Soft robotic finger with variable effective length enabled by an antagonistic constraint mechanism

Compared to traditional rigid robotics, soft robotics has attracted increasing attention due to its advantages in compliance, safety, and low cost. As an essential part of soft robotics, the soft robotic gripper also shows its superior while grasping objects with irregular shapes. Recent research has been conducted to improve grasping performance by adjusting the variable effective length (VEL). However, the existing VEL function achieved by mechanisms such as multi-chamber design or tunable stiffness shape memory material requires a complex pneumatic circuit design or a time-consuming phase-changing process. This work proposes a fold-based soft robotic finger with VEL function from 3D printing. It is experimentally tested and modeled by the hyperelastic material property. Mathematic and finite element modeling is conducted to study the bending behaviour of the proposed soft actuator. Most importantly, an antagonistic constraint mechanism is proposed to achieve the VEL, and the experiments demonstrate that better conformity is achieved. Finally, dual-mode grippers are designed and evaluated to demonstrate the advances of VEL on grasping performance.