Dynamic Characteristics Of Model Research Articles

The Influences of Parameters on the Dynamic Characteristics of a Multi-Foil Aerodynamic Journal Bearing with Bump-Backing Foils: Model Predictions

In this work, the development and implementation of a dynamic characteristics model for a specific multi-foil aerodynamic journal bearing with bump-backing foils (MFJB) is considered. Based on the previously established static characteristics model, the elastohydrodynamic influence is carefully considered, and the perturbation method is adopted, as this model is more effective and computationally efficient. The effects of the operational, structural, and geometric parameters on stiffness and damping coefficients are emphasized. The results show that the eccentricity ratio effects are more intensive when the bearing speed is at a moderately high level, which is no more than approximately 30,000 rpm. The foil thickness has obvious effects on dynamic characteristics, whereas the influence of the elastic modulus is limited. Within the research scope, the eight-foils bearing exhibits a better performance than the four-foils. This paper is designed to provide effective methods and supply theoretical guidance for improving the engineering design and operational stability of bearings.

Study on meshing and dynamic characteristics of herringbone gear pair considering tooth surface wear and modification

Due to errors and tooth surface wear of herringbone gear is inevitable. And tooth surface modification is the key technology to improve gear performance. Therefore, this paper studies the influence of tooth surface uneven wear and modification on herringbone gear pair's meshing and dynamic characteristics with errors. Firstly, herringbone gear pair meshing characteristic analysis model based on discrete tooth surface is established. Secondly, herringbone gear pair bending-torsion coupling dynamic characteristic analysis model considering friction is established, and the dynamic frictional force analysis process is given. Thirdly, combined with Archard's wear theory, the tooth surface uneven wear amount is obtained. The tooth surface uneven wear amount is substituted into meshing matrix as a tooth surface deviation. Finally, the meshing and dynamic characteristics of herringbone gear pair considering tooth surface wear and modification are studied by using the established analysis model of meshing characteristics and dynamic characteristics. The calculation results show that without tooth surface modification, tooth surface wear will deteriorate the meshing and dynamic characteristics rapidly. However, reasonable tooth surface modification can effectively improve meshing and dynamic characteristics of gear pair, so that the gear pair can still maintain stable transmission under wear condition.

Numerical analysis of impact resistance mechanical properties of energy-absorbing columns under static and dynamic loads

To enhance the impact resistance of hydraulic columns, a theoretical analysis method was employed to develop a dynamic characteristic analysis model for conventional columns under impact loads. This model facilitated the derivation of key parameters such as equivalent stiffness, maximum retraction amount, and impact duration. A fluid-solid coupling model for the conventional column was constructed using finite element and coupled Eulerian-Lagrangian (CEL) methods. Subsequently, numerical simulation results were compared and analyzed against theoretical predictions. Based on this analysis, an energy-absorbing column was designed, and its fluid-solid coupling model was established to investigate its mechanical response under static and dynamic impact loads.The findings indicate that under a static load of 2000 kN, when superimposed with impact loads of 200 kJ, 400 kJ, and 800 kJ respectively, the peak impact forces on energy-absorbing columns are 89.20%, 91.72%, and 98.42% lower than those on normal columns. The yield displacements of energy-absorbing columns increase by 142.26%, 109.15%, and 108.41% compared to normal columns. Energy absorption in energy-absorbing columns is 152.11%, 171.80%, and 145.18% higher than in normal columns. Furthermore, initial velocities of energy-absorbing columns are consistently lower compared to normal columns. After reaching initial velocity, energy-absorbing columns exhibit reduced oscillations due to interactions between the energy absorber, column, and hydraulic fluid system under impact loads. Unlike normal columns, energy-absorbing columns mitigate stress concentration at the column head through interactions between the energy absorber, emulsion, and column. Additionally, the impact resistance time of energy-absorbing columns is 2.19, 1.64, and 1.85 times longer than that of normal columns.Energy-absorbing columns outperform conventional columns across six metrics: peak impact force, column yield displacement, energy absorption, column movement speed, stress distribution, and impact resistance time, demonstrating superior mechanical properties in impact resistance.

