A Study on Inter-enterprise Quality Control Function

Self-organization Reconfiguration Based Fractal Networks*

Yongtao Qin, Liping Zhao, Yiyong Yao, and Damin Xu State Key Laboratory for Manufacturing Systems Engineering

Xi’an Jiao Tong University School of Mechanical Engineering,

Xi’an Jiao Tong University Xi’an,Shannxi Province, China

qinyt23419@126.com

* This work is supported by No. 2006AA04Z149 form the National High-Tech. R&D Program for Contemporary Manufacturing Integrated Technology, China.

Abstract - With the increase of product complexity, product quality assurance is no longer completed by isolated enterprise internal quality control. To meet the demand of inter-enterprise quality control function fast reconfiguration, based on fractal and complex networks theory, inter-enterprise quality control fractal networks model is constructed by the fractal characteristic analysis of inter-enterprise quality control function. The self-organization characteristic of this model is researched on the basis of self-organization principle, and the self-organization strategy and the capability evaluation of inter-enterprise quality control function fast reconfiguration have been discussed with the example of the partner enterprises’ self-organization selection in partner enterprises layer of this model. Finally, based on genetic algorithm, the realization method of self-organization is researched, and the result can provide guidance for inter-enterprise quality control..

Index Terms - Fractal, Self-organization, Quality Control, Inter-enterprise

I. INTRODUCTION

Along with the diversification and individuation of consume requirements, the increase of products complexity, the manufacture of products have been extended from a single enterprise to enterprises, consequently, so that the scope of quality control has been extended from internal enterprise to enterprises. Product quality control involves internal factors such as personnel, products, business process, technical improvements, and external factors such as market, demand, the overall technological level of society. In intense market competition, because enterprise environment is a dynamic system, the dynamic and relevant characteristics of enterprise environment’s all basic elements rapidly increase, and the business process of enterprise frequently changes. So the complex and dynamic enterprise environment has been created to inter-enterprise quality control.

Facing the dynamic enterprise environment, the function of quality control should be reconfigured in the aspect of space and time aspects without affecting system’s continuous operation, fast adjust system basic framework and processing mechanism to finish new quality control function

configuration including select enterprise, assign equipment, adjust process, so that new quality control function configuration can adapt to new enterprise environment. The quality control function reconfiguration plays an especially important role in the improvement of quality control efficiency and product competitiveness [1-5]. The researchers at home and abroad have made a number of works [6-9]. In the works, fractal theory provides a new approach to studying quality control function reconfiguration. However, at present the studies of fractal theory focus on internal enterprise quality control problem. To solve the reconfiguration problems of inter-enterprise quality control function, in this paper, based on fractal and complex networks theory, inter-enterprise quality control fractal networks model is constructed by analysis to the fractal characteristic of inter-enterprise quality control function. The self-organization characteristic of this model has been researched on the basis of self-organization principle, and the self-organization strategy and the capability evaluation of inter-enterprise quality control function fast reconfiguration have been discussed with the example of the partner enterprises’ self-organization selection in partner enterprises layer of this model. Finally, based on genetic algorithm, the method of self-organization has been researched, and the result can provide guidance for inter-enterprise quality control.

II. INTER-ENTERPRISE QUALITY CONTROL FRACTAL NETWORKS MODEL

A. The Fractal Characteristics of Inter-enterprise Quality Control Function

The quality control of inter-enterprise manufacturing means that quality control task is allocated, executed, managed, and evaluated in the mode that core enterprise and partner enterprises used as centre and partners, with demand of market and customers as direction, and internal enterprises quality control information can be integrated based on Web [10-12].

When the inter-enterprise quality control task execution is seen as a total unit, the total unit will be decomposed after

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Proceedings of the 2007 IEEEInternational Conference on Robotics and Biomimetics

December 15 -18, 2007, Sanya, China

cooperative partners’ selection, and create some executable quality control task execution subunits. The child quality control task execution subunit also can be seen as a parent unit, and these units will be achieved by quality control task execution subunits’ action. Quality control task execution units could be decomposed as core enterprises, partner enterprises, manufacturing cells, and manufacturing equipments on the basis of inter-enterprise hierarchical structure. Though the quality control task execution units’ input information, output information and constraint conditions are different, function is similar. That is to say, based on some demands, each unit can allocate, execute, manage, and evaluate quality control task. Therefore, based on fractal theory[6-9], inter-enterprise quality control function has fractal characteristic, and fractal characteristic EQFT can be described in (1).

