Author Center
Editor Work
Peer Review
Editorial Entry
Email Alert
RSS2018 Vol. 37, No. 9
Display Method:
2018, 37(9): 1313-1318.
doi: 10.13433/j.cnki.1003-8728.20180028
PDF 988KB
Abstract:
To resolve the conflict between the end trajectory tracking and the obstacle avoidance of a redundant manipulator, a weighted generalized inverse obstacle avoidance algorithm was presented. Its evaluation function called danger field was improved. By weighting the Jacobian matrix and gradient and feeding back the value of the danger field to an improved closed-loop inverse kinematics (CLIK) algorithm, the obstacle avoidance algorithm can avoid joint limits and obstacles. In order to enhance avoidance efficiency, the closed-loop control parameter was designed. In the process of obstacle avoidance, the manipulator can, in advance, cope with task suspension and resumption according to the relationship between value of danger field and threshold set. The numerical simulations results prove that the proposed algorithm is effective by means of Robotics Toolbox for MATLAB.
To resolve the conflict between the end trajectory tracking and the obstacle avoidance of a redundant manipulator, a weighted generalized inverse obstacle avoidance algorithm was presented. Its evaluation function called danger field was improved. By weighting the Jacobian matrix and gradient and feeding back the value of the danger field to an improved closed-loop inverse kinematics (CLIK) algorithm, the obstacle avoidance algorithm can avoid joint limits and obstacles. In order to enhance avoidance efficiency, the closed-loop control parameter was designed. In the process of obstacle avoidance, the manipulator can, in advance, cope with task suspension and resumption according to the relationship between value of danger field and threshold set. The numerical simulations results prove that the proposed algorithm is effective by means of Robotics Toolbox for MATLAB.
2018, 37(9): 1319-1324.
doi: 10.13433/j.cnki.1003-8728.20180063
Abstract:
In order to compile the load spectrum of hydraulic pump in an excavator based on the measured data, a certain kind of hydraulic excavator was tested and the load data of the excavator under typical working conditions was collected. Based on the measured data, the load segmentation of hydraulic pump was standardized according to obvious segmentation characteristics of the working conditions. The data was segmented and connected, and the non-parametric extrapolation method based on load extension was selected to extrapolate it. The results were reasonable compared with the actual operation of the hydraulic pump, which can provide a data foundation for the subsequent test and analysis of hydraulic pump.
In order to compile the load spectrum of hydraulic pump in an excavator based on the measured data, a certain kind of hydraulic excavator was tested and the load data of the excavator under typical working conditions was collected. Based on the measured data, the load segmentation of hydraulic pump was standardized according to obvious segmentation characteristics of the working conditions. The data was segmented and connected, and the non-parametric extrapolation method based on load extension was selected to extrapolate it. The results were reasonable compared with the actual operation of the hydraulic pump, which can provide a data foundation for the subsequent test and analysis of hydraulic pump.
2018, 37(9): 1325-1330.
doi: 10.13433/j.cnki.1003-8728.20180026
Abstract:
It is not possible for a robot whose geometry does not meet the Pieper criterion to obtain a closed kinematic inverse solution. The robot is also known as general robot, and its inverse kinematic problems are usually solved with the numerical method. For the general 6 degree of freedom articulated robot, the iterative idea is still used. The n-th solution is taken as the initial value of the next iteration, which satisfies the high requirement that the initial value of iteration is sufficiently close to the exact solution. In the iterative process, the pseudo inverse matrix of the Jacobian matrix is used instead of inverse matrix, thus avoiding the problem that the robot cannot solve at the singularity. In the trajectory planning algorithm, the four-dimensional spherical linear interpolation method is used to interpolate the starting point and the end point, solving the problem of singularity and transient transition in the Euler angle attitude interpolation method. Finally, simulations in the MATLAB environment are carried out, and their results verify the feasibility of the real-time control of the improved inverse kinematic algorithm.
It is not possible for a robot whose geometry does not meet the Pieper criterion to obtain a closed kinematic inverse solution. The robot is also known as general robot, and its inverse kinematic problems are usually solved with the numerical method. For the general 6 degree of freedom articulated robot, the iterative idea is still used. The n-th solution is taken as the initial value of the next iteration, which satisfies the high requirement that the initial value of iteration is sufficiently close to the exact solution. In the iterative process, the pseudo inverse matrix of the Jacobian matrix is used instead of inverse matrix, thus avoiding the problem that the robot cannot solve at the singularity. In the trajectory planning algorithm, the four-dimensional spherical linear interpolation method is used to interpolate the starting point and the end point, solving the problem of singularity and transient transition in the Euler angle attitude interpolation method. Finally, simulations in the MATLAB environment are carried out, and their results verify the feasibility of the real-time control of the improved inverse kinematic algorithm.
