Author Center
Editor Work
Peer Review
Editorial Entry
Email Alert
RSS2015 Vol. 34, No. 9
Display Method:
2015, 34(9): 1313-1316.
doi: 10.13433/j.cnki.1003-8728.2015.0901
PDF 2512KB
Abstract:
The structure of ribs form in the column of a horizontal machining center was optimized to increase dynamic stiffness of the host. Through the establishment of three-dimensional model and surface model for host, approaching to the working conditions, the modal shape of the host and harmonic response curve of the host with spindle end as the observation point were recorded. Analyzing modal analysis results to find the weak links, and changing the ribs form structure of the column combined with Workbench topology optimization results to remove part of the material, the quality of the cumulative column was reduced up to 931.9 kg accounting for about 9.6%, X direction dynamic stiffness increased to 1.82 times by original structure, and Y direction dynamic stiffness increased 1.37 times.
The structure of ribs form in the column of a horizontal machining center was optimized to increase dynamic stiffness of the host. Through the establishment of three-dimensional model and surface model for host, approaching to the working conditions, the modal shape of the host and harmonic response curve of the host with spindle end as the observation point were recorded. Analyzing modal analysis results to find the weak links, and changing the ribs form structure of the column combined with Workbench topology optimization results to remove part of the material, the quality of the cumulative column was reduced up to 931.9 kg accounting for about 9.6%, X direction dynamic stiffness increased to 1.82 times by original structure, and Y direction dynamic stiffness increased 1.37 times.
2015, 34(9): 1317-1321.
doi: 10.13433/j.cnki.1003-8728.2015.0902
Abstract:
The method of SOC superposition is introduced. In this method the ends of single-opened-chain(SOC) is connected to existing kinematic chain with kinematic pairs and components to obtain a complete topological graph, the relevant character of the mechanism is also described in the basis of topological graph. The superposition of SOC provides a research method for type synthesis of mechanism. With this method, the kinematic chains of under-actuated 3-knuckle finger are acquired, the new type of 2 degrees of freedom(DOF) and 3 DOF finger mechanisms are obtained with deducing topological graphs optimized from the above mentioned Kinematic chain. The present study provides more configurations for under-actuated dexterous hand.
The method of SOC superposition is introduced. In this method the ends of single-opened-chain(SOC) is connected to existing kinematic chain with kinematic pairs and components to obtain a complete topological graph, the relevant character of the mechanism is also described in the basis of topological graph. The superposition of SOC provides a research method for type synthesis of mechanism. With this method, the kinematic chains of under-actuated 3-knuckle finger are acquired, the new type of 2 degrees of freedom(DOF) and 3 DOF finger mechanisms are obtained with deducing topological graphs optimized from the above mentioned Kinematic chain. The present study provides more configurations for under-actuated dexterous hand.
2015, 34(9): 1322-1327.
doi: 10.13433/j.cnki.1003-8728.2015.0903
Abstract:
The impact overloads when boring with Tunnel Boring Machine (TBM) may cause severe cutterhead vibration, which will further affect the efficiency of tunneling. Due to the non-feasibility of physical experiments and complexity of theoretical analysis, computer simulation is an ideal way to study the vibration characteristics of TBM mainframe. Therefore, a TBM mainframe model was built in this paper based on the multi-body system dynamics simulation platform ADAMS, and the TBM tunneling process was simulated. The simulation results show that the radial amplitude of cutterhead is at the 10-1 mm order, which is one order less than the axial amplitude; The radial force between the center part and other parts is at the 102 kN order, which is one order less than the axial force, and the summit frequency of this two forces is different; The radial force between the shield and mainbeam is at the 104 kN order, which is also one order less than the axial force, but the axial force between center part and other parts of cutterhead and the axial force between the shield and mainbeam is quite the same.
The impact overloads when boring with Tunnel Boring Machine (TBM) may cause severe cutterhead vibration, which will further affect the efficiency of tunneling. Due to the non-feasibility of physical experiments and complexity of theoretical analysis, computer simulation is an ideal way to study the vibration characteristics of TBM mainframe. Therefore, a TBM mainframe model was built in this paper based on the multi-body system dynamics simulation platform ADAMS, and the TBM tunneling process was simulated. The simulation results show that the radial amplitude of cutterhead is at the 10-1 mm order, which is one order less than the axial amplitude; The radial force between the center part and other parts is at the 102 kN order, which is one order less than the axial force, and the summit frequency of this two forces is different; The radial force between the shield and mainbeam is at the 104 kN order, which is also one order less than the axial force, but the axial force between center part and other parts of cutterhead and the axial force between the shield and mainbeam is quite the same.
2015, 34(9): 1328-1332.
doi: 10.13433/j.cnki.1003-8728.2015.0904
Abstract:
In order to simulate and analyze the fracture behavior of a single particle under linear movement, numerical simulation was carried out with the finite element analysis software, depending on the operation status of a jaw crusher. 3D models were built with the brittle cracking material, and the Rankine criterion was used to detect the cracking and verify the feasibility of numerical simulation for dynamic crushing behavior. Simulation results show that the single particle crushing under uniaxial compression can be divided into gradual cracking phase and catastrophic fracture phase. The gradual cracking phase includes compaction and micro-crack extension; the maximum counterforce and stress of the jaw crusher increase with increasing tooth pitch, while other parameters of the shape of the jaw crusher stay invariant. The maximum linear stress appears in the addendum arc and tooth root; the mineral crushing effect tends to be better as the tooth pitch increases. The relationships among tooth pitch, performance parameters and optimal tooth pitch under the single factor condition are obtained with the grey theory.
