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Multi-Channel Force Control System for Static Loading
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作者 陈彩可 王军政 +1 位作者 马立玲 李金仓 《Journal of Beijing Institute of Technology》 EI CAS 2003年第S1期1-6,共6页
An eight-channel force loading system is presented, which adopts position control system and force control system switching model, small flow servo valve controlled capacious cylinder system scheme, intelligent PID al... An eight-channel force loading system is presented, which adopts position control system and force control system switching model, small flow servo valve controlled capacious cylinder system scheme, intelligent PID algorithm and distributed load approach. Through the analyses of the equivalent model of valve controlled cylinder force subsystem, a controller based on intelligent PID algorithm is designed, which is not sensitive to the variation of parameters such as environmental stiffness. According to the coupling of multiple load channels, a distributed load approach is employed in the superior monitor computer. Experimental results show that the system designed has high precision and robustness. 展开更多
关键词 electro-hydraulic servo loading system static force loading force control
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Theoretical study of the nonlinear force-loading control in single-molecule stretching experiments
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作者 Xingyu Qi Zilong Guo +1 位作者 Shimin Le Hu Chen 《Communications in Theoretical Physics》 SCIE CAS CSCD 2024年第4期167-175,共9页
Force spectrum measurements with constant loading rates are widely used in single-molecule manipulation experiments to study the mechanical stability and force response of biomolecules.Force-dependent transition rates... Force spectrum measurements with constant loading rates are widely used in single-molecule manipulation experiments to study the mechanical stability and force response of biomolecules.Force-dependent transition rates can be obtained from the transition force distribution,but it is limited to the force range with non-zero force distribution.Although constant loading rate control can be realized with magnetic tweezers,the loading rate range is limited due to the slow movement of permanent magnets.Non-linear exponential and exponential squared force loading functions are more feasible in magnetic tweezers,while there is no theoretical result available for these two kinds of non-linear force loading functions.In this study,we solved the unfolding process of a protein following Bell's model under nonlinear exponential and exponential squared force loading functions,which offer a broader range of unfolding force distribution compared to the traditional constant loading rate experiments.Furthermore,we derived two force loading functions,which can produce uniform unfolding force distribution.This research contributes fundamental equations for the analysis of experimental data obtained through single-molecule manipulation under nonlinear force loading controls,paving the way for the use of nonlinear force control in magnetic tweezer experiments. 展开更多
关键词 single-molecule manipulation magnetic tweezers force loading transition rates force distribution
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Cumulative Deformation of Soft Clay Under Cyclic Loading 被引量:3
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作者 Yan, Shuwang Yan, Chi Zhang, Jianguo 《China Ocean Engineering》 SCIE EI 1993年第3期341-348,共8页
Reconstituted specimens are prepared by means of vacuum preloading. Both static and cyclic triaxial tests are carried out, with the specimens consolidated under different principal stress ratios. A finite element meth... Reconstituted specimens are prepared by means of vacuum preloading. Both static and cyclic triaxial tests are carried out, with the specimens consolidated under different principal stress ratios. A finite element method is put forward for calculating the cumulative deformation of soft clay under cyclic loading. 展开更多
关键词 DEFORMATION Finite element method Loads (forces) Materials testing Ocean engineering Pore pressure Specimen preparation Stresses
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Force Control Compensation Method with Variable Load Stiffness and Damping of the Hydraulic Drive Unit Force Control System 被引量:10
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作者 KONG Xiangdong BA Kaixian +3 位作者 YU Bin CAO Yuan ZHU Qixin ZHAO Hualong 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2016年第3期454-464,共11页
