Human finger joint synergies for a constrained task applied to a dexterous anthropomorphic hand

This work deals with the complex task of unscrewing a bottle cap with a dexterous anthropomorphic hand. To that end, human motion profiles of nine test subjects were recorded using CyberGlove II and the data were analyzed for unscrewing a bottle cap. Results showed that the periodic motions exhibited by the finger joints shared a common frequency for each subject, but differed in amplitude and phase. From the gathered data, a set of sinusoidal trajectories were developed to approximate this motion for a robotic hand. Because the joint trajectories share the same frequency, a single sinusoidal input can be used in the path planning of the robot to achieve this task. A reference joint is given a sinusoidal input, and the remaining joints are scaled in phase and amplitude with respect to this reference joint. This significantly reduces the computational cost and complexity of the task. Simulation results show that the developed sinusoidal trajectories show a close correlation with the motion profiles seen from human experiments. Using the developed sine trajectories, the robotic hand successfully unscrewed the bottle cap in all five conducted trials.