Hidehiko Wada

A Prototype Embedded XML-DA Server and its Evaluations

In current control systems, it is important to get information from field devices just when the information is needed for applications such as maintenance, asset management or diagnosis. However, getting information for those applications is not always easy. Many control systems do not provide enough information for those purposes, because they are designed for its own purpose: to control the plant. Since the devices themselves possess the necessary information, it is desirable for such applications to have direct access via open and standard interfaces. It is shown that an OPC XML-DA (XML data access) server embedded in the device is a possible candidate for this objective. We have developed a prototype server on a small embedded controller. In this paper, we evaluate the experimental system consisting of the embedded OPC XML-DA server and data acquisition application, and discuss where performance bottlenecks are and how the performance can be improved of the server. Finally, we discuss the performance evaluations on the improved server and the architecture which makes effective use of the server

A machinery control system using mobile agents

Flexibility will be one of the key features in future manufacturing systems because the environments that surround manufacturing systems are rapidly changing from day to day. To satisfy this requirement, we propose an autonomous decentralized system using agents. In manufacturing systems using agents, the basic concept should be based on a target product and on work having some information moving around in the system. To realize this concept, we introduce several agents called product agent or machine agent. To verify our proposed concept and architecture, we developed a prototype system. This system was for the Shape Deposition Manufacturing Laboratory of the Robotics Institute at Carnegie Mellon University.

Application of df/ihs to minimum total weighted flow time multiprocessor scheduling problems

In most cases, the scheduling problem for the multiprocessor system is NP- or strong NP-hard. For this problem, we have already proposed a practical optimization algorithm DF/IHS (Depth First/Implicit Heuristic Search), which combines the list-scheduling algorithm and the depth-first search, for the minimum parallel processing time multiprocessors scheduling problem. This paper presents a result of application of DF/IHS to the minimum total weighted flow time problem, which is used in the optimization of memory utilization. The problem of allocating tasks to m processors is considered with or without precedence constraints among the tasks. It was verified that the DF/IHS can be applied to this kind of problem very effectively, where the optimal or highly accurate approximate solution is obtained for the large-scale problem with several hundreds of tasks.