## 4 Experimental Review
### Electromechanical Response Characterization Under Controlled Base Excitation  
The other evaluation was conducted using the constant excitation technique, where a vibrating platform was used for cantilever excitation. In this configuration, the piezoelectric cantilever operated as a sensor, contrasting with its role as an actuator in the initial test setup. Each cantilever was attached to the shaker through a clamping mechanism, and excitation signals were managed using a 33220A function generator (Keysight, Santa Clara, CA, USA). To improve the accuracy of the readings, the output signal was boosted using a VPA2100 MN voltage amplifier (HQ Power, Gavere, Belgium). A KS-93 single-axis accelerometer, with a 5 mV/(m/s\({}^{2}\)) sensitivity rating, was used to monitor excitation levels. The output from the accelerometer, laser control unit, and piezoelectric sensors was collected using a 4224 USB oscilloscope and processed on a computer via Picoscope software (Picoscope 6, Version 6.14). The complete experimental setup is illustrated in Figure 15.  
The outcomes obtained from this second setup are displayed in Figure 16, comparing the excitation acceleration of the vibrating plate with the voltage signals produced by cantilevers, which were operating under open-circuit conditions.  
Analysis of the data reveals that the cantilever with the optimized geometry demonstrated approximately 30% greater efficiency, generating a 1.4 V signal, whereas the standard uniform cantilever reached only 1.07 V. The excitation acceleration remained constant at 14 m/s\({}^{2}\) for both configurations.  
Figure 15: Scheme of the excitation experimental setup.  
Experimental measurements and statistical analysis of the voltage generated by uniformly were performed. During the experiment, the unimorph cantilever base of optimal thickness and constant thickness was excited at the first resonance frequency and the generated voltage was measured. The electrical load was 35 k\(\Omega\). Before each measurement, the unimorph cantilever wires were reconnected to the digital oscilloscope, and the unimorph cantilever wires were reattached to the vibrational plate. This was repeated 8 times. The measurement results are presented in Table 1.  
At first, the main statistical parameters for both unimorph cantilevers were calculated. Results are presented in Table 2.  
Because such processes generally have Gaussian distribution, the use of the 2 \(\times\)\(\sigma\) rule is possible and with 95% probability, the optimal thickness unimorph will generate voltage in the interval 1.27 V-1.53 V. For the constant thickness unimorph this interval is 1.03 V-1.11 V.  
The experimental investigation effectively confirmed the accuracy of the numerical eigenfrequency predictions and demonstrated the advantages of optimized cantilever geometry. The laser-based multipath interferometry system enabled high-resolution frequency analysis without interfering with cantilever dynamics. The optimized design not only matched the target eigenfrequency within a 5% margin but also exhibited approximately 30% higher electrical response under first resonant excitation. These results validate  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **Mean, V** & **Variance** & **Standard Deviation** \\ \hline Optimal thickness unimorph & 1.40 & \(0.44\times 10^{-2}\) & \(0.66\times 10^{-1}\) \\ Constant thickness unimorph & 1.07 & \(0.5\times 10^{-3}\) & \(0.22\times 10^{-1}\) \\ \hline \hline \end{tabular}
\end{table}
Table 2: Main statistical parameters of the unimorph cantilevers generated voltage.  
Figure 16: Electrical potential characteristics by excitation experiment: red—optimal shape cantilever signal, V; blue—uniform shape cantilever signal, V; black—amplitude of shaker excitation, mm.  
the reliability of the numerical model and highlight the improved performance of the optimized cantilever in vibration energy harvesting applications.