Workshop organizers: Mahdi Tavakoli and Ilia G. Polushin
Workshop date: May 23, 2017
Stability analysis of bilateral and multilateral teleoperation systems, particularly in the presence of communication delays, has become a topic of intensive research interest over the last decade. As of today, a number of fundamentally different approaches has been developed to address the haptic teleoperation system stability problem in different settings and from different points of view. The specific results achieved within these approaches are very diverse, and relationships between these results are often not clear. The goal of this workshop is to bring together researchers working in the area, and to create an environment for exchange of ideas towards development of a more unified and comprehensive theory of stability of teleoperation systems. The workshop will include tutorial presentations on different approaches to stability analysis and control design for stability of teleoperation systems given by leading researchers in this area. The workshop will also feature poster presentations related to its topic.
This full-day workshop deals with stability analysis and control design for stability of bilateral teleoperator systems. Stability analysis of bilateral and multilateral teleoperation systems, particularly in the presence of communication delays, has become a topic of intensive research interest over the last decade. As of today, a number of fundamentally different approaches has been developed to address the haptic teleoperation system stability problem in different settings and from different points of view. The specific results achieved within these approaches are very diverse, and relationships between these results are often not clear.
The goal of this workshop is to bring together researchers working in the area of teleoperator systems theory and design, and to create an environment for exchange of ideas towards development of a more unified and comprehensive theory of stability of teleoperation systems. The workshop will include tutorial presentations on different approaches to stability analysis and control design for stability of teleoperation systems. The workshop will also feature poster presentations related to its topic.
08:15 -- 8:30 Introductions, Opening Discussions
08:30 -- 09:00 Stability of Force Feedback Systems: A Survey (Blake Hannaford, University of Washington, USA) (PDF)
09:00 -- 09:30 Absolute Stability in Bilateral Telerobotic Systems (Keyvan Hashtrudi-Zaad, Queen's University, Canada) (PDF)
09:30 -- 10:00 Absolute Stability of Multi-DOF Multi-Lateral Haptic Systems (Mahdi Tavakoli, University of Alberta, Canada) (PDF)
10:00 -- 10:30 Coffee Break
10:30 -- 11:00 Energy Aware Robotics (Stefano Stramigioli, University of Twente, Netherlands)
11:00 -- 11:30 Design Methodology for Haptic Teleoperation with Time Delay and Other Systems (Jordi Artigas, Institute of Robotics and Mechatronics, DLR, Germany)
11:30 -- 12:00 Stability Analysis Using Multiplier Theory and IQC Framework (Joaquin Carrasco, University of Manchester, UK) (PDF)
12:00 -- 13:00 Lunch
13:00 -- 14:00 Poster Presentations, Discussions
14:00 -- 14:30 Passivity and Life Thereafter (Gunter Niemeyer, Disney Research, USA)
14:30 -- 15:00 Stability of Haptic Teleoperation Systems with Projection-Based Force Reflection (Ilia Polushin, Western University, Canada) (PDF)
15:00 -- 15:30 Modulated Time-Domain Passivity Control: A Passivity-Based Approach for Stable Human-Robot Interaction in Haptics-Enabled Telerobotic Systems (Rajni Patel, Western University,
15:30 -- 16:00 Coffee Break
16:00 -- 16:30 Resilient Control of Bilateral Teleoperators (Nikhil Chopra, University of Maryland, College Park, USA) (PDF)
16:30 -- 17:00 New Results on the Control of Bilateral Teleoperators via Energy Shaping (Emmanuel Nuno, University of Guadalajara, Mexico) (PDF)
17:00 -- 18:00 Closing Discussions
Dr. Jordi Artigas, Institute of Robotics and Mechatronics, DLR, Germany.
