Tele-existence Through Video
Yasuyuki YANAGIDA and Susumu TACHI
Research Center for Advanced Science and Technology,
The University of Tokyo
4-6-1 Komaba, Meguro-ku, Tokyo 153 Japan
Phone: +81-3-3481-4468, Fax: +81-3-3481-4580
E-mail: {yanagida, tachi}@star.rcast.u-tokyo.ac.jp
URL: http://www.star.rcast.u-tokyo.ac.jp/
Keywords: Tele-existence, Telepresence, Artificial reality, Virtual reality, Network

1. Introduction
Tele-existence[1-8] is a concept named for the technology which enables a human being tohave a real time sensation of being at the place other than the place where he or she actuallyexists, and is able to interact with the remote and/or virtual environment. The concept oftele-existence was proposed by Tachi et al. in early 1980s. Although tele-existence has its
technological basis on the field of robotics and tele-operation, researchers who are interested ina number of fields, such as tele-communication, human interface, computer simulation/graphics,
computer-aided design, three-dimensional art, etc., found that the key concept can be shared
among those fields of research. The concept of tele-existence, telepresence, virtual reality, andartificial reality can be considered as the same in essence.
In this paper, a historical review of the tele-existence technology is shown and the future
concept of tele-existence over network is introduced.

2. Previous Researches and Applied Examples
2.1 Previous Project in Japan
Tele-existence was adopted as the main concept for the large national project, entitled
Advanced Robot Technology (Research and Development of Task Robot for Potentially
Dangerous Working Environments), and played a major role in that project. The technicalfeasibility of the tele-existence system has been proved both theoretically and experimentally
through a series of tests conducted on prototype hardware models.
2.2 An Example of Tele-existence System at Laboratory
Tachi et al. has developed a prototype hardware system to show the feasibility oftele-existence system. The prototype system consists of a master system, a slave robot, andseveral computers used for control. In this system, the operator’s motion is measured by themaster system, and the slave robot is controlled so that it follows the operator’s motion in realtime. The slave robot is equipped with a pair of stereo cameras, which supplies the image fed
back to the operator.

Figure 1: tele-existence slave anthropomorphic robot
Figure 1 shows the tele-existence slave anthropomorphic robot. The slave anthropomorphicrobot (TELESAR) has 14 degrees-of-freedom: 3 DOFs for head motion, 7 DOFs for right arm
motion, 1 DOF for hand grasp, and 3 DOFs for base locomotion. By implementing a large
numbers of degrees-of-freedom, the human operator’s natural motion can be reflected on therobot’s motion. The right arm is equipped with a 6 DOF force/torque sensor at the wrist and isimpedance controlled in order to enable stable manipulation when the fingertip is contacted tothe environment. The hand grasp is also impedance controlled using strain gauge so that thehand should not crash soft objects being grasped. The head is equipped with a pair of stereo
CCD cameras and stereo microphones, which supplies natural three dimensional sensation ofpresence to the operator.

Figure 2: tele-existence master system
Figure 2 shows the master system, which measures human operator’s motion in real time.

The head motion is measured by using parallel link mechanism equipped with rotary encoders(6 DOFs: 3 for translation and 3 for rotation). Thanks to this mechanism, the system canmeasure the translational motion and rotational motion separately, so that complicated and time
consuming kinematics/inverse kinematics calculation should be avoided. The arm motion ismeasured by a 7 DOF exoskeletal arm, also equipped with rotary encoders. The drawback ofthis system is that the size is considerably big. However, by using these link mechanisms, thissystem can measure the operator’s motion much more exactly and faster than magnetic sensors
used in many virtual reality systems. Also, the output of this system is not influenced by theexistence of metal objects and provides measurement result with less noise. The advantage ofthis system in speed and noise characteristics is important in controlling real robots, rather than
generating graphics images of the virtual environment.
Each personal computer reads the human operator’s motion, calculate the control output
according to the impedance control algorithm in real time. Four personal computers are used tomeasure and control arm motion, hand grasp, base locomotion, and head motion, respectively.
Each part of the system is separated in physical signal level so that it is not necessary for thecomputers to communicate with each other. Thus each computer can do its job independently,
to enable high update rate of the control signal without requiring extensively high performanceCPUs.
The operator wears the helmet with head mounted display (HMD), which is attached to thelink mechanism. The optical alignment of the HMD, i.e., the field of view, etc., is designed
equivalent to the robot cameras. To ensure the operator to recognize the objects in the displayed
image to be exist at the correct position and to feel the fed back video image as natural three
dimensional space, this equivalency is very important. It is also important in tele-existencesystems that the operator can recognize his/her hand exactly in its actual position. Thisrequirement is called self-projection.
The system also provides tele-existence in virtual environment. The human motion
measured by the master system is sent to graphics workstations (Silicon Graphics
Indigo/Indigo2) to generate the image of the virtual environment which is designed equivalent
to the real environment. In this case, the projection parameters in generating computer graphics
image, such as an angle of field of view and an aspect ratio, should be set carefully, such thatthe shape of viewing volume becomes identical to the optical alignment of the HMD.
2.3 An Example of Applied Tele-existence System
In Japan, tele-existence technology has already been applied to several sites. For example,
remote observation system for volcanic activity is working at Mt. Unzen, which had a bigeruption a few years ago and caused a big disaster against the foot of the mountain by its
volcanic ashes, ash flow and debris flow. Human operator can observe the volcanic activity atsafe location as if he/she exists at a place near the crater.

