Robotic hand design enables two-part assembly using one hand
A Reconfigurable Dual-Opposition Architecture for Single-Hand Assembly and Manipulation
Robotics
Summary
Putting two parts together by holding and moving them inside one hand is very tricky. The authors designed a special robotic hand with four fingers that can change how it holds two objects at once, letting it move and assemble them inside the hand. They created a model to describe how the fingers and palm move and tested the hand's ability to grasp, align, and fasten parts both in simulations and real hardware. Their design worked much better than an existing robotic hand, especially when dealing with disturbances or different object sizes.
What this means in practice
- •For robotics engineers: Build robotic hands that can assemble two separate parts inside one hand for tasks like fastening or aligning components.
- •For manufacturing automation teams: Automate single-hand assembly tasks by using robotic grippers that can adapt finger configuration to manipulate multiple parts together.
Authors
William Su, Yunosuke Nakamura, Yixiao Wang, Yitong Li, Mingrui Yu, Huanan Qi, Boyuan Liang, Masayoshi Tomizuka, Jianshu Zhou
Abstract
In-hand assembly is constrained by the need to maintain grasps on two separate parts while controlling their relative motion within a single hand. To enable both in-hand assembly and manipulation, we present a reconfigurable dual-opposition architecture. Specifically, to support simultaneous grasping of two parts and coordinated in-hand manipulation, four independently actuated fingers are organized into two virtual finger (VF) oppositions, with their relative configuration controlled by a reconfigurable palm. To describe hand motion and simultaneous two-object grasping configurations, a kinematic model of the fingers and palm and an object-size-conditioned workspace formulation are built. To further evaluate motion performance and assembly capability, finger-joint motion and palm tracking are characterized, and in-hand assembly is demonstrated through tasks involving grasping, alignment, fastening, and pressing. Ablation experiments further demonstrate the importance of finger abduction/adduction and palm reconfiguration for successful in-hand assembly. In simulation, the proposed hand achieves a mean continuous sphere rotation success rate of 98.6% over diameters of 40-230 mm, compared with 73.8% for the LEAP Hand. After policy fine-tuning with external disturbances, the proposed hand achieves 92.8% success under disturbances from multiple directions, compared with 45.2% for the LEAP Hand. Hardware demonstrations further show in-hand rotation of objects of different sizes using policies trained in simulation. Together, these results show that the proposed architecture supports both assembly of two separately held parts and coordinated manipulation of a single object within one hand.