Design And Experimental Study Of The Olive Harvester

Olive is one of the four woody oleiferous plants in the world.Its planting area and output in China keep rising during the recent years.However,its harvesting still relies on manual plucking,which has obvious problems like insufficient labor force and high harvesting cost,restricting the development of the olive industry.Therefore in this paper,the olive tree with“three open-center” shape is taken as the object to analyze the mechanism of vibration harvesting through dynamic model and finite element simulation.On this basis,relative design and trial manufacture of olive harvester are performed.And the prototype machine is tested finally in this study.The main research contents and conclusions include:(1)Establishment and analysis of harvesting dynamics modelAccording to the principle of vibration harvesting,the simplified method of cantilever beam is used to establish the single eccentric block harvester-olive tree dynamic mode,and solve the differential equation of the system.The results show that the steady-state response of the system changes periodically and is only correlated to the natural properties of the olive tree,vibration frequency and vibration force.In addition,a simplified single pendulum method is applied to establish the olive fruit-peduncle dynamic model,and analyze the conditions of fruit abscission.The results indicate that the fruit abscission is subjected to the natural properties of the olive tree and fruit,vibration frequency and vibration force.The abscission acceleration of olive fruit could be simplified as the ratio between the binding force of fruit and peduncle,and the fruit mass.The fruit abscission standard shall be 90% quantile of the abscission force.(2)Parameter simulation and analysis of olive vibration harvestingThe vibration response of olive tree is analyzed by simulation and experiment methods.The olive tree-vibration motor rigid-flexible coupling model is used to obtain the acceleration of each monitoring point of olive tree.Then the acceleration response of the monitoring points are measured through the acceleration sensors in vibration motor experiment.The results show strong correlation between the simulation acceleration and the experiment acceleration(the average correlation coefficient is 0.73),and the rigid-flexible coupling simulation can better express the experimental results.Taking the main morphological parameters of the olive tree(trunk diameter D,trunk height H,trunk angle A and B)as experimental factors,and vibration frequency and vibration force as response variables,a four-factor and three-level response surface simulation experiment is designed in this study.The vibration frequency range is obtained by modal analysis,from which,the optimal vibration frequency is figured out by sweeping frequency analysis in rigid-flexible coupling simulation.Meanwhile,the optimal vibration force is obtained by monitoring the accelerations of fruit peduncle points under different vibration forces.A polynomial response surface model is built based on the response surface tests.And the results show significant impact of trunk diameter and trunk height on vibration frequency and vibration force.(3)Design and simulation analysis of olive harvesterThe key components and control system of olive harvester are designed.The semicircular eccentric block with a mass moment of 1.2 kg·m is used as the excitation eccentric block,which is driven by a 3k W dual-axis motor.The finite element analysis carried out for the eccentric block shows that the maximum deformation is 0.0016 mm,the maximum equivalent stress is 24.16 MPa,and the first six modes are much greater than the operating frequency.The clamping mechanism is composed of cylinder,fisheye bearing and arc splint,having a clamping range between 80 ～ 240 mm.Driven by SC63-100-TCM cylinder,its clamping force can reach 1870 N.The cantilever and lifting mechanism are designed to adjust the height and clamping angle of the vibration mechanism,for which,the lifting height ranges between 600 ～ 1450 mm,and the rotation angle ranges between ±35°.The crawler chassis is used as the traveling mechanism,the small-scale petroleum generator is applied for providing power,and the control system and remote control system are designed for this mechanism.(4)Experimentation and analysis of the results of an olive harvesterField experiments are carried out with the prototype manufactured in this study.The measurements of amplitudes at the clamping point show that amplitudes at the clamping point vary a lot under different frequencies,namely,rising with the increase of amplitude.The measurements of accelerations at the clamping point on the trunk show that the acceleration here changes periodically,and keeps positive correlation with vibration frequency,which can be fitted as a second-order polynomial.According to the measurements of accelerations at four monitoring points on the trunk and the lateral branches show that,the resonant frequencies of the three points located on the lateral branches are similar to the results of the response surface.The optimal vibration parameters obtained by the response surface model are used to carry out the harvest test,which shows that the percentage of net plucking reaches about 91.76%,achieving effective harvesting of olive basically.