tourbot and webfair -...

The design and development of mobile robots capa-ble of operating and providing services in populat-ed environments is an area that has attracted theinterest of the scientific community throughout thelast decade. Examples of such robots are deployed

in hospitals, museums, trade fairs, office buildings, anddepartment stores. In these environments, the mobile robotsprovide various services, including such tasks as delivering,educating, entertaining, or assisting people [5].

Two recent projects funded by the European Union (EU),TOURBOT (http://www.ics.forth.gr/tourbot) and WebFAIR(http://www.ics.forth.gr/webfair), address the development ofmobile robots capable of operating in populated environmentsin order to provide alternative means of interaction with localand remote visitors, a field that is informally termed “robots inexhibitions.” TOURBOT started in January 2000 and endedsuccessfully in February 2002. This project pursued the devel-opment of an interactive tour-guide robot able to provide indi-vidual access to museums’ exhibits over the Internet. Theresults of TOURBOT were demonstrated through the installa-tion and operation of the system in three museums participat-ing in the project as well as other interested organizations.WebFAIR (which began in December 2001 and ended in May2004) was based on the TOURBOT results and extended rele-vant developments to the more demanding environment oftrade shows. Additionally, WebFAIR introduced teleconferenc-ing between the remote user and on-site attendants andemployed a multirobot platform, thus facilitating simultaneousrobot control by multiple users. Factual information about thetwo projects is summarized in Table 1.

In this article, we present selected techniques developed inthese projects to cope with scientific challenges and techno-logical requirements imposed by the specific application area.Among these are techniques for mapping large environments,

an obstacle-avoidance tech-nique that useslaser and visioninformation to detectobjects invisible to the laserscanner, and an approach to fil-ter out range measurements coming from moving personsduring map construction.

A very important factor for the acceptance of a robotic tourguide by the broader public is the degree to which the systemsmoothly interacts with both Web and on-site visitors. For thisreason, special emphasis was placed upon the development ofappropriate robot-user interfaces in both projects. In this arti-cle, we also describe aspects of the developed interfaces, suchas a speech interface for on-site users and a flexible Web inter-face with enhanced visualization capabilities for remote users.

An important aspect of EU-funded projects is that they donot only provide important technical developments but alsopermit the study of the maturity of technologies as well as thelevel of their acceptance by the broader public. Towards thisend, extensive validation and demonstration trials have beenperformed within both projects. They have ascertained thatthe developed techniques have resulted in a considerablereduction of the system setup time compared to predecessorsystems of lower complexity. Moreover, they have facilitatedthe assessment and validation of the robustness and effective-ness of the system under real conditions. Finally, they haveprovided useful data regarding public response and attitudestoward robotic tour guides. This article also reports on theexperiences gained from these trials.

The TOURBOT-WebFAIR ApproachThe goal of the TOURBOT project was the development of

BY PANOS TRAHANIAS, WOLFRAM BURGARD, ANTONIS ARGYROS, DIRK HÄHNEL, HARIS BALTZAKIS,PATRICK PFAFF, AND CYRILL STACHNISS

TOURBOT and WebFAIRWeb-Operated Mobile Robots for Tele-Presence in Populated Exhibitions

JUNE 2005 IEEE Robotics & Automation Magazine 771070-9932/05/$20.00©2005 IEEE

IEEE Robotics & Automation Magazine JUNE 200578

an interactive TOUr-guide RoBOT (TOURBOT) able toprovide individual access to museums exhibits and culturalheritage over the Web. TOURBOT operates as the user’savatar in a museum, accepting commands over the Web thatdirect it to move in its workspace and visit specific exhibits.The imaged scene of the museum and exhibits is communicat-ed over the Internet to a remote visitor. As a result, the userenjoys a personalized tele-presence in the museum, able tochoose the exhibits to visit as well as the preferred viewingconditions (point of view, distance to the exhibit, and resolu-tion). At the same time, TOURBOT can guide on-site muse-um visitors, providing either group or personalized tours.

The successful course of TOURBOT, and the vision tointroduce similar services to the taxing case of trade fairs,resulted in the launch of the WebFAIR project. The latterwas additionally endorsed by experts in the organization and promotion of large trade shows. Besides the TOURBOTfunctionality, which is now offered in a more demandingenvironment, WebFAIR introduced teleconferencingbetween the remote user and on-site attendants and employeda multirobot platform, facilitating simultaneous robot controlby multiple users.

Focusing on the requirement for autonomous robotmotion, both projects opted for the development of a safe andreliable navigation system. For this purpose, the roboticavatars are equipped with sensors such as laser range-scanners,sonars, and cameras. The navigation system uses this sensoryinformation to adapt the robot’s internal model of the environment in order to plan the robot actions.

