Table of Content

28 November 2014, Volume 35 Issue 11

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Paper

The Design of Auto Clutch Control System for Heavy-duty off-road Vehicles

MIAO Cheng-sheng, ZHAO Yi-nong, LIU Hai-ou, XI Jun-qiang

2014, 35(11):  1729-1735.  doi:10.3969/j.issn.1000-1093.2014.11.001

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A set of automatic clutch control system is designed based on the operating characteristic and structure analysis of heavy-duty off-road vehicle clutch and gas power type hydraulic control mechanism. The functional requirements of automatic separating, engaging and maintaining of the clutch are realized. The system has the function of clutch emergency manual control to ensure the battlefield survivability of heavy-duty off-road vehicles. The collaborative optimization method is used to design the oil cylinder, which is the core component of the automatic operation control. In order to obtain the characteristics of the designed automatic clutch control system, a test bench is designed to test the separation, joint and fixed-point control. The test results show that the response speed and control precision can meet the operating requirement.

Anlysis of Rifling Land Damage Mechanism of Gun Barrel

ZENG Zhi-yin, MA Ming-di, NING Bian-fang, GAO Xiao-ke

2014, 35(11):  1736-1742.  doi:10.3969/j.issn.1000-1093.2014.11.002

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In the live firing of a large caliber gun, a fracture damage was found on the bilateral edge of the lands in an initial segment of barrel. In order to reveal the fault reason and take measure to avoid the recurrence of this fault, a nonlinear finite element analysis model of coupling system formed by barrel and projectile is established based on dynamic nonlinear finite element method. Several influence factors, such as inaccurate bullet loading, initial loading angel, inhomogeneous friction and gap between barrel and bullet, are taken into account synthetically for dynamic response analysis of the coupling system. The influence of impact loading caused by the inaccurate bullet loading on the dynamic behavior of barrel material is investigated. The results show that the equivalent stress caused by projectile in the engraving process of bullet in the initial segment of barrel is already close to the yield limit of barrel material, the impact force between the bearing band and barrel is increasesd by 3.7 times due to the inaccurate loading, and the dynamic fracture toughness of the barrel material is decreased by 35.6%, resulting in a fracture damage on the bilateral edge of lands in the initial segment of barrel. The phenomenon of rifling land damage is recurred in the test of living firing.

Research on Assessment Method for Sensible Gun Recoil

WANG Chang-geng， XU Wan-he， XU Cheng

2014, 35(11):  1743-1749.  doi:10.3969/j.issn.1000-1093.2014.11.003

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Based on the feelings of shooter during shooting, the gun recoil, recoil pressure, impulse of gun acting on shooter, and the acceleration, velocity, displacement of shooting are analyzed. The evaluation factors and evaluation function of sensible gun recoil are ascertained, and the evaluation concept of sensitivity threshold and sensitive recoil impulse is proposed by the method. A new multi-factor evaluation method of sensible gun recoil is proposed. The recoil physical quantity characteristics of Type 79 and 85 submachine guns are analyzed. The analysis result shows that the evaluation method could comprehensively and quantitatively describe the strength of sensible gun recoil.

Effect of Nitration System and Temperature on Nitration Uniformity of Nitrocellulose Fibers

ZHANG Yun-hua, WANG Fei-jun, WANG Wen-jun, SHAO Zi-qiang, LI Jia, GAO Ke-zheng

2014, 35(11):  1750-1755.  doi:10.3969/j.issn.1000-1093.2014.11.004

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The nitrocellulose is synthesized by nitrating the cotton linter with HNO₃/H₂SO₄/H₂O or HNO₃/CH₂Cl₂ as nitration agent. The nitrogen content and its distribution (uniformity of nitration) of nitrocellulose are analyzed by a polarizing microscope. The influences of the components of nitration system and nitrification temperature on the nitrogen content and uniformity of nitrocellulose are studied. The nitrogen content of nitrocellulose obviously decreases with the increase in water content in HNO₃/H₂SO₄/H₂O. The uniformity of nitrocellulose would be improved if the water content increases appropriately. Mixed acids with high sulphuric acid content is employed to give a material of high nitrogen content but bad uniformity. With the increase in HNO₃ content in HNO₃/CH₂Cl₂, the uniformity of nitrocellulose is improved firstly, and then is declined before unchanging. The uniformity of nitrocellulose is improved with the increase in nitration temperature which is conducive to the diffusion of esterification reagents.

