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RSS2019 Vol. 38, No. 7
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2019, 38(7): 985-1018.
doi: 10.13433/j.cnki.1003-8728.2019.20180279
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Abstract:
The recent adverse environment change, such as global warming, rising sea level, and glacier melting, greatly challenges the future of human society, demanding accelerated exploration of green energy technologies. The advancements in micro-nano technology and mechanical-material engineering make it possible to the harvest and utilization of vibration energy, mainly to convert it to electrical energy via electromagnetic conversion, electrostatic conversion, piezoelectric conversion, magnetostrictive conversion, magnetoelectric conversion, and triboelectric nanogeneration, as well as hybrid mechanisms. Among these, triboelectric nanogeneration is the latest research focus. The current status of researches on the mechanisms, materials, structures for vibration energy harvest technologies were reviewed, major achievements of domestic and international researchers were retrospected. The working principles, characteristics, electric output performances of a number of energy harvest methods are explained in detail, and some key problems remain to be solved pertaining to the coupling performance, frequency range, harvest efficiency, integration and longevity in the research on vibration energy harvest technologies are summarized. The trend of future developments of vibration energy harvest technologies are also discussed, hoping to provide a valuable reference for the people in the field of energy harvest.
The recent adverse environment change, such as global warming, rising sea level, and glacier melting, greatly challenges the future of human society, demanding accelerated exploration of green energy technologies. The advancements in micro-nano technology and mechanical-material engineering make it possible to the harvest and utilization of vibration energy, mainly to convert it to electrical energy via electromagnetic conversion, electrostatic conversion, piezoelectric conversion, magnetostrictive conversion, magnetoelectric conversion, and triboelectric nanogeneration, as well as hybrid mechanisms. Among these, triboelectric nanogeneration is the latest research focus. The current status of researches on the mechanisms, materials, structures for vibration energy harvest technologies were reviewed, major achievements of domestic and international researchers were retrospected. The working principles, characteristics, electric output performances of a number of energy harvest methods are explained in detail, and some key problems remain to be solved pertaining to the coupling performance, frequency range, harvest efficiency, integration and longevity in the research on vibration energy harvest technologies are summarized. The trend of future developments of vibration energy harvest technologies are also discussed, hoping to provide a valuable reference for the people in the field of energy harvest.
2019, 38(7): 1019-1023.
doi: 10.13433/j.cnki.1003-8728.2019.20180271
Abstract:
When the vehicle steering is transversely tilting, the active anti-roll bar can output the anti-roll torque and suppress spring deformation of the suspension system, thus enabling the vehicle to have good tilting performance. Based on the sliding mode variable structure control theory, the active lateral stabilizer has a better ability to reduce the lateral tilt of the vehicle than the PID algorithm and the fuzzy control algorithm, but it is always accompanied by the chattering phenomenon when the state of the system reaches the sliding surface. In this paper, a fuzzy fraction sliding mode control method for active anti-roll bar is proposed, the fractional calculus theory is introduced into the sliding surface definition of the controller, and the fuzzy logic is used to adjust the switching gain parameters adaptively. Carsim-Simulink joint simulation is carried out to verify that the proposed control algorithm can reduce roll angle and suppress chattering phenomenon.
When the vehicle steering is transversely tilting, the active anti-roll bar can output the anti-roll torque and suppress spring deformation of the suspension system, thus enabling the vehicle to have good tilting performance. Based on the sliding mode variable structure control theory, the active lateral stabilizer has a better ability to reduce the lateral tilt of the vehicle than the PID algorithm and the fuzzy control algorithm, but it is always accompanied by the chattering phenomenon when the state of the system reaches the sliding surface. In this paper, a fuzzy fraction sliding mode control method for active anti-roll bar is proposed, the fractional calculus theory is introduced into the sliding surface definition of the controller, and the fuzzy logic is used to adjust the switching gain parameters adaptively. Carsim-Simulink joint simulation is carried out to verify that the proposed control algorithm can reduce roll angle and suppress chattering phenomenon.
2019, 38(7): 1024-1028.
doi: 10.13433/j.cnki.1003-8728.2019.20180296
Abstract:
It is difficult for a single signal feature to fully reflect the running status of the equipment. When multi-domain features are used to characterize the equipment operating status, dimension catastrophe will occur to cause classifier performance degradation and degrading the performance of the state monitoring model as the feature dimension increases. To solve this problem, a new fault diagnosis method based on the linear local tangent space alignment (LLTSA) feature dimensionality reduction and extreme learning machine (ELM) model is proposed. Using LLTSA to extract low-dimensional manifolds from the high-dimensional feature space reduces the dimensionality of signal features, and ensures model classification performance. In this method, firstly, the vibration signal is decomposed by complementary ensemble empirical mode decomposition (CEEMD), and the correlation coefficient and kurtosis criterion are used to select the components to reconstruct the vibration signal after the noise reduction. Then, calculate the multi-domain features of the reconstructed signal, and use LLTSA to perform feature dimension reduction. Finally, the ELM fault diagnosis model is established with its low-dimensional essential features to monitor the equipment operating status. The monitoring experiment of the check valve of the high pressure diaphragm pump shows that the characteristic dimension of the vibration signal is reduced, and the redundancy between the features is reduced, which can improve the accuracy of the fault recognition of the ELM model.
