JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Solvability Condition for a Class of Parametric Robust Stabilization Problem

WU Qing-he

2007, 16(4): 379-383.

[Abstract](164)

Abstract:
The robust stabilization problem (RSP) for a plant family P(s,δ,δ) having real parameter uncertainty δ will be tackled. The coefficients of the numerator and the denominator of P(s,δ,δ) are affine functions of δ with ‖δ‖p≤δ. The robust stabilization problem for P(s,δ,δ) is essentially to simultaneously stabilize the infinitely many members of P(s,δ,δ) by a fixed controller. A necessary solvability condition is that every member plant of P(s,δ,δ) must be stabilizable, that is, it is free of unstable pole-zero cancellation. The concept of stabilizability radius is introduced which is the maximal norm bound for δ so that every member plant is stabilizable. The stability radius δmax(C) of the closed-loop system composed of P(s,δ,δ) and the controller C(s) is the maximal norm bound such that the closed-loop system is robustly stable for all δ with ‖δ‖p <δmax(c). using the convex parameterization approach it is shown that maximal stability radius exactly stabilizability radius. therefore, rsp solvable if and only every member plant of p(s,δ,δ) stabilizable.< span>

Numerical Calculation of Artillery-Fuze System Dynamic Characteristics

WANG Ya-bin, LIU Ming-jie, TAN Hui-min

2007, 16(4): 384-387.

[Abstract](197)

Abstract:
A numerical calculation method based on the finite element analysis of dynamic characteristics of artillery-fuze system is discussed in detail. Pretension element is used to mesh the couple structure between artillery and fuze to analyze the change of dynamic characteristics of artillery-fuze system when pre-tightening force varies between artillery and fuze. Numerical calculation of the finite element analysis and actual hammering test of a artillery-fuze system are carried out with the same input to verify the accuracy of numerical calculation. The results show that the finite element model of artillery-fuze system is credible and the calculation accuracy is perfect.

Stability Analysis for Projectile with Wrap-Around Fins

WANG Cheng, NING Jian-guo

2007, 16(4): 388-392.

[Abstract](210)

Abstract:
Based on the stability theory, numerical simulations and theoretical calculations are performed for a projectile with wrap-around fins. Its stability is analyzed and the flow field is simulated with computational fluid dynamics method. Consequently, the pitching moment coefficient of the projectile is further investigated under the conditions of Mach number ranging from 0.3 to 0.8, attack angle from 0 to 8° and yaw angle from 0 to 4°. A trajectory equation is established and its trajectory characteristics are also explored. All the results of theoretical analysis, numerical simulation and trajectory equation agree well with each other, which indicates the projectile is flying steadily at the given conditions. These results provide an effective way for judging the stability of the projectile with wrap-around fins.

Dimensional Analysis on the Perforation of Stiffened Plates by Projectiles

SONG Wei-dong, NING Jian-guo

2007, 16(4): 393-398.

[Abstract](225)

Abstract:
The phenomena attendant to the perforation of truncated oval shape projectile into multi-layered stiffened plates were investigated. Dimensional analysis was employed to give an empirical formula. Then a membership function was introduced to modify the empirical formula. The effects of initial velocities, base plate thicknesses, height and width of stiffener on residual velocities were explored. The predictions of the empirical formula are in reasonably good agreement with those of experiment and numerical results. All these results indicate that the empirical formula is capable of predicting the residual velocity of the projectile penetrating the multi-layered stiffened plates.

Effects of Obstacles on Flame Propagation Behavior and Explosion Overpressure Development During Gas Explosions in a Large Closed Tube

LI Xiao-dong, BAI Chun-hua, LIU Qing-ming

2007, 16(4): 399-403.

