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Singh, Kanwar Bharat. "Virtual sensor for real-time estimation of the vehicle sideslip angle". Sensor Review 40, nr 2 (29.07.2019): 255–72. http://dx.doi.org/10.1108/sr-11-2018-0300.
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Purpose The vehicle sideslip angle is an important state of vehicle lateral dynamics and its knowledge is crucial for the successful implementation of advanced driver-assistance systems. Measuring the vehicle sideslip angle on a production vehicle is challenging because of the exorbitant price of a physical sensor. This paper aims to present a novel framework for virtually sensing/estimating the vehicle sideslip angle. The desired level of accuracy for the estimator is to be within +/− 0.2 degree of the actual sideslip angle of the vehicle. This will make the precision of the proposed estimator at par with expensive commercially available sensors used for physically measuring the vehicle sideslip angle. Design/methodology/approach The proposed estimator uses an adaptive tire model in conjunction with a model-based observer. The performance of the estimator is evaluated through experimental tests on a rear-wheel drive vehicle. Findings Detailed experimental results show that the developed system can reliably estimate the vehicle sideslip angle during both steady state and transient maneuvers, within the desired accuracy levels. Originality/value This paper presents a novel framework for vehicle sideslip angle estimation. The presented framework combines an adaptive tire model, an unscented Kalman filter-based axle force observer and data from tire mounted sensors. Tire model adaptation is achieved by making extensions to the magic formula, by accounting for variations in the tire inflation pressure, load, tread-depth and temperature. Predictions with the adapted tire model were validated by running experiments on the Flat-Trac® machine. The benefits of using an adaptive tire model for sideslip angle estimation are demonstrated through experimental tests. The performance of the observer is satisfactory, in both transient and steady state maneuvers. Future work will focus on measuring tire slip angle and road friction information using tire mounted sensors and using that information to further enhance the robustness of the vehicle sideslip angle observer.
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Sun, Ruiting, Junpeng Ma, Wenli Yang, Shunliang Wang i Tianqi Liu. "Transient Synchronization Stability Control for LVRT With Power Angle Estimation". IEEE Transactions on Power Electronics 36, nr 10 (październik 2021): 10981–85. http://dx.doi.org/10.1109/tpel.2021.3070380.
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Li, Xiaoyu, Nan Xu, Qin Li, Konghui Guo i Jianfeng Zhou. "A fusion methodology for sideslip angle estimation on the basis of kinematics-based and model-based approaches". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 234, nr 7 (24.12.2019): 1930–43. http://dx.doi.org/10.1177/0954407019892156.
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This article introduces a reliable fusion methodology for vehicle sideslip angle estimation, which only needs the Controller Area Network–Bus signals of production vehicles and has good robustness to vehicle parameters, tire information, and road friction coefficient. The fusion methodology consists of two basic approaches: the kinematic-based approach and the model-based approach. The former is constructed into the extended Kalman filter for transient stage and large magnitude estimation, while the latter is designed to be an adaptive scheme for steady-state and small magnitude estimation. On this basis, combining the advantages of the two methods, a weight allocation strategy is proposed based on the front wheel steering angle and transient characteristics of lateral acceleration and yaw rate. The validity of the method is verified by simulation and experiment, and it is proved that the method can be effectively used for the sideslip angle estimation.
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Zhu, Qianfeng, Zhihong Man, Zhenwei Cao, Jinchuan Zheng i Hai Wang. "Parameter Estimation for Robotic Manipulator Systems". Machines 10, nr 5 (19.05.2022): 392. http://dx.doi.org/10.3390/machines10050392.
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In this paper, a novel methodology for estimating the parameters of robotic manipulator systems is proposed. It can be seen that, for the purpose of parameter estimation, the input torque to each joint motor is designed as a linear combination of sinusoids. After the transient responses of joint angles exponentially converge to zero, the steady states of joint angle outputs can be extracted. Since the steady states of joint angles are the equivalent finite Fourier series, the coefficients of the steady state components of joint angles can be further extracted in a fundamental period. With the amazing finding that the steady states contain all dynamic information of manipulator systems, all unknown parameters of the system model can be accurately estimated with the extracted coefficients in finite frequency bands. The simulation results for a two-link manipulator are carried out to illustrate the effectiveness and robustness against measurement noise of the proposed method.
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Singh, Kanwar Bharat. "Vehicle Sideslip Angle Estimation Based on Tire Model Adaptation". Electronics 8, nr 2 (9.02.2019): 199. http://dx.doi.org/10.3390/electronics8020199.
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Information about the vehicle sideslip angle is crucial for the successful implementation of advanced stability control systems. In production vehicles, sideslip angle is difficult to measure within the desired accuracy level because of high costs and other associated impracticalities. This paper presents a novel framework for estimation of the vehicle sideslip angle. The proposed algorithm utilizes an adaptive tire model in conjunction with a model-based observer. The proposed adaptive tire model is capable of coping with changes to the tire operating conditions. More specifically, extensions have been made to Pacejka's Magic Formula expressions for the tire cornering stiffness and peak grip level. These model extensions account for variations in the tire inflation pressure, load, tread depth and temperature. The vehicle sideslip estimation algorithm is evaluated through experimental tests done on a rear wheel drive (RWD) vehicle. Detailed experimental results show that the developed system can reliably estimate the vehicle sideslip angle during both steady state and transient maneuvers.
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de Apráiz, Matilde, Ramón Diego i Julio Barros. "An Extended Kalman Filter Approach for Accurate Instantaneous Dynamic Phasor Estimation". Energies 11, nr 11 (26.10.2018): 2918. http://dx.doi.org/10.3390/en11112918.
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This paper proposes the application of a non-linear Extended Kalman Filter (EKF) for accurate instantaneous dynamic phasor estimation. An EKF-based algorithm is proposed to better adapt to the dynamic measurement requirements and to provide real-time tracking of the fundamental harmonic components and power system frequencies. This method is evaluated using dynamic compliance tests defined in the IEEE C37.118.1-2011 synchrophasor measurement standard, providing promising results in phasor and frequency estimation, compliant with the accuracy required in the case of off-nominal frequency, amplitude and phase angle modulations, frequency ramps, and step changes in magnitude and phase angle. An important additional feature of the method is its capability for real-time detection of transient disturbances in voltage or current waveforms using the residual of the filter, which enables flagging of the estimation for suitable processing.
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Kulah, Serkan, Alexandru Forrai, Frank Rentmeester, Tijs Donkers i Frank Willems. "Robust cylinder pressure estimation in heavy-duty diesel engines". International Journal of Engine Research 19, nr 2 (14.06.2017): 179–88. http://dx.doi.org/10.1177/1468087417713336.
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The robustness of a new single-cylinder pressure sensor concept is experimentally demonstrated on a six-cylinder heavy-duty diesel engine. Using a single-cylinder pressure sensor and a crank angle sensor, this single-cylinder pressure sensor concept estimates the in-cylinder pressure traces in the remaining cylinders by applying a real-time, flexible crankshaft model combined with an adaptation algorithm. The single-cylinder pressure sensor concept is implemented on CPU/field-programmable gate array–based hardware. For steady-state engine operating conditions, the added value of the adaptation algorithm is demonstrated for cases in which a fuel quantity change or start of injection change is applied in a single, non-instrumented cylinder. It is shown that for steady-state and transient engine conditions, the cylinder pressure traces and corresponding combustion parameters, indicated mean effective pressure, peak cylinder pressure, and crank angle at 50% heat release, can be estimated with 1.2 bar, 6.0 bar, and 1.1 CAD inaccuracy, respectively.
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Hao, Liangshou, Leicheng Bai, Fukun Peng, Zhaoyu Lei, Di Wang i Li Tang. "Research on HVDC Supplementary Two-Stage Transient Control and Smooth Switching". Journal of Physics: Conference Series 2479, nr 1 (1.04.2023): 012006. http://dx.doi.org/10.1088/1742-6596/2479/1/012006.
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Abstract HVDC additional transient control is an essential means to elevate the transient stability of AC/DC interconnected systems and the inevitable requirement of intelligent transmission. Two-stage transient additional control and a smooth switching strategy are proposed. By establishing an extended state observer for unbalanced power in the system disturbance, the real-time and accurate estimation of unstable power is realized, and an adaptive emergency power support controller is constructed. The mathematical model of the system is identified by using Total Least Squares-Estimation on Signal Parameters via Rotational Technique (TLS-ESPRIT). Based on the singular value reduction theory, the HVDC additional Active Disturbance Rejection Damping Controller (ADRDC) that can inhibit the low-frequency oscillation of the system is designed. Finally, two switching strategies are designed based on the change in the state of the network fault switch and the change in the power angle oscillation curve. The three-in-feed HVDC system is built in PSCAD, and the simulation analysis is carried out. The simulation results confirm the validity of the proposed method.
