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Active Vibration Control via Shunt Damping


D. Niederberger

Engineered Adaptive Structures IV Conference, Banff, Canada., Center for Acoustics and Vibration, College of Engineering, The Pennsylvania State University.

This presentation gives an overview of adaptive piezoelectric shunt damping. Piezoelectric shunt damping is a popular technique for vibration suppression in smart structures. Techniques encompassed in this broad description are characterized by the connection of electrical impedance to a structurally bonded piezoelectric transducer. Such methods do not require an external sensor, may guarantee stability of the shunted system and only need low or even no power. Piezoelectric shunt impedance designs have included resistors, inductive networks, switched networks, negative capacitors and active impedances. Resonant shunt impedances consisting of resistors, capacitors, and inductors are simple to design and offer considerable effective modal damping. However, the performance of resonant shunt circuits is known to be highly sensitive to variations in the transducer capacitance and structural resonance frequencies. This presentation introduces a new technique for the online tuning of multi-mode resonant piezoelectric shunt damping circuits. We show in simulations and experiments that minimizing the relative phase difference between a reference signal related to vibration and the shunt current, results in optimal tuning of the circuit parameters. This technique is faster to converge and displays significantly less mis-adjustment at the minimum than former online adaptation techniques. Another promising shunt technique is the switching shunt circuit. It allows a small implementation and requires only little power. 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 modeling 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. This presentation investigates two shunt topologies with switches and compares 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.

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