<p> Ground teleoperation of a satellite servicing spacecraft is a challenging task for a human operator, especially when there is significant communications delay between the control station and spacecraft. On-orbit operations are further complicated by a communications time delay between the ground and spacecraft. Operator performance can be improved with the use of a graphical simulation of the robot. By displaying the robot's commanded position, graphical simulation can also mitigate some effects of time delay. This work implemented a visualization tool and commanded display to assist operation of a remote dexterous manipulator. A Fitts' Law experiment was designed to determine the effectiveness of the commanded display in reducing the impact of time delay. The experiment was conducted with a six degree of freedom manipulator over a range of time delays, from 0.0 to 6.0 seconds. The experimental results were analyzed to assess the reduction of task completion time and operator workload.</p>

<p>Cables are used in various fields like construction, sports, communication, and transportation. Two important fields where cables are used for this research are transportation and high-voltage power lines. In the field of transportation, cables are used in cable-riding systems like cable cars, tramways, and gondola lifts. Vibration is induced in these systems. These vibrations are undesirable. </p><p> High-voltage power line cables are important part of our lives. Inspection of these power lines is necessary to eliminate the risk of power outages. Earlier power lines were inspected by skilled humans by crawling along the power lines. This inspection task was replaced by cable riding inspection robots to eliminate the risk to human life. </p><p> This research explains various inspection robots and problems in these types of cable-riding systems. In this research, to determine the vibrations in the cable due to riding load, a new simple cable-mass system was developed. This new cable-mass system makes it easy to develop a control system to reduce the cable vibrations. </p><p> To inspect the power lines, HiBot developed an inspection robot called Expliner that travels along the live power lines. For uninterrupted inspection operation, Expliner traverses obstacles on the power lines with its intelligent acrobatic mode. In this mode, Expliner is subjected to rocking oscillation. This rocking oscillation is also induced in the cables cars. This rocking is undesirable and is unsafe. </p><p> This research introduces a method to reduce rocking in cable-riding systems. This method, called input shaping, is used to run simulations for Expliner traveling along curved cables. This research develops an input shaper to reduce rocking in cable-riding robots like Expliner. </p>

<p> Humans generally have difficulty performing precision tasks with their unsupported hands. To compensate for this difficulty, people often seek to support or rest their hand and arm on a fixed surface. However, when the precision task needs to be performed over a workspace larger than what can be reached from a fixed position, a fixed support is no longer useful. </p><p> This dissertation describes the development of the Active Handrest, a device that expands its user's dexterous workspace by providing ergonomic support and precise repositioning motions over a large workspace. The prototype Active Handrest is a planar computer-controlled support for the user's hand and arm. The device can be controlled through force input from the user, position input from a grasped tool, or a combination of inputs. The control algorithm of the Active Handrest converts the input(s) into device motions through admittance control where the device's desired velocity is calculated proportionally to the input force or its equivalent. </p><p> A robotic 2-axis admittance device was constructed as the initial Planar Active Handrest, or PAHR, prototype. Experiments were conducted to optimize the device's control input strategies. Large workspace shape tracing experiments were used to compare the PAHR to unsupported, fixed support, and passive moveable support conditions. The Active Handrest was found to reduce task error and provide better speed-accuracy performance. </p><p> Next, virtual fixture strategies were explored for the device. From the options considered, a virtual spring fixture strategy was chosen based on its effectiveness. An experiment was conducted to compare the PAHR with its virtual fixture strategy to traditional virtual fixture techniques for a grasped stylus. Virtual fixtures implemented on the Active Handrest were found to be as effective as fixtures implemented on a grasped tool. </p><p> Finally, a higher degree-of-freedom Enhanced Planar Active Handrest, or E-PAHR, was constructed to provide support for large workspace precision tasks while more closely following the planar motions of the human arm. Experiments were conducted to investigate appropriate control strategies and device utility. The E-PAHR was found to provide a skill level equal to that of the PAHR with reduced user force input and lower perceived exertion.</p>

<p> Simulation can be an invaluable tool, particularly in fields such as robotics where physical experiments can be extremely expensive, time consuming, and even dangerous. However, the value of a simulator is directly related to its ability to accurately and reliably model physical phenomena such as intermittent contact. In virtually all multibody simulators available today, the standard methods of contact identification and response treat the free space between pairs of bodies as a convex set, when it is in fact non-convex. To reconcile, simulators typically use very small time steps and employ numerous <i> ad hoc</i> corrections, many of which have become commonplace and include allowing interpenetration to occur, arbitrarily limiting response forces, misrepresenting body geometries, and "freezing" bodies with relatively low velocities. Indeed, a vast body of literature exists addressing the many symptoms of dynamic instability due to poor contact determination. </p><p> I herein present a formulation of non-penetration constraints between pairs of bodies which accounts for all possible combinations of active contact. This is the first formulation that accurately models the body geometries near points of <i>potential</i> contact, simultaneously preventing interpenetration while allowing bodies to traverse accurately through the surrounding free space. Unlike the standard approach, this method does not need to guess at which contacts to enforce. This new formulation is easy to incorporate into existing simulation methods, improves accuracy by many orders of magnitude, and is stable for even large time steps. </p><p> Additionally, I present the RPI-MATLAB-Simulator (RPIsim), an open source tool for efficient research and practical teaching in multibody dynamics. RPIsim is designed to be easy to use and easily extended. Students being introduced to dynamics for the first time have no problem creating and running simulations, even with a limited programming background. Researchers can utilize the existing code base to support work on specific areas since it is easy to replace or extend individual modules of the simulator.</p>

