Coupling Dynamic Model Research Articles

Dynamic modeling and control of a solar sail considering large-amplitude nonlinear vibration

The solar sail spacecraft utilizes Solar Radiation Pressure (SRP) to achieve propulsion, which can realize long-term acceleration without fuel consumption, making it an appealing option for deep space exploration and polar-sitter observation. However, because of the large-scale and high-flexibility of the membrane structure, the solar sail poses challenging dynamic and control issues. Precise dynamic modeling and effective control design can provide theoretical guidance for the efficient functioning of solar sail, which are of great significance and urgently need to be studied. In this paper, a dynamic model that can describe the large-amplitude vibrations of the solar sail is established. Additionally, an attitude tracking controller and a cable-based nonlinear vibration controller are designed to control the attitude motion and flexible vibration of the solar sail. The results show that the established nonlinear rigid-flexible coupling dynamic model is more accurate compared to the linear dynamic model. The polynomial fitting method can characterize the nonlinear dynamics of the solar sail extremely effectively while cutting the program runtime to 5% of the original. Two controllers designed in this paper can make the solar sail maneuver follow the desired trajectory accurately while reducing the sail surface vibration by more than 40%. The research outcomes of this paper can provide references for the dynamic study and active control of large-scale membrane spacecraft.

Adaptive authority dynamic game for human-machine cooperative control

An adaptive dynamic allocation strategy for driving authority based on the non-cooperative game was designed to solve the decision conflict problem between the driver and automatic system in human-machine driving. The coupling dynamics model of human-machine interaction was established according to the coupling mechanism between the driver and the automatic system. Considering the driver’s driving status and the driving risk of vehicles, the driving authority dynamic allocation strategy was designed. On this basis, the human-machine cooperative multi-objective optimal control problem is constructed, and the dynamic allocation control system was designed based on the non-cooperative game theory. The optimal control method was used to solve the Nash equilibrium solution and achieve the optimal authority allocation. The effectiveness of the proposed adaptive authority dynamic allocation strategy was verified under normal and emergency conditions. Results showed that the proposed strategy can effectively reduce human-machine decision conflicts and achieve harmonious human–machine cooperative driving.

An efficient three-dimensional dynamic stiffness-based model for predicting subway train-induced building vibrations

The prediction of train-induced vibration in buildings constructed above the subway is a challenging problem due to its sophisticated system and time-consuming calculation. This paper proposes an efficient three-dimensional (3D) dynamic stiffness-based model (DSM) to predict subway train-induced building vibrations. The DSM has the capability to analytically explore the axial, bending, and torsional vibrations of columns and beams, as well as the flexural and in-plane vibrations of floors and walls induced by the moving train, which few studies have focused on before, and has high computational efficiency compared to the traditional finite element method (FEM). In the DSM, the dynamic stiffness matrices of floors, walls, columns and beams are formulated by the stiffness theory firstly. Then, the global dynamic stiffness matrix of the building is determined following an assembly procedure and the vibration responses of the building can be calculated by the dynamic stiffness equation in the frequency domain. Further, the calculation accuracy and efficiency of the DSM are validated by comparison with a 3D finite element model. Finally, the DSM is used to predict the train-induced vibrations of a building constructed at a subway station based on a subway train-slab track coupled dynamics model. Results show that the building vibrations induced by the moving train are significant in both vertical and horizontal directions and the steel-spring floating-slab track can effectively suppress the train-induced building vibrations.

Observation of enhanced dynamic ΔG effect near ferromagnetic resonance frequency

The field-dependence elastic modulus of magnetostrictive films, also called ΔE or ΔG effect, is crucial for ultrasensitive magnetic field sensors based on surface acoustic waves (SAWs). In spite of a lot of demonstrations, rare attention was paid to the frequency-dependence of ΔE or ΔG effect. In this work, shear horizontal-type SAW delay lines coated with a thin FeCoSiB layer have been studied at various frequencies upon applying magnetic fields. The change of shear modulus of FeCoSiB has been extracted by measuring the field dependent phase shift of SAWs. It is found that the ΔG effect is significantly enhanced at high-order harmonic frequencies close to the ferromagnetic resonance frequency, increasing by ∼82% compared to that at the first SAW mode (128 MHz). In addition, the smaller the effective damping factor of a magnetostrictive layer, the more pronounced ΔG effect can be obtained, which is explained by our proposed dynamic magnetoelastic coupling model.

