Combining Static Analyses and Frequency Domain System Identification to Enhance the Accuracy of a Fixed-Wing UAV Simulation

For over 30 years, the U.S. Army Aviation and Missile Research, Development, and Engineering Center (AMRDEC) has specialized in characterizing the performance of infrared (IR) imaging systems in the laboratory and field. In the late 90’s, AMRDEC developed the Automated IR Sensor Test Facility (AISTF) which allowed efficient deployment testing of Unmanned Aerial Systems (UAS) payloads. More recently, ImageJ has been used predominately as the image processing environment of choice for analysis of laboratory, field, and simulated data. The strengths of ImageJ are that it is maintained by the U.S. National Institute of Health, it exists in the public domain, and it functions on all major operating systems. Three new tools or “plugins” have been developed at AMRDEC to enhance the accuracy and efficiency of analysis. First, a Noise Equivalent Temperature Difference (NETD) plugin was written to process Signal Transfer Function (SiTF) and 3D noise data. Another plugin was produced that measures the Modulation Transfer Function (MTF) given either an edge or slit target. Lastly, a plugin was developed to measure Focal Plane Array (FPA) defects, classify and bin the customizable defects, and report statistics. This paper will document the capabilities and practical applications of these tools as well as profile their advantages over previous methods of analysis.

The United States Army is currently investigating the feasibility/utility of a high resolution Synthetic Aperture Radar (SAR) mode for the detection and subsequent engagement of targets by tactical missiles. A precision dynamic SAR testbed has been designed, constructed and installed by the United States Army Aviation and Missile Command's (AMCOM) Aviation and Missile Research, Development and Engineering Center (AMRDEC) at Redstone Arsenal, Alabama. The purpose of the testbed is to allow the development and evaluation of image formation algorithms, motion compensation techniques, and autofocus algorithms in a controlled and repeatable environment.

The U.S. Army Aviation and Missile Research, Development, and Engineering Center (AMRDEC) has been applying a Government-developed, productivity-oriented, Computational Fluid Dynamics (CFD) methodology to the aerodynamic design of Army missiles. This methodology, dubbed Euler Tunnel Analysis (ETA), uses automated grid generation software and a robust Euler solver to drastically reduce the time required to set up and execute flowfield computations. In addition, it has the capability to exercise the vorticity confinement technique in the field (to preserve tip vortices) and on the body surface (to mimic viscous effects). ETA was applied to a supersonic missile configuration with a high fineness ratio body, low aspect ratio tail fins, and a deflectable nose (used for aerodynamic control). In addition, an equation was derived to relate the surface confinement coefficient to physical parameters. Computations were made with and without vorticity confinement. Afterwards comparisons were made against wind tunnel data to assess ETA’s ability to produce meaningful results. It was found that the equation yielded reasonably successful values for the surface coefficient. It was also observed that the use of surface vorticity confinement improved the accuracy of normal force, pitching moment, and yawing moment calculations.

The Strategic Defense Center of the U.S. Army Aviation and Missile Research, Development and Engineering Center (AMRDEC), System Simulation and Development Directorate (SS&DD) provides modeling and simulation (M&S) tools, providing medium and hi-fi sensor stimulation, and test control frameworks to evaluate performance of integrated defense systems. These systems include hardware and software representations provided by and operated by Service Program Offices or their representatives. The representations are geographically distributed, but linked together to provide a dynamic, real-time, interactive test environment that is centrally controlled and synchronized through Global Positioning System (GPS) sources. The distributed nodes and the central control facility communicate through the Single Stimulation Framework (SSF). Operation of the SSF provides characterization and assessment of the integrated defense systems. This paper will summarize the concept, features, and functions of the SSF. The complex communications will be discussed, as well as the philosophy of stimulating the participating system components externally with consistent scenarios and truth state data that will bypass the simulation of these events by the individual participants.

