JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

TU Hai-feng, LIU Li

2015, 24(2): 143-150. doi:10.15918/j.jbit1004-0579.201524.0201

[Abstract](662) [PDF 427KB](924)

Abstract:
A nonlinear modeling framework is presented for an oceanographic unmanned aerial vehicle (UAV) by using symbolic modeling and linear fractional transformation (LFT) techniques. Consequently, an exact nonlinear symbolic LFT model of the UAV is derived in a standardM-Δform whereMrepresents the nominal, known, part of the system andΔcontains the time-varying, uncertain and nonlinear components. The advantages of the proposed modeling approach are that: it not only provides an ideal starting point to obtain various final design-oriented models through subsequent assumptions and simplifications, but also it facilitates the control system analysis with models of different levels of fidelity/complexity. Furthermore, a linearized symbolic LFT model of the UAV is proposed based on the LFT differentiation, which is amenable directly to a sophisticated linear robust control strategy such as μ synthesis/analysis. Both of the derived LFT models are validated with the original nonlinear model in time domain. Simulation results show the effectiveness of the proposed algorithm.

Novel scheme of high precision inertial measurement for high-speed rotating carriers

WU Qing-ya, JIA Qing-zhong, SHAN Jia-yuan, MENG Xiu-yun

2015, 24(2): 151-157. doi:10.15918/j.jbit1004-0579.201524.0202

[Abstract](697) [PDF 375KB](719)

Abstract:
In order to satisfy the requirement of high precision measurement in a high dynamic environment, a kind of gyro aided multi-accelerometer inertial measurement unit (GAMA-IMU) with six accelerometers and two gyros (6A2G) was proposed in this paper. The available configurations have the problem of low measurement precision in a high dynamic environment due to channel coupling. The three channels were decoupled when calculating the angular velocity in the proposed configuration. The yawing and pitching angular velocity were directly measured by gyros, while only the rolling angular velocity was obtained by the GAMA-IMU indirectly from the rolling angular acceleration and quadratic component of rolling angular velocity. Then a single channel rolling angular velocity calculation model was established and the extended Kalman filter (EKF) was used to do state estimation. Simulations were carried out and results indicated that the calculation precision of the proposed 6A2G configuration could meet the demand of high precision measurement for a high-speed rotating carrier.

Study on influencing factors of adapters separating with the underwater missile

FU De-bin, NIU Qing-lin, LIU Xiao-jun, LI Xia

2015, 24(2): 158-163. doi:10.15918/j.jbit1004-0579.201524.0203

[Abstract](550) [PDF 382KB](683)

Abstract:
To analyze main factors affecting the separation reliability between a missile and adapters for the launching process, a six DOF underwater dynamic model for the missile and adapters is utilized to simulate the separation process, considering elastic forces of separating springs, hydrodynamic forces, gravity and buoyancy. Moreover, a criterion based on the maximum separating distance is put forward to determine whether adapters separate with the missile reliably. The results show that the magnitude and position of elastic force, the wedge angle and mass of the adapter significantly affect the separating process. The local sensitivity analysis for the reference status of design parameters demonstrates that the wedge angle of adapters has the maximum influence about 70.4% on the separating distance.

Fast-solving method for air-to-surface guided bombs' allowable attack area

LI Qiang, XIA Qun-li, CUI Ying-ying

2015, 24(2): 164-168. doi:10.15918/j.jbit1004-0579.201524.0204

[Abstract](481) [PDF 339KB](548)

Abstract:
A new method called local accurate search is put forward to calculate the allowable area for air-to-surface missiles based on the conventional methods. Comparing with traditional methods, the local accurate search method can search the area online and reduce the time of search with the required precision. Combining the traditional flight range table with a model calculation method, the new method employs the local search to find an accurate result, which will meet the fast-calculation requirements for attacking moving targets. In this way, the missiles are adapted for the complex warfare situation.

