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    Volume 52,2024 Issue 6
    • Damped Haptic Feedback for Master-Slave Telemanipulators
      PAN Lei; PAN Mingzhang; LI Jin; LIANG Ke

      Abstract:Telemanipulators have been widely used in space exploration,deep-sea exploration,nuclear facility maintenance and medical surgery due to its unique advantages.However,with the increase of task complexity and safety requirements,telemanipulators are required to have better obstacle avoidance capabilities.Aiming at this problem,a new haptic feedback method was proposed based on variable damping,which could provide the operator with damping force to perceive obstacles in the remote environment to complete the obstacle avoidance task.On this basis,a damping model for obstacle avoidance was proposed to solve the inaccurate problem of traditional haptic methods due to incomplete consideration of factors.In the model,not only the conventional factor of distance was considered,but also the collision of the telemanipulator was predicted according to the new factor of the velocity direction to adjust the damping value online.The experiment results show that the proposed method is effective in improving the safety of teleoperation and the productivity of human operators compared to the teleoperation without haptic feedback.

    • Vibration Analysis and Research of PCB Drilling down Mechanism Based on Rigid Flexible Coupling
      ZHANG Dongdong; HAN Xue

      Abstract:Through the analysis of the drilling error of the PCB numerical control drilling down mechanism,the main reasons affecting the processing accuracy of multilayer PCB boards were found out,and the rigid flexible coupling dynamic characteristics during the spindle systems drilling process were studied.The coupling between the flexible self-centering spindle in the self-aligning coupling and other rigid components were fully considered,and the dynamic equation of the spindle system of the drilling down mechanism was established using Hamiltons principle and modal analysis method.The dynamic response of the electric spindle during the drilling process of the drilling down mechanism was obtained through simulation.The results show that the installation error of the main spindle system of the drilling mechanism,the stiffness of the centering shaft,and the damping of the air bearing supporting the electric spindle have a certain impact on the eccentricity error of the drilling and the flexible vibration during drilling.

    • Milling Temperature Prediction Model and Experimental Study of Fluorphlogopite Ceramic Materials
      JIANG Hancun; MA Lianjie; LI Wenbo; SUN Yang; HAN Zhibin; TAN Yanqing; LI Ming

      Abstract:In order to study the influence of milling speed,feed per tooth,milling width and milling depth on the temperature of fluorophlogopite ceramic material in the milling process,the source of heat in the milling process was analyzed.The temperature mathematical model of the heat transfer of the milling surface heat source to the machined surface was established by the heat source method,and the heat distribution ratio coefficient was optimized to reduce the calculation error of the mathematical model.A single factor test was designed to analyze the influence of main process parameters on the milling temperature of fluorophlogopite ceramics.It is found that the milling temperature increases with the increase of different processing parameters within the parameter range.Finally,the theoretical value calculated by the temperature mathematical model was compared with the experimental value to obtain the consistency of the results.It is found that the error between them is from 1 ℃ to 11 ℃ and within the reasonable error range.

    • Study on the Effect of Non-uniform Preload Force on the Rotary Performance of Spindle System
      NING Yunpeng; YUAN Feng; LIU Jiwen; QIN Dongchen

      Abstract:In order to study the effect of non-uniform preload on the rotary performance of the bearing-spindle system,the bearing-spindle test bench was tested by applying a controlled preload force,and the least-squares circle method was used to evaluate the shaft trajectory;the effect of non-uniform preload on the radius of the shaft trajectory was investigated at different speeds and operating conditions.The results show that even under no-load,the non-uniform preload of the outer ring of the bearing has different effects on the shaft center trajectory;under radial load,a suitable non-uniform preload can gradually improve the rotational performance of the spindle.

    • Research on Mathematical Model and Experiment of Internal Helical Gear by Power Skiving
      ZHOU Xin; GENG Longlong; HAN Zhengyang; JIANG Chuang; WANG Huiliang

      Abstract:In order to solve the problem of efficient machining of internal helical gear,a method for machining internal helical gear by power skiving was put forward.According to the machining principle of internal helical gear power skiving,the mathematical model was established.The equation of cut tooth surface was established and the equation of internal helical gear was derived.An internal helical gear was simulated in Vericut to verify the correctness of the theoretical model.Finally,the cut experiment was carried out,the workpiece was measured,and the precision of tooth met the engineering requirements.The results show that the proposed power skiving method can complete the efficient machining of the internal helical gear and has theoretical and engineering application value.

