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- 01Tribological Behaviors Comparison of Several Stainless Steels under Seawater Lubrication
- 02Comparison of different optimization algorithms used in torque converter design optimization
- 03Research on High Efficient Flank Milling Machining Technology for Similar Ruled 〖JZ〗Surface Integral Impeller Based on Inspection at Original Position
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Study on the Drive Control Strategy of Piezoelectric Valve for Fuel Injection Control
LI Fan; GAO Xiang; WANG Qinpeng; HE Yuhai
Abstract:The response speed of piezoelectric valve in piezoelectric injector determines the performance and accuracy of fuel injection control in internal combustion engines.In order to improve the response speed of piezoelectric valve,a joint simulation model of piezoelectric valve and its drive circuit based on pulse width modulation (PWM) control method was established by MATLAB/Simulink,and a test bench was built to test the performance of piezoelectric valve,and the effect of PWM pulse width and pulse number of injection control signal on the response time of piezoelectric valve was investigated by combining simulation and test.The results show that for the self-researched drive circuit,the PWM pulse width of the injection control signal has an optimal value,and the optimal pulse width is from 0.3 ms to 0.42 ms.Under the multi-pulse control strategy,the response times of piezoelectric valve opening and closing are 0.525 ms and 0.725 ms respectively; under the single-pulse control strategy,the response times of piezoelectric valve opening and closing are 0.5 ms and 0.6 ms respectively,which meet the control requirements for achieving multiple injections in one cycle of an internal combustion engine.Compared with the multi-pulse control strategy,the opening response time of the single-pulse control strategy is shortened by 4.762%,and the closing response time is shortened by 17.2%.
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Research on Feedforward-Feedback Joint Control Strategy Based on Valve-Controlled Cylinder Electro-Hydraulic System
WANG Dawei; WANG Simin; DING Haigang; GONG Zhiqiang; PANG Zhizhen; LI Yalong
Abstract:Valve-controlled cylinder electro-hydraulic system is widely used,and it is important to improve the response,control accuracy and reliability of the system.Traditional closed-loop control is based on feedback error control,which is simple to control,has good stability,and easy to use in complex systems,but there are problems of time lag and stability.As an open-loop control method,feedforward control has the advantages of fast response and no time lag,but the control effect depends on the accuracy of the model.In order to solve the above problems,a feedforward-feedback joint control strategy based on the electro-hydraulic system of valve-controlled cylinder was proposed,and mathematical model of the system was established,the simulation model of the system was built by using AMESim software and the feasibility analysis was carried out;a parameter table of servo valve flow-differential pressure-voltage feedforward was established by experiments.Finally the experimental platform of variable-speed and constant-pressure oil source was established based on Simulink and verified by experiments. The simulation and experimental results show that the combined feedforward-feedback control can improve the control accuracy and responsiveness of the valve-controlled cylinder electro-hydraulic system,and the tracking accuracy is increased by 45% compared with the feedback control method,which has a good comprehensive control effect.
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Identification Method of Servo System Errors and Interpolation Algorithm Errors for EtherCAT Bus
HOU Huan; LI Xianglong; XIE Xiyang
Abstract:Currently,the EtherCAT bus is commonly used in industrial motion control for communication between master and slave stations,and a large amount of motion data information is transmitted on the EtherCAT bus.Based on this,a servo system error and interpolation algorithm error identification method for EtherCAT bus was proposed.The data on the EtherCAT bus during the motion process were captured through ET2000 and WireShark,valid data were filtered to generate .pcapng file,this file and the ENI.xml file of the motion control system were analyzed to obtain target position and actual position information,and finally error analysis were conducted on the obtained position information.Corresponding motion trajectories were designed for various types errors.Multiple sets of motion control experiments were conducted on the machine tool for single axis point motion,two axis interpolation motion,and two axis prospective interpolation motion.Errors such as servo response lag,servo dynamic performance mismatch,tracking error,positional jitter,and interpolation algorithm error were identified,obtaining the motion control accuracy of single axis and the ability of multi axis motion to cooperate with each other.
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Smooth Interpolation of Tool Posture in Five-Axis Machining Based on Kinematics Performance of Machine Tools
LIU Qiguang; XU Jinting; XU Feifei; JIN Xin
Abstract:To address the issues of poor smoothness and abrupt changes in tool posture within five-axis CNC milling,a new interpolation method was proposed,which focused on optimizing the kinematics performance of the machine tool used.Firstly,within the specified critical area of the tool path,interference-free key tool axis directions were determined.The corresponding rotary axis coordinates for these key tool axes were then yielded.Next,the displacements of the rotary axes movements were represented using a continuous B-spline curve.Linear expressions for their kinematic characteristics were then derived,and an optimization objective function was established to minimize the sum of squares of the jerk in the motion of each rotary axis.By solving the optimization model under the constraints of the key tool axes,smooth interpolation of the tool′s posture along the tool path was achieved.Experimental results show that the proposed method can achieve better kinematics performance compared to the traditional method,effectively improving the stability of the machining process.