Un-powered gliding aircraft's ballistic missile optimal design

HE Chang-jian, MENG Xiu-yun

2015, 24(2): 169-172. doi:10.15918/j.jbit1004-0579.201524.0205

[Abstract](802) [PDF 290KB](699)

Abstract:
In this dissertation, un-powered gliding aircraft's optimal extended rangeproblem is discussed. The aircraft movement model was built. According to the degree of coupling, the model can be classified into a simple model or a complicated model. Using an optimal control method, two different movement models gave out the aircraft's attitude angle optimal flight path. Complicated model's optimal solution can be found by the genetic algorithm. This method can transfer the analytic solution of complicated model to a numerical value solution. Comparing the simulation results of different methods, it showed that the genetic algorithm combined with the complicated model's numerical value solution had the best performance in control strategy. This method solved the problem in which the highly coupling complicated model's analytic solution was hard to obtain. It verified that the genetic algorithm has validity in the field of extended range solution searching.

Design and analysis of mechanical self-destruction and self-neutralization mechanism for submunition fuze

XU Sheng-gang, WU Yan-xuan, FAN Ning-jun

2015, 24(2): 173-179. doi:10.15918/j.jbit1004-0579.201524.0206

[Abstract](710) [PDF 1227KB](823)

Abstract:
In order to decrease the unexploded submunition rate and reduce the harmfulness of unexploded submunition, a mechanical self-destruction and self-neutralization mechanism for submunition fuze is proposed in this paper. The definitions of the self-destruction and self-neutralization for submunition fuze are elaborated, and the action principle of the mechanical self-destruction and self-neutralization mechanism is also analyzed. A dynamic model is established with an analysis on centrifugal plate parts, and the feasibility of mechanism motion is also discussed. A virtual prototype of mechanism is formed, and the motion process simulation of the mechanism is performed through a dynamic analysis software ADAMS. The centrifugal experiment results validate that the mechanical self-destruction and self-neutralization mechanism can act reliably.

Resilience approach for heterogeneous distributed networked unmanned weapon systems

JIN Yi-ning, WU Yan-xuan, FAN Ning-jun

2015, 24(2): 180-187. doi:10.15918/j.jbit1004-0579.201524.0207

[Abstract](522) [PDF 785KB](1020)

Abstract:
Disconnection in the distributed heterogeneous networked unmanned weapon systems is caused by multiple weapon units' failure. The technical routes were analyzed to achieve resilience in the disconnection situation. A heterogeneous distributed network model of networked unmanned weapon systems was established. And an approach of adding relay weapon units was proposed to achieve fault tolerance after weapon units' failure due to attack or energy exhaustion. An improved genetic algorithm was proposed to determine and optimize the position of the relay weapon units. Simulation results in the MATLAB show that the improved resilience-based genetic algorithm can restore the network connection maximally when the number of relay units is limited, the network can keep on working after failure, and the implementation cost is controlled in a reasonable range.

Modeling and simulation of the static characteristics of diaphragm spring clutches

XI Jun-qiang, LU Jia, PAN Chun

2015, 24(2): 188-193. doi:10.15918/j.jbit1004-0579.201524.0208

[Abstract](900) [PDF 1256KB](1843)

Abstract:
The diaphragm spring clutch static characteristics to improve the starting quality for cars equipped with automated mechanical transmission (AMT) were modeled and simulated. First, axial stiffness of clutch cushion spring and characteristic curves of diaphragm spring were theoretically and experimentally studied. Then, model of transfer characteristics of the normal force was built, with special conscen on the abrasion of friction discs and the influence of temperature to diaphragm spring. Finally, the model was tested in practical starting for cars equipped with AMT, which showed that the starting quality was significantly improved. The experimental results showed that the proposed model was precise enough to be implemented conveniently.

Effect of cutting speed on residual stress of special coating during remanufacturing

SUN Ye-wang, ZHANG Jia-ying, ZHANG Zhi-jing, XU Bin-shi

2015, 24(2): 194-200. doi:10.15918/j.jbit1004-0579.201524.0209

[Abstract](595) [PDF 2566KB](444)

Abstract:
To study the residual stress of the special coating at different cutting speeds, the cutting of FeAlCrBSiNb coating is analyzed with the finite element method (FEM) and experiment according to the coating characteristics. The CNC machine tool is used to cut the coating and the X-ray stress equipment is used to measure the residual stress of coating. The experimental and FEM results agree with each other. Also, the residual-stress coating depth is deeper and the residual stress of the coating surface is larger with increasing cutting speed. In addition, the residual stress of the coating surface is in the suppression state affected by axial residual stress and circumferential residual stress, and the residual stress of the deeper coating is in the tensile state based on the original state of arc spraying and cutting process.

