15 June 2023, Volume 51 Issue 11
    

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  • Research on Control Strategy of a Cable-Driven Parallel Cleaning Robot
    CHEN Yizong, LI Jian, WANG Shenghai, LIU Kexin, HAN Guangdong, CHEN Haiquan
    Machine Tool & Hydraulics. 2023, 51(11): 1-6. https://doi.org/10.3969/j.issn.1001-3881.2023.11.001
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Cable-driven parallel cleaning robots can effectively replace manual cleaning of facades,but because they are subject to more external interference and all robot movements are linked to ensure that the cables are in tension,it is more challenging to study the motion control problems of cable-driven parallel cleaning robots than traditional parallel robots.Considering the external forces disturbances of the system during actual use process,a system dynamics model containing cable elasticity was established through Newton-Euler method and Lagrange equation.Combining PD feedforward control and traditional PID,a control law containing cable tension optimization algorithm was designed,and the stability of the control algorithm was proved through Lyapunov stability theory;the theoretical tracking performance of the cable-driven parallel cleaning robot was verified when disturbed by external forces through numerical analysis,and the effectiveness of the control algorithm was proved.
  • Automatic Extraction Method of Welding Trajectory from Point Cloud for Robotic Laser Welding
    ZHANG Yuning, GUAN Junnan, ZHU Lina, PAN Tong, XU Jinting
    Machine Tool & Hydraulics. 2023, 51(11): 7-12. https://doi.org/10.3969/j.issn.1001-3881.2023.11.002
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    In order to avoid the complicated computer aided design(CAD)model construction from point cloud and realize the automatic welding of freely placed vertical plates,an automatic extraction method of welding trajectory from point cloud for robotic laser welding was proposed.The uniform sampling method was used to simplify the point cloud,the statistical filtering was applied to eliminate the measuring noise,and the overall tilt correction of the point cloud was performed at the same time.Then a data scanning strategy was established to realize the rapid segmentation of the top and bottom surfaces of the vertical plates.After that,based on the boundary points on the top surface identified by the Alpha Shape algorithm,distance constraints were used to improve the RANSAC algorithm to quickly fit the top boundary of the vertical plates.Subsequently,the key corners of combined vertical plates were identified through quick sorting and restoration of topological relationships of top boundary segments.On basis of these,the automatic extraction of welding trajectory for robotic laser welding was realized.The experimental results show that the proposed method can directly extract the welding trajectory from the point cloud without CAD model reconstruction,realizing automatic welding of freely placed vertical plates.
  • Trajectory Tracking Control of Lower Limb Rehabilitation Robot Based on DDPG
    ZHAO Zirui, TAO Qing, YANG Tao, WU Bin, WANG Di, FANG Jingyao
    Machine Tool & Hydraulics. 2023, 51(11): 13-19. https://doi.org/10.3969/j.issn.1001-3881.2023.11.003
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    Aiming at the problem of high precision trajectory tracking control of lower limb exoskeleton rehabilitation robot used by stroke patients during passive training,a PD control method based on deep deterministic policy gradient was proposed.The joint angles of normal human walking were collected by Vicon 3D motion capture system as the desired joint angles trajectories and the dynamic model of lower limb exoskeleton robot was established.According to each error input and the reward value obtained by interaction with the dynamic model,the own network parameters were dynamically updated to adaptively output the best PD parameters.The simulation results show that compared with the traditional PD control,using this method,the tracking errors of hip,knee and ankle are reduced by 9.4% on average,and the errors tend to converge and tend to zero,indicating that this method can effectively track the desired joint angles trajectories and has good tracking control accuracy to ensure the rehabilitation effect of patients.
  • Sliding Mode and Optimal Combined Control of Flexible Manipulator Based on New Reaching Law
    ZHU Qixin, SUN Wenxin, ZHU Yonghong
    Machine Tool & Hydraulics. 2023, 51(11): 20-26. https://doi.org/10.3969/j.issn.1001-3881.2023.11.004
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to improve the control accuracy of flexible manipulator,a combined control method based on sliding mode control and optimal control was proposed.The dynamic model was constructed by Lagrange method and hypothetical mode method,and then the flexible arm was decoupled by singular perturbation theory to obtain slow and fast varying subsystems.For the slowly varying subsystem,the sliding mode control was used to realize trajectory tracking,a new reaching law was proposed.Based on the power reaching law,the variable speed reaching term was added,the system state variable was introduced,the reaching rate was dynamically adjusted,the exponential term was added to improve the reaching speed,and the hyperbolic tangent function was used to replace the symbolic function to suppress chattering.For the fast varying subsystem,the optimal control was used to suppress the vibration.MATLAB simulation results show that the combined control method has better dynamic performance and robustness than pure sliding mode control.
  • Research on Robot Gripping System Based on Multi-sensor
    WANG Zhengjia, ZENG Yuqing, XU Xinxi, XU Youxi, WANG Chao
    Machine Tool & Hydraulics. 2023, 51(11): 27-33. https://doi.org/10.3969/j.issn.1001-3881.2023.11.005
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    In order to solve the problems of inflexible robot grasping action and low operation precision caused by the single built-in sensor,a robot grasping system based on multi-sensor was proposed.The extended Kalman filter algorithm was used to fuse the position,speed and angle information measured by the robot's built-in sensors to realize the robot's own pose detection.Under this premise,an external sensor was used to complete the automatic identification and positioning of the target.In order to enhance the reliability of information and the distinguishing ability of the system,and perform kinematics modeling of the gripping action of the robot according to the output signal,the hardware and software environment of the gripping system and the transmission circuit were set to complete the whole system design process.The experimental results prove that the robot system designed by the proposed method can achieve precise alignment to the gripping target,the motion characteristics have been significantly improved,the operation error is effectively reduced.