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Research on Temperature Rise and Thermal Deformation of Radial Magnetic Fluid Bearing Stator
CHEN Liwen; SHANG Lin; GAO Dianrong; ZHAO Jianhua; WU Xiaochen
Abstract:A new type of magnetic fluid bearing was proposed,which used electromagnetic suspension bearing as the main support and hydrostatic support as the auxiliary support to realize dual support.It can be adjusted according to the needs.The finite element analysis model of magnetic fluid bearing was established.The flow field,temperature,stress and strain distribution of the bearing were obtained through the fluid solid thermal coupling solution.By adjusting the structural parameters (oil inlet hole diameter,coil turns) and operating parameters (input current,oil inlet flow,rotational speed) of the bearing system,the finite element modeling was carried out respectively.The influence rules of different parameters on bearing temperature rise and stator thermal deformation were solved by simulation with ANSYS software.The results show that the maximum pressure caused by the fluid in the oil inlet hole is 1 MPa,and the maximum flow velocity of the fluid at the oil film is 0.8 m/s.The temperature distribution of the bearing stator is symmetrical,which is conducive to heat dissipation.The research results provide a theoretical basis for the optimal design of the magnetic fluid bearing system.
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Output Force Optimization Analysis of the Macro-micro Composite Actuator Based on Halbach Array
YU Caofeng; YANG Kun; ZHENG Shuang; WEI Yijun; TAO Xuefeng
Abstract:To improve the output force and output force fluctuation of the macro-macro composite actuator,a combination of the Halbach array arrangement of permanent magnets and the addition of an auxiliary yoke to change the relative position of the macro-motion coil to the permanent magnets was used.To verify the effectiveness of the optimization scheme,finite element electromagnetic field simulations were used to analyze the change in output force before and after the optimization of the macro-micro composite actuator,and the optimum size of the permanent magnets for the Halbach array was gotten to increase the output force and reduce the output force fluctuation.Finally,the experimental platform was built to verify the rationality of the optimization scheme.The results show that the optimized solution not only enables the macro-micro composite actuator to achieve an output force of around 95 N at 4 A current levels,but also reduces the output force fluctuations to around 23 N.The rationality of the optimization scheme is verified.
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Thermal Field Analysis and Experimental Study of Oil Lubrication of Aeroengine Spindle Ball Bearing
LIU Huan; WANG Jian; ZHU Haifeng; ZHANG Zhanli
Abstract:Aiming at the problem that the three-point contact ball bearing of aeroengine spindle is easy to be burned when it runs at high speed,the heat generation model of bearing was established by local method.Based on the theory of fluid two-phase flow and coupled heat transfer principle,a bearing fluid-structure coupling model was established.The influence of rotating speed and oil supply on flow field and bearing temperature was analyzed.The bearing temperature rise test was carried out by using the aeroengine ball bearing testing machine,and the simulation results were verified.The results show that with the increase of oil supply,the oil quantity of the bearing outer ring increases significantly and the bearing temperature decreases.When the oil supply reaches 1.2 L/min and the oil supply continues to increase,the cooling effect is weakened.With the increase of the rotating speed,the oil in the bearing chamber decreases,and the temperature of the inner ring increases and the inner ring increases more than the outer ring.With the increase of axial load,the temperature of the inner and outer rings of the bearing increases.The maximum error between the test results and the simulation calculation is 10.27%,which verifies the rationality of the model.
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Experimental Study on Short Arc Composite Machining of Ti-6Al-4V Titanium Alloy Assisted by Ultrasonic Vibration
DING Shengwei; ZHOU Jianping; ZHOU Bisheng; WANG Zijian; MIAO Lijun
Abstract:In view of the abnormal discharge phenomena such as short circuit,partial discharge and secondary discharge caused by particle bridge between electrode and workpiece because of poor chip removal in common short arc machining,a new method of ultrasonic vibration assisted short arc machining was proposed to improve the machining quality of workpiece.The macroscopic characteristics and microscopic morphology of the workpiece after common short arc and composite machining were compared by experiments.The surface morphology,roughness and energy spectrum of the machined surface were measured and analyzed by ultra-depth microscope and electron scanning microscope.The results show that:after the coupling of the two special processing technologies,the surface topography of the workpiece has changed,the surface texture is disordered and homogenized under the action of ultrasonic,the number of electric pitting and surface micro-cracks are significantly reduced,the thickness of the recast layer is reduced from 93.06 μm to 25.39 μm under deep milling,the surface roughness is reduced by more than 16%,and the surface elements of the material are modified.This provides a new way for short arc technology to improve machining quality,material modification and technology coupling development.
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Research on Surface Treatment of Piston of Cam Lobe Hydraulic Motor
ZHANG Hongjuan; CUI Xueshi; YING Hong; LI Ying; LI Chengzhi; SHANG Xiaoming
Abstract:The friction and wear of the piston directly affects the starting torque,working efficiency and service life of the inner curve hydraulic motor.The surface treatment technology can improve the wear resistance of the piston surface,but the existing coating process has the problems of wear and easy peeling.In order to explore the influence of different surface treatments on the friction and wear resistance of the piston,three surface treatment methods of MoS2 coating,DLC coating and QPQ salt bath composite treatment were compared and analyzed.Through the assembly test of the motor,the process flow that is most suitable for the surface strengthening of the internal curve hydraulic motor piston was obtained,and the wear-resistant surface strengthening process method of inner curve hydraulic motor piston was established.The test results show that the combined treatment with QPQ salt bath has the best wear resistance,and the working pressure of the motor can be increased to 25 MPa,which effectively improves the friction and wear problem of the motor roller and piston pair.
