SCYR 2010 - 10th Scientific Conference of Young Researchers – FEI TU of Košice Model of Production Line with Multi-Motor Drive Matúš HRIC Dept. of Electrical, Mechatronic and Industrial Engineering, FEI TU of Košice, Slovak Republic matus.hric@tuke.sk Abstract— Production and finishing industrial lines occurs in the industrial plants dealing with continuous production of materials of various mature that are in form of a web, strip, fiber etc. From control point of view they belong among complex multivariable mechatronic systems where quality of output products depends on quality of the control system. The main variables to be controlled are usually the speed of the processed material and of working machines. The contribution describes a simplified physical model of a production line and its control part. The model is used for teaching and debugging control algorithms of complex systems that are presented by multi-motor drive in this case. Keywords—physical model, PLC, multi-motor drive I. INTRODUCTION Continuous production and finishing lines create essential technological equipment in manufacturing production. They are distinguished by mechanical coupling of individual driving units in multi-motor drive through a moving web. For teaching, explanation of mutual couplings and interactions in the line, for practical realization of the control algorithms by PLCs and for performing other laboratory experiments it is advantageous to use physical models that enable to understand easier principles of control strategy of such complex drive systems [1]. II. PRODUCTION LINE WITH MULTI-MOTOR DRIVE IN PRAXIS The term of multi-motor drive is used to describe all main drives in the technological process used for transport of the processed web which mechanically couples the drives [2]. One group of multi-motor drives is presented by drives of continuous production and finishing lines. The lines are used to perform various technological operations on a moving of a metalic or non-metalic substance. Typical arrangement of the production line is shown in Fig.1. The mechanical energy of traction cylinders for moving the web comes from electrical drives equipped by appropriate control circuits (current-, speed- and position control). In the most cases, the moving web makes elastic mechanical couplings which leads to complexity of the system to be controlled. A generalized production/finishing line in Fig.1consists of: a) The input section ensuring constant material flow – having unwinder, drawing (tractive) cylinders, binding machine (welder), input cartridge (to match with discontinuous material inflow caused by coil exchange on the coiler spindle), b) The technological section, with technological machines for Fig. 1. Typical arrangement of a continuous production line and its parts processing of the material and with combination of tractive Scylinders and working cylinders, material loops, etc., c) The output section, represented by output cartridge, shearing machine to cut the material, and finally the winder. The mechanical subsystem of the technological part is driven by a multi-motor drive. Control system of the electromechanical subsystem ensures a correct collaboration of the drives satisfying technological requirements (constant tension in the material independently from its speed, position of the loop, etc.). It also contains some features of artificial intelligence (automatic identification of material properties and of other parameters, automatic tuning - adjusting the controllers parameters to ensure quality of the final product, etc.), [1]. As a supervisor here acts a superimposed control system ensuring contact with a user: data input and collection of technical and economical data from the technological process. From system point of view one recognizes all basic mechatronic subsystems here: the mechanical, electrical and information ones (Fig. 2). a) b) Fig. 2. Typical look-out of a production line (a) with multi-motor drive on example of a hot strip mill and its generalized model block diagram (b) SCYR 2010 - 10th Scientific Conference of Young Researchers – FEI TU of Košice III. PHYSICAL MODEL OF A CONTINUOUS LINE From the control point off view, the described system of the continuous production line presents a complex MIMO (multi (multiinput, multi-output) output) system in which calculatio calculation and setting the controllers parameters for high control quality is enough difficult and complex task. For teaching and expl explanation of phenomena occurring in the system, it is highly advantageous to use eLearning instruments [2], [3] where phenomena can be animated and slow down in order to analyze add understand them. Finally, verification of correct settingss of the controller parameters causes a problem - they should be verified on a real system. In industrial environment it is impossible to perform any experiment from technical, safety and economical reasons. Here, the simplified laboratory model of a generalized industrial line (Fig. 3) presents a suitable solution. The mechanical part of the model consists of unwinder, 3 cylinders and winder: Altogether there are 5 drives to control. The web consists of a film strip from celluloid material. In the loops among mong the machines there are placed swinging arms that are tensioned by springs enabling to set up a tension in the web. There are also position sensors sensing the ang angle of the arm. This arrangement enables the operator to check by sight whether the web tension nsion in sections among the neighboring cylinders corresponds to the preset reference value. In the bottom onn the left side there is a control panel with the actuating buttons enabling to change modes of the line. Fig. 4. Principal diagram of drive units control in the production line During reconstruction of the model we replaced original analogous speed sensors by incremental sensors and from this reason also original analogous control was replaced by digital control where the digital controller is programmed in