Table of Content

25 August 2012, Volume 23 Issue 16

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#br# Study on Tooth Profile of Planar Enveloping Crown Worm

CHEN Yong-Hong, ZHANG Guang-Hui, CHEN Bing-Kui

2012, 23(16):  1891-1896. 

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Aiming at a new type of planar enveloping crown worm,a mathematical model of the teeth surface was established based on the theory of gear mesh;
the tooth profile was analyzed,namely to study the laws of the parameters on tooth undercut and sharpened middle tooth.A method was presented to equalize the grinding allowance.A sample work piece was manufactured by the NC toroidal worm machine with the
theory of fictitious center distance,and the profile accuracy was tested by coordinate measurement.The validity and feasibility of the optimized method were proved by case
studies,and the sample work piece gains 8 grade profile accuracy.The studies solve the
crucial issues on design,manufacture and test of the planar enveloping crown worm.

Contour-parallel Offset Tool-path Linking without Tool-retraction

DONG Guang-Lei-1, DAI Ning-1, YANG Feng-1, HAN Hou-Nian-1, GUO Bao-Su-1, WANG Yong-2, LV Pei-Jun-2

2012, 23(16):  1896-1902. 

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Contour-parallel offset(CPO) tool path was used widely in the rough machining process for dental restoration. In order to minimize the number of tool-retractions which did not contribute to the actual cutting and optimize the links between tool path loops(TPLs), a CPO tool path linking algorithm based on single root TPLs tree data structure was presented. With the parent/child relationship built during the calculation of TPLs, a single root TPLs tree was constructed, and then it was divided into many subtrees according its topology, as a result all TPLs were split into several grouped TPLs. TPLs in each group were linked by linking point pairs. Finally, a CPO tool path without tool-retraction can be generated by traveling TPLs tree. Several testing results show that this method can obtain CPO tool path without tool-retraction effectively.

Study on Dynamics Performance Index of Automated Fiber Placement Robotic Manipulator

GE Xin-Feng-1, 2, DIAO Dong-Biao-1, LIU Yong-Hua-1, LIU Kai-1

2012, 23(16):  1903-1907. 

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An automated fiber placement robotic manipulator's acceleration was drawn according to the automated fiber placement robotic manipulator kinematics and the acceleration derivation was defined.The acceleration derivation size related Jacobian matrix and Hessian matrix,thus the dynamics performance index of the automated fiber placement robotic manipulator was proposed based on the Jacobian matrix and Hessian matrix.The performance index was used to analyze the dynamics of the automated fiber placement robotic manipulator;the dynamic performance atlases were plotted,the curves between structure size of the automated fiber placement robotic manipulator and the dynamics performance were obtained.The results show that the dynamics performance index based on Jacobian matrix and Hessian matrix impacts on the dynamics performance more greatly comparing with the velocity performance index based on Jacobian matrix.The dynamics performance index based on Jacobian matrix and Hessian matrix is feasible and efficient as a measure of the automated fiber placement robotic manipulator's dynamics.

Research on Operation Smoothness and Noise of Stepping Motor Based on New Type Acceleration/Deceleration Curve and Real-time Control Scheme

LI Xiao-Hu, WANG He, HU Jia-Lin

2012, 23(16):  1907-1911. 

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Based on acceleration/deceleration curves and control scheme,the operation smoothness and noise of stepping motor were analyzed and studied.According to the relation between angular acceleration and angular velocity (a-ω equation),the S-type,e/e-type and Cos-type acceleration/deceleration curves were constructed respectively,in which the flexible impact can be avoided.Then,the control scheme of stepping motor was optimized, including that the smoothness of stepping motor's speed transition was improved,that the controller's calculation speed was enhanced because of calculation's simplification by iterative algorithm,and that storage resources were saved through real-time calculation.The noise experimental results show that compared with the traditional drive scheme,the stepping motor system,which adopts Cos-type acceleration/deceleration curve and real-time control scheme,operates smoothly and has lesser noise during startup process.

