Research On The Picking Device Of Pod Pepper Harvester And Its Loss Reduction Technology

As a key component for pepper mechanical harvesting,the picking device of roller-finger type has become the standard configuration for most self-propelled pepper harvesters in China.However,the existing roller-finger picking device cannot adapt to the planting and growth pattern of the mainland pod pepper,resulting in more ground drop loss and damage when harvesting pod pepper,which seriously affects the increase in yield and income of pod pepper.Starting from the study of the material characteristics and mechanical parameters of pod pepper,this paper takes the human finger as the bionic prototype,analyzes and refines the multi-finger cooperative motion configuration and single-finger rigid-soft material coupling assembly model when picking pod pepper,optimizes the picking finger layout scheme and material assembly of the roller-finger picking device,and establishes a bionic loss reduction model of the picking roller.Based on this model,an optimization study on the loss reduction technical parameters was carried out,and field experiments on pod pepper harvesting were conducted to develop a pod pepper harvester with low ground drop loss rate and low damage rate,providing new research ideas for the development of low loss pod pepper harvesters.The specific research contents are as follows:Study on the material characteristics and mechanical parameters of pod pepper.Through field investigation of the planting and growth status of pod pepper in Fengxian County,Jiangsu Province,the agronomic parameters such as plant height,row spacing,fruit distribution height,and yield per unit area were determined to provide a basis for subsequent design and optimization of pod pepper picking device.Material parameters such as three-dimensional size,moisture content,density,Poisson’s ratio,elastic modulus,and contact parameters such as coefficient of restitution,friction coefficient between the pod pepper and the contact material were measured through experiments.In addition,a well representative three-dimensional model group of pod pepper was established by using reverse engineering reconstruction technology,and the static friction coefficient and rolling friction coefficient between pod pepper and pod pepper were calibrated based on EDEM simulation and RSM optimized test design.The relative error between the verification repose angle and the measured repose angle of pod pepper is within 3.35%,indicating that the calibration parameters are accurate and reliable,laying a parameter foundation for the optimization of loss reduction technical parameters.Design of picking device and establishment of its loss reduction model.Combining the agronomy and material parameters of pod pepper,the overall structure of the picking device was designed.In order to reduce the ground drop loss and damage of pod pepper,a bionic loss reduction model of the picking roller was established with the human fingers as the bionic prototype.This model includes two aspects:on the one hand,a joint motion space configuration of multiple fingers in collaborative layout,knuckles bending,and wrist backward movement during pepper picking was refined to establish a joint motion and collaborative layout scheme model of picking fingers.On the other hand,the coupling assembly mechanism of rigid and flexible materials such as bone-muscle-blood vessel-fascia-skin from inside to outside of a single finger is analyzed to establish a bionic picking finger rigid-soft material coupling assembly model.Parameter optimization of ground drop loss rate for picking device based on EDEM.The picking device model was simplified to establish an EDEM simulation model of the picking frame.Based on the joint motion and collaborative layout scheme model of picking fingers,the influence of picking roller rotation speed V’,pepper feeding speed V’,picking finger bending angle C and number of circumferential rows per group of picking fingers N on the ground drop loss rate of pod pepper in the simulationη_g1 was comprehensively considered.Based on the EDEM simulation model of the picking frame,a four-factor three-level response surface optimization test was conducted withη_g1 as the response value.Through Plackett-Burman test,Steepest ascent test and Box-Behnken test regression model analysis of variance,the optimal loss reduction technical parameter combination value was obtained by solving the model equation with constraints:V’was 210 rpm,V’was 1100 mm/s,C was 162°,and N was 2 rows,when the minimum value ofη_{g 1} was 7.50%.This part of work determines the optimal layout scheme of picking fingers and the optimal picking operation parameters of the picking roller,providing a basis for subsequent optimization of the bionic picking finger rigid-soft material coupling assembly model.Simulation analysis of the collision between pod pepper and fingertip of the picking finger based on Abaqus.The process of picking pod peppers by high-speed rotation of the picking roller was simplified and an instantaneous collision model between pod pepper and fingertip of the picking finger was established.The Abaqus explicit nonlinear dynamic analysis method was adopted to simulate the picking process of the instantaneous collision between pod pepper and the fingertip.Through energy balance analysis and mechanical parameter analysis of the simulation results,it was found that compared with ordinary rigid picking fingertip,bionic picking fingertip based on the bionic picking finger rigid-soft material coupling assembly model have more excellent picking buffering and impact reduction performance:the bionic picking fingers can not only significantly extend the duration of the instantaneous collision stage during picking（extended by 1230%～3480%）,but also effectively reduce its maximum impact force（reduced by93.09%～98.83%）and maximum contact pressure（reduced by 94.45%～99.11%）on pod pepper,which is conducive to reducing the damage of pod pepper.Based on the analysis results,bionic picking fingertip 8-6 was selected as the coupling assembly form of rigid-soft materials for the picking finger,and applied to subsequent field test.Field test of picking device.According to the optimal combination value of the loss reduction technical parameters mentioned above,the picking device was processed and applied to the 4JZ-1700 self-propelled pod pepper harvester for field test of harvesting pepper.By comparing the ground drop loss rate of pod pepper,it was found that the relative error between the ground drop loss rate of pod pepper in simulationη_g1（7.50%）and the nominal ground drop loss rate of pod pepper in field testη_d1（7.91%）was only 5.18%,thus verifying the accuracy of the optimal combination value of the loss reduction technical parameters.By comparing the damage rate of pod pepper,it was found that the damage rate of pod pepper in the picking device equipped with bionic picking fingersη_p2（2.98%）was lower than that equipped with ordinary rigid picking fingersη_p1（3.49%）,indicating that the picking device with bionic picking fingers has better damage reduction effect when picking pod pepper.Thus,the pod pepper picking device is considered to have good loss reduction performance.