AUTOMATED WEAVING METHOD WITH OPTIMIZED SHED OPENING

Abstract

Method for the automated weaving of a woven structure (30) by means of a weaving machine (1), comprising the insertion of a weft thread during the opening of a shed of warp threads, and prior steps of optimization, by an optimization tool (20), of an objective function having a first member evaluating the balance of said warp threads during the shed opening, said balance of the warp threads being evaluated by differences in elongation between the warp threads of an upper opening (10a) of said shed, and of a lower opening (10b) of said shed, and a second member evaluating constraints specific to the weaving machine (1). This optimization comprises the determination of a set of opening parameters that, at least locally, minimize said objective function, and this set of opening parameters is used to set the parameters of the weaving machine (1).

Description

FIELD OF THE INVENTION

The present invention relates to an optimization method for the automated weaving of woven structures, particularly three-dimensional woven structures.

One possible scope of application for such woven structures is the field of the aeronautical industry.

The latter is indeed seeking solutions to address the growing environmental requirements, particularly with regard to reducing fossil fuel consumption. The use of lighter composite materials in aircraft design allows in particular reducing their consumption and thus contributing to reducing the ecological impact.

Composite materials are used in various portions of airplanes, for example, the fan blades in the turbomachines.

Indeed, the turbomachine blades must withstand significant mechanical and thermal constraints, in addition to meeting the weight and space requirement constraints. It has therefore been proposed to replace the metal fan blades (typically titanium) on some airplane models with blades made of a composite material based on woven 3D reinforcements. Such three-dimensional woven structures for fan blades have been proposed in several documents, such as French patent FR3085417.

However, the three-dimensional woven structures can find other applications in the aeronautical field (brake bars for landing gears, etc.) or in many other fields.

Making three-dimensional woven structures requires the use of weaving machines, or looms. These allow for the automation of the weaving per se, but however require an upstream parameterization phase that is generally manual and tedious. This parameterization involves in particular defining the positioning of each of the heddles in the high position (upper shed) and in the low position (lower shed).

Generally, the design of a woven-reinforced composite material is a complex task that requires, in particular, pooling the diverse skills. Particularly, it may require several iterations of exchanges between a design office that provides mechanical specifications of the woven structure and the textile production department that must make the specified structure with the available technical means, in particular based on the specifications of the weaving machine.

A good-quality woven structure is thus the result of an optimized compromise between the characteristics of the required material (warp/weft ratio, fiber volume fraction, etc.) and the constraints required by the weaving (weaves, available yarn count, position in the harness, etc.).

Once the geometry of the desired woven structure has been defined, the weaving machine must be properly parameterized in order to ensure that the weaving provides a high-quality result. This particularly involves defining the weaving speed, the progress of the preform and the positioning of the heddles in the high and low positions (high and low sheds, respectively).

Among all the parameters to be adjusted on a weaving machine, the shed opening is critically important.

Indeed, a correct shed opening is necessary for the rapier to be inserted into the correct location in the shed without impacting the warp yarns. If this were not the case, the textile preform produced would not comply with the specifications. Therefore, the shed must be opened sufficiently so that the weft yarns are inserted into the correct locations between the warp yarns.

Moreover, a good balance between the upper shed and the lower shed must be ensured for the warp tension to remain correct and also in order to avoid weaving errors. In other words, the shed opening must be determined, that is to say the high and low positions of each of the eyelets of the machine.

It is therefore understood that this phase of manually determining the shed opening parameters is long. It therefore involves a substantial extension of the production duration. The time required to correctly define the shed opening can be estimated at around 1 week for a complex woven structure.

It can also involve human errors, which can penalize the quality of the produced structure or require a return to the parameterization phase, thus further extending the production duration.

There is therefore a need to improve current proposals of the state of the art.

SUMMARY OF THE INVENTION

The invention aims to automate at least part of the parameterization of the weaving machine in order to minimize the risk of errors and to accelerate the production of the textile structure, once it has been specified by a design office.

This parameterization aims in particular to determine shed opening parameters (positions of the eyelets in the high and low positions).

