**5.2 Verification of piezoelectric active vibration suppression performance**

After completing the construction of the experimental system, the active control experiment was carried out in the piezoelectric suppression system. First, the system transmissibility curve is measured. The transmissibility curve measures the vibration transfer characteristics from the perspective of the frequency domain, which is a very important criterion. **Figure 15** shows the comparison curves of the system's transmissibility under different control methods. The blue line is the open-loop transmissibility curve of the system, which is not actively controlled and adopts pure passive vibration suppression. In the passive situation, the system has a peak near 30 Hz, which is the resonance peak, which means that the vibration amplitude will increase sharply here, and the vibration suppression effect is poor. At high frequencies, the passive transmissibility curve decays rapidly, which can be considered to have a suppressive effect. When IFF is used for piezoelectric active control, the resonance peak of the system at the natural frequency is attenuated to a certain extent, but the overall attenuation is not large, especially at high frequencies, the attenuation performance cannot be improved. When the AHC is used, the natural frequency of the system is moved forward, the resonance peak at the original natural frequency is greatly attenuated, and better attenuation is also reflected at high frequencies, which can effectively broaden the vibration isolation bandwidth. The specific values of the transmissibility curves under different control modes are shown in **Table 2**.


#### **Table 2.**

*The specific value of the experimental transmissibility curve.*

**Figure 15.** *Transmissibility curves under passive, IFF, and AHC.*

The time-domain vibration signal can reflect the control effect more intuitively, but more details in the frequency domain cannot be revealed. **Figure 16a** shows the time domain acceleration signal when the piezoelectric vibration suppression system is without active control. The red line is the basic excitation signal, the blue line is the load response signal, and the load response signal is the final control target. It can be found that the piezoelectric system can also achieve a certain vibration suppression effect through passive vibration suppression, but it is generally difficult to meet the application requirements. **Figure 16b** shows the time domain information of the piezoelectric vibration suppression system under the AHC. Compared with the pure passive vibration suppression, after the AHC is turned on, the vibration signal at the load end is greatly attenuated. In the piezoelectric vibration suppression system, the AHC method can greatly improve the vibration suppression performance.

**Figure 17** shows the self-power spectrum (PSD) curves with different control methods. In the case of passive vibration suppression (without control), the vibration energy of the load platform at the natural frequency is increased, which means that the vibration signal at the natural frequency is amplified. When AHC is used, the energy around the natural frequency is significantly suppressed because the piezoelectric actuator dissipates part of the energy.

*Active Vibration Suppression Based on Piezoelectric Actuator DOI: http://dx.doi.org/10.5772/intechopen.103725*

**Figure 16.** *Time domain amplitude comparison curve: (a) without AHC; (b) with AHC.*

**Figure 17.** *Self-power spectral density comparison curve: (a) without AHC; (b) with AHC.*

**Figure 18.**

*One-third octave comparison curve: (a) without AHC; (b) with AHC.*

**Figure 18** shows one-third of octave curves with different control methods. When the piezoelectric vibration suppression system adopts passive vibration suppression (without control), the signal of the load platform near the natural frequency is significantly improved, which is also consistent with the self-power spectrum in **Figure 17**. When the AHC is turned on, the signal of the load platform near the natural frequency is attenuated, and the energy is dissipated by the piezoelectric actuator. This also shows that the piezoelectric AHC has a better inhibitory effect on the signal at the natural frequency.
