# Investigation of Roller-Tape Contact Pair Used in Precision Mechatronic System
## 3 Experimental Research of the Tape-Displacement Measuring System  
Tape displacement measuring systems is a major part of the raster generation and control system, which directly affect the accuracy of the scales being produced. A bench was developed for the study of dynamic processes of the tape displacement measuring system. Maintaining constant velocity is very important while working. For the purpose of this experiment, fluctuating velocity of the tape point was measured as absolute vibro-velocity. Three parameters were measured when determining dynamic properties of the research object (Figure 4b): 1--displacement of the steel tape in the vertical direction Z (Figure 4c); 2--velocity of the steel tape in the longitudinal direction Y (Figure 4a); 3--displacement of the tape-angle transducer contact point was derived from angle sensor results. Capacitive displacement sensors CS02 were used to measure vertical displacements, measuring displacements at two points (A and B) of the tape (Figure 4c). Point A was at the raster generation point (there was an additional support under the tape) and point B--on the tape between supports. Figure 4a presents the image of the measurement of absolute steel tape vibrations (variation of point velocity) in longitudinal direction Y.  
Bruel & Kjaer vibration meters were used to measure vibration parameters and Micro-Epsilon meters were used to measure displacement. Displacement meters (Figure 5a,b): a capacitive displacement sensors CS02; b controller DT6220 and demodulator DL6220.Vibration meters (Figure 5c,d): c portable metering result processing, storage and control equipment 3660-D; d triaxial accelerometers 4506. Figure 6 illustrates the block diagram of the research equipment and its relation to the research object (tape displacement measurement system). The obtained measurement results were processed using the software package Origin, also calculating statistical parameters:  
arithmetic average:  
\[\overline{x}=\frac{1}{n}\sum_{i=1}^{n}x_{i} \tag{1}\]  
standard deviation:  
\[S_{D}=\sqrt{\frac{1}{n-1}\sum_{i=1}^{n}\left(x_{i}-\overline{x}\right)^{2}} \tag{2}\]  
Figure 3: Parametric function of two realizations 1, 2 of the tape displacements using angle measuring system and approximation of 6 realizations means, 3 graphs. range  
\[x_{range}=x_{max}-x_{min} \tag{3}\]  
where \(n\) is the number of measurement results, xi-measurement result \(i\). Figure 4: Measurement of vertical tape point displacements (**a**),longitudinal tape (**b**) velocity and displacement of the steel tape in the vertical direction Z (**c**). Figure 5: Instruments for measuring and analyzing vibration and displacement parameters: capacitive displacement sensor CS02 (**a**) with controller DT6220, demodulator DL6220 ad power source (**b**); triaxial accelerometer 4506 (**c**); portable metering result processing, storage and control equipment 3660-D with DELL computer (**d**). The received measurement results are presented in Figures 7-9. Figure 7 illustrates results of vertical displacements of the two points (A and B) (also see Figure 4c) of the tape. Figure 7a presents displacement results of points A and B (also see Figure 4c) in operation (a generated raster distance of 500 mm), and Figure 7b,c illustrates the curve and mean of three realizations, additionally presenting histograms of the mean. Table 1 presents statistical parameters of three realizations of the displacement (A1, A2 and A3 and B1, B2 and B3) of points A and B (also see Figure 4c). The analysis of the results presented in Figure 7 and Table 1 allowed determining that the value of the displacement of tape point A in vertical direction varies by about 37.5 um, and the value of the displacement of tape point B varies by about 53.5 um. The value of displacement of point B is greater because the lower tape part of point B is not supported. The frequency of tape oscillations is very low (0.04 Hz), and oscillations of such frequency are likely to have been caused by deviations in the shape of the tape.