Coupling Dynamic Model Research Articles

Cumulative thermal coupling modeling and analysis of oil-immersed motor-pump assembly for electro–hydrostatic actuator

The Electro–Hydrostatic Actuator (EHA) is applied to drive the control surface in flight control system of more electric aircraft. In EHA, the Oil-Immersed Motor Pump (OMP) serves as the core as a power assembly. However, the compact integration of the OMP presents challenges in efficiently dissipating internal heat, leading to a performance degradation of the EHA due to elevated temperatures. Therefore, accurately modeling and predicting the internal thermal dynamics of the OMP hold considerable significance for monitoring the operational condition of the EHA. In view of this, a modeling method considering cumulative thermal coupling was hereby proposed. Based on the proposed method, the thermal models of the motor and the pump were established, taking into account heat accumulation and transfer. Taking the leakage oil as the heat coupling point between the motor and the pump, the dynamic thermal coupling model of the OMP was developed, with the thermal characteristics of the oil considered. Additionally, the comparative experiments were conducted to illustrate the efficiency of the proposed model. The experimental results demonstrate that the proposed dynamic thermal coupling model accurately captured the thermal behavior of OMP, outperforming the static thermal parameter model. Overall, this advancement is crucial for effectively monitoring the health of EHA and ensuring flight safety.

Dynamic response of high-speed railway vehicle and welded turnout on large-span bridges based on rigid-flexible coupling system

Welded Turnout on Large-span Bridge (WTLB) is a complex multi-layer heterogeneous system and can significantly influence the service performance of High-Speed Railway (HSR). Understanding the coupling dynamic response of the vehicle and WTLB is essential. Previous research did not consider the dynamic behavior of foundations, leading to an underestimation of the vehicle-turnout-foundation coupling dynamic response, particularly when turnouts were laid on large-span bridges. This study proposes a novel modeling method that includes the foundations, to overcome the previous shortcomings by applying a rigid-flexible coupling system. In this approach, the vehicle was modeled as a rigid body sub-model in a Multi-Body Software (MBS), while WTLB was modeled as a flexible bodies sub-model using Finite Element (FE) software. The modal information from the FE model was imported into the MBS software. The two sub-models were coupled by the wheel-rail contact in the MBS environment and then the Vehicle-turnout-bridge Rigid-flexible Coupling Dynamic (VRCD) calculation model was established and it was discovered that the calculation results showed good agreement with the field test data. Through the VRCD model, the safety of the structure, the stability of the vehicle and the comfort of passengers were investigated, as well as several important infrastructure factors. The results demonstrate that this novel method provides accurate calculations and highlights the complex and significant interactions in the vehicle-turnout-bridge system.

Vibration-attitude integrated control of large membrane diffraction space telescope

The development of telescopes with large apertures is driven by the increasing demand for higher imaging resolution and coverage. Large membrane diffraction space telescopes are particularly attractive due to their lightweight nature, ease of folding and unfolding, and high-precision imaging capabilities. However, their substantial size and flexibility make them susceptible to long-duration, low-frequency vibrations during attitude maneuvers, which degrade attitude and imaging accuracy and risk instrument damage. Consequently, an urgent need exists for a high-precision integrated control scheme. In this paper, the integrated control of vibration and attitude in a large space telescope is studied using cable actuators and control moment gyroscopes (CMGs). Since cables can only withstand limited tension, the unilateral and constrained characteristics of the control input are taken into account during the control design process. Firstly, a rigid-flexible coupling dynamic model of the space telescope is established using the velocity variation principle with hybrid coordinates. Additionally, a two-body astrodynamic model is developed to assess the impact of gravity gradient torque. Next, combining the computational torque method and H∞ control theory, an integrated control scheme is proposed, which achieves vibration and attitude control during maneuvers. Then, this paper optimizes the cable actuator positions via the discrete particle swarm optimization (PSO) algorithm and plans various attitude maneuver paths. Finally, numerical simulations are adopted to demonstrate the effectiveness of the control scheme. The results show that this integrated control scheme swiftly suppresses structural vibrations during attitude maneuvers, enabling high-precision attitude control of the space telescope.

