Constantinos Tzafestas | IRAL

Constantinos Tzafestas filby 2024-07-04T15:46:29+00:00

Constantinos Tzafestas

Constantinos TzafestasAssociate Professor

(+30) 210-772-3687
ktzaf@cs.ntua.gr
Office 2.1.11
Full CV

Research Interests

Robotics
Cognitive Assistive Robotics
Human-Robot Interaction
Haptics and Telerobotics
Medical and Surgical Robotics
Virtual Reality
Intelligent Robot Control
Robot Motion Planning
Robot Learning

Courses

Circuit Theory
Robotics I: Analysis – Control – Laboratory
Robotics II: Intelligent Robotic Systems

Recent Research Projects
Publications

Biosketch

Costas S. Tzafestas is an Associate Professor of Robotics at the School of Electrical and Computer Engineering, National Technical University of Athens. He holds an Electrical and Computer Engineering Degree from the National Technical University of Athens (1993), as well as a D.E.A. (1994) and Ph.D. (1998) Degrees on Robotics from the Université Pierre et Marie Curie (Paris 6), France. In 2003 he joined NTUA School of ECE where he currently serves as an Associate Professor of Robotics. He has previously served as a Research Associate at the Institute of Informatics and Telecommunications of the National Center for Scientific Research “Demokritos”, Athens, Greece. His main research interests include cognitive assistive robotics and human-robot interaction, as well as haptics and telerobotics with applications in the field of medical and surgical robotics. His research spans topics related to intelligent robot control, interactive motion planning and robot learning for advanced/dexterous manipulation, also including applications in mobile and field robotics. He has authored or co-authored more than 160 scientific publications and has participated as Project Coordinator, PI, or Scientific Manager in several European and national research projects in the above fields. He currently serves as an Executive Board Editor of the Journal of Intelligent and Robotic Systems.

Recent Research Projects

Softgrip

Softgrip

i-Walk

i-Walk

BabyRobot

BabyRobot

ISupport

ISupport

Mobot

Mobot

Publications

2021

George Moustris, Nikolaos Kardaris, Antigoni Tsiami, Georgia Chalvatzaki, Petros Koutras, Athanasios Dometios, Paris Oikonomou, Costas Tzafestas, Petros Maragos, Eleni Efthimiou, Xanthi Papageorgiou, Stavroula-Evita Fotinea, Yiannis Koumpouros, Anna Vacalopoulou, Effie Papageorgiou, Alexandra Karavasili, Foteini Koureta, Dimitris Dimou, Alexandros Nikolakakis, Konstantinos Karaiskos, Panagiotis Mavridis

The i-Walk Lightweight Assistive Rollator: First Evaluation Study Journal Article

Frontiers in Robotics and AI, 8 , pp. 272, 2021, ISSN: 2296-9144.

Abstract | BibTeX | Links: [PDF]

@article{10.3389/frobt.2021.677542,
title = {The i-Walk Lightweight Assistive Rollator: First Evaluation Study},
author = {George Moustris and Nikolaos Kardaris and Antigoni Tsiami and Georgia Chalvatzaki and Petros Koutras and Athanasios Dometios and Paris Oikonomou and Costas Tzafestas and Petros Maragos and Eleni Efthimiou and Xanthi Papageorgiou and Stavroula-Evita Fotinea and Yiannis Koumpouros and Anna Vacalopoulou and Effie Papageorgiou and Alexandra Karavasili and Foteini Koureta and Dimitris Dimou and Alexandros Nikolakakis and Konstantinos Karaiskos and Panagiotis Mavridis},
url = {http://robotics.ntua.gr/wp-content/uploads/sites/2/frobt-08-677542.pdf},
doi = {10.3389/frobt.2021.677542},
issn = {2296-9144},
year = {2021},
date = {2021-12-30},
journal = {Frontiers in Robotics and AI},
volume = {8},
pages = {272},
abstract = {Robots can play a significant role as assistive devices for people with movement impairment and mild cognitive deficit. In this paper we present an overview of the lightweight i-Walk intelligent robotic rollator, which offers cognitive and mobility assistance to the elderly and to people with light to moderate mobility impairment. The utility, usability, safety and technical performance of the device is investigated through a clinical study, which took place at a rehabilitation center in Greece involving real patients with mild to moderate cognitive and mobility impairment. This first evaluation study comprised a set of scenarios in a number of pre-defined use cases, including physical rehabilitation exercises, as well as mobility and ambulation involved in typical daily living activities of the patients. The design and implementation of this study is discussed in detail, along with the obtained results, which include both an objective and a subjective evaluation of the system operation, based on a set of technical performance measures and a validated questionnaire for the analysis of qualitative data, respectively. The study shows that the technical modules performed satisfactory under real conditions, and that the users generally hold very positive views of the platform, considering it safe and reliable.},
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Danai Efstathiou, Georgia Chalvatzaki, Athanasios Dometios, Dionisios Spiliopoulos, Costas S Tzafestas

Deep Leg Tracking by Detection and Gait Analysis in 2D Range Data for Intelligent Robotic Assistants Conference

2021 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 2021.

BibTeX | Links: [Slides] [PDF]

Xanthi S Papageorgiou, Athanasios C Dometios, Costas S Tzafestas

Towards a User Adaptive Assistive Robot: Learning from Demonstration Using Navigation Functions Conference

2021 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 2021.

BibTeX | Links: [PDF]

2020

Christian Werner, Athanasios C Dometios, Costas S Tzafestas, Petros Maragos, Jürgen M Bauer, Klaus Hauer

Evaluating the task effectiveness and user satisfaction with different operation modes of an assistive bathing robot in older adults Journal Article

Assistive Technology, 0 , 2020, (PMID: 32286163).

BibTeX | Links: [Webpage] [PDF]

A Zlatintsi, A C Dometios, N Kardaris, I Rodomagoulakis, P Koutras, X Papageorgiou, P Maragos, C S Tzafestas, P Vartholomeos, K Hauer, C Werner, R Annicchiarico, M G Lombardi, F Adriano, T Asfour, A M Sabatini, C Laschi, M Cianchetti, A Güler, I Kokkinos, B Klein, R López

I-Support: A robotic platform of an assistive bathing robot for the elderly population Journal Article

Robotics and Autonomous Systems, 126 , pp. 103451, 2020, ISSN: 0921-8890.

Abstract | BibTeX | Links: [Webpage] [PDF]

@article{ZLATINTSI2020103451,
title = {I-Support: A robotic platform of an assistive bathing robot for the elderly population},
author = {A Zlatintsi and A C Dometios and N Kardaris and I Rodomagoulakis and P Koutras and X Papageorgiou and P Maragos and C S Tzafestas and P Vartholomeos and K Hauer and C Werner and R Annicchiarico and M G Lombardi and F Adriano and T Asfour and A M Sabatini and C Laschi and M Cianchetti and A Güler and I Kokkinos and B Klein and R López},
url = {http://www.sciencedirect.com/science/article/pii/S0921889019304968
http://robotics.ntua.gr/wp-content/uploads/sites/2/ICCSetal_I-Support_RAS-2020.pdf},
doi = {https://doi.org/10.1016/j.robot.2020.103451},
issn = {0921-8890},
year = {2020},
date = {2020-04-10},
journal = {Robotics and Autonomous Systems},
volume = {126},
pages = {103451},
abstract = {In this paper we present a prototype integrated robotic system, the I-Support bathing robot, that aims at supporting new aspects of assisted daily-living activities on a real-life scenario. The paper focuses on describing and evaluating key novel technological features of the system, with the emphasis on cognitive human–robot interaction modules and their evaluation through a series of clinical validation studies. The I-Support project on its whole has envisioned the development of an innovative, modular, ICT-supported service robotic system that assists frail seniors to safely and independently complete an entire sequence of physically and cognitively demanding bathing tasks, such as properly washing their back and their lower limbs. A variety of innovative technologies have been researched and a set of advanced modules of sensing, cognition, actuation and control have been developed and seamlessly integrated to enable the system to adapt to the target population abilities. These technologies include: human activity monitoring and recognition, adaptation of a motorized chair for safe transfer of the elderly in and out the bathing cabin, a context awareness system that provides full environmental awareness, as well as a prototype soft robotic arm and a set of user-adaptive robot motion planning and control algorithms. This paper focuses in particular on the multimodal action recognition system, developed to monitor, analyze and predict user actions with a high level of accuracy and detail in real-time, which are then interpreted as robotic tasks. In the same framework, the analysis of human actions that have become available through the project’s multimodal audio–gestural dataset, has led to the successful modeling of Human–Robot Communication, achieving an effective and natural interaction between users and the assistive robotic platform. In order to evaluate the I-Support system, two multinational validation studies were conducted under realistic operating conditions in two clinical pilot sites. Some of the findings of these studies are presented and analyzed in the paper, showing good results in terms of: (i) high acceptability regarding the system usability by this particularly challenging target group, the elderly end-users, and (ii) overall task effectiveness of the system in different operating modes.},
keywords = {},
pubstate = {published},
tppubtype = {article}
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In this paper we present a prototype integrated robotic system, the I-Support bathing robot, that aims at supporting new aspects of assisted daily-living activities on a real-life scenario. The paper focuses on describing and evaluating key novel technological features of the system, with the emphasis on cognitive human–robot interaction modules and their evaluation through a series of clinical validation studies. The I-Support project on its whole has envisioned the development of an innovative, modular, ICT-supported service robotic system that assists frail seniors to safely and independently complete an entire sequence of physically and cognitively demanding bathing tasks, such as properly washing their back and their lower limbs. A variety of innovative technologies have been researched and a set of advanced modules of sensing, cognition, actuation and control have been developed and seamlessly integrated to enable the system to adapt to the target population abilities. These technologies include: human activity monitoring and recognition, adaptation of a motorized chair for safe transfer of the elderly in and out the bathing cabin, a context awareness system that provides full environmental awareness, as well as a prototype soft robotic arm and a set of user-adaptive robot motion planning and control algorithms. This paper focuses in particular on the multimodal action recognition system, developed to monitor, analyze and predict user actions with a high level of accuracy and detail in real-time, which are then interpreted as robotic tasks. In the same framework, the analysis of human actions that have become available through the project’s multimodal audio–gestural dataset, has led to the successful modeling of Human–Robot Communication, achieving an effective and natural interaction between users and the assistive robotic platform. In order to evaluate the I-Support system, two multinational validation studies were conducted under realistic operating conditions in two clinical pilot sites. Some of the findings of these studies are presented and analyzed in the paper, showing good results in terms of: (i) high acceptability regarding the system usability by this particularly challenging target group, the elderly end-users, and (ii) overall task effectiveness of the system in different operating modes.

Christian Werner, Nikos Kardaris, Petros Koutras, Athanasia Zlatintsi, Petros Maragos, Jürgen M Bauer, Klaus Hauer

Improving gesture-based interaction between an assistive bathing robot and older adults via user training on the gestural commands Journal Article

Archives of Gerontology and Geriatrics, 87 , pp. 103996, 2020, ISSN: 0167-4943.

