## 3 Results and Discussion
The analysis of the graphical relationships (Figure 6), obtained as a result of experimental tests of the prototype device for assessing the suitability of potato varieties and hybrids for mechanized harvesting reveals that the most significant force impacts (F = 20.3 N) on the potato tubers occur when they are descending from the finger-type slide on the working surface of the separating drum at a time interval of 9-11 s.  
These results should be explained by the fact that during the movement of the data logger along the separating surfaces of the prototype device for assessing varieties and hybrids for mechanized harvesting, regardless of the progressive speed of the finger-type slide, there is a vertical lift of the conveyer belt made by the intensifier of separation. Its function is to provide additional torque to direct the tubers into the slot and increase the time of its interaction with the separating surface. These facts increase the vertical component of the separation force between the working elements of the finger-type slide and the potato tubers, resulting in a higher force impact on the tubers and increased damage. Analyzing the results of the experimental tests of the force impact on the potato tubers by working units of the prototype device for assessing the suitability of varieties and hybrids for mechanized harvesting, it is necessary to note that the measured value varies within a wide range depending on the location of the tubers on a functioning unit (coefficient of variation--v = 26.9%, standard deviation--\(\sigma\) = 5.52). The time interval of 8.5 to 9.5 s accounts for the highest force action (of up to 22 N) on the potato tuber (Figure 6), here the mean square deviation and the variation coefficient are \(\sigma\) = 5.7 and \(\
u\) = 24.8%, respectively. Figure 6: Force action of the work surface of the pin hummock on potato tuber. As a result of the variance analysis of the two-factor experiment, the main statistical characteristics of the experiment were obtained:  
* Variance of the experimental error, \(S_{y}^{2}=7\);
* Standard error \(S_{kk}=1.16\);
* Error variance, \(S_{kk}^{2}=1.36\);
* Dispersion of reproducibility, \(S_{repr}^{2}=16.33\);
* Dispersion of inadequacy, \(S_{inadap}^{2}=1.368\);
* Tabular value of the tT- criterion, \(t_{T0,05}=4.02\);
* Value of the tabular t-criterion, \(t_{0,05}=3.66\);
* Tabular value of the Fisher criterion at 5% significance level for the resulting equation, \(F_{T}=5.32\);
* The calculated value of the Fisher criterion at the 5% significance level for the resulting equation, \(F=2.2\). The highest force impact (up to 22 N) on the potato tubers occurs in the time interval from 8.5 to 9.5 s (Figure 6), with a standard deviation and coefficient of variation of \(\sigma=5.7\) and \(\
u=24.8\%\), respectively. Thus, the comparative analysis of the force impact of separating surfaces on the potato tubers (Figure 6) reveals that working units more intensively affect commercial yield, ranging between 12 N and 14 N.  
Spectral images of different lesion types detected on dirty potatoes of both varieties recorded the fluorescence spectra shown in Figures 7-11. Spectral image processing includes several steps: image processing, segmentation, normalization of selected objects in the image, and recognition. PCA application to the potato tubers results in visible differences only at 300 nm excitation (Figure 8). The normalization procedure increases the variance described by the first two components, PC1 and PC2, from 51.4% to 63.0%. However, this result does not coincide with the correlation analysis, where data normalization increased the correlation coefficients between the reference potato tubers and the mechanically damaged ones.