The Preparation and Thermal Decomposition Performance of Fullerene Hydrazine Nitrate

GUAN Hui-juan, JIN Bo, PENG Ru-fang, ZHAO Feng-qi, HAN Wen-jing, CHEN Bai-li, CHU Shi-jin

2014, 35(11):  1756-1764.  doi:10.3969/j.issn.1000-1093.2014.11.005

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A new potential energetic combustion catalyst, fullerene hydrazine nitrate, is prepared via a two-step process, in which fullerene hydrazine is prepared with fullerene and hydrazine hydrate, and then fullerene hydrazine reacts with concentrated nitric acid to form fullerene hydrazine nitrate. The chemical structures of products are characterized by FT-IR, UV-visible spectra, elemental analysis and X-ray photoelectron spectroscopy. The thermal stability of fullerene hydrazine nitrate is characterized by differential thermal analysis (DTA) and thermogravimetry analysis (TGA). The results indicate that the product shows a certain thermal stability in dynamic air atmosphere. The thermal decomposition behaviours of RDX and HMX in the absence and presence of fullerene hydrazine nitrate are investigated by using DTA method. The research results show that fullerene hydrazine nitrate can accelerate obviously the decomposition of RDX and HMX. The peak temperatures of the exothermal decomposition are reduced at the different heating rates of 2.5, 5, 10 and 20 ℃/min. The corresponding activation energy of RDX is decreased by about 17 kJ/mol, and that of HMX is reduced by more than 20 kJ/mol.

Multi-frame Iteration Blind Deconvolution Algorithm Based on Improved Expectation Maximization for Adaptive Optics ImageRestoration

ZHANG Li-juan， YANG Jin-hua， SU Wei， JIANG Cheng-hao， WANG Xiao-kun， TAN Fang

2014, 35(11):  1765-1773.  doi:10.3969/j.issn.1000-1093.2014.11.006

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To improve the effect of adaptive optics image restoration, a deconvolution algorithm based on the improved expectation-maximization (EM) algorithm is proposed according to the EM theory. A mathematical model for degenerating the multi-frame adaptive optics images is built. The point spread function (PSF) model changed over time based on phase error is deduced. The AO images are de-noised using the image power spectrum density and the support constraints. The EM algorithm is improved by combining the AO imaging system parameters and regularization technique. A cost function for the joint-deconvolution of multi-frame AO images is given, and an optimization model for their parameter estimation is built. The image-restoration experiments of the analog images and the real AO images are performed to verify the image restoration effect of the proprosed algorithm. The experimental results show that, compared with the Wiener-IBD or RL-IBD algorithm, the iterations of the proposed algorithm is decreased by 14.3%, and its estimation accuracy is significantly improved. The model distinguishes PSFs of the AO images and recovers the observed target images clearly.

Research on Disturbance Rejection Rate Parasitic Loop and Its Dynamics Effect of Strapdown Imaging Seeker

ZHENG Duo， LIN De-fu， SONG Tao， QI Zai-kang

2014, 35(11):  1774-1782.  doi:10.3969/j.issn.1000-1093.2014.11.007

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The disturbance rejection rate parasitic loop in strapdown imaging seeker is analyzed, and the guidance loop reflecting different internal dynamics structure and the model of disturbance rejection rate parasitic loop are established. The effects of time-to-go, different internal dynamics and time delay of seeker on the stability region of disturbance rejection rate parasitic loop are studied. Based on dimensionless adjoint function method, the effects of disturbance rejection rate and different internal dynamics on the proportional guidance system are also studied. The results show that the positive feedback stability region of disturbance rejection rate parasitic loop is affected by time-to-go, and the negative feedback stability region is affected by internal dynamics. The stability of parasitic loop caused by phase lag is mainly affected by the time delay of seeker. The effect of disturbance rejection rate positive feedback on proportional guidance system is more significant than that of the negative feedback. Miss distance increases with the increase in disturbance rejection rate. The internal dynamics structure of guidance system affects the guidance precision.

