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21.
G01 code generated by a computer-aided manufacture (CAM) system is the most common form of tool trajectory in computer numerical control (CNC) machining. A tool path composed of short line segments has discontinuous tangency and curvature, generating large fluctuations of feedrate and acceleration, which in turn produces vibration in a machine tool. To obtain a smooth tool path, many methods on tool-path smoothing have been developed. However, the shortcomings in these methods exist when they are employed in a CNC system. It is difficult to simultaneously to guarantee the following requirements of CNC machining: (1) chord error should be rigidly constrained; (2) G01 points should be interpolated; (3) curvature should be continuous (G2); (4) machining should be applicable to spatial cases; (5) real-time performance of computation is required. Based on these various requirements, this study proposes an interpolation scheme using cubic Bezier curves and includes an adjustment strategy to eliminate deficiencies in the tool path. The tool path generated is G2, chord-error-constrained, G01-point-interpolated, loop-free, and optimized for both stretch and jerk energy. The method is applicable to 3D cases and involves only simple algebraic computations. Thus, the algorithm can be applied to real-time CNC machining. A simulation is conducted to validate the efficiency of the algorithm. In addition, an experiment reveals its advantage over Hermite interpolation in surface quality and machining efficiency. 相似文献
22.
The vibration tests of Laoshan bicycle gymnasium for the Olympic Games are performed under multi-support excitations in order
to verify the effectiveness of multi-support time history method. The excitation sources come from the impact forces acting
on the ring beam of the reticulated structure, on the basis of which the records of motions of each excited point and corresponding
structural vibration responses are all collected. The theoretical analytical model of the structure is further established
and the structural dynamic responses are obtained subjected to the same excitation case via multi-support time history method.
The calculation results are generally in agreement with those of the test in both time domain and frequency domain, which
verify the effectiveness of multi-support time history method. The vibration test can also provide references for long-span
structures under multi-support excitations.
Supported by the National Natural Science Foundation of China (Grant No.50108003) 相似文献
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