Modeling of dynamic characteristics and μ-synthesis control of piezoelectric positioning platform

Abstract The dynamic hysteresis nonlinearity and various uncertainties of the piezoelectric positioning platform are critical factors limiting its high-precision applications. To address this, the dynamic characteristics of the piezoelectric positioning platform under various loads are identified based on the linearization of the Prandtl-Ishlinskii inverse model. The inverse compensation error and load disturbances are attributed to model uncertainties, which are modeled in the frequency domain. A μ-synthesis controller is designed to improve the tracking accuracy of the piezoelectric positioning platform under uncertainty disturbances. Experimental results indicate that with the μ-synthesis controller, the piezoelectric positioning platform achieves a relative error (RE) of less than 2.71% when unloaded. The RE is less than 6.03% for load disturbances of 100g, 200g, and 300g, respectively. These results demonstrate that the designed controller meets the high-precision positioning performance requirements under various load disturbance conditions.

Dynamic characteristic analysis and key parameter optimization of throttling orifice type air damping air spring

Abstract The unique hysteretic characteristic of rubber bellows and the nonlinear flow of internal airflow in the system results in the significant nonlinear dynamic characteristic of throttling orifice type air damping air springs (OADASs). To solve the problem of mathematical representation of dynamic characteristic and key parameters optimization of throttling OADAS, this paper comprehensively considers the hysteretic characteristic of rubber bellows under variable pressure, the nonlinear dynamic characteristic model and linear model of throttling OADAS are established based on the concepts of gas thermodynamics and fluid mechanics. The static and dynamic characteristic tests of the throttling OADAS are conducted, to verify the accuracy and effectiveness of the proposed model, and to reveal the influence laws of excitation amplitude, excitation frequency, and throttling orifice diameter on the quantitative characterization indexes. Finally, a complete throttling orifice diameter optimization method is proposed based on the eight-degree-of-freedom model of the entire vehicle. Optimization results illustrate that the RMS values of the vertical acceleration of the body and the vertical acceleration of the driver are decreased by 19.02% and 38.44%, respectively. Overall, the outcomes of this paper can provide the design idea and theoretical basis for air damping matching and active suspension control.

Dynamic characteristics optimization of elastomer for resistance strain force sensor

PurposeThis paper aims to provide a new method to study and improve the dynamic characteristics of the four-column resistance strain force sensor through the elastomer structure design and optimization.Design/methodology/approachBased on the mechanism analysis method, the authors first present a dynamic characteristic model of the four-column resistance strain force sensors’ elastomer. Then, the authors verified and modified the model according to the Solidworks finite element simulation results. Finally, the authors designed and optimized two types of four-column elastomers based on the dynamic characteristic model and verified the improvement of sensor dynamic performance through a hammer knock dynamic experiment.FindingsThe Solidworks finite element simulation and hammer knock dynamic experiment results show that the relative error of the model is less than 10%, which confirms the accuracy of the model. The dynamic performance of the sensors based on the model can be improved by more than 30%, which is a great improvement in sensor dynamic performance.Originality/valueThe authors first present a dynamic characteristic model of the four-column elastomer and optimize the four-column sensors successfully based on the mechanism analysis method. And a new method to study and improve the dynamic characteristics of the resistance is provided.

Modelling and dynamic characterisation of a double-pendulum overhead crane carrying a distributed-mass payload

In industries, cranes are commonly used for transportation of a distributed-mass payload (DMP). However, analysis of the dynamic characteristics of such a system is limited since most of the research work considered a point-mass payload. This paper presents modelling and analysis of dynamic characteristics of a double-pendulum overhead crane carrying a DMP with and without payload hoisting. Nonlinear dynamic models representing the crane in both scenarios are derived. The effects of varying cable lengths, and carrying different payload masses and lengths on the dynamics of hook and payload oscillations are also studied. Simulations are performed to observe the dynamic characteristics of the crane under several conditions, and experiments are carried out to validate the theory and simulation results, and to assess the accuracy of the derived nonlinear dynamic equations. The results demonstrate that the payload oscillation is significantly affected by changes in the cable lengths and DMP parameters. In addition, satisfactory agreements between simulation and experimental results are achieved, which indicate validity of the nonlinear models and good compliance with the theory. It is envisaged that the dynamic characteristic analyses of the crane can be beneficial in designing efficient controllers, especially in suppressing DMP oscillation.

