This paper introduces a generic performance measurement methodology for identifying and dimensioning the user requirements of laboratory information systems with a view to evaluating and improving their overall user satisfaction. The dynamic Web-based laboratory information system (known as IntraMEL) for the Manufacturing Engineering Laboratories (MEL) in the City University of Hong Kong is used as a case study for formulating, testing and implementing the methodology. The proposed model takes an analytical approach to assess the performance of an information system using psychometric concepts. Through the experience gained from applying the methodology on IntraMEL, a set of performance evaluation guidelines can be established. These evaluation guidelines will be applicable to the information systems in other laboratories and service centres.
In this paper, a reference system architecture is presented which utilizes colour Petri-nets (CPN s), a distributed F ieldbus sensory network and the manufacturing message speci® cation (M M S) model for the control of the¯exible assembly system (F AS) over a distributed communication network. In this architecture, a client and server methodology based on the M M S is utilised where the robots and the conveyor systems are modelled as servers and a CPN based cell controller is modelled as a client which is capable of dispatching the assembly task requirement to the remote devices in a timely, con¯ict and deadlock free manner. One of the distinct features of the proposed controller is the provision of high level interfaces for the de® nition and con® guration of both the assembly task requirement and the structure of the assembly system. It makes the system highly eOE ective for small batch production where recon® guration of the physical system is frequently needed. A case study is presented to demonstrate a real application of the proposed system.
Introduction to MMS-based control of¯exible assembly systemsM anufacturing message speci® cation or MMS (ISO 1990) is an applicatio n protocol in the open system interconnection (OSI) seven layer model. It is designed to support messaging communications amongst programmable devices in a CIM environment. In MMS, a server is a system which has physical control over a set of real devices. The other components of the communication network will be clients who send requests to the server to perform a task. Figure 1 shows their master and slave relationship. MM S describes the behaviour of the communicating systems using an abstract object known as a virtual manufacturing device (VM D). Real physical devices, such as robots and conveyor lines, are mapped to a whole or part of the VMD through the concept of capabilities. Since the behaviour of the VM Ds are standardized and the same semantics can be extracted from the information contained in the MM S protocol data unit, it ensures that all MMS-based devices can communicate amongst themselves regardless of the proprietary communication format imposed by diOE erent vendors. The use of MM S can thus greatly enhance the inter-operability of manufacturing devices in a CIM environment.A revolutionary approach in MMS is the de® nition of`domain and program invocation' which provide¯exibility in the control of dynamic systems. A`domain' is a subset of the VMD which includes the required`capabilities' set and a unique domain content for a speci® c task. M ore than one domain can co-exist and they can be created statically or dynamically according to the requirements of a speci® c
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