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RSS2019 Vol. 38, No. 10
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2019, 38(10): 1477-1481.
doi: 10.13433/j.cnki.1003-8728.20190019
PDF 923KB
Abstract:
The turn-milling combined machining has the advantages of one-time multi-step machining, low surface temperature and small tool wear, which is very suitable for machining complex rotary parts such as landing gear. Machining stability analysis is an effective method to optimize parameters and avoid machining flutter. In low-speed turn-milling combined process, process damping has a significant influence on stability boundary. In this paper, the mechanism of damping in the turn-milling machining is analyzed. The equivalent process damping model is established. The process damping is introduced into the dynamic equation of turn-milling. The stability prediction in turn-milling combined machining considering process damping is realized. The precise stability boundary of the cutting area is analyzed, and the influence of the process damping on the stability boundary is analyzed. Finally, the prediction model for stability considering the process damping is verified by using the milling experiment. The results show that the process damping will increase the stability boundary, and the effect will increase as the cutting speed decreases.
The turn-milling combined machining has the advantages of one-time multi-step machining, low surface temperature and small tool wear, which is very suitable for machining complex rotary parts such as landing gear. Machining stability analysis is an effective method to optimize parameters and avoid machining flutter. In low-speed turn-milling combined process, process damping has a significant influence on stability boundary. In this paper, the mechanism of damping in the turn-milling machining is analyzed. The equivalent process damping model is established. The process damping is introduced into the dynamic equation of turn-milling. The stability prediction in turn-milling combined machining considering process damping is realized. The precise stability boundary of the cutting area is analyzed, and the influence of the process damping on the stability boundary is analyzed. Finally, the prediction model for stability considering the process damping is verified by using the milling experiment. The results show that the process damping will increase the stability boundary, and the effect will increase as the cutting speed decreases.
2019, 38(10): 1482-1489.
doi: 10.13433/j.cnki.1003-8728.20190024
Abstract:
As efficient, environmentally friendly and safe exploration equipment, vibroseis has been widely used in oil and gas exploration field. With the improvement of geological exploration accuracy requirements, the requirements for the accuracy of the vibroseis output signal are getting higher and higher. However, due to the turbulent disturbance in the hydraulic servo valve spool valve, the hydraulic system pressure often fluctuates, which reduces the control precision of the action mechanism and affects the quality of the output signal. In this paper, Fluent software was used to study the flow field disturbance law of sliding valve in the hydraulic servo valve. The analysis shows that the increase rate of turbulent flow disturbance is the maximum when the valve core is just opened, but the small amount of disturbance is not obvious; The internal flow field of the spool valve is distributed symmetrically in a ring shape. As the opening of the valve port gradually increases, the accumulation amount gradually increases, and the internal flow field reaches a full turbulent state. When the throttle aperture on the valve sleeve is 12mm, the turbulence disturbance is the smallest, and the valve body structure is optimized to improve the accuracy of the output signal.
As efficient, environmentally friendly and safe exploration equipment, vibroseis has been widely used in oil and gas exploration field. With the improvement of geological exploration accuracy requirements, the requirements for the accuracy of the vibroseis output signal are getting higher and higher. However, due to the turbulent disturbance in the hydraulic servo valve spool valve, the hydraulic system pressure often fluctuates, which reduces the control precision of the action mechanism and affects the quality of the output signal. In this paper, Fluent software was used to study the flow field disturbance law of sliding valve in the hydraulic servo valve. The analysis shows that the increase rate of turbulent flow disturbance is the maximum when the valve core is just opened, but the small amount of disturbance is not obvious; The internal flow field of the spool valve is distributed symmetrically in a ring shape. As the opening of the valve port gradually increases, the accumulation amount gradually increases, and the internal flow field reaches a full turbulent state. When the throttle aperture on the valve sleeve is 12mm, the turbulence disturbance is the smallest, and the valve body structure is optimized to improve the accuracy of the output signal.
2019, 38(10): 1490-1495.
doi: 10.13433/j.cnki.1003-8728.20190159
Abstract:
The lubrication characteristics and fatigue life of rolling bearings have close relationships with the rheological properties of lubricants and imperfections of materials. The non-Newtonian elastohydrodynamic lubrication (EHL) model, inclusion model and rolling contact fatigue life model were established, the effects of the slide-roll ratio, characteristic shear stress of non-Newtonian fluid and volume fraction of inhomogeneities on the lubrication properties and fatigue life of inhomogeneous material were investigated. The simulation results show that the existence of inhomogeneity can cause remarkable changes in the film pressure and subsurface stress, and induce the reduction of fatigue life. With the increasing of the slide-roll ratio and the characteristic shear stress, the maximum value of von Mises stress increases and the fatigue life decreases. The fatigue life of the material containing compliant inhomogeneity is more sensitive to the changes in the slide-roll ratio and the characteristic shear stress than that of the material containing stiff inhomogeneity. Furthermore, the fatigue life of the inhomogeneous material decreases with the increasing of volume fraction of inhomogeneities.