Abstract | BibTeX | Links: [Webpage] [PDF]

@article{WERNER2020103996,
title = {Improving gesture-based interaction between an assistive bathing robot and older adults via user training on the gestural commands},
author = {Christian Werner and Nikos Kardaris and Petros Koutras and Athanasia Zlatintsi and Petros Maragos and Jürgen M Bauer and Klaus Hauer},
url = {http://www.sciencedirect.com/science/article/pii/S0167494319302390
http://robotics.ntua.gr/wp-content/uploads/sites/2/Improving-gesture-based-interaction-between-an-assistive-bathing-robot-and-older-adults-via-user-training-on-the-gestural-commands.pdf},
doi = {https://doi.org/10.1016/j.archger.2019.103996},
issn = {0167-4943},
year = {2020},
date = {2020-03-01},
journal = {Archives of Gerontology and Geriatrics},
volume = {87},
pages = {103996},
abstract = {Background
Gesture-based human-robot interaction (HRI) depends on the technical performance of the robot-integrated gesture recognition system (GRS) and on the gestural performance of the robot user, which has been shown to be rather low in older adults. Training of gestural commands (GCs) might improve the quality of older users’ input for gesture-based HRI, which in turn may lead to an overall improved HRI.
Objective
To evaluate the effects of a user training on gesture-based HRI between an assistive bathing robot and potential elderly robot users.
Methods
Twenty-five older adults with bathing disability participated in this quasi-experimental, single-group, pre-/post-test study and underwent a specific user training (10−15 min) on GCs for HRI with the assistive bathing robot. Outcomes measured before and after training included participants’ gestural performance assessed by a scoring method of an established test of gesture production (TULIA) and sensor-based gestural performance (SGP) scores derived from the GRS-recorded data, and robot’s command recognition rate (CRR).
Results Gestural performance (TULIA = +57.1 ± 56.2 %, SGP scores = +41.1 ± 74.4 %) and CRR (+31.9 ± 51.2 %) significantly improved over training (p < .001). Improvements in gestural performance and CRR were highly associated with each other (r = 0.80–0.81, p < .001). Participants with lower initial gestural performance and higher gerontechnology anxiety benefited most from the training.
Conclusions
Our study highlights that training in gesture-based HRI with an assistive bathing robot is highly beneficial for the quality of older users’ GCs, leading to higher CRRs of the robot-integrated GRS, and thus to an overall improved HRI.},
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Georgia Chalvatzaki, Petros Koutras, Antigoni Tsiami, Costas S. Tzafestas, Petros Maragos

i-Walk Intelligent Assessment System: Activity, Mobility, Intention, Communication Conference

Proc. 16th European Computer Vision Conference Workshops (ECCVW) – 8th Int’l Workshop on Assistive Computer Vision and Robotics (ACVR-2020), Online, 2020.

BibTeX | Links: [PDF]

2019

Georgia Chalvatzaki, Xanthi S Papageorgiou, Petros Maragos, Costas S Tzafestas

Learn to adapt to human walking: A Model-based Reinforcement Learning Approach for a Robotic Assistant Rollator Journal Article

IEEE Robotics and Automation Letters (with IROS option), 4 (4), pp. 3774–3781, 2019.

BibTeX | Links: [PDF]

Georgia Chalvatzaki, Xanthi S. Papageorgiou, Petros Maragos, Costas S. Tzafestas

Comparing the Impact of Robotic Rollator Control Schemes on Elderly Gait using on-line LRF-based Gait Analysis Conference

Proc. Workshop on Mobile Robot Assistants for the Elderly (MoRobAE) in 2019 IEEE Int’l Conference on Robotics and Automation (ICRA), Montreal, Canada, 2019.

BibTeX | Links: [PDF]

Jack Hadfield, Georgia Chalvatzaki, Petros Koutras, Mehdi Khamassi, Costas S Tzafestas, Petros Maragos

A Deep Learning Approach for Multi-View Engagement Estimation of Children in a Child-Robot Joint Attention Task Conference

2019 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2019), Macau, China, 2019.

BibTeX | Links: [PDF]

Georgia Chalvatzaki, Petros Koutras, Jack Hadfield, Xanthi S. Papageorgiou, Costas S. Tzafestas, Petros Maragos

On-line Human Gait Stability Prediction using LSTMs for the fusion of Deep-based Pose Estimation and LRF-based Augmented Gait State Estimation in an Intelligent Robotic Rollator Conference

IEEE International Conference on Robotics & Automation (ICRA), Montreal, Canada, 2019.

BibTeX | Links: [PDF]

G. Chalvatzaki, P. Koutras, J. Hadfield, X. S. Papageorgiou, C. S. Tzafestas, P. Maragos

LSTM-based Network for Human Gait Stability Prediction in an Intelligent Robotic Rollator Conference

Proc. 2019 IEEE International Conference on Robotics and Automation (ICRA), Montreal, Canada, 2019.

BibTeX | Links: [PDF]

Xanthi S Papageorgiou, Georgia Chalvatzaki, Eleni Efthimiou, Stavroula-Evita Fotinea, Alexandra Karavasili, Costas S Tzafestas, Petros Maragos, Anna Vacalopoulou, Theodore Goulas

User Centered HRI Design for an Intelligent Robotic Rollator Conference

Proc. Workshop on Mobile Robot Assistants for the Elderly (MoRobAE) in 2019 IEEE Int’l Conference on Robotics and Automation (ICRA), Montreal, Canada, 2019.

BibTeX | Links: [PDF]

2018

A C Dometios, Y Zhou, X S Papageorgiou, C S Tzafestas, T Asfour

Vision-Based Online Adaptation of Motion Primitives to Dynamic Surfaces: Application to an Interactive Robotic Wiping Task Journal Article

IEEE Robotics and Automation Letters, 3 (3), pp. 1410-1417, 2018.

Abstract | BibTeX | Links: [PDF]

@article{DZPTA18,
title = {Vision-Based Online Adaptation of Motion Primitives to Dynamic Surfaces: Application to an Interactive Robotic Wiping Task},
author = {A C Dometios and Y Zhou and X S Papageorgiou and C S Tzafestas and T Asfour},
url = {http://robotics.ntua.gr/wp-content/publications/Dometios18_Vision-Based_Online_Adaptation_Motion_Primitives.pdf},
doi = {10.1109/LRA.2018.2800031},
year = {2018},
date = {2018-07-01},
journal = {IEEE Robotics and Automation Letters},
volume = {3},
number = {3},
pages = {1410-1417},
abstract = {Elderly or disabled people usually need augmented nursing attention both in home and clinical environments, especially to perform bathing activities. The development of an assistive robotic bath system, which constitutes a central motivation of this work, would increase the independence and safety of this procedure, ameliorating in this way the everyday life for this group of people. In general terms, the main goal of this work is to enable natural, physical human-robot interaction, involving human-friendly and user-adaptive on-line robot motion planning and interaction control. For this purpose, we employ imitation learning using a leader-follower framework called Coordinate Change Dynamic Movement Primitives (CC-DMP), in order to incorporate the expertise of professional carers for bathing sequences. In this letter, we propose a vision-based washing system, combining CC-DMP framework with a perception-based controller, to adapt the motion of robot’s end effector on moving and deformable surfaces, such as a human body part. The controller guarantees globally uniformly asymptotic convergence to the leader movement primitive while ensuring avoidance of restricted areas, such as sensitive skin body areas. We experimentally tested our approach on a setup including the humanoid robot ARMAR-III and a Kinect v2 camera. The robot executes motions learned from the publicly available KIT whole-body human motion database, achieving good tracking performance in challenging interactive task scenarios.},
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G Chalvatzaki, X S Papageorgiou, C S Tzafestas, P Maragos

Augmented Human State Estimation Using Interacting Multiple Model Particle Filters With Probabilistic Data Association Journal Article

IEEE Robotics and Automation Letters, 3 (3), pp. 1872-1879, 2018, ISSN: 2377-3766.

BibTeX | Links: [PDF]

Mehdi Khamassi, George Velentzas, Theodore Tsitsimis, Costas Tzafestas

Robot fast adaptation to changes in human engagement during simulated dynamic social interaction with active exploration in parameterized reinforcement learning Journal Article

IEEE Transactions on Cognitive and Developmental Systems, 10 , pp. 881 - 893, 2018.

Abstract | BibTeX | Links: [PDF]

@article{BFB99,
title = {Robot fast adaptation to changes in human engagement during simulated dynamic social interaction with active exploration in parameterized reinforcement learning},
author = {Mehdi Khamassi and George Velentzas and Theodore Tsitsimis and Costas Tzafestas},
url = {http://robotics.ntua.gr/wp-content/publications/Khamassi_TCDS2018.pdf},
doi = {10.1109/TCDS.2018.2843122},
year = {2018},
date = {2018-01-01},
journal = { IEEE Transactions on Cognitive and Developmental Systems},
volume = {10},
pages = {881 - 893},
publisher = {IEEE},
abstract = {Dynamic uncontrolled human-robot interactions (HRI) require robots to be able to adapt to changes in the human’s behavior and intentions. Among relevant signals, non-verbal cues such as the human’s gaze can provide the robot with important information about the human’s current engagement in the task, and whether the robot should continue its current behavior or not. However, robot reinforcement learning (RL) abilities to adapt to these non-verbal cues are still underdeveloped. Here we propose an active exploration algorithm for RL during HRI where the reward function is the weighted sum of the human’s current engagement and variations of this engagement. We use a parameterized action space where a meta-learning algorithm is applied to simultaneously tune the exploration in discrete action space (e.g. moving an object) and in the space of continuous characteristics of movement (e.g. velocity, direction, strength, expressivity). We first show that this algorithm reaches state-of-the-art performance in the non-stationary multi-armed bandit paradigm. We then apply it to a simulated HRI task, and show that it outperforms continuous parameterized RL with either passive or active exploration based on different existing methods. We finally test the performance in a more realistic test of the same HRI task, where a practical approach is followed to estimate human engagement through visual cues of the head pose. The algorithm can detect and adapt to perturbations in human engagement with different durations. Altogether, these results suggest a novel efficient and robust framework for robot learning during dynamic HRI scenarios.},
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X S Papageorgiou, G Chalvatzaki, A Dometios, C S Tzafestas

Human-Centered Service Robotic Systems for Assisted Living Conference

Proceedings of the 27th International Conference on Robotics in Alpe-Adria Danube Region (RAAD 2018), 2018.

Abstract | BibTeX | Links: [PDF]

A Zlatintsi, I Rodomagoulakis, P Koutras, A ~C Dometios, V Pitsikalis, C ~S Tzafestas, P Maragos

Multimodal Signal Processing and Learning Aspects of Human-Robot Interaction for an Assistive Bathing Robot Conference

Proc. IEEE Int'l Conf. Acous., Speech, and Signal Processing, Calgary, Canada, 2018.

Abstract | BibTeX | Links: [PDF]

Jack Hadfield, Petros Koutras, Niki Efthymiou, Gerasimos Potamianos, Costas S Tzafestas, Petros Maragos

Object assembly guidance in child-robot interaction using RGB-D based 3d tracking Conference

2018 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), IEEE 2018.

BibTeX | Links: [PDF]

2017

G Chalvatzaki, X S Papageorgiou, C S Tzafestas, P Maragos

HMM-based Pathological Gait Analyzer for a User-Adaptive Intelligent Robotic Walker Conference

Proc. 25th European Conf.(EUSIPCO-17) Workshop: "MultiLearn 2017 - Multimodal processing, modeling and learning for human-computer/robot interaction applications", Kos, Greece, 2017.

