Design And Study On Lightweight And Simplified Cover Bowl And Cover Soil Machine For Tabacco Seedling

Tobacco is an important economic crop in China,which plays an important role in our national economy.The combination of well-cell transplanting and plastic film mulching during the seedling stage of tobacco can preserve the heat and moisture,so that it can significantly promote the growth of tobacco seedlings.The cultivation technology of plastic film mulching has been greatly promoted in China.However,there are no suitable products for plastic film mulching and film collecting for hilly areas in Southwest China at present.More areas are still using manual mulching and manual picking up the residual film which is labor-consuming,costs high and has low efficiency.When the residual film is recycled after harvest,mulch films are seriously aged and broken.A large number of residual films are left in the fields,resulting serious"white pollution".In recent years,agronomists innovatively put forward a idea of replacing plastic film with plastic bowl cover at lower altitude.Relevant tests verified its feasibility.However,the work of covering bowl and covering soil in hilly mountainous areas is still done by hand,which labor-consuming,costs high and has low efficiency.In this situation,developing a kind of lightweight and simplified cover bowl and cover soil machine for tabacco seedling,which provides a practical and effective way for the use of machinery to cover bowls and soil in hilly mountainous areas of Southwest China.The machine includes bowl dropping system,soil covering system and control system.Insert the soil cover push plate into the soil by manpower,press the operation switch,the controller sends out the command,and the bowl dropping screw carries out the bowl dropping work under the drive of the bowl dropping motor;after the bowl dropping is completed,the controller will give an alarm to remind the operator to lift the machine.while the height reached a certain height,the soil cover motor drives the soil cover push plate to carry out the soil cover work,so as to achieve the bowl cover work of the smoke field well cellar.The main research contents are as follows:(1)By reviewing related literature at home and abroad,combining agricultural machinery and agronomy.Determining the design principles,requirements,mechanical structure,control system and working process of the machine.(2)Mechanical structure design of the machine:according to the design principles and requirements,throughing 3D modeling and virtual assembly with proe,analysis on multiple schemes,physical production,field test and comparative optimization.Finally,determining the structure of aluminum frame,vertical spiral gear bowl dropping,plug-in earth covering and linear guide rail lifting device.Analysing and determining the size of each part.(3)Mechanical analysis of the soil cover system is carried out and the soil cover process is simulated by ProE?ANSYS/LS-DYNA and LS-PrePost.The maximum force and moment are 27N and 2000N*mm,the maximum instantaneous power is 22W.The maximum and minimum resistance of the soil cover push plate are 22.26N and2.98N.Selecting the type of the motor combins with the test data.At the same time,the constant torque test is carried out,the corresponding PWM duty cycle is 25.26%and93.97%.And designing the control strategy.The PWM duty cycle is controlled by stages to change the maximum output torque of each stage and current limiting control.(4)Control system design of the cover bowl cover soil machine:according to the design requirements and working principle of the whole machine,the modular design of the hardware circuit and the PCB circuit board design are completed;according to the working process,the flow chart of the control system is determined,the control program is completed and the program is debugged.(5)Output control characteristic test of the control system shows that the control system can control the duty cycle of PWM in stages according to the magnitude of the external load,and the PWM regulation error is not more than 2%.At the same time,it can control the covered motor with constant current,the maximum error is 5.71%,less than 6%.Reducing the motor terminal voltage after the current of the covered motor exceeds 3.5A,thus limiting the current and blocking the covered motor.The current is controlled at 3.7A.If the current value is biger than 3.5A and the duration reaches 2s,the motor will be closed.In the field test,the qualified rate of covering soil with cover bowl shall not be less than 90%,the coefficient of variation between the completion rate of dropping bowl and the qualified rate of covering soil with cover bowl shall be 2%.The test results show that the work effect is good,which meets the expected design requirements.At the same time,the work efficiency can reach less than 4s,that is not less than 5.17hm~2/h.