Research on a Coordinated Control Method of Tractor Electro-Hydraulic Hitch Tillage Depth and Travel Speed Based on Optimal Overall Efficiency and Economic Performance

To improve traction efficiency and reduce fuel consumption during tractor tillage operations, a coordinated control method for electro-hydraulic hitch depth and tractor speed was proposed. Based on theoretical analysis, a dynamic model of the tractor–implement system during tillage was established. The principles of coordinated control were developed, and a comprehensive performance evaluation index considering both efficiency and economic performance of the tractor was proposed to optimize the coordinated control objectives. A depth controller and a speed controller were, respectively, designed based on the sliding mode control algorithm. A hardware-in-the-loop test platform for coordinated control of electro-hydraulic hitch depth and travel speed was established via CAN communication. Comparative experiments were conducted under three operational conditions (Condition 1: tillage depth 16 cm, soil specific resistance 2.5–3.5 N/cm2; Condition 2: 20 cm, 3.5–4.5 N/cm2; Condition 3: 24 cm, 4.5–5.5 N/cm2) against the conventional single depth control method under full throttle. Results demonstrated that the coordinated depth-speed control method improved the overall tractor efficiency-economy by 50.0%, 33.3%, and 26.7% under these respective conditions compared to the single depth control method. This method not only ensures operation quality but also enhances the comprehensive performance of the tractor, effectively improving traction efficiency and reducing fuel consumption. Moreover, it demonstrates better adaptability to varying field conditions.