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Research on Structure Design and Tribological Performance of Scroll Compressor Axial Sealing Mechanism
WANG Nannan; CHI Baotao; YAN Angang; WANG Jikang; YUAN Weiyun; ZHANG Liguo
Abstract:The gas leakage caused by the axial clearance during the operation of the scroll compressor and the friction loss between the sealing material and the scroll end plate greatly reduce the working efficiency of the compressor and adversely affect its working performance.In order to reduce the gas leakage and friction and wear between the dynamic and static scroll plates,a magnetic levitation axial sealing mechanism was proposed.Through the force analysis,the pressure difference of the gas force in the back pressure chamber of the dynamic scroll plate was obtained.Based on the force results,the wear test of PTFE sealing material filled with different graphite content was carried out,and the tribological properties of the axial sealing material were investigated.The research shows that the axial sealing device can effectively reduce the radial leakage caused by the axial clearance.The new magnetic levitation axial sealing mechanism designed by using PTFE sealing material with 25% graphite filling can achieve better sealing and friction reduction effects.
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Research on Stress Wave Vibration Suppression in a Variable Cross Section Rod Based on Forward Feedback Control Method
MA Lei; ZHAO Yifei; YUAN Qinglei; ZOU Kui
Abstract:Based on the basic propagation equation of stress wave,the propagation mode of stress wave in the rod was derived,and the stress wave downstream of the rod was predicted.A feedforward control system was designed to receive the stress wave propagation signal in the upstream of the rod.The received signal was used to excite the piezoelectric ceramic actuator in the downstream rod through the control system,and the actuator excited a normal force in the rod that was proportional to the input voltage.By offsetting the stress in the rod,the amplitude of the stress wave in the rod was reduced to achieve vibration reduction,and finite element simulation was conducted on the output results.The simulation results show that the measurement noise has a significant impact on the vibration reduction of the feedforward control system.The interference wave and noise signal propagated in the rod were modeled,and the state space expression was used to describe the modeling of the interference signal and noise signal.The output of the variance sum of the interference signal and noise signal was obtained,the parameters of the improved feedforward control system were determined,the modified feedforward control system was obtained,and the output of the modified feedforward control system and the stress wave cancellation process in the rod were simulated to verify that the modified feedforward control program effectively reduced the stress wave vibration in the rod.
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Experimental Study on Improving the Friction and Wear Properties of 40Cr Surface with Groove Texture Coating
LI Xiaoqin; LIN Bingjing; HUANG Zhong
Abstract:Simulation and friction and wear experiments were used to investigate the effect of groove texture coating on the friction and wear performance of 40Cr surface.In the simulation experiment,a fluid dynamics model of a more realistic unit groove texture was established using the actual cross-sectional morphology of laser processed textures,and the effects of different groove texture parameter combinations on the friction and wear performance of the model were obtained.In the friction and wear experiments,a multifunctional friction and wear testing machine was used to conduct friction and wear tests on coating samples with different groove textures.A high-precision level meter was used to statistically analyze the wear amount before and after the friction and wear test,and a super depth of field microscope was used to analyze the surface area of the wear marks.The relationship between the friction coefficient,wear amount,wear area and the geometric parameters of the texture was explored.The results show that the vertical oil film pressure increases first and then decreases with the increase of groove texture width; in the actual friction and wear experiment,the existence of groove texture and coating greatly improves the friction and wear performance of the 40Cr sample surface.Except for the difference in the wear amount of the width of 150 μm,the rest of the samples all show a trend of decreasing and then increasing friction coefficient,wear amount,and wear scar area as the width and depth of groove texture increase.The simulation results are mutually verified with the test results.
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Experimental Study on the Process of Jet Mask Electrochemical Discharge Machining
CHEN Chaoda; WU Shaofang; SHAN Liang; SHAO Xiaoqiang; MO Fengrong; HE Haixi
Abstract:The jet mask electrolytic discharge technique was proposed for machining workpieces due to the uncertainty of the discharge breakdown during electrolytic discharge machining,resulting in inconsistent shape and poor quality of the machined workpieces.By analysing the structure of the jet,studying the decay law of the circular turbulent jet flow along the axis and calculating the initial section length,the nozzle and fixture were designed and fabricated.A jet electrolytic machining setup was built and a blue oil mask was prepared on a stainless steel workpiece to experimentally study the effect of machining distance on the shape of the crater.The experiments show that the jet ejected by the nozzle with a conical converging structure has good mechanical properties and can be used to machine the workpiece using the initial section of the jet.A blue oil mask of 50 μm thickness with a skeletonised pattern is applied to the workpiece,which effectively improves the material removal in a fixed domain.The maximum material removal rate is achieved at a machining distance of 2 mm.
