• A Sounding Rocket Attitude Determination Algorithm Suitable For Implementation Using Low Cost Sensors

      Charlton, Mark Christopher; Hawkins, Joseph G. (2003)
      The development of low-cost sensors has generated a corresponding movement to integrate them into many different applications. One such application is determining the rotational attitude of an object. Since many of these low-cost sensors are less accurate than their more expensive counterparts, their noisy measurements must be filtered to obtain optimum results. This work describes the development, testing, and evaluation of four filtering algorithms for the nonlinear sounding rocket attitude determination problem. Sun sensor, magnetometer, and rate sensor measurements are simulated. A quatenion formulation is used to avoid singularity problems associated with Euler angles and other three-parameter approaches. Prior to filtering, Gauss-Newton error minimization is used to reduce the six reference vector components to four quaternion components that minimize a quadratic error function. Two of the algorithms are based on the traditional extended Kalman filter (EKF) and two are based on the recently developed unscented Kalman filter (UKF). One of each incorporates rate measurements, while the others rely on differencing quaternions. All incorporate a simplified process model for state propagation allowing the algorithms to be applied to rockets with different physical characteristics, or even to other platforms. Simulated data are used to develop and test the algorithms, and each successfully estimates the attitude motion of the rocket, to varying degrees of accuracy. The UKF-based filter that incorporates rate sensor measurements demonstrates a clear performance advantage over both EKFs and the UKF without rate measurements. This is due to its superior mean and covariance propagation characteristics and the fact that differencing generates noisier rates than measuring. For one sample case, the "pointing accuracy" of the rocket spin axis is improved by approximately 39 percent over the EKF that uses rate measurements and by 40 percent over the UKF without rates. The performance of this UKF-based algorithm is evaluated under other-than-nominal conditions and proves robust with respect to data dropouts, motion other than predicted and over a wide range of sensor accuracies. This UKF-based algorithm provides a viable low cost alternative to the expensive attitude determination systems currently employed on sounding rockets.
    • Design And Implementation Of A Meteor Tracking Retrofit System For The Hf Radar At Kodiak Island, Alaska

      Parris, Richard Todd; Bristow, William (2003)
      The HF radar at Kodiak Island, Alaska, is part of the SuperDARN network of radars, and was originally designed to detect echoes from ionospheric field-aligned density irregularities. A new digital receiver has been implemented on the radar to allow provide the capabilities required for increased range resolution detection of meteor echoes. A meteor detection algorithm has also been implemented to detect meteor echoes with a range resolution of 4.5 km. The algorithm measures the velocity, range, and altitude of the echoes. This data can be used to derive information about the meteor region winds. The design and implementation of the receiver, the design and implementation of the meteor detection algorithm, and some meteor region wind data derived from the new system are presented. <p>
    • Developing Computer Models To Study The Effect Of Outdoor Air Quality On Indoor Air For The Purpose Of Enhancing Indoor Air Quality

      Marsik, Tomas; Johnson, Ron (2007)
      People in developed countries spend the majority of their time indoors. Therefore, studying the effect of outdoor air quality on indoor air is of a great importance to human health. This thesis presents several dynamic computer models that were developed to study this effect. They estimate indoor pollutant levels based on outdoor levels, ventilation rate, and other factors. Also, an analysis method is presented that allows for quantifying the effect of outdoor air quality on indoor air at a given building based on measured real-time outdoor and indoor pollutant levels. An important part of this method is separating the measured indoor level into two components - a component caused by indoor sources and a component caused by pollutants penetrating from outdoors. This separation is accomplished using a dynamic model, which, unlike some other methods, also allows for processing transient samples and thus simplifies the needed measurements. Outdoor and indoor pollutant levels were measured at eight buildings in Fairbanks, Alaska and the developed method was used to analyze the data. The main focus was on fine particulate matter (PM2.5) and carbon monoxide (CO) - the pollutants of major concern in Fairbanks. The effective penetration efficiency for PM2.5 ranged from 0.16 to 0.69, and was close to unity for CO. The outdoor generated PM2.5 was responsible in average for about 67% of the indoor PM2.5 in residences, and close to 100% in office environments. These results imply that reducing outdoor pollution can have significant health benefits even for people spending the majority of their time indoors. An air-quality control algorithm for a Heating, Ventilation, and Air Conditioning (HVAC) system was developed and tested using one of the models. This algorithm was shown to reduce indoor PM2.5 levels by 65%. Another model was used to study various ventilation options for a typical Fairbanks home with respect to indoor air quality, energy consumption, overall economy, and environmental impact. Using a Heat Recovery Ventilator (HRV) with an additional filter was shown to be the best option. Another model was successfully used to address key factors for radon mitigation in a home located in a radon-prone area.
    • Development Of Resonance Fluorescence Lidar For Studies Of The Aurora

