JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Experimental Investigation of Water-Entry Phenomenon

WEI Zhuo-hui, WANG Shu-shan, MA Feng, LV Quan-zhou, ZHONG Xiao

2010, 19(2): 0127-131.

[Abstract](2283)

Abstract:
In order to investigate the cavity shape and velocity attenuation of steel spheres after high-speed water entry, the high-speed water entry of different water entry angles were performed. The cavity shapes were recorded using high-speed photo recorder, and the velocities after water entry were measured. The diameters of equivalent disk of steel spheres after water entry were obtained from the processing of cavity images. Based on the steady and uncompressing flow assumption, a theoretical model for velocity attenuation of steel spheres with cavity was proposed and calculated results were in good agreement with the experimental results. The second cavity breaking off phenomenon, which has not been reported before, was discovered. The established theoretical model provides a reference for other relative researches.

Simulation of the Impact Between Head and Seat Head Restraint During REC Under Consideration of the Multiphase and Nonlinear Features

HAN Jian-bao, CHEN Ya-nan

2010, 19(2): 0132-135.

[Abstract](2248)

Abstract:
The impact process between car drivers head and seat head restraint during a car rear end collision is simulated, where the multiphase and nonlinear features of the human brain tissues and the foam material of the seat head restraint are considered. Using the FEM-software LS-DYNA, the brain tissue deformation caused by a car REC is calculated. The purpose of this work is to supply references for improving the design of the head protective devices. The results show that the maximum shear strain appears near the boundaries of different phases and there is a great shear strain gradient in the brain tissues.

Investigation on Mechanical Characteristics of Air Jet Acting on Nozzle Vanes of VNT

MA Chao-chen, LV Wei, ZHANG Zhi-qiang, SHI Xin

2010, 19(2): 0136-142.

[Abstract](431)

Abstract:
Extensive experimental studies are performed using force sensors to measure actuating forces of nozzle ring devices of variable nozzle turbines. Torques from pneumatic action applied onto axles of nozzle vanes have been calculated. Test results obtained through repeated experiments are quite congruent, confirming the effectiveness of this simple method. Results have indicated that, with a fixed opening angle of guide vane, pneumatic torque increases with mass flow of air jet in the turbine; moreover, under the same mass flow rate, torque decreases with reducing opening angle, even possibly change direction down to negative. The results have also provided a modus operandi for designing nozzle-adjusting devices as well as validation data for numerical study on changes of pneumatic torque onto guide vanes under full engine operating conditions.

Research on Directly Adaptive Fuzzy Algorithm Based ACC Controller

LI Jing-liang, LIU Zhao-du, YE Yang, SHANG Bing-xu

2010, 19(2): 0143-147.

[Abstract](718)

Abstract:
A directly adaptive fuzzy algorithm is applied in vehicle adaptive cruise control system. The basic principle of the adaptive fuzzy algorithm is analyzed. The initial value of the fuzzy based vector is given by the traditional fuzzy membership. Adaptive law of the adjustable parameters θ is also determined. The directly adaptive fuzzy ACC controller is designed based on Matlab fuzzy toolbox. Matlab-Simulink is adopted to test the function of the adaptive fuzzy ACC controller. The control system is established using a 7 DOF vehicle dynamics model. Simulation results indicate that the principle of the method is correct and it performs well both in cruise and distance keeping.

Effect of Deflected Discs Thickness to the Damping Characteristic of Tube Shock Absorbers

LIU Jian-yong, GU Liang, DONG Ming-ming, ZHONG Shu-xian

2010, 19(2): 0148-152.

[Abstract](702)

Abstract:
Research is conducted on the relationship between thickness of deflected disc and damping force of tube shock absorbers. By analyzing performing characteristics of the throttling valve using throttling theory of small clearance space and thin place deformation theories, mathematical correlation between disc thickness and magnitude of damping force is formulated. Moreover, a rule concerning change of damping force in terms of disc thickness is concluded.

Estimation of Vehicle Speed Based on Wheel Speeds from ASR System in Four-Wheel Drive Vehicles

QI Zhi-quan, MA Yue-feng, LIU Zhao-du, LI Hong-jun

2010, 19(2): 0153-157.

[Abstract](709)

Abstract:
Three major methods currently in the use of determining vehicle speed based on wheel speeds, the minimum wheel speed, minimum wheel speed corrected by slope method and the Kalman filter method, are analyzed, with merits and defects of each approach stated. Through simulations, the Kalman filter method based on minimum wheel speed shows improved accuracy, in addition to better adaptivity to vehicle reference speed. It also can be used to acceleration ship regulation (ASR) in part-time four-wheel drive vehicles.

Study on Steering Control Strategy for High-Speed Tracked Vehicle with Hydrostatic Drive

YANG Lei, MA Biao, LI He-yan

2010, 19(2): 0158-164.