In order to realize the TOURBOT and WebFAIR systems, the consortia developed a multimedia Web interfacethat allows individuals to interact with the tour-guide systemover the Internet. Furthermore, an onboard interface forinteraction with on-site visitors at the exhibition site has beendeveloped. Using the Web interface, people are able to tele-control the robot and to specify target positions for the system. Camera controls are used to choose the part of theexhibition the user wants to observe in more detail. Therobotic tour guide possesses a multimedia information basethat provides a variety of information with respect to theexhibition at various levels of detail. Thus, the system servesas an interactive and remotely controllable tour guide thatprovides personalized access to exhibits with a large amountof additional information. Both the TOURBOT and Web-FAIR systems use video streams to convey observed informa-tion to the user. Additionally, they provide onlinevisualizations of their actions in a virtual three-dimensional(3-D) environment. This allows users to choose arbitraryviewpoints and leads to significant reductions of the requiredcommunication bandwidth.

The use of tour-guide robots has several advantages forthe exhibition visitor as well as for the provider of such aservice. First, TOURBOT and WebFAIR allow for a more

Project: TOURBOT, Contract: IST-1999-12643Funding: 5th Framework Programme, Information Society Technologies (IST)Start Date: 1 January 2000 End Date: 28 February 2002Budget: €1,718,150 EU Contribution: €1,088,790

Consortium—Participant RolesFoundation for Research and Technology—Hellas (Greece) Coordinator/Technology ProviderUniversity of Freiburg (Germany) Technology ProviderFoundation of the Hellenic World (Greece) Technology Broker/End UserUniversity of Bonn (Germany) Technology ProviderTHEON Robotic Systems (Greece) Technology ProviderDeutsches Museum Bonn (Germany) End UserByzantine and Christian Museum of Athens (Greece) End User

Project: WebFAIR, Contract: IST-2000-29456Funding: 5th Framework Programme, Information Society Technologies (IST)Start Date: 1 December 2001 End Date: 31 May 2004Budget: €2,331,142 EU Contribution: €1,269,970

Consortium—Participant RolesACTION Public Relations Hellas LTD (Greece) Coordinator/End UserFoundation for Research and Technology—Hellas (Greece) Scientific Coordinator / Technology ProviderRATIO Consulta SPA (Italy) Technology ProviderIDEASIS Ltd (Greece) Technology ProviderUniversity of Freiburg (Germany) Technology ProviderPolytechnic University of Madrid (Spain) Technology ProviderEnte Fiere Castello di Belgioioso e Sartirana (Italy) End User

Table 1. Factual data of the TOURBOT and WebFAIR projects.

The mobile robots can beoperated over the Internetand provide telepresenceto distant visitors.

JUNE 2005 IEEE Robotics & Automation Magazine 79

effective use of exhibitions. A Web-based tour-guide robotcan serve and educate people day and night since its opera-tional time is not limited to the opening hours of an exhi-bition. Compared to static or even remotely controllablecameras for viewing parts of an exhibition, tour-guiderobots can provide significantly more interaction capabili-ties. The mobility of the robots allows Web visitors tochoose a wide variety of view-points and to get the feelingof “being present” in the exhibition. Moreover, increasedinteraction capabilities with the exhibits themselves can beoffered to the user, which may be useful when visiting ascience or technology museum. Therefore, a scenario suchas “press the red button to watch . . .” and the correspond-ing service offered to the user can easily be implemented.In addition to this increased interactivity, the robotic agentcan deliver high-resolution images over the Web, which isextremely beneficial to professionals and specialists.

The TOURBOT and WebFAIR concept provides visitorsthe ability to individually exploit the expertise stored in thetour-guide robot, which can react flexibly to the requirementsof the visitors. It can, for example, offer dedicated tours ontemporary focuses of the exhibition or, alternatively, giveoverview tours. Furthermore, robots improve the flexibility forthe planning of tours, especially when more than one isdeployed. This allows people, to be served individually even ifthey belong to a larger group. Additionally, robotic tour-guidescontribute to the positive image of an exhibition since theyemphasize state-of-the-art technology and future-orientation.

Table 2 summarizes a comparison of the main features ofthe proposed approach (within TOURBOT and WebFAIR) for accessing exhibition sites and trade fairs withtraditional on-site visits and conventional Web presentations.As evidenced from this table, there is indeed grounds for pur-suing the goals set forth in our projects.

Access to Exhibition Sites and Trade Fairs

Conventional The TOURBOT andEvaluation Feature On-Site Visit Web Presentation WebFAIR Approach

Interaction High Low FairThe visitor is present at The presentation is static The visitor is virtually

the exhibition site. and preprogrammed. present in the exhibitionRemote visitors cannot site through the roboticinteract with on-site people. avatar and can observe

and interact.Quality of information High Low Fair

The user sees the exhibits Storage and communication The visitor can choose with his own eyes. requirements trade off quality. the optimal viewing

parameters (viewpoint, resolution, etc.).

