二維斷面水槽中主動消波控制系統的設計與實作

Abstract

實驗水槽受限於空間尺度，在造波板製造波浪後，會因為各種因素導致反射波在水槽內部不斷形成，持續干擾水槽波況，致使實際波形與預期目標產生偏差。被動式消波雖有製作成本低、材料容易取得等好處，但其三大缺點包含：在固定外形下，僅能針對特定波況消波、占據水槽體積較大、只能配置於水槽末端，因此各大研究單位與企業開始投入主動式消波的開發。主動式消波最大特點是可以直接整合於造波機結構上，使得消波控制不再侷限於水槽末端。其操作流程可概括為三個主要步驟：首先，透過感測元件即時量測並擷取反射波訊號；其次，藉由運算單元計算對應之消波軌跡；最後，將修正後之造波指令即時回授至造波系統，以同步達成造波與主動消波。對於需長時間維持穩定目標波況之水槽實驗而言，即時閉迴路主動消波系統被視為不可或缺，因此，附加主動消波功能的造波機逐漸成為實驗水槽中必要設備。本研究致力於實驗室二維平推式斷面水槽中，加裝主動消波系統的可行性評估、設計與實作。在實驗初期，本文於小型造波水槽，初步驗證主動消波之方法，為主動消波概念奠定基礎。其後，實際對大、小型造波水槽之原有設備加裝主動消波系統進行分析。最終，本文在實驗室大型造波水槽中，使用新型運動控制器，並自行研發出一套完全閉迴路的主動消波系統，成功以疊加消除法消除週期波與孤立波。經本文實測，使用分離式消除週期反射波，消波率至少可以達75%，此外，更可以近乎完全的消除孤立波之反射波。而整合式主動消波可以消除絕大部分造波端的再反射波，足以證明此主動消波的回授控制系統成效顯著。

Due to the spatial constraints of experimental wave flumes, waves generated by the wave paddle often result in reflected waves that continuously form within the flume, persistently interfering with the wave field and causing deviations between the actual and the target wave profiles. While passive wave absorption offers advantages such as low construction cost and easy material availability, it has three main disadvantages: it can only absorb specific wave conditions under a fixed shape, it occupies a large volume of the flume, and it can only be installed at the flume end. As a result, many research institutes and industrial sectors have begun investing in the development of active wave absorption. The greatest feature of active wave absorption is its ability to be directly integrated into the wave maker system, allowing wave absorption control to no longer be confined to the end of the flume. The operational process can be broadly divided into three main steps: first, real-time measurement and extraction of reflected wave signals using sensing elements; second, calculation of the corresponding absorption trajectory by the control unit; and finally, immediate feedback of the corrected wave generation commands to the wave maker system to achieve simultaneous wave generation and active absorption. For flume experiments that require long-term maintenance of stable target wave conditions, real-time closed-loop active wave absorption systems are considered indispensable. Consequently, wave makers equipped with active absorption functions have gradually become essential equipment in experimental wave flumes. This study focuses on the feasibility assessment, design, and implementation of an active wave absorption system integrated into a laboratory two-dimensional piston-type wave flume. In the initial stage, a small-scale flume was used to preliminarily verify the concept of active wave absorption, thus laying the foundation for subsequent development. Following this, analyses were conducted to integrate the active wave absorption system into both small-scale and large-scale flumes. Ultimately, in a large-scale wave flume, a novel motion controller was employed, and a fully closed-loop active wave absorption system was self-developed. Using the superposition principle, both periodic and solitary reflected waves were successfully eliminated. Based on the experimental results, separate active wave absorption can achieve an absorption rate of at least 75% for periodic reflected waves. Moreover, it can almost completely eliminate reflected waves generated by solitary waves. On the other hand, integrated active wave absorption effectively suppresses most of the re-reflected waves from the wave generation boundary, clearly demonstrating the high performance of this feedback control system for active wave absorption.