DIDACTIC SYSTEM FESTO MPS - SORTING STATION AND ITS APPLICATION IN EDUCATION IN THE FIELD OF MECHATRONICS

Slobodan Aleksandrov1, Stanimir Čajetinac 2, Dragan Šešlija3

1 Tehnička škola Trstenik, Trstenik, SRBIJA, E-mail: aleksandrovs@yahoo.com2 VTMŠ, Trstenik, SRBIJA, E-mail: caja.dublje@ gmail.com

3Fakultet tehničkih nauka, Novi Sad, SRBIJA, E-mail: seslija@uns.ac.rs

Summary: The paper deals with the didactic electropneumatic system Festo MPS - sorting station. The system is a smaller version of a real industrial system, with commercially available components and devices. The system is controlled by advanced programmable logical controller equipped with sensors, actuators and communication interface. Modular system provides assembly, connecting, programming, testing, and disassembly of industrial components. The sorting station is designed for education in the fields of mechanics, pneumatics, sensors, electrotechnology, PLC programming, and electropneumatics. 3D simulation software, named Cosimir PLC, is presented in the paper, and it simulates the real operation of the sorting station along with monitoring all parameters of the system, simulation and detection of errors in mechatronic sorting system.

Keywords: Festo MPS, education, PLC, Mechatronics

1. INTRODUCTION

Education in the field of automatic control of the systems and mechatronics demands advanced training systems, which follow automation trends and meet the needs of modern industry. Development of new technologies and their application in industry requires up-to-date teaching material in order to properly educate mechatronics engineers. A mechatronics system is a fusion of mechanical system, sensors, pneumatic, hydraulic and electric actuators, and it is controlled by advanced industrial computer. Since mechatronics comprises many fields, modern didactic systems are necessary for proper education. One of the leading manufacturers of didactic systems for education in the filed of mechatronics is the company Festo. This paper deals with the didactic system for element sorting, and it belongs to Festo's Modular Production System MPS. The distinguishing characteristic of these systems is that they represent real industrial systems with industrial components, but they are smaller and thus suitable for teaching and studying in laboratory conditions. These systems are supported by the software for programming controlling devices, for communication, and the 3D simulation. The basic characteristics of didactic systems, hardware organization of the sorting station, and software for programming and system simulation are presented in the first, second and third part of the paper, respectively.

2. HARDWARE ORGANIZATION OF SORTING STATION

The sorting station is an electropneumatic mechatronic system intended for teaching and studying in the fields of system control and mechatronics, as shown in Fig. 1. The distinguishing property of Festo MPS systems is their modularity, which provides system assembly and disassembly, servicing, replacement, testing, enlargement of the system by new components, and change of the operation algorithm. The electropneumatic system of the sorting station is controlled by the programmable logical controller (PLC) which has available inputs/outputs, which enables additional sensors and actuators to be connected. When hardware components change it is necessary to modify or write a new program, and then to reprogram PLC.

2.1. Hardware description

The sorting station consists of the following modules:

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Sorting conveyor module Slide module Profile plate PLC board Control console Trolley

Figure 1: Sorting station Figure 2: Conveyor with sensors and actuators

The sorting station needs an electrical supply of 24V DC max. 5A and supply by compressed air of 6 bars. The system can work in manual and automatic mode defined by a switch on the control console. The basic function of this system is to sort the materials according to their characteristics. The system has a base with little wheels, and PLC is in it. The control console is at the front upper side of the sorting module. This module consists of the conveyor belt (see Figure 2) which is driven by a DC motor, three photoelectrical sensors for subject detection at the initial part of the conveyor, three single acting pneumatic cylinders with limit microswitches which inform about the position of pneumatic actuators. The pneumatic actuators are controlled by PLC by electromagnetic valves. The storage is composed of three separated fixed parallel belts, which are inclined and where the separated parts having different characteristics are stored. The reflexive photocell is on the top of the storage, and it informs whether the storages are full. The control console is at the front side (Figure 3) and there are buttons used for starting, pausing and resetting the sorting station, as well as signal diodes, which inform on the system state. There are also information indicators, which activate in the case of error detection. The entire system is controlled by PLC Festo FC640 (Figure 4).

Figure 3: Control console of the sorting station Figure 4: PLC board

2.2. Functioning

The main part of the sorting station is the conveyor; around it there are sensors for part detection and pneumatic cylinders for sorting. Black, red and grey cylinder-type objects are sorted. Black and red parts are plastic, while grey parts are metallic. At the entrance of the conveyor, there is a diffusion photo sensor which identifies the incoming part. When PLC receives the signal from this sensor, the motor of the conveyor belt turns on and activates the first pneumatic cylinder - ramp which stops the part to be identified. The identification is done by two sensors: the inductive sensor identifies metal parts, whereas the photo sensor identifies plastic parts because it recognizes red and black color. This sensor is adjustable so during testing it is adjusted to identifying only the red parts. When the red parts are identified, the pneumatic cylinder is withdrawn, and the part goes through the conveyor entrance. Then pneumatic cylinder 2 turns on, and it directs the red parts towards their storage place. When metallic parts are identified, the third cylinder activates, and it directs the parts towards their storage place. If none of these two sensors activates, the red parts are transmitted to the conveyor end, and they are automatically sent to the storage for the red parts. All three storages are parallel and inclined so that the parts slide towards the storage bottom. At the storage top, there is a reflexive photocell which detects when the storage is full. This sensor stops the sorting operation when at least one of the storages is full. Signal lamp on display informs the operator about the error. The sorting station is controlled by PLC Festo FC 640, which is programmed by software Festo FST V4.02.