For these purposes, according to a first aspect, the present invention can be implemented by a method for automated weaving of a woven structure using a weaving machine, this method comprising the insertion of a weft yarn during the opening of the shed of warp yarns, and prior steps of optimizing an objective function having a first member evaluating a balance of said warp yarns during said shed opening, said balance of the warp yarns being evaluated by differences in elongation between the warp yarns of an upper opening of said shed, and of a lower opening of said shed, and a second member evaluating constraints specific to said weaving machine, said optimization comprising the determination of a set of opening parameters minimizing, at least locally, said objective function, and said set of opening parameters being used to parameterize said weaving machine.

According to preferred embodiments, the invention comprises one or more of the following characteristics which can be used separately or in partial combination with each other or in total combination with each other:

• • said woven structure is a reinforcement for composite materials;
  • said optimization comprises the determination of a global optimum of said objective function by introducing a random perturbation;
  • said optimization uses a Basin-hopping algorithm;
  • said opening parameters define a first straight line determining an upper opening of said shed, and a second straight line determining a lower opening of said shed. In very general terms, the shed opening parameters can specify the positioning of the heddles (and therefore of the eyelets) in the upper position and lower position.
  • said second member evaluates a height between an upper opening and a lower height of said shed;
  • said second member evaluates distances between said warp yarns and a rapier of said weaving machine and/or a beater of said weaving machine.

According to another aspect, a computer program is proposed including instructions for implementing a method as previously described.

According to yet another aspect, a weaving tool is proposed including a weaving machine with a woven structure adapted for inserting a weft yarn during the opening of a shed of warp yarns, and a tool for optimizing an objective function having a first member evaluating a balance of said warp yarns during said shed opening, said balance of the warp yarns being evaluated by differences in elongation between the warp yarns of an upper opening of said shed, and of a lower opening of said shed, and a second member evaluating constraints specific to said weaving machine, said optimization comprising the determination of a set of opening parameters minimizing, at least locally, said objective function, and said set of opening parameters being used to parameterize said weaving machine.

Other characteristics and advantages of the invention will appear upon reading the following description of one preferred embodiment of the invention, given by way of example and with reference to the appended drawings.

BRIEF DESCRIPTION OF THE FIGURES

The appended drawings illustrate the invention:

FIG. 1 schematically represents a context of use of the method according to the embodiments.

FIG. 2 schematically represents one example of a weaving machine.

FIG. 3 represents a flowchart of one example of implementation of an automated weaving method for a three-dimensional woven structure according to the invention.

FIG. 4 schematically illustrates a linear modeling of the upper and lower openings of the shed.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

FIG. 1 schematically illustrates a context of use of an automated weaving method.

In the example of this figure, a weaving machine (or loom) 1 produces a woven structure 30 that is typically a three-dimensional woven structure. This three-dimensional woven structure can be used as reinforcement for composite materials.

These composite materials can be used in particular in the field of aeronautics for fan blades in turbomachines, brake bars for landing gears and, more generally, any type of thick three-dimensional textile preforms.

This woven structure can be a thick three-dimensional part, particularly with a thickness greater than 10 or 20 mm. The automatic shed opening optimization method is particularly advantageous for complex woven structures and in particular for thick three-dimensional parts.

The weaving machine 1 may use a set of parameters 43 provided by an optimization tool 20.

This optimization tool may be a computer or any information processing device, including virtualized on a platform (for example of the “cloud computing” type), adapted to this specific optimization task. This adaptation may consist of the deployment of a specific software application.

The optimization tool 20 and the weaving machine 1 may communicate by means of telecommunications networks (not represented in the figure). This may be a local area network, of the Ethernet, Wi-Fi, Bluetooth type, etc., but these telecommunications networks may also comprise longer-distance networks, in particular in the case where the optimization tool is delocalized and, for example, transferred to a remote platform. These telecommunications networks may comprise a network called “Internet” network.

The optimization tool may be based on data 41 provided by a design office and specifying the woven structure 30 to be produced, and on provided data 42 relating to the weaving machine 1.

