Sampled-Data and Harmonic Balance Analyses of Average Current-Mode Controlled Buck Converter

Dynamics and stability of average current-mode control of buck converters are analyzed by sampled-data and harmonic balance analyses. An exact sampled-data model is derived. A new continuous-time model "lifted" from the sampled-data model is also derived, and has frequency response matched with experimental data reported previously. Orbital stability is studied and it is found unrelated to the ripple size of the current-loop compensator output. An unstable window of the current-loop compensator pole is found by simulations, and it can be accurately predicted by sampled-data and harmonic balance analyses. A new S plot accurately predicting the subharmonic oscillation is proposed. The S plot assists pole assignment and shows the required ramp slope to avoid instability.Comment: Submitted to International Journal of Circuit Theory and Applications on August 9, 2011; Manuscript ID: CTA-11-016

Frequency Modulated Continuous Wave Radar and Video Fusion for Simultaneous Localization and Mapping

There has been a push recently to develop technology to enable the use of UAVs in GPS-denied environments. As UAVs become smaller, there is a need to reduce the number and sizes of sensor systems on board. A video camera on a UAV can serve multiple purposes. It can return imagery for processing by human users. The highly accurate bearing information provided by video makes it a useful tool to be incorporated into a navigation and tracking system. Radars can provide information about the types of objects in a scene and can operate in adverse weather conditions. The range and velocity measurements provided by the radar make it a good tool for navigation. FMCW radar and color video were fused to perform SLAM in an outdoor environment. A radar SLAM solution provided the basis for the fusion. Correlations between radar returns were used to estimate dead-reckoning parameters to obtain an estimate of the platform location. A new constraint was added in the radar detection process to prevent detecting poorly observable reflectors while maintaining a large number of measurements on highly observable reflectors. The radar measurements were mapped as landmarks, further improving the platform location estimates. As images were received from the video camera, changes in platform orientation were estimated, further improving the platform orientation estimates. The expected locations of radar measurements, whose uncertainty was modeled as Gaussian, were projected onto the images and used to estimate the location of the radar reflector in the image. The colors of the most likely reflector were saved and used to detect the reflector in subsequent images. The azimuth angles obtained from the image detections were used to improve the estimates of the landmarks in the SLAM map over previous estimates where only the radar was used

God's Tapestry: Understanding and Celebrating Differences

Reivewed by Joseph Tortorici

Relative Stability of the Inner-Current Loop of Peak Current-Mode Controlled PWM DC-DC Converters in CCM

Current-mode control is a commonly adopted method of regulation for pulse-width modulated (PWM) dc-dc power converters in industry, but is not well understood. The advantages of current-mode control over the voltage-mode control include inherent overload and short circuit protection, faster response, line-noise rejection, and multiple converter paralleling. Current-mode controlled system consists of (1) an inner-current loop and (2) an outer-voltage loop, which sets the reference voltage to the inner loop. To ensure stable operation of the multi-loop converter, all the sequential loops in the circuit should be stable with sufficient degree of stability. The research in this dissertation is focused on the relative stability of the inner-current loop in peak current-mode (PCM) controlled PWM dc-dc converters operating in CCM. The operating principle of peak current-mode control is presented. The inner-current loop dynamics of a peak current-mode controlled dc-dc converter is investigated using perturbation theory. Considering its mixed-signal (analog and digital) behavior, the current loop is modeled using sample-and-hold theory. Taking the discrete nature of the inner-current loop into account, a closed-loop transfer function for the current loop is derived in z-domain and an equivalent-hold approximation is used to derive an approximate closed-loop transfer function in the continuous s-domain using modified Pad´e approximation. A general expression for the loop gain of the inner-loop, independent of the converter topology, is derived. Using the loop gain, a measure of relative stability of the inner loop is developed. Expressions for amount of slope compensation required at maximum duty cycle, for the inner loop to be marginally stable and to achieve a specified margin of stability, are derived. Also, expressions for maximum duty cycle at a given amount of slope compensation, for the inner loop to be marginally stable and to obtain a specified margin of stability, are derived. The control current expressions for the inner loop of peak current-mode controlled converters without and with slope compensation are derived. A procedure to design the inner-current loop is developed. Saber Sketch simulation and experimental results are presented to validate the presented theory. The dynamic behavior of the inner-current loop of peak current-mode controlled PWM dc-dc buck converter operating in CCM is analyzed. The critical path power stage transfer functions, the relevant inner-current loop transfer functions, and the control-to-output transfer function of peak current-mode controlled PWM dc-dc buck converter operating in CCM are derived. The presented model is validated using experimental Bode plots

Performing to Reclaim: War Trauma and Female Non-Combatant Recovery in Sylvia Townsend Warner, Virginia Woolf, and H.D.

