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RSS2020 Vol. 39, No. 1
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2020, 39(1): 1-9.
doi: 10.13433/j.cnki.1003-8728.20190073
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Abstract:
In this paper, the dynamic control method of a 2-DOF parallel manipulator under high-speed motion is studied. By tracing the error of the simplified rigid-body dynamic model for parallel manipulator, a modeling method based on the two-coefficient compensation allocation strategy is proposed, and the simplified rigid-body dynamic model for the manipulator is optimized. Based on the simplified model, a dynamic feedforward control method of the manipulator was established. In order to further improve the robustness of the control process, an H∞+ dynamic feedforward control method is proposed. Based on the establishment of the mechanical and electrical joint simulation system of the manipulator, the two control methods are simulated and compared in detail. The simulation results show that the control method proposed in this paper can reduce the influence of the torque disturbance on the output of servo motor and greatly reduce the positioning error of the end of the manipulator, improving the control accuracy of the manipulator.
In this paper, the dynamic control method of a 2-DOF parallel manipulator under high-speed motion is studied. By tracing the error of the simplified rigid-body dynamic model for parallel manipulator, a modeling method based on the two-coefficient compensation allocation strategy is proposed, and the simplified rigid-body dynamic model for the manipulator is optimized. Based on the simplified model, a dynamic feedforward control method of the manipulator was established. In order to further improve the robustness of the control process, an H∞+ dynamic feedforward control method is proposed. Based on the establishment of the mechanical and electrical joint simulation system of the manipulator, the two control methods are simulated and compared in detail. The simulation results show that the control method proposed in this paper can reduce the influence of the torque disturbance on the output of servo motor and greatly reduce the positioning error of the end of the manipulator, improving the control accuracy of the manipulator.
2020, 39(1): 10-15.
doi: 10.13433/j.cnki.1003-8728.20190092
Abstract:
In order to select a rational solid-liquid two-phase flow model for calculating mineral slurry in a lift pump for deep-sea mining, as the deep seabed minerals are characterized by a wide span of grain size and large particle size, the calculation models of coarse particle-homogeneous slurry and of solid-liquid two-phase mixture slurry were selected to carry out the numerical simulation analysis of the lift pump. The simulation results show that the internal flow field obtained by the calculation model of coarse particle-homogeneous slurry is similar to that obtained by the calculation model of solid-liquid two-phase mixture slurry, so the model can be used to analyze the internal flow field of the lift pump in deep-sea mining. This model can save computing time by reducing the number of particle tracking. The comparison of the external characteristics of the lift pump obtained by the two calculation models with the test results show that the pump head and power calculated with the models are in close agreement to the test results, indicating that the models have advantages in calculating the performance of the lift pump.
In order to select a rational solid-liquid two-phase flow model for calculating mineral slurry in a lift pump for deep-sea mining, as the deep seabed minerals are characterized by a wide span of grain size and large particle size, the calculation models of coarse particle-homogeneous slurry and of solid-liquid two-phase mixture slurry were selected to carry out the numerical simulation analysis of the lift pump. The simulation results show that the internal flow field obtained by the calculation model of coarse particle-homogeneous slurry is similar to that obtained by the calculation model of solid-liquid two-phase mixture slurry, so the model can be used to analyze the internal flow field of the lift pump in deep-sea mining. This model can save computing time by reducing the number of particle tracking. The comparison of the external characteristics of the lift pump obtained by the two calculation models with the test results show that the pump head and power calculated with the models are in close agreement to the test results, indicating that the models have advantages in calculating the performance of the lift pump.
2020, 39(1): 16-21.
doi: 10.13433/j.cnki.1003-8728.20190081
Abstract:
Aiming at the problem that isotropic virtual material model can't accurately characterize the difference of normal and tangential performances of bolt-fixed joint surface, in this paper, the dynamic model of bolt-fixed joint surface of machine tool is built with transversely isotropic virtual material, and based on the experimental design and finite element analysis; and a radial basis function (RBF) neural network model of bolt-fixed joint surface of machine tool is made. Based on the modal test results, the optimization objective function is constructed and solved by particle swarm optimization (PSO), the elastic constants of transversely isotropic virtual materials are identified. The results show that the first six vibration modes of the theoretical model basically coincide with the experimental modes respectively, and the error of natural frequency is less than 5.1%. This study shows the effectiveness of the method, and provides a new method for identifying parameters of the fixed joint surface of machine tool bolts.
Aiming at the problem that isotropic virtual material model can't accurately characterize the difference of normal and tangential performances of bolt-fixed joint surface, in this paper, the dynamic model of bolt-fixed joint surface of machine tool is built with transversely isotropic virtual material, and based on the experimental design and finite element analysis; and a radial basis function (RBF) neural network model of bolt-fixed joint surface of machine tool is made. Based on the modal test results, the optimization objective function is constructed and solved by particle swarm optimization (PSO), the elastic constants of transversely isotropic virtual materials are identified. The results show that the first six vibration modes of the theoretical model basically coincide with the experimental modes respectively, and the error of natural frequency is less than 5.1%. This study shows the effectiveness of the method, and provides a new method for identifying parameters of the fixed joint surface of machine tool bolts.
