EP2069116A2

EP2069116A2 - Process for identifying the position of an object in space and process for placing that object in a predetermined position

Info

Publication number: EP2069116A2
Application number: EP07827720A
Authority: EP
Inventors: Federico Giudiceandrea
Original assignee: Microtec SRL
Current assignee: Microtec SRL
Priority date: 2006-09-27
Filing date: 2007-09-26
Publication date: 2009-06-17
Also published as: WO2008038328A2; WO2008038328A3; ITVR20060145A1

Abstract

A process for identifying the position of an object in space comprises a step of illuminating the object with a plurality of rays of light distributed in a known way, for creating a set of illuminated points on the surface of the object and a step of detecting the geometric configuration of the set of illuminated points. Then, a first comparison step between said geometric configuration and a saved three- dimensional surface structure of the object allows the discovery of a substantial correspondence between the geometric configuration detected and at least one geometric configuration belonging to the saved three-dimensional surface structure. Finally, there is an at least implicit step of identification of the position of the object in space based on the comparison between the position in space of the geometric configuration detected and the position of the same geometric configuration detected on the saved three-dimensional surface of the object. The claims also refer to a process for placing an object in space based on the position identification process.

Description

Process for identifying the position of an object in space and process for placing that object in a predetermined position

Technical Field

The invention relates to a process for identifying the position of an object in space and a process for placing that object in a predetermined position using the position identification process. The present invention is intended in particular for use with logs in sawmills, but may advantageously be used for any type of object made of any material.

The present invention allows identification of the position of an object in space before subjecting the object to any type of processing, as well as correction of the position.

Background Art

Given the specific purpose for checking the position of logs in sawmill work lines, reference is frequently made to logs in the description below. However, the considerations must be interpreted in a wide sense as applicable to any object. Interest in using the present invention relative to logs arises because, for each log, there is, depending on the type of wood one intends to obtain from it and depending on the shape of the log, the so-called best possible cutting pattern, that is to say, that which allows waste to be minimised and the quantity of wood obtained to be maximised. Establishing what is the best possible cutting pattern for a log is not the subject matter of the present invention, but once this has been discovered, there remains the problem of suitably positioning the log in the cutting machine, that is to say, positioning it in such a way that it can be cut as required by the best possible cutting pattern. Any deviation from this optimum position increases the waste. For example, if the log has a curvature or a bump and the best cutting pattern requires the log to have the curvature pointing upwards or the bump in a direction set at an angle of 20° to the horizontal plane, then the log must be brought precisely into that position during cutting, otherwise it would be impossible to cut it according to the best possible cutting pattern.

There are, several known ways of positioning the log for this purpose, according to which the log is first gripped and stopped by mechanical elements and then moved to the required position. The disadvantage common to these types of processes is that there is no feedback regarding the precise position to which the log has moved.

This disadvantage is based on the fact that although the shape of the log is sufficiently precisely known from previous readings and measurements, that is to say, its three-dimensional geometric structure is known through a knowledge of the spatial geometric co-ordinates of each point of its surface, there is no equally sufficiently precise knowledge of the position with which it moves to the cutting machine, which is the position to be used as the starting point so that, with the movements caused by the appropriate elements, it is possible to reach the position required by the best possible cutting pattern. Moreover, there are also problems of uncertainty as to whether or not the position required by the best possible cutting pattern is effectively reached, since there are no procedures for checking precise effective performance of the movements required. Reasons why the movements required may not be precisely performed are, for example, any sliding between a mechanical retaining element and the surface of the log, and any difficulty experienced by the mechanical element precisely performing the movement required.

These problems are partly solved with the invention described in Swedish document No. 8803024-2, according to which an identifying mark is applied on a section of the log and the movements of this identifying mark are subsequently detected to check the precision of the movements performed to move the log into the position required by the best possible cutting pattern.

The biggest disadvantage of this process is the fact that there remains the difficulty of precisely knowing the log starting position, meaning that even if it is possible to check that the required movements were performed precisely, there still remains a high degree of error due to that initial imprecision.

As already indicated, said problem may arise with any object whose shape needs to be identified for subsequent processing or movement (for example, for correct storage).

