WO2008110899A2

WO2008110899A2 - Method and plant for surface fairing a structure

Info

Publication number: WO2008110899A2
Application number: PCT/IB2008/000570
Authority: WO
Inventors: Claudio Raggi
Original assignee: Azimut-Benetti S.P.A.
Priority date: 2007-03-12
Filing date: 2008-03-11
Publication date: 2008-09-18
Also published as: WO2008110899A3

Abstract

A surface (2) of a structure (5) is faired using a plant (1) having at least one mobile operating unit (6), which has a rail system (9), along which runs at least one multiple-axis robot (10) controlled by a computer (13), and a tool store (11) for a number of interchangeable tools (12) fitted automatically to the robot (10) to perform a sequence of scanning and finish operations on the surface (2). Which operations are performed by positioning the mobile operating unit (6) next to the structure (5) to perform the scanning and finish operations on at least part (S1; S2) of the surface (2); and, if necessary, re-positioning the operating unit (6) with respect to the structure (5) a sufficient number of times to perform the scanning and finish operations on the whole surface (2).

Description

METHOD AND PLANT FOR SURFACE FAIRING A STRUCTURE

TECHNICAL FIELD The present invention relates to a method and plant for surface fairing a structure .

More specifically, the present invention relates to a method and plant of the type in which at least one computerized operating machine - normally a multiple- axis robot with interchangeable tools - is mounted to move along a structure and perform a programmed sequence of scanning and finish operations on a surface of the structure .

The present invention may be used for surface fairing any fixed or movable structure, but is particularly advantageous for surface fairing the hull and/or superstructure of boats, particularly very large pleasure boats, to which the following description refers purely by way of example. BACKGROUND ART

As applied specifically to boatbuilding, a method and plant of the type described above are described, for example, in EP-1103310, wherein a boat for surface fairing is set up between two fixed parallel rails - at least as long as the boat - of a fairing plant, in which a number of multiple-axis robots, equipped with interchangeable tools, are mounted to move along the rails and/or fitted to a crane travelling along the rails, to : scan the outer surface of the boat ' s hull and/or superstructure to determine any flawed areas; coat the flawed areas with filler, normally cement or similar; shape each coated area to blend it with the surrounding areas,- and clean and paint the shaped areas .

Methods and plants of the type described above have several drawbacks, mainly due to the fixed rails of the multiple-axis robots, and the surface fairing method adopted.

In connection with the above, it is important to bear in mind that, in boatbuilding, a plant of the type described is not normally used for fairing molded boats

- which are substantially finished when removed from the molds, and only need fairing in the event of extensive repair work - but for fairing sheet metal boats, the construction of which is advantageous when the length thereof is about 20-25 m or more.

That is, in plants of the type described, the rails are normally at least 50 m long, are at least 10 m apart, and permanently occupy a dedicated shed that is not only of considerable size and only capable of catering to boats of at most the same length as the rails, but must also be located close to the slipways, in that, though not impossible, manoeuvring a 50-metre boat in a boatyard to the fairing shed is certainly a difficult, high-cost, dangerous job.

From the operating standpoint, and also on account of the fixed rails, plants of the type described must be equipped with extremely long-reach, and therefore very heavy, high-cost, robots. That is, a 50 -metre boat may be as much as 8-10 m wide, and can only be faired in a plant of the type described using robots with a reach of at least 6-7 m, seeing as each must be able to work equally as well on both a maximum-width section and the bow line of the boat.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a boat fairing method that is cheap and easy to implement, while at the same time eliminating the aforementioned drawbacks .

According to the present invention, there is provided a method of surface fairing a structure, in particular, though not necessarily, a boat, as claimed in Claim 1 and preferably in any one of the Claims depending directly or indirectly on Claim 1.

The present invention also relates to a plant for surface fairing a structure.

