Virtual Reality Machines to improve training in Control and Automation

Transcription

1 Virtual Reality Machines to improve training in Control and Automation Abstract. Alfredo R. Izaguirre, Manuel E. Macías Electrical Engineering Department Tecnológico de Monterrey Monterrey N.L., México Current market requirements in industrial sector have motivated the development and adoption of digital manufacturing software tools for control systems design, training, and process optimization to validate and ensure the production system s programming control and automation equipment. This practice, known as Virtual Commissioning, emulates the real process behavior in a computer software environment. This technology represents an opportunity for education where the virtual emulation of real processes can be used to equip Control and Automation laboratories where students can test, validate, and debug their control and automation strategies, contributing to student formation and solving the need of having costly, real industrial machinery to reinforce the understanding of classroom theory, with practice. This is an excellent option for universities without enough resources, mainly in developing countries, where laboratories are commonly equipped with improvised homemade systems that don t represent what students will face in an industrial environment. However, the integration of this technology in education cannot be transparent, as a majority of present market applications are not designed for education and others, don t cover the actual education needs. Because of this a set of features, that intends to enhance the advantage of this type commercial applications is proposed its principal objective is to integrate and motivate the spreading of these tools in education and make them affordable for low-resource universities. In this paper, an application called Virtual Reality Machine (VRM), that covers the set of features needed in education, is introduced. A methodology for VRM creation is also proposed, supported by a set of LabVIEW applications consisting of CAD solid creation, conversion process, assembly process, animation process, and connection process, followed by the automation validation process. Finally, an example of VRM capabilities, scope, usage, and impact in student formation is presented. Introduction. The consumption world market constantly is increasing and changing its requirements. Day by day more and better quality products are asked for customers what shrink the market product life cycle, encourage a more extensive product variety and reduce product launch times. Moreover this is happening while market price erode, global sourcing increases and quality product must to be keep high 1. This represents challenges that manufacturers have to face in a high competition environment what forces companies to implement technologies, processes, and practices that enhance their competiveness and differentiate from the others. Product improvement, constant product offer changing, process standardization and optimization, price and cost reduction, quality, etc. are some of the practice that companies implement daily oriented to accomplish new market requirements. However some of these practices appear to be opposed, by one side having a fresh product offering requires constantly production lines changing what opposes to cost

2 reduction and process standardization. Then to remain successfully in market and in some cases even to survive, companies must be able to keep a constant innovation. This targeted to look for necessary practices and tools that support them to face actual challenges and assurance them that changes in any production aspect, will impact in the planned way all related company sectors. Market globalization has forced that companies increases production quotes motivating that these open plants in other countries, increase production lines, change or totally replace their process and the way of fabricate goods, etc. This growing has brought a bigger organization structure inside companies, more process and equipment to control and manage. In addition at the same time, practices like lean manufacturing, six sigma, QFD, ISO quality certifications and other production quality activities are being implemented. This is translated in more product s specifications, processes and procedures information to handle. For solving this, many software tools focused to different sectors and with different scope have arisen as support for manufacturing companies CAD/CAM (Computer Aided Design/Computer Aided Manufacturing), CAE(Computer Aided Engineering), CAPP (Computer Aided Process Planning), PPC (Production Planning and Control).Some of these can be implemented individually, however in the highest level these are integrated in a software manufacturing suite known as PLM (Product Lean Manufacturing) whose principal objective is to enable companies to achieve the business imperative of timely and cost effective product launches. This software tools oriented to improve and enhance manufacturing s resources and production are known as Digital Manufacturing tools (DM) as merge the virtual and physical manufacturing world. Digital Manufacturing (DM). DM is an integrated suite of software solutions that supports manufacturing process, tool design, and visualization through 3D virtual simulation tools. The factory environment and the production process can be modeled including buildings, production lines, transportation, workflow, and other facilities that represent the complete physical production environment 1. On these environments, manufacturing engineers can validate and optimize the processes, designing, synchronizing, and validating production lines, robotic workcells, machine centers, production equipment, control systems functionality and requirements completely prior to the purchase, installation, and commissioning of physical equipment. In essence, DM facilitates the complete view of product and process design as integral components of the overall product life cycle. This virtual validation and commission have turn more important lately as the looking for major production and trusty processes have causes that totally automated complex manufacturing systems be used more frequently in industry. Because of this there is a section of DM that allows manufacturing engineers to merge virtual models of production equipment with automation and controls what enables the complete validation of controls logic, automation strategies and HMI functionality in a process called Automation Simulation 2. This extended level of manufacturing process design let executing perfect launches and production changes by validating totally all aspect related with the process from the tool and machine design to the final automation strategy. Automation Simulation. Automation simulation involves the entire process of modeling, animation, evaluation, optimization, and validation of controls systems for automation equipment and systems in a

