Affordable weeding robot for small farms on its way

Software architect Douglas Boari of Sony Computer Science Laboratories (CSL) explained that all the details of the software and the design specs of the hardware will be published, as the robot, named Rover, is an open source and open hardware project. “The whole point of this project is accessibility”, he said at the international agricultural robot event FIRA in Toulouse. “But we are also looking at supplying the ROMI Rover in kit form, as a flat pack, IKEA-style.”

ROMI (Robotics for Microfarms) is a sustainability project of a European consortium. The project receives financing from the European Union. ROMI joined forces with Sony CSL to develop the robot.

In 2022 the final design of the hardware will be finished and in-depth testing of the software will take place. ROMI and Sony plan to obtain the feedback of farmers and certification in 2023 and 2024. If farmers will be able to buy the robot as a flat pack, in 2025, the price of the kit will be between € 5,000 (US $ 5,666) and € 10,000 (US $ 11,332). “We have set a doable price”, said researcher Peter Hanappe of Sony Computer Science, at the FIRA.

‘Get it out there as much as possible’

Boari said that farmers are used to working with mechanical equipment and will have no problem putting a Rover together. “The farmers we have been developing with, often fix their own equipment. But we can potentially also send out a completely constructed Rover, depending on what the demand is. We plan to get it out there as much as possible.”

Focus on mechanical weeding

ROMI and Sony focus with the Rover on mechanical weeding. Hanappe: “If we look at vegetable farmers, one of the main issues are biodiversity and soil health. They often have complex farming organisations, with crop covers, living mulch and mixed inter-cropping. For us the main challenge is: how can we use AI and robotics to handle these more complex farm systems efficiently.”

The four-wheel robot combines autonomous navigation and a weeding tool. It uses a camera when driving forward, stops at some point and uses an image segmentation algorithm to detect the crop. It then computes a path for the Rover to clean the soil with a rotary hoe.

This precision tool will remove any small weeds that are there. The size of the tool is 5cm diameter and the Rover tends to leave approximately 1cm buffer. “If you do this once a week, you will keep the weed population under control”, Hanappe explained. Farmers will also be able to use other weeding tools on the robot.

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2,500 m2 per week

The Rover specialises in precision weeding inter-row and intra-row. It can work in lettuce and other low crops in a row width from 0.8m to 1.2m. It can do its work in crops up to 50 centimetres high. ROMI aimed to reach an output capacity of 5,000 m2 per week for its robot but is currently at a point where it estimates it can reach 2,500 m2 per week. “There always will be an element of human involvement and that will slow things down”, Boari said.

To be honest: there always needs to be a human presence

The weeding robot uses a camera to track the crop rows. It can also use the segmentation of the soil. ROMI is currently working on the ability to do a U-turn. “We’re halfway towards our targets”, Boari said. “But to be honest: there always needs to be a human presence.”

Hanappe emphasised that the Rover is a light robot. “It can go in the field when it is still wet and when other devices will get stuck. I think this is an important feature.”

The Rover is electrically powered with a 24V lithium battery. It can work autonomously for 8 hours a day. The robot is 1.5m long, 1.5m wide and 1.4m high. It weighs 140 kg. ROMI and Sony have built 4 Rovers so far.

The Rover was presented previously but has been further developed. According to Hanappe the Rover now uses standard neuro networks to effectively discriminate between the crops and the weeds. “This allows us to do more precise weeding and control bigger weeds”, Hanappe said.

The navigation of the Rover is also new. ROMI has moved away from a rail-based navigation system. The robot can now navigate autonomously along a bed of crops. “Moving to automation has really helped to keep the costs down”, Boari said. There are no plans to integrate GPS.

ROMI tries to keep the costs of the technology components of the Rover down. “We try not to go too high end”, Hanappe said. “We use a single navigation camera in the Rover and adapted a line following algorithm for the navigation, where we detect the crops, follow the crops and adjust the navigation as necessary. If the crops are too dense, we can also follow the soil between the crops. This works quite well.”

Off the shelf components

Hanappe pointed out that the small robot could include high end technology in the future. “We currently use low end technology but I think this is too restrictive. The price of components has come down so much. It’s easy now to find embedded computers or camera sets at very reasonable prices. We think it is possible to just use off the shelf components.”

Gaming components

ROMI uses technology widely used in the gaming world as well, such as the A* algorithm for pathfinding. For manual control ROMI uses a PlayStation controller. ROMI tries to build the frame with standard lightweight aluminium components. Hanappe: “The advantage is that we can go through faster cycles of development. And that we can ship the Rover as a flat pack. ”

Hanappe said that ROMI is looking at the possibility of the end user creating and deploying AI systems on the plants he wants to, so he is not limited to pre-made algorithms. He suggested that it might make an interesting community project with shared data.