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Abstract Hydraulic vibratory hammer is a key equipment during piling process, and mechanical, hydraulic part of the hammer and workload are coupled with each other during operation. The vibration performance depends on the design parameters and the driving system. In order to investigate the vibration performance, a coupled dynamic model is established for hydraulic vibratory hammer, in which the mechanical model of hammer, hydraulic model for driving, and the model of workload are included. The filed test was carried out to validate the dynamic model under idle and operating conditions. Pressure and flow of the hydraulic driving system and acceleration of the mechanical part were obtained during different test conditions. The results of test and simulation were analyzed in time and frequency domain to validate the coupled dynamic model. Then, effects of different eccentric block parameters on the vibration performance were investigated based on the validated model, including radius, thickness, and angle of the eccentric block. Further the design parameters of optimal vibration performance of the hammer are obtained under the constraints of hammer structure, in which the angle is 90°, thickness is 190 mm, and radius is 175 mm. Article Highlights (1) We established a coupled dynamic model of the hydraulic vibratory hammer, including the mechanical model of hammer, hydraulic model for driving, and the simplified model of workload.; (2) The field test is proceeded to validate the model under idle and operating condition; the dynamic response of the mechanical part and hydraulic driving part is analyzed in time and frequency domain; (3) The performance of the hammer is analyzed with the coupled dynamic model, in which better performance of the hammer is obtained. The model-based method also provides a rapid and economical solution for the performance optimization of the hammer.

This study develops a state evaluation approach for an electro-hydraulic drilling system considering the heterogeneous coal rock and hydraulic system variation, aiming at solving the problems of unclear expression of vital evolution information of drilling mechanical behavior and insufficient ability of stability drilling during the coal pressure relief borehole. A coupled dynamic model combines the coal rock drilling resistance model and the electro-hydraulic drilling system model to describe the drilling characteristics. The state and disturbance observers are designed to estimate the drilling state and disturbances with the help of the relevant drilling measurable signals. The electro-hydraulic drilling system with the designed controller achieves high precision and strong robustness. Numerical simulation analysis and experiments are conducted to verify the observability of the drilling disturbances and tracking errors of the electro-hydraulic drilling system, thereby improving the drilling parameters measurability and tracking performances of the system under heterogeneous coal rock geological conditions. [ABSTRACT FROM AUTHOR]

The current research of robots is mainly developing in lightweight, fast speed and large load. The characteristics of flexible robots are mainly reflected in flexible joints and links. However, flexible joints are often assumed to be simply linear. Since the joint of the planetary reducer also needs to consider the flexible deformation and nonlinearity of the structure, this assumption is not applicable to the assumption of this joint. Therefore, considering coupling properties of the more accurate structure and friction, the joints and the flexible links, a more accurate dynamic model of the flexible robot is established. Furthermore, the accuracy of motion and positioning for the flexible robot under the influence of many factors is analyzed. The research is of great significance for flexible robot control. Firstly, the structure of the two-stage planetary gear reducer is analyzed. Using Newton's Euler and force balance principles, the dynamic model of its joint reducer was constructed. Secondly, taking the Euler–Bernoulli beam as the object, using the Lagrange method and the structural damping formula, the coupling dynamic model of the flexible robot is established. Based on the virtual work and variational principles, the input matrix is further modified by friction. Finally, Using MATLAB and the experiment platform, the validity of the coupling dynamics is verified. And then, taking the flexible deformation, the clearance, and friction of the reducer as the influencing factors, the influence characteristics of the flexible robot are analyzed. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A linear engine generator with a compact double-acting free piston mechanism allows for full integration of the combustion engine and generator, which provides an alternative chemical-to-electrical energy converter with a higher volumetric power density for the electrification of automobiles, trains, and ships. This paper aims to analyse the performance of the integrated engine with alternative permanent magnet linear tubular electrical machine topologies using a coupled dynamic model in Siemens Simcenter software. Two types of alternative generator configurations are compared, namely long translator-short stator and short translator-long stator linear machines. The dynamic models of the linear engine and linear generator, validated with lab-scale prototypes, are applied to investigate the influence of alternative topologies of the generator on system performance. The coupled model will facilitate the early design phase and reveal the optimal match of the key parameters of the engine and generator. Then, experimental tests on an integrated compressor cylinder-generator prototype were successfully performed, and it is shown that this concept is feasible and electrical power and compressed working fluid, such as air, can be generated by this prototype. [ABSTRACT FROM AUTHOR]