Abstract | BibTeX | Links: [PDF]

@conference{CPTM_WML17,
title = {HMM-based Pathological Gait Analyzer for a User-Adaptive Intelligent Robotic Walker},
author = {G Chalvatzaki and X S Papageorgiou and C S Tzafestas and P Maragos},
url = {http://robotics.ntua.gr/wp-content/publications/CPTM_WML17.pdf},
year = {2017},
date = {2017-09-01},
booktitle = {Proc. 25th European Conf.(EUSIPCO-17) Workshop: "MultiLearn 2017 - Multimodal processing, modeling and learning for human-computer/robot interaction applications"},
address = {Kos, Greece},
abstract = {During the past decade, robotic technology has
evolved considerably towards the development of cognitive
robotic systems that enable close interaction with humans.
Application fields of such novel robotic technologies are now
wide spreading covering a variety of human assistance function-
alities, aiming in particular at supporting the needs of human
beings experiencing various forms of mobility or cognitive
impairments. Mobility impairments are prevalent in the elderly
population and constitute one of the main causes related to
difficulties in performing Activities of Daily Living (ADLs)
and consequent reduction of quality of life. This paper re-
ports current research work related to the development of a
pathological gait analyzer for intelligent robotic rollator aiming
to be an input to a user-adaptive and context-aware robot
control architecture. Specifically, we present a novel method
for human leg tracking using Particle Filters and Probablistic
Data Association from a laser scanner, constituting a non-
wearable and non-intrusive approach. The tracked positions
and velocities of the user’s legs are the observables of an
HMM, which provides the gait phases of the detected gait
cycles. Given those phases we compute specific gait parameters,
which are used for medical diagnosis. The results of our
pathological gait analyzer are validated using ground truth data
from a GAITRite system. The results presented in this paper
demonstrate that the proposed human data analysis scheme has
the potential to provide the necessary methodological (modeling,
inference, and learning) framework for a cognitive behavior-
based robot control system.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
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A C Dometios, A Tsiami, A Arvanitakis, P Giannoulis, X S Papageorgiou, C S Tzafestas, P Maragos

Integrated Speech-based Perception System for User Adaptive Robot Motion Planning in Assistive Bath Scenarios Conference

Proc. of the 25th European Signal Processing Conference - Workshop: "MultiLearn 2017 - Multimodal processing, modeling and learning for human-computer/robot interaction applications", Kos, Greece, 2017.

Abstract | BibTeX | Links: [PDF]

@conference{DTAGPTM17,
title = {Integrated Speech-based Perception System for User Adaptive Robot Motion Planning in Assistive Bath Scenarios},
author = {A C Dometios and A Tsiami and A Arvanitakis and P Giannoulis and X S Papageorgiou and C S Tzafestas and P Maragos},
url = {http://www.eurasip.org/Proceedings/Eusipco/Eusipco2017/wpapers/ML5.pdf},
year = {2017},
date = {2017-09-01},
booktitle = {Proc. of the 25th European Signal Processing Conference - Workshop: "MultiLearn 2017 - Multimodal processing, modeling and learning for human-computer/robot interaction applications"},
address = {Kos, Greece},
abstract = {Elderly people have augmented needs in performing bathing activities, since these tasks require body flexibility. Our aim is to build an assistive robotic bath system, in order to increase the independence and safety of this procedure. Towards this end, the expertise of professional carers for bathing sequences and appropriate motions have to be adopted, in order to achieve natural, physical human - robot interaction. The integration of the communication and verbal interaction between the user and the robot during the bathing tasks is a key issue for such a challenging assistive robotic application. In this paper, we tackle this challenge by developing a novel integrated real-time speech-based perception system, which will provide the necessary assistance to the frail senior citizens. This system can be suitable for installation and use in conventional home or hospital bathroom space. We employ both a speech recognition system with sub-modules to achieve a smooth and robust human-system communication and a low cost depth camera or end-effector motion planning. With a variety of spoken commands, the system can be adapted to the user’s needs and preferences. The instructed by the user washing commands are executed by a robotic manipulator, demonstrating the progress of each task. The smooth integration of ll subsystems is accomplished by a modular and hierarchical decision architecture organized as a Behavior Tree. The system was experimentally tested by successful execution of scenarios from different users with different preferences.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}

A C Dometios, X S Papageorgiou, A Arvanitakis, C S Tzafestas, P Maragos

Real-time End-effector Motion Behavior Planning Approach Using On-line Point-cloud Data Towards a User Adaptive Assistive Bath Robot Conference

2017 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), Vancouver, Canada, 2017.

Abstract | BibTeX | Links: [PDF]

G Chalvatzaki, X S Papageorgiou, C S Tzafestas

Towards a user-adaptive context-aware robotic walker with a pathological gait assessment system: First experimental study Conference

IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 2017.

Abstract | BibTeX | Links: [PDF]

@conference{CPT17,
title = {Towards a user-adaptive context-aware robotic walker with a pathological gait assessment system: First experimental study},
author = {G Chalvatzaki and X S Papageorgiou and C S Tzafestas},
url = {http://robotics.ntua.gr/wp-content/publications/CPT17.pdf},
doi = {10.1109/IROS.2017.8206388},
year = {2017},
date = {2017-09-01},
booktitle = {IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)},
pages = {5037-5042},
abstract = {When designing a user-friendly Mobility Assistive Device (MAD) for mobility constrained people, it is important to take into account the diverse spectrum of disabilities, which results to completely different needs to be covered by the MAD for each specific user. An intelligent adaptive behavior is necessary. In this work we present experimental results, using an in house developed methodology for assessing the gait of users with different mobility status while interacting with a robotic MAD. We use data from a laser scanner, mounted on the MAD to track the legs using Particle Filters and Probabilistic Data Association (PDA-PF). The legs' states are fed to an HMM-based pathological gait cycle recognition system to compute in real-time the gait parameters that are crucial for the mobility status characterization of the user. We aim to show that a gait assessment system would be an important feedback for an intelligent MAD. Thus, we use this system to compare the gaits of the subjects using two different control settings of the MAD and we experimentally validate the ability of our system to recognize the impact of the control designs on the users' walking performance. The results demonstrate that a generic control scheme does not meet every patient's needs, and therefore, an Adaptive Context-Aware MAD (ACA MAD), that can understand the specific needs of the user, is important for enhancing the human-robot physical interaction.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}

G. Velentzas, C. Tzafestas, M. Khamassi

Bio-inspired meta-learning for active exploration during non-stationary multi-armed bandit tasks Conference

Proc. IEEE Intelligent Systems Conference, London, UK, 2017.

Abstract | BibTeX | Links: [PDF]

@conference{BFB97,
title = {Bio-inspired meta-learning for active exploration during non-stationary multi-armed bandit tasks},
author = {G. Velentzas and C. Tzafestas and M. Khamassi},
url = {http://robotics.ntua.gr/wp-content/publications/Velentzas_Intellisys2017.pdf},
doi = {10.1109/IntelliSys.2017.8324365},
year = {2017},
date = {2017-09-01},
booktitle = {Proc. IEEE Intelligent Systems Conference},
address = {London, UK},
abstract = {Fast adaptation to changes in the environment requires agents (animals, robots and simulated artefacts) to be able to dynamically tune an exploration-exploitation trade-off during learning. This trade-off usually determines a fixed proportion of exploitative choices (i.e. choice of the action that subjectively appears as best at a given moment) relative to exploratory choices (i.e. testing other actions that now appear worst but may turn out promising later). Rather than using a fixed proportion, non-stationary multi-armed bandit methods in the field of machine learning have proven that principles such as exploring actions that have not been tested for a long time can lead to performance closer to optimal - bounded regret. In parallel, researches in active exploration in the fields of robot learning and computational neuroscience of learning and decision-making have proposed alternative solutions such as transiently increasing exploration in response to drops in average performance, or attributing exploration bonuses specifically to actions associated with high uncertainty in order to gain information when choosing them. In this work, we compare different methods from machine learning, computational neuroscience and robot learning on a set of non-stationary stochastic multi-armed bandit tasks: abrupt shifts; best bandit becomes worst one and vice versa; multiple shifting frequencies. We find that different methods are appropriate in different scenarios. We propose a new hybrid method combining bio-inspired meta-learning, kalman filter and exploration bonuses and show that it outperforms other methods in these scenarios.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}

G Chalvatzaki, X S Papageorgiou, C S Tzafestas, P Maragos

Estimating double support in pathological gaits using an HMM-based analyzer for an intelligent robotic walker Conference

IEEE International Symposium on Robot and Human Interactive Communication (RO-MAN), 2017.

Abstract | BibTeX | Links: [PDF]

@conference{CPTM_ROMAN17,
title = {Estimating double support in pathological gaits using an HMM-based analyzer for an intelligent robotic walker},
author = {G Chalvatzaki and X S Papageorgiou and C S Tzafestas and P Maragos},
url = {http://robotics.ntua.gr/wp-content/publications/CPTM_ROMAN17.pdf},
doi = {10.1109/ROMAN.2017.8172287},
year = {2017},
date = {2017-08-01},
booktitle = {IEEE International Symposium on Robot and Human Interactive Communication (RO-MAN)},
pages = {101-106},
abstract = {For a robotic walker designed to assist mobility constrained people, it is important to take into account the different spectrum of pathological walking patterns, which result into completely different needs to be covered for each specific user. For a deployable intelligent assistant robot it is necessary to have a precise gait analysis system, providing real-time monitoring of the user and extracting specific gait parameters, which are associated with the rehabilitation progress and the risk of fall. In this paper, we present a completely non-invasive framework for the on-line analysis of pathological human gait and the recognition of specific gait phases and events. The performance of this gait analysis system is assessed, in particular, as related to the estimation of double support phases, which are typically difficult to extract reliably, especially when applying non-wearable and non-intrusive technologies. Furthermore, the duration of double support phases constitutes an important gait parameter and a critical indicator in pathological gait patterns. The performance of this framework is assessed using real data collected from an ensemble of elderly persons with different pathologies. The estimated gait parameters are experimentally validated using ground truth data provided by a Motion Capture system. The results obtained and presented in this paper demonstrate that the proposed human data analysis (modeling, learning and inference) framework has the potential to support efficient detection and classification of specific walking pathologies, as needed to empower a cognitive robotic mobility-assistance device with user-adaptive and context-aware functionalities.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}

Theodore Tsitsimis, George Velentzas, Mehdi Khamassi, Costas Tzafestas

Online adaptation to human engagement perturbations in simulated human-robot interaction using hybrid reinforcement learning Conference

Proc. of the 25th European Signal Processing Conference - Workshop: "MultiLearn 2017 - Multimodal processing, modeling and learning for human-computer/robot interaction applications", Kos, Greece, 2017., Kos, Greece, 2017.

