Papers by Keyword: Error Compensation

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Authors: Deng Chao Zhu, Yi Fan Dai, Chao Liang Guan, Gui Lin Wang, Gui Peng Tie
Abstract: The adoption of conformal optics system can evidently improve the synthetical performance of infrared missiles. Hot-pressing poly-crystal magnesium fluoride (MgF2) is an ideal material for conformal optics dome. But many problems about machining and surface test of deep aspheric surface have not been solved at present, and there is not much research about the machining characteristics of MgF2 material. In this paper, in-situ measurement system is designed, so positional errors that introduced by repeating installation can be avoided. Then, machining process of MgF2 material by single point diamond turning is studied, and optimized diamond turning process is proposed by experiments in order to obtain low surface roughness. Furthermore, surface accuracy is tested by on-machine measurement system. Based on the result, error compensation process of conformal dome is carried out. Finally, the shape error of the dome is less than 0.8μm PV.
Authors: Wei Wang, Jian Guo Yang
Abstract: In this paper, a combined error model for thermal error compensation of machine tools is presented. Through the analysis of thermal error data of machine spindle at different temperatures, the error variation law is obtained. Experiments on the axial directional spindle deformation on a CNC machine center are conducted to build and validate the proposed models. The experimental validations show that the thermal errors of the machine tool are reduced effectively after applying the error compensation approach. The combined error model performs better than the traditional time series and neural network model in terms of prediction accuracy and robustness, which means that the new model is more suitable for complex working conditions in industrial applications.
Authors: Abderrazak El Ouafi, Michel Guillot
Abstract: Thermally induced errors play a critical role in the control of machining accuracy. They can account for as much as 70% of dimensional errors in produced parts. Since thermal errors cannot totally be eliminated at the design phase, errors compensation appears to be the most economical solution. Accurate and efficient modeling of the thermally induced errors is an essential part of the error compensation process. This paper presents a comprehensive approach for thermal error modeling optimization. The proposed optimization method is based on multiple temperature measurements, Taguchi’s orthogonal arrays, various statistical tools and artificial neural networks to provide cost effective selection of appropriate temperature variables and modeling conditions as well as to achieve robust and accurate thermal error models. The proposed approach can be effectively and advantageously used for real-time thermal error compensation since it presents the benefit of straightforward application, reduced modeling time and uncertainty. The experimental results on a CNC turning center confirm the feasibility and efficiency of the proposed optimization method and show that the resultant model can accurately predict the time-variant thermal error components under various operating conditions.
Authors: Yazhini Chitra Pradeep, Sheng Feng Zhou, Audelia G. Dharmawan, Kevin Otto, I Ming Chen, Peter Chen
Abstract: In precision robotic applications, inaccuracy in workpiece geometry has been a common problem to the precise processing of the workpiece. Due to manufacturing defects and workpiece deformation, the actual geometry of the workpiece deviates from its nominal 3D CAD model which is defined as model error. For many of the existing industrial robotic applications today, the robot path for processing the workpiece is planned based on the nominal 3D CAD model of the workpiece. Hence, the model error of the workpiece leads to error in the robot path planning eventually inducing inaccurate processing. To enhance the accuracy of the robot in processing the workpiece, a framework for in-situ model error compensation has been proposed. Prior to the processing of each workpiece, the proposed technique employs 3D optical laser scanning technology to capture the actual 3D model of the workpiece and compares it with the nominal model to establish the model errors. The nominal path of the robot initially created based on the nominal CAD model is then modified according to the model error. Thus, this step performs the in-situ model error compensation making the robotic task adaptive to the actual workpiece geometry. Experiments have been conducted to verify the proposed framework and an accuracy of up to 30 micrometers has been achieved in model error identification and compensation. The proposed technique can be employed in applications such as high precision robotic tasks, where accuracy of task execution is an important factor.
