  We present a holistic grasping controller, combining free-space position
control and in-contact force-control for reliable grasping given uncertain
object pose estimates. Employing tactile fingertip sensors, undesired object
displacement during grasping is minimized by pausing the finger closing motion
for individual joints on first contact until force-closure is established.
While holding an object, the controller is compliant with external forces to
avoid high internal object forces and prevent object damage. Gravity as an
external force is explicitly considered and compensated for, thus preventing
gravity-induced object drift. We evaluate the controller in two experiments on
the TIAGo robot and its parallel-jaw gripper proving the effectiveness of the
approach for robust grasping and minimizing object displacement. In a series of
ablation studies, we demonstrate the utility of the individual controller
components.
