| Pricklyash is a unique crop in China,with a very long history of cultivation,widely planted in more than twenty provinces and cities in China.Pricklyash Pepper is high edible and has medicinal value.It brings very considerable economic benefits for the majority of farmers every year.At present,pepper picking is mainly by hand.But the pepper branches are long and prickly,the fruit is attached to the oil cells and easy to break,and the physiological characteristics is unique.Then,there are some problems of diffculty in picking low efficiency and hurting of hands.At the same time,pepper picking is seasonal with short time.Although pepper can bring higher economic returns to farmers,the higher picking difficulty and cost let pepper farmers suffer more.Therefore,pepper picking has seriously restricted the further development of China’s pepper industry.To develop a pepper picker with high efficiency,reliablility and easy operation is urgent for the majority of pepper farmers.Based on the unique pepper picking method of branch trimming off in Chongqing,a pepper picker was designed and experimental studied.The main research contents and conclusions of this paper are as follows:(1)In order to provide a basis for determining the structure and working parameters of the pepper picker,the geometric and mechanical properties of the pepper branches were measured.The mean values of yield force,breaking force,yield strength,compressive strength and elastic modulus were427.47 N,480.95 N,8.51 MPa,9.57 MPa and 114.99 MPa,respectively.The intrinsic model was constructed based on the material properties of pepper branches.The density and moisture content of branches were measured by relevant instruments.Based on the geometric and mechanical properties of the pepper branches,the kinetic and kinematic analyses of the working conditions of each component of the picker were carried out.The structure and working parameters of each component were determined through calculations.The edge type of the circular cutter was single blade type.The structural parameters of the towing component and the towing speed were determined.The rotational speed of the moving knife as 2000r/min,and the estimated crushing power consumption as 0.41 k W;The structural parameters of the feeding device were determined.The transmission system scheme was made and the rated power of the motor was calculated as 1.8k W.With the rotational speed as2800r/min and the transmission ratio of the reducer was defined as 20.The minimum diameter of the middle rotating shaft as 22 mm.(2)ANSYS Workbench was used to analyze the strength of the key components of the picker.The results of the static analysis of the frame showed that the maximum equivalent force of the frame was 16.311 MPa,which met the requirements of the strength.The results of the modal analysis of the center rotation shaft showed that its resonance frequency was 33.33 Hz,which was much lower than its minimum inherent frequency and met the safe working requirements.The results of the gear meshing transient dynamics analysis showed that the maximum contact stresses of the master and driven gears were 295.88 MPa and 334.62 MPa respectively,which were lower than the allowable stresses of the gear materials,and the working condition was safe.(3)The prototype was fabricated and tested,and the effects of circular cutter speed,dragging speed and circular cutter on picking efficiency and fruit injury rate were analyzed by single-factor test.The quadratic regression model of each influencing factor on picking effect was obtained by response surface test and analyzed by ANOVA and interaction analysis.The results showed that the best picking effect was achieved when the circular cutter speed was 3800r/min,the dragging speed was 0.48m/s,and the circular cutter edge angle was 15°,and the picking efficiency was 49.77kg/h and the fruit injury rate was 7.7%.According to the shortcomings in the prototype test,an alignment device was supplemented based on PLC control to avoid the pepper branches miss alignment.(4)In order to reduce the power consumption required for branch crushing,the dynamic process of branch cutting and crushing was obtained by using Ls-Dyna for explicit kinetic simulation.The simulation results showed that the dynamic knife received the maximum cutting combined force of9.82 k N when the knife cut into the middle part of the branch,and the average cutting power consumption was 72.62 W during the effective cutting time.In order to reduce the power consumption required for branch crushing,the dynamic knife rotating speed,tool edge angle and cutting gap were selected as the test factors for the three-factor,three-level virtual simulation orthogonal test,and the test results showed that the lowest cutting power consumption was 23.10 W when the dynamic knife rotating speed was 2000r/min and the tool edge angle was 15°. |
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