According to the present invention, there is provided a plant for surface fairing a structure, in particular, though not necessarily, a boat, as claimed in Claim 8 and preferably in any one of the Claims depending directly or indirectly on Claim 8. BRIEF DESCRIPTION OF THE DRAWINGS

A non- limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which: Figure 1 shows a view in perspective of a preferred embodiment of the plant according to the present invention;

Figure 2 shows a larger-scale view in perspective of a detail of Figure 1 ; Figure 3 shows an exploded view in perspective, with parts removed for clarity, of the Figure 2 detail;

Figure 4 shows a schematic side view, with parts removed for clarity, of the Figure 2 detail;

Figure 5 shows a partly sectioned plan view of the Figure 2 detail;

Figure 6 shows a schematic view in perspective of a scanning device forming part of the Figure 2 detail;

Figure 7 shows an example boat surface scanning sequence; Figure 8 shows an example operating diagram of the plant according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Number 1 in Figure 1 indicates as a whole a mobile computerized plant for fairing a surface 2 of a hull 3 and/or superstructure 4 of a boat 5.

With particular reference to Figure 2, plant 1 comprises a mobile operating unit 6 (or a number of mobile operating units 6 variously arranged along boat 5) which is set up next to boat 5, and in turn comprises a rectangular parallelepiped-shaped box 7, preferably of the same size as a large container of maximum 15 m in length, maximum 2.5 m in width, and maximum 3 m in height. In other words, the box can be loaded onto a heavy-duty road vehicle or railroad flat car for troublefree transport to anywhere it is required.

Box 7 has a roof 8 fitted with a rail system 9, which is normally the same length as box 7 and independent of the length of boat 5.

Rail system 9 provides for guiding at least one multiple-axis robot 10 (in the example shown, rail system 9 supports one, but may obviously be fitted with a number of robots 10) which, in the example shown, is a known multiple-axis anthropomorphic robot, which cooperates in known manner with an automatic store 11 of interchangeable tools 12 fitted selectively and automatically to robot 10 to enable robot 10 to perform a sequence of scanning and finish operations on surface 2 under the control of a computer 13 housed in box 7.

With particular reference to Figure 3, box 7 houses a control room 14 comprising computer 13; automatic store 11 of tools 12; and a store 15 of containers 16 containing various coating materials and connectable selectively to a central control unit 17 for pumping the coating materials to robot 10.

With reference to Figure 2, to move operating unit 6 about boat 5, box 7 is fitted underneath with an air cushioning system 18, which is fed with compressed air by a pump station 19 (Figure 3) housed in a compartment 20 (Figure 3) of box 7, and comprises a number of air cushions 21 equally spaced underneath the floor 22 of box 7.

As shown in Figures 4 and 5 , operating unit 6 comprises a number of known powered towing devices 23, which are connectable to box 7 to manoeuvre box 7 easily once air cushions 21 are activated. Once positioned as required, operating unit 6 can be lowered onto the ground by deactivating air cushions 21, and then levelled by means of a levelling system 24 comprising a number of jacks 25 projecting downwards from the periphery of floor 22 to set rail system 9 to a given, preferably flat horizontal, position.

As shown more clearly in Figure 2, operating unit 6 comprises a powered trolley 26 movable along rail system 9 under the control of computer 13; and an adjustable support 27 mounted on trolley 26, controlled by computer 13, and supporting robot 10. More specifically, support 27 is fitted to trolley 26 with the interposition of a powered turntable 28 rotated by computer 13 about an axis 29 perpendicular to the plane of rail system 9. Support 27 comprises an upright 30 integral with turntable 28 and housing a powered screw 31, which is coaxial with axis 29, is controlled by computer 13, and is connected by a screw-nut screw coupling to a bracket 32 projecting from and movable along upright 30, and supporting robot 10.

As shown in Figure 2, robot 10 comprises a base 33; and a further powered turntable 34 interposed between bracket 32 and base 33 to allow base 33 to rotate, with respect to bracket 32 and under the control of computer

13, about a further axis 35 parallel to axis 29.