The lubrication characteristics and fatigue life of rolling bearings have close relationships with the rheological properties of lubricants and imperfections of materials. The non-Newtonian elastohydrodynamic lubrication (EHL) model, inclusion model and rolling contact fatigue life model were established, the effects of the slide-roll ratio, characteristic shear stress of non-Newtonian fluid and volume fraction of inhomogeneities on the lubrication properties and fatigue life of inhomogeneous material were investigated. The simulation results show that the existence of inhomogeneity can cause remarkable changes in the film pressure and subsurface stress, and induce the reduction of fatigue life. With the increasing of the slide-roll ratio and the characteristic shear stress, the maximum value of von Mises stress increases and the fatigue life decreases. The fatigue life of the material containing compliant inhomogeneity is more sensitive to the changes in the slide-roll ratio and the characteristic shear stress than that of the material containing stiff inhomogeneity. Furthermore, the fatigue life of the inhomogeneous material decreases with the increasing of volume fraction of inhomogeneities.
2019, 38(10): 1496-1502.
doi: 10.13433/j.cnki.1003-8728.20190010
Abstract:
In the exploration and development of deep and ultra-deep wells, the phenomenon of stick-slip vibration is widespread, which is not only causes the reduction of the mechanical drilling rate, but also wastes the driving energy. And it will also accelerate the aging and failure of the drill, threatening the safety of drilling seriously. In order to effectively control the stick-slip vibration of the drill string, a new type of torsional vibration tool is proposed in this paper. Secondly, the theoretical model of the drill string system based on the tool is established. Finally, the viscosity reduction characteristics of the new torsional vibration tool are studied by the PID control method. The simulation experiment is carried out on the established theoretical model of the drill string. The results show that the two PID control methods proposed in this paper also can monitor the expected steady-state speed in real time to suppress the stick-slip vibration phenomenon of the drill string system. Compared the two control equations, U2 control equation owns the faster adjustment ability and better control performance, and there is no stick-slip phenomenon in the early stage.
In the exploration and development of deep and ultra-deep wells, the phenomenon of stick-slip vibration is widespread, which is not only causes the reduction of the mechanical drilling rate, but also wastes the driving energy. And it will also accelerate the aging and failure of the drill, threatening the safety of drilling seriously. In order to effectively control the stick-slip vibration of the drill string, a new type of torsional vibration tool is proposed in this paper. Secondly, the theoretical model of the drill string system based on the tool is established. Finally, the viscosity reduction characteristics of the new torsional vibration tool are studied by the PID control method. The simulation experiment is carried out on the established theoretical model of the drill string. The results show that the two PID control methods proposed in this paper also can monitor the expected steady-state speed in real time to suppress the stick-slip vibration phenomenon of the drill string system. Compared the two control equations, U2 control equation owns the faster adjustment ability and better control performance, and there is no stick-slip phenomenon in the early stage.
2019, 38(10): 1503-1508.
doi: 10.13433/j.cnki.1003-8728.20190015
Abstract:
There is a strong nonlinear relationship between the vibration signal characteristics of the bearing and its running state, which leads to the redundancy among selected high-dimensional features when extracting the bearing's operating state features, thus causing the performance degradation of the fault diagnosis model. A fault diagnosis method that combines the Gaussian process latent variable model (GPLVM) with the multi-class optimal margin distribution machine (mcODM) is proposed. The method performs the complementary ensemble empirical mode decomposition (CEEMD) of the vibration signal to obtain its high-latitude characteristics and then uses the GPLVM to reduce the number of dimensions of the high-dimensional features and then uses the features that have reduced dimensions. Then it establishes the mcODM fault diagnosis model. The bearing's fault diagnosis results show that the method can effectively reduce the redundancy among the features of its vibration signals. The mcODM model can obtain higher fault diagnosis accuracy with the margin distribution optimization.
There is a strong nonlinear relationship between the vibration signal characteristics of the bearing and its running state, which leads to the redundancy among selected high-dimensional features when extracting the bearing's operating state features, thus causing the performance degradation of the fault diagnosis model. A fault diagnosis method that combines the Gaussian process latent variable model (GPLVM) with the multi-class optimal margin distribution machine (mcODM) is proposed. The method performs the complementary ensemble empirical mode decomposition (CEEMD) of the vibration signal to obtain its high-latitude characteristics and then uses the GPLVM to reduce the number of dimensions of the high-dimensional features and then uses the features that have reduced dimensions. Then it establishes the mcODM fault diagnosis model. The bearing's fault diagnosis results show that the method can effectively reduce the redundancy among the features of its vibration signals. The mcODM model can obtain higher fault diagnosis accuracy with the margin distribution optimization.
2019, 38(10): 1509-1513.
doi: 10.13433/j.cnki.1003-8728.20190020
Abstract:
For the complexity of downhole operation of horizontal wells in oil and gas development, a conveying tool-Horizontal Well creeper has been adopted in most oilfields, and has achieved good economic benefits. According to the working principle of the creeper, the geometric relationship between the spatial position of a single cable and the stress analysis are firstly established, and then the mechanical analysis of the connecting cable is extended. Combining with the mechanics of the pullback process of the creeper, the expressions of the ground cable tension and the creeper cable head tension are obtained. Finally, the expressions of the ground cable tension and the creeper cable head tension are obtained by comparing with the experimental results. The error between the calculation results and the measured is small, which verifies the reliability of the mechanical model.