It is difficult for a single signal feature to fully reflect the running status of the equipment. When multi-domain features are used to characterize the equipment operating status, dimension catastrophe will occur to cause classifier performance degradation and degrading the performance of the state monitoring model as the feature dimension increases. To solve this problem, a new fault diagnosis method based on the linear local tangent space alignment (LLTSA) feature dimensionality reduction and extreme learning machine (ELM) model is proposed. Using LLTSA to extract low-dimensional manifolds from the high-dimensional feature space reduces the dimensionality of signal features, and ensures model classification performance. In this method, firstly, the vibration signal is decomposed by complementary ensemble empirical mode decomposition (CEEMD), and the correlation coefficient and kurtosis criterion are used to select the components to reconstruct the vibration signal after the noise reduction. Then, calculate the multi-domain features of the reconstructed signal, and use LLTSA to perform feature dimension reduction. Finally, the ELM fault diagnosis model is established with its low-dimensional essential features to monitor the equipment operating status. The monitoring experiment of the check valve of the high pressure diaphragm pump shows that the characteristic dimension of the vibration signal is reduced, and the redundancy between the features is reduced, which can improve the accuracy of the fault recognition of the ELM model.
2019, 38(7): 1029-1034.
doi: 10.13433/j.cnki.1003-8728.2019.20180268
Abstract:
The laser-repaired TC4 titanium alloy and the commercial TC4 titanium alloy substrate are selected as the experiment materials and the dynamic compression tests of two materials are performed by a split hopkinson pressure bar (SHPB) equipment at room temperature, then the true stress-strain curves of two materials are obtained. The results show that the two kinds of specimens have both obvious upsetting and some of the specimens fracture after SHPB tests. The two materials have both the obvious strain rate strengthening effect. Moreover, by comparing the stress-strain curves of two materials under the same strain rates, the dynamic mechanical properties of the laser-repaired TC4 titanium alloy are better than those of the commercial TC4 titanium alloy substrate.
The laser-repaired TC4 titanium alloy and the commercial TC4 titanium alloy substrate are selected as the experiment materials and the dynamic compression tests of two materials are performed by a split hopkinson pressure bar (SHPB) equipment at room temperature, then the true stress-strain curves of two materials are obtained. The results show that the two kinds of specimens have both obvious upsetting and some of the specimens fracture after SHPB tests. The two materials have both the obvious strain rate strengthening effect. Moreover, by comparing the stress-strain curves of two materials under the same strain rates, the dynamic mechanical properties of the laser-repaired TC4 titanium alloy are better than those of the commercial TC4 titanium alloy substrate.
2019, 38(7): 1035-1040.
doi: 10.13433/j.cnki.1003-8728.2019.20180277
Abstract:
Based on the rehabilitation mechanism of the ankle joint and the traction therapy of traditional Chinese medicine, a (2-SPS+PU)&R hybrid ankle rehabilitation robot is developed. The robot can realize not only the three-dimensional rotation required by the ankle joint rehabilitation but also the ankle stretching motion in the lower leg direction. Based on the screw theory, the degree of freedom of the 2-SPS+PU hybrid mechanism is calculated. Its inverse kinematics is analyzed by using the closed-loop vector method. Its velocity Jacobian matrix is solved. Its kinematics is simulated with the ADAMS software. The simulation results show that the hybrid mechanism can reach the motion range needed for ankle joint rehabilitation, i.e., the maximum values of plantar flexion and dorsiflexion are 25° and 20°, respectively; the maximum values of adduction and abduction are all 30°; the maximum values of inversion and eversion are all 20°; the maximum value of stretching motion is 25 mm, satisfying the rehabilitation requirements of an injured ankle joint.