Hydraulic-thermal coupling dynamic models based on mechanism and data-driven methods of the heating networks in integrated energy systems

The district heating is expected to play a crucial role in the decarbonization of integrated energy systems within the context of attaining carbon neutrality. The literature review reveals a research gapin the investigation of models that account for thehydraulic-thermalcouplingdynamiccharacteristics of heating networks in integrated energy systems, particularly those based on the flow-regulation mode. This discrepancy may affect the safety of the heating networksand contribute to the inefficient scheduling of integrated energy systems, which motivates this study. In this study, it refutes the harsh hypotheses in previous studies, making it more closely related to the real hydraulic and thermal conditions of heating networks. A mechanism-driven model is proposed, which involves the coupled hydraulic and thermal dynamic characteristics of heating networks. The modified forward–backward iteration as a calculation method is carried out, which is embedded with the method of characteristic and upwind difference. A data-driven hydraulic-thermal dynamic model is proposed for fast calculations. For model validation and case analysis, three heating networks in the integrated energy systems are utilized. The simulation results indicate that1) The hydraulic and thermal average relative errors between the measured data and the simulation results are 0.396% and 0.091%, respectively, validating the effectiveness of the proposed dynamic mechanism model; 2) Compared to the current quasi-dynamic model, the proposed dynamic mechanism modelcould reflect the characteristics of heating networks more accurately and simulates the dynamic processes with higher resolution. These results demonstrate that the fluctuations of water head and pipe flow can reach 61.24 ∼ 237.53 m and −4.26 ∼ 32.16 kg/s, respectively. The average temperature difference between the two models is around 0.264 °C; 3) Compared to the forward–backward iteration, the modified forward–backward iteration has a superior convergence performance and calculation accuracy; 4) Compared to the quasi-dynamic model, the proposed data-driven model increases the overall accuracy of hydraulic-thermal calculations and significantly reduces the amount of time required. The average calculation time of the data-driven model is 0.0349 s, while those of the quasi-dynamic model and the proposed mechanism model are 352.92 s and 624.13 s, respectively. In conclusion, the proposed mechanism model of hydraulic-thermal coupling calculation and the related data-driven model are suitable for the dynamic simulations of heating networks in integrated energy systems.

Dynamics modelling and influencing factor analysis of a rocket-launcher coupling system considering uncertain parameters

Vibration characteristic is an important factor affecting the motion of rocket in the launcher and its firing performance. In this paper, a rocket-launcher coupling dynamics model is proposed by applying the transfer matrix method for multibody systems. Considering manufacturing error and nonlinear contact force, the dynamics equations of the rocket-launcher coupling system during the whole process of firing are deduced. Combined with the dynamics model and equations, a dynamics simulation system is developed with uncertain parameters. The uncertain parameter description scheme and probability sampling scheme are proposed to obtain dynamics characteristic and firing performance of the system. The relevant tests are carried out to verify simulation results. Then, the factors affecting the firing performance are discussed. In view of the analysis results, the influence weight of initial disturbance on firing precision is 85% under the condition of full-loading continuous firing, and the swing angular velocity of rocket at muzzle is the main influence factor.

Bionic Structure Inspired by Tree Frogs to Enhance Damping Performance.

Magnetic fluid shock absorbers (MFSAs) have been successfully utilized to eliminate microvibrations of flexible spacecraft structures. The method of enhancing the damping efficiency of MFSAs has always been a critical issue. To address this, we drew inspiration from the tree frog's toe pads, which exhibit strong friction due to their unique surface structure. Using 3D printing, we integrated bionic textures copied from tree frog's toe pad surfaces onto MFSAs, which is the first time to combine bionic design and MFSAs. Additionally, this is also the first time that surface textures have been applied to MFSAs. However, we also had to consider practical engineering applications and manufacturing convenience, so we modified the shape of bionic textures. To do so, we used an edge extraction algorithm for image processing and obtained recognition results. After thorough consideration, we chose hexagon as the shape of surface textures instead of bionic textures. For theoretical analysis, a magnetic field-flow field coupling dynamic model for MFSAs was built for the first time to simulate the magnetic fluid (MF) flow in one oscillation cycle. Using this model, the flow rate contours of the MF were obtained. It was observed that textures cause vortexes to form in the MF layer, which produced an additional velocity field. This increased the shear rate, ultimately leading to an increase in flow resistance. Finally, we conducted vibration reduction experiments and estimated damping characteristics of the proposed MFSAs to prove the effectiveness of both bionic texture and hexagon surface textures. Fortunately, we concluded that hexagon surface textures not only improve the damping efficiency of MFSAs but also require less MF mass.