    • Research on Sensorless Field Weak Magnetic Control Technology of Plug in Permanent Magnet Synchronous Motor Spindle
      CAO Weichang; SHAN Wentao; LV Dongxi; LIN Qi; CHI Yunfei

      Abstract:In order to improve the current utilization and robustness of the motorized spindle,based on vector control,the plug in permanent magnet synchronous motorized spindle was studied.The fourth order equation of the maximum torque current ratio control was processed in normalization,and the equation was approximately solved by fitting the curve.The speed range of the spindle was expanded by using field weak magnetic speed regulation.The spindle speed was estimated by sliding mode observer.In order to overcome the chattering problem of traditional sliding mode observer,the Sigmoid function was introduced into the traditional sliding mode observer,the stability of the proposed strategy was deduced and explained by Lyapunov criterion.The high-speed grinding motorized spindle FL170-20-15 in the laboratory was taken as an example,and a simulation experimental platform based on MATLAB was built by using the above algorithm for experimental verification,and the effect of the control strategy was analyzed.The experimental results show that the chattering phenomenon of sliding mode observation is reduced and the robustness of the control system is improved.

    • Research on Dry Cutting Process Parameter Optimization of Ring Network Cabinet Bushing Based on Response Surface Method
      CHEN Zhiqing; JIANG Chaojia; ZHANG Yu; CHEN Hao; GOU Yujiang; HE Gaohui; HE Huibo

      Abstract:Dry cutting is an effective way to repair ablations and cracks on the surface of ring network cabinet bushing.A single-factor test was used to investigate the effect of cutting parameters on cutting forces under uncoated,TiAlCrN-coated and TiAlSiN-coated tools.Based on the single-factor test,the Box-Behnken central combination test method was applied to conduct an experimental study on the cutting working parameters of ring network cabinet bushing using the TiAlSiN-coated tool with optimal performance.A three-factor and three-level quadratic rotational regression orthogonal test was conducted with cutting speed,feed and back cutting as the test factors and tool tangential force,axial force and radial force as the test indexes.By establishing the response surface mathematical model,the influences of each cutting process parameter on the cutting performance were analyzed,and the test factors were comprehensively optimized.The test results show that the significant order of cutting force is back cutting>feed>cutting speed.The optimal combination of parameters is cutting speed 94.589 m/min,feed 0.097 mm/r,back cutting 0.501 mm,and the tool tangential force is 11.75 N,axial force is 34.80 N,radial force is 19.53 N.The results of the validation test generally agree with the theoretical optimization values.

    • Designation and Uncertainty Analysis on the Pressure Drop-Flowrate Characteristic Test Platform for Hydraulic Quick-Action Couplings
      ZHENG Zhijian; QIAN Tingting; QIAN Mi; HE Liang

      Abstract:In order to test the flow capacity of hydraulic quick-action couplings at different fluid medium,flowrate or other working conditions,a pressure drop-flowrate characteristic test platform for hydraulic quick-action couplings was designed,and the matching test software was developed.The No.46 hydraulic oil or water were used as the test medium with its flowrate ranging from 40 L/min to 1 000 L/min.The pressure drop of the applicable hydraulic quick-action couplings was from 0 MPa to 5.0 MPa and the nominal diameter was from 12.5 mm to 51 mm.Besides,according to the standards of ISO 9110-1:2010 and ISO 9110-2:2020,a mathematical model for measuring the pressure drop was established,and the combined uncertainties of pressure drop using the No.46 hydraulic oil or water as the test medium were calculated respectively.The technical parameters of the test platform comply with GB/T 5861—2003.The test platform can also be used to measure the flow coefficient and flow resistance coefficient of the hydraulic quick-action couplings.

