Design and experiment of the rotating shear picking device for green Sichuan peppers

Feeding difficulty and easy clogging have confined the picking efficiency of green Sichuan pepper, leading to the “pile picking”. In this study, a rotating shear picking device was designed for green Sichuan pepper. Firstly, a picking scheme was determined, according to the physical and mechanical properties of prickly ash branches. The specific procedures included the rotating drive, guide feeding, and shearing picking of prickly ash branches. The reciprocating cutters were selected to realize the shear picking. The double-action reciprocating cutters were also designed for their transmission. The structure and motion parameters were determined to meet the requirements of rotary shear picking. Secondly, the simulation model was established to shear the prickly ash branch using ANSYS/LS-DYNA. The orthogonal tests were carried out with the cutting angle of the cutter tooth, the edge angle of the cutter tooth, and the thickness of the cutter tooth as the control factors, while the peak cutting force as the evaluation index. The results showed that the optimal tooth parameters were the cutting angle of 20 °, edge angle of 50°, and tooth thickness of 2.5 mm, with the peak cutting force 3.739 N, which was fully met the requirements of shear picking for the green Sichuan pepper. Finally, the prickly ash branches with fresh green Sichuan pepper were piled in the Sansheng Town, Beibei District, Chongqing, China, in June, 2023. A single-factor experiment was carried out with the branch feeding angle, branch feeding speed, and branch rotational speed as the control factors, while the picking efficiency, net collection rate, and fruit injury rate as the evaluation indices. The branch feeding angle, branch feeding speed, and branch rotation speed were determined in the range of 40°-60°, 20-40 mm/s, and 20-40 r/min, respectively. A three-factor quadratic regression orthogonal combination test was analyzed using Box-Behnken design on the Design-Expert 12. The optimal operating parameters were achieved in the branch feeding angle of 55.035°, the branch feeding speed of 32.04 mm/s, and the branch rotation speed of 29.635 r/min, in the rotating shear picking device for green Sichuan pepper. The performance was predicted as the picking efficiency of 10.78 kg/h, the net collection rate of 95.66%, and the fruit injury rate of 12.06%. The optimized parameters were rounded as the branch feeding angle of 55°, the branch feeding speed of 33.21 mm/s, and the branch rotational speed of 30r/min for the prototype test. Experiment validated that the average picking efficiency of a single person feeding a branch for the green Sichuan pepper was 10.95 kg/h using optimal operating parameters, with an average net collection rate of 95.57%, and an average fruit injury rate of 12.87%. The finding can provide the technical references to develop the picking machines for green Sichuan pepper.