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

Adaptive Positive Position Feedback Control of Flexible Aircraft Structures Using Piezoelectric Actuators

Buffet Adaptively Managed Fin (BAMF) focused on vibrations due to the interaction of aerodynamic forces with aircraft structure. Past failures of F-16 ventral fins due to vibrations provided grounds for control research. The fin used had piezoelectric patches as collocated sensors/actuators. A custom amplifier and transformer were restructured into a system that could safely and reliably run, and adaptive software was created to address issues of system plant changes. Generating a PSD from the fin sensors, the highest peaks were assumed to represent the low damped vibration modes. A PPF controller for each mode was designed and control signals were sent to the fin actuators. Limited data were collected in a wind tunnel behind a custom system that caused buffet by varying vortex strength/shedding frequencies from pods upstream of the fin. While minimal testing was accomplished to optimize gains, the system showed significant PSD peak reductions for the first three modes of the fin up to -14.9, -15.3, and -16.4 dB, respectively. The system maintained stability and effective control even when both sensor input and controller output were saturated

Design, Development, and Testing of Research Payloads on Various Suborbital Flight-Test Platforms

With recent advances in the commercial space industry, suborbital payload launches have become more common and accessible to researchers actively seeking solutions for problems involving prolonged space travel and future missions to Moon and Mars. Suborbital payload missions compared to orbital launches are less expensive and offer faster turnaround times; however, the novelty of this domain provides unique challenges. This multidisciplinary research effort aims to tackle some of these challenges by detailing the design, development, and testing techniques followed in the successful launch and recovery of payload experiments in currently active and upcoming suborbital launch vehicles. The research methodology involves collecting payload requirements, CAD design, computational analysis, mass optimization, 3D printing, vibration, and load testing, model rocketry development, simulation, and launch operations. Structural analysis using FEA and vibration testing on a shaker table shows the compliance of the payload prototypes in the maximum predicted flight environments. Multiphase CFD analysis is used as benchmarking technique to characterize the behavior of payloads containing liquids in microgravity. Hands-on model rocketry has proven as a valuable research platform for subsequent payload deliveries

On the control methedologies of a novel active vibration isolator

The work presented in this thesis is motivated by the need for new and effective methods to isolate vibrations in the rapidly growing technological sector, with particular interest in the control methodologies for active vibration isolation of a proposed isolator. The thesis consists of four major parts. The first part (chapter 2) focuses on the development of dynamic mathematical models for the isolator. The nonlinear force and stiffness models are linearized and a dynamic experimental characterization is conducted to properly identify the system parameters. The characterization also serves as a model validation process. The second part (chapter 3) investigates the ability of the active vibration isolator to perform with a phase compensation technique. This technique is realized by minimizing the 2nd norm of the displacement transmissibility. An automatic on/off tuning algorithm is devised to take full advantage ofboth active and passive modes. Real-time experiments demonstrate the efficacy of the technique. The experimental results also show that with the proposed control scheme, the isolator is able to effectively suppress base excitations taking advantage ofboth active and passive modes

Active Noise Control Using Modally Tuned Phase-Compensated Filters

An active noise control device or an active noise absorber (ANA) that is based on either resonant 2nd - order or 4th - order Butterworth filters is developed and demonstrated. This control method is similar to structural positive position feedback (PPF) control, with two exceptions: 1) acoustic transducers (microphone and speaker) can not be truly colocated, and 2) the acoustic actuator (loudspeaker) has significant dynamics that can affect performance and stability. Acoustic modal control approaches are typically not sought, however, there are a number of applications where controlling a few room modes is adequate. A model of a duct with speakers at each end is developed and used to demonstrate the control method, including the impact of the speaker dynamics. An all-pass filter is used to provide phase compensation and improve controller performance. Two companion experimental studies validated the simulation results. A single mode case using a resonant band-pass filter demonstrated nearly 10 dB of control in the first duct, while a multimodal case using two 4th - order Butterworth band-pass filters show both 10 dB of reduction in the fundamental mode and nearly 8.0 dB in the second