2020, 39(1): 22-27.
doi: 10.13433/j.cnki.1003-8728.20190087
Abstract:
Based on the theory of rigid-flexible coupling dynamics, the PATRAN/NASTRAN and ADAMS software are used to simulate the dynamics of the laryngeal plate, so that the laryngeal block and the flexible plate move to the target position. The simulation results show that if the contact point motion trajectory of laryngeal block and the flexible plate is ignored, the calculated contact force between the laryngeal block and the flexible plate will be too large to meet the requirements. To this end, the trajectory planning of the contact trajectory of the laryngeal block and the flexible plate is considered. Considering the motion coordination of the laryngeal block and the flexible plate, the trajectory of the laryngeal block and the flexible plate contact point is adjusted. The results show that the method satisfies both the laryngeal block and the flexible plate, the contact force can ensure the profile accuracy of the laryngeal block and the flexible plate. This study provides the necessary theoretical basis for the coordinated movement of the laryngeal block.
Based on the theory of rigid-flexible coupling dynamics, the PATRAN/NASTRAN and ADAMS software are used to simulate the dynamics of the laryngeal plate, so that the laryngeal block and the flexible plate move to the target position. The simulation results show that if the contact point motion trajectory of laryngeal block and the flexible plate is ignored, the calculated contact force between the laryngeal block and the flexible plate will be too large to meet the requirements. To this end, the trajectory planning of the contact trajectory of the laryngeal block and the flexible plate is considered. Considering the motion coordination of the laryngeal block and the flexible plate, the trajectory of the laryngeal block and the flexible plate contact point is adjusted. The results show that the method satisfies both the laryngeal block and the flexible plate, the contact force can ensure the profile accuracy of the laryngeal block and the flexible plate. This study provides the necessary theoretical basis for the coordinated movement of the laryngeal block.
2020, 39(1): 28-34.
doi: 10.13433/j.cnki.1003-8728.20190239
Abstract:
Signals of loader's transmission system collected by sensors are always disturbed because of the harsh environment, which is not conducive to data analysis. Therefore, the signal should first be denoised and filtered when studying its working condition. Taking a front axle torque signal of a 5t loader as the research object, the wavelet packet transform method was used to decompose the db9-6 scale after eliminating the trend, and then the reconstructed signal was obtained by the wavelet packet optimal decomposition tree. Compared with the Butterworth denoising and wavelet denoising methods, it is concluded that Butterworth filtering method has phase deviation compared with the original signal, and the signal-to-noise ratio and root mean square error of optimal base decomposition tree of wavelet packet after de-noising are 16.38 and 74.71 respectively, which are similar to the wavelet transform denoising results and more suitable for the fields of working condition identification and artificial intelligence algorithms, etc. The research results could provide a method basis for data signal processing of other similar construction machinery.
Signals of loader's transmission system collected by sensors are always disturbed because of the harsh environment, which is not conducive to data analysis. Therefore, the signal should first be denoised and filtered when studying its working condition. Taking a front axle torque signal of a 5t loader as the research object, the wavelet packet transform method was used to decompose the db9-6 scale after eliminating the trend, and then the reconstructed signal was obtained by the wavelet packet optimal decomposition tree. Compared with the Butterworth denoising and wavelet denoising methods, it is concluded that Butterworth filtering method has phase deviation compared with the original signal, and the signal-to-noise ratio and root mean square error of optimal base decomposition tree of wavelet packet after de-noising are 16.38 and 74.71 respectively, which are similar to the wavelet transform denoising results and more suitable for the fields of working condition identification and artificial intelligence algorithms, etc. The research results could provide a method basis for data signal processing of other similar construction machinery.
2020, 39(1): 35-40.
doi: 10.13433/j.cnki.1003-8728.20190086
Abstract:
To couple the highly complex and dynamic model of the structure of a parallel device and the nonlinear problem in a parallel solar tracking device, this paper analyzed its kinematic characteristics and inverse kinematics, proposed a dynamic modeling theory based on the U-K theory and applied the Lagrangian method to the parallel mechanism. Firstly, the Lagrangian method is used to solve the dynamic model of each branch of the parallel mechanism. Secondly, considering the constraint relationship of the parallel mechanism branch to the moving platform, this paper hierarchical accumulation idea instead of introducing the Lagrangian multiplier. Then the constraint-based dynamics model of the parallel solar tracking device was established. Finally, the established dynamic model is solved and verified with the MATLAB and ADAMS co-simulation. The simulation results show the consistency between theoretical calculation and simulation analysis.
To couple the highly complex and dynamic model of the structure of a parallel device and the nonlinear problem in a parallel solar tracking device, this paper analyzed its kinematic characteristics and inverse kinematics, proposed a dynamic modeling theory based on the U-K theory and applied the Lagrangian method to the parallel mechanism. Firstly, the Lagrangian method is used to solve the dynamic model of each branch of the parallel mechanism. Secondly, considering the constraint relationship of the parallel mechanism branch to the moving platform, this paper hierarchical accumulation idea instead of introducing the Lagrangian multiplier. Then the constraint-based dynamics model of the parallel solar tracking device was established. Finally, the established dynamic model is solved and verified with the MATLAB and ADAMS co-simulation. The simulation results show the consistency between theoretical calculation and simulation analysis.
