Development and performance evaluation of a hydraulic active profiling system for seeding-depth control of a high-speed no-till seeding unit

High-speed no-till operation causes severe opener-downforce fluctuation and makes low-lag seeding-depth regulation difficult. To address this problem, an electro-hydraulic active profiling system integrating terrain preview and bounded feedforward–feedback control was developed for a precision seeding unit. A mechanical relationship linking hydraulic-cylinder output, opener downforce, and seeding depth was established, and an accumulator-assisted hydraulic actuation system with dual proportional pressure-reducing valves was designed to improve pressure stability and dynamic response. Unlike existing hydraulic profiling systems mainly relying on conventional pressure regulation or single-stage feedback adjustment, the proposed system combines hydraulic pressure stabilization, terrain-preview-based feedforward regulation, and bounded residual correction within a unified framework. Co-simulation, bench, and field results showed opener-downforce variation of 1.03%–1.44%, a mean profiling error of 1.57 mm and a mean profiling duration of 0.22 s, and field seeding-depth qualification above 94.7% with a coefficient of variation below 6.37%.