training in automation networks using virtual - indiana university

ETD 351

© Conference for Industry and Education Collaboration American Society for Engineering Education

February 2-4, 2011 San Antonio, Texas

Training in Automation Networks using Virtual Reality Machines

Manuel E. Macías, Victor H. Martínez Electrical and Computing Engineering, ITESM Campus Monterrey

Av. Garza Sada 2501, 64849 Monterrey, N.L. México [email protected], [email protected]

Abstract Nowadays companies need highly qualified professionals to solve tasks in the area of complex automation systems like the Automotive Industry, in which the processes communicates through field networks. However, many universities teach students about Automation Networks in laboratories with inadequate equipment and practices that usually don’t represent real automation systems. Likewise some universities use only buttons and lights to represent the industrial components. This lack of equipment causes that students poor learning of the concepts about Automation Networks; even many students can be disoriented and bored about the subject simply because they can’t understand the concepts with exercises that do not represent a real manufacturing system. Using Virtual Reality Machines (VRMs) to emulate industrial processes, universities can offer improved courses in this Area. The practices would be a representation of real process systems that are found in many industries. Students can now learn how to program the automation system, field networks, and communication services using standard tools to configure, program and communicate the automation controllers. Once the automation machine is programmed, the system is ready to communicate with other programmable controllers using different field networks and communication services. The VRM then interacts with the process memory image of inputs and outputs of the controller, emulating a real process wired to the I/O controller modules. With this approach, students can get a better understanding on how to solve machine tasks, automation networks, and communication services by the time they develop a complex automation system. Universities with this type of laboratories prepare professionals that are better qualified for working in industrial automation with complex systems, such as Automotive, Petrochemical, Water, and Energy Distribution. Index Terms Automation Networks, PROFINET, Training, Programmable Controller and Virtual Reality Machines Introduction In these days the automation systems involve interaction with different processes for perform complex manufacture tasks which create the technology products that sell around the globe. The companies now demand even more competitive engineers not only with strong knowledge but with plenty of experience, well prepared, able to achieve successful the emerging day by day problems5. This experience and knowledge can be acquired in sessions of automation network laboratory.

ETD 351



The implementation of a laboratory for automation networks needs two or more programmable controllers, a distributed inputs and outputs, personal computer and minimum of two processes to be controlled. These last two items are the most expensive and represent at least fifty percent of the cost of the laboratory and also the processes need to be prepared for interaction between them. Because of the high cost that its represent many universities (mainly in Latin America, Middle East and Africa) cannot implement these types of laboratories. Even in universities of developed countries have an automation networks laboratory to practice, the learning of the student is poor, because is very common that those installations are equipped with some lights indicators, buttons, pneumatics pistons, inductive sensors and switches intending to substitute an automation plant. Universities cannot continue teaching automation networks in the same way. The students need to practice how create an automation program in a programmable controllers and how configure the automation networks, to create a manufacture automation systems like exist in the real factories. The purpose of this paper is to explain how to use Virtual Reality Machines (VRMs) as processes when the students are learning automation networks. The learning of automation networks not only implicates how to configure the programmable controllers and automation networks. But also implicates how to create automation software to control the industrial plant and the interaction between the different processes and controllers. For the last year in the Laboratory of Networks for Automation at ITESM Campus Monterrey in the Department of Electrical and Computing, the students have learned how to configure and create automation software that interacts between different processes using Virtual Reality Machines. They developed complex automation systems that communicate between different programmable controllers using field networks as MPI, PROFIBUS, Industrial Ethernet and PROFINET. VRMs for automation networks The VRM is a digital representation of a real system, at this moment the laboratory of Networks for Automation has four different digitals models that are based on didactics models from Staudinger GmbH. These models consist a Transporting and Sorting Line, a Process Line, a Three Axis Portal and an Elevator Tower of four Floors. The last model is the most representative in the context of automation networks, because is common to see them in apartment buildings. VRM was created in CAD software such as Solid Works, Solid Edge or Inventor. The different parts of the process are imported to LabVIEW. The states of the actuators are represented by animations created for the different machine elements. The most common machine elements are pushers, doors, conveyors and chains belts. The states of the sensors are activated by the positions of the machine elements and by user commands.

