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International Review on Compulers an d Softivare fl.RE.CO.S.). Vol. 2, n. 3May 2007

Remote Control on Internet, Long Distance Experiment ofRemote Practice Works, Measurements and ResultsL. Kaddour-EI Boudadi, J, Vareille, P. Le Pare, N. Berrached

Abstract - The aim of ou r work is to control remotely mechanical systems which have nowadayslocal controls. With the development of the e-technologies, improvement of the network in term oflime atid hand-w idth, ihe remote control will he common and will be made usitig networks withouttrue quality of service, even luiprediciable like Internet In a first p art of this paper, w e arepresenting some existing applications we have used. In a second part, we are describing genericsoftware architecture to realize such remote control and a methodo logy to take irtto account theunpredictable nature of the cotnm unicalion media. In the third patt we present experimentalresults of long distance remote control.Copyright 2007 Praise Worthy Prize S.r.t. - All rightsreserved.Keywords: Remote Control. Internet. Methodology, Reliability, Networks

T. IntroductionThe development of the technologies ofcommunication and the standardization of theexchanges of data were very important at the end of the20th century. It was a period of growing usage of these

two technologies and of their industrial applications.Since 1970s, the development of Ihe Internet iscertainly one of the major changes. The Internetnetwork is now accessible from nearly every point ofthe Earth, using various technologies from telephonelines to satellite transmission systems, becoming fasterand faster, cheaper and cheaper, day after day, with thedeveloping of new technologies and the increase innumber of Internet links.The problem to solve is to act remotely. Theimportant issue Is how to use the new technology ofcommunication for the remote control of machines assafely as possible.Today the technology is sufficient to be able tocontrol a production process from any point of theworld using usual tools like a laptop and a telephoneline. The Fig. 1 represents a system for remote actionfrom the expression of the will of the remote user on theleft to the local system which acts on the right. Itappears that the complete system needs energyeverywhere. But the quantity of power consumed totransmit the "will" is smaller compared to the powerconsumption at the right end. The sub-system oftransmission is sensitive to the overflows of data butalso to the breakdowns of power supply at each node.Although the reliability of the equipments increases,

the complexity increases too, then the probability of afailure of the transmission can not be considered equal

The problem that will still remain is the confidenceuser can have in the Internet in terms of Quality ofServices (QoS).One solution to ensure the QoS is to use redundancyfor the power supply everywhere and to use redundancyof the paths followed by the data. Right now, no quality

is guaranteed and in the future, quality could beguaranteed but it will be expensive. W ithout this Qo S. itbecomes really hazardous to perform remote control ofindustrial processes.Nevertheless, in some fields, using Internettechnologies to control production lines or mechanicalsystems is possible, for example in the following fields:Tele-maintenance [1]: with Internet technologies, itis now possible to make remote diagnostics, to solveand repair problems, to prepare maintenance phasesetc...Tele-expertise: some specific operations onmechanical systems can only be made by expert. Ina close future, it will become possible for experts tooperate from their office a machine locatedthe world, just using classic websomewhere intechnologies.Tele-teaching:machines to a lot of universities are usingteach the basics of mechanicalengineering. The profitability of these machines isof course really poor because they are only used afew weeks a year. Why not developing commoncenters, where students may have access to realmachines without being close to them?. One of theproblems of e-learning is to make practicalexperiments. Why not using Internet technologies tolet distant students to m anipulate real systems?


