適用於網際網路控制的流量控制法則與PID控制器設計

Design of Flow Control Algorithm and PID Controller for Internet-based Networked Control Systems

林育暐(Yu-Wei Lin)

指導教授 ： 曾傳蘆

國立臺北科技大學/機電學院/機電整合研究所/碩士(2006年)

摘要

近幾十年來網際網路蓬勃發展，利用網路傳輸控制與回授訊號，進行閉迴路控制已越來越普遍。使用傳統控制理論所設計的控制器在網際網路的不定傳輸延遲影響下，其效能尚有待改進之空間。

有鑑於此，本論文利用新近提出的改良式傳輸協定：控制系統傳輸協定(Control System Transfer Protocol, CSTP)，改良TCP-Like模糊流量控制。根據所監控不同網路狀態下的往返時間(round trip time, RTT)及其變動量，作為使用者端之封包傳送率變動的依據，並透過模糊演算法調整其傳輸速率，期望達到減少命令與資料封包的傳輸延遲。除此之外，本論文亦利用GA演算法由網際網路控制系統之誤差響應進行PID控制器參數的最佳化，以提高控制系統輸出的性能。

最後，本論文以VisSim與VB軟體所開發出之網際網路遠端操控環境為測試平台，驗證所提控制架構在網際網路環境下的控制器性能。由實驗結果可知，本論文所提方法可避免系統受網路傳輸環境所影響，對於時間延遲有較佳的適應能力。

關鍵字

網際網路 ； 往返時間 ； 流量控制 ； 基因演算法 ； PID控制器

並列摘要

In recent decades, Internet has grown rapidly. Internet-based Networked Control System (INCS) which uses Internet to transmit control and feedback signals to perform closed-loop control is getting popular. However, due to the nature of uncertain transmission delay of Internet, the performance of controller designed by conventional control techniques deteriorates.
Based on the Control System Transfer Protocol (CSTP), this thesis proposes a new flow control algorithm to solve the problem. The proposed algorithm also improves the efficiency of TCP-Like flow control algorithm. Using the monitored network states, round trip time (RTT) and the change of RTT, a fuzzy logic reasoning mechanism is proposed to adjust the packet sending rate of the sender and thus the packet transmission delay is reduced. Moreover, using the error response of the considered INCS, a GA-based PID controller is designed at the client to improve the capability of traditional PID controller.

Finally, the research builds up an INCS environment as a testing platform by the VisSim and VB software to verify the performance of the proposed method. From the experimental results, it is seen that the method proposed by this thesis can reduce the influence of network transmission environment and performs well in the presence of time delay.

並列關鍵字

Internet ； round trip time ； flow control ； genetic algorithm ； PID controller

參考文獻

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[12] N. Xi and T. J. Tam, “Action synchronization and control of Internet-based telerobotic systems,” IEEE International Conference on Robotics and Automation, vol. 1, 1999, pp. 219-224.