Development, simulation validation, and wind tunnel testing of a digital controller system for flutter suppression

Flutter suppression (FS) is one of the active control concepts being investigated by the AFW program. The design goal for FS control laws was to increase the passive flutter dynamic pressure by 30 percent. In order to meet this goal, the FS control laws had to be capable of suppressing both symmetric and antisymmetric flutter instabilities simultaneously. In addition, the FS control laws had to be practical and low-order, robust and capable of real time execution within the 200 hz. sampling time. The purpose here is to present an overview of the development, simulation validation, and wind tunnel testing of a digital controller system for flutter suppression

Phase and Amplitude Interferometry Based Radio Frequency Direction Finder

Direction finding (DF) systems have been around for decades, preceding WWII. The main function of these systems is to calculate the direction of arrival of an electromagnetic wave. There are many real-world applications which utilize direction finders and direction-finding techniques, from recreational “fox hunts” to military geolocation systems. The following approach for implementing a direction finding system revolves around the phase and amplitude of a signal that is being radiated at an unlicensed frequency of 2.45Ghz by an RF source. The system is comprised of an antenna array of 4 antennas which can be used receive the radiated signal. By comparing the amplitudes of the signal received by each antenna relative to each other, the quadrant from which the RF source is located in can be identified. By comparing the phase difference, 0° to +/- 180°, of the signal received by each antenna relative to each other, four possible directions can be calculated, one in each quadrant. Using the information discovered from comparing the phase and the amplitudes of the received signal at each antenna, the direction of the RF source can be found. The system runs the direction finding algorithm when the user commands it to from the graphical user interface (GUI), iterates it hundreds of times per second, and averages the found direction to reduce the effects of noise. The direction is then displayed on the GUI

The analysis of ion flow between the human body and local ground

The project was designed to get a better sense of the phenomenon referred to as Earthing. Earthing is defined as the process where the human body is in contact with the earth and can freely transfer ions between the Earth and itself. Those promoting the idea of earthing say that this transfer of ions is important in maintaining a healthy immune system, and they claim that the recent increase in autoimmune diseases is the result of humans being insulated from the ground because of the shoes they wear and the places in which they live

ECG baseline wander reduction using linear phase filters

The continuous real time reduction of baseline wander is a considerable problem in electrocardiography during exercises. Our solution consists of spectral filtering. The legitimacy of high-pass filtering of the ECG by means of digital linear phase filters with a low cut-off frequency as high as the heart rate is shown. The specifications of these filters are derived from experimental results. Special hardware is presented that simultaneously performs the desired real-time filter operation in four ECG leads

A Framework for Evaluating Security in the Presence of Signal Injection Attacks

Sensors are embedded in security-critical applications from medical devices to nuclear power plants, but their outputs can be spoofed through electromagnetic and other types of signals transmitted by attackers at a distance. To address the lack of a unifying framework for evaluating the effects of such transmissions, we introduce a system and threat model for signal injection attacks. We further define the concepts of existential, selective, and universal security, which address attacker goals from mere disruptions of the sensor readings to precise waveform injections. Moreover, we introduce an algorithm which allows circuit designers to concretely calculate the security level of real systems. Finally, we apply our definitions and algorithm in practice using measurements of injections against a smartphone microphone, and analyze the demodulation characteristics of commercial Analog-to-Digital Converters (ADCs). Overall, our work highlights the importance of evaluating the susceptibility of systems against signal injection attacks, and introduces both the terminology and the methodology to do so.Comment: This article is the extended technical report version of the paper presented at ESORICS 2019, 24th European Symposium on Research in Computer Security (ESORICS), Luxembourg, Luxembourg, September 201

Fast recursive filters for simulating nonlinear dynamic systems

A fast and accurate computational scheme for simulating nonlinear dynamic systems is presented. The scheme assumes that the system can be represented by a combination of components of only two different types: first-order low-pass filters and static nonlinearities. The parameters of these filters and nonlinearities may depend on system variables, and the topology of the system may be complex, including feedback. Several examples taken from neuroscience are given: phototransduction, photopigment bleaching, and spike generation according to the Hodgkin-Huxley equations. The scheme uses two slightly different forms of autoregressive filters, with an implicit delay of zero for feedforward control and an implicit delay of half a sample distance for feedback control. On a fairly complex model of the macaque retinal horizontal cell it computes, for a given level of accuracy, 1-2 orders of magnitude faster than 4th-order Runge-Kutta. The computational scheme has minimal memory requirements, and is also suited for computation on a stream processor, such as a GPU (Graphical Processing Unit).Comment: 20 pages, 8 figures, 1 table. A comparison with 4th-order Runge-Kutta integration shows that the new algorithm is 1-2 orders of magnitude faster. The paper is in press now at Neural Computatio

Demonstration of the Zero-Crossing Phasemeter with a LISA Test-bed Interferometer

The Laser Interferometer Space Antenna (LISA) is being designed to detect and study in detail gravitational waves from sources throughout the Universe such as massive black hole binaries. The conceptual formulation of the LISA space-borne gravitational wave detector is now well developed. The interferometric measurements between the sciencecraft remain one of the most important technological and scientific design areas for the mission. Our work has concentrated on developing the interferometric technologies to create a LISA-like optical signal and to measure the phase of that signal using commercially available instruments. One of the most important goals of this research is to demonstrate the LISA phase timing and phase reconstruction for a LISA-like fringe signal, in the case of a high fringe rate and a low signal level. We present current results of a test-bed interferometer designed to produce an optical LISA-like fringe signal previously discussed in the literature.Comment: find minor corrections in the CQG versio

Estimation of frequency response fuction for experimental modal analysis

Thesis (Master)--Izmir Institute of Technology, Civil Engineering, Izmir, 2008Includes bibliographical references (leaves: 125-129)Text in English; Abstract: Turkish and Englishxii, 129 leavesEvery structural system has unique dynamic parameters based on the mass, stiffness and the damping characteristics. If the system is linear and time invariant, dynamic parameters could be shown to be measured and formulated by the Frequency Response Function (FRF). The study of defining the dynamic parameters of a system thru well designed experiments and analysis is called experiment modal analysis. Experimental modal analysis has two major study areas which are modal testing and modal parameter estimation. FRFs are calculated based on the measured data in modal experiment and it is main input to the modal parameter estimation. Based on the measured/synthesized FRF dynamic parameters of the structures considered could be obtained In this study basics of the experimental modal analysis is studied. The primary objective is to see the effects of various testing and analysis parameters on the synthesis of FRF. This goal is achieved by testing and discussion of several simple structural systems.In the thesis general information about experimental modal analysis is presented.The experiment and the modal analysis results of the of the studied systems, which are simple beam, H-frame, square plate and 2D frame, is presented. Selected parameters that are effective on the FRF synthesis is discussed. These parameters are the attachment of the accelerometers, the tip hardness of the impact hammer and the digital signal processing errors such as leakage, windowing, filtering and averaging. The hammer and accelerometers calibrations will be discussed briefly as well. The results are discussed in order to provide some guidance for understanding the effects of the selected parameters on the FRFs