Design And Tests Of High-speed Plug Seeding Transplanting Machine For Greenhouse Based On Parallel Mechanism

Plug seedling transplanting is one of the main operations in agricultural cultivation and transplanting.It is of great significance to study high efficiency automatic transplanting machine and to improve labor productivity,reduce production cost and promote the development of facility productivity.The greenhouse plug seedlings transplanting machines that applied to existing industry are mostly with three-dimensional gantry structure.There are some obvious shortcomings like large size and inertia,low relatively rigidity,high prices and poor flexibility in operating capacity.In view of these problems,this paper intends to design a transplanting machine system with main body of parallel mechanism.Integrating a series of advantages of parallel mechanism like high speed and precision,large relatively stiffness,good dynamic performance and simple to solve institutions inverse solution,it is simple to meet the existing facilities' demands of high cost-effective greenhouse transplanting machine.For the design of the transplanting machine system,the main research contents of this paper are as follows:First of all,studied transplanting objects of seedlings,nursery containers,target containers and relevant parameters.Constructed overall layout of the transplanting machine.According to parameters of the transplanting objects,put forward technical parameters requirements of the main body of parallel mechanism.Secondly,based on topology design method of bearing feature set,topological synthesis of branches that meet requirements of azimuth feature was set to select suitable branch.Combined five kinds of better parallel mechanism and calculated and compared their topological feature parameters.Finally selected the parallel machine model suited to the transplant machine: 2-HSOC{-R//R//R-P4R-} 1-HSOC{-R//R(-P4R)//R-}.Then,mathematical model of the parallel mechanism was established to find pose mapping relationship from moving platform to static platform.Positive and negative solutions and velocity and acceleration equations of the parallel mechanism were obtained.Kinematic theory curve was obtained by MATLAB.Kinematics simulationwas carried out in Pro/E simultaneously.Verified correctness of derivative theory kinematics equation by comparing simulation curve with theoretical curve.Next,five singular shapes of the parallel mechanism were analyzed according to relationship between determinant of Jacobi equation and singularity of mechanism.Limited corresponding angle in the branches according to requirement of pressure angle in connecting rod drive.Used MATLAB to search for reachable space of the parallel mechanism and determined relationship of position and attitude between workspace and the reachable space.Reduced difficulty of parallel mechanism optimization scale by finding some special points on the workspace.Optimal size combination was obtained by searching the optimization objective function of minimum equipment volume.After that,designed a variety of end effectors based on the concept of modular moving platform.Established multi-rigid body model to simulate the peak value of the driving force in ADAMS and explored the influence of changes of quality and centroid to peak torque.Selected drive specifications and predicted maximum acceptable quality of the drive specifications.Finally,fully flexible links model was set and explored the influence of changes of mass to motion error by rigid-flexible coupling multi-body dynamics simulation in ADAMS and verified feasibility of the parallel design.Finally,assembled verification prototype and carried out relevant tests.Established an open loop control system for the prototype.Counted position error of the moving platform to each point and compensated the control system.Turned out that the average positioning error reduced from 7.611 mm to 1.208 mm.Picked a long distance transplanting trajectory to conduct a verification test.Turned out that during working process,the transplanting machine was with low deformation and high accuracy in taking and delivering stage when peak acceleration is 20m/s2(2.04g)and peak velocity is2m/s.