Simulation Of Transient Response Research Articles

Multi-physics simulation on transient thermal response of inductive power transfer pad

Inductive power transfer is an important technological alternative for charging infrastructure, crucial for accelerating the future adoption of electronic vehicles. The magnetic components of an inductive charging pad generate inevitable thermal losses, which, if not properly managed, can exceed the pad’s safe operating temperature. Accurate simulation of both steady-state and transient thermal responses is thus essential for evaluating the pad’s suitability for real-world applications. None of the state-of-the-art thermal prediction proposals in this field, however, are able to perform long-term transient analyses efficiently while being versatile enough to simulate generic case studies. This paper presents a multi-physics methodology that aims to address this gap. The numerical framework comprises three coupled modules: electromagnetic, fluid dynamics, and solid heat conduction. To solve the issue of time-scale discrepancies, only the latter module was solved as a transient problem, while the remaining were approximated as near steady-state physics, continuously updated at every time step. The appropriateness of the resultant hybrid transient solution was verified with a fully transient solution from an equivalent heat-conjugate problem. Finally, the prediction capability of the proposed method was validated by reproducing the thermal responses of a lab-scale charging pad energized at various excitation levels and ambient conditions, both outside of and flush-embedded inside an asphalt slab. The relative errors between the measured and simulated thermal responses were consistently within 10%, demonstrating that the multi-physics approach was able to accurately simulate the long-duration transient temperature rise and drop of the test pad.

A high current efficiency rail-to-rail operational amplifier

ABSTRACT This paper proposes a new single stage high current efficiency rail to rail amplifier (HCE-RTR). Due to the combination of a new constant transconductance control circuit and local common mode feedback (LCMFB) technique, the proposed rail to rail amplifier not only achieves improvements in unity-gain bandwidth (GBW) and slew rate (SR), but also ensures input stage transconductance constancy within the rail to rail voltage range. Based on the SMIC 180 nm process, the post-layout simulation results show that the proposed amplifier achieves rail-to-rail input/output. The simulated open loop AC response shows the DC gain, GBW, and PM are 66.2 dB, 8.2 MHz, and 60.97 o , respectively. When the driving load capacitance is 70 pF, the transient response simulation results show that the proposed amplifier achieves 0.039 µs average 1% settling time, and about 5.73 V/µs average slew rate. Note that under the condition of 1.8 V power supply, the power consumption is only 122.4 µW, proving the proposed amplifier can achieve high current efficiency while maintaining stability.

Simulation of transient response of PID controller in an automated electro-pneumatic system using a single-acting cylinder in a clinical ventilator

Patients with COVID-19 are not eligible for any therapy. Patients who have had respiratory failure and are unable to provide oxygen via noninvasive means obtain supportive care in ICUs. Since the onset of the outbreak, every sick COVID-19 patient has received oxygen via a mechanical ventilator. This study describes and simulates the transient stability of systems in an automated pressure regulator utilizing a single-acting cylinder in a clinical ventilator. These components include horizontal controllers, control devices, connecting tubes, and PID for electro-pneumatic control. Increased system stability and nonlinearity in electro-pneumatic actuator systems are accomplished by the implementation of PID. The redesigned PID control architecture was enhanced with alternative acceleration feedback through the close loop with an integral control method to get the system stable. This introduces the standard value N from the outside vicious circle and applies a form control law to integrate all reference control supply through into the gadget. Even as proportional gain (Kp) gets increased, the controller output would increase proportionately while maintaining the exact degree of accuracy. A derivative term boosts the ability of the Kd regulator to "detect" malfunctions. The integral term of the Ki controller minimizes its set point distortion. The system was updated to make it feasible for transferrable knowledge and competencies by incorporating real industrial components. The completed fluid control system was simulated through FluidSIM, which is frequently helpful for educational purposes.

Three-dimensional simulation and characterization of airborne transient electromagnetic response in rough media

In fractal, porous, and cranny rough media, the diffusion of the electromagnetic (EM) field differs from that in piecewise smooth media. This phenomenon is known as anomalous diffusion. To study the influence of anomalous diffusion on EM signals, we use the fractional time derivative and derive a governing equation describing the subdiffusion process of electric fields in rough media. Three-dimensional forward modeling of the time-domain airborne EM is performed using the finite-difference method and frequency-time transformation. We verify the accuracy of our forward-modeling method by comparing it with semianalytical solutions for a layered earth model. The numerical results indicate that as the conductivity of rough media decreases with time, the amplitude of the EM field decreases during the early periods but increases during subsequent periods compared with nonrough media. The EM field does not diffuse in the classical mode of the “smoke ring,” but instead demonstrates a “trailing pattern,” meaning that it maintains its maximum value at positions close to the source and diffuses outward and attenuates until it vanishes.