Based on the rehabilitation mechanism of the ankle joint and the traction therapy of traditional Chinese medicine, a (2-SPS+PU)&R hybrid ankle rehabilitation robot is developed. The robot can realize not only the three-dimensional rotation required by the ankle joint rehabilitation but also the ankle stretching motion in the lower leg direction. Based on the screw theory, the degree of freedom of the 2-SPS+PU hybrid mechanism is calculated. Its inverse kinematics is analyzed by using the closed-loop vector method. Its velocity Jacobian matrix is solved. Its kinematics is simulated with the ADAMS software. The simulation results show that the hybrid mechanism can reach the motion range needed for ankle joint rehabilitation, i.e., the maximum values of plantar flexion and dorsiflexion are 25° and 20°, respectively; the maximum values of adduction and abduction are all 30°; the maximum values of inversion and eversion are all 20°; the maximum value of stretching motion is 25 mm, satisfying the rehabilitation requirements of an injured ankle joint.
2019, 38(7): 1041-1047.
doi: 10.13433/j.cnki.1003-8728.2019.20180283
Abstract:
In order to study the mechanical behaviour of spiral drum under complex condition of coal seam, the constitutive model for coal and rock materials was constructed based on Drucker-Prager yield criterion. Through the numerical simulation of the cutting process of spiral drum, the stress distribution of the coal and rock mass, the force variation law of the pick and the spiral drum are obtained. In the range of 0°~12°, the mean force of the cutting pick increases with the increasing of dip angle by 30.9%. The increase in traction speed led to the increase in elastic energy and brittleness accumulated in coal and rock mass contact with the cutting pick, and the maximum stress of coal and rock mass increased by 40.1% and 9.3%. The reduce in spiral drum speed led to a decrease in the stress of coal rock body in contact with the pick, and the maximum stress of coal and rock mass reduced by 27.0% and 7.5%. The increase in traction speed and the reduce in rotation speed of spiral drum caused the greatest increase in traction resistance among the three-way forces, with the maximum increased by 91.73%. The load and fluctuation of the spiral drum varied significantly with the nature of cutting object.
In order to study the mechanical behaviour of spiral drum under complex condition of coal seam, the constitutive model for coal and rock materials was constructed based on Drucker-Prager yield criterion. Through the numerical simulation of the cutting process of spiral drum, the stress distribution of the coal and rock mass, the force variation law of the pick and the spiral drum are obtained. In the range of 0°~12°, the mean force of the cutting pick increases with the increasing of dip angle by 30.9%. The increase in traction speed led to the increase in elastic energy and brittleness accumulated in coal and rock mass contact with the cutting pick, and the maximum stress of coal and rock mass increased by 40.1% and 9.3%. The reduce in spiral drum speed led to a decrease in the stress of coal rock body in contact with the pick, and the maximum stress of coal and rock mass reduced by 27.0% and 7.5%. The increase in traction speed and the reduce in rotation speed of spiral drum caused the greatest increase in traction resistance among the three-way forces, with the maximum increased by 91.73%. The load and fluctuation of the spiral drum varied significantly with the nature of cutting object.
2019, 38(7): 1048-1054.
doi: 10.13433/j.cnki.1003-8728.2019.20180282
Abstract:
In order to study the performance of the linear feed system, a test platform is designed. The control system includes motor drive, servo loading motor control and pneumatic control. The measurement system includes sensors layout and measurement software development. The control circuit and controller are designed to control two feed units synchronous linear feed motion. The pneumatic cylinders are used to simulate the cutting force and the feed unit can be loaded with the follower force in three directions. The temperature, displacement, acceleration, torque and grating sensors are properly arranged to test the performance parameters of the feed unit. The measurement software is developed to collect sensor signals and analyze the performance parameters of the assigned units. The influence of the cutting force on the temperature rise and thermal error of linear feed system is analyzed with the designed measurement and controlling system. The results show that the designed test installment and its measurement and control system can be used to test the performance of machine tool linear feed system.
In order to study the performance of the linear feed system, a test platform is designed. The control system includes motor drive, servo loading motor control and pneumatic control. The measurement system includes sensors layout and measurement software development. The control circuit and controller are designed to control two feed units synchronous linear feed motion. The pneumatic cylinders are used to simulate the cutting force and the feed unit can be loaded with the follower force in three directions. The temperature, displacement, acceleration, torque and grating sensors are properly arranged to test the performance parameters of the feed unit. The measurement software is developed to collect sensor signals and analyze the performance parameters of the assigned units. The influence of the cutting force on the temperature rise and thermal error of linear feed system is analyzed with the designed measurement and controlling system. The results show that the designed test installment and its measurement and control system can be used to test the performance of machine tool linear feed system.
