A real-time interpolator for parametric curves. (February 2018)

• Record Type: Journal Article
• Authors: Zhong, Wenbin; Luo, Xichun; Chang, Wenlong; Ding, Fei; Cai, Yukui
• Is Part Of: International journal of machine tools & manufacture. Volume 125(2018)
• Page Start: 133
• Page End: 145
• Publication Date: 2018-02
• Subjects: Real-time interpolator -- Parametric curve -- Lookahead -- Machine dynamics -- Contour error; Machine-tools -- Periodicals; Manufacturing processes -- Periodicals; Machines-outils -- Périodiques; Fabrication -- Périodiques; Electronic journals; 621.902
• DOI: 10.1016/j.ijmachtools.2017.11.010
• Languages: English
• ISSNs: 0890-6955

Abstract

Abstract: Driven by the ever increasing need for the high-speed high-accuracy machining of freeform surfaces, the interpolators for parametric curves become highly desirable, as they can eliminate the feedrate and acceleration fluctuation due to the discontinuity in the first derivatives along the linear tool path. The interpolation for parametric curves is essentially an optimization problem, and it is extremely difficult to get the time-optimal solution. This paper presents a novel real-time interpolator for parametric curves (RTIPC), which provides a near time-optimal solution. It limits the machine dynamics (axial velocities, axial accelerations and jerk) and contour error through feedrate lookahead and acceleration lookahead operations, meanwhile, the feedrate is maintained as high as possible with minimum fluctuation. The lookahead length is dynamically adjusted to minimize the computation load. And the numerical integration error is considered during the lookahead calculation. Two typical parametric curves are selected for both numerical simulation and experimental validation, a cubic phase plate freeform surface is also machined. The numerical simulation is performed using the software (open access information is in the Acknowledgment section) that implements the proposed RTIPC, the results demonstrate the effectiveness of the RTIPC. The real-time performance of the RTIPC is tested on the in-house developed controller, which shows satisfactory efficiency. Finally, machining trials are carried out in comparison with the industrial standard linear interpolator and the state-of-the-art Position-Velocity-Time (PVT) interpolator, the results show the significant advantages of the RTIPC in coding, productivity and motion smoothness. Highlights: The interpolator increases the productivity and motion smoothness significantly. The interpolator limits axial velocities, axial accelerations, jerk and contour error. The lookahead operations are specially designed for enhanced efficiency and accuracy.