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Human Stories

Agro Robots | Which Robots Actually Work On Farms?

Harvesting fruit and vegetables can be repetitive and arduous. The human workforce is dwindling due to lack of interest, and now, the unprecedented disruption of the COVID-19 pandemic. Harvesting crops can be a prime task for agro robots to help us with - so what's out there?

The term ‘robot’ comes from the Czech word ‘roboti’, meaning ‘drudge worker’. Since it was coined in 1920, robots have taken over more and more of the ‘drudge work’ in our lives, including harvesting robots that can help us gather our fruit and veg.

Using Robots To Harvest Crops

Mechanical harvesters were the first step towards robot agriculture - machinery that uses simple, forceful methods (like physically shaking fruit from trees or cutting wheat from the ground) to gather in the harvest. The first mechanical tomato harvester was patented in 1960 - a machine that cut the plants at soil level and then shook them to separate the tomatoes. By 1970, 95% of all California-grown tomatoes destined for tins and sauces were harvested by machine.1

But robots can't harvest all crops. Mechanical harvesting is best suited for crops that won’t be damaged easily (like almonds) or where bruising might not matter, like tomatoes for sauce. But supermarkets have extremely high standards for fresh produce, so more sophisticated agro robots are needed to harvest crops that require a gentle touch. 

Find out why agro-robots still need humans to function

Machine Vision: Agro Robots Need To “See”

Automated harvesters use a combination of machine vision with a grasping tool to pick fruit and vegetables with precision. For some crops, this is relatively straightforward; for example, a robot harvesting wheat only needs to recognise the shape of rows planted in a field, which can be done by emitting lasers at the crop and measuring the reflection.2 But other agro robots need to detect the colour of ripeness, amongst other characteristics. 

To distinguish colours, robots can use machine vision to detect the different wavelengths (and so different colours) of light reflected off leaves and fruit. Some robots could also detect the thermal radiation (heat) given off by fruit, compared to leaves. And while it’s easier to see contrasting colours, it’s not impossible to harvest crops that are largely the same colour: in 2019, Cambridge University, UK, unveiled the Vegebot, which can recognise the shape of a single lettuce in a field of green.

Asparagus is even more challenging to harvest: multiple stems grow at different times, and white asparagus needs to be picked while still underground or it turns green when it sprouts through the soil. So Dutch inventor Ad van Vinken built a robot that can ‘see’ underground: it emits an electrical signal into the ground, and the water in the asparagus conducts that electricity. Sensors detect the difference between that and the surrounding soil, signalling the robot to dig and harvest.4

Copying The Human Hand 

The collecting arm of a harvesting robot needs to be mobile enough to reach into foliage and delicate enough to handle fruit without damaging it. Most robots do this with pincers or claws, and researchers are working to build robots that can mimic the soft dexterity of the human hand.

Some agro-robots go for a different advantage: extra limbs. Although it costs around 777,500 EUR to build, a 1.8m tall raspberry harvesting robot could pick 25,000 berries in a day using its four pincer-like picking hands.5 But why use hands at all? In 2019, a robot that uses suction to pick apples was successfully trialled in New Zealand.6

So far, though, most of these robots are still in development, and are not faster at identifying or harvesting produce than a human. The best strawberry harvesting robot currently picks about 50% of strawberries and moves at 3 inches per second.7 And the Vegebot damages 38% of the lettuce it picks, which is too high for supermarket standards.

But if these design problems can be solved, the cost benefits will be huge. And harvesting robots could be sent out repeatedly to harvest a field, whereas currently, many farmers only harvest a field once to save costs, generating food waste.

The First Fully Autonomous Farms

Agro-robots are not just limited to harvesting one crop type; they could take over entire farming systems. The world’s first fully autonomous outdoor farm, the UK’s ‘Hands-Free Hectare’, managed to plant, tend and harvest 4.5 tonnes of barley and 6.5 tonnes of wheat from a hectare of land in 2017 and 2018 without a single person entering the field. The robots are all classic agricultural machines retrofitted with new technology - like a tractor with a drone autopilot system.8

Now scaled up to a full farm of 35 hectares, it’s already paying dividends: researchers have been able to run the farm from home during the COVID-19 pandemic!9

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