Soft Robotic Palm With Tunable Stiffness Using Dual-Layered Particle Jamming Mechanism

This article presents a novel robotic palm with a dual-layered structure designed to yield high surface conformity and controllable rigidity for enhanced grasping performance. It comprises a vacuum chamber for adjusting the stiffness of the palm via particle jamming and an air chamber for actively controlling the palm deformation. An auto-jamming control scheme that automatically solidifies the palm by sensing the internal pressure of the palm without any tactile sensors or visual feedback was also proposed. Given the design and control of the robotic palm, the performance of the dual-layered jamming mechanism was characterized in terms of shape adaptability and stiffness controllability. The contact surface areas increased by 180% compared with the single-layered robotic palm, and the adjustable stiffness was within a range of 0.20–2.53 N/mm for varying vacuum pressures. Moreover, the palm can act as a universal gripper for small objects, yielding a holding force of up to 13.9 N. The grasping performance of the palm in conjunction with robot fingers was evaluated for various objects for varying palm stiffness. The palm increases the grasping force by 2.0–3.1 times compared with flat skin. Multimodal grasping strategies for various objects were demonstrated by manipulating a robot arm.