Disclosure of the Invention

The present invention therefore has for an aim to develop an alternative process to the known one mentioned above, which will make it possible, at any time, to precisely identify the position of an object in space.

The present invention also has for a technical aim to provide a process which allows an object to be precisely placed in a predetermined position.

This aim is achieved by a process with the features described in the claims herein.

Further advantages and characteristics of the invention are more apparent in the description which follows of examples of embodiments of the process in accordance with the invention, provided by way of example only and without limiting the invention in any way.

Detailed Description of the Preferred Embodiments of the Invention

The position identification process which is the subject matter of the present invention comprises, first of all, an operating step of illuminating the object with a plurality of rays of light distributed in a known way. In this way, the set of rays of light striking the surface of the object creates a set of illuminated points on it.

Although the rays of light may be positioned in any way relative to one another, they are preferably positioned in such a way as to create at least one flat beam of light. However, in the preferred embodiments, the rays of light are positioned in such a way as to create a plurality of flat beams of light positioned in a known way relative to one another. In particular, said flat beams may be spaced out, in such a way that on the object they create a plurality of illuminated lines, or they may be arranged side by side in such a way that on the object they create at least one illuminated band with predetermined width.

Advantageously, the flat beams of light may be emitted in planes positioned transversally to a predetermined direction, such as the direction of movement of the object, or the main direction of extension of the object. Moreover, depending on requirements, the rays of light which may or may not belong to the same beam, may be emitted simultaneously or in a predetermined sequence.

Combined with the illuminating step there is a step of detecting the positions of the illuminated points relative to one another, which allows identification of the geometric configuration in space of the set of illuminated points.

As already indicated, said configuration may consist of a surface (band- shaped or having another shape), one or more lines, or even several points separated from one another.

Advantageously, the detection step is carried out using the laser triangulation technique. This is a know technique widely used in processes for detecting the structure of logs, and which may be implemented in many similar ways.

After the detection step there is a first comparison step between the geometric configuration identified during the detection step and a saved three- dimensional surface structure of the object. The term saved three-dimensional structure refers to the electronic form of it which can be manipulated, created using known detection processes.

The three-dimensional geometric structure of the object may be acquired either during a specific preliminary detection and saving step that is part of the process, or beforehand. In the latter case, it is simply retrieved at the moment of the above-mentioned first comparison step.

The first comparison step is intended to discover a substantial correspondence between the geometric configuration detected and at least one geometric configuration belonging to the saved three-dimensional surface structure. The moment when said correspondence is obtained may be indicated as the discovery step.

It should be noticed that, advantageously, the use of flat beams of light allows the creation of sets of illuminated points in the shape of a line, which, upon virtual placing of the known three-dimensional surface structure over the geometric configuration of the line detected, makes it easier to line up the actual illuminated line with the corresponding virtual line on the known three- dimensional surface structure.

Depending on requirements, at the end of the discovery step, the position of the geometric configuration detected and the saved three-dimensional geometric surface relative to one another may or may not in turn be saved.

Once the correspondence between the geometric configuration detected and a geometric configuration belonging to the saved surface geometric structure has been discovered, it is possible to use simple mathematical calculations to identify the position of the object in space. Said identification (the subject of an identification step) is based on the comparison between the position in space of the geometric configuration detected and the position of the same geometric configuration detected on the saved three- dimensional surface of the object.

Depending on the circumstances, the identification step may be carried out explicitly or implicitly. In the former case the information about the position in space will be used as such, whilst in the latter case it will be used implicitly for other calculations (such as those described below).

The process described above may be applied with the object stationary, or with the object moving in a predetermined direction. In the latter case, the time needed to detect the geometric configuration must be short enough for the object to be considered practically stationary.

As already indicated, the present invention also relates to a process which allows an object to be placed in a predetermined position, starting from any position of that object, and which for that purpose uses the position identification process described above.

This process of placing the object may be used, for example, in the case of logs, to place them in such a way that the best possible cutting pattern can be implemented.

The process of placing the object implemented in accordance with the present invention involves first of all implementation of the operating steps described above to identify the initial position of the object in space.

