| Straw returning directly to the field is an effective cost of using straw to fertilize the soil.However,the existing straw returning machine has single function and strong dependence on operation quality.During the operation,in order to prevent the high-speed rotating crushing knife from entering the soil,the power consumption is high,and the returning machine is lifted by the manipulator.The labor intensity of the manipulator is high,and the straw crushing effect is poor,which affects the planting of the next crop;After returning to the field,the crushed straw is exposed on the ground and does not mix with the soil,straw is not only easy to be blown away by wind and cause fire,but also has slow decomposition rate,which affects the exertion of fertilizer efficiency.In this study,the profiling compound straw mixing soil and returning machine was designed,during the operation,limited the height of the crushing knife shaft from the ground,which was neither buried nor close to the ground surface,reduce power consumption,and improved the stubble breaking effect;The compound structure of crushing device and soil mixing device was adopted to realize the mixing of straw and soil after crushing and improved the decomposition efficiency;The height of the front profiling device was automatically adjusted by the hydraulic cylinder according to the torque of the crushing knife shaft,so as to realized the automatic obstacle crossing after the straw was piled up and blocked.Automatic profiling and obstacle crossing during the operation of the whole machine greatly reduced the labor intensity of the manipulator.The main research contents were as follows:（1）The decomposition characteristics of corn straw were tested.The decay characteristics of corn straw with different cutting length and mixing depth were tested to clarify the change law of corn straw decay rate,predicted the decay cycle of corn straw with different cutting length and mixing depth,and determined the best crushing length and mixing depth,so as to provided data for the design of the profiling compound straw mixing soil and returning machine.（2）The profiling compound straw mixing soil and returning machine was designed.The main technical parameters and power consumption of the profiling compound straw mixing soil and returning machine were calculated,and the main technical parameters and supporting power of the profiling compound straw mixing soil and returning machine were determined.Based on the structural design and theoretical analysis of the key components of the profiling compound straw mixing soil and returning machine,the number and structure of crushing knives were deeply studied to further improved the straw crushing rate and stubble removal rate and ensured that the straw was crushed more finely and thoroughly.（3）Through the relevant theoretical knowledge of dynamics,EDEM was used to simulate and analyze the process of straw congestion and blade penetration of the profiling compound straw mixing soil and returning machine,the variation diagram of resistance and torque of returning cutter shaft under the condition of working obstruction is obtained.Determined the scheme of the profiling system,determined the main parameters and control scheme of the profiling system based on the simulation of the straw crushing device and the data calculation of the profiling system based on EDEM,and selected the appropriate sensor and control system.（4）The prototype is tested in the field,the test showed that:The qualified rate of straw chopping of the profiling compound straw mixing soil and returning machine was92.1%,the unevenness of throwing was 12.4%,the mixing depth was 55.4mm,the uniformity of straw mixing was 85.3%,the stability of mixing depth was 96.7%,the length of straw chopping was 2.9cm,the forward speed was 3.9 km·h-1,and the operation efficiency was 1.06 hm2·h-1 met the relevant national standards. |
