Design and experiment of the stepped transportation tea harvesting and grading integrated machine

Here an integrated machine was designed with the stepped transportation tea harvesting and grading, in order to improve the quality and efficiency of mechanized harvesting for the high-quality tea. The integrated machine utilizes the length differences of different types of tea bud of Longjing 43 to achieve tea bud grading while efficiently harvesting. The reciprocating cutting blades were utilized to pick the tea bud. Multiple sets of dividing parts and belt groups were combined to achieve the clamping and directional transportation of harvested tea bud. Two sets were selected from the stepped belt groups, and the length difference among the different types of tea bud was used to classify the tea bud during transportation. The distance between the blades and belts was used to separate the tea bud unsuitable for picking. Firstly, the theoretical analysis and preliminary experiments were carried out to determine the factors influencing the integrity rate of picking new tea bud and the grading success rate. These factors were the reciprocating frequency of the blades, the longitudinal distance of the blades, the driving wheel speed of the first leaf feeding mechanism belt, and the height difference between the belts of the leaf feeding mechanism, respectively. Secondly, a Box Behnken experiment with four factors and three levels was conducted using Design Expert software. A systematic investigation was implemented to evaluate the interactive effects of various factors on the integrity rate of picking new tea bud and grading success rate of the machine. Regression models were established with the integrity rate of picking new tea bud and grading success rate of the machine as the response values. The influencing factors on the integrity rate of picking new tea bud were the blade reciprocating frequency, the driving wheel speed of the first leaf feeding mechanism belt, and the longitudinal distance of the blades. There was an interactive effect between the reciprocating frequency of the blade and the longitudinal distance of the blade. The influencing factors on the grading success rate were the blade longitudinal distance, as well as the height difference between the belt of the leaf feeding mechanism. Furthermore, these parameters were optimized to maximize the integrity rate of picking new tea bud and grading success rate of the integrated machine. An optimal combination was achieved, where the blade reciprocating frequency was 1600 times/min, the blade longitudinal distance was 12.5 mm, the driving wheel speed of the first leaf feeding mechanism belt was 800 r/min, and the height difference between the belts of the leaf feeding mechanism was 31.5 mm. Finally, these parameters were optimized to prepare a prototype for the picking experiments. As such, the stepped transportation tea harvesting and grading integrated machine can be expected to efficiently realize the picking and grading tea bud. The integrity rate of picking new tea bud and grading success rate of the machine reached 77.9% and 88.7%, respectively. The error between the experimental and the prediction value was less than 5%, indicating the reliable optimization. This finding can provide the theoretical basis and technical support to improve the level of mechanized tea harvesting and grading.