Research on Influence of Selected Factors on Burning Rate of Polyethylene in Solid Fuel Ramjet

CHEN Xiong， CHENG Hong-gang， ZHOU Chang-sheng， ZHU Guo-qiang

2014, 35(11):  1783-1789.  doi:10.3969/j.issn.1000-1093.2014.11.008

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Numerical simulation and direct test methods are used to research the influence of selected factors on the burning rate of polyethylene in a solid fuel ramjet. The influences of air mass flux and fuel internal diameter on average burning rate and local average burning rate are studied. The relationship between reattachment length ratio and step height ratio is analyzed. The results show that the average burning rate of the fuel is increased by power function with the increase in air mass flux, and decreased by power function with fuel internal diameter. The difference between simulation and experimental results is caused by the ignition process and the computational accuracy of turbulent combustion model to predict the heat transfer behind a sudden expansion step. The reattachment length ratio increased by liner function with step height ratio.

A Disturbance Observer-based Inhibition Method for Disturbance Rejection Rate of Seeker

XU Jiao, WANG Jiang, SONG Tao， HU Kuan-rong

2014, 35(11):  1790-1798.  doi:10.3969/j.issn.1000-1093.2014.11.009

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The disturbance rejection rate (DRR) of seeker has the effect on the output accuracy of seeker and the guidance performance.An online inhibition method based on disturbance observer is proposed for the problems of the guidance precision of missile caused by DRR. The errors of seeker models, the output frequency of detector and the effect of measurement noise on DRR inhibition are presented. The result shows that the spring torque and the damping torque are the main factors of the DRR generation, and the missile guidance precision would be reduced. The online inhibition method based on disturbance observer can inhibit DRR effectively; but the errors of seeker models, the output frequency of the detector and the measurement noise reduce the inhibition effects to some extent.

Research on the Noise Characteristic of Pulse Detonation Engine with Nozzles

XU Gui-yang， WENG Chun-sheng， LI Ning

2014, 35(11):  1799-1804.  doi:10.3969/j.issn.1000-1093.2014.11.010

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As an effective approach to improve the thrust performance, the nozzle plays an important role in the control of formation and propagation of pulse detonation engine noise. The experimental system of pulse detonation engine is set up to investigate the formation and control method of detonation noise. The detonation noise characteristic of pulse detonation engine with three nozzles is studied. The results show that the convergent-divergent nozzle has the most significant influence on pulse detonation engine noise to reduce the noise amplitude by 77.13% in 0 ° direction and at 3 000 mm. Large convergence angle would lead to obvious directivity for convergent nozzles. The obvious directivity would be also obtained by divergent and convergent-divergent nozzles with small exit area. The convergent-divergent nozzle with 48 mm throat diameter and the divergent nozzles with 280 and 320 mm exit diameters have the significant impact on reference radius which is reduced from 1 600 mm to 800 mm . The results are of great significance for studying the mechanism of detonation noise and expediting the process of the engineering application.

Research on Distribution of Flow Field in Launching Canister with the Effect of Nozzle Closure

YU Shao-zhen, JIANG Yi, ZHOU Xiao-fei, NIU Yu-sen, SUN Lu-lu

2014, 35(11):  1805-1812.  doi:10.3969/j.issn.1000-1093.2014.11.011

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The overpressure of shock wave is widely used in opening the launching canister. In order to study the formation of shock wave and its effect on the fragile lid with a nozzle closure, a simulation model is established by using a numerical method, in which a dynamic mesh technique is used to update the meshes of flow field. The simulation results are verified with the experimental results. The formation process of jet flow is shown clearly and the changing curves of the overpressure on the back lid with time are obtained from the analysis results. The research results show that the overpressure of shock wave forms on the nozzle closure and then impact the fragile lid. The gas converges from the edge of nozzle closure to the center to form a mainstream. The effects of the mainstream and the shock wave on the back fragile lid are obviously different in impact time and position. The back fragile lid is brittlely deformed under the action of overpressure of shock wave. In the projection area of the nozzle closure, the instantaneous peak first reaches to the maximum value of 5×10⁵ Pa.