Abstract | BibTeX | Links: [PDF]

@conference{BFB98,
title = {Online adaptation to human engagement perturbations in simulated human-robot interaction using hybrid reinforcement learning},
author = {Theodore Tsitsimis and George Velentzas and Mehdi Khamassi and Costas Tzafestas},
editor = {Michael Aron},
url = {http://robotics.ntua.gr/wp-content/uploads/sites/2/MultiLearn2017.pdf},
year = {2017},
date = {2017-08-01},
booktitle = {Proc. of the 25th European Signal Processing Conference - Workshop: "MultiLearn 2017 - Multimodal processing, modeling and learning for human-computer/robot interaction applications", Kos, Greece, 2017.},
address = {Kos, Greece},
abstract = {Dynamic uncontrolled human-robot interaction requires robots to be able to adapt to changes in the human’s behavior and intentions. Among relevant signals, non-verbal cues such as the human’s gaze can provide the robot with important information about the human’s current engagement in the task, and whether the robot should continue its current behavior or not. In a previous work [1] we proposed an active exploration algorithm for reinforcement learning where the reward function is the weighted sum of the human’s current engagement and variations of this engagement (so that a low but increasing engagement is rewarding). We used a structured (parameterized) continuous action space where a meta-learning algorithm is applied to simultaneously tune the exploration in discrete and continuous action space, enabling the robot to learn which discrete action is expected by the human (e.g. moving an object) and with which velocity of movement. In this paper we want to show the performance of the algorithm to a simulated humanrobot interaction task where a practical approach is followed to estimate human engagement through visual cues of the head pose. We then measure the adaptation of the algorithm to engagement perturbations simulated as changes in the optimal action parameter and we quantify its performance for variations in perturbation duration and measurement noise.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}

G Chalvatzaki, X S Papageorgiou, C S Tzafestas, P Maragos

Comparative experimental validation of human gait tracking algorithms for an intelligent robotic rollator Conference

IEEE International Conference on Robotics and Automation (ICRA), 2017.

Abstract | BibTeX | Links: [PDF]

@conference{CPTM_ICRA17,
title = {Comparative experimental validation of human gait tracking algorithms for an intelligent robotic rollator},
author = {G Chalvatzaki and X S Papageorgiou and C S Tzafestas and P Maragos},
url = {http://robotics.ntua.gr/wp-content/publications/CPTM_ICRA17.pdf},
doi = {10.1109/ICRA.2017.7989713},
year = {2017},
date = {2017-05-01},
booktitle = {IEEE International Conference on Robotics and Automation (ICRA)},
pages = {6026-6031},
abstract = {Tracking human gait accurately and robustly constitutes a key factor for a smart robotic walker, aiming to provide assistance to patients with different mobility impairment. A context-aware assistive robot needs constant knowledge of the user's kinematic state to assess the gait status and adjust its movement properly to provide optimal assistance. In this work, we experimentally validate the performance of two gait tracking algorithms using data from elderly patients; the first algorithm employs a Kalman Filter (KF), while the second one tracks the user legs separately using two probabilistically associated Particle Filters (PFs). The algorithms are compared according to their accuracy and robustness, using data captured from real experiments, where elderly subjects performed specific walking scenarios with physical assistance from a prototype Robotic Rollator. Sensorial data were provided by a laser rangefinder mounted on the robotic platform recording the movement of the user's legs. The accuracy of the proposed algorithms is analysed and validated with respect to ground truth data provided by a Motion Capture system tracking a set of visual markers worn by the patients. The robustness of the two tracking algorithms is also analysed comparatively in a complex maneuvering scenario. Current experimental findings demonstrate the superior performance of the PFs in difficult cases of occlusions and clutter, where KF tracking often fails.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}

A Zlatintsi, I Rodomagoulakis, V Pitsikalis, P Koutras, N Kardaris, X Papageorgiou, C Tzafestas, P Maragos

Social Human-Robot Interaction for the Elderly: Two Real-life Use Cases, Conference

ACM/IEEE International Conference on Human-Robot Interaction (HRI), Vienna, Austria, 2017.

Abstract | BibTeX | Links: [PDF]

Mehdi Khamassi, George Velentzas, Theodore Tsitsimis, Costas Tzafestas

Active exploration and parameterized reinforcement learning applied to a simulated human-robot interaction task Conference

Proceedings - 2017 1st IEEE International Conference on Robotic Computing, IRC 2017, 2017, ISBN: 9781509067237.

Abstract | BibTeX | Links: [PDF]

@conference{337,
title = {Active exploration and parameterized reinforcement learning applied to a simulated human-robot interaction task},
author = { Mehdi Khamassi and George Velentzas and Theodore Tsitsimis and Costas Tzafestas},
url = {http://ieeexplore.ieee.org/document/7926511/%0Ahttp://ieeexplore.ieee.org/ielx7/7925476/7926477/07926511.pdf?tp=&arnumber=7926511&isnumber=7926477},
doi = {10.1109/IRC.2017.33},
isbn = {9781509067237},
year = {2017},
date = {2017-01-01},
booktitle = {Proceedings - 2017 1st IEEE International Conference on Robotic Computing, IRC 2017},
pages = {28--35},
abstract = {textcopyright 2017 IEEE. Online model-free reinforcement learning (RL) methods with continuous actions are playing a prominent role when dealing with real-world applications such as Robotics. However, when confronted to non-stationary environments, these methods crucially rely on an exploration-exploitation trade-off which is rarely dynamically and automatically adjusted to changes in the environment. Here we propose an active exploration algorithm for RL in structured (parameterized) continuous action space. This framework deals with a set of discrete actions, each of which is parameterized with continuous variables. Discrete exploration is controlled through a Boltzmann softmax function with an inverse temperature $beta$ parameter. In parallel, a Gaussian exploration is applied to the continuous action parameters. We apply a meta-learning algorithm based on the comparison between variations of short-Term and long-Term reward running averages to simultaneously tune $beta$ and the width of the Gaussian distribution from which continuous action parameters are drawn. We first show that this algorithm reaches state-of-The-Art performance in the non-stationary multi-Armed bandit paradigm, while also being generalizable to continuous actions and multi-step tasks. We then apply it to a simulated human-robot interaction task, and show that it outperforms continuous parameterized RL both without active exploration and with active exploration based on uncertainty variations measured by a Kalman-Q-learning algorithm.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}

X S Papageorgiou, G Chalvatzaki, A Dometios, C S Tzafestas, P Maragos

Intelligent Assistive Robotic Systems for the Elderly: Two Real-life Use Cases Conference

C_PETRA, ACM, Island of Rhodes, Greece, 2017, ISBN: 978-1-4503-5227-7.

Abstract | BibTeX | Links: [PDF]

G. Velentzas, C. Tzafestas, M. Khamassi

Bridging Computational Neuroscience and Machine Learning on Non-Stationary Multi-Armed Bandits Miscellaneous

bioRxiv, 117598, 2017.

Abstract | BibTeX | Links: [PDF]

@misc{BFB96,
title = {Bridging Computational Neuroscience and Machine Learning on Non-Stationary Multi-Armed Bandits},
author = {G. Velentzas and C. Tzafestas and M. Khamassi
},
url = {http://robotics.ntua.gr/wp-content/publications/Velentzas_RLDM2017.pdf},
doi = {10.1101/117598},
year = {2017},
date = {2017-06-01},
address = {Ann Arbor, USA},
abstract = {Fast adaptation to changes in the environment requires both natural and artificial agents to be able to dynamically tune an exploration-exploitation trade-off during learning. This trade-off usually determines a fixed proportion of exploitative choices (i.e. choice of the action that subjectively appears as best at a given moment) relative to exploratory choices (i.e. testing other actions that now appear worst but may turn out promising later). The problem of finding an efficient exploration-exploitation trade-off has been well studied both in the Machine Learning and Computational Neuroscience fields. Rather than using a fixed proportion, non-stationary multi-armed bandit methods in the former have proven that principles such as exploring actions that have not been tested for a long time can lead to performance closer to optimal - bounded regret. In parallel, researches in the latter have investigated solutions such as progressively increasing exploita- tion in response to improvements of performance, transiently increasing exploration in response to drops in average performance, or attributing exploration bonuses specifically to actions associated with high uncertainty in order to gain information when performing these actions. In this work, we first try to bridge some of these different methods from the two research fields by rewriting their decision process with a common formalism. We then show numerical simulations of a hybrid algorithm combining bio-inspired meta-learning, kalman filter and exploration bonuses compared to several state-of-the-art alternatives on a set of non-stationary stochastic multi-armed bandit tasks. While we find that different methods are appropriate in different scenarios, the hybrid algorithm displays a good combination of advantages from different methods and outperforms these methods in the studied scenarios.},
howpublished = {bioRxiv, 117598},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}

2016

John N Karigiannis, Costas S Tzafestas

Model-free learning on robot kinematic chains using a nested multi-agent topology Journal Article

Journal of Experimental and Theoretical Artificial Intelligence, 28 (6), pp. 913–954, 2016, ISSN: 13623079.

Abstract | BibTeX | Links: [PDF]

A Guler, N Kardaris, S Chandra, V Pitsikalis, C Werner, K Hauer, C Tzafestas, P Maragos, I Kokkinos

Human Joint Angle Estimation and Gesture Recognition for Assistive Robotic Vision Conference

Proc. of Workshop on Assistive Computer Vision and Robotics, European Conf. on Computer Vision (ECCV-2016), Amsterdam, The Netherlands, 2016.

Abstract | BibTeX | Links: [PDF]

G Chalvatzaki, X S Papageorgiou, C Werner, K Hauer, C S Tzafestas, P Maragos

Experimental comparison of human gait tracking algorithms: Towards a context-aware mobility assistance robotic walker Conference

Mediterranean Conference on Control and Automation (MED), 2016.

Abstract | BibTeX | Links: [PDF]

X S Papageorgiou, G Chalvatzaki, K N Lianos, C Werner, K Hauer, C S Tzafestas, P Maragos

Experimental validation of human pathological gait analysis for an assisted living intelligent robotic walker Conference

C_BIOROB, 2016.

Abstract | BibTeX | Links: [PDF]

A C Dometios, X S Papageorgiou, C S Tzafestas, P Vartholomeos

Towards ICT-supported Bath Robots: Control Architecture Description and Localized Perception of User for Robot Motion Planning Conference

Mediterranean Conference on Control and Automation (MED), Athens, Greece, 2016.

Abstract | BibTeX | Links: [PDF]

2015

X S Papageorgiou, C S Tzafestas, C Vartholomeos Laschi, R Lopez

ICT-Supported Bath Robots: Design Concepts Conference

C_ICSR, 2015.

Abstract | BibTeX | Links: [PDF]

G Papageorgiou X.S. Moustris, G Pitsikalis V. Chalvatzaki, A Dometios, N Kardaris, C S Tzafestas, P Maragos

User-Oriented Cognitive Interaction and Control for an Intelligent Robotic Walker Conference

17th International Conference on Social Robotics (ICSR 2015), 2015.

Abstract | BibTeX | Links: [PDF]

G Chalvatzaki, X S Papageorgiou, C S Tzafestas

Gait Modelling for a Context-Aware User-Adaptive Robotic Assistant Platform Conference

2015, ISSN: 978-88-97999-63-8.

Abstract | BibTeX | Links: [PDF]

X S Papageorgiou, G Chalvatzaki, C S Tzafestas, P Maragos

Hidden markov modeling of human pathological gait using laser range finder for an assisted living intelligent robotic walker Conference

IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 2015.