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Static Simulation and Experimentation of Proportional Directional Valves
ZHANG Ce; CHEN Lei; MO Yutong; JIN Bo
Abstract:The proportional directional valve is a fundamental component in electro-hydraulic control technology.Its function is to provide continuous control to the speed,direction,position,and output force of hydraulic actuators.During the operation of the proportional directional valve,it is observed that when the voltage command remains constant,an interesting phenomenon occurs:as the differential pressure at the valve port increases,the flow rate does not increase but rather decreases.In order to explain this phenomenon,two static simulation models for the proportional directional valve was developed.The first static simulation model was based on an empirical equation of the flow force and the flow rate at the valve port.The second static simulation model was based on the interpolated equations for the flow force and the orifice flow obtained through numerical calculations of the ANSYS Fluent flow field.The static simulation results show that the orifice flow rate decreases rather than increases because when the differential pressure increases,the increase in flow force leads to a decrease in spool displacement,which in turn leads to a decrease in flow rate.Experimental findings demonstrate that utilizing the derived interpolation formulas based on flow field simulation data for steady-state flow force and orifice flow yields static simulation results is closer to experimental data when compared to traditional empirical formulas.
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Research on Eccentric Loading and Central Overload Performance of Hydraulic Cylinder for Mining
TANG Xiaolong; GAO Yang
Abstract:Mine hydraulic cylinder is an important working component of coal mine hydraulic support,and its performance is directly related to the production safety of the entire fully mechanized mining face.Based on the experimental tests,numerical calculation and simulation analysis,the eccentric loading performance and central overload loading performance of mining cylinders were analyzed.Referring to GB/T 25974.2—2010 "Powered support for coal mine:Part 2:Specification for power set legs and rams",the deflection data of mining hydraulic cylinders under eccentric loading conditions and the stress-strain distribution law of the hydraulic cylinder under the condition of central overload loading were obtained.The numerical calculation model of deflection and strength of mining hydraulic cylinder was verified by test datas.The research results provide reference data for the design and manufacture of the hydraulic cylinder for mining and the inspection of the corresponding hydraulic cylinder performance.
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Comparative Analysis of Mathematical Model of Hydro-Pneumatic Suspension Damping
LI Zeguang; LI Laiping; PEI Jie; WEI Gang
Abstract:In the current research on the dynamic characteristics of hydro-pneumatic suspension cylinder,the elastic force is mainly modeled by the variable gas state equation,and the damping force is modeled by the thin-walled small hole theory.In the real situation,the thickness of the damping hole and the one-way valve is not thin-walled,but has a certain thickness,the thin-walled theory application will lead to the distortion of the model to a certain extent.Therefore,the damping model was established by using the theory of short-hole flow,and the dynamic model of the hydro-pneumatic suspension cylinder were reconstructed by considering the local head loss of the inlet and outlet.The mean absolute error (MAE) and root mean square error (RSME) of the two damping force models were compared with the real acceleration data of the support point on the suspension cylinder.It is verified that both models can simulate suspension vibration well in the low frequency range,but there is a significant deficiency in the medium to high frequency range.The short hole flow theory based model is closer to the true value in the frequency domain.
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Design and Implementation of Vertical Pipe Horizontal Welding Robot Assisted Welding Process Based on Virtual Reality
LUO Yu; GAO Mengmeng; XU Yaobo; REN Feiyan; YU Junjie; TIAN Wenpeng; LIU Boyang
Abstract:The selection of welding process parameters has an important influence on the welding quality.A welding process parameter matching algorithm based on the strategy of horizontal weld bead thickness and constant heat input was proposed for the underflow characteristics of the narrow groove cross welding pool of the J-type laying of riser pipe.Based on the Unity3D development platform and process parameter matching algorithm,the computer-aided welding process module (CAPP) of riser horizontal welding was developed using C#,which expanded the functional module of the virtual reality human-computer interaction system.The computer-aided welding process experiment of vertical pipe horizontal welding was carried out,and the weld was formed well after welding,without welding defects.Experimental results show that the CAPP module can effectively obtain the matched welding process parameters,shorten the welding process development cycle,reduce the process development cost,and effectively improve the intelligent level of the system.
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Design and Analysis of Triaxial Pressurization System for Seabed Environment Simulation
NIE Zhong; ZOU Dapeng; HUANG Junpeng; KAN Guangming; WU Lei; ZHANG Jianan; LONG Jianjun
Abstract:In order to realize the simulation measurement of seabed sediment in situ environment,the seabed environment simulation triaxial compression system was designed.Through the three pressure units of confining pressure,back pressure and axial pressure,the water depth pressure,buried depth pressure of seabed sediments were simulated.The mathematical model of the hydraulic pressurization unit was established,and the bulk elastic modulus of water under different conditions was obtained through the secant bulk elastic modulus equation of the water medium.The effect of different temperature,pressure and seawater salinity on the pressurization performance of the pressurized system was studied.After analysis and test,it is concluded that the influence of temperature change per 1 ℃,pressure change per 1 MPa,and salinity change per 1‰ on the compression performance of the pressurized system is 0.36%,0.14%,and 0.21% respectively.By simulating the elastic modulus change of water volume caused by environmental fluctuation,the 0.6 MPa pressure disturbance changes in the test bin,and the adjustment time for the system to automatically restore the stable state should not exceed 5 s.The experiments show that the overshoot of the system is less than 0.05 MPa,and the test pressure fluctuation within 10 min from 1 MPa to 10 MPa does not exceed ±0.005 MPa.The system pressure control characteristics and anti-interference performance are good,meeting the measurement requirements.
