ASIAGRAPH 2008 PROCEEDINGS

テレイグジスタンス- 過去、現在、未来 -Telexistence--- Past, Present, and Future
舘暲/東京大学
Susumu Tachi/The University of Tokyotachi@tachilab.org

Abstract:

The telexistence technology enables a highly realistic sensation of existence in a remote place without any actual travel.
The concept was proposed by the author in 1980, and its feasibility has been demonstrated through the construction of alterego robot systems such as TELESAR that was developed under the national large scale project on “Robots in Hazardous
Environments” as well as the HRP super-cockpit biped robot system developed under the “Humanoid Robotics Project.” A
mutual telexistence system TELESAR II, which can generate the effect of existing in a remote place in local space using a
combination of an alter-ego robot and the retro-reflective projection technology (RPT), has been developed, and thefeasibility of mutual telexistence has been demonstrated. In this paper, the past, present, and future of the telexistence
technology has been discussed.

Keywords:

telexistence, mutual telexistence, telepresence, teleoperation, master-slave system, virtual reality,
augmented reality, TELESAR, TWISTER, RPT

1. Introduction
Telexistence is fundamentally a concept that refers to thegeneral technology that allows a human being to have a realtime sensation of existing in a place other than where he/she
actually exists and to interact with the remote environment,
which may be real, virtual, or a combination of both. It
also refers to an advanced type of teleoperation system thatenables an operator at the controls to perform remote tasks
dexterously with the feeling of existing in a surrogate robot
working in a remote environment. Telexistence in the realenvironment through a virtual environment is also possible.
In this paper, the development of the telexistence
technology has been historically reviewed; its present status
has been summarized and future prospective has been
discussed.

2. Short History and Present Status of
Telexistence

Figure 1: Emergence and Evolution of telexistence.

2.1. How Telexistence was Conceptualized
and Developed
It has long been a desire of human beings to project
themselves in a remote environment, i.e., to have thesensation of existing in a place other than the one they reallyexist in, at the same time. Another dream has been to
amplify the human muscle power and sensing capability byusing machines while maintaining human dexterity with asensation of actually performing the task.
In the late 1960s, a research and development program
was planned to develop a powered exoskeleton that an
operator would wear in the same manner as a garment.
The concept of Hardiman exoskeleton was proposed byGeneral Electric Co.; an operator wearing the Hardiman
exoskeleton would be able to command a set of mechanicalmuscles that will multiply his/her strength by a factor of 25,

Figure 2: Telexistence System Architecture.

yet, in this union of man and machine, he/she would feel theobject and forces almost as if he/she were in direct contact
with it.
However, the program was unsuccessful because of thefollowing reasons: (1) Wearing the powered exoskeleton
was potentially quite dangerous in the event of themalfunctioning of the machine. (2) Autonomous mode
was difficult to be achieved and everything must be done bya human operator. Thus, the design proved impractical in
its original form.
With the advent of science and technology, however, it
has become possible to realize this dream with a different
concept. The concept of projecting ourselves by using
robots, computers, and a cybernetic human interface isreferred to as telexistence (tel-existence). This concept
extends to include projection in a computer-generated
virtual environment. Figure 1 illustrates the emergenceand evolution of the concept of telexistence.
The concept of telexistence was proposed by the author
in 1980 [1], and it was the fundamental principle of theeight-year Japanese national large scale project of“Advanced Robot Technology in Hazardous Environment,”
which started in 1983 together with the concept of the Third
Generation Robotics.
Telexistence enables a human operator at the controls toperform remote manipulation tasks dexterously with thefeeling that he/she exists in an anthropomorphic robot in aremote environment [2-8].
Fundamental studies for the realization of telexistencesystems were conducted under the national large scale
project “Advanced Robot Technology in Hazardous
Environment,” which was a research and development
program launched for developing a system that avoids theneed for humans to work in potentially hazardous working
environments such as nuclear power plants, under water,and disaster areas.
Through this project, the theoretical consideration andsystematic design procedure of telexistence was established.
An experimental hardware telexistence system wasdeveloped, and the feasibility of the concept wasdemonstrated.
Our first report [3,5] proposed the principle of atelexistence sensory display and explicitly defined its design
procedure. The feasibility of a visual display providing asensation of existence was demonstrated throughpsychophysical measurements performed using anexperimental visual telexistence apparatus.
Figure 3
illustrates the first prototype telexistence visual display
developed.
In 1985, a method was also proposed to develop a
mobile telexistence system that can be driven remotely withboth an auditory and a visual sensation of existence. A
prototype mobile televehicle system was constructed, andthe feasibility of the method was evaluated [9]. Figure 4
presents a prototype telexistence mobile robot, and Fig. 5
illustrates the head-linked display with a sensation ofexistence used in the system.

