利用隱馬可夫模型於腦電圖之壓縮感知式眼動偵測系統與腦機介面設計實作

A Compressive Sensing Aided EEG-based BCI System for Eye Movement Direction Classification Using HMM

朱皓平(Hao-Ping Chu)

指導教授 ： 黃元豪

國立清華大學/電機資訊學院/電機工程學系/碩士(2013年)

摘要

在醫學上測量腦部的儀器逐漸發達，而腦電波圖(EEG)屬於非侵入性的測量儀器，且相較於其他裝置腦電波測量裝置較為便宜，因此，近年來有許多學者投入腦機介面的開發，不只在醫學上的應用，也可提高人類生活的娛樂性。通常會使用無線可攜的EEG裝置來提高方便性，而為了降低可攜裝置電池的消耗以及通訊傳輸頻寬的需求，我們提出了壓縮感知式眼動偵測系統。經由訊號的分析，對腦電波訊號做有效的前置處理，而利用隱馬可夫模型(HMM)將眼動的特徵擷取出來。除此之外，在前端加入了壓縮感測(Compressive Sensing)演算法將訊號壓縮來提高可攜帶性。而為了降低運算複雜度以及提高系統效能，我們改良了系統架構，將前置處理的運算合併在壓縮演算法中並最佳化演算法的參數，讓系統達到良好的效能。在過程中，我們在壓縮感測演算法中發現感測矩陣的選擇，可以大幅提升重建效能。本篇論文針對運算複雜度較高的演算法以硬體實現，由於腦波的取樣率不高，所以我們以硬體成本為考量，採用處理器的架構來設計重建演算法，並以系統驗證的方式在FPGA上進行驗證。最後，我們將會建立一個完整的腦機介面系統，即時的將腦波擷取與辨識，由辨識結果控制電腦的行為，使配戴腦電波儀器者，可直接經由眼動(上下左右)控制電腦進行其他應用。

關鍵字

隱馬可夫 ； 壓縮感知 ； 腦電波 ； 人機系統 ； 眼動偵測

並列摘要

Due to the rapid evolvement of current medical equipments, electroencephalography (EEG) signal measurement becomes more accessible and cheaper for users. Thus, the development of brain-computer interface (BCI) becomes a hot research topic in recent years. BCI is commonly used for medical usage or entertainment applications. For EEG signal acquisition, wireless portable devices are preferred due to their convenience. In the wireless scenario, power and bandwidth become important issues. Therefore, in this thesis we propose the compressive sensing aided EEG classification system to reduce power consumption and communications bandwidth for portable devices.
We apply proper preprocessing for EEG signals to acquire features, and then use hidden Markov model (HMM) to do eye movement direction classification. In addition, we added compressive sensing in the front end to improve transmission efficiency and merge the pre-processing operation into the compression algorithm to reduce the computational complexity. We also do system optimization to achieve better detection performance. A special sensing matrix is developed to achieve better detection performance and lower computation cost. Since the EEG sampling rate is not high, we use a processor-based hardware architecture to design the reconstruction algorithm for compressive sensing to save hardware cost. The hardware blocks are verified on an FPGA board and incorporated with a PC to form a real time BCI system. With the proposed system, users with a EEG headset can control the arrow keys on the computer by moving their eyeballs toward directions of left/right and up/down.

並列關鍵字

HMM ； Compressive Sensing ； EEG ； BCI system ； Eye movement classification

參考文獻

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