Design and optimization of crank-slide type spring-finger cylinder peanut pickup mechanism

This study aims to further reduce the plant leakage and peanut pods loss in the process of peanuts plant picking. The crank-slide type spring-finger cylinder mechanism was selected to determine the swing of spring-finger in different stations. The stress characteristics of peanut plants were also obtained to clarify the movement. The picking station was divided into two stages: shovel picking and pickup picking, according to whether the peanuts left the windrow or not. In the shovel stage, the lowest horizontal height of the spring-finger forward tilt was remained unchanged to effectively increase the shovel picking distance and areas. The theoretical slide of cam was established for the mathematical model. The objective function was used to optimize the mechanism. The maximum shovel shovel-picking distance of the spring-finger on the ground and the minimum radius of the shell were defined as the objective function, while the ground height h₁ of the pickup device, the pushing cut-off angle α, and the height l_MN between the side plate and the ground were as the constraint conditions. An optimization was performed on the initial installation angle, pickup length of spring-finger, crank angle, cylinder radius, top guard dip angle and length of spring-finger of the picking mechanism parameters using NSGA-II. 50 groups of three-dimensional scatter plots were obtained for the parameter solutions and objective functions after 700 generations of evolution. The relationship between the parameters and objective functions of each mechanism was analyzed to verify the solution set. The structure parameters of the mechanism were determined using the thickness of the peanut windrow, the spring-finger picking length, the diameter of the protection plate, and the distance of the shovel picking. ADAMS software was used to establish the mechanism model. The kinematics and dynamics simulation were was carried out to obtain the curve of the spring-finger swing angle and end motion trajectory, which were verified the correctness and feasibility of the mechanism parameters. A comparative simulation showed that the picking length of the spring-finger increased to 135 mm, the diameter of the protection plate decreased to 159 mm, and the picking areas increased by nearly 30% before optimization, which were further verified the rationality of the parameters. Response surface analysis and prototype test in the soil bin demonstrated that the optimal working parameters of the pickup device were obtained as follows: forward speed was 48.0 m/min, rotational speed was 45 r/min, and ground height was 17 mm. Field tests were carried out on the prototype, in order to further verify the adaptability and feasibility of the prototype. Under the two-stage harvesting conditions of peanut plant moisture content of 15%-17%, the peanut plant picking rate was 99.1%, and the fruit loss rate was 1.85%, which were fully meet the production requirements of industry standard NY/T502-2016. The performance of the pickup mechanism was also better than before. This finding can provide theoretical support to optimize the pickup mechanism during the mechanized harvesting of peanuts.