Design and Implementation of a Framework for Remotely Accessible
Contents
1. Oszilloskop Bik Daten Signaleinstellung Trigger Aquirieren b TDS 210 a AUTOSET RUN STOP Speicher it L Alle l schen TRIGGER J CH2 0 1 V O0 0divs M 0 0 VERTICAL A Modus rrr rrer PosmoN Z FOSTON lt p gt posman LEVEL J O O CH1 MENU CH2 FaU Aquisition CH1 2 VOLTS DI VOLTS DI SEC DIY N 1 Grundeinstellung Uber Telematik ort an MAAA Jo a CH 0 0 Figure 5 The Tektronix TDS210 oscilloscope application 5 Conclusion The benefits of remote labs over actual laboratories are found in their increased portability cost effective ness reduced need for teacher intervention increased student interest and control adaptability to various learning styles and learning rates web ready software and self testing Remote labs will satisfy a growing need for truly interactive learning software This paper presented software architecture for the develop ment of remote laboratories The architecture can be used to develop tools to support scientific laborato ries that allow the sharing of unique or expensive instruments Our first experimental findings called for a user manual covering the most frequently asked questions When doing web based exercises it is deceiv ing to play around and not to do any useful work We suggest a strict level based concept to solve this problem When doing experiments the students can gain credits The cr2. client All controls on the virtual device correspond to the control on the real device Thus a virtual device is not just a simulation of a real device Simulations can not be used for the modeling of physical effects e g the development of a clock signal at higher frequencies or the influence of temperature on a circuit Remote labs can be used to aug ment real laboratory experience in science and technology When done effectively this will increase the access of students to knowledge and enhance performance as well as the quality of the educational out come The paper is organized as follows Section 2 reviews some related work The proposed Telematik framework is compared with commercial and non commercial solutions Section 3 presents the software architecture Section 4 gives examples of implemented remote instruments Section 5 concludes the paper 2 Background and Related Work There are several interactive virtual remote labs available on the web 1 8 Physics 2000 8 comprises interactive Java applets through where students can explore elementary physical phenomena Some of these labs are implemented as Java applets or dynamic web pages but without generic methology for the development of such labs Researchers are pursuing the development of remote labs where robots receive commands from students and reproduce virtual experiments in a fully equipped real lab Hagen s faculty of electrical engineering supports a lab exists where s
3. 32 A java native method can use native hardware because it is a part of e g a compiled C program using the native method interface from JNI We use javax comm from Sun Microsystems for the communication over serial and parallel ports However the modeling of other communication protocols such as GPIB is possible by using JNI In the next ring the device driver is modeled as a set of java methods Here a subset of the device s commands has to be specified This set of commands is integrated in the client and not part of the server although RMI Remote Method Invocation could be used Since this methology would increase development time and communication overhead we omitted the use of RMI By using a subset it is possible to increase se curity because it is not possible to send system control messages from the client The next ring contains the device independent communication which is done over TCP IP The server accepts commands as plain text messages since we have no sensitive data which must be encrypted Thus it is possible to test the server implementation without having to implement a GUI for the device Figure 2 shows the basic cli ent server based architecture Client Device dependent DD TEE DD Client DD GUI Code inheritance Commands Replies DD Server Figure 2 The client server based architecture 4 Exemplary deployment of a lab using the Telematik architec
4. Design and Implementation of a Framework for Remotely Accessible Instruments Bernhard Fechner Department of VLSI and Parallel Computing FernUniversit t Hagen Bernhard Fechner fernuni hagen de Abstract Remotely accessible instruments and experiments enhance the experience of students by provid ing a remote interface to a physical device Photorealistic rendering of these devices makes the graphical interfaces easy to understand to use and to learn Students perform their exercises at home just as in a real lab so they can apply their experience directly when working on location Needless to say remote labs are a key to raise the student s interest and improve self paced learning The implementation of a generic re mote control interface for existing instruments and the acquisition and visualization of data is one mile stone on the road to the future in distance learning To avoid obstacles on this way the system architecture should be understandable modular and easy to extend so laboratories with different hardware could be integrated in the lab environment The client software should be platform independent so the users can quickly gain hands on experience because soft and hardware problems e g installations are of no con cern We report experience in developing such a software framework and review some of its capabilities by using an actual deployment as an example Keywords Software design distance learning remote laboratori
