Research On The Key Technologies Of Time-Sensitive Networking And Simulation Model Design

Fieldbus technology has achieved huge success in traditional automation field because of its simple design,reliability and low cost.However,in the era when everything is connected with each other,fieldbus technology cannot satisfy the increasing need for bandwidth.Packet-switch Ethermet is considered as the core communication technology in the next-generation automation field.Nevertheless,traditional Ethernet cannot meet the strict real-time requirement of automation applications.Time-Sensitive Networking(TSN)has revised many extended protocols for traditional packet-switch Ethernet to achieve deterministic transmission.In this paper,we focus on the research of TSN scheduling mechanism and its component design.The TSN simulation model is implemented in discrete event simulator omnetpp to verify the improvement of real-time performance of the system under TSN scheduling mechanism.First,based on the current situation that time-sensitive frames are blocked in message queues during the store-and-forward process of layer 2 switch,we modify the format of the Ethernet frames,shaper and MAC controller to guarantee the network cards can support the frame preemption mechanism.On the basis of the traditional packet-switch Ethermet model,we built TSN models using omnetpp and evaluate the frame preemption mechanism on the different network topologies.Moreover,because of the crystal drift,different nodes in distributed embedded system cannot achieve time synchronization.In view of that,we try to implement time synchronization mechanism at the application layer and data link layer of respective nodes.Then,a comparison is made between these two implementations from two aspects:precision and cost.Finally,after ensuring all the slave nodes synchronize with master node,a time-triggered scheduler based on the gate control list is added to the TSN switch model,and the impact of the cross-flow on the time-triggered scheduling mechanism is evaluated.Research shows that the frame preemption mechanism shortens the time when time-sensitive frames are blocked by low-priority frames.Because of it,the probability that time-sensitive frames are blocked by equivalent-priority and high-priority frames is considerably reduced.Furthermore,the time-triggered scheduling mechanism avoids the occurrence of blocking by protecting bandwidth.According to the simulation results,the end-to-end delay and jitter of the time-sensitive frames can be considerably reduced under the frame preemption mechanism.Besides,at the expense of some bandwidth,the time synchronization mechanism and time-triggered scheduling provides zero jitter transmission for time-sensitive frames.