Researches Concerning the Data Processing used in Feeding and Dosing Systems Optimization

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1 Researches Concerning the Data Processing used in Feeding and Dosing Systems Optimization LUCIANA CRISTEA MIHAELA BARITZ LILIANA ROGOZEA MIHAI MANESCU DIANA COTOROS ANGELA REPANOVICI Precision Mechanics and Mechatronics Department Transilvania University of Brasov Eroilor 29, Brasov ROMANIA Abstract: The paper presents the solution for data processing of intelligent dosing system. The data processing is used to optimize the dosing process of bulk solid material. The hardware part of the dosing system includes a microcontroller board with ADC integrate and a personal computer. The mean of sample products taken from a production line over a period of one hour must not exceed the declared weight or 'nominal quantity'. Weight control is therefore a critical issue and the appropriate authority must approve the weighing system used for checking the weights. Keywords: Vibrating dosing, Data processing, Microcontroller, Automation, Mechatronics. 1. Introduction An automatic dimensional inspection system combines the core aspects of mechatronics (system modelling, simulation, sensors, actuation, real-time computer interfacing, and control) with practical industrial applications. Many modern technological products result from integrating mechanical, electrical and computer systems. This combination of technologies is known as mechatronic systems engineering and such mechatronic systems are found in numerous applications. An Intelligent mechatronic system is capable of achieving given goals under conditions of uncertainty. In contrast to automated systems, which are, by definition, pre-programmed to deliver given behaviour and are therefore predictable, intelligent systems may arrive to specified goals in an unpredictable manner. The recent manufacturing trends aim at delivering wide variety of products with short lifetime and increasing complexity. Because of the dynamics and complexity of the specified tasks, the successful quality is possible only by applying the computers and adequate software and database. In order to optimise an automatic inspection system it is necessary to treat the entire sub-system in an integrative way during the design process. In the world, remarkable preoccupations were achieved in the field of the development and optimisation of the parts handle and in the field of the mechanical characteristic correlation of the automation. The modern automatic inspection system must be based on client server concept, in which the client (user) gives inputs of the information system using the main interface. 2. Theoretical Aspects The user has the possibility to input data concerning his/her own application (part, measuring and process characteristics). After that, the main menu of the system works with databases of parts, measuring and automation process, modular device projects and gives the process results for the most propitious dimensional control structure. The computer processes all the information, tests the analysed system and sets the working parameters to obtain an optimised mechanical system. ISSN: ISBN:

2 The main purpose of this research is to generate optimised feeding, transport, and proportioning and alignment systems for more mechanical efficiency. Because of that, the entire mechanical and electronic structure of the analysed automata is based on a modular concept. Each important component of the automata control system has a modular structure, which assures a very large working flexibility. The vibrating dosing system uses an electromagnet to produce the vibrations on the conveying vibration chute. Depending on the value of the vibration parameters (amplitude and frequency), the bulk solids will flow accordingly. An important advantage of this dosing method is that material is fed in the weight cell 1 uniformly and with smaller impact on the weight scale. The principle of this dosing system is that the flow speed of the material is given by the vibration and the angle of the chute. These two parameters are set by a microcontroller depending on the dosed material [1]. The optimization of the process concerning the speed and the precision of the metering process is made through the chute s angle depending on the rest of the material that should be dosed. The connection between the computer and the interface represents the way the operator communicates with the system. This is made through the graphical interface of an application on the PC. The transfer of the data is bidirectional. Fig. 1. Graphical interface. In fig. 1, the graphical interface is presented. The user can change the parameters of dosing process and see the resultant data and data communication between PC and system. 3. Experimental Aspects For the data processing of the control unit, we used a micro controller produced by Atmel Atmega8535. The micro controller receives on the SPI (Serial Peripheral Interface) the results of the analogous-digital conversion (ADC) and the integrated circuit that realizes the conversion (AD7730) is made by Analogous Devices and is responsible with the processing of the information collected from the weight resistive transducer 5. The ATmega 8535 microcontroller communicates with the PC through the serial interface type RS-232, and the human user can activate through the software application on the PC the following operations: single conversion, calibration, beginning of automatic dosing batch, reset or saving of the dosing data. In fig. 2, the main board with ATmega8535 microcontroller is presented [2]. The ATmega8535 flexible serial interface allows an easy interface to most microcomputers and microprocessors. The serial interface on the AD7730 has the capability of operating from just three wires and is compatible with SPI interface protocols. The three-wire operation makes the part ideal for isolated systems where the minimizing of the number of interface lines minimizes the number of opto-isolators required by the system. Register lengths on the AD7730 vary from 8 to 16 to 24 bits. The 8-bit serial ports of most microcontrollers can handle communication with these registers as one, two or three 8-bit transfers. Figure 3 shows an interface between the AD7730 and the ATmega8535 microcontroller. The diagram shows the minimum (three-wire) interface with CS on the AD7730 hardwired low. In this scheme, the RDY bit of the Status Register is monitored to determine when the Data Register is updated. An alternative scheme, which increases the number of interface lines to four, is to monitor the RDY output line from the AD7730. For interfaces, which require control of the CS input on the AD7730, one of the port bits of the Atmega8535, which is configured as an output, can be used to drive the CS input. ISSN: ISBN:

3 Fig. 2 Main board with ATmega8535 microcontroller. The ATmega8535 is configured in the master mode with its CPOL bit set to a logic zero and its CPHA bit set to a logic one. When the ATmega8535 is configured like this, its SCLK line idles low between data transfers. Therefore, the POL input of the AD7730 should be low hardwired. The AD7730 is not capable of full duplex operation. If the AD7730 is configured for a writing operation, no data appears on the DATA OUT lines even when the SCLK input is active. When the AD7730 is configured for continuous reading operation, the data presented to the part on the DATA IN line is monitored to determine when to exit the continuous reading mode [3]. The software application offers for monitoring purpose the graphs in real time for the measured weight, the theoretical debit flow (according to the number of rotations made by the screw and the constructive dimensions of the dosing screw), angular displacement and angular speed. After the ending of one dosing batch, the application allows the user to save all the data gathered through the transducers from the dosing stand in an Excel worksheet. Mass flow monitoring. The bulk solid material is conveyed by the dosing screw into the weighing vat placed upon a weighing cell that continuously monitors the added weight of material. The weight cell is working on the tensometric principle that modifies the value of the resistance of the Tensometric Bridge with the variation of the vat s weight. The analogical value of the tension from the Tensometric Bridge is converted then into a discrete value by the analogical digital converter, which is built inside the integrated circuit AD7730BN specialized for weighing applications [4]. Fig. 3. Serial peripheral interface between the microcontroller ATmega 8535 and weight conversion integrated circuit AD7730. ISSN: ISBN:

4 The weighing cell is connected directly to AD7730BN integrate without any prior amplification, because the processing of the analogical signal is processed completely by the AD7730BN integrate through the specialized components in it. The result of one conversion represents a numerical value of 24 bits and the conversion resolution will be of units for in tensions within the interval - 40mV and + 40mV5 [6]. The microcontroller communicates with the AD7730BN integrate through a Serial Peripheral Interface (SPI) that uses the following three connections from the microcontroller: data receiving connection (MISO), data transmission connection (MOSI) and one connection for the synchronization of the data (SCK) [5]. Connections between the AD7730 and the bridge are very straightforward in this type of application as illustrated in figure 4. The shown bridge configuration is a six-lead configuration with separate return leads for the reference lines. This allows a force/sense effect on the load cell excitation voltage, eliminating voltage drops caused by the excitation current flowing through the lead resistances. Illustrating a major advantage of the AD7730, the 5 V excitation voltages for the bridge can be used directly as the reference voltage for the AD7730, eliminating the need for precision matched resistors in generating a scaled-down reference. In many load-cell applications, a portion of the dynamic range of the bridge output is consumed by a pan weight or tare weight [7]. Fig. 4. Sketch representing the connections of the weight cell with the weight monitoring integrate AD7730BN Dosing graph Fig. 5 Dosing data saved in excel format In such applications, the 6-bit TARE DAC of the AD7730 can be used to adjust out this tare weight as outlined previously. The communication of the microcontroller with the PC is achieved through the interface RS232 and the human user communicates with the computer using the graphic interface that can activate the following commands: start of the dosing process, establishing of the dosing parameters, finalizing of the dosing process and save the data. The data result of dosing process can be saved in excel format. In figure 5, an example of saved data is shown. 4. Conclusion All these studies are very important in the field of precision mechanics and mechatronics systems. The main purpose of this research is to generate optimised feeding and transport systems for more mechanical efficiency. The modular systems designed in this way are part of the global tendency to achieve the automatic control systems. This system is reorganized to meet the international trends in achieving the automatic control systems. Automatic control has been an essential part of primary processing elements. Computerbased control systems permitted the coordination of machines and production lines, and have enabled management information to be made available directly from the dosing systems. The basic idea underlying modular design is to organize a complex system (such as a large program, an electronic circuit, or a mechanical ISSN: ISBN:

5 device) as a set of distinct components that can be independently developed and then plugged together. Although this may appear a simple idea, experience shows that the effectiveness of the technique critically depends on the manner in which systems are divided into components and the mechanisms used to plug components together. References 1. D. Ola, M. Manescu, L. Gaceu Software Technique for Performance Evaluation of a Volumetric Screw Dosing System for Agro- Foods Bulk Solids, Springer etherlands J. Horn, G. G. Lynium, Weigh Scale Applications for the MCP3551, L.L.C, Microchip, H. A., Janssen, Versuche über Getreidedruck in Silozen, Z. VDI H M. Manescu, L. Cristea, Intelligent Vibrating Dosing System Using Automation Through Microcontroller, Proceedings of the 8 th WSEAS International Conference on Signal Processing, Computational Geometry and Artificial Vision 2008, ISS , ISB , pp I. Moisil Classification methods used in mining clinical data, The Proceedings of the ational Symposium with International Participation, E-Health and Bioengineering, EHB 2007, Revista Medico-chirurgicala a Soc. De Medici si aturalisti din Iasi, Vol.III, Nr.2, Supl.2, pp.: 13-15, 2007, ISSN: XXX, Analog Dialogue, Analog Devices, Norwood, 2000,Volume 34, pag , XXX, Bridge Trnasducer ADC, Analog Devices, Rev.A, pag , ISSN: ISBN: