Abstract The transient response of the controllable negative stiffness (NS) structures filled with magnetorheological fluids (MRFs) to square-wave magnetic field was investigated experimentally. The dynamic response characteristics of the magnetic field source to step up and step down excitations were measured. The samples of NS structure filled with MRFs were prepared and compressed with a constant speed. The square-wave magnetic field responses of the structures were obtained by controlling the switching time of DC power supply under constant current conditions, and the force displacement envelope curves were formed by experiments with different square-wave starting times. Experimental results indicate that the response of the NS structures to step rising magnetic field can be described by the bi-exponential model with a fast and a slow characteristic time. The fast response characteristic times are consistent with the response times of the magnetic field source to step up excitation, and the variation of pressing force is the dynamic response of MRFs in the structure to step rising magnetic field. The slow response times are tens of times longer than the corresponding fast response times, the reason is that the particles inside MRFs can be structured at the presence of magnetic field with the small shear rate of MRFs during compression slowly which induces the pressure continues to increase. The response times of the NS structures to step falling magnetic field are also essentially identical to the response times of the magnetic field source to step down excitation. The results provide important insights into the dynamic response of controllable NS structures, which can promote the applications in vibration control.

The cross beam of a mining linear vibrating screen is prone to cracking under long-term cyclic load. In order to accurately predict the fatigue life of the cracked cross beam, a coupled analysis method of vibration and crack propagation is proposed. A 2D dynamic model of the vibrating screen is established based on the finite element method, which is verified by the vibration test platform. The cracked Euler beam element is used to model the cracked cross beam. The effects of crack depth, amplitude of excitation force, frequency of excitation force, and crack location on the crack-tip stress intensity factor of the cracked cross beam are investigated in detail. In addition, an iterative method is proposed on the basis of the Paris model. The residual service life of the beam under different frequencies of excitation force, amplitudes of excitation force, spring stiffness, crack positions, and degrees of stiffness imbalance are discussed. The results demonstrate that the fatigue life of the beam increases as the frequency of excitation force and spring stiffness increase. The increase of the amplitude of excitation force and spring permanent deformation reduces the fatigue life. The conclusion obtained provide some theoretical guidance for the design and routine maintenance of mining linear vibrating screens.

In order to further reduce the number of particles in the overflow port of a cyclone clarifier, a cone-plate structure with an equiproportionally varying cone-plate radius is proposed. This includes two structures, namely, an equal–proportional gradually shrinking cone-plate radius and an equal–proportional gradually expanding cone-plate radius. In this paper, numerical simulation is used to comparatively study the flow field characteristics and particle separation inside the traditional equal radius, the gradually shrinking radius, and the gradually expanding radius cone-plate cyclone clarifier. The simulation results show that compared with the traditional equal radius cone-plate structure, the gradual shrinking of the cone-plate structure, due to the bottom of the cone-plate radius being small, can better give full play to the cone-plate settling capacity. The gradually expanding cone-plate cyclone clarifier, due to the bottom of the cone-plate radius being large, results in more fine particles entering the overflow pipe and being discharged from the overflow port. Compared with the traditional cone-plate cyclone clarifier, the gradually shrinking cone-plate cyclone clarifier has a significant increase in the removal efficiency of particles of different sizes than the traditional cyclone clarifier overflow port. The removal efficiency of all particles at the overflow of the gradually shrinking cyclone clarifier was increased by 10.32% compared to the conventional cone-plate cyclone clarifier.

Cross beam fracture is one of the common failures of vibrating screens, and crack is the early manifestation of fracture, which is hard to detect. In order to meet the screening requirement of the vibrating screen and improve the service life of the cracked beam, the cracked Euler-Bernoulli beam model is established to investigate the dynamics of the cross beam with a straight crack under different weights of eccentric block, processing capacities, and Rayleigh damping coefficients based on the finite element method in this paper. The local flexibility coefficients are derived from the principles of fracture mechanics and strain release energy and solved by the adaptive five-point Gaussian Legende algorithm. The stiffness matrix of the cracked beam element is calculated through the inverse method of total flexibility. The four order Runge-Kutta algorithm and MATLAB tools are used to solve the dynamic equation of the cracked cross beam. The relationship between the vibration amplitude of the cracked cross beam and the weight of the eccentric block is studied by fitting formulas using the least squares method. The influence of different weights of eccentric block, processing capacities, and Rayleigh damping coefficients on the vibration amplitude and service life of the cracked beam are discussed. The results show that the greater the weight of the eccentric block, the shorter service life of the beam. When the damping is greater, the service life of the cracked beam is longer.