For the complexity of downhole operation of horizontal wells in oil and gas development, a conveying tool-Horizontal Well creeper has been adopted in most oilfields, and has achieved good economic benefits. According to the working principle of the creeper, the geometric relationship between the spatial position of a single cable and the stress analysis are firstly established, and then the mechanical analysis of the connecting cable is extended. Combining with the mechanics of the pullback process of the creeper, the expressions of the ground cable tension and the creeper cable head tension are obtained. Finally, the expressions of the ground cable tension and the creeper cable head tension are obtained by comparing with the experimental results. The error between the calculation results and the measured is small, which verifies the reliability of the mechanical model.
2019, 38(10): 1514-1518.
doi: 10.13433/j.cnki.1003-8728.20190173
Abstract:
Aiming at the poor sinusoidal no-load radial air-gap magnetic density waveform for affecting the distortion of back electromotive force and the output performance of the surface-mounted permanent magnet synchronous motor, and improving the processing costs of the permanent magnet steels with complex structures, a new magnetic pole structure with rectangular permanent magnet steel and convex pole shoe is proposed. The optimum parameters of the pole shoe are obtained by analyzing the influence of the pole shoe parameters on the no-load radial air-gap magnetic density, no-load back electromotive force, cogging torque and permanent magnet steel's eddy current loss by using 3 phases, 18 poles and 54 slot permanent magnet generator simulation model established via finite element simulation software. And the comparison results of output characteristics show that the new magnetic pole with convex pole shoe can make the sinusoidal performance of back electromotive force waveform obviously improved, cogging torque and permanent magnet steel's eddy current loss greatly reduced, and motor output performance significantly improved.
Aiming at the poor sinusoidal no-load radial air-gap magnetic density waveform for affecting the distortion of back electromotive force and the output performance of the surface-mounted permanent magnet synchronous motor, and improving the processing costs of the permanent magnet steels with complex structures, a new magnetic pole structure with rectangular permanent magnet steel and convex pole shoe is proposed. The optimum parameters of the pole shoe are obtained by analyzing the influence of the pole shoe parameters on the no-load radial air-gap magnetic density, no-load back electromotive force, cogging torque and permanent magnet steel's eddy current loss by using 3 phases, 18 poles and 54 slot permanent magnet generator simulation model established via finite element simulation software. And the comparison results of output characteristics show that the new magnetic pole with convex pole shoe can make the sinusoidal performance of back electromotive force waveform obviously improved, cogging torque and permanent magnet steel's eddy current loss greatly reduced, and motor output performance significantly improved.
2019, 38(10): 1519-1525.
doi: 10.13433/j.cnki.1003-8728.20190014
Abstract:
Taking mobile robot as the research object, a kind of eight-wheeled climbing obstacle robot founded on multi-group four-bar linkage is proposed, which has simple control and mechanical structure, high bearing capacity and good obstacle-surmounting performance. The whole suspension structure of the robot is symmetrical and the load platform is integral. The optimized trajectory graph is obtained by kinematics analysis and optimizing the obstacle-surmounting mechanism. The overall scheme design, stability angle analysis and obstacle crossing simulation are carried out to verify the rationality and stability of the robot structure. The load bearing and stability of the robot was also verified by prototype test. The basic performance parameters of the robot are obtained, such as load capacity, obstacle crossing height and slope climbing angle.
Taking mobile robot as the research object, a kind of eight-wheeled climbing obstacle robot founded on multi-group four-bar linkage is proposed, which has simple control and mechanical structure, high bearing capacity and good obstacle-surmounting performance. The whole suspension structure of the robot is symmetrical and the load platform is integral. The optimized trajectory graph is obtained by kinematics analysis and optimizing the obstacle-surmounting mechanism. The overall scheme design, stability angle analysis and obstacle crossing simulation are carried out to verify the rationality and stability of the robot structure. The load bearing and stability of the robot was also verified by prototype test. The basic performance parameters of the robot are obtained, such as load capacity, obstacle crossing height and slope climbing angle.
2019, 38(10): 1526-1534.
doi: 10.13433/j.cnki.1003-8728.20190021
Abstract:
The kinematics model and attitude error model of the single steering wheel AGV path tracking problem are established. Then, using the attitude error and feedforward control as input and the steering wheel speed and the steering wheel deflection angle as output, the single steering wheel AGV path tracking controller is designed. Considering the influence of the curvature mutation of the reference path at the transition between the straight line and the standard arc on the tracking precision and stability of the single steering wheel AGV path, a local path planning method based on continuous curvature is designed and applied to the path tracking controller. Finally, the simulation and prototype experimental results show that the single steering wheel AGV has a swing of about in its steady state, thus verifying the effectiveness and feasibility of the tracking controller.