In order to simulate and analyze the fracture behavior of a single particle under linear movement, numerical simulation was carried out with the finite element analysis software, depending on the operation status of a jaw crusher. 3D models were built with the brittle cracking material, and the Rankine criterion was used to detect the cracking and verify the feasibility of numerical simulation for dynamic crushing behavior. Simulation results show that the single particle crushing under uniaxial compression can be divided into gradual cracking phase and catastrophic fracture phase. The gradual cracking phase includes compaction and micro-crack extension; the maximum counterforce and stress of the jaw crusher increase with increasing tooth pitch, while other parameters of the shape of the jaw crusher stay invariant. The maximum linear stress appears in the addendum arc and tooth root; the mineral crushing effect tends to be better as the tooth pitch increases. The relationships among tooth pitch, performance parameters and optimal tooth pitch under the single factor condition are obtained with the grey theory.
2015, 34(9): 1333-1339.
doi: 10.13433/j.cnki.1003-8728.2015.0905
Abstract:
In order to solve the difficult problem of how to improve a robot's tracking the path of a press brake with high accuracy and great synchronization during bending, the algorithm of path planning and motion control based on the real-time position tracking of the press brake was studied. The simulation and analysis of the path planning with Matlab show that the algorithm can plan the path of the press brake. In addition, the robot's motion control system based on the Googol motion controller and the circuit module for acquiring the position of press brake were designed and developed. The results show that the actual path deviation of the bending robot when the algorithm was adopted is less than 0.8 mm, showing the high-accuracy tracking, higher precision and great synchronization.
In order to solve the difficult problem of how to improve a robot's tracking the path of a press brake with high accuracy and great synchronization during bending, the algorithm of path planning and motion control based on the real-time position tracking of the press brake was studied. The simulation and analysis of the path planning with Matlab show that the algorithm can plan the path of the press brake. In addition, the robot's motion control system based on the Googol motion controller and the circuit module for acquiring the position of press brake were designed and developed. The results show that the actual path deviation of the bending robot when the algorithm was adopted is less than 0.8 mm, showing the high-accuracy tracking, higher precision and great synchronization.
2015, 34(9): 1340-1344.
doi: 10.13433/j.cnki.1003-8728.2015.0906
Abstract:
According to the structural design principle of wind turbine rotor under specified conditions, we optimize the structure of micro wind turbine rotor from three aspects, namely, the number of blade, the shape of blade and the airfoil of blade and three optimum structures are found. With computational fluid dynamics software, FLUENT, a three dimensional flow field simulation model is established with the structural characteristics and actual conditions of micro wind turbine. This simulation model has been verified and used to analyze the aerodynamics performance of the three different wind turbine rotors. As a result, an optimized structural is obtained with comparing the torque and out-put power of different rotors.
According to the structural design principle of wind turbine rotor under specified conditions, we optimize the structure of micro wind turbine rotor from three aspects, namely, the number of blade, the shape of blade and the airfoil of blade and three optimum structures are found. With computational fluid dynamics software, FLUENT, a three dimensional flow field simulation model is established with the structural characteristics and actual conditions of micro wind turbine. This simulation model has been verified and used to analyze the aerodynamics performance of the three different wind turbine rotors. As a result, an optimized structural is obtained with comparing the torque and out-put power of different rotors.
2015, 34(9): 1345-1349.
doi: 10.13433/j.cnki.1003-8728.2015.0907
Abstract:
In order to solve the optimal control problem that boom system follows the movement of distributor boom under artificial traction, a new trajectory planning method based on the stability of pump truck was proposed, which took minimum moving range of the barycentre of the boom system as the optimization goal. The best motion trajectories of the boom system were determined with establishing and solving the nonlinear optimization equations with constraints of kinematic redundancy function. The reliability of the proposed optimization method was verified with comparing the optimized scheme with those obtained with the existing optimization methods. At last, simulation of several different pouring conditions has been developed. The results suggest that the new optimization algorithm is effective in controlling moving range of barycentre of the boom system.
In order to solve the optimal control problem that boom system follows the movement of distributor boom under artificial traction, a new trajectory planning method based on the stability of pump truck was proposed, which took minimum moving range of the barycentre of the boom system as the optimization goal. The best motion trajectories of the boom system were determined with establishing and solving the nonlinear optimization equations with constraints of kinematic redundancy function. The reliability of the proposed optimization method was verified with comparing the optimized scheme with those obtained with the existing optimization methods. At last, simulation of several different pouring conditions has been developed. The results suggest that the new optimization algorithm is effective in controlling moving range of barycentre of the boom system.
2015, 34(9): 1350-1354.
doi: 10.13433/j.cnki.1003-8728.2015.0908
Abstract:
This paper is aimed at controlling coal sample manipulator accurately, and the determination of preferential orientation for inverse kinematics solutions. Getting inverse solutions group through the inverse kinematics analysis and adopting working area partition and positioning method, we obtain the optimization of inverse kinematics solutions. Under the principle of large joints with less move and small with more, based on range of movement of every connecting rod in the working area devided, and verifying the correctness with selecting the working condition of randomly with comparing the target position with the new position caused by inverse kinematics solution. Through analyzing, the accurate positioning of coal sample manipulator and joint movement came out.
This paper is aimed at controlling coal sample manipulator accurately, and the determination of preferential orientation for inverse kinematics solutions. Getting inverse solutions group through the inverse kinematics analysis and adopting working area partition and positioning method, we obtain the optimization of inverse kinematics solutions. Under the principle of large joints with less move and small with more, based on range of movement of every connecting rod in the working area devided, and verifying the correctness with selecting the working condition of randomly with comparing the target position with the new position caused by inverse kinematics solution. Through analyzing, the accurate positioning of coal sample manipulator and joint movement came out.
