Coupling 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.

Research and experiment on active training of lower limb based on five-bar mechanism of man-machine integration system

AbstractIn view of the fact that the current research on active and passive rehabilitation training of lower limbs is mainly based on the analysis of exoskeleton prototype and the lack of analysis of the actual movement law of limbs, the human-machine coupling dynamic characteristics for active rehabilitation training of lower limbs are studied. In this paper, the forward and inverse kinematics are solved on the basis of innovatively integrating the lower limb and rehabilitation prototype into a human-machine integration system and equivalent to a five-bar mechanism. According to the constraint relationship of hip joint, knee joint and ankle joint, the Lagrange dynamic equation and simulation model of five-bar mechanism under the constraint of human physiological joint motion are constructed, and the simulation problem of closed-loop five-bar mechanism is solved. The joint angle experimental system was built to carry out rehabilitation training experiments to analyze the relationship between lower limb error and height, weight and BMI, and then, a personalized training planning method suitable for people with different lower limb sizes was proposed. The reliability of the method is proved by experiments. Therefore, we can obtain the law of limb movement on the basis of traditional rehabilitation training, appropriately reduce the training speed or reduce the man-machine position distance and reduce the training speed or increase the man-machine distance to reduce the error to obtain the range of motion angle closer to the theory of hip joint and knee joint respectively, so as to achieve better rehabilitation.

Experimental and numerical study on the integration of a built-in wave energy converter(BIWEC) and floating platform

Nowadays generating electricity continuously in real waves over extended periods is a big challenge due to harsh ocean environment for wave energy converters (WECs). In this study, in order to enhance the reliability of WEC, a novel BIWEC which can form an integrated system by combing with existing floating platforms is proposed. This design method provides a robust mechanism for using wave energy efficiently and has been validated through the numerical simulations and physical model experiments of integrated systems. In addition, a comprehensive study and analysis on the coupling dynamic characteristics of the integrated system, as well as the influence of different power take-off (PTO) parameters on the power generation performance of BIWEC are conducted. Furthermore, using the typical wave conditions in the South China Sea (2–10 s wave period and 2 m wave height) as an example, the capture power and capture width ratio of BIWEC under various effective motion strokes and mass ratios are investigated. The research results indicate that the BIWEC has the characteristics of dual resonance frequencies, a wide range of wave frequency capture, and high energy conversion efficiency, and the results of the physical experiments are consistent with those of numerical simulations, validating the reliability of the physical experiments. In the physical experimental tests, the average mechanical efficiency of the BIWEC model is 49.17%. The research results presented in this paper have significant implications for the further promoting of commercialization of WEC.

Electromechanical coupling dynamic characteristics of electric drive system for electric vehicle

Electromechanical coupling dynamic characteristics of electric drive system for electric vehicle

Analysis of electromechanical coupling modal and dynamic response characteristics of permanent magnet gear transmission system considering variable load condition

In order to study the influence of electromagnetic (EM) effect and load change on the modal characteristics and dynamic response of gear transmission system driven by permanent magnet synchronous motor (PMSM), a electromechanical coupling dynamic model is established. The composite air gap permeability coefficient is introduced, and the formula of permanent magnet flux linkage under the influence of space harmonic and cogging effect is derived. The variation laws of gear meshing stiffness and bearing support stiffness under the influence of load change are simulated and analyzed. The natural frequency and vibration modal under different load, flux linkage and PI controller gain are revealed. On this basis, the influence of EM effect and load change on the resonance domain is analyzed through frequency sweep analysis and time domain simulation. Results indicate that the 1st order natural frequency and resonance amplitude will increase with the load, and the influence of PMSM EM excitation will gradually dominate. The increase of the flux linkage and speed loop controller gain Kpω will reduce the 1st order natural frequency. When Kpω =123, a new mode appears, and there is a modal transition between the new mode and mode 1 when Kpω =161. The research results can provide theoretical guidance for improving the transmission performance and structure optimization design of the permanent magnet gear transmission system.