Influence of Air Lift on the Stability of Passive Partial Strapdown Platform

DUAN Xiao-min, LI Jie, LIU Jun

2014, 35(11):  1813-1819.  doi:10.3969/j.issn.1000-1093.2014.11.012

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The passive partial strapdown platform which installs in rolling projectile works in the principle of compound pendulum movement under the action of gravity. Projectile flies under the action of air lift, consequently the acceleration in the vertical direction of projectile changes with the change in the lift. Accordingly the restoring torque of the platform cylinder’s equivalent compound pendulum changes, and the stability of the platform would be affected. To research the influence of air lift on the stability of passive partial strapdown platform, the mechanical analyses of the projectile and passive partial strapdown platform cylinder are fulfilled, and the differential equation of motion of the platform’s inner cylinder is established and solved. The stability of passive partial strapdown platform under the action of air lift is simulated. The results show that the larger the air lift is, the more stable the partial strapdown platform is. And when the air lift is less than 0.005 75m_pg (m_p is weight of projectile, and g is acceleration of gravity), the passive partial strapdown platform is unstable. The semi-physical simulation test is done in the three-axis high speed turntable. The dynamic model is proved by the test.

Cruise Missile Path Planning Based on Improved Quantum Evolutionary Algorithm

ZHANG Lei， FANG Yang-wang， CHAI Dong， YONG Xiao-ju

2014, 35(11):  1820-1827.  doi:10.3969/j.issn.1000-1093.2014.11.013

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For the low efficiency of cruise missile path planning, a novel path planning algorithm is proposed based on improved quantum evolutionary algorithm (IQEA). The search space is constructed based on path constraints, and the criteria of path estimation are presented. Probabilistic representation quantum chromosome is introduced to represent all the feasible solutions probabilistically to solve the premature problem. The genetic algorithm is used for reference, and the breeding strategy is introduced to IQEA. The dynamic quantum rotation gate is used to update the chromosomes to realize a good balance between local and global searches . Simulation results show that IQEA with breeding strategy can generate flight path with lower cost rapidly and steadily.

Location of Acoustic Emission of Ceramics Fracturing

CHU Liang, REN Hui-lan, LONG Bo, NING Jian-guo

2014, 35(11):  1828-1835.  doi:10.3969/j.issn.1000-1093.2014.11.014

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AE (acoustic emission) parameter analysis method is considered in the research on ceramics fracturing, but the position of cracks in ceramics is impossible to be located using the method. The initial value selection of Geiger algorithm is optimized. The algorithm is verified by 2-dimensional and 3-dimensional location experiments, and the location accuracy is analyzed according to the experimental results. The average location error of acoustic emission source on a 200 mm×200 mm² flat plate is 1.641 mm, and that on a 50 mm×50 mm×100 mm cube is 3.47 mm. The reasons of the error mainly include the properties of material, the accuracy of acoustic emission testing system and the location algorithm. Lots of microcracks occur and grow in a typical brittle material, such as ceramics, during loading, resulting in acoustic emission (AE).Through the compression test and 3-dimensional locating detection of AD95(95%) alumina ceramic specimens, the acoustic emission characteristics are achieved and the positions of cracks are located by the optimized Geiger algorithm. The location result is in accordance with the actual fracture position, and the formation and propagation of cracks in ceramics can be analyzed by the method.

A Cooperative Navigation Approach and Its Verification of USVs with Leader-fellower Structure

XU Bo, XIAO Yong-ping, GAO Wei, LIU Ya-long, YANG Jian

2014, 35(11):  1836-1845.  doi:10.3969/j.issn.1000-1093.2014.11.015

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The cooperative navigation and localization technology of multi-USVs is an important way to solve the navigation problem in complex environment. For the cooperative navigation and localization of multi-USVs with leader-follower structure, a state space model of cooperative localization is built, and then a linear model is obtained by expanding the nonlinear model around filter value. An extended Kalman filter is designed to fuse the sensor information to locate the slave USV in real time. At last, the relationship among USV distances, angle and accuracy is researched, and the observability analysis of cooperative navigation filter algorithm is done with Lie algebra. The results show that the navigation accuracy is improved effectively by controlling the variations of distances and angles of leader and slave USVs between two adjacent moments, which is verified by simulation and experiment.