Transient Measurements and Simulations Correlate Exchange Ligand Concentration and Trap States in Colloidal Quantum Dot Photodetectors.

Colloidal quantum dot (CQD) photodetectors (PDs) can detect wavelengths longer than the 1100 nm limit of silicon because of their highly tunable bandgaps. CQD PDs are acutely affected by the ligands that separate adjacent dots in a CQD-solid. Optimizing the exchange solution ligand concentration in the processing steps is crucial to achieving high photodetector performance. However, the complex mix of chemistry and optoelectronics involved in CQD PDs means that the effects of the exchange solution ligand concentration on device physics are poorly understood. Here we report direct correspondence between simulated and experimental transient photocurrent responses in CQD PDs. For both deficient and excess conditions, our model demonstrated the experimental changes to the transient photocurrent aligned with changes in trap state density. Combining transient photoluminescence, absorption, and photocurrent with this simulation model, we revealed that different mechanisms are responsible for the increased trap density induced by excess and deficient active layer ligand concentrations.

Simulation of transient dynamic response of a locomotive considering its flexibility and rigidity

Time-domain or transient dynamic response method is the most traditional method used to evaluate the dynamic response of a vibratory system subjected to deterministic inputs. The inertia or damping effects are very crucial in the time scale of loading. The present work determines the time domain analysis of railway locomotive using finite element analysis for Indian tracks. The track inputs are modelled as an ellipsoidal bump, and variations in displacement at different key locations of the truck and carbody models are plotted subjected to standard loading conditions. The response plot of the front and rear locations of the locomotive truck and carbody indicate that these regions are more responsive to wheel inputs in comparison to the mid portion due to unbalanced mass distribution. In the further study vertical-lateral random inputs are measured through track recording car and modelled to express in the form of PSD. These random inputs are provided to finite element modelled flexible bogie frame, and acceleration response is determined. The results obtained are compared with the same obtained from rigid bogie frame formulated using an analytical model. The results obtained from the flexible and rigid body models are found to be in good agreement.

Fast response characteristics of fiber Bragg grating temperature sensors and explosion temperature measurement tests

Transient temperature measurement technology with fast response, harsh measurement environment, and high technical challenges has attracted research interest in the field of temperature measurement. Based on the differential equation of heat conduction at the interface of an optical fiber, the dynamic-response-time formula of the optical fiber was derived, the dynamic response capability of the optical fiber with different diameters was analyzed, and the transient thermal response simulation of the optical fiber was conducted. The theoretical dynamic test response times of optical fibers with diameters of 80, 125, and 145 µm were 30.21, 60.78, and 85.97 ms, respectively. Fast-response fiber Bragg grating (FR-FBG) temperature sensors were designed and manufactured by femtosecond-fabricated FBGs with diameters of 80 and 125 µm. The average response times of the 80 and 125 µm-FR-FBG temperature sensors were 33.2 and 65.3 ms, and the errors between the data and theoretical values were 9.89 % and 7.44 %, respectively. From explosion experiments, it is concluded that the femtosecond grating can be applied to the monitoring of rapid temperature response during explosion, and the response time is related to the diameter of the grating.

Real-time parameter updating for nonlinear digital twins using inverse mapping models and transient-based features

In the context of digital twins, it is essential that a model gives an accurate description of the (controlled) dynamic behavior of a physical system during the system’s entire operational life. Therefore, model updating techniques are required that enable real-time updating of physically interpretable parameter values and are applicable to a wide range of (nonlinear) dynamical systems. As traditional, iterative, parameter updating methods may be computationally too expensive for real-time updating, the inverse mapping parameter updating (IMPU) method is proposed as an alternative. For this method, first, an artificial neural network (ANN) is trained offline using novel features of simulated transient response data. Then, in the online phase, this ANN maps, with little computational cost, a set of measured output response features to parameter estimates enabling real-time model updating. In this paper, various types of transient response features are introduced to update parameter values of nonlinear dynamical systems with increased computational efficiency and accuracy. To analyze the efficacy of these features, the IMPU method is applied to a (simulated) nonlinear multibody system. It is shown that a smart selection of features, based on, e.g., the frequency content of the transient response, can improve the accuracy of the estimated parameter values, leading to more accurate updated models. Furthermore, the generalization capabilities of the ANNs are analyzed for these feature types, by varying the number of training samples and assessing the effect of incomplete training data. It is shown that the IMPU method can predict parameter values that are not part of the training data with acceptable accuracy as well.

