System training set used for simultaneous proportional control. The upper plot shows the open/close motor, and the lower plot shows the wrist rotator. Some parts of the training procedure were discarded, as indicated by the boolean variable in the middle plot. The hand (colored) and prosthesis (white) sketches illustrate how each phase of the training was performed. Each motion is repeated four times, as indicated in the figure (“Demo” and Position 1–3; see Figure 3). There are four comments indicated in the figure: (1) “Negative” voltage is needed to open the prosthetic hand between each repetition (closing). (2) “Positive” voltage is needed to close the prosthetic hand between each repetition (opening). (3) First repetition of each activity is a demonstration for the subject and is thus discarded from the recorded data set. (4) After each motor voltage step, one second of the recorded data set is discarded.