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Wei L.,China Precision Engineering Institute for Aircraft Industry | Shen G.,Beihang University | Huang S.,Beihang University | Guo P.,Beihang University
Beijing Hangkong Hangtian Daxue Xuebao/Journal of Beijing University of Aeronautics and Astronautics | Year: 2011

As its unique morphological features (broad wings with small aspect ratio, complex wing shape), and the distinctive kinematics (low flapping frequency, the stroke plane is nearly perpendicular to the body; no wing rotating, but obviously body pitching and oscillating as wing flapping), butterfly fly is a special research subject in exploring insect high lift mechanisms. In order to take in-depth insight into the bio-fluid mechanics and the high lift mechanisms of butterfly hovering fly, it is necessary to design and manufacture an electromechanical model of flapping butterfly to simulate the flapping modes of the butterfly. A new designed electromechanical model of flapping butterfly which had the wings and the body just like the real butterfly was introduced. The electromechanical model can fix positions and simulate different flapping modes of the butterfly, including the wings' flapping and body's rotation and up-down-oscillating movement. So it is useable for the experiments of flow visualization and particle image velocimetry(PIV).

Shi C.,Beihang University | Shi C.,China Precision Engineering Institute for Aircraft Industry | Li X.,Beihang University | Chen Z.,Beihang University
Chinese Journal of Aeronautics | Year: 2014

The effectiveness of grinding fluid supply has a crucial impact on grinding quality and efficiency in high speed grinding. In order to improve the cooling and lubrication, through in-depth research of self-inhaling internal cooling method and intermittent grinding mechanism, a new spray cooling method used in high speed grinding is proposed. By referring to the structure of bowl-shaped dispersion disk, the grinding wheel matrix with atomization ability is designed; through studying heat transfer of droplet collision and the influence of micro-groove on the boiling heat transfer, grinding segment with micro-groove is designed to enhance the heat flux of coolant and achieve maximum heat transfer between droplets and grinding contact zone. High-speed grinding experiments on GH4169 with the developed grinding wheel are carried out. The results show that with the micro-groove grinding wheel just 5.4% of pump outlet flow rate and 0.5% of spindle energy is needed to reduce the grinding temperature to 200 °C, which means the developed grinding wheel makes cooling high efficient and low energy consuming. © 2014 Production and hosting by Elsevier Ltd. on behalf of CSAA & BUAA.

Huang S.-Q.,Beihang University | Shen G.-X.,Beihang University | Wei L.,China Precision Engineering Institute for Aircraft Industry | Guo P.,Beihang University
Shiyan Liuti Lixue/Journal of Experiments in Fluid Mechanics | Year: 2010

In order to explore the aerodynamic theory involved in butterflies' unique morphology and kinematics, we developed a mechanical system considering the effect of both wings and body, differing from the previous experiments focusing only on flapping wings, to imitate a hovering butterfly. An experiment of dye flow visualization was carried out to reveal the structure of leading edge vortex (LEV), which was the principle source of high lift. The results show that, LEVs presenting during both downstroke and upstroke are not conical or spiral as observed in previous experiments, but continuous across the body in form of column with approximately constant diameter, which are characterized by: obvious spanwise flow existing in the acceleration stage of wing flapping; and vortex breakdown during the deceleration phase. In addition, the fluttering of butterflies seems not a random, erratic wandering, but a kind of adaptive control flying which is beneficial for enhancing lift.

Su P.,Tsinghua University | Ma J.,Tsinghua University | Tan Q.,Tsinghua University | Kang G.,Beijing Institute of Technology | And 2 more authors.
Optical Engineering | Year: 2012

In null computed generated hologram (CGH) test of optical elements, fitting method is needed in null CGH design to generate continuous phase function from the ray-traced discrete phase data. The null CGH for freeform testing usually has a deformed aperture and a high order phase function, because of the aberrations introduced by freeform wavefront propagation. With traditional Zernike polynomial fitting method, selection of an orthogonal basis set and choosing number of terms are needed before fitting. Zernike polynomial fitting method is not suitable in null CGH design for freeform testing; a novel CGH design method with cubic B-spline interpolation is developed. For a freeform surface with 18 × 18 mm2 rectangular aperture and 630 μm peak-to-valley undulation, the null CGH with a curved rectangular aperture is designed by using the method proposed. Simulation and experimental results proved the feasibility of the novel CGH design method. © 2012 Society of Photo-Optical Instrumentation Engineers (SPIE).