2015, 34(9): 1355-1359.
doi: 10.13433/j.cnki.1003-8728.2015.0909
Abstract:
The fluctuations in random design and the uncertainty from environment play essential roles in the security of robust reliability of compliant mechanisms, especially in how to optimize the compliant mechanism. In present study, a 6σ robust design optimization method is proposed as well as the model of stability and optimizing design. The compliant mechanism was optimized from flexibility and steady, in present paper, which was a carrier of flexible cantilever beam. Compared with the traditional deterministic optimization of flexible cantilever beam, the new method could obtain the 8σ level of flexibility robustness. As it shows that the 6σ robust design optimization method could acquire a favorable effect.
The fluctuations in random design and the uncertainty from environment play essential roles in the security of robust reliability of compliant mechanisms, especially in how to optimize the compliant mechanism. In present study, a 6σ robust design optimization method is proposed as well as the model of stability and optimizing design. The compliant mechanism was optimized from flexibility and steady, in present paper, which was a carrier of flexible cantilever beam. Compared with the traditional deterministic optimization of flexible cantilever beam, the new method could obtain the 8σ level of flexibility robustness. As it shows that the 6σ robust design optimization method could acquire a favorable effect.
2015, 34(9): 1360-1364.
doi: 10.13433/j.cnki.1003-8728.2015.0910
Abstract:
According to the critical-depth-of-cut model of brittle materials and combined with Hertz elastic contact theory and kinematics equations, we analyze the removal mechanisms of ultrasonic abrasive impacts theoretically. The Smooth Particle Hydrodynamics (SPH) Method was used to study the mechanisms of crack formation and extension of brittle material under the impact of the abrasive. The results indicate that the critical-depth-of-cut of optical quartz glass is 0.013 μm; if the machining clearance is set to a specific range and the W7 SiC abrasive particle is used, the high-quality surface of optical quartz glass can be polished under the ductile mode when the amplitude of ultrasonic tool is less than 23.87 μm, and the high-efficiency grinding can be realized under the brittle fracture mode when the amplitude is more than 23.87 μm. The simulation results show that the brittle materials performs elastic-plastic deformation in the process of abrasive impacts, and the crack begin to form in the interior of the material when the critical fracture stress is achieved.
According to the critical-depth-of-cut model of brittle materials and combined with Hertz elastic contact theory and kinematics equations, we analyze the removal mechanisms of ultrasonic abrasive impacts theoretically. The Smooth Particle Hydrodynamics (SPH) Method was used to study the mechanisms of crack formation and extension of brittle material under the impact of the abrasive. The results indicate that the critical-depth-of-cut of optical quartz glass is 0.013 μm; if the machining clearance is set to a specific range and the W7 SiC abrasive particle is used, the high-quality surface of optical quartz glass can be polished under the ductile mode when the amplitude of ultrasonic tool is less than 23.87 μm, and the high-efficiency grinding can be realized under the brittle fracture mode when the amplitude is more than 23.87 μm. The simulation results show that the brittle materials performs elastic-plastic deformation in the process of abrasive impacts, and the crack begin to form in the interior of the material when the critical fracture stress is achieved.
2015, 34(9): 1365-1369.
doi: 10.13433/j.cnki.1003-8728.2015.0911
Abstract:
The nickel based superalloy GH4169 is a kind of special and difficult-to-cut materials used in the manufacture of aircraft engine blades, the traditional machining methods are so easy to make the material burns and led to the deformation on blade that it can't ensure the accuracy of surface, form and position. The grinding process test in view of the abrasive belt selection and processing parameter optimization of the abrasive belt grinding on the present material is carried out, emphatically discuss the pros and cons of various types of abrasive belt during processing, make a selection of abrasive belt, optimize and analyze the grinding process parameters. The results show that R270 (P240) abrasive belt is ideal and under certain conditions, it can meet the roughness requirement and realizes larger material removal rate, it can also provide a reference for computerized numerical control belt polishing on the aircraft engine blades.
The nickel based superalloy GH4169 is a kind of special and difficult-to-cut materials used in the manufacture of aircraft engine blades, the traditional machining methods are so easy to make the material burns and led to the deformation on blade that it can't ensure the accuracy of surface, form and position. The grinding process test in view of the abrasive belt selection and processing parameter optimization of the abrasive belt grinding on the present material is carried out, emphatically discuss the pros and cons of various types of abrasive belt during processing, make a selection of abrasive belt, optimize and analyze the grinding process parameters. The results show that R270 (P240) abrasive belt is ideal and under certain conditions, it can meet the roughness requirement and realizes larger material removal rate, it can also provide a reference for computerized numerical control belt polishing on the aircraft engine blades.
2015, 34(9): 1370-1374.
doi: 10.13433/j.cnki.1003-8728.2015.0912
Abstract:
An equal-error step tool path generation algorithm is proposed for the uniformity of the tool path errors in the triangular mesh surface machining. The algorithm combines the linear error and rotational error generated from the movement of tool on the mesh surface as the design tolerance. Under the condition of satisfying the required accuracy, the position of the cutter contact points in each of the tool path is optimized with controlling the design tolerance, and the corresponding cutter location points are generated. It ensures the consistency of the boundary by making full use of the characteristics of the boundary of the mesh surface when generating a tool path of the complete triangular mesh surface. The experimental results indicate that the tool path generated from this algorithm maintains a good border consistency, and significantly improves the machining precision and quality uniformity.
An equal-error step tool path generation algorithm is proposed for the uniformity of the tool path errors in the triangular mesh surface machining. The algorithm combines the linear error and rotational error generated from the movement of tool on the mesh surface as the design tolerance. Under the condition of satisfying the required accuracy, the position of the cutter contact points in each of the tool path is optimized with controlling the design tolerance, and the corresponding cutter location points are generated. It ensures the consistency of the boundary by making full use of the characteristics of the boundary of the mesh surface when generating a tool path of the complete triangular mesh surface. The experimental results indicate that the tool path generated from this algorithm maintains a good border consistency, and significantly improves the machining precision and quality uniformity.