Processing the rig test data of an air filling twin-tube shock absorber

DONG Ming-ming, LUO Zhen-xing, ZHAO Yong-fei

2015, 24(2): 201-206. doi:10.15918/j.jbit1004-0579.201524.0210

[Abstract](847) [PDF 378KB](581)

Abstract:
A separation method is proposed to design and improve shock absorber according to the characteristics of each force. The method is validated by rig test. The force data measured during rig test is the resultant force of damping force, rebound force produced by pressed air, and friction force. Different characters of damping force, air rebound force and friction force can be applied to seperate each force from others. A massive produced air filling shock absorber is adopted for the validation. The statistic test is used to get the displacement-force curves. The data are used as the input of separation calculation. Then the tests are carried out again to obtain the force data without air rebound force. The force without air rebound is compared to the data derived from the former tests with the separation method. The result shows that this method can separate the damping force and the air elastic force.

Transient dynamic analysis and comparison on wedging processes of overrunning clutches with different contact surfaces

WEI Wei, ZHOU Qia, LIU Shu-cheng, YAN Qing-dong

2015, 24(2): 207-212. doi:10.15918/j.jbit1004-0579.201524.0211

[Abstract](702) [PDF 1376KB](676)

Abstract:
The effects of contact surface on dynamic wedging behavior of the roller and inner-ring of the overrunning clutch in a dual-turbine torque converter were investigated to reveal the friction self-locking mechanism and dynamic process. Planar strain clutch models including roller, inner-ring and outer-ring were built, and transient wedging process was analyzed with an explicit dynamics method. The modeling of stress and strain distribution and variation of two kinds of contact surfaces show that there are three stages named slipping, wedging and binding respectively during whole wedging process. Meanwhile the geometric structures of contact surfaces greatly influence the peak stress and strain distribution of the wedging process of the roller and inner-ring. The load bearing performance of contact surfaces with logarithmic spiral curve is better than that with straight line. Our study provides theoretical foundation for design and further optimization of wedging contact surface of an overrunning clutch in a dual-turbine hydrodynamic torque converter.

Path tracking for vehicle parallel parking based on ADRC controller

WANG Jian, ZHAO You-qun, JI Xue-wu, LIU Ya-hui, ZANG Li-guo

2015, 24(2): 213-221. doi:10.15918/j.jbit1004-0579.201524.0212

[Abstract](683) [PDF 839KB](895)

Abstract:
A novel path tracking controller for parallel parking based on active disturbance rejection control (ADRC) was presented in this paper. A second order ADRC controller was used to solve the path tracking robustness, which can estimate and compensate model uncertainty caused by steering kinematics and disturbances caused by parking speed and steering system delay. Collision-free path planning technology was adopted to generate the reference path. The simulation results validate that the performance of the proposed path tracking controller is better than the conventional PID controller. The actual vehicle tests show that the proposed path tracking controller is effective and robust to model uncertainty and disturbances.

Efficient and fair resource allocation in downlink OFDMA systems

SONG Zheng-yu, HOU Shu-juan, WU Si-liang

2015, 24(2): 222-226. doi:10.15918/j.jbit1004-0579.201524.0213

[Abstract](543) [PDF 323KB](620)

Abstract:
A resource allocation problem considering both efficiency and fairness in orthogonal frequency division multiple access (OFDMA) systems is studied. According to the optimality conditions, a downlink resource allocation algorithm consisting of subcarrier assignment and power allocation is proposed. By adjusting the tradeoff coefficient, the proposed algorithm can achieve different levels of compromise between efficiency and fairness. The well-known classic resource allocation policies such as sum-rate maximization algorithm, proportional fairness algorithm and max-min algorithm are all special cases of the proposed algorithm. Simulation results show that the compromise between efficiency and fairness can be continuously adjusted according to system requirements.

