Design, evaluation and optimization in mechatronics.

Dolga, Valer ; Dolga, Lia

Abstract: The paper outlines the modular structure of the mechatronic systems and proposes a specific approach for mechatronic systems design, by combining morphological charts and multi-attribute decision methods. Advantages of this approach are outlined in connection with the optimization of the design solution. The method is exemplified on an autonomous mobile system.

Key words: design, evaluation, optimization, mechatronics, mobile robot.

1. INTRODUCTION

Usually, the "Machine Design" concept, -the design of the structural elements of a machine--is equivalent to "Mechanical Engineering Design". Most recent years, several discrepancies came forward between this definition and the emergence of more and more sophisticated machines. The moment happens together with the coming out and the development of mechatronics as a new engineering domain.

The definitions within the mechatronic concept refer to the optimal design of the electromechanical systems. The concept "Design for X" is also relevant for the mechatronic philosophy. Thereby, the modular concept becomes a goal during a mechatronic design process and brings in a number of advantages for the mating process: simplifies the operations, ensures a higher quality control, improves the possibilities of reconfiguring the system, allows automating the mating process, simplifies the attendance, etc. The optimization of the design for a mechatronic system is a compulsory requirement. The known bibliographical references approach this design both for a singular mechatronic system, and for networks of mechatronic systems (Gausemeier, 2002). The selection of the best solution expects an integration of the innovative concepts like brainstorming, star bursting, sinectics, with multi-criteria based decisions. In addition, a well advised design assumes the evaluation of a constructive solution with respect to various criteria (Shetty & Kolk, 2000).

The paper presents the authors' considerations about the mechatronic design for autonomous mobile systems and the analysis to determine the optimal solution from a set of possible design alternatives. The constructive and functional complexity of the mobile robot on one side, and the authors' own preoccupation on the other side, were determinant in choosing the mobile robot as reference element in this study.

2. CONSIDERATIONS ABOUT THE MECHATRONIC DESIGN

2.1 Modular blocks, methods and principles

In determining the solution for the mechatronic system structure, two principles of the machine theory were applied: the vertical causality (cause--effect); the secondary functions principle (around the main function the system has to perform, a set of several secondary functions are grouped).

The mechatronic design principle at a macro level is shown in Figure 1 (Dolga & Dolga, 2006).

[FIGURE 1 OMITTED]

The initial mechatronic design includes a simultaneous design in the mechanical -, the electrical--the electronic domain and in the domain of information theory. This stage aims a modular design with a task distribution on all over the mentioned domains. It is essential to carry out in sync the following tasks:

* add sensorial elements and actuators to the modular design,

* perform a concurrent data processing,

* evaluate the hardware architecture (microprocessor, bus, etc.) and the software.

Modelling and simulation of the subsystems and of the overall system objectifies the first design stage.

The developed models can be represented from an abstract to a concrete level or from a simple to a detailed level. The systemic approach of the task and the use of different facilities offered through the development methods of a new idea play together an essential role in this development. In this context, the morphological chart offers a series of advantages (Salustri, 2006). An example of decomposing a mechatronic system in subsystems derived from the defined basic functions is shown in Table 1 and a concretization of these functions is given in Table 2.

The evaluation and selection of the "best" variant using the morphological chart is most of times subjective and without a sustainable mathematical support. Therefore, a most appropriate method is the multi-attribute decision method.

One can make an initial evaluation of the variants and one can determine the solution for a certain design by using the Pugh method. Firstly, the optimal solution must be defined with respect to certain decision criteria and afterwards an adequate data processing method must be applied (Dolga, 1999). Intelligent CAD systems allow to get "n" design alternatives [V.sub.i] (i=1 ... n), all of the them being optimized from the constructive point of view. The design process and the selection of the optimal alternative are shown in Figure 2 (Dolga, 1997).

[TABLE 2 OMITTED]

[FIGURE 2 OMITTED]

2.2 About the design and structure of the autonomous mobile system

During the design and enhancement process, the autonomous mobile system was considered as a mechatronic system. The structural development of the autonomous mobile system followed the trend from abstract to complex, in harmony with the mechatronic design principle.

The benefices for the designed product can be obtained by balancing the modelling and the analysis, with respect to the validation of the experiments and the product construction.

In accordance to the presented principles and methods, an autonomous mobile system was designed. The morphological chart of this product is shown in Table 3. The realized autonomous mobile system is shown in Figure 3 (Dolga, 2006).

[FIGURE 3 OMITTED]

3. CONCLUSIONS

Experiments were made on the model of the autonomous mobile system and they will be continued by other tests regarding the spatial displacement way and the capacity to keep an imposed prescribed trajectory. The built model is robust and responses conveniently to different manual- and remote controlled tasks. These qualities were obtained by applying the described design procedures in combination with the multi-attribute decision method. Solutions for improving the model were revealed during the experiments. They concern the realization of an appropriate Labview interface, the insertion of new sensorial elements into the design and the use of the sensor fusion in controlling the mobile robot. But

even at this stage, the original procedure to combine the morphological chart and the multi-attribute decision can be considered as a contribution to turn the mechatronic design into a more efficient process.

4. REFERENCES

Buur, J. (1990). A theoretical approach to mechatronics design, Institute for Engineering Design Tech. (University of Denmark)

Dolga, V. (1999)."PROTRA" A CAD application for force sensors, Proceedings of IFToMM World Congress, pp.2759-2764, ISBN 951-42-5295-0, Oulu, june 20-24, Oulu University Press

Dolga, V. & Bacican, C. (2005). Mobile robot autonomous system equipped by sensorial elements. Proceedings of RAAD'05 14th International Workshop on Robotics in Alpe-Adria-Danube Region, pp.387-392., ISBN 973-718-241-3, Bucharest, may 26-28

Dolga, V. & Dolga, L. (2006). Design and evaluation in mechatronics. Acta Technica Napocensis S. Applied Mat. And Mechanics,Vol. II, p.269-275, ISSN 1221-5872

Gausemeier, J. (2002) From Mechatronics to Self-optimizing, International Journal of Computer Integrated Manufacturing, vol.18, no.7,October 2005, pp.550-560

Roos, F. & Wikander, J., Mechatronics design and optimization methodology, Proceedings of OSTT'05 Symposium on Machine Design, Stockholm Available from: http://www.md.kth.se/~fredrikr/AM2D/ OSTT.pdf Accessed: 2006-02-12.

Salustri, F.A. (2006), Morphological Chart, Available from: http:// deed.ryerson.ca/x/bin/xiki/view/ learning/ Morphological Chart Accessed: 2006-02-12

Shetty, D. & Kolk, A.R. (2000) Mechatronics System Design, Pws Publishing Company, ISBN 0-534-95285-2, Boston

Table 1 Decomposition of a mechatronic system in subsystems
using the main functions of the system

 FUNCTIONS

power voltage ... speed control
control regulator measuring architecture

Table 3. The morphological chart for the mobile robot

 SUB-SOLUTIONS

FUNCTIONS 1 2 3

Directional Two motive Caterpillars Stepping structure
nobility wheels and a
 pivot wheel

Energetic Electrical Electrical
autonomy power network,
 accumulator cable

Guiding Optical CCD Video Laser guide
 guiding sensors

Decision Permanently Autonomous Mixed--Autonomous
autonomy remote & remotely
 controlled controlled

Actuating C.C. motor Step by step
system motor