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RSS2017 Vol. 36, No. 2
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2017, 36(2): 165-171.
doi: 10.13433/j.cnki.1003-8728.2017.0201
PDF 1043KB
Abstract:
Aiming at the under-actuated problem and trajectory tracking control problem existed in hopping robot, the under-actuated bionic compliant hopping hybrid derived by motor and hydraulic cylinder is proposed. Firstly, the kinematical model of under-actuated compliant hopping robot is constructed. The angular motion of each joint is derived by using fifth order polynomial and the dynamic coupling between active joint and passive joint. Whether including the actuators, the motion of the center of mass is described. Secondly, the overall dynamic model including actuator dynamics is presented. The model can be controlled by using combination of partially feedback linearization and pole placement. Finally, the simulation result showed that compliant joints can improve the hopping capability and the proposed control method is feasible.
Aiming at the under-actuated problem and trajectory tracking control problem existed in hopping robot, the under-actuated bionic compliant hopping hybrid derived by motor and hydraulic cylinder is proposed. Firstly, the kinematical model of under-actuated compliant hopping robot is constructed. The angular motion of each joint is derived by using fifth order polynomial and the dynamic coupling between active joint and passive joint. Whether including the actuators, the motion of the center of mass is described. Secondly, the overall dynamic model including actuator dynamics is presented. The model can be controlled by using combination of partially feedback linearization and pole placement. Finally, the simulation result showed that compliant joints can improve the hopping capability and the proposed control method is feasible.
2017, 36(2): 172-177.
doi: 10.13433/j.cnki.1003-8728.2017.0202
Abstract:
In order to analyze the fatigue property of co-use joint with transverse fillet weld and high-stress bolts, fatigue test was performed to contrast fatigue life difference and fatigue mechanism between weld joint and co-use joint. Then the influence of the high-stress bolt on the fatigue life of co-use joint was obtained and the results show that high-stress bolt can effectively extend the fatigue life by reducing the force of weld and restraining the crack propagation which increases the connection stiffness of structure. Meanwhile, the fatigue life of co-use of weld and bolts joint was estimated via equivalent structural stress method. The estimation results was in a well agreement with the test results and the error was less than 10%. It indicated the applicability of equivalent structural stress method to estimate the fatigue life of co-use joint with transverse fillet weld and high-stress bolts.
In order to analyze the fatigue property of co-use joint with transverse fillet weld and high-stress bolts, fatigue test was performed to contrast fatigue life difference and fatigue mechanism between weld joint and co-use joint. Then the influence of the high-stress bolt on the fatigue life of co-use joint was obtained and the results show that high-stress bolt can effectively extend the fatigue life by reducing the force of weld and restraining the crack propagation which increases the connection stiffness of structure. Meanwhile, the fatigue life of co-use of weld and bolts joint was estimated via equivalent structural stress method. The estimation results was in a well agreement with the test results and the error was less than 10%. It indicated the applicability of equivalent structural stress method to estimate the fatigue life of co-use joint with transverse fillet weld and high-stress bolts.
2017, 36(2): 178-183.
doi: 10.13433/j.cnki.1003-8728.2017.0203
Abstract:
This paper presents a compact dual-chamber shooting pneumatic hammer, establishes a dynamic model for its working process. The pneumatic hammer impact velocity, displacement variation with time and the effects of structural and aerodynamic parameters on motion characteristics of the hammer core are obtained through numerical solutions. The simulation results indicate that impact velocity of the core increases with the diameter of the ventilation holes, the trend of the core's velocity changes by the exhaust hole of back pressure gas chamber within a certain size, when the exhaust hole's diameter is smaller, the core's velocity decrease after an initial increase; but when the exhaust hole's diameter increases to a certain value, the core's velocity always increases. The initial volume of preloading gas chamber has no effect on the impact velocity of the core. Moreover, after using the finite element method to simulate the impact collision process of the hammer, the time of impact process and the size of the impact force are obtained. The study shows that this dual-chamber shooting pneumatic hammer has a light structure and large impact force.
This paper presents a compact dual-chamber shooting pneumatic hammer, establishes a dynamic model for its working process. The pneumatic hammer impact velocity, displacement variation with time and the effects of structural and aerodynamic parameters on motion characteristics of the hammer core are obtained through numerical solutions. The simulation results indicate that impact velocity of the core increases with the diameter of the ventilation holes, the trend of the core's velocity changes by the exhaust hole of back pressure gas chamber within a certain size, when the exhaust hole's diameter is smaller, the core's velocity decrease after an initial increase; but when the exhaust hole's diameter increases to a certain value, the core's velocity always increases. The initial volume of preloading gas chamber has no effect on the impact velocity of the core. Moreover, after using the finite element method to simulate the impact collision process of the hammer, the time of impact process and the size of the impact force are obtained. The study shows that this dual-chamber shooting pneumatic hammer has a light structure and large impact force.
2017, 36(2): 184-189.
doi: 10.13433/j.cnki.1003-8728.2017.0204
Abstract:
Aiming at the problem of rolling mill main drive system vibration researches, such as ignoring the influence of asynchronous motor itself, in this paper, considering asynchronous motor magnetic flux leakage coefficient, the stator time constant, rotor time constant and the nonlinear factors of rotors air friction, and putting the air friction into the rolling mill main drive system, the AC motor-rolling mill main drive system of electromechanical coupling model is established. The influences of the asynchronous motor magnetic flux leakage coefficient, the stator time constant, rotor time constant and the air friction coefficient to amplitude and adjusting time of main drive system were analyzed by numerical method.