    • Reliability Sensitivity Analysis of Speed Accuracy of Inlet Throttle Governing Circuit
      GU Jianguo; YANG Junyan; ZHANG Shengdong; YOU Shihui; SHI Xiaolin

      Abstract:In order to improve the working accuracy of machine tool products,taking the inlet throttle governing circuit as the research object,the study on the reliability and sensitivity of its speed accuracy was carried out.The velocity-load characteristics of inlet throttle governing circuit were analyzed systematically,and the velocity expression of hydraulic cylinder piston could be deduced.The stochastical perturbation theory and fourth-order moment technology were used to establish a model for velocity reliability analysis of inlet throttle governing circuit.Finally,the sensitive parameters affecting the speed accuracy were determined by the reliability sensitivity analysis.The research results show that the valve opening of throttle valve has the greatest influence on the reliability of speed accuracy,so the design should be reduced and the tolerance should be strictly controlled in the design process.

    • Research on Air Replacement Technology of WT2000 Series Wind Turbine Gearbox
      SONG Jianxiu; SHEN Liang; OU Huiyu; HE Yichun; ZHANG Jie; LV Xingmei; HUANG Chong; DING Song; HU Hongda

      Abstract:In order to reduce the overall replacement cost of the main gearbox (growth gearbox) of the doubly fed asynchronous wind turbine and make the operation process more concise,based on WT2000 series wind turbines,a main shaft fixing tooling was designed to replace the role of gearbox and fix the rear end of main shaft.Some new operation processes and methods in the air replacement of WT2000 series wind turbine gearbox were explored and practiced.The results show that the proposed structure greatly reduces the operation cost (including crane cost,time and labor cost) of gearbox replacement of WT2000 series wind turbine,the loss of power generation during maintenance is reduced.

    • Permanent Magnet Synchronous Motor Speed Regulation System Based on Adaptive Disturbance Sliding Mode and Improved Reaching Law
      LI Xuyang; LI Xiaoxi; ZHU Qixin; ZHU Yonghong

      Abstract:Aiming at the problems of speed fluctuation and instability when permanent magnet synchronous motor is suddenly loaded,a sliding mode speed control method was proposed based on adaptive disturbance and novel reaching law.The state variables of the system were introduced into the reaching law,and the mathematical relation within the reaching law was improved at the same time,so as to improve the adaptive adjustment ability of the system approach speed and achieve the purpose of improving the comprehensive performance of the system.The load torque was estimated adaptively by using the Lyapunov stability criterion to make the control strategy meet the Lyapunov stability criterion,and reduce the influence of external load on the motor speed at the same time.Finally,the proposed control strategy was compared with the traditional sliding mode control strategy in the Simulink environment.The simulation results show that the proposed control method has faster response and stronger chattering suppression ability.The proposed method can effectively improve the overall performance of the system and achieve more stable speed control.

    • Design of Production Management System of Multi-source Heterogeneous Data in Textile Machinery Workshop
      WANG Yuanzhi; YUAN Yiping; FAN Panpan; PEI Guoqing

      Abstract:Aiming at the integration,transmission and sharing of multi-source heterogeneous data in the production process of textile machinery manufacturing enterprises,combining with the actual production of enterprises,an enterprise-oriented business process model was built,a workshop manufacturing process data management model was established,and the production data was preprocessed for anomaly correction,time registration,timing data complement.The ontology-based heterogeneous data integration method was adopted,which could realize the data integration and sharing of intelligent production in textile machinery manufacturing workshop,and provide data support for digital twin platform and simulation optimization decision.The digital workshop data integration management system was designed and developed.Through the integration of SAP,SCADA and other system data,the production progress tracking,equipment operation monitoring and production-related data statistical analysis were realized,and 3D visualization was carried out in combination with 3D models to meet the data management requirements of the workshop.

