Fig. 1. Schematic diagram of on-line detection equipment for fruit internal quality by near infrared diffuse transmission spectroscopy
1: Porximity switch; 2: Coding mask; 3: Chain wheel; 4: Link chain; 5: Optica fiber; 6: Camera bellows; 7: Optical source; 8: Specimen; 9: Terminal PC; 10: PLC control cabinet; 11: Fruit cup; 12: Bionic boot; 13: Grading export; 14: Electromotor; 15: Reducer; 16: Drive sprocket

Fig. 2. Diffuse transmission testing mechanism (a), Gongli placement position (b)

Fig. 3. Establishment of local model and global model and experimental verification scheme

Fig. 4. Average spectra of fruit No.11 in six directions

Fig. 5. Scatter plot of omnidirectional verification

Table 1. Range, standard deviation and average value of SSC content in calibration set and prediction set

Table 2. Local model and local prediction effect in six directions

Table 3. Global model and prediction effect of A3, A4 and A5 directions

Table 4. Global model and prediction effect of A4, A5 and A6 directions

Table 5. Prediction effects of local model and global model on A1, A2 and A3 direction validation sets

Table 6. Prediction effects of local model and global model on A4, A5 and A6 direction validation sets