2018, 37(9): 1331-1335.
doi: 10.13433/j.cnki.1003-8728.20180047
Abstract:
To quantitatively research load-carrying augmentation performance of lower extremity exoskeleton (LEE), the quantization index, ΔT and μ is put forward. ΔT is defined as sum of difference of three joints torque of the hip, knee and ankle of human before and after wearing LEE. μ is defined as the ratio of ΔT to total power consumption of LEE, p. The kinetic model is established. Based on human gait data, the change of p in a gait cycle is obtained under common gait. Using dynamic analysis software ADAMS, Human simplified simulation model and human-machine integration simulation model are established, and the change of ΔT and μ is analyzed. The result showes that ΔT keep high values in the stance phase, It is concluded that three lower limbs joint torque is greatly reduced at this stage after wearing LEE. μ gets the maximum value in the swing phase, shows that LEE unit power make a greater contribution to human, and the energy utilization rate is high at at this stage.
To quantitatively research load-carrying augmentation performance of lower extremity exoskeleton (LEE), the quantization index, ΔT and μ is put forward. ΔT is defined as sum of difference of three joints torque of the hip, knee and ankle of human before and after wearing LEE. μ is defined as the ratio of ΔT to total power consumption of LEE, p. The kinetic model is established. Based on human gait data, the change of p in a gait cycle is obtained under common gait. Using dynamic analysis software ADAMS, Human simplified simulation model and human-machine integration simulation model are established, and the change of ΔT and μ is analyzed. The result showes that ΔT keep high values in the stance phase, It is concluded that three lower limbs joint torque is greatly reduced at this stage after wearing LEE. μ gets the maximum value in the swing phase, shows that LEE unit power make a greater contribution to human, and the energy utilization rate is high at at this stage.
2018, 37(9): 1336-1343.
doi: 10.13433/j.cnki.1003-8728.20180051
Abstract:
The electromagnetic vibration energy harvester with auxiliary linear oscillator subject to white noise excitation is studied and the dimensionless governing equation is obtained in the paper. The depth of the potential well of the bistable vibration harvester system is related with the stiffness ratio. And the depth of the potential well is expressed by the stiffness ratio. The effect law of the depth of potential well on the power generation of the bistable system under different noise intensity is obtained. And the different optimum stiffness ratio corresponding to different noise intensity is got by means of simulation. The optimum mass ratio and tuning frequency ratio range corresponding to different noise intensity and different depth of the potential well are obtained by making the mass ratio and tuning frequency ratio change continuously. The research results can provide a basis for the study of the bistable electromagnetic vibration energy harvester.
The electromagnetic vibration energy harvester with auxiliary linear oscillator subject to white noise excitation is studied and the dimensionless governing equation is obtained in the paper. The depth of the potential well of the bistable vibration harvester system is related with the stiffness ratio. And the depth of the potential well is expressed by the stiffness ratio. The effect law of the depth of potential well on the power generation of the bistable system under different noise intensity is obtained. And the different optimum stiffness ratio corresponding to different noise intensity is got by means of simulation. The optimum mass ratio and tuning frequency ratio range corresponding to different noise intensity and different depth of the potential well are obtained by making the mass ratio and tuning frequency ratio change continuously. The research results can provide a basis for the study of the bistable electromagnetic vibration energy harvester.
2018, 37(9): 1344-1351.
doi: 10.13433/j.cnki.1003-8728.20180164
Abstract:
To extend the power of the lower limb and complete the human-machine tasks under the specific environment, a wearable assist lower extremity exoskeleton robot is designed and developed in this paper. Firstly, the characteristics of human walking and demanding power of lower limbs are analyzed. Secondly, mechanical design and modelling of the exoskeleton are calculated based on the establishment of virtual prototype and simulation in Adams. Then, the electric-hydraulic servo driving system is designed on account of exoskeleton operations. Finally, ranges of motion and actuators for exoskeleton are investigated and optimized. The proposed indexes, including the matching degree, etc., are verified and which are used for study on relationships between lower limbs and joints of the exoskeleton. Therefore, the experimental results show that the proposed design for the exoskeleton is feasible and effective.
To extend the power of the lower limb and complete the human-machine tasks under the specific environment, a wearable assist lower extremity exoskeleton robot is designed and developed in this paper. Firstly, the characteristics of human walking and demanding power of lower limbs are analyzed. Secondly, mechanical design and modelling of the exoskeleton are calculated based on the establishment of virtual prototype and simulation in Adams. Then, the electric-hydraulic servo driving system is designed on account of exoskeleton operations. Finally, ranges of motion and actuators for exoskeleton are investigated and optimized. The proposed indexes, including the matching degree, etc., are verified and which are used for study on relationships between lower limbs and joints of the exoskeleton. Therefore, the experimental results show that the proposed design for the exoskeleton is feasible and effective.
2018, 37(9): 1352-1358.
doi: 10.13433/j.cnki.1003-8728.20180068
Abstract:
In the multi-objective optimization of planetary gears, traditional particle swarm optimization (PSO) and adaptive weight particle swarm optimization (APSO) algorithms are not easy to converge or fall into local optimum under complex constraints. An improved adaptive weight particle swarm optimization (D-APSO) method is proposed and used to a multi-objective optimization design of the high power density of the planetary gear. With the minimum volume, maximum transmission efficiency and minimum central moment as the multi-objective optimization function, the penalty function method is used to deal with the constraint condition and the planetary gear boundary condition, and the objective is optimized by D-APSO algorithm. The calculation results show that the D-APSO algorithm is superior to the traditional PSO and the APSO algorithms in optimization speed and solution accuracy. While satisfying the carrier performance of the planetary gear system, the D-APSO algorithm can obtain smaller volume, smaller central distance and better transmission efficiency of the planetary gear system.
