Design and development of a smart panel with five decentralised control units for the reduction of vibration and sound radiation

This Technical Report discusses the design and the construction of a smart panel with five decentralised direct velocity feedback control units in order to reduce the vibration of the panel dominated by well separated low frequency resonances. Each control unit consists of an accelerometer sensor and a piezoelectric patch strain actuator. The integrated accelerometer signal is fed back to the actuator via a fixed negative control gain. In this way the actuator generates a control excitation proportional and opposite to the measured transverse velocity of the panel so that it produces active damping on the panel. First the open loop frequency response function between the sensor and the actuator of a single channel has been studied and an analogue controller has been designed and tested in order to improve the stability of this control system. Following the stability of all five control units has been assessed using the generalised Nyquist criterion. Finally the performances of the smart panel have been tested with reference to the reduction of the vibrations at the error positions and with reference to the reduction of the radiated sound. Finally in appendix to this Report, a parametric study is presented on the properties of sensor-actuator FRFs measured with different types of piezoelectric patch actuators. The results of this parametric study have been used in order to choose the actuators to be used for the construction of the smart pane

Smart double panel with decentralised active dampers for control of sound transmission

This report presents the results of a theoretical study of active sound transmission control through a double panel. The double panel material and geometrical properties have been chosen so as to emulate section of an aircraft fuselage, or bodywork of a vehicle. It consists of two plates: an aluminium plate simply supported along all the edges and a honeycomb plate with all the edges free. The two plates, having the same length and width, are connected using elastic mounts, so that a double panel with a thin rectangular cavity between the plates is formed. Since the two plates are linked by the mounting system, and since the air is confined in the cavity between them, they form a structurally and acoustically coupled system. The sound transmission properties of the system are studied in such a way that the aluminium plate (“source panel”) is excited using a plane acoustic wave, while the honeycomb plate (“radiating panel”) radiates sound into free field.The aim of the active control is to reduce the sound transmitted in a broad frequency band, but with a particular focus on the reduction of the sound transmission at lower frequencies of the band. Decentralised velocity feedback control systems (applying active damping) are implemented, with purpose of reducing sound transmission at resonance frequencies. Control sensors and actuators are embedded into the double plate system as a regular array, so that a smart double panel is created. The theoretical study includes analysis of the passive sound transmission in terms of a parametric study, implementation of the active control using skyhook velocity sensors and skyhook force actuators, and the performance/stability analysis in case when reactive actuators and skyhook velocity sensors are used. In the latter case the actuating force is obtained using actuators located in the air cavity which can react off the two plate

I Barison della collezione Enrico Nordio

One of the aspects not well studied yet is about relationships between architects and painters at the end of XIXth and beginning XXth centuries. In this particular case the author analyzes friendship between Giuseppe Barison (1853-1931) and Enrico Nordio (1851-1923). The two friends were very soon in contact for their training in Karl Emil Haase atelier in Trieste and then in Vienna, Nordio becoming an important architect, Barison one of the most relevant painter at the time. Nordio collected many Barison’s paintings as well as Giacomo Zammattio (1855-1927), another important architect between Trieste and Rijeka who was also friend and collegue of Barison in Vienna at the Academy of Fine Arts

Momenti cruciali tra Venini e la Biennale: lettere inedite di Napoleone Martinuzzi

Napoleone Martinuzzi was the artistic director at Venini glass factory from 1925 to 1931. Some new letters discovered during the research for the great exhibition at San Giorgio in Venice but unfortunately after the publication of the catalogue and also after the symposium organized by the Glass Study Centre at Fondazione Giorgio Cini on 5th June, are important to understand the role of him inside the Venini’s organization. There are also some letters related to Biennale of 1930, written to obtained the decoration of the central hall

Veruda alla ricerca di Velázquez: il sivigliano Rafael Senet y Perez a Venezia

A recently discovered portrait by Umberto Veruda, depicting the colleague Rafael Senet y Perez, open to an unknown chapter about Seville painters in Venice at the end of XIX Century and their influence. Veruda, one of the most important painter in the Trieste area at the time, is always linked to Munich or Paris, but his talent tooks from different visual and mental sources, especially Velázquez. A certain number of painters from Seville (birthplace of Velázquez) stayed in Venice hosted at Senet’ home in Campo San Vio when Veruda also was there

Il fantomatico Belli. Pittore girovago nella Francia di fine Ottocento o copista per la regina Vittoria?

From the Parisian collection of Angelo Sommaruga, two paintings signed “Belli” were considered realized by the Italian artist Enrico Belli. The author identified him in Benet Belli, a Spanish painter who was confused in his life with the most known Enrico, who worked in England as a copyist for her Majesty the Queen Victoria. From this point the author traces the works and life of Benet Belli – who travelled from Barcelona to Paris in 1878 – and also of Enrico who left England for India in the same years. Nowadays many paintings by Benet – especially in the French and Italian market of art – are confused and attributed to Enrico; now we know the difference between them

Scaling laws of electromagnetic and piezoelectric seismic vibration energy harvesters built from discrete components

This paper presents a theoretical study on the scaling laws of electromagnetic and piezoelectric seismic vibration energy harvesters, which are assembled from discrete components. The scaling laws are therefore derived for the so called meso-scale range, which is typical of devices built from distinct elements. Isotropic scaling is considered for both harvesters such that the shape of the components and of the whole transducers do not change with scaling. The scaling analyses are restricted to the case of linearly elastic seismic transducers subject to tonal ambient vibrations at their fundamental natural frequency, where the energy harvesting is particularly effective. Both resistive-reactive and resistive optimal electric harvesting loads are considered. The study is based on equivalent formulations for the response and power harvesting of the two transducers, which employ the so called electromagnetic and piezoelectric power transduction factors, \u3a0cm2 and \u3a0pe2. The scaling laws of the transduction coefficients and electrical and mechanical parameters for the two transducers are first provided. A comprehensive comparative scaling analysis is then presented for the harvested power, for the power harvesting efficiency and for the stroke of the two harvesters. Particular attention is dedicated to the scaling laws for the dissipative effects in the two harvesters, that is the Couette air losses and eddy currents losses that develop in the electromagnetic harvester and the material, air and dielectric losses that arise in the piezoelectric harvester. The scaling laws emerged from the study, are thoroughly examined and interpreted with respect to equivalent mechanical effects produced by the harvesting loads

Comparison of smart panels for tonal and broadband vibration and sound transmission active control

This paper presents a comprehensive overview of the principal features of smart panels equipped with feed-forward and feedback systems for the control of the flexural response and sound transmission due respectively to tonal and to stochastic broadband disturbances. The smart panels are equipped with two types of actuators: first, distributed piezoelectric actuators formed either by small piezoelectric patches or large piezoelectric films bonded on the panels and second, point actuators formed by proof-mass electromagnetic transducers. Also, the panels encompass three types of sensors: first, small capacitive microphone sensors placed in front of the panels; second, distributed piezoelectric sensors formed by large piezoelectric films bonded on the panels and third point sensors formed by miniaturized accelerometers. The proposed systems implement both single-channel and multi-channel feed-forward and feedback control architectures. The study shows that, the vibration and sound radiation control performance of both feed-forward and feedback systems critically depends on the sensor-actuator configurations