- Email: [email protected]
Web-based remote experimentation
Copyright ® IFAC Telematics Applications in Automation and Robotics, Weingarten, Germany, 200l
WEB-BASED REMOTE EXPERIMENTATION
Christian Schmid Lehrstuhl for Elektrische Steuerung und Regelung Ruhr-Universitiit Bochum IC-3/J4 J D-44780 Bochum, Germany Phone: +492343224093. Fax: +4923432 04093 E-mail: [email protected]
Abstract: This contribution presents a remote laboratory approach for experimentation with real plants, which uses the communication techniques of the World Wide Web. The aim of this kind of distance learning environment is to facilitate the access to these plants for students and professionals in the area of control engineering. Furthermore, resource sharing among the involved universities reduces money and time for maintenance or development of new experiments. The new approach for remote experimentation incorporates software that uses the powerful computational engine of MA TLAB/SIMULINK together with the Quanser's Win Con real-time system to perform the experiments. Web-based components are used to support the user interface by animation of plant models in virtual reality. The flexible fully Web-based remote laboratory system and its structure including the user interface for an example is described in detail. Copyright ®20011FAC Keywords: Control education, Laboratory education, Web, Virtual reality
opportunities for students to take advantage of a remote laboratory, where an audio-visual interface together with a collaboration tool gives them the feeling of being in the laboratory.
1. INTRODUCTION
One of the salient features of engineering education is the combination of theoretical knowledge with practical experience. The former, in conventional education, consists of lectures and exercises supplemented by lecture notes and textbooks, while, the latter comprises highly resource-demanding laboratory courses. The scarcity of lab facilities and staff limits the student enrolment. Active problem solving and visual feedback on the part of students can provide a valuable insight into the problems. One of the aims in control engineering education is to teach the techniques and possible pitfalls of theorybased design methods when applied in practice. The control system design process involving practical experiments and observing the dynamics of a real plant gives a valuable insight. For this reason, control engineering students have to be in a laboratory to gain hands-on experience. The development in communication techniques has opened new
The World Wide Web successfully demonstrates how current technology can support information sharing among widely dispersed groups. The hypertext coupled with wide area network functionality in the Web is the major reason for exploiting this technology for educational purposes to implement open and distributed hypermedia. The integration of multimedia elements has significantly enhanced the ability to train and educate electronically. Virtual education explores a new way of teaching and learning, which, instead of restricting itself only to enrolled students, addresses a larger audience. It, therefore, is capable also to be used for advanced training.
In this contribution it is shown how control engineering real laboratory experiments can be
509
implemented and offered such that they can be perfonned remotely via the Web. In order to maximise the educational value of running remotely operated experiments, it is important that it as closely as possible resembles running local experiments. Some important factors in this respect are the ability to observe, manipulate and control the experiment in a variety of ways, and the ability to compensate for the remoteness by utilising advanced techniques, like video and audio communication, animation and different virtual- and augmented-reality techniques.
The user access to the experiment server is perfonned only through the Web protocol. The Web server component of the MS Internet Information Server (lIS) software is linked by a small MATLAB Web link DLL to MATLAB'S engine interface. MATLAB commands embedded into the Hyper Text Markup Language (HTML) page code of the user interface are sent to SIMULINK through this DLL attached to the lIS, to get or set parameters in the SIMULINK model on the experiment server. In order to operate a plant, the WinCon server software mirrors these actions between the SIMULINK model on the experiment server and the real-time code running on WinCon clients. On return MATLAB generates JavaScript code, which is transferred through the same channel back and executed in the user interface. The advantage of this configuration is that new experiments with different physical structures can be easily set up, since one can directly write new MATLAB commands embedded in the JavaScript language. On the experiment server only the SIMULINK model and the corresponding MA TLAB M-files have to be rebuild. An important aspect is the safety of the experiment. The experiment has to be protected against any action that would damage or even destroy it. For this reason, all actions on the plant are analysed by this independent and uncontrollable experiment server, which can reject dangerous commands. To evaluate students' work, all communication between user and experiment is logged.
