Browsing by Subject "voltage"

Now showing 1 - 3 of 3
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    EXCESS PASSIVITY BASED CONTROL OF NONLINEAR BUCK-BOOST CONVERTER
    (Office of the Vice Chancellor for Research, 2012-04-13) Gavini, Sree Likhita; Izadian, Afshin
    Buck-boost converters are nonlinear systems and can either step-up or step-down the output voltage. A number of effective non-linear controllers such as sliding mode control, passivity based control, feedback linearization are in use for regulating the voltage of power converters. Direct regulation of voltage in non-minimum phase power converters such as buck-boost converter is challenging, as the zero dynamics of the output voltage are unstable. Consequently, these controllers make use of one-to-one correspondence between the voltage and current equilibriums and exploit the property that when the average output of the buck-boost converter is the inductor current, the system dynamics are stable. So the existing control strategies indirectly regulate the voltage, but their performance is susceptible to circuit parameter variations like load variation. As a result, adaptive versions of the controllers are incorporated to achieve a satisfactory performance, which in turn increases the system complexity. This problem of regulating the non-minimum phase voltage of the power converters continues to challenge and some solutions to this problem are presented based on different energy shaping approaches. The principal investigation in these approaches focuses on characterizing the energy of the system based on the physical structure of the system and uses this energy function description to draw conclusions about the degree of passivity i.e. damping in the system. This work approaches the problem by characterizing the degree of passivity in the system from passivity indices rather than from the system’s energy function, and thus views the problem from a system level rather from a circuit level description. We claim and support our claim from simulation and experimental results that this approach is complementary to existing approaches and uses a linear control to achieve the same objective as direct regulation of voltage and robustness against load variations.
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    LITHIUM-AQUEOUS BATTERY
    (Office of the Vice Chancellor for Research, 2012-04-13) Cavazos, Ana; Mosier, Luke; Chen, Rongrong; Kim, Youngsik
    Due to the exceptionally high energy density Lithium-water batteries have very high storage efficiency. Being able to store more energy is im-portant to many industries including electronics and electric vehicles. This is the reason that much research is being done to optimize and explore new techniques of development for these batteries. The Li-water battery has been designed in this project to test water and other aqueous solutions as the cathode. The lithium in a non-aqueous elec-trolyte acts as the anode of the battery. The solid electrolyte used in the lith-ium water batteries is a glass/ceramic (LISICON). The solid electrolyte acts as a separator allowing the Lithium ions to pass through it without allowing the liquid cathode come into direct contact the Lithium. This paper describes the creation and testing of a Lithium-water battery which uses water and Copper (II) Nitrate as the cathode electrolyte. The purpose of this paper is to compare and contrast the difference in voltage of distilled water and distilled water with Copper (II) Nitrate additives as cath-ode. When the tests were conducted, it was found that Copper (II) Nitrate does in fact increase the voltage of the Lithium-water batteries significantly when compared to the distilled water. These results were expected because of Copper (II) Nitrate’s strong electrolyte properties.
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    THE MEMRISTOR: FREQUENCY RESPONSE OF A HYSTERETIC DEVICE
    (Office of the Vice Chancellor for Research, 2012-04-13) Meijome, Natalia C.; Joglekar, Yogesh N.
    The memristor, postulated in the 1970’s, was recently realized in a tita-nium dioxide thin-film device and is now being commercially developed. Memristor, short for memory resistor, is the fourth fundamental circuit ele-ment whose instantaneous resistance depends not only on the voltage, but also on the history of the voltage applied to it. We investigate the frequency response of the current through a memristor due to an externally applied periodic voltage with the application of an algorithmic code using MATLAB. With these results, we are able to understand the characteristic response that this device displays for each corresponding input voltage frequency. Due to the range of response exhibited, there is the possibility of using this device in circuits to produce entirely new functions. We expect that this analysis will have implications for scientific advancement in both circuitry development as well as neuroscience due to a memristor’s ability to perform logic operations and store information. This work is supported by the Ronald E. McNair Post-Baccalaureate Achievement Program and a UROP grant (N.M.) and the NSF (Y.J.).