Experimental characterization and performance improvement evaluation of an electromagnetic transducer utilizing a tuned inerter

This research reports on the experimental verification of an enhanced energy conversion device utilizing a tuned inerter called a tuned inertial mass electromagnetic transducer (TIMET). The TIMET consists of a motor, a rotational mass, and a tuning spring. The motor and the rotational mass are connected to a ball screw and the tuning spring interfaced to the ball screw is connected to the vibrating structure. Thus, vibration energy of the structure is absorbed as electrical energy by the motor. Moreover, the amplified inertial mass can be realized by rotating relatively small physical masses. Therefore, by designing the tuning spring stiffness and the inertial mass appropriately, the motor can rotate more effectively due to the resonance effect, leading to more effective energy generation. The authors designed a prototype of the TIMET and conducted tests to validate the effectiveness of the tuned inerter for electromagnetic transducers. Through excitation tests, the property of the hysteresis loops produced by the TIMET is investigated. Then a reliable analytical model is developed employing a curve fitting technique to simulate the behavior of the TIMET and to assess the power generation accurately. In addition, numerical simulation studies on a structure subjected to a seismic loading employing the developed model are conducted to show the advantages of the TIMET over a traditional electromagnetic transducer in both vibration suppression capability and energy harvesting efficiency

Variable friction cladding connection for multi-hazard mitigation

Safety and serviceability design of civil infrastructure, including buildings and energy, lifeline, communication, and transportation systems, is critical in providing and maintaining services and benefits to our communities. In modern society, new constructions tend to be more flexible due to advances in material science and construction technologies. A key challenge in the design of these structures is to meet the motion requirements under operational and extreme loadings. The purpose of a motion-based design (MBD) approach is to ensure that motion requirements are met under the design loads, after which strength requirements are verified and met. A popular method under MBD is the inclusion of supplemental damping systems. For instance, several passive damping systems were introduced over the last decades, demonstrating high effectiveness at reducing seismic vibrations for buildings. These traditional passive control systems, although capable of mitigating targeted loads, are restricted to single hazard one-at-a-time due to their limited performance bandwidth. It follows that they become difficult to implement when multiple excitation inputs are considered either combined or individually, termed multi-hazards. Alternatively, one can use high-performance control systems that include active, semi-active and hybrid control systems, to adapt structural responses under different types of hazards. This work proposes and characterizes a novel high-performance control system termed variable friction cladding connection (VFCC). The VFCC leverages the motion of cladding elements to dissipate energy. It consists of friction plates upon which variable normal force is applied through an adjustable toggle system controlled by a linear actuator. When locked, the device acts as a traditional rigid cladding connection with high stiffness for daily operation and also provides maximum friction force to passively dissipate blast energy transferred to the structure. A rubber bumper is integrated to avoid collision between the structure and cladding elements under high impact loads. The VFCC, once activated under wind and seismic hazards, performs as a semi-active damping device that leverages cladding mass to reduce structural vibrations via a feedback control system. Here, a device prototype is fabricated and tested in laboratory to identify and validate its dynamic behavior. Experimental results show that the device prototype functions as designed and demonstrates its high promise for multi-hazard mitigation. In order to effectively implement the VFCC, an MBD procedure is developed and demonstrated on building examples subjected to multi-hazards. The MBD procedure includes the analytical quantification of hazards, identification of structural motion objectives, and iterative design of cladding connection parameters. The MBD approach is first developed for each hazard individually and then extended to multi-hazard design for blast, wind, and seismic loads. Numerical simulations are conducted on several building examples where the VFCC is simulated under a linear quadratic regulator controller (semi-active case) for wind and seismic loadings, and under a locked position (passive-on case) under blast load. An uncontrolled case with a traditional rigid cladding connection is used to benchmark results, and a passive-on case is simulated under wind and seismic loads also for benchmark purposes. Simulation results show that the designed VFCC is capable of reducing the response of the uncontrolled structures under the prescribed performance objectives under multi-hazard loadings. Overall, this work demonstrates the VFCC\u27s high capability of mitigating multi-hazards by leveraging motion of the cladding system, and the promise of the developed MBD approach enabling its holistic integration at the design phase

Generalized harmonic modeling technique for 2D electromagnetic problems : applied to the design of a direct-drive active suspension system