ETD 351



VRM of Four Floored Two Elevator Tower

The main characteristic of the VRM for automation networks is to represent a process that needs to communicate with other process that shares a common purpose. The models of the Sorting Line and the Three Axis Portal were designed to be used in an automation network. The Transport and Sorting Line is a process that sorts the parcels in the different places depending of the color, and the Three Axis Portal process picks up the parcels of the different places depending of the user petitions. The purpose of integration of these two models is to create an automation system that sorts and picks up the parcels for a future manufacture process. The Programmable Controller Platform for Automation Networks Laboratory Network Configurations The programmable controller selected for the laboratory is the SIMATIC S7–315F – 2DP/PN from SIEMENS. The controller has a high performance of communications in the three field networks, which are incorporate in the default hardware: MPI (Multiple Point Interface), PROFIBUS and PROFINET. MPI is a protocol property of SIEMENS. The last two are open

ETD 351



field networks. A field network is the physical element through which the data is transmitted and the communication service is the way that the data is transmitted. MPI and PROFIBUS are networks based in RS-485. These networks are deterministic and can be used for real time communication. The maximum length of the networks is 1, 200 meters between nodes. PROFINET is a very new field networks, that works over Industrial Ethernet, but the main difference between Industrial Ethernet is that PROFINET support real time and deterministic communication between controllers. Services communication The programmable controllers CPU 315F-2 PN/DP can incorporate many communication services that make the controller more flexible for communication tasks. The communication services are designed for transmit information and programmable controllers. Some services incorporate many functions, but these functions depend of the programmable controllers, for example with SIMATIC S7-400 is possible to configure a service that call a function to STOP an specific CPU that can be located a remote station. Global Data Communication is a communication service designed to transmit small amount of information between controllers. This service only works on the MPI field network and is configured in a table where the user selects the memories, inputs and outputs to exchange with other programmable controllers that are connected in the same MPI network.

Configuration table of Global Data Communication

Distributed I/O is one of the most used services in industries. It extends the inputs and outputs of the programmable controller to remote I/O module which can be in a place separate by hundreds of meters (distance that is common in factories). The remote module is cheaper than programmable controller. The service can be configured under PROFIBUS and PROFINET. Decentralized I/O is a service that is similar to Distributed I/O. The main difference is that they shared the I/O between programmable controllers. It only works in a PROFIBUS field network. The service validates the communication between the controllers, for example; if one controller changes its operation status from run to stop the others controllers will fail, because the error of I/O is interpreted by the controller as fail of rack. Component Base Automation (CBA) is one service that works on PROFINET network. This service is created for the purpose of creating modules of technological functions for separate the industrial plant in single machines and process. The main idea is create sub processes that make more flexible the process for possible changes.

ETD 351



Component configuration of the service CBA

S7 communication is one of the most important services. It works on MPI, PROFIBUS and PROFINET. This service is programmed in two parts: the configuration that is created in the NetPro and the System Functions Blocks that are programmed in the user program. The service incorporates commons functions like send, receive, put and get information from other programmable controllers.

S7 communication configuration table in NetPro

Automation Software The students task is to create an automation program in Step7, this program can be developed in basic languages; ladder diagram, functions blocks and statement list. SIEMENS offers in the professional version of the Step7 two additional languages Graphical (Graph) and Structure Control Language (SCL). The advantage of ladder diagram is that it is a graphic language easy to debug complex applications. Statement List is an assembler based language that has many advantages especially in applications that require high performance because is possible to minimize the code of the programmable controller, and can reduces time of execution of the main cycle. Functions Blocks is a language that represent the AND, OR and XOR circuit gates and its performance is similar to the ladder diagram. Graph language is a graphical programming interface for sequential controls that provide a clear overview of the functional scope. SCL is a