This paper provides the dynamic model of an angular-contact ball bearing–elastic rotor system to study its dynamic characteristics when an asymmetric support mode is used. After defining global and local coordinate systems, necessary vectors (such as position, velocity, force and moment vector) are calculated according to the geometric relationship between each part (ball, cage and ring) of the bearing. The interactive forces between each part are obtained based on lubrication theory and Hertz contact theory. A typical rotor is discretized by finite element method (FEM) and each node of the rotor has 5 degrees of freedom (DOFs). Some constraint equations are built to form a coupled dynamic model of angular-contact ball bearing–elastic rotor system. The validity of this coupled model is verified by comparing the numerical results and experimental data. After analyzing the coupled model, it is found that the vibration spectrum of rotor includes the VC (varying compliance) frequencies of two bearings, the bending resonance frequency of rotor and the rotating frequency when the system has asymmetric ball bearings. Moreover, when the preloading forces of bearings increase, the support stiffness becomes larger and the rotor displacement decreases; moreover, the motions of balls and cage become more stable. Generally, the presented coupled model can be applied to analyze the vibration features of all parts in any ball bearing–rotor system comprehensively. [ABSTRACT FROM AUTHOR]

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The flexible manipulato is widely used in the aerospace industry and various other special fields. Control accuracy is affected by the flexibility, joint friction, and terminal load. Therefore, this paper establishes a robot dynamics model under the coupling effect of flexibility, friction, and terminal load, and analyzes and studies its control. First of all, taking the structure of the central rigid body, the flexible beam, and load as the research object, the dynamic model of a flexible manipulator with terminal load is established by using the hypothesis mode and the Lagrange method. Based on the balance principle of the force and moment, the friction under the influence of flexibility and load is recalculated, and the dynamic model of the manipulator is further improved. Secondly, the coupled dynamic system is decomposed and the controller is designed by the multivariable feedback controller. Finally, using MATLAB as the simulation platform, the feasibility of dynamic simulation is verified through simulation comparison. The results show that the vibration amplitude can be reduced with the increase of friction coefficient. As the load increases, the vibration can increase further. The trajectory tracking and vibration suppression of the manipulator are effective under the control method of multi-feedback moment calculation. The research is of great significance to the control of flexible robots under the influence of multiple factors. [ABSTRACT FROM AUTHOR]

A major distinction between the COVID-19 pandemic and previous pandemics is the significant role of social media platforms in shaping public adherence to non-pharmaceutical interventions and vaccine acceptance. The information propagation and individual emotion communication relevant to public health messages have been promoted in the Chinese Sina Microblog, one of the most popular social platforms in China, through two major interaction mechanisms, "commenting" and "forwarding". Here, we develop a hybrid system of macro information propagation dynamics Susceptible-Commenting-Forwarding-Immune model coupled with the micro emotion influence dynamics Hegselmann-Krause model, termed HK-SCFI coupled system, and reveal the mechanisms of individual emotion infection using the commenting and forwarding data (including time point and content) publicly available on public opinion events in the Chinese Sina Microblog. We demonstrate how our data-driven and model-informed analysis can provide quantitative insights into the co-evolution mechanism of individual emotion during information propagation, describe the emergency of emotion clusters, and predict individual emotion evolution trends. Our study shows that multiple interactive mechanisms can facilitate the propagation of public messages and shape public sentiment through online social networks. Our modeling framework can potentially be a tool for designing effective propagation strategies during public health emergencies. • Establish a dynamic modeling framework to analyze the macro information propagation and micro individual emotion evolution. • Consider two unique interaction mechanisms on the social network. • Introduce an individual character as the inherent factor to illustrate the dynamic emotion interaction. • Effective communication strategies are identified for public health emergencies. [ABSTRACT FROM AUTHOR]

