Identification of Admittance Coefficients from in-situ Measurements in Acoustic Cavities

International audienceIn recent decades, sound intensity and quality is taking an increasingly important place in the design process of products like cars or aircrafts. Different types of absorbing materials have therefore been developed and used in such products to achieve this purpose. Acoustical calculations are quite heavy and industries generally have to use numerical tools to predict the influence of absorbing materials on the sound propagation inside cavities. In these ones, the acoustical properties of absorbing materials are described by the admittance (or impedance) coefficient, which is a simplification of the physical model. However, the limits of applicability of this model are not well known and the conditions in which its parameters are measured can differ significantly from the ones in which the materials are really used. In this paper, a model updating technique process is used to identify the parameters required to describe admittance coefficients from sound pressure measurements inside a closed cavity. Updating techniques have been used for many years to improve numerical models, and consist in minimizing an error between the numerical solutions and a set of experimental results. The technique based on the Constitutive Relation Error (CRE), initially proposed by Ladevèze [1] for structural dynamics problems, is an indirect method in which the cost function, called the CRE, is based on an energy norm. The main advantages of this method are that the updated parameters keep a physical meaning, that it allows taking into account the measurement error and that it allows locally evaluating the modeling and measurement errors [2]. In this paper the CRE-based updating technique is applied to the acoustical problem ([3], [4]) in order to identify the admittance coefficients and the local estimators are developed. The method is applied on real 2D (Kundt's tube) and 3D (concrete box) experimental data

Determination of optimal sensor-actuator position for active vibration damping in collocated SISO systems using a pole-zero distance criterion for fast convergence of the search algorithm

The position of the transducers in active control architectures is critical to ensure the performance and has consequently been studied during the last few decades. However, the placement criteria often require the use of extensive search algorithms that demand numerous iterations, leading to prohibitive computational time for large and/or complex structures. To overcome this limitation, this paper investigates the use of the pole-zero (PZ) distance placement criterion as the starting point for a simple gradient algorithm. This open-loop criterion is based on the direct link between the PZ distance and the maximum reachable damping: the obtained position locates in the vicinity of a high damping area which ensures the convergence of the search algorithm, for fewer iterations. A numerical simulation is performed to assess the performance of the proposed approach and compared to a genetic algorithm optimization. A significant reduction of the processing time is observed while the solution shows an improved robustness to transducers misplacement

On the link between pole-zero distance and maximum reachable damping in MIMO systems

peer reviewedThis paper studies the possibility of extending the already proved link between the pole-zero distance and the maximum reachable damping ratio in single input single output (SISO) systems to multiple inputs multiple outputs (MIMO) ones. This extension is shown to be possible when the considered system presents specific properties: (i) it is equipped with collocated transducers with small authority, (ii) the system has a small modal density in the frequency band of interest and (iii) a low authority control law is used. It is indeed demonstrated that when these three conditions are satisfied, the analytical development of the closed-loop poles convergence is equivalent to the one observed with SISO cases, except that the anti-resonances are replaced by the transmission zeros (TZs). Consequently, it is concluded that the maximum reachable damping ratio is directly proportional to the pole-transmission zero distance for such MIMO systems. This conclusion is demonstrated with two numerical examples (a cantilever beam and a simply supported plate) and experimentally validated on a cantilever beam where all the studied systems are equipped with two collocated pairs of piezoelectric patches

Proposal for the deployment of an augmented reality tool for construction safety inspection

The construction site is a hazardous place. The dynamic, complex interaction between workers, machinery, and the environment leads to dangerous risks. In response to such risks, the goal is to fulfill the zero accidents philosophy, which requires the development of safety skills among workers and the provision of tools for risk prevention. In pursuit of that vision, this work studies collective protective equipment (CPE). Traditional methodologies propose visual inspections using checklists, the effectiveness of which depends on the quality of the inspection by the safety advisor (SA). This paper analyses the traditional process of safety inspections in building projects: the traditional methods, main pain points, and bottlenecks are identified, along with the key performance indicators (KPIs) needed to complete these processes correctly. Because of this, a methodology that digitises the CPE inspection process is proposed. Augmented reality (AR) is used as a 3D viewer with an intuitive interface for the SA, and, accordingly, functional requirements are detailed and different information layers and user interfaces for AR applications are proposed. In addition, the workflow and KPIs are shown. To demonstrate the feasibility of the proposal, a proof of concept is developed and evaluated. The relevance of this work lies in providing background for the use of AR in safety inspection processes on construction sites and in offering methodological recommendations for the development and evaluation of these applications.This work has been supported by the Ministry of Science, Innovation and Universities of Spain (MICIU) through the BIMIoTICa project (RTC-2017-6454-7) and by the CONICYT for its economic support to Felipe Muñoz, beneficiary of a pre-doctoral grant (CONICYT—PCHA/International Doctorate/2019-72200306). The authors also acknowledge the financial support from the Spanish Ministry of Economy and Competitiveness, through the “Severo Ochoa Centre of Excellence (2019–2023) under the grant CEX2018-000797-S funded by MCIN/AEI/10.13039/501100011033”.Peer ReviewedPostprint (published version