Title of presentation: Design Methodology for Haptic Teleoperation with Time Delay (and Other Systems)
Abstract: In this talk we will discuss some necessary steps to design stable systems affected by time delay, jitter and data losses. Force-feedback teleoperation has become a paradigm in control as it encompasses many interesting aspects and challenges in a single system: The human is an integral part of the loop; the time delay might be greater or smaller, but it is unavoidable and has strong effects on stability and performance; the hardware, including the communication infrastructure, must fulfill some hard real time requirements to allow very tight control loops. We will see the benefits of a full energy treatment of these systems, the importance of model representations, from the flow diagram to electrical circuits and network representation, and the advantages of passivity as a tool for stability. These will be the main ingredients of a methodology which will allow us to design ANY stable bilateral (and multilateral) control architecture (2, 3, 4 channels, etc.) and in the presence of ANY communication delay value, package loss ratio and jitter. Specific examples will be presented and sustained by some space telerobotics missions conducted in the DLR. Finally, we will also see how these tools can be easily applied in other systems and domains.
Bio: Jordi Artigas received his M.S. in electrical engineering from the Ramon Llull University (Barcelona) in 2003 and received his Ph.D. in automation and robotics from the Technical University of Madrid (UPM). He has been a research engineer in robotics at the Institute of Robotics and Mechatronics of the DLR since 2003. He was a visiting researcher at the PERCRO Laboratory in Scuola Santa Anna (Pisa, Italy) in 2008 and at the Korean University of Technology and Education (Cheonan, Korea) in 2009 and 2012. Currently he is leading the ``Telemanipulation robotic systems'' group in the DLR. He is co-chair of the IEEE Telerobotics Technical Committee since 2012. His main research interests include bilateral control methods for complex telemanipulation systems through delay affected communication infrastructures, physical human-robot interaction, space tele-robotics, haptics and telepresence.
Dr. Joaquin Carrasco, University of Manchester, UK.
Title of presentation: Stability Analysis Using Multiplier Theory and IQC Framework
Abstract: The IQC (integral quadratic constraint) framework has been proposed as a useful tool for analysing bilateral teleoperation systems. In this presentation we will show that it is possible to obtain less conservative conditions when the environment force is assumed to be a monotonic function. This less conservative analysis allows us to improve the transparency without degrading stability properties. The talk will cover underpinning concepts on multiplier theory and its application to bilateral teleoperation.
Bio: Joaquin Carrasco is a Lecturer at the Control Systems Centre, School of Electrical and Electronic Engineering, University of Manchester, UK. He was born in Abarán, Spain, in 1978. He received the B.Sc. degree in physics and the Ph.D. degree in control engineering from the University of Murcia, Murcia, Spain, in 2004 and 2009, respectively. From 2009 to 2010, he was with the Institute of Measurement and Automatic Control, Leibniz Universitat Hannover, Hannover, Germany. From 2010 to 2011, he was a research associate at the Control Systems Centre, School of Electrical and Electronic Engineering, University of Manchester, UK. He has been a Visiting Researcher at the University of Groningen, Groningen, The Netherlands, and the University of Massachusetts, Amherst. His current research interests include absolute stability, multiplier theory, and robotics applications. He is a member of the IFAC technical committee Telematics: Control via Communication Networks.
Dr. Nikhil Chopra, University of Maryland, College Park, MD, USA.
Title of presentation: Resilient Control of Bilateral Teleoperators
Abstract: In this talk, we study cybersecurity attacks in bilateral teleoperation. Specifically, the focus is on content modification attacks wherein an adversary may modify the states being exchanged between the master and slave robots. The talk will discuss various attacks that were theoretically and experimentally studied, their efficacy, and algorithms for protection against general content modification attacks.
Bio: Nikhil Chopra (M'06) received the bachelor's (Hons.) degree in mechanical engineering from the Indian Institute of Technology, Kharagpur, Kharagpur, India, and the Ph.D. degree in systems and entrepreneurial engineering from the University of Illinois at Urbana-Champaign, Urbana, IL, USA, in 2001 and 2006, respectively. He is currently an Associate Professor with the Department of Mechanical Engineering, University of Maryland, College Park, MD, USA. His current research interests include networked control systems, cooperative control of networked robots, and bilateral teleoperation. He is an Associate Editor of the IEEE Transactions on Automatic Control.
Dr. Blake Hannaford, University of Washington, USA.
