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2004 Vol. 30, No. 06

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Steering law design for SGCMGs taking gimbal servo characteristics into account
Wu Zhong, Chou Wusheng
2004, 30(06): 489-492.
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Gimbal servo systems of single gimbal control moment gyroscopes (SGCMGs) are often assumed to have ideal tracking performance during the steering law design. The tracking performance can be decreased due to the finite bandwidth and various disturbances of gimbal servo systems. In order to attenuate the effect of gimbal servo systems on steering performance, a new steering law was presented. This steering law was designed not only based on kinematics, but also dynamics of SGCMGs, and could calculate the control torque for each SGCMG gimbal directly according to the momentum (or torque) command. Since it has no arithmetic singularity, steering error can be made converge to zero exponentially when system singularities do not appear. Comparatively, it has a simple form and is easy to be realized. Simulation results of a certain 4-SGCMG system indicate that the algorithm stated above is feasible.
Development of airborne intelligent power supply system
Li Yunhua, Wang Zhanlin
2004, 30(06): 493-497.
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Aiming at the problems of the increase in orifice loss caused by high pressure and large power of the airborne hydraulic power system, a kind of intelligent power supply system which sets operation mode and reference input according to the assignment of the airplane was proposed. The control and management of the intelligent pump is really a hierarchical computer control system. The upper computer is responsible for the determination of operation mode and reference input. The lower computer, i.e., micro-controller, is responsible for the realization of the control law, the transformation of digit to analogue, and data acquisition. For the convenience of integration, a scheme of micro-controller was presented, it integrated the lower computer, signal condition circuit and servo amplifier, and the micro-controller was developed. The smart hydraulic power supply can select the operating mode and the input of controller according to the flight assignment, and realize the effective management of the power utilization, so that the rising of temperature is effectively restrained and the maneuverability and the existence ability are increased.
Analysis and realization of aircraft structural synchronously economic maintenance and safety inspection
Chen Bo, Bao Rui, Zhang Jianyu, Fei Binjun
2004, 30(06): 498-501.
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The economic performance will be obviously promoted if the maintenance and safety inspection could be carried out at the same time. By studying the influence factors, an analysis method was presented to decrease the repaired times by synchronously performing the economic maintenance and safety inspection. The flowchart of this method was also given. It is adaptive to be used in new aircraft design and analysis, and it is helpful to draw the program of maintenance and inspection. It is also propitious to optimizing the design of aircraft structure. Finally, a calculation example was presented to validate the feasibility of this new analysis method.　　
Automatic program evaluation system base on LAN
Wang Zhuowei, Yin Baolin
2004, 30(06): 502-505.
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The distributed automatic program evaluation architecture provided a more effective, veracious and applicable mechanism to implement a program evaluation system. By using the Trojan technology in passive mode, the architecture ensured the security in communication and evaluation, and it didn't make the evaluation system use any CPU or memory resource when running the sample program. It kept the sample program running in the same environment in developing and evaluating. By using the rule database and the filter program, the flexibility and applicability were improved. The architecture is suitable for many kinds of sample program. An application system was also implemented for the computer programming examinations and programming contest. After many practices, it is proved to be more efective, secure and flexible.
Study for the best selection of rule conditions in automated extraction of fuzzy diagnostic rules
Qi Yi, Shen Shituan, Li Yihua
2004, 30(06): 506-511.
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In the machine learning of fuzzy rules for the diagnostic expert systems, the best selection of rule conditions is one of the most important steps. A new fuzzy nearness function was proposed, and the overlap degree of the rule conditions was evaluated to get an evaluated matrix with this function. An algorithm of the best selection for rule conditions or test points based on the evaluated matrix was designed. The simulation shows that the number of rule conditions, which has to be learned, is decreased largely, consequently, the workload of learning is reduced too. Further more, the method of the best selection of test points can do well to the design of automatic test.
Experiment investigation on transient heat transfer in rotor-stator system with high-positioned air inflow
Luo Xiang, Xu Guoqiang, Ding Shuiting, Tao Zhi
2004, 30(06): 512-515.
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A gas turbine disk was simplified to be a shrouded rotor-stator system with high-positioned air inflow, the rotor was heated at rim. The rotor diameter was 400 mm and its maximal rotating speed was up to 3000 r/min. Transient heat transfer characteristics of the rotor were investigated experimentally as the rotational Reynolds number and the mass flow rate were changed. The results show: the mass flow rate could always have significant effects on average Nusselt number of the rotor. The rates of temperature vs. time in everyplace are almost same. The rotational Reynolds number has a few effects on averaged Nusselt number in this experimental range. The rate of temperature vs. time at high radius is large than that at low radius under different changes of rotational Reynolds number.
High angle-of-attack control law design based on global stability analysis
Li Kang, Fang Zhenping
2004, 30(06): 516-519.