2020, 39(1): 41-46.
doi: 10.13433/j.cnki.1003-8728.20190093
Abstract:
In order to investigate the nonlinear bifurcation characteristics of a split torque-combine power gear transmission, the nonlinear dynamic model of the split torque-combine power gear transmission with multiple backlashes is formulated; the rigid body displacements in dynamic equations are eliminated by adopting the Gaussian elimination technique as well as generalized relative displacement variation; dynamic equations are solved non-dimensionally. Bifurcation route under the excitation of meshing frequency, backlash, general transmission error and damping ratio are taken into account; qualitative and quantitative characteristics of bifurcation behavior are investigated by using a bifurcation diagram, the Poincaré section and the Lyapunov exponent. The investigation results show that an inverse period doubling bifurcation occurs when the meshing frequency increases; the bifurcation node is significantly affected by backlash; transient periodic windows take place inside the chaotic regions when a backlash or general transmission error varies; damping has a restraining effect on the period doubling bifurcation evolution.
In order to investigate the nonlinear bifurcation characteristics of a split torque-combine power gear transmission, the nonlinear dynamic model of the split torque-combine power gear transmission with multiple backlashes is formulated; the rigid body displacements in dynamic equations are eliminated by adopting the Gaussian elimination technique as well as generalized relative displacement variation; dynamic equations are solved non-dimensionally. Bifurcation route under the excitation of meshing frequency, backlash, general transmission error and damping ratio are taken into account; qualitative and quantitative characteristics of bifurcation behavior are investigated by using a bifurcation diagram, the Poincaré section and the Lyapunov exponent. The investigation results show that an inverse period doubling bifurcation occurs when the meshing frequency increases; the bifurcation node is significantly affected by backlash; transient periodic windows take place inside the chaotic regions when a backlash or general transmission error varies; damping has a restraining effect on the period doubling bifurcation evolution.
2020, 39(1): 47-51.
doi: 10.13433/j.cnki.1003-8728.20190088
Abstract:
Aiming at the problem of load extraction in the development of vehicle fatigue durability, a method of using virtual spindle coupling road simulator is proposed to extract the calculated road load quickly. A virtual fatigue and durability test system based on vehicle multi-body dynamic model and virtual spindle coupling road simulator system is established, and the road load spectrum collected by the vehicle in the proving ground is used as the model input condition, the calculated load of the components or subsystems of the vehicle model is extracted and is compared with the experimental data. The research results indicate that the load spectrum of the main components is basically consistent in the time domain, and the extracted load accuracy can meet the requirements of fatigue durability analysis of the whole vehicle and parts.
Aiming at the problem of load extraction in the development of vehicle fatigue durability, a method of using virtual spindle coupling road simulator is proposed to extract the calculated road load quickly. A virtual fatigue and durability test system based on vehicle multi-body dynamic model and virtual spindle coupling road simulator system is established, and the road load spectrum collected by the vehicle in the proving ground is used as the model input condition, the calculated load of the components or subsystems of the vehicle model is extracted and is compared with the experimental data. The research results indicate that the load spectrum of the main components is basically consistent in the time domain, and the extracted load accuracy can meet the requirements of fatigue durability analysis of the whole vehicle and parts.
2020, 39(1): 52-57.
doi: 10.13433/j.cnki.1003-8728.20190090
Abstract:
In order to study the effect of particle radius on the drum load characteristics and coal falling situation during the simulation of the spiral drum cutting process, the EDEM discrete element software was used to simulate the dynamic process of cutting a complex coal wall with a type of shearer drum, the load, load fluctuation and coal falling situation were obtained, and comparing with the value calculated by the auxiliary calculation program based on MATLAB. The results show that the use of discrete particles with different radius will have an impact on results of the drum load and coal falling situation. With the increase of the particle radius, there is no significant change in the drum load, and the average initial velocity of the particles under the cutting of the spiral drum is reduced, the load fluctuation coefficient and the coal loading rate are increased. Compared with the theoretical calculation, the simulation results are closer to the theoretical value and have high accuracy with the coal wall built with 12 mm radius particles. This study provides a reference for the selection of particle radius when EDEM discrete element simulation software is used to simulate the cutting process of shearer.
In order to study the effect of particle radius on the drum load characteristics and coal falling situation during the simulation of the spiral drum cutting process, the EDEM discrete element software was used to simulate the dynamic process of cutting a complex coal wall with a type of shearer drum, the load, load fluctuation and coal falling situation were obtained, and comparing with the value calculated by the auxiliary calculation program based on MATLAB. The results show that the use of discrete particles with different radius will have an impact on results of the drum load and coal falling situation. With the increase of the particle radius, there is no significant change in the drum load, and the average initial velocity of the particles under the cutting of the spiral drum is reduced, the load fluctuation coefficient and the coal loading rate are increased. Compared with the theoretical calculation, the simulation results are closer to the theoretical value and have high accuracy with the coal wall built with 12 mm radius particles. This study provides a reference for the selection of particle radius when EDEM discrete element simulation software is used to simulate the cutting process of shearer.
2020, 39(1): 58-61.
doi: 10.13433/j.cnki.1003-8728.20190085
Abstract:
In allusion to the deficiencies of that most of the current friction and wear testers have a single experimental form, only typical friction and wear experiments can be carried out, and the actual friction conditions of the material of the shovel teeth cannot be simulated. A new type of shovel friction and wear tester is developed. By using the cam-driven multi-link shovel tooth arm movement, the movement state of the shovel tooth in the material is simulated. By employing the Geneva-wheel mechanism and the compaction mechanism to level and compact the material while excavating the shovel tooth, the material status at the time of shovel tooth excavation is simulated. Consequently, the wear performance of the shovel teeth can ne measured under different conditions and materials, and which can provide reliable basis for designing the shovel teeth, testing and comparing the life of different types of shovel.