2019, 38(7): 1055-1060.
doi: 10.13433/j.cnki.1003-8728.2019.20180278
Abstract:
In the design of scroll profiles, aiming at the drawback of profiles:different in expression form and lack of concise and effective profile general model, firstly, integration scroll profile equation is established by vector function and differential geometry theory. The equation breaks the situation that one profile corresponds to one model in the traditional profile study, this equation can not only include circular arc profile, base circle involute and variable radius base circle involute, but can construct new and efficient scroll profiles as well. Then, the mapping relationship between the control coefficients and the geometric performances of the orbiting and the fixed scroll profiles is obtained by studying the change rule of the control coefficients in the function equation. Finally, the strategies of optimum selection for control coefficients are summarized, a series of scroll profiles which satisfy the requirements can be selected with these strategies of optimum selection, and one of the scroll profiles with optimum performance can be sorted out according to the design requirement of the scroll compressor.
In the design of scroll profiles, aiming at the drawback of profiles:different in expression form and lack of concise and effective profile general model, firstly, integration scroll profile equation is established by vector function and differential geometry theory. The equation breaks the situation that one profile corresponds to one model in the traditional profile study, this equation can not only include circular arc profile, base circle involute and variable radius base circle involute, but can construct new and efficient scroll profiles as well. Then, the mapping relationship between the control coefficients and the geometric performances of the orbiting and the fixed scroll profiles is obtained by studying the change rule of the control coefficients in the function equation. Finally, the strategies of optimum selection for control coefficients are summarized, a series of scroll profiles which satisfy the requirements can be selected with these strategies of optimum selection, and one of the scroll profiles with optimum performance can be sorted out according to the design requirement of the scroll compressor.
2019, 38(7): 1061-1066.
doi: 10.13433/j.cnki.1003-8728.2019.20180280
Abstract:
In order to study the influence of milling parameters on surface integrity during the high-speed milling of ultra-high strength steel, high-speed milling experiments were carried out on ultra-high strength steel 16Co14Ni10Cr2Mo with coated carbide inserts based on orthogonal experimental method. The effects of milling speed, feed per tooth and milling depth on three-dimensional surface roughness, surface residual stress and surface microhardness were analyzed, and the milling parameters were optimized. The experimental results show that the three-dimensional surface roughness increases with the milling speed and the feed per tooth. As the milling depth increases, there is a trend of increasing first and then decreasing. The surface residual stress in both directions depends on the milling speed and milling depth. The increase of residual stress vertical to the feed direction σy increases with the increase of feed per tooth, while residual stress along the feed direction σx tends to increase first and then decrease; the surface microhardness does not change much with the increase of milling speed υc, but decreases with the increase of feed per tooth fz and milling depth ap; the feed per tooth fz has the greatest influence on the surface integrity; with the surface integrity and machining efficiency considered, the optimal milling parameter combination is:υc is 150.7 m/min, fz is 0.02 mm/z, and ap is 1.0 mm.
In order to study the influence of milling parameters on surface integrity during the high-speed milling of ultra-high strength steel, high-speed milling experiments were carried out on ultra-high strength steel 16Co14Ni10Cr2Mo with coated carbide inserts based on orthogonal experimental method. The effects of milling speed, feed per tooth and milling depth on three-dimensional surface roughness, surface residual stress and surface microhardness were analyzed, and the milling parameters were optimized. The experimental results show that the three-dimensional surface roughness increases with the milling speed and the feed per tooth. As the milling depth increases, there is a trend of increasing first and then decreasing. The surface residual stress in both directions depends on the milling speed and milling depth. The increase of residual stress vertical to the feed direction σy increases with the increase of feed per tooth, while residual stress along the feed direction σx tends to increase first and then decrease; the surface microhardness does not change much with the increase of milling speed υc, but decreases with the increase of feed per tooth fz and milling depth ap; the feed per tooth fz has the greatest influence on the surface integrity; with the surface integrity and machining efficiency considered, the optimal milling parameter combination is:υc is 150.7 m/min, fz is 0.02 mm/z, and ap is 1.0 mm.
2019, 38(7): 1067-1073.
doi: 10.13433/j.cnki.1003-8728.2019.20180281
Abstract:
Aiming to the various working conditions and the characteristics of multi-axis linkage of the self-developed composite machine tool, the dynamic coupling characteristics of the machine tool on the feed motion of the multi-axis were analyzed. Result indicates that the column is the key structural component that influences the dynamic coupling performance of the machine tool. Taking the column as the optimization goal, and an optimization approach combining BP neural network model with NSGA-Ⅱ algorithm (non-dominated sorting genetic algorithm) was proposed. Then, the BP neural network model was established by sampling points in the design space via the Optimal Space-Filing Design method. The NSGA-Ⅱ algorithm was adopted to optimize the loop approximation on the BP neural network model, and to get the Patero optimal solution. The results show that the first two order natural frequencies are greatly increased and the dynamic performance of the machine tool in X, Y and Z directions decreased by 41.0%, 57.5% and 39.7% respectively after optimization.
