Internet Based HMI in Low-cost Simulators

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1 XXVIII. ASR '2003 Seminar, Instruments and Control, Ostrava, May 6, Internet Based HMI in Low-cost Simulators TAMÁŠ, Jan 1, KLIMÁNEK, David 2 & ŠULC, Bohumil 3 1 Ing., Ústav přístrojové a řídicí techniky, ČVUT v Praze, Technická 4, Praha 6, jan.tamas@humanisti.cz, 2 Ing., david.klimanek@seznam.cz 3 Doc., Ing., CSc., sulc@fsid.cvut.cz Abstract: Low-cost simulators are a new trend in the area of operator training. They are based on engineering simulation, which has become an important, intensively developing field of system simulation with a wide range of industrial applications. This contribution describes experience gained during implementation of an Operator Training Simulator (OTS) of a coalfired power plant and its current enhancement. The simulator is based on a complex model of the plant developed in Matlab, which is connected to an InTouch control panel used in the real plant by the plant personnel. Using existing equipment, software and infrastructure, this solution proves to be very cost-effective, while at the same time providing the same functionality that a complex simulator would. With the ever-continuing spread of the Internet, it becomes natural to enhance the functionality of the simulators by allowing remote users to connect to them via Internet. Latest development of the simulator thus focuses on implementation of a standardized Internet interface between the simulator and the trained personnel. Web services have been chosen as the architecture for this enhancement. Keywords: HMI, Low-Cost, Simulators, Training, Internet. 1 Introduction Desktop personal computers are becoming ever more powerful and therefore are now used in new areas, where previously mostly expensive workstations and servers have been used. One of such areas is the field of operator training simulators (OTS), where personal computers are now capable of bringing satisfactory results in simulation of real world processes. Using such computers helps in significant reduction on the part of both purchase and operational costs. With the spread of Internet it becomes natural to try to expand the capabilities of such simulators by exposing their interface to the rest of the world. 2 Basic Types of Simulators It is not simple to decide how to create a simulator. Different approaches and solutions have a significant impact on price, performance and long-term support of the simulator. The number of different types of simulators has increased with the growing level of computers and applications of information technology. The following basic types of simulators can now be distinguished: learning (basic principles) simulators, engineering (generic) simulators and operator training (full-scope) simulators. Operator training simulators may have three basic hardware configurations, which e.g. the Trax Corporation refers to as:

2 XXVIII. ASR '2003 Seminar, Instruments and Control, Ostrava, May 6, Full stimulation, this configuration means that the process is emulated and the control system and human machine interface (HMI) are used as in a real plan, Partial stimulation, the process and the control system is emulated, but HMI is kept as real, Full emulation, all three parts, i.e. process, control system and HMI are emulated. It can be seen that the human-machine interface plays an important role in an operatortraining simulator. Well-designed human-machine interface emulation can help to provide a very cost-effective solution for operator training simulators. An emulation of the HMI is not a poor substitute for the real system, but can often enlarge the utilization of an operator-training simulator. The operator display screens can look like and work in a way very similarly to real manufacturer displays, and they can use much less special hardware, which is a very cost-effective approach. 3 Low-Cost simulators A new concept of low-cost simulators has emerged from the requirement to keep the development costs of a newly designed operator-training simulator for an existing power plant as low as possible. Cost reduction has been achieved by using the following tools: Standard simulation programs (tested with Matlab/Simulink) for process and control system modeling, Newly developed process-specific object-oriented libraries to supplement the standard offer of the simulation program, Use of visualization software delivered together with the distributed control system of the technological equipment as an HMI tool. The delivered visualization software can be used only if there is a data exchange connection between the visualized object and the simulated object. This communication has been tested with DDE (dynamic data exchange), because this protocol is implemented both in Matlab/Simulink and in InTouch software. Some other versions of possible connections are listed below: Matlab/Simulink model with InTouch mimics. This is software created by MathWorks and Wonderware companies. The InTouch system is significantly spread in power engineering applications. InTouch scripting derived tags in RSView or Visual Basic application running in the background enable simultaneous work of a model and a SCADA application. RSLogix Emulate. This software has been developed by Rockwell Software inc. RSLogix Emulate contains troubleshooting and debugging tools that can emulate most operations of Allen-Bradley PLC-5 and SLC 500 family processors. Invensys Foxboro I/A Series Softpack. Control systems Invensys Foxboro I/A Series Softpack and Yokogawa CS3000 control system have powerful control configuration tools with built in basic and advanced control blocks and strategies. Several models of simple process plants controlled by cascade loops have been developed. Micro-I/A stations are part of the I/A Series family of control products and can be used in a variety of small and large I/A Series systems configurations running with either UNIX or Windows NT platforms.