2. THE WEB-BASED LABORATORY ENVIRONMENT
This paper is devoted to the remote laboratory approach for experimentation with real plants, which uses the communication techniques of the Web. The aim of this distance learning environment is to facilitate the access to these plants for students in control engineering. Furthennore, resource sharing among the involved universities reduces money and time for maintenance or development of new experiments. One important aspect when designing a remote laboratory is to keep all hardware components as simple as possible to guarantee fast and effective maintenance. The same criteria apply to the utilisation of commercial available software packages. The idea is, using software and tools that are already available at most of the educational institutions and that are free on the Web. The networked structure of the remote laboratory environment proposed is shown in Fig. I. It contains seven different types of separate functional units, which may run distributed on different or combined in a low number of computers depending on the resources available.
A WinCon client is a real-time client since it runs the real-time code corresponding to the implemented SIMULINK model. For each plant a separate WinCon client must be available. This client contains the process interface, which builds the hardware connection to the plant via different types of digital and analog I/O-ports using Multi-IIO cards. The Win Con clients run on PCs either with MSWindows 95/98 or NT 4.0 as the operating system.
The student on the user client accesses and operates the laboratory system with a standard Web browser. The user interface on the user client is Web based. Applets are integrated into this user interface for enhancing the Web media. This client will send and receive infonnation to and from the different types of servers. As far as the Web infonnation protocol is used, Web servers will receive and handle user client requests for driving the laboratory system. Other servers are for organisational and enhanced media services.
Microphones and a video cameras are connected to an audio and a video capture interface, respectively, which is included in the media server perfonning live audio and video transmission for trying to obtain the necessary "closeness" to the experiment. "The frame rates using common Web server push technology are too slow for high dynamic systems. Compression standards used over the Internet to reduce the throughput of the streams, like MPEG, were designed for stored videos. H.261 or the newer H.263 is better suited, as it was designed for video conferences over ISDN lines and allows encoding of the video stream in real time. Without help of media elements, like Java applets, Web browsers cannot handle video and audio streams. As the platfonn of the user interface and the media server may be different, a standard protocol is used that can be handled by Java applets. The Real-Time Transport
The operating connection of the user with the real plant goes only through the experiment server. This server runs on a PC under MSWindows NT 4.0 and uses MATLAB/SIMULINK combined with the WinCon server software to communicate with WinCon clients (real-time clients). Win Con is a product of Quanser Consulting, which uses SIMULINK and MATLAB'S Real-Time Workshop for generating application code that runs in the real-time clients (Quanser, 2000).
510
individual experiment, schedules and exclusive access procedures to the experiment are necessary. Users should be able to book laboratory time in advance. They should carry out the whole booking procedure by themselves in order to choose the time most appropriate to their needs. The access server perfonns these operations. The laboratory administrator can create, delete accounts and define quotas for each experiment. Before starting with experiments the students must have received access and then are able to book experimentation time by logging into the access server with help of the user interface on the Web browser. The access server consists of a SQL database, which is managed by a Java application, which uses JOBC classes (Sun, 200 1b). The access server for all experiments is located at FernUniversitat Hagen, Gennany. A detailed description can be found in Rohrig and Jochheim (2000).
Protocol (RTP) allows the transmission of real-time video and audio via the Internet without standardising the video or audio fonnats (Schulzrinne, et al., 1996; Turletti and Huitema, 1996). In the current implementation of the media server, H.261 is used for video and GSM for audio stream encoding. The transport is perfonned via RTP. The software on the media server currently consists of two separate Mbone tools: The Video Conferencing Tool (VIC) (McCanne and Jacobson, 1995) is used to produce the video stream and the Robust Audio Tool (RAT) (Hardman, et al., 200 I) was chosen for the audio stream. A new Java-based combined video and audio capturing, encoding, transcoding and transmitting software is under development, which will use the new JMF 2.1 classes (Sun , 2001a) and the improved H.263 fonnat for video encoding. As only one student at a time receives access to an
access server
user client Web Browser HTML page
Experiment booking
User interface
Access login
,,
, I
I
Inter-university
I I
provider I
' .. _ _ __ - - - - - - - - - - - -
Internet Web server
experiment server
User pages
MATl..ASWeb link
Transmitter
Manual pages
MATLAB
Transcoder
media server
liS
~
Help information
".
Learning material Examples
,~;"
;~
t.;;!'