Aiming to the various working conditions and the characteristics of multi-axis linkage of the self-developed composite machine tool, the dynamic coupling characteristics of the machine tool on the feed motion of the multi-axis were analyzed. Result indicates that the column is the key structural component that influences the dynamic coupling performance of the machine tool. Taking the column as the optimization goal, and an optimization approach combining BP neural network model with NSGA-Ⅱ algorithm (non-dominated sorting genetic algorithm) was proposed. Then, the BP neural network model was established by sampling points in the design space via the Optimal Space-Filing Design method. The NSGA-Ⅱ algorithm was adopted to optimize the loop approximation on the BP neural network model, and to get the Patero optimal solution. The results show that the first two order natural frequencies are greatly increased and the dynamic performance of the machine tool in X, Y and Z directions decreased by 41.0%, 57.5% and 39.7% respectively after optimization.
2019, 38(7): 1074-1078.
doi: 10.13433/j.cnki.1003-8728.2019.20180275
Abstract:
In order to turn out that PID-Control has a better control effect, the anti-swinging characteristic of rigid-pendulum-crane with PID-Control has been studied. The mathematical models of the rigid-pendulum-crane had been established to obtain its state equation. Through MATLAB, the time needed to stop swinging of free crane system and of PID controlled crane system had been simulated after the same unit impact. According to the time, the PID controlled system could significantly suppress the swinging of rigid-pendulum-crane. Besides, the rigid-pendulum-crane experiment platform with STM32F103 as lower machine and LABVIEW as upper machine had been established. It has been verified that the rigid-pendulum-crane with PID-Control can meet the actual engineering needs and greatly improve the efficiency of the rigid-pendulum-crane by the platform.
In order to turn out that PID-Control has a better control effect, the anti-swinging characteristic of rigid-pendulum-crane with PID-Control has been studied. The mathematical models of the rigid-pendulum-crane had been established to obtain its state equation. Through MATLAB, the time needed to stop swinging of free crane system and of PID controlled crane system had been simulated after the same unit impact. According to the time, the PID controlled system could significantly suppress the swinging of rigid-pendulum-crane. Besides, the rigid-pendulum-crane experiment platform with STM32F103 as lower machine and LABVIEW as upper machine had been established. It has been verified that the rigid-pendulum-crane with PID-Control can meet the actual engineering needs and greatly improve the efficiency of the rigid-pendulum-crane by the platform.
2019, 38(7): 1079-1086.
doi: 10.13433/j.cnki.1003-8728.2019.20180274
Abstract:
In order to overcome the difficulty in extracting the suitable features of the shaft orbit and low efficiency of the identification on shaft orbit in fault detection for rotating machines, a shape descriptor, EHF-TCDs, based on Extract height function 1 (EHF1) and Triangular centroid distances (TCDs) is presented to extract feature from the shaft orbit of rotating machines. Smoothing and Fourier transforms are introduced into the shape descriptor to reduce the dimension of the feature matrix. EHF-TCDs shape descriptor has the characteristics of starting point invariance, similarity transformation invariance, noise immunity and low dimension, and can fully characterize shaft orbits. On the basis of EHF-TCDs, a new and efficient method of fault detection for rotating machines is proposed, which uses support vector machine (SVM) to identify the EHF-TCDs feature extracted from shaft orbit. The effectiveness of the proposed method is verified by a noiseless simulated shaft orbit library, four noisy simulated shaft orbit libraries and a measured shaft orbit library, and the recognition rates of experiments all exceeded 99.57%, and the average test time of a single sample does not exceed 0.021 ms.
In order to overcome the difficulty in extracting the suitable features of the shaft orbit and low efficiency of the identification on shaft orbit in fault detection for rotating machines, a shape descriptor, EHF-TCDs, based on Extract height function 1 (EHF1) and Triangular centroid distances (TCDs) is presented to extract feature from the shaft orbit of rotating machines. Smoothing and Fourier transforms are introduced into the shape descriptor to reduce the dimension of the feature matrix. EHF-TCDs shape descriptor has the characteristics of starting point invariance, similarity transformation invariance, noise immunity and low dimension, and can fully characterize shaft orbits. On the basis of EHF-TCDs, a new and efficient method of fault detection for rotating machines is proposed, which uses support vector machine (SVM) to identify the EHF-TCDs feature extracted from shaft orbit. The effectiveness of the proposed method is verified by a noiseless simulated shaft orbit library, four noisy simulated shaft orbit libraries and a measured shaft orbit library, and the recognition rates of experiments all exceeded 99.57%, and the average test time of a single sample does not exceed 0.021 ms.