Electromechanical coupling dynamics for a novel non-resonant harmonic piezoelectric motor

Most of the traditional piezoelectric motors are driven by the resonance of piezoelectric ceramics and can achieve a large output torque. However, these motors also have the defects of high speed and difficulty to adjusting the speed when working. To overcome these issues, a novel non-resonant harmonic rotary piezoelectric motor operating at low speed is presented. Electromechanically coupled vibration has a great influence on the dynamic performance of the piezoelectric motor, which may lead to instability of the output performance of the motor. Therefore, the electromechanical coupling dynamic characteristics of the proposed non-resonant piezoelectric motor are studied in this paper. The working principle of the motor is illustrated, and the electromechanical dynamic model and nonlinear dynamic equations are established. Utilizing the dynamic equations, the coupled natural frequencies, amplitude-frequency characteristics, and dynamic responses of the motor are developed. Meanwhile, the influence of parameters on natural frequency and nonlinear response is analyzed. What's more, the natural frequencies of the system are tested by building an experimental platform. Results show the minimum coupled natural frequency of the motor is 11231 rad/s. The length of the piezoelectric stack, the length, and mass block of the harmonic rod have an important influence on the natural frequency of the proposed non-resonant harmonic piezoelectric motor. The nonlinear piezoelectric effect has a larger effect on the forced response amplitude when the excitation frequency is far away from resonance, but a smaller effect on the forced response amplitude when the excitation frequency is near resonance. What's more, the maximum error between the theoretical natural frequencies and the test frequencies is 3%, which verifies the correctness of the theoretical model.

Dynamic characteristics analysis for gear transmission system in shearer cutting section under different loads

Gear transmission system is an important component of the shearer cutting part. The quality of its performance affects the reliable and high-efficiency operation of the whole system. Multi-rigid body and rigid-flexible coupling models were established respectively, and the dynamic analysis is carried out in the virtual simulation software Adams for the gear transmission system of the shearer cutting section. The dynamic characteristics of the gear transmission system under different load conditions were studied. The effects of constant load torque and step load torque on the dynamic characteristics of the drive system are explored. The research results show that the simulation results obtained from the rigid-flexible coupling model of the gear transmission system are closer to the actual operating conditions. It provides a visual means of dynamic analysis, which is more intuitive and convenient. The research methods and results can provide a reference for the further exploration of the electromechanical coupling dynamic characteristics of the motor-gear transmission system.

Dynamic risk assessment for train brake system considering time-dependent components and human factors

The train brake system (TBS) is a critical segment for the safety of train system whose failure can lead to serious consequences. Due to the dynamic and multi-factors coupling characteristics of TBS failure, it is important to construct a comprehensive risk assessment method to capturing the time-dependent and human factors. This paper proposes a model that incorporates degraded components and human factors into dynamic Bayesian networks to formulate dynamic risk assessment for the TBS. In the proposed method, FT is employed to determine the logical structure of the failure process. DBN is used to capture the dynamic features of TBS failure in which the human factors are modelled by the CREAM method and the degraded components are formulated by MC. Meanwhile, different maintenance strategies are considered in the proposed hybrid method. In particular, we evaluate the degradation of four common failures, that is, the insufficient braking, brake test failure, brake release failure, and wheel lock. The risk-influencing factors of the brake system and their relevance are identified. When considering the cause of brake system failure, we analyse the human factors in the system through the reliability analysis method. The results show that the proposed method is able to capture the spatial variability of parameters and simulates the evolution of brake faults in time and space domains. Some practical suggestions are provided to the operators of the system based on the sensitivity analysis.

A Fuzzy-Logic-System-Based Cooperative Control for the Multielectromagnets Suspension System of Maglev Trains With Experimental Verification

A maglev train is a sustainable public transport method with the characteristics of being green, pollution-free, and low-noise, as well as providing environmental protection. However, the performance of existing maglev control strategies for maglev trains may be deteriorated by various challenges, including disregard of the coordination and synchronization between multiple electromagnets, control input unidirectionality, dead zones, saturation, and finite time stability ability, etc. In this paper, an adaptive fuzzy-based suspension control method based on a multi-electromagnets dynamic coupling model is proposed that can cope with dead zone and saturation problems and guarantee the finite-time of the airgap tracking errors of multiple electromagnets simultaneously. Specifically, a fuzzy-logic system (FLS) is utilized to compensate for the nonlinear input unidirectionality, dead zone, saturation and unmodeled dynamics. Moreover, considering the coupling dynamic characteristics of adjacent electromagnet control modules, a fuzzy-based cooperative suspension controller with adaptive update law is designed. The finite time stability of the presented control strategy is proven with the Lyapunov method. Finally, the suspension frame experimental results are illustrated to validate the effectiveness and robustness of the developed method, whose superior performance is shown by being experimentally compared with some baseline methods.