[Abstract](116)

Abstract:
AutoReaGas was used for the simulations of premixed gas/air mixtures explosion characteristics in obstacle-filled tubes with a cross-section of 0.2 m×0.2 m and the length of 28 m. Numerical analyses provide a quantitative description of dependence of flame propagation speed and explosion overpressure on obstacles number, blockage ratio and interval distance. Computational results indicate that the obstacles play a significant role in determining the flame transmission speed and explosion overpressure in gas explosions. With the increase of blockage ratio, the explosion overpressure gradually rises. Nevertheless, the flame speed does not always increase along with increasing blockage ratio, but subsequently begins to decrease as the blockage ratio increases to some extend. Also, the interval distance between obstacles strongly influences flame behavior and explosion overpressure. When the obstacle interval distance is equal to inner diameter of the tube, the average flame speed in the obstacle zone and the peak overpressure in tube all reach maximum values.

Numerical Investigation of the Performance of an Axial-Flow Pump with Tandem Blades

YU Zhi-yi, LIU Shu-yan, WANG Guo-yu

2007, 16(4): 404-408.

[Abstract](80)

Abstract:
The performance characteristics of an axial-flow pump with tandem blades are studied based on the numerical computations. The arrangement of the pump impellers is established through the analysis of velocity triangles. With the commercial computational fluid dynamics (CFD) software NUMECA, the turbulent flow in the tandem axial-flow pump is simulated in various flow conditions. The detail flow structure in the leading edge region of the rear impeller is described, and the influence of the deflection angle of the rear blade on the head performance is studied. According to the simulation, the performance comparison is made between the tandem axial-flow pump and the conventional two-stage axial-flow pump with a uniform impeller size. Results of the study indicate that the tandem axial-flow pump can work in a wider range with high efficiency.

Research on the Influence of Spring Stiffness on the Electrorheological Isolator

ZHANG Zhen-hua, WANG Juan, ZHANG Shao-hua

2007, 16(4): 409-413.

[Abstract](184)

Abstract:
The problem of electrorheological(ER) technology's application in the vibration isolation system is emphatically studied. Based on the particular characteristics of the electrorheological fluid (ERF) tunable damping, a metal-spring ER isolator is designed and its working principle is mainly discussed. By theoretical analysis of its simplified physical model, the dynamic response of an ER isolator is sensitive to the system equivalent spring stiffness K and ERF damping coefficient C. According to the dynamic performance tests, the result confirms that applying different electric field strength can change the dynamic peculiarity of the metal-spring ER isolator. The configuration design parameters of the ER equipment, such as the stiffness ratio of two fluid chambers and the size of the electric field, are important factors for the tunable range of ER isolator.

Micro-Scale Motion Precision Simulation Method for a New-Type 6-DOF Micro-Manipulation Robot

YE Xin, ZHANG Zhi-jing, WANG Yu-shu

2007, 16(4): 414-418.

[Abstract](109)

Abstract:
A new 6-DOF micro-manipulation robot based on 3-PPTTRS parallel mechanisms in combination with flexure hinges is proposed. The design principle of the mechanism is introduced, and the kinematics analysis method based on differentiation is used to get the (inverse) kinematics equations. Then a micro-scale motion precision simulation method is proposed according to finite element analysis (FEA), and the prediction of robot's motion precision in design phase is realized. The simulation result indicates that the 6-DOF micro-manipulation robot can meet the design specification.

Application of Time Scale to Parameters Tuning of Active Disturbance Rejection Controller for Induction Motor

SHAO Li-wei, LIAO Xiao-zhong, ZHANG Yu-he

2007, 16(4): 419-423.

[Abstract](177)

Abstract:
Active disturbance rejection controller (ADRC) has good performance in induction motor (IM) control system, but controller parameter is difficult to tune. A method of tuning ADRC parameter by time scale is analyzed. The IM time scale is obtained by theoretical analysis. Combining the relations between scale time and ADRC parameters, ADRC parameter tuning in IM vector control based stator flux oriented is obtained. This parameter tuning method is validated by simulations and it provides a new technique for tuning of ADRC parameters of IM.

Grey Prediction Fuzzy Control of the Target Tracking System in a Robot Weapon

WANG Jian-zhong, JI Jiang-tao, WANG Hong-ru

2007, 16(4): 424-429.