  • Kinematic Analysis and Trajectory Planning of Catenary Dual-arm Vehicle
    ZHENG Xuekai, LIU Fang, WEI Wenqing, YANG Yan
    Machine Tool & Hydraulics. 2023, 51(11): 34-39. https://doi.org/10.3969/j.issn.1001-3881.2023.11.006
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    Aiming at the problems of low automation degree and low efficiency of catenary operation vehicle in railway tunnel,a catenary dual-arm operation vehicle was developed,which could complete a series of operations such as reinforcing bar detection,drilling anchor,drawing test,hanging column installation and maintenance.The standard D-H method was used to build the kinematics model of the dual-manipulator system,and the forward and inverse kinematics were analyzed.The posture and position of the end-effector were deduced by homogeneous transformation,and then the accuracy of the model was proved by comparing the results of MATLAB simulation and mathematical calculation.Known the initial position of the dual-arm system and the end posture under working state,quintic polynomial interpolation was adopted to plan trajectory.Each joint displacement,velocity and acceleration curves of the dual-arm system were gotten.It provides reference for the further optimization of the dual-arm system.
  • A Coordination Control Algorithm for Welding Workstation Based on Quaternion Method
    FENG Sang, WANG Bingcheng, CHEN Ai
    Machine Tool & Hydraulics. 2023, 51(11): 40-44. https://doi.org/10.3969/j.issn.1001-3881.2023.11.007
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    For 6R series robot,its kinematics solution computation load is big,traditional method is difficulty to solve it and multiple solution and singularity problems are involved.To solve these problems,rigid body motion was described under the Plucker coordinate system,the quaternion mathematical model and the kinematic mathematical model of 6R series robot were established,and its inverse kinematic solution was obtained.A coordinated linkage algorithm model of robot and position transformer in the workstation was established,including the position coordination algorithm,speed coordination algorithm and attitude coordination algorithm Finally the control program of robot and position transformer was obtained.And a welding robot workstation was built for experimental verification of the algorithm.
  • Research on Improved SURF Matching Algorithm in Parallel Robot
    ZHANG Ningke, REN Jianhua, GAO Ruizhen, WANG Jian, ZHANG Hailei
    Machine Tool & Hydraulics. 2023, 51(11): 45-51. https://doi.org/10.3969/j.issn.1001-3881.2023.11.008
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    Aiming at the problems of low accuracy and long matching time of image matching methods for traditional robots,a new improvement algorithm based on SURF was proposed.The transformation from high dimension to binarization was realized by replacing the descriptor with the BEBLID descriptor based on SURF feature point detection.The method of adaptive setting threshold instead of artificial threshold setting was used to reduce the impact of matching.Combined with the elimination method of false matching point pairs by PROSAC optimization strategy,effective matching point pairs were obtained.The experiments show that compared with the expired improved algorithm,the matching correct rate and matching time of this algorithm are improved by 12.01% and 9.66% respectively.Therefore,in the extraction and matching of feature points,it has higher real-time and accuracy,and can meet the real-time requirements of product detection robot sorting.
  • Computed Torque Control with Neural Network Compensation for Mobile Robot
    LIU Xin, CHEN Changzhong, LUO Qi
    Machine Tool & Hydraulics. 2023, 51(11): 52-58. https://doi.org/10.3969/j.issn.1001-3881.2023.11.009
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    For the mobile robot with dynamic uncertain modeling,modeling error and external disturbance,a computed torque control algorithm with RBF (radial basis function)neural network compensation was designed.The kinematic auxiliary speed control algorithm was designed based on the backstepping method.According to the dynamic ideal nominal model,a general torque controller was designed based on the computed torque method.On this basis,a dynamic model of the mobile robot with uncertain modeling,modeling error and external disturbance was established.The torque controller with RBF neural network compensation controller was designed based on the computed torque method.The weights of the neural network were given by the adaptive law.Finally,the stability of the system was proved by using Lyapunov theory.The simulation results show that neural network has good approximation performance for system uncertainty,compared with general computed torque control,the proposed computed torque control algorithm with RBF neural network compensation has better tracking performance,and the control system has better robustness.
  • Research on Dynamic Model of Coordinated Control of Distribution Network Robot
    ZHAI Dong, GENG Yizhao, LI Jiejing, WU Qian
    Machine Tool & Hydraulics. 2023, 51(11): 59-64. https://doi.org/10.3969/j.issn.1001-3881.2023.11.010
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    According to the characteristics of high risk and low efficiency of manual maintenance of distribution network,a structural model of a new distribution network maintenance robot was proposed.Based on the structure of the robot,the joint dynamics model of the closed chain between the working robot and the working object was established,the system dynamics equations under different working modes were obtained,and the force position hybrid coordinated control system for the robot was designed.The dynamic distribution method of closed-loop internal force was proposed,and the simulation experiment and field operation verify that the force position hybrid coordination control can be used to effectively reduce the closed-loop internal force in the operation process of the robot,which shows that the robot can effectively realize the functions of power distribution maintenance such as stripping,trimming,wiring and so on.
