Fig. 1

Experimental setup and the scheme of closed-loop control. A: Experimental equipment used; B: Testing session with an amputee; and C: Closed-loop control of Hannes hand and its virtual representation. The subject (3) was seated in front of a monitor wearing the armband with EMG sensors (3b) placed equidistantly around the right forearm, and vibromotors (3a) distributed equidistantly around the interior aspect of the right forearm. The virtual reality interface (2) showed the orientation of the target (2b) and the controlled hand (2c) to implement target achievement test. Importantly, during the test, the subjects controlled a real prosthesis (4). The graphical controls (2a) allowed setting the paramenters of the feedback scheme (5). A PC application (6) governed the training of the pattern recognition model and later controlled the real prosthesis, while the prosthesis state (wrist angle and hand aperture) was conveyed to the subject through vibrotactile feedback. The subject wore headphones (7) to block the incidental noise coming from the Hannes prosthesis (4). More details about the setup and the experimental protocol are provided in the text