TY - JOUR
T1 - Closed-loop control of grasping with a myoelectric hand prosthesis
T2 - Which are the relevant feedback variables for force control?
AU - Ninu, Andrei
AU - Dosen, Strahinja
AU - Muceli, Silvia
AU - Rattay, Frank
AU - Dietl, Hans
AU - Farina, Dario
PY - 2014/9/1
Y1 - 2014/9/1
N2 - In closed-loop control of grasping by hand prostheses, the feedback information sent to the user is usually the actual controlled variable, i.e., the grasp force. Although this choice is intuitive and logical, the force production is only the last step in the process of grasping. Therefore, this study evaluated the performance in controlling grasp strength using a hand prosthesis operated through a complete grasping sequence while varying the feedback variables (e.g., closing velocity, grasping force), which were provided to the user visually or through vibrotactile stimulation. The experiments were conducted on 13 volunteers who controlled the Otto Bock Sensor Hand Speed prosthesis. Results showed that vibrotactile patterns were able to replace the visual feedback. Interestingly, the experiments demonstrated that direct force feedback was not essential for the control of grasping force. The subjects were indeed able to control the grip strength, predictively, by estimating the grasping force from the prosthesis velocity of closing. Therefore, grasping without explicit force feedback is not completely blind, contrary to what is usually assumed. In our study we analyzed grasping with a specific prosthetic device, but the outcomes are also applicable for other devices, with one or more degrees- of-freedom. The necessary condition is that the electromyography (EMG) signal directly and proportionally controls the velocity/ grasp force of the hand, which is a common approach among EMG controlled prosthetic devices. The results provide important indications on the design of closed-loop EMG controlled prosthetic systems.
AB - In closed-loop control of grasping by hand prostheses, the feedback information sent to the user is usually the actual controlled variable, i.e., the grasp force. Although this choice is intuitive and logical, the force production is only the last step in the process of grasping. Therefore, this study evaluated the performance in controlling grasp strength using a hand prosthesis operated through a complete grasping sequence while varying the feedback variables (e.g., closing velocity, grasping force), which were provided to the user visually or through vibrotactile stimulation. The experiments were conducted on 13 volunteers who controlled the Otto Bock Sensor Hand Speed prosthesis. Results showed that vibrotactile patterns were able to replace the visual feedback. Interestingly, the experiments demonstrated that direct force feedback was not essential for the control of grasping force. The subjects were indeed able to control the grip strength, predictively, by estimating the grasping force from the prosthesis velocity of closing. Therefore, grasping without explicit force feedback is not completely blind, contrary to what is usually assumed. In our study we analyzed grasping with a specific prosthetic device, but the outcomes are also applicable for other devices, with one or more degrees- of-freedom. The necessary condition is that the electromyography (EMG) signal directly and proportionally controls the velocity/ grasp force of the hand, which is a common approach among EMG controlled prosthetic devices. The results provide important indications on the design of closed-loop EMG controlled prosthetic systems.
KW - Closed-loop systems
KW - Grasping
KW - Haptic interfaces
KW - Prosthetic hand
KW - Vibrations
UR - http://www.scopus.com/inward/record.url?scp=84908371045&partnerID=8YFLogxK
U2 - 10.1109/TNSRE.2014.2318431
DO - 10.1109/TNSRE.2014.2318431
M3 - Journal article
C2 - 24801625
AN - SCOPUS:84908371045
SN - 1534-4320
VL - 22
SP - 1041
EP - 1052
JO - IEEE Transactions on Neural Systems and Rehabilitation Engineering
JF - IEEE Transactions on Neural Systems and Rehabilitation Engineering
IS - 5
M1 - 6807741
ER -