June 2021

42 n ROBOTICS June 2021 www.drivesncontrols.com O n a farm in Hampshire, an odd- looking wheeled machine with an array of three industrial delta robots suspended underneath has been taking part in a trial that could change the way that farmers deal with the perennial problem of weeds. Many farmers are looking for alternatives to traditional chemical-based weedkillers for environmental and other reasons, including a growing resistance to herbicides, and costs that have risen by about 50% in the past ten years. Also, indiscriminate chemical weedkillers can kill beneficial plants, such as clover (which fixes nitrogen in the soil), as well as undesirable weeds, such as black grass. Weedkillers are also an imprecise way of dealing with the problem, with up to 90% going to waste. The search for an alternative to herbicides comes at a time when the weed menace is growing. Research has found that weeds are now cutting wheat yields by more than 50% – compared to less than third 50 years ago. One reason for this is that, as the climate warms, weeds are doing better than the crops. So efforts are underway around the globe to find environmentally acceptable and better targeted alternatives to chemical weedkillers. One approach is to blast the weeds with lasers. Another is to zap them with electricity – an approach being developed by a Warwickshire-based company called RootWave. Its Electricide technology applies an 10–12kV shock to the weed, boiling it from the inside, thus killing the plant which then decomposes naturally. To achieve this effect, the shock has to be applied extremely precisely to each weed. This is where a Hampshire-based start-up called the Small Robot Company comes in. SRC, which was set up four years ago to apply advanced technologies to the agricultural sector, is developing a pair of mobile machines that will form the basis for its weed-zapping system. Spotting the problem The first machine, called Tom, scans a field using an array of sensors including microphones and six high-resolution cameras and sends the data to the cloud where an AI (artificial intelligence) engine analyses the data to pinpoint weeds with sub-millimetre accuracy. GPS-guided Tom can trundle around a field autonomously, covering up to 20 hectares a day and collecting about 6Tb of data in an eight-hour shift. In one trial, the machine scanned a six- hectare field, identifying 12.7m plants, 250,000 of which were weeds. Tom and the AI engine (called Wilma) were developed with the help of a £800,000 grant from Innovate UK. The Tom machines, which are due to enter large-scale trials later this year, are being manufactured by the Northumberland firm Tharsus, which also makes Ocado’s grocery-picking robots. Tom could be in use on more than 100 farms by 2023. The second SRC machine, called Dick, is at an earlier, prototype stage of development. Its role is to move around a field zapping the weeds identified by Tom, and using data supplied by Wilma. The zapper electrodes are mounted on three delta robots supplied by igus, which would normally be found in factories performing pick-and-place applications. Cameras on the machine take images which are analysed by AI to identify the weeds. A master controller communicates with robots’ stepper motor controls and encoders, forming a closed-loop monitoring system that positions the arms precisely over each weed before the high voltage is applied. The machine can kill three weeds every two seconds. At present, the machine is parked above a section of a field while the robot arms tackle the weeds below. It then moves on to another section. A later version may be able to zap the weeds while the vehicle is moving. SRC chose the igus robots for several reasons including their light weight, ruggedness, precision and low cost. The robots are assembled from standard drylin engineering plastic parts, cutting weights and costs. Rival robots can cost up to £20,000, while the igus devices are about £5,000 each. SMC found that the electromagnetic pulses generated by the high-voltage zapping system could interfere with the Industrial robots are escaping the confines of factories and being put to work on farms. In one world- leading project, a UK high-tech start-up is using an array of delta robots to apply miniature “lightning strikes”with millimetre accuracies to kill individual weeds. The consequences could be “gamechanging”. Robots could revamp the way we farm