Once the initial position of the object has been identified, there is a second operating step of comparison between the initial position of the object and the predetermined position which it must reach at the end of the placing process. Finally, checked and controlled on the basis of the results of the second comparison step, there is an operating step of moving the object from the initial position to the predetermined position. hi particular, in a preferred embodiment, the second comparison step involves a virtual manipulation of the saved three-dimensional structure, during which the saved three-dimensional structure is virtually moved from the predetermined position until the geometric configuration detected matches the corresponding geometric configuration discovered on the three-dimensional surface of the object during the discovery step (in practice, the three-dimensional structure of the object is virtually moved from the predetermined position to a position corresponding to the actual object initial position detected).

All of the various steps of the virtual movement are in turn saved. In particular, the virtual movement will consist of rotations relative to one or more axes, and translations in one or more directions.

The movement step is normally performed using elements (mechanical, electrical, hydraulic, pneumatic, etc.) able to grip the object and/or move it in the required way.

Advantageously, once the saved three-dimensional structure virtual movement steps have been saved, the object actual movement step can take place by making the object perform movements of equal extent but with the opposite sign to those performed in the virtual manipulation of the three-dimensional structure.

Preferably, to check implementation of the movement step, the operating steps of the identification process may be repeated several times during the movement step. To compare the various positions detected on each occasion with the final position and therefore also to check the final position, known mathematical techniques are used, since they involve calculating groups of co-ordinates in a three-dimensional space.

Parts of this three-dimensional structure can be treated in the same way for example when part of the known three-dimensional surface structure is placed over the geometric configuration identified on each occasion by the set of illuminated points or the geometric configuration of the illuminated lines. These are numeric comparisons which can be performed using known analytical geometry calculation methods. Application of the process described above to the case of a log to be cut is immediate.

When the log is prepared for cutting it will be moved close to the cutting machine and may have any initial position on the conveyor device.

The configuration (geometric structure) of the log is known. Therefore, the co-ordinates of each point of the log are known, as well as its volume, shape, curvature and all of the other measurements. The set of co-ordinates of the points of which the log consists is known relative to a system of local co-ordinates, that is to say, referring to the log, but as is known from geometry this local system of co-ordinates can be entered in any other reference system, for example that of the cutting machine. Therefore, the three-dimensional structure of the log in its final position, that is to say, the position required by the best possible cutting pattern, can be entered virtually in the cutting machine reference system.

When the log is struck for the first time by a plurality of rays of light (for the identification process), it is still in its initial position, that is to say, any position in which it was put close to the cutting machine.

With the subsequent operating steps (detection step, first comparison step, discovery step and identification step), this initial position is identified in the cutting machine reference system and therefore (in the second comparison step) the deviations of this initial position relative to the final position to be reached become known.

The movement elements can then be programmed and activated, so that the log is moved to this final position.

The subsequent readings (there may be dozens per second) relate to intermediate positions between the initial and final positions and allow an operator to check that the log is moving as required.

Finally, when the deviations are minimal (that is to say, below a preset tolerance threshold) the log may be considered to have reached its final position and the movement elements can be switched off. It should be noticed that, to speed up log processing, during the process the log may be fed in the predetermined direction, provided the extent of the movements is known.

In such a case, the log movement in the predetermined direction is only a known parameter for variation of the co-ordinates and does not involve any type of complications.

The present invention brings important advantages.

The invention is based on the idea of defecting the shape of parts of the surface of the object (such as a log) and searching for and finding these parts in the three-dimensional structure already known beforehand. In this way, information can be obtained about the current position of the object, since it is possible to know which part of the log surface is facing the device that detects the shape of the part of the surface, and how it is positioned.

In this way, it is therefore possible to know precisely the initial orientation of the object (for example, the log starting position), which can be detected with a first reading. Then, with subsequent readings it is possible to check the gradual movement of the object towards the required final position (for example, in the case of a log, to the position it must adopt to allow use of the best possible cutting pattern). Finally, with a final reading it is possible to check that this final position has effectively been reached. Therefore, thanks to the invention it is also possible to simply and rapidly control the external elements which move the object.

Moreover, thanks to the present invention, it is possible to detect the geometric three-dimensional structure of a log at a location different to that where the cutting takes place. The invention allows identification of any position in which the log may be put and so allows much more flexible control of the entire log processing process, which may for example be carried out by a number of different people.