Research on Simulating Method of Different Blast Waves

ZHOU Jie, TAO Gang, ZHANG Hong-wei, PAN Bao-qing

2014, 35(11):  1846-1850.  doi:10.3969/j.issn.1000-1093.2014.11.016

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A method to acquire different blast waves is proposed. The geometrical models of the loading area of shock wave and air basin are established using SolidWorks, and then are divided to the structured grids by using Hypermesh. Material parameters and equation of state are assigned to the model. The curve of internal energy per unit volume and time is calculated with FORTRAN program and revised with the modified formula, then imported into the loading area of shock wave. The required shock wave is acquired by use of finite element program LS-DYNA. The proposed method can used to simulate the dif-ferent blast waves with error of 1.0%. The method provides an effective route for research on blast injury.

Research on Attitude Estimation of Micro UAV Based on Sparse Line Optical Flow Field

GUAN Zhen-yu，LI Jie, YANG Huan, XU Bei-bei, LIU Chang

2014, 35(11):  1851-1859.  doi:10.3969/j.issn.1000-1093.2014.11.017

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A method to estimate the attitude of micro UAV based on the sparse line optical flow field is proposed according to the requirements for UAV vision-based navigation system.The concept of sparse line optical flow field of images is described, and an algorithm of sparse line optical flow field is presented. A new method to estimate the attitudes of micro UAV, including pitch rate, roll rate and yaw rate, is proposed based on the sparse line-optical flow field and the established horizon projection model. The proposed method and the classic Horn algorithm are used to numerically simulate a group of test images for calculating the optical flow field. The results show that the proposed method has the same calculation accuracy as the classic Horn algorithm, while the calculating time-cost of the former is only 6% of Horn algorithm. Taking an aerial image sequence as test samples, an off-line simulation is conducted to verify the method of UAV attitude estimation based on sparse line-optical flow field. The information calculated with the measured values of angular velocity gyro on UAV is compared. The comparative result shows that the proposed method is efficient for estimation of pitch, roll, and yaw rates of UAV. The calculated error of pitch rate is less than ±10(°), while the errors of roll and yaw rates are less than ±5(°)/s .

Design and Analysis of a High-g Capacitive Micro-machined Accelerometer

TAO Yong-kang， LIU Yun-feng， DONG Jing-xin

2014, 35(11):  1860-1866.  doi:10.3969/j.issn.1000-1093.2014.11.018

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A kind of high-g capacitive micro-machined accelerometer with comb structure is proposed for the special demand of high-g acceleration test. It is an in-plane sensitive accelerometer with area-variable differential capacitance. The natural frequency, transverse effect, measuring range and acceleration sensitivity of sensor are designed and analyzed. Simulation results show that, the measuring range of the designed accelerometer is 200 000 g with the acceleration resolution of better than 60 g in 0-10 kHz bandwidth; its natural frequency is 266.2 kHz , and the modal separation ratio is more than 2.5. It is fabricated by silicon-on-glass MEMS technology. The test and the primary shock experiment of sensor are performed. Compared with the existing high-g micro-machined accelerometers, the designed accelerometer has good linearity, small transverse effect, high acceleration sensitivity and strong ability to resist high overload.

Research on Cushioning Characteristics of UAV Soft Landing Airbags

CAI Wen, LI Bin, WEN Jin-peng, WANG Li

2014, 35(11):  1867-1875.  doi:10.3969/j.issn.1000-1093.2014.11.019

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For an unmanned aerial vehicle (UAV) with high-mounted wings, a simplified analytical model is established to analyze the cushioning characteristics of a soft landing airbag system and determine the initial design parameters of the soft landing airbags. A finite element model is established and a series of simulations are conducted to analyze the influence of design parameters and landing attitude angle on cushioning characteristics. Numerical results show that the results obtained by FEM and the analytical model are the same, but the errors of impact response values calculated by two models are still 5%~12.5% because of the introduction of some assumptions in the analytical model; and the existence of initial landing attitude angles makes the pitch and roll motions of UAV much worse in the later stage of landing process, so that the rigid impact occurs easily. However, a vented airbag system is incapable of avoiding the local damage caused by the rigid impact. The study also shows that the proposed hybrid airbag scheme can provide a reliable soft support in the later stage of soft landing process and reduce the risk of suffering the rigid impact.

