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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.
11

Design and development of an autonomous navigation system for an omni-directional four-wheeled mobile robot

Ginzburg, Sasha 01 January 2012 (has links)
A navigation system developed for an omni-directional wheeled mobile robot, called the Omnibot, is presented. This system is developed to enable the Omnibot to autonomously navigate, in a collision-free manner, along predefined paths in indoor structured office or factory-like environments. The navigation system is composed of four integrated subsystems: localization, path- following, velocity control, and obstacle detection. The path-following subsystem is responsible for driving the Omnibot along a given path based on feedback about its location relative to its environment. A localization system that uses a combination of odometry and a novel indoor GPS-like system provides the necessary estimates of the Omnibot's position and orientation (i.e., pose). Using the pose updates from the localization subsystem, the path-following subsystem is able to compute motion commands to drive the Omnibot along the path. Execution of these motion commands is performed by the velocity control subsystem, which uses feedback control to regulate the angular velocities of the motors driving the Omnibot's wheels to produce the required motion of the robot. To ensure collision-free navigation, the Omnibot is equipped with an array of infrared distance sensors for detecting obstacles around its perimeter. Interaction between a human operator and the Omnibot is facilitated with a user-control interface running on a remote workstation. The interface allows the operator to visualize the Omnibot's location within a 3D model of its indoor workspace and provides a means to input commands. Testing of the developed system is performed, and the results confirm its e effectiveness at enabling the Omnibot to perform collision-free autonomous navigation in an indoor structured environment. / UOIT
12

Improvement of Residual Vibrations for Intermittent Positioning Tables

Lin, Cheng-feng 04 September 2004 (has links)
Recently, many industries pursue the goal of automatic high-speed assembly and manufacturing. So how to meet the requirement of high-precision and high-speed automatic assembly equipment is an important issue. In automatic assembly equipment, the inappropriate acceleration or deceleration motion will cause unsuitable inertia force and vibration to the positioning table. In order to reach the high production efficiency level, the problems of shortage of motor power, poor positioning accuracy, residual vibration, and noise shall be analyzed and solved. In previous researches, the researchers all devote to study acceleration and deceleration based on symmetrical time chart. In this paper, we change the accelerating and decelerating phase to reduce inertia force and decrease residual vibration of point-to-point motion. The system model is built to simulate dynamic response of the system. Through the results of simulation and experiment, we will discover the relations between the properties of motion and residual vibration about the high-speed positioning tables. It is expected to improve residual vibrations and design motion profiles according to those effective transient response control charts.
13

Dynamometer emulation of dynamic mechanical loads for testing and commissioning of AC motor drives

Hewson, Chris R. January 1999 (has links)
No description available.
14

Ultra precision visual servo control of micro objects

Kim, Jung Hyun. January 2007 (has links)
Thesis (Ph. D.)--Ohio State University, 2007. / Full text release at OhioLINK's ETD Center delayed at author's request
15

Interactive Animation of Dynamic Manipulation

Abe, Yeuhi, Popovic, Jovan 28 February 2006 (has links)
Lifelike animation of manipulation must account for the dynamicinteraction between animated characters, objects, and their environment. Failing to do so would ignore the often significant effects objectshave on the motion of the character. For example, lifting a heavy objectwould appear identical to lifting a light one. Physical simulationhandles such interaction correctly, with a principled approach thatadapts easily to different circumstances, changing environments, andunexpected disturbances. Our work shows how to control lifelike animatedcharacters so that they accomplish manipulation tasks within aninteractive physical simulation. Our new multi-task control algorithmsimplifies descriptions of manipulation by supporting prioritized goalsin both the joint space of the character and the task-space of theobject. The end result is a versatile algorithm that incorporatesrealistic force limits and recorded motion postures to portray lifelikemanipulation automatically.
16