Figure 4: Prototype Mobile Telexistence Vehicle(Televehicle) .

Figure 5: Head-linked Stereo Display with a
Sensation of Existence.
Figure 3: First Prototype Telexistence Visual Display.

2.2. Telexistence Master-Slave Manipulation
System: TELESAR
The first prototype telexistence master-slave system for
performing remote manipulation experiments was designed
and developed, and a preliminary evaluation experiment oftelexistence was conducted [10-12].
The slave robot employs an impedance control
mechanism for contact tasks and for compensating for errorsthat remain even after performing calibration.
Anexperimental operation of block-building was successfully
conducted by using a humanoid robot called TELESAR(TELExistence Surrogate Anthropomorphic Robot) (Fig. 6).
Experimental studies of the tracking tasks quantitatively
demonstrated that a human being can telexist in a remoteenvironment by using a dedicated telexistence master-slave
system [12]. Figure 7 illustrates a telexistence mastersystem.

Figure 6: TELESAR (Telexistence
Anthropomorphic Robot) at work.

Surrogate

Figure 8: Telexistence
Environment.

in

Real

and

The former can be referred to as “transmitted reality;” thelatter, “synthesized reality.”(Fig. 8)
Synthesized reality can be classified as follows: a virtualenvironment representing a real world and that representing
an imaginary world. Combining transmitted reality andsynthesized reality, which is referred to as mixed reality, isalso possible, and it has a great significance in realapplications. This is referred to as augmented telexistence
to clarify the importance of a harmonic combination of realand virtual worlds.
Augmented telexistence can be used in several situations,for instance, controlling a slave robot in an environment
with poor visibility.
An experimental augmented
telexistence system was constructed using mixed reality.
An environment model was also constructed from thedesign data of the real environment. When augmented
reality is used for controlling a slave robot, the modelling
errors of the environment model must be calibrated. A
model-based calibration system using image measurements
was proposed for matching the real environment with avirtual environment.
An experimental operation in an environment with poor
visibility was successfully conducted by using Telesar (Fig.
6) and the virtual dual. Figure 9 illustrates the virtual
telexistence anthropomorphic robot used in the experiment[13, 14].
A quantitative evaluation of the telexistence
manipulation system was conducted through tracking tasks
by using the telexistence master-slave system. Throughthese experimental studies, it was demonstrated that a

Figure 7: Telexisitence Master Manipulation System.

2.3. Augmented Telexistence
Telexistence can be divided into two categories:
telexistence in a real environment that actually exists at a
distance and is connected via a robot to the place where theoperator is located, and telexistence in a virtual environmentthat does not actually exist but is created by a computer.

VirtualFigure 9: Virtual TELESAR at Work.

human being can telexist in a remote environment and/or acomputer-generated environment by using a dedicatedtelexistence system.
Through these research and development programs, it
has become possible to telexist between places withdedicated transmission links such as optical fiber
communication links, as has been demonstrated by theabove experiments. However, it is still difficult foreveryone to telexist freely through commercial networks
such as the Internet or the next generation worldwide
networks, and more efforts are anticipated.

Figure 12 illustrates an example of an R3 robot system.
Each robot site has a server for its local robot. The type ofrobot varies from a humanoid (high end) to a movable
camera (low end). A virtual robot can also be a local
controlled system.

2.4. R-Cubed
In order to realize a society wherein everyone can freely
telexist anywhere through a network, the Japanese Ministryof International Trade and Industry (MITI) and the
University of Tokyo proposed a long-range national
research and development program, which was dubbed RCubed (R3) in 1995. R3 stands for real-time remoterobotics. The concept of this program was the research anddevelopment of the technologies that enable humanoperators to telexist freely by integrating robots, virtual
reality, and network technology [15].
Figures 10 and 11 present examples of a conceptual
networked telexistence application using R3 robots.