  • Research on a Visual Robot Grasping Control Strategy Algorithm
    MING Xin, LU Danping, CHEN Zhong
    Machine Tool & Hydraulics. 2023, 51(11): 65-71. https://doi.org/10.3969/j.issn.1001-3881.2023.11.011
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    Aiming at the stability and accuracy of visual robot grasping target,a reinforcement learning strategy focusing on exploration method was proposed.The deterministic strategy gradient algorithm with deep concern was adopted.The information of pre-exploration area was selected by using the region of interest recommendation network,and the information was calculated by the adaptive exploration method to adjust the strategy with the change of the target.According to the distance between the end effector and the center of the pre-exploration area,a hierarchical reward function was defined to reduce the miscellaneous information brought by the sparse reward matrix.The training was carried out in Bullet3 environment.The experiments show that the proposed strategy can overcome the problems of poor stability and low convergence efficiency that may occur in the training process,can produce robust control against noise interference,and has a high success rate of grasping.
  • Operation Target Location of Robots Based on Machine Vision
    XU Zheng, ZHAI Jiqing, CHEN Yongqiang, LI Yuan, LE Wenjing
    Machine Tool & Hydraulics. 2023, 51(11): 72-75. https://doi.org/10.3969/j.issn.1001-3881.2023.11.012
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    In order to meet the demands of disorderly sorting and positioning of materials in the manufacturing process,an operation target location system of cooperative robots based on machine vision was designed.Qt was used to develop human-computer interaction interface to realize the functions of image acquisition and processing,communication and control of robot motion.The image was processed by threshold segmentation to obtain the ideal working area.Through the calibration of robot vision system,the conversion between camera pixel coordinates and robot base coordinates was realized,and the workpiece pose recognition in robot coordinate system was obtained.A certain number of workpieces were randomly placed on the robot target grasping platform for test.The results show that the system has advantages in accuracy and speed.
  • Research on Machining Dynamics Model and Optimization Design of Hybrid Robot
    LYU Shixia, FENG Zhixin
    Machine Tool & Hydraulics. 2023, 51(11): 76-83. https://doi.org/10.3969/j.issn.1001-3881.2023.11.013
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    Aiming at the structure of hybrid robot for machining,the dynamic model and optimization design method of hybrid robot were proposed.The dynamic model of the hybrid robot was established,and the three performance indexes of the robot workspace/machine volume ratio,lateral stiffness and low-order mode were comprehensively considered.The influence of design variables on the performance indexes was analyzed.On this basis,the design problem and comprehensive design strategy of the internal parallel mechanism of the robot were formulated,and the structure of the robot was optimized.A multi-DOF hybrid robot experimental platform was buit.The test results show that the designed hybrid robot has good static and dynamic characteristics in a large workspace,and the rationality of the proposed model is verified.
  • Comparative Study on Grinding Force of Two-Dimensional Ultrasonic Vibration Assisted Grinding Alumina Ceramics
    SUN Liye, LI Hongshuang, QIU Zhe, DU Tianhe, MA Lianjie
    Machine Tool & Hydraulics. 2023, 51(11): 84-88. https://doi.org/10.3969/j.issn.1001-3881.2023.11.014
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    The main reasons for the decrease of grinding force are the impact force,the change of material hardness and the application mode of ultrasonic vibration.On the basis of ordinary grinding,the grinding force affect mechanism of adding two-dimensional ultrasonic vibration was analyzed.Under the same grinding parameters,the comparative experiments of ordinary grinding and two-dimensional ultrasonic vibration grinding of alumina ceramics were carried out.The effects of workpiece feed speed,wheel linear speed and grinding depth on grinding force were analyzed.The results show that the normal and tangential grinding forces of two-dimensional ultrasonic grinding are less than those of ordinary grinding,the reduction amplitude of the grinding force decreases with the increase of the workpiece feed speed and the wheel line speed,and increases with the increase of the grinding depth;the normal and tangential grinding forces of ordinary grinding and two-dimensional ultrasonic grinding increase with the increase of workpiece feed speed and grinding depth,and decrease with the increase of wheel linear velocity.
  • Optimization Design of Valve Plate for High Speed Axial Piston Pump Based on Cavitation Characteristics
    CHEN Yuanling, YAN Mingyang, ZHANG Yang
    Machine Tool & Hydraulics. 2023, 51(11): 89-95. https://doi.org/10.3969/j.issn.1001-3881.2023.11.015
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    Taking a high-speed axial piston pump as the research object,a CFD numerical simulation model with cavitation module was built.Based on the simulation model,the cavitation of the piston pump during the rotation process was analyzed.The results show that the cavitation mainly occurs in the piston cavity,and the main reasons for the cavitation are insufficient liquid filling rate and too large jet angle.Aiming at the cavitation mechanism,the opening angle of the valve plate was optimized by combining simulation data with theoretical data.According to the flow field,a valve plate structure with a certain slope at both ends was proposed and optimized.After the optimization of valve plate opening angle and structure,the overall cavitation degree in the piston is reduced by 74.2%,which has obvious inhibition effect on cavitation.