Distributed power allocation over indoor multi-pico stations

FEI Ze-song, GAO Qiang, FU You, Tero Isotalo, Jarno Niemela

2015, 24(2): 227-232. doi:10.15918/j.jbit1004-0579.201524.0214

[Abstract](622) [PDF 1258KB](564)

Abstract:
A low-complexity distributed power allocation algorithm is proposed to reduce the interference and improve the transmitting rate of edge users. Different scenarios are considered and user experience of indoor communication is promoted. The simulation results prove the effectiveness of our algorithm. The proposed power control scheme ensures that more users can achieve their required rate and the fairness of different users is improved. Besides, more than 50% energy can be saved without loss in outage ability, and energy efficiency is also promoted. In addition, the proposed algorithm can be extended to scenarios that the required rates of pico stations can be changed periodically.

Research on inter-satellite measurement technique in high dynamic environment

WANG Yong-qing, SUN Li-da, YANG Li-yun, JIANG Hong-wei, WU Si-liang

2015, 24(2): 233-239. doi:10.15918/j.jbit1004-0579.201524.0215

[Abstract](519) [PDF 367KB](550)

Abstract:
An improved measurement algorithm, based upon the theory of two-way time transfer (TWTT), is proposed to measure satellites with high speeds. The algorithm makes theoretical analyses and corresponding deductions on a relative motion model of two satellites, and eliminates the measurement error caused by the equipment delay when a satellite moves at a high speed. Theoretical analysis and simulation results demonstrate that in comparison with the conventional TWTT algorithm, the proposed algorithm can significantly enhance the measurement accuracy of the inter-satellite ranging and time synchronization, and the algorithm is more effective with the relative velocity between the satellites and transmitting delay becoming larger.

Multi-criteria user selection scheme for learning-based multiuser MIMO cognitive radio networks

WANG Ni-wei, FEI Ze-song, XING Cheng-wen, NI Ji-qing, KUANG Jing-ming

2015, 24(2): 240-245. doi:10.15918/j.jbit1004-0579.201524.0216

[Abstract](473) [PDF 361KB](459)

Abstract:
For multiuser multiple-input-multiple-output (MIMO) cognitive radio (CR) networks a four-stage transmiision structure is proposed. In learning stage, the learning-based algorithm with low overhead and high flexibility is exploited to estimate the channel state information (CSI) between primary (PR) terminals and CR terminals. By using channel training in the second stage of CR frame, the channels between CR terminals can be achieved. In the third stage, a multi-criteria user selection scheme is proposed to choose the best user set for service. In data transmission stage, the total capacity maximization problem is solved with the interference constraint of PR terminals. Finally, simulation results show that the multi-criteria user selection scheme, which has the ability of changing the weights of criterions, is more flexible than the other three traditional schemes and achieves a tradeoff between user fairness and system performance.

Novel attribute-based framework for halftone watermarking

XIE Kun, ZHENG Hai-hong, ZENG Ping, WANG Quan, GUO Tao

2015, 24(2): 246-253. doi:10.15918/j.jbit1004-0579.201524.0217

[Abstract](896) [PDF 3491KB](726)

Abstract:
A novel attribute-based framework is proposed to tackle the problem of halftone watermarking in combination of the spatial/transformation domain. The challenge is that the host image is continuous, while the watermarked halftone is bi-level. To search for a solution, an attribute image is defined as a good connection between the original grayscale image and its halftone image. When the attribute image is used as a watermark carrier, it helps to find the watermarked halftone efficiently by solving a constrained modified direct binary search problem. Experimental results demonstrate that the proposed scheme in comparison with other similar methods maintains high watermark capacity with good image quality, high robustness, processing efficiency and easy decoding. Especially it has a good performance in printing application.

