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RSS2014 Vol. 33, No. 2
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2014, 33(2): 157-163.
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Abstract:
High speed earth missiles are modeled by slender elastic bars. A straight bar with one end applied by a half-sine impulse was studied by adopting a simple mechanical model and simplified boundary conditions. Missiles impacting rigid targets were simulated with LS-DYNA to study the dynamic response. The relation between the stress wave propagation and the acceleration of missiles was analyzed. The acceleration distribution of the missiles over the impacting direction was also investigated. The results show that there exists a large difference between the centroid acceleration of a rigid body and the true value when missiles strike targets. The measured data should be reasonably processed according to the different purposes. The plastic deformation of missiles causes the propagation of plastic stress wave and energy dissipatio, nwhich obviously affects the acceleration distribution on missile, sthe peak values on the acceleration versus time curves are largely reduced.
High speed earth missiles are modeled by slender elastic bars. A straight bar with one end applied by a half-sine impulse was studied by adopting a simple mechanical model and simplified boundary conditions. Missiles impacting rigid targets were simulated with LS-DYNA to study the dynamic response. The relation between the stress wave propagation and the acceleration of missiles was analyzed. The acceleration distribution of the missiles over the impacting direction was also investigated. The results show that there exists a large difference between the centroid acceleration of a rigid body and the true value when missiles strike targets. The measured data should be reasonably processed according to the different purposes. The plastic deformation of missiles causes the propagation of plastic stress wave and energy dissipatio, nwhich obviously affects the acceleration distribution on missile, sthe peak values on the acceleration versus time curves are largely reduced.
2014, 33(2): 164-169.
Abstract:
In order to analyze the adsorptive ability and optimize the transition switching strategy for a wall-climbing robot, the adsorption structure of vacuum absorption for a wall-climbing robot is established. The major factors of the effective pumping speed, conductance，leakage that affect adsorption capacity of the robot are analyzed by using vacuum technique. The leak rate of the sucker and the switching strategy of adsorption system are designed by theoretical analysis and experiment respectively. Then the leak rate's parameters of the sucker are calculated. The val-ues of the leak rate, the response and release curves, and the pressure behavior curves of the switching action of the suckers under three circumstances are given respectively. The effective analyzing method of leakage rate is pro-posed, and the process of dynamic switch is studied. An intuitive and effective way to analyze the adsorptive ability and optimize the transition switching strategy for a wall-climbing robot is provided.
In order to analyze the adsorptive ability and optimize the transition switching strategy for a wall-climbing robot, the adsorption structure of vacuum absorption for a wall-climbing robot is established. The major factors of the effective pumping speed, conductance，leakage that affect adsorption capacity of the robot are analyzed by using vacuum technique. The leak rate of the sucker and the switching strategy of adsorption system are designed by theoretical analysis and experiment respectively. Then the leak rate's parameters of the sucker are calculated. The val-ues of the leak rate, the response and release curves, and the pressure behavior curves of the switching action of the suckers under three circumstances are given respectively. The effective analyzing method of leakage rate is pro-posed, and the process of dynamic switch is studied. An intuitive and effective way to analyze the adsorptive ability and optimize the transition switching strategy for a wall-climbing robot is provided.
2014, 33(2): 170-173.
Abstract:
A new method for describing spatial mechanisms in topological graph with grade edge is presented in terms of the topology theory, and three important matrices in topological graph with grade edge, including adjacency matrix，incidence matrix and circuit matrix are derived. Based on the above-mentioned, the characteristic of those matrixs and the effect of the position relations of kinematic pairs axes in spatial mechanisms on motion charac-teristic are analyzed, and the character strings of structure description for spatial mechanisms is promoted.
A new method for describing spatial mechanisms in topological graph with grade edge is presented in terms of the topology theory, and three important matrices in topological graph with grade edge, including adjacency matrix，incidence matrix and circuit matrix are derived. Based on the above-mentioned, the characteristic of those matrixs and the effect of the position relations of kinematic pairs axes in spatial mechanisms on motion charac-teristic are analyzed, and the character strings of structure description for spatial mechanisms is promoted.
2014, 33(2): 174-177.
Abstract:
A new 4-DOF parallel mechanism, i. e. 2-RPC/2-SPC, which could perform three translations and rota-tion about Y axis, was designed based on the principles of passive chain. The vectors cross product was applied to solve inverse solution for the parallel mechanism. And the forward position problem of the parallel mechanism was derived, then the Jacobian matrix of the mechanism was derived and the velocity, acceleration performance, singu-lar configuration and workspace were analyzed. And a numerical verification was fulfilled for the forward and in-verse solutions results. The forward solution is coincident with the inverse solution.
A new 4-DOF parallel mechanism, i. e. 2-RPC/2-SPC, which could perform three translations and rota-tion about Y axis, was designed based on the principles of passive chain. The vectors cross product was applied to solve inverse solution for the parallel mechanism. And the forward position problem of the parallel mechanism was derived, then the Jacobian matrix of the mechanism was derived and the velocity, acceleration performance, singu-lar configuration and workspace were analyzed. And a numerical verification was fulfilled for the forward and in-verse solutions results. The forward solution is coincident with the inverse solution.
Fuzzy Comprehensive Evaluation for the Configuration Scheme of Fruit and Vegetable Picking Mechanism
2014, 33(2): 178-182.
