Analysis Of Dynamic Characteristics Research Articles

A Framework for Rapidly Predicting the Dynamics of Flexible Solar Arrays in the China Space Station with a Verification Based on On-Orbit Measurement Data

The Chinese space station is a complex structure with large flexible appendages. Obtaining the on-orbit response characteristics of such a structure under different working conditions is a traditional and classic challenge in the field of dynamics. To address the on-orbit dynamics of the China Space Station, the basic equations for dynamic reduction, assembly and data recovery of linear and nonlinear substructures are derived based on the reduction and recovery theory, and a fast coupling analysis framework for flexible systems with nonlinear attachments is formed. This coupling analysis framework is adopted to quickly acquire the dynamic response of the China Space Station during in-orbit operation, thereby guiding the design. Taking SZ-15 radial docking to the Chinese Space Station as the object, the substructure of six nonlinear flexible arrays is reduced, the full flexible dynamic equation of the space station is assembled, and the response of each part of the flexible wing during the docking process is analyzed and recovered. By designing a reasonable and reliable flexible wing test scheme in-orbit, the acceleration at the root and top of the flexible wing during the docking of SZ-15 is obtained. The measured data in-orbit show that the acceleration analysis results of the typical parts of the flexible wing have a good agreement, which verifies the correctness of the fast coupling analysis framework of the flexible system. Hence, the dynamic coupling characteristics analysis of the main structure of the space station and the flexible wing based on this method can better guide the rationality of the design of the dynamic characteristics of the Chinese Space Station.

Dynamical Modeling and Dynamic Characteristics Analysis of a Coaxial Dual-Rotor System

The dual-rotor structure is the primary excitation source of aero-engine vibration. It is essential to study the dynamical model and analyse the dynamic characteristics such as critical speed and the unbalanced response for rotor system dynamics. The coaxial dual-rotor support scheme of an aero-engine was introduced in the previous work, and the physical model with a high-speed flexible inner rotor of a sizeable length-diameter ratio has been designed. Then a finite element dynamic model based on the Timoshenko beam elements and rigid body kinematics of the dual-rotor system is modelled, with the Newmark-β method and Newton-Raphson method used for the numerical calculation to study the dynamic characteristics of the system. Three different simulation models, including beam-based FE (1D finite element) model, solid-based FE (3D finite element) model, and TM (transfer matrix) model, were designed to study the characteristics of mode and the critical speed characteristic of the dual-rotor system. The unbalanced response of the dual-rotor system was analysed to study the influence of mass unbalance on the rotor system. The effect of different disc unbalance phases and different speed ratios on the dynamic characteristics of the dual-rotor system were investigated in detail. The experimental result shows that the beam-based FE model is effective and suitable for studying the dual-rotor system. Conflict of Interest Statement The authors declare no conflicts of interest.

Dynamic characteristics analysis of multi-link mechanism with clearances considering uncertain parameters

As a typical multi-body system, multi-link mechanisms are widely used in industry. Inevitably, there are joint clearances in multi-link mechanisms. Besides under the conditions of manufacturing, assembly and wear, the parameters of the multi-link mechanism can create uncertainty, and joint clearances and uncertain parameters of the multi-link mechanisms deteriorate the dynamic characteristics, this directly leads to a reduction in working accuracy of the mechanisms. At present, the research focus on multi-link mechanism with clearance considering certain parameters, and relatively few research on the multi-link mechanism with clearance considering uncertain parameters, the existing research on uncertain parameters mainly focus on the uncertainty of single parameter, while the research on the dynamic response of the mechanism with multi-clearances considering the uncertainty of multiple parameters is very less. The main purpose of this article is to provide a novel feasible method for studying the dynamic characteristics of multi-link mechanisms with joint clearances under the consideration of interval uncertain parameters and random parameters. Therefore, the dynamic characteristics of mechanism with multiple clearances considering uncertain parameters, which includes interval parameters and random parameters, are investigated in this article. Taking the 6-bar mechanism as the research object, considering clearances, Poisson’s ratios, stiffness coefficients, and driving speed as the uncertain parameters, the dynamic models of 6-link mechanism with multiple clearances considering interval parameters and random parameters are developed respectively. Using Chebyshev polynomial to solve interval parameters and polynomial chaos to solve random parameters, the effects of uncertain parameters such as clearances, Poisson’s ratios, stiffness coefficients, and driving speed on the dynamic response of the mechanism are analyzed, respectively. This research can not only provide a basis for studying the essential dynamic characteristics of multi-link mechanism with uncertain parameters, but also lay the foundation for dynamic optimization design of the real mechanisms.

