Delayed Reference Control for Hotwire Cutting of Expandable Polystyrene Foam

[+] Author and Article Information
Paolo Gallina

Dipartimento di Energetica, University of Trieste, Via A. Valerio 10, 03127 Trieste, Italy

J. Manuf. Sci. Eng 128(1), 360-365 (Apr 05, 2005) (6 pages) doi:10.1115/1.2124990 History: Received April 07, 2004; Revised April 05, 2005

This paper presents the ideation and implementation of a 2-axes robotic system for hotwire cutting of polystyrene plates. In particular, since the quality of the cutting process is strongly affected by, among others, the interaction force between the hotwire and the workpiece, an accurate force control is required. The force control module, which is referred to as delayed reference control (DRC) belongs to the category of nontime based controllers. According to the DRC theory, the desired input reference xd is a function of time and a variable, which plays the role of a time delay: xd(tT). The time delay T is properly calculated on-line according to the measured force signal in such a way to improve the cutting process quality during the interaction phase. DRC theory and its practical implementation on a 2-axes robot are presented as well as an accurate description of the cutting process. In fact, experimental results validate theoretical predictions.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 1

Sketch of the controlled axis which moves the cutting tool along the feed direction

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Figure 2

Interaction force vs hotwire speed for three different materials. Squares, triangles, and x-marks represent experimental results. They refer, respectively, to a steel wire, a copper wire, and constantan wire. Solid lines represent the interpolating lines of the non-null values.

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Figure 3

DRC control scheme

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Figure 4

Interaction force and delay T vs time along a linear path (α is constant)

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Figure 5

Interaction force vs time along a linear path (β is constant)

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Figure 6

Steady state interaction force Fp and errors e=∣d−dm∣ vs α



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