ETD 351



language based in Pascal with the difference that incorporates the typical programmable controller’s elements such as timers, counters, inputs and outputs. Configuring the programmable controller The first step to create an automation task in Step7 is the configuration of the Simatic station. The student needs to incorporate an S7 controller in the project. The S7 station is configured adding the components that are in the S7 Station to automate. The minimum configuration includes adding the next elements: the rack, power supply, control process unit, I/O modules and analog modules. The S7 Station configured must to be the exact match of the S7 station that is in the laboratory. Some important parameters of the configuration are the MPI, PROFIBUS and Ethernet addresses. Programming the automation task The student develops the software to control a single process like a Four Floored Two Elevator Tower. The process is connected to a programmable controller which performs the actions of turn on / off the different actuators depending of the user code that was programmed. When the automation task was resolved, the student is ready to decide which network field and communication service are required for the application, other important aspect is the information needs to be transmitted to the others programmable controllers for synchronize the processes. Configuring the field network and the communication services The automation network is configured in two apps of Step7. The Hardware Manager (HWM) is the app where the user configures the S7 Station. Some automation networks like PROFINET CBA needs to change some special parameters like the communication load of the CPU this id only possible in the HWM. The Service of Distributed and Decentralized I/O are configured in the HWM. The other application that it used is the NETPRO this application bring a graphical view of the different networks. These tools are used to configure the Global Data Communication and the S7 Online table to indicate the communication partners. CBA uses other application that is not included in the Step7, that app is called SIMATIC iMAP.

ETD 351



SIEMENS Networks configuration in SIMATIC NetPro

Testing and Debugging the Automation System When the different automation tasks are resolved and, the network and service are configured, the system is ready to be tested, one problem of testing with a real mechanical devices is the fact that people fear to damage the machines like pistons, motors, robots, conveyors, etc… with the VRM fear will not exist because is not possible to damage a virtual automation process. Eliminating the factor if possible damage to the system the student is more comfortable to continue validating the automation instructions. Making the validation easier, the student can find quickly errors of the automation tasks, creating a better way of learning. When the student is testing the automation system is probably the stage when it is learning more details about the field networks and the service that chose to communicate the different process. When the ambient of testing is not comfortable, the student only will want to resolve the problem not matter the mean. One important characteristic is the physiological impact of the student, if the ambient is not appropriate the person may start to think that not like develops instructions for automation systems. The interaction between the VRMs with the programmable controller The VRM is a software application that runs under Windows XP/Vista/7 in a personal computer. This machine has the characteristic to communicate with a programmable controller. The states of sensors and actuators are transferred to I/O memory. All programmable controllers of any brand have three data types that are update in the start, during or at the end of the main cycle. The most common nomenclature for these data types are the inputs, marks and outputs. The inputs are the signals of sensors, the marks are the auxiliary memory that the user can use for any purpose, and the outputs are signals that turn on / off the actuators.

ETD 351



The VRMs write the inputs and read the outputs states that are in the work memory of the programmable controller. If the programmable controller has an I/O module the VRM cannot write the inputs in the same space of memory that the module use. The state of the actuators in the VRM only reacts depending of the instructions programmed by the user. There source codes that can communicate with programmable controllers (at any filed network) through ACTIVEX or .NET extension. For communicate with SIEMENS S7 programmable controllers was necessary develop a library to transfer the different data types. The library was created in LabVIEW because it is used to develop and program the animations of the VRM. The library has multiples functions, for example it has one for configure, open, close, write and read any data type (inputs, outputs and marks). The configure function makes a connection through S7 Online or TCP/IP for communicate with the programmable controllers. S7 Online is the protocols and physical access used by Step7 to communicate with the programmable controller. The TCP/IP uses the network access to communicate with the programmable controller that is connected in the Ethernet network. The open function only creates the session with the information that was configured. The read function receives the information of the inputs, outputs or marks. The write function sends information of the inputs, outputs or marks. The close function shut down the connection and eliminates the session of communication. The library can work in any field network that is supported by the programmable controller and the computer, the information is transfer in automatic way. The student can choose the field network to communicate with the controller, this make the process of communication transparent. The information of the state of the sensors and outputs is transferred cyclically. The time for transfer the information depends of the speed of the personal computer and the programmable controller used for the automation process (the time between each write and read is less of twelve milliseconds using the CPU315F - 2 DP and the SIMATIC CP 5611).