The kinematics model and attitude error model of the single steering wheel AGV path tracking problem are established. Then, using the attitude error and feedforward control as input and the steering wheel speed and the steering wheel deflection angle as output, the single steering wheel AGV path tracking controller is designed. Considering the influence of the curvature mutation of the reference path at the transition between the straight line and the standard arc on the tracking precision and stability of the single steering wheel AGV path, a local path planning method based on continuous curvature is designed and applied to the path tracking controller. Finally, the simulation and prototype experimental results show that the single steering wheel AGV has a swing of about in its steady state, thus verifying the effectiveness and feasibility of the tracking controller.
2019, 38(10): 1535-1541.
doi: 10.13433/j.cnki.1003-8728.20190016
Abstract:
A novel method of rolling bearing fault detection based on adaptive multiclass relevance vector machines, (A-MRVM) was proposed. Genetic algorithm (GA) was used to optimize MRVM kernel function parameters adaptively, according to the characteristics of fault samples, to solve the uncertainty of artificial parameter selections. Therefore, a novel fault recognition model was constructed based on adaptive multiclass relevance vector machine. The fault identification model was applied in the rolling bearing fault identification experiment. The wavelet packet energies and ensemble empirical mode decomposition (EEMD) energies of rolling bearing vibration signal were extracted respectively as fault features. The fault recognition contrast experiments were implemented using different identification methods. Experimental results indicated that the proposed method can identify the fault type effectively, and verified the method was feasible and superior. Additionally, the method can give more available data to evaluate the possibility of fault type.
A novel method of rolling bearing fault detection based on adaptive multiclass relevance vector machines, (A-MRVM) was proposed. Genetic algorithm (GA) was used to optimize MRVM kernel function parameters adaptively, according to the characteristics of fault samples, to solve the uncertainty of artificial parameter selections. Therefore, a novel fault recognition model was constructed based on adaptive multiclass relevance vector machine. The fault identification model was applied in the rolling bearing fault identification experiment. The wavelet packet energies and ensemble empirical mode decomposition (EEMD) energies of rolling bearing vibration signal were extracted respectively as fault features. The fault recognition contrast experiments were implemented using different identification methods. Experimental results indicated that the proposed method can identify the fault type effectively, and verified the method was feasible and superior. Additionally, the method can give more available data to evaluate the possibility of fault type.
2019, 38(10): 1542-1547.
doi: 10.13433/j.cnki.1003-8728.20190175
Abstract:
In continuous liquid interface production (CLIP), the solid-solid separation between the cured layer and the substrate is transformed into the solid-liquid separation between the cured layer and the liquid resin by using the oxygen inhibition effect, which reduces significantly the separation force and improves the process reliability. However, the adhesion force between the cured layer and the resin still constrain the printing speed and processing reliability at the moment of printing platform moving up. In this paper, the formation mechanism of adhesion force is investigated systematically by using theoretical analysis, numerical simulation and experimental measurement. The result show that the main attribution to the adhesion force formation is the negative pressure (suction force) between the cured part and the liquid resin. The suction force decreases with the increasing of thickness of oxygen inhibition zone and increases with the increasing of section area of printing workpiece, respectively. The adhesion force with different thickness of inhibition zone are measured online through experiments by constructing the cured layer peeling process in CLIP. The experimental results are in a good agreement with the theoretical analysis and simulation results.
In continuous liquid interface production (CLIP), the solid-solid separation between the cured layer and the substrate is transformed into the solid-liquid separation between the cured layer and the liquid resin by using the oxygen inhibition effect, which reduces significantly the separation force and improves the process reliability. However, the adhesion force between the cured layer and the resin still constrain the printing speed and processing reliability at the moment of printing platform moving up. In this paper, the formation mechanism of adhesion force is investigated systematically by using theoretical analysis, numerical simulation and experimental measurement. The result show that the main attribution to the adhesion force formation is the negative pressure (suction force) between the cured part and the liquid resin. The suction force decreases with the increasing of thickness of oxygen inhibition zone and increases with the increasing of section area of printing workpiece, respectively. The adhesion force with different thickness of inhibition zone are measured online through experiments by constructing the cured layer peeling process in CLIP. The experimental results are in a good agreement with the theoretical analysis and simulation results.
2019, 38(10): 1548-1554.
doi: 10.13433/j.cnki.1003-8728.20190012
Abstract:
Aiming at the efficiency of industrial manipulator and the vibration and mechanical wear caused by impact during motion, a time-jerk-optimal trajectory planning algorithm was proposed in this paper. Two mutually coupled and contradictory motion performance indicators of time and jerk were optimized. The trajectory of the task space can be transformed into the corresponding joint spatial position sequence by the inverse kinematics. Interpolation trajectory was constructed in the joint space by a five-order B-spline. The motion constraints of the manipulator were transformed into constraints on the control vertexes of five-order B-spline. The improved penalty function processed the constraints and optimized the objective function by NSGA-Ⅱ(Non-dominated Sorting Genetic Algorithm Ⅱ). Simulation results show that the five -order B-spline trajectory whose indicators of time and jerk are optimized improves the efficiency of the manipulator and guarantees the smallest possible impact during the movement. Finally, the motion control performance of the manipulator is improved.