    • Research on Dry Drilling Technology Based on Eddy Current Cooling and Electrostatic Lubrication
      ZHANG Yanqing; LV Haifeng; HAN Zhanlong; HAN Zhenyu; CHEN Guitao

      Abstract:To reduce the environmental pollution caused by cutting fluid in machining process and the high cost in processing cutting fluid,a dry drilling technology and device with eddy current cooling effect and electrostatic lubrication effect was proposed.The gas was blown into the cutting area after ionization and ozonation to replace the cutting fluid to achieve lubrication and cooling,which could obtain a good chip breaking effect and prolong the tool life.Based on the influence law of the structure parameters on the system discharge performance,ozone concentration and cooling effect,the device structure was optimized to form the dry auxiliary drilling device.The experimental results show that when the electrode taper is 15°,the electrode diameter is 1 mm,the nozzle diameter is 3 mm,the gas flow rate is 20 L/min and the driving voltage is 6 kV,the ozone concentration reaches the peak of 34.2×10-6.By comparing with pure dry cutting,it is found that the cutting temperature of the proposed technology is reduced by 40.9%,the cutting edge of the tool is basically not damaged,and the surface of the chip microstructure is clear and uniform.The experimental results show that the designed eddy current cooling electrostatic lubrication dry drilling technology is superior to the traditional dry drilling technology in terms of cutting effect,cooling effect,tool wear and chip shape,and it can be used in the drilling of six series aluminum.

    • A New Flexible Acceleration and Deceleration Method for Jerk Continuous Smoothing
      WANG Shufeng; MENG Xinyu; DU Yilong

      Abstract:A new flexible acceleration and deceleration control algorithm was proposed to solve the problem of precision and efficiency degradation caused by sudden jerk change in the process of machining micro-segment by CNC.The continuous and smooth motion control curve of jerk was built based on the sine function,and the speed planning of the new flexible acceleration and deceleration algorithm was realized by analyzing the length of the processing line segment of the CNC and the initial and final speed.The simulation and experimental test results show that this algorithm can effectively reduce the vibration caused by the sudden change of jerk and improve the stability and efficiency of NC machining process compared with the traditional S-shaped algorithm.

    • Research and Application of Digital Machining Unit Control System Based on Finite State Machine
      CHEN Jiacai; ZHANG Hu; WEN Shaohua; LIU Yongpo; CHEN Yong

      Abstract:A machining unit of an aerospace enterprise was taken as the research object in the view of some issues including difficulties of equipment control and acquisition,low digitized degree,slow system response existing in the digital control of machining units,and the business process of the unit was analyzed.An information architecture for interworking of the unit in which static basic data and dynamic business data were separated was proposed,and a hardware-oriented data communication module was constructed to realize real-time acquisition and encapsulation of multi-source heterogeneous devices.Based on the design of reactive system,the finite state machine was introduced to carry out the research of production scheduling control strategy,and the robot and workpiece were respectively used as scheduling objects for behavior modeling.Using object-oriented method,the program structure of state machine based on event-driven was improved.Based on these,the system software of the machining unit was developed for digital control of the whole process by using the .NET technology.Finally,the effectiveness and reliability of the as-built system were verified at the production site.

    • Experimental Analysis of Machine Tool Spindle Rotation Accuracy Prediction for Cutting Force Correction
      SUN Bei; ZHANG Lingling; LI Feng; ZHAO Kaishen; WANG Cuifang

      Abstract:In order to improve the control accuracy of machine tool,a method of analyzing spindle rotation accuracy was designed,which could accurately predict cutting force correction.In order to verify the accuracy of rotary accuracy prediction,a set of spindle rotary accuracy analysis system without standard ball was established,the spindle rotation precision test could be carried out according to the specific cutting conditions.The results show that with the change of feed rate and cutting depth,regular synchronization error is formed.The cutting depth is the most affected by the synchronization error factor,and the feed speed is the second.Under the influence of cutting load,the spindle rotation accuracy changes significantly,and the synchronization error is positively correlated with the cutting load.Under variable feed and variable cutting width,the test results are similar to the simulation results,maximum error is 0.2 μm.The roundness error obtained with the condition of cutting width 12 mm and feed speed 1 200 mm/min is consistent with the roundness error at 100 r/min idling.

