Key Technology And Transplanting Mechanism Of Sweet Potato Transplanter With Mechanical Arm

Sweet potato transplanting is an important part of sweet potato production,accounting for approximately 23% of total labor volume.However,the development of mechanical sweet potato transplanting technology in China is slow,and there are few useful transplanting machines and tools.As a result,manual transplantation has been used for a long time,despite its high labor intensity and low transplanting efficiency.Furthermore,the rural labor force structural shortage in recent years has increased market demand for sweet potato transplanting machinery,and sweet potato mechanical transplanting technology has become an important factor limiting the development of the sweet potato industry.In order to solve the problems for the current sweet potato transplanter such as lack of transplanting methods,low operation quality,and missing seedlings in the operation process,a sweet potato transplanter with a mechanical arm is developed in this paper.The machine can control the transplanting track,accomplish various transplanting methods including oblique and horizontal transplanting of potato seedlings,and realize automatic seedling replenishment by monitoring the transplanting condition using a surveillance camera.This research not only provides a usable sweet potato transplanting machine,but also serves as a reference for future innovation,research,and development,or optimization of sweet potato planting machinery.The following are the main research findings.(1)To provide a reference for the establishment of the potato seedling flexible body model,basic physical parameters such as sweet potato seedling size,water content,average density,Poisson's ratio,and elastic modulus are calibrated and measured.Soil particle size distribution,water content,soil density,and soil repose angle are calibrated and measured to provide data for building the discrete element method multi-body dynamics(DEM-MBD)transplanter model and simulating the transplanting process of potato seedlings.(2)Transplanter structure design.The traditional single-degree freedom transplanter is difficult to achieve a variety of sweet potato transplanting trajectories based on agronomic requirements and reference trajectories.A sweet potato transplanter based on a mechanical arm is designed in reference to a multifunctional vegetable transplanting arm.This machine is made up of five major components: the transplanting arm,the seedling replenishment mechanism,the transmission mechanism for potato seedlings,the soil covering mechanism,and the crawler chassis.The transplanting arm and the replenishment mechanism are the most important parts.The sweet potato transplanter's control system is designed,and the system's components are chosen.The sweet potato transplanting control system's timing and sequence are investigated.In the control system,the workflow for the crawler chassis,transplant arm,and potato seedling transmission mechanism is determined.The trapezoidal acceleration/deceleration algorithm is chosen as the stepping motor's control algorithm.The factors influencing motor speed(i.e.,the preset total steps of the stepper motor,the acceleration of the stepper motor in the acceleration stage,the deceleration of the stepper motor in the deceleration stage,and the maximum speed of the motor)are examined,and the MATLAB simulation and motor speed tests are performed.The optimal parameter combination in terms of acceleration and deceleration is obtained by comparing simulation results under different parameter combinations.(3)Research on key technology of transplanting track.The mathematical model of the two-degree freedom mechanical arm is established,and the effects of the simulation period,the length of the seedling picking rod,and the initial rotation angle of the seedling picking claw on the transplanting trajectory are discussed based on the inverse operation of the mechanical arm.The size of the transplanting arm is l ?0.43 m,and the initial rotation angle of the seedling claw is 14.32°???55.93°,as observed in the analysis of the sweet potato transplanting process.In order to achieve the transplanting trajectory of potato seedlings that satisfies the agronomic requirements,the orthogonal test was designed,and the response analysis was performed.Finally,it can be obtained that the optimal length l of the seedling picking rod was 0.43 m and the optimal initial rotation angle of the seedling picking claw ?was 45°.(4)Design and optimization of seedling replenishment target detection algorithm.The detection and control algorithm of the seedling replenishment target based on deep learning is designed,and the missing seedling detection technology based on the improved YOLO algorithm is proposed.By reducing the pyramid level of features,the feed-forward network is optimized,the reuse and fusion of multi-layer features of the network are realized,and the real-time performance of seedling detection is improved.Meanwhile,the attention mechanism is introduced,as a result,the neural network can extract more abundant abstract features and improve the accuracy of seedling target detection.(5)The influence of soil particles on potato seedling transplanting trajectory is clarified using the DEM-MBD coupling method,and the structural parameters of the transplanter are optimized.At first,the Recur Dyn multi-body dynamic model of the transplanter is established.Then,the EDEM soil model is established based on soil particle parameters.Finally,the DEM-MBD coupled simulation is performed.The effects of potato seedling postures in the process of transplanting and transplanter on soil particle disturbance,soil particle on different transplanting trajectories,and soil covering mechanism on different transplanting trajectories of sweet potato were investigated.The results demonstrated that the posture of the flexible body model of potato seedlings satisfies the agronomic requirements of transplanting and that the transplanter could achieve a variety of transplanting trajectories while meeting the design requirements.The transplanter's structural parameters could be further optimized based on the simulation tests: Decreasing the retraction speed of the seedling picking claw could reduce the dust generation without changing the transplanting trajectory;adjusting the installation parameters of the soil covering mechanism,potato seedlings with different transplanting methods can be reasonably planted in the soil ridge;changing the reference trajectory,potato seedlings transplanted by different methods can meet the agronomic requirements.(6)Prototype testing.The sweet potato transplanter prototype is built and tested,and the trajectory test is performed.It can be confirmed that the structural design and the trajectory control algorithm of the mechanical arm are correct.An orthogonal experiment was designed focusing on the main operation factors that affect the transplanting quality of sweet potatoes,i.e.,the operation speed and the seedling feeding exposure length(SFEL).The field experiment demonstrates that the operation speed and the SFEL have an obvious effect on the transplanting effects of sweet potatoes.The optimal parameter combination has a forward speed of 0.2 m/s and an SFEL of 50 mm.The qualified rate of the oblique planting method was 96.8%,the missed planting rate was 2.1%,and the productivity was 40 seeds/min.The qualified rate of the horizontal planting method was 96.9%,the missed planting rate was 2.4%,and the productivity was 40 seeds/min.