Traditional solutions to vibration problems often employ viscoelastic materials which can be heavy, temperature-sensitive
and bulky. Active solutions can provide useful damping but are often complex and expensive. This paper
outlines a passive piezoelectric damping system with an adaptive controller capable of not only providing useful
damping levels, but of modifying the components so as to change the circuit resonant frequency and thereby the damping
effort. Experiments on simple beams and more realistic structures are described and the potential benefits and power
requirements of such a system discussed. Increases in loss factor up to a factor of 10 and a high level of tuning
repeatability were seen.
A comparative study has been made to explore the potential benefits of newly available single-crystal ferroelectric materials
when used in a practical device, in this case an ultrasonic micro-motor. This type of micro-motor exhibits exceptional power-to-weight characteristics, which could be exploited beneficially, for example, in unmanned air-vehicle (UAV) systems. The
operating principles of a range of commercial and experimental motor designs were evaluated objectively in order to identify
areas of performance that can potentially be enhanced using PMN-PT single-crystal piezoelectric ceramics. Based on this
analysis a practical motor design was selected for construction and experimentation. Detailed numerical analysis indicated
that a motor constructed from single crystal PMN-PT could be expected to provide an improvement in motor stall-torque by
up to a factor of 2.8 and a no-load speed improvement by a factor of 1.5 when compared with motors based on standard
polycrystalline lead-zirconate-titanate (PZT) ceramics. In practice single-crystal versions of the motor were found to produce
double the power output of their polycrystalline counterparts. Overall efficiency was found to be improved two-fold. There
were significant discrepancies between the numerical predictions for the single-crystal devices and their measured
performance, whereas the polycrystalline devices were found to perform closely in line with predictions.
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