Based on these data 41, 42, the optimization tool 20 may provide a set of parameters 43 to the weaving machine 1 which allows it to make the woven structure 30 while minimizing the weaving errors. These parameters 43 comprise the parameters set the opening of the shed in the weaving machine 1.

Furthermore, the optimization tool 20 eliminates the need for the manual parameterization of the shed opening, by automatically determining them. Once the specifications of the woven structure 30 to be produced are known, it is thus possible to trigger the production of the woven structure 30 by the loom 1 more quickly and with less risk of errors.

FIG. 2 schematically represents such a weaving machine 1. This diagram is extremely simplified and aims to explain the elements useful for understanding the automated weaving method presented.

Typically, a set of warp yarns, 7a, 7b, 7c, 7d, are stretched between beams (not represented). In the example of the figure, the warp yarns are stretched horizontally (low-warp loom), but they can also be stretched vertically (high-warp loom). In the example, the warp yarns are unwound from a beam located on the right of the figure, and form a preform 2, on the left of the figure.

Each warp yarn (or pick), 7a, 7b, 7c, 7d, passes through an eyelet, respectively 5a, 5b, 5c, 5d, of a respective heddle 6a, 6b, 6c, 6d.

The heddles are typically made of metal wires or string. They are mounted in frames, or blades, suspended from the harness 8 of the loom 1. Each frame, or blade, can be individually actuated in translation perpendicular to the plane of the warp yarns.

In the example of the figure, only 4 warp yarns and 4 heddles are represented for the sake of clarity of the disclosure and of the figure, but it is obvious that a much larger number of yarns and heddles are present for the production of a woven textile.

By raising or lowering the heddles, the corresponding warp yarns are moved away upwards or downwards from their nominal horizontal positions.

Thus, in FIG. 2, the heddles 6a and 6b are translated upwards, which moves away the warp yarns 7a and 7b upwards. The heddles 6c, 6d are translated downwards and move away the corresponding warp yarns 7c, 7d downwards.

Thus, the set of the warp yarns, or shed, is divided into two portions: a high portion or shed 10a, and a low portion or shed 10b.

This opening of the shed allows inserting a weft yarn by means of an insertion device such as a rapier 9. This weft yarn is inserted perpendicular to the warp yarns.

A beater formed of upper (or upper beater) 12a and lower (or lower beater) 12b elements and of a reed (not represented) can then pack the weft yarn against the preceding weft yarns in order to form the fell line 3 of the preform 2. The fell refers to the area between this last inserted weft yarn and the start of the beam around which the preform 2 can be wound.

This process is iterated over time: each time, a different set of heddles can be raised and lowered, according to an ordering dependent on the type of woven structure during production: plain, twill, satin, etc. At each opening, a weft yarn is inserted. The preform 2 is thus formed by interlacing a succession of weft yarns with the web of warp yarns.

Furthermore, in the case of a three-dimensional woven structure, interlinking yarns are inserted in order to secure the different woven layers.

This preform 2 forms a woven textile 30.

This woven structure can then be used to form a composite material, for example by embedding it in a matrix material.

It is proposed to automatically determine the opening of the shed, that is to say the angles formed by the warp yarns 7a, 7b, 7c, 7d with the horizontal plane, when the heddles are translated upwards and downwards. In other words, determining the opening of the shed amounts to determining the upward and downward excursion of the heddles.

As stated previously, these angles should be large enough so that the rapier 9 does not risk hitting the warp yarns 7a, 7b, 7c, 7d. But they must not be too large, on the one hand so that these warp yarns do not risk hitting the beaters 12a, 12b and, on the other hand to avoid imbalances in the tension of the warp yarns between the high and low sheds.

FIG. 3 illustrates a flowchart of one exemplary implementation of the automated weaving method 100.

In a step 110, the optimization tool 20 is provided with the data 41 specifying the woven structure 30 to be produced, and data 42 provided relating to the weaving machine 1.

In a step 120, the optimization tool 20 can determine an objective function.