5. edits are summed up and added to a basic amount of credits The higher the level of questions the more credits a student can get This is a good measurement for the level of preparation because non prepared students might open the labs and simultaneously refer to their textbooks in order to understand the concepts More motivated students get more credits and hence more time The deployed lab is currently a single user lab because not enough hardware is available With more hardware the support of multiple users is possible A future extension will be the support collaborative work 17 18 19 This enables researchers and students to work to gether across geographic and organizational boundaries to solve complex interdisciplinary problems by accessing remote resources The short term goal of remote labs is to serve as a preparation and supplement for actual labs The students are familiarized with devices and procedures before they actually go into the lab and perform experiments The rehearsal of an experiment with little complexity is a cost effective preparation for the use of limited and expensive lab facilities The lab is continuously available on our website References 1 2 3 18 19 20 Deutsches Museum Miinchen remote_lab Das ferngesteuerte Labor im Internet Eberhard von Kuenheim Stiftung Deutschland http www remote lab de California State University Center for Distributed Learning CDL http ww
6. entral challenge is to develop a starting point to allow the rapid easy and flexible creation of remote laborato ries To access many different devices a high level of abstraction from the developer s point of view must be reached The Telematik framework simplifies the integration of new real hardware into a virtual com puter science laboratory furthermore the integration of existing hardware by distinguishing a device de pendent and independent part We have identified two levels of abstraction for a device e Communication here we separate device specific communication commands hardware inter face and general communication over TCP IP Transmission Control Protocol Internet Protocol 12 13 e Front end we separate a device specific part knobs buttons with certain properties of the Graphical User Interface GUI to control a remote device and a generalized version so code in heritance can be used for the simple and fast implementation of new front ends The modeling of a device can be explained by the ring model in Figure 1 The GPIB specification was developed by Hewlett Packard and is also known as IEEE 488 E Independent Modeling Device independen Communication Device Figure 1 The ring model with different levels of abstraction In the centre all hardware dependent I O is modeled Since we have used java we use the Java Native In terface JNI at this level to model communication ports such as RS2
7. es remote control 1 Introduction The need for multimedia technology in distance teaching and learning is being recognized worldwide Network based multimedia and computer related technologies improve and enhance the quality of teach ing and learning Colleges universities and distance learning institutions are faced with a growing number of students particularly at introductory levels urging to learn more In Hagen undergraduate courses in computer science serve a large amount of students 1049 in 2005 with various backgrounds and abilities The challenge is to motivate and excite these students so that each performs to their fullest potential This objective can be best achieved by projecting the lab environment in a web based multimedia technology because students learn science best by experimenting gaining hands on experience raising questions and by solving problems As the instruments in the real lab can be rather fragile and expensive remote labs are a reasonable low cost solution Just like their real equivalents remote instruments respond to students manipulations but rejecting the input of incorrect data such as the choice of a frequency or amplitude out side the specified limits of the connected lab equipment which could lead to system damage A remote instrument is hereby denoted as a projection of the functionality and look and feel of a remote device such as a function generator or an oscilloscope server onto a virtual device
8. itional and or hidden costs e g no GPIB cards General Purpose Interface Bus web cams etc have to be bought to get the system to its fully functionality e Existing experiments can easily be ported re used to remotely controlled labs e Compared with graphical programming languages the coding of device drivers is accomplished faster when using an object orientated programming language like Java when sufficient documen tation is available Therefore the development costs are reduced e Easy adaptation to newer technologies and low development costs through code inheritance The use of creative renderings of objects and their behaviors allows the student to freely experiment in the virtual world The module content complexity of problem solving and sophistication of technical skills are vertically scaled so that each student can move through the module depending on the preparation De velopers can use a graphical composition tool from modern graphical Rapid Application Development RAD Tools to set up the user interface and basic communication The only thing the developer has to do is to implement a subset of the commands the device supports Code inheritance makes the implementa tion of device family based device drivers easy and fast To accomplish this and to ensure the re use of code 9 we used Java Beans 10 11 3 The Telematik Architecture The development and implementation of remote laboratories is a very tedious and costly task A c