Development of Measuring System for Thin Lubrication Film in a Fixed-incline Conformal Contact

CHU Xiao-Dong-1, 2, GUO Yan-Jing-3, LI Xia-2, GUO Feng-2, WANG Wen-1

2012, 23(16):  1912-1916. 

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For the theoretical study of conformal contact lubrication,a traditional measuring system for thin lubrication film in a fixed-incline conformal contacts  was renovated for simultaneous measurement of lubricating oil film thickness and friction in a fixed-incline conformal contacts.The simultaneous measurement method added a degree of freedom to the slider under condition that the slider can be fixed to the needed dip angle relative to the disk.The present measuring system adopted a laser light source and an external coaxial illumination to expand the measurement range of the oil film and the view field of interferograms.A new software was designed to control the acceleration of the servo motor to avoid errors of the interference order recording and acquire more regular interference curves.This paper also presented some fundamentals of multiple beam interferometry principle in measuring the oil film thickness and analysed the resolution ratio of the film thickness and friction.Variation of film thickness and friction with sliding velocity was measured through the system and the results were contrast with the corresponding theories,
which demonstrated the credibility of tested data.At last,the load-carrying capacity of thin film lubrication in a fixed-incline conformal contact was studied with the test apparatus,
and was compared to the theory.Some preliminary analyses were given to account for the differences in the comparison.

#br# #br# Dual-valve Control of a Work Roll Bending System

ZHANG Chang-Ying

2012, 23(16):  1916-1919. 

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Transfer function of matched asymmetric valve cotrolled asymmetric cylinder system was supplied,correcting system load due to asymmetrical characteristics of valve controlled asymmetric roll bending
cylinder system.Control strategy of force control system was studied,such as nonlinearity compensation and dynamic pressure feedback,using matched asymmetric valve to control an asymmetric cylinder.Feasibility employing simultaneous dual-valve to replace matched asymmetric valve in the asymmetric cylinder control system was discussed.Simulation and experimental results verified control strategy concerning dual-valve controlled asymmetric cylinder system.Foundation was established for the analysis and synthesis of asymmetric valve cotrolled asymmetric cylinder system.

#br# Vibration Response Localization of  Bladed Disk with Different Shrouded Fit Modes

WANG Ai-Lun, CAO Xu-Hui, SUN Bo-Hai

2012, 23(16):  1920-1924,1961. 

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A continuous parameter model with different shrouded fit modes was established.The characteristics of vibration localization of bladed disk under different conditions were compared,and the vibration discipline of different bladed disks was researched.The results show that the vibration localization will not appear in bladed disk with loose fit under tuned conditions,and the sub-tuned vibration and faint vibration localization will appear in bladed disk with tight fit under tuned conditions due to frictional factors,
while the vibration localization will appear in bladed disk with loose fit under random mistuned conditions,and the sub-tuned periodic vibration will not appear in bladed disk with tight fit under random mistuned conditions,and the vibration response localization is more complicated.The vibration localization of bladed disk with loose fit is more sensitive to random mistuning than the vibration localization of bladed disk with tight fit.

#br# Dynamics Response Experiment and Analysis of Aviation Pipeline Based on Modal Test

LU Hua-Beng-1, 2, GU Pu-Rong-1, LIU Yong-Shou-1, SUN Bei-2, LI Bao-Hui-1

2012, 23(16):  1925-1929. 

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Aviation pipeline is one of the key components of aircraft;aimed at the influences of damping ratio in dynamics computation,based on MIMO modal test,a pipeline,made of aviation aluminum alloy,its first eight order modal frequencies and damping ratios were obtained.In addition,the pipeline was excited by instantaneous loads and the response data in some regions were gotten in time domain.The mode frequencies were calculated by taking into account the added mass caused by acceleration sensors.Respectively,based on constant damping ratio and modal damping ratio of testing mode,the instantaneous dynamic responses of the pipeline were analyzed and compared with test values.The results show that both of dynamics response amplitudes and the response times in calculation based on modal damping ratio are
closer to test values of the aviation pipeline,it is better than that of the calculated values based on constant damping ratio.The structure with high security requirements,such as aviation pipeline,its response should be calculated based on the modal damping ratio as far as possible. 