2015, 34(9): 1375-1380.
doi: 10.13433/j.cnki.1003-8728.2015.0913
Abstract:
A 2-D axisymmetric finite element model is established for the rotary lip seal. The influences of the difference between lip and shaft diameters, spring stiffness coefficient and the contact surface angle of the air on the contact width and the contact pressure distribution are gotten. Moreover, based on results of the finite element analysis, the pumping rate and the amount of heat generation are estimated with theoretical analysis method. The results show that the amount of heat generation increases linearly and the increasing rate of pumping rate becomes slow as the interference between the shaft and seal increases; with the increase of spring stiffness coefficient, the amount of heat generation increases quickly, whereas, the pumping rate changes little; the pumping rate decreases with the increase of contact surface angel of the air of the oil seal; as the shaft speed increases, the amount of heat generation and pumping rate increase rapidly.
A 2-D axisymmetric finite element model is established for the rotary lip seal. The influences of the difference between lip and shaft diameters, spring stiffness coefficient and the contact surface angle of the air on the contact width and the contact pressure distribution are gotten. Moreover, based on results of the finite element analysis, the pumping rate and the amount of heat generation are estimated with theoretical analysis method. The results show that the amount of heat generation increases linearly and the increasing rate of pumping rate becomes slow as the interference between the shaft and seal increases; with the increase of spring stiffness coefficient, the amount of heat generation increases quickly, whereas, the pumping rate changes little; the pumping rate decreases with the increase of contact surface angel of the air of the oil seal; as the shaft speed increases, the amount of heat generation and pumping rate increase rapidly.
2015, 34(9): 1381-1387.
doi: 10.13433/j.cnki.1003-8728.2015.0914
Abstract:
This paper establishes a discrete mathematical model of the radial magnetic bearing with eight magnetic poles which can decouple the effect of cross coupling. First of all, a conventional digital PID controller is designed based on the discrete model to make the system stable. Considering the actual AMB is a kind of uncertain system, and the poor control performance of the conventional PID controller used in the system which is nonlinear or include uncertain structural parameters and controlled objects influenced by external factors greatly. In this paper, the fuzzy PID controller is designed which achieves the online adjusting function for PID parameters. In view of basic variable sets of the fuzzy PID stay the same which conduct the lower control precision in the practical control process of AMB, this paper designs an improved fuzzy PID controller based on the thought of variable universe of proportion scaling. The simulation results show that the improved fuzzy PID control has better control performance compared with the other control methods.
This paper establishes a discrete mathematical model of the radial magnetic bearing with eight magnetic poles which can decouple the effect of cross coupling. First of all, a conventional digital PID controller is designed based on the discrete model to make the system stable. Considering the actual AMB is a kind of uncertain system, and the poor control performance of the conventional PID controller used in the system which is nonlinear or include uncertain structural parameters and controlled objects influenced by external factors greatly. In this paper, the fuzzy PID controller is designed which achieves the online adjusting function for PID parameters. In view of basic variable sets of the fuzzy PID stay the same which conduct the lower control precision in the practical control process of AMB, this paper designs an improved fuzzy PID controller based on the thought of variable universe of proportion scaling. The simulation results show that the improved fuzzy PID control has better control performance compared with the other control methods.
2015, 34(9): 1388-1393.
doi: 10.13433/j.cnki.1003-8728.2015.0915
Abstract:
To measure the monolithic impeller on coordinate measuring machine(CMM), the dividing apparatus is needed for sampling individual blades. The installation eccentricity between the monolithic impeller and the dividing apparatus will cause eccentric motion, which affects the contact between the measuring head and the blades. Even worse, it reduces the detection accuracy of blade surface. Two measurement strategies are proposed, namely independent coordinate measurement and unified coordinate measurement. The former re-establishes the coordinate system after each dividing operation to lower the eccentricity-induced error. The latter establishes coordinate system only once, while achieves error compensation with calculating the eccentricity between the monolithic impeller and the dividing apparatus.
To measure the monolithic impeller on coordinate measuring machine(CMM), the dividing apparatus is needed for sampling individual blades. The installation eccentricity between the monolithic impeller and the dividing apparatus will cause eccentric motion, which affects the contact between the measuring head and the blades. Even worse, it reduces the detection accuracy of blade surface. Two measurement strategies are proposed, namely independent coordinate measurement and unified coordinate measurement. The former re-establishes the coordinate system after each dividing operation to lower the eccentricity-induced error. The latter establishes coordinate system only once, while achieves error compensation with calculating the eccentricity between the monolithic impeller and the dividing apparatus.
2015, 34(9): 1394-1398.
doi: 10.13433/j.cnki.1003-8728.2015.0916
Abstract:
Real-time collision detection is a bottleneck in a complicated assembly model, the collision detection precision based on face-representation can't satisfy the requirement in a level-assembly model, and the time consuming of solid model can't be accepted if using the global interference check. In order to solve the problem, a new distributed collision detection method was presented. Firstly, Master CAD finishes the collision detection of bounding box with AABB algorithm; based on the load-balance calculation principal, distributes component couples which need accurate collision detection and sends them to Slave CAD. Secondly, Slaves calculate component couples' collision detection and sent the interference results to Master CAD again. The results of simulation showed that the algorithm could improve highly real-time interference check in addition to meet the accuracy requirement.
