An autonomous tractor traverses olive groves: How its capacity to navigate between rows of trees was optimized

A team from the University of Córdoba is developing an autonomous tractor with three different steering modes, allowing it to drive in straight lines, make turns efficiently, and shift modes in response to its trajectories

One of the possible meanings of the name Sergius is "one who serves," hence the name of the robotic tractor that can autonomously perform agricultural tasks in fields of woody crops. This one-of-a-kind vehicle, designed by the University of Córdoba, is part of an Agriculture 4.0 context in which agricultural tasks are being automated. The researchers, with the Rural Mechanization and Technology Group at the University of Córdoba, Sergio Bayano and Rubén Sola, designed the vehicle from the ground up, in collaboration with two companies charged with its mechanical manufacturing and programming.

"On the national market, there are some small autonomous vehicles that can be applied to agriculture, but there were none with a tractor's functionality," explained researcher Rubén Sola. "This vehicle has the same functions as a tractor, but is groundbreaking in that, in addition to being autonomous, it features two independent self-leveling axles with steerable wheels, which makes its control more versatile."

Sergius boasts multiple steering modes: front (or rear) steering, in which a single axle turns; reverse front-rear steering, in which both axles turn, for a smaller turning radius; and a new hybrid steering system in which the front axle turns, and the rear axle also turns, but to a lesser extent, allowing the vehicle to move forward in parallel, correcting the front trajectory and, thus, obtaining enhanced performance in straight lines when the tractor is followingwaypoints.

To evaluate the different modes, the tractor was tested in an intensive olive grove, where it was determined that the inverted mode was optimal for completing turns precisely, and the hybrid mode was the most suitable for straight sections. The tractor is able to shift between its different steering modes according to the needs of its maneuvers.

Sergius, body and "mind"

"The technology we have incorporated is necessary for autonomous navigation: two LiDAR sensors, one in the rear and one in the front; an inertial unit, which measures acceleration and inclination; a digital compass, to monitor the tractor's direction; and a high-precision GPS system," explained researcher Sergio Bayano. "All the programming was carried out using the ROS (Robot Operating System) environment, which, being open source, allows other algorithms to be implemented and code to be shared with other research teams," he stressed.

The vehicle employs a diesel and hydraulic propulsion system because, as the researchers explained: "we know that the future is electric, but agricultural machinery demands a lot of power and torque, so an electric motor would have to be huge, and there would be no batteries that could last a whole day of work."

To control the robot, which can be done using a computer, tablet or mobile, they incorporated two panels: one for the hydraulic system and the robot's different actuators (thebody), and another for its programming and decision-making ("mind"). "We could simplify by saying that one part decides the direction, and the way to head in it, and the other simply caries that out," they clarified.

This work shows that the scientific development is already there, just waiting to be adopted and adapted by companies in the sector that could commercialize it, with researchers willing to collaborate with industry to promote the technology and knowledge generated.

Reference:

Bayano-Tejero, S., Sarri, D., & Sola-Guirado, R.R. (2025). Design and field validation of a Dual-Axle steering system for autonomous tractors. Comput. Electron. Agric., 231, 110000.