In allusion to the deficiencies of that most of the current friction and wear testers have a single experimental form, only typical friction and wear experiments can be carried out, and the actual friction conditions of the material of the shovel teeth cannot be simulated. A new type of shovel friction and wear tester is developed. By using the cam-driven multi-link shovel tooth arm movement, the movement state of the shovel tooth in the material is simulated. By employing the Geneva-wheel mechanism and the compaction mechanism to level and compact the material while excavating the shovel tooth, the material status at the time of shovel tooth excavation is simulated. Consequently, the wear performance of the shovel teeth can ne measured under different conditions and materials, and which can provide reliable basis for designing the shovel teeth, testing and comparing the life of different types of shovel.
2020, 39(1): 62-67.
doi: 10.13433/j.cnki.1003-8728.20190099
Abstract:
The artificial potential field (APF) based on link motion equation is proposed to guide the sampling of improved Transition-based RRT (T-RRT), quickening the convergence speed of the T-RRT algorithm in the motion planning of a robot arm when it is searching the low-cost path in a high-dimensional space. The manipulator model is simplified to improve the efficiency of collision detection and to construct the link motion equation through kinematics analysis. Then the sum of trajectory length of every particle is calculated to build the APF. As a cost function to judge state nodes, the APF guides the state nodes that approach the target position. Besides, in order to raise the expansion speed of the algorithm, the pruning function is introduced to restrict refinement nodes. Various obstacle maps are simulated with MATLAB. Compared with RRT and T-RRT algorithms, our algorithm has the shortest path length, the highest node sampling efficiency, the shortest node average sampling time, with the running time being shortened by about 3/4 and 2/3 respectively. The proposed algorithm can effectively enhance search efficiency, improve the path quality and adapt to environmental change.
The artificial potential field (APF) based on link motion equation is proposed to guide the sampling of improved Transition-based RRT (T-RRT), quickening the convergence speed of the T-RRT algorithm in the motion planning of a robot arm when it is searching the low-cost path in a high-dimensional space. The manipulator model is simplified to improve the efficiency of collision detection and to construct the link motion equation through kinematics analysis. Then the sum of trajectory length of every particle is calculated to build the APF. As a cost function to judge state nodes, the APF guides the state nodes that approach the target position. Besides, in order to raise the expansion speed of the algorithm, the pruning function is introduced to restrict refinement nodes. Various obstacle maps are simulated with MATLAB. Compared with RRT and T-RRT algorithms, our algorithm has the shortest path length, the highest node sampling efficiency, the shortest node average sampling time, with the running time being shortened by about 3/4 and 2/3 respectively. The proposed algorithm can effectively enhance search efficiency, improve the path quality and adapt to environmental change.
2020, 39(1): 68-73.
doi: 10.13433/j.cnki.1003-8728.20190076
Abstract:
Comparing with the CNC, absolute positioning accuracy of the industrial robots is low, and it is difficult to meet the requirements of high-precision machining processes such as grinding, which greatly limits its application development. Aiming at this problem, a calibration method for absolute positioning accuracy of robots based on the distance accuracy is proposed, which takes the optimization and selection of spatial measurement positions into consideration. Firstly, based on the influence of the spatial measurement positions on the measurement accuracy, the Jacobian matrix condition number is used to quantitatively describe the motion performance of the robot. Combining with the motion characteristics of robot joints, the optimal measurement spaces of the robot in joint space and Cartesian space are given. Then the MD-H (Modified D-H method) is used to construct the error model for the robot absolute positioning accuracy. The distance accuracy method is introduced, which is used to avoid the coordinate transformation error. Finally, based on the KUKA robot experimental platform, the calibration experiments were carried out. The results show that the average absolute positioning error of the robot decreases from 1.191 mm to 0.096 mm, which effectively validates the effectiveness of the calibration method.
Comparing with the CNC, absolute positioning accuracy of the industrial robots is low, and it is difficult to meet the requirements of high-precision machining processes such as grinding, which greatly limits its application development. Aiming at this problem, a calibration method for absolute positioning accuracy of robots based on the distance accuracy is proposed, which takes the optimization and selection of spatial measurement positions into consideration. Firstly, based on the influence of the spatial measurement positions on the measurement accuracy, the Jacobian matrix condition number is used to quantitatively describe the motion performance of the robot. Combining with the motion characteristics of robot joints, the optimal measurement spaces of the robot in joint space and Cartesian space are given. Then the MD-H (Modified D-H method) is used to construct the error model for the robot absolute positioning accuracy. The distance accuracy method is introduced, which is used to avoid the coordinate transformation error. Finally, based on the KUKA robot experimental platform, the calibration experiments were carried out. The results show that the average absolute positioning error of the robot decreases from 1.191 mm to 0.096 mm, which effectively validates the effectiveness of the calibration method.
