COLLABORATIVE LEARNING ENVIRONMENT USING DISTRIBUTED MIXED REALITY EXPERIMENT FOR TEACHING MECHATRONICS

F. M. Schaf 1, A. C. Assis1, C. E. Pereira1, C. L. Reichert2, F. Campana2, I. A. Krakheche2

1 Electrical Engineering Department – DELETUniversidade Federal do Rio Grande do Sul – UFRGS

Av. Oswaldo Aranha 103 – Porto Alegre – Brazil – 90035-190E-mails: {fredms, acassis, cpereira}@ece.ufrgs.br

2 Serviço Nacional de Aprendizagem Industrial - SENAIDepartamento Regional do Rio Grande do Sul – DR – RSAv. Assis Brasil 8787 – Porto Alegre – Brazil –91140-001

E-mails: reichert@dr.rs.senai.br, {fabrício, igor}@mecatronica.org.br

Abstract: This work presents a virtual learning environment which uses a distributed mixed reality remote experiment for professional education in the area of Mechatronics. The proposed collaborative environment makes use of the system named deriveSERVER, which has been developed by the Bremen University, and extends it, in order to allow the integration with remote hardware or software used by the students. The remote experiment will be used to enhance lessons used in SENAI-RS, a vocational education institution in southern Brazil, enabling the development of collaborative projects among students at different SENAI sites. Copyright © 2007 IFAC

Keywords: Remote Control, Control Engineering, Learning Systems, Virtual Reality, Pneumatic Systems, Process Automation.

1. INTRODUCTION

Mixed reality laboratories take advantages from virtual laboratories and real laboratories. The use of mixed reality systems for distance learning has been increasing over the last years. SENAI-RS as an important technical education institution in Brazil, have decided to use such techniques for Mechatronics education and established cooperation with the University of Bremen and the Federal University of Rio Grande do Sul to develop a mixed reality application with electro pneumatic devices used in industry.The basic idea of the project was to extend the deriveSERVER (Bruns and Erbe, 2004) developed at University of Bremen to the educational needs of SENAI Mechatronics Technology Center.The system developed by the University of Bremen is a powerful tool to teach not only pneumatics but also system automation and development process (Bruns and Erbe, 2004). The use of hyper bonds provide interface to any discrete pneumatics or electric equipment in the real environment.This project also proposes to enhance the server to be more robust and platform independent. Currently this

server is fixed on commercial programs that are not supported by other browsers and operational systems.This work will be organised into 5 Sections as follows: In Section 2 a shortly description of the system (deriveSERVER) developed by the University Bremen. Then a description of the industrial training in SENAI-RS in Section 3. The proposed enhanced version of deriveSERVER will be presented in Section 4. Finally in Section 5 the results of the running project then in section 6 the concluding remarks.

2. DERIVESERVER DESCRIPTION

2.1 Mixed Reality Remote Experiment

The deriveSERVER is a system that provides remote access to a virtual reality environment (based on 3D virtual models) and also a real experiment. DeriveSERVER stands for distributed real and virtual learning environment for mechatronics and tele-service.The used experiment in the remote and virtual laboratory was a traditional electro pneumatics workbench used in mechatronics with cylinders,

valves with pushbuttons, solenoid valves and much more, providing a simple discrete control.

Fig. 1. Simple arrangement of pneumatics device in a real experiment workbench.

The system provides mixed reality experiments through the extensively use “hyperbonds”. The hyperbond tool realizes a tight coupling between physical and virtual phenomena (Bruns, 2004). Hyperbonds are bridging the gap between reality and virtuality by transmitting physical phenomena (air pressure, electric potential) from one side to the other and vice versa. They follow the theory of Bond graphs which provides a unified view on different systems using the notion of effort and flow (Paynter, 1961). The bond graph theory has been than further developed by Karnopp et al. (1990).

Fig. 2. Simple arrangement of pneumatics device in a virtual experiment workbench.

The system was not designed (developed) to treat analog signals, so analog devices are not used, therefore only discrete control is possible with boolean variables. Solenoid valves can be driven by electrical current, making electrical control possible as typically used in eletro pneumatics systems.

Fig. 3. Local tests mixed reality installation.

2.2 Architecture

The master (server) software of the deriveSERVER system architecture is the ROMAN (Real Object Manager). Other softwares attached are called ROMAN plug-ins (clients). So: the VCK (Virtual Construction Kit), the hyperbond (software and hardware) are plug-ins that communicates with the ROMAN through communication sockets using the specific created ROMAN-protocol.The VCK is the Java developed web interface responsible for managing and displaying the virtual workbench interface to the user. Virtual models (VRML’s) are displayed in this interface by the use of the commercial (free only for personal and non-commercial use) VRML plug-in called Cortona VRML Viewer (ParallelGraphics, 2006). Virtual reality models are manipulated using EAI 2.0 (External Authoring Interface) and Java Scripts. Java Scripts capture the client user inputs (like mouse and keyboard entries) and the EAI, performed in the VRML plug-in (based on the ActiveX Automation Technology), is used to transform the virtual workbench (virtual reality models scene). The real equipment video, used in the mixed reality experiment, is acquired by a simple WebCam. The real video capture is available in the experiment interface using the simple WebCam2000 free open source software (WebCam2000, 2006).

