AUTOMATED DRILLING METHOD FOR AN AIRCRAFT DOOR HONEYCOMB STRUCTURE

Abstract

The invention relates to a method and device for the automated assembly of a honeycomb structure for an aircraft door comprising, on the one hand, longitudinal beams (P) provided with stiffening ribs and a central web extended at its ends by feet and, on the other hand, transverse partitions (C) with right angles, said structure being closed on at least one face by an outer skin, the method being implemented by means of a collaborative robot (R) controlled by a computer program and carrying a series of sensors (31, 32, 33) and a tool (11) for drilling bores (X) intended for the installation of rivets in order to assemble said beams with said partitions, characterized in that said robot, controlled by the program, positions itself to approach the structure by detecting, by means of the sensors, characteristic and accessible areas of the door,allowing it to know its relative position, it then enters each cell (A) where the sensors take over from the program by measuring the distances separating the robot from the beam and the transverse partitions, so as to move the tool iteratively via a suitable algorithm using the sensors and controlling the robot to position said tool for drilling. Figure for the abbreviation: Fig. 1,

Description

Title of the invention: METHOD FOR AUTOMATED DRILLING OF A HONEYCOMB STRUCTURE OF AN AIRCRAFT DOOR Technical field

[0001] The invention relates to the field of aeronautics and, more particularly, to a drilling method for the assembly of an aircraft door structure.

[0002] Generally speaking, such doors comprise a honeycomb structure whose cells (also called pockets) are delimited, longitudinally, by beams having a central core provided with stiffening elements in the form of ribs and extending at its ends by feet and, transversely, by partitions of right-angled section. This honeycomb structure is closed, on at least one face, by a skin formed of a metal plate (aluminium sheet) fixed to the edges of the beams and partitions.

[0003] The connection between the beams and the partitions is ensured by series of rivets placed in aligned bores which are made beforehand by drilling the ribs of the beams and partitions in the interior angles of the cells.

[0004] To date, the various machining and assembly operations carried out on an industrial scale on aircraft doors are carried out using numerically controlled machines or robots carrying drilling tools such as drills. However, these machines are heavy and bulky.

[0005] Under these conditions and to obtain precise positions of the bores intended for riveting, local recalibration techniques are used to ensure that the tool is referenced in relation to holes previously made on the parts to be drilled. When drilling the skin to assemble it to the honeycomb structure, the holes located on the skin are easily accessible because the work is carried out outside the structure and therefore offers an environment where there is sufficient free space for the use of a numerically controlled machine or a robot.

[0006] However, although the precision obtained with this technique is satisfactory, it turns out that current drilling means do not allow automated tasks to be carried out inside a specific cellular structure having a high rate of stiffeners, in particular, due to the extremely small dimensions of the cells. Thus, traditional operations of resetting or repositioning on pre-drillings prove impossible in this situation. In addition, work in these areas is often accompanied by damaging impacts on the structure of the door because these heavy means used are not capable of managing the interferences.

[0007] Therefore, the use of these means requires, first, a taking of re references outside of confined work areas, for example, on drilling points on the upper face of stiffening elements and, then, the use of these references to operate on a "theoretical" basis. As a result, the accuracy of drilling location will depend mainly on the quality of assembly of the structure as well as the precision of the machine used and the reproducibility of its implementation. Thus, traditional operations of recalibration or repositioning on pre-drillings prove impossible in this situation.

[0008] An alternative solution could consist of carrying out recalibrations of the tool on internal points of the structure by using the six axes of a precise robot, for example of the double encoder type, in order to carry out the bores. However, this solution has proven unsuitable for drilling a honeycomb door structure because it generates significant risks of deterioration of this structure. Indeed, oversized robots (whose payload is much greater than necessary) are then used so as not to lose precision despite the on-board loads and the bulk of the control cables and umbilicals. In addition, the programming times of these robots are significant and slow down the development of new complex structures.

[0009] An assembly method, and more particularly for drilling at least one bore in one or more parts of complex structures, is described in patent FR3124410. According to this method, the parts to be assembled are stacked and then clamped between upstream and downstream branches of a clamp of a drilling tool. The upstream branch accommodates a drill equipped with a drill bit and the downstream branch is hollow and open to the outside.

[0010] However, there is currently no lightweight automation solution that allows drilling tools to be positioned quickly and with great precision in a honeycomb structure of the type used in aircraft doors.

[0011] Indeed, the restricted internal volume of the cells in which the precise drilling operations must be carried out does not allow vision systems to be positioned on pilot holes.

[0012] In this context and in order for the drilling operations to be both automatable and applicable to a large number of configurations, the invention sought a solution using lighter means, such as a collaborative robot called a "cobot". Indeed, the use of a collaborative robot allows greater ease of access to the cells of the door structure, reproducibility of the drilling operations (in quality and position), as well as an absence of risks of damage to the structure both in the development phase and in series production.