Title of presentation: Stability of Force Feedback Systems: A Survey
Abstract: This talk will review the basics of force feedback system stability analysis and a few techniques in more detail. Key issues include, characterization of teleoperator performance, trade-offs between stability and performance, and challenging applications such as orbital time delays.
Bio: Blake Hannaford, Ph.D., is Professor of Electrical Engineering, Adjunct Professor of Bioengineering, Mechanical Engineering, and Surgery at the University of Washington. Blake Hannaford received the B.S. degree in Engineering and Applied Science from Yale University in 1977, and the M.S. and Ph.D. degrees in Electrical Engineering from the University of California, Berkeley. From 1986 to 1989 he worked on the remote control of robot manipulators in the Man-Machine Systems Group in the Automated Systems Section of the NASA Jet Propulsion Laboratory, Caltech and supervised that group from 1988 to 1989. Since September 1989, he has been at the University of Washington in Seattle, where he is Professor of Electrical Engineering. He was awarded the National Science Foundation's Presidential Young Investigator Award, the Early Career Achievement Award from the IEEE Engineering in Medicine and Biology Society, and was named IEEE Fellow in 2005. He was at Google Life Sciences from April 2014 to December 2015. His currently active interests include surgical robotics, surgical skill modeling, and haptic interfaces.
Dr. Keyvan Hashtrudi-Zaad, Queen’s University, Canada.
Title of presentation: Absolute Stability in Bilateral Telerobotic Systems
Abstract: Coupled stability in master-slave telerobotic systems directly depends on the dynamic uncertainties imposed by its terminations, i.e. human user and environment dynamics. Passivity theory is one of the most commonly-used stability analysis methods. Since the passivity of a teleoperator results in conservative stability conditions, absolute stability, in particular Llewellyn's criterion is often adopted as a preferred means of coupled stability analysis. In this workshop, we discuss the Llewellyn's criterion and then present a powerful 3D geometrical robust stability analysis method which is based on the notions of wave variables and scattering parameters. The method provides both mathematical and visual aids to determine bounds or regions on the complex frequency response of the passive environment impedance parameters for which a potentially unstable system connected to any user is stable. Furthermore, the method can even be utilized when the environment dynamics are active. As a result, the geometrical method lends to less conservative guaranteed stability conditions compared to the Llewellyn's criterion; thus, promising a better compromise between stability and performance. Utilizing this method, we will also prove that for potentially unstable systems as the user arm damping grows, the environment stability region also grows to include all passive environments.
Bio: Keyvan Hashtrudi-Zaad received the PhD degree in Electrical and Computer Engineering from the University of British Columbia, Vancouver, Canada, in 2000. He then held a consulting position with Motion Metrics International Corporation, Vancouver, where he worked on the development of a dynamic payload monitoring system for heavy duty hydraulic machines. In 2001, he joined the Department of Electrical and Computer Engineering, Queens University, Kingston, Ontario, Canada, where he is currently a Professor and the Director of BioRobotics Research Laboratory. Dr. Hashtrudi-Zaad's research interests include haptics, telerobotics, mechatronics, modeling and controls, and their applications in medicine and biomedical engineering. He has served as the Associate Editor of the IEEE Transactions on Haptics and as a co-organizer of a number of IEEE-sponsored conferences.
Dr. Gunter Niemeyer, Disney Research, USA.
Title of presentation: Passivity and Life Thereafter
Abstract: The telerobotics community has long embraced passivity as an approach to stability for teleoperators and haptic interfaces. Whether in the frequency domain or in the time domain, the approach provides guarantees without detailed knowledge of the world and minimal assumptions. As such it is very robust and well suited for exploration and unplanned tasks. Yet it has also been long recognized that passivity results in conservative solutions. We explore the connection between assumptions and performance and ask the question whether it is time to find a new approach. What assumptions can and should we make? Indeed in no other area of robotics do we attempt to achieve high performance without modelling or learning the world. Can we leverage these developments in telerobotic applications? Is there life beyond passivity?
