JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Missile formation controller design based on disturbance observer and finite-time control

2014, 23(4): 427-434.

[Abstract](955) [PDF 454KB](48)

Abstract:
To keep multiple missiles to fly in a formation, a robust controller for missile formation is designed. Based on the leader-follower formation mode, two formation relative motion models in different coordinate frames are established and compared. The three-dimension model built in a follower reference coordinate frame is chosen due to its control inputs decoupling, then this model is decoupled into three subsystems. For each subsystem a robust formation controller is proposed based on the disturbance observer and finite-time control theory when the external disturbance exits. The stability of the closed-loop system adopting the controller is proved theoretically. Simulation results show that the follower can follow the leader and keep the desired formation despite the external disturbance, which validates the effectiveness of the proposed robust formation controller.

Ground vibration analysis due to a high-speed moving load in a tunnel

QIAN Tao, ZHANG Yong-fa, MA Meng, SHUI Xiao-ping, GUO Yong-gang

2014, 23(4): 435-442.

[Abstract](1029) [PDF 379KB](29)

Abstract:
The surface response of an infinite viscous-elastic half-space due to a moving load in the tunnel is analyzed. The tunnel is modeled as an infinite long Euler-Bernoulli beam without thickness and the concept of the equivalent stiffness is introduced to simulate the half-space. The inverse Fourier transformation and the relative coordinate transform are utilized to transfer a double infinite integral to a double definite integral, which improves the operational efficiency. Then, the analytic solution of the surface response of a half-space due to a moving load in the tunnel is obtained. Finally, the laws of ground vibration responses induced by moving loads in the tunnel are analyzed, considering different tunnel embedded depths and different moving speeds. Results show that the displacement distortion can be obtained by at some special velocities. A theoretical explaination of this phenomenon is provided as well.

Three-dimensional suboptimal guidance law for fly-over and shoot-down smart ammunition via virtual target

YANG Zhe, WU Yan-xuan, FAN Ning-jun, WANG Zheng-jie

2014, 23(4): 443-451.

[Abstract](938) [PDF 547KB](27)

Abstract:
An optimal burst height is required for the fly-over and shoot-down smart ammunition with an EFP warhead at the instant of explosion which brings a special requirement to the miss distance of the terminal guidance law. In this paper, a guidance law based on the virtual target scheme is proposed. First, the practical pursuit-evasion issue between the ammunition and the target with specific miss distance is transformed into a virtual pursuit-evasion problem with zero miss distance. Secondly, a complete three-dimensional pursuit-evasion kinematics model is established without any simplifications. And then, a suboptimal guidance law is designed based on theθ-Dmethod which has constraints of the elevation and azimuth angular velocity of the virtual line of sight (LOS). Finally, in order to verify the performance of the proposed guidance law, three test cases are conducted. Numerical results show that under the proposed terminal guidance law, the smart ammunition not only can fly above the target with an optimal burst height but also have a smaller normal acceleration on the terminal trajectory.

Pressure distribution of combining center cavity slipper for axial piston pump

WANG Ya-jun, YUAN Shi-hua

2014, 23(4): 452-456.

[Abstract](779) [PDF 1053KB](23)

Abstract:
In order to improve lubricating characteristics of slippers in an axial piston pump, the combining center cavity slipper approach was proposed based on slipper shape and moving characteristic. The cylindrical coordinate was used in the lubricant area and mesh was made. The block-weight approach was implemented to deal with non-coincidence of mesh and shallow recess border in numerical method. The finite control volume method was applied in calculating pressure distribution. The flow conservation equation and film thickness model were resolved through Gauss-Siedel relaxation iteration. The calculation and analysis results indicate that compared to the slipper ① slipper pressure distribution is improved; ② hydrodynamic pressure of the combining slipper is greatly increased; ③ inclining degree is greatly reduced; ④ negative pressure in lubricant film disappear. So the combining center cavity slipper is lubricated better.

Co-simulation platform for single-shaft parallel HEVs based on Cruise+Matlab/Simulink

XI Jun-qiang, MA Zheng-jun, HU Yu-hui

2014, 23(4): 457-462.

[Abstract](851) [PDF 637KB](31)

Abstract:
We reversely analyzed the energy management strategy (EMS) for a single-shaft parallel hybrid electric vehicle (HEV), and build a forward co-simulation platform based on Cruise and Matlab. The vehicle dynamics model is built with Cruise, and control model is set up with Matlab/Simulink environment. The data between the two models are transferred by the Matlab API interface in Cruise. After mechanical and signal connections are completed, we establish the computing tasks and take the simulations of vehicle's power performance, economy, and emission performance. The simulation results match the actual measurement results, which show that the co-simulation platform is correct and feasible. The platform can be used not only for a basic simulation platform to optimize further EMS, but also for the development of actual control system.