Robot 10 comprises a first powered arm 36 connected to base 33 to rotate, with respect to base 33, about a horizontal axis 37; a motor 38 fitted to first arm 36 to rotate, with respect to first arm 36, about a horizontal axis 39 parallel to axis 37; a second arm 40 connected to the output of motor 38 to rotate about its own longitudinal axis 41; and a powered toolhead 42 for supporting and operating any tool 12, and which is connected to second arm 40 by a connecting rod 43 to oscillate, with respect to second arm 40, about two parallel axes 44, 45 crosswise to longitudinal axis 41, and about a further axis 46 crosswise to axes 44, 45.

Robot 10 comprises a structured-light scanning device 47 connected to computer 13. Scanning device 47 is preferably fitted to^' Base 33, as in the example shown, or may be one of tools 12 connectable to toolhead 42.

As shown in Figure 6, whether in tool form or connected to base 33, scanning device 47 comprises a bar 48 to which are fixed a structured- light multimedia projector 49 with an optical axis 50, and two digital television cameras 51a, 51b located on opposite sides of projector 49, and the optical axes 52a, 52b of which are set an angle to each other and intersect optical axis 50 at a point C.

A surface Sl (Figure 7) , forming part or all of surface 2, is scanned, using a known "reverse engineering" technique, by projecting onto surface Sl, by means of structured- light projector 49, and simultaneously acquiring, by means of television cameras 51a and 51b, a sequence of black-and-white- fringe images, in which the fringe distribution period is halved between one image and the next . By means of this technique, the portion Sl of surface 2 is acquired in known, fully computerized manner in the form of a cloud of dots with precise 3D coordinates. When, as is normally the case, surface Sl only forms part as opposed to the whole of surface 2 , operating unit 6 is moved along boat 5 to scan a surface S2 adjacent to and overlapping surface Sl at an overlap Z. This operation is repeated, if necessary, for other overlapping surfaces S3, S4 , etc., until the whole of surface 2 is covered.

The individual scans, made from various positions and angles along boat 5, are aligned by determining the 3D coordinates of a given number of markers K in each overlap Z. In this connection, it should be pointed out that scans can only be aligned if each shares at least two markers K with the preceding and succeeding scan. Each marker K, in fact, like all the other dots in the acquired dot cloud, is characterized by a specific coordinate, and therefore by three information items representing 3 degrees of freedom. Consequently, since each individual dot cloud may be likened to a rigid body in space, i.e. a body with six degrees of freedom, only one marker K shared by two adjacent acquisitions, i.e. two adjacent dot clouds, is not enough to align the two acquisitions. Using at least two shared markers K, however, a definite alignment of two adjacent clouds can be achieved, to gradually construct a global dot cloud corresponding to the whole of surface 2.

At this point, the global dot cloud is processed, using an STL or, preferably, IGES representation technique, to obtain a mathematical model of surface 2 representing the real shape of the work surface 2 facing operating unit 2, and which is illustrated for the sake of simplicity by a straightforward curve R in Figure 8. The real shape differs for various reasons from the curve M representing the mathematical model on which construction of boat 5 was based : actual construction never corresponds exactly to the basic mathematic model for construction reasons; the actual acquired surface is deformed by boat 5 being scanned on a slipway as opposed to in water; and the actual acquired surface varies as a function of environmental conditions .