2019, 38(7): 1087-1092.
doi: 10.13433/j.cnki.1003-8728.2019.20180276
Abstract:
Through the study of the heat generation and heat conduction mechanisms of oil-immersed transformer, a controllable heating analog device with internal heat source is developed. Its temperature is measured at several points with a thermocouple sensor. Then, the temperatures of the windings of the heating analog device with internal heat source and the oil-immersed transformer are analyzed and compared. The results show that the top oil temperature of the transformer at the rated power that was developed in the paper is 81.7℃; its bottom oil temperature is 57.7℃, its top winding temperature is 88.5℃, and its bottom winding temperature is 72.9℃. The top oil temperature and key nodal temperature are basically consistent with the temperature of the windings of the large oil-immersed power transformer. The maximum temperature deviation of the transformer at the rated power is 0.5℃, and its maximum temperature deviation at the 1.3 times rated power is 0.6℃.
Through the study of the heat generation and heat conduction mechanisms of oil-immersed transformer, a controllable heating analog device with internal heat source is developed. Its temperature is measured at several points with a thermocouple sensor. Then, the temperatures of the windings of the heating analog device with internal heat source and the oil-immersed transformer are analyzed and compared. The results show that the top oil temperature of the transformer at the rated power that was developed in the paper is 81.7℃; its bottom oil temperature is 57.7℃, its top winding temperature is 88.5℃, and its bottom winding temperature is 72.9℃. The top oil temperature and key nodal temperature are basically consistent with the temperature of the windings of the large oil-immersed power transformer. The maximum temperature deviation of the transformer at the rated power is 0.5℃, and its maximum temperature deviation at the 1.3 times rated power is 0.6℃.
2019, 38(7): 1093-1100.
doi: 10.13433/j.cnki.1003-8728.2019.20180285
Abstract:
Taken the state characteristic of vibration signal of rolling bearing and the "outliers" among the feature values into consideration, a new pattern recognition method, namely agent discriminate model based optimization weighted (ADMOW), is proposed in this paper. Firstly, according to its class similarity, the sample eigenvalues are evaluated. Based on the evaluation result, the eigenvalues are weighted to eliminate the "outliers" resulting in model deviation. The established model is secondly optimized by the particle swarm optimization (PSO) algorithm, hence a more accurate and reliable classification model is correspondingly obtained. Eventually, ADMOW is applied to recognize faults of rolling bearings. The experimental and analytical results indicate that this proposed method can effectively promote the recognition accuracy, compared with the previous pattern recognition methods.
Taken the state characteristic of vibration signal of rolling bearing and the "outliers" among the feature values into consideration, a new pattern recognition method, namely agent discriminate model based optimization weighted (ADMOW), is proposed in this paper. Firstly, according to its class similarity, the sample eigenvalues are evaluated. Based on the evaluation result, the eigenvalues are weighted to eliminate the "outliers" resulting in model deviation. The established model is secondly optimized by the particle swarm optimization (PSO) algorithm, hence a more accurate and reliable classification model is correspondingly obtained. Eventually, ADMOW is applied to recognize faults of rolling bearings. The experimental and analytical results indicate that this proposed method can effectively promote the recognition accuracy, compared with the previous pattern recognition methods.
2019, 38(7): 1101-1108.
doi: 10.13433/j.cnki.1003-8728.2019.20180270
Abstract:
Aiming at the inevitable loss of traction and braking system of high-speed train in operation and the time-varying disturbance caused by external environment, a controller based on optimal predictive control algorithm is designed. Based on train dynamics, the algorithm determines the transfer function of the train model and stabilizes the control system using pole assignment. The established train model is the controlled object of the algorithm, and the additional resistance and basic resistance of the line are taken as the disturbance input of the algorithm, and a disturbance observer is added to further enhance the performance. The stability of the control system and the automatic preview control of train speed are realized. The simulation results show that the optimal preview control algorithm with disturbance observer has good anti-jamming and adaptability, and can make the train run to the desired state within the constraints, and the trajectory can follow the target trajectory well.
Aiming at the inevitable loss of traction and braking system of high-speed train in operation and the time-varying disturbance caused by external environment, a controller based on optimal predictive control algorithm is designed. Based on train dynamics, the algorithm determines the transfer function of the train model and stabilizes the control system using pole assignment. The established train model is the controlled object of the algorithm, and the additional resistance and basic resistance of the line are taken as the disturbance input of the algorithm, and a disturbance observer is added to further enhance the performance. The stability of the control system and the automatic preview control of train speed are realized. The simulation results show that the optimal preview control algorithm with disturbance observer has good anti-jamming and adaptability, and can make the train run to the desired state within the constraints, and the trajectory can follow the target trajectory well.
