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MEMS-Based Low-Cost Flight Control System for Small UAVs

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Tsinghua Science and Technology 2008年第5期13卷 614-618页

作者：付旭周兆英熊威郭奇 State Key Laboratory of precision Measurement Technology and instruments Department of Precision Instruments and MechanologyTsinghua University

Small unmanned air vehicles （UAVs） can be used for various kinds of surveillance and data collection missions. The UAV flight control system is the key to a successful mission. This paper describes a low-cost micro-electro mechanical system-based flight control system for small UAVs. The integrated hardware flight control system weighs only 2. g. The system includes a highly-integrated wireless transmission link, which is lighter than traditional links. The flight control provides altitude hold control and global positioning system navigation based on gain scheduling proportional-integral-derivative control. Flight tests to survey the grass quality of a large lawn show that the small UAV can fly autonomously according to a series of pre-arranged waypoints with a controlled altitude while the wireless video system transmits images of the surveillance target to a ground control station.

关键词： micro-electro mechanical system (MEMS) unmanned air vehicle (UAV) global positioning system (GPS) flight control navigation

High-performance Refractive Index Sensor Based on Photonic Crystal Single Mode Resonant Micro-cavity

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稀有金属材料与工程 2006年第A3期35卷 425-428页

作者： Shengye Huang Junfeng Shi Dongsheng Wang Wei Li State Key Laboratory of precision Measurement Technology and instruments Department of Precision Instruments and Mechanology Tsinghua University Beijing 100084 China

An effective refractive index sensor built with square lattice photonic crystal is proposed,which can be applicable to photonic integrated *** photonic crystal waveguides rather than conventional ridge waveguides are used as entrance/exit waveguides to the *** layers of photonic lattice are set between the photonic crystal waveguides and the micro-cavity to achieve both a high transmission and a high *** plane wave method is utilized to calculate the disperse curves and the finite difference time domain scheme is employed to simulate the light *** the resonant wavelength of about 1500 nm,the resonant wavelength shifts up by 0.7 nm for each increment of Δn=0.001.A transmission of more than 0.75 is *** the position disorder of the photonic crystal doesn't affect the sensitivity of the sensor, the transmission reduces rapidly as the disorder increases.

关键词： optical biosensor refractive index sensor photonic crystal resonant cavity

Study on 6-DOF active vibration-isolation system of the ultra-precision turning lathe based on GA-BP-PID control for dynamic loads

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Advances in Manufacturing 2024年第1期12卷 33-60页

作者： Bo Wang Zhong Jiang Pei-Da Hu department of precision Instrument Tsinghua UniversityBeijing100084People’s Republic of China Institute of Machinery Manufacturing Technology China Academy of Engineering PhysicsMianyang621900SichuanPeople’s Republic of China

The vibration disturbance from an external environment affects the machining accuracy of ultra-precision machining *** active vibration-isolation systems(AVIS)have been developed based on static *** a vibration-isolation load changes dynamically during ultra-precision turning lathe machining,the system parameters change,and the efficiency of the active vibration-isolation system based on the traditional control strategy *** solve this problem,this paper proposes a vibration-isolation control strategy based on a genetic algorithm-back propagation neural network-PID control(GA-BP-PID),which can automatically adjust the control parameters according to the machining ***-isolation simulations and experiments based on passive vibration isolation,a PID algorithm,and the GA-BP-PID algorithm under dynamic load machining conditions were *** experimental results demonstrated that the active vibration-isolation control strategy designed in this study could effectively attenuate vibration disturbances in the external environment under dynamic load *** design is reasonable and feasible.

关键词： Ultra-precision diamond turning lathe Active vibration isolation Six degrees of freedom Dynamic load Genetic algorithm-back propagation neural network-PID(GA-BP-PID)control

Parallel Mechanisms with Two or Three Degrees of Freedom

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维普期刊数据库

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Tsinghua Science and Technology 2003年第1期8卷 105-112页

作者：刘辛军汪劲松李铁民段广洪 Manufacturing Engineering Institute department of precision {2. and mechanology Tsinghua University

Parallel manipulators for the machine tool industry have been studied extensively for various industrial applications. However, limited useful workspace areas, the poor mobility, and design difficulties of more complex parallel manipulators have led to more interest in parallel manipulators with less than six degrees of freedom (DoFs). Several parallel mechanisms with various numbers and types of degrees of freedom are described in this paper, which can be used in parallel kinematics machines, motion simulators, and industrial robots.

关键词： parallel manipulator parallel kinematic machine degree of freedom robot

Step kinematic calibration of a 3-DOF planar parallel kinematic machine tool

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Science China(Technological Sciences) 2008年第12期51卷 2155-2167页

作者： CHANG Peng,WANG JinSong,LI TieMin,LIU XinJun & GUAN LiWen department of precision {2. and mechanology,Tsinghua University,Beijing 100084,China 1. department of precision {2. and mechanology Tsinghua University Beijing 100084 China

