Method for the localization of a tool in a workplace, corresponding system and computer program product

Patent metadata

Field	Value
Publication number	US-9591228-B2
Application number	US-201414335264-A
Country	US
Kind code	B2
Filing date	Jul 18, 2014
Priority date	Aug 5, 2013
Publication date	Mar 7, 2017
Grant date	Mar 7, 2017

Abstract

A method for locating a tool for industrial operations that is positioned in a sequence of operating points of an operating sequence associated to different positions on a component on which work is to be carried out, includes associating a light source to the tool and at least three light sources identifying a position reference triplet fixed with respect to the component. A stereovision apparatus having at least two video cameras acquires at least two respective images of the tool and component. The displacement of the operating points on the component is tracked when carrying out an industrial operation on the component by recognizing positions of the reference triplet and a point of the light source of the tool calculating the position of the operating points of an operating sequence with reference to the position assumed by the reference triplet and evaluating the position of the tool with respect to the calculated position of the operating points.

First claim

What is claimed is:

1. A method for locating a tool for industrial operations that is positioned in a sequence of operating points of an operating sequence associated to different positions on a component on which work is to be carried out,
comprising:
associating a light source to said tool and at least three light sources identifying a position reference triplet fixed with respect to said component,
acquiring, via a stereovision apparatus comprising at least two video cameras, at least two respective images of said tool and component;
tracking a displacement of said operating points on said component, when an industrial operation is being carried out on the component, by:
recognizing positions of the reference triplet and a point of the light source of the tool;
calculating the position of the operating points of an operating sequence with reference to the position assumed by the reference triplet; and
evaluating the position of the tool with respect to the calculated position of the operating points.

2. The method according to claim 1 , further comprising, following upon calculation of the position of the operating points of an operating sequence with reference to the position assumed by the reference triplet, calculating an operating point in the operating sequence closest to the point of the tool and evaluating whether said closest operating point is at a distance less than a limit distance that can be set from the position associated to the source of the tool, and if so, of emitting a signal of correspondence that indicates that the tool is at the required operating point.

3. The method according to claim 1 , further comprising, prior to said tracking operation, an initialization procedure, for initializing the stereovision apparatus, the initialization procedure comprising:
acquiring images of said video cameras that frame a calibration instrument presenting known geometries;
extracting co-ordinates of said known geometries; and
supplying said co-ordinates to a calibration procedure that calculates, on the basis of the position of the video cameras with respect to one another, correction values in order to render the images of the two video cameras epipolar.

4. The method according to claim 1 , further comprising a procedure of characterization of the working environment comprising:
configuring the optics of the video cameras, via filtering, for detecting only the wavelength of the light sources on the component and on the tool;
defining the positions of the reference triplet fixed with respect to the component and distances between said positions; and
storing said positions and distances as reference values for the tracking procedure.

5. The method according to claim 4 , wherein said procedure of characterization of the working environment further comprises recording the positions of the operating sequence, displacing the tool at operating points and recording the successive positions of the tool as positions of the operating sequence.

6. The method according to claim 5 , further comprising recording in a characterization file the position in space of each of the three reference points, and the position in space of each operating point.

7. The method according to claim 5 , wherein said operation of calculating the position of the operating points of an operating sequence with reference to the position assumed by the reference triplet comprises performing a rototranslation of recorded working positions into working positions calculated during tracking, a corresponding rototranslation matrix being obtained on the basis of a matrix comprising the positions of the reference triplet during the recording operation and of a matrix comprising the positions of the reference triplet obtained during the operation of recognition.

8. The method according to claim 4 , wherein said operation of defining the positions of the reference triplet fixed with respect to the component and distances between said positions comprises the following steps:
coupling each point of one of the two images with each point of the other image that has a similar height;
for each pair of points in the two images calculating via the stereovision-calculation procedure the co-ordinates of a hypothetical point;
given the first hypothetical point, calculating its distance from the other hypothetical points;
if said distance is similar to one of the distances of the reference triplet, temporarily storing the corresponding pair of points;
repeating said calculation of the distance for the other hypothetical points and, when the third point of the reference triplet is found, interrupting the calculation.

9. The method according to claim 1 , wherein said operations of the tracking procedure are executed in real time with continuous acquisition of the images.

10. A system for locating a tool for industrial operations that is positioned in a sequence of operating points of an operating sequence associated to different positions on a component on which work is to be carried out, comprising:
a light source associated to said tool and at least three light sources, identifying a position reference triplet fixedly associated to said component, a stereovision apparatus comprising at least two video cameras, and a control module configured for controlling said stereovision apparatus and acquiring images of said video cameras,
said control module being configured for tracking the displacement of said operating points on said component according to the method according to claim 1 .

11. The system according to claim 10 , wherein said light sources are infrared emitting LED's.

12. The system according to claim 10 , wherein said tool is a wrench and said operating points are screwing points.

13. A computer program product that can be directly loaded into the memory of at least one computer and comprises portions of software code for implementing the method according to claim 1 .

Assignees

• Fiat Ricerche
• C R F Societá Consortile Per Azioni

Inventors

• Cisi Alessandro

Classifications

• H04N23/69 Primary

  Control of means for changing angle of the field of view, e.g. optical zoom objectives or electronic zooming · CPC title

• G01C11/02 Primary

  Picture taking arrangements specially adapted for photogrammetry or photographic surveying, e.g. controlling overlapping of pictures · CPC title

• G05B19/402

  characterised by control arrangements for positioning, e.g. centring a tool relative to a hole in the workpiece, additional detection means to correct position (G05B19/19 takes precedence) · CPC title

• H04N13/239 Primary

  using two two-dimensional [2D] image sensors having a relative position equal to or related to the interocular distance (H04N13/243 takes precedence) · CPC title

• G01S5/30

  Determining absolute distances from a plurality of spaced points of known location · CPC title