Client-Server and Gateway Systems for Remote Control in Engineering Education*

Hartmut Ewald Fachbereich Elektrotechnik und Informationstechnik, Rostock University Albert Einstein Straße 2, D-18051 Rostock, Germany George F. Page School of Engineering, Liverpool John Moores University Byrom Street, Liverpool, L3 3AF, England, United Kingdom

With the rapid development of the Internet over recent years, in conjunction with the transmission protocol TCP/IP and the latest version of hypertext (HTML) facilities, new opportunities have come into existence for the use of the network for the remote control of experiments and other practical systems in engineering education. There are two prime benefits: students learn how network systems work and also how remote control technologies operate and the universities save money when students from several institutions utilise the same expensive equipment. Using graphical software environments in client-server systems can be easily designed. Client-server systems have some general advantages when compared with simple Remote-Access Systems (RAS) or proprietary (single-solution) systems. In recent years, gateway systems for remote control have become available for most measurement and instrumentation bus systems and this effectively permits direct access via LAN/Internet with a minimum of the transfer data-rates needed for control.

INTRODUCTION Internet for remote control. It is now possible to design http-based client-server solutions and gateway The remote control of installations and systems has systems for remote control problems with modest been a technical reality in research laboratories and expenditure with the aid of graphical software automated industries for many years, particularly in development packages, such as LabVIEW [1][2] or process control industries. Due to the stringent VEE PRO [3]. demands of industry, a variety of bus systems have The following institutions jointly undertook a remote- been developed to operate at the different hierarchi- control project: cal levels found in automated systems. Some examples of these demands are process control • Liverpool John Moores University, Liverpool, monitoring, the updating of services software at a England, UK; distance and embedded Web-server services. • Hochschule Wismar – University of Technology, At the highest level (Intranet), Ethernet-based Business and Design, Wismar, Germany; systems are frequently utilised to transfer data, using • Rostock University, Rostock, Germany. different protocols. With the rapid development of the Internet within the last ten years, and its associated The goal of this project, which was started four transfer control protocol/Internet protocol TCP/IP, years ago, has been to increase the attractiveness and as well as the use of hypertext documentation as a effectiveness of laboratory work in research by basic technique on the World Wide Web (WWW), remote-controlled experiments. new possibilities have arisen for the utilisation of the An attractive consequence of this development is *A revised and expanded version of a paper presented at that resources are saved because the partners need the 6th UICEE Annual Conference on Engineering not cater for the whole spectrum of possible (and Education, held in Cairns, Australia, from 10 to 14 mostly expensive) research and teaching equipment February 2003. and experiments, which also have to be updated and

201 202 H. Ewald & G.F. Page maintained. Researchers from other locations could the server side. With the introduction of the HyperText control and monitor their own experiments and inves- Mark-up Language (HTML) several years ago, and tigations from a distance. the associated hypertext transfer protocol, the possi- The concept and the advantages of using a bility existed for communication between client and http-based client-server system for remote control server using graphical elements (image maps). have already been discussed elsewhere [4]. The The performance and functionality of http-based availability of gateway systems for LAN/RS232 and client-server systems has been extended through LAN/GPIB have opened up new possibilities for the server extensions such as Java, the Common remote controlled laboratory, particularly for remote Gateway Interface (CGI), JavaScript, Standard Query access systems in general, as well as instrumentation Language (SQL) and many more, which enable the [5-7]. exchange of variables and the preparation of dynamic As an example, this article describes the remote HTML documents. Figure 1 shows the general control of Rostock University’s ultrasonic, eddy- structure of a http-based remote-controlled experiment current and optical (CCD) research measurement using the graphical programming language LabVIEW equipment using a http-based client-server system and and an integrated http Web server (Internet gateway system, including the online visualisation of Toolkit) [3]. the dynamic runs of real research experiments The server itself has to fulfil two important tasks. Firstly, it controls the experiment. In the actual REMOTE CONTROL CLIENT-SERVER version the control of the experiment works with the SYSTEM graphical elements, the so-called virtual instruments, which were developed using the graphical program- Client-server systems have some advantages com- ming language G (by means of the LabVIEW soft- pared with simple Remote-Access Systems (RAS). ware development environment, National Instruments) They have better security, a higher functionality and [1]. The virtual instruments realise the hardware can be administrated more easily and effectively on access to the experiment: analogue and digital server

Client Intranet Browser

Connection - Internet - ISDN/DSL Internet Protocol: TCP/IP

Firewall Intranet

HTTP-Server Remote controlled LAB HTM L-Pages analog/digital I/O-Ports Sensor technique G-Server Intrum entation Bus: - IEE 488.2/IEC 625 - RS 232 Control systems Virtual - U SB Instrum ents (VI)

