Table of Content

30 April 2018, Volume 39 Issue 4

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Contents

2018, 39(4):  0. 

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Paper

Event-triggered Kalman Consensus Filter with Intermittent Measurements and Its Application to the Electro-optical Sensor Network

CHEN Ye, SHENG An-dong, QI Guo-qing, LI Yin-ya

2018, 39(4):  625-634.  doi:10.3969/j.issn.1000-1093.2018.04.001

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This paper focuses on the problem of the too much communication amount of the Kalman consensus filtering (KCF) algorithm in the distributed state estimation. An event-triggered mechanism is proposed to decrease the communication amount among nodes, meanwhile ensuring the estimation accuracy and the consensus of estimated values of each node. The corresponding estimation algorithm is derived. The boundedness of estimated error of the proposed algorithm is also proven. The proposed algorithm is tested in an electro-optical sensor network with intermittent measurements. The result shows that, compared with the classical Kalman consensus filtering algorithm, the proposed algorithm can save the network’s communication resources and ensure the estimation accuracy of each node in the network. Key

Effect of Circlip Constraint on Temperature Field of Multi-disc Clutch

YU Liang, MA Biao, LI He-yan, LI Ming-yang, LI Hui-zhu, SHI Lu-qi

2018, 39(4):  635-644.  doi:10.3969/j.issn.1000-1093.2018.04.002

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In order to investigate the influence of circlip constraint on the contact stress distributions of multi-disc clutch, a 3D finite element model is developed by Abaqus software. The contact stress distribution is obtained by the 3D finite element model, and the temperature distribution is obtained through numerical simulation. The simulated and experimental results show that the concentrated load of circlip results in the uneven distribution of radial contact stress of friction pairs during the clutch engagement process. The closer the friction surface is to the circlip, the larger the contact stress of outer radius of friction surface is, and the more obvious the difference of the radial contact stress is; when the friction pair is away from the circlip, the contact stress gets closer and closer to the piston pressure, and the difference of radial contact stress tends to be ease. The concentrated load of circlip leads to the increase in the radial temperature difference. The temperature in outer radius rises significantly, while the temperature in inner radius increases slowly. Moreover, the temperature fields of friction components in different axial directions are inconsistent, and the friction component near the circlip is more prone to be buckled. The proposed temperature field model is verified effectively by long time, low speed sliding experiments, which can better reflect the actual temperature rise characteristics of the multi-disc clutch.Key

Throttle Slice Opening Size and Damping Characteristics of Cab Damper for Special Vehicles

ZHAO Lei-lei, YU Yue-wei, ZHOU Chang-cheng, LI Xiao-han

2018, 39(4):  645-654.  doi:10.3969/j.issn.1000-1093.2018.04.003

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For cab air suspension of special vehicles, the opening size of the throttle slice is a key issue. A mechanical model of throttle slice is established based on the integrated structure of air spring and damper for a special vehicle cab. The deformation analytic formula of the damping slice is deduced using the principle of elastic mechanics, and is validated through a practical example. The relationship among the slice opening size and the valve parameters is analyzed using the deformation analytic formula. Finally, a piecewise linear simulation model of damper for cab air suspension is built and verified through bench test, and the relative deviations of simulated and experimental damping forces are all less than 6.19%. The results show that the piecewise linear simulation model can truly reproduce the dynamic damping characteristics. Key

Ignition Delay Characteristics of DME/H₂ Lean Mixtures at Low-to-medium Temperature

