Optimal Design of a Motor-Driven Three-Finger Soft Robotic Gripper

This article presents an innovative, motor-driven, three-finger compliant gripper for adaptive grasping of size-varied delicate objects. An optimized compliant finger design is identified numerically through a topology optimization method. A stepper motor is used to actuate three identical compliant fingers, which can operate through elastic bending deformation. Finite-element models are developed to investigate the maximum equivalent stress, input force, and output displacement relations corresponding to the amount of input displacement of the compliant finger. Simulation results show that the proposed finger design is with a lower driving force and a lower maximum equivalent stress during operation comparing to one previous design. The proposed compliant finger is prototyped by three-dimensional printing using thermoplastic elastomer. Experimental results for the input displacement versus input force and input displacement versus geometric advantage relationships of the prototyped finger agree well with simulation results. The developed three-finger soft robotic gripper is mounted on an industrial robot arm to demonstrate its capability in handing size-varied delicate objects, such as egg, fruits, and glass products. Experimental results show that the proposed three-finger gripper can be used to grip object with a maximum weight of 4.2 kg and a maximum object size of 140 mm. The overall weight of the developed three-finger soft robotic gripper is 1.2 kg. The load capacity of the developed gripper can vary according to the friction between gripper and object. The maximum payload of the gripper can be increased to 9.5 kg when an additional antislip foam tape is applied on the grip surfaces of the compliant fingers.