Stability and Sommerfeld effect in a multi-resonant types vibrating system with isolated rigid frame driven by four exciters

The previous studies on the vibrating system with multiple exciters less considered the Sommerfeld effect, which were mainly focused on synchronization and stability problems of the system in the whole resonant region. A dynamical model is proposed in this paper to study the synchronization, stability and the Sommerfeld effect of four exciters in the multi-resonant types vibrating system (MRTVS). In order to improve the power of the system, the vibrating system with two rigid frames is driven by four especially distributed exciters. The motion differential equations of the system are given by Lagrange’s equations, and the dimensionless coupling equations and synchronization criterion are constructed as well by the average method. The theory condition for stability of four exciters in synchronous states is derived from the Hamilton principle. The coupling dynamic characteristics, stability and Sommerfeld effect of the system are discussed numerically. The whole resonant region of the system is divided into three segments by natural frequencies, and the synchronous and stable states in the different resonant types are analyzed respectively. The diversity phenomenon of the nonlinear system is observed, in other words, the system exists multiple stable equilibrium solutions at a certain particular resonant region. Then the Sommerfeld effect around the natural frequencies (NFs) is further revealed. The correctness of theoretical analyses is examined by simulation and the experiment. It’s shown that the reasonable working point in engineering should be selected in the sub-resonant region with respect to the natural frequency of the main vibrating system. The present work can provide theoretical guidance for designing some new types of vibrating machines with high driving power.

Study on Directional Drilling Coupling Dynamics Based on Drill String Rotary Controller

Abstract In the process of long horizontal well in directional drilling, serious contact between drill string and wellbore leads to weight on bit loss. Therefore, this paper proposes a drill string rotary controller (DSC) for directional well, and its function test is completed through the experimental platform. Connected DSC working mechanism, a drill string coupling dynamic model is established under conditions of horizontal well in directional drilling. In the case study, the coupling dynamic characteristics of different units, including drill pipes and bottom-of-hole modules in axial and torsional directions, are studied. The results show that the effective value of drilling rate increases while the axial vibration velocity and amplitude of drill bit decreases. Moreover, in torsional direction, when drill string system is stable state, the rotating angular velocity of different drill pipes, rotary table, and collar is 31.16 rad/s, and the angular velocity of drill bit is 43.19 rad/s, respectively. It indicates the DSC working performance, which enhances the drilling system balance capacity. Overall, different from the sliding friction between wellbore and drill string, the addition of DSC realizes the separation and meshing of drill string and bottom hole modules, which can significantly increase the transition efficiency of weight on bit and torque value. Theoretical and experimental researches prove that the tool can effectively solve the problem of serious weight on bit loss in directional drilling process, and provides a new reference and idea for developing directional drilling technology when facing new challenges.

A modified IHB method for nonlinear dynamic and thermal coupling analysis of rotor-bearing systems

This paper presents a modified incremental harmonic balance (IHB) method to analyze the nonlinear dynamic and thermal coupling characteristics of rotor-bearing systems after thermal balance. The IHB method is modified by tensor contraction and fast Fourier transform (FFT) to efficiently calculate the residual vector and Jacobian matrix. Nonlinear dynamic and thermal full coupling is implemented through the nonlinear part of the Jacobian matrix. The presented method achieves the simultaneous and efficient calculation of the motion and heat balance equations in the frequency domain according to the improvement measures. The effectiveness of the presented method is tested using the vibration response and temperature variation analysis for the coupled thermo-mechanical model of a rotor-ball bearing system. Furthermore, the performance comparisons show the good consistency of results between the presented method and the step-by-step (S-S) method, which is a partitioned iterative solution method for dealing with fully coupled problems in the time domain. The presented method has greater computational efficiency, more accurate temperature prediction, and better recognition of nonlinear phenomena in the system rather than the S-S method. Consequently, the presented method has a broad application prospect in solving fully coupled thermo-mechanical problems of more complex and higher dimensional rotor-bearing systems.