Connection process using the S7 Online

Example the Four Floored Two Tower Elevators The exercise of two towers elevator consists to attend the call buttons that are outside of each tower. For example in the first tower the elevator is in ground floor and one user press the call

ETD 351



button of the fourth floor and if the elevator of the second tower is in the fourth floor. The second elevator will give the service. Other example is when the elevator of the first tower is moving up and a user press the call button to go down of the same tower, the elevator of the second tower will give the service to attend the call button. The main problem of the two towers of elevators is to minimize the time, which the user wait for the elevator to arrive and transport the user. Each Elevator Tower is controlled by individual programmable controller that makes necessary the use of automation networks for communicate the two processes to synchronize the operations to attend the user. The students work in teams to create the automation software of the system of Four Floored Two Elevator Tower, the main exercise consist in minimizing the waiting time of the user. Also the students need to design a human-machine interface (HMI) to communicate with the system of elevators. The HMI has the send and call buttons of each tower like a real elevator. The system has two HMI Panels the particular model is the OP 177B PN/DP from SIEMENS, this type of panel can communicate through any of the three field networks. The VRM and the HMI Panel were connected to the controller through MPI field network. The field network to communicate the controllers is PROFINET and the service used was Component Base Automation, this service was configured with SIMAITC iMAP (the tool of SIEMENS for this automation concept).

The connections of the different devices of the system of Four Floored Two Elevator Tower

The representation of the system shows how the students use two networks for the automation; Multiple Point Interface was used for local connection with the HMI and the VRM. The PROFINET was used to coordinate the two real time processes. Extending the VRMs for using with other programmable controllers There are many applications to transfer data to the programmable controllers one of the most used tools is the OPC Severs (Ole for Process Control). The common applications that offer communication with many brands of programmable controllers are WinCC (from SIEMENS),

ETD 351



Wonderware (from INVENSYS), RSLINX (from Rockwell), NI OPCServer (from National Instruments), INAT OPC Server, etc… The development software like Visual Studio, LabVIEW, Delphi, etc… can transfer data to the OPC Server through data sockets. OPC Sever is designed to work with several programmable controllers of many brands, for example the NI OPC can communicate simultaneously with a multi programmable controllers of SIEMENS, MITSUBISHI, GE FANUC and Allen Bradley. For communication with the last brand is possible to use the libraries that LabVIEW incorporates for EtherNET/IP (Ethernet Industrial Protocol) communication with RSLOGIX 5000 controllers. Benefits of the VRMs The automation network training with VRMs has many advantages, to make students as well as universities benefit using VRMs as processes. Benefits for the university Low cost. Using VRMs the cost is significantly reduced, the automation processes for control to integrate are the items that are most expensive. The programmable controllers, the development suite, the personal computers, and the automation practices represent less of fifty percent of equipment. Brands like SIEMENS and FESTO can offer significant discounts to universities for acquire automation controllers and development suite. Diversity of exercises. The instructors and professors can easily change the practices of the automation networks or even creates more exercises with others VRMs. The field networks and services can easily change the practices making the exercises more complicate and interesting. Better education. The students can learn better and more comfortable. The university can makes better professionals, more prepared and interested in the field of automation networks. It can be a key factor for the companies that operate in different branches like the automotive, petrochemical, water distribution, paper, electronic and mechanical industry. Motivated student. The student feels more prepared and with better skills, when this happens the people who took the class recommend it to the other students of many careers like mechatronic, electronic, electrical mechanical, digital systems and robotic. Evaluation sceneries. The professors and instructors can prove the automation task in different scenarios where the system need to response, this to verify that the automation software works correctly in the worst cases that the process needs to act. Benefits for the student Experience. The student does not leave his education without knowledge about the programmable controllers and development tools. The projects of VRMs processes are hard and demands high knowledge of the automation networks. The student learned the concepts of the field networks and services that are demonstrated with the automation system implemented. Deeper understanding. The VRMs are model in 3D, the students can watch the different operation of the sensors and actuators without code in the programmable controller nor fear of damage the system, this make possible that students interact with the VRM better compared with a real system, making possible that students can visualize the whole interaction between processes.

