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

Andrija Milojević,Žarko Ćojbašić,Sebastian Linß,Heikki Handroos

doi:10.1115/1.4048752

Abstract

AbstractIn 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.

Highlights

In many of today industries where automatization is present, robotic systems are often used to perform different tasks, like pick-and-place, manipulation, handling, assembling or assistance
With shape optimization the optimization of the overall gripper mechanism shape and not the shape of its individual segments is considered. This is done to realize a universal soft robotic compliant gripper with a good trade-off between a high geometrical advantage (GA: ratio of realized output displacement to applied input displacement) and especially a high mechanical advantage (MA: ratio of output force to input force)
The results show that the novel gripper is simple, adaptive and versatile and has various further benefits in comparison to the already existing actuation principles: like a monolithic structure with only a few parts, large possible deformations due to freeness of stress concentration, a good payload to weight ratio, smaller values of inertia of moved masses and a JMR-20-1104

Summary

Introduction

In many of today industries where automatization is present, robotic systems are often used to perform different tasks, like pick-and-place, manipulation, handling, assembling or assistance. The robot comes into contact with objects or workpieces and realizes their gripping and manipulation by using end-effectors. End-effectors, which are known as end-tools, material handling tools, grippers, graspers or robotic hands, represent an essential part of almost every robot. The utilization of the full robot potential depends on the capabilities of its end-effectors. This limits the robot flexibility regarding varying gripping tasks and at the end their application

Methods

Discussion

Conclusion