Regenerative braking control for hybrid electric vehicles under decelerating condition

SHEN Wen-chen, HU Yu-hui, XI Jun-qiang, CHEN Hui-yan

2014, 23(4): 463-468.

[Abstract](852) [PDF 373KB](19)

Abstract:
The operating mode of a single shaft hybrid electric vehicle (SSHEV) in which the electric motor exerts negative torque on the shaft to imitate engine braking is analyzed. The method of determining the quantity of regenerative braking torque is proposed with the premise that the braking intensity required by the driver is satisfied. On this basis, factors that affect torque generated by the motor are listed, and how the battery's temperature and state of charge (SOC) restrict and correct the braking torque is expounded. Finally, road test results show that the motor's constant power or constant torque control is an effective way to recover the mechanical energy during decelerating.

Numerical study on the separation and superposition of the influences from up- and downstream rotors

ZHAO Ben, YANG Ce, HU Liang-jun, MA Chao-chen, ZhANG Ji-zhong

2014, 23(4): 469-480.

[Abstract](738) [PDF 1670KB](16)

Abstract:
A three-dimensional Navier-Stokes solver is used to investigate the separation and superposition of the influences from upstream and downstream rotors in an axial-radial combined compressor for unsteady design applications. The data from rotor/stator and stator/rotor configurations show that the unsteady flow response in axial stator passage is caused only by one rotor. The results from the rotor/stator/rotor configuration revealed the superimposed characteristic of influences from upstream and downstream the rotor. The impact of the superimposed characteristic was studied by analyzing the virtual relative flow angle at the stator exit. The results show that the axial velocity in the passage of axial stator can be influenced by wake from upstream axial rotor and potential field of downstream radial rotor. While they are coupled to have an effect on the unsteady flow in axial stator passage, the excitation or suppression phenomena appear and lead to different levels of deterministic fluctuation kinetic energy. Their locations are determined by the frequencies of the involved influences. In addition, the variability of superimposed characteristic (excitation and suppression) at the stator exit modulates the inlet flow angle for downstream rotor.

Multi-objective route planning approach for timely searching tasks of a supervised robot

LIU Peng, XIONG Guang-ming, LI Yong, JIANG Yan, GONG Jian-wei

2014, 23(4): 481-489.

[Abstract](1150) [PDF 1383KB](31)

Abstract:
To performance efficient searching for an operator-supervised mobile robot, a multiple objectives route planning approach is proposed considering timeliness and path cost. An improved fitness function for route planning is proposed based on the multi-objective genetic algorithm (MOGA) for multiple objectives traveling salesman problem (MOTSP). Then, the path between two route nodes is generated based on the heuristic path planning method A^*. A simplified timeliness function for route nodes is proposed to represent the timeliness of each node. Based on the proposed timeliness function, experiments are conducted using the proposed two-stage planning method. The experimental results show that the proposed MOGA with improved fitness function can perform the searching function well when the timeliness of the searching task needs to be taken into consideration.

Realization of embedded control module for micro assembly line

ZHANG Zhi-jing, ZHANG Gao-yang, JIN Xin

2014, 23(4): 490-494.

[Abstract](853) [PDF 894KB](17)

Abstract:
A modularized, network, reconfigurable architecture and design method of embedded control module is proposed. This control module uses a TMS320F2812 chip as the core, and introduces modularization, network, reconfigurable theory to the design of control module to better meet the flexible and reconfigurable control need of assembly line. The design method of the control module is verified by constructing a control experiment based on controlling of precisionx-ydisplacement platform through a CAN bus. Experimental results show that the controlling repeat position accuracy of precisionx-yplatform by control module is 0.5 μm and the position error is less than 1 μm which meet the needs of micro-adjustment pose of assembly line.

RDF(S) repository privacy protection via inference control

XUE Jin-rong, ZHENG Jun, AN Qiu-sheng

2014, 23(4): 495-501.

[Abstract](850) [PDF 338KB](27)

Abstract:
The privacy protection of resource description framework (schema) (RDF(S)) repository is an emerging topic in database security area. In this paper, entailment rules are investigated based on RDF(S) repository firstly. Then, an idea that uses reasoning closure to judge whether the privacy disclosure caused by inference is existed is proposed. Furthermore, the definitions of implication conditions and information measure of triple statements which gains data hiding algorithm with combining proposition logic reasoning theory are introduced. Meanwhile, a conversion method from conjunctive normal form to disjunctive normal form based minimal hitting sets of set cluster is also proposed. Finally, the experimental results show that our algorithm can prevent privacy disclosure of RDF(S) repository effectively.