Abstract | BibTeX | Links: [PDF]

CS Tzafestas, XS Papageorgiou, GP Moustris, G Chalvatzaki, A Dometios

User-Oriented Human-Robot Interaction for an Intelligent Walking Assistant Robotic Device Conference

Workshop IEEE/RSJ Int'l Conf. on Intelligent Robots and Systems, Invited Session: "Cognitive Mobility Assistance Robots: Scientific Advances and Perspectives", Hamburg, Germany, Sept. 28 - Oct. 02, 2015, 2015.

BibTeX | Links: [PDF]

2014

Sheraz Khan, Athanasios Dometios, Chris Verginis, Costas Tzafestas, Dirk Wollherr, Martin Buss

RMAP: A rectangular cuboid approximation framework for 3D environment mapping Journal Article

Autonomous Robots, 37 (3), pp. 261–277, 2014, ISSN: 09295593.

Abstract | BibTeX | Links: [PDF]

S Khan, A Dometios, C Verginis, C Tzafestas, D Wollherr, M Buss

RMAP: a Rectangular Cuboid Approximation Framework for 3D Environment Mapping Journal Article

37 (3), pp. 261–277, 2014, ISSN: 1573-7527.

Abstract | BibTeX | Links: [PDF]

X S Papageorgiou, G Chalvatzaki, C S Tzafestas, P Maragos

Hidden Markov modeling of human normal gait using laser range finder for a mobility assistance robot Conference

IEEE International Conference on Robotics and Automation (ICRA), 2014, ISSN: 1050-4729.

Abstract | BibTeX | Links: [PDF]

X S Papageorgiou, C S Tzafestas, P Maragos, G Pavlakos, G Chalvatzaki, G Moustris, I Kokkinos, A Peer, B Stanczyk, E -S Fotinea, E Efthimiou

Advances in Intelligent Mobility Assistance Robot Integrating Multimodal Sensory Processing Conference

J_HCII, Springer International Publishing, Cham, 2014, ISBN: 978-3-319-07446-7.

Abstract | BibTeX | Links: [PDF]

2013

Costas S Tzafestas, Spyros Velanas

Telehaptic perception of delayed stiffness using adaptive impedance control: Experimental psychophysical analysis Journal Article

Presence: Teleoperators and Virtual Environments, 22 (4), pp. 323–344, 2013, ISSN: 15313263.

Abstract | BibTeX | Links: [PDF]

@article{Tzafestas2013,
title = {Telehaptic perception of delayed stiffness using adaptive impedance control: Experimental psychophysical analysis},
author = {Costas S Tzafestas and Spyros Velanas},
url = {http://robotics.ntua.gr/wp-content/uploads/sites/2/tzafestas2013.pdf},
doi = {10.1162/PRES_a_00162},
issn = {15313263},
year = {2013},
date = {2013-01-01},
journal = {Presence: Teleoperators and Virtual Environments},
volume = {22},
number = {4},
pages = {323--344},
abstract = {Abstract Telehaptics is the science of transmitting touch-related sensations over computer networks. With respect to robot teleoperation, telehaptics emphasizes more on reliably reproducing physical properties of a remote environment, as mediated over a network through the use of appropriate haptic interfacing technologies. One of the main factors that can cause degradation of the quality of a telehaptic system is the presence of time delays. Inspired by concepts such as impedance-reflection and model-mediated telemanipulation, an adaptive impedance control scheme has been proposed aiming to mitigate some of the problems caused by network delays in a telehaptic system. This paper presents an experimental analysis, which has been conducted to assess the actual performance of the proposed telehaptic scheme in terms of both control and human perception objectives. Firstly, a set of comparative numerical experiments is presented aiming to analyze stability and characterize transparency of the telehaptic system under large time delays. The results show the superior performance of the proposed adaptive impedance scheme as compared to direct force-reflecting teleoperation. Then, a series of psychophysical experiments is described, to evaluate the performance of the telehaptic system with respect to human perception of remote (delayed) stiffness. An analysis of the obtained results shows that the proposed adaptive scheme significantly improves telehaptic perception of linear stiffness in the presence of network delays, maintaining perceptual thresholds close to the ones obtained in the case of direct, nondelayed stimuli. A comparative experimental evaluation of psychometric transparency confirms the superior robustness with regard to time delay of the adaptive impedance telehaptic scheme as compared to state-of-the-art position/force transparentizing methods.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

G.P. Moustris, A.I. Mantelos, C.S. Tzafestas

Active motion compensation in robotic cardiac surgery Conference

2013 European Control Conference, ECC 2013, 2013, ISBN: 9783033039629.

Abstract | BibTeX | Links: [PDF]

G. P. Moustris, A. I. Mantelos, C. S. Tzafestas

Enhancing surgical accuracy using virtual fixtures and motion compensation in robotic beating heart surgery Conference

2013 21st Mediterranean Conference on Control and Automation, MED 2013 - Conference Proceedings, 2013, ISSN: 1050-4729.

Abstract | BibTeX | Links: [PDF]

2012

Sheraz Khan, Nikos Mitsou, Dirk Wollherr, Costas Tzafestas

An optimization approach for 3D environment mapping using normal vector uncertainty Conference

2012 12th International Conference on Control Automation Robotics & Vision (ICARCV), 2012 (December), 2012, ISBN: 978-1-4673-1872-3.

Abstract | BibTeX | Links: [Webpage] [PDF]

Spyros V. Velanas, Costas S. Tzafestas

Model-mediated telehaptic perception of delayed curvature Conference

Proceedings - IEEE International Workshop on Robot and Human Interactive Communication, 2012, ISBN: 9781467346054.

Abstract | BibTeX | Links: [PDF]

John N. Karigiannis, Costas S. Tzafestas

Robustness and generalization of model-free learning for robot kinematic control using a nested-hierarchical multi-agent topology Conference

Proceedings of the IEEE RAS and EMBS International Conference on Biomedical Robotics and Biomechatronics, 2012, ISSN: 21551774.

Abstract | BibTeX | Links: [PDF]

@conference{Karigiannis2012,
title = {Robustness and generalization of model-free learning for robot kinematic control using a nested-hierarchical multi-agent topology},
author = { John N. Karigiannis and Costas S. Tzafestas},
url = {http://robotics.ntua.gr/wp-content/uploads/sites/2/karigiannis2012.pdf},
doi = {10.1109/BioRob.2012.6290276},
issn = {21551774},
year = {2012},
date = {2012-06-01},
booktitle = {Proceedings of the IEEE RAS and EMBS International Conference on Biomedical Robotics and Biomechatronics},
pages = {1140--1147},
abstract = {This paper focuses on evaluating the robustness and knowledge generalization properties of a model-free learning mechanism, applied for the kinematic control of robot manipulation chains based on a nested-hierarchical multi-agent architecture. In the proposed topology, the agents correspond to independent degrees-of-freedom (DOF) of the system, managing to gain experience over the task that they collaboratively perform by continuously exploring and exploiting their state-to-action mapping space. Each agent forms a local (partial) view of the global system state and task progress, through a recursive learning process. By organizing the agents in a nested topology, the goal is to facilitate modular scaling to more complex kinematic topologies, with loose control coupling among the agents. Reinforcement learning is applied within each agent, to evolve a local state-to-action mapping in a continuous domain, thus leading to a system that exhibits developmental properties. This work addresses problem settings in the domain of kinematic control of dexterous-redundant robot manipulation systems. The numerical experiments performed consider the case of a single-linkage open kinematic chain, presenting kinematic redundancies given the desired task-goal. The focal issue in these experiments is to assess the capacity of the proposed multi-agent system to progressively and autonomously acquire cooperative sensorimotor skills through a self-learning process, that is, without the use of any explicit model-based planning strategy. In this paper, generalization and robustness properties of the overall multi-agent system are explored. Furthermore, the proposed framework is evaluated in constrained motion tasks, both in static and non-static environments. The computational cost of the proposed multi-agent architecture is also assessed.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}

Nikos Mitsou, Roderick de Nijs, David Lenz, Johannes Frimberger, Dirk Wollherr, Kolja Kühnlenz, Costas Tzafestas

Gesture and Sign Language in Human-Computer Interaction and Embodied Communication Conference

Spatial Cognition VIII, 7206 , 2012, ISSN: 03029743.

Abstract | BibTeX | Links: [Webpage]

2011

Nikos Mitsou, Irene Ntoutsi, Dirk Wollherr, Costas Tzafestas, Hans Peter Kriegel

Revealing cluster formation over huge volatile robotic data Conference

Proceedings - IEEE International Conference on Data Mining, ICDM, 2011, ISSN: 15504786.

Abstract | BibTeX | Links: [PDF]

2010

John N. Karigiannis, Theodoros I. Rekatsinas, Costas S. Tzafestas

Fuzzy rule based neuro-dynamic programming for mobile robot skill acquisition on the basis of a nested multi-agent architecture Conference

2010 IEEE International Conference on Robotics and Biomimetics, ROBIO 2010, 2010, ISBN: 9781424493173.

Abstract | BibTeX | Links: [PDF]

@conference{Karigiannis2010,
title = {Fuzzy rule based neuro-dynamic programming for mobile robot skill acquisition on the basis of a nested multi-agent architecture},
author = { John N. Karigiannis and Theodoros I. Rekatsinas and Costas S. Tzafestas},
url = {http://robotics.ntua.gr/wp-content/uploads/sites/2/karigiannis2010.pdf},
doi = {10.1109/ROBIO.2010.5723346},
isbn = {9781424493173},
year = {2010},
date = {2010-12-01},
booktitle = {2010 IEEE International Conference on Robotics and Biomimetics, ROBIO 2010},
pages = {312--319},
abstract = {Biologically inspired architectures that mimic the organizational structure of living organisms and in general frameworks that will improve the design of intelligent robots attract significant attention from the research community. Self-organization problems, intrinsic behaviors as well as effective learning and skill transfer processes in the context of robotic systems have been significantly investigated by researchers. Our work presents a new framework of developmental skill learning process by introducing a hierarchical nested multi-agent architecture. A neuro-dynamic learning mechanism employing function approximators in a fuzzified state-space is utilized, leading to a collaborative control scheme among the distributed agents engaged in a continuous space, which enables the multi-agent system to learn, over a period of time, how to perform sequences of continuous actions in a cooperative manner without any prior task model. The agents comprising the system manage to gain experience over the task that they collaboratively perform by continuously exploring and exploiting their state-to-action mapping space. For the specific problem setting, the proposed theoretical framework is employed in the case of two simulated e-Puck robots performing a collaborative box-pushing task. This task involves active cooperation between the robots in order to jointly push an object on a plane to a specified goal location. We should note that 1) there are no contact points specified for the two e-Pucks and 2) the shape of the object is indifferent. The actuated wheels of the mobile robots are considered as the independent agents that have to build up cooperative skills over time, in order for the robot to demonstrate intelligent behavior. Our goal in this experimental study is to evaluate both the proposed hierarchical multi-agent architecture, as well as the methodological control framework. Such a hierarchical multi-agent approach is envisioned to be highly scalable for the control of complex biologically inspired robot locomotion systems.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}

Biologically inspired architectures that mimic the organizational structure of living organisms and in general frameworks that will improve the design of intelligent robots attract significant attention from the research community. Self-organization problems, intrinsic behaviors as well as effective learning and skill transfer processes in the context of robotic systems have been significantly investigated by researchers. Our work presents a new framework of developmental skill learning process by introducing a hierarchical nested multi-agent architecture. A neuro-dynamic learning mechanism employing function approximators in a fuzzified state-space is utilized, leading to a collaborative control scheme among the distributed agents engaged in a continuous space, which enables the multi-agent system to learn, over a period of time, how to perform sequences of continuous actions in a cooperative manner without any prior task model. The agents comprising the system manage to gain experience over the task that they collaboratively perform by continuously exploring and exploiting their state-to-action mapping space. For the specific problem setting, the proposed theoretical framework is employed in the case of two simulated e-Puck robots performing a collaborative box-pushing task. This task involves active cooperation between the robots in order to jointly push an object on a plane to a specified goal location. We should note that 1) there are no contact points specified for the two e-Pucks and 2) the shape of the object is indifferent. The actuated wheels of the mobile robots are considered as the independent agents that have to build up cooperative skills over time, in order for the robot to demonstrate intelligent behavior. Our goal in this experimental study is to evaluate both the proposed hierarchical multi-agent architecture, as well as the methodological control framework. Such a hierarchical multi-agent approach is envisioned to be highly scalable for the control of complex biologically inspired robot locomotion systems.