Study on the Reinforcement Mechanism of High-Energy-Level Dynamic Compaction Based on FDM–DEM Coupling

The high-energy-level dynamic compaction method is widely used in various foundation treatment projects, but its reinforcement mechanism still lags behind the practice. In view of this, a three-dimensional fluid–solid coupling dynamic analysis model was established on the basis of the FDM–DEM coupling method. The variation trends of crater depth, soil void ratio, vertical additional dynamic stress, and pore water pressure during the process of dynamic compaction were analyzed. The results indicate that the curvature of the crater depth fitting curve gradually decreases with the increase in strike times, tending to a stable value. The initial particle structure is altered by the huge dynamic stress induced by dynamic compaction. As strike times increase, the soil void ratio decreases gradually. The vertical additional dynamic stress is the fundamental reason resulting in foundation compaction. Precipitation preloading before dynamic compaction can improve the reinforcement effect of dynamic compaction, making up for the deficiency that the vertical additional dynamic stress attenuates rapidly along the depth direction. The simulated CPT results illustrate that the modulus of foundation soil can be increased by 3–5 times after dynamic compaction. The research results can provide important reference for similar projects.

Research on an Identification Method for Wheelset Coaxial Wheel Diameter Difference Based on Trackside Wheelset Lateral Movement Detection

The wheelset coaxial wheel diameter difference is one of the most common wheel faults of railway vehicles. The existence of the wheelset coaxial wheel diameter difference may lead to the off-load operation of vehicles, resulting in abnormal wheel tread wear, leading to the deterioration of the wheel–rail contact relationship, resulting in the deterioration of the vehicle’s operating stability and comfort, and even leading to an increase in the derailment coefficient, affecting the running safety. In order to monitor the freight car wheelset coaxial wheel diameter difference online, a vehicle–track coupling dynamics model based on a trackside detection method was established, and the response of rail lateral displacement under the condition of the wheelset coaxial wheel diameter difference was analyzed. The results show that the existence of the wheelset coaxial wheel diameter difference can lead to a deviation in the vehicle’s run, with an increase in the wheelset coaxial wheel diameter difference and an increase in the lateral offset of wheelset increases. The impact of vehicle unbalance loading on the lateral movement of the wheelset is much smaller than that of the wheelset coaxial wheel diameter difference. The existence of the wheelset coaxial wheel diameter difference can be better reflected by detecting the wheelset’s lateral displacement. On straight line, the variation of lateral displacement has no infection of vehicle speed, but shows a quadratic growth trend with the wheelset coaxial wheel diameter difference. Based on this, the mapping relationship between the wheelset coaxial wheel diameter difference and wheelset lateral displacement can be obtained. Through a mapping relationship, the size of the wheelset coaxial wheel diameter difference can be reversed precisely through the detection of a trackside lateral movement monitoring system. The reliability of the identification method was verified with a specific test on the trackside monitoring system.

Coupling nonlinearities investigation and dynamic modeling of a tristable combined beam rotational energy harvesting system