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Design and Research of Hydraulic System for Cylindrical Pier Pouring Mold Based on AMESim
XU Quanwen; YIN Zhihong; DING Zhiwei
Abstract:In view of the problem that it is difficult to complete the docking,leveling,internal cleaning and demoulding of the mold in the pouring process of the prefabricated pier by manpower,a set of cylindrical pier pouring mold hydraulic system was designed.By analyzing the working requirements of the mold,the multi-way valve was used to control the whole hydraulic system,and then the composite motion requirements of different actuators were realized.The AMESim simulation model was established and analyzed,and the dynamic characteristic curves of the hydraulic cylinder under different Cv values were obtained,and the hydraulic system was experimentally verified according to the simulation results.The results show that when the rated pressure is set to 16 MPa,the hydraulic system can meet the load requirements of actual work,and can provide sufficient pressure to ensure the speed and stroke requirements of the hydraulic cylinder.When the system Cv value is set in the range from 0.3 to 0.7,it meets the requirements of system speed change and the speed fluctuation is small.The simulation results are basically consistent with the experimental results,which verifies the effectiveness of the hydraulic system.
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Stamping Molding and Die Structure Joint Simulation Analysis Based on Dynaform and Abaqus
ZHAI Lin; HAN Guotai
Abstract:In order to meet the personalized production needs of different sizes stamping parts with multiple specifications and small batches,a new type of adjustable combination stamping die was designed.The female die structures of the stamping die were both composed of four sided blocks,and could achieve position movement in their respective directions.Therefore,they could be reassembled into female die with different sizes,achieving the goal of producing stamping parts with different sizes.Based on the Dynaform platform,the stamping forming process was simulated and analyzed using die surface engineering technology,while the maximum forming pressure was output.On the finite element Abaqus software platform,the maximum forming pressure output by Dynaform was used as the load input of Abaqus to verify the stiffness of the female die assembly block of the adjustable combination mold,ensuring that the displacement inclination not affect product quality,and ensuring the reliability and service life of the stamping die.The results show that the joint simulation based on Dynaform and Abaqus can effectively predict the feasibility of stamping forming process and the rationality of mold structure,providing a theoretical basis for the successful trial of stamping molds.
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Design of Closed Walking Hydraulic System for Engineering Vehicles
LI Lei; LI Limin
Abstract:The walking system of wheeled vehicle is very important to the reliability of vehicle operation,and its preliminary design determines the success or failure of the project.The U-shaped frame support vehicle with complex principle was taken as an example, the principle of walking hydraulic system was analyzed,and parameters such as walking speed,traction force and engine power were calculated.It provides a theoretical basis for the design of closed walking hydraulic system of engineering vehicles,and the waste caused by unreasonable design is reduced.The model has been tested by customers and all indicators meet the expected requirements.
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Research on Frequency Characteristics of an Aeroengine Main Fuel Control System
YANG Yikun; MA Jing; YANG Junjie
Abstract:In order to investigate the frequency response characteristics of the main fuel control system in a certain type of aircraft engine numerical control system,a dynamic mathematical model of the components and the system was established based on force balance equations and flow continuity equations.Using small deviation linearization around the steady-state operating point,transfer functions were developed for the pressure differential module,main fuel metering module,parking control module,and the overall system.Fluent flow field simulation was employed to study the steady-state hydrodynamic characteristics and the factors that affected these characteristics of key components.Based on the results,a Simulink simulation model of the main fuel control system was established to investigate the frequency response characteristics and the natural frequencies of key flaps in depth.The results demonstrate that the frequency response characteristics of the main fuel control system are consistent with practical engineering experience and exhibit high stability margins.The natural frequency of the system corresponds closely to that of the metering valve with the lowest natural frequency in the system.When the component structure is determined,steady-state hydrodynamics have a greater influence on the natural frequency.The research results provide theoretical support for the frequency-domain optimization design of the fuel control system.
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Influence of Misalignment on Meshing Characteristics of Double Circular Arc Gears
YANG Shufeng; WANG Feng; ZHANG Weijie; CHE Jiangning; XU Wenbo
Abstract:In order to investigate the influence of misalignment on the meshing characteristics of double circular arc gear pairs,a gear loading analysis model based on finite element method was established.The contact performance of single tooth convex and concave tooth profiles during the meshing process was studied,and the influence of misalignment on contact performance and transmission error was compared and analyzed.The research results show that during the meshing cycle,the concave tooth profile of the double circular arc gear first contacts and bears a large normal contact force,but the contact stress at the meshing end of the convex tooth profile is the highest,and the contact pressure difference between the convex and concave tooth surfaces is proportional to the torque; misalignment has a significant impact on the contact performance of the tooth surface,the center distance errors easily causes stress concentration at the gear step,and misalignments on the axis plane can cause tooth surface contact deflection， and it has the greatest impact on installation errors.