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R Karamta, Meera, i Jitendra G Jamnani. "Dynamic state estimation of multi-machine power system with UPFC using EKF algorithm". Indonesian Journal of Electrical Engineering and Computer Science 21, nr 2 (1.02.2021): 642. http://dx.doi.org/10.11591/ijeecs.v21.i2.pp642-646.
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Estimation of dynamic state variables in a multi-machine power system connected with UPFC is presented in this paper, using Extended Kalman filter (EKF) algorithm. A two-generator test case is used to estimate the generator rotor angle and rotor speed. The DC link voltage of the UPFC is the additional state variable to be estimated. Dynamic mathematical modeling of the multi-machine system with UPFC is explained in this work. DSE is done under transient condition of three-phase fault.
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Crăciunaş, Gabriela. "Study of Two-Phase Induction Motor with Non-Orthogonal Stator Windings in Sensorless Systems". Acta Universitatis Cibiniensis. Technical Series 74, nr 1 (1.12.2022): 15–20. http://dx.doi.org/10.2478/aucts-2022-0003.
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Abstract In this paper, the operation of a two-phase induction motor (TPIM) with non-orthogonal stator windings is studied, in a stationary reference frame. Through modeling and simulation on the Matlab/Simulink environment, the influence of the electrical shift angle stator windings on the magnetic and electromechanical quantities of the machine, in transient mode, will be highlighted. Also, another problem studied refers to the determination of the rotor flux of the TPIM by the estimation method, thus avoiding the use of the flux sensor. It was decided to use estimators derived directly from the machine equations written in motor mode, estimators used in electrical drives with analog control. And in this case, simulation was used to highlight, in a transient regime, the performance of using these flux estimators.
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Aziz, Nagham Hikmat, i Maha Abdulrhman Al-Flaiyeh. "Critical clearing time estimation of multi-machine power system transient stability using fuzzy logic". International Journal of Electrical and Computer Engineering (IJECE) 13, nr 1 (1.02.2023): 125. http://dx.doi.org/10.11591/ijece.v13i1.pp125-133.
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<span lang="EN-US">Studying network stability requires determining the best critical clearing time (CCT) for the network after the fault has occurred. CCT is an essential issue for transient stability assessment (TSA) in the operation, security, and maintenance of an electrical power system. This paper proposes an algorithm to obtain CCT based on fuzzy logic (FL) under fault conditions, for a multi-machine power system. CCT was estimated using a two-step fuzzy logic algorithm: the first step is to calculate Δt, which represents the output of the FL, while maximum angle deviation (δmax) represents the input. The second step is to classify the system if it is a stable or unstable system, based on two inputs for FL, the first mechanical input power (Pm), the second average accelerations (Aav). The results of the proposed method were compared with the time domain simulation (TDS) method. The results showed the accuracy and speed of the estimation using the FL method, with an error rate not exceeding 5%, and reduced the performance time by about half the time. The proposed approach is tested on both IEEE-9 bus and IEEE-39 bus systems using simulation in MATLAB.</span>
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Mehta, R. C. "Estimation of Angle of Attack in Satellite Launch Vehicle Using Flush Air Data Sensing Systems at Mach 0.5 to 3.0". Scholars Journal of Engineering and Technology 9, nr 7 (1.08.2021): 77–86. http://dx.doi.org/10.36347/sjet.2021.v09i07.001.
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This paper presents an inverse analysis to estimate angle of attack during ascent period of a satellite launch vehicle. Aerodynamic results are numerically computed by solving three dimensional, time dependent, compressible inviscid equations over payload shroud of a satellite launch vehicle. The flush air data system consists of four pressure ports flushed with conical-nose section of the payload fairing and connected to on board differential pressure transducers. The inverse algorithm uses calibrations charts which based on computed and measured data. A controlled random search method is used to predict pitch, yaw and total angle of attack of vehicle from measured transient differential pressure history in flight from Mach numbers range of 0.5 to 3.0. The algorithm predicts the flow direction stepwise with function of flight Mach numbers and can be termed as online method. Flow direction of the launch vehicle is compared with the reconstructed trajectory data. The estimated values of the flow direction are found in good agreement them.
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Ilioudis, Vasilios C. "Sensorless Control of Permanent Magnet Synchronous Machine with Magnetic Saliency Tracking Based on Voltage Signal Injection". Machines 8, nr 1 (19.03.2020): 14. http://dx.doi.org/10.3390/machines8010014.
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This paper presents a sensorless control method of a permanent magnet synchronous machine (PMSM) with magnetic saliency estimation. This is based on a high-frequency injection (HFI) technique applied on the modified PMSM model in the γδ reference frame. Except for sensorless control, an emphasis is placed on the magnetic saliency estimation to indicate a practical approach in tracking PMSM inductance variations. The magnetic saliency is determined using calculations embedded in the speed and position algorithm through current measurements. A notable characteristic of the modified PMSM model is that the corresponding rotor flux integrates both permanent magnet and saliency term fluxes. In applying a HFI technique for sensorless control, the structure of the PMSM flux model is formatted accordingly. A novel inductance matrix is derived that is completely compatible with the HFI methodology, since its elements include terms of angle error differential and average inductances. In addition, a sliding mode observer (SMO) is designed to estimate the speed and angle of rotor flux based on equivalent control applying a smooth function of the angle error instead of a sign one to reduce the chattering phenomenon. The control strategy is principally based on the adequacy of the proposed modified model and on the appropriateness of the SMO structure to successfully track the rotor flux position with the required stability and accuracy. Simulation results demonstrate the performance of the PMSM sensorless control verifying the effectiveness of the proposed algorithm to detect PMSM saliency, speed and position in steady state and transient modes successfully.
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Hou, Guang-Quan, i Chang-Myung Lee. "Estimation of the Defect Width on the Outer Race of a Rolling Element Bearing under Time-Varying Speed Conditions". Shock and Vibration 2019 (3.01.2019): 1–11. http://dx.doi.org/10.1155/2019/8479395.
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Fault diagnosis and failure prognostics for rolling element bearing are helpful for preventing equipment failure and predicting the remaining useful life (RUL) to avoid catastrophic failure. Spall size is an important fault feature for RUL prediction, and most research work has focused on estimating the fault size under constant speed conditions. However, estimation of the defect width under time-varying speed conditions is still a challenge. In this paper, a method is proposed to solve this problem. To enhance the entry and exit events, the edited cepstrum is used to remove the determined components. The preprocessed signal is resampled from the time domain to the angular domain to eliminate the effect of speed variation and measure the defect size of a rolling element bearing on outer race. Next, the transient impulse components are extracted by local mean decomposition. The entry and exit points when the roller passes over the defect width on the outer race were identified by further processing the extracted signal with time-frequency analysis based on the continuous wavelet transform. The defect size can be calculated with the angle duration, which is measured from the identified entry and exit points. The proposed method was validated experimentally.
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Ueda, M., T. Kano i A. Yoshitoshi. "Thermal Ratcheting Criteria and Behavior of Piping Elbows". Journal of Pressure Vessel Technology 112, nr 1 (1.02.1990): 71–75. http://dx.doi.org/10.1115/1.2928590.
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A thermal ratcheting test was performed using an elbow model test specimen subjected to sustained primary load and cyclic thermal transient strains. Under severe loading conditions incremental longitudinal strains are observed in the region where a circumferential angle is around ± π/9 from the side of the elbow, while the elbow cross section was ovalized cycle by cycle causing large circumferential bending strain at around φ = π/2. It was shown by the test and analyses that the maximum primary membrane stress in an elbow is an essential parameter for thermal ratcheting behavior of elbows. Direct application of thermal ratcheting criteria in the ASME Code Case N-47 showed considerable conservative estimation and an improved thermal ratcheting criterion for elbows is recommended.
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Vijayakumar, G., i Ashwani Kumar Kachroo. "Thermal Design of Missile Airframe with Circumferential Variation in Wall Temperature". Applied Mechanics and Materials 592-594 (lipiec 2014): 1807–14. http://dx.doi.org/10.4028/www.scientific.net/amm.592-594.1807.