3 virtual environment. Which represent manufacturing workcell with 2D image or 3D solids elaborated in CAD that may represent from single process with primitive graphics to elaborated production systems, including multiple robots, complex tooling and fixtures, clamp automation and PLCs. Automation Simulation intends mimic and simulate the real process to be automated by animation sequences, with the objective of commissioning and debugging total or partial control logic changes of the manufacturing workcell 2. This can be done even weeks or months before the real machinery be present in shop floor, as control logic strategy is simulated in virtual cell where interaction and control sequences of tooling, robots, clamps, safety devices, electrical, hydraulics and pneumatics, etc. can be tested. Inside automation simulation this practice is known as virtual commissioning and helps to assurance that any change in automation system will cause the desired impact in production, providing to manufacturing and controls engineers an opportunity to ensure controls design before production starts. Virtual Commissioning. Virtual commissioning principal objective is assurances optimizes and validates control and automation implementation and changes in virtual automated production systems prior to real commissioning. This is on state-of-the-art digital manufacturing simulation technology; such depends on advanced simulation methods that truly represent the merging of 3D virtual simulation environment, to accomplish the level of automation and synchronization required, with the physical automation world of control logic and control platforms that perform the production processes 3. Virtual commissioning is carried out on virtual prototypes of production systems and equipment which are based on direct real model capabilities and appearance. Originally was intended for allowing the debugging of the control code on an actual Programmable Logic Controller (PLC) 3. However its scope goes further as allows the user efficiently and cost effectively optimizes and validates any implementation or change in manufacturing processes control strategies, testing different control scenarios, accelerate learning curve and enables control engineers with the ability to reduce costly errors occurrences, and mitigate risks in a virtual environment well before using real equipment to accomplish commissioning. This Virtual Commissioning features have caused that also be used in industry with training purposes, as learning process can be carry out on this. Virtual commissioning is intended to validate control strategies in virtual production system environment and then move these to real production system. However moving is not necessary as if virtual commissioning stops in virtual environment the control strategy validation can be done anyway what makes it useful for validating control engineers programming skills, as the knowledge necessary for controlling virtual production system is exactly the same for controlling the real one. Then automation simulation can be used with didactic objectives as a teaching tool in automation and control curses as offers a process to control where students can observe the correct or incorrect functionality of their control program. This way, automation simulation supported by virtual commissioning is used for industry and for education. In the first one it has two orientations; production systems optimization and validation, and control engineers and laborer training. In the second one it is used in control and automation courses where final applications are used for supporting engineering student s formation with practice. Optimization and Validation.

4 The virtual 3D world created by automation simulation technologies of solid model product, digital mockup, and manufacturing process simulation goes further that only simulate production systems behavior. As its objective is to assurance a control and automation strategy that can be loaded to real automation hardware and controls a real production systems; making the final link to the actual production work environment by the connection to machine control systems. In addition to model and simulate the machine tool, conveyor line, robotic workcell, PLC, etc; automation simulation generates accurate information capable of driving correctly control systems, shorts the ramp-up of production lines during commissioning and product launch, reduces cost, time, design changes, and risk of errors 2. These advantages represent critical factors in product delivery and ultimately company profit or loss; as production lines, workcells, and control systems must be designed, installed, and deployed in the shortest possible time, working correctly with the least amount of test and validation what has become automation simulation in a key piece for manufacturing industry. Automation simulation gives to production engineers the capability of building virtual production systems based on real automation events. What enable them to virtually model, the most correct physical and logical interface and material handling operations that can occur between the components of workcells and production lines. Because it permits control strategies or production scenario construction for experimentation, that would otherwise be expensive and/or time-consuming. This empowers engineers to try ideas in a dynamic, synthetic environment while collecting virtual response data to determine the physical responses of the control system. During virtual commissioning engineers are typically finding over 100 mechanical and electrical errors in logic, HMI, and drawings per cell 1. Problems are normally found and fixed with minimal disruption to operation as are solved more quickly since engineers can narrow them down to items such as physical connections, confident that the validated control code works. With automation simulation consequences two to three man weeks are saved during startup, saving thousands of dollars in engineering and production labor costs. Training. There are two training orientations. For engineers that carry out added value activities in production systems and for laborer who are final machines users. According to orientation automation simulation objective, scope, and usage are different. In training for engineers usually control or manufacturing ones, automation simulation is used for building virtual environments which can emulates real production systems that are already present on shop floor or that will be in a future. The objective of these training simulations is to serves as a virtual commissioning tool where engineers gain a proper understanding of the process testing control strategies; observe production systems limitations and scopes; known production times and response to process changing. These aspects are principally important for beginner engineers or for new ones in a specific area 2. Once that the virtual environment is built engineers training consist in consecutive virtual commissioning on the same simulation. With the objective of acquire the necessary knowledge for understanding and control the production system. Laborers in manufacturing companies receive training when are hired, when are moved from production process, when new machinery is going to be used or a product change is planned, actual manufacturers constantly draw on to some of these situations what means that laborer needs to