Bio: Gunter Niemeyer is a senior research scientist at Disney Research, Los Angeles. His research examines physical human-robotic interactions and interaction dynamics, force sensitivity and feedback, teleoperation with and without communication delays, and haptic interfaces. He received MS and PhD degrees from the Massachusetts Institute of Technology (MIT) in the areas of adaptive robot control and bilateral teleoperation, introducing the concept of wave variables. He also held a postdoctoral research position at MIT developing surgical robotics. In 1997, he joined Intuitive Surgical Inc., where he helped create the da Vinci Minimally Invasive Surgical System. He was a member of the Stanford faculty from 2001-2009, directing the Telerobotics Lab. From 2009-2012 he worked with the PR2 personal robot at Willow garage. He joined Disney Research in 2012.
Dr. Emmanuel Nuno, University of Guadalajara, Mexico.
Title of presentation: New Results on the Control of Bilateral Teleoperators via Energy Shaping
Abstract: Since the fundamental work of Anderson and Spong, in 1989, passivity has been the cornerstone in the stability analysis and in the design of several controllers for bilateral teleoperators. It is widely known that the communication channel imposes variable time-delays. Furthermore, many commercially available robots do not incorporate velocity sensors and velocities are usually estimated using dirty-derivatives. In this talk, the energy shaping plus damping injection principles of passivity-based control are brought to the bilateral teleoperators scenario. As a result, novel controllers that deal with time-delays and with the absence of velocity measurements are designed. Moreover, if sufficient damping is injected in the controller, stability of the equilibrium point is established assuming that the human operator and the environment are passive. When the human and the environment do not inject forces in the system, it is proved that position errors and velocities globally asymptotically converge to zero. The talk also covers the extension of this control methodology to the multiple-local, multiple-remote, teleoperation systems.
Bio: E. Nuno was born in Guadalajara, Mexico, in 1980. He obtained his B.Sc. in Communications and Electronics Engineering from the University of Guadalajara in 2002. He received the Ph.D. degree in Advanced Automation and Robotics from the Technical University of Catalonia, Spain, in July 2008. He has held different research internships at the Laboratoire des Signaux et Systemes, Centrale-SUPELEC, at the Coordinated Science Laboratory at University of Illinois, Urbana-Champaign, at the Institute of Industrial and Control Engineering at the Technical University of Catalonia and at the Engineering Faculty of the National Autonomous University of Mexico. Since 2009 he is a Titular Professor in the Department of Computer Science of the University of Guadalajara, Mexico. His research interests include the control of bilateral teleoperators and the consensus and synchronization of multiple-agents. He has published more than 50 journal and conference papers in these areas. E. Nuno is a member of the IEEE Robotics and Automation Society and the IEEE Control Systems Society.
Dr. Rajni Patel, Western University, Canada.
Title of presentation: Modulated Time-Domain Passivity Control: A Passivity-Based Approach for Stable Human-Robot Interaction in Haptics-Enabled Telerobotic Systems
Abstract: In this talk, a new passivity-based technique will be presented to analyze and guarantee the stability of haptics-enabled robotic/telerobotic systems when there is a possibility of having a source of non-passivity in addition to the conventional non-passive component, i.e., delay in the communication channel. The proposed technique is motivated by safe and optimal implementation of haptics-enabled robotic, cloud-based, and remote telerehabilitation systems. The aim is to perform minimum alteration to the system transparency, in a dynamic and patient-specific manner, by utilizing the quantifiable biomechanical capability of the user’s limb, denoted as Excess of Passivity (EOP), in dissipating interactive energy to guarantee human-robot interaction safety. The design framework is based on the hypothesis that when there is nonpassivity caused by a non-passive environment and/or delay in the communication network, the closed-loop haptics-enabled system remains passive and stable if the quantifiable EOP of the nonlinear biomechanical impedance of the user’s limb can compensate for the total shortage of passivity caused by the non-passivity. This principle is validated and used to design a controller, the Modulated Time-domain Passivity Control (M-TDPC), which is a new member of the family of TDPC techniques. During robotic and telerobotic rehabilitation, the M-TDPC strategy (1) identifies the EOP of the patient?s limb prior to the therapeutic task; (2) monitors in real-time the extent of non-passivity of the administered therapy delivered through the network; (3) calculates in real-time the ``minimum-necessary'' energy, to be damped; and (4) injects time-varying damping. The controller keeps the injected damping as small as possible using the identified EOP of the patient?s limb, causes minimal alterations to the prescribed therapy, and allows the non-passive energy (i.e., therapeutic assistance) to optimally flow from the therapist to the patient.