Spyros V Velanas, Costas S Tzafestas

Human Telehaptic Perception of Stiffness using an Adaptive Impedance Re fl ection Bilateral Teleoperation Control Scheme Conference

In: Proceedings of the IEEE International Workshop on Robot and Human Interactive Communication, ROMAN-2010, 2010, ISBN: 9781424479894.

BibTeX | Links: [PDF]

John N Karigiannis, Theodoros I Rekatsinas, Costas S Tzafestas

Hierarchical Multi-Agent Architecture employing TD ( $łambda$ ) Learning with Function Approximators for Robot Skill Acquisition Conference

Architecture, 2010.

2009

C. Tzafestas, N. Mitsou, N. Georgakarakos, O. Diamanti, P. Maragos, S. E. Fotinea, E. Efthimiou

Gestural teleoperation of a mobile robot based on visual recognition of sign language static handshapes Conference

Proceedings - IEEE International Workshop on Robot and Human Interactive Communication, 2009, ISSN: 19449445.

Abstract | BibTeX | Links: [PDF]

S.E. Fotinea, Eleni Efthimiou, George Caridakis, Olga Diamanti, N. Mitsou, K. Karpouzis, C. Tzafestas, P. Maragos

DIANOEMA: Visual analysis and sign recognition for GSL modelling and robot teleoperation Conference

Language and Speech, 2009.

BibTeX | Links: [Webpage] [PDF]

M. Alifragis, C.S. Tzafestas

Stereo pair matching of archaeological scenes using phase domain methods Conference

IMAGAPP 2009 - Proceedings of the 1st International Conference on Computer Imaging Theory and Applications, 2009, ISBN: 9789898111685.

Abstract | BibTeX | Links: [PDF]

C Tzafestas

Telehaptics: issues of control stability and human perception in remote kineasthetic exploration Conference

18th IEEE International Symposium on Robot and Human Interactive Communication (RO-MAN 2009), Workshop on Robot-Human Synergies, Sept. 27 - Oct. 2 2009, 2009.

2008

Costas S Tzafestas, Kostas Birbas, Yiannis Koumpouros, Dimitri Christopoulos

Pilot Evaluation Study of a Virtual Paracentesis Simulator for Skill Training and Assessment: The Beneficial Effect of Haptic Display Journal Article

Presence: Teleoperators & Virtual Environments, 17 (2), pp. 212–229, 2008, ISBN: 10547460.

Abstract | BibTeX | Links: [Webpage] [PDF]

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abstract = {Effective, real-time training of health care professionals in invasive procedures is a challenging task. Furthermore, assessing in practice the acquisition of the dexterity and skills required to safely perform such operations is particularly difficult to perform objectively and reliably. The development of virtual reality (VR) simulators offers great potential toward these objectives, and can help bypass some of the difficulties associated with classical surgical training and assessment procedures. In this context, we have developed a prototype VR simulator platform for training in a class of invasive procedures, such as accessing central vessels. This paper focuses more particularly on a pilot study treating the specific application case of subclavian vein paracentesis. The simulation incorporates 3D models of all the human anatomy structures involved in this procedure, where collision detection and response algorithms are implemented to simulate most of the potential complications in accordance with the situations encountered in real clinical practice. Furthermore, haptic display is integrated using a typical force feedback device providing the user with a sense of touch during the simulated operations. Our main objective in this study was to obtain quantitative evaluation results regarding the effect of haptic display on performance. Two user groups participated in the study: (I) novice users and (II) experienced surgeons. The system automatically provides quantitative assessment scores of users' performance, applying a set of objective measures that also involve the optimality of the needle insertion path and indicators of maneuvering errors. Training and skill assessment performance of the system is evaluated in a twofold manner, regarding respectively: (a) the learning curve of novice users, and (b) the correlation of the system-generated scores with the actual surgical experience of the user. These performance indicators are assessed with respect to the activation of the haptic display and to whether this has any beneficial effect (or not). The experimental findings of this first pilot study provide quantitative evidence about the significance of haptic display, not only as a means to enhance the realism of the surgical simulation, but especially as an irreplaceable component for achieving objective and reliable skill assessment. Further larger-scale and long-term clinical studies are needed to validate the effectiveness of such platforms for actual training and dexterity enhancement, particularly when more complex sensorimotor skills are involved. [ABSTRACT FROM AUTHOR] Copyright of Presence: Teleoperators & Virtual Environments is the property of MIT Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)},
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Effective, real-time training of health care professionals in invasive procedures is a challenging task. Furthermore, assessing in practice the acquisition of the dexterity and skills required to safely perform such operations is particularly difficult to perform objectively and reliably. The development of virtual reality (VR) simulators offers great potential toward these objectives, and can help bypass some of the difficulties associated with classical surgical training and assessment procedures. In this context, we have developed a prototype VR simulator platform for training in a class of invasive procedures, such as accessing central vessels. This paper focuses more particularly on a pilot study treating the specific application case of subclavian vein paracentesis. The simulation incorporates 3D models of all the human anatomy structures involved in this procedure, where collision detection and response algorithms are implemented to simulate most of the potential complications in accordance with the situations encountered in real clinical practice. Furthermore, haptic display is integrated using a typical force feedback device providing the user with a sense of touch during the simulated operations. Our main objective in this study was to obtain quantitative evaluation results regarding the effect of haptic display on performance. Two user groups participated in the study: (I) novice users and (II) experienced surgeons. The system automatically provides quantitative assessment scores of users' performance, applying a set of objective measures that also involve the optimality of the needle insertion path and indicators of maneuvering errors. Training and skill assessment performance of the system is evaluated in a twofold manner, regarding respectively: (a) the learning curve of novice users, and (b) the correlation of the system-generated scores with the actual surgical experience of the user. These performance indicators are assessed with respect to the activation of the haptic display and to whether this has any beneficial effect (or not). The experimental findings of this first pilot study provide quantitative evidence about the significance of haptic display, not only as a means to enhance the realism of the surgical simulation, but especially as an irreplaceable component for achieving objective and reliable skill assessment. Further larger-scale and long-term clinical studies are needed to validate the effectiveness of such platforms for actual training and dexterity enhancement, particularly when more complex sensorimotor skills are involved. [ABSTRACT FROM AUTHOR] Copyright of Presence: Teleoperators & Virtual Environments is the property of MIT Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Manthos Alifragis, Andreas Mantelos, Costas S. Tzafestas

Web-based remote and virtual programming console of the V+ robotic system Conference

IECON Proceedings (Industrial Electronics Conference), 2008, ISSN: 1553-572X.

Abstract | BibTeX | Links: [PDF]

John N. Karigiannis, Costas S. Tzafestas

Multi-agent hierarchical architecture modeling kinematic chains employing continuous RL learning with fuzzified state space Conference

Proceedings of the 2nd Biennial IEEE/RAS-EMBS International Conference on Biomedical Robotics and Biomechatronics, BioRob 2008, 2008, ISBN: 9781424428830.

Abstract | BibTeX | Links: [PDF]

@conference{Karigiannis2008,
title = {Multi-agent hierarchical architecture modeling kinematic chains employing continuous RL learning with fuzzified state space},
author = { John N. Karigiannis and Costas S. Tzafestas},
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doi = {10.1109/BIOROB.2008.4762862},
isbn = {9781424428830},
year = {2008},
date = {2008-10-01},
booktitle = {Proceedings of the 2nd Biennial IEEE/RAS-EMBS International Conference on Biomedical Robotics and Biomechatronics, BioRob 2008},
pages = {716--723},
abstract = {In the context of multi-agent systems, we are proposing a hierarchical robot control architecture that comprises artificial intelligence (AI) techniques and traditional control methodologies, based on the realization of a learning team of agents in a continuous problem setting. In a multiagent system, action selection is important for cooperation and coordination among the agents. By employing reinforcement learning (RL) methods in a fuzzified state-space, we accomplish to design a control architecture and a corresponding methodology, engaged in a continuous space, which enables the agents to learn, over a period of time, to perform sequences of continuous actions in a cooperative manner, in order to reach their goal without any prior generated task model. By organizing the agents in a nested architecture, as proposed in this work, a type of problem-specific recursive knowledge acquisition is attempted. Furthermore, the agents try to exploit the knowledge gathered in order to be in position to execute tasks that indicate certain degree of similarity. The agents correspond in fact to independent degrees of freedom of the system, and achieve to gain experience over the task that they collaboratively perform, by exploring and exploiting their state-to-action mapping space. A numerical experiment is presented in this paper, performed on a simulated planar 4 degrees of freedom (DOF) manipulator, in order to evaluate both the proposed hierarchical multiagent architecture as well as the proposed methodological framework. It is anticipated that such an approach can be highly scalable for the control of robotic systems that are kinematically more complex, comprising multiple DOFs and potentially redundancies in open or closed kinematic chains, particularly dexterous manipulators. textcopyright 2008 IEEE.},
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Costas Tzafestas, Spyros Velanas, George Fakiridis

Adaptive impedance control in haptic teleoperation to improve transparency under time-delay Conference

Proceedings - IEEE International Conference on Robotics and Automation, 2008, ISSN: 10504729.

Abstract | BibTeX | Links: [PDF]

2007

Nikos C. Mitsou, Costas S. Tzafestas

Temporal Occupancy Grid for mobile robot dynamic environment mapping Conference

2007 Mediterranean Conference on Control and Automation, MED, 2007, ISBN: 142441282X.

Abstract | BibTeX | Links: [PDF]

Nikos Mitsou, Costas Tzafestas

Maximum likelihood SLAM in dynamic environments Conference

Proceedings - International Conference on Tools with Artificial Intelligence, ICTAI, 1 , 2007, ISSN: 10823409.

Abstract | BibTeX | Links: [PDF]

2006

Costas S Tzafestas, Nektaria Palaiologou, Manthos Alifragis

Virtual and remote robotic laboratory: Comparative experimental evaluation Journal Article

IEEE Transactions on Education, 49 (3), pp. 360–369, 2006, ISSN: 00189359.