Aiming at the efficiency of industrial manipulator and the vibration and mechanical wear caused by impact during motion, a time-jerk-optimal trajectory planning algorithm was proposed in this paper. Two mutually coupled and contradictory motion performance indicators of time and jerk were optimized. The trajectory of the task space can be transformed into the corresponding joint spatial position sequence by the inverse kinematics. Interpolation trajectory was constructed in the joint space by a five-order B-spline. The motion constraints of the manipulator were transformed into constraints on the control vertexes of five-order B-spline. The improved penalty function processed the constraints and optimized the objective function by NSGA-Ⅱ(Non-dominated Sorting Genetic Algorithm Ⅱ). Simulation results show that the five -order B-spline trajectory whose indicators of time and jerk are optimized improves the efficiency of the manipulator and guarantees the smallest possible impact during the movement. Finally, the motion control performance of the manipulator is improved.
2019, 38(10): 1555-1560.
doi: 10.13433/j.cnki.1003-8728.20190022
Abstract:
To analyze the impact of the particles on the burrs in ultrasonic machining, the object that the cutting direction burr in the bottom edge of 2A12 aluminum alloy milling, the finite element software based on the explicit dynamic method is applied to simulate the contact impact of single particles. The impact effect of the different position, tool amplitude, particle shape and size on the burrs are studied respectively. The simulated results show that, the degree of burr deformation decreases with the increasing of impact position; the burr shear fracture effect is better with the increasing of tool amplitude, the impact effect that the spherical particle is better than the cubic particle under different particle shape, the impact effect is better as the particle size of the abrasive decreases. The optimal parameters in ultrasonic machining obtained through the comprehensive simulated results are as follows:tool amplitude A=0.048 mm, spherical particle, 80# SiC particle.
To analyze the impact of the particles on the burrs in ultrasonic machining, the object that the cutting direction burr in the bottom edge of 2A12 aluminum alloy milling, the finite element software based on the explicit dynamic method is applied to simulate the contact impact of single particles. The impact effect of the different position, tool amplitude, particle shape and size on the burrs are studied respectively. The simulated results show that, the degree of burr deformation decreases with the increasing of impact position; the burr shear fracture effect is better with the increasing of tool amplitude, the impact effect that the spherical particle is better than the cubic particle under different particle shape, the impact effect is better as the particle size of the abrasive decreases. The optimal parameters in ultrasonic machining obtained through the comprehensive simulated results are as follows:tool amplitude A=0.048 mm, spherical particle, 80# SiC particle.
2019, 38(10): 1561-1568.
doi: 10.13433/j.cnki.1003-8728.20190026
Abstract:
An intelligent online system based on machine vision for perforated workpiece detection is proposed in this paper to solve the large errors and low efficiency in traditional detection methods in industrial production. The system has designed a coarse to fine intelligent detection network. It completes the hole integrity detection of the workpiece, the inspection of the workpiece system conformity and the measurement of the aperture size of the core hole by using the improved Hough transform algorithm and connected domain labeling algorithm. The detection process takes about 10 seconds, and the maximum measurement deviation is less than 0.5 pixel. It can accurately determine the qualification of the workpiece and meets the requirements of real-time, precise, non-contact and high-stability intelligent detection in the production line.
An intelligent online system based on machine vision for perforated workpiece detection is proposed in this paper to solve the large errors and low efficiency in traditional detection methods in industrial production. The system has designed a coarse to fine intelligent detection network. It completes the hole integrity detection of the workpiece, the inspection of the workpiece system conformity and the measurement of the aperture size of the core hole by using the improved Hough transform algorithm and connected domain labeling algorithm. The detection process takes about 10 seconds, and the maximum measurement deviation is less than 0.5 pixel. It can accurately determine the qualification of the workpiece and meets the requirements of real-time, precise, non-contact and high-stability intelligent detection in the production line.
2019, 38(10): 1569-1575.
doi: 10.13433/j.cnki.1003-8728.20190025
Abstract:
Exciting coil is the electromagnetic conversion component, which mainly provides the driving magnetic field for Giant Magnetostrictive Actuator (GMA) and controls its output displacement, and can adjust inputting different current. Therefore, optimizing design the structural parameters and selecting appropriate material of the exciting coil is the key factor to improve the electromagnetic conversion efficiency and give full play to the characteristics of Giant Magnetostrictive Materials (GMM) materials. In this study, the uniformity of magnetic field intensity on the center axis of GMM rod is regarded as the evaluation standard and main design principle by analyzing the working principle of GMA. Exciting coil material is selected through analyzing of its magnetic permeability and the design parameters of exciting coil is optimized by analyzing important factors such as magnetic field intensity and heat loss. Finally, the magnetic circuit of excitation coil is analyzed by using Ansoft Maxwell finite element method. The simulation result shows that the distribution of magnetic field is more uniform and its uniformity is improved to be 98.65%.