The association between sarcoidosis and autonomic dysfunction is demonstrated but poorly known. Heart rate variability (HRV) studies can provide a simple, non-invasive analysis of sympathetic and vagal tone in sarcoidosis. To date, the burden of steroid treatment on HRV has not been investigated. We aim to compare the HRV in sarcoidosis with general population and to explorate the burden of steroid treatment in HRV. Prospective analysis of 30 patients enrolled in Sarcoidosis Clinic of Policlinico Gemelli Hospital compared to 72 healthy control subjects. Continuous EKG recording over 24 hours has been performed and HRV was assessed using time and frequency domain analysis. Results were evaluated using a propensity score matching 1:1. Patients affected by sarcoidosis presented a mean age of 59.7±10.1 y and female gender predominance (n=20, 71.4%) %) while the control group was 54.6±16.0 y. The HRV analysis outlined a remarkable difference when both time / frequency domain were compared to the general, healthy population (ΔSDNN: 89.4±6.7 p=0.0001; ΔrMSSD: 5.7±2.6 p=0.03; ΔLF: 497.0±142.3 p=0.0007; ΔHF: 325.0±159.5 p=0.0442) suggesting a significant impact of sarcoidosis in autonomic activation. Remarkably the lung function tests and scadding stage did not show any relationship with the HRV (p=NS). At the same time, steroid treatment of ≥10 mg/day of prednisone for the previous 3 months was associated with a significant reduction of HRV in time (SDNN: Δ17.2±6.9, p=0.020) and frequency domain (LF: Δ355.2±125.7, p=0.009 and HF: Δ116.2±65.2, p=0.087). Lastly, the propensity score matching did confirm the previous results regarding time/frequency domain analysis. HRV is an effective tool for the autonomic evaluation in patients affected by sarcoidosis. The time (r-MSSD, SDNN, pNN50%) and frequency domain (HF/LF mean) analysis in sarcoidosis suggested that autonomic dysfunction is not related to the lung function or scadding stage though steroid treatment may impact.

Two methods, frequency domain analysis and time domain analysis, are widely applied to modeling wave energy converters (WECs). Frequency domain analysis can evaluate the performance of WECs quickly and efficiently, while it refers to a linear model. When it comes to investigations on nonlinear characteristics of the power take-off (PTO) unit of WECs or control for improving the WECs’ performance, time domain analysis based on a state-space approximation for the convolution term is more desirable. In this paper, a state-space approximation of the convolution term in a time domain analysis of a raft-type WEC consisting of two rafts and a PTO unit is presented. The state-space model is identified through regression in the frequency domain. Verification of such a type of time domain analysis is conducted by comparison of its simulation results with those calculated by using a frequency domain analysis, and there is a good agreement. Finally, the effects of PTO parameters, wave frequency, surge and heave motions of the joint, and quadratic damping PTO on the power capture ability of the raft-type WEC are investigated.

This paper presents an industry-unique approach and improved model-based engineering practices for software reliant aircraft systems aligned with the Future Airborne Capability Environment (FACE™) open system technical reference architecture. A lifecycle toolset is described which fuses systems and software modeling and simulation (M&S) capabilities, modular open system architectures (MOSA), and device and sensor integration techniques into a single package to enable rapid design, development, verification, certification, and deployment of interoperable, platform portable, embedded mission-critical safety-critical avionic systems. TES' MBSE lifecycle toolset, AWESUM™, supports system architecture and virtual integration (SAVI) of cyber-physical system (CPS) assets, and evaluation of these platform assets through simulated mission rehearsals in a network-centric collaborative virtual environment. The result is improved systems product. The toolset has been demonstrated to several aviation-focused communities including the American Helicopter Society International (AHS), the Association of Old Crows (AOC), the FACE Consortium, and the US Army's Aviation and Missile Research Development and Engineering Center (AMRDEC), with favorable response. TES demonstrated a virtual simulation of realistically modeled and simulated multiple dissimilar aircraft platform systems conducting network centric operations (NCO). With the goal of improving flight-safety and enhancing the situational awareness (SA) of the battle-space, virtual missions were executed showing the inter-operations of cyber-physical system (CPS) assets and capabilities from reusable FACE-aligned applications. The simulated battle-space was composed of device-configured simulated flight models of both manned and unmanned rotorcraft platforms operating within a virtual environment of real-world terrain data. The environment included simulated threats and obstacles used to stimulate platform devices that report detections and produce alerts for own-ship flight mishap avoidance. These detections were then packaged into communications messages (VMF) and shared off-platform via NCO to the common operating picture (COP) to enhance the SA operations of the battle space flight group. After a decade of development and use supporting US Army military common software programs for the PM-AME and AMRDEC, TES is now making its industry-unique approach and model-based airworthy systems/software lifecycle product line available to industry. The MBSE lifecycle toolset product suite, referred to as AWESUM™ for AirWorthy Engineering Systems Unified Modeling, is a comprehensive model-based environment aligned to DO-178C, DO-331, AC 20-148, AR 7062, and FACE™. The AWESUM™ tool suite is currently supporting the US Army's Joint Common Architecture project, a model-based avionics architecture for the Joint Multi-Role family of future vertical lift platforms, and two other FACE-aligned US Army Aviation programs within the military communications and aircraft survivability domains. This is TES-SAVi's first publication and presentation to the IEEE. While we have applied our capabilities to the Military Aviation domain, these capabilities can be effectively applied to Aerospace and other domains.

