*3.1.1. Validation of the input-output relationship*

EMG signals were acquired from one subject as explained in the previous section and given as input to the simulator and, simultaneously, to the *Osaka Hand*. In this way, we were able to compare their respective output, which is the angle of the fingers, when both were given the same input.

Figure 5 shows the result of one of these experiments, carried out with a non-amputee subject freely moving the simulated hand. Figure 5(a) shows the inputs of the system: processed EMG signals of the wrist extensor muscle (dashed line) and those of the wrist flexor muscle (solid line). Figure 5(b) shows a comparison between the finger angle of the *Osaka Hand* (thick line) and the one given by the simulator (thin line). The average of the error (difference between the angle given by the simulated hand and that of the real *Osaka Hand*) was 0.85o (s.d. 0.39), with a maximum of 3.54o , which we consider acceptable for our purpose.
