To address the problems of low pickup rates and high rates of wounds in the mechanised harvesting of potatoes under sectional harvesting conditions, a spring-finger potato picker was designed and its overall structure and working principles were described. The kinematic principle of the spring-finger was analysed based on the picking constraints, and the kinematic parameters of the picker were determined. A response surface Box–Behnken Design test design was used to carry out a quadratic orthogonal rotational test, with the speed of the spring-finger, the forward speed of the machine, and the embedded depth as test factors, and the loss rate and the wounded potato rate as evaluation indicators. The test results were optimised and analysed. When the spring-finger speed was 19.57 r/min, the forward speed was 0.61 m/s and the embedded depth was 71.31 mm, the loss rate was 1.18%, and the wounded potato rate was 5.71%. The optimised data were verified, and the results showed that the loss rate of the spring-finger potato picker was 1.48% and the wounded potato rate was 4.98%, meeting the potato picking and harvesting requirements. The research can provide a theoretical basis and design reference for the development and application of sectional potato harvesting machinery.

The poor adsorption stability of the current air-suction sunflower seed-metering devices under high-speed operation leads to unstable seed adsorption posture, as well as increases in the multiple and miss indices. In order to improve the stability of seed adsorption, an air-suction sunflower seed-metering device based on structure-assisted stable suction posture was designed, the movement mechanism of the seed absorption process and the seed-feeding process is analyzed, following which mathematical models of the processes are established, and the key factors affecting the seeding performance were determined. Furthermore, the shape parameter equation of sunflower seeds is fitted, depending on the dimensions and shape parameters, which provides the design basis for the key components of the seed-metering device. Moreover, in order to optimize the seed-metering devices structure, taking the depth, width, and length of the seed suction grooves as experimental factors, as well as the qualified, multiple, and miss indices as evaluation indices, an orthogonal regression experiment considering three factors and three levels is carried out using the Box–Behnken experimental design. Finally, multiple regression models are established and extreme value theory is used to optimize the parameters of the influencing factors and obtain optimal parameter combinations. The optimal parameter combination is as follows: width of the suction groove, 10.5 mm; depth, 3 mm; and length, 23 mm. Results from verification experiments revealed the corresponding experimental indicators, the qualified index is 91.63%, the multiple index is 5.63%, and the miss index is 2.74%, thus meeting the requirements of effective sunflower seed sowing.

To improve the complex process of judging the degree of soil fragmentation during potato-soil separation and to establish a fast and effective judging method. Soil drop experiments were performed using sandy soil from the potato growing region of Hohhot, Inner Mongolia Autonomous Region, China. The effects of soil moisture content, hardness, volume, drop height, inclination of the separating sieve and composition of the separating sieve rod on soil fragmentation were investigated. The fractal dimension and image processing used to quantify soil fragmentation and scattering and obtain quantitative indicators of soil fragmentation. The results showed that the following factors influenced soil fragmentation in descending order of statistical significance: soil hardness, fall height and soil volume. The softer the soil was, the greater the fall height; the larger the soil volume was, the greater the fragmentation. Meanwhile the correlation between the two indicators is extremely high, simplifying assessment of the degree of soil fragmentation. This study clearly shows the influence of the intrinsic physical properties of soil and the external physical parameters of potato excavators on the characteristics of crushed soil. The results can provide a basis for improving the efficiency of potato-soil separation and designing more efficient devices for harvesting potatoes.