Accessing site Low HIgh Highinformation in a The visitor must travel The visitor can visit the The visitor can visit thetimely and comfortable to the exhibition exhibits from a computer exhibits from a computermanner premises and visit it at the comfort of his at the comfort of his

during working days residence at any time. residence at any time.and hours.

Adaptability to Fair Low Highchanges in content The visitor sees the Reorganization of the The visitor sees the current

current content of material is required, a content of the site. Revisitingthe exhibition site costly procedure, especially it has minimal additional cost.but should revisit it for exhibitions with to see any changes. frequent changes in content.

Accessibility to visitors Low High Highwith special needs Travel is required. Only the ability to interact Only the ability to interact

with a computer is required. with a computer is required.Savings in time for Low High High

a typical visitor A significant overhead Almost instantaneous access Almost instantaneous accessis required for visiting to any exhibition site to any exhibition sitea distant site. is given. is given.

Financial savings for Low Fair Higha typical visitor This is the standard The exhibition site is The robotic avatar becomes

model of operation. advertised through the an exhibit by itself. The siteavailability of Web offers an extra service topresentations. both exhibitors and visitors.

Table 2. Access to exhibition sites and trade fairs.


Figure 1 provides a conceptual overview of theTOURBOT and WebFAIR systems. A detailed descriptionof the developed systems is beyond the scope of this article.Instead, we emphasize specific techniques developed in thecontext of the TOURBOT and WebFAIR projects for solv-ing important scientific and technological problems for therealization of the corresponding robotic systems. We specifi-cally report on techniques for environment mapping, obstacleavoidance, and an approach to filter out range measurementscoming from moving persons in the process of map construc-tion. We also present important aspects of the user interfacesof the developed systems.

MappingIn order to navigate safely and reliably, mobile robots must beable to build suitable representations of the environment.Maps are also necessary for human-robot interaction sincethey allow users to direct the robot to specific locations in theenvironment. Our current robotic systems use two differentmapping techniques, depending on the characteristics of theenvironment in which the robot is deployed. In environmentswith a complex shape, our systems employ dense grid mapsand operate according to a discrete hidden Markov model.The model is very efficient in terms of computational perfor-mance, has been proven quite robust with respect to rangemeasurement errors, and can operate regardless of the struc-ture of the workspace. Its main drawback lies in the achievedlocalization accuracy, which depends on the resolution of thegrid. In order to overcome this limitation, an alternative local-ization method has been developed that involves a hybridmodel, i.e., a combination of a discrete (hidden Markov)model and a continuous (Kalman filter) model [3]. This com-bination enables the use of Markovian dynamics for globallocalization and Kalman filter-based tracking for achievingincreased accuracy.

Grid-Based MappingThis grid-based mapping technique employs occupancy gridmaps. In probabilistic terms, the goal of map learning is tofind the map and the robot positions that yield the best inter-pretation of the data d t gathered by the robot. Here the datad t = {u0: t−1, z1: t} consists of a stream of odometry measure-ments u0: t−1 and perceptions of the environment z1: t . Themapping problem can be phrased as recursive Bayesian filter-ing for estimating the robot positions together with a map ofthe environment

p(x1: t, m | z1: t, u0: t−1)

= α · p(zt | xt, m) ·∫

p(xt | xt−1, ut−1)

· p(x1: t−1, m | z1: t−1, u0: t−2)dx1: t−1. (1)

In probabilistic mapping and localiza-tion, it is typically assumed that theodometry measurements are governedby a probabilistic motion modelp(xt |xt−1ut−1), which specifies the like-lihood that the robot is at state xt , giventhat it previously was at state xt−1 andthe motion ut−1 was measured. On theother hand, the observations follow theobservation model p(zt |xt, m), whichdefines the likelihood of the observationzt given the map m for every possiblelocation xt in the environment.

The systems described in this articleapply a Rao-Blackwellized particle filter

Figure 1. Conceptual overview of the TOURBOT and WebFAIRsystems.

On-Site PC

High-Speed Internet Connection

Wireless Connection

Internet

Figure 2. Map generated using our Rao-Blackwellized mapping algorithm. The sizeof the environment is 18 × 51 m. The robot had to close several loops during themapping process.


[13] to estimate a posterior of the path of the robot. Thekey concept in Rao-Blackwellized mapping is to use a par-ticle filter in order to represent potential robot trajectoriesx1: t . Each sample of the particle filter possesses its own map,which is conditioned on the trajectory of that particle. Theimportance weights of the samples are computed accordingto the likelihoods of the observations in the maximum like-lihood map constructed using exactly the positions taken bythis particular particle. The key advantage of this approachis that the samples approximate the full posterior over robotposes and maps at every point in time.

