Mechatronic conception of feeding and dosing systems used in automat inspection systems.

Cristea, Luciana ; Baritz, Mihaela ; Manescu, Mihai 等

1. INTRODUCTION

The research objectives have been underlined within the frame of solving a specific problem raised in the field of machine manufacturing industry- automatic systems for dimensional control productivity improvement characteristics and performances. 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. In this paper are being approached a few aspects concerning the behaviour of feeding and dosing systems for parts control with the aim of achieving the best structures from the efficiency point of view (Alciatore & Histand, 2005).

2. TEORETICAL ASPECTS

In the world, remarkable preoccupations were achieved in the field of the development and optimization of the parts handle and in the field of the mechanical characteristic correlation of the automation. Solid body mechanics considers more and more real factors, that influence the mechanical interaction of bodies, and emphasizes the required and admitted simplifications in order to allow solving of some practical problems by mechanical means. Static behaviour analysis of parts in different feeding systems starts with studying different types of feeding devices. Analyzing the equilibrium limit conditions it can be established that the main static influence factors are:

--the parts current position as related to the box axis;

--the application point of forces F- respectively angle 8;

--the nature of materials in contact and relative movement;

--the position of part gravity centre;

--the parts dimensions;

--the tilting of transporter disk.

[FIGURE 1 OMITTED]

Dynamic behaviour analysis, respectively the writing of the piece movement governing equations with respect to a fixed coordinate system can be done based on analytical mechanics, namely, Lagrange's equations. As well as before, these feeding systems with disk having nests, respectively with rotor having horizontal palettes, can be considered particular types of one disk having inclined nests. In the dynamic behaviour analysis of the spherical piece in these feeding systems one assumes that the ball has two degrees of freedom:--a rotation around OZ0 axis, because of the conveyor disk;--radial displacement because of the interstice between pallets, respectively because of the relative displacement among piece, tub and conveyor as a consequence of manufacturing characteristics of the latter (figl). Nest, two generalized coordinates were chosen: the rotational angle [section] and radiusp. Lagrange's equations related to the fixed system OXYZ, taking into account the generalized coordinated: radius p and rotational angle [section] can be written as follows to get the equation governing the movement in radial direction (see eq. 1).

L = mg [square root of [sin.sup.2] + [[alpha].sub.1] + [sin.sup.2] [alpha].sub.2] - 2 sin [[alpha].sub.1] sin [alpha .sub.2] cos([alpha].sub.1]) + [[alpha].sub.2])/sin([[alpha].sub.1] + [[alpha].sub.2]. (1)

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]; (2)

The relative displacement of both rigid bodies being in contact can be done through gliding or rolling. Lagrange's equation with multipliers has been used to write the equation of movement, together with the nonholonomic couplings leading to a system with 1+s equations having 1+s unknowns: [q.sub.1], ..., [q.sub.s]; [[lambda].sub.1], ..., [[lambda].sub.s]. In case the piece is a spherical (homogeneous) one and it is rolling (with a swivel movement) without gliding between piece and tub a nonholonomic coupling is being achieved The generalised coordinates [x.sub.G], [y.sub.G], [theta], [psi], [phi] satisfied two coupling connections unintegrable, therefore we get a nonholonomic system, a sclerenome one, having three degrees of freedom. In case the tub is inclined the coupling between both bodies becomes holonomous because the rotational axis, at a rolling of the piece without gliding in the plane of inclined tub, keeps a constant direction. From Lagrange's equations have been obtained three prime integrals (2) that allow a reduction of the problems to quadratics.

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (3)

Considering the theoretical analysis, the authors give emphasis to the influence factors that can determine the optimised structure realisation.

Some of the most important factors are:

* the holding elements rotative speed;

* the tank rake;

* the parts' dimensional characteristics;

* the pats' features of constructions;

* the parts' quality coefficient;

* the holding elements dimensional characteristics;

* the holding elements features of constructions;

* the looping unit mechanical characteristics.

3. EXPERIMENTAL ASPECTS

In order to analyse the correlation of the static and dynamic characteristics and the specific functional conditions, the author devised and realised an original testing plant (Balachandra, 2002). The general structure of the testing plant routine is presented in figure 2.

For the automatic monitoring of the dosing process in the case of a volumetric dosing system with vibrator slot, it was built an automatic dosing system using the system presented in figure 3. For the data processing of the control unit it was used a microcontroller produced by Atmel Atmega 8535. The Atmega 8535 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 it is compatible with SPI interface protocols. The three-wire operation makes the part ideal for isolated systems where minimizing the number of interface lines minimizes the number of opto-isolators required in the system. 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. The principal aim of this study consists in the conception of an algorithm that makes the dosing process faster with the maximum precision. We tried to do this optimization though having a fast flow of material at the start and a good precision at the end of the process. That is the motivation that made me to divide the process in two parts. One part where that the angle is graduate change depending on the dosing material. And in the last part the angle remains constant and the power of the chute vibration depend on the rest of the material that remains to be dosed. The algorithm calculates in real time the proportional error. This is obtained from the difference of the value of the material that must be dosed and the material that was dosed. This error is multiplicities with a constant and the result is proportional error.

[FIGURE 2 OMITTED]

[FIGURE 3 OMITTED]

This proportional error is applied on the actuator. In this way is obtained a feedback and a good optimization of process.

4. CONCLUSION

An Automated mechatronic system is capable of handling materials and energy, communicating with its environment and is characterised by self-regulation, which enables it to respond to predictable changes in its environment in a pre-programmed fashion (Tomatis & Brega, 2001). Automatic control has been an essential part of primary processing elements. Computer-based control systems permitted the coordination of machines and production lines, and have enabled management information to be made available from directly from the dosing systems. The automatic control interface of the realized stand can offer a high precision of the dosing of each batch and can help in the understanding of the material behaviour during the transport process. The main purpose of this research is to generate optimised automat dimensional inspection systems for more mechanical efficiency. This method provide an automatic optimised process for dimensional inspection as well as an important data base for selecting the optimal working parameters that can assure the most efficient mechatronical structure used in automation of dimensional control systems. In the near future we will use this method to enable optimisation of all vital parts of the structure of a mechatronic module.

5. REFERENCES

Alciatore, G. & Histand, B. (2005), Introduction to Mechatronics and Measurement Systems, McGraw-Hill Science/Engineering/Math; 3 edition, 2005

Balachandra, R.(2002). Modular Design and Technological Innovation, Report 2002-0, Information Storage Industry Centre, Univ. of California, 2002

Tomatis, N. & Brega, R.(2001). A Complex Mechatronic System from Design to Application, IEEE ASME International Conf." Advanced Intelligent Mechatronics" Proceedings Italy, 2001, pag. 278-283

***(2008) www.atmel.com, Atmel QTouch Library 2.0, Accesed on:2009-01-15

*** (2007) http://www.sigterm.de Tools of Trade for World Domination Accesed on:2009-0i-30