Design And Parameters Optimization Of 3T1R Parallel Transplanting Mechanism

Seedling transplanting can improve the growth quality of crops,shorten the growth cycle,and increase the benefits,these advantages can be further developed by using mechanical transplanting.However,there are still some disadvantages in today‘s transplanting mechanical equipment,and pot seedlings are still transplanted manually in many areas.The main reason is the existing transplanting equipment lack of generality,which leads to the equipment in a low level usage and can’t make the best use of the transplanting mechanism.Or the transplanting equipment has good generality,but the machine is expensive and complex to control,so it is difficult to be popularized and applied.Compared with the existing agriculture machinery,the Intelligent agricultural machinery has improved the working quality greatly by using a number of sensors.Mechanism type is at the core of the transplanting equipment,the main bodies of existing transplanting mechanisms are not suitable to be used as the carrier of intelligent agricultural machinery for the poor generality.Parallel manipulators have received more and more research because of their good generality.This paper explores to use parallel manipulators as the carrier of intelligent agricultural machinery.In parallel manipulators,3T1 R mechanism has been widely used because its end motion characteristics can meet most of the working scenes.There are many researches on 3T1 R mechanism,but the existed 3T1 R parallel manipulators do not suitable used in transplanting for their rotation axis are along the vertical direction.This paper based on the potted seedling transplanting task and Position and orientation characteristic to find a novel 3T1 R parallel mechanism.Its kinematics model is established,the singularity is analyzed based on Jacobian Matrix and the definition of singularity,workspace is obtained according to the numerical method,transplanting trajectory planning and simulation,local dexterity index and local motion / force transfer index analysis is performed respectively,and mechanical structure size optimization based on global motion / force transfer index is carried out for the optimized selected type.The main research contents are as follows:(1)Determine the posture of the end effector according to the seeding transplanting requirements.The position and orientation characteristic set method is used to synthesize the 3T1 R type PMs,then the position and orientation characteristic equation is used to calculate the topological structure information of the mechanism.Combining the topological characteristic of the 3T1 R PMs and the method of choosing the PMs to identify the transplanting parallel manipulator 2PPa RR-2PPa RU.(2)The inverse position solution is derived by founding the kinematic model of the mechanism,and the correctness of the inverse position solution is verified.Then the Jacobian matrix is obtained by derivation of the formula.The singularity of the Parallel seedling transplanting manipulator 2PPa RR-2PPa RU is found through the Jacobian matrix and the definition of singularity.The inverse kinematic singularity and other kinematic singularity is found.(3)Using the numerical method to search for points that meet the constraint conditions in the preset working space,and using the points that meet the constraints to plot the reachable working space of the mechanism.The effect of different links’ dimension and the posture of the end effector on the reachable working space of the mechanism is analyzed.Based on the agronomic characteristics of the seedings and containers,the transplanting trajectories of the mechanism are planned under the working mode of picking seedlings at different points and planting seedlings at the same point,the simulation of the transplanting trajectory is realized by Matlab.(4)The local dexterity index and the local motion/force transmission index are learned to analyze the performance distribution of the accessible working space of the mechanism under different poses independently.The global motion/force transmission index is selected as the optimization index to analyze the global motion/force change trend of the PM under different links’ dimensions.According to the analysis results,the optimized links of the mechanism is selected from the optimized results.Compared with the former sizes,the later has better motion/force transmission performance.In this paper,the motion analysis,performance analysis and parameters optimization of the new parallel manipulator 2PPa RR-2PPa RU is carried out,which lays a solid theoretical foundation for the mechanism in the subsequent application of greenhouse pot seedling transplanting.