This paper presents a novel step kinematic calibration method for a 3 degree-of-freedom(DOF) planar parallel kinematic machine tool,based on the minimal linear combinations(MLCs) of error *** method using mapping of linear combinations of parameters in error transfer multi-parameters coupling system changes the modeling,identification and error compensation of geometric parameters in the general kinematic calibration into those of linear combinations of *** using the four theorems of the MLCs,the sets of the MLCs that are respectively related to the relative precision and absolute precision are *** simple and feasible measurement methods in practice are given,and identification analysis of the set of the MLCs for each measurement is carried *** to the identification analysis results,a step calibration including step measurement,step identification and step error compensation is determined by taking into account both measurement costs and *** experiment shows that the proposed method has the following merits:(1) the parameter errors that cannot influence precision are completely avoided;(2. it reflects the mapping of linear combinations of parameters more accurately and enhances the precision of identification;and(3) the method is robust,efficient and effective,so that the errors in position and orientation are kept at the same order of the measurement *** to these merits,the present method is attractive for the 3-DOF planar parallel kinematic machine tool and can be also applied to other parallel kinematic machine tools with weakly nonlinear kinematics.

关键词： parallel kinematic machine tools kinematic calibration parameter identification minimal linear combinations

A new tracking error detection method using amplitude difference detection for signal waveform modulation multi-level discs

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Chinese Physics B 2010年第10期19卷 319-323页

作者：严明铭裴京潘龙法 Optical Memory National Engineering Research Center Department of Precision Instruments and Mechanology Tsinghua University

The sub-land/sub-pit affects the characteristic of the tracking error signal which is generated by the conventional differential phase detection （DPD） method in the signal waveform modulation multi-level （SWML） read-only disc. To solve this problem, this paper proposes a new tracking error detection method using amplitude difference. Based on the diffraction theory, the amplitude difference is proportional to the tracking error and is feasible to be used for obtaining the off-track information. The experimental system of the amplitude difference detection method is developed. The experimental results show that the tracking error signal derived from the new method has better performance in uniformity and signal-to-noise ratio than that derived from the conventional DPD method in the SWML read-only disc.

关键词： signal waveform modulation multi-level technology tracking error amplitude difference

Optimal Kinematic Design of a 2.DOF Planar Parallel Manipulator

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Tsinghua Science and Technology 2007年第3期12卷 269-275页

作者：吴军李铁民刘辛军王立平 Institute of Manufacturing Engineering Department of Precision Instruments and MechanologyTsinghua University

Closed-form solutions were developed to optimize kinematics design of a 2.degree-of-freedom （2. DOF） planar parallel manipulator. The optimum design based on the workspace was presented. Meanwhile, a global, comprehensive conditioning index was introduced to evaluate the kinematic designs. The optimal parallel manipulator is incorporated into a 5-DOF hybrid machine tool which includes a 2.DOF rotational milling head and a long movement worktable. The results show that the planar parallel manipulator-based machine tool can be successfully used to machine blades and guide vanes for a hydraulic turbine.

关键词： planar parallel manipulator global conditioning index hybrid machine too

High Efficient Methods of Content-based 3D Model Retrieval

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Chinese Journal of Mechanical Engineering 2013年第2期26卷 248-256页

作者： WU Yuanhao TIAN Ling LI Chenggang department of precision {2. and mechanology Tsinghua University Baidu Online Network Technology (Beijing) Company Limited

Content-based 3D model retrieval is of great help to facilitate the reuse of existing designs and to inspire designers during conceptual design. However, there is still a gap to apply it in industry due to the low time efficiency. This paper presents two new methods with high efficiency to build a Content-based 3D model retrieval system. First, an improvement is made on the ＂Shape Distribution （D2.＂ algorithm, and a new algorithm named ＂Quick D2. is proposed. Four sample 3D mechanical models are used in an experiment to compare the time cost of the two algorithms. The result indicates that the time cost of Quick D2.is much lower than that of D2. while the descriptors extracted by the two algorithms are almost the same. Second, an expandable 3D model repository index method with high performance, namely, RBK index, is presented. On the basis of RBK index, the search space is pruned effectively during the search process, leading to a speed up of the whole system. The factors that influence the values of the key parameters of RBK index are discussed and an experimental method to find the optimal values of the key parameters is given. Finally, ＂3D Searcher＂, a content-based 3D model retrieval system is developed. By using the methods proposed, the time cost for the system to respond one query online is reduced by 75% on average. The system has been implemented in a manufacturing enterprise, and practical query examples during a case of the automobile rear axle design are also shown. The research method presented shows a new research perspective and can effectively improve the content-based 3D model retrieval efficiency.

关键词： 3D model retrieval high efficient methods shape descriptor extraction model repository index

Optimal Synchronous Trajectory Tracking Control of Wafer and Reticle Stages

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Tsinghua Science and Technology 2009年第3期14卷 287-292页

作者：王春洪胡金春朱煜尹文生 department of precision {2. and mechanology Tsinghua UniversityBeijing 100084 China

An optimal synchronous trajectory tracking controller was developed for multi-axis systems. The position synchronization error on each axis was defined as the position difference between this axis and the following axes. The following error of each axis, the synchronization error, and its derivative were considered in the cost function. A Riccati equation was deduced from the Hamilton-Pontryagin equation. The optimal control law was set up from the Riccati equation solution. Simulations of a two-axis system show that the synchronization error can be significantly reduced and the synchronization performance can be adjusted based on the parameters in the cost function.

关键词： optimal control cross-coupling motion control synchronized scan