Predicting resource consumption in a web server using ARIMA model

YAN Yong-quan, GUO Ping

2014, 23(4): 502-510.

[Abstract](785) [PDF 427KB](18)

Abstract:
Software aging is a phenomenon observed in a software application executing continuously for a long period of time, where the state of software degrades and leads to performance degradation, hang/crash failures or both. A technique named rejuvenation was proposed to counteract this problem. Rejuvenation in period is not a good idea, because the speed of software aging is not constant, but variable. The key to find an optimal timing to resist aging problem is how to analyze/forecast the resource consumption of aging system. An ARIMA model is applied to forecast resource consumption due to software aging in a running web server. First, order and parameters of ARIMA model need to be identified. Second, it needs to be checked whether the model satisfies stationarity and reversibility. Finally, ARIMA model is used to predict resource consumption. The experiment results indicate that ARIMA model can do better than ANN model and SVM model in the forecasts of available memory and heap memory.

Technology of shipboard two-way microwave time synchronization

FU Yong-jie, LI Dong-guang, LIU Xu-dong

2014, 23(4): 511-518.

[Abstract](825) [PDF 375KB](15)

Abstract:
For the high precision time synchronization demand of ships, advantages and disadvantages of the present time transfer methods are analyzed, the two-way microwave time transfer(TWMTT) method is adopted to resolve the time synchronization problem in the Naval Ship Formation. After expounding the principle and system composition of TWMTT method, the various factors influencing the synchronous precision are analyzed, such as time-interval measurement error, TWMTT equipment delay error, signal propagation error in air, and signal delay error caused by shipping. To improve the time synchronization precision, all the error sources above are deduced with mathematical measures to definite the critical one, and the signal processing measures such as Pseudo code spread spectrum time comparison signal generation technology, FFT fast acquisition technology and precise tracking technology are used into the modem which is the core equipment of the TWMTT. And, calibration method of TWMTT equipment delay are developed. Through theoretical analysis and simulation verification, the precision of shipboard two-way microwave time synchronization can reach 1 ns.

Input series output parallel based multi-modular boost half bridge DC-DC converter with a dynamic control scheme

SOOMRO Amir Mahmood, SYED Amjad Ali, KHIZER Arbab Nighat, LIAO Xiao-zhong, MANZOOR Muhammad Farhan

2014, 23(4): 519-526.

[Abstract](873) [PDF 381KB](22)

Abstract:
Multi-modular system plays an important role in power system architecture because low voltage and low power converters can be connected in any combination parallel or series at input/output side in order to obtained any given power system specifications. Multi-modular boost half bridge DC-DC converter in the configuration of input series output parallel has been investigated in this paper. The boost half bridge DC-DC converters are connected in input series output parallel configuration in order to achieve equal input voltage sharing and output current sharing between the converters. This can be achieved with the help of dynamic control scheme which consists of two loops, a voltage loop and a current loop, for each module. Dynamic behavior of multi-modular converter configuration has been observe by varying the load condition. Moreover, the results obtained through multi-modular converter describe that the system has good dynamic and steady state response. Although two converter modules are focused in this paper but it can be modified to any number of modules.

Angular velocity dynamics identification of small unmanned helicopter using fuzzy model

KHIZER Arbab Nighat, DAI Ya-ping, SYED Amjad Ali, XU Xiang-yang

2014, 23(4): 527-533.

[Abstract](888) [PDF 792KB](18)

Abstract:
Attitude identification method for unmanned helicopter based on fuzzy model at hovering is presented. The dynamical attitude model is considered as basis for attitude control and it is very complex. To reduce the complexity of model, nonlinear model of unmanned helicopter with unknown parameters are to be determined by fuzzy system first and then derivative based gradient method is used to identify unknown parameters of model. Gradient method is used due to ability that fuzzy system is not necessarily to be linear in parameters, therefore all fuzzy sets for input and output can be adjusted. The validity of the proposed model was verified using experimental data obtained by the commercially available flight simulator X-Plane^©. The simulation results showed high accuracy of the modeling method and attitude dynamics data matched well with experimental data.

Feedback-based unequal error protection fountain code over device-to-device broadcast

HUANG Gai-shi, FEI Ze-song, CAO Cong-zhe, XING Cheng-wen, KUANG Jing-ming

2014, 23(4): 534-540.