[Abstract](135)

Abstract:
Grey modeling can be used to predict the behavioral development of a system and find out the lead control values of the system. By using fuzzy inference, PID parameters can be adjusted on line by the fuzzy controller with PID parameters self-tuning. According to the characteristics of target tracking system in a robot weapon, grey prediction theory and fuzzy PID control ideas are combined. A grey prediction mathematical model is constructed and a fuzzy PID controller with grey prediction was developed. Simulation result shows fuzzy PID control algorithm with grey prediction is an efficient method that can improve the control equality and robustness of traditional PID control and fuzzy PID control, and has much better performance for target tracking.

Novel Voltage Scaling Algorithm Through Ant Colony Optimization for Embedded Distributed Systems

ZHANG Li-sheng, DING Dan

2007, 16(4): 430-436.

[Abstract](152)

Abstract:
Dynamic voltage scaling (DVS), supported by many DVS-enabled processors, is an efficient technique for energy-efficient embedded systems. Many researchers work on DVS and have presented various DVS algorithms, some with quite good results. However, the previous algorithms either have a large time complexity or obtain results sensitive to the count of the voltage modes. Fine-grained voltage modes lead to optimal results, but coarse-grained voltage modes cause less optimal one. A new algorithm is presented, which is based on ant colony optimization, called ant colony optimization voltage and task scheduling (ACO-VTS) with a low time complexity implemented by parallelizing and its linear time approximation algorithm. Both of them generate quite good results, saving up to 30% more energy than that of the previous ones under coarse-grained modes, and their results don't depend on the number of modes available.

Research on SINS Alignment Algorithm Based on FIR Filters

LIAN Jun-xiang, HU De-wen, WU Yuan-xin, HU Xiao-ping

2007, 16(4): 437-442.

[Abstract](134)

Abstract:
An inertial frame based alignment (IFBA) method is presented, especially for the applications on a rocking platform, e.g., marine applications. Defining the initial body frame as the inertial frame, the IFBA method achieves the alignment by virtue of a cascade of low-pass FIR filters, which attenuate the disturbing acceleration and maintain the gravity vector. The aligning time rests with the orders of the FIR filter group, and the method is suitable for large initial misalignment case. An alignment scheme comprising a coarse phase by the IFBA method and a fine phase by a Kalman filter is presented. Both vehicle-based and ship-based alignment experiments were carried out. The results show that the proposed scheme converges much faster than the traditional method at no cost of precision and also works well under any large initial misalignment.

Time Slice Analysis Method Based on OTCA Used in fMRI Weak Signal Function Extraction

LUO Sen-lin, LI Li, ZHANG Xin-li, ZHANG Tie-mei

2007, 16(4): 443-447.

[Abstract](169)

Abstract:
The original temporal clustering analysis (OTCA) is an effective technique for obtaining brain activation maps when the timing and location of the activation are completely unknown, but its deficiency of sensitivity is exposed in processing brain activation signal which is relatively weak. The time slice analysis method based on OTCA is proposed considering the weakness of the functional magnetic resonance imaging (fMRI) signal of the rat model. By dividing the stimulation period into several time slices and analyzing each slice to detect the activated pixels respectively after the background removal, the sensitivity is significantly improved. The inhibitory response in the hypothalamus after glucose loading is detected successfully with this method in the experiment on rat. Combined with the OTCA method, the time slice analysis method based on OTCA is effective on detecting when, where and which type of response will happen after stimulation, even if the fMRI signal is weak.

Scattering Centers Measurements by a Modified MEMP Method

LI Shi-yong, SUN Hou-jun, LV Xin, HU Wei-dong

2007, 16(4): 448-454.

[Abstract](267)

Abstract:
A modified matrix enhancement and matrix pencil (MMEMP) method is presented for the scattering centers measurements in step-frequency radar. The method estimates the signal parameter pairs directly unlike the matrix enhancement and matrix pencil (MEMP) method which contains an additional step to pair the parameters related to each dimension. The downrange and crossrange expressions of the scattering centers are deduced, as well as the range ambiguities, from the point of view of MMEMP method. Compared with the Fourier transform method, the numerical simulation shows that both the resolution and precision of the MMEMP method are higher than those of the Fourier method. The processing results of the real measured data for three cylinders prove the above conclusions further.

