Coalition based approach for shop floor agility – a multiagent approach

Dissertation submitted for a PhD degree in Electrical Engineering, speciality of Robotics and Integrated Manufacturing from the Universidade Nova de Lisboa, Faculdade de Ciências e TecnologiaThis thesis addresses the problem of shop floor agility. In order to cope with the disturbances and uncertainties that characterise the current business scenarios faced by manufacturing companies, the capability of their shop floors needs to be improved quickly, such that these shop floors may be adapted, changed or become easily modifiable (shop floor reengineering). One of the critical elements in any shop floor reengineering process is the way the control/supervision architecture is changed or modified to accommodate for the new processes and equipment. This thesis, therefore, proposes an architecture to support the fast adaptation or changes in the control/supervision architecture. This architecture postulates that manufacturing systems are no more than compositions of modularised manufacturing components whose interactions when aggregated are governed by contractual mechanisms that favour configuration over reprogramming. A multiagent based reference architecture called Coalition Based Approach for Shop floor Agility – CoBASA, was created to support fast adaptation and changes of shop floor control architectures with minimal effort. The coalitions are composed of agentified manufacturing components (modules), whose relationships within the coalitions are governed by contracts that are configured whenever a coalition is established. Creating and changing a coalition do not involve programming effort because it only requires changes to the contract that regulates it

Contract representation for validation and run time monitoring

Organisations are increasingly using the Internet to offer their own services and to utilise the services of others. This naturally leads to resource sharing across organisational boundaries. Nevertheless, organisations will require their interactions with other organisations to be strictly controlled. In the paper-based world, business interactions, information exchange and sharing have been conducted under the control of contracts that the organisations sign. The world of electronic business needs to emulate electronic equivalents of the contract based business management practices. This thesis examines how a 'conventional' contract can be converted into its electronic equivalent and how it can be used for controlling business interactions taking place through computer messages. To implement a contract electronically, a conventional text contract needs to be described in a mathematically precise notation so that the description can be subjected to rigorous analysis and freed from the ambiguities that the original humanoriented text is likely to contain. Furthermore, a suitable run time infrastructure is required for monitoring the executable version of the contract. To address these issues, this thesis describes how standard conventional contracts can be converted into Finite State Machines (FSMs). It is illustrated how to map the rights and obligations extracted from the clauses of the contract into the states, transition and output functions, and input and output symbols of a FSM. The thesis then goes on to develop a list of correctness properties that a typical executable business contract should satisfy. A contract model should be validated against safety properties, which specify situations that the contract must not get into (such as deadlocks, unreachable states ... etc), and liveness properties, which detail qualities that would be desirable for the contract to contain (responsiveness, accessibility ... etc). The FSM description can then be subjected to model checking. This is demonstrated with the aid of examples using the Promela language and the Spin validator. Subsequently, the FSM representation can be used to ensure that the clauses stipulated in the contract are observed when the contract is executed. The requirements of a suitable run time infrastructure for monitoring contract compliance are discussed and a prototype middleware implementation is presented.EThOS - Electronic Theses Online ServiceEngineering and Physical Sciences Research Council (EPSRC)GBUnited Kingdo