[0013] This object is achieved, according to the invention, by means of an automated drilling method for a honeycomb structure of an aircraft door comprising, on the one hand, longitudinal beams provided with stiffening ribs and a central core extended to its ends by feet and, on the other hand, transverse partitions with brackets, said structure being closed on at least one face by an external skin, the method being implemented by means of a collaborative robot controlled by a computer program and carrying a series of sensors and a tool for drilling bores intended for the installation of rivets in order to assemble said beams with said partitions, characterized in that said robot, controlled by the program, puts itself in a position of approach to the structure by detecting, by means of the sensors, characteristic and accessible zones of the door thus allowing it to know its relative position then enters each cell where the sensors take over from the program by measuring the distances separating the robot from the beam and the transverse partitions,in order to move the tool in iterative mode via a suitable algorithm using the sensors and controlling the robot to position said tool for drilling.

[0014] According to an advantageous characteristic of the method of the invention, the characteristic zones of the door comprise points and external surfaces of the beams and partitions.

[0015] According to a specific variant of implementation of the method of the invention, the sensors further measure the distance separating the robot from the skin.

[0016] According to another advantageous characteristic of the method of the invention, the distance measurements between the robot and the beam relate, respectively, to the distance separating the robot from the web of the beam and the distance separating the robot from a foot of the beam.

[0017] According to yet another characteristic of the method of the invention, the approach position of the robot is determined via an external reference system using the measurements from the sensors.

[0018] Preferably, the position of the robot is determined via an iterative mode by laser sensors giving a precise position of the drilling tool relative to the intended position of the bores on the beams and partitions.

[0019] According to another characteristic of the method of the invention, the structure is further tightened before and during drilling.

[0020] According to other characteristics of the method of the invention, the drilling is carried out through the stiffening ribs of the beams and the brackets of the partitions.

[0021] Another object of the invention is a device for implementing the method as defined above, characterized in that the drilling tool is mounted on an angled support arm fixed to a flange of the robot. Preferably, the sensors are laser sensors and the robot is a collaborative robot.

[0022] According to a preferred embodiment of the assembly device of the invention, the drilling tool is coupled to a clamping member mounted so as to move opposite.

[0023] According to an advantageous characteristic of the device of the invention, the series of sensors comprises at least two sensors mounted on the support arm of the tool.

[0024] According to an alternative embodiment of the device of the invention, the series of sensors further comprises a third sensor intended to measure the distance separating the tool from the plane to be drilled and the angular position of the tool.

[0025] Yet another object of the invention is a computer program for implementing the automated assembly method as defined above and intended to control the device of the invention.

[0026] The method of the invention uses a collaborative robot which makes it possible to reduce the manufacturing costs of aircraft doors because the drilling and assembly stations of the structure are simplified.

[0027] Furthermore, the method of the invention makes it possible to avoid the risks of deterioration of the structure thanks to the feedback of forces detected by the collaborative robots.

[0028] The method is, moreover, more flexible than previous methods because the device carrying the drilling tool can move easily and quickly over several areas of the production line and the precision of the geometric measurements carried out by the sensors makes it possible to carry out very high quality drilling operations which are reproducible. PRESENTATION OF FIGURES

[0029] Other characteristics and advantages of the invention will emerge from the non-limiting description which follows, with reference to the appended drawings in which:

[0030] [Fig.l] is a flowchart showing the steps of a preferred embodiment of the assembly method of the invention.

[0031] [Fig.2] is an overall perspective view of an embodiment of the device used by the method of the invention.

[0032] [Fig.3] is a detail view of the clamping / drilling tool integrated into the device of [Fig.2].

[0033] [Fig.4] is a detailed view of the clamping / drilling tool of [Fig.3] during the implementation of the method of the invention in an aircraft door structure cell.

[0034] For greater clarity, identical or similar elements are indicated by identical reference signs in the following description and in the figures. Naturally, the embodiments of the invention illustrated schematically by the figures presented above and described below are given only as non-limiting examples. It is explicitly provided within the scope of the invention that different embodiments can be proposed and combined with each other to propose others. DETAILED DESCRIPTION

[0035] The invention relates to aircraft doors and is more particularly concerned with a method and associated device for the automated assembly of a honeycomb structure of an aircraft door. Traditionally, such a structure made of aluminum (or a metal alloy) comprises, on the one hand, longitudinal beams provided with stiffening ribs and a central core extended at its ends by feet and, on the other hand, transverse partitions C with brackets. This structure is previously provided, on a first face, with an outer skin secured to the longitudinal beams and is, where appropriate, after assembly of the transverse inner partitions, closed on its other face by a plate forming a substantially similar facing skin.

[0036] The invention aims to automate the drilling operations of the internal elements of this structure, namely beams and partitions for their assembly. Generally, the drilling processes of such a structure are carried out by means of a collaborative robot controlled by a computer program. This robot carries a series of sensors and a tool (such as a drill bit), for drilling bores intended for the installation of rivets (not shown) for the purpose of assembling the beams P with the partitions C inside the cells A of the structure ([Fig.4]). More precisely, the drilling is carried out through the stiffening ribs of the beams and the brackets of the partitions which are held in contact by clamping.

[0037] Collaborative robots (called "cobots") are light and of restricted dimensions compatible with the dimensions of the cells of the structure and therefore have significant flexibility. However, these robots operate with less precision under variable load and are subject to variations in forces linked to the umbilicus.