The Aviation Development Directorate of the U.S. Army Aviation and Missile Research, Development and Engineering Center (AMRDEC) conducted a drag test of a non-rotating 2/5 scale Lockheed AH-56 Cheyenne main rotor hub in the U.S. Army 7- by 10-foot Wind Tunnel located at NASA Ames Research Center in Moffett Field, CA. The purpose of the test was to quantify the drag reduction on the Cheyenne's unique "door-hinge" style hub when the mechanical control gyro is removed, with the implicit assumption that the control and stabilization functions of the gyro could be replaced by a modern flight control system located somewhere within the aircraft’s outer mold line. The model was tested in a number of non-rotating configurations, orientations, and tunnel conditions. Baseline results compared favorably with historical drag measurements, and showed approximately a 50% reduction in hub drag with the gyro removed, with an additional 10% reduction due to rudimentary streamlining of the bluff outer hub arm.

This book is concerned with circuit simulation using National Instruments Multisim. It focuses on the use and comprehension of the working techniques for electrical and electronic circuit simulation. The first chapters are devoted to basic circuit analysis. It starts by describing in detail how to perform a DC analysis using only resistors and independent and controlled sources. Then, it introduces capacitors and inductors to make a transient analysis. In the case of transient analysis, it is possible to have an initial condition either in the capacitor voltage or in the inductor current, or both. Fourier analysis is discussed in the context of transient analysis. Next, we make a treatment of AC analysis to simulate the frequency response of a circuit. Then, we introduce diodes, transistors, and circuits composed by them and perform DC, transient, and AC analyses. The book ends with simulation of digital circuits. A practical approach is followed through the chapters, using step-by-step examples to introduce new Multisim circuit elements, tools, analyses, and virtual instruments for measurement. The examples are clearly commented and illustrated. The different tools available on Multisim are used when appropriate so readers learn which analyses are available to them. This is part of the learning outcomes that should result after each set of end-of-chapter exercises is worked out. Table of Contents: Introduction to Circuit Simulation / Resistive Circuits / Time Domain Analysis -- Transient Analysis / Frequency Domain Analysis -- AC Analysis / Semiconductor Devices / Digital Circuits

Although one lung ventilation (OLV) is commonly used, little is known about the modulation of the autonomic nervous system with OLV while under general anesthesia. As the frequency domain and time domain analyses are powerful analytic tools, we investigated their modulation during OLV. Patients undergoing thoracic surgery were classified into two groups: those who did (group A, n=8) and those who did not (group N, n=8) receive atropine. After a double lumen tube was placed endotracheally, mechanical ventilation of both lungs (BLV) was established at 18 min(-1) while under isoflurane anesthesia. Electrocardiogram, systolic arterial pressure (SAP), and inspiratory flow (Finsp) were digitally recorded as follows: awake before anesthesia; BLV after anesthesia; BLV after intravenous 10 microg kg(-1) of atropine (group A) or not (group N); left OLV; and right OLV. Power spectral analyses of heart rate (HR) and SAP were computed by determining low-(LF, 0.04-0.15 Hz) and high-frequency (HF, 0.15-0.40 Hz) components, and impulse response analysis was executed among HR, SAP, and Finsp. Impulse responses were assessed by the maximum values in the time domain. In frequency domain analysis, atropine depressed LF and LF/HF but not HF in HR variability, while no difference was observed between right OLV and left OLV. The heart rate to SAP impulse response was maintained at a significantly higher level in group A than in group N (905+/-360 vs. 425+/-375 mmHg beats(-1)min(-1)) at right OLV. A significant difference was also observed between left and right OLV within group N. Impulse response analysis demonstrated that there is a greater effect on autonomic nervous system modulation during right OLV than in left OLV, which mainly results from a parasympathetic neural linkage origin.

In order to test the effect of noise on the various parameters of the SAECG, 83 patients underwent three consecutive recordings at different noise levels. The high noise (HN) recordings had a noise level of 0.60-0.74 microV, the intermediate noise (IN) had 0.31-0.59 microV, and the low noise (LN) had < or = 0.30 microV. For the calculation of noise we used the standard deviation of the mean noise of the composite lead high pass filtered at 40 Hz. The recordings were compared using time-domain, frequency-domain, and spectrotemporal analysis. The time-domain parameters of the LN recordings, using 25-Hz, 40-Hz, and 60-Hz high pass cutoffs, were significantly different from those of the HN or IN recordings (P < 0.05). In the frequency-domain analysis, significant differences were found in some of the parameters of the LN compared to the HN. The spectrotemporal analysis of the X and Z leads also showed significant differences among the LN and the other recordings. In the time-domain analysis, both at 40 Hz and 25 Hz, there were more abnormal LN compared to the HN recordings (P < 0.05). In the spectrotemporal analysis, there were significantly more abnormal HN and IN recordings compared to the LN (P < 0.001 and P < 0.01, respectively). Therefore, the level of noise, even within the acceptable range, can significantly affect the SAECG. In the time domain at the lower noise levels the parameters become more abnormal, while the opposite seems to occur in the spectral and the spectrotemporal analysis.

