本論文提出一個即時手勢辨識演算法。它適用於有無線傳輸功能、穿載式裝置裡使用的低功耗微處理器上執行。此演算法把動作片段對映到符號，而手勢的加速與方向則以字串表達出來，如此可以套用字串匹配演算法辨識手勢。實驗結果顯示，我們的演算法辨識Graffiti字母與一組自定手勢，有相當高的成功辨識率。同時，演算法的複雜度可保持能在八位元微處理器上即時執行與傳輸的範圍內。

This thesis presents a real-time hand-gesture recognition algorithm suitable for implementation on low-power microcontroller units (MCU) for wearable devices with wireless transmission capability. The algorithm performs string matching against a set of patterns that symbolize acceleration and motion directions. Experimental results show that our algorithm can recognize and transmit characters in the Graffiti alphabet and gestures with high accuracy while keeping complexity low enough to be feasible to run on an 8-bit microcontroller unit.

Contents i
Acknowledgments v
1 Introduction 1
1.1 Motivation 1
1.2 Objectives 3
1.3 Approach 3
1.4 Contributions 4
1.5 Thesis Organization 4
2 Related Work 5
2.1 Hidden Markov Model 5
2.2 Dynamic Time Warping 5
2.3 String Matching 6
3 Recognition Method 7
3.1 Levenshtein Distance 7
3.2 Recognition Algorithm 8
3.2.1 Temporal Aggregation of Acceleration 9
3.2.2 Calculation of Trajectory Direction 10
3.2.3 Symbolization of Acceleration 10
3.2.4 Symbolization of Trajectory Direction 11
3.2.5 Spotting 12
3.2.6 Resolving Spotting Conflicts 14
3.3 Complexity Analysis 14
3.3.1 Time Complexity 16
3.3.2 Space Complexity 16
4 Evaluation 18
4.1 Gesture Vocabulary 18
4.1.1 Basic Gestures 18
4.1.2 Graffiti Alphabet 18
4.2 Experimental Setup 19
4.2.1 Wearable Platform 19
4.2.2 Host Device 19
4.2.3 Data Collection 20
4.3 Experimental Results 20
4.3.1 Recognition Accuracy 20
4.3.2 Run-Time Complexity 24
5 Conclusions and Future Work 27
5.1 Conclusions 27
5.2 Future Work 28
5.2.1 Gesture Segmentation Algorithm 28
5.2.2 Target Hardware Platform 28

List of Figures
3.1 The flowchart of our recognition algorithm 9
3.2 Illustration of a sliding window 9
3.3 Effect of the temporal aggregation 9
3.4 A trajectory direction in the two-dimensional Cartesian coordinate system 10
3.5 Symbolization of acceleration of a motion 11
3.6 The four unit vectors in the two-dimensional Cartesian coordinate system in the codebook 12
3.7 Symbolization of direction vectors of a motion 13
3.8 Motion of up-down gesture 14
3.9 Initialization of the three Levenshtein-distance tables for the up-down gesture 15
3.10 Determine each element in the y-axis Levenshtein-distance table 15
3.11 Determine each element in the direction Levenshtein-distance table 16
4.1 Motions of eight basic gestures 18
4.2 Motions of 26 letters and one space in the Graffiti alphabet 19
4.3 The top view of EcoBT Super 20
4.4 EcoBT Super with a button 21
4.5 The testing process of basic gestures 21
4.6 The recognition accuracy of the basic gesture recognition 22
4.7 The recognition accuracy of the handwriting Graffiti recognition 23
4.8 Confusion matrices for the basic gesture recognition (the average accuracy is 87.6%) 24
4.9 Confusion matrices for the user-dependent handwriting Graffiti alphabet recognition
(the average accuracy is 82.5%) 25
4.10 The execution time of recognizing one basic gesture 26
4.11 The execution time of recognizing one letter in Graffiti alphabet 26

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