By comparing curves M and R and using arbitrary parameters on the basis of experience, the builder can obtain an ideal model, represented by curve I, of the shape surface 2 should have . By means of a sequence of known mathematical processes performed by computer 13, the ideal model is located outwards of the real mathematical model represented by curve R, and is moved closer to the real mathematical model to establish a minimum distance, set by the builder, between the two models, and determine an ideal continuous layer L to be added to the real mathematical model to obtain the ideal mathematical model. Computer 13 calculates, portion by portion of surface 2, the integral of ideal continuous layer L, adds a given surplus quantity, calculates the amount of filler material, normally cement, to be applied to surface 2 to obtain a real continuous layer in excess of ideal continuous layer L, and controls operating unit 6 to pump onto surface 2, by means of robot 10 fitted with a spray tool 12 , the amount of material required to obtain the real continuous layer and drawn from containers 16 by central pumping control unit 17. The resulting surface, in excess of the ideal surface, is then finished, i.e. reduced to the ideal surface, by robot 10 fitted with an abrasive tool 12, and is then subjected to further surface finishing operations by robot 10 fitted with appropriate tools 12. In connection with the above, it should be pointed out that reducing the real continuous layer to ideal continuous layer L is also carried out, if necessary, by moving operating unit 6 gradually along boat 5, and working successive portions or surfaces Sl, S2, etc. as shown in Figure 7. Which means that, in this case too, once surface Sl, for example, is finished, scanning device 47 detects markers K in the overlap Z between surface Sl and the next surface S2; and operating unit 6 is moved into the best position to finish surface S2, by first aligning the map of the ideal surface to be obtained by finishing surface S2 with the finished surface of Sl, using markers K as described above. Apart from scanning speed and precision, one of the main advantages of plant 1 afforded by scanning device 47 is that, when setting operating unit 6 to a new position facing surface 2, there is no need to accurately determine the new position or to set operating unit 6 to a precise position. By scanning device 47 simply detecting markers K of the work portion of surface 2, computer 13 is able to requalify, and make directly available for control of robot 10, all the data relative to the work portion of surface 2.

Claims

1) A computerized method of surface fairing a structure (5), in particular, but not necessarily, a boat, by means of at least one operating unit (6) comprising a rail (9) of a given length, and at least one multiple-axis robot (10) which is controlled by a computer (13) , is movable along the rail (9) , and is fitted with tools (12) to perform a sequence of scanning and finish operations on a real surface (2) of the structure (5) ; the method being characterized by employing as an operating unit a mobile operating unit (6) , and by comprising the steps of:

- positioning the mobile operating unit (6) next to the structure (5) ;

- scanning at least part of the real surface (2) by means of a structured- light optical scanning device

(47) ;

- if necessary, re-positioning the mobile operating unit (6) with respect to the structure (5) a sufficient number of times to scan the whole real surface (2) and construct mathematical models; and controlling the robot (10) by means of the computer (13) and on the basis of the mathematical models to perform the finish operations.

2) A method as claimed in Claim 1, and comprising, to perform the scanning operations and at least some of the finish operations, the steps of: - scanning the real surface (2) by means of the structured-light optical scanning device (47) to obtain a first mathematical model (R) of the real surface (2) ;

- obtaining from the first mathematical model (R) a second mathematical model (I) , which differs from the first mathematical model (R) by an ideal continuous layer (L) of varying thickness;

- feeding filler material onto the real surface (2) to form, on the real surface (2), a real continuous layer thicker than the ideal continuous layer (L) ; and

- shaping the real continuous layer to obtain a surface corresponding to the second mathematical model (I) •

3) A method as claimed in Claim 1 or 2 , wherein scanning the real surface (2) comprises: dividing the real surface (2) into a first and at least a second portion (Sl, S2) adjacent to each other; successively scanning said portions (Sl, S2) by moving the mobile operating unit (6) into a position facing each portion (Sl; S2) , and so as to also scan, for each portion (Sl; S2), part of the adjacent portion

(S2; Sl) ; and juxtaposing the scans of the adjacent said portions (Sl, S2) so as to overlap the scans along an overlap (Z) to obtain a complete scan of the real surface (2) .

4) A method as claimed in Claim 3, wherein the step of juxtaposing the scans of two adjacent portions (Sl, S2) is performed by determining a given number, always greater than one, of markers (K) in the overlap (Z) of the two adjacent portions (Sl, S2) , and aligning the two scans by matching the coordinates of said markers (K) in the two scans . 5) A method as claimed in Claim 4, wherein the markers (K) determined in the overlap (Z) are at least two in number .

6) A method as claimed in one of Claims 3 to 5, wherein scanning each said portion (Sl; S2) of the real surface (2) by means of the structured-light optical scanning device (47) comprises constructing the first mathematical model (R) of the portion (Sl; S2) using a "reverse engineering" process.

