11 Aug. Harvesting robot scans plants with laser
To improve the sensor technology of field robots, a team led by Professor Andreas Nüchter from Julius Maximilian University (JMU) in Würzburg has developed a new type of 3D laser scanner system for the Leibniz Institute for Agricultural Engineering and Bioeconomy (ATB) in Potsdam. According to the researchers, the aim is to gain a better understanding of the condition of the plants, for example by reliably measuring the water content of fruits – a criterion that is crucial for determining the right time to harvest.
The ATB team led by researcher Dr. Manuela Zude-Sasse has installed the system on a test site in Potsdam. The 3D laser scanner is mounted on a so-called sensor conveyor station that circles around a plantation of 120 espalier apple trees. According to the researcher, initial tests have been successful.
Robust construction: Rain and temperatures up to +40 °C do not affect the laser scanner.
Image: Michael Bleier / University of Würzburg
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The tests have shown that “we can measure and map the plants effectively,” says Nüchter. This is important for use on harvesting robots, because they need to be able to accurately detect apple trees and other plants—after all, no two plants look exactly alike. “Knowledge of the stage of ripeness is very important for the production of horticultural products in order to optimally control cultivation, harvest time, and storage,” explains Zude-Sasse. “Against the backdrop of increasingly variable growth factors due to global warming, precise data on fruit development is becoming increasingly important – for scientific modeling as well as for the future use of commercial harvesting robots.”
Plants are measured using three wavelengths
The new sensor system will be used continuously on the ATB test site until November 2025 to monitor the 120 apple trees. According to the researchers, the plant scanner is designed to be robust: it can withstand wind and weather and is designed for operating temperatures between 0 and 40 °C.
The sensor system works on the principle of structured light: it projects three wavelengths (520 nm, green / 660 nm, red / 830 nm, near infrared) onto the plants. The reflected signals provide precise spatial information about the plant population. Because the signals are available separately for each wavelength, they open up new possibilities for recording physiological properties of the plants, such as water content.
Still in the experimental stage
The 3D laser scanner was designed exclusively for experimental use. It uses laser light at an intensity that can damage the human eye if looked at directly. For this reason, special care must be taken when operating the system outdoors. The ATB strictly controls access to the measurement area. This ensures that no untrained persons are in the vicinity of the scanner. The lasers pose no danger to the plants themselves.
Core competencies of the research partners
The project builds on the core competencies of JMU Robotics in the development of optical devices and on the ATB’s many years of crop research, where spectral-optical methods for fruit quality analysis have already been developed and comprehensive infrastructures for plant analysis under field conditions have been established. The new 3D plant scanner is intended to further improve the data basis for modeling work and the specifications for future harvest robots.
Source: www.uni-wuerzburg.de
Image: Michael Bleier / University of Würzburg