Abstract:
To ensure design quality of fruit and vegetable picking mechanism, according to the fuzziness and uncer-tainty of mechanism configuration scheme information. the fuzzy comprehensive evaluation method was applied for the optimal selection of mechanism configuration scheme. The importance and relevance of fruit and vegetable pick-ing mechanism performance index was analyzed, the configuration scheme evaluation factor index was formulated and the evaluation hierarchy was constructed. Fuzzy comprehensive evaluation mathematics model was also estab-lished. Fuzzy quantitative method and evaluation membership matrix were defined. The analytic hierarchy method was utilized and the evaluation factor weight set was determined. This fuzzy comprehensive evaluation method was applied to pineapple picking mechanism configuration scheme, and the results show that the evaluation score of the configuration scheme composed by RRP series arm and RR parallel wrist is the highest, evaluation score of the con-figuration scheme composed by 3RPS parallel arm and RR series wrist is the lowest. Evaluation results are consist-ent with the theoretical analysis results. This shows that the evaluation method is reasonable and effective. The fuzzy comprehensive evaluation model provides high efficient intelligent.
To ensure design quality of fruit and vegetable picking mechanism, according to the fuzziness and uncer-tainty of mechanism configuration scheme information. the fuzzy comprehensive evaluation method was applied for the optimal selection of mechanism configuration scheme. The importance and relevance of fruit and vegetable pick-ing mechanism performance index was analyzed, the configuration scheme evaluation factor index was formulated and the evaluation hierarchy was constructed. Fuzzy comprehensive evaluation mathematics model was also estab-lished. Fuzzy quantitative method and evaluation membership matrix were defined. The analytic hierarchy method was utilized and the evaluation factor weight set was determined. This fuzzy comprehensive evaluation method was applied to pineapple picking mechanism configuration scheme, and the results show that the evaluation score of the configuration scheme composed by RRP series arm and RR parallel wrist is the highest, evaluation score of the con-figuration scheme composed by 3RPS parallel arm and RR series wrist is the lowest. Evaluation results are consist-ent with the theoretical analysis results. This shows that the evaluation method is reasonable and effective. The fuzzy comprehensive evaluation model provides high efficient intelligent.
2014, 33(2): 183-188.
Abstract:
Aiming at the uncertainty of fault signals from the gear pump, a new fault diagnosis approach based on improved evidence theory is presented in this paper. Firstly，the evidence theory is improved, and basic probability assignment function is created based on grey incidence analysis of characteristic parameters, which solves the original evidence creation problem in fault diagnosis. Secondly, the cosine between evidence vectors is defined. The original evidence is tested by means of conflict evidence criterion, in which conflicting evidence is modified by credibility and credible evidence is reserved. Finally, the modified evidence is fused in combination formula. The multisensor vibration test for gear pumps proves that this approach owns higher diagnostic precision than classical evidence theory and other representative approaches, and the results testify the validity of the new method. It achieves good diagnostic effect in factual equipment fault diagnosis.
Aiming at the uncertainty of fault signals from the gear pump, a new fault diagnosis approach based on improved evidence theory is presented in this paper. Firstly，the evidence theory is improved, and basic probability assignment function is created based on grey incidence analysis of characteristic parameters, which solves the original evidence creation problem in fault diagnosis. Secondly, the cosine between evidence vectors is defined. The original evidence is tested by means of conflict evidence criterion, in which conflicting evidence is modified by credibility and credible evidence is reserved. Finally, the modified evidence is fused in combination formula. The multisensor vibration test for gear pumps proves that this approach owns higher diagnostic precision than classical evidence theory and other representative approaches, and the results testify the validity of the new method. It achieves good diagnostic effect in factual equipment fault diagnosis.
2014, 33(2): 189-193.
Abstract:
Dynamics simulation of hoisting machinery is very important for making virtual construction system true and assisting real construction projects. Aiming at the simulation of tower crane dynamics, the dynamics module of EON Professional 6.0 software, an advanced development platform for virtual simulation was adopted and the virtual simulation of tower crane dynamics was realized. In the simulation the wirerope was modeled as a flexible body and a virtual construction scene was built to test the overall dynamics simulation of virtual tower crane. The analysis model and the corresponding dynamics equations of tower crane system were structured, and then the simulation of cable swing and cable breaking under special working conditions were achieved. The results show the feasibility of the strategies and methods for overall dynamics simulation of virtual tower crane based on dynamics module of EON Professional 6.0 software with the assistant of dynamics equations, and this approach can be appiled to other hoisting machinery.
Dynamics simulation of hoisting machinery is very important for making virtual construction system true and assisting real construction projects. Aiming at the simulation of tower crane dynamics, the dynamics module of EON Professional 6.0 software, an advanced development platform for virtual simulation was adopted and the virtual simulation of tower crane dynamics was realized. In the simulation the wirerope was modeled as a flexible body and a virtual construction scene was built to test the overall dynamics simulation of virtual tower crane. The analysis model and the corresponding dynamics equations of tower crane system were structured, and then the simulation of cable swing and cable breaking under special working conditions were achieved. The results show the feasibility of the strategies and methods for overall dynamics simulation of virtual tower crane based on dynamics module of EON Professional 6.0 software with the assistant of dynamics equations, and this approach can be appiled to other hoisting machinery.
2014, 33(2): 194-198.
Abstract:
The research on robot kinematics is the basis of controlling and path planning. Firstly, the screw theory was introduced and the kinematical model of the RRRP robot was built based on Lie group knowledge and screw theory. Then, kinematical positive analysis and relative equations were obtained based on the Product of Exponen-tials (POE). Compared with the traditional D-H method, the present method is simpler and has concrete geometry meaning. Lastly, kinematical simulation was done in ADAMS, and it could clearly show the kinematical laws of the robot.. The error value between kinematical equation resolution and simulation data did not beyond 0.05. The result tested the validity of kinematical equations based on the screw theory and POE. It was feasibility for the screw theory to apply to the kinematical analysis of similar multi-rigid-body systems.
