Yoshitomo Ikkai

A high speed scheduling method by analyzing job flexibility and taboo search for a large-scale job shop problem with group constraints

A job shop problem with group constraints is a problem where job schedule in each line is decided, and jobs dealt with the same process have to be grouped for every process of a line. The minimum and maximum size restrictions exist in the total size of jobs in the group. An evaluation function of this problem consists of an average manufactured time needed for completion of all jobs, a number of group changes, and a number of line rests. This research consists of two parts: rapid generation of an initial solution by heuristics and improvement of solutions. In the part of generation of an initial solution, the flexibility of each job according to an influential degree of a whole plan is defined. In the part of improvement, rules, which can improve one of three evaluation items, are prepared. By application of a taboo search, which can apply plural rules, total evaluation can be improved. The proposed method has been applied to some real large-scale job shop problems with group constraints, and its effectiveness is confirmed.

Simulation tool of supply chain model with various structure and decision making processes

To evaluate the control mechanism for a supply chain, simulation is one of the most effective methods. In a supply chain, however, the flows of work, transit and decision-making have complex interrelations, so that it is difficult to easily express a model for simulation. In this paper, the functions needed for supply-chain simulation and a tool equipped with these functions are proposed. By using this tool, modeling and simulating of the supply chain are supported. Flows of work, transit and decision-making are expressed in individually-defined forms, and they are connected and integrated to generate a whole supply-chain model.

Dispatching rule exchangeable optimization planning system

A new method for selection of dispatching rules, called a status selection method is discussed. In this method, the most promising status is selected from tentative statuses that are generated by applying all dispatching rules. Since the dispatching rules and the knowledge of status selection are independent, it is easy to exchange the dispatching rules. From the result of the application of the proposed method to a simple flow shop problem, it is confirmed that the status selection method is effective.<<ETX>>

A deadlock detection algorithm for business processes workflow models

Proposes an algorithm which detects structures of deadlock which have deadlock occurrence possibility. This deadlock detection algorithm finds out all deadlock structures in the business processes workflow model by using deadlock patterns which express deadlock structures by combinations of nodes. There is the problem that some deadlock structures cannot be identified with some deadlock pattern because the deadlock structures cross each other when the algorithm finds deadlock patterns in the business processes workflow model. The problem can be solved by detecting the deadlock structures not by using each deadlock pattern but by using each of the unit into which the deadlock pattern is integrated.

Automatic regeneration system for sequential control programs

To replace or maintain many industrial plants developed in the 1960s is quite hard, because the documents of installed sequential control logics seldom remain. SPAIR is an automatic regeneration method of control logic to cope with this problem. In SPAIR, the control logic for operating plants is automatically regenerated from the input and output data of the control unit and supplementary specification by an inductive learning algorithm. When SPAIR is applied to the regeneration of real operating plants, it is necessary to verify if the regenerated sequential control programs can accurately control such plants. For this purpose, the SPAR-System, in which SPAIR is installed, has been developed. The SPAR-System can edit the data and logic of plants and can verify the inferred logic on the simulation plant model easily.

A simulation method for evaluating product family supply chain

In a supply chain, a slight change of management strategy in one company largely affects the effectiveness of the chain as a whole. In particular, when companies generate product families, the relationships between companies are very complex, so it is difficult to analyse them mathematically. We propose a modelling and simulation method to analyse a product-family supply chain for business process reengineering. By modelling the workflow and transport independently, the structure of the supply chain is expressed. From the simulation results, the various criteria (e.g. stock level, response time, etc.) can be calculated.

Automatic regeneration of sequence programs for operating plants

Today, many plants built in the 1960s will probably be replaced or maintained. However, it is difficult to replace or maintain them because the installed sequential control logic documents are seldom still in existence. Therefore, we have proposed an automatic regeneration method (SPAIR) in order to solve this problem. SPAIR regenerates sequential control logic that is expressed on a ladder diagram from the input and output data of a target control unit and its supplementary specifications, which indicate the information about timers and interior coils. Time series data is compressed and translated into training data using the specifications. The training data are processed by inductive learning and transformed into control logic. We have developed the SPAR-System in order to edit all kinds of data, generate target logic for plants, and to easily verify the inferred logic simulation plant. Simulation experiments confirmed that control logic that is regenerated by SPAIR behaves in the same way as the installed control logic of a target plant model.

A method for mediator identification using queued history of encrypted user information in an incentive attached peer to peer electronic coupon system

An incentive attached peer to peer (P2P) electronic coupon system is proposed in which users forward e-coupons to potential users by providing incentives to mediators. A service provider needs to acquire distribution history by recording it in the e-coupons, since this system is intended for pure P2P communication. This causes problems of dishonestly altering the distribution history. To solve such problems, distribution history is realized in a queue structure. Each element at the initial state consists of dummy UIDs, a secret key, and a digital signature. In recording ones UID, the encrypted UID is enqueued to the queue with a hash value of a dummy UID in the dequeued element, so that malicious users cannot impersonate it. Additionally, a public key queue is applied to generate digital signatures on mobile devices. The availability of the proposed method is evaluated by quantifying risk reduction effects using fault tree analysis (FTA)

A description language based on multi-functional modeling and a supply chain simulation tool

It is difficult to analyze the performance of a supply chain philosophically because of the complexity of the supply chain. Therefore, in order to evaluate the control algorithms for a supply chain, simulation is an effective method. However, it is difficult to describe an entire supply chain because of the large variety and number of components in a supply chain. The paper proposes a description language in which an entire supply chain is described efficiently. It also describes the simulation engine which efficiently determines the execution priority of events, and the simulation tool based on the proposed language which has been developed.

Development of a distributed process control programming tool for function block description

Production plants have been complicated by the diversification of products. In order to control complicated production plants, distributed process control is a powerful approach. In the development of a distributed process control system, it is difficult to develop its software because distributed controllers complicatedly interact with each other. For that reason, the function block model, which is the specification language for distributed process control logic, is being standardized in IEC61499-1. A distributed process control programming tool for function block description is proposed. It is possible to describe control programs hierarchically by using function blocks. The GUI of this tool supplies multi-windows which can simultaneously display function blocks on different hierarchical levels. In this tool, inputted programs can also be verified by a simulation. This tool is applied to the control program description of an automatic carrier system. It has been confirmed that the control program is completely described and simulated by using this tool.