- 學位論文
個人心電圖量測系統之實現
An implementation of individual ECG acquisition system
摘要
本論文提出一個心電圖擷取系統，其中包含心電圖機的製作、QRS波偵測、HRV頻域分析的實現以及小型嵌入式系統的設計。我們利用混合訊號處理器Mixed Signal Processor (MSP) 實現一個低複雜度的心電圖機。為了即時濾除室內電源信號以及肌肉移動所造成的雜訊，利用Equiripple method設計了一個FIR等連波濾波器，並且利用此FIR係數的對稱性，加快2倍濾波的速度及減少2倍的係數儲存量，最後再以MSP430實現此FIR濾波器。信號的儲存是使用FAT16格式存於SD Card，傳送則是利用Bluetooth達成無線傳輸。心電圖QRS複合波偵測演算法的實作上，因考量MSP430的效能，在設計演算法時，就將運算效率考量進去，使用移位或是FIFO的資料結構來加強偵測速度，以至於能夠在MSP430中即時地偵測R波位置，並且提出一個動態調整的閥值，來適應每個人的心跳大小。在HRV的分析方面，由於RR sequence並不是等間隔的取樣，因此需要內插(Interpolation)與重新取樣(Resample)來獲得類似等取樣間隔的訊號，這樣才能進行複立葉轉換，但這種處理會造成某些頻帶的破壞。因此我們使用Lomb method來實現HRV的頻域分析，經過驗證後發現，Lomb method的確比內插與重新取樣的方法獲得更好的頻譜。 在系統架構方面，我們將Timer-trigger cooperative scheduler加入心電圖機中，並定義每個task中所擁有的狀態，讓此scheduler在各個task中的state進行切換，進而達到系統的可維護性(maintainability)、可預測性(predictability)以及即時性(Real-time)。最後利用Unified Modeling Language (UML)中的狀態圖、類別圖、順序圖、部署圖，詳細地描述本系統的行為以及結構。本論文詳細地描述整個系統的實現方法，包含雛型機(prototype)、演算法、系統架構，提供各領域有意研究心電圖的研究者。
並列摘要
An individual ECG acquisition system is proposed in this paper which includes implementation of the ECG recorder, the detection of QRS complex, the HRV frequency analysis and the design of small-scale embedded system. The mixed signal processor (MSP) is used to reduce the complexity of an ECG recorder. To reduce the interference of 60Hz noise from the power line, the MSP is used to implement a finite impulse response (FIR) filter which is designed to be equiripple. The filter structure combines the pipe for the input samples and the symmetrical characteristic of the FIR filter for efficiently computing the convolution. The experimental results show that the output ECG signal with the PQRST feature is easy to be recognized. This ECG signal is recorded for 24hr using a SD card. Furthermore, the ECG signal is transmitted to a smartphone and PC through Bluetooth to decrease the burden of this ECG recorder. In considering the performance of MSP430, the algorithm of detecting QRS complex is implemented using bit-shifting and FIFO data structure to increase detection speed, so that the detection of the real-time R fiducial point can be realized with MSP430. The unevenly sampling interval of RR sequence should be adjusted by interpolation and re-sampling. But this procedure causes the high frequency domain of RR sequence to be destroyed. Therefore, Lomb method is used to implement the frequency analysis of HRV. As the result of verification, show that the Lomb method is better than the conventional method. A time-triggered cooperative scheduler is added in this ECG recorder. Each state of tasks is defined and the tasks are dispatched by the scheduler for the requirements of reliability, maintainability, and predictability in this embedded system. The class diagram, the state diagram, the sequence diagram and the deployment diagram in Unified Modeling Language (UML) are used to describe the proposed system.