XU Yong-hong, TONG Liang, SHI Zhi-cheng, ZHANG Hong-guang

2018, 39(4):  655-663.  doi:10.3969/j.issn.1000-1093.2018.04.004

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To investigate the ignition delay characteristics of DME/H₂ mixtures at low-to-medium temperature, ignition delay times of lean DME/H₂ mixtures (hydrogen mole fraction in the fuel mixtures of 0%, 50%, 60%, 70%, and 85%) were measured using a rapid compression machine in the compressed temperature range of 628-858 K at compression pressures of 12-22 bars, the equivalence ratios of 0.30- 1.00, and the hydrogen blend ratio of 0%-85%. A kinetics model is built to simulate the ignition process using finite element software Chemkin-Pro. The results show that the addition of H₂ to DME mixtures leads to a nonlinear increase in ignition delay time. The inhibition effect of H₂ addition is found to be more pronounced at lower compression pressure with H₂ mole fraction of more than 60%. It is also observed that lean DME/H₂ mixtures show three stage heat release behaviors at lower equivalence ratio of 0.30, i.e., the first stage of low temperature heat release (LTHR) and the second stage of high temperature heat release (HTHR), and the third stage of high temperature heat release. Meanwhile, the three-stage heat release behavior becomes weak as the H₂ mole fraction increases. Further chemical kinetic analysis indicates that DME is mainly consumed during LTHR and the first stage of HTHR whereas H₂ is mainly consumed during the second stage of HTHR. Key

Optimization and Resistance Characteristics of Permanent Magnet Eddy Current Damper under Intensive Impact Load

LI Zi-xuan， YANG Guo-lai， SUN Quan-zhao， WANG Li-qun， YU Qing-bo

2018, 39(4):  664-671.  doi:10.3969/j.issn.1000-1093.2018.04.005

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To study and weaken the demagnetization effect of permanent magnet cylindrical eddy current damper on recoil resistance under intensive impact load, the recoil resistance in different number of permanent magnets is determined using permanent magnet equivalent model according to the working principle of the damper. An eddy current damper dynamic model is established to address the demagnetization effect. The influences of magnetic iron, inner and outer cylinder thicknesses on the resistance characteristics are analyzed. A recoil resistance optimization model is established by segmenting the inner cylinder. Optimized Latin hypercube is designed for experiment. Radial basis function neural network and NSGA-II algorithm are used for multi-objective optimization. The results indicate that platform effect of optimized recoil resistance curve is enhanced. The maximal recoil resistances are reduced by 12.6% and 2.3%, respectively, when demagnetization effect and the recuperator force dominate. The proposed optimization method and objects effectively weaken the demagnetization effect of eddy current damper in the recoil process.Key

Characteristic Analysis of Magneto-rheological Fluid Damper Considering Slip Boundary and Inertial Effect

WANG Jia-gang, YU Yong-gang, LIAO Chang-rong, YE Yu-hao

2018, 39(4):  672-680.  doi:10.3969/j.issn.1000-1093.2018.04.006

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In order to satisfy the adaptability of counterrecoil mechanism of cased telescoped ammunition gun to different ammunitions, a magneto-rheoligical fliud (MRF) damper based on multistage annular channel is proposed, which can satisfy the maximum recoil force and reduce the recoil displacement. The magnetic circuit of magneto-rheological energy absorbers (MREA) is analyzed by using the finite element method, and the relationship between the exciting current and the average magnetic induction intensity in the damping channel is obtained. The model parameters of MR fluid under non- and magnetic fields are identified based on the experimental data obtained by an Anton Paar rheometer. The flow differential equations of MR fluid in the buffering channel are established in considering the inertia effect and the boundary slip. The flow velocity distribution of MR fluid is obtained, and the relationship between piston speed and buffering force of damper is deduced. A MREA is fabricated based on the theoretical analysis above, and a drop hammer impact test bench is set up. Impact tests at different impact speeds are carried out, and the experimental data are compared with the theoretically analyzed results. Results show that the velocity distribution characteristics of magnetorheological fluid are similar under the conditions of different inertia effects and slippage boundary, but the peak value of velocity varies. When the boundary slippage coefficient is 0.000 1, the theoretical buffering force of MRF damper is close to the experimental value. Under the impact velocity of 1.55 m/s, the peak value of buffering force is increased by 15 000 N when the current increases from 0 A to 3 A. Under the impact velocity of 1.90 m/s, the peak value of buffering force is increased by 25 000 N when the current increases from 0 A to 4 A.Key

Numerical Simulation and Experimental Study on Optimization of Individual Rocket Burst Height