Aiming at the problem of rolling mill main drive system vibration researches, such as ignoring the influence of asynchronous motor itself, in this paper, considering asynchronous motor magnetic flux leakage coefficient, the stator time constant, rotor time constant and the nonlinear factors of rotors air friction, and putting the air friction into the rolling mill main drive system, the AC motor-rolling mill main drive system of electromechanical coupling model is established. The influences of the asynchronous motor magnetic flux leakage coefficient, the stator time constant, rotor time constant and the air friction coefficient to amplitude and adjusting time of main drive system were analyzed by numerical method.
2017, 36(2): 190-195.
doi: 10.13433/j.cnki.1003-8728.2017.0205
Abstract:
Dynamical behaviors and stochastic bifurcation of Duffing map are investigated under the random parameters by Charlier polynomial approximation method. In order to clarify the stochastic characteristic of Duffing map, the complex dynamical behaviors of deterministic Duffing map are explored, especially about generation, evaluation and transformation of the dynamical motions. Then, according to the type of random parameters, the corresponding Charlier orthogonal polynomial is applied to achieve the approximation of stochastic Duffing map, which is its extended order equivalent deterministic system, and the ensemble average responses of this equivalent system can be applied to analyze the stochastic bifurcation behaviors. The numerical simulation results show that under the effect of stochastic factors, the periodic bifurcation points move forward, and the convergence parameter interval is shrinking with the increasing random variable intensity.
Dynamical behaviors and stochastic bifurcation of Duffing map are investigated under the random parameters by Charlier polynomial approximation method. In order to clarify the stochastic characteristic of Duffing map, the complex dynamical behaviors of deterministic Duffing map are explored, especially about generation, evaluation and transformation of the dynamical motions. Then, according to the type of random parameters, the corresponding Charlier orthogonal polynomial is applied to achieve the approximation of stochastic Duffing map, which is its extended order equivalent deterministic system, and the ensemble average responses of this equivalent system can be applied to analyze the stochastic bifurcation behaviors. The numerical simulation results show that under the effect of stochastic factors, the periodic bifurcation points move forward, and the convergence parameter interval is shrinking with the increasing random variable intensity.
2017, 36(2): 196-201.
doi: 10.13433/j.cnki.1003-8728.2017.0206
Abstract:
The wrist structure greatly affects the dynamic performance of the haptic master. In order to improve the dynamic performance of the device, we remove the thumb point from the wrist center to improve the wrist structure based on the universal haptic master developed by lab associates. Under the premise of not changing the force information of the end effecter, the maximum removed distance is determined in the condition of not disturbing the sense of the operator caused by additional moment. In the full gravity balance for the haptic master, the wrist structure is improved based on the ergonomics. The mass of the wrist is decreased while the stiffness of the wrist is increased. And the inertia of the haptic master is reduced by 57% which effectively improves the dynamic performance of the haptic master.
The wrist structure greatly affects the dynamic performance of the haptic master. In order to improve the dynamic performance of the device, we remove the thumb point from the wrist center to improve the wrist structure based on the universal haptic master developed by lab associates. Under the premise of not changing the force information of the end effecter, the maximum removed distance is determined in the condition of not disturbing the sense of the operator caused by additional moment. In the full gravity balance for the haptic master, the wrist structure is improved based on the ergonomics. The mass of the wrist is decreased while the stiffness of the wrist is increased. And the inertia of the haptic master is reduced by 57% which effectively improves the dynamic performance of the haptic master.
2017, 36(2): 202-206.
doi: 10.13433/j.cnki.1003-8728.2017.0207
Abstract:
This paper presents the equilibrium and stability of Morris-Lecar(ML)neuron model exposed to induced electric field. Based on the variation of the field-induced membrane depolarization, the equilibrium and bifurcation behaviors of three basic classes of neurons are investigated. The discharge mechanism of neurons simulated by electromagnetic fields is revealed by introducing transformed phase portraits with the equilibrium curve. Results show that bifurcations can lead to the movement of neuronal membrane potential V around the equilibrium curve, and different types of firing patterns, including bursting, synchronous spiking and sub-threshold oscillations. Meanwhile, neurons exhibit different kinds of periodic firing patterns in the simulation of periodic sinusoidal induced electric field. The study can provide theoretical reference for the extremely low frequency electromagnetic field in treating neurological diseases, and has potential application value for the brain cognitive.
This paper presents the equilibrium and stability of Morris-Lecar(ML)neuron model exposed to induced electric field. Based on the variation of the field-induced membrane depolarization, the equilibrium and bifurcation behaviors of three basic classes of neurons are investigated. The discharge mechanism of neurons simulated by electromagnetic fields is revealed by introducing transformed phase portraits with the equilibrium curve. Results show that bifurcations can lead to the movement of neuronal membrane potential V around the equilibrium curve, and different types of firing patterns, including bursting, synchronous spiking and sub-threshold oscillations. Meanwhile, neurons exhibit different kinds of periodic firing patterns in the simulation of periodic sinusoidal induced electric field. The study can provide theoretical reference for the extremely low frequency electromagnetic field in treating neurological diseases, and has potential application value for the brain cognitive.
