The virtual PLC is designed based on the same structure of real PLC as it should mimic the real one. To substitute the real one, the virtual PLC should have role in determining (inferring) the action and generating the command corresponding to the input as the real one does. The virtual PLC replaces the actual PLC unit.
Once the trainees complete wiring, the device I/O code table as shown in Figure 2(b) is generated internally corresponding to the wiring configuration, which is delivered to virtual PLC component. In order to cover various user's arbitrary wiring input, Scene Access Interface (SAI) is used for the implementation. The trainee can also study materials related to a specific session and practice wiring using this virtual composer shown in Figure 2(a). Whereas most input wiring units accept only preassigned (correct) wiring, the virtual composer unit in the proposed system accepts any wiring configuration (even incorrect wiring) from the user. This virtual composer unit receives the initial input from the user (trainee) and supports arbitrary wiring.
The object-based sensor input unit has role in sensing and processing the sensor input and the virtual composer unit has a role in receiving user's (trainee's) arbitrary wiring input. The virtual sensor has two units: the object-based sensor input unit and the virtual composer unit. The proposed system is applied to a real training program of the university's training center linked academia and industry to examine the applicability and feasibility, and the results are analyzed and discussed. There has been hardly any research and development on the proposed training system, especially using virtual interaction based on virtual sensors and actuators for PLC automation equipment.
For instance, virtual sensor components sense trainee's wiring and device inputs, and once it is determined by virtual PLC whether or not they are accurate, the virtual PLC generates command for the correction action, and thus virtual actuator (output device) simulates the corresponding action, whereas incorrect one produces a simulation result of faulty action. In order to allow PLC trainees to handle virtual equipment that models actual high-price equipment such as elevators and conveyors, providing the effects of engaging in hands-on training, the proposed system is composed of three components including virtual sensor (for interacting between user and input devices), virtual actuator (for manipulating and controlling device or equipment), and virtual PLC (for programming and generating command). Based on the virtual sensors and actuators, the proposed system provides PLC trainees with a virtual interaction that is identical to actually handling various types of equipment. In accordance with the increasing importance of training on latest and expensive equipment spurred by the rapid developments in the manufacturing industry, this paper proposes a new virtual interaction based PLC training system using virtual sensors and actuators.
Therefore, most trainees listen to explanations rather than hands-on manipulation, which places limitations compared to actually being able to operate the equipment. Since inadequate manipulation or programming errors by trainees can damage the equipment and there are difficulties involved in continuously replacing and providing the latest and expensive equipment, thus the ones are not used at all or provided only with limited use for the training. Due to the nature of manufacturing industries, PLC automation training requires very expensive latest equipment. The most important group of technical experts in cutting-edge manufacturing industries such as Samsung Electronics and Hyundai Motor Company are PLC automation professionals. Republic of Korea has some of world leading companies in manufacturing industry such as automobile, semiconductor, display, mobile phone, and shipbuilding. Therefore, there is a strong demand for effective training that can provide trainees with quick and safe ways to adapt to the latest equipment. Moreover, due to the nature of latest and expensive equipment, mishandling and/or malfunctioning can result in substantial loss, including personal injuries, equipment damages, manufacturing of defect products, and interruption of the production process. Owing to rapid developments in manufacturing industry's automated production facilities, top-edge equipment required on programmable logic controller (PLC) training is becoming more expensive with shorter replacement cycles.