Research on the optimal pick-up heights and their control strategy for the hydraulic double-row jet collector of the manganese nodule miner

As a superior pick-up device in manganese nodule miners (MNMs), the moving velocity and pick-up height of a hydraulic double-row jet collector (HDJC) are key to its collection performance. In this study, coupled computational fluid dynamics and the discrete element method (CFD-DEM) is employed to numerically explore the optimal pick-up heights for various velocities. The collection efficiency decreases with increasing velocity and pick-up height but stabilizes at velocities below 0.6 m/s and pick-up heights below 115 mm. Lower pick-up heights increase seafloor disturbance. For high collection efficiency and low environmental damage, the optimal pick-up heights are 115 mm at 0.2-0.6 m/s and 105 mm at 0.6-1.0 m/s. Based on these pick-up heights, fuzzy proportional-integral-derivative (PID) control is developed to adjust the HDJC in the MNM multibody dynamics (MBD) model, which integrates hydraulic and control subsystems. This shows high robustness and responsiveness, ensuring excellent trafficability and mining capacity. Velocity, target value, and terrain variations cause significant short-term deviations. On flat ground, the pick-up heights deviate within 5 mm and the pick-up angles remain between +/- 0.025 degrees across all velocities. During movement on flat-slope ground at maximum velocity, deviations in the pick-up height and angle remain below 10 mm and 0.2 degrees.