2017, 36(2): 207-212.
doi: 10.13433/j.cnki.1003-8728.2017.0208
Abstract:
To offer the fundamental of fatigue design of diaphragm spring, the cumulative fatigue damage theory has been used to calculate the fatigue life of diaphragm spring based on the current stress history data, and the impact of working position had been discussed. Loading on large side had been analyzed by using FEM firstly, after that the experimental results have been obtained to verify the FEM calculated results. Secondly the stress data in fatigue test condition had been calculated by using FEM, and the stress data of preloading and unpreloading were removed. With the remaining stress history data, the stress controlled fatigue damage method had been used considering the cycle ratio modification to analyze the fatigue life. To make the process easier Time Step module in Ncode Designlife had been used, the calculated result indicated that the danger point position is same as the previous literature and match with the fatigue test. The calculated accuracy of fatigue damage had been greatly improved, and the danger point position of fatigue damage can be directly calculated, besides, it can not only be used for a diaphragm spring but also for other cyclical working component. At last, the impact of working position had been discussed, which identify that when the working position is between the local maximum value point and the inflection point, and keep a distance to inflection point then a diaphragm spring can behave nonlinear as well as a longer life.
To offer the fundamental of fatigue design of diaphragm spring, the cumulative fatigue damage theory has been used to calculate the fatigue life of diaphragm spring based on the current stress history data, and the impact of working position had been discussed. Loading on large side had been analyzed by using FEM firstly, after that the experimental results have been obtained to verify the FEM calculated results. Secondly the stress data in fatigue test condition had been calculated by using FEM, and the stress data of preloading and unpreloading were removed. With the remaining stress history data, the stress controlled fatigue damage method had been used considering the cycle ratio modification to analyze the fatigue life. To make the process easier Time Step module in Ncode Designlife had been used, the calculated result indicated that the danger point position is same as the previous literature and match with the fatigue test. The calculated accuracy of fatigue damage had been greatly improved, and the danger point position of fatigue damage can be directly calculated, besides, it can not only be used for a diaphragm spring but also for other cyclical working component. At last, the impact of working position had been discussed, which identify that when the working position is between the local maximum value point and the inflection point, and keep a distance to inflection point then a diaphragm spring can behave nonlinear as well as a longer life.
2017, 36(2): 213-218.
doi: 10.13433/j.cnki.1003-8728.2017.0209
Abstract:
In order to study the impact of time delay on the dynamic characteristics and stability of semi-active suspension with sky-hook damping, the 2-DOF mathematic model of semi-active suspension with time delay is first established, then the stability analysis method of the critical time delay of the semi-active suspension and the stability margin are presented based on stability theory. The critical time-delay value is solved by using numerical method, moreover, the critical time delay resulting in instability of the semi-active suspension and the stable areas for non-arbitrary and arbitrary time delay are obtained under various passive damping coefficients and the feedback gains of sky-hook damping coefficients. The simulation model of semi-active suspension with time delay is built, and the influence rules on dynamic performances and stability of the suspension are obtained.
In order to study the impact of time delay on the dynamic characteristics and stability of semi-active suspension with sky-hook damping, the 2-DOF mathematic model of semi-active suspension with time delay is first established, then the stability analysis method of the critical time delay of the semi-active suspension and the stability margin are presented based on stability theory. The critical time-delay value is solved by using numerical method, moreover, the critical time delay resulting in instability of the semi-active suspension and the stable areas for non-arbitrary and arbitrary time delay are obtained under various passive damping coefficients and the feedback gains of sky-hook damping coefficients. The simulation model of semi-active suspension with time delay is built, and the influence rules on dynamic performances and stability of the suspension are obtained.
2017, 36(2): 219-224.
doi: 10.13433/j.cnki.1003-8728.2017.0210
Abstract:
In this paper we addressed the dynamical synchronization between rotors and its robustness for random and pulse disturbances. For a dual-rotor system, we present a control method to realize synchronization between the rotors, which only needs the dynamic response of an elastic support of a rotor. The control method for synchronization by support coupling is proved theoretically. For validation an overhung rotor with two elastic supports were simulated. To examine the robustness of the method, additional pulse and stochastic disturbance forces are exerted on one of the two supports respectively. The results show that the simulation system will reach synchronization with the rotor rapidly. The responses of supports and disks prove that a high accuracy can be attained even under disturbances.
In this paper we addressed the dynamical synchronization between rotors and its robustness for random and pulse disturbances. For a dual-rotor system, we present a control method to realize synchronization between the rotors, which only needs the dynamic response of an elastic support of a rotor. The control method for synchronization by support coupling is proved theoretically. For validation an overhung rotor with two elastic supports were simulated. To examine the robustness of the method, additional pulse and stochastic disturbance forces are exerted on one of the two supports respectively. The results show that the simulation system will reach synchronization with the rotor rapidly. The responses of supports and disks prove that a high accuracy can be attained even under disturbances.
2017, 36(2): 225-231.
doi: 10.13433/j.cnki.1003-8728.2017.0211
Abstract:
As non-diagenetic hydrate does not have cap, it is difficult to directly apply the conventional mining methods. To exploitate non-diagenetic gas hydrate, Academician Zhou Shou Wei proposes a new idea of mining-solid fluidized technology for shallow seafloor hydrate. The key to this new mining technology is to design a comprehensive collection and exploitation mining tool. Therefore, we design a new marine gas hydrate mining tool based on the existing undersea rock-breaking tool, which can smash hydrate in both the vertical and horizontal directions. Besides, this mining tool can achieve rapid poly ballast and efficient chip. By establishing finite element model and making use of Fluent software for flow field analysis, the velocity distribution of the internal fluid can be obtained in different conditions, which can prove the good workability of the tool.
