Cascaded MRAC-Feedforward Composite Control Strategy for Negative Pressure Stabilization of an Electric-Driven Seeding Fan

Bus-voltage fluctuations of unstabilized PTO-driven generators, together with pneumatic load variations, cause negative-pressure instability in electric-driven air-suction seeding fans, degrading seeding quality. This paper proposes a cascaded composite control strategy combining model reference adaptive control (MRAC) with voltage feedforward. Based on time-scale separation, the inner loop uses a PI controller with voltage feedforward for millisecond-level compensation of bus-voltage disturbances, while the outer loop employs output-feedback MRAC against time-varying chamber dynamics. The strategy was compared with PID, fuzzy PID, and cascaded MRAC without feedforward (CMRAC-NFF) through nonlinear simulations, bench tests, and cotton field trials. In nonlinear simulations, a 72-to-65 V voltage step induced a maximum negative-pressure deviation of −0.48 kPa with a 1.08 s recovery time; under combined voltage and seed-suction load disturbances in the simulation environment, the error standard deviation was 0.07 kPa. In bench tests, the mean absolute steady-state deviation remained within 0.12–0.16 kPa across the 7.0–10.0 kPa setpoints. In field tests, the proportion of time outside the ±0.3 kPa tolerance was reduced to 3.84%, with a qualified seeding rate of 96.24%. With feedforward rejecting supply disturbances and MRAC absorbing model uncertainty, the scheme sustained agronomic-grade pressure stability on a 12-row cotton seeder across tested 7.0–10.0 kPa setpoints.