Our approach differs from previous techniques in that ittransforms sequences of laser range scans into odometrymeasurements using range-scan registration techniques [10].The highly accurate odometry data is then used as input tothe particle filter. Since the scan matching yields odometryestimates that are an order of magnitude more accurate thanthe raw wheel encoder data, our algorithm requires fewerparticles than the original approach. Simultaneously, thetransformation of sequences of scans into odometry mea-surements reduces the well-known particle deprivationproblem [18] since the number of resampling operations isalso reduced. In several experiments [8], it has been demon-strated that our approach results in an improved ability tomap large environments.

Figure 2 depicts a map of the entrance hall of the comput-er science building at the University of Freiburg, Germany.The trajectory of the robot is also shown. Although themapped area was large (18 m × 51 m) and the robot had toclose several loops during the mapping process, the resultingmap is highly accurate.

Feature-Based MappingIn the case of structured environments, localization accura-cy can be increased by constructing and employing feature-based maps of the environment, namely maps of linesegments and corner points [2]. In contrast to most existingfeature mapping approaches, our approach avoids theexplicit storage and manipulation of feature-to-feature andfeature-to-pose covariance information by treating mapfeatures as parameters of a dynamical system according towhich the robot state evolves. This results in a learningproblem that is solved via a variant of the expectation max-imization (EM) algorithm. The proposed EM algorithm(see Figure 3) iterates a Kalman smoother-localization step(E-step) and a map recalculation step (M-step) until theoverall process has converged or until a certain number ofiterations have been carried out.

To detect and correctly close loops during mapping, ouralgorithm relies on the global localization capabilities of a

Figure 3. Feature-based mapping, including (a) a block diagram of the algorithm and (b)–(c) line feature maps of an exhibitionsite: (b) original data and (c) and map generated by our algorithm.

Start

Localize RobotForward Pass

Localize RobotBackward Pass

Recompute Map Features

Converged?NoYes

End

FeatureExtraction

MapFeatures

(a)

(b)

(c)


hybrid method based on a switching state-space model [3].This approach applies multiple Kalman trackers assigned tomultiple hypotheses concerning the robot’s state. It handlesthe probabilistic relations among these hypotheses using dis-crete Markovian dynamics. Hypotheses are dynamicallygenerated by matching corner points extracted from mea-surements with corner points contained in the map.Hypotheses that cannot be verified by observations orsequences of observations become less likely and usually dis-appear quickly. The resulting map always corresponds to themost likely hypothesis.

Figure 3(c) shows a typical map of an exhibition site result-ing from this process; the map corresponding to the input datais shown in Figure 3(b).

Mapping in Dynamic EnvironmentsWhereas most contemporary mapping methods are able todeal with noise in the odometry and the sensor data, these

methods assume that the environment is static during map-ping. However, in public spaces such as museums or tradefairs, the environment cannot be regarded as static duringthe robot installation time. The systems described in thisarticle address this issue through an approach that employsan EM-technique. In the E-step, we compute a probabilisticestimate regarding measurements that correspond to staticobjects. In the M-step, we use these estimates to determinethe position of the robot and the map. Experimental resultsprovided evidence that the resulting maps are more accuratethan maps constructed without considering dynamic beams.

Figure 4 shows an application of this approach to dataacquired by a mobile robot in the Byzantine Museum inAthens, Greece. Structures identified by the algorithm as staticare shown in black; the ones belonging to dynamic objects areshown in orange/gray.

Fusion of Laser and Visual DataThe ability to correctly identify objects in the vicinity of therobot is particularly important for robots in real-world environ-ments such as exhibitions; it is a basic precondition for the safe-ty of the robot and the exhibits. A common problem is thatvarious objects, such as chairs, tables, and shelves, are not cor-rectly represented in the two-dimensional (2-D) laser rangescans used for navigation. To overcome this problem, our sys-tems additionally use visual information.

According to the employed method [1], the 2-D structureacquired with the laser-range scanner is used to compute a 2.5-D representation of the environment by assuming verticalplanar walls for all obstacles in the 2-D map. We then exploitcamera information to a) validate the correctness of the con-structed model and b) qualitatively and quantitatively charac-terize inconsistencies between laser and visual data whereversuch inconsistencies are detected. The inconsistencies betweenthe laser and visual data are converted to real-world coordi-nates and accumulated in a 2-D occupancy map.

Figures 5 and 6 illustrate a typical application example in acorridor environment at the Institute of Computer Science(ICS) of the Foundation for Research and Technology–Hellas(FORTH). In this case, the robot travels along a corridor withseveral objects that are invisible to the laser scanner, such as

Figure 4. Map of the populated exhibition hall of the ByzantineMuseum in Athens. Measurements labeled as belonging todynamic objects are shown in orange/gray.

Figure 5. (a)–(b) Images acquired at successive points in time and (c) results of obstacle detection superimposed on the image shownin (b).