Figure 10: Conceptual Image of Mountain Climbing
using R-Cubed Robot.

Figure 10: Conceptual Image of Mountain Climbing
using R-Cubed Robot.

Figure 12: R-Cubed Robot system.

Each client has its teleoperation system. It can be acontrol cockpit with master manipulators and a headmounted display (HMD) or a CAVE Automatic Virtual
Environment (CAVE) at the high end. It is also possible touse an ordinary personal computer system as a control
system at the low end. In order to assist low-end operatorswith controlling remote robots through networks,
RCML/RCTP (R-Cubed Manipulation Language/R-Cubed
Transfer Protocol) is now under development.
An operator accesses the web site describing theinformation of a robot in the form of hypertext and icon
graphics using a WWW browser. Clicking on an icon
downloads a description file, which is written in RCML
format, onto the operator’s computer and launches the
RCML browser.
The RCML browser parses thedownloaded file to process the geometrical information,
including the arrangement of the degrees of freedom of therobot, controllable parameters, available motion ranges,
sensor information, and other pertinent information.
The browser decides the type and number of devices
required to control the remote robot. It then generates agraphical user interface (GUI) panel to control the robot,
plus a video window that displays the images as “seen” by
the robot and a monitor window that lets the operators
observe the robot’s status from outside the robot. The
operator can employ a device such as a 6-degree-of-freedom(DOF) position/orientation sensor instead of theconventional GUI panel to indicate the robot-manipulator’s
endpoint.

2.5. HRP (Humanoid Robotics Project)
On the basis of the R3 program and after conducting a
two-year feasibility study called Friendly Network Robotics(FNR) from April 1996 till March 1998, a National Applied
Science & Technology Project “Humanoid and Human
Friendly Robotics,” or “Humanoid Robotics Project (HRP)”in short, was launched in 1998. It was a five-year project
toward the realization of a so-called R3 Society byproviding humanoids, control cockpits, and remote control
protocols.
11: Conceptual Image
Operation using R-Cubed Robot

FigureofRescueA novel robot system capable of assisting andcooperating with people is necessary for any humancentered system to be used for activities such as themaintenance of nuclear plants or power stations,construction work, supply of aid in case of emergencies ordisasters, and care of elderly people. If we consider such
systems from both technical and safety points of view,
however, it is clearly intractable to develop a completely
autonomous robot system for these objectives.
Robot systems should therefore be realized using a
combination of autonomous control and teleoperated control.
By introducing telexistence techniques through an advanced
type of teleoperated robot system, a human operator can beprovided with information about the robot’s remoteenvironment in the form of natural audio, visual, and force
feedback, thus invoking a feeling of existence inside therobot itself [16].
Thus, in phase 1 of the project, a telexistence cockpit forhumanoid control was developed (Fig. 13), and thetelexistence system was constructed using the developed
humanoid platform.

Figure 14: Telexistence in Humanoid Biped Robot.

A CG (Computer Graphics) model of the robot in thevirtual environment is depicted and updated according to thecurrent location and orientation received from the sensors
located on the real robot. The model is displayed on thebottom-right screen of the surround visual display, and byaugmenting the real images captured by the camera system,
it assists the operator with the navigation of the robot.
Since the series of real images presented on the visualdisplay are integrated with the movement of the motion base,the operator feels a real-time sensation of stepping up anddown.
This was the world-first experiment and success ofcontrolling a humanoid biped robot using telexistence [16].

2.6. Mutual Telexistence: TELESAR II

Figure 13: Telexistence Super Cockpit.

In order to address the problem of narrow fields of view
associated with conventional HMDs, a surround visualdisplay using an immersive projection technology, as that
adopted in the CAVE (CAVE Automatic Virtual
Environment), was developed. The surround visual display
panoramically presents the real images captured by a stereo
multi-camera system mounted on the robot for a wide fieldof view, which allows the operator to have the feeling of onboard motion when he/she uses the robot to walk around.
Various teleoperation experiments performed using thedeveloped telexistence master system confirmed thatkinesthetic presentation by the master system through visual
imagery greatly improves both the operator’s sensation ofwalking and the dexterity at manipulating objects.
If the operator issues a command to move the robot, therobot actually walks toward the goal. As the robot walks
around, real images captured by the multi-camera systemwith a wide field of view are displayed on the four screensof the surround visual display. This makes the operator
feel as if he or she is inside the robot, walking around at the
robot site (Fig. 14).