Audio grabber
SIMULlNK
Frame grabber
WinCon server
TCPflP LAN
WinCon client 1
Encoder
WinCon client n
plants
Fig. 1. Schematic diagram of the remote laboratory structure.
511
__ .,,1
On the left-hand side of the user interface is a working area, where windows can be placed, freely arranged and controlled by the user.
The sharing of experiments offers a unique set of didactic resources for students in engineering. A network of remote laboratories may be established on national, European or international level. The optional provider server takes care of those administrative tasks, which are necessary to link this remote laboratory to a distributed laboratory.
There is a window for displaying the real-time video and playing the audio signals through an JMF applet. The resolution of 288 x 252 pixels, a frame rate of up to 10 frames per second and encoding in H.261 format is a good practical choice for transmission. This set-up guarantees a good animation property, since the time constants of the plant used in this experiment are in the order of 0.1 seconds. It is also acceptable for students, who are using the remote lab from home via ISDN lines.
3. THE USER INTERFACE
The user interface necessary to control the experiment is organised in form of a cockpit. The Web pages and all material are coming from the Web server. Fig. 2 shows the example user interface for an optical tracking system, which has been taken from Junge and Schmid (2000). Besides sliders implemented as Java applets and a graphics browser plug-in, only HTML and JavaScript have been used to organise all actions. The main operating actions (e.g. start/stop an experiment session, or reset the plant to a predefined initial state) are located in the general control panel frame, since these actions do not depend on the type of experiment. The specific commands to operate the plant as well as parameters to modify the characteristics of the reference signal and of the implemented controller are found in the user console panel. The sliders are used for entering continuous data and to facilitate operating the plant.
The lack of a direct physical contact to the experiment and the use of flat operating panels, may lead to a loss of 'practical feeling' . This is compensated by enhanced multimedia components. A VR plant user interface enables the user to operate the real plant manually by mouse actions in the virtual reality scene of the 3-D model. The actions performed with this 3-D model are immediately converted into MA TLAB commands and transferred to the Wineon client. The 3-D plant model is written in the Virtual Reality Modelling Language (VRML). Although the user can inspect the plant by the video
Window control panel
~=--=:lI
'I
j
~l
@!l~~I~~O __ Outy cycl a (....
1.10 j
@ ,:
Reset
~
'i"i"iiiii1" ~ ?
1~
rw~~ ~ P I'D lA"bol Phch
User console panel tonvnand executed
Fig. 2. Screenshot example of the user interface for a optical tracking plant.
512
REFERENCES
camera or tune the controller by listening to the sound the plant produces, a graphical representation of measured signals is needed to show small variations and to generate a report. The diagrams are generated remotely on the experiment server by using standard MATLAB graphical routines. In order to get fast and best results, these diagrams are directly transferred and embedded in a window on the Web page using the Extended Metafile Fonnat (EM F). As this is not a regular Web feature, a graphics browser plug-in has been developed.
Hardman, V., P. Kirstein and A. Sas se (2001). Robust Audio Tool (RAT). http://www-mice.cs.ucl.ac.uklmultimedia! software/rat/index.hnnl Junge, Th.F. and Chr. Schmid (2000). Web-Based Remote Experimentation Using a LaboratoryScale Optical Tracker. Proc. American Control Conference ACC'2000, Chicago, pp. 2951-2954. McCanne, S. and V. Jacobson (1995). VIC - Video Conferencing Tool. http://www-nrg.ee.lbl.gov/vic/
4. CONCLUSIONS
Quanser Consulting Inc. (2000). WinCon 3. J RealTime Digital Signal Processing and Control under Windows 95/98 and Windows NT using SJMULINK and TCP/JP Technology. Markham, Canada.
This contribution presents a new Web-based remote laboratory environment for distance education, which addresses students and learners in control engineering. The user can perfonn experiments using a standard Web browser. The only requirement is to install some browser extensions, which can be downloaded from the Web server and installed simply. The experiment is controlled using JavaScript statements embedded in the Web page. They contain MATLAB commands, which are sent down to the communication server for execution in the MATLAB environment. This concept simplifies and speeds-up the implementation of new experiments due to its availability and flexibility . For an other laboratory plant only some minor sections in the user interface and the MATLAB/SIMULINK part has to be reprogrammed. The total laboratory system can be easily assembled from free available and commericial components.
