Single-Actuator Gripper Using an Antagonistic Cable-Driven Differential Mechanism for Adaptive Fixed-Position Grasping

Abstract

Fixed-position grasping is an efficient strategy in robotic assembly. Adaptive grippers employing differential mechanisms (DMs) can passively compensate for misalignment between gripper and object. However, conventional DMs, such as gear-based differential mechanisms (GDMs), are limited by rotational inertia and friction, generating excessive contact forces that compromise the object’s positional stability and ultimately degrade assembly accuracy. To address this issue, a single-actuator gripper based on an antagonistic cable-driven differential mechanism (CDDM) is proposed, in which differential cable tensions are converted into low-friction pulley rotations to enable low-contact-force adaptive grasping. The kinematic relationship between the CDDM and the gripper stroke is modeled, and a kinematics-based optimization method is developed to minimize the gripper’s dimensions and achieve the prescribed stroke without converging to local optima. Furthermore, the dynamics of the CDDM-based gripper are established to evaluate the contact forces on the object. Finally, an adaptive CDDM-based gripper is built to validate its payload capacity, repeatability, and adaptive performance in fixed-position grasping. Experimental results show that the proposed gripper outperforms a gear-based design, reducing the contact force by 53.28$\%$, a repeatability displacement accuracy of less than 0.30 mm during the long-term operation, and limiting error to 0.28 mm for picks with a 4.02 mm positional offset.