Optimization Of The Structure And Study On Control Of Constant Speed Operation Travel Of Small Automatic Transplanter For Pot Seedlings

As a large vegetable country,the total production and consumption of vegetables in China rank among the top in the world.In recent years,the output,export and planting area of vegetables in China have increased year by year.Among them,the output of protected vegetables accounts for a considerable proportion,and the planting area of protected vegetables has also increased continuously.More than half of the vegetable varieties are planted by transplanting after hole plate seedling raising,.At present,large and medium-sized semi-automatic transplanting machines are mainly used for open field vegetable planting and large and medium-sized facility vegetable planting in China,which can not be used in small and medium-sized facilities.The small transplanters on the market are manned,with large overall size and driven by internal combustion engine,which requires manual placement of cavity plate seedlings,recovery of cavity plate and other operations.In addition,the exhaust gas produced by internal combustion engine will cause greater air pollution,affecting the quality of vegetables,so these small transplanters can’t be used in small and medium-sized facilities.In order to meet the urgent needs of mechanized transplanting of small and medium-sized facilities or simple facilities,it is very important to develop a small fully automatic transplanter with self driving,electric drive and compact size.The prototype of small automatic transplanter developed by the research group has preliminarily solved the problem of mechanization of vegetable transplanting in small and medium-sized facilities or simple facilities,but there is still no empty pot recovery mechanism.In order to maintain the stability of transplanting plant spacing,special personnel are required to control the moving speed and direction of the transplanter in real time,and the structural reliability is insufficient.In view of the above shortcomings,it is proposed to design the cavity tray recovery mechanism suitable for the small transplanter,optimize and improve the structure of the transplanter and redesign the whole machine control system.The main research contents are as follows:Firstly,design of empty pot recovery mechanism and improvement of transplanter chassis structure.The existing transplanters of the research group have not designed the empty pot recovery mechanism.Due to the high transplanting frequency of potted seedlings,the generation of empty trays rapidly,special personnel are required to recover the potted trays,which does not save labor.Therefore,the design schemes of two kinds of recovery mechanism are put forward,and optimize the scheme.Through comprehensive comparison,the belt type empty pot recovery mechanism is selected as the optimal scheme.The chassis frame of the original transplanter is made of aluminum profile and rigidly connected through connectors.Other structural steel working parts of the transplanter and the aluminum chassis are connected and fixed by bolts,which has low connection reliability and is easy to loosen.The integral steel structure chassis and its connection with other components are redesigned to enhance the stiffness and reliability of the chassis.Secondary,strength,stiffness analysis and lightweight design of electric chassis of transplanter.After improving the design of the transplanter chassis frame and its connecting parts,the static and modal simulation of the frame are carried out by using ANSYS.Through the analysis of the simulation results,it is verified that the static and dynamic performance of the newly designed frame structure meet the use requirements;On this basis,the lightweight design is carried out,the chassis structural parameters are optimized,and the weight of the chassis frame of the transplanter is reduced effectively.Then,Research on control strategy of constant speed operation travel system of transplanter.In order to keep the plant spacing stable under the soft and complex walking conditions of the field,and to eliminate the continuous adjustment of the constant speed and direction during operation of transplanter,so as to avoid the situation that one operator cannot take into account the travel control and the placement of the burrow when the planting frequency increases,the control strategy of constant speed operation of transplanter is studied.The cross coupling control strategy and PID control mode are selected to control the driving speed and straightness of the chassis,so that the transplanter can drive in a straight line at a given speed and constant speed.Next,redesign of whole machine control system.Aiming at the problem that the automatic transplanting control and walking control of the original prototype control system adopt PLC and single chip microcomputer respectively,which have poor compatibility with each other.The control hardware is integrated on the basis of the existing transplanter control system,and the planting and traveling of the whole machine are controlled by PLC;The control system is redesigned according to the executive action requirements of each component of the transplanter,mainly including the control system design of the chassis travel system and the empty pot recovery mechanism of the transplanter and the redesign of the whole machine control process,etc.Finally,test and analysis.The newly designed transplanter has been processed,and the experimental analysis is carried out after the commissioning of the whole machine control system,which verifies the rationality of the structural and control system.Through the performance test of the empty pot recovery mechanism,it can be concluded that the design of the empty pot recovery mechanism is reasonable.When the cumulative number of cavity discs is 3,the conveying efficiency and success rate of the pot recovery are the highest.When the cumulative number of cavity discs is more than 3,the success rate will be reduced due to the limitation of the structure.The planting performance test of the transplanter shows that the traveling speed of the transplanter is basically constant during planting,and the speed curve is consistent with the trend of the simulation results;it can be obtained that when the planting frequency is 45 plants / row / min,the planting success rate is more than 97%,the plant spacing variation coefficient is 3.82%,and when the planting frequency is 60 plants / row / min,the planting success rate is more than 95%,and the plant spacing variation coefficient is 3.89%.The performance of the transplanter meets the use requirements.