2020, 39(1): 74-82.
doi: 10.13433/j.cnki.1003-8728.20190257
Abstract:
For revealing of fluid-structure interaction vibration of control valve-pipe conveying fluid control system, the transfer matrix modeling method for the system is studied. Taking a fixed-pinned pipe conveying fluid with a single seat control valve as an example, the valve body is simplified as a rigid body, the valve core-stem-spring diaphragm as a single freedom mass-spring-damping system, the pipe conveying fluid as elastic beams. Considering the fluid-structure interaction inside the control valve and the pipes, the transfer matrix model of the system is build based on linearity hypothesis. The simulation analysis of steady state harmonic time domain and frequency domain responses are carried out under the given operating conditions, and the effectiveness of the transfer matrix model for the valve-pipe system is testified; meanwhile, the influence of fluid-structure interaction on the vibrations response of the pipe system is revealed by comparison with single valve and single pipe model, respectively.
For revealing of fluid-structure interaction vibration of control valve-pipe conveying fluid control system, the transfer matrix modeling method for the system is studied. Taking a fixed-pinned pipe conveying fluid with a single seat control valve as an example, the valve body is simplified as a rigid body, the valve core-stem-spring diaphragm as a single freedom mass-spring-damping system, the pipe conveying fluid as elastic beams. Considering the fluid-structure interaction inside the control valve and the pipes, the transfer matrix model of the system is build based on linearity hypothesis. The simulation analysis of steady state harmonic time domain and frequency domain responses are carried out under the given operating conditions, and the effectiveness of the transfer matrix model for the valve-pipe system is testified; meanwhile, the influence of fluid-structure interaction on the vibrations response of the pipe system is revealed by comparison with single valve and single pipe model, respectively.
2020, 39(1): 83-87.
doi: 10.13433/j.cnki.1003-8728.20190095
Abstract:
Using the cemented carbide tools to conduct the cutting experiments of Lithium disilicate glass ceramics and fluorophlogopite ceramics and the system of laser confocal detection to observe the wear profile, the wear mechanism of tool is investigated. The wear mechanism of tool is proposed, which is the fatigue wear caused by multiple scratches on the hard point of the workpiece. The wear form of tool is the layer-by-layer peeling of the flank contact area. A theoretical model for tool wear was established in terms of the Hertz contact theory and friction fatigue theory. Then the turning experiment was carried out under different cutting parameters to verify the validity of the model and analyze the influence of the cutting parameters on the tool wear. Finally, the results show that the calculated value via model can predict the tool wear greatly well, and the prediction curve via model is consistent with the actual wear curve.
Using the cemented carbide tools to conduct the cutting experiments of Lithium disilicate glass ceramics and fluorophlogopite ceramics and the system of laser confocal detection to observe the wear profile, the wear mechanism of tool is investigated. The wear mechanism of tool is proposed, which is the fatigue wear caused by multiple scratches on the hard point of the workpiece. The wear form of tool is the layer-by-layer peeling of the flank contact area. A theoretical model for tool wear was established in terms of the Hertz contact theory and friction fatigue theory. Then the turning experiment was carried out under different cutting parameters to verify the validity of the model and analyze the influence of the cutting parameters on the tool wear. Finally, the results show that the calculated value via model can predict the tool wear greatly well, and the prediction curve via model is consistent with the actual wear curve.
2020, 39(1): 88-95.
doi: 10.13433/j.cnki.1003-8728.20190091
Abstract:
The deformation of the aircraft engines blade-fixture system is low, which causes the deformation of the blade in the machining process. A displacement sensor closed loop systems for high-resolution deformation is studied and integrated in order to monitor the influence of the high-frequency cutting force on the high-frequency displacement signals in machining, and to evaluate and design the blade-fixture system. Firstly, the relationship between the blade deformation and the cutting force generated when machining the tenon in the multi-point positioning, and clamping tool of the aircraft engines precision forging blade is introduced. Secondly, by means of the simulation analysis results, the position of cutting force on the blade tenon is determined when the blade tenon deforms to the maximum. Thirdly, according to the cutting force and deformation requirements of the test system sampling frequency, resolution and test accuracy, the appropriate displacement sensor is selected. Again, the data acquisition card is selected by the selected displacement sensor type, and the blade deformation closed loop systems are built. Finally, the blade tenon processing experiment was carried out to test the deformation of the blade under the cutting force, and the feasibility of the test system was verified. Describe the problems existing in the test and improve them. Meanwhile, the rationalization suggestion for the future construction of the blade tenon processing test system is put forward.
The deformation of the aircraft engines blade-fixture system is low, which causes the deformation of the blade in the machining process. A displacement sensor closed loop systems for high-resolution deformation is studied and integrated in order to monitor the influence of the high-frequency cutting force on the high-frequency displacement signals in machining, and to evaluate and design the blade-fixture system. Firstly, the relationship between the blade deformation and the cutting force generated when machining the tenon in the multi-point positioning, and clamping tool of the aircraft engines precision forging blade is introduced. Secondly, by means of the simulation analysis results, the position of cutting force on the blade tenon is determined when the blade tenon deforms to the maximum. Thirdly, according to the cutting force and deformation requirements of the test system sampling frequency, resolution and test accuracy, the appropriate displacement sensor is selected. Again, the data acquisition card is selected by the selected displacement sensor type, and the blade deformation closed loop systems are built. Finally, the blade tenon processing experiment was carried out to test the deformation of the blade under the cutting force, and the feasibility of the test system was verified. Describe the problems existing in the test and improve them. Meanwhile, the rationalization suggestion for the future construction of the blade tenon processing test system is put forward.