Development and investigation for rigid-flexible coupling dynamic performances of the morphing wing with clearance joints

Morphing wings have enjoyed much research interest due to their advantages in improving aircraft adaptability to various service environments. A single drive and continuous variable bending morphing mechanism with multiple configurations is proposed. The morphing wing designed based on this mechanism can have the advantages of lightweight, multiple configurations and smooth morphing shapes. Transient aerodynamic loads will destroy the dynamic performance of the wing during the multi-mode morphing process. Therefore, it is crucial to analyze the vibration characteristics for the reliability of the morphing wing. However, it is difficult to obtain its dynamic model and solution because of the complex configuration and the multi-mode morphing. In this paper, a mathematical model for the multi-mode morphing of the morphing mechanism based on lockable joints is described using the constraint equation firstly. Then, a rigid-flexible coupling dynamic model of the morphing wing with clearance joints is established. Finally, the influence of the infective joint and the flexible link on the vibration properties of the morphing wing is analyzed in detail. Moreover, differences in the dynamic parameters between rapid and regular actuation are discussed. The results obtained in this paper have an important engineering value for the design and manufacture of the morphing wing.

Pantograph-Catenary Coupling System Dynamics Analysis with Rigid-Flexible Pantograph for Straddle-Type Monorail

The flexible pantograph of straddle-type monorail has influence on the dynamics performance of pantograph-catenary system. This paper established a rigid-flexible pantograph-catenary-vehicle coupling dynamics model of monorail. By embedded the rigid-flexible pantograph into the vehicle dynamic analysis model, the rigid-flexible pantograph-catenary coupling dynamics model that could consider the random irregularity of track beam ultimately established. The validity of model has been approved by the pantograph dynamics test of Chongqing monorail line 3. The dynamic performance of the pantograph-catenary system, calculated by the dynamics models with rigid and rigid-flexible pantograph are compared in detail. The results show that the pantograph flexibility affects the vibration characteristics and the current collection quality of pantograph-catenary system.

Experimental and numerical investigation of the track structure elasticity induced by resilient fastener on vehicle-track interaction and train running stability

The resilient fastener slab track (RFS track) has found extensive application in urban railways, effectively mitigating vibration and noise resulting from train operations. However, the structure elasticity of the RFS track is higher than the normal slab track (NS track), which can affect train running stability and cause abnormal vibration phenomenon. This paper explores the track structure elasticity on vehicle-track interaction and train running stability through experimental tests and numerical simulations. The vibrational properties of the RFS track and the NS track are obtained through field tests. A 3D metro vehicle-track coupled dynamics model is developed and utilized to simulate the dynamic performance of metro vehicles moving on different track structures. The impact of track structure parameters upon the vehicle-track interaction and train running stability are discussed. The findings indicate that the track structure elasticity can reduce train hunting stability and cause abnormal vibration phenomena in metro vehicles under certain conditions. The reasonable matching of the fastener lateral and vertical stiffness can not only accomplish vibration attenuation but also minimize the impact on train running stability. In addition, the rail surface wear and track gauge variation also exert influence on the running stability and dynamic performances of metro vehicles.

Dynamic behaviors of multiphase vortex-induced vibration for hydropower energy conversion

To satisfy the growing electricity demand, continuous and stable hydropower conversion is particularly critical in tidal power station operation. In the above industrial application, multiphase vortices will be formed, and they suck air and floating items into the flow tube, thus causing irregular pulsation that affects turbine performance. Due to nonlinear characteristics of gas-liquid coupling transfer, dynamic modeling and transition behavior of the multiphase vortex-induced vibration have improtant difficulties. This paper conducts a fluid-structure mechanic optimization model with the dynamic mesh technology to investigate multiphase vortex-induced vibration (MVIV) dynamic behaviors and reveal the internal relation between displacement responses and multiphase flow states. The fluid-induced vibration sensing platform is developed to validate MVIV transition behaviors, and a wavelet packet signal analyzing approach is adopted to acquire energy-spectrum distribution regularities of the vibration distortion state. Results show that the presented optimization modelling strategy can well obtain the MVIV transition behaviors and energy transfer mechanism. The flow flux can control the Ekman transfer intensity, and vibration energy waves take on various frequency components at the critical penetration state. Moreover, impulse energy components and structure evolution properties of high-frequency bands can be utilized to recognize the MVIV distortion peak. It can supply theoretical guidance and technology support for hydropower conversion.

