Study On Combing Characteristics And Device Of Cerasus Humilis Mechanical Harvesting

Cerasus humilis is one of the endemic tree species in China,with high nutritional value and ecological value,and has great potential for development.With the promotion and recognition of the market,its planting area increased year by year,and its development momentum is swift and violent.The low efficiency and high cost of artificial harvesting seriously restrict the development of cerasus humilis industry.In recent years,the research team devoted to the study of mechanized harvesting of cerasus humilis.Dual twin roller mechanical fruit removal device has been developed to improve the harvest efficiency of cerasus humilis.With the continuous expansion of the planting scale of cerasus humilis,more efficient harvesting methods are required.In order to harvest cerasus humilis in the field,the problem of lodging of cerasus humilis branches at maturity period should be solved firstly,and the mechanical damage during batch harvesting should be reduced at the same time.This paper proposed a comb threshing method.The main research contents and conclusions are as follows:(1)The physical characteristics of cerasus humilis were studied.The results of geometric parameters determination showed that the size of different varieties is quite different.Cerasus humilis fruit is oblate and can be regarded as a sphere.The connection force test showed that there are obvious different between different varieties.The only significant factor affecting the connecting force was maturity.The sampling position and fruit diameter had no significant effect on the connecting force.Connecting force can be used as a criterion for judging maturity.The results of branch tensile test showed that the effects of varieties and maturity on the tensile strength of branches were not significant.The results of compression test showed that the compression characteristics of different varieties are quite different under different maturity.With the increase of maturity,the test force,failure stress,elastic modulus,failure energy and firmness of the same variety decrease,while the displacement and failure strain increase.It showed that the degree of maturity increases,and the fruit is more likely to cause extrusion deformation and damage.(2)Based on Hertz theory,the force in threshing process was analyzed.The loss of cerasus humilis was judged by the amount of transverse deformation.The restraint relation of stripping force is obtained.Taking the loss rate as an index,the bench test was carried out on a self-made test-bed.The results of single factor test showed that the loss rate is positively correlated with the comb distance,combing speed and the radius of comb curvature.The orthogonal test determined that the optimum parameters were combing speed of 200 mm/s,comb distance of 8 mm and comb radius of curvature of 6 mm.This parameter is suitable for different cerasus humilis varieties,and the loss rate is less than 15%.(3)Cerasus humilis field harvester is designed and its power source is loader.Using the working characteristics of the loader,the comb is fed from the roots of cerasus humilis.This can solve the lodging problem of cerasus humilis branches.The motion track,velocity and acceleration of the tooth tip during the threshing process were obtained by analyzing the movement of the collecting device.(4)The field experiments were carried out after the trial production and processing of the comb threshing field harvest prototype of cerasus humilis.The statistical results showed that the harvesting efficiency of the harvest prototype was 113.76 kg /h,6.57 times of the manual picking efficiency,and the fruit collection rate was about 79.72 %,the breakage rate was 4.9 %,the comprehensive loss rate was75.81 %,the branches breakage rate was 48 %,and the serious breakage rate was 12 %.(5)The eccentric swing cerasus humilis combing mechanism was designed.It can achieve the horizontal combing of the comb teeth while feeding the comb teeth from the root of branches as much as possible.Through the structural analysis,the eccentricity of the eccentric mechanism,the length relationship of the crank-rocker mechanism,the row number of comb teeth,the comb gear radius and the installation height were determined,and the synchronous belt transmission was adopted.(6)The eccentric swing combing device was trial-produced and processed for bench experiments.Regression test was carried out with the loss rate as the response index and rotation speed of comb wheel,feeding speed and swing angle of comb as the factors.The quadratic polynomial regression model was obtained.The optimum combination of parameters is that the rotational speed of comb wheel is 5 r/min,feeding speed is 0.2 m/s and swing angle of comb tooth is 7.5°.The real value of cerasus humilis loss rate was 6.34% after optimization.