Real-time collision detection is a bottleneck in a complicated assembly model, the collision detection precision based on face-representation can't satisfy the requirement in a level-assembly model, and the time consuming of solid model can't be accepted if using the global interference check. In order to solve the problem, a new distributed collision detection method was presented. Firstly, Master CAD finishes the collision detection of bounding box with AABB algorithm; based on the load-balance calculation principal, distributes component couples which need accurate collision detection and sends them to Slave CAD. Secondly, Slaves calculate component couples' collision detection and sent the interference results to Master CAD again. The results of simulation showed that the algorithm could improve highly real-time interference check in addition to meet the accuracy requirement.
2015, 34(9): 1399-1405.
doi: 10.13433/j.cnki.1003-8728.2015.0917
Abstract:
To compensate the insufficiency of describing the content of 3D models and low recognizing capability based on extraction algorithm of statistical feature, a new approach of 3D model multi-stage filtration of characteristic face retrieval technology is presented. In the off line phase, the model file of IGES format is parsed to get the attribute information of faces. In the on line phase, the characteristic face of model is input with hand-painting for multi-stage filtrating. And precise retrieving is performed according to the eigenvector of model transformed from the statistically classified characteristic face data table. The similarity and ranking is calculated with distance algorithm. The experimental results show that the efficiency and accuracy it improved , and can meet the general requirements of engineering retrieval.
To compensate the insufficiency of describing the content of 3D models and low recognizing capability based on extraction algorithm of statistical feature, a new approach of 3D model multi-stage filtration of characteristic face retrieval technology is presented. In the off line phase, the model file of IGES format is parsed to get the attribute information of faces. In the on line phase, the characteristic face of model is input with hand-painting for multi-stage filtrating. And precise retrieving is performed according to the eigenvector of model transformed from the statistically classified characteristic face data table. The similarity and ranking is calculated with distance algorithm. The experimental results show that the efficiency and accuracy it improved , and can meet the general requirements of engineering retrieval.
2015, 34(9): 1406-1409.
doi: 10.13433/j.cnki.1003-8728.2015.0918
Abstract:
In studying the thermal characteristics of the hydrostatic motorized spindle, heat resources and heat transfer methods were analyzed. The thermo-mechanical coupling model was developed with the finite element analysis of the hydrostatic motorized spindle. The temperature distribution and thermal deformation in different directions were simulated with thermal-structure coupling analysis in a certain condition. The simulation results show that the highest temperature occurs in the front sliding bearing. The maximum axial deformation occurs in the place where the grinding wheel is installed, and the radial deformation is so large that it affects the machining precision.
In studying the thermal characteristics of the hydrostatic motorized spindle, heat resources and heat transfer methods were analyzed. The thermo-mechanical coupling model was developed with the finite element analysis of the hydrostatic motorized spindle. The temperature distribution and thermal deformation in different directions were simulated with thermal-structure coupling analysis in a certain condition. The simulation results show that the highest temperature occurs in the front sliding bearing. The maximum axial deformation occurs in the place where the grinding wheel is installed, and the radial deformation is so large that it affects the machining precision.
2015, 34(9): 1410-1414.
doi: 10.13433/j.cnki.1003-8728.2015.0919
Abstract:
To decrease the interaction between tension zones and prevent the tension fluctuation propagating downstream, we propose a decoupling strategy based on linear active disturbance rejection control (LADRC). First, the dynamic mechanism model of a multi-stage tension system was built. Then, the dynamic interaction between the channels of the multi-stage tension system was treated as disturbances which were estimated with a linear extended state observer (LESO), and the estimated states were employed for state feedback control and compensation. After that we designed the LADRC controller cascading with static decoupling, which decoupled the multi-input multi-output (MIMO) system into a parallel single-input single-output subsystem. The simulation results show that the LADRC controller designed is able to effectively prevent the propagation of tension fluctuation downstream and has better disturbance rejection performance than that of classical decentralized proportional integration differentiation (PID) controller no matter whether for model mismatch or for external disturbance.
To decrease the interaction between tension zones and prevent the tension fluctuation propagating downstream, we propose a decoupling strategy based on linear active disturbance rejection control (LADRC). First, the dynamic mechanism model of a multi-stage tension system was built. Then, the dynamic interaction between the channels of the multi-stage tension system was treated as disturbances which were estimated with a linear extended state observer (LESO), and the estimated states were employed for state feedback control and compensation. After that we designed the LADRC controller cascading with static decoupling, which decoupled the multi-input multi-output (MIMO) system into a parallel single-input single-output subsystem. The simulation results show that the LADRC controller designed is able to effectively prevent the propagation of tension fluctuation downstream and has better disturbance rejection performance than that of classical decentralized proportional integration differentiation (PID) controller no matter whether for model mismatch or for external disturbance.
2015, 34(9): 1415-1418.
doi: 10.13433/j.cnki.1003-8728.2015.0920
Abstract:
In optimization of body-in-white, a large amount of panels will increase the modal sensitivity analysis objects and computation. So with the modal strain energy analysis, the optimizing efficiency will be increased. Based on the finite element analysis model verified with modal experiment, the large deformation parts of body-in-white and the sensitivities of these parts are defined in modal strain energy analysis and sensitivity analysis. According to the sensitivity analysis results, we improve the first modal frequency with adjusting the thickness of the parts. The final results show that after optimization, the first modal frequency is raised from 15.75 Hz to 16.50 Hz, without weight increase of the body-in-white.
In optimization of body-in-white, a large amount of panels will increase the modal sensitivity analysis objects and computation. So with the modal strain energy analysis, the optimizing efficiency will be increased. Based on the finite element analysis model verified with modal experiment, the large deformation parts of body-in-white and the sensitivities of these parts are defined in modal strain energy analysis and sensitivity analysis. According to the sensitivity analysis results, we improve the first modal frequency with adjusting the thickness of the parts. The final results show that after optimization, the first modal frequency is raised from 15.75 Hz to 16.50 Hz, without weight increase of the body-in-white.