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.

Comparative analysis of dynamic load characteristics of artillery steering gear based on different MBD methods

The multi-body dynamics analysis model of the steering gear of a certain type of artillery was established. The dynamic load characteristics of the output gear of the steering gear motor and its driven gear under the given speed and load conditions were calculated based on the three different MBD analysis methods, such as the speed, meshing force, and contact stress. Through the comparative analysis, it was concluded that the calculation results of rigid-flexible coupling analysis were closer to the theoretical value and the fluctuation range was smaller, which provides reference and basis for the prediction of gear fatigue life and the optimization design under dynamic load conditions.

Analysis of dynamic characteristics of whipping effect on l-shaped main steam pipe considering fluid-structure interaction effect

To investigate the whipping effect on the L-shaped main steam pipe utilized in the marine steam systems, the fluid-structure interaction (FSI) method is utilized to numerically analyze its dynamic characteristics. The numerical results illustrate that the dynamic response of whipping effect with rupture position B on the oblique pipe section is more severe with the significantly larger displacement of L-shaped pipe and anti-whip restraints and more complex frequency characteristics than that of whipping effect with rupture position A on the right-angled elbow. The mode transition phenomenon is also observed in the case with rupture position B. The maximum deformation concentrates on different parts when burst of pipes occurs at different positions and the deformation with rupture position B is several times larger than that with rupture position A. The increase of gap between anti-whip restraints intensifies the whipping effect, but it also reduces the maximum restraint force. The friction acts as the resistance in the slip process and thus contributes to the protection against whipping effect. The anti-whip restraints E closed to rupture position B on the oblique pipe section has better performance than anti-whip restraints D in the protection against horizontal whipping effect.

Stability and dynamic characteristics analysis of improved Spar-type wind power floating foundations

Stability and dynamic characteristics analysis of improved Spar-type wind power floating foundations

Multi-timescale analysis and quantification of dynamic regulation characteristics of DFIM-based variable-speed pumped storage units in alleviating wind power fluctuations

To comprehensively clarify the regulating role of variable-speed pumped storage system (VSPS) in alleviating wind power fluctuations, this paper quantitatively evaluates the multi-timescale frequency regulation performance of VSPS in a typical wind-hydro-pumped storage hybrid system (WHPHS). Firstly, the flexible equivalent frequency response models of VSPS and WHPHS are established. Then, the effectiveness of fixed-speed pumped storage system (FSPS) and VSPS in enhancing the stability of dominant hydropower system (HS) in WHPHS is compared, and the dynamic regulation behaviors between VSPS and FSPS are quantitatively evaluated. Based on the operational characteristics, the differences in the allocation of regulation responsibilities between VSPS/FSPS and HS for frequency regulation are clarified. The results indicate that VSPS contributes to an exhaustive improvement in HS stability, reduces the power fluctuation and frequency deviation of WHPSHS. Specifically, in the established simulation scenarios, WHPSHS with VSPS outperforms an equivalent FSPS in reducing frequency deviation frms by 20 %, power fluctuation Is by 40 %, and complementarity Ic by 50 %. Particularly effective in suppressing power fluctuations in range of 0.01 Hz to 0.8 Hz, which decreases the resonant peak of frequency deviation by 61.3 % compared to FSPS. It further highlights the regulatory advantages of VSPS in responding to low-amplitude high-frequency power variations. These findings can provide novel insights into the role of VSPS in mitigating RES fluctuations and energy management strategies in multi-type hybrid systems.