Energy harvesting system is regarded as major units in self-powering of massive sensors of Artificial Internet of Things, whose mechanical dynamics play a crucial role in energy conversion efficiency and overall service performance. During rotational motion, periodic disturbances near resonant regions may lead to a large-amplitude oscillation of the harvesters. Due to the coupling effect of rotation and vibration, the distributions of mass and stiffness are related with local deformation and nonlinear rotational frequency in harvesting system, which are yet to be well understood and it is still an open issue. In this paper, a tristable combined beam rotational energy harvester is proposed to obtain higher energy conversion efficiency. Based on the extended Hamilton’s principle, a comprehensive coupling nonlinearities dynamic model is established with consideration of strain distributions, geometric nonlinearity, centrifugal effect, gravitation effect, and nonlinear rotational frequency. The effect of geometric nonlinearity and gravity on the synergistic transition and form mechanism of the tristable harvesting system is explored under the guidance of the static bifurcation, and the influence mechanism of the geometric nonlinearity and nonlinear rotational frequency on the mechanic and energetic characteristics of the system are thoroughly revealed. Numerical and experimental studies are performed to validate the effectiveness of the established model. Results show that geometric nonlinearity and nonlinear rotational frequency lead to a wider frequency bandwidth and a more complex inter-well snap-through motion. Meanwhile, the established model provides a theoretical fundamental framework of high-performance harvester’s design in large-amplitude complex excitation scenarios, which is conducive to control harvester in actual engineering applications.

Mitigating deepwater jacket offshore platform vibration under wave and earthquake loadings utilizing nonlinear energy sinks

The random vibrations of jacket offshore platforms under wave and earthquake actions can reduce the service life and exacerbate fatigue damage of the offshore platforms. Aiming to mitigate those unwanted vibrations, this paper introduces the nonlinear energy sinks (NES) to the deep-water jacket offshore platform as a passive control device. Its coupling dynamic model is built with assumed parameters of wave and earthquake loads, and the wave forces of the platform structure are calculated by Morison's equation. Further, the optimal parameters of the NES system are obtained by an exhaustive search algorithm under the objective function. The results show that the NES system can effectively contribute to mitigating the maximum, minimum, and root mean squares (RMS) of deck-level responses of the platform structure. What's more, despite various mass or stiffness of platform structure, the NES system not only greatly reduces the response peaks, but also demonstrates a more steady phenomenon, in which the robustness is presented clearly. In this way, it strongly proves the feasibility and robustness of the NES system under wave and earthquake loadings.

Research on complex multimodal vibration characteristics of offshore platform

Abstract The vibration and noise performance of the offshore platforms are significant factors affecting the comfort and physical and mental health of the staff, and are also important indicators for evaluating the status of platforms. Based on the principle of structural dynamics, taking the semi-submersible platform as the research object, this article systematically and comprehensively studies the vibration characteristics and transfer laws of some partial-frame structures to the overall structure by combing theoretical derivation and numerical simulation. Firstly, the coupling dynamic model of the device-plate-platform is established, and the vibration transmission from the excitation source to the platform structure through the coupling system is analyzed theoretically. Secondly, the multimodal vibration mechanism of the plate frame and cabin structure is discussed by considering the plate frame and the plate frame as one. Finally, based on the semi-submersible platform structure, the study of complex multi-modal vibration transfer law of platform structure is carried out, which contributes to the research on multimodal coupled vibration protection of offshore platform structure.

A Transformer‐Based Deep Learning Model for Successful Predictions of the 2021 Second‐Year La Niña Condition

AbstractA purely data‐driven and transformer‐based model with a novel self‐attention mechanism (3D‐Geoformer) is used to make predictions by adopting a rolling predictive manner similar to that in dynamical coupled models. The 3D‐Geoformer yields a successful prediction of the 2021 second‐year cooling conditions that followed the 2020 La Niña event, including covarying anomalies of surface wind stress and three‐dimensional (3D) upper‐ocean temperature, the reoccurrence of negative subsurface temperature anomalies in the eastern equatorial Pacific and a corresponding turning point of sea surface temperature (SST) evolution in mid‐2021. The reasons for the successful prediction with interpretability are explored comprehensively by performing sensitivity experiments with modulating effects on SST due to wind and subsurface thermal forcings being separately considered in the input predictors for prediction. A comparison is also conducted with physics‐based modeling, illustrating the suitability and effectiveness of 3D‐Geoformer as a new platform for El Niño and Southern Oscillation studies.