[Abstract](555)

Abstract:
Steering control strategy for high-speed tracked vehicle with hydrostatic drive is designed based on analyzing the fundamental steering theories of the hydrostatic drive tracked vehicle. The strategy is completed by the cooperation between integrated steering control unit and pump & motor displacement controller. The steering simulation is conducted by using Simulink of Matlab. It is indicated that this steering control strategy can reduce the average vehicle speed automatically to achieve the drivers expected steering radius exactly in the case of ensuring not exceeding the system pressure threshold and no sideslip.

Three-Dimensional Kinematics Simulation of Robot Fighting Platform in Virtual Environment

WANG Jian-zhong, ZHU Li-yao

2010, 19(2): 0165-169.

[Abstract](597)

Abstract:
A method of 3D kinematics simulation of robot fighting platform (RFP) in virtual environment is proposed with the aim of enhancing vision telepresence. Based on the theory of space coordinate transformation, kinematics equations of RFP are formulated; followed by applying a method of modeling using 3DMAX software to build an RFPs 3D geometric model before a 3D kinematics simulation system of RFP is completed based on virtual reality technology and Open Inventor VC++. Test results have indicated that this system can perform RFPs kinematics simulation in virtual environment. It can also imitate RFPs motion states and environmental features well. Moreover, not only can better real-time performances and interactions be achieved but also operators vision telepresence be enhanced, therefore this approach may help lay the foundation for the realization of RFPs teleoperation with vision telepresence.

Component-Based Software Trustworthiness Fuzzy Analytic Hierarchy Process Model

SHI Jian-fei, YAN Huai-zhi, QIN Wei, WANG Wen-tong

2010, 19(2): 0170-176.

[Abstract](713)

Abstract:
For a more accurate and comprehensive assessment of the trustworthiness of component-based software system, the fuzzy analytic hierarchy process is introduced to establish the analysis model. Combine qualitative and quantitative analyses, the impacts to overall trustworthiness by the different types of components are distinguished. Considering the coupling relationship between components, dividing the system into several layers from target layer to scheme layer, evaluating the scheme advantages disadvantages by group decision-making, the trustworthiness of a typical J2EE structured component-based software is assessed. The trustworthiness asses model of the software components provides an effective methods of operation.

Design of an Integrated SITL and HITL Simulation System for the Control of a Loitering Aerial Vehicle

WANG Zheng-jie, FAN Ning-jun, ZHANG Hui

2010, 19(2): 0177-182.

[Abstract](558)

Abstract:
An investigation into the aircraft flight simulation and control system is presented in this paper. The study was firstly focused on the establishment of an integrated hardware-in-the-loop(HITL) platform for aircraft flight simulation based on MATLAB/Simulink+dSPACE. The platform combines the abundant software and hardware resources of dSPACE simulation platform to simulate the flight attitude of an aircraft in six-DOF (degree of freedom) motion. Based on the platform, the study was then focused on the flight numerical simulation by taking a loitering aerial vehicle as an example. An aircraft mathematical model was created for a modular design and off-line numerical simulation based on MATLAB/Simulink. Finally, the study was focused on the control system design of the loitering aerial vehicle and conduct of an HITL simulation experiment for the vehicle pitch control. The experiment verifies the system design and control effectiveness. Research results show that the dSPACE simulation system provides a real time good experimental platform to improve the efficiency of study and development of a flight control system.

A Dual-Channel Secure Transmission Scheme for Internet-Based Networked Control Systems

TIAN De-zhen, DAI Ya-ping, HU Jing-lu, HIRASAWA Kataro

2010, 19(2): 0183-190.

[Abstract](912)

Abstract:
Two significant issues in Internet-based networked control systems (INCSs), transport performance of different protocols and security breach from Internet side, are investigated. First, for improving the performance of data transmission, user datagram protocol (UDP) is adopted as the main stand for controllers and plants using INCSs. Second, a dual-channel secure transmission scheme (DCSTS)based on data transmission characteristics of INCSs is proposed, in which a raw UDP channel and a secure TCP (transmission control protocol) connection making use of SSL/TLS (secure sockets layer/transport layer security) are included. Further, a networked control protocol (NCP) at application layer for supporting DCSTS between the controllers and plants in INCSs is designed, and it also aims at providing a universal communication mechanism for interoperability of devices among the networked control laboratories in Beijing Institute of Technology of China, Central South University of China and Tokyo University of Technology of Japan. By means of a networked single-degree-of-freedom robot arm, an INCS under the new protocol and security environment is created. Compared with systems such as IPSec or SSL/TLS, which may cause more than 91% network throughput deduction, the new DCSTS protocol may yield results ten times better, being just 5.67%.

