Precise and lubrication-free linear technology for autonomous weed robots

Sustainability and efficiency are key requirements of modern agricultural engineering. Kilter, a Norwegian start-up, has taken up this challenge in weed control. Their autonomous agricultural robot AX-1, equipped with GPS, artificial intelligence and a vision system, recognises weeds precisely and applies tiny drops of herbicide only where it is needed - similar to an inkjet printer. This leads to a dramatic reduction in chemical consumption of up to 95 per cent and an increase in yield of 35 per cent, as crops are not damaged by herbicides.

Another goal of the AX-1 engineers was to protect the soil not only chemically, but also mechanically. They therefore had to ensure that the construction of the robot was as light as possible to minimise soil compaction. One particularly complicated area was the adjustment mechanism of the spray module. Adjusting the height for different plant species and growth stages proved difficult with available linear systems, as many solutions are heavy and dependent on lubricants. These lubricants could become a friction-increasing paste combined with the dust on the field and affect reliability.

Kilter uses the drylin SLW-25120 linear module to meet the requirements of the AX-1. The system optimally adjusts the height of the spray module to the plant height by executing precise movements via a trapezoidal lead screw with an electric motor. The system's lead screw nut moves along an axis and is connected directly to the spray module via a carriage.

The design of the drylin SLW-25120 offers decisive advantages for Kilter's agricultural applications. The nut and plain bearing are made of high-performance plastic that contains microscopic solid lubricants, ensuring low-friction dry operation without maintenance. This prevents the mixing of lubricating greases with dust and increases mechanical reliability in the often dusty fields. The system also offers a lightweight feature: the basic mechanism weighs just 5.9kg, with an additional weight of just 0.9kg per 100mm stroke length.

Thanks to the torsion-resistant double-shaft design, the module remains robust even under harsh operating conditions. With a maximum axial load capacity of 2,500N and a radial force of 10,000N, the system is ideal for the spray module of the AX-1, which weighs around 60kg. This stability and high load capacity provide additional safety reserves for shocks and other loads that can regularly occur during use in the field.

By eliminating the need for relubrication, farmers save time and money, while the reliability of the robot is increased in the long term.