2015, 34(9): 1419-1423.
doi: 10.13433/j.cnki.1003-8728.2015.0921
Abstract:
This paper presents studies on the anti-skidding regulation (ASR) for tractor with three axles. The anti-skidding algorithms, i.e. PID controller for engine torque on low friction road and the logic threshold controller for differential braking on the split friction road are designed. An anti-lock braking system (ABS)/ASR controller is developed. Hardware in loop (HIL) simulation bench is built, which is constituted of Trucksim, Labview real-time operating system, and actual steering and brake parts. ABS/ASR electronic control unit (ECU) is tested with typical operation conditions on HIL bench. Experimental results show that the proposed anti-skidding algorithms and the developed ABS/ASR ECU can restrain the skidding of driving wheels effectively, therefore, improve vehicle maneuverability and lateral stabilities.
This paper presents studies on the anti-skidding regulation (ASR) for tractor with three axles. The anti-skidding algorithms, i.e. PID controller for engine torque on low friction road and the logic threshold controller for differential braking on the split friction road are designed. An anti-lock braking system (ABS)/ASR controller is developed. Hardware in loop (HIL) simulation bench is built, which is constituted of Trucksim, Labview real-time operating system, and actual steering and brake parts. ABS/ASR electronic control unit (ECU) is tested with typical operation conditions on HIL bench. Experimental results show that the proposed anti-skidding algorithms and the developed ABS/ASR ECU can restrain the skidding of driving wheels effectively, therefore, improve vehicle maneuverability and lateral stabilities.
2015, 34(9): 1424-1426.
doi: 10.13433/j.cnki.1003-8728.2015.0922
Abstract:
A numerical model for investigating the delamination behavior of laminated composite under fatigue loading is proposed. The model mainly includes three parts, i.e. the constitutive model, a damage criterion and a fatigue evolution law. The propagation of delamination is described with defining the evolution of the damage parameter of the cohesive element. An User Material Subroutine (UMAT) with commercialized finite element software ABAQUS is implemented in the model. Through a cycle jump strategy and an envelope loading curve method, the fatigue delamination propagation of a Double Cantilever Beam(DCB) test is simulated. The numerical simulation data is in a good agreement with the experiment data, and it is verified that the model is capable of simulating fatigue delamination behavior of laminated composite.
A numerical model for investigating the delamination behavior of laminated composite under fatigue loading is proposed. The model mainly includes three parts, i.e. the constitutive model, a damage criterion and a fatigue evolution law. The propagation of delamination is described with defining the evolution of the damage parameter of the cohesive element. An User Material Subroutine (UMAT) with commercialized finite element software ABAQUS is implemented in the model. Through a cycle jump strategy and an envelope loading curve method, the fatigue delamination propagation of a Double Cantilever Beam(DCB) test is simulated. The numerical simulation data is in a good agreement with the experiment data, and it is verified that the model is capable of simulating fatigue delamination behavior of laminated composite.
2015, 34(9): 1427-1430.
doi: 10.13433/j.cnki.1003-8728.2015.0923
Abstract:
An assumption of headrest-airbag is putted forward in this paper: an airbag is added in the interior of front seat headrest, the airbag opens and expands instantly to form the airbag cushion between rear occupant's head and seat in the collision, absorbs impact energy and avoids the occurrence of the secondary collision between head and frontal headrest or seatback, thereby reducing occupant injury. Based on the geometry and feature of one car model, the rear occupant restraint system model is set up with MADYMO simulation software, and the restraint model is verified with the real test. The results of computer simulation show that compared with normal front seat, HIC15(Head Injury Criterion) and neck occipital moment of rear occupant drops by 66.4% and 63.9% respectively, but T3MS (Thorax 3ms Resultant Acceralation) only increases by 5.5% when the headrest-airbag is used.
An assumption of headrest-airbag is putted forward in this paper: an airbag is added in the interior of front seat headrest, the airbag opens and expands instantly to form the airbag cushion between rear occupant's head and seat in the collision, absorbs impact energy and avoids the occurrence of the secondary collision between head and frontal headrest or seatback, thereby reducing occupant injury. Based on the geometry and feature of one car model, the rear occupant restraint system model is set up with MADYMO simulation software, and the restraint model is verified with the real test. The results of computer simulation show that compared with normal front seat, HIC15(Head Injury Criterion) and neck occipital moment of rear occupant drops by 66.4% and 63.9% respectively, but T3MS (Thorax 3ms Resultant Acceralation) only increases by 5.5% when the headrest-airbag is used.
2015, 34(9): 1431-1437.
doi: 10.13433/j.cnki.1003-8728.2015.0924
Abstract:
Because of poor speed stability and complex operation of a continuous multi-brake system, we study the joint brake matching control that uses engine brake, exhaust brake and eddy current retarder. We obtain the characteristics of brake force of different brake systems with road tests and propose the matching control scheme. We also design a joint brake matching control system with the back propagation (BP) neural network. Furthermore, we simulate the control system with Matlab/Simulink software. The simulation results demonstrate that the control system designed by us can make a heavy duty vehicle work at a desired speed on downhill paths with various slopes and that the labor intensity and complexity are reduced, thus improving the driving safety of the heavy duty vehicle.
Because of poor speed stability and complex operation of a continuous multi-brake system, we study the joint brake matching control that uses engine brake, exhaust brake and eddy current retarder. We obtain the characteristics of brake force of different brake systems with road tests and propose the matching control scheme. We also design a joint brake matching control system with the back propagation (BP) neural network. Furthermore, we simulate the control system with Matlab/Simulink software. The simulation results demonstrate that the control system designed by us can make a heavy duty vehicle work at a desired speed on downhill paths with various slopes and that the labor intensity and complexity are reduced, thus improving the driving safety of the heavy duty vehicle.
