241 research outputs found
4° Rapport de M. Luis Sentis Anfruns
No full text4° Rapport de M. Luis Sentis Anfruns. In: Revue internationale de droit comparé. Vol. 5 N°2, Avril-juin 1953. pp. 344-358
4° Rapport de M. Luis Sentis Anfruns
No full text4° Rapport de M. Luis Sentis Anfruns. In: Revue internationale de droit comparé. Vol. 5 N°2, Avril-juin 1953. pp. 344-358
Comparações entre os conjuntos de soluções de Carathéodory e de Sentis
No full textNo presente trabalho são estudadas as soluções generalizadas de Carathéodory e de Sentis para equações diferenciais descontínuas. Dessa forma, são estudadas relações entre os conjuntos de soluções de Carathéodory e de Sentis. A partir de resultados da literatura, são estabelecidos aqui resultados análogos para relações entre as soluções de Carathéodory e de Sentis. Assim, estabelecendo analogias com resultados da literatura, são obtidas aqui comparações entre os conjuntos de soluções de Carathéodory e de Sentis
Design and System Integration of a Compliant Mobile Base APPROVED BY SUPERVISING COMMITTEE:
No full textAshish DeshpandeDedicated to my brothers and my parents – I would never have made it this far without you. Acknowledgments I wish to thank numerous people who have made this work possible, including my main adviser Dr. Luis Sentis for overseeing the entire project, and former colleague Somudro Gupta (’11) for his large work on this project from 2010 to 2011, especially for Trikey Versions 1 and 3. I must further thank Frank Lima, Matt Gonzalez, Josh Petersen, Nick Paine, Sehoon Oh, Vansi Vallabhaneni, Emily Chen, Alan Kwok, and Kwan Suk Kim for aiding in various technical parts of the overall “Dreamer ” project. I also received helpful feedback and relevant knowledge from Dr. Ashish Desphande, the second reviewer of my thesis, and also from courses taught by Dr. Kristin Wood, Dr. Rick Neptune, and Dr. Glenn Masada. I thank the students and Lonny Stern at the Skillpoint Alliance in Austin, Texas, for initiating this project idea and Meka Robotics in San Francisco, California, for assistance in its implementation. I thank my sources of funding for graduate study that have greatl
Manipulation
No full textI would like to thank my advisor, Luis Sentis, for his support and guidance. His passion for robotics drove me to pursue the research described in this thesis. I also thank Benito Fernández for mentoring and working with me throughout my time at UT, and for serving as my second reader. My primary collaborators on the Trikey project have been Pius Wong and Frank Lima, and I am grateful to them for their efforts and their company. I must also acknowledge Nick Paine and Josh Petersen, who have contributed significantly to bringing the base to where it is today, and who have answered many of my hardware and software questions. My other HCRL labmates, including Matt Gonzales, Sehoon Oh, Mike Slovich, and Chris Slaughter have all also helped out in one way or another. I thank Lonny Stern for organizing RoboTech Velocity Prep, and the Del Valle High School students who participated in the program and helped build and name the first prototype of Trikey. I still think the name should have been ”Omnilicious,” but majority rules. I acknowledge Meka Robotics for building Trikey’s electronics, and I thank everyone who helped host Luis and I during our visit. Robby Kelbley and Benjamin Valenti, especially, have been incredibly patient and competent with debugging our software and hardware issues. Finally, I am grateful to all of my classmates and friends at UT who have enriched my experience here, and to my parents and sister for their love and support. v Mechatronics of Holonomic Mobile Base for Complian
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Adaptive compliance shaping with human impedance estimation
No full textRobotics has been a promising and popular research area for the past few decades. Among various applications of robotic, in many cases, human are involved in different manners. Therefore, as an important sub research area of robotics, human robot interaction has drawn decent attention recently. It has been deeply and widely studied. For human robot interaction, human play an important role. Undoubtedly, the more we know about human, the easier we can do human robot interaction and the better performance we can achieve in human robot interaction. One fascinating research topic of human robot interaction would be human in exoskeleton, where human play a key role in the mechanical design of exoskeleton as well as the control strategy design of exoskeleton.
