Design and Experiment of an Underactuated Broccoli-Picking Manipulator

Abstract

Mature broccoli has large flower balls and thick stems. Therefore, manual broccoli picking is laborious and energy-consuming. However, the big spheroid vegetable-picking manipulator has a complex structure and poor enveloping effect and easily causes mechanical damage. Therefore, a broccoli flower ball-picking manipulator with a compact structure and simple control system was designed. The manipulator was smart in structure and stable in configuration when enveloped in flower balls. First, a physical damage test was carried out on broccoli according to the underactuated manipulator’s design scheme. The maximum surface pressure of the flower ball was 30 N, and the maximum cutting force of the stem was 35 N. Then, kinematic analysis was completed, and the statical model of the underactuated mechanism was established. The dimension of the underactuated mechanism for each connecting rod was determined based on the damage test results and design requirements. The sizes of each connecting rod were 50 cm, 90 cm, 50 cm, 90 cm, 50 cm, 60 cm, and 65 cm. The statical model calculated the required thrust of the underactuated mechanism as 598.66–702.88 N. Then, the manipulator was simulated to verify its reliability of the manipulator. Finally, the manipulator’s motion track, speed, and motor speed were determined in advance in the laboratory environment. One-hundred picking tests were carried out on mature broccoli with a 135–185 mm diameter. Results showed that the manipulator had an 84% success rate in picking and a 100% lossless rate. The fastest single harvest time in the test stand was 11.37 s when the speed of the robot arm was 3.4 m/s, and the speed of the stepper motor was 60 r/min.

Leveraging I4.0 smart methodologies for developing solutions for harvesting produce

“…For example, Fan et al ( 2021) investigated multiple apple grasping principles and picking patterns by developing 3D branch-stem-fruit models and conducting finite element simulations in ABAQUS to compute and compare separation forces. An underactuated broccoli gripper design was validated using ADAMS (Automatic Dynamic Analysis of Mechanical Systems) software that measured applied contact forces (Xu et al, 2023). ADAMS software was also used by Mu et al (2020) to validate trajectory motions of the bionic fingers in a kiwifruit robotic end-effector design.…”

Influence of Joint Stiffness and Motion Time on the Trajectories of Underactuated Robots

“…Possible applications of underactuated robots include industrial robots, legged locomotion, and surgical robots [5,6]. There are some studies on underactuated grasping tools [7][8][9]. Moreover, the interest in underactuated robots is increasing, since a fully actuated robot in case of actuator failure becomes an underactuated robot [1].…”

“Eyes”, “Brain”, “Feet” and “Hands” of Efficient Harvesting Machinery

“…In total, 21 papers are published in this Special Issue, including two papers related to the physical property parameter of materials or crops [1,2]. Thirteen papers describe efficient end-effectors and harvesting components ("hands"), with the crop objects harvested including Cabbage [3], Cotton Stalk [4], Potato [5], Dandelion Seed [6], Broccoli [7], Peanuts [8], Rice [9], Supernormal Jujube Branches [10], Silage Corn [11], Small Spherical Fruit [12], Chinese Little Greens [13], Hazelnut [14], and Chinese Milk Vetch (Astragalus sin-icus L.) Seeds [15]. Two papers describe highly adaptable chassis and mobile platforms ("feet"), which focuses on machine-soil relationship [16,17].…”