[0038] The invention nevertheless consists of using such a “cobot” while resolving the drawbacks specific to this type of robot. Thus, according to the method of the invention and as illustrated by the flowchart of [Fig.l], the robot controlled by the program places itself, from a waiting position, in a position of approach to the structure by detecting, by means of the sensors, characteristic and accessible zones of the door thus allowing it to know its relative position. The approach position of the robot is thus determined via an external reference using the measurements from the sensors and is located at the entrance to a cell A of the door structure.

[0039] The characteristic areas of the door consist of points and outer surfaces of the beams P and the partitions C. If necessary, the sensors also measure the distance separating the robot R from the skin of the structure. These sensors are preferably laser sensors giving a precise position of the drilling tool relative to the intended position of the bores X on the beams and the partitions.

[0040] Then, in a second step, the robot R, or at least the tool holder, enters each cell A where the sensors take over the program by measuring the distances separating the robot R from the beam P and the partitions C, so as to move the tool in iterative mode in the cell, via an adapted algorithm using the sensors and controlling the robot to position the tool for drilling. The tool positioned by the robot is associated with a member ensuring prior clamping on the structure as well as during drilling of the bores.

[0041] The distance measurements between the robot and the beam relate, respectively, to the distance separating the robot R from the web of the beam P and to the distance separating it from a foot of this beam. In [Fig.l], a number X of holes are provided to be made in each cell Al, ... An of the structure by cyclical reiteration of the process.

[0042] [Fig. 2] represents an embodiment of a device 1 for implementing the drilling and assembly method described above. In this device, the drilling tool 11 (for example a drill bit) is mounted on a support arm 10 fixed on a flange B of the robot R. The drilling tool 11 is coupled with a clamping member 12 which is mounted opposite on the arm 10 in the manner of a C-shaped jaw. The member 12 is movable in translation so as to adjust its position relative to the tool 11 and to grip the rib of the beam P and the bracket of the partition C before and during drilling, as illustrated by the arrow in [Fig. 4].

[0043] Preferably, the sensors here are laser sensors mounted on the arm 10 in the immediate vicinity of the drilling tool 11 and the clamping member 12. The series of sensors here comprises at least two sensors 31, 32 and, where appropriate, a third sensor 33 intended to measure both the distance separating the drilling tool 11 from the plane to be drilled and its angular position, as illustrated by [Fig. 3].

Claims

Claims

1. Method for automated assembly of a honeycomb structure of an aircraft door comprising, on the one hand, longitudinal beams (P) provided with stiffening ribs and a central core extended at its ends by feet and, on the other hand, transverse partitions (C) with brackets, said structure being closed on at least one face by an outer skin, the method being implemented by means of a collaborative robot (R) controlled by a computer program and carrying a series of sensors (31, 32, 33) and a tool (11) for drilling bores (X) intended for the installation of rivets in order to assemble said beams with said partitions, characterized in that said robot, controlled by the program, puts itself in a position of approach to the structure by detecting, by means of the sensors, characteristic and accessible zones of the door,allowing it to know its relative position then enters each cell (A) where the sensors take over from the program by measuring the distances separating the robot from the beam and the transverse partitions, so as to move the tool in iterative mode via an adapted algorithm using the sensors and controlling the robot to position said tool for drilling.,

2. A method according to claim 1, characterized in that the characteristic areas of the door comprise points and exterior surfaces of the beams and partitions.

3. Method according to one of the preceding claims, characterized in that the sensors further measure the distance separating the robot from the skin.

4. Method according to one of the preceding claims, characterized in that the distance measurements between the robot and the beam relate, respectively, to the distance separating the robot from the web of the beam and the distance separating the robot from a foot of the beam.

5. Method according to one of the preceding claims, characterized in that the approach position of the robot is determined via an external reference system using the measurements from the sensors.

6. Method according to one of the preceding claims, characterized in that the position of the robot is determined via an iterative mode by laser sensors giving a precise position of the drilling tool relative to the intended position of the bores on the beams and partitions.

7. Method according to one of the preceding claims, characterized in that that the structure is tightened before and during drilling.

8. Method according to one of the preceding claims, characterized in that the drilling is carried out through the stiffening ribs of the beams and the brackets of the partitions.

9. Device (1) for implementing the method according to one of the preceding claims, characterized in that the drilling tool (11) is mounted on an angled support arm (10) fixed to a flange (B) of the robot (R).

10. Device according to the preceding claim, characterized in that the sensors (31, 32, 33) are laser sensors.

11. Device according to one of claims 9 or 10, characterized in that the robot is a collaborative robot (R).

12. Device according to one of claims 9 to 11, characterized in that the drilling tool (11) is coupled to a clamping member (12) mounted movably opposite.

13. Device according to one of claims 9 to 12, characterized in that the series of sensors comprises at least two sensors (31, 32) mounted on the arm (10) supporting the drilling tool (11).

14. Device according to the preceding claim, characterized in that the series of sensors further comprises a third sensor (33) intended to measure the distance separating the tool (11) from the plane to be drilled and the angular position of said tool.

15. Computer program for implementing the automated assembly method according to one of claims 1 to 8.

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