Nonlinear dynamics of the spacial vibration system considering the interactions between the frame and materials

The vibration mass of materials is a major technical bottleneck restricting the development of intelligent and upsizing vibration machinery. It cannot be ignored and fluctuates greatly under different working conditions, especially for complex space vibration systems, such as vertical vibration conveyors used to lift materials. This paper investigated the kinematic theory of the material sliding and throwing in three-dimensional space. Firstly, the dynamic coupling model between the machine body and materials is established, the kinematic characteristics of the bulk materials under the sliding and throwing patterns in the space vibration system are investigated, and the kinematics equations of the material under the sliding and throwing patterns are derived. Secondly, the solution procedure of the Wilson-θ method is given and verified by the Discrete Element Method (DEM). Meanwhile, the variations of the steady interval of materials, the path of the machine body, and conveying velocity are further discussed. Finally, the feasibility of the material’s kinematic theory investigation with a view to supplementing the interaction between the machine body and materials is verified by experiments. The results indicate that the system’s interaction force significantly affects the material’s moving patterns and the machine body’s dynamic characteristics.

Uncertainty quantification of mechanism motion based on coupled mechanism—motor dynamic model for ammunition delivery system

In this paper, a dynamic modeling method of motor driven electromechanical system is presented, and the uncertainty quantification of mechanism motion is investigated based on this method. The main contribution is to propose a novel mechanism-motor coupling dynamic modeling method, in which the relationship between mechanism motion and motor rotation is established according to the geometric coordination of the system. The advantages of this include establishing intuitive coupling between the mechanism and motor, facilitating the discussion for the influence of both mechanical and electrical parameters on the mechanism, and enabling dynamic simulation with controller to take the randomness of the electric load into account. Dynamic simulation considering feedback control of ammunition delivery system is carried out, and the feasibility of the model is verified experimentally. Based on probability density evolution theory, we comprehensively discuss the effects of system parameters on mechanism motion from the perspective of uncertainty quantization. Our work can not only provide guidance for engineering design of ammunition delivery mechanism, but also provide theoretical support for modeling and uncertainty quantification research of mechatronics system.

Dynamic modeling and analysis of high-speed aerostatic journal bearing-rotor system with recess

To analyze the dynamic properties of high-speed aerostatic journal bearing with recess, a bidirectional fluid-structure coupling dynamic model is established. The mathematical model is established by coupling the governing equation of the transient air film flow, the flow balance equation, and the rotor motion equation. Based on the trajectory of rotor axis, trajectory of rotor center, Poincare map, time response of rotor, frequency spectrum, mass flow rate, and bifurcation diagram, the influences of operating parameters on the coupling system are analyzed theoretically and experimentally. The results indicate that the system has abundant nonlinear behavior, and the instability parameters of the system are determined. This study provides guidance for the theoretical design and practical operation of this type of system.

A framework of high-order wheel polygonal wear mitigation for China's high-speed trains

High-order wheel polygonal wear is a significant concern on China’s high-speed trains; thus far, no satisfactory solution to prevent polygonal wear has been provided. In this study, a simplified vehicle-track coupling dynamic model was established, and the frequency response functions (FRF) of the wheel-rail force were obtained under multiple wheelsets conditions. After integrating a wheel-rail wear model, the rail localized bending modes (RLBM) were recognized as critical factors for the amplitude-frequency and phase-frequency properties of the wheel-rail force response and further gave rise to the growth of high-order polygonal wear. Consequently, rail dynamic vibration absorbers (DVA) were introduced into the vehicle-track coupling dynamic model as single-degree-of-freedom rigid bodies arranged at equal intervals along the track. The influencing mechanism of rail DVAs on the rail localized bending resonance, as well as the resulting polygonal wear, was investigated in detail. Results suggested that the rail localized bending resonance could be easily suppressed when the tuned frequency of the rail DVAs approaches the resonance frequency. However, due to newly generated resonance peaks, the polygonal wear was observed to persist. The phase-frequency property of the wheel-rail force response is a determining contributor to the growth trend of polygonal wear; therefore, the rail-tuned DVA should be designed to force the phase lag out of the positive growth region, namely 90° to 270°. Our results indicated that a DVA with a tuned frequency of 450 Hz could effectively slow the development of high-order polygonal wear on China’s high-speed trains, and the shorter installation interval of rail DVAs improves the suppression effect. This study proposed a phase-based design rule for rail DVAs to achieve wheel-rail periodic wear mitigation.

