Analysis of an underactuated biomimetic octopus hand for grasping space non-cooperative objects

In this paper, an underactuated biomimetic octopus hand with good adaptability to the shape and size of the grasping object in unknown environment is presented. Based on the grasping task, a quadpod parallel mechanism is introduced as the basic unit of octopus hand in order to make it more flexible. Mobility of the basic unit is calculated as lower-mobility parallel mechanism (PM) by using the screw theory, this basic unit has fewer than six degrees of freedom, which was also verified by the general Grübler-Kutzbach criterion. Two different grasping methods are compared and discussed. Kinematic data of the hand have been obtained from the robotic kinematic equations and three different actuated methods are compared and discussed. The analysis in this paper shows that each unit of the underactuated mechanism has the ability of deformation and can adapt to the irregular shape of non-cooperative objects.