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

Abstract

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 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.

Soft Robotic Grippers for Crop Handling or Harvesting: A Review

“…Fig. 10 presented a multitude of actuators, but among the 78 analyzed papers, only one mentioned power usage [89]. This is an important metric in the development of field robotics, as it, for example, allows to calculate operation time with a certain amount of stored energy.…”

“…Three papers used the Finite Element Method (FEM) to optimize (part of) the structure [86]- [88]. Furthermore, one paper used shape optimization via node wandering [89]. A slight majority, five grippers, were designed using topology optimization [71], [90]- [93].…”

“…It is also worth noting that some possible actuation methods are not found in the analyzed literature, e.g., thermal or hydraulic actuators. The power consumption of the actuators was only reported for one design, namely between 3.9 and 46 Watt in a closed position depending on the object gripped [89].…”

Flexure based gripper to grasp hollow objects by internal surface interaction

“…41 Similar two link parallel grippers based on compliant mechanistic entities are very popular in the recent literature. 42,43…”

“…41 Similar two link parallel grippers based on compliant mechanistic entities are very popular in the recent literature. 42,43 Although the field of gripper design has been widespread; there is a need to develop single part compliant grippers which can hold both rigid and crushable (like a paper cup) from inside. This paper is based on the synthesis of a friction-based gripper intended to hold hollow objects from inside.…”