Figure 1: Structure of an http-based remote controlled laboratory or experiment. Client-Server and Gateway Systems... 203

Remote Controlled Experiments

VLM 200 HP-GPIB- Software - Components Measurement LAN- Client LSC 5000 Devices Measurement-PC IDE: and HP VEE 5.01/ VEE Pro Software - Components LAN- Server LAN HP I/O Libraries IDE: Program: I/O_ Config HP VEE 5.01/ VEE Pro or higher ◊ LAN - Client Installation HP I/O Libraries Gateway HP VEE - Software: Program: I/O_ Config VLM200_LSC5000. vee ◊ LAN - Server Installation Hostname: Spectrum IP - Address: 193.175.188.155 HP VEE Device I/O - Data: vee . io PC - Cards, AT&PCI

KFA - 8I PCI - 20

Software - Components Gateway Software - Components I/O-Driver: kfa8i. dll , kfa8i.h, pci20dll, pci20.h Client HP VEE Service Manager: veesm . exe * eg the LAN - Client HP VEE Remote - Function: init _ Lib . vee

Internet

Figure 2: Structure of a proprietary client-server system for remote-controlled experiments using VEE.

I/O-systems or the standard measurement bus time slot techniques. A software and/or hardware systems such as IEEE 488.2 (GPIB), RS 232 or USB. firewall solution is helpful for these configuration and Secondly, it has to perform its duty as a http server administration problems. at the disposal of requesting clients, which means that the transfer of a requested HTML document, in which REMOTE CONTROL GATEWAY SYSTEM the graphical elements are embedded, is also one of its tasks. The conversion from the graphical elements Gateway technology enables communication between of the virtual instruments of the LabVIEW control pro- a (client) PC and the gateway with instrumentation gram (eg input/output) into the HTML document is bus connectors, such as GPIB or RS232 via a Local performed by a G-server. The G-server is a part of Area Network (LAN). The gateways themselves have the Internet toolkit (National Instruments), which also the structure of a server: the internal server transmits provides virtual instruments for the use of other Internet the data from the LAN to the other bus system (GPIB services, such as the File Transfer Protocol (FTP) or RS232) over layer 3, or higher, of the Open System and e-mail. Interconnection (OSI) references model using Stand- Figure 2 shows the structure of a proprietary cli- ard Instrument Control Library (SICL) software [2]. ent-server system for remote-controlled experiment The SICL software also includes a LAN/GPIB server using the graphical programming language VEE [2]. so that any PC GPIB- interface card could act as a The functionality between client and server can be gateway. The access control could be easily realised extended by means of elements like CGI and Java. by means of a simple IP-list in the Gateway. On Through these technologies, the access rights of the other hand, if a client has the right of access to a clients to stored data from the server, password gateway, then he/she controls everything on the protection and much more can be achieved. These instrumentation bus! include solutions for active task control of IP number Figure 3 shows the general structure of a gate- and/or additional password control for cases where way-based remote-controlled experiment/laboratory more than one client has the right to access the using the graphical programming language VEE PRO remote controlled experiments, using time stamp or [3]. 204 H. Ewald & G.F. Page

Figure 3: Structure of a gateway-based remote controlled laboratory.

ONLINE VISUALISATION up to four cameras) and videostreaming technology, the requirements on dynamic process visualisation can Online visualisation of the remote control process is be eased; this has increased the success and accept- one of the major problems that have to be solved. In ance of remote controlled experimentation [4]. The the first version of a http client-server system using disadvantage of this solution is that the software for LabVIEW software, a one or two simple CCD the remote controlled camera system must be installed camera system, connected on the server via USB, is at the client side of the system, as well as the server used for the visualisation of the dynamic actions of side. the experiment. This can be embedded within the virtual instrument as a static picture (.jpg, .bmp). REMOTE CONTROLLED LABORATORY On the client side, eg from a random PC on the Internet, the HTML document, which was sent by In the first phase of the remote-control project, the the server and had been transferred, will be displayed performance of the http-based client-server system in a browser, and some – also transferred – contents using LabVIEW software with different configurations (such as Java applets) will be executed. In this case, (online visualisation, task control, firewalls) was it is important for the approach used to gain Internet investigated. In the second phase, real and complex control that the clients’ browser is able to implement computer-controlled laboratory experiments were the server-push technology (eg Netscape Navigator) designed [4][8-10]. Complex research experiments because the G-server uses this technology to display involving remote control of ultrasonic, eddy-current the (graphical) control virtual instruments and the and optical sensors have been designed at Rostock client receives a display of the interface and access University and Hochschule Wismar. to the control of the experiment program. For example, the ultrasonic measurement research In the case of the graphical languages, VEE PRO experiment consists of an ultrasonic sensing array, a runs on the client side so that only a small amount of 3-axis scanner to manipulate the ultrasonic sensor, the data and a few instructions need to be transferred server and a remote controlled CCD camera system from the server side to the client. (640 x 480 pixels) with a second (videojet) server to However, it has been found during experiments that observe the dynamic responses. This is shown in a better transfer quality is achieved if a separate (sec- Figure 4. ond) server and streaming video are used [8]. With Experiments within a frequency range from 0.5 to the use of remote controlled high resolution CCD zoom 15 MHz are possible using the continuously tuneable cameras (VCS Corp. video conference system with ultrasonic array. The sensors can work in impulse- Client-Server and Gateway Systems... 205