Impedance Circle Modeling and Dynamic Characteristics Analysis of Contactless Energy Transfer System Under Load Variations in Rotary Ultrasonic Machining

In rotary ultrasonic machining, contactless energy transfer (CET) is developed to transmit energy to the transducer at the series resonant frequency or resonant frequency of the transducer. Specifically, during energy transmission, variations in working conditions such as variable axial forces will change the load of the transducer and introduce undesired dynamic effects into the contactless energy transfer system (CETS). In order to explore the connections between these variations and the working performance more directly and theoretically, a new theoretical model—CETS impedance circle is proposed in this paper to reflect the CETS dynamic characteristics, including the CETS frequency characteristics and the relationships between CETS transfer performances at different frequencies under load variations. With the developed theoretical model, the effect of load variations on the trends of CETS impedance circle is investigated. Moreover, based on the impedance circle and its trends, the CETS frequency characteristics, the effect of primary series compensation, and a comparison of the transfer performances at the two working frequencies are theoretically studied. Finally, the CETS impedance circle theories are experimentally verified, and the experimental results are consistent with the analysis of the theoretical model.

Analysis of Dynamic Wear Characteristics of Joint Contact Friction Pair of Excavators Working Device

The working device of an excavator in construction machinery is prone to damage and wear under ordinary working conditions. Based on a model of an excavator under typical working conditions, the dynamic load-bearing situation of the three main joint friction subsets of the working device is simulated by using the virtual prototype technology; the location of the functional device with high stress is identified based on finite element analysis, and the correctness of the simulation results is verified by designing strain gauges. Based on this, the dynamic contact stress variation law of the contact surface of the end-face friction subsets was explored, and the end-face wear depth was calculated by combining Archard wear theory and finite element wear simulation technology; the specimens were worn on the end-face wear tester, and the surface wear was observed under the scanning electron microscope to summarize the wear mechanism and analyze the element content changes of the worn surface. The results show that the three main joints of the working device produce large dynamic fluctuations and are prone to wear, and the destructive degree is more prominent; the wear process is accompanied by higher temperatures, fatigue wear, and abrasive wear on the wear surface, and the wear depth value of the right end face is significantly larger than that of the left end face. This method has a significant reference value for reliability analysis and optimization improvement when using construction machinery’s main joint friction pairs.

Analysis and design of multi-mode power split hybrid transmission scheme considering mode connection

For heavy-duty truck, multi-mode power split hybrid transmission scheme (MPSHTS) has good adaptability. However, the moment of inertia at both ends of the clutch is large. If there is a large speed difference in the clutch engagement process, it will increase clutch wear, engine stall and other problems. This paper proposed a new design method of multi-mode power split hybrid powertrain, which was different from the proof by exhaustion aiming at mode switching without speed difference. It included: the conditions for achieving mode connection without speed difference was obtained based on the lever method for dynamic characteristic analysis. Evaluation index for power split mechanisms that comprehensively considered power source and transmission system was established. Combining the mode connection conditions and the optimized basic configuration, the characteristic of no speed difference could be ensured by adjusting the power coupling mechanism. A multi-mode scheme based on optimized configuration and work mode requirements could be obtained. Finally, parameter matching and simulation verification on the designed scheme was carried out. It suggested that the designed system improved fuel economy by 4.14% compared with the original scheme.

Correction to: Simplified dynamic characteristic analysis method for parallel manipulators with flexure hinges

Correction to: Simplified dynamic characteristic analysis method for parallel manipulators with flexure hinges

Performance improvement study of nonlinear bionic suspension based on inerter and on–off control strategy

How to improve the dynamic performance of nonlinear suspension systems is a focus of attention. The combination of inerter and on–off control strategy can effectively improve the dynamic performance of linear suspension systems, but it will also bring some adverse effects. This paper puts forward a nonlinear suspension system performance enhancement scheme based on semi-active on–off control strategies of inerter to eliminate the adverse effects of the introduction of the inerter and to enhance the dynamic performance of nonlinear suspension systems. This paper takes the nonlinear double-diamond bionic kangaroo leg suspension system as an example and adopts the above scheme to carry out dynamic modeling, time–frequency domain dynamic characteristics analysis, and control characteristics research. The results show that the dynamic performance of the proposed nonlinear suspension system with passive inerter is partially better than that of the original suspension system in time–frequency domain, while the overall dynamic performance of the proposed nonlinear suspension system with semi-active inerter is better than that of the original suspension system. The proposed nonlinear suspension system with semi-active inerter shows good stability and adaptability under different working conditions, and the proposed control strategies can eliminate the adverse effects of passive inerter. The above results indicate the correctness of the proposed scheme and the effectiveness of the control strategies.

