Performance analysis of cross-coupled controllers for CNC machines based upon precise real-time contour error measurement

被引:36
作者
Conway, Jeremy R. [1 ]
Ernesto, Charlie A. [1 ]
Farouki, Rida T. [1 ]
Zhang, Mei [2 ]
机构
[1] Univ Calif Davis, Dept Mech & Aerosp Engn, Davis, CA 95616 USA
[2] Chinese Acad Sci, Acad Math & Syst Sci, Beijing 100190, Peoples R China
关键词
CNC machines; Contour error; Feedrate; High-speed machining; Open-architecture controller; Real-time interpolator; CURVE INTERPOLATORS; CONTROL DESIGN; SYSTEMS; POLYNOMIALS; ALGORITHM; PLANE; ZEROS; FORM;
D O I
10.1016/j.ijmachtools.2011.08.015
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
Experimental results from the implementation of a cross-coupled control scheme on a 3-axis CNC mill governed by an open-architecture software controller are presented. Unlike prior cross-coupling schemes, which depend on osculating-circle approximations to the commanded toolpath for real-time contour error estimation, the proposed scheme is based on essentially exact contour error computations for free-form curved paths. The implementation illustrates the feasibility of precise real-time contour error computation with a modest (300 MHz) CPU and a 1024 Hz sampling frequency. For a P-type controller and paths with strong curvature variation, the new scheme ensures much better diminution of contour error than earlier methods. The contour error is observed to decrease monotonically as the relative gain is increased, up to a critical gain value that incurs instability. For PI-type controllers, the comparative contour error reduction is more modest, due to their effective suppression of steady-state position error along the path. In practice, the exact contour error measure permits accurate tracking of strongly curved paths using a simple P-type controller, with smaller feedrate fluctuations than a PI-type controller incurs. (C) 2011 Elsevier Ltd. All rights reserved.
引用
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页码:30 / 39
页数:10
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