In the multi-objective optimization of planetary gears, traditional particle swarm optimization (PSO) and adaptive weight particle swarm optimization (APSO) algorithms are not easy to converge or fall into local optimum under complex constraints. An improved adaptive weight particle swarm optimization (D-APSO) method is proposed and used to a multi-objective optimization design of the high power density of the planetary gear. With the minimum volume, maximum transmission efficiency and minimum central moment as the multi-objective optimization function, the penalty function method is used to deal with the constraint condition and the planetary gear boundary condition, and the objective is optimized by D-APSO algorithm. The calculation results show that the D-APSO algorithm is superior to the traditional PSO and the APSO algorithms in optimization speed and solution accuracy. While satisfying the carrier performance of the planetary gear system, the D-APSO algorithm can obtain smaller volume, smaller central distance and better transmission efficiency of the planetary gear system.
2018, 37(9): 1359-1365.
doi: 10.13433/j.cnki.1003-8728.20180034
Abstract:
In order to solve the problem in the usage of the ensemble empirical mode decomposition (EEMD) to extract fault feature in rolling element bearing, a hybrid fault diagnosis method is proposed. First, the morphological filter combining with translation invariant wavelet are served as the pre-filter of the EEMD to effectively eliminate the narrowband pulse and random noises from original signals. Second, aiming to the reasonable selection of the true components from intrinsic mode functions (IMFs), a screening rule is proposed to improve EEMD by selecting IMFs from the vibration signals of rolling element bearings. The autocorrelation functions of both the original signal and each IMF are calculated and normalized. All correlation coefficients are obtained by calculating the autocorrelation functions of the original signal with the autocorrelation functions of each IMF. To eliminate the false IMFs, a hard threshold is defined using the half of the maximum correlation coefficient. Therefore, inspect whether the first two IMFs are reserved, if not, reserving the first two IMFs simultaneously. Simulation and experimental investigations for the fault detection of rolling bearing show that the present hybrid method is effective. The advantages of the present method are:the usage of the pre-filter of the hybrid morphological filter and translation invariant wavelet is efficient to eliminate the interference of the narrowband pulse and the random noises from the rolling element bearings with faults; the real IMFs will be effectively selected form the de-noised signal using EEMD decomposition, and finally the feature frequency will be reliably obtained. This study provides a new way to detect faults of rolling element bearings.
In order to solve the problem in the usage of the ensemble empirical mode decomposition (EEMD) to extract fault feature in rolling element bearing, a hybrid fault diagnosis method is proposed. First, the morphological filter combining with translation invariant wavelet are served as the pre-filter of the EEMD to effectively eliminate the narrowband pulse and random noises from original signals. Second, aiming to the reasonable selection of the true components from intrinsic mode functions (IMFs), a screening rule is proposed to improve EEMD by selecting IMFs from the vibration signals of rolling element bearings. The autocorrelation functions of both the original signal and each IMF are calculated and normalized. All correlation coefficients are obtained by calculating the autocorrelation functions of the original signal with the autocorrelation functions of each IMF. To eliminate the false IMFs, a hard threshold is defined using the half of the maximum correlation coefficient. Therefore, inspect whether the first two IMFs are reserved, if not, reserving the first two IMFs simultaneously. Simulation and experimental investigations for the fault detection of rolling bearing show that the present hybrid method is effective. The advantages of the present method are:the usage of the pre-filter of the hybrid morphological filter and translation invariant wavelet is efficient to eliminate the interference of the narrowband pulse and the random noises from the rolling element bearings with faults; the real IMFs will be effectively selected form the de-noised signal using EEMD decomposition, and finally the feature frequency will be reliably obtained. This study provides a new way to detect faults of rolling element bearings.
2018, 37(9): 1366-1371.
doi: 10.13433/j.cnki.1003-8728.20180065
Abstract:
In order to improve the control performance of a scraper conveyor extensible tail, a new firefly algorithm for the extensible tail PID controller is proposed. According to the dynamic decision domain radius update formula of the standard firefly algorithm, the updating coefficient of the decision domain is improved to enhance the initial search speed and global detection ability of the firefly algorithm. At the same time, the step-length monotone decreasing is used to improve the mobile step length in the position updating formula to enhance the depth search capability of the firefly algorithm. The results show that the accuracy and stability of the new firefly algorithm are better than those of the original algorithm. The model of scraper conveyor extensible tail controller and the PID controller parameters are tuned by the new firefly algorithm. The fitness function is improved by introducing energy indexes and overshoot indexes. The optimized controller of scraper conveyor extensible tail has a good control performance and robustness.
In order to improve the control performance of a scraper conveyor extensible tail, a new firefly algorithm for the extensible tail PID controller is proposed. According to the dynamic decision domain radius update formula of the standard firefly algorithm, the updating coefficient of the decision domain is improved to enhance the initial search speed and global detection ability of the firefly algorithm. At the same time, the step-length monotone decreasing is used to improve the mobile step length in the position updating formula to enhance the depth search capability of the firefly algorithm. The results show that the accuracy and stability of the new firefly algorithm are better than those of the original algorithm. The model of scraper conveyor extensible tail controller and the PID controller parameters are tuned by the new firefly algorithm. The fitness function is improved by introducing energy indexes and overshoot indexes. The optimized controller of scraper conveyor extensible tail has a good control performance and robustness.
