Evaluation And Study Of The Real-time Performance In Wireless Fieldbus-Rfieldbus

The computer networks located in process control field in manufacturing is called industrial control and communication network and play an important role on measuring and controlling of the industrial objects and devices. It is the ground for the modern CIMS system in a manufacturing factory. With the rapid developing of microelectronics it has been grown to the 3rd generation, called FCS(Field Control System). In order to solve the problem to connect many devices and objects which can rotate, move, and shall be temporal mounted, the FCS must be extended with the wireless communication capability. The related researching and practice is one of the popular directions in the industrial control field recently.Compatible with the famous PROFIBUS, RFieldbus is a new High Performance Wireless Fieldbus which can transmit controlling data and TCP/IP-data in wire&wireless way, in industrial field environment. In RFieldbus, DSSS used in wireless domain and RS-485 used in wired domain were integrated in physical layer and on its MAC layer the Token-Passing protocol was implemented. This hybrid wired/wireless infrastructure influence greatly the real-time performance in RFieldbus which has an unique token in heterogeneous segment. In order to analyze and evaluate the transmission real-time property in RFieldbus the following points were studied:1, To analyze the traffic congestion in intermediate gateway because of the different form, length, and rate of the frames transmitted in wired/wireless segment, and present a method to calculate the maximum delay on connecting devices when different frames were transmitted. Subsequently, the transmission process and time property of the SRD, SDN, Token frame in RFieldbus were studied. Consequently, the maximum system return time and transaction time were deduced, and two key parameters TSL, TTO can be calculated prior to the system real construction.And the above method can be implied into the other systems that has the similar heterogeneous integrated structure.2, After the analyses of Token-Passing protocol in PROFIBUS, the dynamic time boundary on tasks with different priorities was researched and a model called RF-P based upon multi-server-single-queue was built. The polling-time on the slaves was transformed into an internal token walking time, and the rest two queues in RFieldbus were transformed into two M/G/1/ systems with two different Poisson-arrival rate, so that the complexities of the time properties in the heterogeneous transmission media can be reflected by different parameters. Upon the Pseudo Conversation Law and the K-limited schedule, an equation of the average waiting time in RF-P model was derived from after the original time-limited schedule was transformed. And the equation was heuristic refined compared with test data. The last result shows the average error of the equation is round 10-20% when system load is lower then 40%. A condition to judge the stable limit of the system was presented also.3, Based on the waiting time equation and the non-linear optimizing theory the relations between the TTR, the distributing of masters and real-time performance was discussed. And it shows that the traffic of the TCP/IP data conflicts with the timeproperty of DP stream. In order to meet the different demands on single queue, and whole system a few scenarios were optimized respective. It was proved that the more balanced the load distributing on the Master station, the better the real-time performance in RFieldbus. Furthermore, it was pointed out that in RFieldbus the prerequisite for the general conclusion that there is a boundary for waiting time in Token networks is: TTR must keep subjected in stable area.