Influence Of Tooth Designs On Electromagnetic Characteristics In Fractional-Slot Permanent Magnet Brushless Machine

Due to factors such as a simpler construction and high torque density, the Permanent Magnet (PM) electric machines are favorable as an alternative to other conventional machine topologies. However, the PM machines may result high torque ripple due to the influences of cogging torque and electronic commutation respectively. In this research, an influence of various stator tooth designs on the electromagnetic characteristics in Fractional-Slot PM machines is investigated using 2D Finite-Element Analysis software, Ansys Maxwell. The influences of having additional thin PM on stator tooth-tip, asymmetric design of stator tooth-tip and the notch numbers and notch dimension are investigated for the purpose of torque ripple reduction at rated condition without degrading the average torque. By introducing these factors, the existing flux flows along the stator iron path would be affected leading to a potential change on the machine’s electromagnetic characteristics. The research has focused into the twelve-slot/ten-pole motor equipped with alternate tooth winding as it results more trapezoidal back-emf and lesser torque ripple. From the investigation, it is confirmed that a reduction of high torque ripple leading to a more constant torque at rated condition is desirable. It is also found that the machine which stator is modified has a significant reduction of torque ripple at about thirty-nine percent. For a verification purpose, the prototype motor design which is based on the lowest output torque ripple is developed and tested. A good agreement between predicted and measured results is achieved. The prototype design is then proposed for the application of robotic system

A Novel Microwave Sensor With High-Q Resonator For High Sensitivity Material Characterization

The use of novel microwave sensor on material characterization is an attractive idea. There are many applications that could benefit from this such as food industry, quality control and biomedical applications. The potential for highly accurate measurements of characterizing the material properties is offered by microwave resonant techniques at single or discrete set of frequencies. Conventionally, coaxial cavity, waveguide, and dielectric resonators have been used for characterizing the properties of materials. However, there are also challenges that arise from these resonators. One of them is the problem of fabricating the sensors which increase the cost and the other one they require large amount of circuit size and consequently require similar processing capability which restrict their use in many important applications. Thus, planar resonant techniques have gained a considerable interest over the past few years due to their advantages such as low cost, ease of fabrication and compact in circuit size. Conversely, these techniques suffer from low sensitivity and poor Q-factors which constrain their use and limit the range of materials characterizing applications. Therefore, this thesis presents novel structures of planar microwave sensors for detecting and characterizing the dielectric properties in common solids materials which produce high Q-factor with capability to suppress undesired harmonic spurious. These planar resonator structures are based on novel metamaterial symmetrical split ring resonator (SSRR) with and without spurlines filters by employing the perturbation theory, in which the dielectric properties of the resonator affect the Q-factor and resonance frequency. The sensors are designed at operating frequency of 2.2 GHz with resonant frequency ranging from 1 GHz to 10 GHz. As a results, the sensors achieve narrow resonance with low insertion loss and high Q sensitivity which peaked up to 652 at 2.2 GHz operating frequency. The circuit size of symmetrical split ring resonator is minimized about 30 % of total size by introducing spurlines filters. By using a specific experimental methodology, practical materials have been used as standards to validate the sensitivity of the sensors for permitting potentially material characterization and determination. In addition, a detailed sample thickness analysis has been carried out and accordingly the mathematical equation is derived to extract the materials with unknown properties. Experimentally, the measured and theoretical results are found in an excellent agreement with a 2 to 3 % possibility of typical error in the permittivity measurements. The average accuracy percentage of the measured results for all cases of the designed sensors is found within 97 to 98 % compared to those in literatures which has an average accuracy percentage of 91 to 92 % for the same tested standard materials. The most significant of using SSRR sensors with and without spurlines filters are to be used for various industrial applications such as food industry, quality control, bio–sensing medicine and pharmacy applications. It is believed that these techniques would lead for a promising solution of characterizing material particularly in determining material properties and quality

Multiple Order Dual-Band Active Ring Filters with Composite Right/Left Handed Cells

In this paper, a novel dual-band active filter topology is presented. The non-linear phase response of a composite right/left-handed cell is used to achieve the desired dual-band performance. Additionally, the proposed structure based on coupled ring resonators yields a very compact solution in which high-order implementations can be easily obtained by cascading multiple rings. The theoretical principles of this type of filters are analyzed in detail. Finally, three prototypes based on first-, second- and third-order structures validate the feasibility of this type of filters. Good agreement between simulations and measurements has been achieved