Orbital Rendezvous and Spacecraft Loitering in the Earth-Moon System

Fouad S Khoury (9368969) 16 December 2020 (has links)
<div>To meet the challenges posed by future space exploration activities, relative satellite motion techniques and capabilities require development to incorporate dynamically complex regimes. ?Specific relative motion applications including orbital rendezvous and spacecraft loitering will play a significant role in NASA's Gateway and Artemis missions which aim to land the ?first woman and next man on the Moon by 2024. In this investigation, relative motion in the restricted 3-body problem is formulated, validated, and tested in a rotating local-vertical-local-horizontal (LVLH)</div><div>frame situated at a target spacecraft and followed by a chaser. Two formulations of the restricted 3-body problem are considered, namely the Circular Restricted 3-Body</div><div>Problem (CR3BP) and the Elliptical Restricted 3-Body Problem (ER3BP). Comparisons between the relative dynamical models in the CR3BP and ER3BP, respectively,</div><div>and other standard relative motion sets of equations such as the Euler-Hill (HCW) model and the Linear Equations of Relative Motion (LERM) are accomplished to identify limitations and inaccuracies pertaining to the in orbits that exist in the CR3BP and ER3BP, respectively. Additionally, the relative motion equations are linearized to develop computational tools for solutions to the rendezvous and space loitering problems in the Earth-Moon system.</div>
17

Comparative Biomechanical Effectiveness of Over-the-Counter Devices for Individuals With a Flexible Flatfoot Secondary to Forefoot Varus

Hurd, Wendy J., Kavros, Steven J., Kaufman, Kenton R. 01 November 2010 (has links)
OBJECTIVES:: Evaluate effects of a new off-the-shelf insert on frontal plane foot biomechanics and compare effectiveness of the new and an existing off-the-shelf insert and a motion-control shoe in neutralizing frontal plane foot biomechanics. Design: Descriptive. Setting: Biomechanics laboratory. Participants: Fifteen uninjured subjects with a flexible flatfoot secondary to forefoot varus. Assessment of risk factors: Three-dimensional kinematic and kinetic data were collected as subjects walked and jogged at their self-selected speed while wearing a motion-control running shoe, the shoe with a new off-the-shelf insert, and the shoe with an existing off-the-shelf insert. Main outcome measures: Frontal plane kinematics and rearfoot kinetics were evaluated during stance. Statistical analysis was performed using a repeated measures analysis of variance and Student-Newman-Keuls post hoc tests (α ≤ 0.05). Results: The new insert and motion-control shoe placed the forefoot in a less-everted position than the existing off-the-shelf insert during walking. There were no differences in forefoot kinematics during jogging, nor were there differences in rearfoot motion during walking or jogging. The rearfoot eversion moment was significantly lower with the new off-the-shelf insert compared with the motion-control shoe and the existing insert during walking and jogging. Conclusions: A new off-the-shelf device is available that promotes more neutral frontal plane biomechanics, thus providing a theoretical rationale for using this device for injury prevention and treatment. The comparative biomechanical effectiveness of a motion-control shoe and the orthotic inserts may assist health care professionals in selecting a device to correct the flatfoot structure.
18