Curvelet Transform-Based Denoising Method for Doppler Frequency Extraction

HOU Shu-juan, WU Si-liang

2007, 16(4): 455-459.

[Abstract](185)

Abstract:
A novel image denoising method based on curvelet transform is proposed in order to improve the performance of Doppler frequency extraction in low signal-noise-ratio (SNR) environment. The echo can be represented as a gray image with spectral intensity as its gray values by time-frequency transform. And the curvelet coefficients of the image are computed. Then an adaptive soft-threshold scheme based on dual-median operation is implemented in curvelet domain. After that, the image is reconstructed by inverse curvelet transform and the Doppler curve is extracted by a curve detection scheme. Experimental results show the proposed method can improve the detection of Doppler frequency in low SNR environment.

Small Area ROM Design for Embedded Applications

CUI Wei, WU Si-liang

2007, 16(4): 460-464.

[Abstract](165)

Abstract:
The compact full custom layout design of a 16 kbit mask-programmable complementary metal oxide semiconductor (CMOS) read only memory (ROM) with low power dissipation is introduced. By optimizing storage cell size and peripheral circuit structure, the ROM has a small area of 0.050 mm2 with a power-delay product of 0.011 pJ/bit at +1.8 V. The high packing density and the excellent power-delay product have been achieved by using SMIC 0.18 μm 1P6M CMOS technology. A novel and simple sense amplifier/driver structure is presented which restores the signal full swing efficiently and reduces the signal rising time by 2.4 ns, as well as the memory access time. The ROM has a fast access time of 8.6 ns. As a consequence, the layout design not only can be embedded into microprocessor system as its program memory, but also can be fabricated individually as ROM ASIC.

New Optimal DWT Domain Image Watermarking Technique via Genetic Algorithm

ZHONG Ning, KUANG Jing-ming, HE Zun-wen

2007, 16(4): 465-470.

[Abstract](195)

Abstract:
A novel optimal image watermarking scheme is proposed in which the genetic algorithm (GA) is employed to obtain the improvement of algorithm performance. Arnold transform is utilized to obtain the scrambled watermark, and then the embedding and extraction of watermark are implemented in digital wavelet transform (DWT) domain. During the watermarking process, GA is employed to search optimal parameters of embedding strength and times of Arnold transform to gain the optimization of watermarking performance. Simulation results show that the proposed method can improve the quality of watermarked image and give almost the same robustness of the watermark.

Fusion of Absolute and Recursive Information to Overcome Jitter and Occlusion in ARToolKit System

LI Yu, WANG Yong-tian, LIU Yue

2007, 16(4): 471-475.

[Abstract](84)

Abstract:
According to the most mature marker based augmented reality system ARToolKit only utilizes absolute information in pose estimation, a novel technique is presented in this paper. The proposed method embeds the recursive information as well to make ARToolKit system smoother by eliminating the jitter and more robust to occlusion conditions. Experiments on the jitter improvement has been performed, the results show that the proposed method is very effective.

Hardware in Loop Simulation for Emergency Communication Mobile Ad Hoc Network

YANG Jie, AN Jian-ping, LIU Heng

2007, 16(4): 476-480.

[Abstract](200)

Abstract:
For the research of mobile Ad hoc network (MANET), hardware in the loop simulation (HILS) is introduced to improve simulation fidelity. The architectures and frameworks of HILS system are discussed. Based on HILS and QualNet network simulator, two kinds of simulation frameworks for MANET multicast emergency communication network are proposed. By running simulation under this configuration and doing experiments with on-demand multicast routing protocol (ODMRP), unicast and multicast functions of this protocol are tested. Research results indicate that HILS method can effectively reduce the difficulty of system modeling and improve precision of simulation, and can further accelerate transition from design to system deployment.

Backscattering Light Model of Seawater for Modulated Lidar Based on the Stationarity of Light Field

JI Hang, MA Yong, LIANG Kun, WANG Hong-yuan

2007, 16(4): 481-485.