5 be trained frequently. Training for laborers uses virtual environments created by automation simulations tools, but these emulations are not intended for a constant virtual commissioning, the objective is to train machine operators that will use real production systems. With virtual automation simulation is available for operators the virtual model of the real production system connected to a human machine interface (HMI) or a control panel similar to what is used in the real machine 2. Then operators can observe how the machine emulation reacts to control device that is the same that will use in the real machine. With emulation, possible human errors during real machine operation can be illustrated, avoiding the risk of costly machinery damage and above all is assurance that the laborer will known what happens when a human mistake occurs. This is achieves without endanger laborer s health or machine hardware. Training simulators play a significant role in reducing the time for plant to go operation and reduces learning curve time and risks, as empowers the plant operators, to perform the needed tasks needed, with a deeply understanding of the machine that is going to be operated. Education. Automation simulation software tools are used with two orientations in education. The first one is their usage principally in Universities focused in control, automation, mechanical, manufacturing and electrical careers. In universities automation simulation tools are taught principally in advanced engineering courses where students learn about the automation tool itself, its features, limitations, scope, etc. What means that students work with the development environment not with final emulations, as the teaching is oriented to the automation simulation tool. The second one automation simulation orientation consists in using final emulation applications for teaching engineering students and supporting automation and control theory taught in classrooms with practice. This is done in laboratories where students control and automation strategies can be tested on emulation of production systems that are really used in industry, without risk to damage costly equipment. This is done taking advantage of the fact that is also possible carry out all the virtual commissioning process, and never deploys the automation in a real model, just like is done for engineers training in industry. Having this emulation enables students to deploy different control strategies in each one of these, makes possible that they relate with different sensors, actuators, machinery functionality, etc. From this point of view, automation simulation well used in education opens the opportunity of solving the problem that faces many universities in what refers to control and automation laboratories equipping. That is the fact of having a process where students practice the knowledge acquired in classrooms. As usually real workcell used in industry are very expensive and universities cannot paid for some of these. For this reason, the possibility of having a variety of virtual emulations process where students increment, reaffirm or practice automation and control skills is an opportunity for educational institutions for complementing and supporting their automation and control courses, and increase the knowledge, abilities and formation of their students. However in market there isn t a big offer of final virtual application. There are only a reduce number of companies like Festo by Ciros Mechatronics, SIEMENS by SIMIT SCE and EasyPLC that offer 3D final application for carry out virtual commissioning and learning automation. Prologix an independent tool offers 2D final virtual applications, others like Delmia Automation by Dassault Systemes, Tecnomatix by SIEMENS, RsTestStand by Rockweel, Unity Pro by Schneider are oriented to give the software tool for building virtual applications and not

6 offer final virtual environments where students can testing and validate their programs. Then from the reduced vendors group in market, there is a more reduce group that offers final applications for training oriented to Educational Institutions whose scope varies. Application particularities cause advantages and disadvantage between final virtual applications what impact directly in the students learning level. Although the strong impact that can cause these final application in education, these have not been broadly used, as these are not as popular in education as could be. Considering their scope in training the lack of popularity has been motivated principally for particular tool disadvantages and the small number of option in market. Automation Simulation software tools in market. Automation Simulation is practically new and has been exploded and developed only for a reduced group of software vendors. The software solutions present in market are very different, everyone with its own particularities and scope. Differences are found principally in aspects like origin, target sector orientation, cost, origin country, visualization capabilities, connectivity supported, licensing, usage complexity, integration level, programming environment, performance, flexibility, graphics quality, etc. 4 The origin of the tools present in market varies as different companies whose orientation are sectors some way related to manufacturing and automation have created these tools, or some others have been developed for a small group of individual programmers with specific purpose. Origin seems to be closely related with tool particularities and scope. Some aspects of the software tool developer company as expertise, know-how, objective, availability of means as previous software developments, products portfolio, etc. dictate some of the principal features of the tool and therefore its scope. Origin of the tools refers to orientation of the company that created or commercializes the software tool. Principally there are three origins of the tools present in market. 1) PLM software tools. 2) Automation hardware and/or software vendors. 3) Software tool from Third Party. PLM software tools. Companies that develop this kind of tools are the beginners in this field and who more are developed and exploded the automation simulation and virtual commissioning concept; the scope of these tools is extended. These are the most broadly used in industry by big companies like GM, Ford, Airbus, etc. as are supported by a renowned company. There are principally two PLM software vendors that offer automation simulation tools inside their product portfolio. These are Delmia from Dassault Systems powered by IBM and Tecnomatix powered by SIEMENS. From these with previous experience in CAD/CAM and CAP software Delmia is the beginner of this technology and who establishes and defines the automation simulation and virtual commissioning concepts, Delmia Automation is the tool offered for this vendor 2. Tecnomatix is more recent and arises from the integration of Unigraphics with SIEMENS; it offers a tool called em-plc oriented to virtual commissioning with SIEMENS s PLCs 5. Automation Hardware or Software Vendors. Automation tools that have been developed and are offered in market for automation hardware manufacturers are part of this classification. In automation technology software is closely related and necessary for using automation hardware. Companies that are automation hardware vendors

7 like SIEMENS, Rockwell, Schneider, ABB, etc. offers in their product portfolio different software application oriented principally to own PLC programming and PLC emulation, some of these also offers automation simulation software that is intended for being virtual emulations developing software. The resulting applications vary in visualization, scope and complexity depending of the vendor. Visualization of these tools goes from primitive 2D objects to importation of 3D solids created in CAD; the scope of these tools is principally oriented to validate PLC programming. Despite these tools don t offer the features and capabilities that offer PLM tools and is scope is more reduced, as its principal objective is to validate automation and control PLC programming, these are considered as automation simulation tools. The principal feature of this kind is that are compatible only with developer automation hardware. SIMIT by SIEMENS, RS TestStand by Allen Bradley and Unity Pro by Schneider are examples of these. Software tools from third party. The origin of tools in this classification is very heterogeneous some of these are developed by software companies with orientation to automation. Despite that aren t part of PLM solutions some of these are supported for renowned software companies with brand positioning and expertise in automation. These are robust and have a high level of integration with proprietary and external applications. Some examples are EasyVeep, Cosimir PLC & Ciros Mechatronics by Festo, InControl and InTouh from Wonderware suite by InvenSys. Tools developed by software companies without automation orientation but with expertise in software developing are also in this classification, either in independent way or by joining with automation hardware manufacturers, taravrcontrol by Tarakos is an example of these. A third division what is principally intended for own training and is the most varied group is integrated for automation simulations tools created for individuals or little groups of programmers principally automations professor or PLC fans, oriented to helping to understanding PLC programming some of these tools have an extended scope and offer other possibilities. However because their origin these aren t so robust and their capabilities are poor compared with tools in others two classifications, EasyPLC, SPS-VISU, Prologix are examples of these. In table 1 in appendix A in the end of the paper is shown a brief resume of the principal features and capabilities of these 12 automation simulation tools in market. These, are the most common used, and cover almost all the tools present in market. In case of some omission, tools mentioned describe well the status and capabilities of simulation tools in market. From table 1 em-plc and Delmia Automation are the most used in industry principally in big companies as have a high integration level and capabilities, however the licensing cost of the tools is high. InControl and InTouch are used for automation companies, who develop final application for industry these are oriented to developing and are based in 2D visualization, licensing is required. RS TestStand Unity Pro, SIMIT in industry version are oriented to middle size companies where are used for manufacturers and for external automation companies for validating PLC programs, these only work with hardware from Allen Bradley, Schneider Electric, and SIEMENS respectively licensing is required for it use. SPS-VISU has achieved integration with SIEMENS 10 however visualization capabilities is poor as only uses 2D graphics. taravrcontrol is also a developing tool final applications this use OPC server what makes possible communicate final application developed on this with any PLC 6 however licensing and somebody that develop applications are necessary. The rest aren t intended for being used in

