Homemade robot sprays strawberries autonomously

The moment the autonomous vehicle exits the strawberry tunnel, it automatically stops spraying and it decreases its speed to 1.8 kilometers per hour. It then finds his way to the next tunnel, following to a pre-programmed route. The front and rear wheels turn, so the spraying robot lines itself up with the next path. The machine then drives into the row, nozzles start spraying again and the speed is increased to 2.4 km/h. RTK GPS keeps the vehicle on the set path.

Covering 3 hectares in 2 hours

More than 2 hours later, the autonomous vehicle has finished spraying in 16 tunnels, covering an area of over 3 hectares. Each tunnel contains 5 rows of strawberries. “We treat the strawberries with the biological agent Serenade,” says grower Niels Huijsmans of HG Eerenburg in Nispen, the Netherlands. “This treatment is repeated every three days. If you had to do that with a tractor driven by an operator, it wouldn’t work. With this vehicle however it’s no problem at all: you prepare the machine, and don’t have to worry about it anymore.”

Huijsmans can monitor the robot with his smartphone. He’s able to continuously see where and in which tunnel the vehicle is, and whether everything is still functioning as intended.

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The robot exits and enters the tunnels fully autonomously. – Photo: Joost Stallen

Not commercially available

The Huijsmans autonomous vehicle is not commercially available. The box-beam frame doesn’t have a protective coating, which would indicate the robot is still a prototype. In terms of operation and functionality however, it is well beyond the prototype stage. The machine has proven to be so reliable that it is used in daily practice: at the moment it is only deployed in tunnel cultivation, the next step will be the use in the cultivation of waiting-bed plants. “Basically, the machine works flawlessly,” says Huijsmans.

The project started when Huijsmans asked Dutch farm equipment company Kriesels about the feasibility of a self-driving tool carrier. “That was a year ago,” says Ruud Bierbooms, who is one of those directly involved in the development of the vehicle.

Don’t spend too long talking about it, but just do it

Bierbooms says it is thanks to the fact the two companies worked so closely together that a fully operational vehicle has been developed in such a short time. “Don’t spend too long talking about it, but just do it. ”

Existing developers of autonomous vehicles were deliberately not called upon. Bierbooms: “Then you would have to work with third parties, and you are and remain dependent on their way of working and the speed with which they develop technology.”

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Trial and error

The frame and suspension were developed by Kriesels. “That was a matter of trial and error. We had an electric motor and a gearbox for the wheel drive. These were attached to each other and tested in the front linkage of a tractor to see if it was powerful enough for what we wanted it to do.”

RTK-GPS

The vehicle uses RTK-GPS to navigate. During the development of the vehicle at Huijsmans, an existing third-party positioning system was initially chosen. That did not work. Bierbooms: “Our GPS technician then developed a system with which we pick up the signals from an average of 32 navigation satellites. The RTK correction signal comes from a server, via a transmitter. The road map has been created with a Trimble GPS system on a tractor.”

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Powered by a generator

The electric motor is powered by a generator on the vehicle. “A generator runs at a fixed speed, which ensures relatively low fuel consumption,” says Bierbooms. It’s also a lot cheaper than an electric drivetrain powered by batteries, which require special motors. There are plans to equip the vehicle with OptrX crop sensors, in order to make variable rate spraying possible.