Robots That Help Harvest Lettuce

Lettuce is a valuable crop in Europe and the United States. But labor shortages make it difficult to harvest; finding sufficient seasonal labor to meet harvesting commitments is one of the sector’s biggest challenges. Moreover, with wages rising faster than producer prices, margins are tight.

In the United Kingdom, agricultural technology and machinery experts are working with IDS Imaging Development Systems in Obersulm, Germany, to develop a robotic solution to automate lettuce harvesting. The team is working on a project funded by Innovate UK and includes experts from the Grimme agricultural machinery factory, the Agri-EPI Centre (Edinburgh), Harper Adams University (Newport), the Centre for Machine Vision at the University of the West of England (Bristol) and two of the UK’s largest salad producers, G’s Fresh and PDM Produce.

Within the project, existing leek-harvesting machinery is adapted to lift the lettuce clear from the ground and grip it between pinch belts. The lettuce’s outer, or “wrapper,” leaves will be mechanically removed to expose the stem. Machine vision and artificial intelligence are then used to identify a precise cut point on the stem to neatly separate the head of lettuce.

Machine vision and AI are used to determine a precise intersection point on the stem.

“The cutting process of an iceberg is the most technically complicated step in the process to automate, according to teammates from G subsidiary Salad Harvesting Services,” explains IDS product sales specialist Rob Webb. “The prototype harvesting robot being built incorporates a GigE Vision camera from the uEye FA family. It’s considered to be particularly robust and is therefore ideally suited to demanding environments. As this is an outdoor application, a housing with IP65/67 protection is required here.”

The choice fell on IDS’ GV-5280FA-C-HQ model, along with Sony’s compact 2/3-in. global-shutter CMOS sensor IMX264.

“The sensor was chosen mainly because of its versatility,” says Webb. “We don’t need full resolution for AI processing, so sensitivity can be increased by binning. The larger sensor format means that wide-angle optics aren’t needed, either.”

In the application, the CMOS sensor comes through with excellent image quality, light sensitivity, and high dynamic range. It delivers almost noise-free, high-contrast 5 MP images in 5:4 format at 22 fps, even in applications with fluctuating light conditions.

The extensive range of accessories, such as lens tubes and trailing cables, is just as tough as the camera housing and screwable connectors (8-pin M12 connector with X-coding and eight-pin binder connector). Another advantage: Camera-internal functions, such as pixel preprocessing, LUT, or gamma, reduce the required computer power to a minimum.

The prototype of the robotic mower has been used for field trials in England. “We’re delighted to be involved in the project and look forward to seeing the results,” says Jan Hartmann, managing director of IDS. “We’re convinced of its potential to automate and increase the efficiency of the lettuce harvest, and not only in terms of compensating for the lack of seasonal workers.” 

Prototype lettuce harvesting robot of Agri-Epicentre (UK)

Issues facing the agricultural sector are indeed complex. According to a forecast by the United Nations Food and Agriculture Organization (FAO), agricultural productivity will have to increase by almost 50 percent by 2050, compared to 2012, due to increasing population. Such a yield expectation represents an enormous challenge for the agricultural industry, which is still in its digitalization infancy compared to other sectors, and is already under high pressure to innovate in view of climatic changes and labor shortages.

Agriculture of the future will be based on networked devices and automation. Cameras are an important building block, and artificial intelligence is a central technology here. Smart applications, such as harvesting robots, can make a significant contribution to feeding the world.

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