  • A Suppression Method for Torque Ripple and Electromagnetic Force Wave of Permanent Magnet Synchronous Motor Spindle
    XIA Pengpeng, YU Shenbo, ZHAI Fengchen, DOU Rutong, YU Zhize, JIANG Shuang
    Machine Tool & Hydraulics. 2023, 51(11): 96-103. https://doi.org/10.3969/j.issn.1001-3881.2023.11.016
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Aiming at the problem of torque ripple and radial electromagnetic force waves in the permanent magnet synchronous motor spindle whose permanent magnet poles are magnetized in parallel and the two sides are parallel,an optimization method of permanent magnet pole structure was proposed to suppress torque ripple and radial electromagnetic force wave.Based on the equivalent surface current method,an air gap magnetic field analytical model of the permanent magnet synchronous motor spindle with an arbitrary outer surface radius of the magnetic pole was established.The effects of rotor air gap magnetic field on torque ripple and radial electromagnetied force wave of stator slotted motor spindle were comprehensively studied.Under the premise that the minimum air gap length remained unchanged,the optimization objectives (the harmonics and amplitudes of the air gap magnetic flux density)were established,and the permanent magnet structure schemes (scheme 1 and scheme 2)that met different optimization objectives were obtained by iterative calculation.Finally,the validity of the analytical model of the rotor air gap magnetic field was verified by the finite element method.The rotor air gap magnetic flux density harmonics,torque ripple,cogging torque,average torque and radial electromagnetic force wave of the original structure motor spindle,the scheme 1 structure motor spindle and the scheme 2 structure motor spindle were compared and analyzed.The results show that the optimization method can be used to obtain permanent magnet magnetic pole structure schemes that meet different optimization objectives,and the comprehensive suppression of specified order magnetic flux density harmonics,torque ripple and radial electromagnetic force wave of the original motor spindle is realized.
  • Manufacturing Process Quality Dynamic Monitoring Based on Logistic Regression Model in Data Rich Environment
    ZHANG Shuai, LYU Chen, YANG Jianfeng
    Machine Tool & Hydraulics. 2023, 51(11): 104-108. https://doi.org/10.3969/j.issn.1001-3881.2023.11.017
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Aiming at the problem of the abnormal information collected from manufacturing process is difficult to use and analysis based on “data rich,information poor”environment of manufacturing workshop in the digital factory,a novelty process quality monitoring technique was proposed based on SPC and Logistic regression.T2 control chart was established by the related data from key stage in MES system.The Logistic regression model was applied to dig abnormal data,and the manufacturing process dynamic monitoring model was optimized by T2 and Logistic model jointly.Taking a plasma-enhanced chemical vapour deposition process of TFT-LCD manufacturing company as example,the feasibility and effectiveness of the process quality monitoring method were verified.The result shows that considering the abnormal information by using Logistic model based on T2 control chart can improve the sensitivity and robust of process quality monitoring.
  • Study on Time-Variant Characteristics of Micro-hole Throttling Aerostatic Thrust Bearing in the Process of Crossing Slots
    YU Hechun, KOU Xinjun, WANG Wenbo, ZHANG Guoqing, WANG Jin, ZHANG Suxiang, YIN Xiaolong
    Machine Tool & Hydraulics. 2023, 51(11): 109-114. https://doi.org/10.3969/j.issn.1001-3881.2023.11.018
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    At present,large air flotation platforms are made of granite platform splicing,and the slots between the splices have a certain impact on the experimental effect.Aiming at the above problems,taking the time-variant characteristics of the micro-hole aerostatic bearing crossing through the slot as the research object,the physical model of the micro-hole throttling aerostatic bearing were established,and the dynamic process simulation of the bearing crossing the slot was carried out by using the dynamic mesh technology combined with CFD software and UDF.The effects of different air film thickness,inlet pressure and slot position on load capacity and pressure distribution were analyzed.The results show that the bearing capacity decreases rapidly when the slot reaches the distribution circle of the micro-hole,and the bearing capacity decreases to the minimum when the slot reaches the center of the bearing;with the increase of gas film thickness,the maximum loss ratio of load capacity increases and finally stabilizes to 0.6;when the slot is located outside the distribution circle of the micro-hole,the bearing surfaces between the edge of bearing and the slot is not work;by increasing the inlet pressure,the overall load capacity improves significantly,but the speed of load capacity loss becomes faster too.
  • Design of Wireless Electronic Handwheel for HNC-8 System
    AN Jianbo, ZHOU Yang, LI Bo, JIANG Tao
    Machine Tool & Hydraulics. 2023, 51(11): 115-119. https://doi.org/10.3969/j.issn.1001-3881.2023.11.019
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The CNC system is equipped with a wired electronic handwheel as standard,due to the constraints of the connecting line,there are many inconveniences in the use process,especially for large gantry machine tools.Therefore,based on wireless radio frequency technology,a low-power,high-reliability wireless electronic handwheel for HNC-8 system was developed.The overall scheme design was carried out,then the signal acquisition circuit,transmission circuit and software module were developed,finally the functional test and verification of the wireless electronic handwheel were carried out.The relevant test results show that the wireless electronic handwheel has all the functions of the wired electronic handwheel,which is easy to operate,stable and reliable,and has good engineering application value.
  • Permanent Magnet Synchronous Motor Optimal Model Predictive Dual Torque Control
    HUANG Xianghui, ZHANG Qiankun, YANG Fang
    Machine Tool & Hydraulics. 2023, 51(11): 120-126. https://doi.org/10.3969/j.issn.1001-3881.2023.11.020
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    Because of the problems of permanent magnet synchronous motor model predictive torque control with a large amount of calculation,the weight factor is difficult to determine and the torque ripple is large,an optimal model predictive dual torque control method was proposed.The cost function of flux linkage and torque were replaced with dual torque of active torque and reactive torque by this method,thereby simplifying the system structure.A compensation function with prediction-correction function was also constructed,and the compensation function was corrected to reduce the impact of the delay problem.On this basis,the sector judgment link was added to reduce the number of candidate voltages from 8 to 3,which greatly reduced the amount of calculation.The simulation results show that the optimized model predictive dual torque control method has lower torque ripple,less calculation,and faster dynamic response.