Exciting coil is the electromagnetic conversion component, which mainly provides the driving magnetic field for Giant Magnetostrictive Actuator (GMA) and controls its output displacement, and can adjust inputting different current. Therefore, optimizing design the structural parameters and selecting appropriate material of the exciting coil is the key factor to improve the electromagnetic conversion efficiency and give full play to the characteristics of Giant Magnetostrictive Materials (GMM) materials. In this study, the uniformity of magnetic field intensity on the center axis of GMM rod is regarded as the evaluation standard and main design principle by analyzing the working principle of GMA. Exciting coil material is selected through analyzing of its magnetic permeability and the design parameters of exciting coil is optimized by analyzing important factors such as magnetic field intensity and heat loss. Finally, the magnetic circuit of excitation coil is analyzed by using Ansoft Maxwell finite element method. The simulation result shows that the distribution of magnetic field is more uniform and its uniformity is improved to be 98.65%.
2019, 38(10): 1576-1581.
doi: 10.13433/j.cnki.1003-8728.20190218
Abstract:
The pros and cons of the membrane type waterproof breathable valve and the mechanical waterproof breathable valve have been compared, and then, based on the mechanical seal theory, the water resistance and gas permeability of the valve have been designed using stepped and zigzag patterns, thereby establishing a waterproof breathable valve entity. A three-dimensional Ansys simulation model was developed to analyze the fluid field and structural strength for the valves with diameters of 2mm, 4mm and 6mm. The results show that the design is effective in consuming gas energy, balancing the pressure difference between the inside and outside of the shell, and in water blocking and draining. Furthermore, the valve with a diameter of 6 mm has the best permeability for gas, which not only can improve the working efficiency of the valve, but also meet the requirements of mechanical performance. The labyrinth waterproof venting valve can effectively improve the service life of electronic components.
The pros and cons of the membrane type waterproof breathable valve and the mechanical waterproof breathable valve have been compared, and then, based on the mechanical seal theory, the water resistance and gas permeability of the valve have been designed using stepped and zigzag patterns, thereby establishing a waterproof breathable valve entity. A three-dimensional Ansys simulation model was developed to analyze the fluid field and structural strength for the valves with diameters of 2mm, 4mm and 6mm. The results show that the design is effective in consuming gas energy, balancing the pressure difference between the inside and outside of the shell, and in water blocking and draining. Furthermore, the valve with a diameter of 6 mm has the best permeability for gas, which not only can improve the working efficiency of the valve, but also meet the requirements of mechanical performance. The labyrinth waterproof venting valve can effectively improve the service life of electronic components.
2019, 38(10): 1582-1588.
doi: 10.13433/j.cnki.1003-8728.20190023
Abstract:
For the problem of gearbox composite fault diagnosis, the multi-sensor information fusion is used based on the deep convolution neural network(CNN)and the D-S evidence theory method. First, the information features of multiple sensors are extracted adaptively based on the CNN model. The information is preliminarily classified based on softmax. Secondly, the output of the CNN model is used as the input of D-S evidence theory. After the basic probability distribution is calculated, decision fusion is made according to the Dempster synthesis rule. In order to validate the effectiveness of this method for composite fault diagnosis of gearbox, BP neural network and D-S evidence theory model are used as comparison. Principal component analysis(PCA)is carried out based on adaptive extraction of features and artificial features. Experiments show that the accuracy of the composite fault diagnosis of gearbox is 84.58%. Compared with single sensor, the accuracy is improved by 7.91%. Compared with BP neural network and D-S evidence theory model, the accuracy is improved by 6.18%. Thus this method is proved effective.
For the problem of gearbox composite fault diagnosis, the multi-sensor information fusion is used based on the deep convolution neural network(CNN)and the D-S evidence theory method. First, the information features of multiple sensors are extracted adaptively based on the CNN model. The information is preliminarily classified based on softmax. Secondly, the output of the CNN model is used as the input of D-S evidence theory. After the basic probability distribution is calculated, decision fusion is made according to the Dempster synthesis rule. In order to validate the effectiveness of this method for composite fault diagnosis of gearbox, BP neural network and D-S evidence theory model are used as comparison. Principal component analysis(PCA)is carried out based on adaptive extraction of features and artificial features. Experiments show that the accuracy of the composite fault diagnosis of gearbox is 84.58%. Compared with single sensor, the accuracy is improved by 7.91%. Compared with BP neural network and D-S evidence theory model, the accuracy is improved by 6.18%. Thus this method is proved effective.
2019, 38(10): 1589-1597.
doi: 10.13433/j.cnki.1003-8728.20190031
Abstract:
The prediction on the remaining useful life of rolling bearings is a key part of bearing health management. However, the two key issues for the prediction of rolling bearing RUL:The selection of start prediction time; For the treatment of false fluctuations in life. In order to solve these two problems, a data-driven rolling bearing RUL prediction method is proposed in this paper. The method first uses the ensemble empirical mode decomposition (EEMD) to denoise the vibration signal, and then selects the SPT point based on the RMS gradient to perform RUL prediction. Finally, in the RUL prediction, the linear regression is used to repair the false life fluctuation. In order to verify the validity of the method, this paper uses simulation data and real data to verify. Experimental results show that the proposed method can effectively select the appropriate SPT and repair the false life fluctuations.
