# A Review on Vibration Control Using Piezoelectric Shunt Circuits
## 3 Experimental Studies
As shunt circuits do not occupy much physical space, such additional peaks represent a net gain based on the performance of the plate silencer. [PERSON] et al. [114] presented the results of a series of experiments that studied the effect of the fluid layer height, viscosity, and free surface waves on the vibration damping of a thin rectangular plate interacting with a fluid. The suppression technique is based on the shunt circuit connected to the piezoelectric elements. The possibility of using the previously proposed mathematical formulation, an approach for calculating the optimal values of the parameters of an RL-circuit in systems with hydrodynamic dissipation, is estimated. The experimental results presented confirm its reliability. It has been demonstrated that the efficiency of vibration damping of a single plate structure changes insignificantly with increasing height of the fluid layer except for some intervals. [PERSON] et al. [86] presented a novel method of realizing unsymmetrical bipolar voltage with the synchronized switching damping (SSD) method, based on a negative capacitance shunt circuit for vibration control is proposed for improvement of the control performance in this study. A resistance and a diode that are added to construct a negative capacitance circuit are used to realize an unsymmetrical bipolar voltage. Compared with unsymmetrical SSDV (SSD based on voltage source circuit), the circuit of unsymmetrical SSDNC (SSD based on negative capacitance) proposed in this paper is much simpler and easier to execute. Experiments and simulations are carried out to verify the designed circuit and the theoretical results of the switched voltage and stability conditions. [PERSON] et al. [115] proposed a shunt damping acoustic black hole (ABH) composite beam by pasting shunt damping instead of ordinary damping on the ABH tip. The energy method is employed to solve the vibration equation of the ABH beam. The admissible function is the Mexican hat wavelet. The proposed method is verified by the finite element method. A vibration experiment of the ABH beam combined with shunt damping is implemented to verify the present method's feasibility and the shunt damping effect. The proposed shunt damping-ABH composite beam could improve the suppression ability in both the low and high-frequency ranges. [PERSON] et al. [116] proposed three piezoelectric shunt damping (PSD) implementations: passive synchronized switch damping on inductor (SSDI), semi-active SSDI, and active synchronized switch damping on voltage source (SSDV) for a single-panel structure mounted on a rigid-frame casing. The nine macro fiber composite (MRC) elements were mounted on the plate based on preliminary simulations in FreeFEM. Then, the theoretical results were validated by an identification experiment. The main research concentrates on the sound pressure level (SPL) and structural vibrations reduction for selected frequencies. The active method provided the highest reduction in vibration up to 5.5 dB for the maximal possible loudspeaker level without overdrive and up to 7.5 dB for lower excitation levels. [PERSON] et al. [117] proposed a novel ring-shaped piezoelectric damper. Meanwhile, vibration control on a single-DOF system is performed by using it. This damper, called a vibration ring, may be used for vibration control of rotating machinery. It has the appearance of a metal ring and can be installed between the supporting structure and the house bearing. Damping is achieved using piezoelectric stack connected with series resonant RL shunts as fundamental element. In order to analyze and demonstrate the performance of such damper, the electromechanical coupling equation of this damper is firstly derived. Next, the force transmissibility between simplified rotor/shaft and supporting structure is obtained from the foregoing equation in Laplace form. Then, the optimum inductance value of shunt circuit is determined. Finally, the performance of vibration ring is demonstrated through simulations and experiment based on a test rig.