Vibration displacement is one of the key parameters in fault diagnosis of vibrating screens. Monitoring of acceleration signals of vibrating screens can be disturbed due to various factors such as on-site working conditions and equipment. In order to obtain accurate displacement signals of vibrating screen, the method for converting vibration acceleration to displacement based on improved Savitzky–Golay (S–G) filter is proposed. The Particle Swarm Optimization (PSO) algorithm is used to optimize the window length of the S–G filter with the fixed polynomial. The filters are cascaded to denoise the signals multiple times. The reasonable regularization parameter of the Smoothed Prior Approach (SPA) is calculated to remove the trend item from the acceleration signals. The vibration displacement is obtained by integrating the preprocessed acceleration data in the frequency domain. The results demonstrate that the objectivity of parameter selection of filter is improved, and the denoising effect is significant. The filtering effect of the filter is further improved after cascading. It becomes better as the number of stages of cascade increases. The vibration displacement can be obtained accurately by the proposed method. The vibration test platform is built to verify the correctness of the method.

The wear of motion pair is a common phenomenon in mechanisms and can significantly affect the dynamic behavior of mechanical systems, posing a huge challenge to the precise dynamic modeling and characteristic prediction of mechanisms. The main contribution of this paper is to propose a multi body system dynamic modeling method and dynamic accuracy reliability model for complex multi-link mechanisms considering irregular wear clearance. Firstly, an accurate dynamic model of a six-link mechanism considering irregular wear clearance is established. Secondly, a dynamic accuracy reliability model considering irregular wear clearance is established. Finally, the differences in dynamic response and nonlinear characteristics of the mechanism before and after wear are compared. The different effects of clearance values and driving speed on wear characteristics, dynamic response and nonlinear characteristics are analyzed in detail. The influences of different contact force models on the dynamic response of mechanism considering wear clearance are analyzed. And the dynamic accuracy reliability of the mechanism before and after wear are analyzed. The results show that wear can lead to irregular wear on the shaft and bearing surfaces, leading to an increase in the vibration frequency and peak value of dynamic response. This further reinforces the chaotic characteristics of the mechanism and reduces the kinematic accuracy and stability of the mechanism.

The disturbance factors such as clearance of kinematic pair, irregular wear and elastic deformation of rods are the main factors leading to decline of performance and accuracy of mechanism. For more accurately predict dynamic behavior, an accurate modeling method of nonlinear dynamic of multi-link mechanism (MLM) under the coupling effect of irregular wear clearance and flexible components was proposed. Wear depth of revolute pair is calculated, the shaft and bearing surfaces are reconstructed, and the wear prediction process is coupled with the flexible multi-body dynamic to obtain a rigid-flexible coupling (RFC) dynamic model containing wearing clearances of multiple revolute pairs. The influence of coupling between irregular wear clearance and elastic deformation of components on dynamics of MLM is studied, and chaos phenomena of this mechanism are discriminated. The influence of different clearance sizes and driving speeds on dynamic response and bifurcation diagram of RFC-Mechanism considering wear clearance is studied. A test platform is built for experimental verification. This paper will provide a systematic and perfect theoretical foundation for the research of nonlinear dynamics of high-precision and high-performance multi-link mechanisms.

