This paper aims to solve the problems of complex structure, poor straw crushing effect and high power consumption of existing straw returning machines. A cutting and crushing device with moving and fixed blades has been developed. The moving blade has collision and automatic retraction functions, which can effectively reduce destructive damage caused by blade obstacles and extend its service life. The double-type single-support cutting method has the advantages of improving the straw crushing effect and reducing the running power consumption. The effects of blade rotational speed, blade offset angle and blade number under the condition of composite single-support cutting were tested according to the uneven ratio of straw throwing and the qualification ratio of straw crushed length. The optimal combination of working parameters of the cutting and crushing device was determined: blade rotational speed of 1968 r/min, blade offset angle of 5°, blade number of 4. The test results show that the uneven ratio of straw throwing is 17.18%, and the qualification ratio of straw crushed length is 92.23%. The operation effect of the side-sweeping straw returning machine was tested on the field. All operating indicators are equipped with cutting and crushing devices, and the results show that all operating indicators meet the technical requirements of straw return.

In order to improve the cleaning effect of the castor shelling mixture, an air-sieve castor cleaning device was developed. The structure of the cleaning device was optimized by experiment and simulation based on the discrete element method. The results show that the sieving efficiency of the square distribution is 98.23% and the loss rate is 2.39%, both of which are better than the triangular distribution. The sieving efficiency in the condition of a 14 mm sieve hole diameter is 98.23%. For the conditions of 15 mm and 16 mm sieve hole diameters, the sieving efficiencies are 96.64% and 96.69%, respectively. Therefore, a sieve hole diameter of 14 mm is more beneficial for the sieving of castor capsules. The sieving efficiency is 94.0–99.5%, and the loss rate is 0.5–3.0% under 5–9° sieve inclination. The cleaning effect is better through comprehensive analysis when the sieve surface inclination is 8°. The parameters of maximum sieving efficiency combination, minimum loss rate combination, and optimal cleaning effect were obtained by optimizing the operating parameters of the cleaning device. The operating parameters were adjusted, and then the three combinations of parameters were tested. It is found that the impurity content of castor seeds is within 1%, which meets the requirements of the device design. This study can provide a reference for developing high-efficiency castor cleaning devices.

Apple is easily damaged in the process of the mechanical harvesting, which reduces the fruit’s quality. It is of great significance to study the damage principle of apple in the transport process of picking platform. In this study, the apple compression test was carried out. The compression and drop process of the fruit was analyzed by the finite element analysis (FEA). The experimental platform of apple harvesting was designed, the conveying process of apple was analyzed. The results of compression finite element analysis showed that when the compression force is greater than 15.0 N, both radial compression and axial compression will be damaged. The results of drop finite element analysis showed that when the drop direction is axial, the maximum contact stress of the peel and kernel decreases with the increase of drop angle, the maximum contact stress of the pulp increases first and then decreases. When the drop direction is radial, the maximum contact stress between pulp and kernel decreases with the increase of drop angle, the maximum contact stress of the peel first decreases and then increases. The simulation results of the harvesting platform transportation showed that the damage rate of apples is less than 10 % when the sub-conveyor belt speed is 0.02 m–0.04 m/s. This study can provide theoretical guidance for the design of the harvesting test platform and the reduction of the damage of apples during transportation.