8 industry as are created for small developing companies, EasyPLC, offers powerful visual process emulations, PLC and HMI programming environment and a suite called machine simulator for building virtual applications. The principal objective of these tools is to be used as virtual environment developing software and don t offer final applications for practicing only EasyVeep, CIROS for Mechatronics and ProLogix are final applications EasyPLC and SIMIT SCE offer some examples, but the rest are developing tools what makes necessary buying the software or hiring a company that develop final applications. All these tools require licensing whose price varies according with the tool. Features for Virtual Commissioning in Education. Despite that automation simulation is practically new and that there aren t and extended offer of these tools in market this technology is being adopted more frequently for manufacturers. In this sector it has had the desired impact principally in the reduction of starting up and learning curve as for laborer as engineers. The impact in learning that automation simulation has in engineers can be moved to educational sector where can impact in the same way to engineering students as these seem to fit in the scenario presented for many educational institutions whose needs in automation and control field are an opportunity for integrating them. Automation Simulation tools in market are principally focused to industry and the context and needs for education are different as there isn t need of adding developing tools but final applications for equipping laboratories with processes to control. Then the contribution that automation simulation software platforms can do to education lies in final application developed in these, not in the developing software. Where students can prove, test and validate their control program, in a process closely to a real industrial one. As can be observed in table 1 From the tools in market only a reduced group of software companies have launched to market final applications with the objective of engineers and students training. However features as, licensing, price, connectivity, quality, etc of each one of these have caused that aren t broadly used in universities. The need to create a virtual final application whose features, be oriented to education arises. In addition application s features must complement students formation with practice, represent closely real processes, accomplish equipping universities needs with a high performance, let the spreading of virtual final applications, enhance their impact in educational sector and at the same time let that these kind of application can be implemented in universities with low resources with the objective of making them available also for universities in developing countries. A set of desired features according to the presented educational context needs are proposed next. In addition an automation simulation final application called Virtual Reality Machine (VRM) that tries to fulfill these features, its developing procedure, and application are described. Set of Features. (1) The student must be capable of analyses and understands the sense of automated process systems their time and space relations and limits, how sensors and actuator mechanically work, how mechanism are formed and impact the process, identify the function and mode of operation of the individual components. For these 3D graphics applications are needed. As there is more

9 visual information transmitted with 3D graphics than with 2D. (2) Applications must be representations of processes found in industry to familiarize students with the operation of the system and to understand the product and the processing method. The ability to experiment with real process models creates an environment close to a real manufacturing system, which is the real objective of training. (3) Interconnection with principal commercial automation software vendors is optimums as with programming as with softplc software. While more relation have students with industry controllers software easier would be their adaptation in industry. Compatibility with softplc or PLC simulators helps for testing programs without a real PLC. (4) Connection with real control devices as PLC, touch panels, etc. As this gives more reality to the process, provides to student industrial hardware familiarization and interaction. The feature of proving and debugging the programming in a real controller takes the students from the process virtuallity to the real PLC controller interconnecting the simulated world with the real world. (5) The final virtual automation application must to add the less possible cost to the solution as the application is software the prices is principally in licensing for this reason licensing for running applications has to be the cheapest possible. (6)The hardware necessary for running the applications, with a high performance, has to be the most common and commercial possible for avoiding high costs. (7) The simulation must to have short response times; high performance and speed when 3D visualizations, simulation and virtual commissioning is being carry out. (8) Easy installation of final applications for avoiding complicated configuration or many and specific installation steps. Virtual Reality Machine (VRM) Concept. There isn t a single term for calling final automation simulation. In market every vendor gives a different name, trying to cover the particularities of everyone. The features of the virtual final application that is going to be presented, explained and developed turn it different from those mentioned in table 1. For this reason the concept of Virtual Reality Machine (VRM) is introduced and defined next. A VRM is a computational application that models and emulates appearance and behavior of a real machine, process or production system. It is based in a set of 3D solids that mimic as close to a real machine as possible, visual, audible and functional aspects of the machine elements, (mechanism and sensors).the VRM dynamic and behavior is controlled by virtual sensors and virtual mechanism defined and programmed during VRM creation process. These are ready for connecting with external devices and sending and receiving control signals from/to either real PLC or SoftPLC. Communication of control signals is done by addressing virtual mechanism and sensors in a VRM s pin out table. By itself a VRM is not capable of carry out controlled sequences as this needs the implementation of a control strategy previously programmed in external automation hardware. This makes that dynamic and functionality of the VRM depends only of the control logic sequences programmed by the user. General Procedure for VRM developing. For every process that is going to be emulated a VRM has to be created. Despite that every VRM has a specific final functionality when these are created share certain general developing aspects that repeat every time that a new VRM is developed. These aspects can be summarized;