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Remote controlE N E R G Y

senso r of the netpromptness &

Fig I Remote controlIn the Nineties, several projects of control ofmechanical systems using Internet as network ofcommunication appeared with varied objectives suchthe Mercury project [2] to prove feasibility, theAustralian t^lerobot [3]-[4]-[5] for the interaction withthe user, Puma Paint [6], mobile roboticsKhepOnTheWeb [7], augmented reality [8], etc.. . .None of them could develop a generic software

architecture taking into account the unforeseeablenature of the network.The use of Internet will reduce the costs of theseactivities and increase the speed and bandwidth in thefuture. Let us also think that the quality of the remotecontrol and the comfort of the user will also increase(?). The problem for the industry is to find aneconomical compromise between the cost of the localcontrol and a local maintenance or the cost of a remotecontrol and a remote maintenance, assuming potentialfailures of the transmissions. When developing suchapplications, we have to think that these activities relyall the time on an unpredictable network and that wehave tobuild them taking into account this parameter.There are works related to network metrology inorder toevaluate its performances [9],These works show that we can know the networkstate in the future. Then, if the network quality isdegraded, it will bepossible toanticipate these chan ges,which is of great interest during machine remotecontrol. Classifications of services for NetworkedControl Systems (NCS) have been developed by J.P.Georges et al. [10]. All these works propose to studyinteractions between temporal performances indicatorsprovided by control theory and the networkperformances evaluation.For this concern, we have used two concepts, thefirst is tocheck the quality of the communication during

is to switch to a safe state under the control of a localintelligence, if the delay of transmission exceeds thereaction's delay of the worker present in the factory.11. Applications

Different applications have been developed usingconcepts explained in this paper Fig. 2.Several of them,such the Ericc robot, the small milling machine, theMentor robot, the motorized cameras, and a modemwere used.

Mo vie C a m e rac r o p h o n e

MechanicaS y s l e m s

MuHiiiiediaS e r v e 'Http S e r v e rAppl icat ionS e rv e r

CUem

m te r r i e tB r o w s e r

Fig. 2. General Architecture

//. /. Ericc Robot and the Milling MachineThis first application [11] concerns the control of a 5DOF robot arm see Fig. 3.This robot may grasp somesmall objects with its pliers and move them to otherplaces. A first camera (Sony EV1-D3I) is placed infront of the robot. As it is motorized, it can makemovements (left, right, up, down) and also has zoomfacilities. It enables the distant user toadjust the imagesto its works. A second camera is placed on the top ofthe robot to give another point of view of the scene. It isa fixed focus and zoom camera, but it provides anembedded web-server to spread video. An audiomodule is also available. This robot is used for teachingby professor from our institution and also by colleagues


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development has been made for a small milling machinefor rapid prototyping and we plan to use it for teachingas well Fig. 4. These two applications show the interestof such a work in the educational context and itsfeasibility. Comments from users help us to improve thewhole system.

fl.2. Mentor RobotThis application [12] concerns the control of another

robot arm with 5 degrees of freedom (Laresi LaboratoryUSTMB in Oran, .Algeria) using augmented reality Fig.5. Ihis application allows an operator to plan andcontrol the robot movement using visual and sensoryfeedback information, the interaction between theoperator and the virtual world through the I/O dataprovide an immersion sensation and an update of thevirtual environment by the real (position) sensoryfeedbacks.

FJg, 3 The user interface of the milling machine

// , 3. Motorized Web-camerasAnother experiment [13] has been settled up to

control a pan, tilt and zoom camera using the VISCAprotocol and has been implemented in an aquariumclose to Brest (France) to look at penguins. 4/5 imagesper second are produced with a size of 192x144 pixels.In this context, the interest of this work is not to protectthe camera and it 's environm ent in case of networkfailures ^damages are physically not possible), but tocheck that the kernel of our software is bug-free. Thisenvironment is also used to study network connections:as soon as a client is connected to the server, theping/pong mechanism is launched and information itcollects are stored. A second camera is installed in thelab.

Fig. 4. Snapshot ofthe user screen

I-ig. 5. The user interface of tlic Menlor robot

// . 4. ModemWe also developed an application which makes itpossible to control a modem through the network. Thisapplication is used to send AT command which will beused to control a phone in Oran (Algeria) from BrestFrance Fig. 6.