As non-diagenetic hydrate does not have cap, it is difficult to directly apply the conventional mining methods. To exploitate non-diagenetic gas hydrate, Academician Zhou Shou Wei proposes a new idea of mining-solid fluidized technology for shallow seafloor hydrate. The key to this new mining technology is to design a comprehensive collection and exploitation mining tool. Therefore, we design a new marine gas hydrate mining tool based on the existing undersea rock-breaking tool, which can smash hydrate in both the vertical and horizontal directions. Besides, this mining tool can achieve rapid poly ballast and efficient chip. By establishing finite element model and making use of Fluent software for flow field analysis, the velocity distribution of the internal fluid can be obtained in different conditions, which can prove the good workability of the tool.
2017, 36(2): 232-238.
doi: 10.13433/j.cnki.1003-8728.2017.0212
Abstract:
In order to reduce the impact caused by dynamic model uncertainty (including parameter uncertainty and unknown load disturbance) on control precision of 3-UPS/PU parallel mechanism, an adaptive sliding mode controller is proposed. Firstly, dynamic model for mechanism with respect to platform workspace is constructed based on the inverse kinematics and virtual work principle. The controller incorporates the nominal dynamic model and sliding mode control theory; an adaptive law is designed by means of the sliding mode surface, which can estimate and compensate the uncertainty online, thus the system robustness is improved; and the system stability is analyzed via Lyapunov function. The present controller has some advantages and which doesn't need to rely on the upper bound of uncertainty, and it is easy to implement due to its simple structure and suitable for complicated uncertain systems such as parallel mechanism. The simulation results show that the present controller can overcome the time-varying uncertainty efficiently and make the average tracking errors of platform freedoms obviously decreased comparing with traditional sliding mode control.
In order to reduce the impact caused by dynamic model uncertainty (including parameter uncertainty and unknown load disturbance) on control precision of 3-UPS/PU parallel mechanism, an adaptive sliding mode controller is proposed. Firstly, dynamic model for mechanism with respect to platform workspace is constructed based on the inverse kinematics and virtual work principle. The controller incorporates the nominal dynamic model and sliding mode control theory; an adaptive law is designed by means of the sliding mode surface, which can estimate and compensate the uncertainty online, thus the system robustness is improved; and the system stability is analyzed via Lyapunov function. The present controller has some advantages and which doesn't need to rely on the upper bound of uncertainty, and it is easy to implement due to its simple structure and suitable for complicated uncertain systems such as parallel mechanism. The simulation results show that the present controller can overcome the time-varying uncertainty efficiently and make the average tracking errors of platform freedoms obviously decreased comparing with traditional sliding mode control.
2017, 36(2): 239-244.
doi: 10.13433/j.cnki.1003-8728.2017.0213
Abstract:
In order to meet the motion flexibility and workspace requirements of a minimally invasive surgical instrument, this paper designed a 6-DOF cable-driven minimally invasive surgical instrument. The six degrees of freedom include yaw degree of freedom of shoulder, pitch degree of freedom of elbow, pitch degree of freedom of wrist, roll degree of freedom, yaw degree of freedom of finger and the fingers' opening & closing degree of freedom. The quick-exchange finger was also designed at the finger part of the surgical instrument, which could effectively save time for replacing a surgical instrument during surgery and reducing the cost of surgery. With the surgical instrument's structural design, kinematics analysis and workspace analysis of the surgical instrument were performed. Finally, the kinematics simulations were carried out to verify the structure's rationality and kinematics' validity of the surgical instrument by comparing the end-effector trajectory analysis results obtained with MATLAB calculation and SolidWorks simulation in a 3-dimensional space.
In order to meet the motion flexibility and workspace requirements of a minimally invasive surgical instrument, this paper designed a 6-DOF cable-driven minimally invasive surgical instrument. The six degrees of freedom include yaw degree of freedom of shoulder, pitch degree of freedom of elbow, pitch degree of freedom of wrist, roll degree of freedom, yaw degree of freedom of finger and the fingers' opening & closing degree of freedom. The quick-exchange finger was also designed at the finger part of the surgical instrument, which could effectively save time for replacing a surgical instrument during surgery and reducing the cost of surgery. With the surgical instrument's structural design, kinematics analysis and workspace analysis of the surgical instrument were performed. Finally, the kinematics simulations were carried out to verify the structure's rationality and kinematics' validity of the surgical instrument by comparing the end-effector trajectory analysis results obtained with MATLAB calculation and SolidWorks simulation in a 3-dimensional space.
2017, 36(2): 245-249.
doi: 10.13433/j.cnki.1003-8728.2017.0214
Abstract:
This paper aims to investigate the power-law fluid flow in microchannel with eletrokinetic effects. In the entire analysis, the electric double layer (EDL) potential is described by the Poisson equation. The flow and transport of the power-law fluid is characterized by the Navier-Stokes equation and the Nernst-Plank equation. Numerical simulation is carried out for all values of the flow behavior index from 0.4 to 1.2. The effects of the flow behavior index, ionic concentration and channel dimension on fluid velocity distribution, streaming potential and apparent viscosity are discussed. The results show that the eletroviscous effect on the flow depends significantly on the flow behavior index. For the shear thinning fluid of the flow behavior index nn>1, the influence of the flow behavior index on the velocity and streaming potential can be neglected in practical application.
This paper aims to investigate the power-law fluid flow in microchannel with eletrokinetic effects. In the entire analysis, the electric double layer (EDL) potential is described by the Poisson equation. The flow and transport of the power-law fluid is characterized by the Navier-Stokes equation and the Nernst-Plank equation. Numerical simulation is carried out for all values of the flow behavior index from 0.4 to 1.2. The effects of the flow behavior index, ionic concentration and channel dimension on fluid velocity distribution, streaming potential and apparent viscosity are discussed. The results show that the eletroviscous effect on the flow depends significantly on the flow behavior index. For the shear thinning fluid of the flow behavior index nn>1, the influence of the flow behavior index on the velocity and streaming potential can be neglected in practical application.