  • Design and Experiment of Working Fluid Ultrasonic Vibration Assisted Electrical Discharge Keyhole Machining Device
    LIAN Haishan, XU Dahua, CHEN Xiaojun, DING Zihan, ZHANG Linpeng
    Machine Tool & Hydraulics. 2023, 51(11): 127-132. https://doi.org/10.3969/j.issn.1001-3881.2023.11.021
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    Electrical discharge machining(EDM)keyhole exists some problems such as low machining efficiency due to low discharge efficiency of electro erosion products,secondary discharge phenomenon due to discharge of electro erosion products and influence on machining accuracy.The cavitation effect and pumping effect generated by ultrasonic vibration in the working fluid can greatly improve the chip discharge and deionization ability of EDM,thus the occurrence of the above problems is reduced to a large extent.A set of working fluid ultrasonic vibration assisted EDM keyhole machining device was designed,which mainly included spindle system,micro-three-dimensional motion platform,ultrasonic vibration working liquid groove and data acquisition system.The spindle system included NSK electric spindle,power transmission structure and tool electrode clamping structure,which could realize high-speed rotation of tool electrode.The EDM keyhole machining control system was developed based on LabVIEW,which included initialization module,rough positioning module,constant voltage tool setting module,real-time voltage subsection control machining module and real-time display module.The experimental study of working fluid ultrasonic vibration assisted EDM was carried out.The experimental results show that the material removal rate and electrode loss rate tend to increase with the increase of EDM voltage.
  • Pulse Power Supply Design and Application of Diamond Grinding Wheel Trimming Machine
    JI Xining, GU Linfeng, LU Xiaochun, GU Hongliang, YU Zhiqiang, WANG Changxi
    Machine Tool & Hydraulics. 2023, 51(11): 133-139. https://doi.org/10.3969/j.issn.1001-3881.2023.11.022
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    Aiming at the human machine interaction mode outmoded of traditional electric spark diamond grinding wheel trimming machine pulse power supply,the power source main vibration pulse anti-interference ability is weak,low discharge efficiency and severe parasitic inductance,an electric spark pulse power supply was designed.Using Mitsubishi PLC as the system main controller,STC8A8K64S4A12 single-chip microcomputer and EPM570T100C5N CPLD programmable logic device were selected as a pulse master chip.At the same time,the hardware and software of the electric spark pulse power supply were designed.A diamond grinding wheel trimming prototype was produced.Based on the stone ink wheel,the discharge processing tests were performed by the diamond grinding wheel as machining workpieces.At the same time,the designed power supply processing performance was checked,it had a process comparison test with traditional electric spark diamond grinding wheel trimming machine.The results show that the designed pulse power control method is simple,the parameter setting is convenient,the discharge waveform anti-interference ability is strong,it is not easy to distortion,the discharge efficiency is high,the surface quality of the processed diamond grinding wheel is high,and the formation surface particle is high integrated.
  • Parameter Analysis and Experimental Research on the End Face Specific Pressure of Floating Oil Seal
    HOU Zhigang, CONG Xiaopeng, LI Jinmin, SUN Bo, YU Dehai
    Machine Tool & Hydraulics. 2023, 51(11): 140-144. https://doi.org/10.3969/j.issn.1001-3881.2023.11.023
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    The structural parameters of the floating oil seal determine the specific pressure of the end face,and then directly affect the sealing effect,so it is of great significance to establish an accurate relationship between the specific pressure of the end face and the structural parameters of the floating oil seal.Abaqus software was used to establish a two-dimensional axisymmetric model of the floating oil seal.The influences of structural parameters such as the geometric parameters of the floating oil seal,the installation distance,and the hardness of the O-ring seal,etc.on the end-face specific pressure were analyzed through simulation orthogonal experiments.The key factors affecting the specific pressure of the end face were analyzed and the regression model between the specific pressure of the end face and the structural parameters of the floating oil seal was obtained.Finally,the accuracy of the regression model was verified by experiments.The results show that the key structural parameters that affect the specific pressure of the end face of the floating oil seal include the installation distance,the waist diameter of the floating seal ring,the cone surface angle of the floating seal seat,the hardness of the seal ring,and the diameter of the cross section of the seal ring.The calculated results of the regression model are in good agreement with the experimental data,which shows that the regression model is in line with the reality and can provide reference for the structural design of floating oil seal.