Each joint of hydraulic drive quadruped robot is driven by the hydraulic drive unit(HDU), and the contacting between the robot foot end and the ground is complex and variable, which increases the difficulty of force... Each joint of hydraulic drive quadruped robot is driven by the hydraulic drive unit(HDU), and the contacting between the robot foot end and the ground is complex and variable, which increases the difficulty of force control inevitably. In the recent years, although many scholars researched some control methods such as disturbance rejection control, parameter self-adaptive control, impedance control and so on, to improve the force control performance of HDU, the robustness of the force control still needs improving. Therefore, how to simulate the complex and variable load characteristics of the environment structure and how to ensure HDU having excellent force control performance with the complex and variable load characteristics are key issues to be solved in this paper. The force control system mathematic model of HDU is established by the mechanism modeling method, and the theoretical models of a novel force control compensation method and a load characteristics simulation method under different environment structures are derived, considering the dynamic characteristics of the load stiffness and the load damping under different environment structures. Then, simulation effects of the variable load stiffness and load damping under the step and sinusoidal load force are analyzed experimentally on the HDU force control performance test platform, which provides the foundation for the force control compensation experiment research. In addition, the optimized PID control parameters are designed to make the HDU have better force control performance with suitable load stiffness and load damping, under which the force control compensation method is introduced, and the robustness of the force control system with several constant load characteristics and the variable load characteristics respectively are comparatively analyzed by experiment. The research results indicate that if the load characteristics are known, the force control compensation method presented in this paper has positive compensation effects on the load characteristics variation, i.e., this method decreases the effects of the load characteristics variation on the force control performance and enhances the force control system robustness with the constant PID parameters, thereby, the online PID parameters tuning control method which is complex needs not be adopted. All the above research provides theoretical and experimental foundation for the force control method of the quadruped robot joints with high robustness. 展开更多
关键词 quadruped robot force control system hydraulic drive unit force control compensation method variable load stiffness and damping simulation
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Test Study on Current Force on Mooring Ships 被引量:1
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作者 Zhang, Furan Zhao, Jun Zhang, Xueqin 《China Ocean Engineering》 SCIE EI 1993年第2期225-242,共18页
In respect of an offshore berthing pillar, the test study result of current force acting on mooring ships is described in this paper. Empirical and semi-empirical relationships of current force coefficient are given a... In respect of an offshore berthing pillar, the test study result of current force acting on mooring ships is described in this paper. Empirical and semi-empirical relationships of current force coefficient are given according to the angle between the flow direction and the ship's longitudinal axis, which are coincident with the result of theoretical analysis. 展开更多
关键词 Flow of water Loads (forces) Mathematical models Numerical methods Ocean currents Ship models SHIPS
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NON-LINEAR DYNAMIC BEHAVIOR OF THERMOELASTIC CIRCULAR PLATE WITH VARYING THICKNESS SUBJECTED TO NONCONSERVATIVE LOADING 被引量:2
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作者 WANG Zhongmin GAO Jingbo +1 位作者 LIHuixia LIU Hongzhao 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2008年第5期65-69,共5页
The non-linear dynamic behaviors of thermoelastic circular plate with varying thickness subjected to radially uniformly distributed follower forces are considered. Two coupled non-linear differential equations of moti... The non-linear dynamic behaviors of thermoelastic circular plate with varying thickness subjected to radially uniformly distributed follower forces are considered. Two coupled non-linear differential equations of motion for this problem are derived in terms of the transverse deflection and radial displacement component of the mid-plane of the plate. Using the Kantorovich averaging method, the differential equation of mode shape of the plate is derived, and the eigenvalue problem is solved by using shooting method. The eigencurves for frequencies and critical loads of the circular plate with unmovable simply supported edge and clamped edge are obtained. The effects of the variation of thickness and temperature on the frequencies and critical loads of the thermoelastic circular plate subjected to radially uniformly distributed follower forces are then discussed. 展开更多
关键词 Non-linear vibration Circular plate with varying thickness Thermal loading Follower force Shooting method
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Operator health risk evaluation of off-highway dump truck under shovel loading condition 被引量:1
