Soft Robotic Compliant Two-Finger Gripper Mechanism for Adaptive and Gentle Food Handling

Abstract

In the field of soft robotics there is still a great need for a versatile, simple, and affordable gripper with a high level of adaptability to unknown objects of different sizes, shapes, and stiffness. Most of the existing soft robotic grippers are complex solutions realized with fluid-mechanically driven actuators, active smart materials, cable-driven actuation, and different form-closure principles. However, soft grippers based on compliant mechanisms are rarely introduced and explored so far. Therefore, we present a novel compliant two-finger gripper mechanism for adaptive and gentle gripping, especially of soft and easily squeezable objects like fruits, vegetables, sweets, and sushi. The structurally inherent adaptability is achieved using an optimally synthesized compliant mechanism in combination with a conventional linear actuator. Furthermore, the two-finger gripper passively realizes pinch (parallel) or/and encompass (power) grasping. It is shown by FEM simulations and confirmed by prototype tests that the developed gripper realizes both pinch and encompass grasping with high adaptability. A special advantage of the gripper is the possibility to achieve gentle food-handling of objects with comparable weight independent of the object shape, size, and position without the need for sensors. Moreover, the precise, safe, and fast manipulation of very delicate objects is exemplarily demonstrated for different sushi pieces using the gripper mechanism with an industrial robotic arm.