This dissertation examines narrative representations of female non-combatant identity authored by Sylvia Townsend Warner, Virginia Woolf, and H.D. between 1916 and 1955, a historical moment consonant with World War I, the interwar era, World War II, and its aftermath. Their depictions of the material reality of war and its devastating impact on selfhood span the genres of the diary, essay, long poem, and novel. I argue that each text forwards a specifically feminist approach to recovery, which manifests in three ways. First, as experimental texts, these works embrace (and mirror) the shattering effects of trauma and loss sustained by non-combatant women, and thereby portray female identity as narrative. Recovery thus entails that the non-combatant acknowledge and integrate the experience of war and identity trauma into her narrative, and redefine self in a way that does not merely replicate her prewar identity. Second, such self-(re)definition occurs through the performative exercise of multiple subjectivity. Put differently, non-combatant women remake self by entering into postwar roles rooted in the intellect, political involvement, artistry, or multiple sexualities. Finally, narrative recovery is emblematic of the authors\u27 collective aim to renounce the restrictive influence of patriarchal ideology upon womanhood. By exercising autonomy, woman equips herself to withstand future disruptions to her reemerging narrative. With the exception of the chapter on Woolf--which approaches Between the Acts (1941) as a return to the exploration of female recovery in Mrs. Dalloway (1925)--this dissertation examines non-canonical texts, tracing shifts in representations of female non-combatant subjectivity throughout the career of each writer. My discussion of Warner includes an essay detailing her employment in a munitions factory (1916); Opus 7 (1927), a long poem featuring a protagonist whose attempts at recovery are tragically flawed; and Summer Will Show (1936), a novel that attributes female autonomy to political involvement and alternative sexuality. Finally, my work on H.D. considers the development of an increasingly transparent autobiographical subject in Within the Walls (1941), The Sword Went Out to Sea (1946-47), and her unpublished diary-memoir, Compassionate Friendship (1955), in which H.D. reflects upon her own experiences of war, writing, illness, and loss

Deterministic Global 3D Fractal Cloud Model for Synthetic Scene Generation

This paper describes the creation of a fast, deterministic, 3D fractal cloud renderer for the AFIT Sensor and Scene Emulation Tool (ASSET). The renderer generates 3D clouds by ray marching through a volume and sampling the level-set of a fractal function. The fractal function is distorted by a displacement map, which is generated using horizontal wind data from a Global Forecast System (GFS) weather file. The vertical windspeed and relative humidity are used to mask the creation of clouds to match realistic large-scale weather patterns over the Earth. Small-scale detail is provided by the fractal functions which are tuned to match natural cloud shapes. This model is intended to run quickly, and it can run in about 700 ms per cloud type. This model generates clouds that appear to match large-scale satellite imagery, and it reproduces natural small-scale shapes. This should enable future versions of ASSET to generate scenarios where the same scene is consistently viewed from both GEO and LEO satellites from multiple perspectives

A low-cost photovoltaic emulator for static and dynamic evaluation of photovoltaic power converters and facilities