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Kinematics and Dynamic Characteristic Analysis of the Differential Planetary Roller Screw Mechanism
QIAO Guan; ZHANG Xiaomin; LIU Fule; GUO Shijie; MA Shangjun
Abstract:Differential planetary roller screw mechanism is a kind of mechanical transmission mechanism with high reduction ratio,which combines ring groove drive with thread meshing.In order to explore the dynamic characteristics of differential planetary roller screw,the structure and motion principle of a novel differential planetary roller screw were studied.The 3D model of the differential planetary roller screw mechanism was established,and the model was imported into the virtual prototype analysis software.The appropriate connection relationship was set up,and the kinematics and dynamics analysis of the 3D model was carried out.The results show that the motion in the virtual prototype is consistent with the motion analysis,which verifies the rationality of the motion analysis.When the load is applied to the nut,the ring groove design between the roller and the nut makes the contact force fluctuation more regular;with the load continues to increase,the contact force fluctuation between the screw and the roller,the nut and the roller also continues to increase,which aggravates the wear inside the mechanism and shortens the operating life of the mechanism.
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Research on the Characteristics of Pilot Controlled Electrohydraulic Directional Valve with High Speed On/Off Valve
WANG Wei; LI Zhiyuan; LU Delai; LIAO Yaoyao; ZHAO Wenbo
Abstract:Aiming at the problems of inaccurate flow control,large pressure impact and groundwater pollution of traditional hydraulic support using emulsion transmission medium electro-hydraulic reversing valve,a pilot proportional valve with water based high-speed switching valve was proposed,to achieve accurate control of the pressure of the main valve control chamber and the displacement of the main valve spool.A hydraulic bridge for pilot control of electro-hydraulic directional valve with high speed on-off valve was proposed.The compound PWM control strategy was proposed for pilot high speed on-off valve,reducing latency by 15.8 ms.The main valve displacement was controlled by pulse frequency modulation and pulse width modulation.The simulation results show that the displacement of main valve core can show proportional opening effect within a certain duty ratio range.The ultimate test findings indicate that using the high-speed on/off valve as a pilot stage enhances the response rate of the main valve.
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Kinematics Analysis and Simulation of Top Beam Welding Manipulator of Hydraulic Support
ZHANG Xin; LIU Changrun; LI Xu; LI Juntao; WANG Peng
Abstract:In response to the current situation of incomplete welding process and high welding difficulty in the welding process of the top beam of hydraulic support,a five degree of freedom welding manipulator was designed to ensure the welding efficiency and quality of the top beam.Based on the improved D-H parameter modeling method,the forward and inverse kinematics of the top beam welding manipulator were analyzed and solved. Monte Carlo method was used to analyze the effective workspace of the hydraulic support top beam welding manipulator.The Robotics Toolbox in MATLAB software was used to model,analyze and simulate the trajectory planning of the welding manipulator,and the angular displacement,angular velocity and angular acceleration curves of each joint were obtained.Adams was used to obtain the real-time tracking trajectory of the manipulator.The analysis and comparison show that the trajectory planning of MATLAB is correct.The analysis and simulation results show that the trajectory of the designed top beam welding manipulator is stable and continuous,meeting the requirements of kinematics.It lays foundation for the dynamic and static analysis,optimization design and motion control of the subsequent top beam welding manipulator.
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Dynamic Modeling and Time-Varying Dynamic Characteristics Analysis of Rigid-Flexible Coupling for Ball Screw Feed System
ZHANG Xinyu; ZHAO Wei; ZHANG Lei; WANG Taiyong
Abstract:During the operation of CNC machine tools,the stiffness and inertia of the multi-axis ball screw feed system will change with the change of the poses of the feeding shafts,resulting in the time-varying characteristics of its dynamic characteristics.The high-fidelity modeling and analysis of the time-varying dynamic characteristics of the multi-axis ball screw feed system has become one of the bottlenecks in the accurate prediction of the contour error of CNC machine tools.Aiming at this problem,a rigid-flexible coupling dynamic modeling and analysis method of ball screw feed system based on Lagrange equation and Ritz series method was proposed.Taking the two-axis ball screw feed system of a five-axis machining center as the specific object,the rigid-flexible coupling dynamic model of the ball screw feed system was established by using the Lagrange equation,and the Ritz series method was used to solve the equation,and the numerical solution of the dynamic model was obtained.The influence of the poses of the feeding shaft on the natural frequency and modal shape of the two-axis feed system was analyzed by using the established dynamic model.It is found that the variation of the natural frequency and modal shape of each order with the poses of the feeding shaft is related to the dominant axis of the corresponding order.As the feed table of the main shaft moves from the fixed end to the support end,the natural frequency of the corresponding order gradually decreases,and the elastic vibration amplitude of the screw body in the corresponding modal mode gradually increases.In addition,the low-order modal shapes of the two-axis feed system are mainly dominated by the bearing shaft,and the high-order modal shapes are mainly dominated by the sub-shafts attached to the bearing shaft.Finally,the application of the proposed method is verified by modal experiments to prove the accuracy of the established dynamic model.The research results have important reference value for the accurate prediction of contour error of CNC machine tools.