[Abstract](1366) [PDF 556KB](17)

Abstract:
To enhance encoding efficiency, an unequal error protection (UEP) broadcast scheme based on one additional feedback is proposed. Different from the equal probability selection for source packets in traditional fountain encoding, the proposed scheme calculates the packet loss ratio (PLR) according to the feedback results in systematic broadcast phase (SBP) and then optimizes the selection probability for source packets to guarantee higher level error protection for those source packets with larger PLRs. Thus the amount of unnecessarily redundant encoded packets during encoding broadcast phase (EBP) is decreased significantly. Numerical results show that the proposed scheme can recover 60% more packets than the traditional non-feedback broadcast scheme at the expense of tolerably only one feedback procedure.

Comparison of shape representation methods for dynamic cell analysis

LI Heng, LIU Zhi-wen, AN Xing, SHI Yong-gang

2014, 23(4): 541-548.

[Abstract](820) [PDF 570KB](24)

Abstract:
To evaluate the performance of basic shape representation methods for the description of dynamic cellular morphology, several frequently-used shape descriptors are compared. The methods are examined by using 50 lymphocyte video clips including two kinds of lymphocyte cells. Our goal is to represent cell shape in each frame accurately, meanwhile precisely classify the two groups of cells based on the cellular morphological variations in the video clips. Experimental results illustrate that in general the region-based shape descriptors outperform the contour-based ones, since the contour-based methods are excessively sensitive and ignorant to cellular internal information. Due to their robustness to noise, the region-based shape descriptors are suitable for dynamic cell representation. Although region-based methods are more time-consuming, they analyze the entire cell area.

HMM-based noise estimator for speech enhancement

XU Chun-dong, XIA Ri-sheng, YING Dong-wen, LI Jun-feng, YAN Yong-hong

2014, 23(4): 549-556.

[Abstract](1028) [PDF 414KB](18)

Abstract:
A noise estimator was presented in this paper by modeling the log-power sequence with hidden Markov model (HMM). The smoothing factor of this estimator was motivated by the speech presence probability at each frequency band. This HMM had a speech state and a nonspeech state, and each state consisted of a unique Gaussian function. The mean of the nonspeech state was the estimation of the noise logarithmic power. To make this estimator run in an on-line manner, an HMM parameter updated method was used based on a first-order recursive process. The noise signal was tracked together with the HMM to be sequentially updated. For the sake of reliability, some constraints were introduced to the HMM. The proposed algorithm was compared with the conventional ones such as minimum statistics (MS) and improved minima controlled recursive averaging (IMCRA). The experimental results confirms its promising performance.

Atmospheric CO₂retrieval with a look-up-table based method by combining near and thermal infrared spectra

WU Jun, FANG Yong-hua, WANG Xian-hua, YE Han-han, JIANG Xin-hua

2014, 23(4): 557-565.

[Abstract](794) [PDF 1061KB](20)

Abstract:
In order to precisely retrieve the atmospheric CO₂, a retrieval method based on both near infrared (NIR) and thermal infrared (TIR) is established firstly. Then a look-up-table (LUT) based fast line-by-line radiative transfer model (RTM) was integrated into the retrieval procedure to accelerate radiative transfer calculations. The LUT stores gas absorption cross-sections as a function of temperature, pressure and wavenumber. It could greatly reduce calculating time in radiative transfer compared to direct line-by-line method. Then retrieval was simulated using NIR, TIR and both bands. The retrieved CO₂profiles suggest joint approach could reconstruct CO₂profile better than those using NIR or TIR alone. Joint retrieval using both bands simultaneously could provide better constrain to CO₂vertical distribution in the whole troposphere.

Synthesis and characterization of poly/organo-montmorillonite composites

ZHANG Qing-shan, LU Bao-ping, YAO Peng-jun, LI Yun-zheng

2014, 23(4): 566-570.

[Abstract](870) [PDF 1111KB](30)

Abstract:
The incorporation of clay nanoplatelets into biodegradable polymers is considered to be one of the best combinations for developing environmentally-benign high-performance materials. We utilized organo-montmorillonite (OMMT) in ring-opening polymerization of bisphenol A diglycidyl ether and adipic acid to prepare biodegradable linear poly(bisphenol A diglycidyl adipate)/organo-montmorillonite (PBA/OMMT) nanocomposites. The products were analyzed by XRD, TEM, 1H NMR, GPC, DSC and TGA. The results demonstrated that PBA/OMMT nanocomposites were successfully formed and sufficient for the ordinary heating process. OMMT was beneficial for the modification of PBA hydroxyl polyesters on branched rate and polydispersity.

2014 Vol. 23, No. 4