Path Tracking Control of Autonomous Agricultural Tractor: A Nonsmooth Sampled-Data Approach

This work proposes a nonsmooth sampled-data protocol for the path tracking control of an autonomous agricultural tractor (AAT) with the objective of enhancing the system control performance in terms of its digital realization. To begin with, based around the kinematic model of AAT, a path-following offset system is established through explicitly incorporating the disturbance. Subsequently, a continuous-time nonsmooth controller is constructed for such a system under the disturbance-free condition. With this groundwork laid, a nonsmooth sampled-data controller is devised for the AAT in light of the discrete-time characteristic of the global positioning system—real-time kinematic (GPS-RTK) system during the digital operation. Thenceforth, a rigorous Lyapunov-based analysis is provided to confirm the convergence to a domain around the origin for the considered entire system. Lastly, the comparative simulations and experiments are performed to reveal that the developed controller can offer the superior tracking performance over the smooth sampled-data controller and the Stanley controller, whilst the AAT follows the desirable path.