The prediction on the remaining useful life of rolling bearings is a key part of bearing health management. However, the two key issues for the prediction of rolling bearing RUL:The selection of start prediction time; For the treatment of false fluctuations in life. In order to solve these two problems, a data-driven rolling bearing RUL prediction method is proposed in this paper. The method first uses the ensemble empirical mode decomposition (EEMD) to denoise the vibration signal, and then selects the SPT point based on the RMS gradient to perform RUL prediction. Finally, in the RUL prediction, the linear regression is used to repair the false life fluctuation. In order to verify the validity of the method, this paper uses simulation data and real data to verify. Experimental results show that the proposed method can effectively select the appropriate SPT and repair the false life fluctuations.
2019, 38(10): 1598-1605.
doi: 10.13433/j.cnki.1003-8728.20190017
Abstract:
To improve the stability of an independent drive electric vehicle under the extreme conditions, a direct yaw moment decision algorithm based on the neural network PID control strategy is proposed. The algorithm controls the side-slip angle and yaw rate and carries out the torque distribution. Based on the deviation between the linearized characteristic parameters of the 2-DOF (two degrees of freedom) vehicle model and the actual vehicle control target, the moment is optimized to update the weight of the neural network, and the direct yaw moment required to track the ideal side-slip angle and yaw rate is calculated. Through the dynamic load estimation of the front and rear axles of the electric vehicle, the direct yaw moment distribution of each driving wheel is taken into account by considering the saturation torque of the driving motor and the pavement constraints. The algorithm is applied to the CarSim/Simulink joint simulation model. The simulation results show that the algorithm can guarantee the stability of the emergency steering on a smooth road, the emergency lane transfer at the medium speed and the stability of high-speed overtaking under wet and slippery conditions.
To improve the stability of an independent drive electric vehicle under the extreme conditions, a direct yaw moment decision algorithm based on the neural network PID control strategy is proposed. The algorithm controls the side-slip angle and yaw rate and carries out the torque distribution. Based on the deviation between the linearized characteristic parameters of the 2-DOF (two degrees of freedom) vehicle model and the actual vehicle control target, the moment is optimized to update the weight of the neural network, and the direct yaw moment required to track the ideal side-slip angle and yaw rate is calculated. Through the dynamic load estimation of the front and rear axles of the electric vehicle, the direct yaw moment distribution of each driving wheel is taken into account by considering the saturation torque of the driving motor and the pavement constraints. The algorithm is applied to the CarSim/Simulink joint simulation model. The simulation results show that the algorithm can guarantee the stability of the emergency steering on a smooth road, the emergency lane transfer at the medium speed and the stability of high-speed overtaking under wet and slippery conditions.
2019, 38(10): 1606-1611.
doi: 10.13433/j.cnki.1003-8728.20190011
Abstract:
The industrial crucible for carrying aluminum liquid needs to be heated again before casting aluminum alloy parts. This results in energy waste, increases cost and transforms the properties of aluminum liquid. In order to improve the capability of storing the heat of aluminum liquid, a new inverted conical crucible with multi-layer material and vacuum lining is designed. The numerical simulation is carried out, and the heat loss function of the crucible is derived from the simulation results. The calculation results show that when the thickness of the vacuum layer is 29.49 cm, the heat loss rate of the crucible is 20%. In order to verify the correctness of the heat loss function of the crucible, a physical model of the crucible was built. The results show that the numerical simulation error of the field acquisition temperature of the temperature sensor is less than 5%, indicating that the numerical simulation results have high reliability. Compared with the traditional crucible, the heat loss of the current crucible decreases by more than 10%, and the crucible does not need to be reheated.
The industrial crucible for carrying aluminum liquid needs to be heated again before casting aluminum alloy parts. This results in energy waste, increases cost and transforms the properties of aluminum liquid. In order to improve the capability of storing the heat of aluminum liquid, a new inverted conical crucible with multi-layer material and vacuum lining is designed. The numerical simulation is carried out, and the heat loss function of the crucible is derived from the simulation results. The calculation results show that when the thickness of the vacuum layer is 29.49 cm, the heat loss rate of the crucible is 20%. In order to verify the correctness of the heat loss function of the crucible, a physical model of the crucible was built. The results show that the numerical simulation error of the field acquisition temperature of the temperature sensor is less than 5%, indicating that the numerical simulation results have high reliability. Compared with the traditional crucible, the heat loss of the current crucible decreases by more than 10%, and the crucible does not need to be reheated.
2019, 38(10): 1612-1618.
doi: 10.13433/j.cnki.1003-8728.20190013
Abstract:
As an important component of satellite in communication with the earth, the performance of antenna directly affects the communication quality. Hoop deployable antenna was the research object. In the real orbital environment of space, the corresponding analysis model was established via Stefan-Boltzman thermal radiation and Fourier thermal conduction theory, and the temperature distribution of the antenna was studied. Then through the elasticity mechanics and the finite element theory, the thermal deformation analysis model was established. The influence of temperature on surface accuracy and tension distribution of antenna was analyzed. The study result shows that the uneven temperature distribution in orbit can make the surface accuracy of hoop deployable antenna worse by different degrees; and the tension ratio is significantly increased in some positions with worse uniformity of antenna tension distribution.