3 XXVIII. ASR '2003 Seminar, Instruments and Control, Ostrava, May 6, Operator Training Simulator for the Opatovice Power Plant PC PC Matlab DDE Protocol InTouch Suite Link InTouch Protocol Operator Control Panels (Mosaic) PC InTouch Operator Control Panels (Mosaic) Instructor Station Operator Station Figure 1. Configuration of Matlab/Simulink model The InTouch system has been used by the Opatovice Power Plant. A complex dynamic model of a coal boiler composed of submodels of fuel supply, combustion chamber and evaporator involving models of the other components such as superheater, water feeding system, turbine etc. including non-linear steady state properties, has been created with the use of an objectoriented library [JAVED, 2002]. Because the Opatovice power plant uses InTouch software for control and visualization we have focused on HMI performed by this software. Figure 2. InTouch Control Panel of the Plant The developed OTS has following configuration: Instructor Station o One high speed PC with large memory o Matlab/Simulink model, and InTouch mimics. Operator Station o Two regular PCs for the Operator station, o Only InTouch mimics on both PCs. This OTS provides the following features:

4 XXVIII. ASR '2003 Seminar, Instruments and Control, Ostrava, May 6, Friendly graphic human-machine interface both for the trainee and for the instructor, using the same software for visualization and monitoring as the control system fully identical to the operator interface, Trainees can not only work with the same screens but can also use the same control devices, e.g. operator panel, as in real operation, Computer supported education, performing an automatic evaluation of the trainee s ability to follow operational rules and procedures. 3.3 Engineering Models of Power Units in Simulink Several engineering simulators in Matlab/Simulink preceded the described operator-training simulator. They have been successfully used in engineering applications [ŠULC NEUMAN 2000], mainly for controller design, parameter tuning and for external combustion control with optimum combustion point tracking and minimization of harmful emissions or for oxygen probe fault detection. Creating these engineering models of power plant units with coal-fired boilers has proved Matlab and Simulink to be efficient supporting tools. A direct use of Matlab for establishing operator interface was also tested with good results, e.g. with the conclusion that it is possible to approach industrial requirements in a sufficient extent. The methodology of creating engineering models in Matlab/Simulink has been in the center of attention for several years and created a good experience for OTS development. 4 Internet Based Simulators With the ever-continuing spread of the Internet, it becomes natural to enhance the functionality of the simulators by allowing remote users to connect to them via Internet. Several possibilities of the type of client connection have been studied and implemented in the past, including design of a proprietary communication protocol between client and server parts of a remotely controlled laboratory experiment [Tamáš, 2002]. This solution proved to be fully functional, allowing students to control the laboratory experiment remotely. The architecture was based on a standard HTTP protocol with a custom-made application protocol. However, the disadvantages of this approach were the fact that the solution has been non-standardized and the scaling of the application protocol has been difficult. Figure 3. Scheme of a web services architecture

5 XXVIII. ASR '2003 Seminar, Instruments and Control, Ostrava, May 6, Web services architecture proved to be a good alternative, addressing both disadvantages of the previous implementation of remote control. Web services are both standardized (using HTTP as the transport protocol and XML as the data format) and open (allowing designer to define own tags for data transport). This approach not only allows operator training simulators or remotely controlled experiments to be accessed remotely, but it also allows the remote party to design its own client side program, thus a much greater use of a single server can be accomplished. Figure 4. Example of a client program for a remote control experiment Main advantage of this approach is its scalability and openness. Scalability ensures that the whole system can be easily upgraded and more functionality can be added to the server side in the future. The fact that this solution is open brings new possibilities in cooperation with other facilities and research centers that may be interested in the use of the server side program (which in our case is a power plant model). Such facilities are able to design their own client side program, based on their requirements and aims. No changes to the server side need to be made in case such clients are correctly designed and connect to the server. New functions can also easily be added to the server, without disrupting the functioning of the current clients. Openness is ensured due to the fact that web services are based on well-accepted standards, mainly HTTP as the communication protocol (which has already proved to be functioning faultlessly) and XML as the language for transferred data. Web service is clearly described using an XML Schema and WSDL (web services description language). It allows remote party to fully understand the web service and especially the required format of input data and available functions as well as the format of output data. Both XML Schema and WSDL are themselves XML documents, which is another advantage of this architecture (as the files used to describe the service are of the same format as the actual service). Implementation of this approach of remote access to both operator training simulators and laboratory experiments is currently taking place. First experience shows that this approach will most probably be a step in the right direction and will bring new possibilities especially in the newly developed field of low-cost simulators.

6 XXVIII. ASR '2003 Seminar, Instruments and Control, Ostrava, May 6, Conclusions Low-cost simulators proved to be a good alternative to traditional simulators. Web services architecture seems to be a better option than a proprietary communication protocol both in the case of remote access to laboratory experiments and in remotely controlled operator-training simulators. Main disadvantages of the proprietary solution (nonstandardized protocol and difficult scaling) are overcome using web services, as they are based on well-known and well-documented standards (HTTP and XML). Previously unforeseen benefits of this architecture may also be discovered when final implementation takes place. 6 Acknowledgements The research work has been supported by the grant No. 02/01/1347 of the Grant Agency of the Czech Republic. 7 References NEUMAN, P., ŠULC, B., DLOUHÝ, T Non-linear model of a coal fired boiler applied to an engineering simulator. Preprints of IFAC Symposium on Power Plants and Power Systems Control 2000, Brussels NEUMAN, P., ŠULC, B., ZÍTEK, P JAN, J. A Soft Computing in Object Oriented Nonlinear Modeling and Control of Thermo-Fluid Dynamic Systems. Ph.D. Thesis. Czech Technical University, ŠULC, B., TAMÁŠ, J Using web services to control lab experiment and power plant simulator. Accepted for IFAC Symposium on Advances in Control Education, Oulu, Finland TAMÁŠ, J Performing Laboratory Experiments in Control Engineering via Internet. Diploma thesis (in Czech). Czech Technical University, 2002.