Improving profinet IRT frame packing using ethernet control characters

Profinet IRT makes use of dynamic frame packing (DFP) in order to support very short cycle times. The applied packing order is highly dependent on the network topology, and thus the scheduling must be recalculated offline every time the network structure is changed. This study presents a proposal for an automatic packing mechanism (APM) that is based on subframes with delimiters using control characters. As a consequence the subframe positions can be recognized by each device, which makes a scheduling dispensable. Furthermore, APM achieves better performance than DFP, especially in star or tree topology. The paper also presents experimental validation results.