Analysis of Radiation Patterns in Three-Phase Motor with the Stator Winding as a Circular Array of Antenna

Department of Electrical EngineeringThis thesis presents method of estimating radiated emission (RE) occurring in stator winding of three-phase motor drive system. The stator winding of given reference motor model is assumed as circular array of radiating antennas. Radiation patterns can be obtained by calculation of magnetic vector potential of balanced three-phase current source distribution. Analysis in far-field radiation region boundary instead of near-field radiation region is proceeded in the condition of the CISPR 25 standard. Radiation patterns are estimated in fixed measurement distance within various frequency band. Radiation region boundary classification is defined under the given frequency range. Far-field condition is essential progress to justify the proposed approach. The radiation patterns can be estimated by 3D full-wave electromagnetic simulation using finite element method (FEM). Each radiation patterns can be calculated by analyzing both theta (??) component and phi (??) component. The fields are analyzed in case when ??=90?? and ??=90??. Radiated electric fields can be measured in every single degree. The harmonic frequency that excites the far-field radiation can be any integer multiple of the fundamental line frequency. When the harmonic number is multiple of three, the radiated electric fields suppress each other due to the balanced current distribution. However, when harmonic number is not multiple of three, the current source involved in motor operation has appropriate sequence. The meaningful radiation patterns can be analyzed with the correctly involved three-phase current excitation. The stator winding coils are closely positioned, mutual coupling effect among the coils cannot be neglected. The multi-port RLC network circuit model is proposed to compensate in order to calculate proper radiation patterns. Loop of coil contains two axial and two end-turn current direction. Each magnetic vector potential can be obtained by summing each phase current density. The phi-directional electric field is origin by current distribution of end-winding component of current source. On the other hand, the theta-direction electric field is related to axial component. The analysis of radiation patterns represents the dominant radiation component in AC motor operation.clos

Hydrodynamic focusing micropump module with PDMS/nickel-particle composite diaphragms for microfluidic systems

In this research, a rapid prototype of multi-fluidic speed-modulating (MFSM) micropump which enables modulation of hydrodynamic focusing in micro-fluidic flow has been designed, fabricated, and characterized. The size of the entire module is 33 mm x 25 mm x 8 mm and comprises of three MFSM micropumps to achieve hydrodynamic focusing. These pumps are simultaneously operated by the same actuation source. Each micropump consists of Tesla-type valves in the bottom layer and PDMS/Ni-particle composite (PNPC) diaphragm in the middle layer. The deflection of the diaphragm is obtained by the external pneumatic force, and the permanent magnet controls the displacement resulting from interaction between the magnetic field and the PNPC diaphragm. Analyses of the magnetic modulation force, the flow rate of the MFSM micropump, and the hydrodynamic focused channel modulation are presented. The individual micropump can pump DI water at flow rate of 107 ìl/min, and the combination of the three micropumps is able to make the flow rate of 321 ìl/min within a hydrodynamic focusing channel. This research successfully examines the possibility of modulation of a neighboring channel flow rate through interaction with a magnetic force field to achieve hydrodynamic focusing of flow in the central channel. With appropriate magnetic interaction with diaphragm, the central channel flow width can also be varied. This technique can be utilized for possible application in drug delivery system (DDS), lab-on-a-chip (LOC) or micro total analysis system (ìTAS), and in a point of care testing (POCT) system

Clinical Probe Utilizing Surface-Enhanced Raman Scattering (SERS) for In-Situ Molecular Imaging Applications

In this research, a clinical probe utilizing Surface-Enhanced Raman Scattering (SERS) is developed for molecular imaging application which is a visualizing technology to support early diagnosis by providing images in molecular level. In addition to other molecular imaging applications using magnetic resonance, light, and ultrasound, Raman spectroscopy has great potential in terms of non-invasiveness, safety, imaging agent-free, and scanning multiple molecules at a time. However, the critical limitation of Raman spectroscopy using in-vivo molecular imaging application is the inherent low sensitivity of Raman effect. The challenge is overcome by employing SERS enhancing Raman scattering with concentrated electromagnetic oscillation in nanometallic structures. This phenomenon gives normal Raman spectroscopy more capabilities for diverse applications, especially for a clinical Raman probe of molecular imaging. The imaging apparatus is composed of three parts: SERS substrate with nanostructures, probe with gradient index (GRIN) lens, and signal transmission system from the spectrometer and the probe. For a transparent SERS substrate, electrochemically etched porous silicon (PS) is employed as a master mold from which a transparent UV epoxy is cast, and different thicknesses of gold (Au) are sputtered over the cast nanostructures. Rhodamine 6G solutions on the transparent SERS substrates are characterized and analyzed with various aspects in a fluidic cell. In addition to the transparent SERS substrate, a clinical probe is customized with the optical analysis of gradient-index (GRIN) lens in order to focus laser beam on SERS substrate. A transmission system, called “articulated arm” is built with multiple rotating joints which reflect laser light 90 degree. The clinical probe is assembled with transmission system, and the scanned Raman signals are transmitted from the target specimen to the Raman spectrometer. Some measurement results of a gelatin block contains Rhodamine 6G demonstrate that the developed remote probe using SERS and articulated arm show promising remote Raman detections for molecular imaging applications

Finer: Investigating and Enhancing Fine-Grained Visual Concept Recognition in Large Vision Language Models

Recent advances in instruction-tuned Large Vision-Language Models (LVLMs) have imbued the models with the ability to generate high-level, image-grounded explanations with ease. While such capability is largely attributed to the rich world knowledge contained within the Large Language Models (LLMs), our work reveals their shortcomings in fine-grained visual categorization (FGVC) across six different benchmark settings. Most recent state-of-the-art LVLMs like LLaVa-1.5, InstructBLIP and GPT-4V not only severely deteriorate in terms of classification performance, e.g., average drop of 65.58 in EM for Stanford Dogs for LLaVA-1.5, but also struggle to generate an accurate explanation with detailed attributes based on the concept that appears within an input image despite their capability to generate holistic image-level descriptions. In-depth analyses show that instruction-tuned LVLMs exhibit modality gap, showing discrepancy when given textual and visual inputs that correspond to the same concept, preventing the image modality from leveraging the rich parametric knowledge within the LLMs. In an effort to further the community's endeavor in this direction, we propose a multiple granularity attribute-centric evaluation benchmark, Finer, which aims to establish a ground to evaluate LVLMs' fine-grained visual comprehension ability and provide significantly improved explainability

ARMP: Autoregressive Motion Planning for Quadruped Locomotion and Navigation in Complex Indoor Environments

Generating natural and physically feasible motions for legged robots has been a challenging problem due to its complex dynamics. In this work, we introduce a novel learning-based framework of autoregressive motion planner (ARMP) for quadruped locomotion and navigation. Our method can generate motion plans with an arbitrary length in an autoregressive fashion, unlike most offline trajectory optimization algorithms for a fixed trajectory length. To this end, we first construct the motion library by solving a dense set of trajectory optimization problems for diverse scenarios and parameter settings. Then we learn the motion manifold from the dataset in a supervised learning fashion. We show that the proposed ARMP can generate physically plausible motions for various tasks and situations. We also showcase that our method can be successfully integrated with the recent robot navigation frameworks as a low-level controller and unleash the full capability of legged robots for complex indoor navigation.Comment: Submitted to IRO