## 3 Data Acquisition and Preprocessing of EMG Signals  
The aim of this study is to classify 17 types of motion from EMG signals. The 17 motions include 6 forearm/wrist movements (pronation, supination, flexion, extension, hand grasping and hand opening) as shown in Figure 2, flexion and extension of the five fingers, and a rest state (no movement). In this work, an EMG-based control system is designed as illustrated in Figure 3 to achieve the aim of classifying these 17 motions. As depicted in Figure 3, the system consists of three subsystems: the data acquisition system, the EMG signal processing system, and the interface system. The data acquisition system records EMG signals in a noninvasive fashion using six EMG sensors (IDPAD series manufactured by Oisaka Electronic Equipment Ltd., Hiroshima, Japan). These signals are sampled at 200 Hz using a 12-bit analog-digital converter (ADC) and then sent to the signal processing system to undergo further processing. The EMG signal processing system processes the EMG signal and classifies the arm/hand motion. The interface system displays EMG signal waveform, movement cues, as well as classification results in real-time. The software is developed using MATLAB/Simulink(r) (made by MathWorks, Natick, MA, USA) environment. The proposed algorithm is executed after being built by Simulink real-time workshop. In this study, six EMG sensors are positioned on the flexor carpi radialis muscle, flexor carpi ulnaris muscle, flexor digitorum profundus muscle, flexor pollicis longus muscle, extensor carpi  
Figure 1: Overview of current electromyography (EMG) based pattern recognition studies illustrating the number of electrodes used and the number of movements classified. Figure 2: Six forearm motions. radialis longus muscle and extensor pollicis longus muscle of the left arm as shown in Figure 4[35]. The functions of each muscle are summarized in Table 1. Muscles acting on the hand can be divided into two groups: extrinsic and intrinsic muscles. Intrinsic muscles of the hand are muscles which are located within the hand itself. On the other hand, extrinsic muscles are located in the anterior and posterior compartments of the forearm. Extrinsic muscles are responsible for crude movements of hand whereas intrinsic muscles control fine movements. Controlling the prosthesis using intrinsic hand muscles has the advantage of providing finger control independent of wrist motion [32], but depending on the level of amputation, the required region may not be available. For this reason, this study will only concentrate on extrinsic muscles. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Channel Number** & **Muscle** & **Function** \\ \hline \multirow{3}{*}{1} & Flexor carpi radialis muscle & Flexion of the hand at the wrist, pronation of the forearm (works along with other muscles which pronate \\  & & the forearm) \\ \hline
2 & Flexor carpi ulnaris muscle & Flexion of the hand at the wrist \\ \hline
3 & Flexor digitorum profundus muscle & Flexion of the fingers (excluding the thumb) \\ \hline
4 & Flexor pollicis longus muscle & Flexion of the thumb \\ \hline
5 & Extensor carpi radialis longus muscle & Extension of the wrist, assists movements of the digits \\ \hline
6 & Extensor pollicis longus muscle & Extension of the thumb \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Muscle of the forearm and their functions. Figure 4: Electrode positions. The positions of the six electrodes are selected with reference to previous work [35]. Figure 3: System Architecture. According to the standards for reporting EMG data, significant EMG activity occurs in the 5-450 Hz bandwidth [36]. To analyze EMG signals in this bandwidth, most studies uses a clinical grade EMG acquisition device which samples data at 1000 Hz or higher. However, these instruments are expensive, making practical social use difficult or prohibitive.