Table of Content

23 July 2012, Volume 30 Issue 4

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Signal and Information Processing

Design of Imitation Digital Camouflage

YU Jun, SHUANG Xiao

2012, 30(4):  331-334.  doi:10.3969/j.issn.0255-8297.2012.04.001

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The paper proposes a new method of generating imitation digital camouflage based on the background images. First, convert the color space of the background pattern. Dominant colors are extracted using the K-means clustering analysis. The minimum size of digital unit is determined by the detection distance. Finally, the digital camouflage spots are generated. The effect of camouflage is assessed by Canny edge detection. Experimental result shows that the generated digital camouflage can effectively change the original contour of the target, and can be perfectly blended with the background to achieve a good camouflage effect.

Comprehensive Performance Evaluation of Steganalysis Based on Combination Weight and TOPSIS

LI Kai-da, ZHANG Tao, PING Xi-jian, LI Xing

2012, 30(4):  335-342.  doi:10.3969/j.issn.0255-8297.2012.04.002

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 According to the different requirement of different applied fields of steganalysis, this paper proposes
a steganalysis algorithm comprehensive evaluation method based on combination weight and TOPSIS.
The method contains five performance indexes including true positive rate, false positive rate, reliability, detection
error and detection speed. First, the entropy weight is put forward to give weights, then considering
the defect of entropy weight and the estimator’s experience and intent, the AHP is used to give subjective
weights, then the final weights are given by assembled weighting method. The evaluation and comparison
to performance of steganalysis algorithm are implemented by using TOPSIS algorithm. Experimental results
show that the evaluation algorithm can not only be applied to choose the best steganalysis method aim to
different requirements of each index in different applications, but also can conduct to improve the steganalysis
algorithm.

Identification of Sine Driving Force of Duffing Oscillator Based on Extended Kalman Filter

RUI Guo-sheng1, ZHANG Yang1;2, ZHANG Song1;2, MIAO Jun1;2

2012, 30(4):  343-348.  doi:10.3969/j.issn.0255-8297.2012.04.003

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In studying Duffing oscillator systems, a basic model using sine function as a periodic driving force
and the system oscillator’s movement are analyzed. Extended Kalman filter is used to process and estimate
the Duffing oscillator system according to the change of the Kalman gain in the filtering process. A method
using the Kalman gain to identify the periodic force is proposed, which can be used for weak signal detection
with a Duffing oscillator. Simulations show performance improvement as compared with the Lypunov exponent
method.

Object Retrieval Based on Exact Euclidean Locality Sensitive Hashing

ZHAO Yong-wei, LI Bi-cheng, GAO Hao-lin

2012, 30(4):  349-355.  doi:10.3969/j.issn.0255-8297.2012.04.004

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 The problem of object retrieval is often addressed with the BoVW (bag of visual words) method. There are several problems in the traditional BoVW such as low time efficiency and large memory consumption,and synonymy and polysemy of visual words. In this paper, an object retrieval method based on exact Euclideanlocality sensitive hashing (E2LSH) is proposed. E2LSH is used to hash local features of the training dataset,and a group of scalable random visual vocabularies is constructed. Then, the visual vocabulary histograms and index files are created according to these random vocabularies. The term frequency vectors are weighted with tf-idf strategy. Similarity matching between histogram of the query object and index files is made to accomplish object retrieval. Experimental results show that accuracy of the proposed method is substantially improved compared to the traditional methods. The method is applicable to large scale datasets.

Electronic Engineering

On-Chip Memory Dynamic Optimization for Embedded Linux

WU Jian-ping, FANG Pan, LING Ming, ZHANG Yang

2012, 30(4):  356-362.  doi:10.3969/j.issn.0255-8297.2012.04.005

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An on-chip memory (scratch-pad memory, SPM) dynamic optimization approach (auto profile
and page swap, APPS) for Linux user process is explored to improve system performance and reduce power
consumption. The SPM page zone is added to the memory model of Linux kernel by a virtual memory system.
The dynamic allocation mechanism for the SPM page frame is implemented based on the SPM page zone.
The general interface function for the SPM page frame assignment is provided for other processes. Based on
optimization for user program including code, stack and BSS segment, the APPS scheme is introduced. This
method can automatically analyze the hot-spots of processes in kernel mode and transmit them to the SPM
zone by a dedicated DMA channel. Therefore, the multi-process user program will be dynamically optimized.
Experimental results show that the proposed approach can improve the system performance.

Phase Difference Measurement for Current Sensor Based on FastICA

GONG Guo-liang, LU Hua-xiang, LIU Pei-hua, CHEN Tian-xiang

2012, 30(4):  363-368.  doi:10.3969/j.issn.0255-8297.2012.04.006

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Phase difference of a current sensor is susceptible to environmental impact. In order to improve
reliability and accuracy of the on-line insulation monitoring system, a phase difference measurement method
for current sensor on-line monitoring is proposed. In the method, independent component analysis (ICA) is
used to extract the test signal from the output of current sensor. An ICA model is established, and a method
given to compensate the number of observed signals and its components. To solve the problem that phase
errors are different in different test runs, an evaluation index of the mixing matrix is proposed to find the most
accurate result. Experimental results indicate that for a signal with SNR=10.9 dB, the percentage of phase
errors below 0.06± is raised form 51.4% to 81% by using the evaluation index.

