Balloon Pin-Array Gripper: Two-Step Shape Adaptation Mechanism for Stable Grasping Against Object Misalignment

This letter introduces a balloon pin-array gripper combining shape adaptability to various objects, stable holding by multipoint contact, and isotropic grasping performance. This is particularly useful when the shape or position of the objects cannot be accurately determined because of sensor limitations. This gripper has multiple pins whose tips are covered by flexible balloons. The gripper can adapt to the shapes of objects in two steps: axial sliding of the pins and radial inflation of the balloons. This study focuses on the effect of the layout of pins on grasping and proposes a simulation model to quantify the characteristics of each layout. Simulations showed that the concentric layout enables stable grasping by ensuring many pins contact the object, regardless of misalignment. Experiments using a prototype gripper demonstrated a trend consistent with the simulation results, proving the validity of the simulation model.