10 organized and separated in a set of steps according to their developing objective. In every one of these steps a developing method is followed. Conjunction of all steps integrate a general VRM developing procedure that can be clearly separated in 6 steps: 3D CAD creation, Conversion process, Assembly process, Animation process and Validation process, every one of VRM developing method stages and its procedures are described next. In figure 1 is shown the organization of stages, order and their interaction inside general procedure, the VRM s part that is created in every one of these and some application tools used for helping in the VRM developing. 3D CAD Creation. Figure 1. General procedure for VRM developing. The first step for creating the VRM is the Virtual Machine Elements (VME) modeling in CAD software, the only requirement from the CAD software to use is that it has the capability for saving the solid created in VRML 2.0 (97) 12 format. Requirement that must be accomplished for future conversion in LabVIEW. Two consideration must to be taking in care when modeling in CAD software that later are reflected in the VME due to VRML structure features. The first one is solid number. When the VRML file is converted in a VME this turns in a LabVIEW Virtual Instrument (VI) turning the solid information in LabVIEW code part. This make more efficient the final application, extends manipulation capabilities, and enhance the features that can be represented, accessed or gotten from it before or during simulation running. This is deeper detailed in Solid Conversion Section. The second is solid functionality for defining if a part or an assembly is going to be created is necessary consider the dynamic that will have the solid to model in the final VRM. Similar to real machine in VRM there are two classes of VMEs, dynamic VMEs, that move as result of a PLC input signal and static VMEs that are part of the VRM structure, this has to be considered when the decision of what solid include in an specific VRML that is going to be converted is taken.

11 Conversion Process. Once that the VRML file is created it is processed in an application that has been developed called VRML-VME Converter. The VRML file structure contains in ASCII code the complete information that defines the solid, this is separated in object nodes, where each one of this contains information about the triangle s coordinates vertex, normal, color values and index of each solid part that forms the solid 12. The application recognizes this structure and processes the VRML files, gets and organizes the important data required for render the new file in LabVIEW. Then the VRML file is processed only once by LabVIEW. As result a VME (Virtual Machine Element) is created. This is a LabVIEW Virtual Instrument (VI), which represents exactly the solid models as the VRML file, since nothing of information is lost during the conversion. Once that the process finishes the new VME in saved in a library. Then the VME now is a LabVIEW native file and has all the information necessary for representing and rendered the 3D solid without need of VRML or any CAD software or file. Having the 3D solid as VME represents some advantages as: faster execution time, deeper control of the 3D solid, integration of VME code to other LabVIEW applications, makes available the usage of some special properties because all solid data are available during execution. There are two classes of VME for Virtual Mechanisms and VME for Environment. VME for Virtual Mechanism: A Virtual Machine Mechanism (VMM) is integrated by two or more VMEs which are related by at least one dynamic action one over another and at least one of them is affected by a change of signal received from the external controller. Inside VME for Mechanism classification there are two VME types: VME part this is gotten when a VRML that contains information of individual part is converter. VME assembly this is gotten when a VRML that contains information from solids set is converter. Both can be affected with translational and rotational movement or color and shape change animation. VME for Environment: This VME type objective is to serve as VRM decoration exclusively this represents for example floor, walls or any other solid in the scene that has not connection with the real controller. This can have movement or be static during VRM functionality. Assembly Process. A set of virtual machine mechanisms (VMM) is used for creating a VRM. These VMMs are integrated by a set of animated VMEs which first have to be placed spatially in their corresponding position inside the VRM in a previous VRM assembly process, for this, a process similar to the assembly that is carried out in CAD software, where assemblies or parts have to be placed in certain (X,Y,Z) coordinates has to be done. However as LabVIEW is not intended for being a CAD Software this process is not easy and friendly to realize. This assembled has to be done because when a set of VME s are called and rendered in the same LabVIEW scene by default are placed in the position where were saved in CAD software during the Solid Creation stage, usually this position is the origin (0,0,0) however this can be any point in the space and not precisely the correct place inside the VRM final assembly, for this reason a set of VMEs when are rendered are placed normally overlapped in origin and is necessary to place them in their correct spatial position.

