Seedling Standing Mechanism Study And Device Optimization Of Rape Carpet Seedling Mechanical Transplantation

Rape is one of the most important oil crops in China.Rice-rape rotation is the main planting system in this region.Because of the late harvest of rice,direct sowing leads to insufficient growth period of rape.It is necessary to transplant.The domestic rape transplanter has low operating efficiency,which can not adapt to the sticky soil condition of rice stubble.In order to improve the present situation of rape transplanting,a rape carpet seedling transplanter is designed.Its transplanting efficiency can reach 400 plants/(row·min),which is more than 10 times of existing chain-clamped transplanter.However,the root neck of rape is thin and long.Under the condition of high-speed operation,lying phenomenon often occurs,which leads to the problems of low seedling standing rate and high seedling wounded rate.In order to solve the above problems,the seedling standing mechanism was studied.Starting with the morphological and mechanical characteristics of rape carpet seedling,a dynamic model of rape carpet seedling in the planting process was constructed.The movement posture of rape carpet seedling block,the influence factors of seedling standing and action mechanism were studied.The optimization scheme was expounded.In this paper,the main work and main conclusions were as follows:1.The morphological characteristics of rape carpet seedlings with different seedling ages were tested.Normal distribution test and linear fitting method were used to study the distribution-concentration degree and growth rule of morphological characteristic parameters.The fitting relationship between the normal adhesion force,tangential adhesion force,friction coefficient and the moisture content of substrate were established.2.The kinematic model of planting mechanism with planetary elliptic gears was established for rape carpet seedling transplanter.The motion trajectory,velocity and acceleration equations of planting mechanism were obtained.3.Combined with high-speed photography observation test,the reasons of seedling standing or seedling lying after transplanting were investigated.Firstly,the problem of seedling block falling-off in migration stage was explored.Combined with the motion trajectory and acceleration equation of seedling needle,the critical conditions for seedling falling-off were investigated.The action mechanism of holding seedling block by seedling needle was elucidated.The main factors that affected the seedling falling-off and the critical value of each factor were obtained.The accuracy of the theoretical analysis model was proved by high-speed photography test.Secondly,the problem of the unstable landing posture of seedling block in the stage of pushing the seedling block into soil was explored.The dynamic equation of seedling block was established.The variation regulation of seedling posture in contact with soil under different operating parameters was analyzed.The results of theoretical analysis showed that,the main factors which affected the seedling falling-off were the substrate moisture content,the rotation speed of planting mechanism and the longitudinal picking seedling quantity.The main factors affecting the movement of seedling block in the stage of pushing seedling into the soil were the forward velocity of transplanter,the rotation speed of planting mechanism and the longitudinal picking seedling quantity.In order to improve the seedling quality,it is necessary to ensure that the seedling needle can hold the seedling block stably and the seedling fit the seedling needle as far as possible.In addition,we can reduce the forward speed of transplanter,increase the longitudinal picking seedling quantity,and match the rotation speed of planting mechanism at the same time.In view of the main factors affecting the seedling standing quality,the improvement measure which optimize the operating parameters of rape carpet seedling transplanter by response surface test method was proposed.4.The Box-Benhnken central combination test method was used to optimize the transplanting parameters of rape carpet seedling transplanter.An optimization model was established between the vertical angle of rape carpet seedling and the forward speed of transplanter,the row spacing and the longitudinal picking seedling quantity.The optimum parameters were obtained as follows:the longitudinal picking seedling quantity was 15 mm,the forward speed was 0.8 m/s,the row spacing was 16 cm,and the vertical angle was 78.63°.The absolute error was 1.39° with the predicted value.5.In order to obtain stable and reliable seedling standing rate,the auxiliary seedling standing mechanism was designed.The results showed that the auxiliary seedling standing mechanism could adjust the movement posture of rape carpet seedling.It could effectively solve the problem that when rape seedlings were too high,the blades were overweight or the root necks were too thin,the neck of seedling in the migration stage was bent or the seedling drove the whole seedling block to lie down.This study made some contribution to perfect the rape carpet seedling transplanting theory,and provided a theoretical and practical reference for the design and performance improvement of rape carpet seedling transplanter.