As an important component of satellite in communication with the earth, the performance of antenna directly affects the communication quality. Hoop deployable antenna was the research object. In the real orbital environment of space, the corresponding analysis model was established via Stefan-Boltzman thermal radiation and Fourier thermal conduction theory, and the temperature distribution of the antenna was studied. Then through the elasticity mechanics and the finite element theory, the thermal deformation analysis model was established. The influence of temperature on surface accuracy and tension distribution of antenna was analyzed. The study result shows that the uneven temperature distribution in orbit can make the surface accuracy of hoop deployable antenna worse by different degrees; and the tension ratio is significantly increased in some positions with worse uniformity of antenna tension distribution.
2019, 38(10): 1619-1625.
doi: 10.13433/j.cnki.1003-8728.20190018
Abstract:
An axisymmetric vector exhaust nozzle is a kind of mechanically retractable thrust vector nozzle. First, with the analytic geometry method, the kinematics models of the A8 throat and the A9 nozzle area are accurately established for the non-vector state of the cold axisymmetric vector exhaust nozzle. Second, by building a three-dimensional entity and through the ADAMS and MATLAB data exchange, the dynamic simulation analysis of the kinematics models is carried out, the rationality of structural design is validated and the accuracy of the nozzle area is controlled. The results show that the maximum absolute error in the nozzle area is only -3.7 mm2 and that the mean relative error is only -0.045%, indicating that the kinematics model can provide an accurate theoretical basis for the control and simulation of the axisymmetric vector exhaust nozzle.
An axisymmetric vector exhaust nozzle is a kind of mechanically retractable thrust vector nozzle. First, with the analytic geometry method, the kinematics models of the A8 throat and the A9 nozzle area are accurately established for the non-vector state of the cold axisymmetric vector exhaust nozzle. Second, by building a three-dimensional entity and through the ADAMS and MATLAB data exchange, the dynamic simulation analysis of the kinematics models is carried out, the rationality of structural design is validated and the accuracy of the nozzle area is controlled. The results show that the maximum absolute error in the nozzle area is only -3.7 mm2 and that the mean relative error is only -0.045%, indicating that the kinematics model can provide an accurate theoretical basis for the control and simulation of the axisymmetric vector exhaust nozzle.
2019, 38(10): 1626-1631.
doi: 10.13433/j.cnki.1003-8728.20190029
Abstract:
Wing structure bore harsh composite aerodynamic force and heat environment in high-speed flight. Theoretical analysis and finite element calculation were carried out in order to study the thermal buckling and modal characteristics for grid frame wing structure. The critical temperature of thermal buckling and thermal modal parameters under homogeneous or inhomogeneous temperature for the model was obtained. It demonstrated the critical temperature of thermal buckling for grid frame wing structure is higher than plate wing structure's, the thermal physics parameters of material had more prominent effect on thermal modal than elastic parameters under high temperature, and the natural frequencies of grid frame wing structure under inhomogeneous temperature was different from under homogeneous temperature.
Wing structure bore harsh composite aerodynamic force and heat environment in high-speed flight. Theoretical analysis and finite element calculation were carried out in order to study the thermal buckling and modal characteristics for grid frame wing structure. The critical temperature of thermal buckling and thermal modal parameters under homogeneous or inhomogeneous temperature for the model was obtained. It demonstrated the critical temperature of thermal buckling for grid frame wing structure is higher than plate wing structure's, the thermal physics parameters of material had more prominent effect on thermal modal than elastic parameters under high temperature, and the natural frequencies of grid frame wing structure under inhomogeneous temperature was different from under homogeneous temperature.
2019, 38(10): 1632-1640.
doi: 10.13433/j.cnki.1003-8728.20190003
Abstract:
To study the changes in the tip clearance of a 12-stage high-pressure compressor rotor in different engine operation conditions, with its thermal, mechanical and aerodynamic loads considered, a modified and reduced theoretical model was set up. With the model, the changes in different engine operation conditions were studied. Then the 3D model of the compressor rotor was built and more changes in the tip clearance were studied through computer simulation, which turned out to coincide with the changes in different engine operation conditions. The great changes in the moment of the tip clearance were simulated with the finite element analysis software ANSYS. The fluid-solid-thermal coupling method was adopted; the precise radial displacement of the compressor rotor and the compressor case along the axial direction was obtained, and the changes in the maximum tip clearance were calculated. In the maximum tip clearance, the compressor blade may probably scratch the compressor case. The study has a reference value for determining the tip clearance in compressor installation and the distribution of coating.
To study the changes in the tip clearance of a 12-stage high-pressure compressor rotor in different engine operation conditions, with its thermal, mechanical and aerodynamic loads considered, a modified and reduced theoretical model was set up. With the model, the changes in different engine operation conditions were studied. Then the 3D model of the compressor rotor was built and more changes in the tip clearance were studied through computer simulation, which turned out to coincide with the changes in different engine operation conditions. The great changes in the moment of the tip clearance were simulated with the finite element analysis software ANSYS. The fluid-solid-thermal coupling method was adopted; the precise radial displacement of the compressor rotor and the compressor case along the axial direction was obtained, and the changes in the maximum tip clearance were calculated. In the maximum tip clearance, the compressor blade may probably scratch the compressor case. The study has a reference value for determining the tip clearance in compressor installation and the distribution of coating.
