Position-Based Force Control for In-Hand Manipulation Using a Soft-Rigid Hybrid Two-Finger Hand

Soft grippers have attracted attention as a safe and adaptable means of grasping fragile or irregularly shaped objects. However, challenges remain in performing advanced tasks such as in-hand manipulation. This study proposes a soft-rigid hybrid two-finger hand that integrates position-controlled motors and flexible links, based on a design concept that combines the mechanical properties of rigid and flexible components. The proposed hand directly drives the flexible links using position-controlled motors, enabling active control of the interaction between the flexible structure and the environment. Leveraging this feature, a position-based force control strategy is introduced, in which fingertip positions are adjusted to shift the equilibrium of the flexible links, indirectly modulating the contact force through their passive deformation. The effectiveness of the proposed method is validated through simulations of object grasping tasks, demonstrating stable and dexterous in-hand manipulation.