Internet Based Laboratories in Engineering Education Adnan Salihbegovic, Omer Tanovic Faculty of Electrical Engineering, University of Sarajevo Zmaja od Bosne bb, 71000 Sarajevo, Bosnia and Herzegovina
[email protected],
[email protected] Abstract. In Internet based laboratory (I-Lab), the lab devices and pilot plants are tested, controlled and programmed through a client program or standard web browser at remote computer. Control panels of HMI interface and user-controlled webcam allow monitoring the measurement devices or test plant behavior providing visual and audio feedback. As an online lab can be used from many locations and at any time, it can be utilized much more than a conventional lab in omni present omni tempore fashion. The paper presents such online Internet accessible laboratory built at the Faculty of Electrical Engineering in Sarajevo within the laboratory for HMI/SCADA systems. Web enabled HMI software with OPC communication to PLC controller is used to provide full monitoring and control to remote user, while integrated videoconferencing software is used to implement the rest of the functionalities.
Keywords.
Remote control laboratories, distance learning, e – learning, internet technologies, web based education, web services, thin clients.
1. Introduction With the Internet, many new, emerging and innovative ways to enhance learning and expand educational opportunities have become realizable. Advancing technology has opened many doors in education. The next step in this direction was interactivity at teaching. Student is now able to, not only to see what is involved, but he or she is able to learn from hands on experience [5] and [15]. Using computers can be a very effective way of accomplishing this. Students are more motivated and can learn more effectively if they have the opportunity to conduct experiments [3],[6]. Experiments allow students to compare reality with simulations, collaborate with each
other, and give them opportunity to follow their curiosity [2]. Unfortunately, many engineering courses do not include lab component because of significant expense and space considerations, not to mention distance students, whose number is timidly increasing on science and engineering courses as well [5]. In response to this, I-Lab created remote web-accessible laboratories are providing a new framework for science and engineering courses. Remote laboratories allow for much more efficient use of laboratory equipment and give students the opportunity to conduct experiments from the comfort of their home, with an Internet browser [11]. While distance learning in various forms is not new, distance learning laboratory courses are a fairly recent development. The development of laboratories for distance learners is vital for those higher education institutions preparing or already offering on-line (distance education) courses in science, engineering and technology [5]. Just as for students who are physically present in the laboratory, distance learners must perform “real” experiments, acquire “real” data and run into “real” problems. For this to happen the distant learners must have control of the laboratory equipment, which requires the development of remote-controlled laboratories [13]. It must be determined what equipment needs to be controlled. Not only measurement devices such as meters or oscilloscopes but power supplies and valves as well. It must also be determined whether video is required. We always choose to provide video feedback link because even in cases where video is not required to perform the exercise, students are less likely to believe they are controlling real equipment if they can’t see it. Lastly, the method by which students will gain access and control the equipment must be chosen along with how that access will be controlled [12], [8]. The remote lab system should be designed and integrated to include a simple user interface
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through Web browser, instrument networking and control interfacing modules, instrument operation monitoring and lab scheduling subsystems. Architecture should include the following features to enable collaboration among various legacy subsystems (both software and hardware) [8], [9]: Adopting open network communication (Ethernet and TCP/IP) Supporting distributed measurement and control application development Enabling rapid system development that supports related technologies and legacy components (for example, an RS232 enabled digital multimeter, IEEE 488-bus interface, Labview or HMI Web server, analog and digital I/Os, and legacy software) Enabling visual feedback through a Web camera Supporting a Web browser client, and other Web clients Supporting remote procedure calls from web clients to Lab Web server through variety of interactive web software tools like Java Servlet, applets, Java Remote Method Invocation, Visual Basic clients, C clients, Visual C++ clients, C# clients, etc.