#br# Improvement of 3D Contact Problem FEA under Variable Friction Condition

LI Qun-Song-1, SHU,YING 2, TAN Hai-Lin-1, ZHANG Ji-Qing-3

2012, 23(16):  1929-1933. 

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The three-dimensional elastic contact problem with the variable friction model was studied.The contact conditions were imposed along the contact nodes' normal and sliding directions.The program packages for contact solution were designed using FORTRAN language,which were applied to investigate an
example of contact problem with a velocity-correlation friction model.The variations of nodes'contact states and contact forces with sliding velocity  were examined.Eventually,the validity of the proposed algorithm and the designed program packages were verified by comparing the computed results with that obtained from the commercial software.

Finite Element Modeling and Testing of the Three-dimensional Vibrations of a Simplified Elevator Traveling Cable

XIAO Chen, YAN Zhi-Hong

2012, 23(16):  1934-1938. 

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A typical elevator travelling cable was simulated by a steel band which forms a loop with the fixed-fixed boundary conditions.And the modal testing method was discussed for this steel band. The three dimensional vibrations of a steel band,including the vibrations within and out of the loop plane,were measured respectively.A three dimensional element finite model of the steel band was built to predict its natural frequencies and the associated mode shapes.The modal testing results were consistent with FE method.The reasons of the tangle and hit wall of the traveling cable were analyzed.And effective measures should be taken to improve the dynamics property of the traveling cable. 

A New Method for Improving Kinematics Accuracy of Parallel Robot Based on Improved PSO

DU Xi-Gao, XIE Beng, TIAN Pei-Chao, LIU Ban

2012, 23(16):  1938-1942. 

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Aiming at a kinematics accuracy problem of the parallel robot,caused by the deviation between the desired trajectory and the ideal trajectory generated by the mechanism errors based on the task trajectory planning process,a new method to improve the kinematics accuracy of the parallel robot was proposed herein:First,the continuous task was discretized to some ideal pose points based on the accuracy requirements,and the mechanism errors were transformed into drive rod errors based on the pose error model of  the parallel robot.Then an improved particle swarm algorithm was developed based on the population permutation entropy and the particle velocity activation mechanism,which can complete combinatorial optimization of the drive rod parameters for compensating the pose errors of the parallel robot,
so as to correct the desired trajectory and improve the kinematics accuracy.The feasibility and validity of the proposed algorithm were shown by the MATLAB and ADAMS simulation.

Trajectory Planning Method for a Flexible Load  Electro-hydraulic Position Servo System

LI Guang, LIU Ling-Hua

2012, 23(16):  1943-1946. 

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This paper presented an investigation into development of trajectory planning strategies for an electro-hydraulic position servo system with a flexible load;the final aim was to eliminate the residual vibration of the flexible load.The motion trajectory was obtained by superimposing cubic polynomials onto a ramp,
a cycloid,and a simple harmonic function.The coefficients of the equations were determined by initial and final conditions of rigid load movement and the constraint condition that the free vibration amplitude of flexible load was zero.A fuzzy controlling strategy was used to the electro-hydraulic system for tracking presented desired optimizing trajectory.The numerical simulations were carried out to demonstrate the control performance of the proposed approach. 

Strategy of Smith Estimated Compensation Control in Continuous Casting Mould Liquid Level Control

ZHANG Jia-Yan, JIAN Hong, FENG Xu-Gang, LI Chao-Ming

2012, 23(16):  1947-1951. 

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The existence characteristics of nonlinear and strong coupling and pure time-delay,as well as the disturbance factors in the mould liquid level control systems,have made its control more difficult to obtain satisfactory results.Through the studying of the nonlinear PID control strategy based on the Smith estimate
compensation,and the MATLAB simulation and analysis in the identification model of mould liquid level control system,then the control strategy was put  into use.The results show that this control strategy can improve the control system dynamic quality and anti-jamming performance obviously and achieve the good application effects.

