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ATMOSPHERIC ENTRY
Title
ATMOSPHERIC ENTRY.
Creator
Martin, Dillon A, Elgohary, Tarek, University of Central Florida
Abstract / Description
The development of atmospheric entry guidance methods is crucial to achieving the requirements for future missions to Mars; however, many missions implement a unique controller which are spacecraft specific. Here we look at the implementation of neural networks as a baseline controller that will work for a variety of different spacecraft. To accomplish this, a simulation is developed and validated with the Apollo controller. A feedforward neural network controller is then analyzed and...
Show moreThe development of atmospheric entry guidance methods is crucial to achieving the requirements for future missions to Mars; however, many missions implement a unique controller which are spacecraft specific. Here we look at the implementation of neural networks as a baseline controller that will work for a variety of different spacecraft. To accomplish this, a simulation is developed and validated with the Apollo controller. A feedforward neural network controller is then analyzed and compared to the Apollo case.
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Date Issued
2017
Identifier
CFH2000354, ucf:45874
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFH2000354
A Smart UAV Platform for Railroad Inspection
Title
A Smart UAV Platform for Railroad Inspection.
Creator
Debevec, Ryan, Elgohary, Tarek, Xu, Yunjun, Lin, Kuo-Chi, University of Central Florida
Abstract / Description
Using quadcopters for analysis of an environment has been an intriguing subject of study recently. The purpose of this work is to develop a fully autonomous UAV platform for Railroad inspection The dynamics of the quadrotor is derived using Euler's and Newton's laws and then linearized around the hover position. A PID controller is designed to control the states of the quadrotor in a manner to effectively follow a vision-based path, using the down facing camera on a Parrot Mambo quadrotor....
Show moreUsing quadcopters for analysis of an environment has been an intriguing subject of study recently. The purpose of this work is to develop a fully autonomous UAV platform for Railroad inspection The dynamics of the quadrotor is derived using Euler's and Newton's laws and then linearized around the hover position. A PID controller is designed to control the states of the quadrotor in a manner to effectively follow a vision-based path, using the down facing camera on a Parrot Mambo quadrotor. Using computer vision the distance from the position of the quadrotor to the position of the center of the path was found. Using the yaw controller to minimize this distance was found to be an adequate method of vision-based path following, by keeping the area of interest in the field of view of the camera. The downfacing camera is also simultaneously observing the path to detect defects using machine learning. This technique was able to detect simulated defects on the path with around 90% accuracy.
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Date Issued
2019
Identifier
CFE0007623, ucf:52555
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007623
Color-Ratio Based Strawberry Plant Localization and Nutrition Deficiency Detection
Title
Color-Ratio Based Strawberry Plant Localization and Nutrition Deficiency Detection.
Creator
Kong, Xiangling, Xu, Yunjun, Elgohary, Tarek, Fu, Qiushi, Wu, Dazhong, Wang, Liqiang, University of Central Florida
Abstract / Description
In recent years, precision agriculture has become popular anticipating to partially meet the needs of an ever-growing population with limited resources. Plant localization and nutrient de?ciency detection are two important tasks in precision agriculture. In this dissertation, these two tasks are studied by using a new color-ratio(C-R) index technique. Firstly, a low cost and light scene invariant approach is proposed to detect green and yellow leaves based on the color-ratio (C-R) indices. A...
Show moreIn recent years, precision agriculture has become popular anticipating to partially meet the needs of an ever-growing population with limited resources. Plant localization and nutrient de?ciency detection are two important tasks in precision agriculture. In this dissertation, these two tasks are studied by using a new color-ratio(C-R) index technique. Firstly, a low cost and light scene invariant approach is proposed to detect green and yellow leaves based on the color-ratio (C-R) indices. A plant localization approach is then developed using the relative pixel relationships of adjacent plants. Secondly, the Sobel operator and morphology techniques are applied to segment the target strawberry leaf from a ?eld image. The characterized color for a speci?c nutrient de?ciency is detected by the C-R indices. The pattern of the detected color on the leaf is then examined to determine the speci?c nutrient de?ciency. The proposed approaches are validated in a commercial strawberry farm.
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Date Issued
2019
Identifier
CFE0007666, ucf:52482
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007666
Energy-optimal Guidance of an AUV Under Flow Uncertainty and Fluid-Particle Interaction
Title
Energy-optimal Guidance of an AUV Under Flow Uncertainty and Fluid-Particle Interaction.
Creator
De Zoysa Abeysiriwardena, Demuni Singith, Das, Tuhin, Kumar, Ranganathan, Elgohary, Tarek, Behal, Aman, University of Central Florida
Abstract / Description
The work presented gives an energy-optimal solution to the guidance problem of an AUV. The presented guidance methods are for lower level control of AUV paths, facilitating existing global planning methods to be carried out comparatively more efficiently. The underlying concept is to use the energy of fluid flow fields the AUVs are navigating to extend the duration of missions. This allows gathering of comparatively more data with higher spatio-temporal resolution. The problem is formulated...
Show moreThe work presented gives an energy-optimal solution to the guidance problem of an AUV. The presented guidance methods are for lower level control of AUV paths, facilitating existing global planning methods to be carried out comparatively more efficiently. The underlying concept is to use the energy of fluid flow fields the AUVs are navigating to extend the duration of missions. This allows gathering of comparatively more data with higher spatio-temporal resolution. The problem is formulated for a generalized two dimensional uniform flow field given a fixed final time andfree end states. This allows the AUVs to navigate to certain spatial positions while maintaining the required temporal resolution of each segment of its mission. The simplistic way the problem is posed allows an analytical closed form solution of the Euler-Lagrange equations. Two dimensional thrust vectors are obtained as optimal control inputs. The control inputs are then incorporated into afeedback structure, allowing the particle to navigate in the presence of disturbance in the flow field. Further, the work also explores the influence of fluid-particle interaction on the control cost and behavior of the particle. The concept of changing the cost weights of the optimal cost formulation in situ has been introduced. Potential applications of the present concept are explored through anobstacle avoidance scenario. The optimal guidance methods are then adapted to non-uniform flow fields with quadratic and discontinuous spatial variation being the primary focus.
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Date Issued
2018
Identifier
CFE0007169, ucf:52282
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007169