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　　A global stability analysis was presented to guide high angle-of-attack (AOA) control law design for nonlinear aircraft dynamic system. Bifurcation analysis was firstly explored to investigate the structural stability of nonlinear aircraft dynamic system at high AOA. Then by reasonably selecting equilibrium points, eigenstructure assignment was applied to design gain scheduling control law at high AOA and the extension of stable flight region to high AOA was achieved. By using time domain numerical simulations, the domains of attractor for stable equilibrium points at high AOA were estimated. In contrast to other methods, global asymptotic stability of nonlinear aircraft dynamic system is obtained other than Lyapunov local asymptotic stability. 　
Analysis of wave propagation in the built-up structures of rod-beam and beam-beam
Xing Yufeng, Wang Lijuan
2004, 30(06): 520-523.
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The impact problems of a rod on a Timoshenko beam and a Timoshenko beam on another Timoshenko beam were analyzed by means of the indirect mode superposition method(IMSM). A rod on a beam and a beam on another beam are both typical built-up structures. The displacement compatible equations of the two problems were established by IMSM on the basis of the individually obtainedmode functions and frequencies of impactors and targets, and solved by numerical integration step by step. The numerical analysis by making use of dimensionless variables show the propagation of the longitudinal waves along rod, and the longitudinal and transverse waves along beam, and the mutual transition and reflection between the longitudinal waves and the transverse waves in the impact built-up structures in detail.
DTW based quantitative fault diagnosis of gas path component in turbofan
Xu Bo, Tang Hailong, Li Xingshan
2004, 30(06): 524-528.
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A quantitative fault diagnosis method was presented based on pattern recognition principles for gas path component in turbofan. The method consists of a preprocessing step for multivariate dynamic data, where the magnitude dependent information is standardized, and a similarity assessment step via DTW (dynamic time warping). DTW is a flexible pattern matching method used in the area of speech recognition. The method was designed to classify faults independently of inconsistencies in the operating processes of turbofan ground test-runs. Quantitative diagnosis was fulfilled by the subdivision of fault pattern database according to the fault degree of gas path component. Case studies show that the method has a low false alarm rate and a high capability in isolating faults, and moreover, it is also robust with measuring noise and other uncertainties.
Visualization of network topology with hierarchical display layout
Xie Hongman, Qian Depei, Luan Zhongzhi, Chen Heng
2004, 30(06): 529-533.
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The network topology discovery is indispensable for a network management system．Visualizing the topology of complex network systems is an efficient way to grasp the topological structure of the network quickly．A new visualization method,which applies to the display of the topology of middle or small scale network,was proposed．It visualized the topology based on hierarchical structure with the major devices being separated from the minor devices in the different hierarchy．The major devices were hierarchically displayed on screen from top to bottom．This method also allowed the administrator to change the layout of the topology display flexibly．The basic concept and important techniques in implementing the method were presented．
System architecture and software design of high-dynamic GPS signal simulator
Kou Yanhong, Chang Qing, Zhang Qishan
2004, 30(06): 534-538.
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The hardware-in-the-loop system architecture of GPS simulator was presented, which was flexible, expansible and capable of real rime test, and a data-collecting GPS receiver was introduced into the system. The mathematic model of high-dynamic GPS signal was derived, and it was suggested to add two parameters to emulate high-dynamic effects. The structure of the simulator software was established. A software design instance and its simulation results were given. The simulator designed can provide a realistic high-dynamic signal environment for parameters measurement, software and hardware debug, performance test and evaluation of GPS UE.
Modeling and analysis of a force interaction system
Luo Yangyu, Wang Dangxiao, Zhang Yuru
2004, 30(06): 539-542.
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To improve the performance of a force interaction system, it is necessary to understand the effect of respective parameter on the system through modeling and analysis. Considering a 1\|DOF force interaction system, the human operator in the system was modeled as a combination of passive impedance and an active input, and the virtual environment was assumed to be passive. Through analogous treatment between the force interaction system and an electrical network system, two-port stable theory was used to derive the stability condition of the system. The effect of transmission stiffness on the system stability was particularly emphasized. The results provide important insight to the system performance and are applicable to the design of a force interaction systems.
Experiment study of pilots' situation cognitive level
Liu Wei, Yuan Xiugan, Ge Heng, Han Y
2004, 30(06): 543-546.
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The aim of this work is to study the problem of situation cognitive (SC) which is an active direction in aviation ergonomics field. Based on previous research results, the experimental and questionnaire systems for evaluating pilots' situation cognitive were built up. After theoretical consideration and analysis of experimental of results, which involves in four key aspects: the relation between pilots' scan (attention) strategy/workload and difficulty of duty, the relation between pilots' workload/experience and their situation cognitive when they are driving in different task phases, the situation cognitive distances between advance pilots and student pilots were opened out primarily, which benefit cabin designing and evaluating pilots' training performance.
Study on DFR method under corrosive environment for fatigue analysis
Zhang Jianyu, Bao Rui, Chen Bo, Fei Binjun
2004, 30(06): 547-550.