Thermal performance of a novel Trombe wall integrated with direct absorption solar collector based on phase change slurry in winter

This research proposes a novel Trombe wall system using direct absorption solar collector based on phase change slurry (DPTW). The dynamic coupling model of the DPTW system is established, and its accuracy is verified. The indoor temperature of the room under heating conditions in January is simulated. Simulation results indicate that the DPTW system has higher indoor thermal comfort. The indoor personnel activity area temperature was within the range of 18.5–24 °C for 148.4 h, which was 167% longer than that of the traditional Trombe wall system (TW). The indoor thermal comfort index PMV is in the range of −0.5∼0.5 for 119.2 h, an increase of 121% compared with the TW system. In addition, the DPTW system reduces the heat load in winter, which is 39% less than that of the TW system in January. The proportion of solar energy utilization is higher, and the solar fraction of the DPTW system can be increased by 45% at lower temperatures. According to the performance of January, the DPTW system is more robust. Therefore, the TW system can be substituted by the DPTW system because the DPTW system can better maintain the indoor temperature and reduce heating energy consumption.

A general structural design method, dynamics modeling and application study for built-in sandwich annular traveling wave piezoelectric transducers

This study first summarized a piezoelectric excitation source arrangement guideline for sandwich annular traveling wave transducers, which can excite ideal traveling waves for driving while ensuring consistent circumferential stiffness of the annular transducer. Consequently, a general structural design method was proposed for annular sandwich traveling wave piezoelectric transducers operating with out-of-plane traveling waves based on the above-mentioned arrangement guideline. Moreover, to study the vibration characteristics of the designed transducer based on the proposed method, an electromechanical coupled dynamics model was developed using the dynamic substructure method combined with the Lagrange equation. This model is universal and has guiding significance for the design and optimization of the same type of annular traveling wave piezoelectric transducers. Thereafter, the feasibility of the transducer structure design method and the correctness of the developed dynamics model were verified through appropriate vibration measurement experiments on the transducer prototype. The measured ideal mode shape and regular elliptical motion verified the feasibility of the transducer design method, and the comparison between the vibration measurement and theoretical model calculation results confirmed the correctness of the developed dynamic model. Finally, an application study of the proposed built-in sandwich traveling wave transducer was conducted to investigate its driving characteristics. The proposed transducer was used to drive a rotor to build a traveling wave piezoelectric motor. In addition, output performance experiments of the motor prototype were conducted. The experimental results indicated that under the driving conditions of 300 N pre-pressure, 500 Vpp voltage, and 19 kHz exciting frequency, the no-load speed of the motor was 19.04 RPM, its stall torque was 1.2 N·m, the maximum output power of the entire machine reached 0.6453 W, and its maximum output efficiency was 15.87%. Moreover, the normal operation of the rotating motor further verified the feasibility of the transducer structure design approach and the reliability of the drive application. The structural design method and the corresponding dynamic model proposed in this study are expected to have important guiding significance for the design and optimization of sandwich-type annular traveling wave transducers. Furthermore, the application investigation in this study provides a typical example for the traveling wave transducer.

Two-Dimensional Eulerian-Exponential-Law Acoustic Black Hole Structure for Energy Harvesting

Thin plates are widely used in engineering, so it is of great value to explore energy harvester based on this type of structure. Acoustic black hole (ABH) is helpful for the energy harvesting of thin plate. However, the traditional power-law ABH needs to be improved in the low-frequency energy harvesting. Thereupon, a new Eulerian-exponential-law for ABH is proposed, and a two-dimensional ABH structure based on the Eulerian-exponential-law is designed for harvesting low-frequency energy. This paper constructs a simple electromechanical coupling dynamic model for the Eulerian-exponential-law ABH energy harvester (EAEH). This model has low computation complexity as the dimension of thin plate is reduced by the Kronecker product of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> -direction and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</i> -direction beams’ modes. Combining the element division and modal analysis of beam, a new method with high computational efficiency is proposed for calculating the base functions of thin plate with two-dimensional ABH, and its effectiveness and accuracy are validated by the result of finite element analysis. Under different excitation frequencies, the voltage and power responses of EAEH are simulated, and their validity is verified by the experimental results. Moreover, EAEH is compared with the power-law ABH energy harvester through the simulation and experiment. The comparative results show EAEH has lower resonant frequencies and higher output of voltage and power.