2020, 39(1): 96-101.
doi: 10.13433/j.cnki.1003-8728.20190316
Abstract:
The acoustic performance of the muffler is affected by the airflow regenerative noise. In order to improve the actual performance of the muffler, the LES-FEM method is used to investigate the flow regeneration noise of the expansion chamber muffler. Firstly, the effect of structural layout, flow velocity and expansion cavity transition structure on regeneration noise is analyzed for the single expansion chamber muffler. The results show that the turbulent kinetic energy and regenerative noise generated by the inner tube muffler are the smallest; when the flow velocity is increased, the muffler turbulent kinetic energy and regenerative noise sound power level are increased; taking the arc transition section can better improve the regenerative noise in the middle and high frequency. Secondly, the regenerative noise of the muffler with multi-chamber expansion chamber is analyzed and optimized. According to the location of maximum turbulence, the arc structures of different sizes are added at the end of the inner tube and the inlet and outlet tube. The total sound power level of the regenerative noise of the muffler was reduced by 9.44 dB, with significant noise reduction effect.
The acoustic performance of the muffler is affected by the airflow regenerative noise. In order to improve the actual performance of the muffler, the LES-FEM method is used to investigate the flow regeneration noise of the expansion chamber muffler. Firstly, the effect of structural layout, flow velocity and expansion cavity transition structure on regeneration noise is analyzed for the single expansion chamber muffler. The results show that the turbulent kinetic energy and regenerative noise generated by the inner tube muffler are the smallest; when the flow velocity is increased, the muffler turbulent kinetic energy and regenerative noise sound power level are increased; taking the arc transition section can better improve the regenerative noise in the middle and high frequency. Secondly, the regenerative noise of the muffler with multi-chamber expansion chamber is analyzed and optimized. According to the location of maximum turbulence, the arc structures of different sizes are added at the end of the inner tube and the inlet and outlet tube. The total sound power level of the regenerative noise of the muffler was reduced by 9.44 dB, with significant noise reduction effect.
2020, 39(1): 102-108.
doi: 10.13433/j.cnki.1003-8728.20190077
Abstract:
Due to the parasitic displacement of the straight beam flexible hinge, it is difficult to get the high precision motion of the MEMS mechanism. A novel flexible hinge with plane symmetrical and offset porous characteristics is presented. The finite element calculation model for flexible hinge is established, and its feasibility and correctness is checked with the closed-form compliance equation. Compliance, precision and modal analysis of flexible hinges of same porosity but different combination are calculated. The results show that the porous structure enhances the compliance of hinges. With the same porosity, the compliance and rotation precision of the symmetrical pore characteristics hinge are higher than that of the offset pore hinge, and the 3×3 symmetric arrangement of the porous structure can improve the deflection of the hinge free end by 20%, the center rotation precision is improved by 11.97%. The relationship between the free-end load-displacement of the flexible hinge and the porous structure is approximately linear. Those results provides a new idea for applying the porous hinges to the specific precision, large rotation angle and multi-direction forces.
Due to the parasitic displacement of the straight beam flexible hinge, it is difficult to get the high precision motion of the MEMS mechanism. A novel flexible hinge with plane symmetrical and offset porous characteristics is presented. The finite element calculation model for flexible hinge is established, and its feasibility and correctness is checked with the closed-form compliance equation. Compliance, precision and modal analysis of flexible hinges of same porosity but different combination are calculated. The results show that the porous structure enhances the compliance of hinges. With the same porosity, the compliance and rotation precision of the symmetrical pore characteristics hinge are higher than that of the offset pore hinge, and the 3×3 symmetric arrangement of the porous structure can improve the deflection of the hinge free end by 20%, the center rotation precision is improved by 11.97%. The relationship between the free-end load-displacement of the flexible hinge and the porous structure is approximately linear. Those results provides a new idea for applying the porous hinges to the specific precision, large rotation angle and multi-direction forces.
2020, 39(1): 109-116.
doi: 10.13433/j.cnki.1003-8728.20190102
Abstract:
The piston is sealed in the cylinder of hydraulic hammer driven by hydro-pneumatic that converts hydraulic energy to impact energy. The frame will be shocked during working. It was difficult to measure the piston states (displacement and velocity) and unknown dynamics (including frictional resistance and un-modeling dynamics, etc., these are called nonlinear terms) directly by sensor. Therefore, the dynamics model of piston was built and the dynamics model was decomposed into linear and non-linear parts. The observer theory and neural networks method were employed to design a neural networks augmented observer (NNAO). A radial basis function neural network (RBFNN) was located in feedback channel of observer which was applied to modeling the unknown dynamics. The weights training adaptive algorithms was derived and simplified for were updated on line. In this way, the problem of measuring physical parameters was transformed into the states estimation of piston motion and unknown dynamic modeling. The Lyapunov function was constructed, and the roundedness and dynamic convergence of the error were analyzed for the neural network augmented observer. The NNAO was validated by simulation using the Van der Pol chaotic oscillators systems. Finally, the NNAO was applied to measure states of the hydraulic piston and the results show that the NNAO is effective to estimate displacement and velocity of the piston, unknown dynamic detection as well as the impact energy of hydraulic hammer is measured.
