This paper considers the RL shunt damping of rotationally periodic structures with an array of regularly spaced piezoelectric patches. The technique is targeted to the damping of a specific mode withnnodal diameters. For this particular case, one can take advantage of the shape of the targeted mode to organize the piezoelectric patches as a modal filter (in parallel loops) which reduces the demand on the inductors of the tuned inductive shunt. In the case of a perfectly rotationally periodic structure, it is possible to organize 4npiezoelectric transducers (PZT patches) in two parallel loops of 2npatches each. In this way, the demand on the inductors is reduced by4n2as compared to independent loops, which may allow a fully passive integration of the RL shunt in a turbomachinery application. The method is first illustrated experimentally on a circular plate; it is then applied to a prototype of an industrial bladed drum. The influence of blade mistuning is investigated.

This article presents a strategy for enhancing the performance of the synchronized switch damping on inductor technique used for the semiactive control of structural vibrations. This enhancement is achieved by adding a negative capacitance to the resonant circuit that dissipates the energy converted by a piezoelectric transducer embedded in the structure. A unidimensional spring-mass system shunted synchronously to a resonant circuit is studied analytically, and the main parameters governing the performances of the system are highlighted. Experimental results obtained with a synthetic negative capacitance demonstrate the enhancement of the performance of synchronized switch damping on inductor and confirm the parametric dependencies identified analytically.

This paper examines the possibility of constructing deformable mirrors for adaptive optics with a large number of degrees of freedom from silicon wafers with bimorph piezoelectric actuation.The mirror may be used on its own, or as a segment of a larger mirror. The typical size of one segment is 100-200 mm; the production process relies on silicon wafers and thick film PZT deposition technology; it is able to lead to an actuation pitch of the order of 5 mm, and the manufacturing costs appear to grow only slowly with the number of degrees of freedom in the adaptive optics.

This paper presents a unimorph deformable mirror intended to be used as secondary corrector in space telescopes. The deformable mirror consists of a single-crystal silicon wafer (76.2 mm diameter, 500 μm thickness) covered with an optical coating on the front side and an array of 25 independent piezoelectric transducer (PZT) actuators acting in d mode on the back side. The mirror is mounted on an isostatic support with three position linear actuators controlling the rigid-body motion. The first part of the paper presents the experimental results obtained with the manufactured prototype. The mirror was tested in terms of root mean square (RMS) wavefront error, open-loop long-term stability, voltage budget for active control, rigid-body actuation, reflectivity, and dynamic response. The prototype is fully compliant with the requirements set by the European Space Agency (ESA). The second part of the paper, purely based on numerical simulations, presents a robust way to face thermal distortion, inherent to unimorph architecture.

We discuss the concept of lightweight segmented bimorph mirrors for adaptive optics. The segment consists of a monocrystal silicon substrate actuated by an array of in-plane piezoceramic (PZT) actuators with honeycomb electrodes. We focus on technological aspects of the segment design that are critical for space applications and describe a single segment demonstrator. The morphing capability of the segment is evaluated experimentally. We also discuss the local deformations (dimples) associated with the shape of the electrodes acting on the PZT array.