Enabling flexible automation system hardware: Dynamic reconfiguration of a real-time capable field-bus

The increasing demand for adaptive and flexible machines and plants raises the need for components and systems that can be dynamically reconfigured. Therefore, production facilities are especially needed to allow for connecting or disconnecting machine modules at runtime to allow for flexible production orders and varying product types. Many highly sophisticated approaches e.g. multi-agent systems and service-oriented architectures support reconfiguration at the application layer, but the communication link between the components' hardware has not yet been appropriately considered. However, the deterministic behavior of a field-bus is required to perform such a system reconfiguration of plants without violating the maximum cycle time of control applications. Considering these constraints, two different approaches are presented and discussed in this paper - a single-master and a multi-master approach. Based on an extension of the standard EtherCAT state machine, it is shown how flexibility can increase by reconfiguration of the field-bus communication. An evaluation of the reconfiguration time illustrates the impact to the control application.