//. 5. Network QualityThe Internet network is working using the "besteffort" strategy., which means that any user may send

information and that there are no priorities betweenthem. This strategy implies that characteristics for aconnection between a user (or client) and a server isdepending on, of course, some physical constraints(mainly type of the network, distance, number of nodes)and also depending on the overall use of the Internet. Itis then really difficult to propose a model for theInternet network and in many cases, Internet has to beconsidered as a black box, which takes inputs and maydeliver outputs after some time.

II.6. Managing Network UnreliabilityIn the context of remote control, the choice of TCP to

send order is obvious to be sure that orders are


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L Kaddour-EI Boudadi, J. Vareille, P. Le Pare, N . Berrached

transmitted as well as to have a rather stabletransmission delay.3t>ro)M tProductiquc: Robot Ence A Zanra n p U e -

Fig. 6, llic user interlace ol th i . ' Modem l-axA way to measure it is to use a Ping/Pong method:one side of the system send a request (ping) and theother has to answer it immediately (pong). This methodis easy to implement, does not disturb the genera!working of the system (client/server/network) and givesinformation, which may be exploited in two differentways:

1. Statistical way: when the pon g is coming back, themeasure made corresponds to the previous state ofthe connection. This information, associated withprevious ones, gives to the server and the client ageneral idea of the quality of the connection whichmay have an impact on the remote control and theway a user will be confident in the system: forexample, he will not try any critical operation if itscontiection looks bad.2. Dynamical way: when one side of the system issending a ping (or pong), watchdogs may be setupto monitor the waiting time. If it overruns somepredefined limits, some autonomous decisions maybe taken to prevent any damage on the wholesystem. So this ping pong cannot be replaced by an

The Ping/Pong method acts as a sensor, which givesinformation about the network quality. Basically, onecan decide that the connection is correct when the delayobserved is lower than a limit and incorrect in the othercases. This implies two different states for the systemunder control and transitions between them. Moregenerally, mechanical systems may have differentstates. A specification tool called Gemma 2 has beendefined to model these different states. It is composedof three main areas (?): Initialisation, Working andDefect. Each area Is itself composed of sub-areas, whichcorresponds to sub-cases. For example, the Workingarea is When an engineer has to specify the way amechanical composed of 6 subareas like "FI: normalproduction", "F2: start procedure" or "F6: operatingtest".AvBfaga rouiid trip linw In ms100 .^, ,^, >,. 500 800

Fig 7. RTT versus countrySystem is working, he will describe, in eachinteresting sub-area, what the system will do and alsothe transition condition (Boolean expression dependingon input or interval values) that may exist between thedifferent states. Moreover, the "Dl: emergency stop", isa specialized sub-area that may be reached from anyother sub-area. The Gemma tool may be seen as a

generic Statechart [14].We have used a m ethodological too l, Gemma-Q [15],that may be used to specify how to take into accountnetwork distortion in a remote control application. ThePing/Pong measures the whole round trip time from onejava-thread to another java-thread and back includingthe network, the two operating systems and treatmentsby the application level of the language Java at bothsides. The small frame used for the ping pong is time-stamped, and could bring emergency commands.Each sub-area of the Gemma is splitted in sub-sub-areas., connected by specific transitions., depending onthe network quality. Six different quality levels havebeen defmed; the border between qualities may varyfrom one application to another one depending on itsconstraints.


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Cmrto lei l System J Internet J C l i e n t

: S*nd inloiTiuiioTi luin^ tor I D>>uinic dncj I Onm nunicstionIStDillDik

Pig 8 Software ArchitectureA G e m m a - 0 h a s t o b e de f i n e d f o r e a ch d e v i c e d r i v e r( T o o l I nt e r f ac e ) t o c o n t r o l , an d h as t o b e i m p l e m e n t e do n t h e d e v i c e , i f i t h a s r e s o u r c e s t o m a n a g e t h ei m p l e m e n t a t io n o r o n a c o m p u t e r c o n n e c t e d t o it wi t h asa f e l i nk ( l i ke a se r i a l l i nk) . U se r w ho w i l l c re a t e h i so w n ap p l i c at i o n w i l l a l s o h a ve t o de f i n e a nd i m p l e m e n ta G e m m a - Q , w h ic h m a y o r n o t o v e r l a p th e d e v i ce ' s o n e .