(a) (b) (c)


tables, fire extinguishers, and a wall cabinet. Figure 5(a) and(b) shows the images grabbed by the robot at two consecutivemoments in time. Figure 5(c) shows the results of obstacledetection. Regions with inconsistencies are marked withcrosses. It can be seen that objects that cannot be detectedwith only the range finder are successfully detected with theproposed technique. Finally, Figure 6 shows the occupancygrid maps obtained without considering visual information[Figure 6(a)] and after fusing vision and laser information [Fig-ure 6(b)]. The map generated by our algorithm provides amore accurate representation of the environment, which canbe used to prevent the robot from colliding with obstacles notvisible in the range scans.

InterfacesRobots in museums and exhibitions should be able to interactwith on-site visitors in a natural way and allow distant visitorsto feel like they are present at the site. Thus, the employmentof intuitive human-robot interfaces is of paramount impor-tance to the acceptance and success of the overall system. Theinterfaces should be tailored to the type of user; clearly thereare similarities as well as important differences between distantand on-site users.

Web InterfaceA variety of Web-based tele-operation interfaces for robotshave been developed over the last several years, including theMercury Project [6], the “Telerobot on the Web” [7], andTele-Garden [16]. The mobile robotic platforms Xavier,Rhino, and Minerva [4], [15], [17] could also be operatedover the Web. Their interfaces relied on client-pull and serv-

er-push techniques to provide visual feedback of the robot’smovements; this includes images taken by the robot as well asa Java-animated map indicating the robot’s current position.However, their interfaces do not provide any means to reflectchanges in the environment. Three-dimensional graphicsvisualizations for remote robot control have already been sug-gested by Hirukawa et al. and Marin et al. [11], [12], allowingremote users to carry out manipulation tasks with a mobilerobot by controlling a 3-D graphics simulation of the robot.

The Web interface developed within TOURBOT andWebFAIR has been designed to provide enhanced functionalityand ease of use. Besides providing live streaming video from theexhibition site, the interface also allows personalized control ofthe robot(s), a feature that was not provided in the interfaces ofprevious systems such as Xavier, Rhino, and Minerva [14].Remote users can control the robot exclusively for a fixedamount of time, which is generally set to ten minutes per ses-sion. During this time, the user can direct the robot to anydesired location in the exhibition. The user can also select from

Figure 6. Occupancy grid maps computed based on the fusion of vision and laser data: (a) the map computed from the laser-range data and (b) the map after combining vision and laser data.

(a) (b)

A very important factor for theacceptance of a robotic tour guide

by the broader public is the degreeto which the system smoothlyinteracts with both Web- and

on-site visitors.


a list of predefined guided tours or direct the robot to visit par-ticular exhibits or locations in the exhibition. Furthermore, theuser can control the pantilt unit of the robot to request therobot to move around an exhibit in order to view it from vari-ous directions and to grab high-resolution images.

A screenshot of the Web interface is shown in Figure 7.The left side contains the list of exhibits and predefined toursoffered to the user. Live streaming video as well as a Javaapplet animating the robot in a 2-D floor plan (map) areshown in the center of the screen. This floor plan can also be

used to directly move the robot to an exhibit or toan arbitrary location in the exhibition. Betweenthe map and the live video stream, the interfaceincludes control buttons as well as a message win-dow displaying system status messages. The rightpart of the interface is used to display multimediainformation regarding visited exhibits and to pro-vide links to relevant background information.

Enhanced VisualizationsWeb users strongly depend on the accuratevisualization of the robot’s environment and themoving people therein to grasp what is goingon at the exhibition site and understand whythe robot is carrying out its current actions. Forthis purpose, we also developed a control inter-face that provides the user with a virtual realityvisualization of the environment, including therobot and the people in its vicinity. Dependingon the level of detail of the virtual reality mod-els used, Internet users can obtain visualizations

Figure 7. Web interface of the TOURBOT system for exclusive control overthe robot.

Figure 8. The enhanced 3-D visualization allows arbitrary viewpoints: (a) the real and (b) the virtual view through the robot’scameras and (c) the robot guiding three people through the museum and (d) a bird’s eye view of the scene.

(a) (b) (c) (d)

with quality comparable to video streams, yet at muchlower bandwidths. As an example, consider Figure 8,which shows two sequences of visualizations provided dur-ing the operation of the system in the Deutsches MuseumBonn, Germany, in November 2001 along with imagesrecorded with a video camera and with the robot’s on-board camera. As can be verified, the visualization is almostphoto-realistic and the animated avatars capture the behav-ior of the people in the scene quite well.

Onboard InterfaceIn addition to interacting with remote users, robots shouldinteract with on-site visitors as well. For this purpose, a prop-erly enhanced version of the Web interface is displayed in atouchscreen mounted at the rear side of the robot.

