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 modelling 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 ciruit can be implemented in small analog electronic chips that allows integrating it in smart materials.

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Abstract-This paper describes a theoretical and experimental study to show how an electrical damper or an electrical dynamic absorber, implemented using an electromagnetic actuator and an accelerometer, can control vibration transmission through a vibration isolator. The electrical damper is realized by feeding back the equipment velocity to the actuator with constant gain. The electrical dynamic absorber is realized by feeding back the equipment acceleration through a second-order low-pass filter. Because it is found that the plant on a flexible base is asymptotically similar to that on a rigid base, the optimal parameters of the control filter are determined analytically, independent of the base dynamics. Experimental results show that the electrical dynamic absorber has a similar performance to the electrical damper. The maximum reduction in transmitted vibration achieved was about 38 dB for both methods. It is also shown that the electrical dynamic absorber is more robust to undesirable dynamics outside the control bandwidth. Another advantage of the electrical dynamic absorber is that it does not require an integrator to transform acceleration into velocity.Index Terms-Acceleration-position feedback (APF), direct velocity feedback (DVFB), electrical damper, electrical dynamic absorber, vibration control.

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This article presents a successful extension of passive R-L shunt damping to piezoelectric ceramic elements working in direct 3-3 mode and a performance comparison to elements working in indirect 3-1 mode. A new circuit topology is implemented to synthesize the very large inductances required by the low inherent piezoelectric device capacitance at relatively low frequencies. This allows for efficient tuning of the R-L circuit to the structure resonance frequency to be damped. The vibration suppression performance of monolithic piezoelectric ceramic actuators and active fiber composites is compared in this study. For this purpose, different actuators are bonded on aluminum cantilever plates. An integrated FE model is implemented for the prediction of structure resonance frequencies, optimum values for electric components, and the resulting vibration suppression performance. The passive structure, bonded active patch, and shunted electrical network are analyzed within the same FE model. Active fiber composite patches working in the direct 3-3 mode show equivalent specific damping performance compared to conventional monolithic 3-1 actuated patches. Issues related to the sensitivity of R-L shunts to variations in environmental and operational conditions are discussed in this study. In short, monolithic actuators operating on the 3-1 piezoelectric effect seem to be the best for use in R-L shunting.

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. However, the contro.! 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 optimization 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 two 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 heuristic switching law would be very difficult.