Browsing by Subject "array"
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Item Circular sensor array and nonlinear analysis of homopolar magnetic bearings(Texas A&M University, 2007-04-25) Wiesenborn, Robert KyleMagnetic bearings use variable attractive forces generated by electromagnetic control coils to support rotating shafts with low friction and no material wear while providing variable stiffness and damping. Rotor deflections are stabilized by position feedback control along two axes using non-contacting displacement sensors. These sensor signals contain sensor runout error which can be represented by a Fourier series composed of harmonics of the spin frequency. While many methods have been proposed to compensate for these runout harmonics, most are computationally intensive and can destabilize the feedback loop. One attractive alternative is to increase the number of displacement sensors and map individual probe voltages to the two independent control signals. This approach is implemented using a circular sensor array and single weighting gain matrix in the present work. Analysis and simulations show that this method eliminates runout harmonics from 2 to n-2 when all sensors in an ideal n-sensor array are operational. Sensor failures result in reduced synchronous amplitude and increased harmonic amplitudes after failure. These amplitudes are predicted using derived expressions and synchronous measurement error can be corrected using an adjustment factor for single failures. A prototype 8-sensor array shows substantial runout reduction and bandwidth and sensitivity comparable to commercial systems. Nonlinear behavior in homopolar magnetic bearings is caused primarily by the quadratic relationship between coil currents and magnetic support forces. Governing equations for a permanent magnet biased homopolar magnetic bearing are derived using magnetic circuit equations and linearized using voltage and position stiffness terms. Nonlinear hardening and softening spring behavior is achieved by varying proportional control gain and frequency response is determined for one case using numerical integration and a shooting algorithm. Maximum amplitudes and phase reversal for this nonlinear system occur at lower frequencies than the linearized system. Rotor oscillations exhibit amplitude jumps by cyclic fold bifurcations, creating a region of hysteresis where multiple stable equilibrium states exist. One of these equilibrium states contains subharmonic frequency components resulting in quasiperiodic rotor motion. This nonlinear analysis shows how nonlinear rotor oscillations can be avoided for a wide range of operation by careful selection of design parameters and operating conditions.Item Modeling and design of compact microwave components and systems for wireless communications and power transmission(Texas A&M University, 2004-09-30) Zepeda, PaolaThe contribution of the work here presented involves three main topics: Wireless Power Transmission (WPT) technology, phased array systems, and microwave components design and modeling. The first topic presents the conceptual design of a WPT system at 2.45GHz with 90% efficiency and 1MW of DC output power. Second, a comparative study between 2.45 and 35GHz WPT operation is provided. Finally, the optimization of a taper distribution with reduced thermal constraints on a sandwich transmitter is realized. For a 250- and 375-m antenna radius, 89.7% of collection efficiency with 29% reduction in maximum power density (compared to the Gaussian), and 93% collection efficiency with 39% reduction of maximum power density, are obtained respectively with two split tapers. The reduction in maximum power density and the use of split taper are important to alleviate the thermal problems in high power transmission. For the phased array project, the conceptual design of a small-scale system and in-depth analysis using two main approaches (statistical and field analysis) is realized. Practical aspects are addressed to determine the phased array main design features. The statistical method provides less accurate results than the field analysis since it is intended for large arrays. Careful theoretical analysis led to good correlation between statistical, field analysis and experimental results. In the components chapter, efficient loop transitions used in a patch antenna array are designed at K- and W-band. Measured insertion loss (IL) K-band loop is under 0.4dB. The K- and W-band antenna array measured broadside gains are 23.6dB at 24.125GHz and 25dB at 76.5GHz with return loss under 9.54dB from 24 to 24.4GHz and 12 dB from 75.1 to 77.3GHz, respectively. Also, a multilayer folded line filter is designed at 5.8GHz and compared to planar ring filters. Improved measured bandwidth from 2GHz to 7.5GHz and IL of 1.2dB are obtained with approximately half the size of a planar ring resonator. Thirdly, a simplified switch model is implemented for use in broadband phased-shifters. The model presents very good fit to the measured results with an overall total error under 3%, magnitude error less than 8%, and phase errors less than ?0.4?.Item Mutable Detector Array Software for the Detection of Gamma Emissions in Classrooms and the Field(2012-10-19) Hearn, Gentry CharlesDetector arrays are required for many applications in health and defense. Whether searching for contraband or controlling radioactive spread after an event, a "passive" data collection strategy is a key component. This can take the form of portal monitors attached to a fixed location or a movable array, attached to a vehicle or person, which searches for abnormalities in the radiation background. The main goal of this project was to create software that would allow the digiBASE-E to be used to create arrays of gamma detection instruments and gather data over a long span of time. To take full advantage of the digiBASE-E, the software focused on the list mode capabilities of these devices. List mode attaches a timestamp to each detection event. Every particle detected can be traced to a particular point in time, and the full history of the device?s detection over the acquisition period can be reconstructed. The list mode ability of the digiBASE-E is a powerful tool for producing arrays of detectors, as a more familiar spectrum can be generated for any arbitrary section of time, even after-the-fact. The software package, called "CraneWow", was field tested at the Port of Tacoma in August of 2011. Perl scripts included as part of the package were used to partially analyze the data collected, allowing for verification of the proof-of-concept's success. The software was written in C/C++, with supplemental scripts written in Perl to facilitate processing of the data once collected. Additionally, a user manual and programming guide were written to allow easy use and maintenance of the software.