In order to ensure the most reasonable distribution of wheat seeds in the field to improve seeding quality and uniformity, a set of negative pressure precision seed-metering device was designed, which shares a hollow shaft. Every seed-metering device can sow two rows of wheat. By the STAR-CCM+, the analysis of nephogram, vectogram and streamline graph showed that more ideal structural parameters of the seed-metering device are 0.5 mm width of the slit sucking seed (WSS), 150-200 mm diameter of the seed-metering disc (DSD), 2.0 mm axial depth of air chamber in the seed-metering disc (ADS), and arc-shaped cross-section shape of the ring groove sucking seed (CSGS). Single-factor test on the JPS-12 test-bed analyzed the influence of the CSGS, WSS, DSD, and ADS on the qualified index (I_q), multiple index (I_mul), miss index (I_miss) and coefficient of variation of qualified seed spacing (CV). Through the orthogonal on the JPS-12 test-bed, it is found that the influence of vacuum negative pressure and seed-metering device shaft speed is significant on the I_q, I_miss and I_mul. Based on these, the structural parameters of the seed-metering device were optimized. The DSD is 180 mm, the WSS is 0.7 mm, the ADS is 2.5 mm, and the CSGS is arc-shaped. The optimization seed-metering device was tested on the JPS-12 test-bed. The I_q is 86.66%, the I_miss is 5.09%, the I_mul is 8.25%, and the CV is 24.50%. These testing results fully coincide with the standard JB/T 10293-2013 Specifications of single seed drill (precision drill). The seed-metering device meets fully the requirements for wheat precision seeding.

Aiming at the problem of poor uniformity of maize sowing caused by ground wheel slip, an electronic control seed-metering system (ECSMS) for maize single seed precision sowing was designed and a mathematical model for motor control of the ECSMS was determined. The PID parameters were set by Z-N method and fuzzy control. The fuzzy PID control design and Simulink simulation were completed by MATLAB, which reduced response time of the system by 0.23 s and improved the control accuracy. Experiments on the JPS-12 test bench show that the qualification index (QI) of maize seed-metering device with the ECSMS increases by 4.47%, the multiples index (MI) decreases by 1.96%, the miss index (MIX) decreases by 2.81%, and the coefficient of variation (CV) of qualified seed spacing decreases by 5.06%, and the sowing uniformity has been greatly improved. Test results of the soil-tank test bench show that the system has good sowing uniformity and stability. And the QI is 96.74%, the MI is 2.15%, the MIX is 1.10%, and the CV of qualified seed spacing is 16.24%. Under different setting seed spacing and different sowing operation speed, the change range of seeding quality index was within 10%. The results of field sowing test show that the QI was 84.21%, the MI was 2.63%, the MIX was 7.89%, and the CV of qualified seed spacing was 22.15%, which meet the requirements of JB/T 10293-2013 ‘Specification for single seed planters (precision planters)’ and the agronomic requirements for maize precision sowing. The system runs stably and reliably in practical operation and has good operation performance.