UK farmbot field trial demonstrates new approach to weeding

Jon Excell reports

Earlier this spring, in a chilly corner of a windswept field in Hampshire, the first seeds of what could be a new agricultural revolution were sown, as a UK built precision weeding robot – with more than a passing resemblance to a mechanised alien invader - completed its first set of successful field trials.

Developed by agritech startup the Small Robot company, Dick -as the robot is named - is claimed to be the world’s first non-chemical robotic weeding system for cereal crops.

Designed to destroy weeds at an individual plant level the system is at the vanguard of a new approach to low impact farming, that is tapping into advances in robotics, imaging and artificial intelligence to provide a targeted alternative to the high impact, herbicide-dependent methods that dominate modern farming and which are becoming increasingly unsustainable.  Rather than using chemicals to deal with problem plants, Dick simply despatches them with a blast of high voltage electricity.

As previously reported by The Engineer the robot is actually part of a suite of robotic systems, including crop monitoring robot “Tom” and an AI system called Wilma that the company plans to sell as a service to farms across the UK and beyond.

Tom, which was launched as a commercial product earlier this year and is manufactured by Northumberland firm Tharsus can be controlled either manually or autonomously and trundles around the field imaging individual plants in high resolution detail.

The system is capable of mapping around 20 Hectares and 6 terabytes which are uploaded to the cloud and analysed by “Wilma”, an AI system that identifies the crops, spots undesirable weeds,  and supplies intelligence and data to the farmer. According to the company, future versions of the system will even be able to assess soil health and biodiversity by gathering data on birdsong and pollinators.

This data can then be sent to Dick, which is despatched to destroy the offending weeds using a series of robotically controlled zappers on its underbelly.  “Using artificial intelligence, the robots can recognize the weeds in the [camera] shot and target the robotic arm onto those weeds,” explained Andy Hall, head of prototyping at the Small Robot Company.

Developed by another UK agritech startup, RootWave, these zappers deliver 10 - 12,000 volt blasts of electricity to the weed, however Hall told The Engineer that the company is also exploring the potential use of  other technologies such as lasers, and potentially the development of a hybrid system that could use different techniques depending on the conditions.

The zappers are moved into position by three delta robot arms (parallel robots consisting of three arms connected to universal joints at the base) supplied by polymer bearing specialist igus UK.

Stepper motors linked to controllers help position the delta robot directly over the weeds. The motors have encoders, which help the delta know what position it is in, whilst Dick’s master controller and AI “speak” to the igus motor controller to synchronise the robot’s position with the delta arm, forming a closed loop monitoring system.  “The Dick robot moves to one side, a camera takes a photo of the weed, the AI identifies it as a weed, and then AI decides where to zap it,” explained igus engineer Angelos Bitivelias. “The kinematics of the delta makes it well suited to the end effector and the belt drive means the zapper is always parallel to the ground below.”

SRC’s Andy Hall said that the igus delta robot – which was originally developed for pick and place industrial applications -  was chosen for its relatively low cost and durability.

“The affordability, precision, durability and reliability of the igus delta robots are perfect for this and new agricultural applications,” said igus UK Managing Director, Matthew Aldridge. He added that one of the key features of the delta components is they are lubrication-free, and therefore less prone to becoming clogged up with soil and water in a muddy field.

Following the successful field trials this April, Tom and Dick will now enter further trials in which the force required to destroy different types of weeds will be explored in greater detail.

SRC and igus are also looking to work on different applications for the technology such as  spot spraying, spot fertilizing or slug killing “Our robotic platform incorporating the igus arm could have many different technologies bolted on - and the world’s our oyster on that,” said SRC’s Andy Hall.

If adopted at scale the approach pioneered by SRC could have a major impact.  Despite the UK using ever increasing amounts of herbicides and fungicides, yields have remained static for more than a quarter of a century, and the huge tractors and harvesters used on farm around the world are compacting soils and forcing farmers to use ever more intensive methods.  Systems like those developed by SRC could help farmers find a way out of this damaging feedback loop.

“This is a major technological milestone which will enable automated, precision, per-plant weeding both at scale and autonomously, for the first time providing a post-chemical future for arable farmers,” Said Ben Scott-Robinson, CEO and Co-founder, Small Robot Company. “We’ve now proved we can deliver per plant weeding: a world first. The focus for us now is being able to move forward to deliver this, repeatedly, and at scale. This will be game-changing.