Every gardener knows the problems posed by weeds. They choke your chosen plants, take valuable nutrients from the soil and make harvesting any crops incredibly hard. This is why so many of us have spent long hours with various garden tools fighting the never-ending battle against these unwelcome visitors.
Of course when it comes to large-scale agriculture, a few hours with a trowel aren’t really going to get the job done, which is why farmers spend billions each year on herbicides designed to address the problem. Herbicides have been and are extremely effective, of course, and modern levels agriculture would have been impossible to achieve without them. But they come with their own set of problems.
For one thing, herbicides are by their nature an indiscriminate solution to the problem. They have to be sprayed everywhere in order to be effective, which inevitably means that large amounts of them are wasted as they are not sprayed onto the weeds they are designed to kill. The result is that, according to research undertaken by Harper Adams University, as much as 96% of chemical inputs designed to kill weeds is wasted, costing the industry billions worldwide each year.
Their indiscriminate nature also means that weedkillers cannot distinguish between ‘good’ weeds and ‘bad’ weeds, instead killing them both. This is unfortunate, as some weeds, such as clover, can help to ‘fix’ nitrogen in the soil, ensuring it remains an excellent growing medium.
Finally, a big issue with weedkillers is plants developing resistance to them, meaning a long and costly ‘arms race’ becomes necessary to keep herbicide technology ahead of plant evolution. An example of this is ‘Black-grass‘, a native annual grass weed that occurs throughout the UK but is found mainly in the cereal growing areas of southern and eastern England. It rarely occurs outside of cultivated land and is most abundant in winter crops. Some black-grass populations have developed resistance to some widely used graminicides and this has contributed to an increase of the weed on conventional farms. This not only affects cereal yields, but black-grass suffers from ergot (Claviceps purpurea) and this can result in contamination of the grain at harvest. The fungus is the same strain that infects wheat. This problem currently costs UK agriculture approximately £400m per year in lost revenue – a figure that is expected to exceed £1 billion within the decade, as herbicide resistance is increasing all the time.
One solution to this problem is so-called ‘per plant’ farming, which seeks solutions that are more discriminating. One of these is offered by UK-based agri-tech start-up Small Robot Company, which has unveiled a number of developments in this area.
Small Robot Company co-founder Sam Watson-Jones. “We started from the premise that there has to be a better, more intelligent and less wasteful way of doing this. That’s what’s made our recent work so exciting,” he says.
Andy Hall, SRC’s head of prototyping, agrees, saying: “We’re really into individual plant farming – dealing with each plant by itself and with each weed individually. ”The work takes the form of the world’s first non-chemical weed killing robot that can destroy weeds at an individual plant level, making it an exciting, low impact technology for farming where the currently necessary blanket spraying of herbicides involves costly wastage, with detrimental impact on the environment. In addition, soil degradation from herbicides and soil compaction reduces crop yields. Small Robot Company with key partners igus and Rootwave have demonstrated the world’s-first self-driving robot that can identify and kill weeds with a specialised ‘zapper’ device using electricity.
The weedkilling wheeled robot, called ‘Dick’, fitted with igus’s delta robot arms, successfully identified individual weeds using artificial intelligence (AI) and vision technology, and zapped them at a media event in East Tytherley, Hampshire in April. The zapper end effector is supplied by Rootwave. Small Robot Company (SRC) has developed three robot variants for farming applications – Tom, Dick and Harry.
Leading motion plastics company igus’s delta robot, used commonly in industry for pick-and-place operations, manoeuvres the zapper into place using an integrated motor and encoder, linked to the Dick robot’s master controller. The three igus delta arms fitted to each Dick can destroy weeds simultaneously.
igus was selected as the preferred delta robot manufacturer due to the light weight, precision and low cost. Many competing delta robots cost up to £20,000 while the igus delta is about £5,000, developed at this price as part of igus’ Low-Cost Automation division for R&D applications, but possessing robust engineering suitable for commercial scale-up.
SRC has been the beneficiary of more than £1million in government Innovate UK grants. This includes an £800,000 grant for its ‘Wilma’ artificial intelligence weed recognition and ‘Tom’ weed mapping technology. This was one of the largest single agritech grants made under Innovate UK’s innovation scheme in 2018.
Overall, SRC has secured more than £2.5 million in funding to date, including £1.2 million from its previous Crowdcube raise, and more than £1million in government Innovate UK grants. This includes an £800,000 grant for its ‘Wilma’ artificial intelligence weed recognition and ‘Tom’ weed mapping technology. This was one of the largest single agritech grants made under Innovate UK’s innovation scheme in 2018.
Also at the event, the ‘Tom’ monitoring robot uses proprietary Wilma artificial intelligence (AI) to scan the field for weed patches which it uses to define a path for ‘Dick’ to follow. Dick is then dispatched to ‘seek and destroy’, and the Dick robot can now both identity specific weeds in a patch and kill them.
This two-robot approach demonstrates SRC’s ‘end-to-end service’ model, using multiple robots with AI working together to scan the field on a plant level then take action. Furthermore, SRC and igus are looking to work on different actions, where Tom and Dick could combine again for spot spraying, spot fertilising or slug killing, for example.
The igus delta robot’s components and control system is key to the weed killing operation, where ease of use and cost are paramount. Firstly, the delta units are made from standard drylin parts, making assembly easy and low cost. They have been thoroughly field tested to ensure they cope with wet mud and water splash.
Stepper motors are linked to controllers that help position the delta robot directly over the weeds. The motors have encoders, which help the delta know what position it is in, with good industrial protocols so they are easy to programme. The SRC’s robot’s, i.e. 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.
igus Low-Cost automation engineer Angelos Bitivelias has worked with universities and industrial companies on delta robots for applications like fruit picking, so he brings the knowledge of how the igus delta can be best modified for the weed killing application.
“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,” says Angelos. “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.”
An essential feature of the delta and igus components is they are lubrication-free. Lubricated moving parts like the belt drive and bearings would potentially clog up with soil and water in a muddy field, but igus polymers and parts are designed to be dry running.
Precision is also a strong feature. “The milestone we’ve hit is that we can now take action at the plant level,” says Andy Hall. “Using artificial intelligence, the robots can recognise the weeds in the [camera] shot and target the robotic arm onto those weeds. At that point we can do anything we want. Our robotic platform incorporating the igus arm could have many different technologies bolted on – and the world’s our oyster on that.” In fact, such is the precision of this solution that the system can distinguish clover from other, more harmful and pernicious weeds.
The affordability, precision, durability and reliability of the igus delta robots are perfect for this and new agricultural applications, says Managing Director of igus UK, Matthew Aldridge. “Because the delta is lightweight and low-cost it has opened up new opportunities for these robots to be used in mobile applications, proving a new technology in a harsh outdoor environment. Igus is planning to work with SRC on new industrial applications where precise and low impact actions are needed on farms and potentially other scenarios.”
“To prove the power of per plant farming, we are focused on answering the biggest problem that farmers face at the moment, which is weeding,” comments Ben Scott-Robinson, CEO and co-founder of SRC. “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.”