2.3. PLC programming

The sorting system is controlled by PLC FEC - FC 640 having 32 digital inputs, 16 outputs, serial interface RS 232 used for programming, and Eternet connector. The main advantage of this PLC is its support to TCP/IP protocol and integrated WEB server, too. This Eternet network support enables identification of static IP address of PLC, connection into LAN network, access to the system through the local network or through WEB searching from any place on earth. PLC programming is done by Festo Software tools V.4.10.50, by LADDER diagram and Statement List Languages (STL). This software provides programme writing, compiling, error detecting, and PLC programming. Figure 5 shows the display of the software for PLC programming. There is a possibility to communicate on-line with PLC, to make tests in real time, to monitor the state of input and output variables, to monitor the state of counter and timer, and to monitor the state of special memory variables. By adding drivers for TCP/IP and WEB support, it makes PLC connect into Eternet network; thus, system parameters can be monitored from any network computer and remote system control is available, too. Application software Festo IPC server is used for using network resources of PLC, and it provides safe remote access to the systems and support to Windows applications.

Figure 5: Software for PLC programming

3. MECHATRONICS EDUCATION WITH SORTING STATION

3.1 Possibilities

These systems enable training in a large number of activities, as shown in Table 1.

Table 1: Fields in which sorting station is appliedApplication Knowledge and skills

Mechanics Identification of mechanical components Assembly and disassembly of mechanical components Designing and modeling of mechanical components

Pneumatics Identification and use of pneumatic components and devices Designing and connecting of pneumatic installation Detecting and eliminating the errors at pneumatic systems

Sensors Identification of the sensor type and its purpose Setting and connecting different sensor types Testing the proper operation of sensors and their replacement

PLC Identifying the structure of different types of PLC Connecting sensors and actuators PLC programming and testing

Electrical engineering

Identification and use of electric symbols Designing and connecting the electrical installation Detecting and replacement of faulty electrical installations Identification, connecting, and stating-up electrical motors

Internet technologies Connecting mechatronic systems within computer networks Remote access by Internet PLC as a WEB server

3.2 Simulation of a real system

Figure 6: Cosimir PLC - the software for 3D simulation

Figure 7: State of input and output of the sorting station

Testing and diagnosis of real systems are a basis for adopting knowledge and skills in the fields of system control and mechatronics. Some students show fear and antagonism because of real electrical and pneumatic systems. Today advanced computers have huge processor power so 3D simulation of real systems motivates students to adopt the fundamental working principles of real systems. This simulation enables virtual simulation of dynamics of mechatronic systems. This software can test and diagnose real complex mechatronic systems in the virtual environment. Festo's software for 3D simulation of real systems controlled by PLC is COSIMIR PLC. This software is a PC software intended for 3D simulation, testing and diagnosis of MPS series Festo systems.

3D model of the sorting station is shown in Figure 6. The programmes for simulation of the operation of real mechatronic systems can be defined by this program, and current examples delivered along with MPS systems can be used. The values of input and output variables in real time can be monitored during system simulation (Figure 7) and during the programme being realised. The line of programme code being realized is marked, which provides visual monitoring the effect of each command.A very important feature of this software is its possibility to simulate real error (dump, sensor or actuator failure) in the virtual environment. Error simulation is done by graphical checking of wanted signal. When an error is set, the system tests the conditions for operation start-up and does not allow 3D simulation of the system. All system errors are archived in Fault log file. The errors eliminated are marked in green while the errors which are not eliminated are marked in red. When the cause of the error is eliminated the system simulation may start.

Figure 8: Simulation of the operation and state of variables of the sorting station

By activating the command Manual operation (Figure 8), the system tests each module while the state of input sensors and output actuators is being monitored. The active module is marked by a red diode, whereas the active input and output variables are marked in green. Cosimir PLC can be widely applied but the new version of the programme, named CIROS, has additional functions and models.

4. CONCLUSION

The didactic mechatronic system presented in the paper provides application of theoretical knowledge by 3D simulation of real complex systems and practical training with industrial components. Festo MPS didactic systems make preconditions for acquiring applicable knowledge and skills in the filed of PLC programming, connecting, testing, detecting and servicing the failures in the field of pneumatics, electronics and electrical engineering. Thanks to the combination of traditional teaching, electronic studying, programmes for modeling and simulation, internet technologies and modern didactic mechatronic systems, new knowledge can be adopted in an interesting way in all scientific fields. Advanced didactic systems are rather expensive so not every school or college can afford them. Owing to fast internet, connection of didactic systems into computer networks, remote access to real laboratories and distance training, didactic systems can be used from any place on earth when the above described system is available.

REFERENCES

[1][2] Festo Distributing station, CD 648811, www.festo-didactic.de/services>MPS[3] Festo software tools, Automating with FST, 682300, en0402HN[4] Yeung, K.;Chow.S.: The modular production system (MPS):an alternate approach for control technology in

design and technology. In: IDATER 98 Loughborough University, Hong Kong SAR, People’s Republic of China

[5] Račić, M.;Jovanović, J.: Comparative analysis of mechanical and mechatronic design. In: Proceedings of 9th

International Conference Research and Development in Mechanical Industy - RaDMI 2009, Vrnjačka Banja, Serbia, 16-19. September 2009. Edited by Predrag Dašić.