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Missile airframe experiences large variations in wall temperature along the circumference due to high angle of attack, especially at hypersonic speeds, which leads to large thermal stresses and bending loads. Such a situation with large wall temperature variations occurs due to high angle of attack during flight. Thermal design of the airframe involves the estimation of local flow parameters and heat flux distribution. Kinetic heating analysis has been carried out for the prediction of heat load distribution on missile airframe considering hypersonic flow with high angle of attack for a particular flight trajectory. Out of a set of possible flight trajectories, a trajectory producing minimum circumferential variation in wall temperature, as concluded through kinetic heating analysis, is finalized. Transient three dimensional heat transfer analysis of the airframe is carried out for prediction of wall temperature distribution for proper selection of material of construction of airframe so that it retains its strength at elevated temperatures. Parametric study has been carried out considering various combinations of airframe wall thickness in presence of external thermal protection coating and internal insulation for the finalized trajectory. Based on the present analysis, airframe configuration having axially variable wall thickness corresponding to the selected flight trajectory is finalized. The validation of the methodology adopted for the analysis has been carried out with respect to airframe temperature data acquired during flight.
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Gabrielson, Thomas B., i Daniel C. Brown. "Fireworks". Journal of the Acoustical Society of America 153, nr 3_supplement (1.03.2023): A216. http://dx.doi.org/10.1121/10.0018701.
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Once a year, in many parts of the country, transient acoustic sources light up the sky. A fourth-of-July fireworks display provides an excellent opportunity for exploring array-based detection and direction-of-arrival determination. Multiple-boom events are difficult to process; however, less-frequent single-boom events are often sufficiently isolated in time for unambiguous interpretation. Cross-correlations between channels of a four-microphone array provide time delays for angle-of-arrival determination and measures for event detection. The distinct time-domain wave shapes and high signal-to-noise enable straightforward checks of the cross-correlation delays. In addition, a chirp sequence broadcast from a known location provides a ground-truth measurement and opportunities to implement matched filtering and envelope processing. Detection strategies can include received power, rate of change of power, normalized cross-correlation coefficient, or Fisher F-statistic. A least-squares fit by plane-wave approximation gives an estimate of the actual slowness vector, which, in turn, permits estimation of error and of local sound speed. Conversion of the slowness vector to arrival azimuth and elevation angles provides a simple exercise in 3D interpretation. The homework exercise can be as simple as determination of inter-sensor time delays or as complicated as demonstrating a scheme for automatic detection and interpretation.
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Seifelnasr, Amr, Xiuhua April Si i Jinxiang Xi. "Visualization and Estimation of Nasal Spray Delivery to Olfactory Mucosa in an Image-Based Transparent Nasal Model". Pharmaceutics 15, nr 6 (5.06.2023): 1657. http://dx.doi.org/10.3390/pharmaceutics15061657.
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Background: Nose-to-brain (N2B) drug delivery offers unique advantages over intravenous methods; however, the delivery efficiency to the olfactory region using conventional nasal devices and protocols is low. This study proposes a new strategy to effectively deliver high doses to the olfactory region while minimizing dose variability and drug losses in other regions of the nasal cavity. Materials and Methods: The effects of delivery variables on the dosimetry of nasal sprays were systematically evaluated in a 3D-printed anatomical model that was generated from a magnetic resonance image of the nasal airway. The nasal model comprised four parts for regional dose quantification. A transparent nasal cast and fluorescent imaging were used for visualization, enabling detailed examination of the transient liquid film translocation, real-time feedback on input effect, and prompt adjustment to delivery variables, which included the head position, nozzle angle, applied dose, inhalation flow, and solution viscosity. Results: The results showed that the conventional vertex-to-floor head position was not optimal for olfactory delivery. Instead, a head position tilting 45–60° backward from the supine position gave a higher olfactory deposition and lower variability. A two-dose application (250 mg) was necessary to mobilize the liquid film that often accumulated in the front nose following the first dose administration. The presence of an inhalation flow reduced the olfactory deposition and redistributed the sprays to the middle meatus. The recommended olfactory delivery variables include a head position ranging 45–60°, a nozzle angle ranging 5–10°, two doses, and no inhalation flow. With these variables, an olfactory deposition fraction of 22.7 ± 3.7% was achieved in this study, with insignificant discrepancies in olfactory delivery between the right and left nasal passages. Conclusions: It is feasible to deliver clinically significant doses of nasal sprays to the olfactory region by leveraging an optimized combination of delivery variables.
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Alamri, Yahya Ahmed, Nik Rumzi Nik Idris, Ibrahim Mohd. Alsofyani i Tole Sutikno. "Improved Stator Flux Estimation for Direct Torque Control of Induction Motor Drives". International Journal of Power Electronics and Drive Systems (IJPEDS) 7, nr 4 (1.12.2016): 1049. http://dx.doi.org/10.11591/ijpeds.v7.i4.pp1049-1060.
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<p>Stator flux estimation using voltage model is basically the integration of the induced stator back electromotive force (emf) signal. In practical implementation the pure integration is replaced by a low pass filter to avoid the DC drift and saturation problems at the integrator output because of the initial condition error and the inevitable DC components in the back emf signal. However, the low pass filter introduces errors in the estimated stator flux which are significant at frequencies near or lower than the cutoff frequency. Also the DC components in the back emf signal are amplified at the low pass filter output by a factor equals to . Therefore, different integration algorithms have been proposed to improve the stator flux estimation at steady state and transient conditions. In this paper a new algorithm for stator flux estimation is proposed for direct torque control (DTC) of induction motor drives. The proposed algorithm is composed of a second order high pass filter and an integrator which can effectively eliminates the effect of the error initial condition and the DC components. The amplitude and phase errors compensation algorithm is selected such that the steady state frequency response amplitude and phase angle are equivalent to that of the pure integrator and the multiplication and division by stator frequency are avoided. Also the cutoff frequency selection is improved; even small value can filter out the DC components in the back emf signal. The simulation results show the improved performance of the induction motor direct torque control drive with the proposed stator flux estimation algorithm. The simulation results are verified by the experimental results.</p>
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Gudmundsson, G. Hilmar, Andreas Bauder, Martin Lüthi, Urs H. Fischer i Martin Funk. "Estimating rates of basal motion and internal ice deformation from continuous tilt measurements". Annals of Glaciology 28 (1999): 247–52. http://dx.doi.org/10.3189/172756499781821751.
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AbstractOver a two-year period, continuous measurements of temporal changes in tilt, conducted with a string of tilt meters in a borehole on Unteraargletscher, Bernese Alps, Switzerland, have been used to estimate the basal-motion component. This estimation is based on a comparison of the measurements with synthetic tilt curves, computed using a parameterization of a simplified flow field. The best agreement is found for a ratio of basal motion to forward motion due to ice deformation (slip ratio) equal to about 1.2. Measured tilt curves exhibit a number of different transient features. While an overall increase in tilt angle is observed at every tilt-meter location, two of the sensors recorded anomalous tilt behaviour. These anomalies are characterized by sudden and drastic variations in tilt. A particularly intriguing example of such short-term tilt variations was recorded with a tilt meter positioned 40 m above the bed during the 1997 summer melt season.
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Xu, Wenzhe, Grzegorz Filip i Kevin J. Maki. "A Method for the Prediction of Extreme Ship Responses Using Design-Event Theory and Computational Fluid Dynamics". Journal of Ship Research 64, nr 01 (1.03.2020): 48–60. http://dx.doi.org/10.5957/jsr.2020.64.1.48.
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The design of a naval vessel requires accurate estimation of the extreme loads and motions that it will experience during its lifetime. Operation in large seaways in which the ship-wave interaction is highly nonlinear and transient leads to design events such as maximum internal loads due to global wave bending, local slamming loads, extreme roll, combinations of the global wave bending and local slamming, and many others. In this article, a method is presented that allows for nonlinear analysis to be used to predict events with user-specified rareness. The core of the method combines probability, frequency, and time-domain analyses to generate short time-window sea environments that lead to extreme dynamical events. The Office of Naval Research Tumblehome geometry is analyzed for the extreme roll angle when advancing in stern quartering irregular seas. 1. Introduction The design of a naval vessel requires accurate estimation of extreme loads and motions that it will experience during its lifetime. Specific quantities of interest are the maximum slamming load during wet-deck impact, maximum acceleration at different locations on the vessel, maximum green-water load on the bow structure or helicopter deck, maximum roll angle, or frequency of occurrence of capsize, to name a few. It is important to recognize that a ship lifetime is decades long, and the exposure time in different severe storms over the lifetime is of the order of weeks, if not months. Furthermore, because of the random nature of the sea and, hence, the dynamical response of the ship, the extreme response is also random and should be characterized statistically. This means that a single lifetime realization in a given seaway by either model tests or numerical simulation only gives one sample of the extreme response, and multiple lifetime realizations are required to characterize the extreme response.