2015, 34(9): 1438-1441.
doi: 10.13433/j.cnki.1003-8728.2015.0925
Abstract:
Considering that the vehicle state error derives from the different initial states and parameters between the real vehicle and the reference model, we propose the optimal control for the active four-wheel steering vehicle with only the initial state difference, which can make the 4WS to follow the reference model very quickly. And for the 4WS with the two differences, optimal control is adopted to design the sliding mode in order to eliminate the state error caused by the initial state difference. On this basis, the fractional sliding mode control is designed to eliminate the state error caused by the parameter difference. And the simulation results show that the fractional sliding mode control can make the 4WS to track the reference model very quickly, although the parameters between the 4WS model and the reference model are mismatched. It is proved that the fractional sliding mode control is effective.
Considering that the vehicle state error derives from the different initial states and parameters between the real vehicle and the reference model, we propose the optimal control for the active four-wheel steering vehicle with only the initial state difference, which can make the 4WS to follow the reference model very quickly. And for the 4WS with the two differences, optimal control is adopted to design the sliding mode in order to eliminate the state error caused by the initial state difference. On this basis, the fractional sliding mode control is designed to eliminate the state error caused by the parameter difference. And the simulation results show that the fractional sliding mode control can make the 4WS to track the reference model very quickly, although the parameters between the 4WS model and the reference model are mismatched. It is proved that the fractional sliding mode control is effective.
2015, 34(9): 1442-1445.
doi: 10.13433/j.cnki.1003-8728.2015.0926
Abstract:
Regarding the real axles of a passage car as the research object, based on the result of static analysis, we simulate the fatigue life of the rear axles with means of two prediction methods: the nominal stress method and local stress-strain method. The rear axles are acquired with two heat treatments. With the standards of the fatigue bench test results, the calculation results and testing results are compared to find which method' result is closer to the actual conditions of bench tests. The compared result shows that the fatigue analysis results of the real axle structure with the stress-strain method is more accurate when the working stress of low cycle fatigue approaches or exceeds the material's yield strength.
Regarding the real axles of a passage car as the research object, based on the result of static analysis, we simulate the fatigue life of the rear axles with means of two prediction methods: the nominal stress method and local stress-strain method. The rear axles are acquired with two heat treatments. With the standards of the fatigue bench test results, the calculation results and testing results are compared to find which method' result is closer to the actual conditions of bench tests. The compared result shows that the fatigue analysis results of the real axle structure with the stress-strain method is more accurate when the working stress of low cycle fatigue approaches or exceeds the material's yield strength.
2015, 34(9): 1446-1450.
doi: 10.13433/j.cnki.1003-8728.2015.0927
Abstract:
To further study the variation of the structure and surface morphology in the fatigue process of metals, a low cycle fatigue test was performed with the T2 copper, and images of the surface microscopic morphology were obtained with remote microscope. The image processing and feature extraction were achieved utilizing image gray level histogram and gray co-occurrence matrix (GLCM) method in the program of matlab. It was found that the surface morphology and its values were closely related with fatigue damage through image feature extraction and analysis in different cycle time.
To further study the variation of the structure and surface morphology in the fatigue process of metals, a low cycle fatigue test was performed with the T2 copper, and images of the surface microscopic morphology were obtained with remote microscope. The image processing and feature extraction were achieved utilizing image gray level histogram and gray co-occurrence matrix (GLCM) method in the program of matlab. It was found that the surface morphology and its values were closely related with fatigue damage through image feature extraction and analysis in different cycle time.
2015, 34(9): 1451-1454.
doi: 10.13433/j.cnki.1003-8728.2015.0928
Abstract:
On the basis of the crack tip blunting theory and fracture criterion of notched elements, when the blunted crack tip radius ρ reaches the critical blunted crack tip radius value ρc, the cracked element can be considered as notched element. A simple model for predicting plane-strain fracture toughness KIc for ductile materials was obtained on the assumption that there was a direct relationship between ρc and the deformation capacity of the hypothetical material element located ahead of the notch tip, i.e., elongation δ. The analysis on the model show that the value of KIc is apparently related to the elasticity modulus and the elongation. Furthermore, for a given material KIc is associated exclusively with δ. The mechanical properties test, including smooth tensile test and KIc test for 2124 aluminum alloy were carried out with specimens with different heat treatment state and different orientation directions. The experimental results show a significant linear correlation between KIc and δ, which verify the correctness of the present model.
On the basis of the crack tip blunting theory and fracture criterion of notched elements, when the blunted crack tip radius ρ reaches the critical blunted crack tip radius value ρc, the cracked element can be considered as notched element. A simple model for predicting plane-strain fracture toughness KIc for ductile materials was obtained on the assumption that there was a direct relationship between ρc and the deformation capacity of the hypothetical material element located ahead of the notch tip, i.e., elongation δ. The analysis on the model show that the value of KIc is apparently related to the elasticity modulus and the elongation. Furthermore, for a given material KIc is associated exclusively with δ. The mechanical properties test, including smooth tensile test and KIc test for 2124 aluminum alloy were carried out with specimens with different heat treatment state and different orientation directions. The experimental results show a significant linear correlation between KIc and δ, which verify the correctness of the present model.
