Design And Research Of Stretchable Style Pick-Up Device For Tomato Seedling Transplanters

Xinjiang is the largest tomato growing place in China.At present,plastic trays are used to grow seedlings.The transplanting of seedlings conforms to the regional climate characteristics.It is widely used for the advantage that can improve the survival rate of seedlings.At present,the transplanting of seedlings is mostly carried out by manual or relying on semi-automatic mechanical farming.Such planting methods could not meet the needs of large-scale planting,the automatic transplanters can meet the needs of large-scale tomato planting.The seedling picking technology is the core of the transplanter.The seedling picking device is one of the important parts of the transplanting machine.The device with automatic seedling picking and whole row picking has raised widely concern.We proposed the stretchable slice type seedling pick-up device,and designed the key components of the device.Carried out simulations to achieve accurate seedling picking,and reduce the leaves`damage and substrates`break-up.The main research contents of this thesis are as follows:(1)Clarify the research objects,and use the trays with 128 holes and"Riegel 87-5"tomato plug tray,they are chosen as the research objects.Measure the length of the upper and lower sides of the hole,the depth of the hole was measured for the same time.The characteristics of the tomato seedlings(height,leaf spread,quality,moisture content,etc.)were be explored as well.The substrate compression test was carried out,and the maximum compression force was obtained at the moment when the substrate was damaged.The force analysis was carried out on the tomato seedlings,and the equilibrium equation under the picking state was established,so as to obtain the factors affecting the seedling extraction.The overall design of the stretchable slice-type seedling picker is proposed,the components of the mechanism are clarified,and the realization method and working principle of the motion are analyzed.The motion model of the seedling picker was established,and the motion function of the two points A and B at the end of the picking needle was established,which mainly included the expressions of displacement,velocity and acceleration.On the basis of establishing a function model,the horizontal and vertical displacements of points A and B and the compression amount of the matrix were used as evaluation parameters,and were used as evaluation indicators for accurate seedling picking and low-loss seedling picking.(2)According to the shape parameters and physical characteristics of the research object,design the key components of the seedling picker:the length of the pushrod S,the length of the stretchable slice l _F,and the length of the pick-up needle l _P.According to the force analysis results during picking,combined with the motion model,the influence on the effect of precise seedling picking was analyzed.The design parameters of the components were optimized by the optimization order,and the kinematic analysis software ADAMS was used to simulate the motion.We got the better combination for the three parameters:The length of the pushrod S is 50 mm,the length of the pick-up needle l _P is 24 mm,the length of the stretchable slice l _F is70mm.Under this combination,the displacement characteristics,speed and acceleration characteristics of the movement were verified,and the simulated seedling picking trajectory met the requirements of accurate seedling picking.Besides,the speed and acceleration characteristics met the requirements of low-loss seedling picking.(3)Analyze the working state of the seedling pick-up device in the four processes:picking-sending-release-returning.Combining the pulling test and the compression test of seedlings,obtain the force at different stages in the picking process.Use ANSYS Workbench to carry out static analysis of the pick-up device,and obtain the static simulation results.The structure of the device was further optimized,and the material of the device was changed at the same time.Results of the second optimization simulation meet the stress requirements of the device.(4)Build a seedling-taking test bench to realize the movement of the picker:transportation,release and return.Completed the overall assembly of the seedling picker,install the horizontal and vertical screw of the test bench.Connect the seedling picker control system,and use the electric push rod to realize the picking and release actions of the picker.The trajectory experiment of the device was carried out,and the test process was continuously photographed to obtain the actual running trajectory.Measure the displacement measurement values of points A and B.Measurements of the displacements are slightly smaller than the size of the hole,which can meet the actual demand for picking.The test of taking seedlings showed that the seedling device had a better effect on the plug seedlings with a moisture content of 35.41%for 40 days.At this time,the success rate of seedling picking was 85.16%,the leaf damage rate was 19.53%,and the substrate damage rate was 1.25%.