Bio: Rajni V. Patel received the PhD degree in Electrical Engineering from the University of Cambridge, England, in 1973 and currently holds the position of Distinguished University Professor and Tier-1 Canada Research Chair in the Department of Electrical and Computer Engineering with cross appointments in the Dept. of Surgery and the Dept. of Clinical Neurological Sciences at Western University, London, Ontario, Canada. He also serves as Director of Engineering for Canadian Surgical Technologies and Advanced Robotics (CSTAR), Canada. He has served on the editorial boards of the IEEE Transactions on Robotics, the IEEE/ASME Transactions on Mechatronics, the IEEE Transactions on Automatic Control, and Automatica. Since 2000, his research has focused on the development of technologies and techniques incorporating robotics, haptics and teleoperation for applications in minimally invasive interventions and in rehabilitation therapy for movement disorders.
Dr. Ilia Polushin, Western University, Canada.
Title of presentation: Stability of Haptic Teleoperation Systems with Projection-Based Force Reflection
Abstract: In this talk, an overview of theoretical as well as experimental results related to stability of teleoperators and haptic systems with projection-based force reflection algorithms will be presented. The main idea behind the projection-based force reflection (PBFR) is to decompose the reflected force into the “interaction” and the “motion-generating” components, and attenuate the latter while applying the former in full. This allows for attenuation of the induced master motion and consequently stability improvement. Specifically, using PBFR, the gain between the force reflection signal and the corresponding induced master motion can be made arbitrarily low by choosing the weighting coefficient in the force reflection algorithm. This is accomplished by utilizing certain fundamental characteristics of human force sensing and without paying the price in terms of transparency deterioration. Within the passivity-based framework, application of PBFR algorithms allows for arbitrary increase of the existing excess of passivity without increasing the physical damping of the haptic device. In this talk, the existing theoretical and experimental stability results will be summarized and discussed within both small-gain and passivity frameworks, and open problems will be formulated.
Bio: Ilia G. Polushin is an Associate Professor in the Department of Electrical and Computer Engineering, Western University, London, ON, Canada. He received the Candidate of Sciences degree in Automatic Control from Saint-Petersburg Electrotechnical University, Russia, and the PhD degree in Electrical Engineering from Carleton University, Canada. His research interests are in the general area of robotics and control. He is currently an Associate Editor for the Control Engineering Practice. He was the recipient of the Best Conference Paper Award at the 2006 IEEE International Conference on Mechatronics and Automation.
Dr. Stefano Stramigioli, University of Twente, Netherlands.
Title of presentation: Energy Aware Robotics
Abstract: In this talk, physical and mathematical reasons will be given for a paradigm which can ensure stable behaviour in interaction with all kind of passive environments independently of transmission or calculation delays. A theorem will be also presented which formalizes a necessary condition for passivity in order to achieve stability with such interactions.