12 Inheritance. Inheritance is defined as parent and child relations among VMEs that command how rotational and translational transformations applied on one VME affect others VMEs in a VRM. Inheritance must be specified for a correct VMM functionality. Whether this is defined, when a movement transformation is applied to one parent VME this affects also its children VME but when is applied to a child VME this affect only itself. VMEs inheritance structures can vary from one single branch to a set of branches complexly related in the VRM. Complexity of relations depends directly of the VMM dynamic relations and functionality inside the VRM. Subassembly concept. To fulfill the requirements of the VRM functionality and defined inheritance, a subassembly must be specified. A subassembly is a set of VMEs or others subassemblies which are affected dynamically by the same transformation. In addition it contains an internal inheritance structure which relates all the subassembly components. Subassemblies are generally used for VMM definition as the elements inside a subassembly can be affected individually by transformations, defining their dynamic relations inside the VMM and the subassembly as a whole can also be affected by a different transformations, defining its dynamic relations inside the VRM. Then as these two transformations need to be handled in the VRM subassemblies must to be used and defined considering the VRM s functionality and its VMM. Assembler. The VME assembly process carry out in LabVIEW is time consuming, is complex and requires a complicated programming structure. This motivated the developing of a LabVIEW native application called Assembler, whose principal objectives are: Optimizing VRM assembly process, reducing programming time, organizing VME s data and turning friendly VME transformations addition. The Assembly process has two principal objectives; placing VMEs in their correct spatial position and establishes inheritance relations. The first one is repetitive for every VME that is assembled and the second one differs only a little depending of the complexity of the mechanism. The Assembler takes advantage of this repetitively letting that the user set only some parameters as X, Y, Z position, angle and axis for spin and inheritance definition, these data are processed, organized and structured only once every time that the VRM is executed this way of assembly the VMEs reduces the programming time as avoids that the user generates all the programming structure optimizing the assembly process. The file gotten from this process is a Virtual Machine Assembly (VMA). In figure 2 is shown the Assembly process in a VRM this is composed in total for 8 VME which are organized in one static VME that is the principal assembly parent and 7 dynamic VMEs. Three of the dynamic VME are parents in subassembly 1, 2 and 3 and four of them are individual VME subassembly 3. In a) is shown the VME origin position when they are rendered, in b) subassembly 1 which contains 1 VME and to the subassembly 2, in its principal branch, is moved and only the principal assembly parent keeps in its positions. In c) subassembly 2 which contains 1 VME and to the subassembly 3, in its principal branch, is moved. In d) the subassembly 3 which contains 4 VME, in its principal branch, is moved. In e) the 4 individual

13 VME inside subassembly 3 are moved. In f) a top view of all VMEs in the VRM is shown in g) and h) the assembly process is illustrated when one VME is placed in its correct position. In i) the final correct assembly is shown. As was mentioned a subassembly can contains VMEs or other subassemblies for example subassembly 1 contains 1 VME and subassembly 2, but as subassembly 2 contains also 1 VME and to subassembly 3 and subassembly 3 contains 4 VMEs subassembly 1 could be referred as a subassembly that have 7 VME in all its branch structure or that contains 1 VME and to subassembly 2 in its principal branch just like in CAD. Animation Process. In this process is defined the internal programming of the VRM. It includes all aspect related to VRM functionality as VME movements inside the virtual machine mechanism (VMM), sensors programming, conditions validations, signal generations, is necessary to specify that this procedure doesn t refer to VRM programming control but animation sequences required for VMR acts dynamically according to control sequences received from external controller. This process is done in LabVIEW using the necessary operations, conditions, structures, subvis, validation and instructions that the VRM needs for having a behavior the closest to the real process as possible. For achieving this objective many aspects have to be considered as a VRM not only involves VMM functionality but all aspects related with the process emulated and its environment. Then Animation depends of every VRM functionality and the way that programming is done vary according to VRM s logic programmer. Despite every VRM has a particular internal programming according to its functionality some important and general aspects independent of the VRM can be underlined in animation programming. These are VMM programming, virtual sensors programming and extra animations programming. VMM Programming. Figure 2. Process of placing VMEs in their correct position. During the animation programming VME are grouped and turned in a Virtual Machine Mechanism (VMM) using inheritance defined in the Assembly process. A VMM is integrated by

14 two or more VMEs which are related by at least one dynamic action one over another and at least one of them is affected by a change of signal received from the external controller. In VMM VMEs behave as actuator. This means that when a change in an external signal is received VME are affected during VRM execution usually with transformation operations like rotation, escalation, translation, color change, etc. until other change in the signal is received for achieving this behavior. In VMM four tasks must be carried out, these are: validating the reception of an external signal, recognizing of the signal, deciding what action to take and execute the action. Virtual sensors programming. The reception and processing of signals from the external controller is closely related with VMM functionality as these are validated and processed inside the VRM. However the response of VMM according to these signals has to feedback it somehow to the external controller as in the control programming running in it the effects of these signals have to be validated for achieving a correct control of the process. In a real process, signals are sent from the process through many types of sensors that are placed in a specific position. As VRM emulates totally a real process, this sending of signals must also be done, for this, virtual sensors are used. These are individual VME or part of VMM; that in addition include programming oriented to emulate the behavior of the real sensor and generates the signals that a real one would generate. When certain conditions inside sensor programming accomplished a change in virtual sensor s state occurs; this is reflected in the same indicator that communicates with the external controller which is established in connection process, this means that the output of a virtual sensor gotten after validations must affect the same variable in the programming that serves as input to the external controller something similar to real sensor. Extra-Animation Programming. In addition of VMM and virtual sensors programming other animations sequences are also required in VRM, these don t relate directly with VMM or virtual sensors functionality and their objective is making more real the VRM functionality. For example VME color change, VME or a VME part appearing or disappearing, movement of some VME that aren t VMM s part inside the scene, change of inheritance, addition of the real sounds to VMM movements, and any other animation required for the correct process s visualization that the VRM emulates and doesn t receive or send signals from/to external controller In addition sometimes controlled extraanimations have to be used because some sequences are difficult to program in LabVIEW as this is not intended for being an emulation process program then the use of extra-animations helps to solve these difficulties. Connection Process. After animation process the application gotten still cannot be considered as a VRM as this still has not connection to external control devices. This means that a control strategy cannot be carry out on this as a VRM has not internal control sequences saved. At this stage it can be considered only as a VM (Virtual Machine). Then for accomplishing the control and automation functionality, is necessary the connection of the external controller outputs with VM s VMM inputs and external controller inputs with VM s virtual sensors. Similar to real automated control

