Intelligent distributed control systems

Context: The paper(2) deals with distributed reconfigurable embedded control systems following the component-based International Industrial Standard IEC61499 in which a Function Block (abbreviated by FB) is an event-triggered software component owning data and a control application is a distributed network of Function Blocks. Nowadays, limited related works have been proposed to address particular cases of reconfigurations without considering distributed architectures. Our first problem is to be able to handle all possible forms of reconfigurations that can be applied at run-time to distributed Function Blocks. In this case, a coordination between devices of the execution environment should be applied to guarantee safe and coherent distributed reconfigurations. A second problem is to find the sufficient solutions for the correct implementation of this reconfigurable distributed architecture. Objective: The paper defines an implementable multi-agent architecture for automatic and coherent reconfigurations of distributed Function Blocks. Method: To address all possible industrial forms, we classify the reconfiguration scenarios into three levels. The first level deals with additions-removals of Function Blocks to-from the system's implementation. The second deals with updates of compositions of blocks, and the third deals with updates of data. We define a Reconfiguration Agent for each device of the execution environment, and a unique Coordination Agent for coordinations between devices. Each Reconfiguration Agent to be modelled by nested state machines applies local reconfiguration scenarios in the corresponding device after coordinations with the Coordination Agent. We propose an Inter-Agents Communication Protocol to support correct and coherent reconfigurations of distributed devices. This protocol is based on Coordination Matrices to be handled by the Coordination Agent in order to define all reconfiguration scenarios that should be simultaneously applied in distributed devices. We propose XML-based implementations for both kinds of agents where XML code blocks are exchanged between devices to guarantee safety distributed reconfigurations. The contributions of the paper are applied to two Benchmark Production Systems available in our research laboratory. Results: The communication protocol is successfully applied to our platforms where simulations are executed to check distributed and coherent reconfiguration scenarios. The Reconfiguration and Coordination Agents are implemented in this platform by following the International Standard IEC61499. We show in addition XML-based successful interactions between devices when distributed reconfigurations are applied. Conclusion: The paper successfully defines a multi-agent architecture for IEC61499 distributed reconfigurable embedded systems where Coordination and Reconfiguration agents are proposed to allow feasible and coherent distributed reconfigurations by using a defined communication protocol. This architecture is implemented in XML and applied to real industrial platforms. (C) 2010 Elsevier B.V. All rights reserved.