Highlights • During crab walking of hexapod, impact forces are generated, whenever the swing leg touches the ground. • Both specific energy consumption and dynamic stability margin decrease with the increase in trunk body velocity. • Specific energy consumption increases but dynamic stability margin decreases with the increase in body height. • Both specific energy and dynamic stability margin increase with the body stroke, lateral offset, crab angle. • Both specific energy consumption and dynamic stability margin increase with the increase in duty factor. Abstract This paper deals with the development of a dynamical model related to crab walking of a hexapod robot to determine the feet forces' distributions, energy consumption and dynamic stability measure considering the inertial effects of the legs on the system, which has not been attempted before. Both forward and inverse kinematic analyses of the robot are carried out with an assigned fixed global frame and subsequent local frames in the trunk body and joints of each leg. Coupled multi-body dynamic model of the robot is developed based on free-body diagram approach. Optimal feet forces and corresponding joint torques on all the legs are determined based on the minimization of the sum of the squares of joint torques, using quadratic programming (QP) method. An energy consumption model is developed to determine the minimum energy required for optimal values of feet forces. To ensure dynamically stable gaits, dynamic gait stability margin (DGSM) is determined from the angular momentum of the system about the supporting edges. Computer simulations have been carried out to test the effectiveness of the developed dynamic model with crab wave gaits on a banking surface. It is observed that when the swing leg touches the ground, impact forces (sudden shoot outs) are generated and their effects are also observed on the joints of the legs. The effects of walking parameters, namely trunk body velocity, body stroke, leg offset, body height, crab angle etc. on power consumption and stability during crab motion for duty factors (DFs) like 1/2, 2/3, 3/4 have also been studied. [ABSTRACT FROM AUTHOR]

Roller groups as the key part of pipe belt conveyor, it forces belt wrapped into round tube in operation. At present, the design of roller mainly through empirical formula, taking bigger safety coefficient to design, which is easily caused some roller premature failure during operation because of the limited load is not reasonable. A type pipe belt conveyor is taken as an example,the coupled dynamic model is set up by considering the conveyor belt elasticity. The contact forces of rollers in constant speed and uniform acceleration are analyzed. Comparing with the rigid dynamic model analysis results,the average value of contact force reduced by approximately 80% ,and the fluctuating value increased about more than four times. It developed the larger alternating load to cause fatigue failure easily. At last,the experiment is taken to verify the coupled model analysis results in constant speed. The conclusions can provide a guidance for dynamic load and fatigue life research in full load operation condition. [ABSTRACT FROM AUTHOR]

Gearbox body flexibility has a great influence on the dynamic response and load sharing among the planetary gears. In this paper, through investigating the coupling boundary conditions between planetary gears transmission subsystem and the gearbox body subsystem, a new dynamic model that integrates gearbox body flexible supporting stiffness is developed to simulate the effects of gearbox body flexibility on the dynamic response and the dynamic load sharing. The numerical results demonstrate that the dynamic transmission error and the dynamic mesh force are obviously lower in the system with the gearbox body flexibility than without it Furthermore, peak position also gradually moves towards to the lower frequency when gearbox body flexibility is included. In addition, the dynamic loading factor tends to be decreased when gearbox body flexibility is taken into account, which is also verified by experiments conducted on a planetary gear test rig. [ABSTRACT FROM AUTHOR]

Aimed at the vibration of whole aero-engine, a coupled dynamic model of rotor-ball bearing-stator of aero-engine is built. By means of the lumped mass method, taking into account the nonlinear rub-impact, bearing failure force and deformation of the casing, the dynamic equation of the system containing typical rub-impact is derived. The response of the system under different conditions is obtained by using the fourth order Runge-Kutta numerical integration algorithm. By adopting the finite element analysis software ANSYS, the finite element model of the rotor shaft is established and the first six-order natural frequencies of the rotor system are acquired. Taking advantage of the parameters of the signal in time domain and frequency domain, frequency characteristics are extracted as the fault features. The single-point rubbing experiment is carried out in the test rig, and the working speed is higher than the first critical speed, so the rotor shaft is flexible rotor. By the methods of spectrum and cepstrum analysis, the rub-impact characteristics of the casing vibration acceleration time series data are analyzed. The results show that the casing vibration acceleration has obvious impact characteristics; the impact frequency is equal to the product of rotating frequency and number of the blades; the impact frequency component and its multiple-frequencies are demonstrated in the frequency spectrum; the strength of impact is modulated by the rotating frequency, so that there are families of side bands on impact frequency and both sides of frequency doubling, and the interval of sideband equals the rotating frequency. The frequency components of the rotating frequency and its frequency doubling are clearly shown in the cepstrum. By comparing the simulation and experiment, the rubbing characteristics found out in this paper has enough accuracy. [ABSTRACT FROM AUTHOR]