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Zhang, Yanli, Xiang Qin, Xin Li, Jun Zhao i Yushuo Liu. "Estimation of Shortwave Solar Radiation on Clear-Sky Days for a Valley Glacier with Sentinel-2 Time Series". Remote Sensing 12, nr 6 (13.03.2020): 927. http://dx.doi.org/10.3390/rs12060927.
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Downward surface shortwave radiation (DSSR) is the main energy source for most glacial melting, and Moderate Resolution Imaging Spectroradiometer (MODIS) and Landsat Thematic Mapper (TM) data have been used extensively in the inversion of input parameters for estimating DSSR. However, for valley glaciers under complex climatic conditions, the values of MODIS atmospheric products, especially aerosol products, are often invalid, and TM images are always saturated with snow. Furthermore, an estimation model based on optical satellite images must simultaneously consider terrain and atmospheric effects and the transient nature of ice/snow albedo. Based on a high-resolution (12 m) digital elevation model (DEM), the newly launched Sentinel-2 satellites, rather than MODIS and TM, were used to provide input data for our published mountain radiation scheme in a valley glacier. Considering Laohugou Glacier No. 12 as the study area, 62 typical Sentinel-2 scenes were selected and spatiotemporal DSSR variations on the glacier surface were obtained with a 10 m spatial resolution during a mass-balance year from September 2017 to August 2018. Ground-based measurements on 52 clear-sky days were used for validation and the mean bias error (MBE = −16.0 W/m2) and root-mean-square difference (RMSD = 73.6 W/m2) were relatively low. The results confirm that DSSR is affected mainly by the solar zenith angle and atmospheric attenuation in flat areas of valley glaciers, while in areas with complex terrain, the DSSR received by the glacier surface is affected primarily by the terrain and ice/snow albedo, which exhibits very high spatial heterogeneity.
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Geetesh Waghela, Tushar A Patil, Bhoopendra Tiwari i Ashok Kumar Patidar. "Performance Prediction, Optimisation and Validation of a CNG Engine Intake Manifold of a Commercial Vehicle Using Transient CFD Analysis". ARAI Journal of Mobility Technology 3, nr 2 (18.04.2023): 582–90. http://dx.doi.org/10.37285/ajmt.3.2.4.
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Developing countries like India have large consumer markets driven by huge demands. Commercial vehicles play a critical role in full filing these demands. Commercial vehicles increasingly face stringent emission norms criteria and hence designing an ICE-powertrain with optimum operating efficiency becomes paramount. Intake manifold is the critical part of an internal combustion engine that supplies fuel/ air mixture to all the cylinders combustion chambers. It ensures a uniform mixture at cylinder inlet for better mixing inside the cylinders for better volumetric efficiency. Uneven distribution of fuel/air mixture causes unstable torque and unburnt fuel which fails to meet the emission norms. It also results in uneven temperatures in each cylinder because of cylinder misfiring. In current paper, 3D Computational Fluid Dynamics (CFD) simulations are carried out to investigate the variance and uniformity of CNG/air mixture at the outlet of intake manifold. Commercial CFD tool Ansys Fluent is used to study the flow distribution of mixture inside the manifold and runners. Initial estimation of flow pattern is done by performing a steady state simulation to predict the uniformity index of CNG at cylinder inlet. For detailed investigation, transient simulation is performed by taking fresh air and CNG mass flow rate as a function of crank angle. In this paper, mesh dependence study was done initially to achieve an optimum cell count with good accuracy. A detailed transient analysis using multi-species modelling for air & CNG was done using automated scripts with time steps as small as 1 degree crank angle rotation coupled with injection pressure and injection timing study. This helped to identify critical areas and optimise the design to improve the mass flow rate variance from 15-20% for baseline case to 6-7% for final design, and also improve the uniformity index. It also helped reduce the CNG engine mis-firing issue. The results have been well validated with Laboratory Test Results.
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Zhang, Jianwu, Benben Chai i Xingyang Lu. "Active oscillation control of electric vehicles with two-speed transmission considering nonlinear backlash". Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics 234, nr 1 (1.10.2019): 116–33. http://dx.doi.org/10.1177/1464419319877332.
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The nonlinear backlash can influence the driveability of the electric driveline due to the lack of the traditional clutches and torsional damper devices. During the stand-start, regenerative braking and gear shift process of the electric drive system equipped with two-speed transmission, the request of transient traction motor change will transverse the powertrain backlash, which will excite the driveline oscillations coupled to the first rigid mode of the entire powertrain, referred as shuffle or shunt. These vibrations are transmitted to the chassis, causing deterioration in passenger comfort. In this paper, the nonlinear driveline model including the traction motor, half shaft, driveline backlash, and car wheel are developed. Then, dual extended Kalman filter method is employed to estimate vehicle mass and half shaft torsional angle of the proposed driveline. Based on the estimated information, a hierarchical architecture of the active oscillation compensation is proposed to alleviate the vibration in both contact and backlash mode. The experimental results show that the estimation method is effective and the vehicle shuffle can be significantly decreased by the developed control algorithm.
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Senyuk, Mihail, Murodbek Safaraliev, Aminjon Gulakhmadov i Javod Ahyoev. "Application of the Conditional Optimization Method for the Synthesis of the Law of Emergency Control of a Synchronous Generator Steam Turbine Operating in a Complex-Closed Configuration Power System". Mathematics 10, nr 21 (26.10.2022): 3979. http://dx.doi.org/10.3390/math10213979.
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Stochastic renewable sources of energy have been causing changes in the structure and operation of power systems. High penetration of this type of generation results in decreased inertia of a power system, increased active power fluctuations, and a higher probability of false tripping of emergency control devices. Traditional algorithms of emergency control are not adaptable and flexible enough for systems with high penetration of renewables and flexible alternating current transmission systems. Integration and development of phasor measurement units make it possible to create adaptable emergency control systems, which would require minimal pre-defined data. The purpose of this study is to develop an adaptable algorithm of turbine fast valving control synthesis and transient stability estimation for a generator. The suggested algorithm is based on the equal area criterion in the domain synchronous generator Torque—Load angle. The measurements of the generator operation under consideration are used as the input data for the steam turbine fast valving control synthesis. Thus, the algorithm becomes adaptable because no pre-defined parameters of a power system model are required.
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İskender, İres, Yıldürüm Üçtug˘ i H. Bülent Ertan. "Steady‐state modeling of a phase‐shift PWM parallel resonant converter". COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 25, nr 4 (1.10.2006): 883–99. http://dx.doi.org/10.1108/03321640610684051.
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PurposeTo derive an analytical model for a dc‐ac‐dc parallel resonant converter operating in lagging power factor mode based on the steady‐state operation conditions and considering the effects of a high‐frequency transformer.Design/methodology/approachA range of published works relevant to dc‐ac‐dc converters and their control methods based on pulse‐width‐modulation technique are evaluated and their limitations in output measurement of higher output voltage converters are indicated. The circuit diagram of the converter is described and the general mathematical model of the system is obtained by deriving and combining the mathematical models of the different converter blocks existing in the system. The derived mathematical model is used to study the steady‐state and transient performance of the converter. The deriving procedure of the analytical model for a parallel resonant converter is extensively given and the analytical model obtained is verified by simulation results achieved using MATLAB/SIMULINK and the program written by the authors.FindingsThe paper suggests an analytical model for dc‐ac‐dc parallel resonant converters. The model can be used in the output voltage estimation of a converter in terms of its phase‐shift angle and the dc‐link voltage.Research limitations/implicationsThe resources in the library of the authors' university and also the English resources relative to dc‐ac‐dc converters reachable through the internet were researched.Practical implicationsThe analytical model suggested can be used in estimating the output voltage of the converters used in high‐voltage applications or where there are difficulties in employing sensors in measurement of the output voltage due to high price or implementation problems.Originality/valueThe originality of the paper is to present an analytical model for dc‐ac‐dc parallel resonant converters. Using this model makes it possible to estimate the output voltage of the converter using the dc‐link voltage and the phase‐shift angle. The proposed model provides researchers to regulate the output voltage of the converters using feed‐forward control technique.
