Time domain passivity control for delayed teleoperation

Tesis Doctoral para la obtención del Título de Grado de Doctor. x, 204 p. : il., diagr. Fecha de defensa de la Tesis Doctoral: 9 de julio de 2014. Calificación: Sobresaliente cum laudemTelepresence combines dierent sensorial modalities, including vision and touch, to produce a feeling of being present in a remote location. The key element to successfully implement a telepresence system and thus to allow telemanipulation of a remote environment is force feedback. In a telemanipulation, mechanical energy is conveyed from the human operator to the manipulated object found in the remote environment. In general, energy is a property of all physical objects, fundamental to their mutual interactions in which the energy can be transferred among the objects and can change form but cannot be created or destroyed. In this thesis, we exploit this fundamental principle to derive a novel bilateral control mechanism that allows to design stable teleoperation systems with any conceivable communication architecture. The rationale starts from the fact that the mechanical energy injected by a human operator into the system must be conveyed to the remote environment and vice versa. As will be seen, setting energy as a control variable allows a more general treatment of the system than the more conventional setting of specic system variables, as can be position, velocity or force. Through the Time Delay Power Network (TDPN) concept, the issue of dening the energy ows involved in a teleoperation system is solved with independence of the communication architecture. In particular, communication time delays are found to be a source of virtual energy. This fact is observed with delays starting from 1 millisecond. Since this energy is intrinsically added, the resulting teleoperation system can be non-passive and thus become unstable. The Time Delay Power Networks are found to be carriers of the desired exchanged energy but also generators of virtual energy due to the time delay. Once these networks are identied, the Time Domain Passivity Control approach for TDPNs is proposed as a control mechanism to ensure system passivity and therefore, system stability. The proposed method is based on the simple fact that this intrinsically added energy due to the communication must be transformed into dissipation. Then the system becomes closer to the desired one, where only the energy injected from one side of the system is conveyed to the other one. The resulting system presents two qualities: On one hand, system stability is guaranteed through passivity, independently from the chosen control architecture and communication channel; on the other, performance is maximized in terms of energy transfer delity. The proposed methods are sustained with a set of experimental implementations using dierent control architectures and communication delays ranging from 2 to 900 milliseconds. An experiment that includes a communication Space link based on the geostationary satellite ASTRA concludes this thesisPeer Reviewe

KONTUR-2: Force-feedback Teleoperation from the International Space Station

This paper presents a new robot controller for space telerobotics missions specially designed to meet the requirements of KONTUR-2, a German & Russian telerobotics mission that addressed scientific and technological questions for future planetary explorations. In KONTUR-2, Earth and ISS have been used as a test-bed to evaluate and demonstrate a new technology for real-time telemanipulation from space. During the August 2015' experiments campaign, a cosmonaut teleoperated a robot manipulator located in Germany, using a force-feedback joystick from the Russian segment of the International Space Station (ISS). The focus of the paper is on the design and performance of the bilateral controller between ISS joystick and Earth robot. The controller is based on a 4-Channels architecture in which stability is guaranteed through passivity and the Time Delay Power Network (TDPN) concept. We show how the proposed approach successfully fulfills mission requirements, specially those related to system operation through space links and internet channels, involving time delays and data losses of different nature

Shared control for robotic on-orbit servicing

A shared control approach is proposed to reveal the synergies of visual servoing and telepresence in a robotic on-orbit servicing scenario. Both methods, visual servoing and telepresence, have their respective strengths and are subject to challenges for the task at hand. In a shared control approach, the advantages of a human operator in the loop, its ability to react and adapt to unanticipated and versatile change of conditions, outlast. While the visual servoing, for a controlled range of conditions, has the ability to achieve the task autonomously and, running on-board, without performance degradation due to the communication delay. In the proposed approach, the autonomy module can support the operator and reduce his workload. Already implemented as well as future features and ideas are presented in the following