Active vibration control in building-like structures submitted to earthquakes using multiple positive position feedback and sliding modes

This work deals with the structural and dynamic analysis of a building-like structure consisting of a three-story building with one passive/active vibration absorber. The base of the structure is perturbed using a shaker, providing excitation forces and noisy excitations emulating ground transportation, underground railways and earthquakes, quite common in Mexico City. It is considered a realistic seismic record of 8.1Mw occurred at Mexico City, containing some resonant frequencies of the structure. The mechanical structure is modeled using Euler-Lagrange methodology and validated using experimental modal analysis techniques. The active control scheme is synthesized to actively attenuate the noise and vibration system response, caused by noisy excitation forces acting on the base, by employing Multiple Positive Position Feedback and Sliding Mode Control to improve the closed-loop system response and, simultaneously, attenuate three vibration modes. Simulation and experimental results describe the overall system performance

Piezoelectric digital vibration absorbers for vibration mitigation of bladed structures

Climate change and resource scarcity pose increasingly difficult challenges for the aviation industry requiring a reduction in fossil fuel consumption. To address these problems and increase the efficiency of aircraft engines, some of their parts are now manufactured in one piece. For example, a rotor of the compressor stage of an airplane engine consist of a drum with a large number of blades and is called BluM. These structures are lightweight and feature low structural damping and high modal density. Their particular dynamic characteristics require sophisticated solutions for vibration mitigation of these structures. This is precisely the starting point of this thesis. Based on a digital realization of piezoelectric shunt circuits, we provide a damping concept that is able to tackle the complex dynamics of bladed structures and to mitigate their vibrations. To this end, multiple digital vibration absorbers (DVAs) are used simultaneously. Two new strategies to tune these DVAs are proposed in the thesis, namely the isolated mode and mean shunt strategies. These strategies not only take advantage of the fact that multiple absorbers act simultaneously on the structure, but they also address the problem of closely-spaced modes. In order to target multiple families of BluM modes, these strategies are incorporated in a multi-stage shunt circuit. The concepts are demonstrated experimentally using two bladed structures with increasing complexity, namely a bladed rail and a BluM. Both methods exhibit excellent damping performances on multiple groups of modes. In addition, they prove robust to changes in the host structure which could, e.g., be due to mistuning. Thanks to their digital realization, DVAs are also easily adjustable. Finally, this thesis reveals the parallel that exists between resonant piezoelectric shunts with a negative capacitance and active positive position feedback (PPF) controllers. Based on this comparison, a new H∞ norm-based tuning rule is found for a PPF controller. It is demonstrated using both numerical and experimental cantilever beams. To this end, a method that accounts for the influence of modes higher in frequency than the targeted one is developed.Le changement climatique et la raréfaction des ressources posent des défis de plus en plus complexes à relever pour l'industrie aéronautique. Un de ces défis est la réduction de la consommation en énergies fossiles. Pour accroître l'efficacité des moteurs d'avion, certains de leurs composants sont désormais fabriqués en une seule pièce. Dans le cas des compresseurs, ces pièces monoblocs sont appelées BluMs et sont constituées d’un tambour avec un grand nombre d'aubes. Ce type de structures bénéficie d'un allègement significatif, ce qui conduit à un faible amortissement structurel. De plus, ces pièces monoblocs présentent une densité modale élevée en raison du nombre important de diamètres nodaux. Ces caractéristiques dynamiques particulières nécessitent des solutions d'amortissement sophistiquées. Cette thèse de doctorat aborde cette problématique. En exploitant le concept d'absorbeur de vibration digital (DVA), nous proposons une nouvelle technique d'amortissement des structures aubagées. Deux nouvelles stratégies d'accordage de ces DVA sont développées dans cette thèse, à savoir la stratégie du mode isolé et la stratégie du shunt moyen. Ces méthodes tirent non seulement parti du fait que plusieurs absorbeurs agissent simultanément sur la structure, mais elles s'attaquent aussi au problème des modes proches en fréquence. Afin de cibler plusieurs familles de modes, ces stratégies ont été incorporées dans un circuit de shunt à plusieurs étages. Les concepts sont testés expérimentalement sur deux structures aubagées de complexité croissante, à savoir un rail à aubes et un BluM comme application finale. Ces méthodes permettent d'obtenir d'excellentes performances d'amortissement sur plusieurs groupes de modes. Elles s'avèrent également robustes face à des variations de la structure, dues par exemple à un désaccordage de celle-ci. Il est à noter que, grâce à leur caractère digital, ces méthodes sont facilement adaptables. Finalement, nous révélons le parallèle qui existe entre les shunts piézoélectriques résonants avec une capacitance négative et le contrôleur actif à rétroaction positive de position (PPF). Sur base de cette comparaison, de nouvelles règles d'accordage basées sur la norme H∞ sont développées pour le contrôleur PPF. Leur efficacité est démontrée à la fois numériquement et expérimentalement sur une poutre encastrée-libre. Dans ce but, une méthode prenant en compte l'influence des modes dont la fréquence est supérieure au mode ciblé a été mise sur pied au moyen de facteurs de correction