The research on robot kinematics is the basis of controlling and path planning. Firstly, the screw theory was introduced and the kinematical model of the RRRP robot was built based on Lie group knowledge and screw theory. Then, kinematical positive analysis and relative equations were obtained based on the Product of Exponen-tials (POE). Compared with the traditional D-H method, the present method is simpler and has concrete geometry meaning. Lastly, kinematical simulation was done in ADAMS, and it could clearly show the kinematical laws of the robot.. The error value between kinematical equation resolution and simulation data did not beyond 0.05. The result tested the validity of kinematical equations based on the screw theory and POE. It was feasibility for the screw theory to apply to the kinematical analysis of similar multi-rigid-body systems.
2014, 33(2): 199-203.
Abstract:
In order to investigate the influence of the backlash and other nonlinear factors to system vibration, a nonlinear dynamic model of a single-stage spur gear pair system with three degree-of-freedom is established in this paper, wherein the backlash, the time-varying stiffness, the torsion motion and the transmission error are consid-ered. The nonlinear three-degree-of-freedom equations are solved by employing variable step-size Runge-kutta methods and the bifurcation diagrams are obtained. The nonlinear dynamic characteristic of the system is discussed for the varying of the exciting frequency, classified based on bifurcation diagrams, top Lyapunov exponent (TLE) diagram, Poincaré maps and FFT spectrum. The Hopf bifurcation, saddle-node bifurcation and doubling bifurcation are found in the different values of the exciting frequency and their bifurcation points are given. There are two routes from periodic motion to chaos motion. The one is from period-4 motion to chaos by Hopf bifurcation, and the other is from period-3 motion and period-3 by saddle-node bifurcation.
In order to investigate the influence of the backlash and other nonlinear factors to system vibration, a nonlinear dynamic model of a single-stage spur gear pair system with three degree-of-freedom is established in this paper, wherein the backlash, the time-varying stiffness, the torsion motion and the transmission error are consid-ered. The nonlinear three-degree-of-freedom equations are solved by employing variable step-size Runge-kutta methods and the bifurcation diagrams are obtained. The nonlinear dynamic characteristic of the system is discussed for the varying of the exciting frequency, classified based on bifurcation diagrams, top Lyapunov exponent (TLE) diagram, Poincaré maps and FFT spectrum. The Hopf bifurcation, saddle-node bifurcation and doubling bifurcation are found in the different values of the exciting frequency and their bifurcation points are given. There are two routes from periodic motion to chaos motion. The one is from period-4 motion to chaos by Hopf bifurcation, and the other is from period-3 motion and period-3 by saddle-node bifurcation.
2014, 33(2): 204-207.
Abstract:
The load distribution of double-decker ball bearing is analyzed in this paper. The traditional methods to analyze the bearing load distribution are always based on the assumption of rigid races and half infinite space boundary conditions utilizing Hertz contact theory.. As the traditional results are not entirely realistic, the finite element method (FEM) is put forward with mapped meshing on ball sphere and increasing the mesh density of the contact area. This method is adopted to analyze the contact stress and deformation at the contact points under different load conditions. And the results based on FEM analysis are compared with the theoretical results using Hertz contact theory. Finally, the calculated results of FEM are also verified by relevant experiments.
The load distribution of double-decker ball bearing is analyzed in this paper. The traditional methods to analyze the bearing load distribution are always based on the assumption of rigid races and half infinite space boundary conditions utilizing Hertz contact theory.. As the traditional results are not entirely realistic, the finite element method (FEM) is put forward with mapped meshing on ball sphere and increasing the mesh density of the contact area. This method is adopted to analyze the contact stress and deformation at the contact points under different load conditions. And the results based on FEM analysis are compared with the theoretical results using Hertz contact theory. Finally, the calculated results of FEM are also verified by relevant experiments.
2014, 33(2): 208-211.
Abstract:
Based on autofrettage technology of elastic plastic theory, the stress distribution of fracturing fluid cylinder was obtained by the elastic plastic nonlinear finite element analysis for a domestic fracturing pump, which was employed to research how to improve fatigue life of the fluid cylinder by using autofrettage technology or improving machining accuracy. Through comparing the maximum stress under different autofrettage pressure levels，the best auto-frettage pressure level of fluid cylinder's intracavity intersection was determined as 420.6 MPa. According to S-N design criteria, a prediction life of fluid cylinder could be conducted by using Msc. Fatigue code. Results indicated that the fatigue regions of autofrettage fluid cylinder had been transferred to inner places and had been deviated from the fatigue danger zone, namely intracavity intersection. The intracavity intersection was effectively protected, and the stress peaks of the fluid cylinder reduced by 30.61% and its minimum fatigue life increased by 6.97 times after autofrettage. Compared with improving machining accuracy, the autofrettage technology can increase the fluid cylinders life much more effectively.
Based on autofrettage technology of elastic plastic theory, the stress distribution of fracturing fluid cylinder was obtained by the elastic plastic nonlinear finite element analysis for a domestic fracturing pump, which was employed to research how to improve fatigue life of the fluid cylinder by using autofrettage technology or improving machining accuracy. Through comparing the maximum stress under different autofrettage pressure levels，the best auto-frettage pressure level of fluid cylinder's intracavity intersection was determined as 420.6 MPa. According to S-N design criteria, a prediction life of fluid cylinder could be conducted by using Msc. Fatigue code. Results indicated that the fatigue regions of autofrettage fluid cylinder had been transferred to inner places and had been deviated from the fatigue danger zone, namely intracavity intersection. The intracavity intersection was effectively protected, and the stress peaks of the fluid cylinder reduced by 30.61% and its minimum fatigue life increased by 6.97 times after autofrettage. Compared with improving machining accuracy, the autofrettage technology can increase the fluid cylinders life much more effectively.