Rohrig, C. and A. Jochheim (2000). Java-based Framework for Remote Access to Laboratory Experiments. JFAC/JEEE Symposium on Advances in Control Education, ACE 2000, Gold Coast, Australia. RSVL (2001). Real Systems in a Virtual Laboratory, http://www.esr.ruhr-uni-bochum.delRsvle Schulzrinne, H., S. Casner, R. Frederick, V. Jacobson (1996). RFC 1889. RTP: A Transport Protocol for Real-Time Applications http://www.nonnos.org/rfc/rfcI889.txt Sun Microsystems (2001a). Java Media Framework API. http://java.sun.comlproductsljava-media! jmf/index.html
An evaluation fonn has been elaborated and given to students of control engineering to assess the quality of this remote laboratory environment. Based on the feedback received, an overall positive resonance could be noticed. The quality of the user interface as well as the graphics has been approved. Controlling a real remote plant through a virtual reality 3-D model caused a surprise among the users. They have readily accepted this kind of experimentation, which is available around the clock. This result has corroborated us to continue in adding other experiments and plants into this environment.
Sun Microsystems (200 1b). JDBC Data Access API. http://java.sun.comlproducts/jdbc/ Turletti, T. and C. Huitema (1996). RFC 2032. RTP Payload Format for H.261 Video Streams, http://www .normos.orglrfc/rfc2032.txt
Acknowledgements This work was partly supported by the 'Innovationsfond 2000' of the Ruhr-Universitat Bochum, by the 'Universitatsverbund MultiMedia des Landes Nordrhein-Westfalen' under project contract 19-23-98 and by the EU 1ST Programme under project contract 1ST-1999-20827.
Remote experiments are standard experiments in our basic control laboratory course. From April 2000 the optical tracker plant is used in the control courses of the Gennan open university FemUniversitat Hagen. A Ball-and-Beam experiment has been released in April 200 I. A hydraulic drive experiment will come soon. All experiments are accessible on the Web round the world and round the clock, supposed the User has been granted a login id with password (RSVL, 200 I).
513
WEB-BASED REMOTE EXPERIMENTATION
Christian Schmid Lehrstuhl for Elektrische Steuerung und Regelung Ruhr-Universitiit Bochum IC-3/J4 J D-44780 Bochum, Germany Phone: +492343224093. Fax: +4923432 04093 E-mail: [email protected]
Abstract: This contribution presents a remote laboratory approach for experimentation with real plants, which uses the communication techniques of the World Wide Web. The aim of this kind of distance learning environment is to facilitate the access to these plants for students and professionals in the area of control engineering. Furthermore, resource sharing among the involved universities reduces money and time for maintenance or development of new experiments. The new approach for remote experimentation incorporates software that uses the powerful computational engine of MA TLAB/SIMULINK together with the Quanser's Win Con real-time system to perform the experiments. Web-based components are used to support the user interface by animation of plant models in virtual reality. The flexible fully Web-based remote laboratory system and its structure including the user interface for an example is described in detail. Copyright ®20011FAC Keywords: Control education, Laboratory education, Web, Virtual reality
opportunities for students to take advantage of a remote laboratory, where an audio-visual interface together with a collaboration tool gives them the feeling of being in the laboratory.
1. INTRODUCTION
One of the salient features of engineering education is the combination of theoretical knowledge with practical experience. The former, in conventional education, consists of lectures and exercises supplemented by lecture notes and textbooks, while, the latter comprises highly resource-demanding laboratory courses. The scarcity of lab facilities and staff limits the student enrolment. Active problem solving and visual feedback on the part of students can provide a valuable insight into the problems. One of the aims in control engineering education is to teach the techniques and possible pitfalls of theorybased design methods when applied in practice. The control system design process involving practical experiments and observing the dynamics of a real plant gives a valuable insight. For this reason, control engineering students have to be in a laboratory to gain hands-on experience. The development in communication techniques has opened new
The World Wide Web successfully demonstrates how current technology can support information sharing among widely dispersed groups. The hypertext coupled with wide area network functionality in the Web is the major reason for exploiting this technology for educational purposes to implement open and distributed hypermedia. The integration of multimedia elements has significantly enhanced the ability to train and educate electronically. Virtual education explores a new way of teaching and learning, which, instead of restricting itself only to enrolled students, addresses a larger audience. It, therefore, is capable also to be used for advanced training.