9. on the Java version the student is running but not on the browser Current commercial products have a number of disadvantages compared to our solution e They are not free e They are platform dependent e The source code is not available and therefore not adaptable e The programmer has to learn a non standard graphical programming language therefore the development time will increase in comparison with traditional programming languages like C C or Java e No code inheritance e Elements such as knobs etc are not freely definable It should be mentioned that commercial solutions offer a wide variety of drivers for different devices and a large library of definable elements With the graphical programming language code can be inherited by using the same basic elements Source code availability is important because it makes the software less error prone and more maintainable Furthermore the user is not dependent on a company where the products may quickly change or will not be supported any more We overcome these shortcomings through a number of advantages Documentation e Source availability better documentation improvement e Direct control over the existing device no simulation Data Management e Data won from experiments can be quickly and easily exported and analyzed using external solu tions like MathLAB Excel MathCAD or SPSS etc e Printing to any printer including network printers and faxes is possible Cost e No add
10. ope To do this in real time a webcam is connected to Telematik3 Over an integrated web interface all functions of the lab can be accessed without knowing the experimental setup In case of a non terminating DSP program e g an endless loop waiting infinitely for an external event there must be the possibility to remotely reset the DSP board There are several ways to do this We dis covered the possibility to apply the reset signal externally and used the experiment selector for this opera tion The selector produces the necessary reset signal at a certain signal combination on the parallel port For remote administration a virtual network computer service is running on all servers Firewall 1 Services Services VNC Virtual Network Computer VNC Virtual Network Computer Peries Apache Web Server a S a aa a VNG Virtual Network Gomputer COM Server for function generator e COM Server for oscilloscope Personal Firewall telematik3 telematik2 telematik1 COM1 Function generator HAMEG 8131 2 Port 1100 ee ee SAL COM2 Oscilloscope Tektronix TDS210 Port 1102 COMz2 DSP Port 1101 i LPT1 Experiment selector 8g WebCam 1 Figure 3 Experimental setup 4 1 The Function Generator Client Application A function generator is a signal source which provides precision waveform signals e g sine square or triangular over a frequency range The instrument also provides a continuously variable am
11. pen Learning and Distance Education ICDE 1999 Vienna Austria 1999 W Laaser M Gerke H Hoyer Teaching Control Theory by Multimedia 19 World Conference on Open Learning and Distance Education ICDE 1999 Vienna Austria 1999 C Rohrig A Jochheim The Virtual Lab for Controlling Real Experiments via Internet IEEE Inter national Symposium on Computer Aided Control System Design CACSD 99 Kohala Coast Island of Hawaii Hawaii August 1999 A Haake M Bourimi J Haake T Schiimmer B Landgraf Endbenutzer gesteuerte Gruppen bildung in gemeinsamen Lernriumen DeLFI 2004 Die 2 e Learning Fachtagung Informatik GI Edition Lecture Notes in Computer Science GI e V Bonn 2004 pp 235 246 A Haake M Bourimi J Haake T Schiimmer B Landgraf CURE Eine Umgebung fiir selbstor ganisiertes Gruppenlernen i com Zeitschrift fiir interaktive und kooperative Medien 2004 A Haake M Bourimi J Haake T Schiimmer B Landgraf Supporting flexible collaborative dis tance learning in the CURE platform Proceedings of the Hawaii International Conference On Sys tem Sciences HICSS 37 TEEE Press 2004 Analog Devices DSP Microcomputer ADSP 2181 http www analog com UploadedFiles Data_Sheets 505104853ADSP2181_d pdf 1998
12. plitude level Figure 4 shows the function generator interface For better operation all basic default settings are inte grated in the client Funktionsgenerator Bei Eg Frequenz p MHz FUNCTION GENERATOR HANME G Amplitude Hz Funktion is Wobbelbetriet Grundeinstellungen MHz Frequenz Amplitude Uber Telematik Figure 4 The HAMEG8 131 2 function generator application 4 2 The Oscilloscope Client Application The oscilloscope Figure 5 draws the graph of an electrical signal In most applications the graph shows how signals change over time the vertical Y axis represents voltage and the horizontal X axis repre sents time An oscilloscope is therefore a linear voltage indicating device A spot on a display screen is caused to deflect in proportion to the applied voltage The vertical position of the spot depends on the Y amplifier input while horizontal position of the spot is determined by the waveform applied to the X amplifier input The oscilloscope has a time base generator circuit that generates a voltage that varies linearly with time When this voltage is applied to the X amplifier the voltage applied to the Y amplifier can be observed with respect to time The time base generator circuit is also connected to the trigger cir cuitry which controls the starting instant of the waveform Any output from the oscilloscope can be cap tured and copied in the report document as pure data