Development of Mathematical Model for Coupled Dynamics of Small-Scale Ocean Current Turbine and Generator to Optimize Hydrokinetic Energy Harvesting Applications

Development of Mathematical Model for Coupled Dynamics of Small-Scale Ocean Current Turbine and Generator to Optimize Hydrokinetic Energy Harvesting Applications

Modelling of electromechanical coupling dynamics for high-speed EHT system used in HEV and characteristics analysis

As the development of hybrid electric vehicle (HEV) to high-speed, heavy-load, the electromechanical coupling vibration becomes the bottleneck in high-speed electromechanical hybrid transmission (EHT) system. To explore the dynamics characteristics and optimization direction for high-speed EHT system, an electromechanical coupling dynamics model under multi-source excitations is established with lumped-distributed parameter method and verified with experiment data. The dynamics model shows higher accuracy in both time and frequency domain analysis. On this basis, firstly, the comparison between lumped-shaft and distributed-shaft model is studied under time and frequency domain. Comparing with the lumped-shaft model, the distributed-shaft model shows higher accuracy, and can better reflect the coupling vibration of multi-stage planetary gears (PGs). Secondly, the inherent vibration model is derived, and the effect of electromechanical coupling and high-speed working conditions on inherent vibration characteristics are studied. Thirdly, a new method called ‘machine-electricity-magnet coupling interface’ is proposed to reveal the coupling vibration phenomenon. In addition, the signal of stator current and electromagnetic torque includes the frequency of PGs, which is a basis on the fault diagnosis and state monitor of EHT system. Last but not the least, the vibration acceleration of EHT system is analysed under variable speed and load working conditions. Rotation speed and gear meshing force is found as the main influencing factor of series EHT system, and the specific optimization direction is also given.

Rigid-flexible coupling dynamic modelling and dynamic accuracy analysis of planar cam four-bar mechanism with multiple clearance joints

Combination mechanism of conjugate cam and four-bar is a complex type of multi-body system, in which the coupling problems such as cam profile law, flexible deformation of connecting rods, and multiple joint clearance collision make it difficult to model and optimise its dynamics. Just as the beating-up mechanism of high-speed rapier looms for multi-layer weaving is a representative conjugate cam four-bar mechanism. In response to the current development of textile machinery in the direction of high-speed and precision, and in order to improve the work efficiency and operational accuracy of the conjugate cam four-bar beating-up mechanism, the following work is done for the purpose of taking into account the multi-joint clearance and the flexible rod based on the mechanism. Firstly, based on Kane's equation, a multi-body dynamic model with multiple clearances is established combined with clearance collision theory. Secondly, a dynamic model of a rigid-flexible coupling system with multiple revolute clearances is established using finite element method combined with modal synthesis technology. Subsequently, the variables separation method and mode superposition method are used to solve the dynamic equations of the coupled system. Finally, numerical examples are used to analyse the effects of clearance quantity, clearance size, mode truncation order, cam speed, and component material properties on the dynamic response and accuracy of the system. The results show that, in the rotational speed range of 600–800 rpm, the dynamic performance of the system is little affected by the speed; Through comparative analysis of multiple materials, it is found that selecting carbon fibre composite materials has the smallest impact on the motion accuracy of the system. In this paper, the clearance collision model, finite element model and rigid-flexible coupling dynamic model are integrated, which are applied to the cam-linkage combined multi-body mechanism, and the dynamic problems of the actual machine are analysed and solved.

Analysis of the dynamic contact behaviour of high-speed train transmission gear excited by wheel defects

Studies on wheel flatness and polygonal wear have demonstrated that wheel defects cause severe impact forces at the wheel–rail interfaces. This study investigated the dynamic contact mechanical behaviour of high–speed train transmission gears when subjected to wheel defects. First, a train-track coupling dynamics model was established, considering the localized contact characteristics of transmission gears. This model was developed using the slice method and the Hertz contact model, exploring the spatial coupling effects between the gear contact interface and the train–track interface. Subsequently, the dynamic model was employed to extract essential contact mechanical parameters of the transmission gear under the influence of wheel defects, including gear meshing load, gear contact stress, and sliding velocity. Furthermore, an analysis was conducted to uncover and elucidate the mechanism by which wheel flatness and polygonal wear impact the dynamic contact behaviour of the transmission gear. This study underscores the importance of considering wheel defects when assessing the contact fatigue and wear performance of high-speed train transmission gears.

