以 Petri Net 設計之自動化程序遠端監控系統

Abstract

近年來，由於網際網路的快速發展，使得自動化程序之即時監控與管理不再受限於局部的區域來執行。對於以網際網路為基礎的遠端製造系統，本文闡述其一系列以Petri net為基礎，在程序控制，遠端監控，與網路管理系統上之設計與實現的方法，以達成系統之正常安全與運作。 對於日益複雜的製造系統，傳統之階梯圖程序控制設計，不但變的相當複雜，而且對於製程變動的彈性處理也更加困難。有鑑於此，本文先提出一套以法則為基礎的評估方法，來驗證Petri net在程序控制器設計上優於階梯圖的特性。之後，本文提出一套以Petri net為基礎，而以階梯圖實現之系統化設計方法，來發展製造系統之程序控制器。 在遠端監控系統中，本文提出一個以監督器 (supervisor) 監控人類行為的架構，來預防與禁止不正當的遠端人為操作。本文使用Petri net來塑造命令層中真實系統的抽像模型，合成出監督器，並進一步使用Java 技術將監督器實現成一智慧型代理人(intelligent agent)。藉由遠端受控系統的狀態回饋，我們發展的監控代理人會防止在違反安全規格下的命令，藉以降低及減少人為失誤所產生的影響。此外，在上述的監控系統中，為了降低監控器的合成複雜度，我們提出一個階層式的遠端監控架構，使得監督器的合成需有較少的狀態空間，藉以降低設計與實現的複雜度。 此外，對於大型遠端監控系統中各種不同的感測、致動、與控制元件，為了管理網路中各元件所收發的大量監控訊息，本文整合Petri net於統一建模語言(unified modeling language, UML)中，以系統化地從建模，設計，分析，驗證，來實現簡易網路管理協定 (simple network management protocol, SNMP) 代理人。本研究所提出之遠端網路管理方法，已經成功地應用在台灣大哥大的行動交換機房之環境安全遠端監控系統上。

Applications of the Internet technology become more popular in the modern industry. This thesis proposes the systematic design and implementation of remote supervision systems for automated processes via the Petri nets (PN) approach to achieve 1) the sequence controller, 2) the supervisor, and 3) the device management system, respectively. As automated systems become more complex, traditional ladder logic diagram (LLD) design of sequence controllers becomes more difficult and inflexible. Thus, this thesis presents a rule-based evaluation to adequately compare the LLD and PN, and verify the superiority of PN. Then, since LLD is still widely used today in real industry, this thesis proposes a PN-based method systematically leading to the final LLD implementation for the sequence controller design. In remote control systems, to prevent abnormal operations of humans, a remote supervisory scheme is proposed so that undesirable human operations are prohibited. PN is employed to synthesize both the remote supervisor and the local controller, and the Java technology is employed to implement the intelligent agent for on-line supervision. According to the status feedback through the Internet, the developed supervisory agent provides allowable commands for operators and disables those operations that violate safety specifications. The possibility of human errors can be thus reduced. Moreover, to reduce the complexity of mentioned supervisory system design, this thesis further proposes a hierarchical structure with a smaller state-space size in supervisor synthesis so as to reduce the design complexity. Furthermore, to integrate diverse network elements and construct a large-scale and distributed systems for remote supervision systems, this thesis integrates the PN into the unified modeling language (UML) to achieve modeling, design, analysis, verification, and implementation of simple network management protocol (SNMP) agents in the present framework. The developed management system has been successfully applied to a mobile switching center of Taiwan Cellular Corporation for the remote supervision and management of its various environmental devices.