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作者 申焱华 许敏 +2 位作者 金纯 高玉 魏福林 《Journal of Central South University》 SCIE EI CAS CSCD 2015年第7期2655-2664,共10页
To evaluate the operator health risk exposed to whole-body vibration(WBV) while the electric-shovel loads the ore on the truck body, the semi-truck mathematical model and 3-D virtual prototype were built to simulate t... To evaluate the operator health risk exposed to whole-body vibration(WBV) while the electric-shovel loads the ore on the truck body, the semi-truck mathematical model and 3-D virtual prototype were built to simulate the high shockwave of truck cab under the shovel loading. Discrete element method was utilized to accurately estimate the impacting force on the truck body. Based on the ISO 2631-5 criteria, the Sed is about 0.56 MPa in both models, which means that the dump operators have a high probability of adverse health effects over long-term exposure to these vibrations. The 4-DOF operator model was built to investigate the biodynamic response of seated-human body exposed to WBV in terms of the transmission of vibrations through the body. The results show that the response peak is in the frequency range of 4-6 Hz corresponding to the primary body resonant frequency. 展开更多
关键词 dump truck loading operation impacting force discrete element method
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ITERATIVE COMPUTATION METHOD FOR NONLINEAR FORCED VIBRATION EQUATION ON HELICOPTER MAIN ROTOR LOAD
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作者 Liu Xiangjian Shen Xinkang Xue Zhengzhong( Chinese Helicopler Rcsearch and Development institute,Jindezhen , China, 333001 ) 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 1995年第1期22-28,共7页
ITERATIVECOMPUTATIONMETHODFORNONLINEARFORCEDVIBRATIONEQUATIONONHELICOPTERMAINROTORLOADLiuXiangjian;ShenXinka... ITERATIVECOMPUTATIONMETHODFORNONLINEARFORCEDVIBRATIONEQUATIONONHELICOPTERMAINROTORLOADLiuXiangjian;ShenXinkang;XueZhengzhong(... 展开更多
关键词 rotary wings vibration effects load (forces) iterative solution
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Dynamic Response Analysis of Risers Subjected to Combined Wave and Current Loading
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作者 Nie, Wu Yu, Xiukun +1 位作者 Ma, Chunyan Li, Weiyang 《China Ocean Engineering》 SCIE EI 1993年第2期147-156,共10页
A dynamic response analysis in the frequency domain is presented for risers subjected to combined wave and current loading. Considering the effects of current, a modified wave spectrum is adopted to compute the linear... A dynamic response analysis in the frequency domain is presented for risers subjected to combined wave and current loading. Considering the effects of current, a modified wave spectrum is adopted to compute the linearized drag force. An additional drag force convolution term is added to the linearized drag force spectrum, therefore the error is reduced which arises from the truncation of higher order terms in the drag force auto-correlation function. An expression of linearized drag force spectrum is given taking the relative velocity into account. It is found that the additional term is a fold convolution integral. In this paper dynamic responses of risers are investigated, while the influence of floater motion on risers is considered. The results demonstrate that the accuracy of the present method reaches the degree required in time domain analysis. 展开更多
关键词 Drag Dynamic loads Dynamic response Frequency domain analysis Loads (forces) Ocean currents Spectrum analysis Time domain analysis VELOCITY Water waves
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Development of the artificial seabed technology and implementation pretrial well in the South China Sea 被引量:3
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作者 郭永峰 纪少君 唐长全 《Journal of Marine Science and Application》 2009年第3期246-251,共6页
This paper introduces the recent highly significant activity of China Oilfield Services Ltd. (COSL) in the South China Sea, where COSL conducted pretrial drilling in June of 2008. The paper discusses some key resear... This paper introduces the recent highly significant activity of China Oilfield Services Ltd. (COSL) in the South China Sea, where COSL conducted pretrial drilling in June of 2008. The paper discusses some key research and new practices which led to the fabrication of related equipment which was evaluated in the trial. The market for deepwater drilling in the world has grown over the past 10 years but there are few drilling vessels or platforms suitable for drilling in deepwater or super deepwater. China needs equipment capable of deepwater drilling operations. COSL has some semisubmersible platforms, but they are only considered suitable for operations in water depths less than 475 m. An enabling technology, referred to as an artificial seabed, has been under development by COSL since 2004, and it applies the research results and experiences of many experts in deepwater drilling. COSL hopes this technology will allow drilling to depths of approximately 1 000-1 500m with its current platforms. The paper presents research progress and improvements in fabrication and necessary upgrades to equipment for extending deepwater drilling. The pretrial well was executed at a water depth of nearly 500m. COSL will drill the trial well around 2009 at the same location in the South China Sea. 展开更多
