Low-frequency reverberant sound fields are usually suppressed by means of either adaptive feedforward control
or Helmholtz resonator. In this paper, an electrical impedance is connected to the terminals of an acoustic
loudspeaker, the mechanical dynamics, and hence acoustic response can be made to emulate a sealed acoustic
resonator. No microphone or velocity measurement is required. In some cases, the required electrical circuit is
simply the parallel connection of a capacitor and resistor. Experimental application to a closed acoustic duct
results in 14 dB pressure attenuation of a single acoustic mode.
The scientific community has put significant efforts into the
manufacturing of sensors and actuators made of piezoceramic fibers
with interdigitated electrodes. These allow for increased
conformability, integrability in laminate structures and offer
high coupling factors. They are of particular interest for damping
applications. This paper presents a comparison between
piezoceramic monolithic actuators and Active Fiber Composites
(AFCs) for shunt damping. For this purpose, the different
actuators were bonded on aluminum cantilever plates, respectively
embedded in a glass fiber composite cantilever plate. The
vibration suppression was attained by converting the electric
charge by means of the converse piezoelectric effect and
dissipated through robust resonant shunt circuits. A new circuit
topology was used, which enables efficient damping even with low
piezoelectric capacitance. An integrated FE model was implemented
for prediction of the natural frequencies, the optimum values for
the electric components and the resulting damping performance.
Patches working in the direct 3-3 mode show much better specific
damping performance than the 3-1 actuated patch. The comparison
between monolithic and AFC actuators shows that AFCs fulfill
integrability and performance requirements for the planned damping
This paper presents a new control approach for piezoelectric switching shunt damping. Recently, semi-active controllers have been used to switch piezoelectric materials in order to damp vibration. These switching shunt circuits allow a small implementation and require only little power supply. However, the control laws to switch these shunts are derived heuristically and therefore it remains unclear, if a better control law for a given shunt topology exists. We present a new control approach based on the Hybrid System Framework. This allows the modelling of the switched composite system as a hybrid system. Once the hybrid system description is obtained, a receding horizon optimal control problem can be solved in order to get the optimal switching sequence. As the computation time to solve this optimisation problem is too long for real-time applications, we will show that the problem can be solved off-line and the solution stored in a look-up table. This allows a real-time implementation of the switch controller. Moreover, control rules can be derived from this look-up table, and we will demonstrate that in some situations the controllers proposed in previous papers generate near optimal switching. In this paper, we will investigate several shunt topologies with switches and compare the performance between the heuristically derived control laws and the optimal new control laws. Simulations and experiments show the improvement with the new controllers. This is very promising, since this new control approach can be applied for more complex shunt circuits with many switches, where the derivation of a switching law would be very difficult.
This paper presents an application of resonant piezoelectric shunt
damping to reduce sound radiated by a clamped square aluminium
plate. The plate is mounted in a duct system and excited by plane
waves. The sound radiation of the plate is evaluated by measuring
the volume velocity and radiated sound power. Results show a
significant reduction of the radiated sound power, if the resonant
shunt circuit is tuned around the first natural frequency of the
plate. Additionally, the performance of the online-tuned resonant
shunt for varying operating conditions is compared with a not
online-tuned shunt. It is shown that the online-tuned shunt keeps
optimal noise reduction for varying temperature.
This paper presents a new adaptation technique for R-L shunted piezoelectric patches (PZT) bonded on mechanical structures for single mode vibration suppression. For the implementation of the adaptive R-L shunt circuit, a new variable inductor circuit controlled by transistors is developed. Additionally, a new modeling method for shunted PZTs based on equivalent transformer and gyrator circuits is presented. This leads to a comprehensive model that simplifies the search for optimal shunt circuits. Furthermore, it allows simulating the system consisting of the structure, the PZT patch and a complex transistor or other non-linear shunts on standard electronic simulators like PSpice or Saber. Damping performance of R-L shunted piezoelectric devices is very sensitive to environmental factors changing the circuit’s resonance frequency corresponding to the damped vibration mode. This requires fast adaptive tuning of the R-L shunted circuit, which is implemented using a new adaptation technique. The tuning direction of this adaptation law is obtained by detecting the phase shift between the velocity of the mechanical structure and the current in the shunt circuit. As the exact value of the phase for this technique is not required, one can reduce the adaptation problem to multiplication and integration of current and velocity. The performance of the presented new adaptive R-L shunt is compared with the common adaptation law based on minimizing the RMS value of the strain and then experimentally verified. The adaptive R-L shunt, which minimizes the phase-shift, can tune to the optimal parameters within seconds, but it needs an additional velocity sensor. In contrast, the R-L shunt minimizing the RMS value works without extra sensors, but needs some minutes to tune optimally. The new adaptive R-L shunt circuit can be implemented in small analog electronic chips that allows integrating it in smart materials.