<p> Spacesuits utilized a rubberized layer of material to contain a pressurized atmosphere to facilitate respiration and maintain the physiologic functions of the astronaut residing within. However, the elasticity of the material makes it resistant to deformation increasing the amount of work required during movement. This becomes particularly fatiguing for the muscle groups controlling the motion of the hands and fingers. To mitigate this a robotic system was proposed and developed. The system built upon previous concepts and prototypes discovered through research efforts. It utilized electric motors to pull the index, ring, and middle fingers of the right hand closed, ideally overcoming the resistive force posed by the pressurized elastic material. The effect of the system was determined by comparing qualitative and quantitative data obtained during activities conducted with and without it within a glove box. It was found that the system was able to offload some of this elastic force though several characteristics of the design limited the full potential this device offered. None the less, the project was met with success and provides a solid platform for continued research and development.</p>

<p> The <i>Cool Robot</i> is a solar powered autonomous robot designed to support summertime science campaigns in the Polar Regions. While the overall design was proven in a previous deployment to Summit Greenland, it lacked the robustness for longer campaigns, and the ergonomics of accessing the interior of the robot were arduous and time consuming. The objectives of this thesis were to 1) redesign the solar panel system for improved performance in wind and rough terrain and for easier assembly and access to inside of the robot chassis, 2) update the power system controls and electronics for reliable and robust operation, 3) update all electrical systems using common, off-the-shelf components, 4) establish a common code base and communication protocol used by other similarly designed robots, 5) provide permanent data logging capability to evaluate mobility and the power system performance, and 6) develop and implement a sensor-based framework for detecting and avoiding dangerous levels of tilt which could result in roll-over. All of these objectives aim to increase the performance reliability of the <i>Cool Robot</i>. The data logging capability allows for collecting data to evaluate performance of the new power system. The reliability of the <i>Cool Robot</i> will be tested during a summer mission to Summit Greenland.</p>

We present a visual servoing system for an amphibious legged robot. That is, a monocular-vision based servoing mechanism that enables the robot to track and follow a target both underwater and on the ground. We used three different tracking algorithms to track and localize the target in the image, with color being the tracked feature. Tracking is performed based on the object's color, color distribution and color distribution with a probabilistic kernel. Output from the tracker is channeled to a proportional-integral-derivative controller, which generates steering commands for the robot controller. The robot controller in turn takes the steering commands and generates motor commands for the six legs of the robot. A large class of significant applications can be addressed by allowing such a robot to follow a diver or some other moving target. The system has been evaluated in the open water and under natural lighting conditions, and has successfully performed tracking and following of a wide variety of target objects.

This thesis presents a statistical learning framework for inferring geometric structures from images. Specifically, the proposed framework computes dense range maps of location sin the environment using only intensity images and very limited amount of range data as an input. This is achieved by integrating and analyzing the statistical relationships between the visual data and the available depth on terms of small patches. The scientific issue is to represent this correlation such that it can be used to recover range data where missing. Markov Random Fields are used as a model to capture the local statistics of the intensity and range. / Experiments on real-world data are conducted under different configurations to demonstrate the feasibility of the method. In particular, our application is in mobile robotics, where inferring the 3D layout of indoor environments is a critical problem for achieving exploration and navigation tasks. The modeling of a large-scale environment involves the acquisition of a huge amount of range data to extract the geometry of the scene, and is often performed using sophisticated but costly hardware solutions. This task is physically demanding and time consuming for many real systems. By using the proposed framework, it is demonstrated that we can learn the geometric characteristics of the environment from the incomplete sensory data to build a 3D model of it. / The contributions of this thesis are mainly three: First, it demonstrates the viability of the use of very limited range data together with intensity to recover complete dense range maps. Second, it presents a complete framework for building a 3D model of an indoor environment using a mobile robot. And third, it analyses and outlines the advantages and limitations encountered when dealing with large indoor environments. / An additional contribution is the use of the method we propose for range estimation to an alternative problem: color correction and augmentation with the specific application to underwater images.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-05, Section: B, page: 3085. Adviser: Steven M. LaValle. Includes bibliographical references (leaves 125-136) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 68-11, Section: B, page: 7445. Adviser: Steven M. LaValle. Includes bibliographical references (leaves 134-145) Available on microfilm from Pro Quest Information and Learning.