2017, 36(2): 250-256.
doi: 10.13433/j.cnki.1003-8728.2017.0215
Abstract:
A new type of aircraft wing support platform is designed. The main structure is a parallel mechanism composed of a moving platform, a static platform and three identical PRS branch chains, being more suitable for aircraft models. A method for the dimensional synthesis of the parallel mechanism was proposed. When the moving platform is under force and torque change, a static performance evaluation index is proposed to minimize the maximum actuation and the constraint force of the links by using the static force Jacobian matrix of the parallel mechanism. Taking into account the actually required constraints, we use the monotonic analysis to study the parallel global static performance and the constraint conditions that have varying scale parameters in order to optimize the scale parameters of the conditions. Finally we prove the effectiveness of the method with numericalexamples.
A new type of aircraft wing support platform is designed. The main structure is a parallel mechanism composed of a moving platform, a static platform and three identical PRS branch chains, being more suitable for aircraft models. A method for the dimensional synthesis of the parallel mechanism was proposed. When the moving platform is under force and torque change, a static performance evaluation index is proposed to minimize the maximum actuation and the constraint force of the links by using the static force Jacobian matrix of the parallel mechanism. Taking into account the actually required constraints, we use the monotonic analysis to study the parallel global static performance and the constraint conditions that have varying scale parameters in order to optimize the scale parameters of the conditions. Finally we prove the effectiveness of the method with numericalexamples.
2017, 36(2): 257-261.
doi: 10.13433/j.cnki.1003-8728.2017.0216
Abstract:
To explore the stress distribution and laws induced by ultrasonic deep rolling with longitudinal-torsional (UDRP-LTV) vibration, the finite element method was adopted to study the residual stress in Q345 steel. The distribution of the component stress along the depth direction was studied, and the effects of the static pressure, rolling speed, longitudinal and torsional vibration amplitude on the residual stress were analyzed. The results show that the distribution of the residual stress in the surface layer is homogeneous after UDRP-LTV treatment, and the surface stress is compressive. The compressive stress firstly increases and then decreases along the depth. The maximum residual stress and the depth of the residual stress layer increase with the increasing of static force, and decrease with the increasing of rolling speed, while the surface residual stress and the depth of the maximum longitudinal residual stress slightly change. The depth of the transverse residual stress slightly increases with the increasing of amplitude, but the amplitude and depth of the maximum surface residual stress and the depth of the longitudinal residual stress slightly change. And the effect of the phase on the residual stress may be ignored.
To explore the stress distribution and laws induced by ultrasonic deep rolling with longitudinal-torsional (UDRP-LTV) vibration, the finite element method was adopted to study the residual stress in Q345 steel. The distribution of the component stress along the depth direction was studied, and the effects of the static pressure, rolling speed, longitudinal and torsional vibration amplitude on the residual stress were analyzed. The results show that the distribution of the residual stress in the surface layer is homogeneous after UDRP-LTV treatment, and the surface stress is compressive. The compressive stress firstly increases and then decreases along the depth. The maximum residual stress and the depth of the residual stress layer increase with the increasing of static force, and decrease with the increasing of rolling speed, while the surface residual stress and the depth of the maximum longitudinal residual stress slightly change. The depth of the transverse residual stress slightly increases with the increasing of amplitude, but the amplitude and depth of the maximum surface residual stress and the depth of the longitudinal residual stress slightly change. And the effect of the phase on the residual stress may be ignored.
2017, 36(2): 262-268.
doi: 10.13433/j.cnki.1003-8728.2017.0217
Abstract:
Applying warp, flatness, size accuracy as an objective of quality in injection molding of ultra-thin plate plastic parts, models were established between the quality objective and the process variables which were based on Kriging method. And, with the NSGA-II (Non-dominated Sorting Genetic Algorithm II), a Pareto-optimal solution of quality multi-objectives was obtained. After that, the optimal solution which met the design requirements would be sought by using the vague evaluation, which realized the multi-objectives optimization of quality in the injection molding of ultra-thin plastic parts. The optimization process was applied to the ultra-thin light guide production practice which would greatly improve the molding precision and enhance the robustness of the injection molding process as well as prove the correctness and effectiveness of the optimization process, and provide a reliable theoretical method for the ultra-thin plastic parts manufacturing.
Applying warp, flatness, size accuracy as an objective of quality in injection molding of ultra-thin plate plastic parts, models were established between the quality objective and the process variables which were based on Kriging method. And, with the NSGA-II (Non-dominated Sorting Genetic Algorithm II), a Pareto-optimal solution of quality multi-objectives was obtained. After that, the optimal solution which met the design requirements would be sought by using the vague evaluation, which realized the multi-objectives optimization of quality in the injection molding of ultra-thin plastic parts. The optimization process was applied to the ultra-thin light guide production practice which would greatly improve the molding precision and enhance the robustness of the injection molding process as well as prove the correctness and effectiveness of the optimization process, and provide a reliable theoretical method for the ultra-thin plastic parts manufacturing.
