Clusters’ Vibration Coupling Simulation And End Effector Design & Testing For Grape Picking

In the robot picking fruit clusters, fast operation may cause oscillation of suspension stems and lead to loss of fruit. The fruit stalk mechanical model were simple or whole cluster that with the continuous vibration fruit harvest as the goal.The grape as the research object, first of all,the end effector is optimized, and the shearing test proved that the optimization results can meet the requirements; Finally, the simulation model based on the physical and mechanical properties of the string fruit is established, and the relationship between the excitation rate and the shedding rate is studied that based on the deviation degree. The main research work of this paper is as follows:(1) Study on physical properties and mechanical properties of grape clusters. At first, the data of peduncle length and angle of the plumb line are derived that based on the statistics of stem growth characteristics and grain physical properties, and concluded that a single fruit grain can be approximated as a sphere And found that the compressive,shear mechanical properties of the main stem and mechanical properties of the viscoelastic stage of the stem hinge can be characterized by the Kelvin model.(2) The design and testing of end effector. The main stem of the grape as the object of operation, by analyzing the clamping and shearing of end effector, the problem of insufficient output power of the existing mechanism is found. The optimization design of the transmission structure and the finger end mechanism are carried out; The kinematics and dynamics simulation analysis of the mechanism is carried out by using ADAMS software, which proves that the optimized mechanism is reasonable and effective; Finally, through the comparison test before and after optimization, it further proves that the optimization mechanism has good effect, and can meet the requirements of high speed operation.(3) The establishment and analysis of rigid flexible coupling vibration model of fruit clusters. According to the analysis of the special characteristics of the clamping and cutting of the fruit stalk,and a flexible rod-hinge-rigid rod-mass sphere compositemodel is proposed. By the 3D scanning and flexible rod replacement of the stem system and the normal state of the fruit grain and stem hinge, a simulation model of grape fruit stalk vibration was established. It is found that the different stages of simulation and test of the fruit grain of swing angle of mean and standard deviation of the difference were within 2% and 6.6%. It is proved that the model is reasonable.(4) Joint modeling and biased picking analysis. In order to explore the influence of the clamping and shearing excitation on the vibration and shedding of clusters, the main stems contain compression and shear characteristics are coupled, by that, the joint simulation system is established. Based on the joint simulation model, the deviation analysis is carried out firstly, and the simulation experiment is carried out under different degrees of deviation. It’s found that the deviation of the picking process has a significant effect on the vibration. Therefore, under high-speed operation, by reducing the degree of deviation to reduce vibration shedding is feasible(If picking time was0.57 s, shedding rate did not exceed 0.95%).In summary, based on the optimal design of the end effector and the establishment of the coupled model of grape vibration, the law of vibration and shedding of cluster picking machine is studied in this paper.And the work carried out in this paper provides an important basis for the realization of the fruit picking requirements about reducing vibration &prevent fall off, and provides a reference for the analysis of all kinds of fruit picking.