1 2

1 2

1 2

. { . . ... ... . }

. { . . ... ... . }

. { . . ... ... . }

c c c n c

i c c c n c

i c c c n c

ee Q pe Q pe Q pe Q

EQFT pe Q c Q c Q c Q

c Q e Q e Q e Q

=

= =

=

� � �� � �� � �

(1)

Where ee is core enterprise, pe is partner enterprises, c is

manufacturing cell, e is equipment. cQ is quality control unit.

{ , , , , }cQ G D A S F= (2) Where:G is quality control task planning cell, D is quality

control task allocation cell, A is quality control task execution cell, S is quality control task management cell, F is quality control task evaluation cell.

B� The Self-organization Characteristics of Inter-enterprise Quality Control Fractal Networks Model

According to the fractal characteristic of inter-enterprise quality control function, based on fractal and complex networks theory, inter-enterprise quality control task execution units can be constructed as network nodes by the encapsulation of object-oriented technology. The constraint relationships among nodes are established based on hierarchical structure among enterprises, the demand of quality control, and the relationship of product configuration. Based on network nodes and constraint relationships, combined with some quality control methods and supporting technologies, inter-enterprise quality control fractal networks model is established, and it can be showed as fig. 1. 1) Node: Rounds in fig.1 represents nodes in the fractal network. Based on the encapsulation of object-oriented technology, nodes can be constructed by the quality control units of inter-enterprise hierarchical structure, including core enterprises, partner enterprises, manufacturing cell, and

2 1L X

2 2L X2 nL X1 1L X4 1L X

3 nL W

3 nL X

3 1L X

3 2L X

3 2L X

3 2L X

3 1L X

3 1L X

3 nL X

3 nL X

4 2L X

4 nL X

4 1L X

4 2L X 4 nL X

4 1L X

4 2L X4 1L X

4 1L X

4 1L X

4 1L X

4 1L X

4 1L X

4 2L X

4 2L X

4 2L X

4 2L X

4 2L X

4 2L X

4 nL X4 nL X

4 nL X

4 nL X

4 nL X

4 nL X

4 nL X

2 1L W2 nL W

2 2L W

4 nL W

4 nL W

4 nL W

4 nL W

4 nL W

4 nL W

4 nL W

4 nL W

4 nL W

4 1L W

4 1L W

4 1L W

4 1L W

4 1L W

4 1L W

4 1L W

4 1L W

4 1L W

3 1L W4 2L W

4 2L W

4 2L W

4 2L W

4 2L W

4 2L W

4 2L W

4 2L W

4 2L W

3 1L W

3 1L W

3 2L W

3 2L W

3 2L W3 nL W

3 nL W

Fig.1 Inter-enterprise quality control fractal networks model

equipment quality control unit. i jL X is the jth node in the

ith layer. 2) Constraint relation: Solid lines in fig.1 represents the

management constraint between upper layer nodes and lower layer ones, and dashed lines in fig.1 represents the coordination constraint relation among nodes at the same layer. The connection among each node has been supposed to be bidirectional symmetry, namely, connecting edge is undirected edge.

NR is constraint relation among nodes.

00,1

00, 1, 2 kk

MRNR

CR ==

� � � �= =� � � �� � � �

1

1, 10, 1, 2 k=

−� �= � �� �

(3)

Where: MR is the management constraint of upper layer nodes to lower layer ones. 1MR = represents there is management constraint between upper layer nodes and lower layer nodes.

0MR = represents there isn’t management constraint between upper layer nodes and lower layer nodes.

1MR = − represents lower layer nodes be used as backup selection or reference to upper layer nodes. CR is coordination constraint relation among nodes at the same layer. 0CR = represents there is rejection coordination constraint relation, 1CR = represents there is competition coordination constraint relation,

2CR = represents there is necessity coordination constraint relation.

0k = represents quality control function need no reconfiguration, 1k = represents quality control function need reconfiguration

The connecting weight of management constraint is introduced to reflect the variation probability of nodes’ cooperation, and express the management degree of upper nodes to lower ones.

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i kLW is connecting weight kW in the ith layer. The value

of kW is dependent on production capacity, personnel

resources, response time, and so on. This model could obtain quality input information from

exterior, and output quality control information by the constraint relations among nodes. So it is an open system. Meanwhile, the constraint relations among nodes are affected by quality control resources, standards, and consumer requirement of external world, so that this model’s structure will extend, and make operation status tending to order. Based on above features, self-organization characteristic of this model can be formed. The fundamental principle of self-organization means that order system can adapt to environment, feed back the change of environment into the interior of system, and achieve its own evolution on the basis of adjust and reconfigurate basic module. Based on the fundamental principle of self-organization[13-14], the quality control model could continually obtain the information of quality control, extend own structure by the variation of nodes, and constraint relations among nodes, so that nodes can uniform independence with integrity, achieve whole benefit with exerting individual performance to the maximum extent. It can adapt to exterior change, gain intelligent character, and further cooperative and adaptive character. As a result, this model has self-organization characteristic, so that its structure can be reconfigured, splited , radiated, and extended on the basis of product or task’s change.