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Salvatierra-Rojas, Ana, Victor Torres-Toledo i Joachim Müller. "Influence of Surface Reflection (Albedo) in Simulating the Sun Drying of Paddy Rice". Applied Sciences 10, nr 15 (24.07.2020): 5092. http://dx.doi.org/10.3390/app10155092.
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The sun drying of agricultural products is a complicated process involving heat transfer, mass transfer, and variable weather conditions. Surface reflection (albedo), a crop’s radiative property, plays an essential role in energy balance, and understanding its contribution can improve the thermal analysis. In this study, field experiments were conducted in the Philippines to explore the influence of surface albedo on the sun drying of paddy rice. First, we implemented energy and mass balance equations in a transient model with the surroundings using a graphical programming language in Matlab/Simulink®. Second, we identified the influence of albedo on the sun drying model by using a sensitivity analysis. Third, we investigated the relationship of paddy rice albedo and the solar zenith angle. Lastly, we integrated the albedo function into the sun drying model. The simulation outputs were validated with field experiments. A better estimation of the measured exit temperature and instantaneous mass were obtained when a variable albedo was applied. This study makes clear that introducing a variable albedo has a positive impact on model improvement. This information is important for application in solar drying technologies, so that the drying process can be better assessed.
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Frooqnia, Amir, Carlos Torres-Verdín, Kamy Sepehrnoori i Rohollah Abdhollah-Pour. "Transient Coupled Borehole/Formation Fluid-Flow Model for Interpretation of Oil/Water Production Logs". SPE Journal 22, nr 01 (21.07.2016): 389–406. http://dx.doi.org/10.2118/183628-pa.
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Summary Interpretation of two-phase production logs (PLs) traditionally constructs borehole fluid-flow models decoupled from the physics of reservoir rocks. However, quantifying formation dynamic petrophysical properties from PLs requires simultaneous modeling of both borehole and formation fluid-flow phenomena. This paper develops a novel transient borehole/formation fluid-flow model that allows quantification of the effect of formation petrophysical properties on measurements acquired with production-logging tools (PLTs). We invoke a 1D, isothermal, two-fluid formulation to simulate borehole fluid-phase velocity, pressure, volume fraction, and density in oil/water-flow systems. The developed borehole fluid-flow model implements oil-dominant and water-dominant bubbly flow regimes with the inversion point taking place approximately when the oil volume fraction is equal to 0.5. Droplet diameter is dynamically modified to simulate interfacial drag effects, and to effectively account for variations of slip velocity in the borehole. Subsequently, a new successive iterative method interfaces the borehole and formation fluid-flow models by introducing appropriate source terms into the borehole fluid-phase mass-conservation equations. The novel iterative coupling method integrated with the developed borehole fluid-flow model allows dynamic modification of reservoir boundary conditions to accurately simulate transient behavior of borehole crossflow taking place across differentially depleted rock formations. In the case of rapid variations of near-borehole properties, frequent borehole/formation communication inevitably increases the computational time required for fluid-flow simulation. Despite this limitation, in a two-layer reservoir model penetrated by a vertical borehole, the coupling method accurately quantifies a 14% increase of volume-averaged oil-phase relative permeability of the low-pressure layer caused by through-the-borehole cross-communication of differentially depleted layers. Sensitivity analyses indicate that the alteration of near-borehole petrophysical properties primarily depends on formation average pressure, fluid-phase density contrast, and borehole-deviation angle. A practical application of the new coupled fluid-flow model is numerical simulation of borehole production measurements to estimate formation average pressure from two-phase selective-inflow-performance (SIP) analysis. This study suggests that incorporating static (shut-in) PL passes into the SIP analysis could result in misleading estimation of formation average pressure.
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Juliawan, Nadhie, Hyoung-Seog Chung, Jae-Woo Lee i Sangho Kim. "Estimation and Separation of Longitudinal Dynamic Stability Derivatives with Forced Oscillation Method Using Computational Fluid Dynamics". Aerospace 8, nr 11 (19.11.2021): 354. http://dx.doi.org/10.3390/aerospace8110354.
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This paper focuses on estimating dynamic stability derivatives using a computational fluid dynamics (CFD)-based force oscillation method, and on separating the coupled dynamic derivatives terms obtained from the method. A transient RANS solver is used to calculate the time history of aerodynamic moments for a test model oscillating about the center of gravity, from which the coupled dynamic derivatives are estimated. The separation of the coupled derivatives term is carried out by simulating simple harmonic oscillation motions such as plunging motion and flapping motion which can isolate the pitching moment due to AOA rate (Cmα˙) and the pitching moment due to pitch rate (Cmq), respectively. The periodic motions are implemented using a CFD dynamic mesh technique with user-defined function (UDF). For the validation test, steady and unsteady simulations are performed on the Army-Navy Finner Missile model. The static aerodynamic moments and pressure distribution, as well as the coupled dynamic derivative results from the pitching oscillation mode, show good agreement with the previously published wind tunnel tests and CFD analysis data. In order to separate the coupled derivative terms, two additional harmonic oscillation modes of plunging and flapping motions are tested with the angle of attack variations from 0 to 85 degrees at a supersonic speed to provide real insight on the missile maneuverability. The cross-validation study between the three oscillation modes indicates the summation of the individual plunging and flapping results becoming nearly identical to the coupled derivative results from the pitching motion, which implies the entire set of coupled and separated dynamic derivative terms can be effectively estimated with only two out of three modes. The advantages and disadvantages of each method are discussed to determine the efficient approach of estimating the dynamic stability derivatives using the forced oscillation method.
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Raj, A. Anto Lourdu Xavier, i A. Mairo Macrino. "Multiple Heterogeneous Information Source". International Academic Journal of Science and Engineering 8, nr 1 (7.05.2021): 45–52. http://dx.doi.org/10.9756/iajse/v8i1/iajse0806.
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Today, this fault location analysis is completed within the digital signal processing method. Scenario packet transmission source of some of the attacks and intruders get data packets, and route alters identity problem before cumulative. Reduces processing time can find significant speed advantage and the accuracy of the classical method of calculation failure and presents a simple analog implementation. Back-propagation time is modeled as a fault location estimation of each repeated signature and the switches along with the network. Rapid Packet Transmission Algorithm (RPTA) by a certain load distribution, which leads to restrictions to avoid packet loss. Due to increased packet transmission, improving technology to limit non-destructive testing costs is in great demand. Our algorithm means that each candidate seriously and error detection mechanisms and can provide any fault tolerance of the routing path assessment. Simulation results with different fault resistance indicate that these methods are robust, fault-type, and the initial angle of the disorder. To find the faulty segment, use the transient to the common connection point. Good accuracy for complex network topologies also reduces the overhead generation region by implication checking logic; thus, compared to the typical failure locations of the techniques developed to reduce the total number of required effects, this solution charm.
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Zou, Yufei, Susan M. O’Neill, Narasimhan K. Larkin, Ernesto C. Alvarado, Robert Solomon, Clifford Mass, Yang Liu, M. Talat Odman i Huizhong Shen. "Machine Learning-Based Integration of High-Resolution Wildfire Smoke Simulations and Observations for Regional Health Impact Assessment". International Journal of Environmental Research and Public Health 16, nr 12 (17.06.2019): 2137. http://dx.doi.org/10.3390/ijerph16122137.
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Large wildfires are an increasing threat to the western U.S. In the 2017 fire season, extensive wildfires occurred across the Pacific Northwest (PNW). To evaluate public health impacts of wildfire smoke, we integrated numerical simulations and observations for regional fire events during August-September of 2017. A one-way coupled Weather Research and Forecasting and Community Multiscale Air Quality modeling system was used to simulate fire smoke transport and dispersion. To reduce modeling bias in fine particulate matter (PM2.5) and to optimize smoke exposure estimates, we integrated modeling results with the high-resolution Multi-Angle Implementation of Atmospheric Correction satellite aerosol optical depth and the U.S. Environmental Protection Agency AirNow ground-level monitoring PM2.5 concentrations. Three machine learning-based data fusion algorithms were applied: An ordinary multi-linear regression method, a generalized boosting method, and a random forest (RF) method. 10-Fold cross-validation found improved surface PM2.5 estimation after data integration and bias correction, especially with the RF method. Lastly, to assess transient health effects of fire smoke, we applied the optimized high-resolution PM2.5 exposure estimate in a short-term exposure-response function. Total estimated regional mortality attributable to PM2.5 exposure during the smoke episode was 183 (95% confidence interval: 0, 432), with 85% of the PM2.5 pollution and 95% of the consequent multiple-cause mortality contributed by fire emissions. This application demonstrates both the profound health impacts of fire smoke over the PNW and the need for a high-performance fire smoke forecasting and reanalysis system to reduce public health risks of smoke hazards in fire-prone regions.