2. Concepts behind building remote labs These online Internet accessible labs are important in several learning situations. Apart from possibility to use I-Labs in-situ with students hands-on performing their lab works assignments and exercises, one can envisage several scenarios of distant utilization of these lab facilities. The first scenario of distance lab usage is when teacher or instructor is demonstrating operation in the Lab through live videoconferencing session, where he/she is performing tests and measurements in-situ and hands-on for remote classroom, usually explaining to the students how they can remotely do exercises, collect data and process them from their distant locations. Second application scenario is integration of reality into live lectures and seminars (conditionally named reality lectures). In this situation, teachers present to classroom audience live but remotely guided experiment or demonstration eventually assisted by local lab technician. In this scenario, the Lab is brought online to the classroom.
The third of these is the complete distance learning scenario. In this situation, students execute a laboratory exercise from their homes or places of employment. Individual learners are remote from each other so that collaboration provided with videoconferencing part of the software tools is vital. Economic, space, and cost issues are extremely important and must be considered in setting-up any distance as well as conventional learning environment. Online Laboratories hold promise of being substantially cheaper to setup and maintain than conventional laboratories, requiring less space to run the experiments and being accessible to much larger audience and utilized round the clock. So, what kind of experiments and exercises in engineering education are candidates for building these remote internet accessible laboratories? It is well known that software demonstrations of abstract concepts can be very beneficial in helping students to obtain a deeper understanding of hard – to – grasp topics. As an example, the concept of frequency content in a time-domain signal can be effectively illustrated by using an interactive multimedia approach where students can change the amplitudes of the various spectral components and view the waveform of the resulting audio signal while listening to it at the same time. This type of illustration can be carried out in a class by the instructor or, better still, undertaken by the students individually in the context of experimenting. Some software packages used for lab experiments in measurements are very well equipped and prepared for this kind of upgrade to remote operation. The most widely used is Labview software package from National instruments that has much built-in functionality to enable remote monitoring, visualization and control of the experiments involving measurements like: web server broadcasting its front panel screens to the Internet being accessible to the remote user with standard Internet browser. Furthermore, Labview is supporting a broad family of I/O modules and daq software drivers, enabling tight integration of PC running Labview and any measurement setup or test bed. Adding to this, rich library of instrument drivers, as well as Labview support for video and audio sensors like cameras and microphones, makes it perfect candidate for implementation of Internet based remote Lab facility, running either simulated or live physical experiments [3].
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Recognizing these potentials of Labview software as building component for remotely accessible labs, we have designed several experiments based on these software and hardware components to be built as remote labs. Next potential area of putting it on the web for remote access and experimenting in engineering curriculum courses, are the ones in modelling and simulation. Here again, as Labview is dominant software package for any kind of experiments based on measurement, Matlab/Simulink software is dominating in all lab works and tutorials when it comes to modelling and simulation. Matlab/Simulink models can be used for simulation of the physical dynamical systems or involved in the partial implementation and control of the physical system through ‘’hardware in the loop’’ approach. Matlab/Simulink is again supporting tight integration with hardware through drivers for I/O modules and various serial and TCP/IP communication protocols. Necessary links between Matlab/Simulink blocks and remote users can be implemented either via Labview front panels interconnecting Matlab/Simulink with Labview through SIT (Simulation interface toolkit) of National Instruments using TCP/IP protocol, or using OPC connectivity of new version of Matlab/Simulink (after version 7.0), to interconnect these variables with web enabled HMI software packages. Third area in engineering education which is almost naturally giving itself to remote Internet access and usage is family of courses on human machine interface with variety of computer based and networked process control systems, encompassing PLCs, DCS and PC based monitoring and control systems in industry. These systems are today overwhelmingly built with web enabled HMI interface, enabling remote access, monitoring and control of any component connected to their distributed nodes containing PLC controllers, PC based softPLCs and various sensors and actuators connected to them through I/O modules or with variety of field buses. Having these HMI/SCADA systems as building blocks it is not difficult to envisage myriad of test beds and pilot plant installations, previously used only in local labs to train students on the operation and control of these systems, tuning of controller parameters and protocols in filed buses, are now remotely accessible for all of these functions and actions.