2018, 37(9): 1372-1379.
doi: 10.13433/j.cnki.1003-8728.20180070
Abstract:
It is difficult to measure the sideslip angle, whose observer is designed with the UKF. A hierarchical control strategy was put forward for a distributed drive electric vehicle to control wheel torque when the vehicle was accelerating while swerving. For the upper hierarchical control strategy, a robust sliding mode control was used to calculate the desired yaw moment and to improve the stability caused by model errors and parameter inaccuracy. For the lower hierarchical control strategy, the Lagrange multiplier algorithm was carried out to distribute tire torque and improve vehicle stability and efficiency. The model was simulated with MATLAB/Simulink; the simulation results show that the method can effectively improve vehicle stability and efficiency.
It is difficult to measure the sideslip angle, whose observer is designed with the UKF. A hierarchical control strategy was put forward for a distributed drive electric vehicle to control wheel torque when the vehicle was accelerating while swerving. For the upper hierarchical control strategy, a robust sliding mode control was used to calculate the desired yaw moment and to improve the stability caused by model errors and parameter inaccuracy. For the lower hierarchical control strategy, the Lagrange multiplier algorithm was carried out to distribute tire torque and improve vehicle stability and efficiency. The model was simulated with MATLAB/Simulink; the simulation results show that the method can effectively improve vehicle stability and efficiency.
2018, 37(9): 1380-1386.
doi: 10.13433/j.cnki.1003-8728.20180020
Abstract:
A universal post-processing algorithm for 5-axis CNC machine was proposed and applied to an orthogonal AC-type double turret machine. In this paper, experiments on the flank face grinding of a ball-end milling tool was conducted in the AC-type double turret machine. After verifying the post-processing algorithm, a "virtual grinding wheel" method was put forward to optimize the machining path roughly under the machine's moving structural constraints. Considering the fact that the steps of C-axis rotate and cause big non-linear errors and overcut of the workpiece in the singularity region, which is normal in machine tools with a C-axis, the machining path in this region was optimized further with the cubic B-spline curve fitting method. The simulation and eventual grinding results verify the feasibility of this method.
A universal post-processing algorithm for 5-axis CNC machine was proposed and applied to an orthogonal AC-type double turret machine. In this paper, experiments on the flank face grinding of a ball-end milling tool was conducted in the AC-type double turret machine. After verifying the post-processing algorithm, a "virtual grinding wheel" method was put forward to optimize the machining path roughly under the machine's moving structural constraints. Considering the fact that the steps of C-axis rotate and cause big non-linear errors and overcut of the workpiece in the singularity region, which is normal in machine tools with a C-axis, the machining path in this region was optimized further with the cubic B-spline curve fitting method. The simulation and eventual grinding results verify the feasibility of this method.
2018, 37(9): 1387-1395.
doi: 10.13433/j.cnki.1003-8728.20180181
Abstract:
Reasonable application of mechanical design knowledge can help improve the efficiency and quality of innovative design. The proposal based on the mechanical design process in cloud manufacturing, a deconstructive approach of design knowledge based on the behavior-structure-knowledge model is provided. And then, in this paper a novel optimal selection strategy of mechanical design knowledge based on Rough-ANP is proposed. The novel approach makes use of the strength of rough set theory in handling vagueness and uncertainty and the superiority of analytic network process (ANP) in non-independent hierarchy evaluation. Finally, a case is presented to demonstrate the effective auxiliary function of the novel approach.
Reasonable application of mechanical design knowledge can help improve the efficiency and quality of innovative design. The proposal based on the mechanical design process in cloud manufacturing, a deconstructive approach of design knowledge based on the behavior-structure-knowledge model is provided. And then, in this paper a novel optimal selection strategy of mechanical design knowledge based on Rough-ANP is proposed. The novel approach makes use of the strength of rough set theory in handling vagueness and uncertainty and the superiority of analytic network process (ANP) in non-independent hierarchy evaluation. Finally, a case is presented to demonstrate the effective auxiliary function of the novel approach.
2018, 37(9): 1396-1400.
doi: 10.13433/j.cnki.1003-8728.20180017
Abstract:
It is a reality that the superfinishing process of ball bearing ring raceway is insensitive to geometric precision, and the traditional grinding process of ring raceway is difficult to reach high shape accuracy and low surface roughness. This paper explored the final processing technology for ball bearing ring raceway, and a new processing method of ELID (electrolytic in-process dressing) profile grinding for ball bearing ring raceway based on circular trace feed was proposed. Firstly, the advantage of this method was analyzed in grinding principle. Secondly, the ELID profile grinding experiment of ball bearing ring raceway based on workpiece cathode was carried out. The Ra of processed surface was measured and reached 0.19 μm. The results show that the application of ELID grinding technology in grinding ring groove of ball bearings effectively reduces surface roughness under the condition of workpiece cathode, and the method of ELID profile gringding for ball bearing ring raceway based on circular trace feed is rational. Finally, in order to meet the technological requirements, the feed mechanism of circular trace was designed, which provided the construction of profile grinding experimental platform of ball bearing ring raceway with principle design.
