Design and simulation of an integrated end-effector for picking kiwifruit by robot

Abstract

The harvesting of fresh kiwifruit is a labor-intensive operation that accounts for more than 25% of annual production costs. Mechanized harvesting technologies are thus being developed to reduce labor requirements for harvesting kiwifruit. To improve the efficiency of a harvesting robot for picking kiwifruit, we designed an end-effector, which we report herein along with the results of tests to verify its operation. By using the established method of automated picking discussed in the literature and which is based on the characteristics of kiwifruit, we propose an automated method to pick kiwifruit that consists of separating the fruit from its stem on the tree. This method is experimentally verified by using it to pick clustered kiwifruit in a scaffolding canopy cultivation. In the experiment, the end-effector approaches a fruit from below and then envelops and grabs it with two bionic fingers. The fingers are then bent to separate the fruit from its stem. The grabbing, picking, and unloading processes are integrated, with automated picking and unloading performed using a connecting rod linkage following a trajectory model. The trajectory was analyzed and validated by using a simulation implemented in the software Automatic Dynamic Analysis of Mechanical Systems (ADAMS). In addition, a prototype of an end-effector was constructed, and its bionic fingers were equipped with fiber sensors to detect the best position for grabbing the kiwifruit and pressure sensors to ensure that the damage threshold was respected while picking. Tolerances for size and shape were incorporated by following a trajectory groove from grabbing and picking to unloading. The end-effector separates clustered kiwifruit and automatically grabs individual fruits. It takes on average 4–5 s to pick a single fruit, with a successful picking rate of 94.2% in an orchard test featuring 240 samples. This study shows the grabbing–picking–unloading robotic end-effector has significant potential to facilitate the harvesting of kiwifruit.