A modular passivity framework for multilateral teleoperation applications

In the past few years multilateral teleoperation systems that enable the interaction and coupling of several robotic devices gained in importance as this concept promises especially an increase of ergonomics and precision in teleoperation systems. The challenge in the control of such multi-robot setups is the generalization of the stability proof independent of the num-ber of robotic agents involved. Particularly in the presence of time delay in the communication channel the use of passivity control methods are wide-ly used in bilateral as well as multilateral systems. In literature it was shown that the passivity concept also provides a modular framework that allows for the generalization of stability proofs rendering a frequency-based analysis unnecessary. This paper provides an overview on the exist-ing framework modules and their application to different bilateral commu-nication architectures

Time-delayed Telepresence Introduction to passivity based bilateral control

In this presentation a short introduction to the telepresence concept is given, with the focus on the haptic channel. The active nature of delayed communication channels can induce the system to instability. The trade-off between stability and the compromised transperency of such delayed channels is here discussed. Two methodes which are aimed at passivity are presented to overcome the obstacled delayed telepresence, and a new method which aims the design at transparency is proposed

Passivity-based Stability in Explicit Force Control of Robots

Direct force control of robots is challenging, particularly since the interaction with the environment can render the robot unstable. This paper presents the results of novel approaches for passivity-based stability for a particular direct force control method, namely explicit force control. A step-by-step procedure to passivate and stabilise the control loop is presented and it explains how Time Domain Passivity Approach, a passivity-based tool widely used in teleoperation and haptics has been extended and applied in explicit force control. The electrical circuit and network-port representations derived in the process allows the analytical evaluation of the system and can be applied in other control architectures as well. The stability methods are presented both qualitatively and quantitatively with simulations and hardware experiments. A discussion about the results obtained and the energy behavior is also provided. Results are promising and suggest that these methods can be used for stable and high-bandwidth force control of robotic manipulators

A taxonomy for heavy-duty telemanipulation tasks using elemental actions

In the maintenance of large scientific facilities, telemanipulation procedures can involve various subprocedures which in turn are made up of a sequence of subtasks. This work presents a taxonomy which describes a set of elemental actions for heavy-duty telemanipulation, along with an example of these actions in a standard maintenance subprocedure. As maintenance tasks are often very different at high-level, this generalized way of deconstructing tasks allows a highly adaptable approach to describe the sequence of any procedure, which can then be used for such applications as task monitoring, automation or detection of incomplete tasks. We describe in detail the properties of each elemental action and apply the taxonomy to an example subprocedure to show how the process can be generalizable.An automatic state-machine creation stage is shown, which would be used at the task scheduling stage to simplify calculations carried out during the moment-by-moment execution of the task. © 2013 Owen-Hill et al.The research leading to these results has received funding from the European Community’s Seventh Framework Programme (FP7-PEOPLE-2010-ITN) as part of the PURESAFE Initial Training Network.Peer Reviewe

Integrating Measured Force Feedback in Passive Multilateral Teleoperation

In teleoperation systems, the master robot receives force feedback from the remote slave side. Thus, the human operator can perceive the contact between the slave robot and its environment. Application of a force sensor at the slave robot improves the performance of the telepresence system in terms of transparency. Still, so far no Approach allowing measured force feedback in time delayed multilateral Systems that allow the interaction of multiple agents can be found in literature. To this end, this paper presents a multilateral setup with passive measured force feedback based on the time domain passivity approach. Besides this solution to measured force feedback in multilateral systems, the presented approach promises improvements compared to other time invariant and model based approaches for measured force feedback also when applied to bilateral systems. Experiments are presented to allow for a performance analysis of the proposed system design

Force-feedback teleoperation of on- ground robots from the international space station in the frame of the KONTUR-2 experiment

The issues on creation and using of the haptic interface for remote control of on-ground robots from the Russian Segment of the International Space Station (ISS RS) in the frame of “KONTUR-2” space experiment are presented. Force-feedback as key technology of this system ensures elements of telepresence of operator in the environment where robot operates using visual and tactile feedback in a closed control loop. Results of space sessions on control of on-ground robots from the ISS RS are presented