Research On Theory And Key Technology For Look-Ahead Control In High Speed Machining

To deal with overshooting, mechanical harmful vibrations and data starvation caused by sharp corner or high curvature of tool path, a new look-ahead algorithm for high speed cutting machining is proposed by this paper. Compared to traditional numerical control, look-ahead control can analyze tool path,find dangerous points and deal with dangerous situations in machining automatically. Therefore machining productivity and accuracy can be improved efficiently. According to the goal of look-ahead control and considering both discrete and parametric curve tool path, this paper places emphases on acceleration and deceleration algorithm, discrete points interpolation algorithm, parametric curve interpolation algorithm and error compensation algorithm combined with the research of the National High Technology Research and Development Program (863 Program):"Microfluidic chip-oriented micromold manufacure equipments research" (2002AA421150) and the Special Project for Key Mechatronic Equipment of Zhejiang Province: "Medium and high class numerical control system" (2006C11067). At last, new look-ahead algorithm is proposed.In terms of configuration of look-ahead algorithm, the basic is acceleration and deceleration algorithm. Discrete points interpolation algorithm and parametric curve interpolation algorithm are necessary tools. Error compensation algorithm is necessary accessory. The paper firstly researches the principle of acceleration and deceleration algorithm and velocity blending algorithm for discrete tool path used in traditional numerical control system. Then according to the multiformity and practicality of polynomial, the acceleration and deceleration construction algorithm of polynomial is proposed. Under specific polynomial construction method, innovative velocity link method for small short straight lines is proposed.For the necessity of data analysis and parametric curve interpolation, the partial and overall interpolations algorithms for discrete tool path are used. Chasing method and Newton iterative method are applied in parametric curve interpolation algorithm. Due to the wider and wider use of parametric curve in high speed cutting machining and to guarantee the universality of look-ahead control, interpolation methods based on Taylor series and predictor-corrector are expatiated. Furthermore, interpolator adapted to tool path is introduced. To guarantee the systemic and integrality of look-ahead control algorithm and based on buffer command generation method, error even compensation algorithm is proposed.Finally look-ahead control algorithm is proposed based on analysis of dangerous points,complement of points on discret tool path,partition of parametric tool path according to acceleration and deceleration,solution of optimal feedrate at dangerous points and arrangement of acceleration and deceleration for machining. On-line experiments shows look-ahead control is necessary for high speed cutting machining and guarantees productivity and accuracy efficiently.