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Artykuły w czasopismach na temat "Transient Angle Estimation"
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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.
Rozprawy doktorskie na temat "Transient Angle Estimation"
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Dinesh, Mukta. "High Performance Hybrid Drive for Induction Motor Using Transient Angle Estimation and Control". Thesis, 2014. https://etd.iisc.ac.in/handle/2005/4564.
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Induction motors are widely used in industry because of their ruggedness, higher power/ weight ratio and low maintenance. The development of variable frequency drives for induction motors have resulted in higher performance. These variable frequency drives use different control strategies to achieve high performance. The most widely used control strategies are namely - V/f or Scalar control and Vector control (which uses the concept of field orientation).
Scalar control strategy is highly rugged, robust because it is insensitive to any motor parameter variations such as the rotor resistance during motor operation. The control is modeled on the steady state model of the induction motor and has a good steady state response. During dynamic conditions (load and slip dynamics), the control strategy fairs rather poorly. Vector control on the other hand is modeled on the dynamic model of the induction motor. The dynamic response of vector control is excellent. But the dynamic model of the induction motor takes into account the motor parameters, and any change in the parameters during the course of the motor operation results in instability. It is very sensitive to motor parametric changes and therefore, parametric adapted control strategies must be incorporated to ensure a stable response in vector control. Vector control operation also ensures stator currents to stay within their rated limits.
With the merits and demerits seen in both scalar and vector control strategies, in this thesis we propose a control scheme which is a hybrid of the scalar and vector controls. That is, we wish to merge the merits of V/f control and vector control to form a Hybrid control strategy. The hybrid control is dominated by V/f control in order to provide the steady state response. Only during dynamics, a separate modified vector control module (based on the dynamic model of the induction motor) is incorporated to handle the dynamic response.
In the hybrid control, the ruggedness and robustness of V/f control is maintained with the addition of faster dynamic response.
The inputs that are available for motor control are - Supply Voltage, frequency and phase angle of the applied voltage. V/f control uses voltage and frequency as its control inputs. Vector control uses all the three parameters as its control inputs. Voltage and frequency control inputs are required for steady state response of the machine. Whereas, the phase angle control input is the parameter that is fast acting and comes into picture during transient conditions. Hence the name, transient angle. For fast dynamics, control of the phase angle or transient angle of the rotating flux space vector is essential. In this thesis, the effects of the phase angle control input on the dynamic response are studied and methods to estimate the transient angle component are proposed.
Części książek na temat "Transient Angle Estimation"
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Gjonaj, Erion, Yun Ouedraogo i Sebastian Schöps. "Modelling of Droplet Dynamics in Strong Electric Fields". W Fluid Mechanics and Its Applications, 107–25. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-09008-0_6.
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AbstractWe describe a modelling approach for the simulation of droplet dynamics in strong electric fields. The model accounts for electroquasistatic fields, convective and conductive currents, contact angle dynamics and charging effects associated with droplet breakup processes. Two classes of applications are considered. The first refers to the problem of water droplet oscillations on the surface of outdoor high-voltage insulators. The contact angle characteristics resulting from this analysis provides a measure for the estimation of the electric field inception thresholds for electrical discharges on the surface. The second class of applications consists in the numerical characterization of electrosprays. Detailed simulations confirm the scaling law for the first electrospray ejection and, furthermore, provide insight on the charge-radius characteristics for transient as well as steady state electrosprays.
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Cui, Xunxue, Kegen Yu i Songsheng Lu. "TDOA-Based Acoustic Direction Finding". W Advances in Wireless Technologies and Telecommunication, 193–231. IGI Global, 2018. http://dx.doi.org/10.4018/978-1-5225-3528-7.ch005.