//. 7 Software ArchitectureA s o f t w a r e a r c h i t e c t u r e [ 1 6] h a s a l s o b e e n d e f m e d t o

m a k e r e m o t e c o n t r o l o f in du s t r ia l m e c ha ni c al s y s t e m sp o s s i b l e . It i s b a s e d o n a s e t o f i n d e p e n d e n t m o d u l e sr t m n i n g i n p a r a l l e l . O n th e l e ft s i d e o f Fi g 8, t h e s e r v e rs i d e i s r e p r e s e n t e d . It i s b a s i ca l l y c o m p o s e d o f t h r e em a i n p r o c e s s e s : G r o o r n w h i c h is i n c h a r g e o f t he i n i t i alc o n n e c t i o n , D e v i c e M a n a g e r . w h i c h m a n a ge s t h ed i ff e r e n t d e v i c e s t h a t c an b e co n t r o l l e d a n dC o n n e c t i o n M a n ag e r w h ic h m a n ag e s t h e d i ff e r e n tc o n n e c te d c l i e n ts a cc o r d i n g t o th e C o n t r o l A l g o r i t h mm o d u l e . T hi s o n e i s c ho o s e d b y t h e d e s i g n e r o f t h es y s t e m d e p e n d i n g o n t he ap p l i c a t i o n : m a s t e r / s l a ve . ,p r i o r i t y , t i m e o u t . .. T o o I In t e r f a c e . a r e s p e c i a l i z e dm o d u l e s t h at c o n t r o l s p e c i fi c t o o l .

T h e r i g h t s i d e o f " F i g . 8 " r e p r e s e n t s t h e c l i e n t s i d e ,P r o c e s s e s a r e l o a d e d i n a w e b n a v i g a t o r u s i n g J a v aA p pl e t t e c h no l o g y . R e m o t e C l i e n t M an ag e . r a c t s as ar o u t e r b e t w e e n t h e T o o I G ui p r o c e s s e s a n d t h e N l S e n d e ra nd N I R e c e i v e r . o n e . A T o o I G ui c o r r e s p o n d s t o ag r a p h i ca l u s e r i n t e r f a ce t o c o n t r o l a s p e c i f i c t o o l : us e rm ay s e n d o r d e r s an d r e c e i v e i n fo r m a t io n t h r o u g h t h e m .O n e T o o I G u i . i s a s s o c i a t e d t o o n e T o o I In t e r f a c e a n d t oo n e r e al m e c h a ni c al s y s t e m . N .I pr o c e s s e s a r e u s e d t oc o m m u n i ca t e w i th t h e s e r v e r s i d e .

W h e n a c l i e n t w a nt s t o t a k e co n t r o l o f t he s y s t e m , he

c o m m u n i ca t i o n w i t h t h e G r o o m , u s i n g T C P / IP p r o t o c o !b a s e d o n s o c k e t . If c o n n e c t i o n i s a cc e p t e d . G r o o m w i l li nfo r m t h e C l i e n t M a n ag e r a nd t h e D e v i c e M a n ag e r . As e t o f p r o c e s s e s L o c a t C l i e n t M a n a g e r a n d a ga i n N Ip r o c e s s e s w i l l b e s t a r t e d t o t a k e i n c h a r g e t h i s n e wc l ie n t . I f h e g e t s t h e c o n t r o l o f th e s y s t e m ( d e p e n d i n g o nt h e C o n t r o l A l g o r i t h m ) , t he n h e w i l l be a bl e t o s e n dc o m m a n ds t o t he s y s t e m . In p ar a l l e l , an d. p r o c e s s e s a r el a un ch e d t o o b s e r v e d y n a m i c al l y t h e n e t w o r k .