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Maly, Milan, Jaroslav Slama, Ondrej Cejpek i Jan Jedelsky. "Searching for a Numerical Model for Prediction of Pressure-Swirl Atomizer Internal Flow". Applied Sciences 12, nr 13 (22.06.2022): 6357. http://dx.doi.org/10.3390/app12136357.
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Numerical prediction of discharge parameters allows design of a pressure-swirl atomizer in a fast and cheap manner, yet it must provide reliable results for a wide range of geometries and operating regimes. Many authors have used different numerical setups for similar cases and often concluded opposite suggestions on numerical setup. This paper compares 2D (two-dimensional) axisymmetric, 3D (three-dimensional) periodic and full 3D numerical models used for estimation of the internal flow characteristics of a pressure-swirl atomizer. The computed results are compared with experimental data in terms of spray cone angle, discharge coefficient (CD), internal air-core dimensions, and velocity profiles. The three-component velocity was experimentally measured using a Laser Doppler Anemometry in a scaled transparent model of the atomizer. The internal air-core was visualized by a high-speed camera with backlit illumination. Tested conditions covered a wide range of the Reynolds numbers within the inlet ports, Re = 1000, 2000, 4000. The flow was treated as both steady and transient flow. The numerical solver used laminar and several turbulence models, represented by k-ε and k-ω models, Reynolds Stress model (RSM) and Large Eddy Simulation (LES). The laminar solver was capable of closely predicting the CD, air-core dimensions and velocity profiles compared with the experimental results in both 2D and 3D simulations. The LES performed similarly to the laminar solver for low Re and was slightly superior for Re = 4000. The two-equation models were sensitive to proper solving of the near wall flow and were not accurate for low Re. Surprisingly, the RSM produced the worst results.
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Frostig, Danielle, Sylvia Biscoveanu, Geoffrey Mo, Viraj Karambelkar, Tito Dal Canton, Hsin-Yu Chen, Mansi Kasliwal i in. "An Infrared Search for Kilonovae with the WINTER Telescope. I. Binary Neutron Star Mergers". Astrophysical Journal 926, nr 2 (1.02.2022): 152. http://dx.doi.org/10.3847/1538-4357/ac4508.
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Abstract The Wide-Field Infrared Transient Explorer (WINTER) is a new 1 deg2 seeing-limited time-domain survey instrument designed for dedicated near-infrared follow-up of kilonovae from binary neutron star (BNS) and neutron star–black hole mergers. WINTER will observe in the near-infrared Y, J, and short-H bands (0.9–1.7 μm, to J AB = 21 mag) on a dedicated 1 m telescope at Palomar Observatory. To date, most prompt kilonova follow-up has been in optical wavelengths; however, near-infrared emission fades more slowly and depends less on geometry and viewing angle than optical emission. We present an end-to-end simulation of a follow-up campaign during the fourth observing run (O4) of the LIGO, Virgo, and KAGRA interferometers, including simulating 625 BNS mergers, their detection in gravitational waves, low-latency and full parameter estimation skymaps, and a suite of kilonova lightcurves from two different model grids. We predict up to five new kilonovae independently discovered by WINTER during O4, given a realistic BNS merger rate. Using a larger grid of kilonova parameters, we find that kilonova emission is ≈2 times longer lived and red kilonovae are detected ≈1.5 times further in the infrared than in the optical. For 90% localization areas smaller than 150 (450) deg2, WINTER will be sensitive to more than 10% of the kilonova model grid out to 350 (200) Mpc. We develop a generalized toolkit to create an optimal BNS follow-up strategy with any electromagnetic telescope and present WINTER’s observing strategy with this framework. This toolkit, all simulated gravitational-wave events, and skymaps are made available for use by the community.
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YAN, Mingmin, Hiroki TAMURA i Koichi TANNO. "A Study on Gaze Estimation System of the Horizontal Angle Using Electrooculogram Signals". IEICE Transactions on Information and Systems E97.D, nr 9 (2014): 2330–37. http://dx.doi.org/10.1587/transinf.2013lop0018.
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Aviles-Ramos, C., A. Haji-Sheikh, J. V. Beck i K. J. Dowding. "Estimation of Thermophysical Properties by the Spectral Method—Development and Evaluation". Journal of Heat Transfer 123, nr 1 (10.07.2000): 24–30. http://dx.doi.org/10.1115/1.1336507.
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This paper reports the evaluation of a spectral technique for estimating thermophysical properties. It demonstrates that one can construct a virtual quasi-steady periodic experiment from a limited but properly selected set of transient non-periodic data. In the spectral domain, the phase angles of the responses at different locations relative to a periodic input signal depend on the thermophysical properties. For the purpose of this evaluation, the transient temperature responses to a surface heat flux input are analytically obtained at pre-selected sensor locations. The transient data are converted to periodic data, phase angles are computed, and thermophysical properties are estimated. All deviations from known property values due to numerical errors are reported.
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Lai, Yening, Ling Zhu, Xueping Pan, Jinpeng Guo, Dazhuang He i Wei Liang. "Online Estimation of the Mechanical Parameters of a Wind Turbine with Doubly Fed Induction Generator by Utilizing Turbulence Excitations". Energies 15, nr 6 (21.03.2022): 2277. http://dx.doi.org/10.3390/en15062277.
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In this paper, a new method using wind turbulence excitation is proposed to estimate the parameters of the mechanical system (drivetrain and pitch angle controller) in a Doubly Fed Induction Generator (DFIG) Wind Turbine (WT). Firstly, simulations were carried out for a DFIG WT under turbulence excitations. The spectral contents of the responses imply that the transients of the electrical system (generator and converter), which are much faster than those of the mechanical system, can be neglected when estimating the mechanical parameters. Based on this, a simplified model related to the mechanical system of the DFIG WT was derived by applying the model reduction technique. Secondly, the parameter sensitivity of Power Spectral Density (PSD) was used to quantify the impacts of individual parameters on the dynamics of the mechanical system, and the influential parameters were selected on the basis of the sensitivity results. Finally, a weighted least-squares optimization problem, which is suitable for a system with close oscillation modes, was formulated for parameter estimation. The estimation results based on two different types of optimization methods were compared, and their estimation accuracies validate the effectiveness of the proposed method.
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NAGAMATSU, Takashi, Mamoru HIROE i Hisashi ARAI. "Extending the Measurement Angle of a Gaze Estimation Method Using an Eye Model Expressed by a Revolution about the Optical Axis of the Eye". IEICE Transactions on Information and Systems E104.D, nr 5 (1.05.2021): 729–40. http://dx.doi.org/10.1587/transinf.2020edp7072.
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Nikitenko, M. N., M. B. Rabinovich i M. V. Sviridov. "Determination of formation dip and strike from transient LWD electromagnetic measurements". Russian Journal of Geophysical Technologies, nr 2 (13.01.2022): 36–48. http://dx.doi.org/10.18303/2619-1563-2021-2-36.
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An original method has been developed for estimating formation dip and strike from transient induction LWD data, based on focusing in the time domain. The focusing consists in decomposing the measured signals into a time series and diagonalizing the matrix of focused magnetic field components. We have implemented the method and comprehensively tested it in horizontally-layered media used for LWD data inversion to solve geosteering problems and evaluate the formation resistivity. Estimates of the angles contribute to reliable geosteering when choosing a direction of drilling, as well as when inverting data for a complex earth model. A significant reduction in the resource intensity of inversion and model equivalence is achieved by reducing the number of determined parameters.
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Utrata, Grzegorz, Jaroslaw Rolek i Andrzej Kaplon. "The Novel Rotor Flux Estimation Scheme Based on the Induction Motor Mathematical Model Including Rotor Deep-Bar Effect". Energies 12, nr 14 (12.07.2019): 2676. http://dx.doi.org/10.3390/en12142676.