    • Development of a New Flexible Fixture for Honeycomb Panel Assembly Manipulators
      DENG Sanxing; YANG Mengmeng; AN Hongen; LI Keqiang

      Abstract:Aiming at the difficulty of automatic handling of honeycomb panels due to the characteristics of various sizes,low stiffness and fragility,a new flexible fixture for assembly manipulator based on adjustable ring was designed.The special requirements of honeycomb panel fixture performance were studied,and on this basis,a concept of flexible fixture based on wire rope loop was proposed.Based on the static geometric ring,a flexible fixture with adjustable ring was further designed.In order to further improve the flexibility,a matching combined mode loop control method was designed to effectively change the geometry of the loop.Finally,a prototype composed of six rings was prepared and tested to determine the best clamping parameters of different honeycomb plates and quantify the clamping force.The results show that the clamping force first increases to the maximum and then decreases for both 0.7 mm rope and 1 mm rope,which confirms the hypothesis that the ring size is related to the stroke.Among them,the 0.7 mm rope does not damage any material,which has greater flexibility.Under the condition of no damage,the flexible fixture can be effectively applied to automatic clamping of various types of honeycomb panels with high flexibility and sensitivity.

    • Research on Flow and Pressure Pulsation Characteristics of Ship Draining System
      LIU Yushen; LUO Xiaohui; CHANG Wenqi

      Abstract:The draining system plays an important role in the draining of sewage in ships.The flow and pressure pulsation generated by the draining system are the main reasons for the vibration and noise of the system.One of the keys to reduce the flow and pressure pulsation and suppress the noise is to master the characteristics of pressure pulsation.A simulation model of draining system was established by analyzing the structure principle of low-noise piston pump and the pipeline structure of draining system.An experimental platform was built to verify the accuracy of the model.Finally,the characteristics of the draining system and different factors affecting the pressure pulsation were studied based on the model.The results show that the main frequency of flow and pressure pulsation is 5 Hz and 20 Hz;the opening of valve and length of pipeline have great influence on pressure pulsation while the pump parameter has little influence;the subsequent design and optimization of the draining system should give priority to the outlet pipeline.

    • Modeling,Simulation and Optimization of an Aeroengine Speed Regulator
      YANG Mengke; MA Jing; WANG Jian; HU Yonghao

      Abstract:In order to solve the problem of speed down-regulation of an aeroengine under the condition of large and slow speed,the speed regulator was taken as the research object,and the model was built on the AMESim platform according to its mechanical mechanism and working principle.The accuracy of the model was verified by simulation using the test results and speed feedback regulation characteristics.After that,the mechanism of the fault was analyzed.Through simulation,it was determined that the main influencing factors were throttle angle,engine inlet temperature,centrifugal fly weight structure parameter change,and spring stiffness coefficient attenuation in the regulator.Combined with the actual working conditions,the above three faults were eliminated.Finally,the optimization schemes such as adding preload compensation to the spring in the regulator and replacing with the new material were given to solve the fault problem.

    • Influence of Rotor Eccentricity on the Dynamic Response of Misalignment-Rubbing Rotor
      ZHANG Lingyun; LI Luan; HE Xiaoying; LIU Zhong; XIONG Zhonggang

      Abstract:For vibration problems caused by coupling faults in misalignment-rubbing rotor systems with rotor eccentricity,a dynamic model of the sliding bearing-rotor system was established under the condition of misalignment-rubbing coupling,and a series of strong nonlinear couplings were considered,such as the misalignment force of the gear coupling,the oil film force of the sliding bearing,the rotor eccentricity and rubbing.Based on multi-parameter and multi-objective co-simulation,the relationship between key parameters and system response was obtained,and the concepts of maximum rubbing force and duty cycle in the field of telecommunications were introduced to quantitatively characterize the dynamic characteristics of the rotor model.The results show that the existence of misalignment leads to even frequency multipliers such as 2× and 4× in the system,and the axis center trajectory of system shows the shape of “8”.The change of eccentricity directly affects the type and distribution of periodic motion of the system.When the eccentricity changes from small to large,the first-order and second-order critical speeds of the system increase significantly,which directly limit the response amplitude of the oil film force.However,the 2× frequency amplitude generated by misalignment is unaffected.Finally the reasonable value range of eccentricity is obtained.