2014, 33(2): 212-216.
Abstract:
Based on the combination of FSI and computational aeroacoustics, the influence of lateral pattern structure size and cross-section shape on air-pumping noise was analyzed. Firstly, the deformation of lateral grooves was obtained by finite element analysis using Abaqus software; Secondly, the noise simulation model of the airflow field around a single lateral pattern groove in the footprint was established, and then the deformation of grooves surfaces got from Abaqus software was incorporated into this model to simulate tread pattern displacement of rolling tire. Finally, air-pumping noise of lateral pattern groove was predicted by flow field analysis. The results show that air-pumping noise of lateral pattern groove decreases as groove length increases, but it increases as groove width increases; the tread groove's cross-sectional shape has greatly influence on air-pumping noise, but the influence of groove depth is not significant.
Based on the combination of FSI and computational aeroacoustics, the influence of lateral pattern structure size and cross-section shape on air-pumping noise was analyzed. Firstly, the deformation of lateral grooves was obtained by finite element analysis using Abaqus software; Secondly, the noise simulation model of the airflow field around a single lateral pattern groove in the footprint was established, and then the deformation of grooves surfaces got from Abaqus software was incorporated into this model to simulate tread pattern displacement of rolling tire. Finally, air-pumping noise of lateral pattern groove was predicted by flow field analysis. The results show that air-pumping noise of lateral pattern groove decreases as groove length increases, but it increases as groove width increases; the tread groove's cross-sectional shape has greatly influence on air-pumping noise, but the influence of groove depth is not significant.
2014, 33(2): 217-220.
Abstract:
Notching, fracture spliting, and assembling bolts with a constant torque are the three core processes in connecting rod fracturing splitting technologies. Comparing the domestic fracture splitting of connecting rod and the assembling bolts with a constant torque with that abroad, the equipment is completed on two machines so as to increase the cost and energy consumption of equipment and decrease the manufacturing efficiency. A hollow open and/or close pin device, having the dual functions of top tight connecting rod shoulder bits and transport bolts is designed, and the overall design of this machine and the fluid, pressure and control systems are all presented. Through the engineering testing, the change of diameter for the connecting rod hole before fracture splitting and after assembling is analyzed, which fully meets the technical requirements.
Notching, fracture spliting, and assembling bolts with a constant torque are the three core processes in connecting rod fracturing splitting technologies. Comparing the domestic fracture splitting of connecting rod and the assembling bolts with a constant torque with that abroad, the equipment is completed on two machines so as to increase the cost and energy consumption of equipment and decrease the manufacturing efficiency. A hollow open and/or close pin device, having the dual functions of top tight connecting rod shoulder bits and transport bolts is designed, and the overall design of this machine and the fluid, pressure and control systems are all presented. Through the engineering testing, the change of diameter for the connecting rod hole before fracture splitting and after assembling is analyzed, which fully meets the technical requirements.
2014, 33(2): 221-223.
Abstract:
Aiming at the sliding and mixed sample problems in the metallic materials sampling process, an analysis for the shortage of current sampling head structure is done. Combining special working condition of the metal materials sampling, the claw in the bottom of sampling head with the function of cutting and straight moving slide bar mechanism with the function of synchronized cleaning are designed, the main dimensions of the mechanism are optimized，the working process and principle of the sampling head are illustrated. The stability in the cutting process of hardening layer is analyzed, and the sampling head can timely slice off the hardening layer without sliding is conclu-ded. In the end，the working stability of the sampler is improved and the phenomenon of mixed sample is eliminated.
Aiming at the sliding and mixed sample problems in the metallic materials sampling process, an analysis for the shortage of current sampling head structure is done. Combining special working condition of the metal materials sampling, the claw in the bottom of sampling head with the function of cutting and straight moving slide bar mechanism with the function of synchronized cleaning are designed, the main dimensions of the mechanism are optimized，the working process and principle of the sampling head are illustrated. The stability in the cutting process of hardening layer is analyzed, and the sampling head can timely slice off the hardening layer without sliding is conclu-ded. In the end，the working stability of the sampler is improved and the phenomenon of mixed sample is eliminated.
2014, 33(2): 224-228.
Abstract:
The joint surface of a grounding machine tool has weak dynamic characteristics, so we use experimental tests and computer simulations to study them in order to improve the performance of the grinding machine tool. We establish the three-dimensional contact stiffness model of the key joint surface of the bolt in the grinding machine tool so as to take into consideration its normal and tangential stiffness. The contact stiffness model is verified by comparing the experimental results with the finite element analysis results and is then used to improve the design of the joint surface and analyze the dynamics of the grinding machine tool. In the new design, the number of bolts is increased and the bolt preload is upgraded. The nonlinear characteristics of the grinding machine tool are correctly dealt with to predict its performance on the whole.
The joint surface of a grounding machine tool has weak dynamic characteristics, so we use experimental tests and computer simulations to study them in order to improve the performance of the grinding machine tool. We establish the three-dimensional contact stiffness model of the key joint surface of the bolt in the grinding machine tool so as to take into consideration its normal and tangential stiffness. The contact stiffness model is verified by comparing the experimental results with the finite element analysis results and is then used to improve the design of the joint surface and analyze the dynamics of the grinding machine tool. In the new design, the number of bolts is increased and the bolt preload is upgraded. The nonlinear characteristics of the grinding machine tool are correctly dealt with to predict its performance on the whole.
2014, 33(2): 229-232.