关键词 deep water artificial buoyancy seabed model test maximum loading forces pretrial well
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Experimental study and calculation of flexural capacity of RC beams strengthened with GFRP sheets
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作者 王文炜 李果 《Journal of Southeast University(English Edition)》 EI CAS 2004年第2期229-234,共6页
Nine reinforced concrete (RC) beams strengthened by glass fiber reinforced polymer (GFRP) sheets and three control beams are tested. Four parameters are considered in this experimental program included the concrete st... Nine reinforced concrete (RC) beams strengthened by glass fiber reinforced polymer (GFRP) sheets and three control beams are tested. Four parameters are considered in this experimental program included the concrete strength, the reinforcement ratio, the number of GFRP sheets, and the shear span ratio. It is shown that the application of GFRP sheets can increase the ultimate flexural capacity. The effect of the concrete strength, the reinforcement ratio and the number of GFRP sheets on load capacity is obvious. The shear span ratio can affect the failure mode of RC beams strengthened by GFRP sheets. A theoretical model for flexural behavior of the strengthened RC beam is also developed. 展开更多
关键词 Bending (deformation) Glass fibers Loads (forces) Reinforced concrete
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Characteristic Aerodynamic Loads and Load Effects on the Dynamics of a Floating Vertical Axis Wind Turbine 被引量:1
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作者 Zhengshun Cheng Puyang Zhang 《Transactions of Tianjin University》 EI CAS 2017年第6期555-561,共7页
The development of offshore wind farms in deep water favors floating wind turbine designs, but floating horizontal axis wind turbines are facing the challenge of high cost of energy (CoE). The development of innovativ... The development of offshore wind farms in deep water favors floating wind turbine designs, but floating horizontal axis wind turbines are facing the challenge of high cost of energy (CoE). The development of innovative designs to reduce the CoE is thus desirable, such as floating vertical axis wind turbines (VAWTs). This study demonstrates the characteristics of aerodynamic loads and load effects of a two-bladed floating VAWT supported by a semi-submersible platform. Fully coupled simulations are performed using the time-domain aero-hydro-servo-elastic code SIMO-RIFLEX-AC. It is found that thrust, lateral force, and aerodynamic torque vary considerably and periodically with the rotor azimuth angle. However, the variation in the generator torque can be alleviated to some extent by the control strategy applied. Moreover, the variations of platform motions and tensions in the mooring lines are strongly influenced by turbulent winds, whereas those of tower-base bending moments are not. The tower-base bending moments exhibit notable two-per-revolution (2P) response characteristics. © 2017 Tianjin University and Springer-Verlag GmbH Germany 展开更多
关键词 Aerodynamic loads AERODYNAMICS Bending moments Loads (forces) Mooring cables Offshore wind farms Wind power
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Investigation of Micro-mechanical Response of Asphalt Mixtures by a Three-dimensional Discrete Element Model 被引量:1
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作者 侯曙光 ZHANG Dong +1 位作者 HUANG Xiaoming ZHAO Yongli 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2015年第2期338-343,共6页
The micro-mechanical response of asphalt mixtures was studied using the discrete element method. The discrete element sample of stone mastic asphalt was generated first and the vehicle load was applied to the sample. ... The micro-mechanical response of asphalt mixtures was studied using the discrete element method. The discrete element sample of stone mastic asphalt was generated first and the vehicle load was applied to the sample. A user-written program was coded with the FISH language in PFC3 D to extract the contact forces within the sample and the displacements of the particles. Then, the contact forces within the whole sample, in asphalt mastic, in coarse aggregates and between asphalt mastic and coarse aggregates were investigated. Finally, the movement of the particles in the sample was analyzed. The sample was divided into 15 areas and a figure was drawn to show how the balls move in each area according to the displacements of the balls in each area. The displacements of asphalt mastic balls and coarse aggregates were also analyzed. The experimental results explain how the asphalt mixture bears vehicle load and the potential reasons why the rutting forms from a micro-mechanical view. 展开更多
