Beijing Key Laboratory of Precision

Beijing, China

Beijing Key Laboratory of Precision

Beijing, China
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Liu Y.,Tsinghua University | Wu J.,Tsinghua University | Wang L.,Beijing Key Laboratory of Precision | Wang J.,Tsinghua University
MATEC Web of Conferences | Year: 2017

With the development of the aerospace industry, the hybrid machine tool for machining the complicated curved surface is becoming a research hotspot. The S-shaped test specimen proposed by Chengdu Aircraft Industrial Company is an effective test method to verify the ability of machining the complicated curved surface for a machine tool. Considering the spatial parallel kinematic manipulator in a hybrid machine tool provides the complicated orientation motion and its design of structure dimension affects the accuracy of the machine tool, this paper investigates the issue about dimension synthesis of the manipulator based on S-shaped test specimen. By establishing models of the S-shaped test specimen and parallel kinematic manipulator, the motion trajectory of the parallel kinematic manipulator for machining S-shaped test specimen is obtained. According to the motion trajectory and expected performance indices, the result of dimension synthesis for the manipulator is plotted and a set of suitable dimensions is achieved. With the analysis result in this paper, it is helpful to improving the accuracy of machining the S-shaped test specimen. © The Authors, published by EDP Sciences, 2017.

Wang J.,Tsinghua University | Wang J.,Beijing Key Laboratory of Precision | Zhang C.,Beijing Institute of Electronic System Engineering | Feng P.,Tsinghua University | And 3 more authors.
International Journal of Advanced Manufacturing Technology | Year: 2016

Subsurface damage (SSD) induced by the rotary ultrasonic face machining (RUFM) considerably influences the technological application of the optical components. However, currently, there is no method to detect the depth of SSD in real time. For the purpose of precise and nondestructive evaluation of the SSD depth generated in RUFM processes, a predictive model was developed by applying the indentation fracture mechanics of brittle material. This was the first time that the correlation between the measured cutting force and SSD depth had been established. It was found that the SSD depth was directly proportional to the exponent of the measured cutting force (namely dSSD=γFc χ). Using this model, the depth of SSD could be predicted rapidly and precisely in the RUFM of optical glass even in real time using the measuring cutting force. Subsequently, this method was verified by conducting RUFM tests on K9 glass specimens with Sauer Ultrasonic 50. Meanwhile, the cutting force and SSD depth were compared experimentally between RUFM and conventional grinding (CG) process, indicating that RUFM is a beneficial manufacturing method for optical glass with reduced cutting force and SSD depth. © Springer-Verlag London 2015.

Wang L.,Tsinghua University | Wang L.,Beijing Key Laboratory of Precision | Liu Y.,Tsinghua University | Liu Y.,Beijing Key Laboratory of Precision | And 6 more authors.
International Journal of Advanced Robotic Systems | Year: 2016

Error modeling is the foundation of a kinematic calibration which is a main approach to assure the accuracy of parallel manipulators. This article investigates the influence of error model on the kinematic calibration of parallel manipulators. Based on the coupling analysis between error parameters, an identifiability index for evaluating the error model is proposed. Taking a 3PRS parallel manipulator as an example, three error models with different values of identifiability index are given. With the same parameter identification, measurement, and compensation method, the computer simulations and prototype experiments of the kinematic calibration with each error model are performed. The simulation and experiment results show that the kinematic calibration using the error model with a bigger value of identifiability index can lead to a better accuracy of the manipulator. Then, an approach of error modeling is proposed to obtain a bigger value of identifiability index. The study of this article is useful for error modeling in kinematic calibration of other parallel manipulators. © 2016 The Author(s).

Xu C.,Tsinghua University | Zhang J.,Tsinghua University | Zhang J.,Beijing Key Laboratory of Precision | Feng P.,Tsinghua University | And 5 more authors.
International Journal of Machine Tools and Manufacture | Year: 2014

An understanding of the contact characteristics of a spindle-holder joint in machine tools calls for an in-depth analysis of its performance under machining conditions. This study specifically aims to model a spindle-holder taper joint to predict the stiffness and stress distribution under different clamping and centrifugal forces. A spindle-holder taper joint subjected to clamping and centrifugal forces was modeled using the finite element method. The stress distribution of the interface was revealed and it was found that the von-Mises stress had a non-linear distribution because of the clamping force of the holder. The centrifugal forces were included in the model to analyze the deformation of the joint. At high speed the centrifugal force caused a stress concentration at the large end of the holder. A typical 7/24 taper joint of a BT50 holder was investigated to identify the stiffness using a special experimental platform. The axial and radial stiffnesses, as well as the hysteresis cycles were obtained to predict the contact characteristics with different clamping forces. The experimental results showed that the model presented in this study was efficient in predicting the characteristics of the spindle-holder joint. The method presented is useful in identifying the dynamics of a spindle-holder and can thus be used to optimize the spindle system. © 2014 Elsevier Ltd.

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