Microwave Response of Planar Metamaterial Structured by Asymmetrically Split Rings

SHI Jin-hui, LIU Ran, YU Sheng-wu, ZHU Zheng, GUAN Chun-ying

2012, 30(4):  369-373.  doi:10.3969/j.issn.0255-8297.2012.04.007

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 In the paper, Fano resonances in a planar metamaterial with asymmetrically split rings are investigated
using the finite element method. Excited surface current distributions are presented. The transmission
spectrum of the metamaterial is also fitted based on the Fano formula. The electromagnetic response of each
metallic ring is studied individually. It is found that the Fano resonances are due to the coupling between
two asymmetric metallic resonators. Further, effects of the structural parameters on the Fano resonance are
analyzed. Finally, dependence of Fano resonance on polarization rotation angles of the incident electromagnetic
waves is studied. Simulation results reveal that polarization rotation angles of incident electromagnetic waves
provides an easy approach of tuning the performance of metamaterials.

Computer Science and Applications

Finding Key Host of Network through Iterative Matrix

ZHONG Shang-qin1;2, LIU Fu-qiang3, XU Guo-sheng1;2, YANG Yu1;2, YAO Wen-bin1;2

2012, 30(4):  374-378.  doi:10.3969/j.issn.0255-8297.2012.04.008

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Security of the key host is of prime importance to the overall network, but locating the key host
difficult. This paper gives a definition of key hosts, provides their classification, and propose an approach to
finding the key hosts. The method uses the host-based attack graph and the theory of iterative matrix. By
computing and sorting the security properties of each host, the network security administrator can identify
key hosts and the corresponding key critical-conditions. Appropriate measures can then be taken to protect
the key hosts and enhance the overall network security. Experiment shows that this approach can be applied
to the analysis of network security, and is useful for the enhancement of network security.

Performance Evaluation for Complex Queueing System under Exhaustive-Service Policies Based on Petri Nets

FANG Huan1;2, LU Yang1;3, GE Fang-zhen1, HUANG Zhen-jin1

2012, 30(4):  379-386.  doi:10.3969/j.issn.0255-8297.2012.04.009

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Since it is difficult to obtain analytical solutions of performance indices for complex queueing
systems, a method for finding approximate solutions is presented based on Petri net. With the CPN tools, a
Petri net model is constructed for queueing system under four vacation policies. Based on the mathematical
formula for performance indices, performance indices and expected profits are calculated from the dynamic data
collected by Data Collector in the simulation. The results show that the method based on model simulation
is effective, the models and the performance analysis method based on the models have flexible scalability,
reusability and a friendly interface.

Relationship between Process Expression and Liveness of Bounded Petri Nets

YAN Chun-gang1;2, WANG Ming-xin1;2, LIU Guan-jun1;2

2012, 30(4):  387-390.  doi:10.3969/j.issn.0255-8297.2012.04.010

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 Process of Petri nets can present the concurrent semantic of Petri nets, which is an effective way for
analyzing and verifying the Petri net properties. This paper studies the relationship between process expression
and liveness of bounded Petri nets, and provides theorems of liveness determination for bounded Petri nets
and their synchronous composition nets. The paper also explores the relationship between process expressions
and traps and siphons.

Using Hierarchical Structure Glowworm Swarm Algorithm for Function Optimization

LI Yong-mei1;2, ZHOU Yong-quan1, WEI Jun2

2012, 30(4):  391-396.  doi:10.3969/j.issn.0255-8297.2012.04.011

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Based on artificial glowworm swarm optimization algorithm and cooperation in hierarchical social
organization, a new hierarchical glowworm swarm optimization (HGSO) is proposed. A mutation operator is
added into the HGSO. Tests on four standard functions show that the HGSO algorithm in the high dimension
function optimization has better performance than the basic artificial GSO algorithm.

Nearest Neighbor Rule Condensation Algorithm Based on Artificial Endocrine System

ZHAO Li1;2, WANG Lei1, XU Qing-zheng1

2012, 30(4):  397-407.  doi:10.3969/j.issn.0255-8297.2012.04.012

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The main disadvantage in most prototype reduction algorithms is the excessive computational cost
especially when the prototype size is large. To deal with the problem, we present a new prototype reduction
method in which an artificial endocrine system is embedded. The method remains only for points on boundaries
between different classes. The amount of reduced rules of the reference set can be revised by granularity of
the lattice. The proposed method can get a consistent subset in a divide-reduce-coalesce manner, making it
more efficient and effective than other algorithms. The proposed approach has been tested using 11 different
datasets. The experiments show that the algorithm can give correct results when the size of dataset is large.