An objective function refers to a function that serves as a criterion for determining a solution to an optimization problem. It associates a value with an instance of an optimization problem. The aim of the optimization problem is then to minimize or maximize this function, ideally to find a global optimum.

This objective function includes a first member evaluating a balance of the warp yarns during the warp opening. This balance corresponds to the one between the upper and lower sheds.

It also comprises a second member evaluating constraints specific to the weaving machine.

The problem is thus formulated as an optimization (of the first member) under constraint (second member) in which it is sought to determine a set of opening parameters minimizing, at least locally, this objective function.

The opening parameters are chosen to allow the one-to-one parameterization of the loom.

Also, the parameters are chosen to form a relatively restricted optimization space in order to seek a compromise on the combinatorics of the problem and the accuracy of adjustment of a loom.

Given these elements, it was chosen to assume that the opening of the upper 10a and lower 10b sheds form a linear configuration in the depth of the harness 8. This allows modeling the shed opening by two independent straight lines (one for the upper shed and one for the lower shed) and by the positioning of the preform in the height.

The upper shed refers to the set of warp yarns that are “open upwards” that is to say passing through raised heddle eyelets in the upper half of the harness, and the lower shed refers to the set of warp yarns that are “open downwards” that is to say passing through lowered eyelets in the lower half of the harness.

In other words, the upper shed corresponds to the upper opening of the shed, and the lower shed corresponds to the lower opening of the same shed.

Each straight line can be modeled by two parameters, for example a vertical position of the corresponding eyelet on a given heddle (for example, the heddle closest to the fell), and a slope coefficient.

FIG. 4 illustrates this modeling.

In this figure, the preform 2 includes three planes, or layers, of preform P₀, P₁, P₂.

Each plane corresponds to a warp yarn belonging to the upper shed and a warp yarn belonging to the lower shed. Each plane therefore corresponds to a row of heddles in the depth of the harness.

A yarn can be modeled in the high position and low position, and the optimization then aims to minimize the maximum deviation between the high and low positions of this yarn.

According to one embodiment, a set of insertions can be considered. In this set, some yarns will always remain in the high shed, others in the low shed, and others will occupy the high shed and the low shed. The optimization can be implemented only for these last yarns: it can then be sought to minimize the maximum deviation between the high and low positions of these yarns alone.

The draw-in is defined by the user: the latter can specify the positioning of the preform warp yarns relative to the available positions on the upper and lower straight lines.

Thus, the point A in the fell is the endpoint of two warp yarns, one coming from the upper shed and passing through the eyelet B, and the other coming from the lower shed and passing through the eyelet C.

The straight line defining the upper shed can be written: y_S+a_S(x_i−x₀), with:

• • y_S: ordinate of the highest eyelet, corresponding to the heddle H₀ closest to the fell;
  • a_S: slope coefficient;
  • x_i and x₀: abscissa, respectively, of an eyelet in i of the upper shed and of the eyelet of ordinate y_S.

The straight line defining the lower shed can be written: y_I+a_I(x_i−x₀), with:

• • y_I: ordinate of the lowest eyelet, corresponding to the heddle H₀ closest to the fell;
  • a_I: slope coefficient

y₀ can be the ordinate, or height, of the preform. For example, it could be the vertical position of the midplane of the preform 2.

Optimizing the shed opening therefore amounts to finding the optimized values for this 5-tuple vector [y₀, y_S, a_S, y_I, a_I].

Thus, thanks to the proposed modeling, the number of shed opening parameters (initially 2 parameters per eyelet) is reduced to 5 parameters.

Knowing these opening parameters defining two straight lines, it is possible to directly determine the translations to be performed for each heddle in order to obtain this opening.

As seen previously, the objective function can be formulated as the balance between the upper shed and the lower shed of the warp yarns during the insertion of a weft yarn (that is to say during the shed opening).

This balance can be estimated by the differences in elongation between the warp yarns of the upper shed and of the lower shed.

More specifically, this balance can be modeled by considering each pair of yarns starting from the same level of the fell line 3.

For example, the lengths AB and AC can be considered.

