Design And Analysis On Vibratory Fruit Harvesting Mechanism With Three-dimensional Excitation

With the growth of orchard area and fruit yield in recent years, it is still a big problem for farmers to harvest fruit efficiently in China. Because the shaking-type harvester can make mature fruit detached quickly and effectively, the existing fruit harvesters are mostly shaking type, but the efficiency of shaking type harvester is not high enough. Because of this, the effect of various dimensional excitations on fruit tree was discussed in this paper. After comparing the distribution of acceleration response on the fruit tree by simulation under different kinds of displacement pattern, the three-dimensional shaking method was proposed and the vibratory harvesting mechanism with three-dimensional effect was designed. Then the kinematics and dynamics of the mechanism were analyzed, and major parameters of the component dimension were optimized. Finally, the prototype of this mechanism was built to be tested and compared with other machine, which is to inspect the effect of this shaking method. The main contents of thesis are as follows:1. A Chinese hickory tree model was established for transient dynamics analysis by finite element software(ANSYS). One-dimensional shaking method was discussed, and then the influence of its loading direction on the acceleration response of tree was analyzed. Simulation results show that the loading direction of one-dimensional shaking method has remarkable effect on the acceleration response, but it is difficult to make fruit tree branches produce enough big acceleration response in all directions with a single directional exciting force. So, the three-dimensional shaking method was proposed on the basis of one-dimensional and two-dimensional shaking method, which has effect not only on the cross section direction of fruit tree’s branch, but also on the axial direction. After analyzing the acceleration response of different kinds of shaking method and revolving speed ratio of three-dimensional displacement pattern, the conclusions are as follows: 1) fruit tree shaken by three-dimensional load has a more uniform acceleration than by one-dimensional and two-dimensional load; 2) it has the most uniform acceleration distribution when the speed ratio of crank in the spatial linkage shaking mechanism is 1:1.2. According to the generation method of three-dimensional displacement load and the dynamics simulation result of fruit trees, the vibratory fruit harvesting mechanism with three-dimensional effect was designed, which mainly consists of the box, the spatial linkage shaking mechanism, the driving mechanism and the clamping mechanism. The transmission ratio of the driving mechanism can be changed to obtain different three-dimensional displacement load. And kinematics and dynamics of the spatial linkage shaking mechanism were analyzed.3. After kinematics analysis of the spatial linkage shaking mechanism, the stroke and acceleration that were affected by the change of related parameters was calculated with MATLAB software. In order to achieve the optimization objective of the maximum acceleration, genetic algorithm was used to optimize parameters of this mechanism. The ranges of parameters were determined by constraints of the spatial linkage shaking mechanism. Then optimization software was written based on MATLAB platform and the optimization result was: l AB=0.025 m, l BC=0.180 m, l BH=0.095 m, l CD=0.050 m, l EF=0.017 m, l FG=0.139 m, l GI=0.170 m, l IK=0.330 m. Finally, the simplified model of the spatial linkage shaking mechanism was establish according to the optimization result, and simulation result shows that the maximum torque that cranks need which is calculated in ADAMS is 2.18N·m.4. A prototype of vibratory fruit harvesting mechanism with three-dimensional effect was manufactured and assembled according to the result of parameter optimization and dynamics simulation. Then the dynamic response experiment of fruit tree was carried out. In order to evaluate the performance of the vibratory fruit harvesting mechanism with three-dimensional effect, an eccentric block type vibration motor was used in this experiment, and accelerations of test points on fruit tree were measured by data acquisition and analysis instrument. Statistics results indicate that three directions of test point on the tree had obvious acceleration response to the three-dimensional effect vibratory harvester; it only caused obvious acceleration at the cross section of the branch by the eccentric block type vibration motor, but the acceleration was small at the axis direction of the branch. Finally, the variation coefficients of mean acceleration of test points were calculated with two shaking methods. Results show that it had a smaller variation coefficient when the tree was excited by three-dimensional effect vibratory harvester, which means it takes less time to shake the branches when using the three-dimensional effect vibratory harvester, and the harvesting efficiency can be improved.