Analysis of Structural Reliability Sensitivity Based on Dimensionality Reduction and Visualization Technique

LI Hao-chuan, SUN Zhi-li , WANG Hai

2014, 35(11):  1876-1882.  doi:10.3969/j.issn.1000-1093.2014.11.020

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For the implicit reliability problem with multiple dimensions, the reliability sensitivity of structure is analyzed by applying the dimensionality reduction and visualization technique. The design point is found based on iHLRF method, and the step size of finite difference is determined according to the modeling computational precision. The plane is divided into two parts of safe domain and failure domain by a straight line, and the final position of the straight line is determined by calculating the responses corresponding to several data points nearby its initial position. The dimensionality and nonlinearity do not affect the accuracy of the proposed method, which also has relatively high efficiency. Finally, the reliabilities of two structural systems and the reliability sensitivities of various influencing factors are calculated, which provides a theoretical basis for designing the structural systems. The examples show that these theories and formulas are rational and efficient.

Dynamic Evaluation Methods for Equipment Technical Condition Based on Multi-dimensional Characteristic Parameters

WANG Shao-hua, ZHANG Yao-hui, HAN Xiao-hai

2014, 35(11):  1883-1890.  doi:10.3969/j.issn.1000-1093.2014.11.021

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According to the fact that current condition evaluation models lay more emphasis on the static observations of characteristic parameters and less on trend information inherent in sequential observations, a new condition evaluation model with static and dynamic evaluations is proposed. For the weighting of multi-dimensional characteristic parameters, a mutative scale chaos algorithm is applied to achieve optimal objective weighting, and a static condition evaluation model is established. Based on static evaluation, a “distance” which measures real-time deteriorating speed and standard deteriorating speed is opted to modify the static evaluation result. NSD-WKFCM (neighbor sample density weighted kernel fuzzy C-means) clustering algorithm is used to solve standard vector of deteriorating speed. A dynamic adjusting function based on “distance” combined with its parameter optimization algorithm is proposed, and the complete dynamic condition evaluation model is established. A case study is performed to verify the effectiveness of the model.

Investigation of Ultrasonic Elliptical Vibration Milling of Thin-walled Titanium Alloy Parts

JIANG Xing-gang, LIANG Hai-tong, LU Hui-min, DAI Jian-dui, ZHANG De-yuan

2014, 35(11):  1891-1897.  doi:10.3969/j.issn.1000-1093.2014.11.022

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An ultrasonic elliptical vibration milling (UEVM) method is proposed for low precision and large cutting force in milling of thin-walled titanium alloy part. The equation set of ultrasonic vibration milling tool tip trajectory is given. The linear speed characters of tool nose and the mechanism of cutting force reduction are analyzed. In the experiment of comparing milling with regular milling (RM) with an ultrasonic elliptical vibration milling cutter shank system which is self-developed, it is proved that the ultrasonic elliptical vibration milling has outstanding characteristics in reducing the cutting force, restraining tool offset and improving the precision. The possible reasons causing these characters are also given. Because of its excellent features, the ultrasonic elliptical vibration milling could be a new way to solve the problem in milling thin-walled titanium alloy part.

Research on Power Consumption Characteristics of Double-row Tapered Roller Bearings

DENG Si-er, HU Guang-cun, DONG Xiao

2014, 35(11):  1898-1907.  doi:10.3969/j.issn.1000-1093.2014.11.023

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Based on the dynamic theory of rolling bearings, the nonlinear dynamic equations and friction power consumption mathematical models are established for double-row tapered roller bearings. Fine integral method and predict-correct Adams-Bashforth-Moulton multi-step method are used to solve the equations. The influences of different working conditons, structural parameters and process parameters on bearing friction power consumption are analyzed. The results show that the friction power consumption increases slowly and then linearly increases with the rise in capsized moment and rotating speed. The rotating speed has an obvious effect on friction power consumption, and a lower speed should be selected as much as possible under the premise of meeting the operating requirements. The increase in lateral load ratio makes the friction power consumption of impacted side increase and the friction power consumption of unfixed side decrease. The difference of friction power consumptions of the two sides increases. The bearing friction power consumption increases with the rise in big rim angle, and decreases with the increase in curvature radius of roller end surface. For the odd waviness orders of rollers, the friction power consumption of bearing firstly increases and then decreases with the increase in the waviness amplitude; for the even orders, the friction power consumption of bearing increases with the rise of the waviness amplitude.