Design Methodology for a Magnetic Levitation System Based on a New Multi-Objective Optimization Algorithm

Multi-objective (MO) optimization is a developing technique for increasing closed-loop performance and robustness. However, its applications to control engineering mostly concern first or second order approximation models. This article proposes a novel MO algorithm, suitable for the design and control of mechanical systems, which does not require any order reduction techniques. The controller parameters are determined directly from a special type of rapid analysis of simulated transient responses. The case study presented in this article consists of a magnetic levitation system. Certain difficulties such as the nonlinearity identification of the magnetic force and duo magnetic field sensor scheme were addressed. To point out the advantages of using the developed approach, the simulations as well as the experiments performed with the help of the created algorithm were compared to those made with common MO algorithms.

Monte Carlo Simulation of Transient Response of Coaxial Cable Irradiated by Intense Pulsed Gamma Rays

To obtain the transient current law of typical coaxial cable irradiated by intense pulsed gamma rays, the irradiation effect experiment of intense pulsed gamma rays on typical coaxial cable was carried out on the “Qiangguang-1” accelerator, and the relationship between the amplitude of pulsed current in the center conductor of coaxial cable and the instantaneous gamma dose rate was measured. The simulation model of irradiation effect of intense pulsed gamma rays on the coaxial cable is presented. By using the Monte Carlo particle transport method, the electron charge deposition rate in the center conductor and the outer shielding conductor of different types of coaxial cables under intense pulsed gamma irradiation is calculated. The calculated results are basically consistent with the experimental results. When the gamma ray energy is greater than 0.6 MeV, the electron charge deposition rate in the center conductor of coaxial cable first increases, then decreases, and then increases with the increase of gamma ray energy. When the gamma ray energy is greater than 0.1 MeV, the number of electrons deposited in the center conductor of the cable per unit length increases with the increase of gamma ray energy. The number of electron charges deposited in the outer shielding conductor layer is greater than that deposited in the center conductor for typical coaxial cable. The gamma radiation sensitivity of the coaxial cable increases at the same gamma ray intensity when the cable is obliquely irradiated.

A Subcircuit-Based Model for the Accumulation-Mode MOS Capacitor

The accumulation-mode metal-oxide-semiconductor (MOS) capacitor is commonly employed to implement MOS varactors in frequency-tuning circuits for radio frequency (RF) and analog applications. A subcircuit model for the accumulation-mode MOS (AMOS) capacitor based on the Berkeley Short-channel IGFET Model (BSIM) for the MOS field effect transistor (MOSFET) is presented. The proposed model accurately fits the capacitance-voltage (C-V) characteristics of an AMOS capacitor fabricated in a submicron CMOS process over the full range of operating gate voltages. The model also accounts for the impact of the distributed series resistance on the transient response of the AMOS capacitor. Notably, the gate capacitance and the associated series resistance are modeled as a distributed resistor-capacitor (RC) network to derive a subcircuit-based model with the bias-dependent resistance of the accumulation layer modeled as a voltage-controlled resistor (VCR). The proposed model is evaluated based on SPICE simulation of the intrinsic transient response of the AMOS capacitor using a basic circuit, representing the distributed RC network associated with the MOS device structure. Fine tuning of the effective series resistance in the subcircuit model can be achieved by fitting the measured data characterizing the charge–discharge behavior of the AMOS capacitor to the simulated data characterizing the intrinsic transient response generated by SPICE.

The Crucial Importance of Air Valve Characterization to the Transient Response of Pipeline Systems

Air valves are often crucial components in an air management strategy for pressurized water conveyance systems. However, the reliability of characteristic curves of air valves found in product catalogs is quite variable. This paper evaluates the consistency of a selection of product curves to basic air flow principles. Several recurring issues are identified: catalogs that present identical curves for admission and expulsion (they are, in fact, quite distinct); admission curves that are inconsistent with the isentropic inflow model; inflow (admission) curves actually consistent with the shape of the isentropic outflow model; limited validity curves that encompass only part of the subsonic flow regimen; and unclear or unstated specifications regarding the conditions under which the characterization tests were performed or their results displayed. To examine the significance of these representational issues related to air valve capacity on system behaviour, this paper uses a case study involving the simulated transient response arising from a pump trip at the upstream end of a rising water line having a distinct high point fitted with an air valve. It is found that employing inaccurate air valve characteristics in a transient simulation may potentially result in appreciable or even dangerous simulation errors.