III. INTER-ENTERPRISE QUALITY CONTROL FUNCTION SELF-ORGANIZATION RECONFIGURATION

A. The Strategy of Inter-enterprise Quality Control Function Self-organization Reconfiguration

In the process of quality control, including quality control task’s planning, allocation, execution, and evaluation, the new quality control function created by dynamic enterprise environment can fast reconfigure on the basis of the self-organization characteristic of inter-enterprise quality control fractal networks model. Inter-enterprise quality control function fast reconfiguration’s logic structure can be showed as fig. 2

Firstly, based on the demand of inter-enterprise quality control created by market and consumer, and the manufacture resource of enterprise, combined nodes and constraint relationships among nodes, inter-enterprise quality control fractal networks model is constructed. Based on self-organization characteristic of this model, directed by evaluation mechanism, quality control task can fast and reasonablely plan quality control task. The nodes of this model can fast reconfigure to realize quality control function mapped in this model’s logic meaning aspect. The nodes

Fig.2 The logic structure of inter-enterprise quality control function self-organizationr econfiguration

present the quality control function of core enterprise, partner enterprises, machining unit, and equipment in this model’s physics meaning aspect. Partner enterprises can self-organization select in partner enterprises layer, equipment can self-organization assign in machining unit layer, process can self-organization adjust in equipment layer in this model’s physical meaning aspect to realize the inter-enterprise quality control function reconfiguration. Finally, based on evaluating mechanism, the effect of inter-enterprise quality control function reconfiguration is evaluated, and it can meet the demand of quality control or not.

The self-organization strategy and capability evaluation of inter-enterprise quality control’s fast reconfiguration are discussed with the example of the partner enterprises’ self-organization selection in the partner enterprises layer of this model, and the logic structure of partner enterprises self-organization selection can be showed as fig. 3.

The demands of market and

consumer

The rmanufactureresource of enterprise

Decision-making

mechanism

Partner enterprisesCore enterprise

Manufacturing resource cell

Evaluation mechanism

Enterprise role cell

Fig.3 The logic structure of partner

enterprises’ self-organization selection

On the basis of the demands of market and consumer, and

the manufacture resource of enterprises, decision-making

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mechanism can determine the roles of core and partner enterprises, so that it can complete enterprise role cell’s function. According to the direction created by the evaluation mechanism of partner enterprises selection, enterprise role cell interaction with quality control method cell, manufacturing resource cell, and inter-enterprise framework cell, so that it can generate a cycle structure. The cycle structure can self-organization select partner enterprises by adjust enterprises’ number, combination, or order, and the time of cooperation, and so on. To meet the demand of function cooperation among cells, each cell can independently adjust operation to optimize whole quality control benefit. Directed by the evaluation mechanism of partner enterprises selection, each cell’s operation operation is manipulated by the self-organization characteristic of inter-enterprise quality control fractal networks model. Evaluation mechanism only monitor the coordination situation among cells, and adjust the operation of problematic cell in the case of the self-organization effect can’t be satisfied.

Based on self-organization select partner enterprises, cycle structure can input personnel, equipment, information flow, and output new inter-enterprise quality control correlative service. Its resources and information can exchange with exterior, and can complete quality control function fast reconfiguration quality control. The problem of partner enterprises selection can be described as a optimization problem, namely confirm a set: 1 2 0{ , ,... }k k nE E E E < <= . kE is

partner enterprise that is selected and take a part in inter-enterprise quality control.

Because some factors influence partner enterprises self-organization selection such as time(T), cost(C), quality(Q), risk(R), the evaluation mechanism can be described as a evaluation function: min( ) { min min min min }Q T C RO w Q w T w C w R= × + × + × + ×

(4) where k

iQ , kiT , k

iC , kiR is partner enterprise kE .finish the

no. i quality control task’s quality evaluation, time, cost and risk, respectively. For the agreement of quality evaluation’s analysis with others, quality evaluation’s numerical value is low presents that the quality control effect is better.

Cw , Tw , Qw , Rw is quality evaluation, time, cost and risk

influence weight value, respectively, and 1T Q R Cw w w w+ + + = . [0,1]h ∈ , 0h = represents partner

enterprise kE isn’t selected, 1h = represents partner

enterprise kE is selected.