the PLC. Fig. 5 shows arrangement of the apparatus in the distribution box (power converter, PLC, supply sources for IRC, auxiliary switching relays and breaker apparatuses). Fig. 5. A view into reconstructed distributing distribut box of the physical model The superimposed speed controller was realized by the PLC Siemens S7- 400 with the technological card FM 458 that in the programming environment S7 CFC (Continuous (Continuo Function Chart) from Siemens gives a possibility to interconnect and set up common, or user’ss function blocks - similarly like it is done in the Matlab-Simulink program. program It should be noted that the technological card FM-458 458 is used frequently in many technological solutions in industry. industry Fig. 3. Physical model of a continuous production line The driving cylinders in the line are driven by DC motor drives that are supplied by the analogous Allan Bradley converter. For the outer speed controller originally there was used a microprocessor system MS-80 80 with A/D D/A transducers sducers and network of transputers, where several modern control algorithms were debugged, [4].. Gradually, in line with development of the IT and automation technologies technologies, the systems and its control part have been changed gradually. After modernization only analogous AC/DC DC converter and the mechanical part remained. IV. INNOVATED CONTROL OF A PHYSICAL MODEL Control of electrical drives of a line requires using an underimposed current controller for each drive implemented in each converter module that are connected with an overimposed speed controller. Fig. 6. Output of controlling signals through limiters and D/A transducers and their following addressing and input into a superimposed circuit Fig. 7 shows scheme of a part art of logical commanding that was developed in PLC in the programming language la LAD. SCYR 2010 - 10th Scientific Conference of Young Researchers – FEI TU of Košice Fig. 9. Speed response and its simulated time course in the linear region at the reference signal step corresponding to 5% of nominal value Fig. 7. A Part of logical commanding of drives in the program STEP 7 and programming language LAD ATION V. PRACTICAL UTILIZATION The physical model is used for laboratory experimentation in several subjects of study, like:: Model Models of Dynamical Systems, Controlled Drives, Mechatronic Production Systems Systems, Control of Assembling Lines by PLCs,, Controlling and Visualisating Systems, and Control of Mechatronic Production Systems that are taught at the author’s department at Technical University of Kosice. The students practicallyy verify theoretical knowledge from system dynamics fundamentals, control of electrical drives drives, design methods for drive controllers and their realization by programming the PLC. They learn deeply the case studies from field of multi/motor drives control and compare obtained time responses from simulation with those go got from the laboratory model. Moreover, they have a chance to tune the controllers and follow behavior of the systems at changed system parameters. A common example of the physical model utilization is in case of teaching subject ct of Controlled Drives. Fig. 8 shows the speed response to a small reference value step. It shows that the speed controller is tuned properly and its time response corresponds to the simulated time course (on the right side). Fig. 9 shows the speed response se and large value of the reference signal without using ARW connection. The students have chance to modify the control program, to change the controller parameters and to observe the system behavior and responses to the changes. Fig. 8. Speed response and its simulated time course in the linear region at the reference signal step corresponding to 5% of nominal value VI. CONCLUSION The presented physical model of a continuous production line containss all features of mechatronic systems and it offers a unique chance for students to understand control principles of complex drive systems with multi-motor multi drives. Moreover it offers a safe experimentation on modern control systems presented by PLCs, [5]. At their programming the students performs experiments on the most modern automatic equipments that causes a secondary effect for the graduates from the concerned study program – increasing of their value and competiveness on the labor market. The originall model was recently substantially renovated and we continue in this renovation by exchanging of the gears among the motors and driving cylinders. The previous gears having large backlash will be exchanged for planed gear with the backlash of 2’ which will give chance to employ a more precise control and thus to implement more complex algorithms .The physical model also suitable for research at design and verification of new control structures and algorithms for HIL (Hardware-In-the-Loop) (Hardware simulation that have recently become a standard at verification of mechatronic systems control REFERENCES [1] BRANDENBURG, G. – WOLFERMANN, W.: State observers for multimulti motor drives in processing machines with continuous moving webs,” in Proc. Power Electronics and Applications Conf. (EPE’85), Brussels, Belgium, 1985, pp. 3.203–3.210. [2] JEFTENIC, Borislav – BEBIC, Milan – STATKIC, Sasa: Controlled Multi-Motor Motor Drives. In: International Symposium on Power Electronics, Electrical Drives, Automation and Motion, SPEEDAM 2006. 20 23. 26.5.2006, pp. 1392 – 1398. [3] FEDÁK, Viliam – FETYKO, Ján – REPIŠČÁK, Martin: Computer Supported Education for Industrial Mechatronics Systems, In: Proc. of Computer Based Learning in Science Int. Conf., CBLIS 2005, Zilina, 2. - 6.7.2005. ISBN 9963-607-63-2, 2, pp. 19-27. 19 [4] FEDOR, Pavol – Perduková, Daniela – Timko, Jaroslav: Study of Controlled Structure Properties with Reference Model. Acta Technica, ČSAV 46, 2001, pp.167-179. 179. ISSN 0001-7043. 0001 [5] Virtual Laboratory of Mechatronic Systems Control: Control http://andromeda.fei.t uke.sk/, (in Slovak).