This paper presents a state-of-the-art review of the recent advances in computer methods for analysis and design of switched circuits in both time and frequency domains. It also presents new research results on time-domain analysis and sensitivity of switched nonlinear circuits, time- and frequency-domain statistical analysis of switched linear and nonlinear circuits, and efficient modeling and analysis of clock feedthrough and charge injection in switched linear circuits. In time-domain analysis, the modeling of switches and its effect on the simulation of switched circuits are investigated. Formulation methods for these circuits are examined. Inconsistent initial conditions arising from ideal switching are investigated and numerical methods that derive the consistent initial conditions are examined. Sampled-data simulation (SDSIM) of switched linear circuits including clocked sigma-delta modulators is investigated. SDSIM is extended to switched nonlinear circuits. Time-domain sensitivity of switched linear and nonlinear circuits is analyzed using SDSIM. Efficient time-domain statistical analysis of switched linear and nonlinear circuits is introduced, and their effectiveness is assessed using Monte Carlo simulation. Methods that compute the effect of the clock jitter of periodically switched linear (PSL) circuits are examined. Time-domain noise analysis of PSL circuits is investigated. In frequency-domain analysis, exact frequency analysis of multiphase PSL circuits is reviewed. Sensitivity analysis of these circuits is examined in detail. Adjoint network theory and its usefulness in noise and sensitivity analysis of switched linear circuits are studied. Group delay of PSL circuits is investigated briefly. Efficient modeling and analysis of clock feed-though and charge injection of PSL circuits are introduced. Distortion and sensitivity of periodically switched nonlinear circuits with mild nonlinearities are investigated. Finally, frequency-domain noise analysis of PSL circuits is examined.

Cold heading die is one of the key components of high speed screw cold heading machine.As the vulnerable parts, the die should be monitored and fault diagnosed. In this paper, the arithmetic average algorithm based on time domain is adopted to denoise the load signal of the mold, and then the load signal after denoising is processed by time-domain tolerance matching and frequance-domain principal value analysis, so as to identify faults. The simulation results show that the timedomain arithmetic average algorithm can effectively improve the signal-to-noise ratio (SNR), the obvious fault signals can be identified by time-domain tolerance matching, and the fault data close to the standard signal can be further judged by frequency domain principal value analysis. Tolerance matching in time domain and principal value analysis in frequency domain provide an effective means for diagnosing die faults of high speed screw cold heading machine.

The United States Army Aviation and Missile Research, Development and Engineering Center (AMRDEC) has utilized Infrared (IR) cameras to analyze boundary layer transition on additively-manufactured and aluminum wings in half-scale wind tunnel testing. The primary goal of the testing was to collect transition data for validation of Computational Fluid Dynamic (CFD) models with traditional oil flow visualization methods. A secondary goal was to collect transition data using IR thermographic imagery. Using non-contact IR cameras allow for more measurements to be collected in a given time. This work focuses on the IR cameras, the testing (setup, results, and lessons learned), and post analysis of the data. Brief descriptions of the test assets and the cameras are given, followed by a description and discussion of strengths and weaknesses of different methods used to accentuate the thermal signature of the transitions. Lining the wing with a selfadhesive liner can increase the contrast of the transition signature passively, but active heating with a central heating element was shown not to be as effective. General lessons learned for test setup, camera selection, and techniques to increase thermal transition signature are provided within each section. By examining several runs, general observations about the airflow transitions are made. Image processing techniques were utilized to analyze the transition. These techniques and resulting toolsets for data analysis are described. Some of the initial results were analyzed to make some comparisons between the traditional oil flow visualization methods and the thermal imaging methods. The report shows that the oil does not affect the repeatability of the thermal signature, but that the transitions determined by the oil flow analysis and the thermal image do differ slightly. Also, the oil flow is able to visualize a region known as the laminar boundary layer separation, whereas, at this time, this phenomenon is still not apparent in the thermal imagery. Further analysis is ongoing to determine if that separation can actually be seen with this specific test configuration.

Auburn University, through the Army's aviation and missile research, development and engineering center (AMRDEC) has been supporting the unmanned systems initiative (USI) program in three research areas related to unmanned aerial vehicle (UAV). A major element in this work is the development of a high fidelity modeling and simulation testbed to support the USI program. This paper describes the testbed and the verification and validation of the testbed.