The analysis of stability of networked control systems based on industrial switched ethernet

In order to enhance the stability of networked control systems(NCS) constructed by switched Ethernet, proposed a new kind of flow control approach based on PAUSE operation defined in 802.3x. During the implementation of flow control, the switch monitors its input and output buffers to prevent buffer overflow. Based on the analysis of structure of PAUSE frame, a general method was provided to design the high and low buffer mark level for analyzing the basic timing characteristics of input and output buffers in PAUSE operation, then, the time delay of the store-and-forward mechanism can be determined effectively. Paper gave a simple method for evaluating effective bandwidth based on output bandwidth, input bandwidth and switchpsilas processing speed, and calculated the response time for multiple sensors simultaneously to transmit the same packets to a target actuator. The simulated results indicate the proposed PAUSE operation can prevent buffer overflow, decrease the total response time delay to meet the requirement of hard real-time communication in industrial control field.