2019, 38(7): 1109-1117.
doi: 10.13433/j.cnki.1003-8728.2019.20190042
Abstract:
In order to improve the friction performance of cylinder liner piston ring, the surface textures of different shapes were machined through laser etching technology. Under the same rotational speed and different applied loads, the influence of the piston rings with different surface textures on the tribological performance of cylinder liner-piston ring was studied with a computer-controlled reciprocating friction and wear tester. The experimental results show that the friction coefficients of elliptical, circular and square textures of piston rings reduced by 1.1%, 18.3% and 14.1% respectively at a load of 400 N, and 35.3%, 35.3% and 19.1% at a load of 600 N respectively. Through the comprehensive analysis of friction coefficient, surface topography and contact resistance, the piston ring of circular pit texture has the best performance in reducing the friction coefficient and wear and improving the lubrication condition of oil film.
In order to improve the friction performance of cylinder liner piston ring, the surface textures of different shapes were machined through laser etching technology. Under the same rotational speed and different applied loads, the influence of the piston rings with different surface textures on the tribological performance of cylinder liner-piston ring was studied with a computer-controlled reciprocating friction and wear tester. The experimental results show that the friction coefficients of elliptical, circular and square textures of piston rings reduced by 1.1%, 18.3% and 14.1% respectively at a load of 400 N, and 35.3%, 35.3% and 19.1% at a load of 600 N respectively. Through the comprehensive analysis of friction coefficient, surface topography and contact resistance, the piston ring of circular pit texture has the best performance in reducing the friction coefficient and wear and improving the lubrication condition of oil film.
2019, 38(7): 1118-1125.
doi: 10.13433/j.cnki.1003-8728.2019.20190051
Abstract:
An embedded fin thermoelectric conversion system for marine diesel exhaust duct is proposed, and its structure is designed in a new way. Then the three-dimensional model of the thermoelectric conversion system is established to analyze the flow field, temperature field and electric field distribution characteristics of embedded thermoelectric module in exhaust duct under different conditions. Finally, the test device of the exhaust duct thermoelectric conversion system is built to verify the accuracy of the numerical analysis. The results show that:the analysis results are in good agreement with the experimental results. The maximum generation power error is less than 5%. The generation power of embedded fin module is about 3.2 times higher than that of non-embedded fin module. In the process of system design, the relationship between fin height, fin number and flow field characteristics, pump power and net power all should be taken into account to achieve maximum power generation. The device increases the heat transfer area through the fin, reduces the thermal resistance, and further improves the power generation performance of the thermoelectric module.
An embedded fin thermoelectric conversion system for marine diesel exhaust duct is proposed, and its structure is designed in a new way. Then the three-dimensional model of the thermoelectric conversion system is established to analyze the flow field, temperature field and electric field distribution characteristics of embedded thermoelectric module in exhaust duct under different conditions. Finally, the test device of the exhaust duct thermoelectric conversion system is built to verify the accuracy of the numerical analysis. The results show that:the analysis results are in good agreement with the experimental results. The maximum generation power error is less than 5%. The generation power of embedded fin module is about 3.2 times higher than that of non-embedded fin module. In the process of system design, the relationship between fin height, fin number and flow field characteristics, pump power and net power all should be taken into account to achieve maximum power generation. The device increases the heat transfer area through the fin, reduces the thermal resistance, and further improves the power generation performance of the thermoelectric module.
2019, 38(7): 1126-1131.
doi: 10.13433/j.cnki.1003-8728.2019.20180273
Abstract:
Zinc coated layer is a kind of microscopic object which is easily neglected in the stamping process of galvanized steel sheet, but it influences the stamping formability of steel sheet. Therefore, based on nano-indentation test and cup protrusion test, the mechanical properties of zinc coated layer of advanced high strength hot dip galvanized steel sheet DP600 are studied. Firstly, the load-displacement curve and the elastic modulus of zinc coated layer are obtained based on nano-indentation test. Then, the nano-indentation process is simulated by using software ABAQUS, and the dimension analysis of nano-indentation is carried out with Π theorem. Constitutive model for zinc coated layer are deduced from the above analysis. Finally, the present model is applied to the numerical simulation of cup protrusion test, and the results are compared with the experimental. The results show that the accuracy of numerical simulation by considering zinc coated layer is closer to the cup protrusion test than those without considering the zinc coated layer.
Zinc coated layer is a kind of microscopic object which is easily neglected in the stamping process of galvanized steel sheet, but it influences the stamping formability of steel sheet. Therefore, based on nano-indentation test and cup protrusion test, the mechanical properties of zinc coated layer of advanced high strength hot dip galvanized steel sheet DP600 are studied. Firstly, the load-displacement curve and the elastic modulus of zinc coated layer are obtained based on nano-indentation test. Then, the nano-indentation process is simulated by using software ABAQUS, and the dimension analysis of nano-indentation is carried out with Π theorem. Constitutive model for zinc coated layer are deduced from the above analysis. Finally, the present model is applied to the numerical simulation of cup protrusion test, and the results are compared with the experimental. The results show that the accuracy of numerical simulation by considering zinc coated layer is closer to the cup protrusion test than those without considering the zinc coated layer.
