| Black soil region of northeast China,as one of the three black soil regions in the world,is the most important commodity grain base and major corn-producing area in China.The frequent ploughing of traditional tillage leads to fine topsoil,bare surface,severe wind and water erosion,and aggravated soil degradation;meanwhile,the unreasonable treatment such as straw burning results in increased haze,which seriously jeopardize national food security and sustainable agricultural development.The implementation of conservation tillage technology,with the core of straw stubble returning to the field,less or no-tillage sowing and subsoiling and soil-preparation,can effectively protect the soil and restore soil fertility.However,the traditional conservation tillage model is difficult to be widely applied in the black soil region of northeast China,where the temperature is lower,the cultivated soil is drought and hardening,straw stubble is stout,numerous,and non-perishable.In view of the above problems,a new agronomic technique combining traditional ridge tillage and conservation tillage is adopted in northeast China,that is,the ridge tillage method is used to increase the soil temperature and reduce the compaction of planting belt,at the same time,combined with straw stubble management,subsoiling and soil-preparation as well as other technologies,to further achieve high-efficient water saving,soil protection,and yield improvement.Under the ridge tillage and conservation tillage technology model,a large amount of corn stubbles will remain in the ridge planting areas after the autumn harvest.If sowing occurs in the same planting area next year,the unrotten stubbles will interfere with normal sowing.In addition,the black soil region of northeast China is a high-cold and drought-prone area with high soil strength,where subsoiling operations are often required to improve the soil environment.The stubbles will also affect the passing performance of subsoiler,resulting in increased resistance to subsoiling operations.Therefore,aiming at the agronomic requirements of the combination of stubble breaking and efficient subsoiling,based on the resistance reduction design of both stubble breaking and soil subsoiling,this paper designs a new stubble breaking and subsoiling combined machine for ridge tillage and conservation tillage technology mode,and the main research results are as follows:(1)Design of stubble breaking device based on dynamic bionic.According to the locust(Locusta migratoria manilensis)mouthparts with the function of efficiently cutting plant fibers,a dynamic bionic stubble breaking device was designed by the coupling of structure bionic and movement bionic,which can enable two stubble cutters to perform cutting operations in reverse and isokinetic rotation mode.Furthermore,the device can simultaneously simulate the morphologic characteristics and movement patterns of locust mouthparts in cutting plant fibers,so as to realize the coupling bionic design.By clarifying the relationship between forward rotating and reverse rotating stubble breaking blades,it was concluded that the optimum monomer numbers of the two blades were 6 and 12,respectively.The planetary gear shifting mechanism was designed,and the relevant parameters were determined,including the gear modulus of 3 mm,the teeth numbers of sun gear,planetary gear and inner ring of 29,13 and 55,respectively.By connecting with two stubble cutters,the planetary gear shifting mechanism can make the stubble cutters realize their reverse and isokinetic rotation cutting mode.On the basis of the Arduino platform,an intelligent speed control system was designed to ensure that the stubble cutters can still work at a constant speed during machine braking and acceleration.Finally,through theoretical analysis,test verification and other methods,the influence of structure parameters and operation parameters on the stubble cutting performance of the device was clarified,thus achieving the purpose of improving machine passability and cutting efficiency.(2)Design of bionic vibration subsoiling device based on subsoiling depth intelligent control system.By studying the resistance reduction characteristics of subsoiler,a subsoiling device integrating bionic structure,self-excited vibration and intelligent control was designed.Taking rabbit claw toe as bionic prototype,the outline curve of the claw toe with high-efficiency soil breaking function was applied to the edge structure of subsoiler handle to realize the design of bionic resistance reduction structure.A self-excited vibration subsoiling mechanism based on torsion spring vibration was designed,and the corresponding key components were analyzed.By determining the relevant parameters of torsion spring and positioning disc,the subsoiler realized the self-excited vibration resistance reduction.Meanwhile,in order to judge the depth of subsoiling,the movement process of bionic vibration subsoiler was analyzed theoretically.The results showed that the subsoiler was prone to unstable subsoiling depth under the condition of high subsoiling resistance.In addition,using fuzzy control technology to realize the intelligent algorithm,a set of subsoiling depth intelligent control system was designed,which can improve subsoiling performance and stabilize operation state by applying thrust to the subsoiler.Finally,the resistance reduction performance of the whole subsoiling device was verified by experiments,which showed that the maximum reduction of subsoiling resistance was 25.3%.(3)Design of dynamic bionic stubble breaking and subsoiling combined machine.The main working parts of the combined machine were designed,including machine frame,dynamic bionic stubble breaking device,concave disc stubble cleaning device,gear box,bionic vibration subsoiling device.Specifically,the machine frame was arranged in longitudinal connection,and the corresponding modal analysis was carried out.According to the structural characteristics of the whole machine,a multistage deceleration and commutation transmission scheme was designed.The dynamic bionic stubble breaking device was determined to be driven by the tractor output shaft,and the parameter design of the key chain transmission was also carried out.In addition,the gear box adopted symmetric gear transmission,and the corresponding gear parameters were designed,at the same time,finite element analysis and check of the box and gear shaft were carried out by using ANSYS Workbench software.The working principle of the concave disc stubble cleaning device was analyzed,and the structure parameters of the profiling mechanism and the stubble cleaning disc were optimized.Furthermore,the self-excited vibration scheme of the subsoiling device was improved,and the key spring was designed theoretically.(4)Field test verification.The performances of the stubble breaking and subsoiling combined machine,including stubble cutting rate,cutting torque and blade wear,were better than those of 1GH-130 ridge cropping machine with L-shaped blade,and the performances of subsoiling resistance and subsoiling depth stability were better than those of 1SZL-7 subsoiling machine with chisel type subsoiler.The above test results showed that the stubble breaking device of the combined machine can well complete ridge stubble breaking operation,with the minimum stubble cutting rate of 94.1%;and the cutting torque was reduced by 19.1%~21.6% in comparison to the L-type blade,which indicated that the working performance was superior to the traditional 1GH-130 ridge cropping machine.In addition,the subsoiling resistance of subsoiling device was reduced by 14.3%~19.5% in comparison to the chisel type subsoiler,and even,under the same working conditions,the subsoiling depth stability of the combined machine was significantly superior to the traditional 1SZL-7 subsoiling machine. |
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