Abstract:
To solve the problems of system vibration and heater failure which are caused by excessive flow pulsation of the aircraft deicing system, the flow formula of the double-acting reciprocating pump system is derivated, and the causes of flow pulsation are analyzed in this paper. The flow superimposing features of 3 double-acting pumps are got by using the simulation software AMESim (advanced modeling environment for performing simulations of engineering systems) . Then, a new suppression method of legitimately increasing the connecting rod length is proposed, and the effect of both the methods of increasing the length and phase dispersion is analyzed. The results show that: the flow pulsation rate decreases significantly by using phase dispersion method，and the pulsation rate decreases as the connecting rod increases, but this phenomenon will disappear as the increasing of length and pump number. By the combination of the two methods above, the flow pulsation rate can be controlled fewer than 14%.
To solve the problems of system vibration and heater failure which are caused by excessive flow pulsation of the aircraft deicing system, the flow formula of the double-acting reciprocating pump system is derivated, and the causes of flow pulsation are analyzed in this paper. The flow superimposing features of 3 double-acting pumps are got by using the simulation software AMESim (advanced modeling environment for performing simulations of engineering systems) . Then, a new suppression method of legitimately increasing the connecting rod length is proposed, and the effect of both the methods of increasing the length and phase dispersion is analyzed. The results show that: the flow pulsation rate decreases significantly by using phase dispersion method，and the pulsation rate decreases as the connecting rod increases, but this phenomenon will disappear as the increasing of length and pump number. By the combination of the two methods above, the flow pulsation rate can be controlled fewer than 14%.
2014, 33(2): 233-238.
Abstract:
In order to obtain the influence law of temperature on the dynamic characteristics of water/ oil separation process, a Reynolds Stress Model(RSM) of the water/ oil separation flow field in Vacuum oil purifier and the phase transition equations of water droplets evaporation are established by considering factors such as the water/oil/vapor three-phase flow, water droplets evaporation phase transition etc. The influences of different temperature on oil/ water/vapor three-phase volume fraction distribution in the water/oil separation process and the axial dehydration rate are obtained. The results show that the dynamic characteristics of the oil/water/vapor three-phase flow in different temperatures is rather complex, and the influence of temperature on the efficiency of dehydration of the water/oil separation is significant, and the present study provides a theoretical foundation for the further research of the water/oil separation mechanism of the vacuum oil purifier.
In order to obtain the influence law of temperature on the dynamic characteristics of water/ oil separation process, a Reynolds Stress Model(RSM) of the water/ oil separation flow field in Vacuum oil purifier and the phase transition equations of water droplets evaporation are established by considering factors such as the water/oil/vapor three-phase flow, water droplets evaporation phase transition etc. The influences of different temperature on oil/ water/vapor three-phase volume fraction distribution in the water/oil separation process and the axial dehydration rate are obtained. The results show that the dynamic characteristics of the oil/water/vapor three-phase flow in different temperatures is rather complex, and the influence of temperature on the efficiency of dehydration of the water/oil separation is significant, and the present study provides a theoretical foundation for the further research of the water/oil separation mechanism of the vacuum oil purifier.
2014, 33(2): 239-242.
Abstract:
The ultracapacitor/battery hybrid system integrates the best characteristics of the high energy density of the battery and the long cycle life of the ultracapacitor. The mathematical model of the ultracapacitor/battery hybrid system was set up, and the main characters of it such as the peak power enhancement and the correlative factors were studied and analyzed in this paper. The ultracapacitor/battery hybrid system was put forward and utilized in a stand-alone Photovoltaic (PV) system. The model and control algorithm of the system were developed. The results show that the battery could work in the optimized charge and discharge condition when the PV power and load power are pulsating, so that the current of the battery is quite smooth. The small charge and recharge cycles due to irradiation variation can be reduced effectively.
The ultracapacitor/battery hybrid system integrates the best characteristics of the high energy density of the battery and the long cycle life of the ultracapacitor. The mathematical model of the ultracapacitor/battery hybrid system was set up, and the main characters of it such as the peak power enhancement and the correlative factors were studied and analyzed in this paper. The ultracapacitor/battery hybrid system was put forward and utilized in a stand-alone Photovoltaic (PV) system. The model and control algorithm of the system were developed. The results show that the battery could work in the optimized charge and discharge condition when the PV power and load power are pulsating, so that the current of the battery is quite smooth. The small charge and recharge cycles due to irradiation variation can be reduced effectively.
2014, 33(2): 243-248.
Abstract:
In order to meet the requirement of patient with lower limb rehabilitation and reduce the cost, a lower limb rehabilitation training apparatus which has good man-machine fusion and simple mechanical structure is presented. The apparatus can provide passive training, active training, resistance training and functional electrical stimulation training, and then that can meet the requirement of patients with different degrees of damage and disabilities. A rigid link model for lower limb is proposed on the basis of the analysis for lower limb movemen. Mean-while, the human lower limbs and the rehabilitation training apparatus are considered as a whole and a man-machine model with plane closed-loop hinges is abstracted based on the HAM(Human Adaptive Mechatronics) theory. The statics of the man-machine model is analyzed and the statics mathematical models are established when the patient taking resistance training. The virtual prototype of the man-machine model is built and the statics simulation is performed, the results verified the correctness of the previous analysis.
In order to meet the requirement of patient with lower limb rehabilitation and reduce the cost, a lower limb rehabilitation training apparatus which has good man-machine fusion and simple mechanical structure is presented. The apparatus can provide passive training, active training, resistance training and functional electrical stimulation training, and then that can meet the requirement of patients with different degrees of damage and disabilities. A rigid link model for lower limb is proposed on the basis of the analysis for lower limb movemen. Mean-while, the human lower limbs and the rehabilitation training apparatus are considered as a whole and a man-machine model with plane closed-loop hinges is abstracted based on the HAM(Human Adaptive Mechatronics) theory. The statics of the man-machine model is analyzed and the statics mathematical models are established when the patient taking resistance training. The virtual prototype of the man-machine model is built and the statics simulation is performed, the results verified the correctness of the previous analysis.
