Automatic Steering Control for Agricultural Tractors in Vineyards

Advanced Driver Assistance Systems (ADAS) and autonomous driving systems are relevant in the agricultural field, since they can ease personnel of demanding and repetitive tasks while increasing precision and productivity. This is particularly true in constrained environments represented by intensive and high value cultivations, like vineyards and orchards. Anyway, these contexts present numerous challenges: positioning accuracy in the range of centimeters is required in an environment with continuously-changing vegetation, reduced maneuvering space and unstable terrain. This paper presents an ADAS of level 3 for an agricultural tractor in a vineyard, focusing on its control system. The goal of the developed controller is to bring the vehicle at a desired distance from the crop rows and keep it aligned to them, so that the operator only has to set the tractor advancement speed and can focus on the ongoing agricultural procedures. This is achieved through a Linear Quadratic Integral (LQI) controller that relies on a control-oriented model of the system describing the dynamics of the vehicle position with respect to the vines. The system proves to be effective and easily tunable in order to obtain the desired behavior. An extensive experimental campaign validates the closed-loop system performance. In particular, the controller attains a steady state error of 5 cm, using a steering angle with Root Mean Square (RMS) of 1.05 deg.