Fig. 4. DeriveSERVER interaction architecture.

According to the Fig. 4 the mixed reality interface is available in the internet displaying the real video capture and the virtual workbench using the Internet Explorer (IE) web browser from Microsoft, Java Runtime Engine from Sun Microsystems and the

Cortona VRML client plug-in for IE. The dash-dot line displays the path covered by the virtual-real signal.This software and hardware architecture provides a reliable system capable simulate (virtual workbench) and use real equipment to improve education in basic pneumatics (also mechatronics), system automation and system process development.

2.3 E-learning Courses

The University of Bremen already has an e-Learning platform for student guidance and document repository, but not yet a mechatronics course. This mixed reality system is used to enhance some engineering courses with practical experimentation.

3. SENAI INDUSTRIAL TRAINING

3.1 Training Structure

The SENAI Mechatronics Technology Center in Caxias do Sul, Brazil (SENAI-Mecatrônica, 2006), offers technical school for young students that are interested in becoming a technician in mechatronics. The course has over 2000 hours of training divided into 1600 hours of study classes and 400 hours of practice into industry. The study classes are used to teach most of the technician basics, like: Technical Drawing, Electricity and Electronics Principles, Computation and Programming, Hydraulics and Pneumatics, Control Systems and Devices, Management Principles and also basic technical English language.The course of pneumatics use didactical material from FESTO didactics (FESTO Didactics, 2006), like MPS (Modular Production Stations) and others, and from DEGEM Systems (DEGEM, 2006) to teach beyond pneumatics, control systems instrumentation and CLP programming. For further student practice SENAI also offers pneumatics and CLP simulators so that students can practice and test projects at home.

3.2 E-learning Courses

The entire SENAI-RS institution uses at least 3 different custom e-Learning platforms to give students a collaborative environment, common space sharing and teacher feedback. The first one is TELEDUC, a software developed by the University of Campinas (Unicamp -Brazil), under free license. TELEDUC has been subject of research for the past six years (Otsuka and da Rocha, 2002). The second is WebEnsino (Ilog, 2006), developed and commercially offered by ILOG – Brazil, licensed to SENAI-RS. The third one is the MOODLE platform (MOODLE, 2006), used recently under free license (GPL) in this project.All courses, elaborated by the SENAI educational personnel, follow the competence-based model aimed at professional skills that are coherent with the contemporary market and productive world demands. Therefore, the courses follow a specific methodology, called the Challenge Methodology

(SENAI-DN, 2002), that has his main development approaches in the PBL (Problem Based Learning; SENAI-DN, 2002) and in the Problematization Methodology (Berbel, 1999).

4. PROPOSED ENHANCED VERSION

As realizing the advantages hidden in this educational tool, SENAI an UFRGS proposes to enhance the deriveSERVER system in order to become a full collaboration learning environment for teaching mechatronics principles and applications on automation systems in the industry. SENAI plan to use the mixed reality experiments to enhance students’ education. With this system the students can be at home performing experiments with also collaborative groups, promoting “distributed learning” (Auer et al., 2003) and “team learning” (Faltin et al., 2002) by the use of the virtual learning environment (VLE). For this system the VLE used will be MOODLE (MOODLE, 2006) with created courses of electro pneumatics systems according to the SENAI’s educational methodology For educational use and to improve the robustness of the system a few tests with students will be made to identify faults and difficulties of the system.

Fig. 5. Proposed enhanced version of the deriveSERVER.

The system, as it is today, hangs on software dependencies that are not desirable neither to the University of Bremen nor to the SENAI and UFRGS. Research for an appropriate VRML viewer that can run on other browsers, such as Mozilla, and be

independent of Microsoft ActiveX Technology will be made. To promote implementation of enhanced control techniques, a PLC will be attached on the system. This way, students can drive experiment equipments by programming the PLC. This will occur first through the hyperbond interface than could be expanded to be one more plug-in that communicates with ROMAN.For even more reality to the experiment a research of continuous system adaptation is planned. With this adaptation, control techniques, such as PID, can be used.To provide educational back up to the student, SENAI will create a complete pneumatics equipment use and applications in mechatronics course. This course will be also written in English for use in the University of Bremen as cooperation exchange.All desirable students’ interaction is shown in Fig 5, where the system enhanced version is depicted. With these enhancements students can perform several hardware and software combinations using the hyperbond interface. The connections between different hyperbond interfaces (of different purposes) is made in the virtual experiment (VCK) that is available through the internet, LAN or WAN. An user mobile hardware for remote or local interaction is also subject for the enhanced version. Desired is also a interface to allow external simulator interaction.

Fig. 6. Simulated and real systems interaction.

The project enhanced system will be capable of interaction with remote/local software/hardware. The main idea is to allow students to interact both with real and virtual systems; either at the technical plant or at the computer-based automation side. The possible interactions are shown in the Fig. 6.