In this contribution it is shown how control engineering real laboratory experiments can be
509
implemented and offered such that they can be perfonned remotely via the Web. In order to maximise the educational value of running remotely operated experiments, it is important that it as closely as possible resembles running local experiments. Some important factors in this respect are the ability to observe, manipulate and control the experiment in a variety of ways, and the ability to compensate for the remoteness by utilising advanced techniques, like video and audio communication, animation and different virtual- and augmented-reality techniques.
The user access to the experiment server is perfonned only through the Web protocol. The Web server component of the MS Internet Information Server (lIS) software is linked by a small MATLAB Web link DLL to MATLAB'S engine interface. MATLAB commands embedded into the Hyper Text Markup Language (HTML) page code of the user interface are sent to SIMULINK through this DLL attached to the lIS, to get or set parameters in the SIMULINK model on the experiment server. In order to operate a plant, the WinCon server software mirrors these actions between the SIMULINK model on the experiment server and the real-time code running on WinCon clients. On return MATLAB generates JavaScript code, which is transferred through the same channel back and executed in the user interface. The advantage of this configuration is that new experiments with different physical structures can be easily set up, since one can directly write new MATLAB commands embedded in the JavaScript language. On the experiment server only the SIMULINK model and the corresponding MA TLAB M-files have to be rebuild. An important aspect is the safety of the experiment. The experiment has to be protected against any action that would damage or even destroy it. For this reason, all actions on the plant are analysed by this independent and uncontrollable experiment server, which can reject dangerous commands. To evaluate students' work, all communication between user and experiment is logged.
2. THE WEB-BASED LABORATORY ENVIRONMENT
This paper is devoted to the remote laboratory approach for experimentation with real plants, which uses the communication techniques of the Web. The aim of this distance learning environment is to facilitate the access to these plants for students in control engineering. Furthennore, resource sharing among the involved universities reduces money and time for maintenance or development of new experiments. One important aspect when designing a remote laboratory is to keep all hardware components as simple as possible to guarantee fast and effective maintenance. The same criteria apply to the utilisation of commercial available software packages. The idea is, using software and tools that are already available at most of the educational institutions and that are free on the Web. The networked structure of the remote laboratory environment proposed is shown in Fig. I. It contains seven different types of separate functional units, which may run distributed on different or combined in a low number of computers depending on the resources available.
A WinCon client is a real-time client since it runs the real-time code corresponding to the implemented SIMULINK model. For each plant a separate WinCon client must be available. This client contains the process interface, which builds the hardware connection to the plant via different types of digital and analog I/O-ports using Multi-IIO cards. The Win Con clients run on PCs either with MSWindows 95/98 or NT 4.0 as the operating system.
The student on the user client accesses and operates the laboratory system with a standard Web browser. The user interface on the user client is Web based. Applets are integrated into this user interface for enhancing the Web media. This client will send and receive infonnation to and from the different types of servers. As far as the Web infonnation protocol is used, Web servers will receive and handle user client requests for driving the laboratory system. Other servers are for organisational and enhanced media services.
Microphones and a video cameras are connected to an audio and a video capture interface, respectively, which is included in the media server perfonning live audio and video transmission for trying to obtain the necessary "closeness" to the experiment. "The frame rates using common Web server push technology are too slow for high dynamic systems. Compression standards used over the Internet to reduce the throughput of the streams, like MPEG, were designed for stored videos. H.261 or the newer H.263 is better suited, as it was designed for video conferences over ISDN lines and allows encoding of the video stream in real time. Without help of media elements, like Java applets, Web browsers cannot handle video and audio streams. As the platfonn of the user interface and the media server may be different, a standard protocol is used that can be handled by Java applets. The Real-Time Transport
The operating connection of the user with the real plant goes only through the experiment server. This server runs on a PC under MSWindows NT 4.0 and uses MATLAB/SIMULINK combined with the WinCon server software to communicate with WinCon clients (real-time clients). Win Con is a product of Quanser Consulting, which uses SIMULINK and MATLAB'S Real-Time Workshop for generating application code that runs in the real-time clients (Quanser, 2000).