One of the Internet accessible labs at the Faculty of EE in Sarajevo that is described in more details in the continuation of this paper is built on these HMI software packages. Finally, fourth area for collaborative, over the Internet, exercises and tutorials for the distant learning students, or even for local students to have more time for individual training and improvement, are the courses teaching on software tools that are web based per-se, as are majority of the software tools for 2D and 3D design like AUTOCAD, CATIA, PRO/ENGINEER, etc, as well as the courses in web design, e-commerce, Internet economy, to name the few [14]. They all can be introduced to the students through the first form of scenario described in the introductory part of this paper, and then left to students to exercise and develop skills, seeking eventually support from the fellow colleagues or instructor whenever they need it, utilizing videoconferencing part of the software in which these training software tools are embedded.
3. Structure of online internet accessible Labs Typical online Internet accessible laboratory consists of: lab device, instrument or pilot plant with
equipment for telepresence of remote users enabling them to see and hear what is going at the lab location videoconferencing equipment or at least builtin chatting capabilities for collaboration among students and instructor control software allowing users to perform experiments, program lab devices and/or run pilot plant lab scheduling and management software, assigning to users time to use the lab work assignments for students (each with an example solution for the Instructor ) tutorial background information on the experiments, including instructions on how to run pilot plant Online labs should support distributed group work over the internet. Software to control and program the lab devices runs on a central server or other machines connected to it and located in the lab itself, and according to the description from the
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Figure 1. Network topology of the remote Lab system
previous chapter is based on one of the standard software packages like Labview, Matlab/Simulink, or any HMI/SCADA software with web accessibility. Integrating videoconferencing software with one of these software packages, we have provided necessary tools to the instructor to administer the student lab access times and access rights via part of control and management built into videoconferencing software. Work assignment text and hypermedia course material for the experiment are available over the internet from the same site.
4. Description of one implementation of the I- Lab In implementation of one of the online Internet labs, we have made use of readily available software packages and open communication protocols to integrate them together and made remote Lab Internet and online accessible, belonging to abovementioned group of remote labs built on top of HMI/SCADA software products. In our online lab, whose topology is depicted on Fig. 1, it is possible to monitor and control (by the authorized users), pilot plant from anywhere in the world using standard Web Browser.
Laboratory experiments and running of the pilot plant can be observed online on one of the screens of Web browser, through one or two pan, tilt and zoom web cameras controlled remotely by users, that are sending their streaming signals via ftp server running web server of HMI application created to connect remote clients to the pilot plant controller, or alternatively, it can use video and audio link provided within superimposed videoconferencing software as shown on Fig. 2. Pilot plant itself consists of three tanks interconnected in-between through direct pipe connections and in parallel with pumps, in order to crate different plant configurations with various dynamics. Lowest lying is reservoir from which the water is pumped to top most tank using bottom installed pump. Two servo control valves are controlling the flows in bypass line and return line taking water from the third lowest tank back to reservoir. Level transmitters measuring tank levels, as well as pumps and control valves signals are connected via analog and digital input and output modules to Siemens PLC controller of the type S7-300, which is programmed in Step7 programming language to control the tank levels with variety of PID and fuzzy controller algorithms, and performing all protection functions which are preventing the equipment from being damaged or water spillage from
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Figure 2. HMI monitoring and control software embedded into videoconferencing one
overflowing tanks, due to inadvertent control from remote users. Siemens S7-300 PLC controller is connected via MPI interface (Siemens proprietary serial multidrop bus connection) to the PC computer within the Lab on which is installed and running WinCC software package of the same manufacturer used as HMI (human machine interface) for the local lab users, that are carrying lab experiments within the Laboratory. On this server PC there is also installation of videoconferencing client software running as java applet and providing support for locally installed web camera and microphone. To connect remote users via Intranet within the Faculty, or distance users connecting via Internet, we are running together with WinCC its module of OPC Server DA, which is providing industry standard OPC communication protocol for real-time process data exchange. One of the OPC DA client connected to the WinCC OPC Server is HMI software application built on top of another HMI software application (IWS from Indusoft) , which is running in Instructor PC and has dual networks connection to local Intranet network as well as external Internet. That software application is running as Web server