SUN Tao, ZHANG Guo-wei, WANG Yi-ming, GUO Shuai

2018, 39(4):  681-687.  doi:10.3969/j.issn.1000-1093.2018.04.007

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A finite element model of warhead and a calculation model of ground coordinate of a fragment are established to give full play to the air burst power of antipersonnel warhead, and the dynamic detonation of warhead is numerically simulated by using ANSYS/LS-DYNA software. According to the initial velocity and flying direction of fragments in simulation, the velocity attenuation formula of fragment in air and the 78 J killing criterion of personnel, the coordinates of the effective lethal fragment on the ground are calculated, and the distribution of the effective lethal fragments on the ground targets at different burst heights is analyzed. The results show that the warhead meets the lethality requirements when burst height is about 8 m. The experimental results are in good agreement with the simulated results. Key

Trajectory and Dynamic Simulations of Two-dimensional Trajectory Correction Projectile with Fixed Canards

HAO Yong-ping，CHEN Chuang，ZHANG Jia-yi，PAN Lei

2018, 39(4):  688-697.  doi:10.3969/j.issn.1000-1093.2018.04.008

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To investigate the correction ability of two-dimensional trajectory correction projectile with fixed canards，a dynamics simulation model of two-dimensional trajectory correction projectile is established by using joint simulation of Fluent and Adams. The simulation methods for despinning and attitude determination of canards in the simulation environment are presented based on the correction principle of canards. In the environment of Adams, the direct monitoring of real-time roll angles of canards is achieved by establishing Marker monitoring points on the canard model. The crosswind forces increasing from 1 N to 10 N are simulated，the horizontal deviation is increased by 36.5% to 298.0% relative to no cross wind，and the trajectory correction is simulated under the interference of 10 N crosswind force，0.5° lateral angle of jump and 0.5° angle of jump. The results show that the correction of lateral deflection under the condition of 10 N crosswind force is up to 90% relative to the uncorrected lateral deflection，and the impact lateral and longitudinal deviations under the interference of jump angle can be greatly reduced. The comparison of semi-physical simulation experiment and live firing test shows that the simulation method has some rationality，and can be used in studying and testing the two-dimensional trajectory correction projectile. Key

Damage Effect of Low Velocity Projectile Perforating into Multi-layered Reinforced Concrete Slabs

DAI Xiang-hui, DUAN Jian, ZHOU Gang, CHU Zhe, WANG Ke-hui, GU Ren-hong, LI Ming, YANG Hui, SHEN Zi-kai

2018, 39(4):  698-706.  doi:10.3969/j.issn.1000-1093.2018.04.009

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The damage effect of large-scale projectile perforating into four-layered thin reinforced concrete (RC) slabs is investigated through experiment and numerical simulation. The truncated-ogive-nosed projectile with a mass of 280 kg is launched from a 300 mm diameter balance gun to impact on four-layered thin RC slabs with the unconfined cylinder compressive strength of 41.8 MPa at the striking velocity of 337 m/s. A damage model of thin RC slabs is presented based on the post-test macro-analysis of the damage area of RC slabs, which consists of front and rear craters. The related factors of damage effect are obtained and analyzed in detail. A finite element model is established, and the software LS-DYNA is employed to simulate the perforation process. The numerically simulated and experimentally measured values of residual velocity and kinetic energy consumption are compared, with the maximum deviations of 0.82% and 6.21%, respectively. The simulated results are in good agreement with the experimental results. The proposed finite element model can be used for the performance evaluation of projectile perforating into multi-layered slabs.Key

Study of the Failure Mechanism of Fiber Reinforced Composite Laminates Subjected to Fragment Cluster Penetration and theEquivalent Method for Armor Piercing Ability of Fragment Cluster