15 systems where control device s I/O are interconnected for communication with manufacturing process s sensors and actuators by voltage signals that are carry usually over electrical wires. This is done in VM through a connection procedure whose objective is turning VM into VRM addressing, organizing and describing in a Pin Out table the VRM s VMM and virtual sensors for being available for the external controller. However the VRM is a software application that emulates mechanism and sensors therefore physical devices don t exist and wires for carry signals cannot be placed. Then connection between VM and external controller also has to be emulated by software, what does that VRM s connection process be particular. This is integrated by 3 steps: Identification, addressing and programming. Identification. Once that animation process finishes, the VM gotten has all controls and indicators used for its programming. These include as those that help to VRM s animation programming as controls and indicators that need to be used for the external controller for starting or stopping VMM in case of controls or from where the change of virtual sensor s state can be read for the external controller in case of indicators. Then the first step for connection process is, identify and separate the signals that external controls and indicators affect. For this must be considered what signals needs the control programmer engineer or student for carry out the correct control strategy on the VRM. Addressing. After indentifying VMM and virtual sensors signals is necessary to give a hardware address to everyone of the signals used for external connection. However as wire cannot be placed for interconnecting external controllers outputs with VM inputs and vice versa this has to be emulated by software. Then for addressing VM with external controller is necessary to make a mapping of external controller addresses with the names of the signals used in VM s LabVIEW programming as the PLC programmer uses this addressing in the control program which by the addressing access to the LabVIEW signal name. The LabVIEW signal name is used for internal VM programming. VRM addressing, specifies the address of every one of its virtual sensors and VMM inside the VRM that the user can affects. The final addressing is organized, presented and described in a Pin Out table similar to those used in real automated control systems. Programming. Once that every one of the VMM and VRM s virtual sensors have been addressed. VMMs are linked with external controller outputs and VRM s virtual sensors with external controller inputs by interconnection and communication programming inside the VRM connection process. Interconnection programming: As VRM receives and sends change of signals state from/ to the external controller. There is a programming part inside VRM oriented to the reception of signals. Whose objective is to get from the external controller the state of each one of signals used for VMM; and other programming part oriented to sending of signals. Its objective is recollecting, organizing and sending the state of each one of the virtual sensors signals. Communication Programming: Once that VRM s I/O mapping is done in interconnection programming. Is necessary a programming part oriented to send and receive the data to/ from the external

16 controller and doing the communication task. For this has been developed a set of ActiveX libraries programmed in.net whose instructions are called and reprogrammed in LabVIEW these communicates the VRM with PLC software libraries. Automation validations Process. Once created the VRM, a general validation of its functioning have to be done before of creating the executable file of the LabVIEW VRM program and finish the VRM creation process. In this process is validated the complete functioning of the VRM and is assurance that the VRM correct functioning depends totally of the correct control sequences programmed in the external controller by the VRM s user. This means that if a mistake occurs or there is an incorrect visualization this depends totally of the control program created for the PLC programmer not of the VRM functionality. The validations carried out in this process are: Validation of VMM functionality, virtual sensor s signal validation, animation validation, automation validation. (1) VMM functionality validation: VMMs are activated first by LabVIEW front panel s controls and later by signals change sent from PLC software. In general is checked that VMMs functioning is correct and the closest to the real mechanism. This is done by validating that VMMs start or stop when receive the correct signal, that visually their functioning is the correct, that spatially they don t crash with other VMMs or VMEs, that their dimensions are correct, that their movement is adequate and according to the signal or control sequences that are receiving, etc.(2) Virtual sensor s signal validation: virtual sensors are activated from VRM s and its estate is checked first in VRM s front panel and later in PLC software. In this process is validated that sensors activate enough time for being read for the PLC. The activation time depends of the sensor s limits programmed in LabVIEW. In addition is also validated that sensors are in the correct X, Y, Z coordinate when change the estate of their signal.(3) Animation validation: By the VRM functioning is validated that correct animations executes in way and time that have to be executed. For example if a translational or rotational movement affect the VME in the desired way, that color change of the VME is activated in the correct moment and that the VME changes to the color needed, in general that visually the behavior of the VRM is the correct. (4) Automation validation: For this validation an automation task that uses virtual sensors and VMMs addressing of the VRM is created, debugged, loaded, tested and monitored in PLC software. With this is assurance that VRM s signals change of VMMs and virtual sensors are interchanged correctly and that with these signals is possible carry out correct control sequences. VRM Application. After validation process VRM s process creation finishes. Then now from a LabVIEW project the VRM program is compiled and an executable file and an installer of the final VRM LabVIEW program are created 15. The installer makes possible that LabVIEW developed application behave as a any commercial software when is installed in PC. The capability of turning VRM in an executable file has the advantages of: VRM portability, minimums software required for execution, organization of all files in a single one, easy installation. But the principal advantage is that licensing is not required for VRM execution and can be used in PCs only installing a LabVIEW runtime which is gotten free from LabVIEW website. This makes possible that VRM be practically free and one viable learning option for control engineers, automation