Video streams and enhanced visualizations are not pro-vided to on-site visitors since they are not actuallyrequired. Instead, the onboard interface makes extensiveuse of speech synthesis and commercial speech recognitionsoftware capable of understanding sets of simple phrases;this set varies depending on the task athand. Figure 9 shows a scene in whicha per son interacts with the robotAlbert during the Hannover trade fairin 2001 in Germany. Here the personasked several questions of the robot(Who are you? Where are you from?What are you doing here?) andrequested information about the time.Depending on the input of the user,the robot can dynamically generatespeech output.

Another very important aspect ofrobotic systems is their ability to alter thefacial expressions of their mechanicalheads based on their internal status. Cur-rently, there are three different facialexpressions, namely “happy,” “neutral,”and “angry.” These facial expressions areimplemented by modifying the shape ofthe eyebrows and the mouth. Combinedwith a variety of voice messages, therobots use these expressions to inform theon-site visitors regarding their internalstatus. For example, if the paths of therobots are not obstructed by the on-sitevisitors, the robots appear happy. In theopposite case, “mood” changes progres-sively in time. Moreover, the head of therobot is controlled so that it looks towardsthe direction of intended motion.

System Installationand DemonstrationIn the framework of the TOURBOTproject, a number of demonstration


Figure 9. Person interacting with Albert during a Hannovertrade fair demonstration.

Figure 10. (a) Robot Lefkos operating in the exhibition of the Foundation of theHelenic World. (b) Robot Rhino operating in the Deutsches Museum Bonn. (c) RobotLefkos operating in the Byzantine and Christian Museum. (d) Robot Albert operatingin the Belgioioso Exhibition Center in Italy.

(a)

(b)

(c) (d)

trials were undertaken on the premises of the participatingmuseums. Factual information on these events is as follows:

◆ Foundation of the Hellenic World, Athens, Greece, 28May–2 June, 2001. Exhibition: “Crossia, Chitones,Doulamades, Velades—4,000 Years of Hellenic Cos-tume.” The exhibition area comprised 2,000 m2. Dur-ing the trial, the robot operated approximately 60 h,

covering a distance of 14 km. More than 1,200 Webusers observed the exhibition through TOURBOT. Atypical situation, in which the robot Lefkos guides visi-tors through the museum, is shown in Figure 10(a).

◆ Deutsches Museum Bonn, Bonn, Germany, 6–11November 2001 [see Figure 10(b)]. Exhibition: “Part ofthe permanent exhibition, highlighting scientific

achievements that were awardedthe Nobel Prize.” The exhibitionarea in which the robot movedcomprised about 200 m2. The sys-tem operated about 60 h, coveringa distance of 10 km. Approximately1,900 Web visitors had a lookaround the museum via the robot.

◆ Byzantine and Christian Muse-um, Athens, Greece, 3–7December 2001 [see Figure10(c)]. Exhibition: “ByzantiumThrough the Eyes of a Robot.”The exhibition area was about330 m2. During the tr ial, therobot operated 40 h, covering adistance of 5.3 km. The numberof Web users was small in thistrial, due to the volume of on-site visitors. Since the first day ofthe tr ial at the Byzantine andChristian Museum, a large num-ber of (on-site) visitors werecoming to the exhibition. This


Figure 11. Screen shot from the GUI for the RoboTalk event.

> Albert calls Rhino!> live from muenchen: here you can see the blue box.

Start Abort Continue Back to Start

Robot Rhino Robot Albert

Figure 12. Synchronization of the tours given by Rhino and Albert in the Deutsches Museum Bonn and the Deutsches MuseumMunich.

(a) (b)

forced the TOURBOT team to make the decision todevote significantly more system time to on-site visitors asopposed to Web visitors.

Additionally, TOURBOT was installed and operated for alonger period of time (October 2001–February 2002) at theHeinz Nixdorf MuseumsForum (HNF) in Paderborn, Ger-many. This was in the framework of the special exhibition“Computer.Gehirn” (Computer.Brain) with a focus on thecomparison of the capabilities of computers/robots and humanbeings. In June 2002, TOURBOT was introduced for oneweek in the Museum of Natural History of the University ofCrete, Heraklion, Greece.

Within the WebFAIR project, a prototype event calledRoboTalk aimed to coordinate two robots installed in two dif-ferent exhibitions. The event lasted four days (19–22 June2003), during which the mobile robots Rhino and Albert wereinstalled in the Deutsches Museum Bonn and the DeutschesMuseum in Munich, respectively.

