| Transplanting the seedlings from the high density seedling tray to the low density seedling tray and filling the empty holes with healthy seedlings is often used in the production of modern greenhouse seedling breeding.However,seedling transplanting is a labor intensive work,the working style is dominated by manual operation at this stage,the working efficiency is limited and cost high,it is difficult to meet the needs of intensive seedling production in the modern greenhouse.Therefore,it's urgent to design an automatic transplanting equipment to match the working demanding.Delta parallel mechanism has the characteristics of high speed,high precision and strong flexibility,it's very suitable for seedling transplanting and gap filling.Therefore,a seedling transplanting and gap filling robot was built based on the three DOF Delta parallel mechanism and pneumatic manipulator.The main research contents are as follows.1)The reachable workspace of the plug seedling transplanting robot was obtained by building the single chain constraint equations of the Delta parallel mechanism;Determining the design workspace considering the woking requirements of seedling transplanting and gap filling.Taking the the condition number of Jacobian matrix as the penality condition,a dimensional synthesis target function was built considering the size and kinematic performances of the plug seeding transplanting robot for the purpose of making the reachable workspace close to the needing workspace,then the dimensional synthesis for the plug seedling transplanting robot were obtained by using of the genetic algorithm.2)In order to improve the efficiency and quality of transplanting and gap filling,selecting the scheme of transplanting in columns as the working scheme by comparing the working scheme of transplanting in rows and transplanting in columns.The trajectory planning of transplanting and gap filling were carried out based on the woking requirements,selecting the quintic polynomial motion law as the principle of operation for the moving platform.The movement rule of the moving platform in the transplanting area is fitted to the rotation law of the three active joints of the Delta parallel mechanism by isochronous interpolation,inverse kinematics and velocity fitting based on the inverse kinematics model and the moving platform motion law of the transplanting and gap filling robot.Design the working process of transplanting and gap filling,making the transplanting and gap filling robot can achieve the function of transplanting and gap filling from one seedling tray to another seedling tray.3)Buliding the virtual prototype model of transplanting and gap filling robot based on the dimensional synthesis and the trajectory planning.Selecting two of the longest transplanting path as the simulation model,then the virtual prototype model simulation was carried out,the speed and acceleration curve were shown in the simulation results,the law of change of the speed and acceleration curve is in line with the requirements,the rationality of trajectory planning is verified.The angular velocity,angular acceleration and torque curve of the three active joints of the Delta parallel mechanism were also obtained,which could provide some important theoretical basis for the construction of control system.4)Based on the mechanism dimensions,tracjectory planning and simulation analysis,a physical prototype was built and transplanting experiment was carried out.the experiment results showed,the success rate of plug seedling transplanting was decreasing when the the transplanting acceleration was increasing,the success rate of plug seeding transplanting exceeded ninety-five percent,the success rate of plug seeding filling exceeded ninety percent,transplanting rate can reach 2149 plants per hour when the transplanting acceleration is 30m/s2,which demonstrated the practicability when the Dealt parallel mechanism was used in plug seedling transplanting and the rationality of the dimensional synthesis and trajectory planning. |
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