510
individual experiment, schedules and exclusive access procedures to the experiment are necessary. Users should be able to book laboratory time in advance. They should carry out the whole booking procedure by themselves in order to choose the time most appropriate to their needs. The access server perfonns these operations. The laboratory administrator can create, delete accounts and define quotas for each experiment. Before starting with experiments the students must have received access and then are able to book experimentation time by logging into the access server with help of the user interface on the Web browser. The access server consists of a SQL database, which is managed by a Java application, which uses JOBC classes (Sun, 200 1b). The access server for all experiments is located at FernUniversitat Hagen, Gennany. A detailed description can be found in Rohrig and Jochheim (2000).
Protocol (RTP) allows the transmission of real-time video and audio via the Internet without standardising the video or audio fonnats (Schulzrinne, et al., 1996; Turletti and Huitema, 1996). In the current implementation of the media server, H.261 is used for video and GSM for audio stream encoding. The transport is perfonned via RTP. The software on the media server currently consists of two separate Mbone tools: The Video Conferencing Tool (VIC) (McCanne and Jacobson, 1995) is used to produce the video stream and the Robust Audio Tool (RAT) (Hardman, et al., 200 I) was chosen for the audio stream. A new Java-based combined video and audio capturing, encoding, transcoding and transmitting software is under development, which will use the new JMF 2.1 classes (Sun , 2001a) and the improved H.263 fonnat for video encoding. As only one student at a time receives access to an
access server
user client Web Browser HTML page
Experiment booking
User interface
Access login
,,
, I
I
Inter-university
I I
provider I
' .. _ _ __ - - - - - - - - - - - -
Internet Web server
experiment server
User pages
MATl..ASWeb link
Transmitter
Manual pages
MATLAB
Transcoder
media server
liS
~
Help information
".
Learning material Examples
,~;"
;~
t.;;!'
Audio grabber
SIMULlNK
Frame grabber
WinCon server
TCPflP LAN
WinCon client 1
Encoder
WinCon client n
plants
Fig. 1. Schematic diagram of the remote laboratory structure.
511
__ .,,1
On the left-hand side of the user interface is a working area, where windows can be placed, freely arranged and controlled by the user.
The sharing of experiments offers a unique set of didactic resources for students in engineering. A network of remote laboratories may be established on national, European or international level. The optional provider server takes care of those administrative tasks, which are necessary to link this remote laboratory to a distributed laboratory.
There is a window for displaying the real-time video and playing the audio signals through an JMF applet. The resolution of 288 x 252 pixels, a frame rate of up to 10 frames per second and encoding in H.261 format is a good practical choice for transmission. This set-up guarantees a good animation property, since the time constants of the plant used in this experiment are in the order of 0.1 seconds. It is also acceptable for students, who are using the remote lab from home via ISDN lines.
3. THE USER INTERFACE
The user interface necessary to control the experiment is organised in form of a cockpit. The Web pages and all material are coming from the Web server. Fig. 2 shows the example user interface for an optical tracking system, which has been taken from Junge and Schmid (2000). Besides sliders implemented as Java applets and a graphics browser plug-in, only HTML and JavaScript have been used to organise all actions. The main operating actions (e.g. start/stop an experiment session, or reset the plant to a predefined initial state) are located in the general control panel frame, since these actions do not depend on the type of experiment. The specific commands to operate the plant as well as parameters to modify the characteristics of the reference signal and of the implemented controller are found in the user console panel. The sliders are used for entering continuous data and to facilitate operating the plant.
The lack of a direct physical contact to the experiment and the use of flat operating panels, may lead to a loss of 'practical feeling' . This is compensated by enhanced multimedia components. A VR plant user interface enables the user to operate the real plant manually by mouse actions in the virtual reality scene of the 3-D model. The actions performed with this 3-D model are immediately converted into MA TLAB commands and transferred to the Wineon client. The 3-D plant model is written in the Virtual Reality Modelling Language (VRML). Although the user can inspect the plant by the video
Window control panel
~=--=:lI
'I
j
~l
@!l~~I~~O __ Outy cycl a (....