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PID Parameter Optimization Based on Improved Sea Horse Optimization Algorithm
SHU Yibin; LI Lijun; ZHANG Zhenhe; QI Hao; LIU Jiangyi
Abstract:In order to solve the problem of poor global optimization ability and slow convergence speed of sea horse optimization (SHO) in PID parameter tuning,and improve the optimization quality of PID parameters,an improved sea horse optimization (ISHO) was proposed.Tent chaotic mapping was used to increase the initialization diversity of sea-horse populations and improve the convergence speed.The escape energy regulation strategy was introduced to improve the conversion mechanism between global search and local development of the algorithm,so as to improve the global optimization ability of the algorithm.The improved sea horse optimization was compared with the traditional sea horse optimization,Ziegler-Nlichols,gray wolf optimization and particle swarm optimization.The simulation results show that the improved sea horse optimization optimizes PID parameters with the advantages of shorter adjustment time,higher system control accuracy and faster convergence speed,which provides a reference for parameter optimization of PID control system.
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Analysis of Static and Dynamic Characteristics of B-550E High-Speed Engraving Machine
LI Zhou; ZHOU Junrong; ZHAO Tianyi
Abstract:Taking the B-550E high-speed engraving machine as the research object,the finite element model of the whole machine was established in ANSYS Workbench software,and the static and dynamic characteristics were analyzed.The static characteristics of the machine under gravity and the combined action of gravity and milling force were analyzed,and the weak links of the static stiffness of the machine tool structure system were found.Through modal analysis,the first 6 natural frequency and main mode shape of the whole machine were obtained,and on this basis,the harmonic response analysis of the whole machine was carried out,and the amplitude-frequency characteristic curves of the whole machine in all directions under the excitation of milling force were obtained.The results show that the first 2 order natural frequencies have a great influence on the dynamic performance of the machine tool.The maximum deformation and stress of the whole machine occur in the headstock,and the main vibration modes of the first 2 order natural frequencies are the main headstock components,so the key component affecting the dynamic performance of the machine tool is the headstock.
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Simulation of Hydraulic System of Lifting Support for Disassembly and Assembly of Tunnel Boring Machine
LI Nan; LIU Yanjun; WANG Guozheng; LI Heng; HU Rui; XU Liping; LI Yuesong
Abstract:Aiming at the problem that the tunnel boring machine (TBM) cannot meet the large open space required for debugging due to space limitation in the construction site,a hydraulic system of the lifting support for the disassembly and assembly of TBM was developed.The hydraulic system consisted of four groups of lifting units,by which the lifting and support of TBM was realized through synchronous movement of four groups of lifting units.The hydraulic lifting system consisted of four four-stage hydraulic cylinders,hydraulic control system,laser displacement sensor and frame.Based on AMESim,the hydraulic simulation models of four-stage hydraulic cylinder,variable displacement pump and the proportional throttle valve as well as the whole jacking unit were established.And the speed,displacement and pressure curves of the hydraulic cylinder movement under load were analyzed through simulation.The results show changing the input signal of the proportional throttle valve can achieve a change in the speed of the four stage hydraulic cylinder.The pump outlet pressure can be adjusted by a proportional relief valve.Under the rated load of 2.5 × 105 N,the pressure of the stage changing working chamber of the fourth stage cylinder gradually increases.As the stage changes,the extension speed of the piston rod gradually increases.Compared with theoretical calculations,the AMESim simulation results of the quick disassembly hydraulic system lifting unit in the TBM tunnel established are basically consistent with the theoretical values.
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Optimal Design and Research for Column of Mineral Direct Drive Turning-Milling Compound Center
XIAO Jie; TANG Xiaoteng
Abstract:The column of the mineral direct-drive turning-milling compound center is generally a solid structure,which has problems such as heavy structure,material waste,and high manufacturing cost.Taking the CXK80 mineral material column as the research object,the dynamic and static performance analysis and heat transfer analysis were carried out.Then,reducing the weight of the mineral material column,improving its strength and stiffness were set as optimization objectives.The topology optimization and multi-objective dimension optimization based on genetic algorithm were used for lightweight design.The simulation results show that the weight of the optimized mineral material column is reduced by 14.2%,the temperature on the guide rail embedding surface is decreased by 21%,and the first two modal frequencies of the column are correspondingly improved.To verify the effectiveness of the simulation analysis,modal hammer impact experiments were conducted.The experimental data and simulation data are basically consistent with an error within 3%,achieving the goal of reducing the weight of the mineral material column and saving manufacturing costs.