The piston is sealed in the cylinder of hydraulic hammer driven by hydro-pneumatic that converts hydraulic energy to impact energy. The frame will be shocked during working. It was difficult to measure the piston states (displacement and velocity) and unknown dynamics (including frictional resistance and un-modeling dynamics, etc., these are called nonlinear terms) directly by sensor. Therefore, the dynamics model of piston was built and the dynamics model was decomposed into linear and non-linear parts. The observer theory and neural networks method were employed to design a neural networks augmented observer (NNAO). A radial basis function neural network (RBFNN) was located in feedback channel of observer which was applied to modeling the unknown dynamics. The weights training adaptive algorithms was derived and simplified for were updated on line. In this way, the problem of measuring physical parameters was transformed into the states estimation of piston motion and unknown dynamic modeling. The Lyapunov function was constructed, and the roundedness and dynamic convergence of the error were analyzed for the neural network augmented observer. The NNAO was validated by simulation using the Van der Pol chaotic oscillators systems. Finally, the NNAO was applied to measure states of the hydraulic piston and the results show that the NNAO is effective to estimate displacement and velocity of the piston, unknown dynamic detection as well as the impact energy of hydraulic hammer is measured.
2020, 39(1): 124-128.
doi: 10.13433/j.cnki.1003-8728.20190082
Abstract:
The static and dynamic mechanical behaviors of the jellyrolls of lithium-ion battery cell of electric vehicles are investigated by conducting in-plane constrained compression tests of representative volume element (RVE) specimens. The test results indicate that the load carrying behavior of the RVE specimens is characterized by the buckling, the kink and shear band formation, and the final densification of the jellyroll components. The specimens have obvious differences in the compressed mechanical behavior between the quasi-static loading condition and dynamic loading conditions. It is mainly shown that with the increase of loading velocity, the stress enhancement became more obvious and the deformation mode of the specimen also changed. Finally, the inertial effect of specimen structure and the strain rate effect of jellyroll materials are presented to explain the dynamic effect in the jellyroll RVE specimens under in-plane constrained compression.
The static and dynamic mechanical behaviors of the jellyrolls of lithium-ion battery cell of electric vehicles are investigated by conducting in-plane constrained compression tests of representative volume element (RVE) specimens. The test results indicate that the load carrying behavior of the RVE specimens is characterized by the buckling, the kink and shear band formation, and the final densification of the jellyroll components. The specimens have obvious differences in the compressed mechanical behavior between the quasi-static loading condition and dynamic loading conditions. It is mainly shown that with the increase of loading velocity, the stress enhancement became more obvious and the deformation mode of the specimen also changed. Finally, the inertial effect of specimen structure and the strain rate effect of jellyroll materials are presented to explain the dynamic effect in the jellyroll RVE specimens under in-plane constrained compression.
2020, 39(1): 129-136.
doi: 10.13433/j.cnki.1003-8728.20190098
Abstract:
The existing methods for the topological optimization of a compliant mechanism still have some difficulties in optimizing its hinge-like and grey topology. In order to obtain a clear and optimal topology without any hinge, a structural topological optimization method is proposed. Firstly, we construct a weighted combination compliance function, which can comprehensively characterize the local stiffness characteristics of the input and output ends of the compliant mechanism. Then, by introducing the small change constraints of the weighted combination mechanism, the Heaviside density projection and a varied constraint scheme, we establish an optimization model with steady changes in the configuration of the compliant mechanism. Finally, in combination with the MMA algorithm, a topological optimization method for compliant mechanism with steady changes in configuration is formulated. The numerical simulation results show that, compared with the existing methods, the proposed method has simple calculation formulae and can obtain a clear optimal topology without hinges.
The existing methods for the topological optimization of a compliant mechanism still have some difficulties in optimizing its hinge-like and grey topology. In order to obtain a clear and optimal topology without any hinge, a structural topological optimization method is proposed. Firstly, we construct a weighted combination compliance function, which can comprehensively characterize the local stiffness characteristics of the input and output ends of the compliant mechanism. Then, by introducing the small change constraints of the weighted combination mechanism, the Heaviside density projection and a varied constraint scheme, we establish an optimization model with steady changes in the configuration of the compliant mechanism. Finally, in combination with the MMA algorithm, a topological optimization method for compliant mechanism with steady changes in configuration is formulated. The numerical simulation results show that, compared with the existing methods, the proposed method has simple calculation formulae and can obtain a clear optimal topology without hinges.
2020, 39(1): 137-143.
doi: 10.13433/j.cnki.1003-8728.20190089
Abstract:
The steady heat transfer topology optimization model for orthotropic material structure is established based on the variable density method. The heat transfer topology optimization of variable section beam and circular saw blade is performed. The thermal compliance is reduced by 68.78% and 74.82%, and the weight reduction is of 39.03% and 23.75%. The effect of the orthotropic factors and off-angle on the optimal topology and heat dissipation of orthotropic material structure were emphasized. The results show that the heat dissipation increases with the increasing of orthotropic factors. The heat dissipation performance of composite materials is superior and inferior to isotropic material when the orthotropic factors is less than and greater than 1, respectively. The orthotropic factors and off-angle of the variable cross section beam have great influence on the optimal topology and heat dissipation, while for the circular saw blade with symmetrical geometry and thermal load, the off-angle has no effect on the optimal topology and temperature distribution. The off-angle of variable cross section beam is suggested to choose in the range of 60°~75°, and the better topology can be obtained by choosing orthotropic factors and off-angle reasonably in the structural optimization for heat transfer topology of orthotropic material.