关键词 asphalt mixture discrete element method micro-mechanical response vehicle load contact force displacement
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Local Joint Flexibility Multibrace Tubular Joints
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作者 Chen, Tieyun Zhang, Huiyuan 《China Ocean Engineering》 SCIE EI 1993年第2期125-138,共14页
The local joint flexibility matrix of multibrace tubular joints (uniplanar and multiplanar joints) is defined. The formulation for computing the elements of local flexibility factor matrix of multibrace tubular joints... The local joint flexibility matrix of multibrace tubular joints (uniplanar and multiplanar joints) is defined. The formulation for computing the elements of local flexibility factor matrix of multibrace tubular joints by semi-analytic method is presented in this paper. The stiffening effect of unloaded braces and cross-flexibility between braces are discussed. Using the local flexibility of unibrace joints instead of that of multibrace joints in conventional structural analysis will lead the result to an unsafe side. 展开更多
关键词 DEFORMATION Flexible structures Loads (forces) Mechanical properties Numerical methods Production platforms Structural analysis
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Three-Dimensional Thermal-Stress Analysis of Semi-infinite Transversely Isotropic Composites
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作者 TOKOVYY Yuriy BOIKO Dmytro GAO Cunfa 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI CSCD 2021年第1期18-28,共11页
By making use of the direct integration method,an exact analysis of the general three-dimensional thermoelasticity problem is performed for the case of a transversely isotropic homogeneous half-space subject to local ... By making use of the direct integration method,an exact analysis of the general three-dimensional thermoelasticity problem is performed for the case of a transversely isotropic homogeneous half-space subject to local thermal and force loadings.The material plane of isotropy is assumed to be parallel to the limiting surface of the halfspace.By reducing the original thermoelasticity equations to the governing ones for individual stress-tensor components,the effect of material anisotropy in the stress field is analyzed with regard to the feasibility requirement,i.e.,the finiteness of the stress field at a distance from the disturbed area.As a result,the solution is constructed in the form of explicit analytical dependencies on the force and thermal loadings for various kinds of transversely isotropic materials and agrees with the basic principles of the continua mechanics.The solution can be efficiently used as a benchmark one for the direct computation of temperature and thermal stresses in transversely isotropic semi-infinite domains,as well as for the verification of solutions constructed by different means. 展开更多
关键词 three-dimensional problem analytical solution transversely isotropic composites semi-infinite model force and thermal loadings finite stress distributions
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Structural Analysis of Platforms with the Effect of Joint Flexibility
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作者 Mu, Yang Zhang, Shengkun 《China Ocean Engineering》 SCIE EI 1993年第3期243-252,共10页
A modified space beam element is presented in this paper to consider the local joint flexibility of T, Y tubular joints subjected to axial forces and in-plane bending moments for analysis of platforms. Two numerical e... A modified space beam element is presented in this paper to consider the local joint flexibility of T, Y tubular joints subjected to axial forces and in-plane bending moments for analysis of platforms. Two numerical examples are shown to verify the efficiency and validity of the method presented here. 展开更多
关键词 Bending (deformation) Joints (structural components) Loads (forces) Mathematical models Ocean engineering Structural analysis WELDS
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STUDY ON ACTIVE CONTROL FOR A FLEXIBLE BEAM UNDER THE CONDITION OF ZERO GRAVITY
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作者 员超 宗光华 张启先 《Chinese Journal of Aeronautics》 SCIE EI CSCD 2000年第1期51-58,共8页
The system of coupling structure with controlling is a kind of dynamic feedback system in which the mechanical load and the actuator/controller interact. The mechanical system and the control system can be considered ... The system of coupling structure with controlling is a kind of dynamic feedback system in which the mechanical load and the actuator/controller interact. The mechanical system and the control system can be considered integrally as a close system, and the driving forces actuating the mechanical load can be taken as inner forces in the coupling structure system with controlling. Therefore, one can use the method for dealing with conservative systems to simplify greatly modeling and analyses. The relative equilibrium state of motion of the flexible beam under the condition of zero gravity is studied by using the energy method, in which the characteristics of structure and controlling are considered synthetically. And further, the stability conditions for the relative equilibrium state of the system have been found. If the stability conditions are used as controlling parameters of motion of the system, the kinetic energy of the flexible beam can be converted advantageously into the electromagnetic energy of the motor and controller as well as the vibration of the flexible structure can be reduced rapidly. The results in the research provide a kind of very simple and effective real-time control method reducing the vibration of the flexible beam. The method has been verified in many kinds of experimental systems of flexible beams. 展开更多
