Design and Development of a New Bioinspired Hybrid Robotic Gripper for Multi-Mode Robust Grasping

This paper presents the design and development of a novel bioinspired rigid-soft hybrid robotic gripper with versatile grasping primitives and enhanced robustness. It achieves variable joint/tissue stiffness by resorting to hybrid ratchet joints and phalanges. For the first time, the proposed hybrid ratchet joint (HRJ) can selectively switch to four modes to generate tunable flexion/extension locking torque by activating specific clutching ratchets with soft-cell structures. The multi-layer hybrid phalanx can exert suction-lift grasp and adjustable contact stiffness, which are theoretically modeled and experimentally validated by mounting them on articulated fingers. With the proposed HRJs and hybrid phalanges, a tendon-based hybrid gripper is designed and fabricated to evaluate the grasping performance for universal picking and manipulation. Extensive grasping tests are conducted in six representative primitives (including suction-lift and suction-pinch), demonstrating the multi-mode grasping capability in extremely thin and wide objects. Compared with conventional gripper configurations, the proposed hybrid phalanges and HRJs improve the grasping force and enveloping stiffness by 205.1% and 97.9%, respectively.
Note to Practitioners
—For automated grasping of diverse objects, a bioinspired robotic gripper is proposed to enable adjustable compliant stiffness and suction-lift motion. With the same mobility as conventional tendon grippers, the reported hybrid gripper exhibits wide-range adjustable stiffness and demonstrates versatile adhesive primitives and enhanced robustness in grasping tasks. Experimental investigation is conducted to verify the tissue suction effect and stiffness modulation, demonstrating their contributions to grasping operations in terms of suction-augmented primitives and improved grasping stability. With the characteristics of HRJs and hybrid phalanges, the gripper actuation strategies are elaborated via six representative primitives, including parallel grasp, suction-lift, and newly defined suck-pinch. Extensive grasping trials are demonstrated to pick thin, large, and tiny objects (e.g., wide plates, toolboxes, and tweezers). The experimental results validate the feasibility and superiority of the proposed hybrid gripper design by fusing intrinsic dexterity, manipulability, and compliance from rigid and soft mechanisms.