2014, 33(2): 249-252.
Abstract:
According to the requirements of the structure of electric wheel with dynamic-damper, the cross slider mechanism was used as its power transmission mechanism. By building the kinematic model, the kinematic analysis was conducted for the speed properties of the mechanism and the movement rules and space of the middle part. The electric wheel was simulated using ADAMS software and the results showed that it was feasible to use self-lubricating composite material PEEK in the structural design to solve the wear problems existed in the friction pairs of the cross slider mechanism. According to the simulation results, the inner diameter, outer diameter and the length of sliding channel were designed and calculated. The mechanical efficiency of the transmission mechanism was analyzed and the calculated efficiency was 98.8%.
According to the requirements of the structure of electric wheel with dynamic-damper, the cross slider mechanism was used as its power transmission mechanism. By building the kinematic model, the kinematic analysis was conducted for the speed properties of the mechanism and the movement rules and space of the middle part. The electric wheel was simulated using ADAMS software and the results showed that it was feasible to use self-lubricating composite material PEEK in the structural design to solve the wear problems existed in the friction pairs of the cross slider mechanism. According to the simulation results, the inner diameter, outer diameter and the length of sliding channel were designed and calculated. The mechanical efficiency of the transmission mechanism was analyzed and the calculated efficiency was 98.8%.
2014, 33(2): 253-256.
Abstract:
The CFD (computational fluid dynamics) commercial software CFX was used to numerically simulate the air flow in the cooling fan of a certain type of motorcycle engine in order to discover the defects of original blade design and to carry out the optimal design of the cooling fan by changing its blade shape. The numerical simulation shows that, without changing the speed of the crankshaft of the motorcycle engine, our new design can improve the air volume and efficiency of the cooling fan. The comparison of the measured temperature of air that flows throughthe cylinder reveals that the improved design of the cooling fan lowers the average temperature at the cylinder by 1.5 ℃, thus achieving the purpose of enhancing the cooling effect of a motorcycle engine.
The CFD (computational fluid dynamics) commercial software CFX was used to numerically simulate the air flow in the cooling fan of a certain type of motorcycle engine in order to discover the defects of original blade design and to carry out the optimal design of the cooling fan by changing its blade shape. The numerical simulation shows that, without changing the speed of the crankshaft of the motorcycle engine, our new design can improve the air volume and efficiency of the cooling fan. The comparison of the measured temperature of air that flows throughthe cylinder reveals that the improved design of the cooling fan lowers the average temperature at the cylinder by 1.5 ℃, thus achieving the purpose of enhancing the cooling effect of a motorcycle engine.
2014, 33(2): 257-262.
Abstract:
Research on the problem of layout optimization is actually to find the solution of a combinatorial optimization problem. The constraints involved in the solving process are the design parameters in combinatorial optimization problem, this paper the problem of personnel layout of cabin was studied based on the artificial fish algorithm. Considering the complexity and particularity of DSV cabin, multi-objective optimization is adapted to obtain the optimal layout design scheme. In order to validate the effectiveness of the proposed scheme, the layout scheme is simulated and JACK software was used to evaluate the layout scheme and the rationality of the layout was confirmed. The present study proves the effectiveness of artificial fish algorithm to DSV cabin layout optimization design and provides theory support and guidance for future design work.
Research on the problem of layout optimization is actually to find the solution of a combinatorial optimization problem. The constraints involved in the solving process are the design parameters in combinatorial optimization problem, this paper the problem of personnel layout of cabin was studied based on the artificial fish algorithm. Considering the complexity and particularity of DSV cabin, multi-objective optimization is adapted to obtain the optimal layout design scheme. In order to validate the effectiveness of the proposed scheme, the layout scheme is simulated and JACK software was used to evaluate the layout scheme and the rationality of the layout was confirmed. The present study proves the effectiveness of artificial fish algorithm to DSV cabin layout optimization design and provides theory support and guidance for future design work.
2014, 33(2): 263-266.
Abstract:
Battery performance directly affects vehicle performance, while SOC estimation is one of the most important functions in electric vehicle battery management system, and which is also a technical key needing to solve. Based on the experimental data of battery characteristics, an equivalent circuit model for lithium battery is established to estimate the SOC of lithium batteries. Constructing the model for battery in Matlab, and the correction effect of Kalman filtering algorithm on the SOC estimation using Ah counting algorithm is studied. The results show that the present model for battery can effectively simulate the battery characteristics. The SOC estimation algorithm combining with the open circuit voltage algorithm, Ah counting algorithm and Kalman filtering algorithm can effectively solve the inaccurate and accumulative error problems of initial SOC.
Battery performance directly affects vehicle performance, while SOC estimation is one of the most important functions in electric vehicle battery management system, and which is also a technical key needing to solve. Based on the experimental data of battery characteristics, an equivalent circuit model for lithium battery is established to estimate the SOC of lithium batteries. Constructing the model for battery in Matlab, and the correction effect of Kalman filtering algorithm on the SOC estimation using Ah counting algorithm is studied. The results show that the present model for battery can effectively simulate the battery characteristics. The SOC estimation algorithm combining with the open circuit voltage algorithm, Ah counting algorithm and Kalman filtering algorithm can effectively solve the inaccurate and accumulative error problems of initial SOC.
2014, 33(2): 267-270.