Videojet- Server

Web-Camera 1 Web-Camera 2 Firewall HTTP-Server-PC Test piece Scanner table

Internet Ultrasonic, Eddy-current 3axis-Controller and optical equipment

Figure 4: Remotely-controllable ultrasonic, eddy-current and optical measuring equipment [9]. echo or in continuous mode. All experiments are ments, are recorded as packed files and then trans- designed in such a way so that the ultrasonic sensors ferred to the PC. The users can then repeat an have to be water-coupled. The ultrasonic equipment experiment as often as they wish and, if necessary, and the 3-axis scanner are controlled by the server under various configurations in order to be able to evalu- over a serial interface (RS232). By utilising the equip- ate the results of different instrument settings. ment for the ultrasonic sensors, it is possible to design In order for this to be accomplished, a manual a variety of research experiments to capture the remote-controlled installation is planned. This installa- so-called A-, B- and C-scan ultrasonic signals, such tion (positioning of the ultrasonic sensor, the eddy- as profile measurements on surfaces and building up current test piece or optical sensor plus other configu- in stages to 3-D measurements on solids. rations) makes online visualisation of the experiment The structure of the Web page of the remote- necessary. It has been found that with a simple Web control project using LabView is shown in Figure 5 camera of 320 x 240 pixels and a reasonable picture (eddy-current and ultrasonic laboratory). transmission quality, a continuous and stable data In the case of the eddy-current research experi- transfer rate of at least 7 Kbyte/s is needed. Router, ments, such as surface or thin film inspection and also hub and switcher technologies reduce the effective crack detection, the sensor is a coil probe that is transmission rate of high-speed Internet connections connected with the eddy-current equipment and has a [11][12]. frequency operation range from 10 Hz to 10 MHz. In this context, the access rights for the clients from The control and the various data streams are also the server-administration are an important part of the transmitted to the http server over a serial interface functionality of the experiment. Furthermore, it can (RS232). also be influenced by which clients have the access The optical sensors consist of line and matrix CCD rights and the ability to control the experiment. camera systems with a serial interface (RS232) or a Administration would be easier over direct ISDN high-speed analogue data-acquisition system to http telephone line connection but – would also be more server using the VEE PRO software, as shown in expensive. Figure 6. An advantage of this solution is the opportu- nity of utilising the remote controlled function, which CONCLUSION allows for the inclusion of a personal driver for special hardware on the server side. Optical inspec- With the aid of the LabVIEW and VEE PRO software, tion problems could also be investigated using these http-based client-server systems and gateway systems methods. for the remote control of experiments were developed, It is essential for the actual development of the built and tested. One example involves a complex project that real data, rather than simulated measure- experiment using ultrasonic, eddy-current and optical 206 H. Ewald & G.F. Page

Starting page Server call and 1st authentification (password and (index.htm) IP-number)

Identification 2nd authentification (user name & 2nd password) (formular.vi)

LAB Examples Scanner setup: area and scanning points (remote.htm) from NI

Configuration Setup

Remote with the Automatically or manually controlled experiment, experiments web-camera remote controllable (Web) zoom-cameras with different resolutions Manual control with the experiments web-camera

Data transmission Transmission of the data, configuration setup and visualisation tool Configuration transmission

