Delicate Jamming Grasp: Detecting Deformation of Fragile Objects Using Permanent Magnet Elastomer Membrane

Jamming grippers can grasp objects of various shapes with simple control. However, grasping fragile objects is challenging, as a secure grasp requires firm pressing, which can potentially damage delicate objects. Thus, it is important to achieve an appropriate pressing distance for damage-free grasping. Consequently, the detection of the deformation of objects during grasping is required. In this study, we introduced a tactile sensing method using a Permanent Magnet Elastomer (PME) membrane to detect the initial deformation of grasping objects. During pressing, the transition occurs from a phase in which the gripper primarily deforms to a phase in which the object deforms exposing the object to damage. This phase transition can be detected from the inflection point in magnetic field data, and objects, such as roll cakes or potato chips, can be grasped without being damaged. Moreover, we showed that using multiple magnetometers enables the detection of local deformations of the PME membrane, enabling the gripper to determine the parts of the grasping object that are likely to be deformed. This study enables jamming grippers to delicately grasp fragile objects without damaging them, thus extending their use in sectors, such as the food industry.