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.

Two-stage peanut harvesting is one of the most popular mechanized ways in China. Among them, the commonly used pickup device can be equipped with the spring teeth cylinder in large and medium-sized picking and harvesting machines. There are some challenges, including plant throwing, stacking, missing picking, and fruit falling damage. At the same time, the spring teeth can circularly scratch into and out of the ground during the operation of the pickup device, leading to dust. The efficiency of peanut picking and harvesting can be seriously restricted to increase the loss of pods falling during harvesting. The action of the pickup time on the ground has also exacerbated the dust pollution. This study aims to combine the structure of the toothed drum mechanism in the new type of pickup device with the shovel teeth and double-cylinders for bunch upright peanuts. According to the upright peanut plant shape, strip laying, motion posture and dynamics during picking, the peanut pickup device consisted of shovel teeth, a pushing cylinder, and a picking cylinder (referred to as a double cylinder). The better performance of picking peanuts was achieved in the sequential coordination with four beats of shovel pluck pick delivery. The traditional single-toothed drum pickup device was replaced in this case. The shovel tooth structure of the circular arc working surface was designed to determine the range of shovel tooth radius using geometric relationships. The structure of pushing teeth and picking teeth was designed with a backward inclination angle. The structure and rotation radius of two rollers were determined to design the semi-enclosed protective plate structure with the specific parameters. The motion parameters of the unit were obtained to simulate the range of picking speed ratio after ADAMS simulation. A prototype of a combined peanut pickup device was conducted to develop the shovel teeth, picking cylinder, pushing cylinder, and half guard board in field performance tests. According to Box Behnken central combination design, an orthogonal experiment was conducted on the peanut plant picking rate and peanut pod drop rate as experimental indicators, while the unit forward speed, picking speed ratio, and shovel teeth radius as experimental factors. The test results indicate that the shovel teeth double cylinder combined peanut pickup device operated smoothly, where there were no plant throwing, pile up, and dust from bullet teeth during peanut picking; The mean value of picking rate of peanut plant was 99.22%, and the mean value of pod loss rate was 1.84%, when the forward speed was 1.2 m/s, the picking speed ratio was 1.2, and the shovel teeth radius was 498 mm under field experimental conditions. The findings fully met the requirements for peanut picking.