Calculation and Analysis of Internal Flow Field of a Double Nozzle Flapper Valve of Two-stage Electro-hydraulic Servo Valve

LIU Xiang-Hui-1, 2, GAO Dian-Rong-1

2012, 23(16):  1951-1956. 

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The double nozzle flapper valve is the pre-stage of a two-stage electro-hydraulic servo valve, its structural parameters have an important influence on the performance of electro-hydraulic servo valves. This paper used the flow field computation software to compute the flow field of the nozzle's different structural parameter combinations, and also analyze the liquid flow property, as velocity characteristics, pressure characteristics, flow characteristics, etc. The results show that the flow rates increase as the the diameter, the end grinding and the external angle of the nozzle increase. But the differential pressure of the nozzle flapper valve decrease. And there is nearly no influence while changing the length of the nozzle, the inner angle of the nozzle and the cavity inner diameter of the nozzle. Through the comparisons and analyses the optimal combination of the structural parameters are found out,which can give the references  and provide a basis for the design of the nozzle of double nozzle flapper electro-hydraulic servo valves. 

Research on Diagnosis Method to Train's Vibration Frequency Band-varying Fault Based on Uniform Angle Sampling

WANG Jing-1, 2, CHEN Te-Fang-1, HUANG Cai-Lun-2

2012, 23(16):  1957-1961. 

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Wheelset of  train's faults affected by factors such as speed fluctuation,and the vibration signal will act as an overall spectrum band migration.Using the general fault diagnosis method of rotating machinery lead to misdiagnosis or missed diagnosis due  to  spectrum-line migration.To solve this problem,the dynamic response between such various factors and the fault characteristics was researched in-depth.The whole system coupling dynamic model of the fault characteristics and  frequency band-varying factors was established based on fault mechanism analysis.The relationship between the working state parameters and fault characteristics was revealed.The uniform angle sampling method and characteristics spectral analysis method were established.In the end,the train's  frequency band-varying fault identification methods were summarized,and the accuracy was verified through the practical applications.

Research on Virtual Prototype Simulation of Compound Planetary Gear Train Sets

Liu Zhenhao1,2,Wu Shijing1,Qian Bo3,Wang Xiaosun1

2012, 23(16):  1962-1966. 

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Based on the typical structure of Ravigneaux compound planetary gear train sets,the transmission ratio and meshing frequency of the system were analyzed. In order to obtain the changing patterns of contact force of Ravigneaux compound planetary gear train sets.a 3-D solid model of the sets was established by SolidWorks software and the virtual prototype of the system was built based on ADAMS software.The computation method for contact force of gear meshing was introduced based on Hertz theory.The transmission ratio of the system was verified.The changing pattern and the spectrum characteristics of the synthetic contact force between small sun gear and short planet gear,that of x direction and y direction were simulated.The simulation results show that the ampltude of contact force fluctuated obviously,which had notable periodic property.The contact force of x direction and y direction has the same frequency spectrum and phase difference of  90°.The rotational frequency and frequency multiplication of 1 to 7 of meshing frequency are in the frequency spectrum of contact force,which have explict modulating characteristics.The virtual prototype researches of Ravigneaux compound planetary gear train sets can provide some references to improve the system dynamic characteristics and achieve dynamic design.

Weibull Reliability Analysis in Small Samples Based on LSSVM

Zhang Xinfeng1;Zhao Yan2

2012, 23(16):  1967-1971. 

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Based on LSSVM,a method of improved Weibull reliability analysis was proposed.The parameters
of Weibull distribution and reliability life were analyzed by the Weibull probability paper drawn by MATLAB.The analysis result comparisons were made by LSSVM,SVM and least square method.The numerical results show that the precision of the method based on LSSVM is higher than that of the least square method,and higher than that of SVM.The method based on LSSVM can improve the analysis precision and efficiency in small samples.The reliability analysis based on LSSVM is another choice of Weibull reliability analysis.