Vibration Control of Reinjection Pump Room Pipeline System Based on Dynamic Characteristic Analysis

The reinjection pump room plays a crucial role in industries such as petroleum and chemical engineering. Its main responsibility is to safely and effectively inject treated wastewater, exhaust gas, or other fluid substances into the formation, aiming to achieve resource recycling and environmental protection. However, the pipeline system of the reinjection pump room usually has complex spatial distribution, long span, and multi-point elastic support characteristics, which may cause structural vibration during operation, and have adverse effects on the stable operation, safety, and surrounding environment of the equipment. Therefore, in the pipeline design stage, it is crucial to conduct in-depth vibration analysis of complex pipeline systems to ensure that harmful resonance phenomena do not occur in the pipeline under working conditions. Given the potential impact of pipeline system vibration on equipment performance and surrounding environment, effective suppression of pipeline system structural vibration is of great practical significance. This article focuses on the vibration control strategy of the reinjection pump room pipeline system based on dynamic characteristic analysis. By conducting in-depth research on the dynamic characteristics of pipeline systems, including vibration frequency, modal analysis, and vibration transmission paths, the aim is to propose a set of targeted vibration control measures.

Dynamic Contact Characteristics Analysis of Heavy-duty Track Rollers

As an important component of the crawler walking device, the track roller needs to withstand strong impact and is prone to failure, which can lead to serious economic losses. This paper focuses on the track roller of the spreader as the research subject and investigates the dynamic contact characteristics between the track roller and the track plate. Using RecurDyn software, a virtual prototype model of the crawler walking device is established to analyze the variation in a vertical dynamic load of the track roller under different working conditions. Simultaneously, a finite element model of the contact between the track roller and the track plate is developed using Ansys Workbench, and its accuracy is verified using Hertz contact theory. Finally, the study discusses various influencing factors on the contact characteristics, including load, curvature of the contacting bodies, and material yield strength. The results indicate that the track rollers experience the highest dynamic load when climbing a slope, reaching a maximum load of 1191.44 kN. Moreover, the maximum contact stress is 1750.4 MPa, and the maximum Mises stress is 921.34 MPa during this operation. Importantly, when the load reaches 1218 kN, the maximum Mises stress of the track roller is 930.2 MPa, which may lead to roller failure after prolonged use. These findings provide valuable insights for the design and optimization of heavy-duty track rollers and offer significant assistance for various tracked vehicles.

Experiment-based analysis of dynamic characteristic of the ejector for the hydrogen recirculation system of the PEM fuel cell using active periodic pressure excitation

The ejector-driven hydrogen recirculation system plays an important role in enhancing efficiency of the PEM fuel cell. It's necessary to have deep knowledge of dynamic characteristic of the ejector for optimizing system state, but until now related research is not adequate. In this paper, dynamic characteristic of the ejector for the hydrogen recirculation system of the PEM fuel cell is studied using active periodic pressure excitation. Test plant is set up and active periodic pressure excitation with small amplitude is superimposed on steady pressure at the ejector primary flow inlet. Experiment result shows that in frequency domain, amplitude ratio of dynamic pressure at primary flow inlet to the dynamic delta-pressure, equal to pressure at mixing outlet minus that at backflow inlet, is independent of excitation frequency for each steady operating point. In the complex coordinate, vector of dynamic pressure at primary flow inlet is in parallel with that of dynamic delta-pressure, for all frequencies and for all stable operating points. Furthermore, amplitude ratio of dynamic pressure at primary flow inlet to dynamic delta-pressure exhibits linearity with entrainment ratio of the ejector for all stable operating points. Experiment on the 120 kW fuel cell system validates the same dynamic characteristic.

Clinical characteristic, common sites, and geographical distribution of pediatric tuberculosis patients in Southwest China.