L'effet des différentes combinaisons d'adjuvants chimiques et liants sur la maniabilité des bétons autoplaçants à haute performance destinés aux réparations

Il est bien connu que l’hiver québécois est particulièrement agressif pour les ouvrages en béton. Les organismes publics doivent de plus en plus compter avec des travaux de réfection afin de réparer les structures existantes pour en prolonger la durée de vie. Le but de cette recherche est de développer un béton autoplaçant destiné aux travaux de réparation qui puisse faciliter la construction d’ouvrages minces et fortement renforcés. Cinq différents adjuvants et quatre différents liants hydrauliques ont été utilisés pour la fabrication d’un tel béton autoplaçant. Deux différentes approches ont été utilisées : l’une avec un faible rapport eau/liant sans agent colloïdal et l’autre avec un rapport eau/liant modéré avec agent colloïdal. La stabilité dynamique, la stabilité statique et les paramètres rhéologiques ont été mesurés lors des différents essais. Les propriétés du béton autoplaçant incluaient un étalement de 660 ± 20 mm et une stabilité statique limitée à une valeur maximale de 0,5%, mesurée avec une colonne de tassement de 700 mm. Des fibres ont été incorporées au béton autoplaçant et ses propriétés ont été améliorées jusqu’à un étalement de 700 ± 20 mm.Abstract : It is well known that the winter in Quebec is particularly harsh and poses high demand on concrete performance, especially that used in infrastructure applications. Government agencies, in charge of repair and rehabilitation of such infrastructure, must work to restore the concrete and to extend the lifetime of structures. The objective of this research is to develop high-performance, self-consolidating concrete intended for repair applications that will facilitate the casting of slim and highly reinforced sections while ensuring adequate durability and service life. The performance of fresh concrete made with several Chemical admixture and hydraulic binder combinations has been evaluated. In total, five different brands of admixtures along with four binder types were used in this investigation. Two different approaches were used in proportioning the concrete to ensure proper stability: the use of low water-cementitious ratio, or the use of a moderate water-cementitious ratio (w/cm) with a Viscosity-Enhancing Agent (VEA) to enhance cohesiveness. Optimized mixtures were assessed for key workability characteristics, including: static stability, dynamic stability, and rheological parameters. The mixtures had initial slump flow of 660 ± 20 mm and maximum surface settlement of 0.5%. Some mixtures were made with synthetic fibres and initial slump flow of 700 ± 20 mm

Modeling and analysis of power processing systems: Feasibility investigation and formulation of a methodology

A review is given of future power processing systems planned for the next 20 years, and the state-of-the-art of power processing design modeling and analysis techniques used to optimize power processing systems. A methodology of modeling and analysis of power processing equipment and systems has been formulated to fulfill future tradeoff studies and optimization requirements. Computer techniques were applied to simulate power processor performance and to optimize the design of power processing equipment. A program plan to systematically develop and apply the tools for power processing systems modeling and analysis is presented so that meaningful results can be obtained each year to aid the power processing system engineer and power processing equipment circuit designers in their conceptual and detail design and analysis tasks