Study on Characteristics of Electromagnetic Interference Caused by Metro Train Movement

With the rapid development of the urban power grid and metro system, their mutual influence has become more and more serious. The dc magnetic bias of the transformer caused by the metro becomes the main research direction. In this paper, the characteristics of dynamic electromagnetic coupling between metro trains and transmission lines are studied. First, the motion equation of the metro is written out according to the running law of the train, and three coupling relations are given according to the position of the train. The calculation method of dynamic induced voltage is deduced. Then the influence of parallel length and distance between the metro and transmission line on induced voltage is studied. The dynamic induction voltage increases first and then decreases with the increase of the parallel length of the metro and transmission line and decreases with the increase of the distance between them. It is proposed that the electromagnetic coupling of a single train has limited influence on the dc magnetic bias of transmission lines, but the influence of dynamic electromagnetic coupling cannot be ignored when multiple trains are running simultaneously.

Research on dynamic coupling characteristics of magnetic fluid and gas medium interface in sealing devices

The widths and shapes of sealing interfaces are key indicators for characterizing the sealing stability of dynamic and static magnetic fluid seals. In this study, the interface of a magnetic fluid seal was numerically simulated and changes in the interfacial shape and width were tested and verified using a magnetic fluid seal device. The results showed that the pressure resistance decreased with an increase in seal clearance, and the magnetic fluid seal interface generated a small leakage channel. Following the complete formation of the leakage channel, the static seal gradually failed. During failure, the interface width of the magnetic fluid became narrow. At a certain pressure, the maximum pressure resistance decreased as a function of the rotational speed. Compared with a static seal, more small leakage channels and bubbles were generated. In constant conditions, such as fixed sealing clearance speed during dynamic and static sealing, the change in the width of the magnetic fluid interface of the dynamic seal was 5–7 times that of the static seal.

Grey-Wolf-Optimization-Algorithm-Based Tuned P-PI Cascade Controller for Dual-Ball-Screw Feed Drive Systems

Dual-ball-screw feed drive systems (DBSFDSs) are designed for most high-end manufacturing equipment. However, the mismatch between the dynamic characteristic parameters (e.g., stiffness and inertia) and the P-PI cascade control method reduces the accuracy of the DBSFDSs owing to the structural characteristic changes in the motion. Moreover, the parameters of the P-PI cascade controller of the DBSFDSs are always the same even though the two axes have different dynamic characteristics, and it is difficult to tune two-axis parameters simultaneously. A new application of the combination of the grey wolf optimization (GWO) algorithm and the P-PI cascade controller is presented to solve these problems and enhance the motion performance of DBSFDSs. The novelty is that the flexible coupling model and dynamic stiffness obtained from the motor current can better represent the two-axis coupling dynamic characteristics, and the GWO algorithm is used to adjust the P-PI controller parameters to address variations in the positions of the moving parts and reflect characteristic differences between the two axes. Comparison of simulation and experimental results validated the superiority of the proposed controller over existing ones in practical applications, showing a decrease in the tracking error of the tool center and non-synchronization error of over 34% and 39%, respectively.

Research on Processing the Feature Model of Converter Station Based on Machine Learning

The current traditional converter station feature model processing method uses switching functions to model converter station equipment, which leads to poor processing results because it ignores the dynamic coupling characteristics between the second harmonics inside the converter station. In this regard, a machine-learning-based switching station feature model processing method is proposed. By combining different terminals to determine their port parameters, constructing the characteristic impedance model of the converter station, using time-domain recursive convolution to calculate the voltage levels at each key point of the AC system, and finally calculating the magnitude as well as the phase angle constants, the time-varying model of the multi-harmonic converter can be fixed. In the experiments, the computational accuracy of the proposed method is verified. The analysis of the experimental results shows that the proposed method has a high component amplitude and excellent computational performance when the characteristic model of the converter station is processed.