      Su, Liguo; Collins, Richard L. (2007)
      In this thesis I present resonance fluorescence lidar studies of the middle and upper atmosphere. I focus on two specific applications; lidar measurements of heat fluxes in the mesosphere, and lidar measurements of auroral nitrogen ions in the thermosphere. In the heat flux study, I determine the limitations in state-of-the-art sodium Doppler wind-temperature lidar measurements. I conduct statistical analysis of current lidar measurements using analytical and Monte Carlo techniques and extend them to consider future measurements. I find that the expected biases for summertime flux measurements in polar regions will be larger than the geophysical values of the fluxes. In the nitrogen resonance lidar study, I conduct a simulation of the measurements under realistic auroral conditions and found that current lidar systems should be able to make statistically significant measurements of the nitrogen profile at a resolution of 6 km and 300 s. I develop a prototype nitrogen resonance lidar system operating at 390 nm. This lidar system is based on an existing dye laser-based iron resonance lidar system that operates at 372 nm. I designed and implemented a tuning control system that allows 1 pm resolution in the laser tuning. I made a set of field measurements and found that the performance of the prototype lidar was less than expected. I conduct an engineering analysis of the measurements and conclude that the lower than expected performance is due to the lasing characteristics of the dye laser.
    • Hybrid Electric Power Systems In Remote Arctic Villages: Economic And Environmental Analysis For Monitoring, Optimization, And Control

      Agrawal, Ashish N.; Wies, Richard (2006)
      The need for energy-efficient and reliable electric power in remote arctic communities of Alaska is a driving force for research in this work. Increasing oil prices, high transportation costs for fuels, and new environmental standards have forced many utilities to explore hybrid energy systems in an attempt to reduce the cost of electricity (COE). This research involves the development of a stand-alone hybrid power system model using MATLABRTM SimulinkRTM for synthesizing the power system data and performing the economic and environmental analysis of remote arctic power systems. The hybrid model consists of diesel electric generators (DEGs), a battery bank, a photovoltaic (PV) array, and wind turbine generators (WTGs). The economic part of the model is used to study the sensitivity analysis of fuel cost and the investment rate on the COE, the life cycle cost (LCC) of the system, and the payback time of the system. The environmental part of the model calculates the level of various pollutants including carbon dioxide (CO2), nitrogen oxides (NOx), and the particulate matter (PM10). The environmental analyses part of the model also calculates the avoided cost of various pollutants. The developed model was used to study the economics and environmental impacts of a stand-alone DEG system installed at the University of Alaska Fairbanks Energy Center, the wind-diesel-battery hybrid power system installed at Wales Village, Alaska, and the PV-diesel-battery hybrid power system installed at Lime Village, Alaska. The model was also used to predict the performance of a designed PV-wind-diesel-battery system for Kongiganak Village. The results obtained from the SimulinkRTM model were in close agreement with those predicted by the Hybrid Optimization Model for Electric Renewables (HOMER) software developed at National Renewable Energy Laboratory (NREL).
    • Role Of Antennas And The Propagation Channel On The Performance Of An Ultra Wide Band (Uwb) Communication System

      Venkatasubramanian, Arun; Sonwalkar, Vikas (2007)
      The objectives of this dissertation are to experimentally and numerically quantify the effect of antennas and the propagation channel on the performance of an Ultra Wide Band (UWB) receiver. This work has led to the following new results: (1) the variation in the time duration of the impulse response of the oval dipole in the vertical plane is within 5% up to an angle theta = 60° off the broadside direction (theta = 90°); at larger angles a factor of six elongation in the time duration of the impulse response along the antenna axis (theta = 0°) is observed, (2) for an axial ratio of 0.5, the oval dipole has a Voltage Standing Wave Ratio (VSWR) of 2:1 (~11% reflection coefficient) in a 3.1 GHz bandwidth with a lower cut off frequency of 2.8 GHz; for an axial ratio of 2.0 this scales to 0.5 GHz bandwidth with a lower cut off frequency of 1.75 GHz, (3) a new theoretical model has been developed for UWB pulse propagation over the ground which takes into account the geometrical properties of the propagation channel (such as the heights of the transmitter (h1) and the receiver (h2) over the ground) and the nature of the radiated UWB pulse (such as pulse duration (taup) and cycle time (tauc)), (4) an improvement in bit error rate by up to a factor of 100 can be achieved for a matched filter receiver by careful orientation of the transmitting and the receiving oval dipole antennas used in the measurements presented in this dissertation.
    • Speed -Sensorless Estimation And Position Control Of Induction Motors For Motion Control Applications

      Barut, Murat; Bogosyan, Seta; Hawkins, Joseph G.; Wies, Richard W.; Bracio, Boris (2006)
      High performance sensorless position control of induction motors (IMs) calls for estimation and control schemes which offer solutions to parameter uncertainties as well as to difficulties involved with accurate flux and velocity estimation at very low and zero speed. In this thesis, novel control and estimation methods have been developed to address these challenges. The proposed estimation algorithms are designed to minimize estimation error in both transient and steady-state over a wide velocity range, including very low and persistent zero speed operation. To this aim, initially single Extended Kalman Filter (EKF) algorithms are designed to estimate the flux, load torque, and velocity, as well as the rotor, Rr' or stator, Rs resistances. The temperature and frequency related variations of these parameters are well-known challenges in the estimation and control of IMs, and are subject to ongoing research. To further improve estimation and control performance in this thesis, a novel EKF approach is also developed which can achieve the simultaneous estimation of R r' and Rs for the first time in the sensorless IM control literature. The so-called Switching and Braided EKF algorithms are tested through experiments conducted under challenging parameter variations over a wide speed range, including under persistent operation at zero speed. Finally, in this thesis, a sensorless position control method is also designed using a new sliding mode controller (SMC) with reduced chattering. The results obtained with the proposed control and estimation schemes appear to be very compatible and many times superior to existing literature results for sensorless control of IMs in the very low and zero speed range. The developed estimation and control schemes could also be used with a variety of the sensorless speed and position control applications, which are challenged by a high number of parameter uncertainties.