  • Study of Transient Cavitation Characteristics of Shaped Valve Cavities in Coal Mine Hydraulic Safety Valves
    LUO Yuanqing, WANG Chuanli, HE Tao, ZHANG Wenbiao, DU Minggang, ZHANG Mingwen
    Machine Tool & Hydraulics. 2023, 51(11): 145-149. https://doi.org/10.3969/j.issn.1001-3881.2023.11.024
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    The safety valve is a key component of hydraulic support hydraulic pressurization in coal mines,but the high vaporization pressure of the aqueous medium causes the hydraulic components to be prone to cavitation at the throttle port.In order to study in depth the transient cavitation flow field distribution in the shaped cavity of the coal mine hydraulic safety valve,the simplified shaped cavity flow field of the safety valve was verified separately by Fluent software for grid and time step independence,after determining the number of grids and time steps,transient analysis of the shaped cavity flow field was carried out.The results of the transient simulation show that there is a certain periodic cavitation flow inside the flow field,the front and rear ends of the turbulent kinetic energy band promote the generation,development,and collapse of cavitation clouds,and the variation trend of cavitation period is opposite to that of turbulent kinetic energy value.The velocity vortex and the turbulent kinetic energy strips generated by the high-speed jet area are important factors affecting the periodic variation.
  • Research on Hydraulic Synchronous Jacking System for Aircraft Refitting Based on Active Disturbance Rejection
    WANG Tao, ZHU Shaogen, TANG Jie, YAO Hanlin
    Machine Tool & Hydraulics. 2023, 51(11): 150-154. https://doi.org/10.3969/j.issn.1001-3881.2023.11.025
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    Before the aircraft modification operation,the aircraft needs to be jacked up by multiple jacks.Due to the factors such as manual operation and the installation accuracy of components in the hydraulic cylinder of the jack,the positions of both sides are not synchronized in the jacking process.Based on the mathematical models of the hydraulic jack in the process of anti disturbance,the active disturbance rejection synchronization control strategy was adopted,the electric-hydraulic proportional “master-slave”control system simulation model of the double cylinder was built to study the stability of the hydraulic jack in the process of anti disturbance.The simulation results of “master-slave”ADRC model were compared with those of traditional PID control.The results show that the auto disturbance rejection controller can be used to effectively reduce the synchronization error of the master-slave double cylinder,the disturbance in the working condition is compensated,and the accuracy and disturbance rejection ability of the jacking system are improved.
  • Simulation Research on Electro-Hydraulic Control System of Intelligent Fully Mechanized Mining Face Based on AMESim
    SUN You, LI Yongan, WANG Hongwei, DU Huifeng
    Machine Tool & Hydraulics. 2023, 51(11): 155-161. https://doi.org/10.3969/j.issn.1001-3881.2023.11.026
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    Taking the electro-hydraulic control system of the intelligent fully mechanized mining face as the research object,the working principle of the system was introduced,the working principle and structural characteristics of the five-piston emulsion pump,unloading valve and electro-hydraulic reversing valve group were analyzed,and the mathematical models of the key components were established.Based on AMESim simulation software,the simulation models of the key components of the system were constructed,the system was simulated under different working conditions,and the influence of the key structural parameters of the unloading valve on the pressure characteristics of the system was analyzed.The results show that the simulation model is accurate,the performance of the hydraulic system is good,the flow simulation results of the emulsion pump are consistent with the traditional calculation method,and the effects of different orifice parameters of the unloading valve on the pressure characteristics of the system are different.
  • Robust Temperature-Sensitive Points Selection and Thermal Error Modeling for Machine Tools
    YIN Jing, SONG Feihu, WANG Mengke, LYU Changfei
    Machine Tool & Hydraulics. 2023, 51(11): 162-167. https://doi.org/10.3969/j.issn.1001-3881.2023.11.027
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    Aiming at the VMC1165B vertical machining center,the thermal characteristics and temperature field of the machine tool were analyzed,and based on experimental data,the thermal mechanism analysis and temperature field boundary condition calculation were avoided.Four robust temperature-sensitive points were selected by fuzzy clustering and Pearson correlation coefficient method to establish the thermal error model,and the predictive performance of the model was verified.It was compared with the thermal error prediction model of non-robust temperature-sensitive points selected by fuzzy clustering combined with grey correlation degree.The results show that the maximum residual of machine tool X axis of the robust temperature-sensitive points thermal error prediction model is reduced by 25.44%,while the maximum residual,mean absolute error and mean square error of the machine tool Y axis decrease by 25%,23.03% and 33.25%,respectively.
  • Simulation Analysis of Double Side Countersunk Riveting of Carbon Fiber Reinforced Composites
    QU Ligang, SHAO Shuai, LI Jing, LYU Guangming
    Machine Tool & Hydraulics. 2023, 51(11): 168-173. https://doi.org/10.3969/j.issn.1001-3881.2023.11.028
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    Riveting technology is widely used as a non-detachable connection method in the aircraft assembly process,and carbon fiber reinforced composite materials have become popular in the aviation industry due to their excellent mechanical properties.In the process of riveting carbon fiber reinforced composites,the deformation of rivets can make damage to the riveted carbon fiber reinforced composites,affecting the quality of the riveting and its service life.Aiming at this problem,the finite element simulation software ABAQUS was used to create a 3D model of composite double-sided countersunk riveting,a VUMAT user material custom program was written through the ABAQUS subprogram interface,the advantages of the Hashin criterion and the Puck criterion were taken as the three-dimensional failure criterion,and a reasonable stiffness degradation method was selected to analyze the progressive damage of the composite material after riveting.Through the simulation of the composite material riveting process by ABAQUS,the forming law of the rivet in the riveting process is gotten,the main damage failure forms of the composite laminate are the compression and stretching of the matrix and the fiber compression,the expansion directions of the damage failure are gotten.
