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: AUTOMATED DRILLING METHOD FOR 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, such doors comprise a honeycomb structure whose cells (also called pockets) are delimited, longitudinally, by beams having a central web provided with stiffening elements in the form of ribs and extending at their ends into feet, and, transversely, by partitions with an L-shaped cross-section. This honeycomb structure is closed, on at least one face, by a skin formed of a metal plate (aluminum 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 the partitions in the internal corners of the cells.

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

[0005] Under these conditions, and to obtain precise positioning of the bores intended for riveting, local alignment techniques are used, ensuring that the tool is referenced to pre-drilled holes in 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, thus providing an environment with sufficient free space for the operation of a CNC machine or a robot.

[0006] However, although the accuracy achieved with this technique is satisfactory, current drilling methods do not allow for automated tasks within a specific honeycomb structure with a high stiffener ratio, particularly due to the extremely small dimensions of the cells. Thus, traditional realignment or repositioning operations on pre-drilled holes prove impossible in this situation. Furthermore, working in these areas often results in damaging impacts on the door structure because the heavy equipment used is unable to manage interference.

[0007] Consequently, the use of these methods requires, first, taking reference points outside the confined work areas, for example, at drilling points on the upper face of the stiffening elements, and then using these reference points to operate on a "theoretical" basis. As a result, the accuracy of the drilling location will depend primarily on the quality of the structure's assembly, as well as the precision of the machine used and the reproducibility of its operation. Thus, traditional realignment or repositioning operations on pre-drilled holes prove impossible in this situation.

[0008] An alternative solution could consist of realigning the tool at internal points of the structure using the six axes of a precision robot, for example, a dual-encoder type, to perform the drilling. However, this solution has proven unsuitable for drilling a honeycomb door structure because it generates significant risks of damage to this structure. Indeed, oversized robots (whose payload is much greater than necessary) are then used to avoid loss of precision despite the onboard loads and the bulk of the control cables and umbilicals. Furthermore, the programming time for these robots is significant and slows down the development of new, complex structures.

[0009] A method for assembling, 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 the upstream and downstream arms of a collet of a drilling tool. The upstream arm accommodates a drill bit, and the downstream arm 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 high precision in a honeycomb structure of the type constituting aircraft doors.

[0011] Indeed, the restricted internal volume of the cavities 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 drilling operations to be both automated 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 for easier access to the recesses of the door structure, reproducibility of drilling operations (in terms of quality and position), and an absence of risk of damage to the structure during both the development and mass production phases.

[0013] This objective 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 web extended at its ends by feet and, on the other hand, transverse partitions 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 controlled by a computer program and carrying a series of sensors and a tool for drilling bores for the insertion 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 allow it to know its relative position, then it enters each cavity where 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 iteratively via a suitable algorithm using the sensors and controlling the robot to position said tool for drilling.

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

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

[0016] According to another advantageous feature 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 feature of the method of the invention, the approach position of the robot is determined via an external reference frame using 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 feature of the method of the invention, the structure is further tightened prior to and during drilling.

[0020] According to other features 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 movably opposite it.

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

[0024] According to one 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 the implementation of the automated assembly process 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] In addition, 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 process is also more flexible than previous processes because the device carrying the drilling tool can move easily and quickly over several areas of the manufacturing line and the precision of the geometric measurements made by the sensors makes it possible to carry out very high quality drilling operations which are reproducible. PRESENTATION OF THE FIGURES

[0029] Other features and advantages of the invention will become apparent from the following non-limiting description, with reference to the accompanying drawings in which:

[0030] [Fig. 1] is a flowchart showing the steps of a preferred implementation method of the assembly process of the invention.

[0031] [Fig.2] is an overview in perspective of one embodiment of the device used by the process of the invention.

[0032] [Fig.3] is a detailed view of the clamping / drilling tool integrated into the device of the [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 a cell of an aircraft door structure.

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

[0035] The invention relates to aircraft doors and, more particularly, to a method and associated device for the automated assembly of a honeycomb structure for an aircraft door. Traditionally, such a structure made of aluminum (or a metal alloy) comprises, on the one hand, longitudinal beams with stiffening ribs and a central web extended at its ends by feet, and, on the other hand, transverse C-shaped partitions. This structure is first provided, on one face, with an outer skin attached to the longitudinal beams and is, where applicable, after assembly of the internal transverse 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 the purpose of their assembly. Generally, the drilling processes for such a structure are carried out using 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 insertion of rivets (not shown) in order to assemble the beams P with the partitions C inside the cells A of the structure ([Fig. 4]). More specifically, 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 lightweight and compact, compatible with the dimensions of the structure's cells, and therefore offer significant flexibility. However, these robots operate with less precision under varying loads and are subject to stress variations related to the umbilicus.

[0038] The invention nevertheless consists of using such a "cobot" while resolving the drawbacks inherent in this type of robot. Thus, according to the method of the invention and as illustrated by the flowchart in [Fig. 1], the robot, controlled by the program, moves from a waiting position to an approach position to the structure by detecting, by means of sensors, characteristic and accessible areas of the door, thereby allowing it to determine its relative position. The robot's approach position is thus determined via an external reference frame using the measurements from the sensors and is located at the entrance of a recess A in the door structure.

[0039] The characteristic zones of the door consist of points and external surfaces of the beams P and the partitions C. Where applicable, the sensors measure, in In addition, the distance separating the robot R from the structure's surface. These sensors are preferably laser sensors providing a precise position of the drilling tool relative to the intended position of the bores X on the beams and partitions.

[0040] Then, in a second step, the robot R, or at least the tool holder, enters each cavity A where the sensors take over from the program by measuring the distances separating the robot R from the beam P and the partitions C, so as to move the tool iteratively within the cavity, via a suitable algorithm using the sensors and controlling the robot to position the tool for drilling. The tool positioned by the robot is associated with a device ensuring prior clamping to the structure as well as during the 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. 1], a number X of holes are planned to be drilled in each cell Al, ... An of the structure by cyclical iteration of the process.

[0042] Figure 2 shows an embodiment of a device 1 for implementing the drilling and assembly process described above. In this device, the drilling tool 11 (for example, a drill bit) is mounted on a support arm 10 fixed to a flange B of the robot R. The drilling tool 11 is coupled with a clamping member 12 which is mounted opposite it on the arm 10 in the manner of a jaw C. The member 12 is movable in translation so as to adjust its position relative to the tool 11 and to clamp the rib of the beam P and the angle bracket of the partition C before and during drilling, as illustrated by the arrow in Figure 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 includes at least two sensors 31, 32 and, where applicable, 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

Demands

1. An automated assembly method for a honeycomb structure of 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, then it 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 a suitable algorithm using the sensors and controlling the robot to position said tool for drilling.

2. Method according to claim 1, characterized in that the characteristic areas of the door include points and external surfaces of the beams and partitions.

3. A method according to any one of the preceding claims, characterized in that the sensors also measure the distance separating the robot from the skin.

4. A method according to any 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. A method according to any one of the preceding claims, characterized in that the approach position of the robot is determined via an external reference frame using measurements from the sensors.

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

7. A method according to any one of the preceding claims, characterized in that the structure is clamped prior to and during drilling.

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

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