Translation torsion coupling dynamic modeling and nonlinearities investigation of non-circular planetary gear systems

Translation torsion coupling dynamic modeling and nonlinearities investigation of non-circular planetary gear systems

A Parameter-Driven Methodology of Wheel Flat Modeling for Wheel–Rail Impact Dynamics

A wheel flat is a typical wheel defect that significantly impacts the wheel–rail system, posing substantial challenges to vehicle operation safety. In the existing literature, the wheel flat plane model does not account for the contribution of the width direction to the impact response and thus cannot accurately reveal the wheel–rail contact state with a flat. This paper systematically proposes a three-dimensional analytical model that considers multiple worn stages and constructs a spatial complex surface reconstruction model for flats based on NURBS technology. A vehicle–track coupled dynamics model, considering the geometry of the flat, is established to investigate the effects of flat geometry on the wheel–rail impact response and contact relationship in detail. The results show that in the subcritical regime, the wear degree of the flat predominantly affects the impact force, while in the transcritical regime, both the wear degree and velocity together determine the magnitude of the wheel–rail impact force. As the wear degree increases, the moment of wheel lateral jump occurs earlier. The spatial modeling method for flats proposed in this paper offers a novel technical approach for accurately simulating the dynamic behavior of wheel–rail contact when a flat is present.

Performance investigation of a novel free piston Stirling pump for reverse osmosis desalination systems

Renewable energy (RE)-powered desalination technology is considered a cleaner and promising alternative for alleviating energy exhaustion and environmental pollution resulting from traditional desalination. Currently available solar thermal reverse osmosis (RO) desalination systems are based on the organic Rankine cycle. With the aim to expand the driving mode of reverse osmosis desalination as well as simplify the transmission chain and reduce mechanical energy losses, a novel hydraulic free piston Stirling pump (FPSP) is developed and a simple model is designed and tested for conceptual validation. A free piston Stirling pump - powered reverse osmosis desalination system is presented, and a thermodynamic–dynamic coupling model is established. A parametric analysis is performed with an emphasis on the effects of temperatures, charge pressure, spring stiffnesses, damping coefficients, and masses on the system performance, including the frequency, power output, water yield, and efficiency. Results showed that the frequency in the pumping process was higher than that in the suction process because of the different loads. Within the range investigated, the performance improved as the hot-end temperature, charge pressure, spring stiffnesses, and damping coefficient of the power piston increased, while it deteriorated with a decrease in the damping coefficient of the displacer and the piston masses. Specifically, the power output and water yield reached the optimum value as the cold-end temperature was maintained around 310 K. Under representative parameter conditions, the power output could reach 12.15 kW and the water yield was approximately 6.07 × 10−4 m3/s. In addition, the temperatures and charge pressure influence the system efficiency most.

Impact of Train Formation on the Dynamic Responses and Operational Safety of High-Speed Trains under Non-Uniform Seismic Ground Motion

The study of dynamic responses and operational safety of high-speed trains under seismic excitation has increasingly relied on numerical simulation as the most effective and convenient research approach. The majority of studies only focus on single-car formation, and fewer utilize train models with actual standard formation, inevitably resulting in differences in dynamic characteristics of train models and simulation results. Furthermore, trains also have different standard formations in different countries and operating scenarios. Therefore, the influences of train formation on the dynamic responses and operational safety of trains under seismic action are investigated. Hence, a detailed train/vehicle–track coupled dynamics model was established to simulate trains under non-uniform seismic ground motion. Moreover, due to wheel–rail contact simulation being the key factor constraining simulation efficiency, based on the influence pattern of train formation, whether fewer train formations can achieve the same simulation accuracy as the 8-car standard formation is also explored in this paper considering seismic wave propagation effect. Results indicate that variation in train formation can influence the dynamic responses of a coupled system significantly from both the perspective of wheel–rail interaction and vehicle kinematic responses. Moreover, the 5-car formation model can better meet the accuracy requirement and significantly improve computational efficiency compared to 8-car formation model.