It is a reality that the superfinishing process of ball bearing ring raceway is insensitive to geometric precision, and the traditional grinding process of ring raceway is difficult to reach high shape accuracy and low surface roughness. This paper explored the final processing technology for ball bearing ring raceway, and a new processing method of ELID (electrolytic in-process dressing) profile grinding for ball bearing ring raceway based on circular trace feed was proposed. Firstly, the advantage of this method was analyzed in grinding principle. Secondly, the ELID profile grinding experiment of ball bearing ring raceway based on workpiece cathode was carried out. The Ra of processed surface was measured and reached 0.19 μm. The results show that the application of ELID grinding technology in grinding ring groove of ball bearings effectively reduces surface roughness under the condition of workpiece cathode, and the method of ELID profile gringding for ball bearing ring raceway based on circular trace feed is rational. Finally, in order to meet the technological requirements, the feed mechanism of circular trace was designed, which provided the construction of profile grinding experimental platform of ball bearing ring raceway with principle design.
2018, 37(9): 1401-1407.
doi: 10.13433/j.cnki.1003-8728.20180057
Abstract:
It is difficult to resolve the chip breaking and discharge in the staggered teeth boring and trepanning association (BTA) drilling. The effect of the tool-chip contact length on chip deformation and breaking in the staggered teeth BTA drilling is analyzed with the geometric deformation model of chip breaking we built in the paper. We adopt the finite element method (FEM) simulation software of DEFORM-3D to establish the drilling model for simulation. The rules that govern formation and deformation of every cutting tooth chipping are analyzed; the distribution laws with the drilling radius and drilling condition of the tool-chip contact length are studied. The simulation results are verified by experiments. The results show that the simulation is reliable. The drilling radius has a great influence on the deformation of chips and tool-chip contact length. The tool-chip contact length of the cutting teeth increases with the increase of the feed and material strength and the decrease of the speed.
It is difficult to resolve the chip breaking and discharge in the staggered teeth boring and trepanning association (BTA) drilling. The effect of the tool-chip contact length on chip deformation and breaking in the staggered teeth BTA drilling is analyzed with the geometric deformation model of chip breaking we built in the paper. We adopt the finite element method (FEM) simulation software of DEFORM-3D to establish the drilling model for simulation. The rules that govern formation and deformation of every cutting tooth chipping are analyzed; the distribution laws with the drilling radius and drilling condition of the tool-chip contact length are studied. The simulation results are verified by experiments. The results show that the simulation is reliable. The drilling radius has a great influence on the deformation of chips and tool-chip contact length. The tool-chip contact length of the cutting teeth increases with the increase of the feed and material strength and the decrease of the speed.
2018, 37(9): 1408-1414.
doi: 10.13433/j.cnki.1003-8728.20180027
Abstract:
Aiming at the difficult detection of inner and outer ring faults in the rolling bearings with different damage degrees under the influence of background noise, a new evaluation method of damage degree based on the complementary ensemble empirical mode decomposition(CEEMD) and Lempel-Ziv complexity(LZC index for short) is proposed. First of all, vibration signal of fault rolling bearing is decomposed into a number of intrinsic mode function (IMF) components. Then, the effective IMF component is picked up based on the kurtosis maximum criterion so that the comprehensive index of Lempel-Ziv complexity can be calculated. Finally, the damage degree of the fault rolling bearings is judged based on the variation rule of Lempel-Ziv complexity, and the value interval of Lempel-Ziv complexity is determined reasonably among rolling bearings with different degrees according to 6 sigma principle. The experimental results of this method to damage degree evaluation of rolling bearings have shown the effectiveness and feasibility of the proposed method.
Aiming at the difficult detection of inner and outer ring faults in the rolling bearings with different damage degrees under the influence of background noise, a new evaluation method of damage degree based on the complementary ensemble empirical mode decomposition(CEEMD) and Lempel-Ziv complexity(LZC index for short) is proposed. First of all, vibration signal of fault rolling bearing is decomposed into a number of intrinsic mode function (IMF) components. Then, the effective IMF component is picked up based on the kurtosis maximum criterion so that the comprehensive index of Lempel-Ziv complexity can be calculated. Finally, the damage degree of the fault rolling bearings is judged based on the variation rule of Lempel-Ziv complexity, and the value interval of Lempel-Ziv complexity is determined reasonably among rolling bearings with different degrees according to 6 sigma principle. The experimental results of this method to damage degree evaluation of rolling bearings have shown the effectiveness and feasibility of the proposed method.
