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研究生: 李佳聲
Li, Chia-Sheng
論文名稱: 適用於電容式觸控面板之壓力感測及電觸覺回饋系統開發
Design of Force Sensing and Electro-tactile Feedback System for Capacitive Touch Panels
指導教授: 林志隆
Lin, Chih-Lung
學位類別: 碩士
Master
系所名稱: 電機資訊學院 - 電機工程學系
Department of Electrical Engineering
論文出版年: 2012
畢業學年度: 100
語文別: 英文
論文頁數: 49
中文關鍵詞: 電容式觸控面板壓力感測被動式觸控筆電觸覺
外文關鍵詞: Capacitive touch panel, force sensing, passive stylus, electro-tactile feedback
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  • 本論文探討於電容式觸控面板上存在之手寫能力不足及手感缺乏兩方面問題,並提出解決方案。藉由峰值偵測演算法及卡爾曼濾波器之訊號處理,得以在不改變硬體架構的情況下,使電容式觸控面板達成壓力感測的能力,並降低雜訊干擾而導致的不準確性,亦藉此實施防止掌面誤觸的設計,大幅增強手寫功能的實用性。另一方面,為解決觸控面板之手感缺乏問題,本論文提出基於電容式觸控面板架構之電觸覺回饋系統,提供使用者不僅僅操控上的演進,更真實的在面板上觸摸到虛擬化的材質表面,進而帶出更多的應用。
    由於市售之電容式觸控面板並無支援壓力感測之能力,所提供的Z軸資訊包含過多之雜訊以致於無法使用。本論文前段藉由探討面板特性,實作被動式觸控筆,並於觸控面板端程式實作峰值偵測演算法,分析訊號之強度,並藉由卡爾曼濾波器使訊號平滑漸變,降低雜訊干擾之效應。所獲得之壓力感測不僅能幫助重建數位簽名之軌跡,更能幫助判斷手指或是觸控筆等不同的觸控媒介,進而達成防止掌面誤觸的能力。實驗結果採用三組預定路徑隨機繪圖,顯示在未套用本演算法之情形下,軌跡之Z軸平滑程度範圍為0.522418~1.16449;套用卡爾曼濾波器後Z軸平滑程度增加至47.77714~94.56591,有效的降低雜訊干擾並維持快速的反應時間。藉由此技術開發手寫板應用程式以及虛擬鋼琴成為其應用端以驗證此技術之合用性。
    本論文後段探討觸控面板手感方面的缺乏,以至於在使用虛擬鍵盤時,無法感受到如同實體按鍵的觸覺,而導致誤觸的機率上升。因此提出使用電振動為原理之觸覺回饋系統,基於電容式觸控架構提供使用者觸覺之回饋。實驗採用7位受測者之統計數據,顯示71.43%的受測者可於50Vp-p弦波驅動時感受到電振動觸覺,其中42.86%能於75Vp-p時分辨觸覺的增強,顯示所提出之電觸覺回饋系統可以成功作用。

    This thesis emphasize on the user’s experiences of capacitive touch panel for the issue of handwriting and tactile sensation performance. Thus presents a new simple passive 3D stylus and its associated stroke reconstruction algorithm that detects the x,y-directional position and z-directional strength without the help of a force sensor. The proposed algorithm can successfully detect touch information while eliminating noise. Moreover, unintended touch will be recognized and its effects are eliminated while the desired signal will be accessed by the touch system to enhance the handwriting experience. The results of experiments on a touch panel system were analyzed, demonstrating the effectiveness of the proposed stylus and its stroke reconstruction algorithm. The smoothness of uncorrected raw data is 0.522418~1.16449, while the corrected data becomes 47.77714~94.56591, insuring the usability of the proposed method.
    Meanwhile, tactile sensation is achieved by electro-vibration technology, which provides friction modulation on the static panel to create tactile sensations such as touching the keyboard or something with a shape. The system is built based on a capacitive touch structure. Seven participants show that the recognition rate is 71.43% when driven voltage is set to 50Vp-p. Furthermore, 42.86% of participants feel an intensification of sensation when the driven voltage is set to 75Vp-p in the capacitive-type structure.

    Chinese Abstract i English Abstract ii Acknowledgements iii Contents iv Table Captions vi Figure Captions vii Chapter 1 Introduction 1 1.1 Background 1 1.1.1 History 1 1.1.2 Technologies overview 2 1.2 Motivation 4 1.2.1 Handwriting experience 4 1.2.2 Tactile sensation 7 1.2.3 System target 8 1.3 Thesis organization 9 Chapter 2 Capacitive touchscreen 10 2.1 System configuration 10 2.2 Scanning method 13 2.3 Firmware architecture 15 Chapter 3 Design of force sensing system 18 3.1 Peak calibration algorithm and passive stylus 18 3.1.1 Passive stylus and operation principle 18 3.1.2 Software architecture 19 3.2 Kalman filter based smoothing algorithm 23 3.2.1 Kalman filter 23 3.2.2 Adaptive Kalman filter 25 3.3 Experiment result 28 3.3.1 Peak calibration result 28 3.3.2 Static force measurement 28 3.3.3 Dynamic force measurement 30 3.3.4 Smoothness 31 3.3.5 Distinguishing between finger and stylus to identify unintended touch 34 3.4 Software application 35 3.4.1 Drawing tablet 35 3.4.2 Virtual piano 36 Chapter 4 Design of electro-tactile feedback system 37 4.1 Prior works of haptic touchscreens 37 4.2 Proposed electro-vibration system 40 4.2.1 Operation principle 40 4.2.2 Hardware structure 41 4.3 Experiment result 42 Chapter 5 Conclusions and future work 44 5.1 Conclusions 44 5.2 Future work 45 References 46 Vita 49

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