References Conclusion and outlooks • The efficiency of the switch is critical for high damping performance • The energy required for the switch is harvested from an additional piezo • Minima and maxima detection obtained by a low pass filter Piezo Sensor Energy Harvesting Switch Piezo Actuator Max Min detection Testing and results Introduction and objectives Working principle of piezoelectric shunt damping Stiffness compromise in the design for damping Analytical modeling Piezoelectric vibration damping using autonomous switching shunt T. Delpero, A. Bergamini, P. Ermanni Centre of Structure Technologies, ETH Zurich, CH-8092 Zurich, http://www.structures.ethz.ch • Completely autonomous switching shunt with high damping performance and robust to changes in natural frequencies of the structure has been developed • Very good agreement between analytical prediction and experimental values for the loss factor • Importance of the concurrent design of stiffness and damping 1. Delpero T., Bergamini A., Ermanni P., “Shunted Piezoelectric Damping: Identification of the Electromechanical Parameters and Prediction of the Dissipated Energy”, Proc. ICAST 2011, 028 2. Delpero T., Di Lillo L., Bergamini A., Ermanni P., “Piezoelectric Vibration Damping Using Autonomous Synchronized Switching On Inductance”, Proc. SMASIS 2011, 5239 Self-powered SSDI enhanced by energy harvesting module Objectives • To date, damping treatments are considered as an add-on to structures that are designed according to well established procedures based on conventional (i.e. non- adaptive) materials. • This project will include the exploitation of damping treatments, such as shunted piezoelectric elements, as an additional variable in the design process. Voltage Displacement -γV M V M SSDS SSDI SSDV SS V M + V s -γV M - V s Resonant • In the SSDI, the voltage on the piezo is in anti-phase with the velocity, so that the resulting force counteracts the vibrations of the structure • The dissipated energy is proportional to 1+ 1− . The quality factor of the switch γ is crucial for achieving high damping performance. Shaker Specimen Force sensor Laser PC with Labview PXI Card (response) PXI Card (stimulus) Laser controller Force Sensor Laser Amplifier Shaker Shunt Oscilloscope -25 -20 -15 -10 -5 0 38 40 42 44 46 48 50 52 Displacement / Force [dB] Frequency [Hz] Open Circuit Self-powered SSDI Resonant Shunt Aluminum plate [200 x 60 x 2 mm] 2 piezo patches [100 x 30 x .2 mm] -12.5 dB 77% amplitude reduction 0% 2% 4% 6% 8% 0 0.003 0.006 0.009 0.012 Loss factor η Kij2 SSDI γ=.72 Resonant Shunt SSDI γ=.33 SSDI γ=.60 A B C B’ Shunting technique SSD State Switching SSDS Synchronized Switching Damping on Short Circuit SSDI Synchronized Switching Damping on Inductance Resonant Shunt Loss factor K ij 2 4 K ij 2 4 1+ 1− K ij 2 K ij 2 Loss factor prediction using an energy approach • Each shunting technique corresponds to a different hysteresis in the Voltage- Displacement diagram. • The area of the hysteresis corresponds to the dissipated energy Voltage in anti-phase with velocity Self-powered implementation Experimental assembly Vibration reduction measurements The relationship between the damping performance η, the generalized coupling coefficient Kij and strain energies U, suggest the need for a compromise between the stiffness of the structure and the piezoelectric: K ij 2 = U piezo U structure k ij 2 1−k ij 2 The concurrent equal consideration of damping properties, geometry and material in the design phase is expected to allow for better design solution. K ij = Electromechanical coupling coefficient Structure Mechanical Energy Piezoelectric Transducer Electrical Energy Electrical circuit Energy Dissipated Loss factor – coupling coefficient diagram