降低網路控制系統資料傳輸率之研究

Abstract

論文內容將探討網路控制系統伴隨傳送延遲的問題。網路產生的傳輸延遲往往會對網路控制閉迴路造成負面的影響,例如:降低系統的穩定度和造成控制效能變差。論文中將會先引入未考慮網路狀況的單一直流馬達系統，然後針對此一單一系統用極點位移的方式設計控制器。最後再將設計出來的控制器加上網路系統完成整個系統的架構。網路造成的延遲可大致分為兩種:一種是固定的延遲, 另一種是隨機的延遲，本論文將探討前者對網路控制系統的影響。我們為了降低網路的使用率，使網路發揮更大的功能並且維持整個控制系統的穩定性，我們將訂出一個傳輸誤差的範圍，控制行為將依據此一標準來決定控制行為。系統中央控制器會根據最新的系統狀態來決定是否更新控制命令，傳輸誤差的範圍也是跟系統最新狀態有關。根據此控制法則，可以降低耗用之網路資源並且保證系統的穩定度。系統傳輸誤差是網路實際應用上的一種無法避免的現象且將會於文中定義。模擬將會以兩個不同直流馬達和線性不穩定系統來作驗證。文中也將討論網路產生延遲的影響。

A network system considering network-induced delay is presented in this thesis. Network-induced delay may have advert influences on networked closed-loop control system such as performance degradation and system destabilization. We will first introduce single DC motor plant without considering networked control systems, and design individual controller for DC motor using pole placement method. Then, the overall networked control systems will be introduced. There are two types of network-induced delay: one is fixed delay; the other is random delay. The former is adopted in the thesis. In order to reduce network usage and maintain system stability, control input signals are sent under certain boundary conditions. Central controller sends control signals according to present states or former control states of the plants. The network usage can be reduced and overall system stability can be guaranteed, too. Transmission error is a practical phenomenon in NCS and will be defined in the thesis. Examples of controlling two DC servo-motors or two linear unstable systems through network will be demonstrated, and the effects caused by network-induced delay will also be shown in simulations and discussed in the thesis.