Revolute clearance and translational clearance often exist in planar mechanisms, which affect accuracy and stability of mechanisms. By using Lagrangian multiplier method, based on the optimized length of each component in the six-bar mechanism, the rigid-body system dynamic equation considering the coupling action of dry friction revolute clearance and translational clearance is established. By using Baumgarte constraint stabilization methodology and combining judgment of contact state at clearance, the general solution strategy of the system dynamic equation considering dry friction revolute and translational clearance is given. The effects of different clearance types on the dynamics of the mechanism are compared and analyzed. Then, chaos phenomena are identified by Poincare map, phase trajectory map and largest Lyapunov exponent. Influence of different friction models on dynamics is studied. The influence of lubrication/dry friction revolute clearance on nonlinear dynamic is analyzed. Influence of various loads on dynamic behavior is analyzed. Effect of various driving speeds on dynamic response and nonlinear characteristic is studied. Finally, correctness of dynamics model dry friction revolute clearance and translational clearance is verified by ADAMS. It is found that the coupling action of clearance affects stability, leading to the decline of performance. Therefore, it is necessary to study dynamics of mechanism with clearance.Kindly check and confirm the corresponding author mail id is correctly identified.it is right

In order to enable quadruped robot to independently adjust its gait planning parameters according to change of terrain without terrain sensing system, a static gait planning method based on GRU（Gate Recurrent Unit） model was proposed. Firstly, a method of generating continuous rectangular trajectory for swing foot was presented, which can ensure swing foot of robot move smoothly to target landing point on unknown terrain. Then, a planning method which can change the trajectory of body by adjusting parameters was proposed. Finally, GRU model and step times of each swing foot are used to realize prediction of the adjustable parameters in body trajectory planning, so that quadruped robot can generate a motion adapted to the change of terrain, and energy consumption and self-stability were considered in motion planning. The experimental results show that the proposed method is correct and effective.

A indirect time-domain coupling dynamic mathematical model of mining vessel–lifting pipe was established by combining the analysis method of mining vessel and lifting pipe in this paper. The vessel–pipe coupling experiments under various wave conditions were performed at the China National Ocean Technology Center, and a dynamic computer simulation of the coupled model was conducted to verify the effectiveness of the experiment and simulation. To simulate the coupling dynamic behavior, we established the hydrodynamic model of the vessel using AQWA software to determine the response amplitude operators (RAOs). Subsequently, the obtained RAO matrix was merged into an OrcaFlex model to analyze the dynamics of the mining vessel–lifting pipe interaction. In addition, the influencing factors of vessel–pipe coupling dynamics were estimated quantitatively, including regular wave, buffer mass, and sailing velocity. The findings show that the coupling effect has a significant impact on the vessel–pipe dynamic behavior, which has a strong relevance with surface waves, but a weak relevance with sailing velocity. In the process of changing the wave direction from 180° to 90°, the tension at the top of the pipeline increases by 19.31% and the coupling time decreases by 66.67%.

In order to research the variation law of the longitudinal resistance coefficient of the ore bin in the marine mining system under different length-diameter ratio, external shape, additional weight and Reynolds number, a set of experimental system for testing the resistance coefficient was designed and built independently. By analyzing the experimental results, it can be seen that under the same conditions, the resistance coefficient decreases gradually with the increase of Reynolds number and finally fluctuates around a certain value. Increasing the excitation displacement will reduce the overall resistance coefficient of the ore bin. The smaller the length-diameter ratio is, the larger the corresponding force value when the vibration acceleration of the ore bin is 0, and the larger the overall resistance coefficient is. The resistance coefficient of the cylindrical section is greater than that of the rectangular shape. In order to reduce the longitudinal vibration and the transverse towing offset, the shape of the ore bin should be cylindrical in actual design and production. At low Reynolds number, the increase of added weight will increase the resistance coefficient, while at high Reynolds number, the change of added weight will not cause the change of resistance coefficient.