Numerical simulation of effects of operating conditions on the molecular weight of polypropylene using a response surface method

HONG Dong-feng, SUI Shu-hui, WU Wen-hui

2015, 24(2): 254-259. doi:10.15918/j.jbit1004-0579.201524.0218

[Abstract](611) [PDF 950KB](749)

Abstract:
A L₄₆3⁵Box-Behnken design was used for developing a model to predict and optimize the molecular weight (M_w) of polypropylene (PP); a second-order polynomial regression equation was derived to predict responses. The significance of variables and their interactions were tested by means of the ANOVA with 95% confidence limits; the standardized effects were investigated by Pareto chart, the optimum values of the selected variables were obtained by analyzing the response surface contour plots. The optimizedM_wvalue of 1.217×10⁵g/mol was very close to the industrial value ((1.22±0.004)×10⁵g/mol) at the optimum values.

Effect of solvent on the crystal morphology of royal demolition explosive

WANG Dong-xu, CHEN Shu-sen, LI Yan-yue, YANG Jia-yun, WEI Tian-yu, LI Li-jie

2015, 24(2): 260-268. doi:10.15918/j.jbit1004-0579.201524.0219

[Abstract](646) [PDF 2126KB](1020)

Abstract:
Important crystal faces that dominate the crystal morphology of royal demolition explosive (RDX) in vacuum were analyzed with the attachment energy (AE) method. Molecular dynamics (MD) simulations were used to calculate the interaction energies between these crystal faces and different solvent molecules for an attachment energy correction. Growth habits in the presence of different solvents were generated. The results showed that some crystal faces in solutions became morphologically more important than that in vacuum while others became less important. Thus, crystal shape and surface property changed a lot with the variation of crystal faces. The results from calculation were in agreement with those from the re-crystallization experiment, which indicated that cyclohexanone (CH) was a promising solvent to modify the crystal morphology of RDX for obtaining products with regular shape and high purity, while butyrolactone (BL) played a great role in improving the surface electrostatic property of RDX.

Investigation on experimental method of low-impedance materials using modified Hopkinson pressure bar

MIAO Ying-gang, LI Yu-long, DENG Qiong, TANG Zhong-bin, HU Hai-tao, SUO Tao

2015, 24(2): 269-276. doi:10.15918/j.jbit1004-0579.201524.0220

[Abstract](767) [PDF 759KB](557)

Abstract:
To increase the detectability of split Hopkinson pressure bar (SHPB) of low-impedance materials, modifications were conducted on traditional SHPB apparatus with a PMMA tube to output transmitted signal, and weak signals were further amplified by semiconductor strain gauges. Experiments on soft rubbers and cushioning foam materials were carried out. In order to analyze the accuracy of the experimental results, the stress equilibrium issues involved in the assumptions of SHPB were investigated. First, by way of re-constructing loading process of incident wave, the stress-strain curve was obtained, along with the stress equilibrium ratio of specimen. Secondly, the influences on the accuracy of stress-strain curves were investigated through the elastic modulus comparisons. And the results illustrate that the bilinear incident wave from experiments can ensure the stress equilibrium deformation of specimen after 2 normalized times, much sooner than ramp incident waves. Moreover, it even facilitates specimen deformation with a constant strain rate. The results confirm that the detectability of the modified SHPB can be down to tens kPa with enough accuracy level.

Quantification of CP4-EPSPS in genetically modifiedNicotiana tabacumleaves by LC-MS/MS with¹⁸O-labeling

ZHANG Mei, SHAN Ke-ming, XU Wei, LIN Fan-kai, DENG Yu-lin

2015, 24(2): 277-284. doi:10.15918/j.jbit1004-0579.201524.0221

[Abstract](838) [PDF 403KB](770)

Abstract:
The CP4-EPSPS gene is widely used in herbicide-tolerant plants/crops all over the world. In this study, a method was developed by coupling liquid chromatography with high sensitivity to tandem mass spectrometry to quantify the amount of CP4-EPSPS expression inNicotiana tabacumleaves. The quantification of protein was converted to measure the unique peptide of CP4-EPSPS protein. One peptide unique to CP4-EPSPS was synthesized and labeled with H₂¹⁸O to get¹⁸O stable isotope labeled peptide. The peptide served as the internal standard. The validated method had good specificity and linearity. The intra-and inter-day precisions and accuracy for all samples were satisfactory. The results demonstrated that the novel method was sensitive and selective to quantify CP4-EPSPS in the crude extract without time-consuming pre-separation or the purification procedures.

2015 Vol. 24, No. 2