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This chapter focuses on estimating the azimuth and elevation angles of a sound emitter based on time-difference-of-arrival (TDOA) measurements using an array of acoustic sensors. The TDOA-based direction-finding problem is appropriate because in a range of scenarios the source only emits a transient signal and TDOA measurements provide a simple method of finding the direction of the received signal. Given the measurement of TDOA, three methods for calculating the actual bearing of an acoustic source are considered—algebraic calculations based on trigonometric functions, linear least squares, and nonlinear least squares—and these results are also compared with the Cramer-Rao lower bound (CRLB). In this chapter, a comprehensive analysis of TDOA-based direction-finding methods is presented with regard to different application conditions, while their estimation performances are analysed with both simulation and field experimental results produced by 3-D microphone array.
Streszczenia konferencji na temat "Transient Angle Estimation"
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Yd, Sumith, i Shalabh C. Maroo. "A New Algorithm for Contact Angle Estimation in Molecular Dynamics Simulations". W ASME 2015 13th International Conference on Nanochannels, Microchannels, and Minichannels collocated with the ASME 2015 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/icnmm2015-48569.
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It is important to study contact angle of a liquid on a solid surface to understand its wetting properties, capillarity and surface interaction energy. While performing transient molecular dynamics (MD) simulations it requires calculating the time evolution of contact angle. This is a tedious effort to do manually or with image processing algorithms. In this work we propose a new algorithm to estimate contact angle from MD simulations directly and in a computationally efficient way. This algorithm segregates the droplet molecules from the vapor molecules using Mahalanobis distance (MND) technique. Then the density is smeared onto a 2D grid using 4th order B-spline interpolation function. The vapor liquid interface data is estimated from the grid using density filtering. With the interface data a circle is fitted using Landau method. The equation of this circle is solved for obtaining the contact angle. This procedure is repeated by rotating the droplet about the vertical axis. We have applied this algorithm to a number of studies (different potentials and thermostat methods) which involves the MD simulation of water.
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Xu, Shuonan, Zhe Wang, Robert Prucka, Zoran Filipi, Michael Prucka i Hussein Dourra. "Physical Model for Real-Time Simultaneous Estimation of Intake Mass and Cylinder Pressure in an SI Engine". W ASME 2016 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/icef2016-9396.
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Stringent emission regulations require spark ignited (SI) engines to operate at stoichiometry to enable the use of a three way catalyst (TWC). Thus, accurate prediction of the intake charge mass flow rate is paramount. Current speed-density air mass-flow prediction techniques require extensive calibration for predicting volumetric efficiency, while mass air flow (MAF) meter based approaches suffer from a loss of accuracy during transients. This work aims to provide an alternative, i.e. a model based air charge estimation algorithm that can reduce calibration effort and provide a universal solution across engine platforms. An additional objective is to minimize the number of required sensors and associated cost. The foundation is established with a 0-D physics-based air charge model, where air flow through intake and exhaust valves is modeled on a crank-angle basis, without the need to measure in-cylinder pressure. The proposed algorithm solves differential equations for cylinder pressure and mass flow rate in/out of the cylinder to simultaneously obtain instantaneous pressure and mass-flow estimations, hence eliminating the need to install cylinder pressure transducers. An additional benefit is the robustness of the new model, due to its ability to self-compensate for an error in the intake runner pressure or initial estimation of the cylinder pressure. The model has been validated with GT-Power simulations and steady-state engine tests with multiple actuator sweeps. Transient tests and real-time implementations were performed as well.
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Abdulhamitbilal, Erkan, Sinan Şal i Elbrous M. Jafarov. "A Mathematical Model for Windmilling of a Turbojet Engine". W ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/gt2021-58503.