  • Research on Large Tonnage Multi-cylinder Synchronous Lifting System Based on Genetic Algorithm
    KONG Han, CHEN Aosong, LI Nan, AN Xiaoyu, LI Gang, SHI Anqi, XU Liping
    Machine Tool & Hydraulics. 2023, 51(11): 174-179. https://doi.org/10.3969/j.issn.1001-3881.2023.11.029
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    Aiming at the problem that the load imbalance of the hydraulic support tunnel boring machine(TBM)main engine affects the stability of the multi-cylinder synchronous support control system during the disassembly and assembly process of the TBM,a large-tonnage multi-cylinder hydraulic synchronous support control system was designed,each hydraulic component was simplified to establish the system mathematical model.Based on the traditional PID control method,the genetic optimization algorithm was introduced to set the PID parameters,and the MATLAB/Simulink simulation software was used to compare with the conventional PID parameter setting empirical data method.The simulation results show that the adjustment time is shortened by 60%,the steady-state error is reduced by 52.38%,the maximum tracking error is reduced by 48.57%,and the average tracking error is reduced by 51.62%.The anti-interference performance is more robust,indicating that the designed control algorithm can meet the stability requirements of the large-tonnage multi-cylinder hydraulic synchronous lifting system.
  • Cause Analysis and Engineering Control Research on Grinding Scratch
    FENG Keming, CAO Weifei, DU Xiaoxu, ZHAO Jinzhui, HUA Manli, FENG Bingqiang
    Machine Tool & Hydraulics. 2023, 51(11): 180-187. https://doi.org/10.3969/j.issn.1001-3881.2023.11.030
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    Grinding is one of the important supports for the development of modern equipment manufacturing industry.However,in the process of grinding,especially in precision and ultra-precision grinding,grinding scratches occur from time to time,which seriously puzzles the application and development of grinding technology.To this end,through a large number of grinding sites and parts surface grinding scratch detection and measurement,combined with cutting,tribology,physics,materials,imaging related knowledge,all kinds of grinding scratches in grinding engineering were carded and analyzed comprehensively.The main technical characteristics of grinding scratches were investigated;based on the two grinding methods of grinding wheel peripheral grinding and end face grinding,the formation processes of single abrasive grain grinding scratches and agglomerate abrasive grain grinding scratches were revealed,the main factors influencing grinding scratch were summarized,and the technical measures were put forward.
  • Fault Diagnosis of Rolling Bearing Based on WTD-AR Specturm and MEA-BPNN
    JIN Zhihao, WANG Hong, CHEN Guangdong, HAN Linyang
    Machine Tool & Hydraulics. 2023, 51(11): 188-193. https://doi.org/10.3969/j.issn.1001-3881.2023.11.031
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    Aiming at the problem of poor robustness of rolling bearing fault diagnosis model under noise interference,a fault diagnosis method based on the combination of wavelet threshold denoising (WTD),AR spectrum and mind evolutionary algorithm (MEA)optimization back-propagation neural network (BPNN)was proposed.Taking the original vibration signal as the input,the wavelet method was used to decompose and reconstruct the original signal to filter out high-frequency noise,then the Burg algorithm was used to estimate the parameters of the AR model to extract the power spectrum features of the noise-reduced signal,finally the feature vector and the corresponding label were used as the input and output of MEA-BPNN neural network to train,then the diagnosis was realized.The proposed method was compared with some advanced artificial neural network diagnostic methods to test the performance of the diagnostic model.The research results show that the WTD-AR spectrum-MEA-BPNN diagnostic model can effectively reduce the noise interference of bearing vibration signals,achieve feature enhancement and has higher resolution;compared with traditional neural networks,the training speed is faster,and the fault type can be identified in a shorter time with high recognition rate.
  • Bearing Fault Feature Extraction Method Based on WTD and CEEMD
    ZOU Tengxiao, WANG Linjun, LIU Yang, CAI Kanglin, CHEN Baojia
    Machine Tool & Hydraulics. 2023, 51(11): 194-198. https://doi.org/10.3969/j.issn.1001-3881.2023.11.032
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    Aiming at the problem that bearing fault signals are often mixed with noise and the fault features are difficult to accurately extract,a bearing fault feature extraction method was proposed based on wavelet threshold denoising (WTD)and complementary ensemble empirical mode decomposition (CEEMD).The WTD was used to denoise the original signal.The denoised signal was performed CEEMD decomposition to obtain a series of intrinsic mode functions (IMF);then the correlation between each IMF and the denoised signal was calculated.The useful IMFs were obtained by setting the threshold of the cross-correlation coefficient.Finally,the useful IMFs were reconstructed and the envelope spectrum was used to extract the fault characteristic frequency of the reconstructed signal.The measured signals show that the proposed method can reduce the noise interference and effectively extract fault characteristic information,which proves that it has high feasibility and strong practicability in a noisy environment.
  • Fault Simulation Analysis of Hydraulic Shift Buffer System for a Certain Type of Vehicle
    DONG Jiahui, LI Huanliang, CHEN Wei
    Machine Tool & Hydraulics. 2023, 51(11): 199-205. https://doi.org/10.3969/j.issn.1001-3881.2023.11.033
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    The hydraulic shift buffer system is the core system of the vehicle to reduce the shift shock and improve the shift quality.The failure of shift,shift shock,and serious local heating of the system are closely related to the abnormal state of the hydraulic shift buffer system.Based on the theoretical analysis of the hydraulic shift buffer system,the AMESim simulation software was used to model the system,and the simulation results were compared with the calculation data of the mathematical model and the data curves of the bedstand to verify the feasibility of the simulation model.The fault simulation analysis of the system was carried out by typical fault factors such as injection orifice blockage,valve core stuck,spring fatigue aging and so on.The quantitative influence results of the front end blockage of the shift buffer system,the displacement of the buffer valve core,and the spring stiffness of the pressure-holding valve on the buffer oil pressure characteristics were obtained,and the specific fault phenomena were analyzed combined with the shift oil pressure curve.