Improvement of the delayed neutron precursor transport model in RELAP5 for liquid-fueled molten salt reactor

The Liquid-Fueled Molten Salt Reactor (LF-MSR) with high-temperature molten salt is one of the Generation IV nuclear power systems. One of the significant differences between the LF-MSR and the Pressurized Water Reactor (PWR) is that the delayed neutron precursors (DNP) circulate in the primary loop of the LF-MSR and leads to different neutron kinetics between LF-MSR and PWR. Consequently, a system code for PWR is not applicable to LF-MSR, and the safety analysis code RELAP5-TMSR is modified by adding a one-dimensional DNP transport model to improve its applicability to LF-MSR. A second-order Godunov method is adopted in this 1-D DNP model. Then the improved code is tested with experimental benchmarks from Molten Salt Reactor Experiment (MSRE) designed and operated by Oak Ridge National Laboratory (ORNL) and the results show good consistency. Moreover, the modified RELAP5-TMSR code is applied to analyzing transient characteristics of the single-fluid Molten Salt Breeding Reactor (MSBR) so that the applicability of the modified RELAP5-TMSR code is further verified. It is concluded that the one-dimensional DNP transport model can describe effectively the movement of the DNP and the improved RELAP5-TMSR code is suitable for modeling and simulation of reactor transient responses in LF-MSR.

A Temperature-Aware Large-Signal SPICE Model for Depletion-Type Silicon Ring Modulators

We present a large-signal SPICE model for the depletion-type silicon ring (RM) modulator that includes temperature dependence. The model is based on the temperature-dependent equivalent circuit for the RM and allows easy simulation of RM modulation characteristics in SPICE. The accuracy of the model is verified with the measurement results of 25-Gb/s NRZ modulation at several different temperatures. In addition, simulation of the temperature-dependent transient responses of the RM together with the RM temperature control circuit is demonstrated in the standard IC design environment.

Numerical Simulation and Validation of Aerodynamics of Static and Dynamic Spoilers

Spoilers play a vital role in the flight control systems of modern transport aircraft. Because of their efficiency and fast deflection rates, they are widely used to assist in roll control or for gust load alleviation purposes. Simulating the aerodynamic behavior of spoilers still is a challenging task, as deflecting a spoiler always induces flow separation. The work presented in this paper therefore focused on extending the application range of DLR, German Aerospace Center’s in-house flow solver TAU by verifying and validating it for spoiler applications. In a first step, the work focused on steady and unsteady simulations of static and dynamic spoiler deflections in the low-speed regime. It was shown that the chosen numerical approach is well suited to reproduce the surface pressure distribution for static spoiler deflections of up to 50 deg. Above that, the simulated transient aerodynamic response was found to be in good agreement with experimental data for a variety of deflection times and deflection angles.

Synthesis of landing dynamics on land-base high performance aircraft considering multi-variate landing conditions

Consideration of standard landing cases from technical guideline document is the traditional design practice followed to ascertain aircraft landing loads. A rationale approach on landing load generation and its impact on flexible airframe dynamic response is explored, considering multi-variate landing conditions for the first time on land-base high performance aircraft. Methodology on nonlinear landing dynamic response simulation is developed by amalgamating inputs such as nonlinear nose and main landing gear dynamic models, aircraft rigid body dynamics, low speed aerodynamic and thrust forces. True representation of landing gear nonlinear oleo-pneumatic strut and tire characteristics, variable geometric strut structural stiffness and nonlinear spin-up friction resulted in satisfactory correlation of vertical and longitudinal dynamic response simulation with experimental drop test results. The adequacy of lateral dynamic model is established from the compatibility condition of landing gear and tire dynamics. A down selection methodology is worked out considering total probability and first order sensitive multi-variate landing parameters such as pitch, roll and vertical descent speed, taking into account the plausible statistical variation. Transient dynamic response simulation is then performed for the critical landing cases, on a flexible airframe finite element model by inputting landing load time history as base excitation motion. The dynamic amplification of acceleration response on flexible fuselage nose location from the simulation, is verified with flight data accelerometer frequency response. The application of flexible dynamic responses in ensuring the structural integrity of airframe is elaborated. The proposed methodology on landing load generation is pragmatic, in comparison with the traditional design practice and provides insight during early design phase thereby achieving landing gear subsystem development in-unison with airframe structural clearance aspects.