It is possible to write that these lengths LAB, LAC are:

$\begin{array}{cc}{L}_{AB}=\sqrt{{\left(x_A-x_B\right)}^2+{\left(y_A-y_B\right)}^2}& \left[\mathrm{Math}.1\right]\end{array}$

$\begin{array}{cc}\mathrm{And}{L}_{AC}=\sqrt{{\left(x_A-x_C\right)}^2+{\left(y_A-y_C\right)}^2}& \left[\mathrm{Math}.2\right]\end{array}$

More generally, for each pair i of warp yarns arriving at the fell line, the lengths of the segments L_Si, L_Ii can be considered:

$\begin{array}{cc}\{\begin{array}{c}{L}_{Si}=\sqrt{{\left(x_i-x_{Hi}\right)}^2+{\left(y_i-y_{Si}\right)}^2}\\ L_{\mathrm{Ii}}=\sqrt{{\left(x_i-x_{Hi}\right)}^2+{\left(y_i-y_{\mathrm{Ii}}\right)}^2}\end{array}& \left[\mathrm{Math}.3\right]\end{array}$

with:

• • x_i, y_i the coordinates of the point in the fell line where the pair of warp yarns arrives,
  • x_Hi, y_Si the coordinates of the eyelet where the warp yarn of the upper shed passes, and
  • x_Hi, y_Ii the coordinates of the eyelet where the warp yarn of the lower shed passes, and

Since the eyelets move vertically, they have the same abscissa x_Hi in the upper shed and in the lower shed.

According to one embodiment, the balance of the warp yarns during the shed opening can be estimated through these yarn elongations, for example by considering the maximum of the differences between two yarns of a pair of warp yarns:

$\begin{array}{cc}\{\begin{array}{c}{\mathrm{diff}}_i=❘L_{\mathrm{Si}}-L_{\mathrm{Ii}}❘\\ {\mathrm{obj}}_E={\max }_i\left({\mathrm{diff}}_i\right)\end{array}& \left[\mathrm{Math}.4\right]\end{array}$

The balance objective, obj_E, is therefore evaluated by the maximum, for any warp i, of the difference between the two warp yarns of the pair.

These warps can be those modeled, that is to say those taken into account in the modeling, because it is possible, according to one embodiment, to exclude from the modeling warps that remain in the upper or lower shed during a set of insertions.

The objective function also comprises constraints and in particular constraints specific to the weaving machine. These constraints are applied on all the yarns.

Generally, these constraints aim to avoid the collisions between the warp yarns and the obstacles (rapier 9, high 12a and low 12b beaters), as well as to meet a maximum height between the upper shed and the lower shed.

The first constraint, c₀, corresponds to the shed height that is to say the maximum vertical deviation between the eyelets of the upper shed 10a and the eyelets of the lower shed 10b.

This constraint can be expressed:

$\begin{array}{cc}{c}_{0,i}=\max \left(y_{Si}-y_{\mathrm{Ii}}-F_{\max };0\right)& \left[\mathrm{Math}.5\right]\end{array}$

For a warp i, if the deviation between the eyelets (y_Si−y_Ii) is below a threshold Fmax, then the constraint c_0,i is zero. This threshold depends on the type and geometry of the harness. It is physically the maximum displacement admissible by the heddles.

Other constraints aim to avoid the collision between the warp yarns and the obstacles in the loom elements, particularly the rapier and the beater.

According to one embodiment, these obstacles are modeled by circles that is to say a point and a radius. It is then sufficient, for each obstacle, to compare a distance between the warp yarns and the centers relative to the radius, through a safety margin. For the beater, its upper portion 12a (modeled by a first circle), and its lower portion 12b (modeled by a second circle) are distinguished.

It can be provided that each constraint is zero if the warp yarn passes on the right side of the obstacle and at a sufficient distance, and equal to the distance between this warp yarn and the obstacle.