T h i s a r c h i t e c t u r e h a s b e e n d e s i g n e d a s a k e r n e l o fs e r v i c e s t h a t w i l l t a k e i n c h a r g e t h e c o n n e c t i o n , t h em a na g e m e n t o f us e r s a n d t o o l s , t he s u p e r v i s i o n o f th en e t w o r k . A r o u n d i t. i n d e p e n d e n t m o d u l e s h av e b e e nde f i ne d t o m a na ge a spe c i f i c t o o l a nd ca n be a dde d t ot h e w ho l e s y s t e m u s i n g s o m e " p l ug an d pl a y "m e c h a ni s m . In t h e s am e w a y , t h e C o n t r o l A l g o r i t h m c anb e ch o s e n i n a s e t o f c o m p o n e n t s .

III. Experim ent ResultsA ft e r 18 m o n t h s o f u s e s , s t a t i s t i c s s h o w t h at t h i s

m o t o r i z e d w e b c am h as be e n c o n t r o l l e d b y 1 80 00p e o p l e , co m i n g fr o m a ll o v e r t h e W o r l d , us i n g m o d e ml i n e , x D S L s o l u t i o n s o r L o c al A r e a N e t w o r k . T h e m e a nr o u n d t im e t r i p ( t i m e n e e d e d f o r a pa ck e t m a ke aP i n g /P o n g ) is r e s p e c t i v e l y a r o u n d 8 0 0 m s . 2 0 0 m s a nd1 5 0m s . It r e a l l y s h o w s t h a t c o n t r o l l i n g s u c h a s y s t e m i sp o s s i b l e w i t h t h e n o w a d a y s I n t e r n e t t e c h n o l o g i e s a n di n f r a s t r u c t u r e s .

S i n c e 2 00 1 w e h a ve s t o r e d t h e d a t a o f m o r e t h a n 140 0 0 c o n n e c t i o n s o f m o r e t ha n o n e m i n u t e . T h e l as t t h r e ey e a r s t h e pe r f o r m a nc e s o f I nt e r n e t h av e b e e n i n cr e a s e dd r a m a t i ca l l y .W e c o l l e c t t h e v a l u e s o f e a c h R T T o f e a c hc o n n e c t i o n i n h t m l f il e s o n o u r s e r v e r , s o w e c an a c c e s s


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MySq! data base manager and we have written sometypical requests to analyze the quality of theconnections. The Fig. 7 generated early in 2003 showsmean values of RTT versus the country of the remotecontroller [17 ].Although our RTT cannot be compared with ICMPpings, the results of measures performed during theCAIDA are similar in term of RTT times.Other figures show some records performed duringremote practice works.The data about a remote control of the millingmachine from Oran are displayed on the figure Fig. 9.Ihe RTT are mostly close to the mean value of about300 ms, but there are many exceptional values. Thesecond diagram presents the frequencies of the RTT.The presence of several peaks separated by the samedistance of about 55 ms seems to be an effect of thecomputer used for the server, a Pentium II 450 MHz,and of the operating system windows 98. It correspondsto the refreshment period of the OS. The third diagramshows the cumulated frequencies. 95% of the RTT arebetter than 500 m s, but 1% are worst than 3000 m s. Foran industrial application we have to choose a criterionof reliability. The safe remote control is usable onlywith slow processes. With a perfect network and fixeddelay of transmission., this diagram should be a simplestep at the fixed delay. About a remote control of theWeb-Cam Similimi from Guadeloupe Fig. 10 we cansee that the behaviour during the night on the side of theserver is better. But if the network was perfect we couldsuppose that the shape of the diagram should be a stepat the CAIDA project are similar in terms of RTT timevalue of 160 ms. We don't know the path used by thedata, the length of this path is probably over 8.000 km.So the operational speed of the data is 2*8,000 / 0.16 =100,000 km/s, the half of the light speed in opticfibbers!