2018, 37(9): 1415-1420.
doi: 10.13433/j.cnki.1003-8728.20180031
Abstract:
In order to solve the engineering application problem of the traditional pressure system driven by control valve or asynchronous motor associated with the rising temperature and complex structure which may result in the sensitiveness of oil pollution, poor pressure retaining accuracy and low efficiency, a novel leakage compensation pressure retaining method for a direct drive volume control electro-hydraulic servo system is proposed and implemented based on analysis of the speed regulation performance and efficiency of a permanent magnet synchronous AC servo motor that integrates the simple structure and high reliability of a gear pump. While retaining the pressure of the servo system, according to the flow continuity equation, the output flow of the gear pump only needs to compensate for the leakage of a rotary hydraulic cylinder. Compared with the traditional pressure retaining system, this servo system has the advantage of simple structure, high reliability and energy saving. Through the experiments on the actual flow of the gear pump and the leakage of the rotary hydraulic cylinder, the mathematical relationship between gear pump speed and servo system pressure is obtained, and the pressure retaining mathematical model is established. Meanwhile, the experiments on the step response of the servo system demonstrate its dynamic performance. The experimental results show that the output of the servo system is in good agreement with its input. The servo system satisfies requirements for pressure retaining.
In order to solve the engineering application problem of the traditional pressure system driven by control valve or asynchronous motor associated with the rising temperature and complex structure which may result in the sensitiveness of oil pollution, poor pressure retaining accuracy and low efficiency, a novel leakage compensation pressure retaining method for a direct drive volume control electro-hydraulic servo system is proposed and implemented based on analysis of the speed regulation performance and efficiency of a permanent magnet synchronous AC servo motor that integrates the simple structure and high reliability of a gear pump. While retaining the pressure of the servo system, according to the flow continuity equation, the output flow of the gear pump only needs to compensate for the leakage of a rotary hydraulic cylinder. Compared with the traditional pressure retaining system, this servo system has the advantage of simple structure, high reliability and energy saving. Through the experiments on the actual flow of the gear pump and the leakage of the rotary hydraulic cylinder, the mathematical relationship between gear pump speed and servo system pressure is obtained, and the pressure retaining mathematical model is established. Meanwhile, the experiments on the step response of the servo system demonstrate its dynamic performance. The experimental results show that the output of the servo system is in good agreement with its input. The servo system satisfies requirements for pressure retaining.
2018, 37(9): 1421-1425.
doi: 10.13433/j.cnki.1003-8728.20180041
Abstract:
In order to separate the thermal error component from the radial runout of the machine tool spindle, a novel method is proposed to separate the thermal error components of the spindle by putting four sensors along the circumference of the spindle and using the method of the periodic truncation differential processing. The four-eddy-current displacement sensor and plurality of temperature sensors are arranged in the radial direction of a vertical machining center to obtain the test data. The thermal error components are separated by using equal cycle truncation and differential processing. In the end and the roundness error and rotation error components is separated by using discrete Fourier transform. The results show that the thermal error, roundness error and rotation error are 4.04 μm, 5.30 μm and 5.40 μm, respectively.
In order to separate the thermal error component from the radial runout of the machine tool spindle, a novel method is proposed to separate the thermal error components of the spindle by putting four sensors along the circumference of the spindle and using the method of the periodic truncation differential processing. The four-eddy-current displacement sensor and plurality of temperature sensors are arranged in the radial direction of a vertical machining center to obtain the test data. The thermal error components are separated by using equal cycle truncation and differential processing. In the end and the roundness error and rotation error components is separated by using discrete Fourier transform. The results show that the thermal error, roundness error and rotation error are 4.04 μm, 5.30 μm and 5.40 μm, respectively.
2018, 37(9): 1426-1430.
doi: 10.13433/j.cnki.1003-8728.20180163
Abstract:
The present development of acceleration sensor technology provides a new way to the intelligent interaction of wearable devices. Nowadays, many researchers are interesting in identifying human activities through the data obtained by the accelerometers integrated in the wearable devices, and then inferring the behavior intentions for intelligent human-computer interaction. An efficient method of recognizing elbow-wrist activities is presented based on the recurrent neural network framework in this paper. The proposed method can deeply exploits the relevant sequential information embedded in the wearable tri-axis accelerometer data via a single-gated recurrent neural network. The experimental results show that the method proposed in this paper is more reliable than traditional machine learning methods, and is more concise in network structure to achieve an acceptable performance of elbow-wrist activity recognition compared with the current mainstream recurrent neural network algorithms.
The present development of acceleration sensor technology provides a new way to the intelligent interaction of wearable devices. Nowadays, many researchers are interesting in identifying human activities through the data obtained by the accelerometers integrated in the wearable devices, and then inferring the behavior intentions for intelligent human-computer interaction. An efficient method of recognizing elbow-wrist activities is presented based on the recurrent neural network framework in this paper. The proposed method can deeply exploits the relevant sequential information embedded in the wearable tri-axis accelerometer data via a single-gated recurrent neural network. The experimental results show that the method proposed in this paper is more reliable than traditional machine learning methods, and is more concise in network structure to achieve an acceptable performance of elbow-wrist activity recognition compared with the current mainstream recurrent neural network algorithms.
2018, 37(9): 1431-1436.
doi: 10.13433/j.cnki.1003-8728.20180023
Abstract:
The local mean decomposition (LMD) and approximate entropy methods were proposed to extract features of an analog circuit in order to process the non-linear and non-stationary faulty circuit signals. These signals were firstly decomposed into the sum of product functions(PF) according the LMD algorithm. Approximate entropy features, as the feature vectors of the signals, were calculated with the first three product functions. The complexity of output response signals varies from different faulty circuits; the complexity of the PF after LMD are greatly different for the same reason. Meanwhile, the approximate entropy can represent the time complexity so that the features of the faulty circuit can be effectively extracted by combining the LMD with the approximate entropy algorithms. Finally the kernel Fisher discriminant analysis was used to classify faults and detect them accurately. The simulation results show that this feature extraction method can not only extract the features of a faulty circuit but also classify them accurately, and the average classification accuracy is 97.86%.