2015, 34(9): 1455-1460.
doi: 10.13433/j.cnki.1003-8728.2015.0929
Abstract:
Aiming at the time that specimen with high temperature is in contact with bars with low temperature in different temperature environments, we use ABAQUS software to simulate heat conduction and temperature distribution between specimen and bars at different contact times. Then, Laser velocimetry is used to measure achievable contact time in accordance to SHPB experiment at high temperatures and high strain rates with pneumatically synchronous mechanism. The reliability of pneumatically synchronous mechanism and the validity of experimental test are analyzed. As the results show, the temperature of specimen will drop more than 10% if the contact time exceeds about 200 ms. When the initial temperature of specimen is 1 200 ℃, the core temperature of bars ends will exceeds about 250 ℃ which is the allowable temperature of metal bar if the contact time exceeds 500 ms. By means of fine-tuning, pneumatically synchronous mechanism in the present SHPB experiment at high temperatures and high strain rates introduced in order to achieve a cold-hot contact time of 10 ms. The present test method of SHPB experiment at high temperatures and high strain rates is credible verified via testing.
Aiming at the time that specimen with high temperature is in contact with bars with low temperature in different temperature environments, we use ABAQUS software to simulate heat conduction and temperature distribution between specimen and bars at different contact times. Then, Laser velocimetry is used to measure achievable contact time in accordance to SHPB experiment at high temperatures and high strain rates with pneumatically synchronous mechanism. The reliability of pneumatically synchronous mechanism and the validity of experimental test are analyzed. As the results show, the temperature of specimen will drop more than 10% if the contact time exceeds about 200 ms. When the initial temperature of specimen is 1 200 ℃, the core temperature of bars ends will exceeds about 250 ℃ which is the allowable temperature of metal bar if the contact time exceeds 500 ms. By means of fine-tuning, pneumatically synchronous mechanism in the present SHPB experiment at high temperatures and high strain rates introduced in order to achieve a cold-hot contact time of 10 ms. The present test method of SHPB experiment at high temperatures and high strain rates is credible verified via testing.
2015, 34(9): 1461-1466.
doi: 10.13433/j.cnki.1003-8728.2015.0930
Abstract:
The objective is to investigate a bird strike experiment in typical metal stiffened plate. Comparing with the traditional contact test methods, the 3D displacement curves of measured points in bird strike region for the stiffened metal plate is high accuracy and more reliable by applying digital image processing technology of non-contact measurement. Based on the high-speed video data, the numerical bird body should be simulated with a fluid constitutive model. Finally, the most dangerous impact point of the typical stiffened plate is determined with comparing the experimental results of different impact point, and the influence of different connection strength is confirmed by verifying the joining strength between the different bridge and skin.
The objective is to investigate a bird strike experiment in typical metal stiffened plate. Comparing with the traditional contact test methods, the 3D displacement curves of measured points in bird strike region for the stiffened metal plate is high accuracy and more reliable by applying digital image processing technology of non-contact measurement. Based on the high-speed video data, the numerical bird body should be simulated with a fluid constitutive model. Finally, the most dangerous impact point of the typical stiffened plate is determined with comparing the experimental results of different impact point, and the influence of different connection strength is confirmed by verifying the joining strength between the different bridge and skin.
2015, 34(9): 1467-1471.
doi: 10.13433/j.cnki.1003-8728.2015.0931
Abstract:
To improve the shape accuracy of profile in the roll-bending, the springback law Z shaped profile in roll-bending is experimentally investigated, the relation between the forming radius of profile and displacement of the side roll is established and the forming parameters for roll-bending is obtained with considering the springback. A 3D model for the roll-bending forming is proposed, and ABAQUS software is employed to analyze the influence of the main roller size, clamp force and friction coefficient on the curvature radius of each section in the longitude direction. The results show that the bigger main roller size is, the better the uniform distributed curvature. The reasonable clamp force and the range of friction coefficient of this Z shaped profile were given in this paper. With adopting these optiumu parameters obtained with FE simulation, the roll-bending experiments were carried out, and the the shape accuracy for final formed profile was improved.
To improve the shape accuracy of profile in the roll-bending, the springback law Z shaped profile in roll-bending is experimentally investigated, the relation between the forming radius of profile and displacement of the side roll is established and the forming parameters for roll-bending is obtained with considering the springback. A 3D model for the roll-bending forming is proposed, and ABAQUS software is employed to analyze the influence of the main roller size, clamp force and friction coefficient on the curvature radius of each section in the longitude direction. The results show that the bigger main roller size is, the better the uniform distributed curvature. The reasonable clamp force and the range of friction coefficient of this Z shaped profile were given in this paper. With adopting these optiumu parameters obtained with FE simulation, the roll-bending experiments were carried out, and the the shape accuracy for final formed profile was improved.
2015, 34(9): 1472-1476.
doi: 10.13433/j.cnki.1003-8728.2015.0932
Abstract:
According to the characteristics of reflector antenna design and its working conditions, a new discrete variable optimization model under multiple load conditions is developed. In the model, the gain of antenna is introduced to consider the relationship between electrical performance and deformation of antenna structures. In this model, the antenna weight or gain is adopted as the objective functions and the weighted compliance is used as the constraints. The proposed method is applied to the structural optimization design of a reflector antenna. The results show that traditional optimization methods can improve the stiffness of antenna structure, but can not increase their electrical performance. While in the allowed limitations, both the requirements for the electrical performance and structural stiffness of antenna structure can be satisfied with the proposed coupling optimization design.
According to the characteristics of reflector antenna design and its working conditions, a new discrete variable optimization model under multiple load conditions is developed. In the model, the gain of antenna is introduced to consider the relationship between electrical performance and deformation of antenna structures. In this model, the antenna weight or gain is adopted as the objective functions and the weighted compliance is used as the constraints. The proposed method is applied to the structural optimization design of a reflector antenna. The results show that traditional optimization methods can improve the stiffness of antenna structure, but can not increase their electrical performance. While in the allowed limitations, both the requirements for the electrical performance and structural stiffness of antenna structure can be satisfied with the proposed coupling optimization design.