In this study, a coal mine water flocculation system was established. A series of flocculation tests were carried out at different structural parameters (cylinder height, cone-plate insertion depth and cone-plate spacing) to better investigate the effect of the cone-plate clarifier on coal mine water treatment performance. Sixteen sampling points were set up in the system for data monitoring to generate the required data. The cone-plate clarifier was divided into five zones for flocculation analysis. The increased cylinder height facilitated the flocculation of particles in the micro flocculation zone and the settling of particles in the settlement zone. The chemicals used are polyaluminum chloride (PACl), Fe3O4 and polyacrylamide (PAM), corresponding to doses of 60 mg/L, 40 mg/L and 6 mg/L, respectively. Insufficient insertion depth of the cone-plate will cause the small flocs that have not been fully flocculated to enter the exit pipe zone directly through the cone-plate, while too much insertion depth will cause the large floc in the settlement zone to re-enter the exit pipe zone. The flocculation effect of small flocs increased as the cone-plate spacing decreased, which is consistent with the shallow pool theory. When the cone plate spacing was too narrow, the amount of fluid was reduced and the increase in fluid velocity reduced the flocculation effect. Curve fitting was conducted for Suspended solids(SS) and turbidity removal efficiency under each structural parameter to derive the variation of SS and turbidity removal efficiency under different structural parameters. The regression models of SS and turbidity removal efficiency on the cylinder height, cone-plate insertion depth and cone-plate spacing were established based on the curve fitting results, and the regression models were verified to be well fitted based on the comparison of experimental results. Finally, the optimal values of SS and turbidity removal efficiency were found based on the regression model. The flow rate of the cone-plate clarifier is 0.6 m3/h. The SS removal efficiency reached 96.82% when the cylinder height was 708 mm, the cone-plate insertion depth was 367 mm and the cone-plate spacing was 26 mm. The turbidity removal efficiency reached 86.75% when the cylinder height was 709 mm, the cone-plate insertion depth was 369 mm and the cone-plate spacing was 26 mm.

为了研究复杂阶梯状扬矿管在采矿船升沉运动和海流作用下的纵向振动特性,利用连续弹性杆振动理论,对5000?m长扬矿管纵向振动性能进行分析.?首先,根据达朗贝尔原理建立扬矿管纵向振动数学模型,采用分离变量法推导管道固有频率方程;然后,进行振型的质量归一化处理;最后,利用ABAQUS软件建立扬矿管有限元模型,对管道的纵向动态响应进行研究.?研究结果表明:扬矿管的一阶纵向共振频率处于矿区海浪能量集中的频带内,随着中间矿仓质量的增加扬矿管固有频率减小,中间矿仓质量对高阶固有频率的影响更加明显;随着海浪频率的增加,纵向振幅、轴向力和轴向应力先增大后减小,并在一阶固有频率时达到峰值,其峰值分别发生在扬矿管5000、0、1000?m处;随着采矿船升沉幅值的增加,扬矿管的动态响应逐渐增大,当升沉幅值大于1.5?m时,扬矿管动态响应的增长速度变缓;扬矿管发生一阶纵向共振时,振动位移和轴向力先增大后作等幅稳态振荡;随着海水深度的增加,沿管长方向的振动幅值逐渐增大,振动平衡位置发生下移,振动响应时间发生延迟,同时轴向力和轴向应力逐渐减小,且轴向应力在每两级阶梯管间急剧变大.

The large-scale retired lithium-ion batteries (LIBs) from electric vehicles provide considerable social, economic, and environmental benefits in echelon utilization compared to the immediate recycling. However, the diversity of retired LIBs in chemistry, packaging, energy density, and manufacturer make it hard to screen and sort for the echelon utilization. Therefore, from a new perspective of parallel configuration, this paper assesses the discharge characteristics of multi-type retired lithium-ion batteries to obtain the screening and regrouping criteria for improving utilization. Firstly, we experimentally study the discharge current and state of charge distributions of different type of packs with retired cells in parallel. According to the results, the mathematical relationship between cell-to-cell parameter and current distribution within parallel-connected cells is unraveled, and find that the slop of open circuit voltage and the product of cell resistance and capacity are the key factors for the inhomogeneities. To further improve utilization of various retired cells, we connect cells with different packing and chemistry in parallel. Results demonstrate that the cells with the same chemistry can be connected in parallel even with different packing and energy density. For the different chemistry, the parallel manner is suitable for combining NMC and NCA, however, not for LMO and NCA. Finally, compared with the traditional methods, the proposed regrouping methodology is validated based on a case study to ensure continuing safety and improve utilization, and find the consistency of resistance is more important than that of capacity for retired cells in parallel.

