Dissertation > Industrial Technology > Metallurgy and Metal Craft > Metal cutting and machine tools > Program control machine tools, CNC machine tools and machining

Theory and Design of Multi-axis Motion Control System Applicable to Sculptured Surface Machining

Author QiaoZhiFeng
Tutor WangTaiYong
School Tianjin University
Course Mechanical Engineering
Keywords multi-axis NURBS interpolation RTCP 3D tool compensation S-shape acceleration/deceleration
Type PhD thesis
Year 2012
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With the development and wide application of multi-axis machine tools, themulti-axis motion control technologies applicable to sculptured surface high speedand high precision machining have got more and more attention. In view of this, thethesis mainly researched on the multi-axis NURBS interpolation technology, generalRTCP (Rotation Tool Center Point) control technology,3D tool compensationtechnology, S-shape acceleration/deceleration method with nanometer accuracy andthe theory and design of multi-axis motion control system used for the sculpturedsurface machining.Motivated by the excellent machining performance achieved by the three-axisNURBS interpolation, a weak realtime multi-axis NURBS interpolation method isproposed. The method using two NURBS curves, respectively, describe the movementof the tool tip point and the tool axis vector. Bézier polygons are used for the fast andhigh accuracy linearization of the two NURBS curves.The coordinate transformation and nonlinear error control methods for majorfive-axis machine tools are studied. Based on this, a generic rotation tool center pointmanagement module is designed to realize the coordinate transformation and adaptivenonlinear error control for multi-axis machine tools.In view of the3D tool compensation problem of five-axis sculptured surfacemachining, a triple NURBS interpolation method is further proposed, which uses thethird NURBS curve to describe the movement of the cutter contact vector. Throughthis way, the tool radius and length compensation problem of the multi-axils NURBSinterpolation could be effectively solved. A simulation experiment is also done toverify the proposed method.As closely related to the high speed machining of multi-axis machine tools, themulti-axis S-shape acceleration/deceleration method with look ahead function andnanometer accuracy is also researched in this thesis. It mainly includes the study ofmulti-axis linear interpolation technology, corner speed control technology, backwardand forward trajectory planning technology. The S-shaped speed curve is divided into10types, and the parameter solution formulas for each type are given. A nanometeraccuracy S-shape acceleration/deceleration method based on32-bit processor is also proposed.Finally, the theory and design method of multi-axis motion control system usedfor the sculptured surface machining is further studied. The affecting factors ofmulti-axis motion system’s accuracy and speed are summarized. The design methodsof HMI (Human Machine Interface) module, NCK module and the PLC module arediscussed to make a complete theory. The overall effectiveness of the proposedfive-axis NURBS machining scheme is demonstrated by the five-axis machining of animpeller’s flow channel.

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