LI Dian, HOU Hai-liang, ZHU Xi, CHEN Chang-hai, LI Mao

2018, 39(4):  707-716.  doi:10.3969/j.issn.1000-1093.2018.04.010

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To study the protection design of fiber reinforced composite laminates subjected to fragment cluster penetration, the failure mechanism of fiber reinforced laminates subjected to fragment cluster penetration is studied by using the transient nonlinear finite element, and the failure process and failure mode of fiber reinforced composite laminates under fragment cluster penetration are analyzed, the enhancement effect of fragment penetration ability is clarified, and the influence factors of fragment number, initial velocity and spacing are studied. Based on the above research, an equivalent method of armour piercing ability is proposed. The results show that the penetration ability of fragment cluster is stronger than that of single fragment, and can be equivalent with that of single fragment with increased length, which provides the reference for the armor protection design method of structure when penetrated by fragment cluster.Key

Research on Loading Method of Simulation Ignition Shock Testing for Solid Rocket Propellant at Low Temperature

ZHANG Huai-long, JIAN Xiao-xia, ZHOU Wei-liang, XIAO Le-qin

2018, 39(4):  717-723.  doi:10.3969/j.issn.1000-1093.2018.04.011

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A simulation ignition shock test device with controllable pressure is designed using propellant quenched combustion experimental principle to deal with the structure failure problem of solid propellant at low temperature, which can be caused by the coupling effect of high speed loading. The simulation ignition shock against propellant is made by the gas produced from the combustion of ignition material. The ignition pressure is calculated using the formula of chamber volume and weight of ignition material, and the quenched pressure is controlled by rupture disc. The ignition pressure and ignition mode have great influence on the gas pressurization rate according to p-t and dp/dt-t curves of the ignition shock process. Pressurization rate can be up to 2 000 MPa/s in weak ignition case and 5 000 MPa/s in strong ignition case, which is higher than real motor ignition rate. The pressure is controllable (the pressure deviation is less than ±5%) in repeated experiments. The testing is expected to be used to simulate the ignition shock process for solid propellant at low temperature. Key

Optimization Design of Missile-borne Semi-strapdown Platform Based on Nested Structure of Double Bearing

ZHENG Tao, LI Jie, HU Chen-jun, JIANG Gui-lin, GUO Li-qiang, QIAN Hai-ning

2018, 39(4):  724-730.  doi:10.3969/j.issn.1000-1093.2018.04.012

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In order to further reduce the swing angular rate of the platform and improve the accuracy of the solution in the case that the rotational inertia and eccentricity of platform are unchanged, a double bearing nested structure is proposed to reduce the bearing friction force. The nested structure can be used to achieve the secondary isolation of the missile roll angular rate by the internal and external bearing nesting. The theoretical data of friction moments of double bearing nested structure and single bearing structure are obtained by using the operating principle of semi-strapdown platform and SKF bearing friction force algorithm. It is found that the friction moment generated by the double bearing nested structure is 35.7% of the friction moment of single bearing. The ground semi-physical simulation test is necessary to verify the theoretical analysis. The simulated results show that the swing angular rate and roll error of double bearing nested structure-based semi-strapdown inertial navigation system are 50% less than those of semi-strapdown platform with single bearing structure. Double-bearing nested structure is more conducive to high-precision solution than single-bearing structure. Key

Blind Identification of Turbo Codes on Trellis Termination at High Bit Error Rate

WU Zhao-jun, ZHANG Li-min, ZHONG Zhao-gen

2018, 39(4):  731-742.  doi:10.3969/j.issn.1000-1093.2018.04.013

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In order to overcome the low fault tolerance and high computational complexity of the existing algorithms for identification of code length, frame synchronization, bit rate and other parameters of Turbo codes on trellis termination, a new recognition algorithm with high fault tolerance is proposed. Because the differencing result of two initial code elements of each frame is zero, a new differential sequence analysis matrix can be constructed. The code length can be recognized by changing the columns of the analysis matrix and conducting the specific matrix transformation. The decision threshold of definitized zero and random zero is solved based on the minimax criterion, and then the frame synchronization is identified by traversing the definitized zero. According to the actual project and the coding constraints, the code rate and the number of registers can be identified by traversing their possible values. Simulated results show that the distribution of differential definitized zero positions agrees with the three summarized features, the decision threshold can effectively be used to recognize the definitized zero point, at the same time, the performance of the algorithm in the bit error tolerance is strong, and the recognition rate of various parameters can reach more than 96% when bit error is up to 0.20, besides, the required amount of data symbols and computation complexity is far less than the existing algorithm.Key

