Performance analysis of CNC interpolators for time-dependent feedrates along PH curves
✍ Scribed by Yi-Feng Tsai; Rida T. Farouki; Bryan Feldman
- Publisher
- Elsevier Science
- Year
- 2001
- Tongue
- English
- Weight
- 539 KB
- Volume
- 18
- Category
- Article
- ISSN
- 0167-8396
No coin nor oath required. For personal study only.
✦ Synopsis
Virtually any desired time variation V (t) of the feedrate along a curved path can be realized by real-time CNC interpolator algorithms for the Pythagorean-hodograph (PH) curves: the only stipulation is that V (t) should admit a closed-form indefinite integral F (t). Different feedrate variations V (t) can be accommodated with minimal modifications to the core algorithm by employing a modular function call to define F (t). Such time-dependent feedrate capability is invaluable in high-speed machining applications, where it can ensure smooth acceleration and deceleration control of a CNC machine under extreme torque or power demands on the axis drives. Empirical results from implementations of these time-dependent feedrate interpolators on an openarchitecture 3-axis mill are presented, highlighting their exceptional performance and versatility. These results also furnish a compelling illustration of a basic defect of "traditional" (piecewiselinear/circular) G code path descriptions-namely, the fundamental conflict between geometrical path accuracy (which entails use of many short G code segments) and the accurate and smooth maintenance of rapid commanded feedrates.