SOFT ROBOTIC PINEAPPLE GRIPPER

Abstract

The pineapple is a tropical plant with an edible fruit and is the most economically significant plant in the family Bromeliaceae. Pineapples grow as a small shrub and is normally propagated from the suckers produced at the roots of pineapple plant, typically mature within a year. Mature pineapples weigh between 0.5-1.75 kg (Thomas and Dinesh, 2020). At present, pineapples are harvested and handled manually which results in musculoskeletal symptoms (MSS) and er- gonomic risks. Developing automatic harvest equipment is helpful for alleviating labour shortages, lightening labour intensity, improving picking efficiency, reducing production cost. Designing an end-actuator for pineapple is one of the key problems for developing automatic pineapple harvest equipment. The main objectives of this study were to design and develop a Soft robotic pineapple gripper and its performance evaluation. The physical and mechanical properties of pineapple were measured using standard measuring instruments. Design optimisation of the soft gripper was done. Pneumatic type actuation is selected for actuating the gripper and liquid silicone rubber is selected as the material of fabrication. Simulation of gripper finger was done by conducting Finite Element Analysis of individual finger of the gripper (Kultongkham et al., 2021). Individual fingers of the soft gripper was fabricated by casting the material into 3D printed moulds. Gripper casing for arranging the fingers were developed by using GI sheet. Developed soft robotic gripper consists of a Pneumatic pressure control system and control unit. There will be two solenoid valves, one act as inlet and other exit, these can be controlled by using relays which in turn gets command from the Raspberry Pi 4. A program is written in python-based Integrated Development Environment (IDE) in the Raspberry Pi named ‘Thonny’ for its timely execution. Bending angle of each of the individual grippers were measured at different pressure level. All the six fingers showed a similar trend of bending angle variation. The force generated from each of the fingers were determined by using a Force Sensor, FSR-406. Bearing capacity of the gripper is also analysed and found that a

weight of around 1.5 kg can be gripped by the gripper easily. Finally, damage rate of pineapple was evaluated (Bentini et al., 2006) and noted that no significant damage was caused to the pineapple while gripping.