Dynamic characteristics testing and modeling in electromagnetic-thermal-force coupling of electromagnetic devices using parallel finite element simulation

Electromagnetic systems of Electromagnetic devices involve multiphysics coupling of electromagnetic fields, electrical circuits, mechanical motion, and temperature fields. When the digital prototype model has a large number of meshes, the commercial finite element software also has the disadvantage of long computation time in the simulation of dynamic characteristics of electrical apparatus. This paper proposes a transmission line method (TLM) based digital modeling method for the electromagnetic-thermal-force coupling to test and evaluate the static and dynamic characteristics of electromagnetic devices more accurately and efficiently. The case study is developed on a direct current (DC) contactor, and the dynamic characteristics testing and modeling in the electromagnetic-thermal-force coupling of the contactor are investigated. The numerical results of the finite element method (FEM) model for the electromagnetic system of the contactor are compared with the commercial FEM software Altair Flux and the experimental results, which demonstrate the exceptional accuracy of the proposed digital modeling method for the multiphysics coupling of the DC contactor. Meanwhile, the dynamic characteristics of the DC contactor at different ambient temperatures are measured and evaluated, and the comparison with the experimental measurements shows the applicability of the proposed digital prototype model at different ambient temperatures. Compared with the conventional Newton-Raphson (NR) iteration, when dividing fine mesh and extremely fine mesh, the TLM parallel computing significantly improves the efficiency of solving the dynamic characteristics of multiphysics coupling by about 35 % and 44 % with the same computational accuracy, respectively. The dynamic characteristics evaluation method combined with digital modeling technology and experimental measurements proposed in this paper demonstrates high accuracy and solving efficiency, making a notable contribution to the field of design and optimization of electromagnetic devices.

Dynamic performance prediction and experimental analysis of wet clutch actuator considering thermal flow characteristics

The hydraulic actuator system (HAS) for wet clutches in heavy-duty vehicle transmissions is required to have a fast response and high precision in the pressure regulation procedure. Conventional pressure control valves for HAS are almost slide spool structures, which perform a large flow force at a high flow rate. An open-center spool structure is designed and developed in this paper, which is a combination of a traditional slide spool and a valve sleeve. It has an orifice-groove combination throttling orifice, which can take into account the large through-flow capacity and small flow force. Firstly, to deeply understand the mechanism of pressure variation in the clutch chamber, a high-fidelity dynamic characteristic mathematical model of HAS considering the oil temperature is proposed. Secondly, the functional relationship between the oil temperature on the medium physical property parameters and the orifice thermal flow parameters in the model is deduced in detail. An experimental bench to measure the pressure valve dynamic performance and actuator pressure regulation characteristics in a wide temperature domain is then designed and implemented to validate the accuracy of the simulation model. Finally, the mechanisms of oil temperature and system pressure on pressure impact and pressure response are quantitatively analyzed in association with a supervised learning algorithm. The feasible domains of the two adjustable variables are also explored. This study provides a new perspective on dynamic control and energy saving of HAS pressure valves and a new method for the prediction of HAS performance under complicated operating conditions.

Study and Modeling of Nonlinear Dynamic Characteristics of DC-DC Converters with Amnesia Loads