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Abstract The transient windmilling characteristic of a modern turbojet engine under different flight conditions and altitudes is obtained with numerous tests conducted at an Altitude Test Facility (ATF). A simple and practical mathematical model for predicting the transient and steady-state rotational speed of a simple turbojet engine in flight has been developed. The method is derived from Froude’s momentum theory or disk actuator theory and implemented to a turbojet engine. A correction factor is introduced to match with test results of KTJ-3200 being indigenously developed by Kale R&D Inc. The present model’s predictions are compared with the test data of Microturbo TRI 60 engine and KTJ-3200 engine. The estimation of the present windmilling model fits very well with test results of two different engines within an error band of ±1.2% for various atmosphere conditions depending on flight speed, altitudes and temperature. The present model is compared with loss modeling windmilling estimation methods described in literature which requires large amount of inputs as blade angle, blade pitch and component efficiencies. The comparison with the available windmilling model at literature shows that both models capture the terminal speed estimation very well. However, the model in literature is not able to capture the transient engine speed, which is important for missile applications as the missile can be fired before the engine reaches to terminal speed. The difference between the test data and the available model during transients is up to 50%. The present model matches perfectly with test data even at transients. It is more practical and much simpler than the available windmilling model in the literature to estimate the both transient and terminal windmilling speed of the turbojet engines. The agreement between the present model, KTJ 3200 test data, windmilling method available in the literature and test data of Microturbo TRI 60 is very good for most of the ranges investigated.
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Paldan, Jesse R., Jeremy P. Gray i Vladimir V. Vantsevich. "Sensor Signal Limitations in Wheel Rotational Kinematics Estimation Model". W ASME 2015 Dynamic Systems and Control Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/dscc2015-9769.
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Wheel encoders play an important role in providing information about rotational kinematics of vehicle wheels. The sensor signals are utilized in critical vehicle systems responsible for vehicle safety, traction and braking performance, and stability of motion. This paper starts with an analysis of different types of sensors that have been used in rotational wheel kinematics estimations and controls. The main attention is given to sensor signal limitations related to the accuracy of measurement and response time that are important for agile-to-real-time tire dynamics estimation. A detailed analysis of the wheel rotational velocity estimation process is presented for a conventional Hall Effect digital sensor. Through an analytical modelling, it is shown that this sensor can limit its accuracy due to an increased time for signal information assembly caused by the number of impulses and transient (unsteady) rotational motion in unstable road conditions. A new concept of a rotational kinematics sensor is proposed and modeled as a multi-domain mechatronic system that includes new mechanical elements as well as electrical and magnetic components. The sensor concept provides a smooth continuous signal through the full rotational angle of the wheel and precise information about the rotational velocity and its changes in different unstable road conditions. Computational examples of both sensors (digital and proposed) are demonstrated with the use of a quarter-car model moving over a random road profile in stochastic gripping and rolling resistance conditions. A comparison of the two sensors’ accuracy to estimate the rotational velocity of the wheel is done with regard to an “ideal” sensor with a unity transfer function.
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Sunder, Sankar, i Joseph L. Smith. "Kissing Heat Transfer Between the Wraps of a Scroll Pump". W ASME 1996 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/imece1996-0269.
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Abstract Conductances associated with the various modes of internal heat transfer in a scroll pump are estimated. Heat transfer through transient contact between scroll wraps (kissing heat transfer) is found to be a dominant mode of heat transfer between discharge and suction sides of the pump. Such heat transfer is characterized by significant steady-state heat fluxes across the wraps of a scroll pump. Experiments on a specially instrumented scroll compressor provide evidence of significant heat fluxes across the wraps of the scroll pump. Estimation of the contact angle between wraps based on Hertzian stresses, as well as an oil film demonstrate that kissing heat transfer is a plausible mechanism of heat transfer in these pumps. Contact angles inferred from experimental data are also shown to be of the same order of magnitude as those predicted by hertzian stress calculations. It is shown that the heat fluxes observed in the kissing heat transfer experiment are too large to be explained by convection between gas and wall in the scroll pump.
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Tudón-Martínez, Juan C., Jorge de Jesús Lozoya-Santos, Carlos A. Vivas, Ruben Morales-Menendez i Ricardo A. Ramirez-Mendoza. "Model-Free Controller for a Pick-Up Semi-Active Suspension System". W ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-88495.