Abstract | BibTeX | Links: [PDF]

@article{3_64,
title = {Virtual and remote robotic laboratory: Comparative experimental evaluation},
author = {Costas S Tzafestas and Nektaria Palaiologou and Manthos Alifragis},
url = {http://robotics.ntua.gr/wp-content/uploads/sites/2/Virtual_and_remote_robotic_laboratory_comparative_experimental_evaluation.pdf},
doi = {10.1109/TE.2006.879255},
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year = {2006},
date = {2006-01-01},
journal = {IEEE Transactions on Education},
volume = {49},
number = {3},
pages = {360--369},
abstract = {This paper describes the development and experimental evaluation of an e-laboratory platform in the field of robotics. The system in its current configuration is designed to enable distance training of students in real scenarios of robot manipulator programming. From a technological perspective, the research work presented in this paper is directed towards the adaptation of concepts and techniques developed in the field of telerobotics and virtual reality, and their integration in such e-laboratory settings. This paper focuses particularly on the educational impact of such systems. The goal is to assess the performance of e-laboratory scenarios in terms of the efficacy of training provided to students. The results of a pilot experimental study are presented, providing a comparative evaluation for three training modalities: real, remote, and virtual training on robot manipulator programming. The experiments were conducted according to an evaluation protocol specially designed for the considered target training task, using scoring charts to obtain quantitative performance measures and assess the performance of the student groups participating in the course. Training, as a dynamic process, is approached according to a classical three dimensional model, and performance scores are accordingly assessed in these dimensions (namely: low-level versus mid and high-level skills and understanding). The obtained results reveal certain differences between the three groups, particularly as related to the low-level skill training score, giving some insight about the training `dimensions' that are expected to be mostly affected by the absence of physical (or realistic virtual) presence in a real hands-on experimentation. Statistical analysis indicates, however, that, despite these apparent differences, such e-laboratory modules can be integrated quite effectively in practical scenarios, creating virtual training environments that can provide adequate learning elements, as related p-$backslash$n-$backslash$narticularly to mid and high-level skill acquisition. Further work and large-scale studies are still needed, though, in order to explore the extent to which such a general conclusion is valid in different training settings, and to form the basis of a more theoretical evaluation for a comprehensive understanding of the pedagogical differences between real, virtual, and remote learning/training methodologies and experiences},
keywords = {},
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This paper describes the development and experimental evaluation of an e-laboratory platform in the field of robotics. The system in its current configuration is designed to enable distance training of students in real scenarios of robot manipulator programming. From a technological perspective, the research work presented in this paper is directed towards the adaptation of concepts and techniques developed in the field of telerobotics and virtual reality, and their integration in such e-laboratory settings. This paper focuses particularly on the educational impact of such systems. The goal is to assess the performance of e-laboratory scenarios in terms of the efficacy of training provided to students. The results of a pilot experimental study are presented, providing a comparative evaluation for three training modalities: real, remote, and virtual training on robot manipulator programming. The experiments were conducted according to an evaluation protocol specially designed for the considered target training task, using scoring charts to obtain quantitative performance measures and assess the performance of the student groups participating in the course. Training, as a dynamic process, is approached according to a classical three dimensional model, and performance scores are accordingly assessed in these dimensions (namely: low-level versus mid and high-level skills and understanding). The obtained results reveal certain differences between the three groups, particularly as related to the low-level skill training score, giving some insight about the training `dimensions' that are expected to be mostly affected by the absence of physical (or realistic virtual) presence in a real hands-on experimentation. Statistical analysis indicates, however, that, despite these apparent differences, such e-laboratory modules can be integrated quite effectively in practical scenarios, creating virtual training environments that can provide adequate learning elements, as related p-$backslash$n-$backslash$narticularly to mid and high-level skill acquisition. Further work and large-scale studies are still needed, though, in order to explore the extent to which such a general conclusion is valid in different training settings, and to form the basis of a more theoretical evaluation for a comprehensive understanding of the pedagogical differences between real, virtual, and remote learning/training methodologies and experiences

Nikos C. Mitsou, Spyros V. Velanas, Costas S. Tzafestas

Visuo-haptic interface for teleoperation of mobile robot exploration tasks Conference

Proceedings - IEEE International Workshop on Robot and Human Interactive Communication, 2006, ISSN: 1-4244-0565-3.

Abstract | BibTeX | Links: [PDF]

I Kaklamanos A Vezakis G Polymeneas G Bonatsos Κ. Birbas C. Tzafestas

Spatial ability can predict laparoscopic skill performance of novice surgeons Conference

10th World Congress of Endoscopic Surgery and 14th International Congress of the European Association for Endoscopic Surgery (EAES), Β$epsilon$$rho$ο$łambda$ί$nu$ο, 13-16 Sept. 2006., 2006.

D Christopoulos I Kaklamanos G Bonatsos Κ. Birbas C. Tzafestas

Virtual paracentesis simulator (DEX): impact of haptic interaction on the learning curve Conference

10th World Congress of Endoscopic Surgery and 14th International Congress of the European Association for Endoscopic Surgery (EAES), Β$epsilon$$rho$ο$łambda$ί$nu$ο, 13-16 Sept. 2006., 2006.

2005

N Palaiologou, C Tzafestas

Training scenarios for students on virtual and remote robotic laboratory platforms Journal Article

2005.

BibTeX | Links: [Webpage]

CS Tzafestas, N Palalologou, M Alifragis

Experimental evaluation and pilot assessment study of a virtual and remote laboratory on robotic manipulation Conference

IEEE International Symposium on Industrial Electronics (ISIE'05), p.1677-1683, Dubrovnik, Croatia, Jun 20-23, 2005, 2005, ISBN: 0-7803-8738-4.

Abstract | BibTeX | Links: [PDF]

@conference{Tzafestas2005,
title = {Experimental evaluation and pilot assessment study of a virtual and remote laboratory on robotic manipulation},
author = { CS Tzafestas and N Palalologou and M Alifragis},
url = {http://robotics.ntua.gr/wp-content/uploads/sites/2/ISIE2005_Tzafestas_Palaiologou.pdf},
isbn = {0-7803-8738-4},
year = {2005},
date = {2005-01-01},
booktitle = {IEEE International Symposium on Industrial Electronics (ISIE'05), p.1677-1683, Dubrovnik, Croatia, Jun 20-23, 2005},
pages = {1677--1683},
abstract = {Practical training in experimental laboratory scenarios is indeed of great importance since mere lecturing is not sufficient enough to complete students' education in many engineering disciplines. Synchronous and asynchronous distance learning platforms have many advantages such as attending courses from a distance (e.g. in virtual classroom environments). However remote “elaboratory” systems are just now beginning to develop. In this paper, the development of a “virtual and remote laboratory platform” in the field of robotics and the methodology of its experimental evaluation are discussed. In the past, in our prior work [10], a first pilot experimental study was conducted according to a special evaluation protocol, in order to evaluate system performance regarding remotely training students to program robot manipulation tasks using the robot's Teach Pendant. The results of the first pilot study are encouraging enough. In this paper, we are focusing on the methodology of the evaluation protocol and discuss ways to extend this study amongst three groups: group-I trained the “classical way” on the real robot, group-II (remote) trained remotely on the graphical user interface of the remote laboratory platform, and group-III (virtual) also trained on the user interface, but using only the “virtual robot” functionalities of the platform with no remote real robot connection on the loop. Initial results are showing the need for developing real training scenarios in the frame of remote laboratory education aiming to achieve effective learning schemes for students in the engineering field.},
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}

K Birbas C. Tzafestas

Haptic Interaction in Simulating the Paracentesis of Great Vessels for Clinical Skill Enhancement Conference

WorldHaptics'2005, First Joint Eurohaptics Conference and Symposium on Haptic Interfaces for Virtual Environment and Teleoperator Systems, Pisa, Italy March 18-20, 2005, 2005.

John N. Karigiannis, Costas S. Tzafestas

Multi-agent architecture with continuous reinforcement learning in fuzzy state-space for robot manipulation control Conference

International Conference on Integrated Modeling and Analysis in Applied Control and Automation, IMAACA 2005, Held at the International Mediterranean Modeling Multiconference, I3M 2005, 2005.

Abstract | BibTeX | Links: [Webpage]

2004

C S Tzafestas, Y Koumpouros, K Birbas

Paracentesis modeling and VR-based interactive simulation with haptic display for clinical skill training and assessment Conference

in Proceedings of The International Conference on Integrated Modeling & Analysis in Applied Control & Automation (IMAACA'2004), Special Session on: Virtual Reality and Haptics for Modeling, Design and Interactive Simulation. I3M: International Mediterranean Modeling Multiconference, Genoa, Italy, October 28-31 2004, 2004.

BibTeX | Links: [PDF]

C. S. Tzafestas, Y. Koumpouros, K. Birbas

Haptic interaction in VR-based paracentesis simulation for dexterity enhancement and assessment Conference

International Congress Series, 1268 (C), 2004, ISSN: 05315131.

Abstract | BibTeX | Links: [PDF]

CS Tzafestas, M Alifragis

Development and experimental evaluation of a remote laboratory platform for teaching robot manipulator programming Conference

Proc. Int. Conf. łdots, (c), 2004.

BibTeX | Links: [PDF]

C S Tzafestas Y Koumpouros G Bonatsos K. Birbas I.G. Kaklamanos

Dexterity enhancement and assessment of training in paracentesis of great vessels by using a virtual reality based interactive system (DEX system) Conference

(poster), 90th Annual Clinical Congress, American College of Surgeons, October 10-14, 2004, New Orleans, LA, USA, 2004.

C S Tzafestas, M Alifragis, N Palaiologou, S.C.A Thomopoulos, A -E Exarchou, A Kroys, R Kunicke

Virtual Robotic Laboratory : Applying web-based teleoperation technologies to distance training in robot manipulator programming Conference

Rev 2004: 1st International Conference on Remote Engineering and Virtual Instrumentation, 2004.

BibTeX | Links: [PDF]

2003

Costas S Tzafestas

Whole-Hand Kinesthetic Feedback and Haptic Perception in Dextrous Virtual Manipulation Journal Article

IEEE Transactions on Systems, Man, and Cybernetics Part A:Systems and Humans., 33 (1), pp. 100–113, 2003, ISSN: 10834427.

Abstract | BibTeX | Links: [PDF]

2002

Costas S Tzafestas, Petros Maragos

Shape connectivity: Multiscale analysis and application to generalized granulometries Journal Article

Journal of Mathematical Imaging and Vision, 17 (2), pp. 109–129, 2002, ISSN: 09249907.

Abstract | BibTeX | Links: [PDF]

2001

S.G. Tzafestas P.A. Prokopiou, C S Tzafestas

A New Partitioned Robot Neurocontroller: General Analysis and Application to Teleoperator Modeling Uncertainties Compensation Journal Article

2001.

BibTeX | Links: [PDF]

C S Tzafestas, S G Tzafestas

Full-State Modeling, Motion Planning and Control of Mobile Manipulators Journal Article

2001.

BibTeX | Links: [PDF]

Costas S. Tzafestas

Teleplanning by human demonstration for VR-based teleoperation of a mobile robotic assistant Conference

Proceedings - IEEE International Workshop on Robot and Human Interactive Communication, 2001, ISBN: 0780372220.