2017, 36(2): 269-272.
doi: 10.13433/j.cnki.1003-8728.2017.0218
Abstract:
In order to overcome low contrast and uneven brightness of magnetic tile surface image with much impulsive noise, a new segmentation method based on lower envelope gray-scale contrast was proposed in this paper. Firstly, the scanning-line gray-scale contrast is defined and every row scanning-line is optimized by envelope. Then the max gray-scale contrast is computed, the point in the defect area is confirmed and the "skeleton" of defect is got. Finally, the whole defect area by extending the "skeleton" with 8-adjacency connectivity is obtained. The experimental results show that the proposed method could obtain a good result of defect extraction in much impulse noise environment and fits on various defects, which lays a good foundation for subsequent feature extraction and recognition classification of defects.
In order to overcome low contrast and uneven brightness of magnetic tile surface image with much impulsive noise, a new segmentation method based on lower envelope gray-scale contrast was proposed in this paper. Firstly, the scanning-line gray-scale contrast is defined and every row scanning-line is optimized by envelope. Then the max gray-scale contrast is computed, the point in the defect area is confirmed and the "skeleton" of defect is got. Finally, the whole defect area by extending the "skeleton" with 8-adjacency connectivity is obtained. The experimental results show that the proposed method could obtain a good result of defect extraction in much impulse noise environment and fits on various defects, which lays a good foundation for subsequent feature extraction and recognition classification of defects.
2017, 36(2): 273-278.
doi: 10.13433/j.cnki.1003-8728.2017.0219
Abstract:
In order to precisely and efficiently identify different types with different degree of fault rolling bearing. An intelligent fault diagnosis method based on localized fisher discriminant score (LFDS) is put forward. At first, the feature extractions of time domain, frequency domain and time-frequency from vibration signal are prepared; then use LFDS to select the most sensitive feature subset from the original feature set; finally, the sensitive low dimension feature data set is fed into least squares support vector machine algorithm to recognize the fault type. The proposed method was verified by the typical fault vibration signal of rolling bearing. According to the example result, the feature subset selected by LFDS can reveal the differences among the different types with different degree.
In order to precisely and efficiently identify different types with different degree of fault rolling bearing. An intelligent fault diagnosis method based on localized fisher discriminant score (LFDS) is put forward. At first, the feature extractions of time domain, frequency domain and time-frequency from vibration signal are prepared; then use LFDS to select the most sensitive feature subset from the original feature set; finally, the sensitive low dimension feature data set is fed into least squares support vector machine algorithm to recognize the fault type. The proposed method was verified by the typical fault vibration signal of rolling bearing. According to the example result, the feature subset selected by LFDS can reveal the differences among the different types with different degree.
2017, 36(2): 279-285.
doi: 10.13433/j.cnki.1003-8728.2017.0220
Abstract:
In consideration of the characteristics of high speed motorized spindle product degradation process such as having multiple degradation characteristic variables, and the degradation process being smooth and slow, the two-dimensional Wiener process model was established, in which some unknown parameters were viewed as random variables followed the normal distribution; while the maximum likelihood method combined with virtual augmented samples method and the Bootstrap method which were proposed to solve the problem of small sample were used to estimate the unknown parameters. Then, the resulting product life, the life distribution function and probability density function of reliability function were obtained. Finally, the rationality and accuracy of the method proposed was verified by analyzing the degradation data of two grinding motorized spindles.
In consideration of the characteristics of high speed motorized spindle product degradation process such as having multiple degradation characteristic variables, and the degradation process being smooth and slow, the two-dimensional Wiener process model was established, in which some unknown parameters were viewed as random variables followed the normal distribution; while the maximum likelihood method combined with virtual augmented samples method and the Bootstrap method which were proposed to solve the problem of small sample were used to estimate the unknown parameters. Then, the resulting product life, the life distribution function and probability density function of reliability function were obtained. Finally, the rationality and accuracy of the method proposed was verified by analyzing the degradation data of two grinding motorized spindles.
2017, 36(2): 286-291.
doi: 10.13433/j.cnki.1003-8728.2017.0221
Abstract:
Segment erector often exists starting impact phenomenon during its rotation due to its high stiffness and the large rotational inertia of segment, which leads to the difficulty of precise control in erector system. Aiming at this problem, a fuzzy control algorithm was proposed based on the speed control method of rotating system in this paper. By using joint simulation technology to simulate the starting condition of segment erector, the fuzzy control algorithm for the compensation of the system dynamic responses was studied. The proposed fuzzy control algorithm was written into the system electronic control unit (ECU), and real vehicle test was carried on in the co-operative corporation. The simulation and test results show that the fuzzy control algorithm can effectively improve the dynamic performances of the erector and can well restrain the starting impact phenomenon.
Segment erector often exists starting impact phenomenon during its rotation due to its high stiffness and the large rotational inertia of segment, which leads to the difficulty of precise control in erector system. Aiming at this problem, a fuzzy control algorithm was proposed based on the speed control method of rotating system in this paper. By using joint simulation technology to simulate the starting condition of segment erector, the fuzzy control algorithm for the compensation of the system dynamic responses was studied. The proposed fuzzy control algorithm was written into the system electronic control unit (ECU), and real vehicle test was carried on in the co-operative corporation. The simulation and test results show that the fuzzy control algorithm can effectively improve the dynamic performances of the erector and can well restrain the starting impact phenomenon.
2017, 36(2): 292-297.
doi: 10.13433/j.cnki.1003-8728.2017.0222
Abstract:
The dynamic model of a new type of powertrain magnetorheological (MR) suspension system was built and experiments on its dynamic characteristics were carried out. The numerical fitting method that establishes the relationship between the current and the controllable damping force is applied as a theoretical model to control the MR suspension system. With the equivalent stiffness and equivalent damping of the powertrain MR suspension system considered, the model of MR semi-active suspension system was constructed. The fuzzy-PID switching control strategy was designed for the MR semi-active suspension system. Then its vibration isolation performance was simulated under different working conditions. The simulation results show that the MR semi-active suspension system has good effects on vibration isolation with the use of the fuzzy-PID switching control strategy.