The third figure,. Fig. 11, shows the RTT of oneexperiment made during the day, and the reducedperformance of the transmission.During the experiments between Brest and Oran weused the ICMP commands ping and traceroute tocompare.Example of ping:Statistic Ping for 193.52.16.98:

Paquets: sent - 20, receive - 14, lost = 6 (lost30%),Approximate duration of the loops in milliseconds:Minimum ^ 444ms, Maximum = 732ms, Average= 583msIt means that 30% of the paquets were considered aslost because they were over the allowed limit of 1000ms. Our values were similar, during the experiment themean value of our RTT was 566.20 ms, the maximum6500 ms. the minimum 156 ms and the median 391 ms.But our system gives more information, and is usefulfor the remote control.

Example of traceroute:Determination of the route towards pclimi4.univ-brest.fr [193.52.16.100] with a maximum of 30 jumps .1 107ms 131 ms 82.101.184.1292 114 ms 107 ms 119 ms 81.22.57.13 124 ms 287 ms 119 ms 10.100.100.54 339 ms 347 ms * So3-2-l-0-grtmaddrr2.red.telefonica-wholesales.net[213.140.50.17]5 282 ms 393 ms 419 ms GE6-0-0-0-grtadrrl.red.telefonica-wholesale.net [213 140.37.129]6 318 ms 345 ms 323 ms S06-O-O-O-grtpaix 1 .red.telefonica-wholesale.net [213.140.36.134 ]7 317 ms 299 ms 335 ms renater.sflnx.tm.fr[194.68.120.102]8 339 ms 359 ms 503 ms nri-a-posI-0-O.cssi.renater.fr [ 193.51.179.3]9 318 ms * 364 ms rouen-pos2-0.cssi.renater.fr[193.51.179.22]10 353 ms 383 ms 719 ms caen-pos2-O.cssi.renater.fr [ 193.51.180.21 ]11 509 * * rennes-posl-0.cssi.renater.fr[193.51.180.18]12 362 ms 251 ms * megalis-rennes.cssi.fr[181.51.181.125]13 326 ms 335 ms * 193.101.145.514 603 ms 623 ms 514 ms 193.101.145.2615 1035 ms 875 ms 851 ms 193.48.78.19816 853 ms 743 ms 695 ms 193.50.69.25017 * * * D^lai d'attente de la demande depass618 331 ms 347 ms 442 ms pclinii4.univ-brest.fr[193.52.16.100]Given route.

The path determined by the tracert command fromOran to Brest shows (hat the data travel from Oranthrough Alger, Paris, Rouen, Rennes, and then Brest.The great-circle distance between Oran and Brest isabout 1400 km, the data don't travel along the shorterway but a way over 2000 km. The operational speed ofthe data reach 2000*2/0.6 - 6.667 kni/s the 30th of thelight velocity in optics fibbers. We can expect that thisoperational speed will increase in the next years, if thisincreasing is upper than 3 times, we will be under thelimit of 200 ms considered as the maximum acceptabledelay for teleoperation with force feed-back.We can also note that between time where we madethe experiments and the end of the year 2006, times ofping ICMP decreased in a considerable way. Whatgives a considerable idea of the futures improvement ofInternet Netw orks.Example of ping 2006:Statistics Ping for 193.52.16.98:Paquets : sent = 87, receive = 86, lost = I (lost1%),

Approximate duration of the loops in milliseconds:Minimum ^ 58 ms, Maximum ^ 120ms, Average =


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moan of Iho RTT Inma 298.24standard deviation in ms 524,97mimrtium in ms 50mawmum in ms 5270median in ms 220RTT

- 3000

lOOO0

measured RTT remola control or the mill ing machine ISEL tabtuary 2nd 200S 13h23 from Oran [Algeria}

romote array

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