Abstract The chaos phenomenon is a seemingly random irregular motion occurring in a deterministic system, which is an inherent characteristic and prevalent phenomenon of amnesia-loaded DC-DC converter nonlinear systems. Nonlinear dynamics and chaos theory guide the text, and we create an amnesia-loaded DC-DC converter system model using an amnesia resistor. We analyze the stability of the system using Filippov theory, and analyze the nonlinear dynamic characteristic behavior of the amnesia-loaded DC-DC converter using the time-domain waveform diagram, bifurcation diagram, and phase-track diagram. This paper talks about the slope compensation method and the parametric resonance perturbation method for control analysis. These methods are used to stop the chaotic behavior that happens in the amnesia-loaded DCDC converter. The system maintains a stable state when the reference current is less than 4.732A and the supply voltage exceeds about 17.966V, maintaining an amplitude of the maximum eigenvalue below 1. When the load resistance is 50Ω, the capacitance is 43 uF, the inductance is 2.8 mH, and the reference voltage is 2.05 volts, the amnesia-loaded DC-DC converter suffers from obvious chaos. To restore the system to a steady state by applying the ramp compensation method, the slope of the ramp signal will need to increase as the reference current increases. Loading amnesia onto the DC-DC converter achieves a stable cycle 1 state when the perturbation phase’s fluctuation range falls between 4.35 and 6.15. A nonlinear dynamic analysis of the amnesia-loaded DC-DC converter helps find the stable parameters of the amnesia-loaded DC-DC converter and improve the design of the converter.

Modeling of dynamic characteristics for hydraulic drive under nonstationary load

The methodology for estimating the transient response and frequency characteristics for volumetric hydraulic drive under nonstationary load is proposed. The methodology is based on obtaining the transfer function for the speed of movement for the drive output link according to the load. To obtain the transfer function, the nonlinear mathematical model of translational hydraulic drive has been compiled, including the motion equations for the hydraulic cylinder piston, the equations of continuity in the pressure and drain cavities, taking into account compressibility of the working fluid. Hydraulic losses are described by quadratic dependence. In addition to the generally arbitrary load acting on the hydraulic cylinder rod, the resistance force proportional to the speed of movement of the hydraulic cylinder piston is also considered. By linearization of the mathematical model, the transfer function for the speed of movement on load is established in the form of fractional rational function of the third order. The dependences for calculating the coefficients of the transfer function is determined. The example of calculating the transient response, amplitude and phase frequency characteristics is given. The presented results can be used in the design and modernization of technological equipment with hydraulic drives.

Modeling and simulation of dynamic characteristics of a green ammonia synthesis system

Green ammonia production system driven by renewable electricity will be under frequent dynamic operation due to the fluctuation of renewable energy. The nonlinear dynamic model of a green ammonia synthesis system is developed and the dynamic responses of PEM (proton exchange membrane) electrolysis subsystem, PSA (Pressure swing adsorption) subsystem and ammonia synthesis subsystem during the start-up process and under the fluctuation of renewable electrical current are analyzed. The start-up dynamic results show that the hydrogen production rate of PEM electrolysis system is positively correlated to the current. The nitrogen output of PSA system is affected by the adsorption time, adsorption pressure, bed length, and air velocity. A start-up period of 300 min from the warmed-up state to the design state can maintain the temperature rise rate of the ammonia synthesis reactor at approximately 40 K/h. The dynamic results under step fluctuations of electrical current show that the PEM electrolysis subsystem and the PSA subsystem response fast compared to the ammonia synthesis reactor and buffer tanks. Using large buffer tanks to smooth the fluctuation allows the system to slide with the variation of renewable current to some extent, resulting in a higher outlet ammonia fraction when the current increases. Different volume ratios of the hydrogen tank to the nitrogen tank volume can lead to different variations of the hydrogen/nitrogen ratio. PID controllers can effectively maintain the bed temperatures, hydrogen/nitrogen ratio, and pressure of the ammonia synthesis reactor at their set points despite fluctuations in renewable electrical current. Buffer tanks are necessary to compensate for the imbalance between the flow rate fluctuation caused by current change and the flow rate regulation caused by PID controllers.

Dynamic Characteristic and Performance Analysis of Claw Vacuum Pumps with Multi-Claw Rotors

The number of lobes of multi-claw rotors determines the performance of claw vacuum pumps including the pumping speed, dynamic characteristics, and operating conditions. In order to reveal the effects of the number of lobes on rotor performance, in this study, a geometric model of multi-claw rotors was established. The structure and geometric performance of multi-claw rotors including suction port and discharge port, pumping speed, and volumetric utilization ratio were compared. Furthermore, a dynamic characteristic model of claw rotors was established, and, therefore, axial gas forces, radial gas forces, and gas resistance torques of multi-claw rotors were obtained. The results indicate that double-claw rotors increased 34.67 % and 4.59 % in terms of pumping speed and volumetric utilization ratio compared to single-claw rotors, and triple-claw rotors showed similar increases as double-claw rotors. The triple-claw rotors have a 49.39 % and 31.38 % reduction in compression duration compared to the double-claw rotors and single-claw rotors. The gas resistance torques of the multi-claw right rotors are consistently more than that of the left rotors, which demonstrates that the multi-claw right rotors are more suitable to serve as the driving rotors. The research contents of this paper are of great theoretical significance for the selection of rotor lobes and the design of claw vacuum pumps with prominent dynamic characteristics.