The winter North Atlantic Oscillation (NAO) is a crucial part of our understanding of Eurasian and Atlantic climate variability and predictability. In this study, we developed effective prediction schemes based on the interannual increment prediction method and verified their performance based on the climate hindcasts of the coupled ocean--atmosphere climate models. This approach utilizes the year-to-year increment of a variable (i.e. a difference in a variable between the current year and the previous year, e.g. DY of a variable) as the predictand rather than the anomaly of the variable. The results demonstrate that the new schemes can generally improve prediction skill of the winter NAO compared to the raw coupled model's output. Also, the new schemes show higher skill in prediction of abnormal NAO cases than the climatological prediction. Scheme-I uses just the NAO in the form of year-to-year increments as a predictor that is derived from the direct outputs of the models. Scheme-II is a hybrid prediction model that contains two predictors: the NAO derived from the coupled models and the observed preceding autumn Atlantic sea surface temperature in the form of year-to-year increments. Scheme-II shows an even better prediction skill of the winter NAO than Scheme-I. [ABSTRACT FROM AUTHOR]

The floating foundation is designed to support a 1.5 MW wind turbine in 30 m water depth. With consideration of the viscous damping of foundation and heave plates, the amplitude-frequency response characteristics of the foundation are studied. By taking into account the elastic effect of blades and tower, the classic quasi-steady blade-element/momentum (BEM) theory is used to calculate the aerodynamic elastic loads. A coupled dynamic model of the turbine-foundationmooring lines is established to calculate the motion response of floating foundation under Kaimal wind spectrum and regular wave by using the FAST codes. The model experiment is carried out to test damping characteristics and natural motion behaviors of the wind turbine system. The dynamics response is tested by considering only waves and the joint action of wind and waves. It is shown that the wind turbine system can avoid resonances under the action of wind and waves. In addition, the heave motion of the floating foundation is induced by waves and the surge motion is induced by wind. The action of wind and waves is of significance for pitch. [ABSTRACT FROM AUTHOR]

This investigation was primarily to establish assessment criteria for axial fluctuations of head sheaves in a multi-rope friction mine hoist. Large axial fluctuating displacements of head sheaves can excite intense transverse vibrations in inclined ropes, which can result in dangerous collision between two adjacent ropes. A coupled dynamic model was established and then validated by experimental tests and numerical simulations. In this case, it can be concluded that double rotational frequency of head sheave is the primary excitation frequency and rope tension can change the resonance frequency range. Finally, to avoid large transverse displacements of inclined ropes in a multi-rope friction hoist, based on response–excitation displacement curves, assessment criteria for axial fluctuating displacements of head sheaves were established. [ABSTRACT FROM AUTHOR]

A full time-domain two-dimensional (2-D) numerical model was established for the coupled dynamic analysis of submerged floating tunnel (SFT) structures. For hydrodynamic loads, a second-order time-domain potential flow numerical model was developed and a higher-order boundary element method (HOBEM) was applied to discretize the body boundary and the free surface boundary. The elastic rod theory was used to analyse the cable force to the SFT. Hinged boundary conditions were used at the junction of the mooring line and the structure. The viscous damping coefficient of the submerged cylinder was obtained through a decay physical model test, which was employed in the numerical simulation. In the coupled dynamic analysis, the motion equation for the hull and dynamic equations for the mooring lines were solved simultaneously using the Newmark- β method. The coupled analysis numerical model was applied in an SFT simulation with waves of different frequencies. The influences of viscous damping, buoyancy weight ratios (BWRs), and mooring stiffness distributions on the first- and second-order motion responses and tension of the mooring lines are analysed in detail, and some significant conclusions are presented. • A second-order coupled numerical model is developed to investigate the wave-SFT-mooring system under wave action in time domain. • A decay test is conducted to calculate the viscous damping coefficient of the submerged cylinder, which is employed in the numerical simulation. • The viscous damping weakens the resonance effect induced by the natural frequency of the structure. • The BWR has a great influence on the tension of the mooring system, and a smaller BWR is recommended here. • In the investigation of mooring stiffness effect on the motion response, the stiffness of the inclined anchor chain is recommended to be larger than that of the vertical one. [ABSTRACT FROM AUTHOR]