Abstract | BibTeX | Links: [PDF]

C S Tzafestas, S G Tzafestas

Mobile Manipulators: Full-State Modeling, Motion Planning and Control Conference

17th Intl. Conference on CAD/CAM, Robotics and the Factories of the Future (CARS & FOF '2001), Durban, South Africa, July 2001, 2001.

C S Tzafestas

Multimodal Teleoperation Interface integrating VR Models for a Mobile Robotic Assistant Conference

Proc. 10th International Workshop on Robotics in Alpe-Adria-Danube Region (RAAD'2001), Vienna, Austria, May 16-18, 2001, 2001.

A. Sofou, C. Tzafestas, P. Maragos

SEGMENTATION OF SOILSECTION IMAGES USING CONNECTED OPERATORS Conference

Proc. Int'l Conf. on Image Processing (ICIP-2001), Thessaloniki, Greece, Oct. 2001, 2001, ISBN: 0780367251.

BibTeX | Links: [PDF]

2000

C S Tzafestas, P A Prokopiou, S G Tzafestas

A differential motion planning algorithm for controlling multi-robot systems handling a common object Journal Article

Control and Cybernetics, 29 (2), pp. 566–584, 2000, ISSN: 03248569.

Abstract | BibTeX | Links: [PDF]

C S Tzafestas, Ph Coiffet

Dexterous haptic interaction with virtual environments: hand-distributed kinesthetic feedback and haptic perception Journal Article

38 (2), pp. 433–476, 2000, ISSN: 02329298.

Abstract | BibTeX

Costas S Tzafestas, Dimitris Valatsos

VR-based Teleoperation of a Mobile Robotic Assistant : Progress Report Conference

in Proc: European Workshop on Service and Humanoid Robots (Servicerob'2001), pp.51-56, Santorini, Greece, 2001, (c), 2000.

BibTeX | Links: [PDF]

Petros Maragos, Giorgos Stamou, Spyros Tzafestas

A lattice control model of fuzzy dynamical systems in state-space ∗ Conference

in Mathematical Morphology and Its Application to Image and Signal Processing, J. Goutsias, L. Vincent and D. Bloomberg, Editors, Kluwer Academic Publishers, Boston, 2000, pp. 61--70, 70 (ii), 2000.

BibTeX | Links: [PDF]

C. S. Tzafestas, Ph Coiffet

Dexterous haptic interaction with virtual environments: hand-distributed kinesthetic feedback and haptic perception Conference

Proc. IARP First International Workshop on Humanoid and Human Friendly Robotics, Tsukuba, Japan, October 26-27, 1998, 38 (2), 2000, ISSN: 02329298.

Abstract | BibTeX

1999

Costas S. Tzafestas, Spyros G. Tzafestas

Recent algorithms for fuzzy and neurofuzzy path planning and navigation of autonomous mobile robots Conference

Systems Science, 25 (2), 1999, ISSN: 01371223.

Abstract | BibTeX | Links: [PDF]

S G Tzafestas, C S Tzafestas

Virtual Reality in Telerobotics: The State-of-the-Art Conference

Proc. IEEE Intl. Symposium on Industrial Electronics (ISIE'99), Bled, Slovenia, July 12-16, 1999, 1999.

BibTeX | Links: [PDF]

P Maragos, S G Tzafestas

Min-Max Control with Application to Discrete Event Dynamic Systems Book Chapter

Advances in Manufacturing, pp. 217–230, Springer London, London, 1999, ISBN: 978-1-4471-0855-9.

Abstract | BibTeX | Links: [PDF]

1998

Costas S Tzafestas, Platon A Prokopiou, Spyros G Tzafestas

Path Planning and Control of a Cooperative Three-Robot System Manipulating Large Objects Journal Article

Journal of Intelligent and Robotic Systems: Theory and Applications, 22 (2), pp. 99–116, 1998, ISSN: 09210296.

Abstract | BibTeX | Links: [PDF]

A Kheddar, C Tzafestas

Fitting tele-operation and virtual reality technologies towards teleworking Conference

FIR'98, 4th French-Israeli łdots, 1998.

BibTeX | Links: [Webpage] [PDF]

1997

Costas S Tzafestas, Nacer K M'Sirdi, N Manamani

Adaptive Impedance Control Applied to a Pneumatic Legged Robot Journal Article

Journal of Intelligent & Robotic Systems, 20 (2), pp. 105–129, 1997, ISSN: 0921-0296.

Abstract | BibTeX | Links: [PDF]

S G a Tzafestas, T E a Krikochoritis, C S b Tzafestas

Robust Sliding-mode Control of Nine-link Biped Robot Walking Journal Article

Journal of Intelligent and Robotic Systems: Theory and Applications, 20 (2-4), pp. 375–402, 1997, ISSN: 09210296.

Abstract | BibTeX | Links: [Webpage] [PDF]

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title = {Robust Sliding-mode Control of Nine-link Biped Robot Walking},
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doi = {Doi 10.1023/A:1007924731253},
issn = {09210296},
year = {1997},
date = {1997-01-01},
journal = {Journal of Intelligent and Robotic Systems: Theory and Applications},
volume = {20},
number = {2-4},
pages = {375--402},
abstract = {A nine-link planar biped robot model is considered which, in addition to the main links (i.e., legs, thighs and trunk), includes a two-segment foot. First, a continuous walking pattern of the biped on a flat terrain is synthesized, and the corresponding desired trajectories of the robot joints are calculated. Next, the kinematic and dynamic equations that describe its locomotion during the various walking phases are briefly presented. Finally, a nonlinear robust control approach is followed, motivated by the fact that the control which has to guarantee the stability of the biped robot must take into account its exact nonlinear dynamics. However, an accurate model of the biped robot is not available in practice, due to the existence of uncertainties of various kinds such as unmodeled dynamics and parameter inaccuracies. Therefore, under the assumption that the estimation error on the unknown (probably time-varying) parameters is bounded by a given function, a sliding-mode controller is applied, which provies a successful way to preserve stability and achieve good performance, despite the presence of strong modeling imprecisions or uncertainties. The paper includes a set of representative simulation results that demonstrate the very good behavior of the sliding-mode robust biped controller.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

A. Kheddar, C. Tzafestas, P. Coiffet

The hidden robot concept-high level abstraction teleoperation Conference

Proceedings of the 1997 IEEE/RSJ International Conference on Intelligent Robot and Systems. Innovative Robotics for Real-World Applications. IROS '97, 3 , 1997, ISBN: 0-7803-4119-8.

Abstract | BibTeX | Links: [Webpage] [PDF]

P Coiffet A. Kheddar C. Tzafestas, I Mazon C Laugier & R Chellali T. Kotoku K. Tanie

Parallel, Multi-Robot Long-Distance Teleoperation Conference

Proc. 1997 IEEE International Conference on Advanced Robotics (ICAR'97), pp.1007-1012, Monterey, CA, USA, July 7-9, 1997, 1997.

BibTeX | Links: [PDF]

Spyros G. Tzafestas, Platon A. Prokopiou, Costas S. Tzafestas

Telemanipulator neurocontrol using multiple RBF networks Conference

IEEE International Symposium on Intelligent Control - Proceedings, 1997.

Abstract | BibTeX | Links: [PDF]

S. G. Tzafestas, P. A. Prokopiou, C. S. Tzafestas

Robust telemanipulator control using a partitioned neural network architecture Conference

IEEE International Conference on Neural Networks - Conference Proceedings, 3 , 1997, ISSN: 10987576.

Abstract | BibTeX | Links: [PDF]

Costas Tzafestas, Philippe Coiffet

Computing optimal forces for generalized kinesthetic feedback on the human hand during virtual grasping and manipulation Conference

Proceedings of the 1997 IEEE International Conference on Robotics and Automation, ICRA. Part 3 (of 4), 1 , 1997, ISSN: 10504729.

Abstract | BibTeX | Links: [Webpage] [PDF]

P A Prokopiou C.S. Tzafestas S.G. Tzafestas

Incremental Control of Three Cooperating Robots in Large-Object-Transfer Operations Conference

Proc. 2nd MATHMOD: Mathematical Modeling IMACS Symposium, Vienna, Feb.5-7, 1997, 1997.

T E Krikochoritis S.G. Tzafestas, C S Tzafestas

Robust and Adaptive Control of Biped Robot Walking Conference

Proc. 1st MobiNet Symp. on Mobile Robotics Technology for Health Care Services (MOBINET'97), Athens, Greece, May 15-16, 271-286, 1997, 1997.

1996

A Kheddar, C Tzafestas, P Coiffet, T Kotoku, K Tanie

Multi-robot teleoperation using direct human hand actions Journal Article

Advanced Robotics, 11 (8), pp. 799–825, 1996, ISSN: 15685535.

Abstract | BibTeX | Links: [PDF]

@article{Kheddar1996,
title = {Multi-robot teleoperation using direct human hand actions},
author = {A Kheddar and C Tzafestas and P Coiffet and T Kotoku and K Tanie},
url = {http://robotics.ntua.gr/wp-content/uploads/sites/2/kheddar1996.pdf},
doi = {10.1163/156855398X00343},
issn = {15685535},
year = {1996},
date = {1996-01-01},
journal = {Advanced Robotics},
volume = {11},
number = {8},
pages = {799--825},
abstract = {This paper presents a novel concept for teleoperation using direct human hand(s) actions which we called 'the hidden robot' concept. The proposed teleoperation scheme is composed of three main components: the operator/ computer loop, the execution loop and between them the bilateral transformation modules linked by the communication channel. Within the operator/computer master loop, the operator performs what we call a 'virtual task', without being constrained by the slave robot. At this stage, the bilateral transformation layer is in charge of extracting, at the low level, pertinent parameters from the virtual task and transforming them onto robot control signals. The execution loop performs control of the slave robot(s) to achieve the desired task, described by the virtual one. At this stage, the transformation layer extracts pertinent data to provide feedback when possible and needed. It also makes sure that the task is being performed correctly in the real site; otherwise, it takes necessary recovery procedures or informs the operator to procede in a different way. We will describe in detail each component, highlighting the originalities of our approach. We will also present the experiment performed by applying this concept to long-distance, simultaneous teleoperation of four slave robots with different kinematics and situated at different locations in France and in Japan. The experimental task consisted of assembling a four-piece puzzle. All the robots had to perform the same task in parallel. We will discuss the experimental results presented in this paper, concering long-distance teleoperated robot control and round-trip communication time delay. The experiment demonstrated the feasibility of the proposed scheme and gave guidelines related to the direct use of the operator hand, within an intermediate representation, as a guide for task execution.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

Tzafestas C S S.G. Tzafestas M. Raibert

Robust Sliding Mode Control Applied to a 5-link Biped Robot Journal Article

1996.

BibTeX | Links: [PDF]

C Tzafestas, P Coiffet

Real-time collision detection using spherical octrees: virtual reality application Conference

Robot and Human Communication, 1996., 5th IEEE International Workshop on, 1996, ISBN: 0780332539.

Abstract | BibTeX | Links: [PDF]

1993

M Raibert, S Tzafestas, C Tzafestas

Comparative simulation study of three control techniques applied to a biped robot Conference

International Conference on Systems, Man and Cybernetics, Le Touquet, France, 1993.

BibTeX | Links: [PDF]