Abstract:
Aiming at the requirements of frequently replacing different working devices to adapt different practical operations for the multifunctional rescue vehicle at work, a general connector for connecting the working arm of rescue vehicle and working device was designed and studied in this paper. The general connector could improve work efficiency and realize one machine with multiple function. The three-dimensional model of the general connector was built by Pro/E. By creating the seamless link between Pro/E and ANSYS, the three dimensional model was imported into ANSYS. Under static load, the static strength analysis for the key forced parts was made. At last the stress nephogram and strain graph of general connector was obtained. The results show that the structural design of the general connector is conformed to work requirements.
Aiming at the requirements of frequently replacing different working devices to adapt different practical operations for the multifunctional rescue vehicle at work, a general connector for connecting the working arm of rescue vehicle and working device was designed and studied in this paper. The general connector could improve work efficiency and realize one machine with multiple function. The three-dimensional model of the general connector was built by Pro/E. By creating the seamless link between Pro/E and ANSYS, the three dimensional model was imported into ANSYS. Under static load, the static strength analysis for the key forced parts was made. At last the stress nephogram and strain graph of general connector was obtained. The results show that the structural design of the general connector is conformed to work requirements.
2014, 33(2): 271-275.
Abstract:
Transmission rate of the vibration between engine and automotive body will have a significant influence on the ride comfort of vehicle. Aiming at the problem of high degree of vibration transfer from engine to body existed on a type of automobile, energy decoupling method is applied to the field of powertrain mounting system optimization. A dynamic model of the powertrain mounting system is built while the differential equations of motion are established. Then the powertrain mount system optimization platform is developed based on the MATLAB software. The modeling and optimization for the powertrain mounting system was completed by using this platform and ADAMS software, respectively. Analysis and comparison of the optimized results showed that it is feasible to apply this platform to conduct an optimization for the vibration isolation of the powertrain mounting system.
Transmission rate of the vibration between engine and automotive body will have a significant influence on the ride comfort of vehicle. Aiming at the problem of high degree of vibration transfer from engine to body existed on a type of automobile, energy decoupling method is applied to the field of powertrain mounting system optimization. A dynamic model of the powertrain mounting system is built while the differential equations of motion are established. Then the powertrain mount system optimization platform is developed based on the MATLAB software. The modeling and optimization for the powertrain mounting system was completed by using this platform and ADAMS software, respectively. Analysis and comparison of the optimized results showed that it is feasible to apply this platform to conduct an optimization for the vibration isolation of the powertrain mounting system.
2014, 33(2): 276-281.
Abstract:
The existing skeleton frames were formed with a large amount of welded joints. Performances of welded joints directly influence the frame structure and the vehicle movement stability, safety and dynamic performance. To improve the performances of the skeleton frame, this paper puts forwards the“subtracting areas with small stress”method. By parametric design technique of ANSYS software, the skeleton frame was divided into some system module spaces contacted with the skeleton frame. The stress distribution of whole skeleton frame was obtained, the small stress areas were cut off and then another turn of strength analysis was conducted. Several iterations of calculation and resection were conducted to obtain the minimum weight with the requirements of strength and stiffness. Finally the minimum division was adopted according to manufacturing and assembly technology requirements to get the high performance steel skeleton frame structure.
The existing skeleton frames were formed with a large amount of welded joints. Performances of welded joints directly influence the frame structure and the vehicle movement stability, safety and dynamic performance. To improve the performances of the skeleton frame, this paper puts forwards the“subtracting areas with small stress”method. By parametric design technique of ANSYS software, the skeleton frame was divided into some system module spaces contacted with the skeleton frame. The stress distribution of whole skeleton frame was obtained, the small stress areas were cut off and then another turn of strength analysis was conducted. Several iterations of calculation and resection were conducted to obtain the minimum weight with the requirements of strength and stiffness. Finally the minimum division was adopted according to manufacturing and assembly technology requirements to get the high performance steel skeleton frame structure.
2014, 33(2): 282-288.
Abstract:
Driving cycle research has an important value on the aspects of technical development and certification of new vehicle,vehicle's pollutants emission characteristics and fuel economy analysis as well as risk evaluation in traffic control. In order to develop vehicle's driving cycle suitable for the actual mixed traffic situation of urban roads,the typical driving cycles and its applicable scope in U. S. A,ECE and Japan was introduced systematically based on inducing a large number of literatures. And the key technology such as road test design,data processing technology and construction method in driving cycle development were analyzed. Finally,aiming at the research on driving cycle of Chinese city,the future research directions and suggestion were put forward.
Driving cycle research has an important value on the aspects of technical development and certification of new vehicle,vehicle's pollutants emission characteristics and fuel economy analysis as well as risk evaluation in traffic control. In order to develop vehicle's driving cycle suitable for the actual mixed traffic situation of urban roads,the typical driving cycles and its applicable scope in U. S. A,ECE and Japan was introduced systematically based on inducing a large number of literatures. And the key technology such as road test design,data processing technology and construction method in driving cycle development were analyzed. Finally,aiming at the research on driving cycle of Chinese city,the future research directions and suggestion were put forward.
2014, 33(2): 289-292.
Abstract:
A vehicle frame is an important component that bears the whole vehicle and is subject to the impact load caused by road roughness. It is difficult to use the existing formulae to accurately calculate the time history of load at various joints. Therefore we use the ADAMS/Car software to establish the model of the whole vehicle and set its relevant parameters. Through simulation and calculation, we obtain the time history of load at the joint between the frame of the vehicle and its suspension. The comparison of the simulation results with experimental results shows that the two types of results are basically consistent, thus proving the validity of the model. The simulation results provide a foundation for the subsequent analysis of vehicle frame fatigue.