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During torque transients, rotor electromagnetic parameters of an induction motor (IM) vary due to the rotor deep-bar effect. The accurate representation of rotor electromagnetic parameter variability by an adopted IM mathematical model is crucial for a precise estimation of the rotor flux space vector. An imprecise estimation of the rotor flux phase angle leads to incorrect decoupling of electromagnetic torque control and rotor flux amplitude regulation which in turn, causes deterioration in field-oriented control of IM drives. Variability of rotor electromagnetic parameters resulting from the rotor deep-bar effect can be modeled by the IM mathematical model with rotor multi-loop representation. This paper presents a study leading to define the unique rotor flux space vector on the basis of the IM mathematical model with rotor two-terminal network representation. The novel rotor flux estimation scheme was validated with the laboratory test bench employing the IM of type Sg 132S-4 with two variants of rotor construction: a squirrel-cage rotor and a solid rotor manufactured from magnetic material S235JR. The accuracy verification of the rotor flux estimation was performed in a slip frequency range corresponding to the IM load adjustment range up to 1.30 of the stator rated current. This study proved the correct operation of the developed rotor flux estimation scheme and its robustness against electromagnetic parameter variability resulting from the rotor deep-bar effect in the considered slip frequency range.
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Cui, Zhengyang, i Yong Wang. "Nonlinear Adaptive Line-of-Sight Path Following Control of Unmanned Aerial Vehicles considering Sideslip Amendment and System Constraints". Mathematical Problems in Engineering 2020 (28.02.2020): 1–11. http://dx.doi.org/10.1155/2020/4535698.
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With growing worldwide interests in commercial, scientific, and military issues, there has been a corresponding rapid growth in demand for the development of unmanned aerial vehicles (UAVs) with more reliable and safer motion control abilities. This paper presents a new nonlinear path following scheme integrated with a heading control law for achieving accurate and reliable path following performance. Both backstepping and finite-time techniques are employed for developing the path following and heading control strategies capable of minimizing cross-track errors in finite-time with elegant transient performance, while the barrier Lyapunov function scheme is adopted to limit turning rates of the UAV for preventing it from capsizing which may be induced by overquick steering actions. A fixed-time nonlinear estimator, based on UAV kinematics, is designed for estimating the uncertainties with sideslip angles caused by external disturbances and inertial motions. To avoid the complicated calculation of derivatives of virtual control terms in backstepping, command filters and auxiliary systems are likewise introduced in the design of control laws. Extensive numerical simulation studies on a nonlinear UAV model are conducted to demonstrate the effectiveness of the proposed methodologies.
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Sakharov, Vladimir Vasilievich, Alexandr Aleksandrovich Chertkov i Yaroslav Nikolayevich Kask. "Modal synthesis of estimator of unmeasured state variables for ship course stabilization system". Vestnik of Astrakhan State Technical University. Series: Management, computer science and informatics 2022, nr 4 (31.10.2022): 7–17. http://dx.doi.org/10.24143/2072-9502-2022-4-7-17.
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The purpose of the study is to apply automation technologies and digitalization in estimating the unmeasurable variables of the ship course stabilization system to control the high-tech software and hardware and, thus, to intensify the use of ships at a qualitatively new level, as well as to improve the reliability and efficiency of their operation. It has been stated that estimating the vector of state variables in real time requires to use methods and computational algorithms
of stochastic and, in particular, binomial filtering. It is emphasized that for improving the reliability and accuracy of estimating the parameters of the system under perturbations of the roll angle, angular rotation speed or measurement noise there are required compromise solutions that take into account the required values of the system's speed and stability. It is shown that digitalization of mathematical and physical ship models, producing the adequate decisions, taking into account a wide range of environmental influences and navigation conditions allow to synthesize ship control complexes in the class of digital predictive systems with a transition to the control of unmanned objects. There has been considered the modal method of synthesis of the vector estimator of the state of full dimension (Kalman observer) which can obtain estimates of unmeasured state variables of the course stabilization system with measured output and input of the system by developing a model of the state of the extended system ‘object–observer’, which ensures stability of the ship on the course. A model and an algorithm for estimating unmeasured state variables by using binomial filtering algorithms, matrix laboratory tools and computer modeling technologies in the MATLAB environment are proposed. The proposed algorithm for the synthesis of a vector evaluator of unmeasured state variables is implemented in the form of a program compiled in MATLAB codes and demonstrated in calculating a two-dimensional dynamic observer for an unstable object of control. The obtained estimates of unmeasured variables, as well as the results of modeling the dynamic reactions of the course stabilization system correspond to the specified speed and stability transient processes of the ship object when transferring it into the steady state under the new initial conditions.
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Feifei, Gou, Liu Chuanxi, Ren Zongxiao, Qu Zhan, Wang Sukai, Qin Xuejie, Fang Wenchao, Wang Ping i Wang Xinzhu. "Transient Pressure Behavior of Complex Fracture Networks in Unconventional Reservoirs". Geofluids 2021 (3.11.2021): 1–11. http://dx.doi.org/10.1155/2021/6273822.
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Unconventional resources have been successfully exploited with technological advancements in horizontal-drilling and multistage hydraulic-fracturing, especially in North America. Due to preexisting natural fractures and the presence of stress isotropy, several complex fracture networks can be generated during fracturing operations in unconventional reservoirs. Using the DVS method, a semianalytical model was created to analyze the transient pressure behavior of a complex fracture network in which hydraulic and natural fractures interconnect with inclined angles. In this model, the complex fracture network can be divided into a proper number of segments. With this approach, we are able to focus on a detailed description of the network properties, such as the complex geometry and varying conductivity of the fracture. The accuracy of the new model was demonstrated by ECLIPSE. Using this method, we defined six flow patterns: linear flow, fracture interference flow, transitional flow, biradial flow, pseudoradial flow, and boundary response flow. A sensitivity analysis was conducted to analyze each of these flow regimes. This work provides a useful tool for reservoir engineers for fracture designing as well as estimating the performance of a complex fracture network.
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Furtat, I. B., Y. A. Zhukov i N. S. Slobodzyan. "Overview of Models and Methods for Control of Stepper Motors". Mekhatronika, Avtomatizatsiya, Upravlenie 24, nr 7 (9.07.2023): 352–63. http://dx.doi.org/10.17587/mau.24.352-363.
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A review of models and algorithms for control of a stepper motor (SM) is presented. Due to high accuracy, improved power density, economy and reliability compared to other synchronous motors, stepper motors are widely used in various practical applications and scientific equipment. In aviation and space technology, step motors are actively used in actuating systems, such as drives for the movement of elements of large-sized structures, guidance, and stabilization systems, etc. The article describes some existing stepper motor control algorithms, which are both based on the knowledge of the parameters of the stepper motor model, and on the absence of this or that information. Of the many described algorithms, four were selected (PID controller, exact feedback linearization algorithm, adaptive control with partially unknown parameters and adaptive control with completely unknown parameters), which showed the best results of transient processes in tracking the angle of the rotor of the SM behind the reference value. A comparative numerical analysis among these four algorithms is also given, which showed that the best results of transients are demonstrated by adaptive controllers (in the sense of the smallest error in steady state), while the worst results are demonstrated by the PID controller. It is noted that the studied PID controller contains much fewer feedback loops compared to other algorithms, which simplifies the choice of adjustable parameters and reduces the dynamic order of the closed system, however, the design is based on knowing the exact parameters of the drive and is also sensitive to external disturbances. On the contrary, adaptive approaches successfully solve the problem of estimating parametric and functional perturbations, but their implementation is associated with significant difficulties.
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Feng, Ye, Xueshan Zhao, Lijun Gou, Jianfeng Wu, James F. Steiner, Yufeng Li, Zhenxuan Liao, Nan Jia i Yuan Wang. "Estimating the Spin of the Black Hole Candidate MAXI J1659-152 with the X-Ray Continuum-fitting Method". Astrophysical Journal 925, nr 2 (1.02.2022): 142. http://dx.doi.org/10.3847/1538-4357/ac4163.
