| Cigar tobacco has become a new growth point for the tobacco industry,which is a kind of drying tobacco consisted of dried and fermented tobacco leaves.In view of the current problems of lack of special machinery for whole plant harvesting,the tedious manual sorting process and heavy workload and the low efficiency of cigar tobacco plants,which due to cigar tobacco is large in their ripening period and is not suitable for contact with soil when picking,based on the analysis of the research status machinery development and the requirements of tobacco harvesting a rotary clamping whole plant harvester for cigar tobacco was developed.It is mainly composed of walking device,clamping device,cutting device and central rotating device,which can realize a series of operation processes such as clamping,cutting and transmission,in order to reduce the labor intensity of whole cigar tobacco harvesting,and explore the harvesting direction of the whole cigar leaf.The research content and summary are as follows:(1)Cigar tobacco plants were tested and analyzed for the appearance characteristics and mechanical and physical characteristics of cigar tobacco plants during the suitable harvest period,and determined the position of the center of gravity of the harvested plants.The appearance characteristics test concluded that: The average plant height of cigar tobacco leaf plants in the harvest period was 1063.5 mm,the planting specification was 1234 plants per mu(1.85 plants per square meter),the number of leaves left was about 9,the stem was about 22.85 mm thick and the variation was 18.32%,the xylem thickness of the whole main stem ranged from0.66～3.90 mm,the phloem thickness ranged from 0.68 ～ 1.64 mm,and the moisture content ranged from 80.1%～90.2%,the xylem thickness of the cutting site was1.92 mm,the phloem thickness was 1.16 mm,and the moisture content was 86.1%.The results of measuring the position of the center of gravity of the plants after harvest showed that the height of the plants after harvest was about 639 mm,the mass was about 380.3 g,and the position of the center of gravity was about 296 mm above the cutting stubble.The results of force tests showed that the Poisson’s ratio was 1.33,the elastic modulus was 1.93 MPa,the shear strength near the cutting part was 2.98 MPa,and the shear modulus was 0.45 MPa.The above showed that the main stem of cigar tobacco plant has certain strength and toughness during the suitable harvest period,which provides a basis for the optimization of the parameters of the cutting motor and the clamping drive motor in the later stage.(2)The overall design and parameters of the rotary clamping whole plant harvester for cigar tobacco were analyzed and determined,and the possibility and stability analysis of the whole machine was carried out.The structure,process flow and main technical parameters of the cigar tobacco harvester were identified according to the requirements of planting and harvesting.The harvester included central rotating device,clamping device,cutting device and walking device,and the whole machine can achieve independent drive,stable clamping,stem cutting,rotary transmission and other processes.The harvesting method of the whole machine was single row and single plant harvesting,the clamping device was 750 mm up ground,and the cutting device was 640 mm up ground.The walking performance of the whole machine showed that: the maximum climbing degree was about 25°,the maximum downhill degree was about 38°,the minimum rollover degree was about 35°,and the theoretical turning radius was about 450 mm.(3)The structural design and parameter analysis of key components of the rotary clamping whole plant harvester for cigar tobacco were carried out.It mainly included :(1)According to the agronomic requirements of cigar tobacco planting and whole plant harvesting,the walking device adopts a triangular tracked upland clearance chassis,the width of the track wheels was 180 mm,the minimum ground gap of the walking device was 415 mm,and the distance between the inner measurement of the track wheels on both sides was 725 mm.(2)According to the determination of the diameter of the main stem of cigar tobacco plants,the clamping arm of the clamping device was designed to be 60 mm,the minimum clamping diameter was 20 mm,and a saw was set in the center of the clamping to limit the freedom of the clamped plant.The clamping arms on both sides were driven by the servo and synchronously opened and closed by the transmission mode through the meshing of the wheel,which could achieve a maximum opening and closing of 120°,a steering block output torque of6.37 N·m,a module of the meshing wheel was 0.5,The normal,radial and tangential forces on the meshing gear teeth were calculated to be 542.30 N,185.44 N and509.60 N,respectively.(3)The cutting device used a DC motor to drive a single disc knife to achieve stem cutting,and an electric push rod was designed to change the relative position of the cutter,and the telescopic speed of the electric push rod was 30 mm per second.Based on the ANSYS modal analysis of the disc cutter,the dangerous rotational speeds were proposed as 18510,18562,32080.2 and 32110.2 r/min.The output torque of the DC motor was 3.27N·m,the size of the disc cutter was 150 mm.(4)The central rotating device was driven by a stepping motor to realize rotation transmission.The torque of the stepper motor was 8.5N·m,the radius of rotation was369 mm.The force between the clamping device and the stalk in the tangential plane of the rotation process was analyzed,and the theoretical maximum speed of the central rotation device was 268.8r/min,and the actual speed was 9.38～12.5r/min.(4)The stability and gear speed matching test,bench test and field test of the rotary clamping whole plant harvester for cigar tobacco were carried out.It mainly included:(1)The walking performance and gear speed matching test of the whole machine showed that the harvester could drive normally on a ramp of 12°;The turning radii of cement hard pavement and field soft pavement were 865 mm and 960 mm,respectively,and the straight-line offset was 0.80% and 1.00%,respectively.The gear speed matching on cement hard pavement was: 1.06 m/s in first gear,1.87 m/s in second gear,5.22 m/s in third gear,and 0.72 m/s in reverse gear,and the gear speed matching on soft pavement in the field was: 0.90 m/s in first gear,1.53 m/s in second gear,5.03 m/s in third gear,and 0.61 m/s in reverse gear.(2)A comprehensive evaluation index consisting of tobacco breakage rate,clamping failure rate and cutting failure rate was proposed.The two-bench test took the speed of the disc knife and the forward speed of the tool as the factor index,and the cutting failure rate as the evaluation index,and carries out the single-factor test and the two-factor three-level interaction experiment.The single-factor test results showed that the speed of the disc knife was 40～50 r/s,the forward speed of the tool was 0.7～0.9 m/s,and the cutting failure rate was low.The interactive experimental results showed that the forward speed of the tool and the speed of the disc knife had a significant effect on the cutting failure rate,and the speed of the disc knife has a greater influence on the cutting failure rate.The optimal parameter combination was a disc knife speed of 45 rolls per second and a push rod speed of 0.7 m/s,corresponding to a cutting failure rate of8.33%.(3)Field experiments showed that the cigar tobacco plant after harvest was cut whole,the stubble height was about 430 mm,the comprehensive evaluation of the harvester was 7.46%.All the test indicators basically met the harvesting needs of the whole cigar tobacco plant. |
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