HAMPSHIRE, UK—British agricultural technology start-up Small Robot Co. has invented a mobile delta autonomous mobile robot that can weed agricultural fields without using chemicals.

The wheeled robot is equipped with three delta robots that independently position “zappers” to kill weeds using electricity. The zappers were supplied by another British agritech start-up RootWave.

The weed-killing robot, called “Dick,” works in concert with a monitoring robot, “Tom,” that uses machine vision and artificial intelligence to identify weed patches and transmit their locations to Dick. Dick is then dispatched to “seek and destroy” the weeds along the route provided by Tom.

Dick is the world’s first autonomous mobile robot that can destroy weeds individually without the use of chemicals. The technology represents an alternative to blanket spraying of herbicides, which is wasteful and can adversely affect the environment.

In the future, Tom and Dick could work together for other applications, such as spot spraying, spot fertilizing or slug killing. Another autonomous robot, Harry, is being developed for planting operations.

Delta robot arms from igus were selected for the machine because of their precision, light weight, low-cost and self-lubricating operation. More commonly used in industry for pick-and-place operations, the delta robot maneuvers the zapper into place using an integrated motor and encoder, linked to Dick’s master controller. Many competing delta robots cost more than $25,000, while the igus delta is approximately $6,400.

The igus delta robot’s components and control system are key to the weed killing operation, where ease of use and cost are paramount. Firstly, the delta units are made from the company’s 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 program. Dick’s master controller and software “speak” to the igus motor controller to synchronize 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,” says igus automation 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.”

An essential feature of the delta and igus components is they are self-lubricating. 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, head of prototyping at Small Robot. “Using artificial intelligence, the robots can recognize 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.”  

Following successful field trials in April, the next stage for Tom and Dick are efficacy trials, measuring the force required to destroy the weeds, including the comparison of different varieties, to ensure that they are totally destroyed and not partially killed.