Device And Control System Design Of Pomelo Picking

Pomelo is usually planted in hilly and mountainous areas,and currently relies mainly on manual harvesting.It is of great significance to realize mechanized harvesting to improve production efficiency.The picking device is one of the core working parts of mechanized picking.In this paper,the structure and control system design of the pomelo picking device were carried out according to the characteristics of pomelo picking operation.The main research contents are as follows:(1)The overall functional analysis of pomelo picking device.On the foundation of the analysis of the action characteristics of pomelo artificial picking,the conclusion that pomelo picking device should have the functions of fruit holding and fruit stalk cutting was determined.Moreover,the performance requirements of the pomelo picking device control system were determined,and the working process of the control system was clarified.Therefore,the overall structure of the pomelo picking device included two parts:the holding part and the cutting mechanism;the holding parts could realize the stable holding of different diameter pomelo fruit without damaging pomelo fruit;the cutting mechanism could drive the saw blade to accurately reach the fruit stalk according to the information obtained by the sensor and quickly achieve complete cutting,and then reset.(2)Overall structure design of pomelo picking device.The overall structure of the pomelo picking device was designed,including the supporting part and the cutting mechanism.The holding part was bowl-shaped,with an inner diameter of 200mm and a height of 100mm for holding the target fruit during picking.The cutting mechanism was composed of the cutter and the transmission mechanism,which consisted of gear,rack,saw blade,stepper motor,high speed DC motor and saw blade protection shell.A circular saw blade was driven by a high speed DC motor to cut along the radial direction of the fruit stalk.The main speed of the saw blade V was 31.40m/s,the feed speed U was52mm/s,the cutting force F_twas 4.98N,and the cutting power P was 156.47W.Additionally,the limit block was designed to limit the front,back and left of the curved rack to ensure that it could move according to the predetermined trajectory.The three-dimensional model of pomelo picking device was created in the Solidworks,and the motion simulation was carried out in the Adams.The simulation results showed that the design could satisfy the functional requirements.(3)Design of pomelo fruit information acquisition system.The information of fruit is one of the basic bases of picking device action control.The resistance strain pressure sensor was selected to obtain the weight information of the fruit,the signal conversion module was HX711 A/D,the XLHW50CM infrared diffuse reflection proximity sensor was used to obtain the position information of the fruit,and the main controller was STM32F103 microcontroller unit.The acquisition,analysis and display mode of weighing sensor signal were determined,and in addition,the program to reduce the interference of shock vibration on weight signal was designed.Finally,the real-time display of the weight and specification level information of pomelo fruit on the LCD screen was realized,and the acquisition and output of the position judgment signal of the pomelo in the holding part were realized.(4)Control system design of pomelo picking device.According to the working process analysis of the pomelo picking device,the functional requirements and design ideas of the control system were determined.The STM32F103ZET6 core board microcontroller unit,3.2 inch ILI9341 LCD screen,J-5718HB2401 stepper motor,EBF-MSD4805 driver,775 high-speed DC motor,YK-08 control relay module and other components were selected to construct the control system.The hardware structure diagram,the circuit diagram of each part of the control system and the PCB diagram of the development board were designed,and besides,the hardware welding and construction were completed.The main program and subprogram flow and flow chart were designed,and the system control program was written and debugged.After debugging,the control system of pomelo picking device was proved to be able to achieve the expected function.(5)The whole machine construction,debugging and functional test of pomelo picking device.The pomelo picking device was assembled,and 30 pomelo samples with stalk diameter of 4～7mm and weight range of 400～1100g were selected for functional test.The results showed that the holding part could stably hold the fruit;the weighing sensor could accurately obtain the weight data of pomelo fruit.The weighing accuracy of each weight grade was 83.3%～88.9%,and the average operation time was 10.33～10.85 s.The cutting mechanism could finish the stroke and cut fruit stalk.The research results showed that the designed pomelo picking device could complete the preset operation process,basically satisfy the functional requirements of picking operation,and could provide technical basis and solutions for the subsequent research and development of pomelo picking robots.