    • Compound Sliding Mode Control of Double-Pump Sub-chamber Control Electro-Hydraulic Load-Simulation System
      ZHANG Junqi; WANG Chengwen; ZHAO Erhui

      Abstract:Aiming at problems of high energy consumption,nonlinear friction and steering engine’s movement disturbances in valve- controlled electro-hydraulic load-simulation system,a double-pump-controlled scheme was proposed,and the sliding mode control was adopted to ensure the robustness of system.The mathematical model of double-pump sub-chamber control electro-hydraulic load-simu lation system was established.On this basis,aiming at problem of poor dynamic characteristics of the single-pump control system,force- total pressure compound control strategy was designed to make it have similar dynamic characteristics as the valve-controlled system.For the poor tracking effect problem caused by the chattering of traditional sliding mode control,an equivalent sliding mode controller based on fuzzy reaching law was proposed,and its stability was analyzed theoretically.Finally,through co-simulation,the feasibility and effectiveness of designed control strategy and controller were verified.The results show that the proposed compound control electro-hydraulic load-simulation system has good tracking effect and it can significantly reduce the system energy consumption.

    • Modeling and Characteristic Analysis of Pulsating Grouting System Based on AMESim
      LI Fengling; YOU Qingru; PENG Chunlei

      Abstract:In order to understand the mechanical characteristics of the pulsating grouting system and the control characteristic of pressure and other parameters,through the analysis of the composition and working principle of the pulsating grouting system,a simulation model of the pulsating grouting system was established based on the AMESim simulation platform.In order to verify the correctness of the model,the pressure and flow data of the slurry pipeline monitored at the construction site were compared with the output data of the simulation model.The results show that the simulation model can accurately simulate the dynamic curves of the system,and the average relative error of pressure and flow are 6.4% and 7.6% respectively,which verifies the correctness of the model.According to the change of grouting conditions,through simulation model analysis,the change curves of the pressure and flow characteristic in the slurry pipeline are obtained under different pumping frequency,slurry viscosity,pipeline length and other conditions.

    • Optimization Design of Pre-boost Zone for Spherical Valve Pair of Miniature Axial Piston Pump
      LIU Wei; WU Huaichao; HOU Gang; WANG Peijin; CAO Mingyuan; ZHU Bin

      Abstract:In order to improve the flow distribution performance of the spherical valve pair of the high-speed and high-pressure miniature axial piston pump,taking the spherical valve pair of the unidirectional rotating miniature axial piston pump as the research object,the structure of pre-boost zone was optimized.The mathematical models of the instantaneous pressure in the pre-boost transition zone,the flow area of the triangular groove and the depth angle of the triangular groove were established.Then particle swarm optimization algorithm was used to optimize the structure of the pre-boost zone.Finally,the original model and the optimized model were imported into Fluent for comparative analysis.The structure optimization results are as follows:depth angle β=16.1°,width angle α=56.3°,opening angle ϕ =12.7°,error angleφ0 =1.2°.After optimization,the pressure pulsation rate in the pre-boost overpressure zone is reduced by 4.6% compared with the original structure,the flow distribution performance of the spherical valve pair of the miniature axial piston pump is improved.

    • Trajectory Planning and Dynamic Optimal Control of Excavator
      ZHOU Youming; LIU Kailei; YIN Penglong; KANG Shaopeng; QIANG Hongbin

      Abstract:Taking the excavator as the research object,the mathematical models of kinematics and dynamics of the excavator working device were established.The motion trajectory was discretized by using the 5-degree polynomial interpolation method.The discrete motion trajectory program was compiled using MATLAB and its calculation results were compared with the ADAMS simulation results,the dynamics model parameters were determined.The Simulink and ADAMS joint simulation model based on the dynamics model was established.In the dynamic control,the PD control method was used,and the trajectory planning joint simulation was conducted and tested.The results show that the motion trajectory control method based on the dynamic model can effectively avoid the sudden change of the starting and ending positions and the output force of the hydraulic cylinder.With the PD control method in dynamic control,the obtained convergence trend is nearly 50% higher than that of the unoptimized one.The output force of the hydraulic cylinder changes stably with an error of about 5%,which improves the control accuracy of the automatic excavation motion trajectory.