Optimization Algorithm for Minimum Exposure Path in Wireless Sensor Networks Considering Maximum Exposure

YANG Ting-hong, FANG Hai-yang, JIANG Da-li, FANG Ling

2018, 39(4):  743-752.  doi:10.3969/j.issn.1000-1093.2018.04.014

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Most of current methods for solving the minimum exposure path in wireless sensor networks do not consider the maximum exposure path. The information of maximum exposure is integrated into Dijkstra algorithm (DA), and a Dijkstra algorithm considering maximum exposure (DAME) is proposed. Then the target guiding self-avoiding random walk with intersection (TGSARWI) algorithm is combined with DAME to build TGSARWI DAME. TGSARWI DAME algorithm can avoid the sections of greater exposures in finding the minimum exposure path. Meanwhile, it can maintain the feature of TGSARWI DA, which can cut computation complexity. Simulated results indicate that TGSARWI DAME can reduce maximum exposure by 14.7%, and get the similar path exposure obtained by the TGSARWI DA with the average relative error of less than 2.2%. TGSARWI DAME is evaluated by comparing it with DA. Although the path exposure increases slightly, the maximum exposure decreases significantly. The proposed algorithm could be applied to the important fields, such as battlefield crossing, in which multiple sensors are deployed.Key

Influence of Process Parameters on Composition and Wear Resistance of Electrodeposited Cobalt Nickel Alloy Plating

YAN Bing-hui， WEI Guang-ning， LI Chen-xia， LI Xue-song

2018, 39(4):  753-762.  doi:10.3969/j.issn.1000-1093.2018.04.015

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The nanocrystalline cobalt nickel alloy plating was prepared on carbon steel surface by using electrodeposition technique. The nanocrystalline and low friction coefficient of cobalt nickel alloy plating materials with good anti-friction properties are obtained by means of ultrasonic dispersion and mechanical stirring. The influences of current density, temperature, pH value and other process parameters on the composition and wear resistance of alloy plating are studied. The microstructure, phase structure and component content of the plating surface are analyzed by using scanning electron microscopy (SEM), field emission scanning electron microscope, and X-ray diffractometer, and UNMT1 micro/nano composite material mechanics testing system is used to investigate micro wear performance of plating. The results show that the alloy plating has fine organization and uniform structure, the process parameters have greater influences on micro friction coefficient of the alloy layer, and the minimum average friction coefficient of alloy plating is 0.18 for the current density of 1.5 A/dm², temperature of 50 ℃, and pH=4.0, and the alloy has good micro friction and wear performance. Key

Experimental Research on Dynamic Shear Behavior of Ultrafine-grained Copper Prepared by Equal Channel Angular Pressing

SONG Peng-fei, DONG Xin-long, FU Ying-qian, SUO Tao

2018, 39(4):  763-771.  doi:10.3969/j.issn.1000-1093.2018.04.016

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The thermal stability of ultra-fine-grained (UFG) copper microstructure prepared by equal channel angular pressing (ECAP) method and its influence on the mechanical properties of the material are studied. The Hopkinson pressure bar and MTS hydraulic servo testing machine are used to test ECAP ultrafine grained copper and annealed pure copper samples under strain controlled loading. The evolutions of its dynamic shear deformation behavior and microstructure are studied by digital image correlation method and the microscopic and XRD analysis of “frozen” recovered samples. The test shows that the ECAP UFG copper has strain hardening characteristics under quasi-static shear loading; the shear stress-strain curve presents strain softening characteristics at high strain rate; and the adiabatic shear dynamic recrystallization zone results in strain hardening rate being negative at high loading rate. The recrystallization temperature of ultrafine grained copper calculated by plastic work is only 325 K. Therefore, the adiabatic shear instability of ultrafine grained copper at high strain rate is easy to occur. Key