Resilience-Mechanism-Based Dynamic Resource Allocation in Dispersed Computing Network

When degradation occurs in a dispersed computing network, mitigating the persistent effects of failures and improving the disposal efficiency is an open problem. However, the occurrence of failed nodes in a dispersed computing network is a random and low-probability incident. Further, the resilient resources for emergency allocation are from devices with complex spatial locations in practice. These factors pose challenges to the resource allocation problem using resilience mechanisms. In this article, we explore and analyze a resilience mechanism for dispersed computing networks as an optimization model. We investigate a resilience-aware dynamic resource allocation model to cope with a degraded dispersed computing network and obtain better emergency response at a lower cost. The uncertainties of node failures are uniquely explored to capture failure nodes more precisely and initiate the resilience mechanism for such nodes. In addition, we propose a novel approach to deal with the dynamic and complex coupling characteristics of decision variables in the model. This approach incorporates the induced artificial fish swarm algorithm with dynamic system simulation to generate and improve the scheme for the allocation of resilient resources. Finally, numerical simulation results verify the improved performance of our model and the effectiveness of the algorithm.

Stability and coupling dynamic characteristics of a vibrating system with double rigid body driven by two motors considering energy balance

The present work mainly focuses the coupling dynamic characteristics and energy transfer relation of the system of double rigid bodies (RBs) driven by two motors, and then explores the ideal working state of the system. The motion differential equations of the system are established by Lagrange equation. Then the energy balance method and Hamilton's principle are employed to deduce the synchronization condition and stability criterion of the system. Then the numeric analyses are introduced to investigate the influence of excitation frequency on the amplitude, stable phase difference and energy of the system. Besides, the accuracy of theoretical research is demonstrated by the computer simulation and experiment. The research results indicate that, the anti-resonance state is the ideal working state of the proposed system; the elastic potential energy between two RBs is suddenly increased owing to the decrement of absolute value of stable phase difference of the system around anti-resonance state, which is used to magnify the relative motion between two RBs and weaken the vibration of the RB2. The results can help us understand the relationship between coupling dynamic characteristics and synchronous behaviors of the system with double RBs from the view of energy transfer.

Coupling dynamic characteristics of high-speed water-entry projectile and ice sheet

An ice sheet on the water surface will affect the water-entry process dynamic characteristics. Therefore, studying the process of high-speed projectiles passing through the ice sheet and entering the water is of great strategic significance. Based on the coupled Eulerian–Lagrangian (CEL) method, this study verifies the accuracy of the numerical solution for the high-speed water entry problem of projectiles. The elastoplastic constitutive model is used to simulate the mechanical behavior of the sea ice. The numerical results are compared with the experimental data to verify the applicability of the material model to the high-speed collision problem. Herein, the conditions of no ice and ice sheet thicknesses of 0.2, 0.6, and 1.0 m are considered. During the high-speed water entry process of projectiles, the evolution of the cavity is analyzed and compared with or without ice. Furthermore, the influence of the ice sheet on the axial load characteristics of the structure is presented. Simultaneously, general conclusions are afforded by observing the formation and propagation of cracks for the three ice sheets with varying thicknesses.

Electromechanical Coupling Dynamic and Vibration Control of Robotic Grinding System for Thin-Walled Workpiece

The robotic grinding system for a thin-walled workpiece is a multi-dimensional coupling system composed of a robot, a grinding spindle and the thin-walled workpiece. In the grinding process, a dynamic coupling effect is generated, while the thin-walled workpiece stimulates elastic vibration; the grinding spindle, as an electromechanical coupling actuator, is sensitive to the elastic vibration in the form of load fluctuations. It is necessary to investigate the electromechanical coupling dynamic characteristics under the vibration coupling of the thin-walled workpiece as well as the vibration control of the robotic grinding system. Firstly, considering the dynamic coupling effect between the grinding spindle and thin-walled workpiece, a dynamic model of the grinding spindle and thin-walled workpiece coupling system is established. Secondly, based on this established coupling dynamic model, the vibration characteristics of the thin-walled workpiece and the electromechanical coupling dynamic characteristics of the grinding spindle are investigated. Finally, a speed adaptive control system for the grinding spindle is designed based on a fuzzy PI controller, which can achieve a stable speed for the grinding spindle under vibration coupling and has a certain suppression effect on the elastic vibration of the thin-walled workpiece at the same time.