  While compliant grippers have become increasingly commonplace in robot
manipulation, finding the right stiffness and geometry for grasping the widest
variety of objects remains a key challenge. Adjusting both stiffness and
gripper geometry on the fly may provide the versatility needed to manipulate
the large range of objects found in domestic environments. We present a system
for actively controlling the geometry (inflation level) and compliance of
Soft-bubble grippers - air filled, highly compliant parallel gripper fingers
incorporating visuotactile sensing. The proposed system enables large,
controlled changes in gripper finger geometry and grasp stiffness, as well as
simple in-hand manipulation. We also demonstrate, despite these changes, the
continued viability of advanced perception capabilities such as dense geometry
and shear force measurement - we present a straightforward extension of our
previously presented approach for measuring shear induced displacements using
the internal imaging sensor and taking into account pressure and geometry
changes. We quantify the controlled variation of grasp-free geometry, grasp
stiffness and contact patch geometry resulting from pressure regulation and we
demonstrate new capabilities for the gripper in the home by grasping in
constrained spaces, manipulating tools requiring lower and higher stiffness
grasps, as well as contact patch modulation.
