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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. Source

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. Source

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. Source

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). Source

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. Source

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