Entity

Time filter

Source Type


Fang C.-X.,Tsinghua University | Fang C.-X.,Beijing Key Laboratory of Precision Ultra precision Manufacturing Equipments and Control | Zhang H.,Tsinghua University | Zhang H.,Beijing Key Laboratory of Precision Ultra precision Manufacturing Equipments and Control | And 3 more authors.
Jisuanji Jicheng Zhizao Xitong/Computer Integrated Manufacturing Systems, CIMS | Year: 2015

Aiming at the feed-rate planning problem in CNC high-speed high-precision machining, a time-optimal feed-rate planning method with the constraints of velocity, viscous friction, torque and contour error was researched. A complete feed-rate planning model including contour error constraint and speed smoothing factor was established and was converted into a static optimal model through parameterization method. To improve the algorithm efficiency for this static optimization problem, the non-convex object function and constraints were transformed into convex optimization through reformulation, which could obtain global optimal solution in polynomial solving time. Simulation results demonstrated the effectiveness of the proposed approach. The computation time and impact of speed smoothing factor was also analyzed. ©, 2015, CIMS. All right reserved. Source


Fang C.-X.,Tsinghua University | Zhang H.,Tsinghua University | Ye P.-Q.,Tsinghua University | Liang W.-Y.,Gansu Engineering Research Center for Machine Tool
Jisuanji Jicheng Zhizao Xitong/Computer Integrated Manufacturing Systems, CIMS | Year: 2014

To improve the high speed machining efficiency of Numerical Control (NC) and to make the algorithm more effective, a dynamic contour error constraint model in feed-rate planning of continuous micro line segment trajectories was proposed, which established the constraint condition of contour error on velocity of end point. A parallel feed-rate planning algorithm based on Graphics Processing Unit (GPU) was presented, and the trajectories were divided equably by introducing feed-rate planning concept, which could improve the load balancing of parallel computing as well as make each parallel line compute independently. The experiment result showed that the proposed algorithm could realize the smooth feed-rate and guarantee the contour accuracy requirements. The efficiency of parallel algorithms was improved exponentially compared with the traditional method. Source


Zhang H.,Tsinghua University | Yu C.,Tsinghua University | Wang R.,Tsinghua University | Ye P.,Tsinghua University | Liang W.,Gansu Engineering Research Center for Machine Tool
Qinghua Daxue Xuebao/Journal of Tsinghua University | Year: 2014

The dynamic behavior of the support directly affects the dynamic behavior of a machine tool. Thus, the support joint parameters are needed for accurate dynamic models of machine tools. This paper presents a method to identify the equivalent stiffness and damping of support joints. A 3-D stiffness-damping model is used to replace the support joint of the machine tool bed in the dynamic model. The support joint parameters are identified by modal testing which shows the natural frequencies and the damping ratios of several vibration mode shapes of the machine tool bed. However, the method is unable to identify the joint parameters for all support states. To solve this problem, this model first identifies the joint parameters for a bed with a uniform mass in the symmetrical support state, and then repeats the modal testing as the normal force on the support joint is changed to relate the joint parameters to the normal force to identify the joint parameters for any support state. The results show that the stiffness and damping both increase with increasing normal force on the support joint. Finite element method (FEM) simulations are used to verify the parameters identification results with the FEM model for the support joint parameters consistent with the experimental results. Source


Fang C.,Tsinghua University | Zhang H.,Tsinghua University | Ye P.,Tsinghua University | Liang W.,Gansu Engineering Research Center for Machine Tool | Li W.,Gansu Engineering Research Center for Machine Tool
Qinghua Daxue Xuebao/Journal of Tsinghua University | Year: 2014

Feed-rate planning models must be accurate to improve contouring performance and efficiency. Quadrant protrusion errors caused by friction forces are an important source of contour error in high-speed contouring of complex curves. A theoretical analysis is given here to describe the relationships among the curvature, feed rate and quadrant protrusion error. Then, experiments with a wide range of parameters are used to develop a friction error model for feed-rate planning with the friction error as a constraint. Tests show that the model can accurately estimate the friction error and guarantee the contour accuracy requirements. Source

Discover hidden collaborations