Enhanced symmetrical split ring resonator for metallic surface crack detection

An enhanced sensor based on symmetrical split ring resonator (SSRR) functioning at microwave frequencies has been proposed in order to detect and characterize the metal crack of the materials. This sensor is based on perturbation theory, in which the dielectric properties of the material affect the quality factor and resonance frequency of the microwave resonator. Conventionally, coaxial cavity, waveguide, dielectric resonator techniques have been used for characterizing materials. However, these techniques are often large, and expensive to build, which restricts their use in many important applications. Thus, the enhanced bio-sensing technique presents advantages such as high measurement sensitivity with the capability of suppressing undesired harmonic spurious and permits potentially metal crack material detection. Hence, using a High Frequency Structure Simulator (HFSS) software, the enhanced sensor is modeled and the reflection S11 is performed for testing the aluminum metal with crack and without crack at the frequency range of 100 MHz to 3GHz. Variation of crack width and depth has been investigated and the most obvious finding emerged from this study is that the ability of detecting a minimum of sub-millimeter crack width and depth which is a round 10 m width or depth where the minimum shift of reflected frequency is recorded at 6.2 MHz and 3 MHz for crack width and depth respectively. The enhanced SSRR provides high capability of detecting small crack defection by utilizing the interaction between coupled gap resonators and it is useful for various applications such as aircraft fuselages, nuclear power plant steam generator tubing, and steel bridges and for others that can be compromised by metal fatigue

Antenna-coupled TES bolometer arrays for CMB polarimetry

We describe the design and performance of polarization selective antenna-coupled TES arrays that will be used in several upcoming Cosmic Microwave Background (CMB) experiments: SPIDER, BICEP-2/SPUD. The fully lithographic polarimeter arrays utilize planar phased-antennas for collimation (F/4 beam) and microstrip filters for band definition (25% bandwidth). These devices demonstrate high optical efficiency, excellent beam shapes, and well-defined spectral bands. The dual-polarization antennas provide well-matched beams and low cross polarization response, both important for high-fidelity polarization measurements. These devices have so far been developed for the 100 GHz and 150 GHz bands, two premier millimeter-wave atmospheric windows for CMB observations. In the near future, the flexible microstrip-coupled architecture can provide photon noise-limited detection for the entire frequency range of the CMBPOL mission. This paper is a summary of the progress we have made since the 2006 SPIE meeting in Orlando, FL

Antenna-coupled TES bolometer arrays for CMB polarimetry

We describe the design and performance of polarization selective antenna-coupled TES arrays that will be used in several upcoming Cosmic Microwave Background (CMB) experiments: SPIDER, BICEP-2/SPUD. The fully lithographic polarimeter arrays utilize planar phased-antennas for collimation (F/4 beam) and microstrip filters for band definition (25% bandwidth). These devices demonstrate high optical efficiency, excellent beam shapes, and well-defined spectral bands. The dual-polarization antennas provide well-matched beams and low cross polarization response, both important for high-fidelity polarization measurements. These devices have so far been developed for the 100 GHz and 150 GHz bands, two premier millimeter-wave atmospheric windows for CMB observations. In the near future, the flexible microstrip-coupled architecture can provide photon noise-limited detection for the entire frequency range of the CMBPOL mission. This paper is a summary of the progress we have made since the 2006 SPIE meeting in Orlando, FL

A detector of small harmonic displacements based on two coupled microwave cavities

The design and test of a detector of small harmonic displacements is presented. The detector is based on the principle of the parametric conversion of power between the resonant modes of two superconducting coupled microwave cavities. The work is based on the original ideas of Bernard, Pegoraro, Picasso and Radicati, who, in 1978, suggested that superconducting coupled cavities could be used as sensitive detectors of gravitational waves, and on the work of Reece, Reiner and Melissinos, who, {in 1984}, built a detector of this kind. They showed that an harmonic modulation of the cavity length l produced an energy transfer between two modes of the cavity, provided that the frequency of the modulation was equal to the frequency difference of the two modes. They achieved a sensitivity to fractional deformations of dl/l~10^{-17} Hz^{-1/2}. We repeated the Reece, Reiner and Melissinos experiment, and with an improved experimental configuration and better cavity quality, increased the sensitivity to dl/l~10^{-20} Hz^{-1/2}. In this paper the basic principles of the device are discussed and the experimental technique is explained in detail. Possible future developments, aiming at gravitational waves detection, are also outlined.Comment: 28 pages, 12 eps figures, ReVteX. \tightenlines command added to reduce number of pages. The following article has been accepted by Review of Scientific Instruments. After it is published, it will be found at http://link.aip.org/link/?rs

Compact planar microwave blocking filters

A compact planar microwave blocking filter includes a dielectric substrate and a plurality of filter unit elements disposed on the substrate. The filter unit elements are interconnected in a symmetrical series cascade with filter unit elements being organized in the series based on physical size. In the filter, a first filter unit element of the plurality of filter unit elements includes a low impedance open-ended line configured to reduce the shunt capacitance of the filter