Influence of flexural-torsional couplings and rotational effects on vibration behaviour of tapered thin-walled anisotropic biconvex beam

Accurate modelling and prediction of dynamic characteristics for rotating thin-walled blades have drawn attention as it is an essential part of structural health monitoring for various engineering and civil applications such as wind turbine, helicopter and aeroplane blades. With the advent of structural tailoring techniques, various non-classical effects and couplings implicitly affecting the behaviour of such structures are yet not fully explored. In this regard, the present work proposes a numerical model for finding the free vibration characteristics of anisotropic tapered biconvex closed cross-section beam under rotating conditions. The model is derived based on energy method following the Ritz approximation. Circumferentially asymmetric stiffness (CAS) ply configuration is considered in order to study the impact of flexural torsional coupling on the vibration characteristics. Transverse shear effects, primary and secondary warping were also included in the current model. Mode switching phenomenon is dissected elaborately for the first few frequencies under rotating and nonrotating conditions. The impact of rotational effects like centrifugal acceleration, centrifugal warping, inertial warping on the first few frequencies is also demonstrated. An iterative technique is adapted to solve the equations having these rotational effects. Modal Assurance Criterion (MAC) is done in order to judge the consistency of the modes at different rotating speeds.

Free Vibration and Dynamic Analysis on Free-Constrained Layer of Graphene Based on Composite Conical Shell via Jacobi–Ritz Method

Excessive vibration has always been a serious problem for conical shell structures, while the application of the graphene-based free-constrained layer (GFCL) based on carbon fiber-reinforced composite (CFRC) structure is a novel way to improve structural performance. An analytical model for vibration and dynamic characteristics of the GFCL-CFRC conical shell resting on the Winkler–Pasternak elastic foundation with arbitrary boundary conditions is constructed, and four types of GFCL porosity distribution and GFCL dispersion pattern are considered in this model. The multi-segment technique and virtual spring technique are utilized to simulate arbitrary boundary conditions. Then, the first-order shear deformation theory (FSDT) and Hamilton’s principle are employed to obtain the motion equation of the GFCL-CFRC conical shell, and the motion equation of the GFCL-CFRC conical shell is solved by the Ritz method. In conclusion, the dispersion mode of GFCL, thickness ratio of GFCL, and fiber angle have influence on the dynamic performance. With a reasonable design, the dynamic performance of the GFCL-CFRC conical shell can be further improved.

Research on Machining Error Control Method Driven by Digital-twin Model of Dynamic Characteristics of Machining System

The position of each component structure in the machining space of the machining system directly affects the machining quality of the workpiece. In this paper, RBF neural network is used to study the spatial dynamic characteristics of the translational axes of five-axis CNC machine tools. It is the basis for building an evolvable knowledge base. Process evaluation, information feedback, and iterative optimization of thin-wall parts were carried out using digital-twin technology. Firstly, the model simulation of the translational machining space of a three-dimensional five-axis CNC machine tool is carried out by using the finite element method. The RBF neural network predicts the natural frequency of a translational machining space dynamic characteristics. It is further used to construct the dynamic characteristic spectrum of the translational space of CNC machine tools. Secondly, the machine tool flush space cutting process is built with a digital-twin system to optimize the iterative mechanism for machining process optimization. Finally, the method’s effectiveness was verified by experiments on milling thin-walled parts on a dual-turntable five-axis CNC machine and by contouring error measurement experiments. The results show that the average error of the optimized thin-wall contour is reduced by 26.9%. The iterative mechanism can continuously optimize the machining error and improve the machining accuracy. The iterative mechanism can continuously optimize the machining error and improve the machining accuracy.