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A model-free controller for the full semi-active suspension system of a pick-up truck is proposed. The controller is focused in the passengers comfort and stability of the vehicle. A Combinatory quasi-Optimum Damping (COD) controller defines the best combination of damping force by analyzing the frequency response of the vehicle for all possible combinations among the semi-active dampers. The solution is defined in bandwidths by using a frequency estimation module of the road profile based on a Kalman filter. A model in CarSim™ was used as Software-in-the-Loop (SiL). The semi-active suspension system is composed by four experimental Magneto-rheological (MR) damper models. Simulation results show the controller benefits in comfort in the Bounce Sine Sweep (BSS) test, specially at frequencies close to the resonance frequency of the sprung mass (reduction of 50%). In the Double-Lane Change (DLC) test, the COD controller improves the roll control by reducing 28% the roll rate and 21% the roll angle. For the FishHook (FH) test, the improvement is high-lighted in the vehicle slip angle (reduction of 26%); however, the transient response of the yaw angle, yaw rate and lateral acceleration is better when the COD controller is used because the oscillations have lower amplitude with shorter settling time.
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Yang, Jianfu, Tzu-Hao Huang, Shuangyue Yu, Xiaolong Yang, Hao Su, Ann M. Spungen i Chung-Ying Tsai. "Machine Learning Based Adaptive Gait Phase Estimation Using Inertial Measurement Sensors". W 2019 Design of Medical Devices Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/dmd2019-3266.
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This paper presents a portable inertial measurement unit (IMU)-based motion sensing system and proposed an adaptive gait phase detection approach for non-steady state walking and multiple activities (walking, running, stair ascent, stair descent, squat) monitoring. The algorithm aims to overcome the limitation of existing gait detection methods that are time-domain thresholding based for steady-state motion and are not versatile to detect gait during different activities or different gait patterns of the same activity. The portable sensing suit is composed of three IMU sensors (wearable sensors for gait phase detection) and two footswitches (ground truth measurement and not needed for gait detection of the proposed algorithm). The acceleration, angular velocity, Euler angle, resultant acceleration, and resultant angular velocity from three IMUs are used as the input training data and the data of two footswitches used as the training label data (single support, double support, swing phase). Three methods 1) Logistic Regression (LR), 2) Random Forest Classifier (RF), and 3) Artificial Neural Network (NN) are used to build the gait phase detection models. The result shows our proposed gait phase detection with Random Forest Classifier can achieve 98.94% accuracy in walking, 98.45% in running, 99.15% in stair-ascent, 99.00% in stair-descent, and 99.63% in squatting. It demonstrates that our sensing suit can not only detect the gait status in any transient state but also generalize to multiple activities. Therefore, it can be implemented in real-time monitoring of human gait and control of assistive devices.
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Yuan, Ping, Hsueh-Erh Liu, Chih-Wei Chen i Hong-Sen Kou. "Analysis of Temperature Response in Biological Tissue With Sinusoidal Temperature Oscillation on the Skin". W ASME 2008 Heat Transfer Summer Conference collocated with the Fluids Engineering, Energy Sustainability, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/ht2008-56493.
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This study investigates the transient temperature response in biological tissue with sinusoidal temperature oscillation on the skin surface. Based on the Laplace transform, an exact solution of the Pennes bioheat transfer equation has been derived which includes the whole time domain from the initial transient oscillation to the final steady periodic oscillation. Furthermore, the exact solutions of special cases under no perfusion rate, constant temperature, and the combination of those two assumptions are demonstrated in this study. The primary application for this type of analysis is to assess the blood perfusion rate in the skin by imposing a periodic temperature load onto the skin surface. Through the noninvasive measurement of the maximum heat flux or minimum heat flux on the skin, equation (15) can be utilized to estimate the blood perfusion rate in living tissues. The results show that both the larger perfusion rate and greater tissue depth decrease the amplitude of the sinusoidal temperature response. A larger perfusion rate can also reduce the unstable duration for the estimation of the blood perfusion rate. Meanwhile, the shift of phase angle related to the sinusoidal temperature variation increases with tissue that is deeper and has lower perfusion rate.