    • Stability Control and Simulation of Motor Speed in Pump-Control-Motor Hydraulic System
      HAN Yu; ZOU Bingyan

      Abstract:In the pump-control-motor hydraulic system,due to the sudden change of external load,the engine speed will change,which will lead to the change of the variable pump speed,and eventually the hydraulic motor speed fluctuation is too large and the adjustment time is too long.Aiming at the closed hydraulic system of variable pump and fixed motor,the mathematical model was constructed in detail,the block diagram of transfer function was obtained,and the reasons for the fluctuation of motor speed due to load change were analyzed.A feedforward compensation control method was proposed,which could compensate the flow change caused by the speed disturbance of the variable pump by changing the swash plate swing angle of the variable pump in real time.The compensation function was deduced,and the simulation analysis was carried out for step 100% load,step 20% load condition and ramp 100% load,ramp 20% load condition.The results show that the motor speed fluctuation with feedforward compensation control is reduced by 3.87% at most,and the adjustment time is shortened by at most 1.77 s.

    • AMESim Dynamic Simulation and Parameter Optimization for Hydraulic Governor
      TANG Sijia; HUANG Xinfeng; LIU Yang; JIANG Junxia

      Abstract:The governor plays a key role in the flight stability and engine safety of propeller aircraft.The design structure of hydraulic governor and its working principle were analyzed;AMESim models of governor,hydraulic system and actuator were established,and dynamic characteristics were simulated and analyzed;the single-factor influence analysis of governor dynamic characteristics was conducted,and the main design parameters included control valve mass,counterweight mass and spring stiffness,etc..Then the optimal design parameters were obtained through multi-factor influence analysis.The optimized governor model was verified by dynamic simulation.The results show that after the optimization of governor parameters,the oscillations amplitude of speed regulation and the oscillations number are significantly reduced,increasing the stability of the governor system,and its performance is greatly improved,which can better meet the requirements of engine and propeller speed regulation.

    • Bearing Fault Diagnosis Based on Principal Component Analysis and Multi-domain Feature Fusion
      ZHOU Lingmeng; DENG Feiqi; ZHANG Qinghua; SUN Guoxi; SU Naiquan; ZHU Guanhua

      Abstract:To solve the problem that it is difficult to distinguish bearing fault state under complex working conditions,a bearing fault diagnosis method of multi-domain feature fusion based on principal component analysis was proposed.The vibration acceleration signals was collected,and the new dimensionless features in time domain,amplitude spectrum features in frequency domain and empirical mode decomposition features in time frequency domain were extracted to fully described the bearing state.The extracted features were fused and reduced in dimension by the principal component analysis method,it can effectively reduce the complexity of diagnostic models and the difficulty of data analysis.Finally,a suitable convolutional neural network was selected to classify,the verification was performed by the petrochemical unit fault diagnosis experimental platform.The results show that the multi-domain fusion feature diagnosis is better than the single domain feature diagnosis,the convolutional neural network classification model has higher diagnostic accuracy than other classical classification models,the diagnostic accuracy of the fusion diagnosis classification method reaches 86%.

    • Bearings Fault Detection Based on Deep SVDD-CVAE with Adaptive Threshold
      LIU Yunfei; ZHANG Kai; JIAN Ziqian; ZHENG Qing; ZHANG Yuehong; YUAN Zhaocheng; JIAO Ziyi; DING Guofu

      Abstract:Bearings fault alarms by condition monitoring can effectively avoids catastrophic accidents.The fault detection method based on data time series feature reconstruction can avoid the degradation of model accuracy caused by insufficient fault data because only normal data is used for training.However,the fault threshold determination in such methods depends on a large amount of historical data,which has a great impact on the detection accuracy.Therefore,a bearing adaptive threshold fault detection method was proposed based on deep SVDD-CVAE.A CVAE feature compression extraction framework was constructed with ConvLSTM as the basic unit for enhancement extraction of time series signals,so as to extract the weak features of bearing faults.The SVDD was combined to adaptively learn the feature space hypersphere to realize the adaptive determination of the fault detection threshold.Finally,the deep SVDD-CVAE framework was iteratively optimized by global error loss backpropagation.The experimental results show that the proposed method can effectively extract weak bearing fault features and adaptively determine the threshold value with a detection accuracy of 97.7% on IMS bearing dataset.