7) A method as claimed in Claim 6, wherein the "reverse engineering" process comprises the steps of:

- projecting onto each said portion (Sl; S2) by means of a structured- light projector (49), and simultaneously acquiring by means of two television cameras (51a, 51b) set at an angle to each other and connected to the computer (13), a sequence of black-and- white-fringe images, in which the fringe distribution period is halved between one image and the next;

- processing said images on the computer (13) to acquire said portion (Sl; S2) in the form of a cloud of dots with precise 3D coordinates; and

- processing the dot cloud by means of an STL or IGES representation technique to obtain the first mathematical model (R) of said portion (Sl; S2) . 8) A computerized plant for surface fairing a structure (5), in particular, but not necessarily, a boat; the plant (1) comprising at least one mobile operating unit (6) positioned next to the structure (5) and in turn comprising a rail (9) of a given length independent of the length of the structure (5) , at least one multiple-axis robot (10) movable along the rail (9) , a number of automatically interchangeable tools (12) fittable to the robot (10) , a structured-light optical scanning device (47) for performing a sequence of scanning operations on a real surface (2) of the structure (5) to obtain information relating to the real surface (2), and a computer (13) for processing said information and controlling the robot (10) to perform a sequence of finish operations on the real surface (2) .

9) A plant as claimed in Claim 8, wherein the rail (9) is a system of rails.

10) A plant as claimed in Claim 8 or 9 , wherein the operating unit (6) comprises a rectangular parallelepiped-shaped box (7) with a roof (8) ; the rail (9) being located on said roof (8) and extending longitudinally along the roof (8) .

11) A plant as claimed in Claim 10, wherein the box (7)^' is the^""" size ^"o^'f a container for tyred wheel and/or rail transportation.

12) A plant as claimed in one of Claims 8 to 11, and comprising air-cushion means (21) for pneumatic support and frictionfree displacement of the operating unit ( 6 ) .

13) A plant as claimed in Claim 12, and comprising levelling means (24) for setting the rail (9) to a given position when the air-cushion means (21) are deactivated.

14) A plant as claimed in Claim 12 or 13, and comprising towing means (23) for moving the operating unit (6) when the air-cushion means (21) are activated.

15) A plant as claimed in one of Claims 10 to 14, wherein the box (7) houses a control room comprising the computer (13) .

16) A plant as claimed in one of Claims 10 to 15, wherein the box (7) houses an automatic tool-change device . 17) A plant as claimed in one of Claims 10 to 16, wherein the box (7) houses a coating material store (15) ; the store (15) being connectable directly to the robot (10) .

18) A plant as claimed in one of Claims 8 to 17, and comprising a powered trolley (26) moved along the rail (9) by the computer (13) ; and a support (27) supporting the robot (10) and mounted on the trolley (26) .

19) A plant as claimed in Claim 18, wherein the support (27) supporting the robot (10) comprises an upright (30); a powered turntable (28) interposed between the upright (30) and the trolley (26) to permit rotation of the upright (30) , with respect to the trolley (26) and by the computer (13) , about a vertical axis (29) ; and a powered bracket (32) supporting the robot (10) and moved along the upright (30) by the computer (13) . 20) A plant as claimed in Claim 19, wherein the robot (10) comprises a base (33) ; and a further powered turntable (34) interposed between the bracket (32) and the base (33) to permit rotation of the base (33), with respect to the bracket (32) and by the computer (13), about a further vertical axis (35) .

21) A plant as claimed in one of Claims 8 to 20, wherein the robot (10) is a multiple-axis anthropomorphic robot having a toolhead (42) at one end for any one of said tools (12) . 22) A plant as claimed in one of Claims 8 to 21, wherein the structured-light optical scanning device (47) is movable with the robot (10) .

23) A plant as claimed in Claim 22, wherein the structured-light optical scanning device (47) comprises a structured- light multimedia projector (49) ; and two digital television cameras (51a, 51b) located on opposite sides of the projector (49) and having respective optical axes (52a, 52b) at an angle to each other.