The local mean decomposition (LMD) and approximate entropy methods were proposed to extract features of an analog circuit in order to process the non-linear and non-stationary faulty circuit signals. These signals were firstly decomposed into the sum of product functions(PF) according the LMD algorithm. Approximate entropy features, as the feature vectors of the signals, were calculated with the first three product functions. The complexity of output response signals varies from different faulty circuits; the complexity of the PF after LMD are greatly different for the same reason. Meanwhile, the approximate entropy can represent the time complexity so that the features of the faulty circuit can be effectively extracted by combining the LMD with the approximate entropy algorithms. Finally the kernel Fisher discriminant analysis was used to classify faults and detect them accurately. The simulation results show that this feature extraction method can not only extract the features of a faulty circuit but also classify them accurately, and the average classification accuracy is 97.86%.
2018, 37(9): 1437-1443.
doi: 10.13433/j.cnki.1003-8728.20180014
Abstract:
The TCLPR-1 cylinder liner-piston ring friction and wear testing machine was designed and built in this paper. Two groups of tests under the same running conditions was conducted by using this testing machine. The cylinder pressure, cylinder temperature, contact resistance of lubrication oil film between the cylinder liner and the piston ring, the average friction force and the crankshaft speed were real-timely collected to analyze the movement of the cylinder liner-piston ring. The results show that the operating condition of the cylinder liner-piston ring is coincided with the actual operation. It certified that the designed TCLPR-1 testing machine could be used to study the tribological performances of the cylinder liner-piston ring.
The TCLPR-1 cylinder liner-piston ring friction and wear testing machine was designed and built in this paper. Two groups of tests under the same running conditions was conducted by using this testing machine. The cylinder pressure, cylinder temperature, contact resistance of lubrication oil film between the cylinder liner and the piston ring, the average friction force and the crankshaft speed were real-timely collected to analyze the movement of the cylinder liner-piston ring. The results show that the operating condition of the cylinder liner-piston ring is coincided with the actual operation. It certified that the designed TCLPR-1 testing machine could be used to study the tribological performances of the cylinder liner-piston ring.
2018, 37(9): 1444-1449.
doi: 10.13433/j.cnki.1003-8728.20180016
Abstract:
The active vibration control device of thrust bearing which can reduce the longitudinal vibration of the propeller shaft is introduced in this paper. The mathematical models of hydraulic system for the longitudinal vibration of thrust bearing and active vibration reduction hydraulic control device are established; Based on the MATLAB software, the exciting force by the propeller, the longitudinal vibration displacement and acceleration of the propulsion shafting are analyzed in the simulation. The results show that the active damping hydraulic control device can effectively solve the contradiction between the dynamic stiffness and the bearing stiffness of the propulsion shaft system. And it has the characteristics of low longitudinal displacement range, low acceleration response amplitude and obvious effect of vibration reduction, It can provide technical support for vibration reduction of ship propulsion shafting.
The active vibration control device of thrust bearing which can reduce the longitudinal vibration of the propeller shaft is introduced in this paper. The mathematical models of hydraulic system for the longitudinal vibration of thrust bearing and active vibration reduction hydraulic control device are established; Based on the MATLAB software, the exciting force by the propeller, the longitudinal vibration displacement and acceleration of the propulsion shafting are analyzed in the simulation. The results show that the active damping hydraulic control device can effectively solve the contradiction between the dynamic stiffness and the bearing stiffness of the propulsion shaft system. And it has the characteristics of low longitudinal displacement range, low acceleration response amplitude and obvious effect of vibration reduction, It can provide technical support for vibration reduction of ship propulsion shafting.
2018, 37(9): 1450-1458.
doi: 10.13433/j.cnki.1003-8728.20180022
Abstract:
This paper studies the influence of the surface quality and loading mode on the fatigue behavior of the clean 42CrMo steel in the high-cycle to very high-cycle fatigue regimes. Two kinds of specimens with different surface roughness are investigated to study the influence of surface quality. The high-cycle fatigue (HCF) and very high-cycle fatigue (VHCF) tests under both constant amplitude loading and variable amplitude loading are conducted to study the influence of loading mode. The Miner's rule is used to estimate the fatigue life under the variable load amplitudes. Fracture surface examination is adopted to investigate the microscopic fatigue behavior under different surface qualities and loading regimes. The influence of the low stress amplitude below the fatigue limit is also analyzed. It can provide a theoretical foundation to guide the processing and application of clean 42CrMo high strength steel.