    • Rolling Bearing Performance Degradation Trend and Life Prediction Based on CNN-LSTM
      JIANG Guangjun; YANG Jinsen; MU Dongming

      Abstract:As a key component of machine tool spindle,the remaining useful life prediction of rolling bearings directly determines the remaining life of the whole mechanical equipment.If the health status or damage of rolling bearings cannot be predicted in time,it will not only affect the formulation of maintenance strategies,but also cause cascading failures,which is likely to cause catastrophic accidents of mechanical equipment.Aiming at the problem of adaptive fault feature extraction and intelligent diagnosis of rolling bearing vibration signals under big data,a life prediction model combining convolutional neural network and long short-term memory network (CNN-LSTM) was constructed,which could avoid the influence of manual participation and realize the complementary advantages of the network.The degradation state and residual life of rolling bearings were predicted,and compared with convolutional neural network (CNN) and long short-term memory neural network (LSTM).The experimental results show that CNN-LSTM has higher prediction accuracy.

    • Bearing Intelligent Fault Diagnosis Based on Edge Graph Attention Network
      DU Yue; NING Shaohui; DUAN Panlong; DENG Gongye; ZHANG Shaopeng

      Abstract:The data based on Euclidean space contains the relation information of nodes and edges,which has more information than the data in traditional Euclidean space.However,the traditional graph convolution and graph attention network focus on the extraction of node information,while the edge information is not fully used.Aiming at this,by combining viewable algorithm and edge graph attention network (EGAT),irregular data based on non-Euclidian space were applied to bearing fault diagnosis.The diagnosis process was divided into two steps:the viewable algorithm was used to convert the original signal into graph data;EGAT was used to learn fault features,and then fault diagnosis could be carried out.The experimental results show that the graph convolutional network can achieve 100% accuracy in a single bearing fault classification task,which indicates that the proposed method has a distinct role in bearing fault diagnosis.

    • Aircraft Fault Inspection System Based on Machine Vision
      YUAN Zhongda; CHENG Xiuquan; WANG Dawei

      Abstract:Aiming at the current aircraft maintenance inspection with manual visual inspection,low efficiency and human factors,a nondestructive inspection system of aircraft parts surface based on image recognition and machine deep learning was designed.The images of aircraft fuselage and engine parts taken by the first-line aircraft maintenance personnel of an airline company were collected and sorted out.The image set was preprocessed,including channel extraction,Sobel filtering and binarization.Finally,Blob analysis was used to make the features extraction and analyze for the processed images.The system runs fast,has high accuracy and can recognize the image continuously automatically.Using machine vision technology to carry out nondestructive testing on the surface of aircraft parts can not only improve the production efficiency,but also remove the influence of human factors on aircraft flight safety,so as to further improve the flight safety of aircraft.The practice shows that the system is stable and reliable,and has high application value.

    • Wind Turbine Fault Detection and Control Based on SCADA Data Collaboration
      ZHANG Yuantian; ZHOU Keyu

      Abstract:In order to detect the fault of the gearbox safely and reliably without stopping the machine,and realize the fault-tolerant control operation of the wind turbine under the gearbox fault condition,a design scheme for fault detection and fault-tolerant control of the wind turbine gearbox was proposed based on the supervisory control and data acquisition (SCADA) data collaboration.The system model and SCADA solution framework of the wind turbine were introduced.The fault detection and health indicators of the wind turbine system were obtained through regression modeling,exception analysis and integrated learning.Then,the output power of the wind turbine was derated using fuzzy logic control,so as to achieve fault tolerant control operation of the wind turbine under gearbox fault conditions.Finally,the simulation was performed,and the results were compared with an actual 2 MW wind turbine system.The experimental results show that the fault detection and fault-tolerant control scheme can effectively realize the fault detection of the gearbox,and deration control to the output power of the wind turbine is performed with fault,so as to reduce the bearing stress of the blade and tower,and the temperature of the gear box bearing and lubricating oil are effectively reduced.

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