Three-dimensional modeling and time-delay stability analysis for robotics docking simulation

Hardware-in-the-loop simulations of two interacting bodies are often accompanied by a time delay. The time delay, however small, may lead to instability in the hardware-in-the-loop system. The present work investigates the source of instability in a two spacecraft system model with a time-delayed contact force feedback. A generic compliance-device based contact force model is proposed with elastic, viscous, and Coulomb friction effects in three dimensions. A 3D nonlinear system model with time delay is simulated, and the effect of variations in contact force model parameters is studied. The system is then linearized about a nominal state to determine the stability regions in terms of parameters of the spring-dashpot contact force model by the pole placement method. Furthermore, the stability analysis is validated for the nonlinear system by energy observation for both the stable and unstable cases

Development of Immersive and Interactive Virtual Reality Environment for Two-Player Table Tennis

Although the history of Virtual Reality (VR) is only about half a century old, all kinds of technologies in the VR field are developing rapidly. VR is a computer generated simulation that replaces or augments the real world by various media. In a VR environment, participants have a perception of “presence”, which can be described by the sense of immersion and intuitive interaction. One of the major VR applications is in the field of sports, in which a life-like sports environment is simulated, and the body actions of players can be tracked and represented by using VR tracking and visualisation technology. In the entertainment field, exergaming that merges video game with physical exercise activities by employing tracking or even 3D display technology can be considered as a small scale VR. For the research presented in this thesis, a novel realistic real-time table tennis game combining immersive, interactive and competitive features is developed. The implemented system integrates the InterSense tracking system, SwissRanger 3D camera and a three-wall rear projection stereoscopic screen. The Intersense tracking system is based on ultrasonic and inertia sensing techniques which provide fast and accurate 6-DOF (i.e. six degrees of freedom) tracking information of four trackers. Two trackers are placed on the two players’ heads to provide the players’ viewing positions. The other two trackers are held by players as the racquets. The SwissRanger 3D camera is mounted on top of the screen to capture the player’

Development of immersive and interactive virtual reality environment for two-player table tennis

Although the history of Virtual Reality (VR) is only about half a century old, all kinds of technologies in the VR field are developing rapidly. VR is a computer generated simulation that replaces or augments the real world by various media. In a VR environment, participants have a perception of “presence”, which can be described by the sense of immersion and intuitive interaction. One of the major VR applications is in the field of sports, in which a life-like sports environment is simulated, and the body actions of players can be tracked and represented by using VR tracking and visualisation technology. In the entertainment field, exergaming that merges video game with physical exercise activities by employing tracking or even 3D display technology can be considered as a small scale VR. For the research presented in this thesis, a novel realistic real-time table tennis game combining immersive, interactive and competitive features is developed. The implemented system integrates the InterSense tracking system, SwissRanger 3D camera and a three-wall rear projection stereoscopic screen. The Intersense tracking system is based on ultrasonic and inertia sensing techniques which provide fast and accurate 6-DOF (i.e. six degrees of freedom) tracking information of four trackers. Two trackers are placed on the two players’ heads to provide the players’ viewing positions. The other two trackers are held by players as the racquets. The SwissRanger 3D camera is mounted on top of the screen to capture the player’sEThOS - Electronic Theses Online ServiceGBUnited Kingdo

Hierarchical controller for highly dynamic locomotion utilizing pattern modulation and impedance control : implementation on the MIT Cheetah robot

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (pages 105-111).This thesis presents a hierarchical control algorithm for quadrupedal locomotion. We address three challenges in developing a controller for high-speed running: locomotion stability, control of ground reaction force, and coordination of four limbs. To tackle these challenges, the proposed algorithm employs three strategies. Leg impedance control provides programmable virtual compliance of each leg which achieve self-stability in locomotion. The four legs exert forces to the ground using equilibrium-point hypothesis. A gait pattern modulator imposes a desired footfall sequence. The control algorithm is verified in a dynamic simulator constructed using MATLAB and then in the subsequent experiments on the MIT Cheetah robot. The experiments on the MIT Cheetah robot demonstrates high speed trot running reaching up to the speed of 6 m/s on a treadmill. This speed corresponds to a Froude number (Fr = 7.34), which is comparatively higher than other existing quadrupedal robots.by Jongwoo Lee.S.M

