Papers by Author: Dong Gao

Abstract: Titanium alloy is difficult cutting materials,the samples of toolwear features are hard to acquire because of short tool life. In terms of the characteristic, Support Vector Machine (SVM) is proposed in this paper to monitor tool condition, the energy ratio of six different frequency bands of acoustic emission (AE) signal are extracted as cutting tool state features , SVM is trained and tested using these features ,Good classification results were achieved by using test set.

Abstract: Tool wear condition monitoring has been an effective method in improving the production efficiency and process automation. In this paper, to analysis the cutting force features in tool wear condition monitoring of difficult to cut materials, we first remove the direct current components and apply a fast Fourier transformation to the cutting force to observe the features in different frequency bands. A wavelet packet transformation is then adopted to the cutting force to observe the relationship of energy ratio and tool wear states.

Abstract: Volumetric error has large effect on machine tool accuracy; improving CNC machine tool accuracy through error compensation has received significant attention recently. This paper intends to represent volumetric error measurement based on laser tracker. The volumetric error is modeled by homogenous transformation matrix with each coordinate corresponding to each motion axis. Based on parts of spatial points volumetric error, the geometric errors which affect volumetric positioning error are verified through particle swarm optimization with the L₂ parameters as the target function. The chebyshev orthogonal polynomials are applied to approximate geometric errors.

Abstract: Magnetic flux pinning takes place between the high-temperature superconductors and magnets which can form non-contacting linkages between the individual components. This interaction is proposed for use in in-orbit assembly. This paper develops a flux pinned revolute joint which fits for the reconfiguration of modular spacecraft and details the reconfiguration mechanisms of the novel joint. Moreover, the process of reconfiguration is simulated via the rigid body dynamics. Furthermore, two flux pinned modules are constucted to confirm the feasibility of the designed flux pinned rovolute joint for reconfiguration on a testbed.

Abstract: The flux pinned force attracts our eyes, where the levitating system is widely investigated for the transportable application. Although plenty of experiments can lead to many significant consequences, the mechanism has been not understood completely since the enormously complicated behavior and quantum effect involve. In this paper, in order to calculate the flux pinned force analytically, the image-dipole model is adopted and improved and the simple and precise expression of magnetic strength is utilized, so the flux pinned vertical force can be calculated in analytical form. In addition, the experimental data in case of zero field-cooling and field-cooling experiment can be collected in our experimental table and the comparison is completed between the precise and simple formula and the experimental data, the precise version of expression fro flux pinned vertical force can correspond to the experimental data well.

Abstract: Nickel-based alloy Inconel718 is a difficult-to-cut material due to lower thermal conductivity, affinity to react with tool material, the cutting tools wear very rapidly due to the high cutting temperature and high cutting force. It is important to choose tool material reasonably. In this paper, cutting performance of the multi-layer CVD-coated (TiN/Al2O3/TiC) tool and PVD-coated (TiAlN) tool were evaluated by cutting temperature, cutting force, tool wear and tool life. The results showed that PVD-coated (TiAlN) tool was suitable for cutting Inconel718.

Abstract: The thermal deformation of ram system in a heavy-duty CNC milling-boring machine tool has a serious effect on its accurateness. This paper analyses quantificationally the temperature field and deformation field of the ram system, and gives the ram’s heat sources, calculating quantity of heat and transferring type of heat. And then a finite element analysis is performed, the analyzing results provide basic theoretical data for thermal error compensation in machine tools.

Abstract: Thermal error of machine tool is the main in total machine tool error, and obviously impairs the accuracy of the machined workpieces. Ram is a very important component of heavy-duty floor type boring-milling machine, and its thermal deformation is a significant source causing errors in machining process. Aiming at the thermal elongation of heavy type milling boring machine tool ram, the machine tool thermal errors are measured and compensated. Temperature compensation function in NC system is applied. Experiment results shows that 90% ram positioning error can be compensated.

Abstract: Heavy-duty NC machine tool is difficult and costly to evidently improve their precision via manufacturing technology only. It is proved being an effective approach to improve machine tool manufacturing precision based on software error compensation. In this paper, an error compensation algorithm based on reconstructing NC program is discussed. Following comprehensive discussion on basic algorithm of positioning error compensation in detail, linear interpolation and circular interpolation movement error compensation algorithm are further sketched in brief. To decrease the machining error, NC program is reconstructed before actual machining. The experiment results show that error compensation methods based on reconstructing NC program can improve profile accuracy of heavy-duty NC machine tools obviously.

Abstract: Synthetic error of CNC machine tool, mainly including geometric error and thermal error, is generally affected by many factors. And temperatures that include environment temperature and temperature asymmetry of machine tool are most important factor. Aiming at geometric error and thermal error mainly, this paper proposed a real-time synthetic error compensation solution for CNC machine tool based on Differential Resolver Function (DRF). The principle of this solution is offsetting the origin of workpiece coordinate system when implementing the NC code in machine tool. After real-timely collecting machine tool coordinates position and thermal key points’ temperatures, synthetic errors are calculated by the synthetic model that is beforehand constructed and stored in compensation equipment, and then the pulses that represent coordinate system origin offsetting value are generated and sent into NC system by DRF to realize synthetic error compensation of CNC machine tool.