Research on Attitude Analysis of Hydraulic Support Based on Column Length

The existing hydraulic support attitude monitoring and control methods integrate multiple sensing technologies, but it is difficult to apply and promote due to unclear monitoring mechanisms, complicated types, and a large number of sensors. Aiming at the problem of attitude monitoring and control of hydraulic support, firstly, the kinematics mathematical model of hydraulic support is established by the key marker point method and the two-dimensional bar system model, and the forward and inverse solution algorithm of hydraulic support attitude based on the double-drive length of front and rear columns is proposed. Secondly, the rigid body dynamics simulation model of hydraulic support is constructed to verify the theoretical analytical model and prove the correctness of the algorithm. The rigid body simulation model can be used as the attitude monitoring system of hydraulic support. Thirdly, considering the influence of material elastic deformation, a rigid-flexible coupling dynamic simulation model of hydraulic support is established to explore the influence of elastic deformation of components on the attitude of hydraulic support and its causes. On this basis, the rigid-flexible coupling dynamic simulation model of the hydraulic support with clearance is established by replacing the revolute pair in the simulation model with the solid axis pin connection unit. The influence of the axis pin connection clearance on the attitude of the hydraulic support and its causes are explored, and the actual attitude and change characteristics of the hydraulic support under simulated real conditions are obtained. Finally, considering the force compression of the hydraulic cylinder of the column, the rigid-flexible and machine-liquid coupling dynamic simulation model of the hydraulic support with clearance is constructed.

Simulation of flip-flow screening adhesive organic fertilizer particles based on DEM-MBD coupling method

For screening adhesive organic fertilizer particles, a Discrete Element Method (DEM) and Multi-Body Dynamics (MBD) coupling model of screening adhesive organic fertilizer particles using a flip-flow screen is established. Then, the velocity, the distribution and the trajectory of the particles during the screening process are observed. Finally, the effects of the surface energy γ, the rotational speed n, the tensional amount ∆l and the feed rate M are investigated. The results show that the flip-flow screen could provide a high velocity for depolymerization of agglomerated particles and separation of adhesive particles from the screen panels, so adhesive organic fertilizer particles can be successfully screened by using the flip-flow screen and organic fertilizer particles in an easily absorbed range are obtained. With the increase of γ, both the flow rate and the screening efficiency decrease. With the increase of n, both first increase and then slightly decrease. With the increase of ∆l, both increase at a low n, or slightly decrease at a high n. With the increase of M, the screening efficiency decreases, while the total flow rate first increases and then decreases. Through adjusting n, ∆l, M, flip-flow screen can also be used to screen other adhesive particles.

Assessment of random dynamic behavior for EMUs high-speed train based on Monte Carlo simulation

A novel statistical method was developed to obtain a dynamic response with irregular line excitations and independent uncertain parameters. The proposed approach combines a three-dimensional vehicle-track coupling dynamics model and uncertainty parameters. Moreover, a new method is used to treat the dynamic indices: derailment coefficient, vertical/lateral wheel/rail force, vertical/lateral car body acceleration, and wheel reduction ratio. The model is validated by comparing simulations (deterministic) results with field measurements, which provide excellent agreement with limited data. According to the findings, the results reveal that the high vibration effect arises when the uncertainty parameter in the dynamic system exists. The total fit effects, the consistency of the vehicle safety, and the tail fit effects are determined for selecting the best method. Therefore, regarding the approach, the lognormal and extreme maximum distribution values may be the appropriate assumed distribution for dynamic safety under limited data.

Multifactor dynamic coupled model for building fire evacuation: Case study of the Karamay Friendship Palace fire

Occupant evacuation during a building fire is a complex system that includes several highly coupled subsystems, such as building characteristics, occupant characteristics, fire behavior, and evacuation behavior. To study the interaction mechanism between these subsystems to maximize occupant safety during fire evacuation in a building, a multifactor dynamic coupled model based on the Fire Dynamic Simulator and floor field cellular automata model for occupant evacuation in a fire was established. In the model, the dynamic impact of smoke diffusion on occupant movement direction and speed, decrease in occupant health points caused by smoke and trampling, and changes in occupant exit choices in the presence of closed exits were considered in detail. The catastrophic fire accident in the Friendship Palace of Karamay, Xinjiang, China, in 1994 was used as the analysis case, in which the spatial model of the Friendship Palace was reconstructed according to real data and architectural design methods. The safety exits open or closed, radius Rtra, possibility of information transmission Psuc, and wait time twait were discussed to study the influence of these parameters on the evacuation process and results. The study shows that the model could reproduce a fire accident well with Rtra = 4, Psuc = 0.5, and twait = 30. The closed exits increased evacuation time by over 120.3 % and resulted in 439 deaths. These conclusions are important for providing better estimates, guiding architectural designs, and enhancing building safety management.

Coupled dynamic modeling and characteristic analysis of an underactuated bionic scorpion robot arm during polarizer attachment motions

Coupled dynamic modeling and characteristic analysis of an underactuated bionic scorpion robot arm during polarizer attachment motions