Both robots were connected via the Internet so that visitors in one exhibition could participate in the tours given bythe other robot. Whenever one robot arrived at an exhibit, itcommunicated this to the other robot. The latter would stopand provide the video and audio data received from the otherrobot. In this way, visitors of one museum could also see exhibitspresented by the other robot at the remote site. Figure 11 showsthe user interface of the robots during this event. In addition toinformation about the exhibition, this interface includes a win-dow showing the video stream obtained by the other robot. Fig-ure 12 shows two particular trajectories of Rhino and Albertduring the event. While Figure 12(a) shows the trajectory takenby Rhino in Bonn, Figure 12(b) depicts the path of Albert inMunich. The points in space where the two robots were syn-chronized are labeled by the numbers in the figure.

In April 2004, another event was organized within theWebFAIR project at Belgioioso Exhibition Center, Italy. Dur-ing this event (which lasted two days, spanning an annuallyorganized vintage fashion exhibition), robot Albert traveled adistance of about 2 km during 10 h of operation in an envi-ronment that was very challenging for robot navigation. At thesame time, Albert provided teleconferencing capabilities toremote users [Figure 10(d)].

Installation TimeThe large number of test installations of the TOURBOTand WebFAIR systems required the development of sophis-ticated tools for the set-up of the overall system. The mostcrucial part of the overall procedure is the generation of thenavigation map. However, based on the techniques describedearlier in this article, the overall mapping process could in allcases be accomplished within several hours.

Another time-consuming process is the generation of themultimedia content that is presented to the users and thedefinition of task-specific information (e.g., location withinthe map of designated exhibits, definition of tours, etc.) Forthis purpose, the TOURBOT and WebFAIR systemsinclude multimedia databases containing site-specific HTML

pages, images, audio, video sequences, and other material.Most of the multimedia information pertinent to theexhibits can be obtained directly from the exhibition sitessince pictures, text, and other relevant material are oftenalready packaged in existing Web presentations.

The whole setup can therefore be accomplished in lessthan two days. This is an enormous speedup compared toprevious tour-guide systems. Figure 13 shows the timerequired to install the Rhino and Minerva systems [4], [17]in comparison to that of the TOURBOT system. As can beseen, the TOURBOT system requires significantly less timeto set up than Rhino and Minerva. Our experience withtour-guide robots in exhibition sites suggests that 3-D mod-els of exhibitions’ premises are generally not available. Theautomatic generation of such models with the mobile robotitself is a subject of ongoing research [9].

Reactions of the PublicAn interesting study was carried out in the context of theabove trials regarding the visitor-robot interaction patterns.This study was planned and executed during the trial in theByzantine and Christian Museum, Athens, Greece. Based onthe observations during the previous trials, the human-robot-interaction was qualitatively classified into four behaviors:watching the robot, moving towards the robot, touching therobot, and using the touchscreen. The frequency of the occur-rence of these behaviors for the cases of adults and children is


Figure 13. Time required to install the different tour-guide sys-tems Rhino, Minerva, and TOURBOT.

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Rhino Minerva Tourbot

TOURBOT operates as the user’savatar in a museum, acceptingcommands over the Web that

direct it to move in its workspaceand visit specific exhibits.

summarized in Figure 14.Considering these results, one may come to some pre-

liminary conclusions regarding the human-robot-interac-tion. Most visitors turn/move to the robot when they seeit, whether immediately or after watching it for a time. Thisindicates that the robotic platforms attract the interest of thevisitors. The smaller counts that were observed in thefourth behavior (using the touchscreen) are mostly due toonly one person being able to use the touchscreen at anypoint in time. Comparing adults and children, it can bestated that children are uninhibited and natural in theirbehavior. Significantly more counts relate to the behavior“moving towards the robot” than to “watching it.” On thecontrary, adults tend to exhibit a more “reserved” behaviortowards the robot. The performance in the correct use ofthe robot is better in adults than in children.

ConclusionsIn this article, we presented a number of techniques thatare needed for realizing Web-operated mobile robots.These techniques include effective map-building capabili-ties, a method for obstacle avoidance based on a combina-tion of range and visual information, and advanced Weband onboard robot interfaces. In addition to video streams,our systems provide high-resolution virtual reality visual-izations that also include the people in the vicinity of therobot. This increases the flexibility of the interface andsimultaneously allows a user to understand the navigationactions of the robot.

The techniques described in this article have been suc-cessfully deployed within the EU-funded projects TOUR-BOT and WebFAIR, which aimed to develop interactivetour-guide robots able to serve Web- as well as on-site visi-tors. Technical developments in the framework of these pro-jects have resulted in robust and reliable systems that havebeen demonstrated and validated in real-world conditions.Equally important, the system setup time has been drasticallyreduced, facilitating its porting to new environments.