The dynamic model of a new type of powertrain magnetorheological (MR) suspension system was built and experiments on its dynamic characteristics were carried out. The numerical fitting method that establishes the relationship between the current and the controllable damping force is applied as a theoretical model to control the MR suspension system. With the equivalent stiffness and equivalent damping of the powertrain MR suspension system considered, the model of MR semi-active suspension system was constructed. The fuzzy-PID switching control strategy was designed for the MR semi-active suspension system. Then its vibration isolation performance was simulated under different working conditions. The simulation results show that the MR semi-active suspension system has good effects on vibration isolation with the use of the fuzzy-PID switching control strategy.
2017, 36(2): 298-302.
doi: 10.13433/j.cnki.1003-8728.2017.0223
Abstract:
Matrix cracking and delamination may occur when composite structures exposed to impact. Generally, these crack interfaces remain closely contact. Such incipient damage may fail to be detected if the strain generated by the excitation is too small to open the contact interface. To overcome this deficiency, a new kind of damage detection for composites with different amplitude of excitation by using time reversal method is proposed. Applying different amplitude excitation voltage on the piezoelectric(PZT) transducers which are used to generate and receive Lamb wave signal, an experiment is set to detect impact damage in a composite plate based on the time reversal theory. Experimental results demonstrate that although the time reversal reconstructed signal is similar to which in an intact plate when a low amplitude excitation is applied, it does not indicate the presence of damage in the structure. When the excitation amplitude exceeds a certain threshold, the reconstructed signal would be different from the original excitation signal. Damage indexes of each path are defined with the correlation coefficient between the original excitation signal and the reconstructed signal. An imaging algorithm is developed to locate the impact damage on the plate. It turns out that the damage can be accurately detected and located.
Matrix cracking and delamination may occur when composite structures exposed to impact. Generally, these crack interfaces remain closely contact. Such incipient damage may fail to be detected if the strain generated by the excitation is too small to open the contact interface. To overcome this deficiency, a new kind of damage detection for composites with different amplitude of excitation by using time reversal method is proposed. Applying different amplitude excitation voltage on the piezoelectric(PZT) transducers which are used to generate and receive Lamb wave signal, an experiment is set to detect impact damage in a composite plate based on the time reversal theory. Experimental results demonstrate that although the time reversal reconstructed signal is similar to which in an intact plate when a low amplitude excitation is applied, it does not indicate the presence of damage in the structure. When the excitation amplitude exceeds a certain threshold, the reconstructed signal would be different from the original excitation signal. Damage indexes of each path are defined with the correlation coefficient between the original excitation signal and the reconstructed signal. An imaging algorithm is developed to locate the impact damage on the plate. It turns out that the damage can be accurately detected and located.
2017, 36(2): 303-307.
doi: 10.13433/j.cnki.1003-8728.2017.0224
Abstract:
In order to get the mechanism of single loading fracture and cyclic loading fracture of the bond fabricated by friction stir welding(FSW), the extremely low cycle fatigue (ELCF) features of the FSW specimen and standard matrix material 2124-T851 aluminum alloy have been studied. The results show that, in the extremely low cycle fatigue life zone, the S-N Curve of FSW specimen is corresponding with power function relationship but there is a large dispersion of data, and with the longer of the specified fatigue life, the FSW specimen has a higher decrease in strength of specified fatigue life(SSFL). Supposing that the limit of fatigue life is defined as 1 cycle, single loading fracture and cyclic loading fracture have a unified macro variable rule and the micro fracture mechanism also has the characteristics of continuous evolution. Obvious fatigue source region can not be observed on extremely low cycle fatigue fracture surface. With the increasing of extremely low cycle fatigue life, the type of FSW fracture characteristics turns the normal mode into shear mode.
In order to get the mechanism of single loading fracture and cyclic loading fracture of the bond fabricated by friction stir welding(FSW), the extremely low cycle fatigue (ELCF) features of the FSW specimen and standard matrix material 2124-T851 aluminum alloy have been studied. The results show that, in the extremely low cycle fatigue life zone, the S-N Curve of FSW specimen is corresponding with power function relationship but there is a large dispersion of data, and with the longer of the specified fatigue life, the FSW specimen has a higher decrease in strength of specified fatigue life(SSFL). Supposing that the limit of fatigue life is defined as 1 cycle, single loading fracture and cyclic loading fracture have a unified macro variable rule and the micro fracture mechanism also has the characteristics of continuous evolution. Obvious fatigue source region can not be observed on extremely low cycle fatigue fracture surface. With the increasing of extremely low cycle fatigue life, the type of FSW fracture characteristics turns the normal mode into shear mode.
2017, 36(2): 308-313.
doi: 10.13433/j.cnki.1003-8728.2017.0225
Abstract:
Two-dimensional Otsu algorithm was improved in order to segment the defects of low contrast and complex noise in cold rolling of thin strip. In order to avoid searching threshold in a large two-dimensional space, two-dimensional Otsu algorithm of two-dimensional histogram has decomposed. The algorithm solves threshold in the image pixel gray histogram and gray histogram neighborhood pixels respectively. The balance factor to the pixel neighborhood grayscale was added in solving the segmentation threshold and using the threshold as the best image segmentation threshold. Finally, the segmentation result was analyzed through a large number of experiments, comparing with two-dimensional Otsu algorithm, Quantum-behaved particle swarm optimization (QPSO) and improved algorithm. The results show that the method can quickly and efficiently split out various defects on the surface of cold rolled thin strip in computer vision.
