A Hand-Wrist Control Strategy Based on Human Upper Limb Kinematics

The human wrist has a fundamental role in grasping tasks since it accurately controls the hand posture. The current commercial prosthetic systems lack several functionalities proper of the human wrist which could increase task success, especially for the most complex ones, and could reduce cognitive effort thanks to the detection of slip events. The analysis of the human wrist-hand kinematics and dynamics could be a starting point for reaching such goals. In particular, by studying the correlations between grip forces and wrist rotation speed, an innovative hand-wrist control strategy was developed aimed at improving the performance of the prosthetic system in grasping and manipulation tasks during Activities of Daily Living (ADLs). Preliminary early stages tests in a simulation environment were performed to evaluate the control strategy performance in two different ADL tasks, i.e. object picking and placing and pouring water, in three different conditions: I) stable grasp; ii) slip event; iii) tangential force variation. Two control parameters were considered to compare the simulated system with the real one. The results demonstrated the prosthetic hand-wrist system can reproduce the expected behaviour.