For example, the log seller will detect the three-dimensional geometric structure and reconstruct it and save it in an electronic form using known processes. Such an electronic form allows many virtual manipulation operations to be applied to the three-dimensional structure according to which it is possible to see the shape of the log on screen, rotate it, move it, enlarge it, etc. The log purchaser, who has to cut it, will enter the electronic form of the log three- dimensional structure in the computer of his cutting machine, so as to be able to perform the same virtual manipulations.

It should also be noticed that the present invention is relatively easy to produce and even the cost linked to implementation of the invention is not very high.

The invention described above may be modified and adapted in several ways without thereby departing from the scope of the inventive concept. All details of the invention may be substituted by other technically equivalent elements and, in practice, all of the materials used, as well as the shapes and dimensions of the various components, may be any according to requirements.

Claims

1. A process for identifying the position of an object in space, characterised in that it comprises the following operating steps: a step of illuminating the object with a plurality of rays of light distributed in a known way, the set of rays of light striking the surface of the object creating a set of illuminated points on it; a step of detecting the positions of the illuminated points relative to one another, which allows identification of the geometric configuration of the set of illuminated points; a first comparison step between the geometric configuration identified during the detection operating step and a saved three-dimensional surface structure of the object; during the first comparison step there is also a step of discovering a substantial correspondence between the geometric configuration detected and at least one geometric configuration belonging to the saved three-dimensional surface structure; and an at least implicit step of identification of the position of the object in space based on a comparison between the position in space of the geometric configuration detected and the position of the same geometric configuration detected on the saved three-dimensional surface of the object.

2. The process according to claim 1, characterised in that the illuminating step involves positioning rays of light in such a way as to create at least one flat beam of light.

3. The process according to claim 2, characterised in that the illuminating step involves positioning rays of light in such a way as to create a plurality of flat beams of light positioned in a known way relative to one another.

4. The process according to claim 3, characterised in that the flat beams are spaced out.

5. The process according to claim 3, characterised in that at least part of the flat beams are positioned side by side.

6. The process according to any of the claims from 2 to 5, characterised in that the flat beams of light are emitted in planes positioned transversally to a predetermined direction.

7. The process according to claim 6, characterised in that the predetermined direction corresponds to an object direction of movement.

8. The process according to claim 6, characterised in that the predetermined direction corresponds to a main direction of extension of the object.

9. The process according to any of the foregoing claims, characterised in that the rays of light belonging to the beams are emitted simultaneously or in a predetermined sequence.

10. The process according to any of the foregoing claims, characterised in that the detection step is carried out using the laser triangulation technique.

11. The process according to any of the foregoing claims, characterised in that at the end of the discovery step, the position of the geometric configuration detected and the saved three-dimensional geometric surface relative to one another is in turn saved.

12. The process according to any of the foregoing claims, characterised in that it also comprises a preliminary step of detecting and saving the three-dimensional geometric structure of the object.

13. The process according to any of the foregoing claims, characterised in that it is implemented as the object moves in a predetermined direction.

14. The process according to any of the foregoing claims, characterised in that it is applied to identify the position of a log in space.

15. A process for placing an object in a predetermined position, characterised in that it comprises the following operating steps: the operating steps for identifying the initial position of the object in space, carried out in accordance with any of the foregoing claims; a second operating step of comparison between the initial position of the object and the predetermined position that it must reach; and an operating step of moving the object from the initial position to the predetermined position, the movement step being controlled on the basis of the results of the second comparison step.

16. The process according to claim 15, characterised in that the second comparison step involves a virtual manipulation of the saved three-dimensional structure, during which the saved three-dimensional structure is virtually moved from the predetermined position until the geometric configuration detected matches the corresponding geometric configuration discovered on the three- dimensional surface of the object during the discovery step, the virtual movement also being saved.

17. The process according to claim 16, characterised in that the movement step is carried out by making the object perform movements of equal extent but with the opposite sign to those performed in the virtual manipulation of the three- dimensional structure.

18. The process according to claim 15, 16 or 17, characterised in that the identification operating steps are repeated several times during the movement step.