Adaptive gripper with soft sheets for a uniformly distributed grasping force

This study presents the mechanism of an adaptive gripper for grasping various objects including deformable objects. The gripper has soft sheets and passive joints. Two joints of each finger are controlled by only a single actuator, and a total of four degrees of freedom (DOF) are included. It finely controls the grasping force with a simple position control method. The numerical model of the soft sheet that is used in the gripper is proposed to estimate the grasping force. Experimental tests including stiffness evaluation and grasping tests are performed to investigate the performance of the gripper. The results show that the stiffness of the finger changes based on the grasping area and the grasping force is widely contributed. This allows the gripper to softly grasp deformable objects with the center of the soft sheet. The results also confirmed that it is possible to grasp heavy objects by pushing soft sheets into them and to grasp small objects by using fingertips that possess high stiffness.