DSP BASED SIGNAL PROCESSING UNIT FOR REAL TIME PROCESSING OF VIBRATION AND ACOUSTIC SIGNALS OF SATELLITE LAUNCH VEHICLES
AffiliationIndian Space Research Organisation
KeywordsAcoustic Data Processing
Vibration Data Processing
Real time Processing
Digital Signal Processor
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AbstractMeasurement of vibration and acoustic signals at various locations in the launch vehicle is important to establish the vibration and acoustic environment encountered by the launch vehicle during flight. The vibration and acoustic signals are wideband and require very large telemetry bandwidth if directly transmitted to ground. The DSP based Signal Processing Unit is designed to measure and analyse acoustic and vibration signals onboard the launch vehicle and transmit the computed spectrum to ground through centralised baseband telemetry system. The analysis techniques employed are power spectral density (PSD) computations using Fast Fourier Transform (FFT) and 1/3rd octave analysis using digital Infinite Impulse Response (IIR) filters. The programmability of all analysis parameters is achieved using EEPROM. This paper discusses the details of measurement and analysis techniques, design philosophy, tools used and implementation schemes. The paper also presents the performance results of flight models.
SponsorsInternational Foundation for Telemetering
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Processing High Purity Zirconium Diboride Ultra-High Temperature Ceramics: Small-to-Large Scale ProcessingPham, David (The University of Arizona., 2016)Next generation aerospace vehicles require thermal protection system (TPS) materials that are capable of withstanding the extreme aerothermal environment during hypersonic flight (>Mach 5 [>1700 m/s]). Ultra-high temperature ceramics (UHTC) such as zirconium diboride (ZrB₂) are candidate TPS materials due to their high-temperature thermal and mechanical properties and are often the basis for advanced composites for enhanced oxidation resistance. However, ZrB₂ matrix impurities in the form of boron trioxide (B₂O₃) and zirconium dioxide (ZrO₂) limit the high-temperature capabilities. Electric based sintering techniques, such as spark plasma sintering (SPS), that use joule heating have become the preferred densification method to process advanced ceramics due to its ability to produce high density parts with reduced densification times and limit grain growth. This study focuses on a combined experimental and thermodynamic assisted processing approach to enhance powder purity through a carbo- and borocarbo-thermal reduction of oxides using carbon (C) and boron carbide (B₄C). The amount of oxides on the powder surface are measured, the amount of additive required to remove oxides is calculated, and processing conditions (temperature, pressure, environment) are controlled to promote favorable thermodynamic reactions both during thermal processing in a tube furnace and SPS. Untreated ZrB₂ contains 0.18 wt%O after SPS. Additions of 0.75 wt%C is found to reduce powder surface oxides to 0.12 wt%O. A preliminary Zr-C-O computational thermodynamic model shows limited efficiency of carbon additions to completely remove oxygen due to the solubility of oxygen in zirconium carbide (ZrC) forming a zirconium oxycarbide (ZrCₓOᵧ). Scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) with atomic scale elemental spectroscopy shows reduced oxygen content with amorphous Zr-B oxides and discreet ZrO₂ particle impurities in the microstructure. Processing ZrB₂ with minimal additions of B₄C (0.25 wt%) produces high purity parts after SPS with only 0.06 wt%O. STEM identifies unique “trash collector” oxides composed of manufacturer powder impurities of calcium, silver, and yttrium. A preliminary Zr-B-C-O thermodynamic model is used to show the potential reaction paths using B₄C that promotes oxide removal to produce high-purity ZrB₂ with fine grains (3.3 𝜇m) and superior mechanical properties (flexural strength of 660MPa) than the current state-of-the-art ZrB₂ ceramics. Due to the desirable properties produced using SPS, there is growing interest to advance processing techniques from lab-scale (20 mm discs) to large-scale (>100 mm). The advancement of SPS technologies has been stunted due to the limited power and load delivery of lab-scale furnaces. We use a large scale direct current sintering furnace (DCS) to address the challenges of producing industrially relevant sized parts. However, current-assisted sintering techniques, like SPS and DCS, are highly dependent on tooling resistances and the electrical conductivity of the sample, which influences the part uniformity through localized heating spots that are strongly dependent on the current flow path. We develop a coupled thermal-electrical finite element analysis model to investigate the development and effects of tooling and current density manipulation on an electrical conductor (ZrB₂) and an electrical insulator, silicon nitride (Si₃N₄), at the steady-state where material properties, temperature gradients and current/voltage input are constant. The model is built based on experimentally measured temperature gradients in the tooling for 20 mm discs and validated by producing 30 mm discs with similar temperature gradients and grain size uniformity across the part. The model aids in developing tooling to manipulate localize current density in specific regions to produce uniform 100 mm discs of ZrB₂ and Si₃N₄.
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Mineral processing in a less developed country: Bauxite processing in Ghana.Agbolosoo, Emmanuel Kwami. (The University of Arizona., 1991)The purpose of this dissertation is to evaluate the feasiblity of alumina production in Ghana to replace imported alumina for the production of aluminum. It spells out the conditions which led to the existing bauxite-alumina-aluminum trade in the country. The structure of the economy of Ghana is examined to show the contributions of the important sectors to the total income of the country, and its dependence on a few export commodities for revenue. The plan to build a dam for the generation of hydroelectric power was linked to the establishment of an integrated aluminum industry based on the exploitation of domestic bauxite reserves. As the country could not finance the project alone, foreign assistance was sought. VALCO, a subsidiary of Kaiser and Reynolds, was formed to undertake the project. The agreement reached with VALCO was that a smelter would be built to use imported alumina for ten years, during which time a refinery would be built to feed the smelter from domestic sources. However, after ten years this could not be achieved, and the smelter continues to use imported alumina. A model of the world aluminum economy is used for analyzing the sensitivity of price to production and consumption expansion. The results show that industry demand is sensitive to the level of industrial activities in the developed countries, and less sensitive to the own price and cross price variables of aluminum in both the short and long run. On the other hand, supply is inelastic to the own price and the rate of capacity utilization in the short run, but elastic to both variables in the long run. An appraisal of opening a bauxite mine and an alumina refinery at Kibi is undertaken. The results show the levels of bauxite and alumina prices and the costs of construction at which the project is feasible. The shadow values and weights used are permittd to vary with changes in the economy's foreign trade and the balance of payments.