The introduction of permanent magnets has significantly improved the performance and efficiency of advanced actuation systems. The demand for these systems in the industry is increasing and the specifications are becoming more challenging. Accurate and fast modeling of the electromagnetic phenomena is therefore required during the design stage to allow for multi-objective optimization of various topologies. This thesis presents a generalized technique to design and analyze 2D electromagnetic problems based on harmonic modeling. Therefore, the prior art is extended and unified to create a methodology which can be applied to almost any problem in the Cartesian, polar and axisymmetric coordinate system. This generalization allows for the automatic solving of complicated boundary value problems within a very short computation time. This method can be applied to a broad class of classical machines, however, more advanced and complex electromagnetic actuation systems can be designed or analyzed as well. The newly developed framework, based on the generalized harmonic modeling technique, is extensively demonstrated on slotted tubular permanent magnet actuators. As such, numerous tubular topologies, magnetization and winding configurations are analyzed. Additionally, force profiles, emf waveforms and synchronous inductances are accurately predicted. The results are within approximately 5 % of the non-linear finite element analysis including the slotted stator effects. A unique passive damping solution is integrated within the tubular permanent magnet actuator using eddy current damping. This is achieved by inserting conductive rings in the stator slot openings to provide a passive damping force without compromising the tubular actuator’s performance. This novel idea of integrating conductive rings is secured in a patent. A method to calculate the damping ratio due to these conductive rings is presented where the position, velocity and temperature dependencies are shown. The developed framework is applied to the design and optimization of a directdrive electromagnetic active suspension system for passenger cars. This innovative solution is an alternative for currently applied active hydraulic or pneumatic suspension systems for improvement of the comfort and handling of a vehicle. The electromagnetic system provides an improved bandwidth which is typically 20 times higher together with a power consumption which is approximately five times lower. As such, the proposed system eliminates two of the major drawbacks that prevented the widespread commercial breakthrough of active suspension systems. The direct-drive electromagnetic suspension system is composed of a coil spring in parallel with a tubular permanent magnet actuator with integrated eddy current damping. The coil spring supports the sprung mass while the tubular actuator either consumes, by applying direct-drive vertical forces, or regenerates energy. The applied tubular actuator is designed using a non-linear constrained optimization algorithm in combination with the developed analytical framework. This ensured the design with the highest force density together with low power consumption. In case of a power breakdown, the integrated eddy current damping in the slot openings of this tubular actuator, together with the passive coil spring, creates a passive suspension system to guarantee fail-safe operation. To validate the performance of the novel proof-of-concept electromagnetic suspension system, a prototype is constructed and a full-scale quarter car test setup is developed which mimics the vehicle corner of a BMW 530i. Consequently, controllers are designed for the active suspension strut for improvement of either comfort or handling. Finally, the suspension system is installed as a front suspension in a BMW 530i test vehicle. Both the extensive experimental laboratory and on-road tests prove the capability of the novel direct-drive electromagnetic active suspension system. Furthermore, it demonstrates the applicability of the developed modeling technique for design and optimization of electromagnetic actuators and devices

Structural interaction with control systems

A monograph which assesses the state of the art of space vehicle design and development is presented. The monograph presents criteria and recommended practices for determining the structural data and a mathematical structural model of the vehicle needed for accurate prediction of structure and control-system interaction; for design to minimize undesirable interactions between the structure and the control system; and for determining techniques to achieve the maximum desirable interactions and associated structural design benefits. All space vehicles are treated, including launch vehicles, spacecraft, and entry vehicles. Important structural characteristics which affect the structural model used for structural and control-system interaction analysis are given

Recent Advances in Centrifuge Modeling of Seismic Shaking

This State-of-the-Art paper focuses primarily on aspects of dynamic centrifuge modeling related to simulation of earthquake effects. New shaker mechanisms and model containers are described and soil- container-shaker interaction is discussed. Progress in dealing with scale effects such as particle size, rate dependent material properties and conflicts in dissipation and generation time scale factors is also described. Issues related to repeatability and value of model testing are also discussed

A Controllable Flexible Micropump and a Semi-Active Vibration Absorber Using Magnetorheological Elastomers