Resistive-inductive piezoelectric shunts with negative capacitances and positive position feedback - a comparative study

editorial reviewedBy drawing a parallel between the controller parameters of a piezoelectric inductive-resistive (RL) shunt with a negative capacitance (NC) and the active control method positive position feedback (PPF), we prove that there exists an equivalence between the controller parameters and their receptance functions. Based on these findings, exact H∞ tuning rules for RL shunts are extended to the use of a NC to eventually find optimal values for the design of a PPF controller. In addition, a closed-form expression of the maximum amplitude of the frequency responses is provided. Using these rules, a thorough comparison in terms of performance and stability margins between the RL shunt with NC and the PPF is performed and discussed

On transmission Zeros of piezoelectric structures

The evaluation of transmission zeros is of great importance for the control engineering applications. The structures equipped with piezoelectric patches are complex to model and usually require finite element approaches supplemented by model reduction. This study rigorously investigates the influence of mesh size, model reduction, boundary conditions (free and clamped), and sensor/actuator configuration (collocated and non-collocated) on the evaluation of transmission zeros of the piezoelectric structures. The numerical illustrations are presented for a thin rectangular plate equipped with a single pair of piezoelectric voltage sensor/ voltage actuator. Through the examples considered in this study, a link is presented between the static response (or static deflected shape) and the transmission zeros of the piezoelectric structures. This interesting observation forms the basis of: (i) a local mesh refinement strategy for computationally efficient estimation of the transmission zeros and (ii) a physical interpretation of the pole-zero pattern in the case of piezoelectric structures. The physical interpretation developed in this study helps in qualitatively explaining the pole-zero patterns observed for different configurations. It is also shown that this understanding of the relation between the static deformed shape and the transmission zeros can be used by the practitioners to modify the pole-zero pattern through a careful selection of the orientation and the size of the piezoelectric patches

Passive control of a periodic structure using a network of periodically-coupled piezoelectric shunt circuits

This work proposes a method to synthesize an electrical network which, when coupled to a complex periodic or nearly-periodic structure through an array of piezoelectric transducers, provides multimodal vibration mitigation. The structure is decomposed into multiple substructures and a reduced-order model is built for each of them. From these models, it is possible to synthesize a network with simple algebraic transformations. The link between these transformations and electromechanical modal coupling is derived, and conditions are given in order to guarantee the passivity of the electrical network. The proposed approach is illustrated on a bladed rail, for which damping of one or multiple families of blade modes is demonstrated

Low frequency high resolution optical inertial sensors

Nowadays, sensors’ resolution limits their performance at low frequency which reduces their operating range. Sensors with a good resolution at low frequency are required to improve the performance of gravitational wave detectors in the sub-Hz frequency range. We are currently developing an inertial sensor with a sufficient resolution at low frequency from 10 mHz to 100 Hz. We are focusing on the improvement of different characteristics of the sensor, among others, its compactness and its thermal noise mitigation. The readout consists of a long-range Michelson interferometer fed by a 1550 nm laser and whose signal is measured by InGaS photodetectors. The use of InGaS photodetector in our interferometer will allow better resolution for future sensor projects. The inertial mass is connected to the frame by a fused silica flexure joint to limit internal damping. Then, translational guidance is implemented to allow the use of a flat mirror. The actual sensor developed at the Precision Mechatronics Laboratory has a resolution of 2x10^(-13) m/√Hz at 1 Hz. Our goal is to reach the same resolution with a compact version: 10x10x10 cm^3