Accelerated Thermal Cycling Test and Failure Analysis of Electrical Connectors

LUO Yan-yan, WANG Zhen, LI Xiao-ning, LIU Lei

2014, 35(11):  1908-1913.  doi:10.3969/j.issn.1000-1093.2014.11.024

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The rapid development of space technology has put forward higher requirements for electrical connector reliability. The reliability issues of electrical connectors under thermal cycling conditions are presented. A thermal cycling test scheme combined with the accelerated life test theory is proposed for electrical connectors. The accelerated thermal cycling test is carried out. It is found that the value of contact resistance increases slowly with the number of thermal cycles. The extrapolated value of thermal cycling life is calculated by gray model. Finally, the failure analysis on the jack of typical samples is illustrated. It is indicated that the crystal size rises, the fragmentation degree of the sub structure and the dislocation density increase, and there is more β′phase appearing in the jack of samples after test. The result shows that the change of microstructure is the fundamental reason for the stress relaxation phenomenon of jacks and the contact reliability degradation of electrical connectors.

Fault Diagnosis of Tiltrotor Aircraft via Improved Discrete Wavelet-OMELM

YAN Feng, CHEN Xiao, WANG Xin-min, PENG Cheng, HU Ya-zhou

2014, 35(11):  1914-1921.  doi:10.3969/j.issn.1000-1093.2014.11.025

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An improved discrete wavelet-optimization method-based extreme learning machine (OMELM) algorithm is presented for the fault diagnosis of flight control system in tiltrotor aircraft. An adaptive heuristic wavelet denoising method is used to denoise the sampled signal. Feature vector of each layer is extracted using Parseval energy after the discrete wavelet decomposition of fault signal. The energy feature is normalized as the improved OMELM network input, and then the actuator fault models is classified using the improved OMELM network. Finally, an XV-15 tiltrotor aircraft mode is validated by simulation. The results show that the method has a higher average recognition rate, and needs a short diagnosis time.

Research Notes

Adaptive Robust Control of Rotational Chain Shell Magazine

ZOU Quan, QIAN Lin-fang, XU Ya-dong, JIANG Qing-shan, LIU Yan-hui

2014, 35(11):  1922-1927.  doi:10.3969/j.issn.1000-1093.2014.11.026

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An adaptive robust control scheme with integral sliding surface is proposed for the precision position control of the rotational chain shell magazine. The integral operation sliding surface is embedded into the traditional adaptive robust control, and the steady state position tracking error is reduced. Constant robust feedback gain is replaced by nonlinear robust feedback gain, and the transient performance is improved. Mathematical analysis shows that the proposed control scheme can achieve better transient performance and has smaller steady state position tracking error. Simulation results in three conditions (empty-loading, half-loading and full-loading) show that the proposed control scheme is insensitive to parameter variations and external disturbance. Compared with the traditional adaptive robust control scheme, the proposed control scheme has higher position precision and better control performance.

Dynamic Modeling and Peak Torque Prediction of Servo Motor for a 3-DOF Parallel Humanoid Mechanical Leg

LI Yan-biao, LI Jing-min, JI Shi-ming, ZHENG Chao, ZHAO Zhang-feng

2014, 35(11):  1928-1936.  doi:10.3969/j.issn.1000-1093.2014.11.027

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In order to make up for the deficiencies of the humanoid robot structure and to improve the versatility and adaptability of mechanical leg, the dynamics property of a parallel mechanical leg is discussed in detail. The inverse kinematics transmission equations for the mechanical leg are derived analytically. Then a dynamics model of the mechanical leg is established using the second Lagrange method. The expressions of inertia moment, Coriolis force-centrifugal force, and gravity are obtained by derivation. Based on the above dynamics model, the peak prediction model of servo motor for the mechanical leg is defined. The change rules of angular velocity and driving torque caused by the mechanical leg servo motor are analyzed, and the dynamics property of the mechanical leg is obtained. Finally the peak prediction model of servo motor for the mechanical leg is validated, and the estimated maximum peak torque is 3.195 N·m. The results show that the angular speed and driving torque of mechanical leg display present periodic variation. The peak prediction model of servo motor can provide theoretical base for the selection of the mechanical leg servo motor.