A Novel Simple, Adaptive, and Versatile Soft-Robotic Compliant Two-Finger Gripper With an Inherently Gentle Touch

In soft robotics, there is still a great need for a universal but simple gripper that realizes a high level of adaptability as well as a gentle touch to a wide variety of unknown objects of different size, shape, stiffness, and weight without the use of sensors or vision. Various, mostly complex grippers already exist based on certain actuation concepts. However, each solution has specific limitations, especially regarding gripping different soft and delicate objects. Therefore, this paper introduces a new approach to design a simple, adaptive, and versatile soft robotic two-finger gripper that is based on compliant mechanisms. More specifically, an inherently gentle touch is realized by utilizing an optimally synthesized mechanism with distributed compliance in combination with a conventional linear actuator. It is shown by finite elements method (FEM) simulations that the gripper realizes a high force and motion transmission at the same time. Furthermore, it is demonstrated by tests with a gripper prototype that reliable, safe, and fast grasping as well as manipulation are possible for a wide variety of objects. It is shown that beside regular and stiff objects also very challenging objects can be easily gripped, e.g., small, irregular, soft, and squeezable objects like fruits, berries, and vegetables. Moreover, it is confirmed that the developed compliant two-finger gripper can be used beneficially without sensors and control for differently sized and shaped objects with a comparable weight.