A new prototype of a mutual telexistence master-slave
system was designed and developed [17-24]. The mutual
telexistence master-slave system is based on the RTP and iscomposed of three subsystems - slave robot TELESAR II,
master cockpit, and viewer system - as shown in Fig.15.
The robot constructed for this communication system iscalled“TELESAR
II(Telexistence
Surrogate
Anthropomorphic Robot II).” In order to use this system
for telecommunication, we designed the robot by focusing
on reproducing human-like realistic movements.
TELESAR II has two human-sized arms and hands, a torso,
and a head. Its neck has two DOFs, which can rotate
around its pitch and roll axes. Two CCD cameras areplaced inside its head for a stereoscopic vision. It also has
four pairs of stereo cameras located on top of its head for a
3D surround display for the benefit of the operator. A
microphone array and a speaker are also employed for an
auditory sensation and verbal communication. Each arm
has seven DOFs, and each hand has five fingers with a totalof eight DOFs.
To control the slave robot, we developed a mastercockpit for TELESAR II. The cockpit consists of two
master arms, two master hands, a multi-stereo display
system, speakers and a microphone, and cameras for
capturing the images of the operator in real time. In orderthat the operator can move smoothly, each master arm has a
6-DOF structure so that the operator’s elbow is free of
constraints. To control the redundant seven DOFs of theanthropomorphic slave arm, a small orientation sensor isplaced on the operator’s elbow. Therefore, each masterarm can measure 7-DOF motions for each corresponding
slave arm, while the force is fed back from each slave arm toeach corresponding master arm with six DOFs.

Figure 15: TELESAR II Master-Slave System.

The master arm is lightweight, and its impedance iscontrolled so that the operator feels as if he/she is inside theslave robot. It is important that the master should transmit
the exact amount of force to the operator and the slave robot
should maintain a safe contact with humans in a remoteenvironment. The impedance-control-type master-slave
system adopted by us can achieve the force presentation.
Moreover, a safe compliant contact can be maintained withhumans because the slave is subjected to impedance control.
The motion of the robot’s head is synchronized with the
motion of the operator’s head; these motions are measured
by using a head tracker in the master cockpit.

torso of the robot. In the case of the telexistence system,
however, collision detection is not required to be performed.
The operator calculates it subconsciously. This is aremarkable feature of the telexistence system. Despite this,we calculated the collision limit, and collision can beprevented even if the operator fails to avoid collision (failsafe mechanism or safety intelligence system). Figure 16
presents a general outline of the impedance-control-type
master-slave teleoperation system used in this study.
Figure 17 illustrates a general view of TELESAR II(left) and the structure of its arm (right).

Figure 17: General View of TELESAR II (left)

and structure of its arm (right).
Figure 18 presents a general view of the master cockpit
of TELESAR II. The most distinctive feature of the
TELESAR II system is the use of an RPT viewer system.
Both the motion and the visual image of the operator areimportant factors to be determined for the operator to feelthe existence at the place where the robot is working. In
order to view the image of the operator on the slave robot
such that the operator is inside the robot, the robot iscovered with a retro-reflective material, and the image
captured by the camera in the master cockpit is projected on
the TELESAR II. TELLESAR II acts as a screen, and aperson seeing through the RPT viewer system observes therobot as if it is the operator because of the projection of thereal image of the operator onto the robot.

Figure 16: Impedance Control of TELESAR II.

The operator can easily control the hands of TELESAR
II because the motions of the operator’s hands are measured
by the master cockpit manipulators and controlled bymaster-slave methods. In the case of an autonomous robot
system, a precise computation of motions is required to be
performed to prevent the collisions of the arms, hands, orFigure 18: TELESAR II Master Cockpit.