  • Early Fault Detection of Rolling Bearing Based on KECA and BO-SVDD
    LI Zixuan, GAO Bingpeng
    Machine Tool & Hydraulics. 2023, 51(11): 206-213. https://doi.org/10.3969/j.issn.1001-3881.2023.11.034
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    In order to realize earlier fault detection of rolling bearings,a rolling bearing early fault detection method was proposed based on kernel entropy component analysis (KECA)and Bayesian optimization (BO)algorithm optimized support vector data description (SVDD).The time domain and frequency domain features and wavelet packet decomposition node energy features of the bearing vibration signal were extracted to form a multi-dimensional feature matrix;then,the multi-dimensional feature matrix was reduced in dimensionality by using KECA,and the effective features were extracted;finally,the characteristic indexes of the normal state of the bearing were selected to train the model,and the penalty factor and kernel width of the SVDD were determined by using the BO algorithm,and then the early fault detection model was obtained.The model was used for bearings early fault detection under different working conditions in XJTU-SY data set.The results show that KECA can effectively extract feature information and reduce the interference of redundant information.On the whole,the model can detect the occurrence of faults earlier and has better robustness and generalization ability.
  • Reliability Analysis Method for High Precision CNC Machine Tool Based on RBF Neural Network
    BAI Na, ZHAO Luyan, HUANG Zaihui
    Machine Tool & Hydraulics. 2023, 51(11): 214-218. https://doi.org/10.3969/j.issn.1001-3881.2023.11.035
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    Reliability analysis of high-precision CNC machine tools can quickly solve the problem of CNC machine tool failure.In order to improve the accuracy of reliability analysis of high-precision CNC machine tools,a reliability analysis method of high-precision CNC machine tools based on RBF neural network was designed.Using the multi-body system model,the NC machine tool was modeled,the internal characteristics of the machine tool were extracted,the fault data were classified and processed,and the fault data distribution fitting was completed.On this basis,the reliability evaluation index of CNC machine tool was established,and the RBF neural network was trained to realize the reliability analysis of high-precision CNC machine tool.The experimental results show that the positioning error of the proposed reliability analysis method for high-precision CNC machine tools is small,and the failure mode frequency of CNC machine tools can be accurately counted,which ensures the reliability analysis effect and improves the reliability analysis accuracy of CNC machine tools.
  • Research on Fault Feature Extraction Method Based on EMD-AR Spectrum Frequency Band Energy Features
    QIN Zhiying, YANG Hanggang, ZHAO Yuejing
    Machine Tool & Hydraulics. 2023, 51(11): 219-223. https://doi.org/10.3969/j.issn.1001-3881.2023.11.036
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    A method to extract the energy features of frequency bands based on EMD-AR spectrum estimation was proposed by combining the empirical mode decomposition (EMD)and AR power spectrum parameter estimation model.The EMD-AR spectrum curve was obtained by empirical mode decomposition of the vibration signal and AR spectrum estimation of the top groups of intrinsic mode functions (IMFs)that accounted for the larger energy after decomposition;then,the EMD-AR spectrum curve was segmented according to the frequency band and the energy of each segment was summed up and normalized as the feature value.By building a gearbox fault test bench,vibration signals were collected for EMD-AR spectrum frequency band energy feature extraction,and the obtained feature values were input into SVM for training and diagnosis.The results show that the fault diagnosis model obtained by this feature extraction method combined with SVM has a high recognition accuracy and can effectively and accurately perform diagnosis and recognition.
  • Research on Fault Diagnosis of External Hydraulic Pipeline of Aero-Engine Based on Bi-GRU Model
    HUANG Xufang, ZHAO Ping, FENG Ling, ZHANG Li
    Machine Tool & Hydraulics. 2023, 51(11): 224-232. https://doi.org/10.3969/j.issn.1001-3881.2023.11.037
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    Aiming at the problem that fault identification of aviation hydraulic pipeline is difficult due to noise interference,a deep learning hydraulic pipeline fault diagnosis method based on Bi-GRU was proposed.The Bi-GRU neural network model was used to extract time series features from hydraulic pipeline data.Then,based on the measured vibration data of the hydraulic pipeline with the same noise,the data were input into five fault diagnosis models including Bi-GRU,GRU,RNN,SVM and BPNN for training.Finally,in order to further demonstrate the learning ability of BI-GRU model for the characteristics of different fault types of aviation hydraulic pipelines,t-SNE dimension reduction algorithm was used to visualize the characteristics of hydraulic pipelines.The results show that:based on Bi-GRU aviation fault diagnosis method,the accuracy can reach 99.60%,which is obviously better than the other four kinds of neural network model such as GRU,the Bi-GRU model shows better feature extraction ability on the hydraulic pipeline data containing noises,which can effectively extract the hydraulic pipeline fault data characteristics,so as to realize the intelligent identification of the hydraulic pipeline fault.
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ShangHai Ship and Shipping Research Institute Co,.Ltd.
ISSN 1674-5949
CN 31-2023/U
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