Research on the Quality Control Factors of Special-shaped Surface in Solid-liquid Two-phase Abrasive Flow Polishing

LI Jun-ye， ZHOU Zeng-wei， ZHANG Xin-ming， ZHOU Li-bin

2018, 39(4):  772-779.  doi:10.3969/j.issn.1000-1093.2018.04.017

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In order to study the effectiveness of polishing a special-shaped surface with abrasive flow，the standard k-ε model and SIMPLEC algorithm are used，the polishing of rifled tube with polygonal spiral surface by the solid-liquid two-phase abrasive flow at different inlet pressures is numerically simulated to obtain the variations of dynamic pressure，turbulent kinetic energy and turbulent intensity at the near wall surface of polygonal spiral surface with the inlet pressure，and the effect of inlet pressure on the polishing quality of surface is explored. The solid-liquid two-phase flow polishing test is made to verify the accuracy of numerical analysis，and the morphologies of inner surface of rifled tube before and after the processing are detected. The results show that the surface roughness can be effectively improved by the solid-liquid two-phase abrasive flow，the texture of inner surface becomes smoother，its surface topography is ideal，and the surface roughness decreases from 1.450 μm to 0.296 μm after polishing; with the increase in inlet pressure，the surface textures of irregular surface parts after abrasive flow polishing are more compact，and the surface quality is improved obviously. Key

Research on Collision Detection in Ultrasonic Automatic Testing of Rotary Assembly

WANG Xuan-run， NI Pei-jun， YI Bing， LI Xiong-bing

2018, 39(4):  780-786.  doi:10.3969/j.issn.1000-1093.2018.04.018

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In order to solve the collision in the detection process of robotic ultrasonic automatic detection system, the ultrasonic detection system is divided into collision and stationary bodies, and the collision detection algorithm based on the distance field is introduced. Based on the kinematics equation of robot, the collision detection is carried out in the virtual environment of the ultrasonic automatic detection system, and the anti-collision detection of the system during the detection process of magnesium alloy shell is realized. The variation law of the shortest distance between the stationary body and the collision body is analyzed by comparing the detected results of different scanning parameters, and the ultrasonic detection process optimization of magnesium alloy shell is realized. The experimental results show that the improved algorithm can improve the efficiency of collision detection by 80.62%, which can meet the requirements of collision efficiency during ultrasonic testing of magnesium alloy shell and guarantee the same precision as the traditional distance field detection algorithm at the critical position.Key

Design of Military Wheel-leg Hybrid Quadruped Robot

QU Meng-ke， WANG Hong-bo， RONG Yu

2018, 39(4):  787-797.  doi:10.3969/j.issn.1000-1093.2018.04.019

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A military wheel-leg hybrid quadruped robot is developed, which can move by the dynamic driving wheels on the road without being damaged at high speed, and can walk by stepping alternately in the ruins with its mechanical legs, and can skate on a flat road by the wheels without dynamic driving. The robot can walk at the maximum speed with the minimum energy consumption. A new type of metamorphic mechanical leg based on the 3-PUPS parallel mechanism is proposed, and its kinematic analysis is done. The effects of dimension parameters of 3-PUPS mechanism on its kinematic and static evaluation indexes are analyzed by defining performance evaluation indexes. A set of the structural parameters of mechanical leg is selected, and an experimental prototype of mechanical leg is developed. A general mechanism model of wheel-leg hybrid quadruped robot is established, and the relationship among robot's parameters and its kinematic and static evaluation indexes is revealed. A set of structural parameters of wheel-leg hybrid quadruped robot is selected, and the overall design of wheel-leg hybrid quadruped robot is completed. The pose of mechanical leg experimental prototype is measured using a special robot calibration system. Experimental results show that the maximum error of mechanical leg motion platform along x axis is 0.041 mm, the maximum error along y axis is 0.040 mm, the maximum error along z axis is 0.040 mm, the maximum error of the attitude angle around z axis is 0.041°, the maximum error of attitude angle around y axis is 0.043°, and the maximum error of attitude angle around x axis is 0.045°. The experimental prototype of mechanical leg meets the design requirements.Key