2019, 38(7): 1132-1137.
doi: 10.13433/j.cnki.1003-8728.2019.20180272
Abstract:
Based on the RSSR spatial mechanism, the biorthogonal RSSR differential mechanism for ailerons was designed; the analytical model of differential mechanism was built; the kinematic characteristics under different link lengths were obtained by transforming the coordinates of open kinematic chains with the D-H method. The mathematical expressions for the kinematic analysis of the differential mechanism were derived through using the link length method; the link length conditions were determined in accordance with the aileron control accuracy requirements. The simulation analysis model was built with the multi-body dynamics software ADAMS to verify the theoretical analysis. The results show that the biorthogonal RSSR differential mechanism for ailerons can realize the differential drive of the left and right ailerons with the same deflection angle and that the constant transmission ratio of approximately 1 can be achieved through a specific rod length configuration.
Based on the RSSR spatial mechanism, the biorthogonal RSSR differential mechanism for ailerons was designed; the analytical model of differential mechanism was built; the kinematic characteristics under different link lengths were obtained by transforming the coordinates of open kinematic chains with the D-H method. The mathematical expressions for the kinematic analysis of the differential mechanism were derived through using the link length method; the link length conditions were determined in accordance with the aileron control accuracy requirements. The simulation analysis model was built with the multi-body dynamics software ADAMS to verify the theoretical analysis. The results show that the biorthogonal RSSR differential mechanism for ailerons can realize the differential drive of the left and right ailerons with the same deflection angle and that the constant transmission ratio of approximately 1 can be achieved through a specific rod length configuration.
2019, 38(7): 1138-1142.
doi: 10.13433/j.cnki.1003-8728.2019.20190061
Abstract:
In order to analyze the reliability of failure data under random censored more accurately, an reduction method based Exception Maximization(EM) algorithm for random censored data are proposed, which based on the statistics. Firstly, collecting failure data of IDG component of B737NG aircraft, determine that the life distribution type is two parameter Weibull distribution with K-M estimation method and MATLAB software; secondly, estimating the unknown parameters of Weibull distribution by EM algorithm for random censored data; finally, analyzing reliability and maintainability of IDG failure data. The analysis results show that the reliability analysis accuracy is much higher in the case of considering censored data under the Weibull distribution, the new results can be used in developing maintenance plan and optimizing maintenance scheme for IDG of B737NG aircraft.
In order to analyze the reliability of failure data under random censored more accurately, an reduction method based Exception Maximization(EM) algorithm for random censored data are proposed, which based on the statistics. Firstly, collecting failure data of IDG component of B737NG aircraft, determine that the life distribution type is two parameter Weibull distribution with K-M estimation method and MATLAB software; secondly, estimating the unknown parameters of Weibull distribution by EM algorithm for random censored data; finally, analyzing reliability and maintainability of IDG failure data. The analysis results show that the reliability analysis accuracy is much higher in the case of considering censored data under the Weibull distribution, the new results can be used in developing maintenance plan and optimizing maintenance scheme for IDG of B737NG aircraft.
Experimental Study on Self-lubricating Technology of Cross Axis Universal Joint for High Lift System
2019, 38(7): 1143-1148.
doi: 10.13433/j.cnki.1003-8728.2019.20190104
Abstract:
Cross axis universal joints are widely used in transmission subsystem of Aircraft High Lift System. For S82, B23 and self-lubricating coating three kinds of materials of universal joint, the experiment is designed, and the wear and transmission efficiency of universal joint are tested. The test results show that the self-lubricating material across axis universal joint is minimum wear and maximum transmission efficiency. In addition, the calculation methods of transmission efficiency and wear for cross axis universal joint are proposed in this paper, which can be used to calculate the transmission efficiency and end of life wear of cross axis universal joint by using the installation angle in aircraft.
Cross axis universal joints are widely used in transmission subsystem of Aircraft High Lift System. For S82, B23 and self-lubricating coating three kinds of materials of universal joint, the experiment is designed, and the wear and transmission efficiency of universal joint are tested. The test results show that the self-lubricating material across axis universal joint is minimum wear and maximum transmission efficiency. In addition, the calculation methods of transmission efficiency and wear for cross axis universal joint are proposed in this paper, which can be used to calculate the transmission efficiency and end of life wear of cross axis universal joint by using the installation angle in aircraft.