1.10 j
@ ,:
Reset
~
'i"i"iiiii1" ~ ?
1~
rw~~ ~ P I'D lA"bol Phch
User console panel tonvnand executed
Fig. 2. Screenshot example of the user interface for a optical tracking plant.
512
REFERENCES
camera or tune the controller by listening to the sound the plant produces, a graphical representation of measured signals is needed to show small variations and to generate a report. The diagrams are generated remotely on the experiment server by using standard MATLAB graphical routines. In order to get fast and best results, these diagrams are directly transferred and embedded in a window on the Web page using the Extended Metafile Fonnat (EM F). As this is not a regular Web feature, a graphics browser plug-in has been developed.
Hardman, V., P. Kirstein and A. Sas se (2001). Robust Audio Tool (RAT). http://www-mice.cs.ucl.ac.uklmultimedia! software/rat/index.hnnl Junge, Th.F. and Chr. Schmid (2000). Web-Based Remote Experimentation Using a LaboratoryScale Optical Tracker. Proc. American Control Conference ACC'2000, Chicago, pp. 2951-2954. McCanne, S. and V. Jacobson (1995). VIC - Video Conferencing Tool. http://www-nrg.ee.lbl.gov/vic/
4. CONCLUSIONS
Quanser Consulting Inc. (2000). WinCon 3. J RealTime Digital Signal Processing and Control under Windows 95/98 and Windows NT using SJMULINK and TCP/JP Technology. Markham, Canada.
This contribution presents a new Web-based remote laboratory environment for distance education, which addresses students and learners in control engineering. The user can perfonn experiments using a standard Web browser. The only requirement is to install some browser extensions, which can be downloaded from the Web server and installed simply. The experiment is controlled using JavaScript statements embedded in the Web page. They contain MATLAB commands, which are sent down to the communication server for execution in the MATLAB environment. This concept simplifies and speeds-up the implementation of new experiments due to its availability and flexibility . For an other laboratory plant only some minor sections in the user interface and the MATLAB/SIMULINK part has to be reprogrammed. The total laboratory system can be easily assembled from free available and commericial components.
Rohrig, C. and A. Jochheim (2000). Java-based Framework for Remote Access to Laboratory Experiments. JFAC/JEEE Symposium on Advances in Control Education, ACE 2000, Gold Coast, Australia. RSVL (2001). Real Systems in a Virtual Laboratory, http://www.esr.ruhr-uni-bochum.delRsvle Schulzrinne, H., S. Casner, R. Frederick, V. Jacobson (1996). RFC 1889. RTP: A Transport Protocol for Real-Time Applications http://www.nonnos.org/rfc/rfcI889.txt Sun Microsystems (2001a). Java Media Framework API. http://java.sun.comlproductsljava-media! jmf/index.html
An evaluation fonn has been elaborated and given to students of control engineering to assess the quality of this remote laboratory environment. Based on the feedback received, an overall positive resonance could be noticed. The quality of the user interface as well as the graphics has been approved. Controlling a real remote plant through a virtual reality 3-D model caused a surprise among the users. They have readily accepted this kind of experimentation, which is available around the clock. This result has corroborated us to continue in adding other experiments and plants into this environment.
Sun Microsystems (200 1b). JDBC Data Access API. http://java.sun.comlproducts/jdbc/ Turletti, T. and C. Huitema (1996). RFC 2032. RTP Payload Format for H.261 Video Streams, http://www .normos.orglrfc/rfc2032.txt
Acknowledgements This work was partly supported by the 'Innovationsfond 2000' of the Ruhr-Universitat Bochum, by the 'Universitatsverbund MultiMedia des Landes Nordrhein-Westfalen' under project contract 19-23-98 and by the EU 1ST Programme under project contract 1ST-1999-20827.
Remote experiments are standard experiments in our basic control laboratory course. From April 2000 the optical tracker plant is used in the control courses of the Gennan open university FemUniversitat Hagen. A Ball-and-Beam experiment has been released in April 200 I. A hydraulic drive experiment will come soon. All experiments are accessible on the Web round the world and round the clock, supposed the User has been granted a login id with password (RSVL, 200 I).
513