A mulch film collector is one type of picking mechanism in the recycling of mulch film at present. However, the conventional configuration cannot fully meet large-scale production, such as severe film clamping, the requirement for cotton stalks crushing, and low film content. The existing drum-type pickup mechanism of mulch film has also serious film enwinding and a low film content rate of recovered mulch film. In this study, a mulch film recycling machine was developed with the stalk pressing type in the cotton field. The mulch film pickup mechanism with drum type was selected along with the one-film and six-row machine cotton harvesting and planting mode in Xinjiang. The cotton stalks' recycling and reliability greatly contributed to the resource utilization of cotton stalks. A box was added to bundle the stalk. A guided pickup roller of mulch film was built with anti-winding and impurity cleaning functions. A pneumatic film removal device was also added to rapidly remove the film. The film picking, film stripping and contamination removal operation were realized in the improved device at one time. The structural parameters of the stalk box, mulch film picking roller and film removal mechanism were also determined using kinematic and kinetic analysis. The working parameters of key components were analyzed after optimization. The front tilt angle of the stalk box was designed to be 30° considering the congestion and the forward resistance of the machine. The motion position and oscillation of the hook teeth at each station of the film pickup roller were combined to clarify the motion trajectory of the roller center. The mathematical model of the slide profile curve was established using the analytical method. The kinetic analysis of the film pickup roller was carried out, where the rotation speed range of the roller was determined to be 41-68 r/min. A systematic investigation was implemented to explore the relationship between the full pressure at the outlet of the film removal hood and the rotation speed of the film removal shaft using aerodynamics. The rotation speed of the film removal impeller was 980 r/min. To verify the operational performance of the device, A three-factor, three-level response surface test was conducted with the machine advancing velocity, the depth of hook-tooth into the soil and the rotation speed of the film pickup roller as the test factors, and the film pickup rate and the film content rate as the test indexes. The response surface model of each factor was established to optimize for better operational performance. The test results showed that the significant effects of the test factors on the film pickup rate were ranked as the rotation speed of the film pickup roller, the machine advancing velocity, and the depth of hook-tooth into soil. The significant effects of the test factors on the film content rate were the rotation speed of the film pickup roller, the depth of hook-tooth into soil, and the machine's advancing velocity. The best operation was achieved, when the rotation speed of the film pickup roller was 65 r/min, the machine advancing velocity was 5 km/h, and the depth of hook-tooth into the soil was 50 mm. The optimized performance was verified for the average film pickup rate was 86.8 % and the average film content rate was 14.9 %. The findings can provide a strong reference to design the subsequent machines for the stalk-collect mulch film.

Cotton stalk is one of the most high-quality biomass resources with a wide range of applications, such as building boards, chemical product raw materials, fuel, and papermaking. China is one of the major cotton-producing countries in the world. The planting area (3×106 hm²) has been ranked third in 2022, leading to the very abundant cotton stalk resources. The cotton stalks can be fully utilized to accelerate the green and low-carbon development of agriculture. Mechanical harvesting can be expected to efficiently remove the cotton stalks from the field. However, the current uprooting machine also needs to be improved and optimized for the cotton stalk. In this research, a clamping-type uprooting device with variable stiffness was designed for a high uprooting rate and low clamping breakage rate. The variable rigidity clamping was adjusted as follows. The flexible rubber clamping was used to prevent the cotton stalk from breaking; A rigid support structure was designed on the outside of the rubber block to obtain a greater clamping force. The better performance was achieved by clamping tightly without breaking the cotton stalk. The uprooting was also improved for the two scenarios of breakage and slippage. The device often consisted of a dividing disk, variable stiffness clamping and pulling mechanism, and tensioning guide mechanism. The dividing disk was used for the orderly feeding of cotton stalks; The variable stiffness clamping and pulling mechanism was used to realize the clamping and pulling of cotton stalks; The tensioning guide mechanism was to effectively control the clamping force and gap of cotton stalks. Two sets of chains were utilized to drive multiple clamping blocks, indicating a simple and reliable structure. Moreover, the frictional heating of traditional flexible belt mechanisms was avoided in this structure. A mechanical analysis was carried out on the cotton stalk pulling motion and the interaction between the variable stiffness clamp and the cotton stalk. The critical structural dimensions and operating parameter ranges were determined for the variable stiffness clamping device. A systematic investigation was made to clarify the influencing factors on the quality of clamping and pulling. The response surface method (RSM) was used to analyze the effects of the forward speed, the rotational speed of the active sprocket, and the clamping force on the stalk uprooting performance of the variable stiffness clamping and pulling device. The field test validated the simulation. The results showed that there was very consistency between the experimental and theoretical predictions, when the forward speed was 0.68 m/s, and the sprocket speed was 95 r/min. The tension force was 1 792 N, and the cotton stalk uprooting rate was 94.70%. The relative error between the measured and predicted uprooting rate value was 1.67%, which was less than 5%. The leakage rate and breakage rate of variable stiffness clamping and uprooting devices were 3.99% and 1.32%, respectively, compared with the existing devices of 5.19% and 3.68%, respectively. Therefore, the leakage rate and breakage rate of the device were reduced by 23.1% and 64.13%, respectively, compared with the former. The variable stiffness gripper effectively reduced the cotton stalk breakage to realize the whole stalk uprooting. The finding can provide new ideas to design the variable stiffness clamps, in order to optimize and improve the cotton stalk pullers.

To improve the survival rate of larvae during material separation after biotransformation of existing residual film mixtures of Protaetia brevitarsis larvae, this paper adopts the method of combining physical test and EDEM simulation test, and selects Hertz Mindlin with JKR contact model to calibrate the discrete element simulation contact parameters of the Protaetia brevitarsis larvae and the frass mixture. First, the cylinder lifting method was used to determine the actual repose angle of the mixture of larvae and frass. The collision recovery coefficients between larvae-frass and steel, static friction coefficient, kinetic friction coefficient and the collision recovery coefficient between larvae were measured through physical tests such as the inclined plane method. The Plackett-Burman test was then used to screen out the factors that have a significant impact on the repose angle: Poisson’s ratio of frass, frass-frass rolling friction coefficient, frass JKR surface energy, frass-larvae JKR surface energy. The optimal value intervals of four significant factors were determined based on the steepest climb test, Based on the Box-Behnken response surface analysis test, the second-order regression model between the repose angle and four significant factors was determined, and variance and interaction effects were analyzed. And with the actual repose angle as the goal, the significant factors were optimized and the optimal parameter combination of the four significant factors was determined. The simulation test of material repose angle and screening was carried out with the optimal parameter combination, and compared with the physical test. It was found that the maximum relative errors of the two tests were 1.48% and 3.79% respectively, indicating that the calibrated parameter values are true and reliable, It can provide a reference for the discrete element simulation of the transportation and separation of the Protaetia brevitarsis larvae-frass mixture.