关键词 Actuators Control systems Feedback control GRAVITATION Kinetic energy Loads (forces) Motion control Numerical methods System stability Vibration control
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EXPERIMENTAL STUDIES ON DYNAMIC PROPAGATION OF CRACKS UNDER BIAXIAL COMPRESSION
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作者 Yu, Hengwen Song, Jinliang +1 位作者 Feng, Deyi Jian, Chun 《Acta Mechanica Solida Sinica》 SCIE EI 1994年第3期211-220,共10页
This paper deals with the initiation and non-coplaner propagation of cracks under biaxial compression. The running process of the propagating cracks is successfully recorded with the method of dynamic photoelasticity.... This paper deals with the initiation and non-coplaner propagation of cracks under biaxial compression. The running process of the propagating cracks is successfully recorded with the method of dynamic photoelasticity. A series of important fracture parameters such as cracks propagating velocity, critical opening loading and initial angle of cracks growth under biaxial compression is calculated. Results show that the stress field in front of the non-closed crack tip under biaxial compression is a mixed-mode singular field, the dynamic propagation of the new tensile cracks is just stable and shows distinct stages, but the unstable crack appears under high loads and results in the rupture of the matrix. 展开更多
关键词 Failure (mechanical) FRACTURE Fracture mechanics Loads (forces) PHOTOELASTICITY Stability Stresses VELOCITY
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DAMAGE ANALYSIS BY BOUNDARY ELEMENT METHOD
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作者 Z.Z.Cen G.Swoboda F.Ito 《Acta Mechanica Solida Sinica》 SCIE EI 1994年第3期245-255,共11页
The response of cracked bodies subjected to loading was investigated by the boundary element method in this paper. The two-law elastic-cohesive-softening model was used for crack propagation analysis. The interface co... The response of cracked bodies subjected to loading was investigated by the boundary element method in this paper. The two-law elastic-cohesive-softening model was used for crack propagation analysis. The interface conditions for uncracked, craze, open crack, adhesive crack and slid crack parts were discussed and the corresponding incremental iteration algorithm was given. A simplified damage propagation model was presented. The technique has been applied to some specific examples which give the evidence that the method is satisfactory and efficient. 展开更多
关键词 ALGORITHMS Boundary element method Crack propagation Cracks Dynamic response ELASTICITY Fracture mechanics Interfaces (materials) Iterative methods Loads (forces) Mathematical models
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Implementation of Particle Swarm Optimization Algorithm in Matlab Code for Hyperelastic Characterization
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作者 Talaka Dya Bale Baidi Blaise +1 位作者 Gambo Betchewe Mohamadou Alidou 《World Journal of Mechanics》 2021年第7期146-163,共18页
The purpose of this paper is to demonstrate the applicability of Particle Swarm Optimization algorithm to determine material parameters in incompressible isotropic elastic strain-energy functions using combined tensio... The purpose of this paper is to demonstrate the applicability of Particle Swarm Optimization algorithm to determine material parameters in incompressible isotropic elastic strain-energy functions using combined tension and torsion loading. Simulation of rubber behavior was conducted from the governing equations of the deformation of a cylinder composed of isotropic hyperelastic incompressible materials. Four different forms of strain-energy function were considered based respectively on polynomial, exponential and logarithmic terms to reproduce load force (N) and torque (M) trends using natural rubber experimental data. After highlighting the minimization of the objective function generated in the fitting process, the study revealed that a particle swarm optimization algorithm could be successfully used to identify the best material parameters and characterize the behavior of rubber-like hyperelastic materials. 展开更多
关键词 Particle Swarm Optimization Hyperelastic Models Tension-Torsion Test Load force Torsional Couple
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