Viet Phuong Bui

Electromagnetic Actuator Design Analysis Using a Two-Stage Optimization Method With Coarse–Fine Model Output Space Mapping

Electromagnetic actuators are energy conversion devices that suffer from inefficiencies. The conversion losses generate internal heat, which is undesirable, as it leads to thermal loading on the device. Temperature rise should be limited to enhance the reliability, minimize thermal disturbance, and improve the output performance of the device. This paper presents the application of an optimization method to determine the geometric configuration of a flexure-based linear electromagnetic actuator that maximizes output force per unit of heat generated. A two-stage optimization method is used to search for a global solution, followed by a feasible solution locally using a branch and bound method. The finite element magnetic (fine) model is replaced by an analytical (coarse) model during optimization using an output space mapping technique. An 80% reduction in computation time is achieved by the application of such an approximation technique. The measured output from the new prototype based on the optimal design shows a 45% increase in air gap magnetic flux density, a 40% increase in output force, and a 26% reduction in heat generation when compared with the initial design before application of the optimization method.

An Efficient Simulation Technology for Characterizing the Ultra-Wide Band Signal Propagation in a Wireless Body Area Network

This paper presents an efficient simulation technology to characterize the Ultra-Wide Band signal propagation between the antennas in close proximity to a human body, where the human body works as a Wireless Body Area Network. The first technique is the hybrid Method of Moments and asymptotic Physical Optics in which the formulation is extended for modeling the dielectric body. The second technique combines the modification of the Multilevel Fast Multipole Algorithm with the Impedance Boundary Condition. These two techniques drastically reduce the computational complexity to model and simulate an electrically very large and complex structure including antennas and human body. Numerical examples showing the effects of the human body on the Ultra-Wide Band signal transmission between two antennas are presented to demonstrate the efficiency of our proposed method.

Millimeters-Stroke Nanopositioning Actuator With High Positioning and Thermal Stability

This paper presented the design and modeling of a novel nanopositioning actuator that delivers millimeters stroke with high positioning and thermal stability. This actuator comprises a unique electromagnetic driving module (EDM) articulated from a segmented dual-magnet (DM) configuration, and flexurebased supporting bearings realized via a flexible membrane concept. In this paper, the fundamental insights on how to design and model the proposed segmented DM configuration are presented in detail. The remainder of this paper focuses on the thermal modeling of the unique EDM and the stiffness modeling of the unconventional flexure-based bearings. Subsequently, all theoretical models are evaluated through experimental investigations conducted via a developed prototype. The prototype also achieved an average positioning stability of ±10 nm with a thermal stability of ±0.1°C throughout a traveling range of 2 mm (±1 mm). Such actuator is useful for applications where direct feedback on the end effector is impossible.

AN EFFICIENT HYBRID TECHNIQUE FOR ANALYSIS OF THE ELECTROMAGNETIC FIELD DISTRIBUTION INSIDE A CLOSED ENVIRONMENT

This paper presents an e-cient hybrid simulation technique for analysis of the electromagnetic fleld interactions between multi-transmitters and receivers located within a closed environment. The Method of Moments/circuit method is flrst used for modeling of the transceivers and their nearby surrounding to obtain the equivalent sources/receivers. Then, an approach that combines the asymptotic method and the ray tracing technique is deployed to calculate the long-distance coupling between a pair of transmitter and receiver. The acceleration algorithms for ray tracing have been developed to deal with more complex scenarios. The seamless combination between the circuit, numerical, and asymptotic approaches is the key to get accurate simulation results. Several numerical examples and experimental results are presented to demonstrate the e-ciency of the proposed technique.

EM Performance of Conductive Composite Laminate Made of Nanostructured Materials for Aerospace Application

This paper presents the characterization of electro-magnetic (EM) performance of conductive composite laminate in consideration for aeronautic design. Novel nanocomposite resin was prepared by incorporating nanofillers into neat epoxy, resulting in remarkable improvement of its electrical conductivity. The planar structure of conductive composite laminate, which consists of 33 layers of woven fabric carbon fiber sandwiched in the nanocomposite, was then fabricated under the optimal conditions offering many times higher conductivity than the composite laminate using neat resin. Simulations of newly-developed composite laminate exposed to lightning strike were performed. The comparative studies show that conductive composite laminate provides better lightning protection property than composite laminate with epoxy resin. The simulated shielding effectiveness of the composite panel is in good agreement with measured results in both S and X microwave bands. The shielding effectiveness of the conductive composite laminate characterized at the frequency above 1 GHz is less than 10% different from that of conventional composite with copper wire mesh on the outer layer currently-used in aerospace industry. The result of this study shows promising aspect in the EM design using nanostructured composite laminate.