This study is focused on magneto-fluid-solid interaction analysis of a soft magnetorheological elastomer (MRE) controllable flexible micropump. In addition, material characterizations of MRE, modeling, fabrication and testing of a MRE-based vibration absorber system are investigated.Theoretical modeling and analysis of a controllable flexible magnetically-actuated fluid transport system (CFMFTS) is presented. For the first time, soft magnetorheological elastomer (MRE) is proposed as an actuation element in a fluid transport system (micropump). The flexible micropump can propel fluid under a fluctuating magnetic field. Magnetic-fluid-solid interaction analysis is performed to determine deflection in the solid domain and velocity of the fluid under a magnetic field. The effects of key material and geometric system parameters are examined on the micropump performance. Two- and three-dimensional analyses are performed to model the asymmetric deflection of the channel under a magnetic field. It is successfully demonstrated that the proposed system can propel the fluid in one direction.In addition, a novel semi-active variable stiffness and damping absorber (VSDA) is modeled, built and tested. Magnetically induced mechanical properties of MRE and their controllability are investigated by quasi-static and dynamic experiments. The VSDA is modeled, using springs, dashpots and the Bouc-Wen hysteresis element, fabricated and implemented in a scaled building to assess performance. Experiments are performed on a single VSDA, integrated system of four VSDAs, and a scaled building supported by four VSDAs. To demonstrate feasibility, a scaled, two-story building is constructed and installed on a shake table supported by four prototype VSDAs. The properties of VSDAs are regulated in real time by varying the applied magnetic field through the controller. A scaled earthquake excitation is applied to the system, and the vibration mode is controlled by a Lyapunov-based control strategy. The control system is used to control displacement and acceleration of the floors. Results demonstrate that the proposed VSDA significantly reduces acceleration and relative displacement of the structure

The Convergence of Parametric Resonance and Vibration Energy Harvesting

Energy harvesting is an emerging technology that derives electricity from the ambient environment in a decentralised and self-contained fashion. Applications include self-powered medical implants, wearable electronics and wireless sensors for structural health monitoring. Amongst the vast options of ambient sources, vibration energy harvesting (VEH) has attracted by far the most research attention. Two of the key persisting issues of VEH are the limited power density compared to conventional power supplies and confined operational frequency bandwidth in light of the random, broadband and fast-varying nature of real vibration. The convention has relied on directly excited resonance to maximise the mechanical-to-electrical energy conversion efficiency. This thesis takes a fundamentally different approach by employing parametric resonance, which, unlike the former, its resonant amplitude growth does not saturate due to linear damping. Therefore, parametric resonance, when activated, has the potential to accumulate much more energy than direct resonance. The vibrational nonlinearities that are almost always associated with parametric resonance can offer a modest frequency widening. Despite its promising theoretical potentials, there is an intrinsic damping dependent initiation threshold amplitude, which must be attained prior to its onset. The relatively low amplitude of real vibration and the unavoidable presence of electrical damping to extract the energy render the onset of parametric resonance practically elusive. Design approaches have been devised to passively minimise this initiation threshold. Simulation and experimental results of various design iterations have demonstrated favourable results for parametric resonance as well as the various threshold-reduction mechanisms. For instance, one of the macro-scale electromagnetic prototypes (∼1800 cm3) when parametrically driven, has demonstrated around 50% increase in half power band and an order of magnitude higher peak power (171.5 mW at 0.57 ms−2) in contrast to the same prototype directly driven at fundamental resonance (27.75 mW at 0.65 ms−2). A MEMS (micro-electromechanical system) prototype with the additional threshold-reduction design needed 1 ms−2 excitation to activate parametric resonance while a comparable device without the threshold-reduction mechanism required in excess of 30 ms−2. One of the macro-scale piezoelectric prototypes operated into auto-parametric resonance has demon-strated notable further reduction to the initiation threshold. A vacuum packaged MEMS prototype demonstrated broadening of the frequency bandwidth along with higher power peak (324 nW and 160 Hz) for the parametric regime compared to when operated in room pressure (166 nW and 80 Hz), unlike the higher but narrower direct resonant peak (60.9 nW and 11 Hz in vacuum and 20.8 nW and 40 Hz in room pressure). The simultaneous incorporation of direct resonance and bi-stability have been investigated to realise multi-regime VEH. The potential to integrate parametric resonance in the electrical domains have also been numerically explored. The ultimate aim is not to replace direct resonance but rather for the various resonant phenomena to complement each other and together harness a larger region of the available power spectrum