Automatic differentiation approach for solving one-dimensional flow and heat transfer problems

Traditional reactor system analysis tools are confronted with challenging difficulties in model development, low accuracy, and poor convergence. To solve these problems, the automatic differentiation (AD) method that allows the automatic numerical calculation of derivatives of functions was adopted to develop the reactor system code in this paper. For the simulation of single-phase models, the steady and transient responses were presented to investigate the effects of the spatial and temporal discretization schemes on modeling accuracy and efficiency. Meanwhile, the comparison of convergence performance between the automatic differentiation using operator overloading (ADOO) and the traditional hand-coded method was completed. Further, in the case of two-phase flow problems, the high-order discrete schemes were applied in this code. It was demonstrated that the reactor system code with single-phase and five-equation two-phase flow models, which adopted the high-order discretization and the ADOO method, performed very well for one-dimensional flow and heat transfer problems.

Data driven reaction mechanism estimation via transient kinetics and machine learning

• Reaction mechanism characterization via experimental transient kinetic measurements. • Integration of well-defined reactor physics and machine learning. • Data-driven kinetic coefficients estimation via machine learning. • Reaction mechanism classification through rate and gas concentration correlation. • Validation of reaction mechanism applied to CO oxidation on platinum. Understanding the set of elementary steps and kinetics in each reaction is extremely valuable to make informed decisions about creating the next generation of catalytic materials. With structural and mechanistic complexities of industrial catalysts, it is critical to obtain kinetic information through experimental methods. As such, this work details a methodology based on the combination of transient rate/concentration dependencies and machine learning to measure the number of active sites, the individual rate constants, and gain insight into the mechanism under a complex set of elementary steps. This new methodology was applied to simulated transient responses to verify its ability to obtain correct estimates of the micro-kinetic coefficients. Furthermore, data from an experimental CO oxidation on a platinum catalyst was analyzed to reveal that Langmuir-Hinshelwood mechanism drives the reaction. As oxygen accumulated on the catalyst, a transition in the apparent kinetics was clearly defined in the machine learning analysis due to the large amount of kinetic information available from transient reaction techniques. This methodology is proposed as a new data driven approach to characterize how materials control complex reaction mechanisms relying exclusively on experimental data.

Finite element simulation for sensitivity measurement of a shear horizontal surface acoustic wave micro pressure sensor with a groove structure

Shear horizontal surface acoustic wave (SH-SAW) sensors have great application potential due to their advantages of easy integration, miniaturization and suitability in liquid environments. In this paper, the finite element method is used to analyse a new SH-SAW micro pressure sensor, in which there are many groove structures along the direction of wave propagation on the delay path. We use the transient response simulation method to calculate and analyse the output voltage signal at the output interdigital transducer and surface average stress at the delay path of this new SH-SAW sensor, and its pressure sensitivity is analysed by uniformly applying an appropriate surface pressure on the resonant beam formed after grooving. The simulation results show that the surface average stress can be enhanced in a certain range of groove depth during the vibration of the groove structure. When the groove depth and width are set to 0.7 μm and 0.5 μm, respectively, the sensitivity of the SH-SAW sensor with a groove structure is four times higher than that of the traditional SH-SAW sensor. The increase of pressure sensitivity is the result of the increase of average stress caused by the groove structure. The new groove structure SH-SAW sensor provides a new basis for research on high-sensitivity micro-pressure sensors and lays a foundation for subsequent device design and manufacture.

Transient Dynamic Simulation Analysis of Pressure Sensor for the Electrothermal Chemical Gun

The electrothermal chemical gun's pressure sensor is impacted by the high pressure, strong transient gas during the firing. By using the finite element method, combining the theory of interior ballistic, the transient dynamics response simulation calculation of electrothermal chemical gun pressure sensor by the action of high pressure gas was carried out during the launch. The change of stress and strain for each part of the pressure sensors under loading was obtained. Results show that the sensor structure deforms under the action of high-pressure gas, and the stress and strain value of the sensor components reaches the maximum when the loading pressure is maximum, among which the stress and strain of seal diaphragm of the sensor is the maximum. the results can be used as reference for the design of the pressure sensor of electrothermal chemical gun.