Spatial and Timing Regulation of Upper-Limb Movements in Rhythmic Tasks

Rhythmic movement is vital to humans and a foundation of such activities as locomotion, handwriting, and repetitive tool use. The spatiotemporal regularity characterizing such movements reflects a level of automaticity and coordination that is believed to emerge from mutually inhibitory or other pattern generating neural networks in the central nervous system. Although many studies have provided descriptions of this regularity and have illuminated the types of sensory information that influence rhythmic behavior, an understanding of how the brain uses sensory feedback to regulate rhythmic behavior on a cycle-by-cycle basis has been elusive. This thesis utilizes the model task of paddle juggling, or vertical ball bouncing, to address how three types of feedback---visual, auditory, and haptic---contribute to spatial and temporal regulation of rhythmic upper-limb movements. We use a multi-level approach in accordance with the well-known dictum of Marr and Poggio. The crux of this thesis describes a method and suite of experiments to understand how the brain uses visual, audio, and haptic feedback to regulate spatial or timing regularity, and formulate acycle-by-cycle description of this control: to wit, the nature and algorithms of sensory-feedback guided regulation. Part I motivates our interest in this problem, by discussing the biological ``hardware'' that the nervous system putatively employs in these movements, and reviewing insights from previous studies of paddle juggling that suggest how the ``hardware'' may manifest itself in these behaviors. The central experimental approach of this thesis is to train participants to perform the paddle juggling task with spatiotemporal regularity (in other words, to achieve limit-cycle behavior), and then interrogate how the brain applies regulates closed-loop performance by perturbing task feedback. In Part II, we review the development of a novel hard-real-time virtual-reality juggling simulator that enabled precise spatial and temporal feedback perturbations. We then outline the central experimental approach, in which we perturb spatial feedback of the ball at apex phase (vision), and timing feedback of collision- (audio and haptic) and apex-phase events to understand spatial and timing regulation. Part III describes two experiments that yield the main research findings of this thesis. In Experiment 1, we use a sinusoidal-perturbation-based system identification approach to determine that spatial and timing feedback are used in two dissociable and complementary control processes: spatial error correction and temporal synchronization. In Experiment 2, a combination of sinusoidal and step perturbations is used to establish that these complementary processes obey different dynamics. Namely, spatial correction is a proportional-integral process based on a one-step memory of feedback, while temporal synchronization is a proportional process that is dependent only on the most recent feedback. We close in Part IV with a discussion of how insights and approaches from this thesis can lead to improved rehabilitation approaches and understanding of the physiological basis of rhythmic movement regulation

An adaptive framework for changing-contact robot manipulation

Many robot manipulation tasks require the robot to make and break contact with other objects in the environment. The interaction dynamics of such tasks vary markedly before and after contact. They are also strongly influenced by the nature and physical properties of the objects involved, i.e., by factors such as type of contact, surface friction, and applied force. Many industrial assembly tasks and human manipulation tasks, e.g., peg insertion, stacking, and screwing, are instances of such `changing-contact' manipulation tasks. In such tasks, the interaction dynamics is discontinuous when the robot makes or breaks contact but smooth at other times, making it a piecewise continuous dynamical system. The discontinuities experienced by a robot during such tasks can be harmful to the robot and/or object. Designing a framework for smooth online control of changing-contact manipulation tasks is a challenging open problem. To complete any manipulation task without data-intensive pre-training, the robot has to plan a motion trajectory, and execute this trajectory accurately and smoothly. Many methods have been developed for the former part of the problem in the form of planners that compute a suitable trajectory while considering relevant motion constraints and environmental obstacles. This thesis focuses on the relatively less-explored latter (i.e., plan execution) part of the problem in the context of changing-contact manipulation tasks. It does so by developing an adaptive, task-space, hybrid control framework that enables efficient, smooth, and accurate following of any given motion trajectory in the presence of piecewise continuous interaction dynamics. The framework makes three key contributions. The first contribution of this thesis addresses the problem of controlling a robot performing continuous-contact tasks in the presence of smoothly-changing environment dynamics. Specifically, we provide a task-space control framework that incrementally models and predicts the end-effector wrenches, and uses the discrepancies between the predicted and measured values to revise the predictive (forward) model and to achieve smooth trajectory tracking by adapting the impedance parameters of a force-motion controller. The second contribution of the thesis expands our framework to handle interaction dynamics that can be discontinuous due to making and breaking of contacts or due to discrete changes in the environment. We formulate the piecewise continuous interaction dynamics of the robot as a hybrid dynamical system with previously unknown discrete dynamic modes. We propose a corresponding hybrid framework that incrementally identifies new or existing modes, and adapts the parameters of the dynamics models within each such mode to provide smooth and accurate tracking of the target motion trajectory. The third contribution of the thesis focuses on handling contact changes and reducing discontinuities in the interaction dynamics during mode transitions. Specifically, we develop a framework with a contact anticipation model that incrementally and probabilistically updates its estimates of when contact changes occur due to making or breaking contact, or changes in the properties of objects. The estimated contact positions are used to guide a transition to (and from) special `transition phase' controllers whose parameters are adapted online to minimise discontinuities (i.e., to minimise spikes in force, jerk etc) in the regions of anticipated contacts. The stated contributions and each part of the framework are grounded and evaluated in simulation and on a physical robot performing illustrative changing-contact manipulation tasks on a tabletop. We experimentally compare our framework with some baselines to demonstrate the importance of building an incremental, adaptive framework for such tasks. In particular, we compare our controller for continuous-contact tasks with representative baselines in the adaptive control literature, and demonstrate the benefits of an incrementally-updated predictive (forward) model. We also experimentally evaluate the ability of our hybrid framework to accurately identify and model the dynamics of discrete dynamic (contact) modes, and justify the need for online updates by comparing the performance of a state of the art offline methods for hybrid dynamical systems. Finally, we evaluate the ability of our framework to accurately estimate contact positions and minimise discontinuities in the interaction dynamics in motion trajectories involving multiple contact changes

Aeronautical engineering: A continuing bibliography with indexes, supplement 98

This bibliography lists 399 reports, articles, and other documents introduced into the NASA scientific and technical information system in June 197

Virtual Reality Games for Motor Rehabilitation

This paper presents a fuzzy logic based method to track user satisfaction without the need for devices to monitor users physiological conditions. User satisfaction is the key to any product’s acceptance; computer applications and video games provide a unique opportunity to provide a tailored environment for each user to better suit their needs. We have implemented a non-adaptive fuzzy logic model of emotion, based on the emotional component of the Fuzzy Logic Adaptive Model of Emotion (FLAME) proposed by El-Nasr, to estimate player emotion in UnrealTournament 2004. In this paper we describe the implementation of this system and present the results of one of several play tests. Our research contradicts the current literature that suggests physiological measurements are needed. We show that it is possible to use a software only method to estimate user emotion