Research on Product Design Knowledge Push for Collaboration

JIANG Cui-Qing, LI Bin-Sheng, GAO Jia-Fei, DING Yong

2012, 23(16):  1972-1977. 

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Knowledge push is an important way to improve the efficiency of knowledge acquisitions in collaborative designs of mechanical products.By analyzing the deficiencies of existing researches on design knowledge,knowledge module was firstly introduced to describe the knowledge demand model of the design process,and then a method of updating the knowledge demand model of the design process was proposed.Secondly,a push model of product design knowledge for collaboration was proposed,with the ideas as follows:when a  designer received a design task,the system searched firstly the knowledge modules of knowledge demand model in a way based on emantic extension of
concepts,and then filtered the pushing knowledge according to the designer's knowledge level.Finally,the knowledge was pushed to the designers,thus the purpose of actively providing personalized knowledge service for designers was achieved in the process of product design.

Mechanics Analysis of  Spherical Film Sensitive Component Based on Nano-Newton Force Detection

LEI Tie-Hao, LIU Yong-Hua

2012, 23(16):  1978-1981. 

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In order to realize the precise measurement of  the nN-level micro-force in the industrial technological field,a kind of spherical film,with about 700nm thick and around 50mm in diameter,was used as sensitive component.Distort will be formed when nN-level particles were put on the spherical film.According to the deformation of spherical film,we can get the gravity of the particle.By using the ANSYS software,a mechanics model of the spherical film was built.Adopting the orthogonal experimental method to design some experimental situations,then mechanics analysis of the spherical film was processed in these situations.
And then the experimental results were manipulated by using the least square fitting algorithm that was based on the singular value decomposition.Furthermore,fitting formula was obtained to describe the relationship of deformation,the parameters of spherical film,and the gravity of particles.Comparing the experimental data from situations and the calculating data from fitting formula,we can conclude that when controlling the force in the range of 2~10μN the detecting error will be less than 1%.

#br# Study on Influence of Crowning Parameters on EHL Performance of Cylindrical Rollers

SUN Gao-Xiang-1, GUAN Dian-Zhu-1, HUA Tong-Shu-2

2012, 23(16):  1982-1984,1990. 

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Rollers are usually crowned on their ends in engineering, and the crowning parameters include crowning length and crowning radius.With the multilevel method and Eyring theological model,the effects of the crowning parameters on the lubrication performances were studied. It is concluded that the minimum filmthickness may locate at either the crowning beginning place or the roller edge.When the minimum filmthickness located at the roller edge, lubrication failure would appear.The effects of the crown length and crown radius on the lubrication performance were studied.It shows that the crowning parameters should be designed according to EHL calculation on the basis of working conditions to optimize the lubrication conditions and load distributions and realize full film lubrication. 

Study on Approach to Enhance Precision Fault Tolerance Ability for Spherical Parallel Mechanisms Based on Over-constrained Redundancy Actuation

CHEN Shi, FAN Shou-Wen

2012, 23(16):  1983-1990. 

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The side effects of error sources on the motion precision of a spherical parallel mechanisms were treated as a kind of mechanical system faults,a new concept named precision fault tolerance and its basic idea were presented herein.Degree of precision fault tolerance(DOPFT) was defined as an index for describing the precision fault tolerance ability of the spherical parallel mechanisms. Based on screw theory and over-constrained analysis, m-RRR(m≥4) spherical parallel mechanisms were designed, which had the same kinematic performance with spherical 3-RRR parallel mechanism.Their precision fault tolerance performances were compared via computation of DOPFTs,simulation researches were also conducted. Simulation results show that the fault tolerance strategy based on DOPFT can enhance the motion precision of spherical parallel mechanism and eliminate side effect of error sources on the motion precision of spherical parallel mechanisms effectively.