For example, for the upper beater 12a, it is possible to write:

$\begin{array}{cc}{c}_{1,i}=\max \left(d_{i,1}+\alpha \times R_1;0\right)& \left[\mathrm{Math}.6\right]\end{array}$

with:

• • d_i,1: distance between the warp yarn i and the upper beater 12a. It can be assumed that this distance d_i,1 is signed by the differences in abscissa.
  • α represents a safety margin. α=1.1 can be proposed
  • R₁ is the radius of the upper beater.

For the rapier 9, a criterion c₂ concerning the upper shed and another criterion c₃ concerning the lower shed can be defined.

For example, it is possible to write:

$\begin{array}{cc}{c}_{2,i}=\max \left(\alpha \times R_2-d_{i,2};0\right)& \left[\mathrm{Math}.7\right]\end{array}$

with:

• • d_i,2: distance between the warp yarn i of the upper shed and the rapier 9. It can be assumed that this distance d_i,2 is signed by the differences in abscissa.
  • α represents a safety margin. α=1.1 can be proposed
  • R₂ is the radius of the rapier 9.

For the lower shed, it is for example possible to write:

$\begin{array}{cc}{c}_{3,i}=\max \left(d_{i,3}-\alpha \times R_2;0\right)& \left[\mathrm{Math}.8\right]\end{array}$

with:

• • d_i,3: distance between the warp yarn i of the lower shed and the rapier 9. It can be assumed that this distance d_i,3 is signed by the differences in abscissa.
  • α: a safety margin. α=1.1 can be proposed
  • R₂: the radius of the rapier 9.

A fifth constraint may concern the low beater 12b and its relative position relative to the warp yarns of the lower shed 10b. This is in some ways the symmetrical criterion of the criterion c_1,i.

For example, it is possible to write:

$\begin{array}{cc}{c}_{4,i}=\max \left(\alpha \times R_4-d_{i,4};0\right)& \left[\mathrm{Math}.9\right]\end{array}$

with:

• • d_i,4: distance between the warp yarn i and the lower beater 12b. It can be assumed that this distance d_i,4 is signed by the differences in abscissa.
  • α represents a safety margin. α=1.1 can be proposed
  • R₄ is the radius of the lower beater 12b.

It can be noted that the constraints c_1,i and c_3,i on the one hand and c_2,i and c_4,i on the other hand follow different directions because the distances are signed by the difference in abscissa.

The constraints c_1,i, c_2,i, c_3,i and c_4,i are zero if the unsigned distance is greater than the radius of the corresponding obstacle plus a margin (of 10% in the examples above with α=1.1).

During an insertion of a weft yarn (which therefore implies the opening of the shed), the global constraint can be expressed as the sum of the constraints previously described for the set of the warp yarns.

Thus, this global constraint c can be written:

$\begin{array}{cc}c={\max }_i\left(c_{0,i}\right)+{\max }_i\left(c_{1,i}\right)+{\max }_i\left(c_{2,i}\right)+{\max }_i\left(c_{3,i}\right)+{\max }_i\left(c_{4,i}\right)& \left[\mathrm{Math}.10\right]\end{array}$

The optimization phase can consider an objective function including a first member obj_E evaluating a balance of the warp yarns during the shed opening, and a second member c evaluating the constraints.

This objective function f(v) can then for example be written:

$\begin{array}{cc}f\left(v\right)={\mathrm{obj}}_E\left(v\right)+k·c\left(v\right)& \left[\mathrm{Math}.11\right]\end{array}$

k is a hyperparameter of the optimization method and can be set by the user. It influences the relative importance of the constraints relative to the optimization of the balance of the sheds. It is a penalty factor normally linked to the geometry of the problem. It can be comprised between 10 and 200.

v represents the desired 5-tuple vector. In other words, an optimization of the objective function f(v) in the space of the possible v is sought.

As seen previously, this 5-tuple is defined by v=[y₀, y_S, a_S, y_I, a_I]. The 5-tuple of opening parameters providing this optimum can then be used to parameterize the weaving machine 1.

Step 130, in FIG. 3, consists in searching for a pair v, f(v) that minimizes the objective function f(v).

A step 140 of producing the woven structure can then be implemented using the weaving machine 1. To do so, the parameters determined by the optimization tool 20 can be used.