Among all those applications, the augmentation exoskeleton is especially interesting due to its ability to amplify human. As mentioned previously, human properties are important for the design of exoskeleton. Unfortunately, despite many inspiring and deep studies about human properties and various proposed human models, human remains to be a complicated system that is hard to predict and model. Furthermore, human is a dynamic system whose parameters keep changing with time, bringing more challenges. As we all know, limited understanding of the control plant will limit the performance of the controller and bring difficulties in the design of a controller. In fact, the performance of many existed controller for augmentation exoskeleton is limited by using conservative values of human property parameters. A straightforward way to solve this problem is to estimate human properties online. Under this circumstance, the main challenges are to develop a control strategy, whose performance can be exploited using the estimation of human properties and a reliable method to online estimate human properties. This thesis mainly presents an adaptive compliance shaping control strategy with human impedance estimation and a brief review of a newly proposed complex stiffness model of human.Mechanical Engineerin
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A framework for whole body augmentative exoskeleton control
No full textIn this thesis, I present two primary contributions towards more capable augmentative exoskeleton systems including (1) the design and implementation of a robot-agnostic, high-level control infrastructure for better real-time performance and (2) a cohesive framework for whole-body augmentative exoskeleton control in a high-degree-of-freedom (dof) exoskeleton system. Both contributions were part of a larger project, in which our team designed and built a form-fitting lower-body augmentative exoskeleton with the objective to enhance a pilot's load carrying ability without sacrificing speed or maneuverability. Modern high-level control systems require excellent timing and low communication latencies to ensure stable, robust, and high-performance multijoint control. Towards this end, I designed and implemented a nodelet-based high-level controller wrapper that abstracts away and optimizes many of the implementation details involved in building such a control infrastructure. My first iteration of improvements used ROS's (Robot Operating System) intraprocess communication protocol along with proper integration of our RT-preempt kernel to ensure reliable, low-jitter timing performance and low-latency communication. I then helped to design infrastructure improvements that further reduced round-trip times via full system synchronization. My high-level control infrastructure has enabled significant advances for a variety of projects in the Human-Centered Robotics Lab (HCRL), including the development of a controller for an augmentative exoskeleton and dynamic walking using the lab's point-foot bipedal robot, Mercury. The second major contribution in this thesis is an algorithm that I developed for whole-body augmentative exoskeleton control. It uses a model of the exoskeleton to cancel static, gravitational loads, and measured cuff forces to attenuate human-exo interaction forces, including inertial loads and those caused by disturbances from the environment. The key contribution of this control scheme relative to other exoskeleton transparency controllers is how this algorithm (1) handles contact switching given the corresponding discrete changes in the dynamics and (2) routes the needed reaction forces to the ground given the underactuated, floating-base dynamics with contact constraints. I formulate a Quadratic Programming (QP) optimization problem to solve for permissible reaction forces and actuator torques that come as close as possible to providing the desired dynamic attenuation behavior of the controller while also satisfying wrench-cone constraints for each of the exoskeleton's contacts. A relaxation variable, penalized in the cost function, ensures the solver can always find a feasible solution, and cost function weights penalizing contact point accelerations and reaction force magnitudes are smoothly interpolated to ensure continuous torque commands as the system switches between two discrete sets of contactsMechanical Engineerin
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Mobile Application and Server Management System for Autonomous Robot Deliveries
No full textThe Short to Medium Range Autonomous Delivery System (SMADS) is an end-to-end
platform to connect UT Austin-affiliated customers to autonomous delivery robots on UT
Austin campus. The SMADS system integrates several subsystems, including two iOS
mobile applications, a two-server communication structure and a robot autonomy stack with
localization and navigation algorithms, into a global system architecture. This thesis describes
the steps taken to develop and integrate the customer-facing iOS App, Texas Bolter, the
Manager App and the two-server system comprised of the App Server and the robot servers.
Furthermore, this work presents the results of the week long deployment of the SMADS
system, delivering free lemonades to specific UT Austin buildings. The recorded issues are
discussed and future work is presented. The SMADS system successfully completed 27 trips
on varying robot platforms to various locations, demonstrating the robot-agnostic nature of
the app and server management system — a useful feature for future human-robot interaction
research.Aerospace Engineerin
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Short to medium autonomous delivery system (SMADS)
No full textThis thesis presents the software stack that is the Short to Medium Autonomous Delivery System (SMADS), a framework developed as a team effort that enables autonomous deliveries by robots on the University of Texas at Austin campus. The goal of this work is to achieve long-term robot autonomy with the particular use case of last mile delivery, all while integrating a novel, highly modular, open-source software architecture to support a heterogeneous fleet of robots and a mobile application to facilitate customer interaction. The contributions detailed in this thesis include development of such a framework, integration of individual development work with those of other team members, and results from deployment of the system over a five-day period.Mechanical Engineerin
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Dynamically consistent trajectory planners and human-aware controllers for human-centered robots
No full textFor robots to successfully be deployed as human assistants in a variety of applications, it is critical that the robots' controllers and planners are designed with the considerations of both the robots' and humans' abilities and needs. In space applications, where energy is a finite and limiting resource in missions, it may prove necessary to exploit the energy storing-component of series elastic actuators to meet the efficiency needs, while operating in harsh and varied environments. In human-occupied workplaces, robots can only provide the needed support to humans if the robot controller can properly reason about and react to humans' requirements and capabilities. This thesis presents and assesses strategies to address these kinds of scenarios. In Chapter 2, we present a trajectory optimization scheme based on sequential linear programming to leverage the energy-storing capabilities of series elastic actuators for high-performance tasks. We discuss the current limitations in optimization strategies for series elastic actuated robots. One of the difficulties of this planning problem is respecting all relevant, low-level actuator constraints and handling system nonlinearities in a computationally efficient manner. Our simulation and hardware experiments demonstrate the leveraging of compliance for faster motions as compared to those that are achieved by the compliant systems' rigid counterparts. Chapter 3 addresses the need for reactive synthesis to be employed to automatically devise human-aware robot controllers for scenarios in which humans and robots continuously collaborate. Through this approach, it is possible to synthesize high-level control policies that are formally guaranteed to meet human requirements. We present a case study in which a robot seeks to deliver work to a human so that the human is productive, but not stressed by her work backlog. We demonstrate the achievement of a human productivity-informed controller using a mobile manipulator robot that picks up and delivers work based on work backlog. One of the challenges of this problem is devising human productivity models that are practical and accurate. We explore a toy scenario in the hope that this research will introduce methodologies that can be generalized for more practical casesMechanical Engineerin
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