The data report of a large sample, dynamic epidemiology, and characteristic analysis of pediatric tuberculosis (TB) in Southwest China is not clear. Herein, we conducted descriptive dynamic epidemiology, characteristic analysis and geographical distribution study of pediatric TB inpatients in Southwest China for more than 20 years. Patients with pediatric TB were recruited from October 2002 to September 2022 in Southwest of China based on etiology or clinical confirmation. Extract hospitalization medical record information for each patient. The geographical distribution chart of cases is used to display the trend of case flow segmented every 5 years. Among 3,024 pediatric TB patients with an average age of 9.11 ± 4.39, 17.49% (529) had pulmonary tuberculosis (PTB), 9.06% (274) had extrapulmonary tuberculosis (EPTB), and 73.45% (2,221) had combined TB. The most common form of EPTB is disseminated TB (28.98%), followed by TB lymphadenitis (20.56%), pleural TB (19.72%), and TB meningitis (19.68%). Children aged 0-4 years had a high risk of TB meningitis and a severe symptoms, while children in the elderly age group had a high risk of pleural TB. In the past 20 years, hospitalized TB pediatric cases mainly came from Sichuan, Tibet, Qinghai, Yunnan and other places. The number of patients from ethnic minorities, especially Tibetans, showed an upward trend on a yearly basis (χ2 = 401.43, P < 0.001). Public health investment and effective management in pediatric TB should be further strengthened.

Dynamic Characteristics Analysis and Finite Element Simulation of an Ancient Timber Building under Environmental Excitation

This study investigates the vibration response and dynamic characteristics of the Shigudeng Pavilion under environmental excitation, employing a comprehensive approach that includes vibration response measurements, theoretical analysis, and finite element numerical simulation. An in-depth examination of the appearance and stress status of the Shigudeng Pavilion in Yao Ancient Village in southern Hunan was conducted, and the horizontal acceleration of different floors of the pavilion under environmental excitation was ascertained through field measurements. The NExT-ERA method was utilized to identify the modal parameters (frequency, damping ratio, and vibration pattern) of the measured timber construction. Subsequently, a finite element analysis model of the ancient timber building was developed and refined using ANSYS Workbench finite element software. This study proposes a specific repair plan addressing apparent defects and structural damage in the measured ancient timber building, offering theoretical and technical references for the conservation and repair of similar structures.

Generation multi-scroll chaotic attractors using composite sine function and its application in image encryption

In this paper, a composite sine function is proposed and applied in a chaotic system, which is capable of generating definite number of chaotic attractors. The proposed composite sine function possesses infinite breakpoints, but it can produce a fixed number of scrolls by adjusting its parameters. Compared to other chaotic systems with multiple scrolls chaotic attractors, the realization circuit of the chaotic system with compound sine function allows obtaining different numbers of scrolls by adjusting only one resistance value. As a result, the circuit structure remains unchanged despite variations in the number of scrolls. Various analytical methods are applied to study the dynamical behaviors of the proposed chaotic system, including Lyapunov exponent, equilibrium point, bifurcation diagram, phase diagram, spectral entropy and C0-algorithm. Furthermore, based on the analysis of dynamical characteristics, the electronic circuits of the proposed system are given on Multisim circuit simulation software, and the multi-scroll chaotic attractors exhibit consistency with the numerical simulation results. Finally, we incorporated the proposed chaotic system into a Deoxyribonucleic acid coding algorithm for image encryption, and this method exhibits excellent encryption efficiency and high level of security.

Structural design and dynamic characteristics analysis of braided composite two-stage gear transmission system

In order to realize the lightweight design of the transmission system, the braided composite material is applied to the two-stage gear transmission system. According to the structural characteristics of the two-stage gear reducer box, the whole box is designed to be assembled with the braided base and the box wall. Woven composite materials are applied to the web parts of mixed metal composite gears to realize the design goal of lightweight gears. Then, under the assumption of ignoring the influence of friction, bearings and other factors on the system, the dynamic model of the two-stage gear transmission system considering the box is established. By normalizing and dimensionless processing of the equations, the dimensionless differential equations of motion are obtained. The fourth-order Runge–Kutta method is used to analyze the relationship between the connection parameters and the dynamic characteristics of the system under the two working conditions of rigid and flexible connection between the composite base and the box wall.Through the analytical analysis of vibration displacement of two-stage gear reducer and box, the theoretical basis is found for the numerical analysis results. Finally, the dynamic characteristics of the transmission system are studied by vibration resonance analysis through high and low frequency interference. It is found that in a certain frequency range, with the decrease of the mass and moment of inertia of the transmission parts corresponding to the mixed metal composite gear, the amplitude-frequency characteristic Q of the lightweight gear and gearbox transmission system is slightly lower than that of the common gear and gearbox system, and the stability of the system is increased, and the dynamic characteristics of the system are improved.