Enhancing of ventilation efficiency of premise due to linear diffuser

AbstractThis article is directed on increase of the premise ventilation efficiency by using linear diffusers. The aim of the work was to carry out theoretical research, experimental investigations and numerical modeling of the linear diffuser air dynamic characteristics, to obtain the graphs and analytical equations for determination of the linear diffuser necessary parameters and to encrease of efficiency air distribution in the room. Graphs of air velocity dependence on current coordinate and plates angle have been created and approximated by empirical equations. There was established that air velocity decreases intensively with increasing current coordinate and decreases with increasing of the plates angle.

Dynamic Characteristic Model of Giant Magnetostrictive Transducer with Double Terfenol-D Rods.

Giant magnetostrictive transducer can be widely used in active vibration control, micro-positioning mechanism, energy harvesting system, and ultrasonic machining. Hysteresis and coupling effects are present in transducer behavior. The accurate prediction of output characteristics is critical for a transducer. A dynamic characteristic model of a transducer is proposed, by providing a modeling methodology capable of characterizing the nonlinearities. To attain this objective, the output displacement, acceleration, and force are discussed, the effects of operating conditions on the performance of Terfenol-D are studied, and a magneto-mechanical model for the behavior of transducer is proposed. A prototype of the transducer is fabricated and tested to verify the proposed model. The output displacement, acceleration, and force have been theoretically and experimentally studied at different working conditions. The results show that, the displacement amplitude, acceleration amplitude, and force amplitude are about 49 μm, 1943 m/s2, and 20 N. The error between the model and experimental results are 3 μm, 57 m/s2, and 0.2 N. Calculation results and experimental results show a good agreement.

Development of Model-Based PEM Water Electrolysis HILS (Hardware-in-the-Loop Simulation) System for State Evaluation and Fault Detection

Hydrogen is attracting attention as a good energy-storage medium for renewable energy. Among hydrogen production technologies using renewable energy, water electrolysis is drawing attention as a key technology for green hydrogen production using renewable energy. In particular, polymeric electrolyte membrane water electrolysis systems have several advantages compared to other types of water electrolysis technologies, such as small size and mass, high efficiency, low operating temperature, and low power consumption. However, until now, proton-exchange membrane (PEM) water electrolysis systems have not been reliable. In this study, system failure diagnosis techniques were presented among the various methods for improving reliability. We developed PEM water electrolysis stack models and system models to predict the performance of the system and analyze the dynamic properties using MATLAB/Simulink® 2018a, which have been validated under various conditions. The developed dynamic characteristic simulation model applies hardware-in-the-loop simulation (HILS) technology to configure experimental devices to interact in real-time. The developed PEMWE HILS system accepts signals that control the system, operates the experimental setup and simulation model in real-time, and diagnoses the system’s failure based on the results.

Non-uniform heat generation model of pouch lithium-ion battery based on regional heat generation rate

The non-uniform distribution of temperature seriously affects the cycle performance, cycle life and safety of the pouch lithium-ion batteries. In this paper, a dynamic non-uniform heat generation model is developed to the high complexity and low precision of the modeling and characterization of dynamic non-uniform thermal characteristics of the pouch battery. Firstly, the regional heat generation rate of different regions is estimated by the particle swarm optimization based on the cell surface temperature to build a non-uniform heat generation model. Then, the battery's temperature distribution characteristics and heat generation distribution characteristics under the effect of ambient temperature, state of charge and discharge rate are analyzed. Furthermore, combined with the three-dimensional heat transfer equation, a three-dimensional heat model with non-uniform a heat source is modeled by COMSOL, the dynamic non-uniform temperature distribution of the battery is simulated at different ambient temperatures and discharge rates, and then the local temperature at any location of the battery is obtained. Finally, the simulated value of the local temperature is compared with the experimental value, and the average error under constant current discharge condition is less than 1 °C, and the relative error under dynamic current condition is less than 3 %. The result shows that the model can accurately estimate pouch lithium-ion batteries' dynamic non-uniform heat generation distribution under different working conditions.