Analysis of mechanical properties for tea stem using grey relational analysis coupled with multiple linear regression

Abstract

To improve the picking quality of tea plucking machine, the relationship between mechanical properties of tea stem and their influence factors was studied. Tea variety of Zhongcha 108 was selected as test sample to analyze the grey correlations of stem segment number, stem diameter, stem inter-node distance, moisture content, fracture deflection, moment of inertia, young's modulus, hemicellulose content, cellulose content, lignin content to mechanical properties (bending and shearing strength). Further, multiple parameter optimization and model establishment were performed using partial least squares regression (PLSR), principal component analysis (PCA) + multiple linear regression (MLR), grey relational analysis (GRA) + MLR. The results showed that the cellulose content, bending strength, shearing strength, stem diameter and moment of inertia generally increased with stem segment number. For bending and shearing strength, GRA (0.6) + MLR method was suitable to establish the model. The values of adjusted Rc2 and RMSEC of bending strength were 0.8634 and 3.3264 N, and these values of shearing strength were 0.9730 and 0.2573 N. Besides, adjusted Rp2 values of bending and shearing strength were 0.9443 and 0.9125, RMSEP values were 2.8580 N and 0.7211 N, respectively. The GRA-MLR model is accurate and effective method to investigate the mechanical properties of tea stem for designing a suitable cutting equipment.