Two-dimensional Otsu algorithm was improved in order to segment the defects of low contrast and complex noise in cold rolling of thin strip. In order to avoid searching threshold in a large two-dimensional space, two-dimensional Otsu algorithm of two-dimensional histogram has decomposed. The algorithm solves threshold in the image pixel gray histogram and gray histogram neighborhood pixels respectively. The balance factor to the pixel neighborhood grayscale was added in solving the segmentation threshold and using the threshold as the best image segmentation threshold. Finally, the segmentation result was analyzed through a large number of experiments, comparing with two-dimensional Otsu algorithm, Quantum-behaved particle swarm optimization (QPSO) and improved algorithm. The results show that the method can quickly and efficiently split out various defects on the surface of cold rolled thin strip in computer vision.
2017, 36(2): 314-318.
doi: 10.13433/j.cnki.1003-8728.2017.0226
Abstract:
The forming limit in single point incremental forming of 1060 aluminum sheet was studied by experiment. The thickness distribution of different part of conical part was compared. The increase in forming angle will result in thinning the top of forming part, and the rupture was prone to generate on the thinning part soa s to affect the forming limit. The forming limit was represented with maximum forming angle in the single point incremental forming. The effect of the processing parameters on the maximum forming angle was analyzed, it is concluded that the layer step will affect the maximum forming angle of sheet, the circumferential speed of tool head had no significant effect on the maximum forming angle, and finished workpieces with different shape will lead to different maximum forming angle. Finally, the forming limit curve(FLC) of 1 mm thickness aluminum sheet was plotted according to the experiment results.
The forming limit in single point incremental forming of 1060 aluminum sheet was studied by experiment. The thickness distribution of different part of conical part was compared. The increase in forming angle will result in thinning the top of forming part, and the rupture was prone to generate on the thinning part soa s to affect the forming limit. The forming limit was represented with maximum forming angle in the single point incremental forming. The effect of the processing parameters on the maximum forming angle was analyzed, it is concluded that the layer step will affect the maximum forming angle of sheet, the circumferential speed of tool head had no significant effect on the maximum forming angle, and finished workpieces with different shape will lead to different maximum forming angle. Finally, the forming limit curve(FLC) of 1 mm thickness aluminum sheet was plotted according to the experiment results.
2017, 36(2): 319-322.
doi: 10.13433/j.cnki.1003-8728.2017.0227
Abstract:
Acoustic pressure in the enclosed cavity affected by particle damping was studied. By inducing the formula of acoustic pressure, the law of acoustic pressure changing with modal shape function was unveiled. The modal shapes of the enclosure cavity were analyzed by the modal test. By equipping the board of which relative displacement is the maximum in lower-order modal shapes of the enclosure cavity with particle damper, the vibration of the lower-order modal is reduced. Then the acoustic pressure of the target point in the enclosure cavity is reduced. The results show that compared with none particle damper, the decrease of the acoustic pressure root mean square(RMS) at the target point in the enclosure cavity is the most, from 107.99 dB to 104.08 dB, decreased by 3.91 dB when particle damper was equipped on the board of which relative displacement is the maximum in first modal shape of the enclosure cavity.
Acoustic pressure in the enclosed cavity affected by particle damping was studied. By inducing the formula of acoustic pressure, the law of acoustic pressure changing with modal shape function was unveiled. The modal shapes of the enclosure cavity were analyzed by the modal test. By equipping the board of which relative displacement is the maximum in lower-order modal shapes of the enclosure cavity with particle damper, the vibration of the lower-order modal is reduced. Then the acoustic pressure of the target point in the enclosure cavity is reduced. The results show that compared with none particle damper, the decrease of the acoustic pressure root mean square(RMS) at the target point in the enclosure cavity is the most, from 107.99 dB to 104.08 dB, decreased by 3.91 dB when particle damper was equipped on the board of which relative displacement is the maximum in first modal shape of the enclosure cavity.
2017, 36(2): 323-328.
doi: 10.13433/j.cnki.1003-8728.2017.0228
Abstract:
A uniform straight wing was selected to develop an uncertainty quantification and parameter sensitivity analysis method based on the probabilistic flutter. Firstly, the structural equations of motions were presented by applying the extended Hamilton's principle, and a certain flutter velocity was obtained by analyzing the eigenvalue solution. The probabilistic distribution of flutter failure was estimated by using Monte Carlo simulation considering random uncertain variables to satisfy normal distribution. Then line sampling technique was developed to select the important parameters by using the sensitivity analysis under 0.1% probabilistic flutter failure. Finally, the results indicated that the decrease in the mean and the variability of the length of span as well as chord, or the increase in the mean of bending stiffness and torsional stiffness could reduce the probability of flutter failure.
A uniform straight wing was selected to develop an uncertainty quantification and parameter sensitivity analysis method based on the probabilistic flutter. Firstly, the structural equations of motions were presented by applying the extended Hamilton's principle, and a certain flutter velocity was obtained by analyzing the eigenvalue solution. The probabilistic distribution of flutter failure was estimated by using Monte Carlo simulation considering random uncertain variables to satisfy normal distribution. Then line sampling technique was developed to select the important parameters by using the sensitivity analysis under 0.1% probabilistic flutter failure. Finally, the results indicated that the decrease in the mean and the variability of the length of span as well as chord, or the increase in the mean of bending stiffness and torsional stiffness could reduce the probability of flutter failure.