The revolute pair and translational pair are the two most important kinematic pairs in planar mechanism. Their clearances directly affect the accuracy of planar mechanism. In addition, flexible components will also lead to a certain degree of vibration and shaking of the mechanism, which will seriously affect the stability. In this paper, considering the coupling effect of revolute clearance pair, translational clearance pair and elastic deformation of components, an accurate dynamic modeling method of rigid-flexible coupling multi-link mechanism (MLM) considering revolute clearance and translational clearance is proposed to accurately predict the nonlinear behavior. Clearance models of revolute pair and translational pair are established, the flexible element model is established based on the absolute node coordinate formulation (ANCF), and the nonlinear dynamic equation of rigid-flexible coupling six-bar mechanism considering the clearance of revolute pair and translational pair is built by Lagrange multiplier method (LMD). Dynamic response and chaos identification are researched. Chaos identification is determined qualitatively and quantitatively by phase diagram, Poincaré map and largest Lyapunov exponent. Influences of different clearance values and driving speeds on nonlinear dynamic behavior of mechanism are discussed. Bifurcation diagrams varying with clearance size and driving velocity are studied, respectively. Dynamic modeling method is compared and verified by ADAMS. The experimental platform of six-bar mechanism is built to further verify the correctness of theoretical model.

With the development of high-speed and lightweight mechanisms, and the continuous improvement of manufacturing accuracy requirements in industrial production, clearance joints have increasingly become one of the key factors affecting dynamics performance. Poor clearance will seriously compromise stability, accuracy, and dynamics performance. Based on a genetic algorithm, an efficient modeling methodology for the dynamics optimization of a planar complex multi-link mechanism containing multiple clearance joints is put forward. The model comprises a 2-degree of freedom (DOF) nine-bar mechanism that can be used as the main transmission mechanism of a hybrid drive multi-link press, which is taken as the research object. The optimization objective is to minimize the maximum acceleration of the slider and minimize the difference between the actual central trajectory and the ideal trajectory. By optimizing the quality parameters of key components, an optimal solution for the design parameters is obtained, and the effects of the different optimizations of the objective functions on dynamics response are compared and analyzed. At the same time, a new modeling and calculation methodology of the dynamics accuracy and reliability of a complex multi-link mechanism in terms of multiple clearances is proposed, and the effect of optimization on dynamics accuracy and the reliability of the mechanism is analyzed. Based on the optimization results obtained by taking the minimum difference between the actual center trajectory and the ideal trajectory as an optimization objective, the nonlinear characteristics before and after optimization are analyzed through a phase diagram and Poincaré map. A test platform was built to study the dynamics of the mechanism with clearances. Research not only provides a basis for the dynamics optimization of a multi-link mechanism containing clearances but also provides reference significance for the reliability analysis of a multi-link mechanism containing clearances.

Abstract. A reliable optimization of dynamic vibration absorber (DVA) parameters is extremely important to analyze its dynamic damping characteristics and improve its vibration suppression performance. In this paper, we will discuss a parameter optimization method of the Voigt and three-element DVA models according to the H∞ optimization criterion. The particle swarm optimization method is an effective heuristic optimization algorithm; however, it is easy to lose diversity and fall into local extremum. To solve this problem, the adaptive multiswarm particle swarm optimization (AM-PSO) is used to search the solution of the DVA models. Particles in AM-PSO are adaptively divided into multiple swarms, and the variable substitution learning strategy is utilized to reduce their computational complexity and improve the algorithm's global search capability. In addition, the AM-PSO method is employed to optimize the parameters of DVA models and compared with the genetic algorithm and PSO. The simulation results show that the AM-PSO algorithm has superior performance. Also, the adaptive multiswarm numerical design method discussed herein will push the field towards practical applications, including traditional DVA and related complex three-element DVA.