This paper studies the influence of the surface quality and loading mode on the fatigue behavior of the clean 42CrMo steel in the high-cycle to very high-cycle fatigue regimes. Two kinds of specimens with different surface roughness are investigated to study the influence of surface quality. The high-cycle fatigue (HCF) and very high-cycle fatigue (VHCF) tests under both constant amplitude loading and variable amplitude loading are conducted to study the influence of loading mode. The Miner's rule is used to estimate the fatigue life under the variable load amplitudes. Fracture surface examination is adopted to investigate the microscopic fatigue behavior under different surface qualities and loading regimes. The influence of the low stress amplitude below the fatigue limit is also analyzed. It can provide a theoretical foundation to guide the processing and application of clean 42CrMo high strength steel.
2018, 37(9): 1459-1464.
doi: 10.13433/j.cnki.1003-8728.20180074
Abstract:
The offshore platform with the development of heat treatment process of Q690 high strength steel as the background, without change in the composition of the materials, according to the new Q-P-T heat treatment process, the high yield strength and tensile strength of steel are effectively improved. The temperature field of oil quenching and Q-P-T heat treatment process of steel plate is simulated via numerical simulation, and the variation of temperature with the time is obtained under different heat treatment conditions. Besides, the optimum heat treatment process was determined by simulating and comparing the tissue composition and content of the materials under different heat treatment processes. In heat treatment experiments, different heat treatment processes were used to treat the original material to compare the mechanical properties of the materials under different heat treatment processes. The experimental data show that the strength and ductility of the steel plate treated with Q-P-T process are greatly improved comparing with the other processes. The results show that the microstructure of Q-P-T steel is composed of martensite, retained austenite and dispersed carbide. These microstructures are of the great importance to improve the strength and ductility of steel.
The offshore platform with the development of heat treatment process of Q690 high strength steel as the background, without change in the composition of the materials, according to the new Q-P-T heat treatment process, the high yield strength and tensile strength of steel are effectively improved. The temperature field of oil quenching and Q-P-T heat treatment process of steel plate is simulated via numerical simulation, and the variation of temperature with the time is obtained under different heat treatment conditions. Besides, the optimum heat treatment process was determined by simulating and comparing the tissue composition and content of the materials under different heat treatment processes. In heat treatment experiments, different heat treatment processes were used to treat the original material to compare the mechanical properties of the materials under different heat treatment processes. The experimental data show that the strength and ductility of the steel plate treated with Q-P-T process are greatly improved comparing with the other processes. The results show that the microstructure of Q-P-T steel is composed of martensite, retained austenite and dispersed carbide. These microstructures are of the great importance to improve the strength and ductility of steel.
2018, 37(9): 1465-1471.
doi: 10.13433/j.cnki.1003-8728.20180044
Abstract:
To predict the fatigue life of the component accurately, a good strategy is to combine several suitable models for the prediction, but the weight value of the traditional method is a determined value. In order to improve the prediction accuracy, weight changeable combination forecasting method has been paid more and more attention. However, estimating the predicted results in the project is not sufficient to provide adequate decision information, and it is necessary to estimate the confidence interval. This paper presents a multi-model comprehensive confidence interval forecasting method based on Bootstrap and variable weight. Bootstrap is used to sample the combined data, based on the re-sampling samples, the weights of each model are obtained by variable weight combining method, and finally the confidence interval is predicted by the quantile method. The method is applied to the engineering example to verify the rationality and feasibility of the proposed method.
To predict the fatigue life of the component accurately, a good strategy is to combine several suitable models for the prediction, but the weight value of the traditional method is a determined value. In order to improve the prediction accuracy, weight changeable combination forecasting method has been paid more and more attention. However, estimating the predicted results in the project is not sufficient to provide adequate decision information, and it is necessary to estimate the confidence interval. This paper presents a multi-model comprehensive confidence interval forecasting method based on Bootstrap and variable weight. Bootstrap is used to sample the combined data, based on the re-sampling samples, the weights of each model are obtained by variable weight combining method, and finally the confidence interval is predicted by the quantile method. The method is applied to the engineering example to verify the rationality and feasibility of the proposed method.
2018, 37(9): 1472-1476.
doi: 10.13433/j.cnki.1003-8728.20180130
Abstract:
Surface hardening is an important way to improve mechanical performance of aircraft gears. A large number of aircraft gear failure is related to gear hardened layer, therefore to determine mechanical properties of gear hardened layer is very critical. Due to surface hardening, mechanical properties of gear materials are not uniform. So it is difficult to determine the properties of materials with the traditional mechanical test methods. In the paper, the approximate relationship between the Vickers hardness and the yield strength of the surface hardened layer of aircraft gear is analyzed based on the comparison and analysis between the Vickers hardness experimental results and the simulated via ABAQUS. That it provides a new way to determine the material mechanical parameters of heterogeneous materials and full use the working ability of surface hardening parts.
Surface hardening is an important way to improve mechanical performance of aircraft gears. A large number of aircraft gear failure is related to gear hardened layer, therefore to determine mechanical properties of gear hardened layer is very critical. Due to surface hardening, mechanical properties of gear materials are not uniform. So it is difficult to determine the properties of materials with the traditional mechanical test methods. In the paper, the approximate relationship between the Vickers hardness and the yield strength of the surface hardened layer of aircraft gear is analyzed based on the comparison and analysis between the Vickers hardness experimental results and the simulated via ABAQUS. That it provides a new way to determine the material mechanical parameters of heterogeneous materials and full use the working ability of surface hardening parts.
