*3.4.2. Preprocessing procedures*

Computational Intelligence in Electromyography Analysis – 352 A Perspective on Current Applications and Future Challenges

**Figure 11.** Block diagram of the calibration routine.

The movements with MVC used for the calibration of each channel are shown in the table 1.

0 Biceps Forearm flexion 1 Flexor carpi ulnaris Hand abduction 2 Flexor carpi radialis Hand adduction 3 Extensor digitorum Hand contraction 4 Pronator teres Forearm rotation 5 Brachioradialis Forearm rotation 6 Palmaris longus Wrist flexion 7 Extensor carpi ulnaris Wrist extension

Channel x Muscle Movement

**Table 1.** Representation of movement defined for each channel calibration.

Were used mathematical procedures typically used in the myoelectric signal analysis to preprocess the signal and generating one or more characteristics of interest to the classification stage.

The techniques used are this stage was (for further details consult Favieiro, 2011):


The signal is analyzed in periods of 50 ms, since it provides a comprehensive overview of the signal but, at the same time, specific, since it does not occur in tests muscle relaxation in period shorter than the determined, resulting in an efficient analysis of runtime system and results. To perform the windowing of the signal, the period in which a muscle contraction occurs were developed a routine in Labview which analyses the signal every 50 ms, where each channel is analyzed simultaneously, ensuring if in these data windows occurs a signal peak with value above the threshold. To consider that a movement is taking place is necessary to satisfy the following assumptions:


With these assumptions satisfied, it is considered that a movement is occurring, and in turn, the signal is windowed in all channels simultaneously, considering the same time based for the beginning and end of the muscle contraction. Another assumption considered important is if two sequential movements were spaced in time by up to 3 seconds, they will be considered one single movement and the beginning time of the first movements and the end time of the second are used to define a new single window containing these two movements. Thus, ensuring that complex movements are not considered two or more distinct movements by the signal windowing.

The set time of 3 seconds has been based on in the resting time of the Subject, which is 3 seconds. Thus, the windowing of a movement is determined only after a time longer than 3 seconds without the occurrence of a movement, only then is possible to analyze the windows stored in each channel, calculating the rms value from each channel in the occurrence time of a muscle contraction.