5. RESULTS

5.1 Hyperbond enhancements

The hyper-bond SW (software) interface was modified to support, additional to FESTO EasyPort HW (hardware), OPC (OPC Foundation, 2006) communication, and parallel/serial port HW communication. Thanks to the client-server architecture (communication sockets) of the hyperbond to the experiment manager (ROMAN), students can use local hardware attached to simple parallel PC port to interact with the experiment.The Fig. 7 illustrates hardware interactivity and his communication interfaces. The discontinued arrows show the enhancements in the system interactivity.

Students can manipulate all the interfaces in a single experiment locally or remotely.The virtual pneumatics workbench (VCK interface), accessible through the internet web browser, links the hyperbond I/O to every software or hardware attached to the system.

Fig. 7. Hyperbond new communication interfaces.

5.2 PC parallel port hardware as hyperbond I/O

Using the modifications in the hyperbond software to allow parallel port I/O interaction a simple hardware was developed for an inexpensive hardware data acquisition, since almost all computers have a parallel port. The developed hardware expands the original 8 bits of the parallel port to 64 bits of I/Os (32 inputs and 32 outputs), so that it can use twice more equipments then the EasyPort (16 I/Os) from FESTO, used in the original project of the deriveSERVER. All electronics used to create this inexpensive hardware (circuit) are digital ICs commonly found at the market. The acquisition part of circuit uses four 74LS151 (1-of-8 Line Data Selector/Multiplexer) connected in parallel. The software (driver) perform 8 successive reads, reading 4 bits each cycle, creating the correct 32 bits variable. The control part uses four 74LS164 (shift register) and four 74LS573 (latch).

The first 74LS164 has his input connected to parallel port sending 32 bits serialized. The last output (QH) is connected to input of the second 74LS164 as a carry chain. Each 74LS151 has its outputs connected directly to inputs of one 74LS573. When the software has finished the 32 bits serial flow, it activates a parallel pin connected to 74LS573’s output enable (/OE).As described the developed board (hardware) is very simple and even students can create it themselves at home.

5.3 OPC-DA compliant client in the hyperbond interface

The OPC-DA communication interface is very reliable and broadly used. The most advanced and largely used simulators, SCADA softwares and industrial controller devices (CLPs) already come with OPC-DA Servers implementations. For that purpose a simple interface was developed to allow OPC Server to deriveSERVER interaction through an enhanced hyperbond with OPC client interface. The implementation is very simple using ATL-COM objects.This new hyperbond interface allows communication with any OPC-DA compliant servers. This way, largely extending the interaction of new experiments (in the deriveSERVER) with external devices and simulators.

5.4 Possible interactions

With the hyperbond new interfaces, students can use either own hardware or own simulator compliant with any of the interfaces. SENAIs PLC logic simulator, named Relés, was modified to address his inputs and outputs directly to the PC parallel port, so the hyperbond interface reads/writes the parallel port interacting indirectly with the simulator. The same can be accomplished with an OPC-DA compliant simulator or software.

5.5 E-learning Courses and integration

Special courses in the e-learning system MOODLE were developed to help student perform and understand the theory involved in the mixed reality experiments. Educational material was carefully designed to embrace Portuguese and English languages. The selection of the language is controlled in the MOODLE system. The deriveSERVER system was integrated in the MOODLE interface so that students can learn collaboratively in a common virtual environment (VLE). The VLE contains didactic materials divided into 4 major courses:

• Devices Manual• Use of the deriveSERVER system• Experiments Guide• Basic Eletro Pneumatics

The first course contains all documentation of the eletro pneumatic devices involved in the experiments separated into sensors, actuators and other devices. The second course contains didactic material (step by

step tutorial) used to teach students to perform experiments using the deriveSERVER. The experiment guide course is used to control the sequence of experiments (in the deriveSERVER) that the student should do accordingly to his performance. The last course, but the most important, must contain all theory material of basic pneumatics commonly used by teachers in SENAI classes.

Fig. 7. MOODLE Devices Manual course at SENAI.

6. CONCLUDING REMARKS

This work is a part of cooperation between the University of Bremen, UFRGS and SENAI.The system allows integration of different remote equipments or simulators providing a common environment to remote collaboration of remote experiments. This is especially important to cost effective remote experimentation, since among remote experimentation partners, real hardware must not be duplicated acquired.EAI 2.0 is today not yet supported by other plug-ins different from Cortona, despite all tests with different VRML plug-ins we couldn’t change this undesired dependency. This has direct effect on the dependent use of the IE web browser and the Windows Platform for the system.

Fig. 8. SENAI Caxias deriveSERVER installations.

This project was estimated to fulfil preliminary goals in one year. With the enhancements success, SENAI

decided to extend the project duration in another semester of development and testing.The Fig. 8 depicts the current SENAI installation of the enhanced systems that is slightly different from those displayed in the Fig. 3 from the installations of the Bremen University.

ACKNOWLEDGEMENTS

This project has been partly supported by SENAI-DN, SENAI-RS and CAPES.Especial thanks to the researchers of the ArtecLab in the University of Bremen, for the collaboration and information exchange.

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