Free Shape Paths in Industrial Robots

•Date: Octoer, 2012•Linked to: AESOP

Contact information

Tampere University of Technology,

FAST Laboratory,

P.O. Box 600,

FIN-33101 Tampere,

Finland

Email: fast@tut.fi

www.tut.fi/fast

Conference: 38th Annual Conference of the IEEE Industrial Electronics Society

Title of the paper: Free Shape Paths in Industrial Robots

Authors: Luis E. Gonzalez Moctezuma, Andrei Lobov, Jose L. Martinez Lastra

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Free Shape Paths in Industrial Robots

Authors: Luis E. Gonzalez Moctezuma, Andrei Lobov, Jose L. Martinez Lastra

Tampere University of TechnologyFactory Automation Systems and Technology Lab

IECON 2012, Montreal, Canada25-28.10.2012

Outline

• Motivation

• Bezier curves

• Curve approximation: arc and linear segments

• Comparison

• Implementation

• Conclusions

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Motivation (1/2)• 2008: 1.3 million of industrial robots

• Simple movements in industrial robots– Linear– Circular

• Need for free shape paths in robotic applications:– Welding– Fluid dispensing– Painting processes– Interaction and cooperation with humans

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Motivation (2/2)

• How to enable standard industrial robots to perform free shape paths?

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Bezier curves (1/2)• Introduced by Pierre Bezier – Renault

• Curves described by a parametric function

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Bezier curves (2/2)

• Control, flexibility, intuitive

• Use and tools in:– Industrial design– CAD– 3D modelling– Vector-based drawing

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Approximation by arc segments

• Implementation of algorithm proposed by: Riskus, Aleksas. “Approximation of a Cubic Bezier Curve by Circular Arcs and Viceversa”

– Find inflection points (curvature change in sign)– Segments subdivided to reach biarcs <90°

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Approximation by linear segments• 1) Evaluate directly on the polynomial

function: Numerically unstable

• 2) Use the De Casteljau algorithm– Uses parameter t – and Bezier descriptors

Numerically stable

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Comparison: arc Vs linear segments

*

*Interpolations can be computed in the target (industrial robot controller)

Implementation• SCARA robot (~15 years old)

• De Casteljau algorithm within the robot controller

• Transfer to controller just Bezier descriptors

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System in action

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Video link

Conclusions

• Approach to implement free shape paths in generic industrial robots.

• Bezier curve descriptors can be storage as standard points

• Feasible to implement the Decasteljau algorithm within robot controllers

• Current and future industrial robotic applications might need free shape path capabilities to cooperate with humans and other machines

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Questions?

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