## 3 Experiments and Results
### Experiments  
For this work, a total of four experiments were executed combining rotation and no rotation of the bracelet with and without the correction of orientation proposed here. The details of each experiment are presented below. _Experiment 1_ : In this experiment, we evaluated the performance of the proposed algorithm when: (a) there is no rotation of the bracelet for training and testing, and (b) there is no correction of the orientation of the training and testing EMGs. This experiment simulates the ideal scenario where each user trains and tests the recognition model with EMGs acquired placing the bracelet always in exactly the same orientation. For this experiment, all users wore the bracelet, for training and testing, in the orientation recommended by Thalmic Labs, the manufacturer of the Myo armband. This recommended position implies that a user should wear the bracelet in such a way that pod number 4 is always parallel to the palm of the hand. _Experiment 2_ : In this experiment, we evaluated the performance of the proposed algorithm when: (a) there is no rotation of the bracelet for training, but there is rotation for testing, and (b) there is no correction of the orientation of the training and testing EMGs. In this experiment, the training EMGs were acquired with the bracelet placed in the orientation recommend by the manufacturer of the Myo armband. _Experiment 3_ : In this experiment, we evaluated the performance of the proposed algorithm when: (a) there is no rotation of the bracelet for training, but there is rotation for testing, and (b) there is correction of the orientation of the training and testing EMGs. In this experiment, the training EMGs were also acquired with the bracelet placed in the orientation recommend by the manufacturer of the Myo armband. _Experiment 4_ : In this experiment, we evaluated the performance of the proposed algorithm when: (a) there is rotation of the bracelet for training and testing, and (b) there is correction of the orientation of the training and testing EMGs. In this experiment, the training EMGs were also acquired with the bracelet placed in the orientation recommend by the manufacturer of the Myo armband. _Experiment 4_ : In this experiment, we evaluated the performance of the proposed algorithm when: (a) there is rotation of the bracelet for training and testing, and (b) there is correction of the orientation and testing EMGs. This experiment simulates a general scenario where the user trains the recognition model using an orientation different from the orientation of testing. The experiments described above are summarized in Table 2.  
_Simulation of rotation of the bracelet_ : All the EMGs of the dataset used for this work were acquired with the users wearing the bracelet in the orientation recommended by Thalmic Labs. To simulate rotations of the bracelet, we assume that, by default, the pods of the Myo armband are ordered according to the sequence \(S=0,1,...,7\). Then, with uniform probability, we selected randomly a number \(r\) from the set \(\{-3,-2,-1,0,+1,+2,+3,+4\}\). Then, we simulate the rotation of bracelet by computing the new sequence \(\widetilde{S}=\widetilde{s}_{1},\widetilde{s}_{2},...,\widetilde{s}_{8}\) of the pods, where \(\widetilde{s}_{i}=mod(s_{i}+r,8)\), with \(s_{i}\in S\) and \(i=1,2,...,8\). Note that, in this way, we simulated rotations of the bracelet clockwise and counterclockwise in steps of 45 degrees. _Protocol for model evaluation_ : The recognition model was designed and trained using the EMGs of the 60 users from the training subset processed according to the settings established for each experiment. Likewise, for testing, we used the EMGs of the 60 users from the testing subset. For each user from the testing subset, the model was trained using the 25 training EMGs for each gesture to be recognized and the five EMGs of the hand relaxed.