Efficient Motion Planning and Control for Underwater Gliders

Mahmoudian, Nina 15 October 2009 (has links)
Underwater gliders are highly efficient, winged autonomous underwater vehicles that propel themselves by modifying their buoyancy and their center of mass. The center of mass is controlled by a set of servo-actuators which move one or more internal masses relative to the vehicle's frame. Underwater gliders are so efficient because they spend most of their time in stable, steady motion, expending control energy only when changing their equilibrium state. Motion control thus reduces to varying the parameters (buoyancy and center of mass) that affect the state of steady motion. These parameters are conventionally controlled through feedback, in response to measured errors in the state of motion, but one may also incorporate a feedforward component to speed convergence and improve performance. In this dissertation, first an approximate analytical expression for steady turning motion is derived by applying regular perturbation theory to a realistic vehicle model to develop a better understanding of underwater glider maneuverability, particularly with regard to turning motions. The analytical result, though approximate, is quite valuable because it gives better insight into the effect of parameters on vehicle motion and stability. Using these steady turn solutions, including the special case of wings level glides, one may construct feasible paths for the gliders to follow. Because the turning motion results are only approximate, however, and to compensate for model and environmental uncertainty, one must incorporate feedback to ensure convergent path following. This dissertation describes the development and numerical implementation of a feedforward/feedback motion control system intended to enhance locomotive efficiency by reducing the energy expended for guidance and control. It also presents analysis of the designed control system using slowly varying systems theory. The results provide (conservative) bounds on the rate at which the reference command (the desired state of motion) may be varied while still guaranteeing stability of the closed-loop system. Since the motion control system more effectively achieves and maintains steady motions, it is intrinsically efficient. The proposed control system enables speed, flight path angle, and turn rate, providing a mechanism for path following. The next step is to implement a guidance strategy, together with a path planning strategy, and one which continues to exploit the natural efficiency of this class of vehicle. The structure of the approximate solution for steady turning motion is such that, to first order in turn rate, the glider's horizontal component of motion matches that of "Dubins' car," a kinematic car with bounded turn rates. Dubins car is a classic example in the study of time-optimal control for mobile robots. For an underwater glider, one can relate time optimality to energy optimality. Specifically, for an underwater glider travelling at a constant speed and maximum flight efficiency (i.e., maximum lift-to-drag ratio), minimum time paths are minimum energy paths. Hence, energy-efficient paths can be obtained by generating sequences of steady wings-level and turning motions. These efficient paths can, in turn, be followed using the motion control system developed in this work. / Ph. D.
19

Motion Control Theory Needed in the Implementation of Practical Robotic Systems

Mentz, James 04 May 2000 (has links)
Two areas of expertise required in the production of industrial and commercial robotics are motor control and obstacle navigation algorithms. This is especially true in the field of autonomous robotic vehicles, and this application will be the focus of this work. This work is divided into two parts. Part I describes the motor types and feedback devices available and the appropriate choice for a given robotics application. This is followed by a description of the control strategies available and appropriate for a variety of situations. Part II describes the vision hardware and navigation software necessary for an autonomous robotic vehicle. The conclusion discusses how the two parts are coming together in the emerging field of electric smart car technology. The content is aimed at the robotic vehicle designer. Both parts present a contribution to the field but also survey the required background material for a researcher to enter into development. The material has been made succinct and graphical wherever appropriate. / Master of Science
20

Industrial robot motion control for joint tracking in laser welding

Gao, Jiaming January 2016 (has links)
Laser welding is used in modern industrial production due to its high welding speed and good welding performance comparing to more traditional arc welding. To improve the flex-ibility, robots can be used to mount the laser tool. However, laser welding has a high require-ment for the accuracy in positioning the laser tool. There are three main related variables which affect the laser welding accuracy: robot path accuracy, workpiece geometry and fixture repeatability. Thus, joint tracking is very important for laser welding to achieve high quality welds. There are many joint tracking systems which were proposed in recent years. After receiv-ing the joint information, a control system is necessary to control the robot motion in real-time. The open control system for the industrial robot is one trend for the future. A lot of methods and systems are proposed to control the robot motion. Some systems can achieve a high accuracy in the experiments. However, it is still hard to apply them in practical indus-trial production. Thus more commercial solutions appear to overcome the robot motion problem nowadays. They are very useful to realize practical applications. ABB EGM path correction module, a new function of Robotware, is one of the com-mercial solutions for robot motion control in real time. In the experiments presented in this work, a computer is used to simulate a sensor to create a path correction signal. To test its feasibility for the laser welding application, many experiments are conducted. One was to test the robot path repeatability when there is no correction message sent to the robot. Another was to test the level of accuracy EGM can achieve during the correction process. Different types of paths and three different speeds were separately carried out. The results showed that it is possible to use the EGM in the laser welding application. In the EGM feasibility test, there exists deviation in the z-direction. Since these deviations are less than 0.2mm, it will have a minor influence the laser welding performance, implying that the EGM path correction can be applied in practical production.

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