Visualisation tool download

Figure 5: Structure of the Web page of the remote-control project using LabView. sensors. If Java is used as a software platform, all location and at any time. Furthermore, they can access to the hardware components must be made repeat experiments at any time. In addition, students using programming methods, eg by an OSGI-Sever, will obtain real data from the experiments – not simu- which can be very time-consuming [13]. lated results. The online visualisation of remote-controlled The financial advantages to universities can be experiments and the interactive control possibilities is considerable. If a consortium of, say, eight universi- one of the most important challenges that have to be ties were to share the use of their equipment via the solved. In the case of a data transfer transmission Internet then the savings in capital outlay would be rate >100 kbit/s videojet (videostreaming) technology over 80%. They would also have access to a greater could be a powerful contender. range of experiments and equipment for the main Client-server systems are more difficult to imple- courses than they could afford on their own and ment but have greater potential. HTTP servers are major rigs could be built as a central resource. easier to implement but they need a high transmission rate (virtual instruments). Proprietary client-server sys- REFERENCES tems are faster but are also less flexible. Gateway-systems are easier to install but the rights 1. LabVIEW 6.0. Manuals, Austin: National Instru- of access must be carefully controlled. They can also ments (2000). reduce installation and services costs. They are easier 2. VEE 6.0. Manuals, Palo Alto: Agilent Technolo- to handle and there are no limits for the programming gies (2000). language used. Gateways are available for all stand- 3. LabVIEW 6.0 Internet Developers’ Toolkit for ard measurement and industrial bus systems. Access G (G-Server) Manual. Austin: National Instru- can be controlled by a simple firewall. ments (2000). It is the contention of the authors that remote- 4. Ewald, H. and Page, G.F., Performing experiments control experiments should be an integral part of by remote control using the Internet. Global J. engineering education. The advantages for students of Engng. Educ., 4, 3, 287-292 (2000). in being exposed to these technologies is that they gain 5. Agilent, Agilent E2050B LAN/GPIB Gateway. an insight into modern uses of protocols, LANs and Data sheet, Palo Alto: Agilent Technologies the Internet. They can access experiments from any (2001). Client-Server and Gateway Systems... 207

IEC-Bus 625/ IEEE 488 HP VEE

Multimeter HP 34401A Computer + HP-IB Card Serial Interface (optional ) RS 232

Analog Output 1 ADC KFA-8I CCD-Camera LSC 5000

DAC PCI-20 Speed Meter VLM 200

Current Converter MOVIRET108 Transport Devices FP120

Tachometer Generator

Counter HP 53131A Incremental Encoder IGR M2 -

Figure 6: Configuration and structure of the proprietary client server remote controlled laboratory using VEE Pro (optical sensor laboratory with an optical speed- and distance sensor VLM200 and a high resolution line CCD- camera LSC5000). 208 H. Ewald & G.F. Page

6. Agilent, Agilent E2050B LAN/GPIB Gateway. 1992-2001, he was a professor of sensor techniques Overview, Palo Alto: Agilent Technologies at Hochschule Wismar – University of Technology, (2001). Business and Design, Wismar, Germany. 7. Intelligent Instrumentation, Ethernet Data Acqui- His main research fields are pattern recognition, sition Systems - Ethernet/Serial Interface: User measurement instrumentation and control, and Manual. Tucson: Intelligent Instrumentation non-destructive testing. He received the Marie- (1999). Curie-Research Grant (Marie-Curie Fellowship) from 8. VCS Videojet-Server, Video-Audio-Data-Over- the European Union (EU) to the University of Limer- IP, Manual. Nürberg: VCS Video Communica- ick, Ireland, in 1998. He is a member of the German tion System (1999). Society of Non-Destructive Testing and a member 9. Schulz, T., HTTP-Server System for Remote of the Organising Committee of annual conferences Control via the Internet. Masters Thesis, of Artificial Neural Networks in Engineering Hochschule Wismar (in German) (2000). (ANNIE). 10. Wolf, R., Gateway Systems for Remote Control. Masters Thesis, Hochschule Wismar (in German) George Page was born and (2000). went to school in Lanca- 11. Rees, M.J. and Coe, J.T., CCNA Routing and shire in England, United Switching. Bonn: MITP Verlag (in German) Kingdom. He attended the (2000). universities of Wales (at 12. Halsall, F., Multimedia Communications. Harlow: Bangor), Manchester and Addision Wesley (2001). Liverpool. His initial subjects 13. OSGI: Open Source Gateway Initiative, Review were physics and math- (1999). ematics but his current teaching and research inter- BIOGRAPHIES ests are in the field of intelligent control systems and novel uses of the Internet. Hartmut Ewald is a profes- He has considerable experience in engineering sor of technical electronics education and has served on numerous national and and sensor techniques in the international committees. He has been an examiner in Department of Electrical control engineering for the British Engineering Council, Engineering and Information guest editor for several international journals, and is Technology at the University the author of one book and many papers and of Rostock, Rostock, articles. He has taught for the Open University and Germany, since 2001. He for Liverpool John Moores University in the UK. He graduated as an electrical also has close links with several universities in France engineer in 1978, received a and Germany. He returned to the School of Engineer- doctorate in physics in 1983, ing at Liverpool John Moores University from and the habilitated doctor’s degree in 1991. From Hochschule Wismar in 1999.