More specifically, in this step 140, the 5-tuple value of the opening parameters v that corresponds to this minimized objective function f(v) can be used to parameterize the shed opening of the weaving machine 1. The weaving machine 1 can produce the woven structure by inserting a weft yarn during the opening of the shed of the warp yarns according to these opening parameters v.

Different algorithms can be used to determine an optimum (v, f(v)). It should be noted that a global optimum is not necessarily required: indeed, it is important to obtain a good shed opening, which meets the constraints c and achieves a good balance obj_E of the upper and lower sheds, but it may be unimportant whether or not there are better solutions in the space of the v.

An algorithm that yields a local minimum can be envisaged.

Preferably, it may be sought to avoid the blockages in the local minima of the objective function and use for example a random perturbation algorithm to avoid such blockages.

One possible algorithm is that of “Basin-hopping”.

This algorithm is based on a global optimization technique that iterates by performing random perturbation of the coordinates, by performing a local optimization and accepting or rejecting new coordinates based on a minimized function value. It is particularly well suited for obtaining global optimizations in a large-dimensional space.

This algorithm was introduced in Wales, David J.; Doye, Jonathan P. K. (1997 Jul. 10). “Global Optimization by Basin-Hopping and the Lowest Energy Structures of Lennard-Jones Clusters Containing up to 110 Atoms”. The Journal of Physical Chemistry A. 101 (28): 5111-5116. arXiv:cond-mat/9803344.

The Basin-hopping algorithm is available in libraries and can therefore be easily used. For example, for use in Python language, an available implementation can be accessed: https://docs.scipy.org/doc/scipy/reference/generated/scipy.optimize.basinhoppin g.html#scipy.optimize.basinhopping

Obviously, once again, other existing or future algorithms can be envisaged for implementing this optimization phase.

Of course, the present invention is not limited to the examples and the embodiment described and represented, but is defined by the claims. It is in particular susceptible of numerous variants accessible to those skilled in the art.

Claims

1. A method for automated weaving (100) of a woven structure (30) using a weaving machine (1), comprising the insertion of a weft yarn during the opening of a shed of warp yarns, and prior steps (110, 120, 130) of optimizing an objective function having a first member evaluating a balance of said warp yarns during said shed opening, said balance of the warp yarns being evaluated by differences in elongation between the warp yarns of an upper opening (10a) of said shed, and of a lower opening (10b) of said shed, and a second member evaluating constraints specific to said weaving machine, said optimization comprising the determination of a set of opening parameters (43) minimizing, at least locally, said objective function, and said set of opening parameters being used to parameterize said weaving machine.

2. The method according to claim 1, wherein said woven structure (30) is a reinforcement for composite materials.

3. The method according to claim 1, wherein said optimization comprises the determination of a global optimum of said objective function by introducing a random perturbation.

4. The method according to claim 1, wherein said optimization uses a basin-hopping algorithm.

5. The method according to claim 1, wherein said opening parameters define a first straight line determining an upper opening of said shed, and a second straight line determining a lower opening of said shed.

6. The method according to claim 1, wherein said second member evaluates a height between an upper opening and a lower height of said shed.

7. The method according to claim 1, wherein said second member evaluates distances between said warp yarns and a rapier (9) of said weaving machine (1) and/or a beater (12a, 12b) of said weaving machine (1).

8. A computer-readable recording medium including instructions for, when executed by a processor, implementing a method according to claim 1.

9. A weaving tool including a weaving machine (1) with a woven structure (30) adapted for inserting a weft yarn during the opening of a shed of warp yarns, and an tool (20) of optimizing an objective function having a first member evaluating a balance of said warp yarns during said shed opening, said balance of the warp yarns being evaluated by differences in elongation between the warp yarns of an upper opening (10a) of said shed, and of a lower opening (10b) of said shed, and a second member evaluating constraints specific to said weaving machine, said optimization comprising the determination of a set of opening parameters (43) minimizing, at least locally, said objective function, and said set of opening parameters being used to parameterize said weaving machine (1).