17 students, universities laboratories, training centers, etc. regardless their economic possibilities. After installation when VRM is executed for being controlled, initially a configurations box like shown in figure 3 is displayed. In this the users choose the type of connection that want to establish between the external controller and the VRM according to the controller that they have available and the communication protocols this handles. In figure 3 in box are shown a set of communication protocols available for one VRM, in this example these are PLCSIM, Industrial Ethernet, TCP/IP, MPI/ Profibus, WinLC. Communications Protocols handled for the VRM. Figure 3. VRM Connection configuration. According to the protocol chosen is necessary write the address of the external device used for control the VRM. This is the number that indentifies the controller where data are going to be sent and received, this is necessary for communication libraries and varies depending of the protocol.vrm is a new virtual commissioning tool that so far has only be tested and validated with SIEMENS automation hardware and software and whose communications libraries have been developed oriented to this vendor as VRM doesn t use OPC communication. This affects VRM application only in interconnection capabilities, the VRM concept and developing procedure if the same regardless the external controller s brand. VRM developing continues oriented to adding OPC communication and developing communications libraries for others automation hardware vendors as Allen Brandley, Schneider, ABB, etc. as VRM concept is intended to be used with any commercial external controller vendor. In figure 4 is shown the VRM communication diagram when SIEMENS hardware and software are used for automate the VRM. This illustrates the VRM s communication with external control devices 15.

18 Figure 4 shows, that there are two options for using the VRM; with S7PLCSIM or a real controller. If PLCSIM connection is chosen VRM and PLCSIM will communicate only by software this means that won t be connection to a real hardware and the VRM s user will work with a PLC emulation PLCSIM musts be installed and running in the PC that will communicate with the VRM, monitoring of the I/O signal and manual activation of actuators can be done in the PLCSIM software in figure 5 a) is shown a VRM using PLCSIM. When TCP/IP, Industrial Ethernet, MPI/Profibus, WinLC protocol is used is necessary to have an external PLC with the communication interface that support the protocol that is chosen in figure 5 b) is shown the same VRM being controlled by an external controller and in box is shown SIMATIC S7 software used as for programming the machine as for monitoring the execution of the program. Automation equipping solution. Figure VRM controlled by PLCSIM. Figure 5. VRM controller options. For plenty accomplishing its objective, automation and control laboratories need an infrastructure that in addition of counts with industrial automation hardware and software also includes a process or plant where students implement, test, debug and validate their control and automation strategies. However this represents the highest costs for laboratory equipping and in the best scenario laboratories are equipped with few real automated devices used in industry which for their high cost are used commonly only for professors with demonstrative objective. Training workstations of vendors as Festo, FISHER tecnics, etc as consequence of their price, are used only for a reduced number of universities. Other practice is testing students control programs in a set of individual industrial sensors and actuators that activate according to the control programmed, however these don t represent a real industry manufacturing process. A common practice is the construction of home-made systems that are a set of buttons, actuators and led indicators that with imagination try to represent a process. The construction of primitive structures as elevator, mixer, etc. is also a common practice. In addition that any one of these options has a cost some of these don t achieve to impact totally in the students understanding as some students don t visualize the essence and sense of automation and control strategy carried

19 out on these. For this reason the automation and control laboratory station shown in figure 6 is proposed. This represents a viable solution to the lack of equipment that face many universities, as the highest cost of laboratories equipment is represented for the process to control, what is solved with the VRM as this emulates a real process. Even a set of VRM s can be used for students as many VRM can be installed in the same PC. In addition VRM makes possible that laboratory has a set of VRMs in every station without additional cost what means that every student can has his/her own process to automate. The Automation Lab Workstation proposed is integrated for a Real PLC, a touch panel and a PC where VRM executes, in addition in this PLC and Touch panel software is also installed. Figure 6. Automation & Control Laboratory equipping proposed. VRM s impact and interaction with students. For illustrating the impact of the proposed automation learning platform, is used a laboratory equipped with SIEMENS CPU315F PLC and a SIEMENS Touch Panel as hardware and SIMATIC S7 and SIMATIC WinCC as control developing software and as plant a VRM called Process Line which represents a machining process which has 19 Input addresses and 15 output addresses. In addition to automation hardware and software and to the VRM in laboratory students receive a pin out table with the address and description of all VRM s virtual sensors, VMM and document with the plant description that includes the description of the process that is represented for the VRM, description of the functionality and position of virtual sensors and VMM and VRM dynamic, this information is all what they need for starting with their automation task. The objective of automation is according to the criteria of the laboratory s professor as VRM can serves as for carry out simple control sequences as for a total automation of the process that

20 represents. In laboratory the students develop the control strategy that is going to be implemented on the VRM just like is done in a real process, this depends totally of the user knowledge and what is asking for the professor. There aren t restrictions in programming the VRM, interruptions, counters, memories, timers, etc can be used without affecting its functionality. Once that the student finishes his/her automation task in SIMATIC S7 and the HMI programming in WinCC the control programs created are compiled and downloaded to their respective automation hardware. Then having the external controller turned on and the VRM in execution, the automation strategy programmed for student is tested and validated on the VRM checking that the functionality of the behavior of the VRM is correct and goes according to what was asked for professor. The user interaction with the VRM is shown in figure 7, here is observed that students do three principal tasks in laboratory: 1) Task developing. Where students program and debug their automation strategy. 2) Hardware programming. This is the process where the program developed is compiled and downloaded to the automation hardware. 3) Test and Validation stage. Where students validate their control program and skills and the teacher secure that students have acquire the knowledge transmitted in classroom and that have the capability of implementing and using these knowledge in automated systems that are very close or equal to used in industry. Figure 7. VRM s Interaction with students.