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Anders, Jens, Peter Leslie i Lars-Erik Stacke. "Rotor Drop Simulations and Validation With Focus on Internal Contact Mechanisms of Hybrid Ball Bearings". W ASME Turbo Expo 2013: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gt2013-95816.
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Active Magnetic Bearings technology is becoming more and more a standard in Oil and Gas turbo machinery. Touchdown bearings are an important element of all machines levitated by magnetic bearings. Frequently implemented as hybrid ball bearings, they constitute the only mechanical link between the rotor spinning at high peripheral speed and the stator. Since both sides carry fragile parts, any uncontrolled contact must be avoided. Extensive testing has been done in industry. When unplanned down-time would have a high system impact or when repair options are limited (upstream equipment, subsea operation), elaborate testing campaigns are common. A complement, if not an alternative, are computer based transient rotor drop simulations. They allow reducing uncertainties and help qualifying designs. In most cases, simulations use rotor dynamics models combined with contact models allowing an estimation of shaft behavior during a drop. We present a new approach for transient rotor drop simulations, where detailed calculation of the interior ball bearing mechanics is at the center of the model. This is possible by using a multiple-bodies simulation code, which was initially developed for pure ball bearing calculations and implements contact models including lubrication, wear, and geometry imperfections. Here, the same code is used to model entire shaft systems, associated with preloaded touchdown bearings. This technique allows not only to understand and to analyze failure patterns that determine bearing lifetime (contact stress, heat, and deformation), but also to take into account interactions of the bearing itself with the rest of the system. After a feasibility study for validating the capability of simulating rotor drops, three models were realized for three different types of machines of increasing complexity that were all validated by actual drop tests. The last model is a supercritical horizontal shaft system (200kg) representing an actual Oil and Gas application in reduced scale. Simulated shaft behavior was successfully compared to drop test recordings. The output was analyzed for internal bearing mechanics (contact pressures and contact angle, sliding or rolling friction) and could be correlated with evidence found on the bearings from the drop tests.
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Escobar, Jose, Ismail Celik i Albio Gutierrez-Amador. "Verification Issues Related to CFD Simulations of Flow Around Circular Cylinders". W ASME 2013 32nd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/omae2013-10824.
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The classical problem of flow around a stationary smooth circular cylinder is used to evaluate Computational Fluid Dynamics (CFD) transient simulations using two approaches; Body Fitted Grid (BFG) and Immersed Boundary Method (IBM). BFG simulations were performed using a commercial CFD code ANSYS-FLUENT and IBM simulations using an in-house CFD code DREAM. Two dimensional simulations were performed at three different Reynolds numbers; 1 × 103, 1 × 105, and 5 × 105. Each of the cases was simulated using a coarse, medium and fine mesh. CFD simulations were evaluated using the following quantities; drag coefficient, lift coefficient, pressure coefficient, separation angle and the Strouhal number of the first harmonic of the lift coefficient. Average, and amplitude of the evaluation quantities are reported for every case. Simulations showed the grid dependence of the results, e.g. finer meshes captured higher harmonics of the drag coefficient which coarse meshes smeared due the large numerical viscosity. IBM simulations were also affected by the symmetry of the computational grid. Predicted quantities follow previously reported experimental trends fairly well except in the critical flow regime. Two dimensional calculations using turbulence models were performed for the case of Re = 1 × 105, and Re = 5 × 105. Turbulent results showed the importance of the grid resolution near the cylinder wall in capturing the physics of the problem. Three dimensional calculations were also performed and results are compared to those obtained from the two dimensional simulations. As may be expected, discretization error estimation methods using three grid calculations are not satisfactory for this highly unsteady flow problem, especially near the critical regime, 1 × 105 < Re < 5 × 105. This paper dwells on various issues related to verification of calculations for such highly unsteady flows.