Orientation Mechanism Based on Insect Polarization Navigation

GUAN Gui-xia, CHEN Jia-bin, YAN Lei, WU Tai-xia, WU Bo

2010, 19(2): 0191-195.

[Abstract](615)

Abstract:
A method to determine the direction angle for bionic navigation is proposed. In order to do it, observation models of polarized light were obtained through full-sky imaging polarimetry, and the symmetry line (solar meridian) was detected firstly; then the angle between solar meridian and the system moving direction was derived from simultaneous model, and the relative position of the sun was calculated by astronomical knowledge; finally, the direction angle for bionic navigation was evaluated by utilizing sun azimuth to revise the angle between solar meridian and the system moving direction. This study improves previous conception with the changing solar meridian as a reference direction (0°) and provides a theoretic foundation for polarized light to be applied into navigation.

Study of Polarization Image Color Fusion Method Based on Color Transfer

WANG Xia, LI Hai-lan, WEN Xuan, JIN Wei-qi, BAI Ting-zhu, ZHANG Xiao

2010, 19(2): 0196-201.

[Abstract](711)

Abstract:
Based on the characteristics that human eyes are sensitive to brightness and color, the lightness information of visible image and degree of linear polarization and polarization angle were fused in hue-saturation-value(HSV) space. To meet the observation of human eyes, hue adjustment based on color transfer was carried out to the fused image and hue was adjusted by polynomial fitting method. Hue adjustment method was improved considering the complicated real mapping relationship between hue gray scale of fused image and reference template image. The result shows that the color fusion method presented in this paper is superior to the traditional pseudo-color method and it is helpful to recognize the target from the environment correctly. The fusion result can reflect the difference of objects polarization characteristic, and get a natural fused image effect.

Performance of Optical Sampling Based on SHG in CPPLN Waveguide

NING Chun-mei, YANG Ai-ying, CUI Jian-min, SUN Yu-nan

2010, 19(2): 0202-206.

[Abstract](632)

Abstract:
Sampling efficiency and bandwidth of the optical sampling system based on second harmonic generation (SHG) in chirped periodically poled LiNbO₃(CPPLN) are numerically researched. A broad sampling bandwidth can be obtained by adjusting chirp coefficient and waveguide length of CPPLN, and sampling efficiency can be improved by using higher pump power, increasing waveguide length and choosing appropriate chirp coefficient. Results show that both sampling bandwidth and efficiency in CPPLN waveguides are controllable and that CPPLN waveguides are more suitable for multiwavelength optical sampling systems.

Improved Berlekamp-Massy Algorithm and Its Software Implementation on DSP

ZHANG De-sheng, AN Jian-ping, FAN Yuan-yuan

2010, 19(2): 0207-210.

[Abstract](593)

Abstract:
Based on the Berlekamp-Massy (BM) algorithm for Reed-Solomon(RS) decoding, an improved version is proposed, which focuses on how to find the error locator polynomial using least iterative operations. The conditions to end the iterative operations is derived. As a special case, criterion of only one error symbol in one received codeword is derived as well. Steps are listed concerning the implementation of the improved iterative decoding algorithm, which is carried out as software on the platform of TIs C6416 DSP. Decoding performance and decoding-delay of both improved and original algorithms under different (n,k) conditions are simulated. The results of simulations demonstrate that the improved algorithm has less computational complexity when the number of errors in a received codeword is relatively small. Therefore, in channels with low noise power spectrum density, the improved algorithm results in less decoding-delay than BM algorithm.

Spatial Target Detection Based on the Measurement of Equivalent Blackbody Temperature

ZHOU Yan-ping, SHU Rui, LU Chun-lian

2010, 19(2): 0211-216.

[Abstract](591)

Abstract:
At low SNR cases, the distinction between spatial point-target and interferences as decoys is still a very difficult problem. Based on the characteristics that target and interferences as decoys and noise had different radiation intensity and radiation changing frequency, the concept of the equivalent blackbody temperature (EBT) was built and the calculation model of EBT was designed. The model could effectively reduce the interference of the space environment and fully show the radiation differences between point-target and interferences as decoys. It would be very effective in the detection of the target. In order to detect the target, the effective estimator of EBT was designed according to the observed data, and the system error and the variation range of the estimator of EBT were estimated. Finally the multi-frame estimator was designed to improve the estimation stability of EBT, and the use of this estimator would identify the point-target more effectively.

Numerical Study on the Mixing Performance of Screw Mixing Elements and Conventional Screw Elements

CHEN Jin-nan, LIU Jie, CAO Ying-han, PENG Jiong

2010, 19(2): 0217-223.