A vehicle frame is an important component that bears the whole vehicle and is subject to the impact load caused by road roughness. It is difficult to use the existing formulae to accurately calculate the time history of load at various joints. Therefore we use the ADAMS/Car software to establish the model of the whole vehicle and set its relevant parameters. Through simulation and calculation, we obtain the time history of load at the joint between the frame of the vehicle and its suspension. The comparison of the simulation results with experimental results shows that the two types of results are basically consistent, thus proving the validity of the model. The simulation results provide a foundation for the subsequent analysis of vehicle frame fatigue.
2014, 33(2): 293-297.
Abstract:
The hot tension for hot forming part of AA5182 aluminum alloy are carried out at the strain rates of 0.0015s-1, 0.015s-1, 0.15s-1, and 1.5s-1, and the developed Johnson-cook constitutive model for the simulation of frontal impact is presented. The energy absorbing performance and mechanical properties for the vehicle body of hot forming part of AA5182 aluminum alloy are analyzed. The results show that the higher the flow stress and the lower the fractured strain of hot forming part of AA5182 aluminum alloy with the increasing of strain rate. The intrusion displacement of the hot forming 5182 aluminum alloy parts is appropriate for the satisfaction of vehicle body, there is a better energy absorbing performance and mechanical properties of hot forming part of AA5182 aluminum alloy for the vehicle body. Therefore the hot forming part of 5182 aluminum alloy can be applied to vehicle body design.
The hot tension for hot forming part of AA5182 aluminum alloy are carried out at the strain rates of 0.0015s-1, 0.015s-1, 0.15s-1, and 1.5s-1, and the developed Johnson-cook constitutive model for the simulation of frontal impact is presented. The energy absorbing performance and mechanical properties for the vehicle body of hot forming part of AA5182 aluminum alloy are analyzed. The results show that the higher the flow stress and the lower the fractured strain of hot forming part of AA5182 aluminum alloy with the increasing of strain rate. The intrusion displacement of the hot forming 5182 aluminum alloy parts is appropriate for the satisfaction of vehicle body, there is a better energy absorbing performance and mechanical properties of hot forming part of AA5182 aluminum alloy for the vehicle body. Therefore the hot forming part of 5182 aluminum alloy can be applied to vehicle body design.
2014, 33(2): 298-302.
Abstract:
According to the application requirements for high-speed and lightweight of the overrunning spring clutch，after analyzing the spring torque variation，the spring-sectional variation law and spring spiral equation are established based on the equal strength principle. The MATLAB and Pro/E are applied to establish the three-di-mensional model of the variable cross-section spring. The stress of the spring clutch in transfer process and the ra-dial，axial，tensional stiffness characteristics of the spring are numerically analyzed by the finite element method. The results illustrate that the design of the variable cross-section spring has the uniform stress during the torque transmission process and achieves the goal of light-weight and equal life. The radial rigidity of the variable section spring is nonlinear，and the torsion rigidity and axial rigidity are linear.
According to the application requirements for high-speed and lightweight of the overrunning spring clutch，after analyzing the spring torque variation，the spring-sectional variation law and spring spiral equation are established based on the equal strength principle. The MATLAB and Pro/E are applied to establish the three-di-mensional model of the variable cross-section spring. The stress of the spring clutch in transfer process and the ra-dial，axial，tensional stiffness characteristics of the spring are numerically analyzed by the finite element method. The results illustrate that the design of the variable cross-section spring has the uniform stress during the torque transmission process and achieves the goal of light-weight and equal life. The radial rigidity of the variable section spring is nonlinear，and the torsion rigidity and axial rigidity are linear.
2014, 33(2): 303-308.
Abstract:
Considering the effect of docking speed and angles on the dynamic characteristic in the docking process of cone-perch docking mechanisms for spacecraft, a finite element model for dynamic contact of a cone-perch docking mechanism was established by using a software ANSYS/LS-DYNA. Based on the explicit dynamics of finite element method, a fully integration algorithm was adopted to control hourglass, and calculation was accelerated by setting density of element and adopting mixed time integral arithmetic. The dynamic characteristics for cone-perch docking mechanism was analyzed, which obtains the dynamic response of docking mechanisms and the stress fluctuation of structures in the docking process. According to the analysis result, the parameters of dynamic characteristics increases with the increasing of docking speed and angles, and it is possible for significant change of dynamic characteristics being caused by the hole size.
Considering the effect of docking speed and angles on the dynamic characteristic in the docking process of cone-perch docking mechanisms for spacecraft, a finite element model for dynamic contact of a cone-perch docking mechanism was established by using a software ANSYS/LS-DYNA. Based on the explicit dynamics of finite element method, a fully integration algorithm was adopted to control hourglass, and calculation was accelerated by setting density of element and adopting mixed time integral arithmetic. The dynamic characteristics for cone-perch docking mechanism was analyzed, which obtains the dynamic response of docking mechanisms and the stress fluctuation of structures in the docking process. According to the analysis result, the parameters of dynamic characteristics increases with the increasing of docking speed and angles, and it is possible for significant change of dynamic characteristics being caused by the hole size.
2014, 33(2): 309-312.
Abstract:
This paper established the motion equations of the double-rotor system based on transfer matrix method (TMM). The transient response of the system under sudden unbalance load has been simulated by using Newmark-β integration method. The results show that a sudden unbalance on the system will cause large fluctuations which have the same frequency with natural fluctuations. The fluctuations are influenced by the damping、sudden unbalance levels and operating speed. Sudden unbalance on different disc will cause different influence on the response amplitude at critical speed.
This paper established the motion equations of the double-rotor system based on transfer matrix method (TMM). The transient response of the system under sudden unbalance load has been simulated by using Newmark-β integration method. The results show that a sudden unbalance on the system will cause large fluctuations which have the same frequency with natural fluctuations. The fluctuations are influenced by the damping、sudden unbalance levels and operating speed. Sudden unbalance on different disc will cause different influence on the response amplitude at critical speed.