broadcasting html versions of its HMI screens using ActiveX technology to all clients connecting to it using standard Web browsers (either Internet Explorer or Netscape but not Firefox). Remote users are connecting either within Faculty Intranet local network (wired or wireless) in application like described live lectures (reality lectures) or demonstration and tutorial held outside the Lab itself, when the number of participants outnumber limited Lab capacity to host them locally. On this Instructor PC we are also running moderator version of videoconferencing software allowing Instructor all carry out all previously mentioned scheduling and managing activities in lab allocation to remote users. Fig. 3 is illustrating the scenario when the Instructor is demonstrating the operation of the pilot plant to his remote student audience, being able to ask the questions or even remotely control while the experiments are online demonstrated to them. Majority of the Lab users connect to Lab and work remotely via Internet from the commodity of their own home and at the time they choose, complying with time schedule and booking in case that are going to carry active experiments on the Lab and pilot plant itself, which is
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Figure 3. Instructor from within the local Lab is demonstrating remote Lab control to the distant users
determined by Instructor who make this schedule and send automatically email notifications of allocated time slots from the management part of video conferencing software. Group online work and exchange of information between the online participants, is automatically enabled through the videoconferencing software via both audio link as well as built-in chatting text windows. To further enhance online connectivity to the Lab, we have equipped the Lab PC server with connection to mobile phone unit (via Bluetooth connection to PC) and service software driver that integrates this communication channel to the HMI application. Now, the control software is capable to send SMS messages based on process events (like alarms) to specified mobile recipients or to accept remote commands sent via mobile phone as SMS text coded messages. Furthermore, making use of standard OPC communication protocols used in this Project, we can readily exchange live process data from pilot plant with many software applications in real time running on any computer within the Faculty on local Intranet. The good example for this depicted on the above Figure No.1, is connection via OPC tags to Matlab/Simulink ( from Version 7.0 on) so that we can readily implement the
‘’hardware in the loop” configuration, in which we use Simulink to configure control structure algorithms and closed the control loop via pilot plant real physical object in the loop.
5. Description of the possible remote ILab experiments The remote Intranet/Internet accessible user to the pilot plant is capable of doing the following set of exercise and experiments: carrying out monitoring and control of pilot plant control loops tuning the controller parameters and observing and recording effects of parameter changes for reporting and data analysis using pilot plant live data as signal sources to archive them and further process offline in various signal processing, identification and simulation applications using pilot plant live data as OPC signals in OPC client enabled applications like Matlab/Simulink to implement experiments like “hardware in the loop”, in which Simulink is used as analysis and synthesis tool of various control structures and algorithms acting upon
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live physical plant, with all its intricacies and nonlinearities using pilot plant live data as OPC signals in various online identification packages like Matlab system identification toolkit (SIT, IDENT), for online identification and model building tool.
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6. Conclusions Despite limited perception confined to computer screen and the surrounding sound at Lab test site, and without true hands-on perception and experience, online remote laboratory user is in many aspects in advantage to his local Lab fellow user, not only that he can use it at his own pace and time in omni present omni tempore fashion, but in collaborative team that he/she decides to join. Internet based forms of learning have been broadened to encompass live physical experiments, which, although much more complicated to implement in comparison to lecture modules, are bringing these expensive teaching tools to broader audience promoting ideas of interinstitutional joint laboratory assets. In described implementation, we have joined the remote monitoring and control capabilities of modern web based HMI software with interconnectivity and virtual presence possibilities of videoconferencing software to achieve new synergic effects of the two evolving technologies. The results so far are more than encouraging.
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