Design And Research Of Nondestructive Detecting And Automatic Grading Machine Of Litchi Based On Machine Vision

Grading of litchi is an important section of its processing after harvesting,also the key of the realization of litchi of high quality get high price.With the employment of automatic grading machine of litchi not only could improve the labor condition and efficiency.However,it's has the shortcomings of mechanically automatic litchi grading machine that single grading criteria and deal damage to litchi easily.Reduction of damage to litchi and intelligent grading with multi-standards could brought out with the help of machine vision method.In order to realize nondestructive detection of litchi,a proposal of automatic litchi grading machine with nondestructive detection based on machine vision,a detailed design to machine section and control section was performed,a simulation analysis and research to single arrangement and conveying system and execution system were made,besides,a real model of grading machine was developed and its working parameters was optimized with experiment.The following main research works were completed:1)Overall design and research of automatic grading machine of litchi.According to the principle of quality detection and classification of fruit and vegetable by machine vision and the actual production demand of litchi,an overall design proposal of automatic litchi grading machine with nondestructive detection was come out.,component systems and electric control system was designed detailed,structure composition of single arrangement and conveying system and execution system were analyzed,key parts of systems were designed,and key parameters of system was analyzed and calculated.2)A simulate analyze of single arrangement and conveying system based on discrete element method.A discrete element simulation model of single arrangement and conveying system based on EDEM was constructed,with which a single arrangement and conveying experiment of litchi was performed,the effect of broken arch and uniform fruit with small turnable during arranging process was analyzed and the forecast of damage of litchi during the arrangement and conveying was analyzed.The result was shown that litchi would accumulate and arched while the big turnable and small turnable rotated in same direction which blocks the arrangement and causes cavity;the accumulate and arched of litchi would eases while the big turnable and small turnable rotated reverse which costs more time to finish the arrangement process;the accumulate and arched of litchi could eases effectively causes less cavity while small turnable rotated and change direction periodically and cost least time to finish the arrangement process.Besides the average compression force to litchi during single arrangement and conveying process was less than the threshold value which would deal damage.3)Optimization of parameters single arrangement and conveying system.The model of automatic grading machine of litchi was made and made single factor test and orthogonal test about single arrangement and conveying process.The influence of work and structural parameters of conveying system on the arrangement and conveying indices of litchi(stuck frequency and cavity rate)were researched.What's more,comprehensive optimization to influence factors was carried out by means of the construction of regression models and the combination of them.What's more,the optimized parameters were tested experimentally.The result was shown that: Stuck frequency and cavity rate increase while the rotation speed of big turnable,the rotation period of small turnable and the feeding weight increase,besides the cavity rate increases while the offset coefficient of amplitude of small turnable and number of holes of big turnable increase;the major factor that influence stuck frequency is feeding weight and the next factor is the revolution speed of big turnable,while the major factor that influence cavity rate is also feeding weight and the next two factors are the offset coefficient of amplitude of small turnable.Within the scope of the test,the best parameters of the delivery device are as follows: the rotation speed of big turnable is 7.35 rpm,the rotation amplitude of small turnable is 14.30 rpm,the period of small turnable is 16.93 s,the offset coefficient of amplitude of small turnable is 0.33,the rotation speed of small turnable changes linearly?the feeding volume is 1.31 kg,the number of holes of big turnable is 10,with which the stuck frequency and cavity rate are 0 and 6% respectively.4)Fluid structural interaction simulation research of grading execution system.The finite element model of pneumatic grading execution system was made with which a statics fluid structural interaction simulation and dynamic ALE fluid structural interaction simulation during grading execution was carried out.The influence of different blow out air pressures on the damage to litchi were analyzed with stress distribution diagram,and motion parameters in the process of litchi grading execution was also analyzed.The result was shown that: the airflow speed in compressed air exit increased linearly while blow out air pressure increases,and the region that air pressure acts is concentrated;the maximum stress inside the litchi didn't exceed the threshold value that causes damage on flesh,so that litchi wouldn't get internal damage;it took less than 0.2s to finish grading execution;and the minimum speed of litchi that blow out of grading execution system is 0.3m/s.