Simulation Analysis on the Stress and Fatigue Life of a Special Equipment's Wire Rope

DU Wen-zheng, MA Bao-zhu, CAO Da-zhi

2018, 39(4):  798-809.  doi:10.3969/j.issn.1000-1093.2018.04.020

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The stress and fatigue life of 6×36 WS wire rope of a special equipment under axial tension and the bending state around the pulley are studied to analyze the stress distribution and fatigue failure of steel wire rope during the working process. A finite element model of the steel wire rope is established，and the stress distribution under the axial tension and the bending state around the pulley are simulated and analyzed. Then the fatigue test of the steel wire is carried out to obtain the fatigue life data. Based on the fatigue data of the steel wire and the finite element analysis results of the rope，the fatigue life simulation analysis of the wire rope is carried out according to Miner linear accumulated damage theory. The results show that the stress of steel wire rope is larger in the contact areas of the adjacent wires and rope strands, and the contact area between wire rope and pulley. The greater the stress is，the shorter the fatigue life is. Key

Research on Nonlinear Analysis Method of a New Flexible Pavement

LI Lin, BAI Bin-sheng, CHENG Ying, MEI Zhi-yong

2018, 39(4):  810-815.  doi:10.3969/j.issn.1000-1093.2018.04.021

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In order to predict the static mechanical performance of flexible pavement laid on swampy ground under vehicle load, Duncan-Chang constitutive model is selected to simulate the nonlinear elastic properties of ground soil. The flexible pavement is simplified as a mechanical model of membrane-beam element, and the large deformation and contact nonlinearity of flexible pavement are also consisted. A nonlinear analysis model of flexible pavement structure is established by using the finite element analysis software ABAQUS, and the deformation and internal force response of the flexible pavement under load are obtained. The numerical analysis result is verified with the load test result. The result shows that the nonlinear analysis method of flexible pavement structure based on Duncan-Chang constitutive model can meet the requirements of engineering analysis. Key

Analysis of Plate Non-parallelism Error of Capacitance Displacement Sensor in Thrust Measurement of Space-borneMicro-thruster

WANG Da-peng, JIN Xing, ZHOU Wei-jing, LI Nan-lei

2018, 39(4):  816-824.  doi:10.3969/j.issn.1000-1093.2018.04.022

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The plate non-parallelism error of capacitance displacement sensor is studied to improve the thrust measurement accuracy of space-borne micro-thrusters. The relation between the plate non-parallelism error and variable torsional angle is analyzed by taking a typical torsion balance for example. Based on the property of that the plate non-parallelism error and width cosine error are all independent of the direction of torsional angle, a calibration method is presented, and an experimental instrument is designed. A sensor with range of 1 mm and effective radius of 3.5 mm is calibrated with an increment of 0.5°, and the deviation between the non-parallelism error and its theoretical value is 17.4%. The calibrated results show that the measured thrust error derived from non-parallelism error is rapidly increased to 3.25% when the steady-state torsional angle gets close to the maximum negative angle; and it is gradually increased to 0.04%, corresponding to the measured thrust error of 0.1 μN, when the steady-state torsional angle gets close to the maximum positive angle; the effective radius of plate is not more than 7 mm when the measured thrust error is less than the order of magnitude of μN.Key

Walking-aid Robot for Rehabilitation of Person with Disabled Lower Limbs

QIAO Yu， MU Yu， LYU Yun-qi， GAO Xue-shan

2018, 39(4):  825-832.  doi:10.3969/j.issn.1000-1093.2018.04.023

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A walking-aid robot is designed for rehabilitation training of person whose is lower limbs are disabled. The robot is characterized by high security, high intelligence and friendly man-machine interaction. The structure of the robot is presented,and the trajectory of the robot is obtained by analyzing its kinematics and dynamics. The motion control systems for straight walking and turning of robot are set up based on the mathematical model.The ergonomics and appearance design of the robot are studied to achieve the combination of function and appearance. The feasibility and effectiveness of the walking-aid robot is demonstrated through simulation experiments.Key