In testing maximum power point tracking (MPPT) algorithms running on electronic power converters for photovoltaic (PV) applications, either a PV energy source (PV module or PV array) or a PV emulator is required. With a PV emulator, it is possible to control the testing conditions with accuracy so that it is the preferred option. The PV source is modeled as a current source; thus, the emulator has to work as a current source dependent on its output voltage. The proposed emulator is a buck converter with an average current mode control loop, which allows testing the static and dynamic performance of PV facilities up to 3 kW. To validate the concept, the emulator is used to evaluate the MPPT algorithm of a 230-W experimental microinverter working from a single PV module.This work is supported by the Spanish Ministry of Science and Innovation under grant ENE2009-13998-C02-02.González Medina, R.; Patrao Herrero, I.; Garcerá Sanfeliú, G.; Figueres Amorós, E. (2014). A low-cost photovoltaic emulator for static and dynamic evaluation of photovoltaic power converters and facilities. Progress in Photovoltaics. 22(2):227-241. https://doi.org/10.1002/pip.2243S227241222Prapanavarat, C., Barnes, M., & Jenkins, N. (2002). Investigation of the performance of a photovoltaic AC module. IEE Proceedings - Generation, Transmission and Distribution, 149(4), 472. doi:10.1049/ip-gtd:20020141Durán, E., Andújar, J. M., Galán, J., & Sidrach-de-Cardona, M. (2009). Methodology and experimental system for measuring and displayingIâ Vcharacteristic curves of PV facilities. Progress in Photovoltaics: Research and Applications, 17(8), 574-586. doi:10.1002/pip.909Piliougine, M., Carretero, J., Mora-López, L., & Sidrach-de-Cardona, M. (2011). Experimental system for current-voltage curve measurement of photovoltaic modules under outdoor conditions. Progress in Photovoltaics: Research and Applications, 19(5), 591-602. doi:10.1002/pip.1073Sanchis, P., López, J., Ursúa, A., Gubía, E., & Marroyo, L. (2007). On the testing, characterization, and evaluation of PV inverters and dynamic MPPT performance under real varying operating conditions. Progress in Photovoltaics: Research and Applications, 15(6), 541-556. doi:10.1002/pip.763Kjaer, S. B., Pedersen, J. K., & Blaabjerg, F. (2005). A Review of Single-Phase Grid-Connected Inverters for Photovoltaic Modules. IEEE Transactions on Industry Applications, 41(5), 1292-1306. doi:10.1109/tia.2005.853371Kondrath, N., & Kazimierczuk, M. K. (2012). Comparison of Wide- and High-Frequency Duty-Ratio-to-Inductor-Current Transfer Functions of DC–DC PWM Buck Converter in CCM. IEEE Transactions on Industrial Electronics, 59(1), 641-643. doi:10.1109/tie.2011.2134053Tan, Y. T., Kirschen, D. S., & Jenkins, N. (2004). A Model of PV Generation Suitable for Stability Analysis. IEEE Transactions on Energy Conversion, 19(4), 748-755. doi:10.1109/tec.2004.827707Villalva, M. G., Gazoli, J. R., & Filho, E. R. (2009). Comprehensive Approach to Modeling and Simulation of Photovoltaic Arrays. IEEE Transactions on Power Electronics, 24(5), 1198-1208. doi:10.1109/tpel.2009.2013862Shengyi Liu, & Dougal, R. A. (2002). Dynamic multiphysics model for solar array. IEEE Transactions on Energy Conversion, 17(2), 285-294. doi:10.1109/tec.2002.1009482Mekki, H., Mellit, A., Kalogirou, S. A., Messai, A., & Furlan, G. (2010). FPGA-based implementation of a real time photovoltaic module simulator. Progress in Photovoltaics: Research and Applications, 18(2), 115-127. doi:10.1002/pip.950Mohan N Undeland T Robbins W Power electronics: converters, applications and design (3rd edn) 2003Garcera, G., Figueres, E., Pascual, M., & Benavent, J. M. (2004). Robust model following control of parallel buck converters. IEEE Transactions on Aerospace and Electronic Systems, 40(3), 983-997. doi:10.1109/taes.2004.1337469Vorperian, V. (1990). Simplified analysis of PWM converters using model of PWM switch. Continuous conduction mode. IEEE Transactions on Aerospace and Electronic Systems, 26(3), 490-496. doi:10.1109/7.106126Packiam, P., Jain, N. K., & Singh, I. P. (2011). Microcontroller-based simple maximum power point tracking controller for single-stage solar stand-alone water pumping system. Progress in Photovoltaics: Research and Applications, n/a-n/a. doi:10.1002/pip.1207Chuanzong F Shiping S Simulation studying of MPPT control by a new method for photovoltaic power system Electrical and Control Engineering (ICECE), 2011 International Conference on 2011 10.1109/ICECENG.2011.605791

Documentation of the one-person show of paintings and drawings

Includes pictures of paintings and drawings.The following work is presented in partial fulfillment of the requirements for the Master of Fine Arts degree at Northern Illinois University. The work was produced between November 1979 and June 1980. It was presented in an exhibition from June 21, 1980 through June 28, 1980 in the Graduate Gallery of the Visual Arts Building, Northern Illinois University, DeKalb, Illinois.M.F.A. (Master of Fine Arts

The visibility of music

In fulfillment of the requirements for a Master of Fine Arts degree, three dances were choreographed and performed at the Martha B. Knoebel Dance Theater located on the California State University, Long Beach campus. The dates each of these works premiered were October 14, 2010, April 28, 2011, and October 13, 2011. The dances were 10 minutes, 9 minutes, and 16 minutes in length, respectively. As If Falling Up was an exploration into the musical score as well as an investigation into eliminating gender to instead showcase the dancers' bodies as tools by which the dance was created. The Art of Breathing was created as a visual representation of the Bach cantata to which it was set. The Aesthetic of the Cool was created to explore the juxtaposition between set choreographic material and structured improvisational scores and how both respond to the musical accompaniment