Model Analysis and Experimental Investigation of Soft Pneumatic Manipulator for Fruit Grasping

Abstract

With the superior ductility and flexibility brought by compliant bodies, soft manipulators provide a nondestructive manner to grasp delicate objects, which has been developing gradually as a rising focus of soft robots. However, the unexpected phenomenon caused by environmental effects, leading to high internal nonlinearity and unpredictable deformation, makes it challenging to design, model, and control soft manipulators. In this paper, we designed a soft pneumatically actuated manipulator consisting of four soft actuators, as well as a flange, and investigated the influence of structural parameters on the output characteristics of the manipulator through finite element analysis (FEA). To enhance the bending deformation of the soft actuator, annular rings were employed on the soft actuator. A mathematical model for the bending deformation of air cavities was established to explore the relationship between the driving pressure and the bending angle based on the Yeoh strain energy function. Moreover, an end-output force model was established to depict the variation of the force output with the bending angle of the soft actuator, which was then experimentally validated by adopting the manufactured manipulator. The soft actuator studied in this paper can bend from 0° to 110° under an applied pressure of 0–60 kPa, and the maximum grasping load of the soft manipulator is 5.8 N. Finally, practical tests were conducted to assess the adaptability of the soft manipulator when grasping delicate fruits, such as apples, pears, tomatoes, and mangoes, demonstrating its broad application prospects in nondestructive fruit harvesting.

Intelligent Soft Robotic Grippers for Agricultural and Food Product Handling: A Brief Review with a Focus on Design and Control

“…The inclusion of fiber reinforcement significantly enhances the grippers' robustness and output force. These grippers exhibit high flexibility and have been successfully used to handle various agricultural products such as tomatoes, [117] apples, [118] mangos, pears, [119] eggs, [120,121] peppers, pomegranates, and even large items like watermelon and pumpkin using large grippers. [101] However, there are two shortcomings that limit the use of pneumatic grippers for agricultural products.…”

Perceptual Soft End-Effectors for Future Unmanned Agriculture

“…This is because their system design is simpler compared to hydraulic-driven end-effectors, and the load capacity can meet the requirements of most agricultural products. Among pneumatic-driven soft end-effectors, the most common approach is to utilize a cavity structure component for harvesting agricultural products [ 84 , 85 , 86 , 87 ]. Suction cups are also a simple and practical type of soft end-effector.…”

Experimental investigation on enhancement in pure axial deformation of soft pneumatic actuator (SPA) with cap ring reinforcement

“…Coils [37] have been incorporated into the soft actuator while molding to amplify its bending deformation capabilities. An anisotropic layer [38] has been introduced within conventional Dielectric Elastomer Actuators to interlink bending and twisting deformations, optimizing the fibre spacing and orientation within this layer.…”