**4.2. Result for automatic identification**

Recognition rate for insertion is shown in Table 2.


**Table 2.** Recognition rate for insertion operation

Recognition rate for other operations is shown in Table 3.


**Table 3.** Recognition rate for automatic identification

The threshold value *THi* (*i*=1,2,3*H*, 3*L*) determined through trial and error is shown in Table 4.

Distinction of Abnormality of Surgical Operation on the Basis of Surface EMG Signals 257

Situation Normal Posture Straining Sudden

Recognition rate[%]

Normal field 39 1 14 28 Posture field 2 24 4 7 Straining field 2 20 23 31 Sudden field 8 33 28 23 Total count 51 78 69 89

> Normal 76.5 (39/51) Singular 81.8 (193/236) Posture 30.8 (24/78) Straining 33.3 (23/69) Sudden 25.8 (23/89)

As shown in Table 5, the normal and the singular operation of insertion could be distinguished with 76.5% and 81.8% accuracy, respectively. However, the accuracy of recognition of the singularity (i.e., "Posture," "Straining," or "Sudden") of the operation is

As one of the reasons of this low recognition rate in the singularity distinction, the following cause is considered. In the states of "Posture", "Straining" and "Sudden", the singular

In order to examine efficiency of each feature, namely average absolute value, center-ofgravity and spectrum ratio, in the feature vector defined by equation (13), singular operation was recognized by SOM using the three-dimensional feature vector which consists of each

From Table 7, it turns out that the average absolute value contributes to distinction of normal operation compared with the center-of-gravity and the spectrum ratio, and conversely, the center-of-gravity and the spectrum ratio contribute to the whole singularity

Based on the above result, to raise the singularity recognition rate in each state (Posture, Straining, and Sudden), singularity distinction was performed repeatedly by combining three kinds of features in the feature vector (Average absolute value, Center-of-gravity, and

As a result, the best singularity recognition rate was obtained for the following six-

*MAV MAV cog MAV cog cog Xs MAV MAV MAV cog cog cog* <sup>=</sup> 

12 2 3 33

, , ,,,

112

*T*

(14)

operation is similar, and the difference does not appear easily in the feature vector.

feature only. Singularity recognition rate for each feature is shown in Table 7.

distinction compared with the average absolute value.

dimensional feature vector removing the spectrum ratio.

Spectrum ratio) through trial and error.

**Table 5.** The number of hexagon counted in each field on SOM

**Table 6.** Recognition rate for singularity distinction

approximately 30%.

Recognition rate for singularity distinction is shown in Table 6.


**Table 4.** Threshold values

As shown in Table 3, each surgical operation could be identified with more than 80% accuracy.
