration absorbers and Helmholtz resonators

Estève, Simon J. 28 May 2004 (has links)
A new passive treatment to reduce sound transmission into payload fairing at low frequency is investigated. This new solution is composed of optimally damped vibration absorbers (DVA) and optimally damped Helmholtz resonators (HR). A fully coupled structural-acoustic model of a composite cylinder excited by an external plane wave is developed as a first approximation of the system. A modal expansion method is used to describe the behavior of the cylindrical shell and the acoustic cavity; the noise reduction devices are modeled as surface impedances. All the elements are then fully coupled using an impedance matching method. This model is then refined using the digitized mode shapes and natural frequencies obtained from a fairing finite element model. For both models, the noise transmission mechanisms are highlighted and the noise reduction mechanisms are explained. Procedures to design the structural and acoustic absorbers based on single degree of freedom system are modified for the multi-mode framework. The optimization of the overall treatment parameters namely location, tuning frequency, and damping of each device is also investigated using genetic algorithm. Noise reduction of up to 9dB from 50Hz to 160Hz using 4% of the cylinder mass for the DVA and 5% of the cavity volume for the HR can be achieved. The robustness of the treatment performance to changes in the excitation, system and devices characteristics is also addressed. The model is validated by experiments done outdoors on a 10-foot long, 8-foot diameter composite cylinder. The excitation level reached 136dB at the cylinder surface comparable to real launch acoustic environment. With HRs representing 2% of the cylinder volume, the noise transmission from 50Hz to160Hz is reduced by 3dB and the addition of DVAs representing 6.5% of the cylinder mass enhances this performance to 4.3dB. Using the fairing model, a HR+DVA treatment is designed under flight constraints and is implemented in a real Boeing fairing. The treatment is composed of 220 HRs and 60 DVAs representing 1.1% and 2.5% of the fairing volume and mass respectively. Noise reduction of 3.2dB from 30Hz to 90Hz is obtained experimentally. As a natural extension, a new type of adaptive Helmholtz resonator is developed. A tuning law commonly used to track single frequency disturbance is newly applied to track modes driven by broadband excitation. This tuning law only requires information local to the resonator simplifying greatly its implementation in a fairing where it can adapt to shifts in acoustic natural frequencies caused by varying payload fills. A time domain model of adaptive resonators coupled to a cylinder is developed. Simulations demonstrate that multiple adaptive HRs lead to broadband noise reductions similar to the ones obtained with genetic optimization. Experiments conducted on the cylinder confirmed the ability of adaptive HRs to converge to a near optimal solution in a frequency band including multiple resonances. / Ph. D.
10

Control of Sound Transmission with Active-Passive Tiles

Goldstein, Andre L. 31 August 2006 (has links)
Nowadays, numerous applications of active sound transmission control require lightweight partitions with high transmission loss over a broad frequency range and simple control strategies. In this work an active-passive sound transmission control approach is investigated that potentially addresses these requirements. The approach involves the use of lightweight stiff panels, or tiles, attached to a radiating base structure through active-passive soft mounts and covering the structure surface. The resulting double-partition configuration was shown to have good high frequency passive isolation, but poor low frequency transmission loss due to the coupling of the tiles to the base vibration through the air gap. The low frequency transmission loss performance of the partition was increased by using the active mounts to cancel the local volume velocity of the tiles. The use of a decentralized control approach with independent single channel controllers for each tile facilitates the implementation of a multiple tile system in a large scale application. A coupled structural-acoustic model based on an impedance mobility matrix approach was formulated to investigate the potential performance of active-passive tile approach in controlling sound transmission through plates. The model was initially applied to investigate the sound transmission characteristics of a double-panel partition consisting of a single tile-plate configuration and then extended to model a partition consisting of multiple-tiles mounted on a plate. The system was shown to have significant passive performance above the mass-spring-mass resonance of the double-panel system. Both feedback and feedforward control approaches were simulated and shown to significantly increase the transmission loss of the partition by applying control forces in parallel with the mounts to reduce the tile normal velocity. A correspondent reduction in sound radiated power was obtained over a broad frequency range limited by the tile stiffness. The experimental implementation of the active-passive tile approach for the control of sound transmission through plates was also performed. Two main experimental setups were utilized in the investigations, the first consisting of a single tile mounted on a clamped plate and the other consisting of four active tiles mounted of a simply supported plate. Tile prototypes were implemented with lightweight stiff panels and integrated active-passive mounts were implemented with piezoelectric Thunder actuators. Both analog feedback and digital feedforward control schemes where designed and implemented with the objective of reducing the normal velocity of the tiles. Experimental results have demonstrated significant broad frequency range reductions in the sound transmission through the partition by active attenuation of the tile velocity. In addition, the experiments have shown that decentralized control can be successfully implemented for multiple tiles systems. The active-passive sound transmission control characteristics of the systems experimentally studied were observed to be in accordance with the analytical results. / Ph. D.

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