Bio: Stefano Stramigioli received the M.Sc. with honors (cum laude) in 1992 and the Ph.D with honors (cum laude) in 1998. Between the two degrees he has been working as a researcher at the University of Twente, has started his enterprise and received the Dutch Institute of System and Control certificate. Since 1998 he has been faculty member first as assistant, associate and currently full professor in Advanced Robotics. He is an IEEE Fellow and has been an IEEE RAS officer for many years. He is currently leading a growing group of about 50 people (http://www.ce.utwente.nl). He has been Editor in chief of the IEEE Robotics and Automation Magazine, which he brought from the seventh to the first place in the ranking of the Impact Factor among all journals on Robotics. He has furthermore been Editor in Chief of the IEEE ITSC Newsletter and guest editor for others. He is member of the Editorial Board of the Springer Journal of Intelligent Service Robotics. He has been an AdCom member of the IEEE Robotics and Automation Society, he has been the founder and chair of the Electronic Products and Services of the IEEE Robotics and Automation Society and he has been serving as Vice President for Membership of the same society for two consecutive terms. He is involved in different projects related to Control and Robotics for medical, inspection and home and care applications. Nationally, he has been a member of the Management team of the graduate school DISC, is the chair of RoboNED, the national platform coordinating all academic, industrial and governmental institutions on Robotics and responsible for producing a Strategic Research Agenda for Robotics for the Netherlands and he is one of the initiator of the LEO (www.leo-robotics.eu) robotics center. He has been the UT representative for the formation of the 3TU CoE on Intelligent Mechatronic Systems and the 3TU Master on System and Control. He has served as the UT representative of the Management Team of the Mechatronica Valley Twente. He is member of the program board of the STW national research program on Autonomous Sensors Systems. He has been the 2009 recipient of the IEEE-RAS distinguish service award and he is a member of the 3TU Center of Excellence on Intelligent Mechatronics Systems. He has been invited many times as speaker at international schools, workshops and conferences for lecturing or plenary speeches, and he has numerous national and international cooperations. He has been teaching Modeling, Control and Robotics for under and post-graduates. He is currently serving as the Vice President for Research of euRobotics, the private part of the PPP cooperation with the European Commission known as SPARC, the biggest robotic civil program worldwide.
Google Scholar: https://scholar.google.com/citations?user=BvmnBz4AAAAJ
Research Gate:\\ http://www.researchgate.net/profile/Stefano\_Stramigioli
Dr. Mahdi Tavakoli, University of Alberta, Canada.
Title of presentation: Absolute Stability of Multi-DOF Multi-lateral Haptic Systems
Abstract: Multi-degree-of-freedom (DOF) multi-lateral haptic systems involve teleoperation of several robots in physical environments by several human operators or collaborative interaction of several human operators in a virtual environment. An m-DOF n-lateral haptic system can be modeled as an n-port network where each port (terminal) connects to a termination defined by m inputs and m outputs. The stability analysis of such systems is not trivial due to dynamic coupling across the different DOFs of the robots, the human operators, and the physical/virtual environments, and unknown dynamics of the human operators and the environments exacerbate the problem. Llewellyn's criterion only allows for absolute stability analysis of 1-DOF bilateral haptic systems (m = 1, n = 2), which can be modeled as two-port networks. The absolute stability of a general m-DOF bilateral haptic system where m > 1 cannot be obtained from m applications of Llewellyn's criterion to each DOF of the bilateral system. Also, if we were to use Llewellyn's criterion for absolute stability analysis of a general 1-DOF n-lateral haptic system where n > 2, we would need to couple n-2 terminations of the n-port network to (an infinite number of) known impedances in order to reduce it to an equivalent two-port network; this is a cumbersome process that involves an infinite number of applications of Llewellyn's criterion. In this talk, we present a straightforward and convenient criterion for absolute stability analysis of a class of m-DOF n-lateral haptic systems for any $m \ge 1$ and $n \ge 2$.
Bio: Mahdi Tavakoli is an Associate Professor in the Department of Electrical and Computer Engineering, University of Alberta, Canada. He received his BSc and MSc degrees in Electrical Engineering from Ferdowsi University and K.N. Toosi University, Iran, in 1996 and 1999, respectively. He received his PhD degree in Electrical and Computer Engineering from the University of Western Ontario, Canada, in 2005. In 2006, he was a post-doctoral researcher at Canadian Surgical Technologies and Advanced Robotics (CSTAR), Canada. In 2007-2008, he was an NSERC Post-Doctoral Fellow at Harvard University, USA. Dr. Tavakoli's research interests broadly involve the areas of robotics and systems control. Specifically, his research focuses on haptics and teleoperation control, medical robotics, and image-guided surgery. Dr. Tavakoli is the lead author of Haptics for Teleoperated Surgical Robotic Systems (World Scientific, 2008).