A Study on Fuzzy WEDM Process with Workpieces of Variant Height

本文目的在於改善線切割放電加工機在切割工件厚度變化處之不穩定現象。文中先以實驗求得不同厚度與伺服電壓下之進給速率，設此進給速率為理想進給速率。再設計一模糊控制器，以間隙電壓、間隙電壓變化量與目前進給速率和理想進給速率之差距為控制器之輸入變數制定模糊控制法則，對厚度變化之瞬間制定控制策略，在加工時由控制器推論出適合之進給速率。 由實驗結果顯示，本文所設計之控制系統，可在經過工件段差時，推論出最適當的進給速率，大幅度穩定加工狀態與提升暫態性能。且進給速率在控制下皆未產生超越量(overshoot)或震盪，避免了因進給速率過度加速所造成之危機。加工過程中，進給速率在穩態時最大變動量約0.05mm/min。The purpose of this study is to overcome the instability occurring in the Wire-EDM process when the cutting wire is encountering the abrupt change of the height of the workpieces. An algorithm which is able to estimate the optimal feed rate automatically during the Wire-EDM process is proposed. A fuzzy controller with multiple control rules for different changing conditions of the height of the workpieces is designed. The most appropriate feed rate is calculated by the fuzzy controller according to the present gap voltage and the estimated workpiece height. Experiments have shown that sat factory performance is obtained with the assistance of the fuzzy controller. The Wire-EDM process becomes stably without overshoot and oscillation even when the height of the workpiece changes abruptly. The transient performance is also enhanced, and the maximum variation of feed rate in the steady state during the Wire-EDM process is 0.05mm/min.致謝...............................................................一 摘要...............................................................二 英文摘要...........................................................三 目錄...............................................................四 圖目錄.............................................................六 表目錄.............................................................九 符號說明...........................................................十 第一章 緒論........................................................ 1 1-1 引言........................................................1 1-2 文獻回顧....................................................2 1-3 研究目的與方法..............................................6 1-4 本文結構....................................................8 第二章 放電加工原理介紹............................................ 9 2-1 放電加工原理................................................9 2-2 放電基本轉換過程及火花結構.................................12 2-3 放電電源及波形.............................................14 2-4 線切割放電加工之特性.......................................18 第三章 模糊理論之介紹............................................. 21 3-1 模糊理論概述...............................................21 3-2 集合理論...................................................23 3-3 模糊控制器.................................................25 3-3.1 歸屬函數.............................................26 3-3.2 模糊分割.............................................27 3-3.3 模糊控制規則.........................................29 3-3.4 模糊推論.............................................29 3-3.5 解模糊化.............................................30 3-4 模糊控制之特點.............................................31 五 第四章 實驗設備與實驗規劃......................................... 32 4-1 實驗設備與材料.............................................32 4-2 伺服進給系統原理...........................................36 第五章 模糊控制器之研究........................................... 38 5-1 不同厚度與相異間隙電壓下所對應之加工進給速率...............38 5-2 本實驗之控制系統之設計.....................................40 5-2.1 輸入及輸出變數.......................................40 5-2.2 控制器之架構.........................................41 5-2.3 模糊化介面...........................................43 5-2.4 進給速率之控制策略...................................45 5-2.5 解模糊化介面.........................................51 5-3 控制程式之流程圖...........................................51 5-4 控制方法之分析與比較.......................................53 5-4.1 切割薄至厚的工件.....................................54 5-4.2 切割厚至薄的工件.....................................60 5-5 控制結果討論...............................................67 第六章 結論與建議................................................. 69 參考文獻...........................................................7