Our current research extends the navigation capabilitiesof the robotic systems by further enhancing existing com-petences and introducing novel ones. Specific capabilitiesthat are studied include obstacle avoidance in the cases ofobjects that are not visible by the laser scanner, 3-D map-ping, mapping in dynamic environments, predictive navi-

gation, and multirobot coordination [5]. Moreover, in thecontext of the above projects, additional issues have beenaddressed, such as a) how to adapt this technology in orderto fit the long-term operational needs of an exhibition site,b) how to evaluate the robotic system in terms of its impactto the main function and objectives of the exhibition site(financial impact, accessibility, marketing and promotion,and impact on visitor demographic), and c) how to evalu-ate the content and educational added value to museumand exhibition visitors and generate a feedback to the tech-nology developers in order to improve the robotic avatarsand further adapt to the needs of the users.

AcknowledgmentsThis work has partly been supported the InformationSociety Technologies (IST) Programme of the Commis-sion of the European Communities under contract num-bers IST-1999-12643 and IST-2000-29456. The authorswould also like to thank the members of the IST projectsTOURBOT and WebFAIR for helpful comments andfruitful discussions.

KeywordsWeb-operated robots, robots in exhibitions, navigation com-petences, remote visualization.

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Figure 14. The reactions of visitors to the robotic tour guide: (a) adult visitors and (b) children.

Watching the RobotMoving Towards the RobotTouching the RobotUsing the Touch-Screen

Watching the RobotMoving Towards the RobotTouching the RobotUsing the Touch-Screen

(a) (b)

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Panos Trahanias is a professor with the Department of Com-puter Science, University of Crete, Greece, and the Institute of Computer Science (ICS), Foundation for Researchand Technology—Hellas (FORTH), Greece. He received hisPh.D. in computer science from the National Technical Uni-versity of Athens, Greece, in 1988. He has been a research asso-ciate at the Institute of Informatics and Telecommunications,National Center for Scientific Research “Demokritos,” Athens,Greece. From 1991–1993, he was with the Department ofElectrical and Computer Engineering, University of Toronto,Canada, as a research associate. His research interests are incomputer vision, vision-based robot navigation, telematicsapplications, and virtual and augmented reality applications.

Wolfram Burgard studied computer science at the Universi-ty of Dortmund, Germany, and received his Ph.D. degreefrom the Department of Computer Science at the Universityof Bonn in 1991. Since 1999, he has been an associate pro-fessor at the Department of Computer Science at the Univer-sity of Freiburg, where he heads the research laboratory forAutonomous Intelligent Systems. His areas of interest areartificial intelligence and robotics, including mobile robot

navigation, multirobot systems, state estimation, human robotinteraction, activity monitoring, and networked robots.

Antonis Argyros is an associated researcher at the Instituteof Computer Science (ICS) of the Foundation for Researchand Technology (FORTH) in Heraklion, Crete, Greece. Hereceived his Ph.D. from the Department of Computer Sci-ence, University of Crete, Greece, in visual motion analysis.He has been a postdoctoral fellow at the Royal Institute ofTechnology in Stockholm, Sweden, where he worked onvision-based, reactive robot navigation. In 1999, he joinedthe Computational Vision and Robotics Laboratory of ICS-FORTH, where he has been involved in many research anddevelopment (R&D) projects in image analysis, computervision, and robotics. He has also served as a visiting associateprofessor at the Computer Science Department of the Uni-versity of Crete. His current research interests include com-putational vision and robotics, particularly the visualperception of motion and three-dimensional structure, visualtracking, the development of robot behaviors based on visualinformation, and panoramic vision.

Dirk Hähnel studied computer science at the University ofBonn. Currently, he is a Ph.D. student at the Department ofComputer Science of the University of Freiburg. His areasof interest are mobile robot navigation and learning two-and three-dimensional maps with mobile robots.

Haris Baltzakis received a diploma in electrical engineeringfrom the Democritus University of Thrace in 1997 and theM.Sc. and Ph.D. degrees in computer science from the University of Crete in 1999 and 2004, respectively. He is cur-rently a postdoctoral researcher at the Institute of ComputerScience of the Foundation for Research and Technology—Hellas (FORTH), Greece. His research interests include computer vision and autonomous robot navigation.

Patrick Pfaff studies computer science at the University ofFreiburg and is currently working on his diploma thesis in thegroup for Autonomous Intelligent Systems at the University ofFreiburg. His research interests lie in the field of mobile robot-ics, especially outdoor navigation.

Cyrill Stachniss studied computer science at the Universityof Freiburg and received his diploma degree in 2002. Currently, he is a Ph.D. student in the research lab forAutonomous Intelligent Systems at the University of Freiburg.His research interests are in the field of mobile robot explo-ration, simultaneous localization and mapping (SLAM), andcollision avoidance.

Address for Correspondence: Prof. Panos Trahanias, Institute ofComputer Science (ICS), Foundation for Research and Tech-nology-Hellas (FORTH), Vasilika Vouton, PO Box 1385,GR 71110, Heraklion, Crete, Greece. E-mail:[email protected].


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