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Via transfer the influence of corrosive environment on fatigue life to that on detail fatigue rating equivalently, the DFR method under corrosive environment for fatigue analysis was established. The relation between the ratio of fatigue life under corrosive and normal environment and the corrosive convert coefficient of DFR was obtained by the standard S-N curve equation, thus the determination method of the convert coefficient was presented, in which the parameter c was shown to have little influence on its precision. Based on the assumption that the influence of pre-corrosion on ground and the influence of corrosion in flight are independent, a method for separation pre-corrosion and corrosion fatigue was proposed.
Experimental investigation on effects of blade negative bowing in turbine stator cascades
Chen Haisheng, Tan Chunqing, Kang Shun, Liang Xizhi
2004, 30(06): 551-556.
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The outlet flowfield and static pressure on blade surfaces of the classical turbine stator cascades with straight and -10°、-20° bowed blades were measured in the linear cascade wind tunnel. Effects of blade negative bowing on secondary flow, total pressure loss and outlet flow angle were analyzed quantitatively, mechanism of the effects was discussed as well. The results show that the negative bowing results in the "C" shape distribution of static pressure on blade surfaces, which is the main reason for the variation of characteristics of flowfield, however the aerodynamic performances of cascades can not be improved by negatively bowed blades.
Design and implementation of development environment for RTEMS
Bao Zheng, Li Hongbing, Jin Huihua
2004, 30(06): 557-560.
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In the development of embedded application, the embedded operating system becomes more important. Its development environment is also an essential part. RTEMS is an open embedded operating system. The design of development environment for RTEMS was implemented. The methods include: connecting the host and target machine by ethernet or serial port, establishing the cross compile tools, remote downloading and debugging by various communication protocols, setting up configuring and scaling of modules, etc. This environment is easy to handle and of graphics user interface. This design provides an embedded development platform and spreads the use of RTEMS. The system has been in use in fields of education and research.
Improved BP neural network in design of aircraft antiskid braking system
He Heng, Wu Ruixiang
2004, 30(06): 561-564.
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The construction of Sp (perfect slip ratio) identifier with back-propagation neural network was proposed to prevent skidding and have the best braking effect in the aircraft braking process. In order to improve the learning ability of the network, a type of self-adaptive learning rate method, second-order learning rate method, was introduced. Some problems in the practice of this method were discussed and the solutions were presented. A third-order learning rate method was deduced based on the method. The method of reasonable configuration of active functions was proposed. The combination of these methods renders better learning precision and speed.
Reliability allocation and optimization for complex systems
Lu Xiangbin, Li Xiaogang, Lin Feng
2004, 30(06): 565-568.
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A new method of distribution and optimization of reliability of complex systems was presented. The problem of distribution and optimization of reliability complex systems which were constructed on component level was reduced to the problem of nonlinear programming by building practical cost-reliability function and nonlinear programming model which considered the effect of cost in the distribution and optimization of reliability. In order to gain feasible numerical solution in the nonlinear programming problem, an improved genetic algorithm which had self-adaptation function was proposed. By using this method, distribution and optimization of reliability of more complex system can be solved effectively and efficiently.
Analysis for optical extend in light-pipe illumination system
Lü Yong, Zheng Zhenrong
2004, 30(06): 569-571.
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Based on optical extend, non-imaging optics was used to optimize the light-pipe lighting system. The transfer of optical extend in light-pipe was analyzed. The detailed analysis and experiment show that a balance between the section size of the light-pipe and the F number of the light beam should be reached to acquire best performance. Theoretically the optimal ratio of the height of the light-pipe to the radius of the light beam is 1.535, it will change slightly in the different systems. So a new method to limit the facula was presented to improve illumination efficiency of light-pipe.
Study on stability of air-to-air missile in firing-back attack
Zhang Huaming, Jiang Yuxian
2004, 30(06): 572-576.
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A method to solve the instability of an air-to-air missile’s attitude angle motion during its velocity pass through zero in case of that the missile fires back was proposed. The idea of the method is to increase the thrust of the missile’s booster. It results in that the velocity of the missile transforms from negative into positive quickly, and it constrains the divergent attitude angle the missile in an allowable margin. Furthermore, the attitude perturbation convergent since the missile’s attitude motion becomes stable. The qualitative analysis of the dynamic procedure of the missile’s attitude angle changing was made in the same case. The principle feasibility of the method, and the effects of the steady stability coefficient, initial perturbation of the angle of attack, initial value of back-firing velocity on the missile’s attitude motion were analyzed quantitatively by use of simulation. The results shows that the method is valid.
Staggered finite volume method for turbomachinery viscous flow field numerical investigation
Li Minjiang, Gui Xingmin
2004, 30(06): 577-582.
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A compact staggered mesh limited control volume scheme was used in a three dimensional steady computational fluid dynamics (CFD) code to solve the favre-averaged Navier-Stokes equations and k-ε turbulence model equations more tightly, after Fourier analysis for odd-even decoupled mode in several staggered mesh discretizations. NASA Rotor 67 flow field was calculated and flow structures in terms of relative mach numbers were presented. The excellent agreement between simulations and experiments not only under design condition, but also un-design condition demonstrates the code's predictive capability. The cause of the discrepancies was also discussed. Meanwhile the code has the advantage of calculation efficiency compared with some other software.

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