3. R3 [R-Cube]: Real-time Remote Robotics Project
A new project, named R-Cube[9], has just started. Japanese government, Universities, andCompanies have jointly composed a working group, studied and investigated on the concept andtechnological elements for the future robotics technologies. This working group will develop
into a feasibility study project conducted by MITI (Ministry of International Trade and Industry)of Japan from April, 1996. This feasibility study will be taken place for two years, and if thestudy is successful, the project will further develop into a large national project.
R-Cube is an abbreviation for Real-time Remote Robotics, and its concept is based on theintegration of tele-existence/virtual reality technology and networking technology. This project
aims at developing human-centered, real time remote robot systems, which can work incooperation with human being. The field of application includes supporting elderly people’sliving activities considering a coming society composed largely of elderly people, supportingtasks in severe environment, preventing disaster, and supporting home automation, byintegrating technologies of virtual reality and robotics.
To other R-Cube Stations

R-Cube Station

RouterR-CubeBooth

Home
Computer

Control
Booth
Home
Robot

Robots for Rent
HomeSite2

Site1

R-Cube
Booth

OfficeComputerOfficeRobot

R-CubeBooth

R-Cube
Booth

OfficeTask Robots
Task Robots

Figure 3: Concept of R-Cube Network

In the concept sketch of R-Cube, robots work not only in artificial and arranged
environments such as factories, but also work in natural and/or unarranged environments, suchas homes, streets, construction sites, areas suffering from disaster, mountains, seas and so on. Inother words, these robots work not only in manufacturing activities but also in people’s ordinary
living activities. Human operators are located in the safe cockpit and manipulate remote robots,
experience the remote environment and act freely in those environment, feeling as if he or she
exists in the remote environment with a sensation of presence. The concept of R-Cube network
is shown in Figure 3.
According to the concept of R-Cube, robots are considered as the interface between
computers and physical world. Robots are connected to the computers, and operators and robots
communicate with each other through computer networks. This communication includes control
command from operators to robots and sensory information (visual sensation, auditory sensation,tactile sensation, etc.) obtained by robots. Thus human being will be able to take action not only
to the information stored in computers but also the “real world” through networks and robots.
An example of experimental system based on the similar concept can be found in “InternetControlled Robot” at University of South California[10].

4. Conclusion
R-Cube project has just started to develop real time remote robot system over network. Its
concept can be regarded as the one that make the concept of the tele-existence more concrete.
If this concept comes true, people will be able to exist all over the world, regardless of where heor she actually exists. Of course, there are a number of difficult problems to be solved. For
example, how to implement “safe” robots which can work together with human beings, how tocontrol robots autonomously when the connection between the operator and the robot isdisabled, how to transmit huge amount of information to control remote robot in real time and tofeedback sensory information to the human operators, and so on. However, by solving these
problems step by step, the study will be expected to be successful and developing into the nextstage of robotics technology.

References[1] S. Tachi and Abe: “Study Report on Tele-existence, No. 1 —Design of Visual Display—”,
Proceedings of the 21st Conference of the Society of Instrumentation and Control
Engineers (SICE), pp. 167-168 (1982) [in Japanese][2] S. Tachi et al.: “Tele-existence (I) Design and Evaluation of a Visual Display withSensation of Presence”, Proceedings of the 5th Symposium on Theory and Practice ofRobots and Manipulators (RomanSy 84), pp. 245-254, CISM-IToMM, Udine, Italy (1984)[3] S. Tachi and H. Arai: “Design and Evaluation of a Visual Display with a Sensation ofPresence in Tele-existence System”, Journal of the Robotics Society of Japan, Vol. 7, No. 4,
pp. 314-326 (1989) [in Japanese][4] S. Tachi, H. Arai and T. Maeda: “Development of An Anthropomorphic Tele-existence
Slave Robot”, Proceedings of The International Conference on Advanced Mechatronics(ICAM), pp. 385-390, Tokyo, Japan (1989)

[5] S. Tachi: “Tele-Existence”, Journal of Robotics and Mechatronics, Vol. 4, No. 1, pp. 7-12
(1992)[6] E. Oyama, N. Tsunemoto and S. Tachi: “Remote Manipulation Using Virtual
Environment”, Proceedings of the Second International Symposium on Measurement andControl in Robotics (ISMCR '92), pp. 311-318, Tsukuba, Japan (1992)[7] Y. Yanagida and S. Tachi: “Virtual Reality System with Coherent Kinesthetic and VisualSensation of Presence”', Proceedings of the 2nd International Conference on Advanced
Mechatronics (ICAM '93), pp. 98-103, Tokyo, Japan (1993)[8] S. Tachi and K. Yasuda: “Evaluation Experiments of a Teleexistence Manipulation
System”, Presence, Vol. 3, No. 1, pp. 35-44 (Winter 1994)[9] URL http://www.irofa.com/rcube/index.html (currently provided only in Japanese)[10]URL http://www.usc.edu/dept/raiders/story/index.html