The pipeline design is one of the important contents of coal preparation plant design. At present, pipeline of coal preparation plant mainly depends on the manual design, which is difficult, time-consuming and difficult to guarantee the quality of pipeline layout. When A* algorithm is applied to the automatic layout of three-dimensional pipeline in coal preparation plant, the searched path does not meet the requirements of pipeline design. In order to solve the above problems, an automatic pipeline layout method for coal preparation plant based on optimized A* algorithm is proposed. Based on the pipeline layout rules of coal preparation plant, the layout space model of coal preparation plant is established. The grid and numerical processing are carried out on the layout space model. Aiming at the problem that the path searched by the A* algorithm has excessive bending, the evaluation function of the A* algorithm is optimized. To solve the problem of the slow search speed of the A* algorithm, dynamic weight are introduced into the evaluation function. Aiming at the problem that the pipeline path searched by the A* algorithm after the above optimization will bypass the required equipment, the direction-oriented strategy is introduced to improve the engineering practicability of pipeline layout. To improve the A* algorithm's operation efficiency, the Open table's array structure is replaced with the minimum binary heap structure. The simulation result shows the following points. ① After optimizing the evaluation function of the A* algorithm, the bending times of the pipeline path are reduced by about 80%. The ben is right angle, which accords with the actual situation of the pipeline layout in the coal preparation plant. After introducing the dynamic weight, the operation efficiency is improved and the path quality can be guaranteed. ② The path length of the pipeline before and after the direction-oriented strategy is introduced has no change. The lengths meet the basic constraint rule of the pipeline layout of the coal preparation plant. After the introduction of the direction-oriented strategy, the pipeline is more likely to be planned near the equipment with specific requirements for the pipeline. And the pipeline has a tendency to be arranged side by side. This indicates that the pipeline layout after the introduction of the direction-oriented strategy meets the requirements of the optimal overall layout, and is more consistent with the coal preparation engineering application. ③ The efficiency of A* algorithm after Open table optimization is improved obviously. The longer the pipeline path and the more obstacles in the middle, the more significant the efficiency improvement of the A* algorithm. The software system of automatic pipeline layout in the coal preparation plant is designed and developed. The application example of the optimized A* algorithm is verified. The results show that the optimized A* algorithm improves the efficiency and quality of piping design in the coal preparation plant, and has better visibility.

This paper analyzes the variation law of the pipe lateral vibration characteristics, it was treated as a beam model, and was dispersed into several subunits based on the FEM. The corresponding stiffness and mass matrix of the pipe was deduced by using Hermite interpolation function, and the overall dynamic balance equation was established. The lateral vibration under different pipe lengths, thicknesses and towing speeds are solved by integral method. The results show that the pipe vibration trend decreases first and then increases, and the vibration value at the ore bin is larger than that at the pump set, and the value at the top is the largest, and the least value location can change with the length increase. Increasing length and thickness can reduce lateral vibration value, while increasing speed can increase the value. Neither the thickness nor the towing speed will change the location where the least value occurs. The vibration intensity will increase with the decrease of pipe length and thickness and the increase of towing speed.

The lifting pipe is a key component of deep sea mining whose dynamic response directly affects the safety of the lifting operation. The objective of this paper was to investigate the effects of heave motion and sailing velocity of mining vessel and the buffer mass on the dynamic response of lifting pipe. First, an equivalent model of the lifting pipe was established, and the natural frequency and dynamic response of the lifting pipe equivalent model were determined with consideration of the wave action by the method of separated variables. Secondly, the reliability of the equivalent model was verified by simulating a 5000 m stepped pipe with OrcaFlex software. Then the dynamic displacement, axial tension, axial stress of the lifting pipe under different sea conditions and sailing velocities were studied, and the main factors affecting the dynamic response of the pipe described. By comparing the simulation results of actual and equivalent models, the equivalent model can be used to analyze the longitudinal vibration characteristics of the lifting pipe. The sailing velocity of the mining vessel has little effect on the dynamic response of the lifting pipe, but the surface wave has a significant effect.