Zhang L.,Nanjing University of Aeronautics and Astronautics | Liao W.,Nanjing University of Aeronautics and Astronautics | Yang H.,China Precision Engineering Institute for Aircraft Industry
Advanced Materials Research | Year: 2010

A miniaturized CNC (Computerized Numerical Control) milling machining equipment was mentioned for micro milling processing. The equipment has a highest spindle speed of 90000rpm and the positioning accuracy of submicron. Furthermore, it described the design of CNC servo system of precision stage driven by linear motor. The servo experiments results verified the excellent static and dynamic performance of the system. The machining tests included a plane with a surface roughness of 215nm using a end milling cutter of Φ0.2μμm, micro straight slots with a dimension error range of 1-2μm using a ball-end cutter of Φ0.2μm and some complex structures. The analysis results of these tests show that the system is able to fulfill the micro milling machining of micro components. © (2010) Trans Tech Publications.

Zhou J.,Nanjing University of Aeronautics and Astronautics | Chen W.-F.,Nanjing University of Aeronautics and Astronautics | Qu S.-P.,China Precision Engineering Institute for Aircraft Industry
Jisuanji Jicheng Zhizao Xitong/Computer Integrated Manufacturing Systems, CIMS | Year: 2010

To improve machining accuracy of workpieces, a local error compensation method based on tolerance was proposed. And the machining errors were compensated actively by modifying Numerical Control (NC) codes. Error values of parts surface were analyzed, and according to tolerance requirements, the critical deflection areas beyond tolerance range were obtained, and actual cutting depth of the areas was amended to compensate local errors. Tool path with error compensated values was re-planned when actually modified cutting depth was decided. And then step and row spacing were determined according to actual machining accuracy. By post-processing, modified NC codes were achieved for workpiece machining. An example was used to demonstrate the feasibility of this approach.

Jiang X.,University of Science and Technology Beijing | Liu B.,University of Science and Technology Beijing | Yang H.,China Precision Engineering Institute for Aircraft Industry
Advanced Materials Research | Year: 2012

Reverse positioning is a significant positioning method of rotary table, the positioning displacement error caused by clamping cannot be neglected. Since the direct acting factors are numerous, the mechanism and value of the displacement error are difficult to test. In this paper, we took the general rotary table as the experiment object, designed and manufactured a set of device that could analyze the reverse positioning. According to various measurement conditions, first the stress-strain of all the components was calculated based on the finite element analysis. Then the displacement errors were measured on the experimental device. Finally the comparison between the simulation and the experiment results allowed the improvement of the model, algorithm analysis and the structure of the experimental device. As the theoretical results continued to get close to the measured values, on the basis of the process above can we conclude the influencing factors and the possibility to reduce the error, thus develop a new approach for the reduction of the reverse positioning error. © (2012) Trans Tech Publications, Switzerland.

Xu G.-Z.,China Precision Engineering Institute for Aircraft Industry | Meng F.-J.,China Precision Engineering Institute for Aircraft Industry
Zhongguo Guanxing Jishu Xuebao/Journal of Chinese Inertial Technology | Year: 2011

Flight simulation turntables are widely used in the Hardware-In-The-Loop (HWIL) to increase the reality of simulation. But the turntable's motion also brings dynamic errors, transport delays, non-linearity, etc. to HWIL and degrades the performance of simulation. In this paper, a Kalman filter is used to estimate state variables of flight tables. The close loop control system with feed-forward techniques is acquired to improve the turntable's dynamic characteristic by reducing the turntable's low frequency phase lag. A new method is used to identify the moment of inertia, and the estimated parameters are used to replace the role of manual tuning by adjusting the controller automatically for good dynamic response. The experiments show that the small-signal distortion is reduced to one fifth of the original one, and dynamic simulation performance has been significantly improved.

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