ETD 351



Real processes. The VRMs are based in real processes, the actuators and the inputs have the same characteristics functions of the real machines. The automation software can download to programmable controller with the real process wired in the I/O module, proving that the real process and VRM are equal. Comfortable students. The students are more optimistic about the automation tasks; they can make any quantity of errors in the VRM without the fear of damaging the system. The students learn errors that are more common in the mechanical systems. Other aspects that the students learn is safety in the automation processes, because with the VRMs are possible to simulate errors in the sensors, actuators and mechanical parts of the systems. More time to work. The students get more time to work. This is possible because is very easy to duplicate the VRMs, the laboratory only need a personal computer, a programmable controller and VRM license for get other station for two students. The cost per station is low compared with a station with real a process. Conclusions The VRMs reduce the cost of implementation of laboratory of automation networks. Using VRMs the course can take more technical material about important aspects of real time communications like time synchronization and motion control. The SIMATIC programmable controllers perform a real time communication through different networks so they are used to explain different aspects about protocols and communication systems. The course has practices of the different communication services using VRMs as process to demonstrate the specific capabilities of the services. The students learn the process to create an automation tasks using Step 7 to control the VRMs that are connected to programmable controller. The students need to know how the VRMs are connected to the programmable controller. It is necessary to explain that a real process will interact the same way as a VRM does. The VRMs makes the course “Automation Networks” one, were the students can learn the concepts of automation like programming, equipment configuration and the implementation of a complex automation system. The students interact with processes without the fear of make mistakes, making the process of learning more comfortable and interactive with real processes that are represented in VRMs. This condition make possible to develop the mental visualization about how the processes works and its relation with the programmable controllers and networks in the automation systems. An important aspect to consider is that many students will see the VRM as a video game, so is very important to explain how the VRM represents a real system. When the students finish the automation task using the VRM they can download the program to the programmable controller that has the real system connected to its I/O modules. This is very useful to demonstrate that the VRM works equal to the real system.

ETD 351



Bibliography 1. Berger, H. (2007). Automating with STEP7 in STL and SCL. Erlangen: Publicis Corportate Publishing.

2. Berger, H. (2008). Automating with Step 7 in LAD and FBD. Erlangen: Publicis Corporate Publishing.

3. Erick A. Salazar, M. E. (2009). Virtual 3D Controllable Machine Models for implementation of Automations Laboratories. IEEE Frontiers in Education Conferennce (pp. T2C1 - T2C5). San Antonio: Electrical and Computing Engineering, ITESM Campus Monterrey.

4. Gomis, M. G. (2007). A Chemical Process Automation Virtual Laboratory to Teach PLC Programming. Int. J. Engng, Vol. 23 No. 2.

5. Guridi, M. E. (2010). Computer Emulations t Support Training in Automation. In L. A. Guedes, Programmable Logic Controller (pp. 151-160). Croatia.

6. Jeffrey Travis, J. K. (2008). LabVIEW for Everyone. Upper Saddle River: Prentice Hall.

7. Josef Weigmann, G. K. (2003). Decentralization with PROFIBUS DP/DPV1. Erlangen: Publicis Corporate Publishing.

8. Manuel E. Macias, E. D. (2007). Extending the Laboratory Concept with Computer Emulations in Automation. IEEE Frontiers in Education Conference (pp. S3G-18 - S3G18-22). Milwaukee: Electrical and Computing Engineering, ITESM Campus Monterrey.

9. Mueller, J. (2005). Controlling with SIMATIC. Nuremberg: Publicis Corporate Publishing.

10. Raimond Pigan, M. M. (2008). Automating with PROFINET. Erlagen: Publicis Publishing.

11. Rick Bitter, T. M. (2007). LabVIEW Advanced Programming Techniques. Boca Raton: CRC PRESS.

training in automation networks using virtual - indiana university

Documents