## 5 Experimental Part
### Diagnosis Results  
During the experiment, vibration signals were acquired as the output. To analyze the frequency characteristics of these signals, the FFT technique was employed. The resulting spectra from this analysis of the tooth belt transmission due to overtension, captured along two axes, are presented in Figure 12a,b.  
Figure 12: The spectral analysis of the output vibration signal by X-axis (**a**) and Y-axis (**b**) for the overtension fault of tooth belt transmission.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Characteristic** & **Value** \\ \hline Measuring ways & 3 axes (XYZ) \\ Measuring range & \(\pm\)4 g \\ Output signal & 0.5–4.5 V \\ Resolution & 4 mg \\ Sensitivity error & \(\pm\)2\% \\ Output refresh rate & 3 ms \\ \hline \hline \end{tabular}
\end{table}
Table 3: Technical specification of DIS QG40N.  
The graphs depict two signal types: a reference signal representing the transmission belt's normal tension (as per factory settings) and a faulty signal indicating overtension caused by a shift in the pulley axes' center. As seen from the reference signal, the nominal frequencies of the HCR gearbox were at the level 50, 100, and 150 Hz.  
The additional noises that manifest between the main frequencies are oscillations of other robot parts that cannot be rigidly fixed, such as cable lines and protective metal structures. The nominal amplitude of the robot structure oscillations should not exceed 0.3 g. Considering the low noise amplitude, the presence of various frequency ranges, and the appearance of additional frequencies when the robot breaks down, which can be used to determine the type of damage, noise can be disregarded for the optimization and simplification of algorithm operations.  
The belt overtension in the tooth belt transmission results in frequent oscillations occurring at the transition points within the robot's operational area. Transition points refer to instances in which the robot changes direction during its movement. Consequently, the tension of the belt affects the robot's performance only at specific locations within its operational space. Furthermore, the spectrum analysis highlights that the frequencies of vibration of the belt overtension are at the level of 200-250 Hz.  
The resulting spectral analysis of the screw transmission, captured along two axes, in the case of the heating fault, is presented in Figure 12(a),b.  
In contrast to the negative consequences of overtension in the belt, damage to the torque transmission worm can result in significant disturbances throughout the entire path of the robot's movement, affecting not only specific points.  
These vibrations can lead to increased stress on the robot's servos, reduced positioning accuracy, and significant wear on other components of the mechanism. Furthermore, an analysis of the vibration spectrum indicated that these vibrations were not cyclic but rather stochastic, making their elimination and reduction of their impact more challenging. One proposed method to mitigate the effects of errors in the robot's design is to increase the torque in the servo drive to prevent potential gear jamming. Also, the frequency vibration diapason is wider than that in the case of the overtension fault and is equal to 200-450 Hz.  
Based on subsequent comparisons of the frequency spectra, it is possible to develop a fuzzy logic algorithm that will determine the extent of damage in the transmission and propose corresponding speed and torque patterns for the robot control system.