  We propose a novel tri-fingered soft robotic gripper with decoupled stiffness
and shape control capability for performing adaptive grasping with minimum
system complexity. The proposed soft fingers adaptively conform to object
shapes facilitating the handling of objects of different types, shapes, and
sizes. Each soft gripper finger has an inextensible articulable backbone and is
actuated by pneumatic muscles. We derive a kinematic model of the gripper and
use an empirical approach to map input pressures to stiffness and bending
deformation of fingers. We use these mappings to achieve decoupled stiffness
and shape control. We conduct tests to quantify the ability to hold objects as
the gripper changes orientation, the ability to maintain the grasping status as
the gripper moves, and the amount of force required to release the object from
the gripped fingers, respectively. The results validate the proposed gripper's
performance and show how stiffness control can improve the grasping quality.