Control and System

Backstepping Terminal Sliding Mode for Flight Control Based on Nonlinear Disturbance Observer

WANG Jian-hao1, HU Jian-bo1;2, ZHANG Bo-feng2

2012, 30(4):  408-414.  doi:10.3969/j.issn.0255-8297.2012.04.013

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A backstepping terminal sliding mode control scheme based on nonlinear disturbance observer
(NDO) is proposed in the presence of model nonlinearity, aerodynamic parameter and moment disturbance
uncertainties for maneuvers flight. The control scheme removes the priori condition of the upper bound of
uncertainties by using NDO to approximate uncertainties. Explosion of complexity is avoided by combining
dynamic surface control with the design virtual controller. A fast terminal sliding mode control strategy is then
used to improve convergence and steady-state tracking accuracy of the system. Using the Lyapunov stability
theorem, all signals in the closed loop system are guaranteed to be ultimately uniformly bounded. Simulation
of a nonlinear six-degree-of-freedom maneuvering flight of an aircraft is done. The results show effectiveness
of the proposed control scheme.

Trajectory Tracking Control of Quad-rotor UAV Based on Quaternion

LI Guang-chun, WANG Lu, WANG Zhao-long, XU De-xin

2012, 30(4):  415-422.  doi:10.3969/j.issn.0255-8297.2012.04.014

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Because a complete mathematical model of a quadrotor is complicated, the controller design is
usually based on a simplified model. In this paper, we analyze the limitation of such simplification, and consider
nonlinear trajectory tracking control based on its original model. A tracking error control system consisting
of two independent subsystems is established to track the expected trajectory. The attitude subsystem is
described using the quaternion of rigid body’s rotation as the system state. A backstepping based approach is
proposed to stabilize the subsystems exponentially. Based on the global stability criterion of cascade systems
and analysis of the properties of coupled parts, globally exponential stability of the system is proved. Simulation
results show that the proposed method enables the quadrotor to track a trajectory.

Descriptor Fuzzy Control for Nonlinear Systems

WANG Yu-fei, JIANG Chang-sheng, WU Qing-xian

2012, 30(4):  423-426.  doi:10.3969/j.issn.0255-8297.2012.04.015

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A robust tracking control scheme is proposed for nonlinear systems based on the T-S fuzzy model.
An ordinary fuzzy model is transformed to a fuzzy descriptor model. The tracking performance index is
designed, and the robust tacking controller design method presented based on linear matrix inequality. Computational
complexity is decreased, and conservation also reduced as the limitations on the undetermined
matrices are relaxed. The method is applied to control an inverted pendulum system, showing that the angle
and angular rate can track the reference signals accurately and rapidly. The simulation results demonstrate
effectiveness of the proposed method.

Relative Pose Decoupled Iterative Determination Algorithm for UAV Aerial Refueling

WANG Long1, DONG Xin-min1, JIA Hai-yan2

2012, 30(4):  427-432.  doi:10.3969/j.issn.0255-8297.2012.04.016

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 Considering the coupled and nonlinear relationship between the relative pose in the line of sight
equations, an iterative decoupling algorithm is proposed to determine relative pose. Application of the method
to aerial refueling is discussed. Based on the pseudo-range of satellite navigation, an observation matrix is
constructed by using line of sight vectors. The relative position are updated by the least square method, and
then the relative attitude is updated. By introducing an iterative error, convergence of the iterative algorithm
is proved. The trace of error variance matrix is used to analyze the effect of feature geometry configuration
on the precision. Simulation results show that the proposed algorithm can improve performance by 23% and
40% in speed and robustness than Gaussian least square differential correction (GLSDC), respectively. Steady
state errors of relative pose are 0.1 m and 0.2± lower respectively. The precisio can satisfy the relative pose
requirements of UAV aerial refueling during docking.

Instrumental Variable Covariance Method and Asymptotic Analysis for Aircraft Flutter Model Parameter Identification

WANG Jian-hong, ZHU Yong-hong, XIAO Xuan

2012, 30(4):  433-440.  doi:10.3969/j.issn.0255-8297.2012.04.017

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 When the observed input-output data are corrupted by observed noise in an aircraft flutter statistic
model, one should obtain accurate parameters of the model. We combine the instrumental variable identification
method and covariance matching method to develop a new method: the instrumental variable covariance
method. In the statistic model of aircraft flutter, we introduce some instrumental variables to develop a covariance
function. We present the procedure to solve the criterion function and partial derivatives expression. We
derive the asymptotic covariance matrix expression obtained with the proposed method, and use the asymptotic
covariance matrix expression to verify effectiveness of the method, and design the external excitation
signal. The method is applied to identify the transfer function in the current loop of a flight simulator and
parameters of an aircraft flutter model. The simulation shows effectiveness of the method.