13. tudents can remotely control robots 14 15 16 After the experiment is finished the students reached the goal to control the robot such in a way that it reaches a certain target the robot returns to a pre defined state Visually advanced computer science lab exercises are offered through the Howard Hughes Medical Institute by Bio Interactive 7 Bio Interactive is a collection of learning modules where students can interactively explore topics in cardiology neuro physiology and the human immune system Here user action is restricted mostly to clicking on the vari ous instruments For a realistic learning experience the users should be able to perform the exact operations as they would on the real instrument Slider widgets are used in most of the aforementioned work For the actual instrument this might not be the case For instance we might need to rotate a dial to set a particular value rather than slide a marker across a slider Current solutions from academic institutions have the following disadvantages e Insufficient availability downtimes browser dependencies e No generic methology special solutions for existing lab equipment e Partially unavailable source codes e Elements such as knobs etc are not freely definable Some solutions are based on platform independent Java applets But it is a general known problem that the execution of Java applets can be browser dependent Since we use Java applications we are only de pended
14. ture Our remote lab consists of a function generator a DSP digital signal processor development board and an oscilloscope each with specific pre programmed behaviors interface look and feel and commands to control the device To load programs onto the development board the extraction of the communication protocol was necessary As every device specific part the protocol was implemented directly in the server structure Students select the binary file they produced at home The file is uploaded using the client soft ware The server receives the binary file extracts the data converts it in the device specific protocol and uploads the data to the development board Then it will start the program execution When the program starts a feedback is given to the user The student interacts with the devices in order to attain a set of given goals i e the study of DSPs microcontrollers communication protocols etc Users can access the lab via wireless LAN local area network or any other network connection Figure 3 shows the experi mental setup It consists of two main servers telematik1 telematik3 The server telematik2 is only listed for completeness A primary firewall protects the subnet against malicious attacks All web based accesses go to the webserver running on server telematik1 Telematik also runs the servers for the function gen erator and the digital oscilloscope both connected to the serial ports All servers run Microsoft Windo
15. w cdl edu M W Davidson K I Tchourioukanov and M Abramowitz Virtual scanning electron microscopy applet Olympus America Inc and The Florida State University 1998 http micro magnet fsu edu primer java electronmicroscopy magnify 1 index html M Duguay The TeleLearning Experience http www telelearn ca Virtual Laboratory National University of Singapore NUS http vlab ee nus edu s g vlab authfinal html M V Goldman Physics 2000 interactive applets University of Colorado Boulder CO http www colorado edu physics 2000 Howard Hughes Medical Institute Virtual laboratories http www biointeractive org LEYBOLD DIDACTIC GmbH Remote Lab Versuch http remote lab leybold didactic de cgi nm_rclShow_cgi exe E Gamma R Helm R Johnson and J Vlissides Design Patterns Elements of Reusable Object Oriented Software Addison Wesley Longman Inc Reading MA 1995 IBM Inc Bean markup language At http www alphaWorks ibm com tech bml Sun Microsystems Inc JavaBeans API specification At http www javasoft com beans Defense Advanced Research Projects Agency DARPA Transmission Control Protocol RFC 793 Sept 1981 At http www fags org rfcs rfc793 html Defense Advanced Research Projects Agency DARPA Transmission Control Protocol RFC 791 Sept 1981 At http www ietf org rfc rfcO791 txt C R hrig A Jochheim Remote Control of Laboratory Experiments 19 World Conference on O
16. ws 2000 With few changes the system is able to run on any java capable system where the javax comm in terface is available Every server is running a personal firewall blocking all accesses from non local IP addresses Over a virtual private network VPN connection students are able to get a local IP and access the lab Telematik1 also runs the experiment selector The selector is a development from the technical lab in Hagen It integrates simple filter experiments such as high band and lowpass on a printed circuit board A PHP script is used to access the board and to switch between experiments outputs Additionally the output can be switched to the DSP digital signal processor development board from analog devices This board holds the popular ADSP2181 20 signal processor A DSP client which is based on the Telematik framework is able to load and execute programs on the board The output of the DSP board is connected to the experiment selector Remember that the outputs of the high band lowpass and the DSP board are connected to the selector The output of the function generator is connected to the experi ment selector and to channel 1 of the oscilloscope The output of the experiment selector is connected to the oscilloscope channel 2 So the outputs from the filters and the DSP can be manipulated by the func tion generator depending on the experiment selection The original and the modified signal can be ob served on the oscillosc
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