Papers by Keyword: NURBS Interpolation

Abstract: SOPC becomes popular nowadays, which combines software and hardware in a single chip. In this paper, a multi-axis motion controller is implemented based on a SOPC system with a NIOSII processor in a single FPGA chip. The motion controller includes DDA module, spindle module and NURBS calculation module realized in Verilog HDL. DDA algorithm is used to drive the motors while spindle module is to drive the spindle. Because of NURBS recursive nature, NURBS calculation module is used to accelerate the calculation which takes the advantage of parallel structure. The NIOSII processor realizes the feedrate scheduling, in which constant feedrate is adopted. The second-order interpolation algorithm is used to control the feedrate.

Abstract: This paper based on the interpolation point check calculation process, which uses the movement aixs of the CNC system on the velocity and acceleration components checking , instead of the traditional motion characteristics of the checking calculation. In this way, we can avoid complex NURBS curve derivative computation and simplify the process of the interpolation point calibration. Therefore, it also can ensure the precision of curve machining based on curve, at the same time, the interpolation speed and acceleration control strictly in the scope of the corresponding axis servo system capacity. Whats more, we can ensure that processing does not appear too large shock and vibration at any time.

Abstract: Modern CNC system adopts the NURBS interpolation for the purpose of achieving high-speed and high accuracy performance. However, in conventional control architectures, the computation of the basis functions of a NURBS curve is very time consuming due to serial computing constraints. In this paper, a novel multiprocessor-based motion controller on chip utilizing its high-speed parallel computing power is proposed to realize the NURBS interpolation. The motion control algorithm and I/O control are also embedded in the chip to implement real-time control and NURBS interpolation simultaneously. The experimental tests using an X-Y table verify the outstanding computation performance of the multiprocessor-based motion controller on chip. The result indicates that shorter sampling time (0.1 ms) can be achieved for NURBS interpolation and high-accuracy motion control.

Abstract: In order to exploit the advantages of five-axis flank milling method for space free surface machining to the full, a definition of non-equidistant dual-NURBS tool path is presented first. On this basis, the constraint of velocity of points on the tool axis and the constraint of scanning area of the tool axis are deduced. Considering both of these constraints, an adaptive feed five-axis dual-NURBS interpolation algorithm is proposed. The simulation results show that the feedrate with the proposed algorithm satisfies both of the constraints and the machining time is reduced by 38.3% in comparison with the constant feed interpolator algorithm.

Abstract: To improve machining efficiency and accuracy for surface, a method of machining Non-Uniform Rational B-spline (NURBS) surface based on IGES was put forward. The algorithms for surface information processing machining path planning and real time locus interpolation involved in this method have been worked out from the research results. A prototype of the CNC milling system with “PC+PMAC motion controller” is designed by toolpath planning, coordinate transformation and acceleration-deceleration control, which using VC ++ and openGL in Windows NT + RTX system platform. The simulation experiment was conducted to test the effectiveness and accuracy of the proposed method.

Abstract: NURBS interpolation has many advantages over the traditional linear or circular interpolation in high-speed machining. The existing work in this regard focuses on adaptive feed interpolation considering the chord error constraints and tangent acceleration limits. However, regardless of the dynamic characteristics of individual axis, performance will inevitably suffer when the system is called upon to execute a complex trajectory beyond the range of its capabilities. The intent of the present work is to provide an optimal feed interpolation method respecting both the chord error constraint and the drive constraint of each axis. A look-ahead scheme is applied with a moving window to augment the calculation efficiency for real-time application. Simulations are performed to verify the resulting feedrate, acc/dec profiles and the real-time performance of the proposed interpolator.

Abstract: For the improvement of the system real-time capability, the DSP Curve Surface interpolator has been designed to ensure high speed, high precision requirement for the machining of complexity curve surface. The hardware and software has been designed. The changeable feedrate interpolation algorithm of limit curve error has been studied. Furthermore, the algorithm has been applied to the interpolation and has well real-time capability to satisfy the requirement of high capability CNC by experimentation.