The impact of hail ice cubes on composite structures (such as solar cells) causes actual defects. This article presents a series of tests, in which solar cell modules were exposed to hail simulation testbed balls, allowing to assess the following: the impact energy, which causes the major defects in solar cells; the formed micro-cracks in the structure of solar cells, resulting in the loss of power generated by a solar cell; and the solar cell parameters necessary for modelling. In addition, this article presents a digital analysis of hail simulation. Information received from the digital analysis was used to optimize the structure of solar cells in order to improve its resistance properties. The aim of this study was to present a simple method for experimental hail simulation. The proposed hail impact estimation method can be successfully applied to study the influence of the mechanical–dynamic impact of photovoltaic (PV) modules of different structures on the technical characteristics of these modules (structural stability, power generation, etc.). The study showed that PV modules are subjected to an irreversible effect of the excitation force (i.e., micro-cracking) and it can reduce the generated power by 2.33% to 4.83%.

In the paper, the spread of intensity of linear positioning table system vibrations is examined and an analysis of their parameters upon applying the theory of covariance functions is carried out. For the investigation, two linear positioning tables were chosen; for them, different lubricants were used: universal lubricant Loctite 8103 and lubricant Braycote 601EF for working in vacuum. The results of measurements of the vibration intensity in four fixed points upon varying the speed of the carriage were recorded on the time scale in form of arrays (matrices). The estimates of cross-covariance functions of the arrays of results of measurements of the digital vibration intensity were calculated. The estimates of auto-covariance functions of single arrays upon changing the quantization interval on the time scale were calculated too. For the calculations, the software developed upon using Matlab7 package of procedures was applied.

Spherical lenses were used in conventional industry for a long time, but new types of lenses have been created during the innovation processes. One type of lenses is aspherical. Two main parameters describing the quality of aspherical lenses are accuracy of the form shape and surface roughness. These parameters can be obtained after the last operation - polishing. The technical parameters that have the biggest influence on the form shape and surface roughness were investigated in this experiment, and optimal technical parameters for the polishing process were established. Melted quartz "UVFS" was used in this research, the investigations were carried out according to full factorial design. The five-axis CNC machine Schneider SCPA100 was used for polishing and the profilometer Nanoscan 855 was used for measurements. After the analysis of the results, it was found out that the speed of rotation and penetration depth are the most important factors in the polishing process. To obtain the best shape, it is necessary to use the smallest chosen values of rotation speed and penetration depth, whereas the parameters for surface roughness polishing change conversely. The smallest value of surface roughness R-z was 0.06 mu m, and shape deviation was 2.6 mu m. Optimal polishing parameters for the best quality of aspherical lenses are provided.

In the paper, the optical system of a precise bar length measuring comparator is analysed. The requirements for such a system are determined and systematized. The impact of the resolution, signal discretization frequency, image blurring, bar edge measurement indeterminacy and camera noise on measuring the bar width and establishing the bar position is discussed upon. Various algorithms have been analysed and finally a bar edge identification algorithm oriented to the scale calibration accuracy and the high processing speed was proposed. In the end of the paper, conclusions are provided.