Disturbance observer based adaptive sliding mode control for driving motor speed regulation in Maize Electric Fertilizer Applicator

Electric fertilizer applicators significantly improve the uniformity, stability, and efficiency of summer maize fertilization. However, the complex soil environment in farmlands introduces uncertainties such as parameter variations, load disturbances, frictional resistance, and positioning errors, which degrade the control accuracy and robustness of the driving motor. To address these challenges, this study proposes a disturbance observer (DO)-based adaptive sliding mode control (ASMC) method. First, a control model for the soil-straw coupling system of the electric fertilizer applicator (EFA) was established, accounting for parameter variations and external load disturbances, thereby simplifying controller design. Second, a convergence rate mechanism was introduced to accelerate convergence time, ensuring the system reaches the sliding surface within a finite time, with the convergence rate being adjustable through parameter design. Additionally, a disturbance observer was designed to estimate both mismatched and matched disturbances, enabling feedforward compensation to improve tracking accuracy and reduce system chattering. Experimental results demonstrate that the proposed method achieves high control accuracy and robustness, ensuring rapid and stable state regulation for the EFA. This work provides new ideas for the design of smart agricultural machinery controllers and effectively promotes the control upgrade of agricultural electromechanical systems.