[Abstract](552)

Abstract:
The flows of rigid polyvinyl chloride (R-PVC) in co-rotating twin screw extruders with screw mixing elements and regular screw elements were simulated by using the finite element method. The three-dimensional, non-isothermal flow fields of R-PVC in the two kinds of screw elements were calculated. The mixing performance of each type of element was studied by the particle tracking analysis method. The results show that the temperature distribution and shear-rate distribution are more uniform in the flow channel with screw mixing elements than in the flow channel with regular screw elements. Screw mixing elements provide better distributive and dispersive mixing performance but worse conveying capacity than regular screw elements.

Progress in Researches on Biodegradable Starch-Based Materials

ZHANG Qing-shan, NING Zhuo-yuan, LI Yun-zheng

2010, 19(2): 0224-231.

[Abstract](559)

Abstract:
As one type of environment-friendly polymer, biodegradable starch-based materials have been widely explored in recent years and considered one of the most promising plastics in the future. Currently, either synthetic biodegradable aliphatic polyesters or certain natural polymers are usually blended with thermoplastic starch to enhance hydrophobicity and service performance of starch-based materials. The main deficiency lies in the low compatibility between starch and polyester phases. Therefore amphiphilic compatibilizers, such as hydroxyl functioned polyesters, need to be developed in the future. Moreover, multi-phase blending systems including two or more polyester phases are also supposed to be designed.

Thermal Sense Prediction Model for Definite Human Group in Indoor Case

ZHANG Chun-cheng, CHEN Xiang-guang, XU Yuan-qing

2010, 19(2): 0232-236.

[Abstract](721)

Abstract:
In order to build a prediction model of the indoor thermal comfort for a given human group, the original predicted mean vote (PMV) equation is reconstructed and simplified, the modified PMV equation is named PMVR (PMV for region), where five variables are needed to be fitted with the dataset of actual thermal sense of a definite human group. As the fitting algorithm, the particle swarm optimization algorithm is used to optimize the solution, and a fixed PMVR can be finally determined. Experiment results indicate that for a definite human group, PMVR is more accurate on the prediction of thermal sense compared with some other models.

Effects of Nano-Filler on the Thermal and Fire-Resistant Properties of Ethylene-Vinyl Acetate Copolymer

DU Jian-xin, HAO Jian-wei, CUI Yan-xia

2010, 19(2): 0237-240.

[Abstract](567)

Abstract:
Sepiolite (S9, B10, B20, B40) and boehmite have been added to an intumecent flame retardant (IFR) system to produce the halogen-free and fire-resistant ethylene-vinyl acetate copolymer (EVM) rubber. The rubber contains ammonium polyphosphate (APP) as acid source, double pentaerythritol (D-PER) as carbon source and melamine (MN) as gas source. The effects of nano-filler sepiolite and boehmite on the fire-resistant property of EVM rubber based on IFR system were investigated. The test results show that the system with nano-filler of sepiolite B10 has the best fire-resistant property. The process of smoke emission and thermal decomposition, the element composition of char surface and the micro morphology of intumecent char layer of the EVM IFR system with nano-filler were also studied by NBS chamber, thermogravimetric (TG) analysis, X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM).

Monotone Set-Valued Function Defined by Set-Valued Choquet Integral

SUN Hong-xia, ZHANG Qiang

2010, 19(2): 0241-245.

[Abstract](872)

Abstract:
Structural characteristics and absolute continuities of monotone set-valued function defined by set-valued Choquet integral are discussed. Similar to the single-valued monotone set function, several important structural characteristics of set-valued function are defined and have been proven the same as those in the original set functions, such as null-additivity, weakly null-additivity, order continuity, strong order continuity and property(S). A counterexample shows that order continuity and strong order continuity of the original set functions are no longer kept in a monotone set-valued function when Choquet integrably bounded assumption is abandoned. Four kinds of absolute continuities are defined for set-valued function, and all been proven valid with respect to the original set functions.

Empirical Study of Brand-Customer Relationship Based on Customer Lock-In in Chinese Banking

LIU Feng-jun, WANG Liu-ying

2010, 19(2): 0246-252.

[Abstract](509)

Abstract:
The central construct of customer lock-in (CL) is measured and its role along with that of consumer loyalty in influencing the brand-customer relationship is tested. Using data collected from focus groups, a measurement model for CL is developed, and a structural equation model consisted based on literature review and our own theory is established. Moreover, the moderating effects of CL on the relationship between perceived value (PV) and brand relationship quality (BRQ), as well as that between BRQ and brand loyalty (BL) based on data collected through a survey have been tested. Results indicate that consumer satisfaction is a critical factor in establishing brand-customer relationship, and the attitudinal brand loyalty is the key to obtain brand behavioral loyalty. Furthermore, CL tactics, such as decreasing consumers learning cost and transactional cost facilitate the relationship building between customer and brand, while involuntary lock-in may have an adverse effect in the relationship building process. In addition, involuntary lock-in and loyalty program help in obtaining consumers behavioral brand loyalty but not their attitudinal loyalty.

2010 Vol. 19, No. 2