Design and Development of a Co-axial Passive Flexion Mechanism-based Gripper for Irregular Objects

Humans hand has a complex functionality to achieve stable and reliable gripping of irregular-shaped objects. This paper aims to design a three-finger anthropomorphic gripper and endow the designed hand with natural grasping functions. We introduce a passively adjustable flexion finger mechanism that can change a flexion finger angle according to the irregular-shaped objects. Each finger of the gripper has a torsional spring and has placed co-axially, connected in series on an equilateral triangular palm. The required stiffness of the flexion angle and object safety condition is analyzed. The variation of the flexion joint stiffness for the minimum to maximum flexion angle is evaluated. Practical experiments using a wide range of obj ects under different grasping scenarios are performed to demonstrate the grasping capability of the integrated gripper.