Modeling of transmission characterisation in aircraft cabins with a hybrid technique

A hybrid technique which combines the integral equation (IE) method and the multiple image theory (MIT) is presented for modeling the electromagnetic wave propagation in a closed environment like aircraft cabins. The IE method with a method of moments (MoM) procedure is employed for analyzing the transmitting antenna. The obtained current on each basis function is acting as a source, and all its multiple images with reference to the wall planes for multiple reflections up to a given order are found out. The multiple images are then used to track the multiple reflected ray paths and further used for the calculation of reflected fields. Since no unknowns are used on the cabin walls, the hybrid technique is well suited for electrically large cabin problems. Numerical examples are presented to demonstrate the accuracy and capability of the presented technique.

Efficient wireless link modeling for marine drone application under harsh offshore environment

Tasks to be carried out in maritime are usually expensive due to the use of the manned vessels with large operational crews that includes the safety of life and property at sea environment. Utilization of drones has potential to significantly improve the efficiency and safety of marine and offshore operations. Examples include remotely operated inspection for navigation, surveillance or monitoring ship conditions including emissions, unmanned offshore delivery from shore and search & rescue operations. With defining of new technology as marine drones in such applications, ensuring robust control under harsh offshore environments is the critical issue that needs to be addressed before marine drones can be adopted for widespread commercial use. One of the key research areas to ensure the robust control and operation of marine drones is wireless communication link between drone and control station [1]. The main radio-wave propagation mechanism for near sea-surface applications in an evaporation duct is illustrated in Figure 1.

Model-assisted NDT for sub-mm surface-breaking crack detection in alloys

A model has been developed to quickly and accurately simulate the response of eddy current probe to sub-mm crack in alloy. Electromagnetic (EM) modeling technique employed a fast and yet stable integral equation (IE) method. Enhanced detection can be achieved via an EM circuit co-simulation approach, which significantly boosted the response signals above the background noise threshold. With this, surface breaking cracks is detected by the resonant frequency-shifting of eddy current response. The developed model was validated by comparing simulated results to the experimental response obtained using an eddy current data collection system.

Electrical resonance eddy current sensor for submillimeter defect detection

Electrical resonance based eddy current methods are being investigated and developed for the detection of sub-millimeter surface defects in low conductivity material such as superalloy in aircraft. The probe has high sensitivity due to the noise elimination by evaluate the relative resonance shift on the impedance change cause by material properties variance. This method has reported analytically with experimental validation recently. In this paper, the detecting system includes the coil sensor and the coaxial connection is modelled using full wave electromagnetic simulation with integration of the circuit co-simulator. The finite element simulation is to study the probe behavior while the circuit model simulator is used to investigate the influence of the component such as capacitance and resistance in the detection system. With our model, further investigation on the sensitivity of the detection system due to the variation of sensor parameters, such as ferrite core and liftoff as well as and capacitance and effective resistance from the electronic component, is performed. This study not only contributes to the optimization and sensitivity enhancement of the detecting system, but also provide accurate detection of submillimeter defect.

Inversion-based imaging using lagrange polynomial parameterization and genetic algorithm optimization

A fast crack profile reconstitution method is developed using eddy current probing scheme. The technique employed genetic algorithm (GA) optimization together with boundary element method (BEM) to evaluate the shape of the cracks that are described by using the Lagrange polynomial (LP). In doing so, the shape of the open cracks could be obtained. Compared to the pixel-based description of the cracks, the LP description could significantly reduce the number of the unknowns, and this increases the efficiency of the global searching by the GA. This technique has greatly improved the efficiency of the inversion solver. Numerical tests are shown to validate the interests.