This paper discusses the robust trajectory tracking control of an autonomous tractor-trailer in agricultural applications. Firstly, considering the model parameter uncertainties and various disturbances, the kinematic and dynamic models of the autonomous tractor-trailer system are established. Moreover, the coordinate transformation is adopted to convert the trajectory tracking error into a new unconstrained error state space model. On this basis, the prescribed performance control (PPC) technique is designed to ensure the convergence speed and final tracking control accuracy of the tractor-trailer control system. Then, this paper designs a double closed-loop control structure. The posture control level adopts the model predictive control (MPC) method, and the dynamic level adopts the sliding mode control (SMC) method. At the same time, it is worth mentioning that the nonlinear disturbance observer (NDO) is designed to estimate all kinds of system disturbances and compensate for the tracking control system to improve the system’s robustness. Finally, the proposed control strategy is validated through comparative simulations, demonstrating its effectiveness in achieving robust trajectory tracking of the autonomous tractor-trailer system.

A composite sliding mode control based on the load characteristic of the permanent magnet direct-driven system is presented for a mining scraper conveyor. First, the mathematical model of a permanent magnet synchronous motor is established based on the coordinate transformation theory. Subsequently, the soft switching sliding mode observer (SS-SMO) is designed to observe the change of load torque in real time. The composite sliding mode speed controller of PMSM is designed on the basis of non-singular terminal sliding mode control, in which the observed load torque is used for feed-forward compensation. The chain characteristics of a scraper conveyor are described by the Kelvin-Vogit model, and the dynamic model of the overall scraper conveyor system is established with the distinct element method. Next, according to the coupling relationship between the permanent magnet direct-driven system and the scraper conveyor, the electromechanical coupling simulation model is established using the MATLAB/Simulink module. The simulation results demonstrate that the composite sliding mode controller of the permanent magnet direct-driven system can achieve smooth starting of the scraper conveyor, and the effectiveness of the designed controller is illustrated by comparing the controller with the related reference. In addition, the designed SS-SMO can estimate the load torque precisely, enhance system robustness and suppress the chattering of the control system caused by the load change.

Modeling of working environment and coverage path planning method of combine harvesters