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Abnormal Diagnosis Method of 3D Printing Based on Machine Vision
HUANG Zhoulin; ZHOU Min; LI Xinyan; SHEN Fei
Abstract:In order to solve the problem of printing failure caused by abnormal conditions such as plug,broken wire and warping in 3D printing process,a detection platform was built and an improved YOLOv5 algorithm with Xception was proposed to complete real-time anomaly detection,achieving the goal of timely processing and printing success rate improvement.The YOLOv5 algorithm was reconstructed by improving the head,trunk and bottleneck block of YOLO algorithm,improving the identification frame rate and reducing the parametes.Then the output part was improved so that the abnormal images with similar features were collected and input into Xception algorithm to improve the accuracy of abnormal recognition and classification.Finally,the Qt cross-platform development framework was used to design a printing abnormal diagnostic system human-computer interaction interface software.The results show that the accuracy rate of the improved fusion algorithms in self-built 3D printing abnormal data set recognition is 88.75%,which is 3.22% higher than the original YOLOv5 algorithm,and the average recognition frame rate is 28 f/s,which is increased by 40.0%.It can meet the actual printing recognition accuracy and real-time requirements.
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A Method for Wind Turbine Bearing Deterioration Index Construction and Fault Diagnosis by Combining POA-VMD and Autoencoder
LI Junqing; GENG Jiya; GUO Xiaoyu; LIU Ruoyao; HU Xiaodong; HE Yuling
Abstract:In order to solve the problems that the construction and fault diagnosis of bearing performance deterioration index are highly dependent on expert experience,many constraints and single practical application scenarios,a method for the construction and fault diagnosis of wind turbine bearing deterioration index was proposed,which combined the pelican optimization algorithm (POA),variational mode decomposition (VMD),and autoencoder.Firstly,the POA-VMD algorithm was used to decompose the vibration signals of the entire lifespan of the bearing into K intrinsic mode functions (IMF) by the adaptive approach,and K individual autoencoders were constructed for each IMF to capture their distinctive characteristics.Then the autoencoders were trained with the decomposed results of the normal vibration signals as the training sample,and bearing degradation index was constructed based on the output result of the model after the training was completed,and the early weak failure of the bearing was monitored with the help of the deterioration index.Finally,the envelope spectrum analysis of the IMF component reconstruction results of the vibration signal at the time of fault was carried out to determine the fault type.Experimental results validate that this method can not only clearly show the deterioration process of the bearing,but also have a high sensitivity to early weak faults,and can accurately diagnose the type of fault after the fault occurs.
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One-Dimensional Convolutional Migration Learning-Based Bearing Fault Diagnosis for Cross-Condition CNC Machine Tools
JIANG Guangjun; LUAN Yu; GONG Yongzhi
Abstract:As an important core part of machine tools,rolling bearings plays an important role in ensuring the normal operation of machine tools.However,in the actual working environment,the working condition of machine tools often changes according to different working requirements,which will have a certain impact on the speed and load of machine tool bearings,resulting in the mechanical vibration signal of the bearing showing non-stationarity,nonlinear and non-periodic characteristics.At present,the bearing fault diagnosis methods based on deep learning are data-dependent,requiring the training (source domain) and test (target domain) data sets to have the same data characteristics and the presence of sufficient labeled data with fault information.However,since machine tools operate under non-stationary conditions,the training model built on one condition cannot be directly applied to another condition.In order to solve this problem,based on transfer learning (TL) technology,a model combining one-dimensional convolutional neural network (1-DCNN) and transfer learning was designed.In this model,one-dimensional convolutional network was used to extract the fault feature information directly from the original vibration signal,and the common features of the two domains were extracted by adversarial strategy migration.The difference measurement of domain distribution was used to narrow the feature distribution of the two domains and realize the fault diagnosis of bearing migration across working conditions.Finally,12 groups of migration tasks were constructed to verify the superiority of the designed model.The results show that the designed transfer learning neural network model based on one-dimensional convolution can directly achieve real-time monitoring of machine tool bearing faults.The designed model greatly improves the performance of migration fault diagnosis by combining adversarial strategy transfer and measurement domain distribution difference transfer strategies,which can better extract common features of the source and target domains.Among the 12 migration tasks constructed in the experiment,it is superior to the other two migration strategies and can perfectly complete the migration fault diagnosis task.
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Fault Analysis of Hydraulic Locking Circuit of a Special Vehicle in Large Temperature Difference Environment
LEI Kaiwen; QU Wubin; WANG Yuejin; ZHANG Genyuan
Abstract:By analyzing the fault phenomenon of hydraulic locking circuit of a special vehicle in a large temperature difference environment,the calculation model was established and the test fixture was designed to verify .It is shown that in the environment of large temperature difference,the pressure change of fluid medium in the hydraulic locking circuit is obvious,which exceeds the maximum opening pressure of the two-way hydraulic lock when the temperature is rising,and the difference is large compared with the design value of the circuit.Finally,the measures to solve the fault under the condition of large temperature difference were put forward.The test proves that the method of increasing the hydraulic lock control ratio or manually reducing the oil pressure of the lock circuit can solve the fault.It provides certain reference for engineering design and application.