The steady heat transfer topology optimization model for orthotropic material structure is established based on the variable density method. The heat transfer topology optimization of variable section beam and circular saw blade is performed. The thermal compliance is reduced by 68.78% and 74.82%, and the weight reduction is of 39.03% and 23.75%. The effect of the orthotropic factors and off-angle on the optimal topology and heat dissipation of orthotropic material structure were emphasized. The results show that the heat dissipation increases with the increasing of orthotropic factors. The heat dissipation performance of composite materials is superior and inferior to isotropic material when the orthotropic factors is less than and greater than 1, respectively. The orthotropic factors and off-angle of the variable cross section beam have great influence on the optimal topology and heat dissipation, while for the circular saw blade with symmetrical geometry and thermal load, the off-angle has no effect on the optimal topology and temperature distribution. The off-angle of variable cross section beam is suggested to choose in the range of 60°~75°, and the better topology can be obtained by choosing orthotropic factors and off-angle reasonably in the structural optimization for heat transfer topology of orthotropic material.
2020, 39(1): 144-149.
doi: 10.13433/j.cnki.1003-8728.20190084
Abstract:
Since the chemical treatment can affect the mechanical properties of fused deposition modeled (FDM) parts, the hot vapor smoothing treatment for the surfaces of FDM parts via chloroform solution was carried out. The effects of the treatment time, treatment temperature and concentration of polishing solution on both tensile strength and bending strength of FDM parts were studied. The results showed that both tensile strength and bending strength of the parts were reduced after chemical treatment. With the increasing of treatment time, treatment temperature and concentration of polishing solution, the tensile strength and bending strength of the parts decreased. At a treatment time of 10 min and treatment temperature of 60℃, the concentration of the polishing solution had small effect on the both tensile strength and bending strength of the parts.
Since the chemical treatment can affect the mechanical properties of fused deposition modeled (FDM) parts, the hot vapor smoothing treatment for the surfaces of FDM parts via chloroform solution was carried out. The effects of the treatment time, treatment temperature and concentration of polishing solution on both tensile strength and bending strength of FDM parts were studied. The results showed that both tensile strength and bending strength of the parts were reduced after chemical treatment. With the increasing of treatment time, treatment temperature and concentration of polishing solution, the tensile strength and bending strength of the parts decreased. At a treatment time of 10 min and treatment temperature of 60℃, the concentration of the polishing solution had small effect on the both tensile strength and bending strength of the parts.
2020, 39(1): 150-156.
doi: 10.13433/j.cnki.1003-8728.20190083
Abstract:
With the development of the aerospace industry, more and more large-scale orbital mechanisms will be applied in aerospace engineering to meet different mission requirements. A circular space deployable mechanism for applying the spacecraft solar array is designed is this paper. It mainly includes the design of synchronization mechanism, self-locking hinges and drive mechanism. Finally, based on the dynamics of multi-body system software, Adams and RecurDyn, the driving mechanism and the four-unit fan-shaped space deployable mechanism are respectively powered. The simulation results show that the present space deployable mechanism can realize the multi-level expansion and has the reliability and controllability of deployment.
With the development of the aerospace industry, more and more large-scale orbital mechanisms will be applied in aerospace engineering to meet different mission requirements. A circular space deployable mechanism for applying the spacecraft solar array is designed is this paper. It mainly includes the design of synchronization mechanism, self-locking hinges and drive mechanism. Finally, based on the dynamics of multi-body system software, Adams and RecurDyn, the driving mechanism and the four-unit fan-shaped space deployable mechanism are respectively powered. The simulation results show that the present space deployable mechanism can realize the multi-level expansion and has the reliability and controllability of deployment.
2020, 39(1): 157-164.
doi: 10.13433/j.cnki.1003-8728.20190080
Abstract:
In order to study the vibration reliability of aeroengine blisk under the influence of random stiffness mistuning, a radial basis function extreme response surface method (RBFERSM) is proposed by combining the radial basis function artificial neural nets (RBFANN) with extreme response surface method (ERSM). The material density, angular velocity and amplitude of force of the blisk are taken as random input variables, the extreme response of blisk vibration as the output response, the RBFERSM is constructed with the sample points, which are sampled by Latin hypercube sampling method. Than a large number of input random variables are sampled with Monte Carlo method and are taken into the RBFERSM to calculate the output responses. The results show that vibration reliability of the mistune blisk is reduced and its vibration failure is more likely to occur. By comparing with MCM and ERSM, it concluded that RBFERSM in this study can improve the calculation efficiency on the premise of ensuring the accuracy of calculation.
In order to study the vibration reliability of aeroengine blisk under the influence of random stiffness mistuning, a radial basis function extreme response surface method (RBFERSM) is proposed by combining the radial basis function artificial neural nets (RBFANN) with extreme response surface method (ERSM). The material density, angular velocity and amplitude of force of the blisk are taken as random input variables, the extreme response of blisk vibration as the output response, the RBFERSM is constructed with the sample points, which are sampled by Latin hypercube sampling method. Than a large number of input random variables are sampled with Monte Carlo method and are taken into the RBFERSM to calculate the output responses. The results show that vibration reliability of the mistune blisk is reduced and its vibration failure is more likely to occur. By comparing with MCM and ERSM, it concluded that RBFERSM in this study can improve the calculation efficiency on the premise of ensuring the accuracy of calculation.
