Investigation on the Bending Behavior of Tea Stalks Based on Non-Prismatic Beam with Virtual Internodes

Wenchao Wu,Zehui Jiang,Yongguang Hu

doi:10.3390/agriculture12030370

Abstract

The study aims to fully explicate the bending behavior of tea stalks under the condition of large deflection, which is crucial to improve the working performance of mechanized harvesting equipment. The mechanical model of the stalk was assumed to be a non-prismatic beam with virtual internodes that could differ from actual internodes. With the model, the stalk can be freely divided into multiple virtual internodes, whose flexural rigidities can be determined by solving an optimization problem, and deflection curves can be predicted after determining the positions of virtual nodes under given loads. Moreover, a novel method was proposed to obtain the deflection curve of the stalk based on the techniques of binocular vision and non-uniform rational B-spline (NURBS) curve fitting. The results show that R-squared values of fitted 2nd-degree NURBS curves of bending shape of tea stalks range from 0.9576 to 0.9964, with an average of 0.9797. The results indicate that flexural rigidity decreases from the bottom to the top of the tea stalk, and the deflection curve could be predicted more precisely with the model of piecewise flexural rigidities than that of average flexural rigidity. The study could be applied to the optimization design of the cutter and adaptive adjustment techniques of operational parameters for tea picking machines.

Highlights

Labor shortage and low mechanization have become huge challenges for tea harvest in China [1–3], it is urgent to develop efficient and reliable mechanized tea picking technology.Commonly used tea picking machines [4] harvest tea shoots with the cutter composed of double reciprocating multi-teeth blades like combine-harvesters, but the machine usually results in poor quality of harvested tea shoots due to broken leaves and bad cut surface on the stem
We focused on investigating the bending behavior of individual tea stalk to provide a fundamental basis for the optimization design of the cutter and adaptive adjustment techniques of the operational parameters for tea picking machines
The study focused on the bending behavior of tea stalk under the condition of large deflection

Summary

Introduction

Used tea picking machines [4] harvest tea shoots with the cutter composed of double reciprocating multi-teeth blades like combine-harvesters, but the machine usually results in poor quality of harvested tea shoots due to broken leaves and bad cut surface on the stem. It is necessary to analyze interaction between the tea stalk and the cutter for understanding what determines the working performance of the machine. The tea stalk is first bended and clamped and cut off by the teeth of the blades. The bending shape of the stalk and the cut position on the stalk are vital factors that together determine whether the harvested tea shoot can satisfy the processing needs. It is significant to study the bending behavior of tea stalks to design or optimize the cutter and determine operational parameters such as cutting height, forward speed, and cutting frequency for the machine

Methods

Findings

Discussion

Conclusion