A robotic citrus harvesting system designed to protect fresh-market fruit quality has shown promising results in orchard trials while using a simple cutting mechanism.
The system uses a V-shaped guide to position each orange’s stem near the cutting blades. Instead of relying on extra motors to position the cutter, the robot moves its arm to guide the stem into place. Leaving short stems is important for fresh-market citrus because long stems can puncture neighboring fruit during packing, handling and transportation.
In trials involving 100 navel oranges, the system successfully detached every targeted fruit. Researchers found that 92% of the oranges had stems shorter than 10 millimeters, while 52% met the more demanding target of 2 millimeters or less. The average remaining stem length was 3.1 millimeters.
The redesigned cutting attachment weighed just 0.5 kilograms, down from 1.5 kilograms, and required only two actuators, compared with four in the earlier design. These changes could make robotic harvesting equipment less complex and easier to integrate into automated harvesting platforms.
Cutting performance was best when stems were relatively straight and unobstructed. In those cases, average remaining stem length was about 1 millimeter. Irregular stems, sharp angles and interference from nearby branches or fruit made precise cutting more difficult.
Each harvesting cycle took 38.6 to 55.1 seconds per orange, depending on operating speed. Researchers identified movement planning and obstacle avoidance as areas needing improvement. Therefore, the technology is not yet ready for commercial use.
An article about the research was published in Smart Agricultural Technology. It was written by Brendan Chinnock, Andrei Catalan, Daniel Yang, Nicole Oliva, Alexander Ellis, The Nguyen and Alaeddin Bani Milhim of California State University, Fresno.
The findings represent progress toward automated harvesting that considers fruit quality as well as picking efficiency. Although the system is not yet a replacement for hand harvesting, its simpler design could help advance practical robotic harvesting solutions for fresh-market citrus. Further testing under different orchard conditions will be needed to determine its commercial potential.
Read the research: “Passive stem-centering end-effector for controlled residual stem length: Integration and orchard evaluation on a robotic citrus harvesting platform”
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