B. The Realization Method of Inter-enterprise Quality Control Function Self-organization Reconfiguration

The self-organization process is affected by many factors, such as time (T), cost (C), quality (Q), risk (R) (reputation of services provided by nodes) are important evaluation index to select nodes, so it is a multi-objective optimization problem [15-16]. Evolutionary algorithm has the fundamental condition and characteristics to realize the algorithm of self-organization in distributed evolution system. Genetic

algorithm has giant advantage to solving combined optimization problems in a large searching space[17-18]. Therefore, the multi-objective optimization genetic algorithm of the evolutionary algorithm is adopted to realize self-organization method.

The research of nodes self-organization reconfiguration’s realization method in the logic meaning aspect of model provides a direction to realize the method of inter-enterprise quality control function self-organization reconfiguration in the physical meaning aspect of model.

Evaluating mechanism can evaluate the effect of inter-enterprise quality control function self-organization reconfiguration in the quantization degree. Evaluating function can finish evaluating mechanism, and can be established by objective function in genetic algorithm. Objective function in genetic algorithm is expressed, as follows.

1) The minimum time of quality control task execution. Because node need to timely complete quality control task, and communicate with other node, the time of quality control task execution include internal time that complete quality control task, and external time that communicate with other node, that is to say, external time is the time of quality information transmission. The minimum time of quality control task execution is as follows.

( ) min( )in outobj T T T= + 1 2

,0 0

min( ( ) ( , ))N N

i i mi i

T j T j k− −

= == +� � (5)

where ( )iT j is internal time that quality control task is

completed by i layer j node i jL X , , ( , )i mT j k is external time

that transmit i layer j node i jL X to m layerk node m kL X .

2) The minimum risk of quality control. The node’s service, reputation, historical record, and so on can influence node self-organization reconfiguration, so that node risk evaluation need a quantified risk evaluating value j

ir to

evaluate the minimum risk of quality control.

11( ) min{ max }

n kj

ijiobj R r

=== � (6)

3) Best processing quality. Quality evaluation jiQ to

evaluate quality in the process of nodes reconfiguration:

1 1( ) min{ ( )}

n kj j

i ii j

obj Q w Q= =

= �� (7)

where jiw is the quality weight of backup node i jL X which is

the jth node in the ith layer, and . 4) The least total cost of operation. The least cost C

includes two parts: one is processing control quality cost of nodes inC , the other is transportation cost of adjacent

nodes outC , the least total cost of operation can be expressed

in (8). ( ) min( )in outobj C C C= +

1 2

, 10 0

min( ( ) ( , ))N N

i i ii i

C j C j k− −

+= =

= +� � (8)

1 1 1}Q T C R

n n nk k k ki i i i

i i iw hQ w hT w hC w hR

= = == × + × + × + ×� � �

11

nj

ii

w=

=�

1736

where ( )iC j is process quality control cost completed by

node i jL X , , 1( , )i iC j k+ is the transportation cost which from

the candidate node i jL X to m kL X .

Because some constraint conditions such as time constraint, risk constraint, and processing quality evaluation constraint can restrict the fast reconstruction of inter-enterprise quality control function, multi-objective optimization genetic algorithm need to consider the constraint conditions. Based on fast reconfiguration’s evaluation mechanism that can be used as fitness function, arrangement coding modes that can make multi-population independently evolve and optimum individual termly exchange, and niche fitness that can share and keep population diversity, multi-objective optimization genetic algorithm can obtain self-organization effect.

IV CONCLUSION

Based on fractal and complex networks theory, and analysis to the fractal characteristic of inter-enterprise quality control function, inter-enterprise quality control fractal networks model is constructed by node constructed based inter-enterprise quality control unit, constraint relationships among nodes are established based on hierarchical structure among enterprises, quality control demand, and so on. The self-organization characteristic of this model has been researched on the basis of self-organization principle, and the self-organization strategy and capability evaluation of inter-enterprise quality control’s fast reconfiguration have been discussed with the example of the study of partner enterprise’s self-organization selection in partner enterprises layer of this model. It directs self-organization to select partner enterprises, assign equipment, and adjust process. Finally, based on multi-objective optimization genetic algorithm, self-organization reconfiguration’s realization method in the logic meaning aspect of model has been researched, so that it can realize the method of inter-enterprise quality control function self-organization reconfiguration, and the result can provides a method support for inter-enterprise product quality control.

ACKNOWLEDGMENT

This work was supported by grant No. 2006AA04Z149 form the National High-Tech. R&D Program for Contemporary Manufacturing Integrated Technology, China

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