[Abstract](103)

Abstract:
The backscattering signal, which arises from the pulsed laser traveling through water, has limited the lidar system sensitivity and underwater target contrast. The transmitted optical carrier is modulated to be ultrashort pulsed laser and it is effective to suppress the backscattering to adopt the coherent detection technology by identifying the modulation envelope. A nonstationary light field is formed in seawater by the ultrashort pulsed laser. The inherent relationship between the nonstationary light field formed by modulated lidar and the stationary light field formed by conventional lidar was discussed and the backscattering light model of the stationary light field for the ultrashort pulsed laser was proposed. The backscattering signal in modulated lidar system was processed and analyzed in the frequency domain on the basis of the model.

Effect of Dissolved Oxygen on Operation of EGSB

LI Hui-li, LV Bing-nan, LI Qing-wei

2007, 16(4): 486-491.

[Abstract](85)

Abstract:
An expanded granular sludge bed (EGSB) reactor was adopted to study the dissolved oxygen (DO) effect on the operation. With the chemical oxygen demand (COD) 800-1 800 mg/L, pH 6.0-7.3, volume loading rate (VLR) 5.4-11.5 kg COD/(m3·d), the operational behaviors of EGSB reactor was researched. And the max DO concentration which influenced steady operation of EGSB reactor was determined by contrasting the changes due to different concentrations of the influent DO. With the COD 1 200-2 000 mg/L, VLR 7.2-12.0 kg COD/(m3·d), the operational characteristic of EGSB reactor was researched by aerating the recycle effluent. The results was: when the DO concentration of influent was under 3.0 mg/L, the removal efficiency of COD was 82%-90% and the operation of the EGSB reactor was steady; when the DO concentration of influent was over 3.0 mg/L, the oxidation-reduction potential (ORP) fluctuated greatly and the operation of the EGSB reactor was instable; the acidified wastewater of saccharide whose pH value was 5.1-6.5 could be treated by aerating the recycle effluent and the efficiency of COD was up to 85%-92%.

Technology Progress and the Market Power of Middlemen

SUI Ji-gang, LI Jian

2007, 16(4): 492-495.

[Abstract](210)

Abstract:
The normative mathematic model is used to analyze the effect of the technology progress on middlemen. The incomes of traders and middlemen in different transaction mechanisms are compared on the base of static transaction models which are followed by the dynamic factor of technology progress. It can be found that the indirect trade is dominant in the circumstance where search cost is high. With the technology progress, the search cost trends to decrease. The increase in direct trade will have influence on the middlemen. But the middlemen will not disappear; its market power is dependent not only on the absolute level of the technology, but also on the comparative level of the technology adopted by the different transaction mechanisms.

Influence of Non-Uniform Magnetic Field on Quantum Teleportation in Heisenberg XY Model

SHAO Bin, YANG Tie-jian, ZHAO Yue-hong, ZOU Jian

2007, 16(4): 496-499.

[Abstract](120)

Abstract:
By considering the intrinsic decoherence, the validity of quantum teleportation of a two-qubit 1D Heisenberg XY chain in a non-uniform external magnetic field is studied. The fidelity as the measurement of a possible quantum teleportation is calculated and the effects of the non-uniform magnetic field and the intrinsic decoherence are discussed. It is found that anti-parallel magnetic field is more favorable for teleportation and the fidelity is suppressed by the intrinsic decoherence.

Geometric Structures of Stable Time-Variant State Feedback Systems

ZHONG Feng-wei, SUN Hua-fei, ZHANG Zhen-ning

2007, 16(4): 500-504.

[Abstract](155)

Abstract:
A new technique for considering the stabilizing time-variant state feedback gains is proposed from the viewpoint of information geometry. First, parametrization of the set of all stabilizing time-variant state feedback gains is given. Moreover, a diffeomorphic structure between the set of stabilizing time-variant state feedback gains and the Cartesian product of positive definite matrix and skew symmetric matrix satisfying certain algebraic conditions is constructed. Furthermore, an immersion and some results about the eigenvalue locations of stable state feedback systems are derived.

2007 Vol. 16, No. 4