#br# Finite Element Analysis on Bolted Joints Based on Three-dimensional Accurate Modeling Method

HE Beng-1, 2, LIU Guang-Bi-1, GU Xie-Shui-3, ZHOU Dan-1, HUANG Hai-Hong-1, WANG Yan-1

2012, 23(16):  1991-1996. 

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According to the modeling difficulties and imprecision caused by incomplete thread in the process of finite element analysis for bolt, a spiral modeling method and a simplified three-dimensional axisymmetric modeling method were adopted separately. By comparing the results of stress distribution on each circle of the screws and the maximum of equivalent stress at the roots of the threads calculated from two different numerical models, the reasons for the difference between the two different modeling methods were obtained. The results show that both of the two methods have preferable precision, which ensure accurate analysis of the stress distribution on each node of bolt threads, while the modeling of the spiral modeling method is more difficult. In comparison, the results of the three-dimensional axisymmetric modeling method can reflect the mechanical properties of the axial bolt preferably, and provide the theoretical basis for optimal design of structures.

#br# Study on Constant Power Characteristics of Hydraulic System of Winding Belt Device

WANG Dao-Meng, HOU You-Fu

2012, 23(16):  1997-2000. 

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To study the constant power characteristics of hydraulic system of a winding belt device,a mathematical model for theoretical analysis was established to analyze the impacts of relevant parameters on system performance,then a simulation model was built to discuss the influences of load fluctuation on system pressure,flow and hydraulic pump motor speed.The experimental table was putted up to test the constant power characteristics of the system.The results show that the system has a fairly good constant power characteristics;the simulation model can test the constant power characteristics of the system effectively .Research results herein provide technical support for the improved design of the winding belt device hydraulic system.

#br# Unified Energy Density Design of Trough CPV Collector

SUN Hou-Huan, YANG Mou-Cun

2012, 23(16):  2000-2004. 

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A model of energy concentration ratio about general trough CPV collector was established.The reason why energy density was not uniform was analyzed and how to improve it was discussed.The simulation and analysis results show only small slope of trough collector cross section line can give uniform energy density.Then,a new structure was presented,that is,solar cells were arranged as “V” shape trough.The energy concentration ratio model of new collector was also established.The effects of collector parameters on energy density distribution were investigated.Finally,the new collector parameters were optimized with PSO method.Simulation and optimization results show that standard deviation of new collector energy concentration ratio is less than 30% of general one.

#br# Research on Order of Dominance of Car Fuel Consumption under Complicated Road Conditions Based on GS Theory

ZHANG Gong-1, 2, JIANG Chao-１, YAN Xiao-Lei-１, WANG Shu-Jian-３

2012, 23(16):  2005-2009. 

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The traditional ways based on the statistical method are hard to analyze multi-affect mutually on car's running fuel consumptions under the complicated road conditions.This paper introduced the Grey-system theory into research of multi-affecting factors in car fuel consumptions,analyzed the series factors of the vehicle mass,displacement of engine,the energy-saving techniques when car was running under
complicated road conditions and sequencing the order of dominance about them,which was academically valuable.Tested by theory and laboratory experimental analysis,the way put forward is practical and provides an effective measure for the optimization of car fuel consumption under complicated road conditions.

#br# Research on Operating Characteristics and Driving Method of High-speed On-off Valve in Clutch Starting

JIA Jing-Jing-1, 2

2012, 23(16):  2010-2014. 

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In general pulse width modulation (PWM) signal driven,the high-speed on-off solenoid valve opening and closing time are longer,slower reaction,which affected the high-speed on-off solenoid valve control performance.In order to improve the control performance of the high-speed valve,on the basis of the analyses in the operating characteristics of high-speed on-off valve,a multi-hybrid driving method was designed to shorten the opening and closing time,reduce the pressure fluctuations in pressure control to improve the control performance of  the valve.In vehicle clutch control,the use of the above method can improve the starting performance,and the engine speed is relatively stable,the driven plate speed increasing trend fluctuation is smaller.