Evaluation study of the transmission delay effects in a practical networked cascade control system

This paper demonstrates the practical design and implementation of two common network-based control approaches using Foundation Fieldbus and Industrial Ethernet as two emerging alternatives for the conventional methods. The presented approaches utilize a Smar Foundation Fieldbus controller (DFI-302) for function block implementation and a remote Siemens programmable logic controller (S7-315-2DP) for networked cascade control system implementation. A proper network platform has been designed to link these two controllers to a real pilot plant via Industrial Ethernet and Foundation Fieldbus. This paper investigates the effect of network data transmission delay on the resulting control performances. The obtained observations illustrate the control performance degradation due to large transmission delay in the implemented cascade control configuration.