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Abstract As a transient X-ray binary, MAXI J1659-152 contains a black hole candidate as its compact star. MAXI J1659-152 was discovered on 2010 September 25 during its only known outburst. Previously published studies of this outburst indicate that MAXI J1659-152 may have an extreme retrograde spin, which, if confirmed, would provide an important clue as to the origin of black hole spin. In this paper, utilizing updated dynamical binary system parameters (i.e., the black hole mass, the orbital inclination, and the source distance) provided by Torres et al., we analyze 65 spectra of MAXI J1659-152 from RXTE/PCA, in order to assess the spin parameter. With a final selection of nine spectra matching our f sc ≲ 25%, soft state criteria, we apply a relativistic thin disk spectroscopic model kerrbb2 over 3.0–45.0 keV. We find that inclination angle correlates inversely with spin, and, considering the possible values for inclination angle, we constrain spin to be −1 < a * ≲ 0.44 at a 90% confidence interval via X-ray continuum fitting. We can only rule out an extreme prograde (positive) spin. We confirm that an extreme retrograde solution is possible and is not ruled out by considering accretion torques given the young age of the system.
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Wadee, Khoury, Nasser Aram i Tamás Szemes Péter. "Three phase induction motor modelling and control using vector control in LabVIEW". MATEC Web of Conferences 184 (2018): 02019. http://dx.doi.org/10.1051/matecconf/201818402019.
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In this paper, a speed control system for a three-phase induction motor was modelled and designed within LabVIEW software environment. After structuring the dynamical model of the motor, a current controller was developed to stabilize the system and avoid a wind-up situation. Then, a speed controller was designed, using PID and Field Weakening techniques, to generate the reference current values. The field-weakening algorithm is used to achieve stability at speeds that are higher than the nominal one. An estimator is used to calculate the flux angle and the electro-mechanical speed of the motor. As a result, the system achieved the desired speed with good transient and steady state responses. In addition, the system proved to be robust when the torque load is applied in all cases.
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Sáenz, P. J., K. Sefiane, J. Kim, O. K. Matar i P. Valluri. "Evaporation of sessile drops: a three-dimensional approach". Journal of Fluid Mechanics 772 (8.05.2015): 705–39. http://dx.doi.org/10.1017/jfm.2015.224.
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The evaporation of non-axisymmetric sessile drops is studied by means of experiments and three-dimensional direct numerical simulations (DNS). The emergence of azimuthal currents and pairs of counter-rotating vortices in the liquid bulk flow is reported in drops with non-circular contact area. These phenomena, especially the latter, which is also observed experimentally, are found to play a critical role in the transient flow dynamics and associated heat transfer. Non-circular drops exhibit variable wettability along the pinned contact line sensitive to the choice of system parameters, and inversely dependent on the local contact-line curvature, providing a simple criterion for estimating the approximate contact-angle distribution. The evaporation rate is found to vary in the same order of magnitude as the liquid–gas interfacial area. Furthermore, the more complex case of drops evaporating with a moving contact line (MCL) in the constant contact-angle mode is addressed. Interestingly, the numerical results demonstrate that the average interface temperature remains essentially constant as the drop evaporates in the constant-angle (CA) mode, while this increases in the constant-radius (CR) mode as the drops become thinner. It is therefore concluded that, for increasing substrate heating, the evaporation rate increases more rapidly in the CR mode than in the CA mode. In other words, the higher the temperature the larger the difference between the lifetimes of an evaporating drop in the CA mode with respect to that evaporating in the CR mode.
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Mancosu, F., D. Speziari, M. Ceresa i P. Sbarbati. "A New Methodology to Get Reliable Input Data for Handling Simulations". Tire Science and Technology 27, nr 3 (1.07.1999): 176–87. http://dx.doi.org/10.2346/1.2135983.
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Abstract This paper presents a methodology to obtain tire and vehicle parameters suitable for handling simulations, describing the experimental activity needed, a vehicle model, and an appropriate identification algorithm. The vehicle model has four degrees of freedom and takes into account roll movements, load transfers among the four tires, and lateral tire forces, described by the Magic Formula with transient behavior. The resulting system has 10 state variables. A vehicle was equipped with standard sensors used by vehicle manufacturers in handling maneuvers and wheel vector transducers that measure the displacements and angles of the four hubs with respect to the chassis. Handling tests were performed, and some of the results were used to identify the tire Magic Formula coefficients and part of the vehicle parameters, using an Extended Kalman filter. The remaining tests were used for the validation: the results showed good agreement between simulations and measurements, confirming the validity of the model and the accuracy of the parameters' estimation.
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Benmoussa, Amine, i Pedro Vieira Gamboa. "Effect of Control Parameters on Hybrid Electric Propulsion UAV Performance for Various Flight Conditions: Parametric Study". Applied Mechanics 4, nr 2 (25.04.2023): 493–513. http://dx.doi.org/10.3390/applmech4020028.
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Nowadays, great efforts of ongoing research are devoted to hybrid-electric propulsion technology that offers various benefits, such as reduced noise and pollution emissions and enhanced aircraft performance and fuel efficiency. The ability to estimate the performance of an aircraft in any flight situation in which it may operate is essential for aircraft development. In the current study, a simulation model was developed that allows estimating the flight performance and analyzing the mission of a fixed-wing multi-rotor Unmanned Aerial Vehicle (UAV) with a hybrid electric propulsion system (HEPS), with both conventional and Vertical Takeoff and Landing (VTOL) capabilities. The control is based on the continuous specification of pitch angle, propulsion thrust, and lift thrust to achieve the required conditions of a given flight segment. Six different missions were considered to analyze the effect of control parameters exhibiting the most influence on the UAV mission performance. An appropriate set of control parameters was selected through a multidimensional parametric study. The results show that the control parameters, if not well tuned, affect the mission performance: for example, in the deceleration transition, a longer time to reduce the cruise speed to stand still may be the result because the controller struggles to adjust the pitch angle. In addition, the implemented methodology captures the effects of transient maneuvers, unlike typical quasi-static analysis without the complexity of full simulation models.
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Bevly, David M. "Global Positioning System (GPS): A Low-Cost Velocity Sensor for Correcting Inertial Sensor Errors on Ground Vehicles". Journal of Dynamic Systems, Measurement, and Control 126, nr 2 (1.06.2004): 255–64. http://dx.doi.org/10.1115/1.1766027.
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This paper demonstrates the ability of a standard low-cost Global Positioning System (GPS) receiver to reduce errors inherent in low-cost accelerometers and rate gyroscopes used on ground vehicles. Specifically GPS velocity is used to obtain vehicle course, velocity, and road grade, as well as to correct inertial sensors errors, providing accurate longitudinal and lateral acceleration, and pitch, roll, and yaw angular velocities. Additionally, it is shown that transient changes in sideslip (or lateral velocity), roll, and pitch angles can be measured. The method utilizes GPS velocity measurements to determine the inertial sensor errors using a kinematic Kalman Filter estimator. Simple models of the inertial sensors, which take into account the sensor noise and bias drift properties, are developed and used to design the estimator. Based on the characteristics of low-cost GPS receivers and IMU sensors, this paper presents the achievable performance of the combined system using the covariance analysis from the Kalman filter. Subsequent simulations and experiments validate both the error analysis and the methodology for utilizing GPS as a velocity sensor for correcting low-cost inertial sensor errors and providing critical vehicle state measurements.
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Saderla, S., R. Dhayalan i A. K. Ghosh. "Parameter Estimation from Near Stall Flight Data using Conventional and Neural-based Methods". Defence Science Journal 67, nr 1 (23.12.2016): 03. http://dx.doi.org/10.14429/dsj.67.9995.
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<p>The current research paper is an endeavour to estimate the parameters from near stall flight data of manned and unmanned research flight vehicles using conventional and neural based methods. For an aircraft undergoing stall, the aerodynamic model at these high angles of attack becomes non linear due to the influence of unsteady, transient and flow separation phenomena. In order to address these issues the Kirchhoff’s flow separation theory was used to incorporate the nonlinearity in the aerodynamic model in terms of flow separation point and stall characteristic parameters. The classical Maximum Likelihood (MLE) method and Neural Gauss-Newton (NGN) method have been employed to estimate the nonlinear parameters of two manned and one unmanned research aircrafts. The estimated static stall parameter and the break point, for the flight vehicles under consideration, were observed to be consistent from both the methods. Moreover the efficacy of the methods is also evident from the consistent estimates of post stall hysteresis time constant. It can also be inferred that the considered quasi steady model is able to adequately capture the drag and pitching moment coefficients in the post stall regime. The confidence in these estimates have been significantly enhanced with the observed lower values of Cramer-Rao bounds. Further the estimated nonlinear parameters were validated by performing a proof of match exercise for the considered flight vehicles. Interestingly the NGN method, which doesn’t involve solving equations of motion, was able to perform on a par with the MLE method.</p>