Authors: Hao Huang, Xiang Yang Lei, Jian Wang, Qiao Xu, Liang Yu He, Yin Biao Guo
Abstract: The causes of machining errors are very complicated and apt to mutual influence in aspheric grinding, so it is difficult to improve machining accuracy by control one cause. To compensate the machining error of large aspheric grinding, an error-compensation technique using on-machine profile measurement system in three axes grinding machine are presented. To verify the effectiveness of the compensation machining and the reliability of the measurement system, experiments on high-precision grinding machine were performed. Moreover, the compensation machining with the on-machine measurement substantially decreases the machining errors and improve machining accuracy by more than 45%, compared with the non-compensation machining.
Authors: Sheng Bao, Xi Zhang, Ping Fa Feng
Abstract: The efficiency of manufacturing structural parts can be improved by using on-machine inspection system. It is difficult to separate the valid information from hundreds of points and correct the errors by rotating and translating the workpiece coordinate system directly, especially for five-axis CNC machines. In this paper, a practical method is designed to correct errors easily. By using the least square method, an error reference frame is constructed, and the relation between the compensation values and coordinates of the theoretical points is derived. An example of aircraft structural parts is presented to validate the design.
Authors: Yang Li, Ji Zhao, Shi Jun Ji, Xin Wang
Abstract: A new method compensating geometric error components of a four-axis horizontal machine tool is presented in this paper. Homogeneous transformation matrices (HTMS) and error conversion are integrated in the compensation strategy. A mathematical model which contains 29 geometric error components is established based on HTMS and the errors in X, Y and Z directions are obtained through calculation. The errors in three directions are compensated by shifting the corresponding axis. But the configuration of this machine tool is X-axis, Z-axis, B-axis, C-axis without Y-axis, so the errors in X, Y and Z directions need to be converted into X, Z and C directions which is different from the traditional machine tools. The errors after conversion are used to compensation directly. This approach is significant for the error modeling and compensation which is an easy and efficient way to improve the precision of the four-axis machine tools.
Authors: Shi Zheng Sun, Dong Lin Peng, Fang Yan Zheng
Abstract: In order to improve time-grating sensor’s measurement accuracy, which is influenced by stability of the components, temperature and mechanical processing in precision measuring procedure. A novel compensation method based on Fourier series approach and least square is presented. With this method, the measurement error is separate into a lot of harmonics, and the optimal parameters of compensation are evaluated by least square method. The accuracy analysis certificates that time-grating sensor’s measurement error is reduced from ±14.8′′ to ±2.5′′ by applying the error compensation method, which is compensated about 80% compared with no compensation. Sensor’s accuracy is effectively improved.
Authors: Zhi Chao Zheng, Jin Yue
Abstract: This paper describes a novel GPS/INS loose integrated navigation algorithms which is intended for applications with GPS signal is obtained at intervals of an hour or even longer. Since the constant errors of IMU can be removed greatly by dual-axis modulation, stochastic error introduced by the gyros of IMU is the main systemic error source which leads the azimuth error to divergent as a function of time, the novel method called Two Point Correction (TPC) is applied to compensate the stochastic error. The psi-angle differential equations are used to estimate the azimuth error of INS. As a result, the methods implemented for the real system and the performance is significantly enhanced, while the required numerical methods are simple and efficient.
Authors: Q.J. Liu, J.H. Yue, Y.F. Wang, J.C. Dong, Tai Yong Wang
Abstract: This paper proposed a new and effective parametric curve interpolation algorithm with error compensation capability for high speed machining. The proposed algorithm is developed from the first-order Taylor expansion interpolation algorithm and the speed-controlled interpolation algorithm. It is also incorporated the geometry features of the machined curves, the dynamic characteristics of machine tools and the adaptive error control. The proposed algorithm achieves high surface accuracy and avoids feedrate fluctuations. Simulation results have demonstrated the effectiveness and satisfactory performance of the proposed algorithm.
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