In our laboratory at the University of Tokyo, a new typeof visual display termed an RPT display is being developed,
which uses a retro-reflective material as its projection
surface. The retro-reflective surface functions as a special

screen. In the RPT configuration, a projector is arranged at
the axial symmetric position of the operator’s eyes withreference to a half mirror, with a pinhole placed in front of
the projector to ensure an adequate depth of focus.
The face and chest of TELESAR II are covered by aretro-reflective material. A ray incident from a particular
direction is reflected in the same direction from the surfaceof the retro-reflective material.
Because of thischaracteristic of the retro-reflective material, an image is
projected onto the surface of TELESAR II without
distortion. Since many RPT projectors have been used indifferent directions and different images are projected
corresponding to the cameras placed around the operator,
the corresponding images of the operator can be viewed.
Figure 19 illustrates an example of the projected imagesof an operator onto its surrogate robot.

sensation to each finger of the operator to realize haptic
telexistence.

3. Future Prospect of Telexistence
Figure 21 shows examples of applications of telexistencesystems in our society. Researches conducted on virtual
reality and telexistence are attempts on releasing humanbeings from spatial restrictions and time constraints.

Figure 19: Projection of an Operator to the Robot.

Figure 20 indicates a slave hand (left) and a master hand(right) of the telexistence system. The slave hand consistsof five fingers with five finger-shaped haptic sensors.
Each haptic sensor comprises a transparent elastic body, twolayers of blue and red markers, and a CCD camera; it canmeasure the distribution of both the magnitude and directionof force.

Figure 20: Haptic Telexistence.

The master hand follows a compact exoskeleton
mechanism called “circuitous joint,” which covers the large
workspace of the operator’s finger. It can provide an
encounter-type force feedback to the operator.
The
encounter-type force feedback avoids unnecessary contact
sensation and enables unconstrained motion of theoperator’s fingers. Each finger tip has an electrocutaneous
display unit attached to it in order to present the tactile

Figure 21: Examples of Future Usage of Telexistence.

Based on this perspective, the applications oftelexistence may be given as follows:(1) To provide substitutes for manual labor in
potentially dangerous working environments such as
nuclear facilities, ocean engineering, disaster prevention,and space activities and to apply to construction work andmining;(2) To apply to secondary industries, i.e.
manufacturing industries, using a telemachining system as
a new production support tool;(3) To apply to primary industries such as agriculture(telefarmers) and fishing (telefishermen);(4) To apply to tertiary industries including cleaning,
maintenance, and other services;(5) To apply to leisure, amusement, and gameindustries in the form of telexistence travel;(6)To apply to medical fields such as in micro-surgery
and telesurgery;(7) To apply to communication industries such ascommunication with a sensation of existence;(8) To apply to the education industry, for example,
using experience simulators;(9) To apply to support tools (CAD, IMS) for
designing virtual products;(10) To apply to the design field, including interior
designing, for developing virtual environments;(11) To apply to scientific-engineering researches
using virtual scientific visualization as a tool;(12) To apply to researches conducted on the behaviorof humans and other living creatures using displays
providing a sensation of existence;(13) To provide a new medium of communication that,by embracing linguistic and pictorial expressions andgoing beyond them, may be used to express ideas andsensibility.

4. Conclusion
The telexistence technology was historically reviewed,
current advancements in telexistence, including mutual
telexistence and haptic telexistence, were studied, and future
prospects of telexistence were outlined.
Telexistence is a concept that allows humans to be
emancipated from the restrictions of time and space and thatallows them to exist at a “location” defined by inconsistenttime and space, or a virtual space.
It will provide human beings with a tool forcommunication,
control,creation,entertainment,
experience/education, or elucidation (human tools for 3C’s
and 3E’s).

Acknowledgement
This study on TELEXISTENCE has been conducted incollaboration with many of the former and present students,
affiliates, and staff members of the Tachi Laboratory at the
University of Tokyo, including Hirohiko Arai, Taro Maeda,
Yasuyuki Inoue, Kenichi Yasuda, Taisuke Sakaki, Eimei
Oyama, Yasuyuki Yanagida, Naoki Kawakami, Ichiro
Kawabuchi, Masahiko Inami, Dairoku Sekiguchi, Hiroyuki
Kajimoto, Hideaki Nii, Yoshitaka Zaitsu, Yoshiaki Asahara,
Kiyohiro Sogen, Shuhei Nakagawara, Riichiro Tadakuma,
Kouichi Watanabe, Kouta Minamizawa, and Katsunori Sato.

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