A method for optimizing the control of the traction trajectory of large curvature core mold weaving

Abstract

The present invention relates to the field of composite material weaving, and in particular to a method for optimizing the traction trajectory of large curvature core mold weaving, comprising the following steps: establishing a coordinate system according to the relative positions of a traction robot and a braiding machine; in the coordinate system, the large curvature core mold is equivalent to multiple sections of equivalent core molds; adjusting the posture of the equivalent core mold by controlling the traction trajectory and traction speed of the traction robot, so that the feeding direction of the equivalent core mold is perpendicular to the cross section of the braiding point; advancing the equivalent core mold after the posture adjustment by controlling the traction trajectory and traction speed of the traction robot until the braiding operation on the equivalent core mold is completed. The optimization control method of the present invention can effectively reduce the error in the braiding process of large curvature complex structure core molds; at the same time, it solves the process defects such as local yarn accumulation and unsmooth traction trajectory when using an industrial robot to pull a core mold with a variable cross-section, large curvature bending and other characteristics for braiding, and ensures a stable braiding angle and coverage.

Description

Technical Field

[0001] The invention relates to the field of composite material weaving, in particular to a method for optimizing and controlling a traction trajectory of a large-curvature core mold weaving. Background Art

[0002] In recent years, carbon fiber composite materials (hereinafter referred to as composite materials) have become one of the most important structural materials widely used in aerospace and other fields due to their advantages such as high specific strength, high specific stiffness and good designability. Composite materials are made of preforms woven with reinforcing fibers and various matrix materials. The weaving errors such as the weaving angle and coverage of the woven preform directly affect the mechanical properties of the composite materials. In the weaving technology for special-shaped core molds, the traction process of the core mold requires not only continuous adjustment of the posture to meet the constraints, but also precise control of the core mold feed speed. Industrial robots are widely used in the field of composite material weaving because of their flexibility, precision and efficiency; however, in the actual weaving process of preforms, the running trajectory of the robot end is mostly obtained by manual teaching, which is difficult to accurately meet the posture transformation constraint requirements of complex core molds. At present, in the process of using industrial robots to pull core molds with variable cross-sections, large curvature bends and other characteristics for weaving, solving process defects such as local yarn accumulation and unsmooth traction trajectory, and ensuring the stability of the weaving angle and coverage are one of the problems that need to be solved urgently. Summary of the invention

[0003] In view of the deficiencies in the prior art and the needs of actual engineering, in a first aspect, the present invention provides a method for optimizing the control of the traction trajectory of large-curvature core mold weaving, comprising the following steps: establishing a coordinate system according to the relative positions of a traction robot and a weaving machine, the coordinate system comprising a basic coordinate system and a tool coordinate system; in the coordinate system, the large-curvature core mold is equivalent to multiple sections of equivalent core molds; adjusting the posture of the equivalent core mold by controlling the traction trajectory and traction speed of the traction robot so that the feeding direction of the equivalent core mold is perpendicular to the cross-section of the weaving point; advancing the equivalent core mold with adjusted posture by controlling the traction trajectory and traction speed of the traction robot until the weaving operation on the equivalent core mold is completed. The optimization control method of the present invention takes into account the change of convergence length when the traction robot adjusts the traction trajectory, adopts a dynamic weaving point plane, takes the axis of each discrete core mold perpendicular to the weaving point plane during steady-state weaving as a spatial constraint, and uses the transition weaving length from the initial weaving point to the stable weaving point during the weaving process to adjust the posture of the core mold, so that the core mold can perform weaving feed movement under the premise of achieving the spatial constraint, thereby avoiding large coverage fluctuations in the bending section of the preform, and controlling the traction speed to make the weaving enter the stable stage as soon as possible. The optimization control method of the present invention can effectively reduce the error in the weaving process of the core mold with large curvature and complex structure, and improve the mechanical properties of the preform; at the same time, it solves the process defects such as local yarn accumulation and unsmooth traction trajectory in the process of using industrial robots to pull the core mold with variable cross-section, large curvature and other characteristics for weaving, and ensures stable weaving angle and coverage.

[0004] Optionally, the coordinate system is established according to the relative positions of the traction robot and the braiding machine, comprising the following steps: taking the traction robot's fulcrum on the ground as the origin o, the ground as the xoy plane, and the z axis perpendicular to the xoy plane to construct a basic coordinate system o-xyz; taking the traction robot's traction core mold contact point as the origin o T , the flange surface of the traction robot is x T o T y T plane, perpendicular to x T o T y T The plane is z T Axis, build tool coordinate system o T -x T y T z T .

[0005] Optionally, the large curvature mandrel is equivalent to a multi-segment equivalent mandrel in the coordinate system, comprising the following steps: in the tool coordinate system, O(i) is used to represent the coordinates of discrete points on the central axis of the large curvature mandrel, where i=0, 1, 2…, n-1, |O(i)-O(i-1)|=d; the large curvature mandrel is divided into a multi-segment cylinder using the discrete points; the cylinder is equivalent to a cylinder, and the cylinder is defined as an equivalent mandrel, and the approximate radius of the equivalent mandrel satisfies the following formula:

[0006]

[0007] Among them, r i represents the approximate radius of the equivalent core mode of the i-th segment, r O(i-1) represents the radius of the large curvature core mold section corresponding to the i-1th discrete point, r O(i) Represents the large curvature core mold cross-section radius corresponding to the i-th discrete point.

[0008] Optionally, the posture of the equivalent core mold is adjusted by controlling the traction trajectory and traction speed of the traction robot so that the feeding direction of the equivalent core mold is perpendicular to the weaving point section, including the following steps: obtaining the starting traction point coordinates of the traction trajectory in the current weaving stage; obtaining the angle between the axial vector of the equivalent core mold and the normal vector of the weaving point section; obtaining the length of the braided fabric weaved by the braiding machine on the equivalent core mold when adjusting the posture of the equivalent core mold; using the angle in combination with the length of the braided fabric to obtain the first target traction point coordinates after the traction robot adjusts the posture of the equivalent core mold; by controlling the traction trajectory and traction speed of the traction robot, the feeding direction of the equivalent core mold is perpendicular to the weaving point section, and the equivalent core mold is moved from the starting traction point coordinates to the first target traction point coordinates.

[0009] Optionally, the step of obtaining the angle between the axial vector of the equivalent mandrel and the normal vector of the braiding point cross section comprises the following steps: obtaining a first axial vector of the equivalent mandrel, wherein the first axial vector satisfies the following equation:

[0010]

[0011] in, represents the first axial vector, O(i) represents the coordinates of the i-th discrete point in the tool coordinate system, and O(i-1) represents the coordinates of the i-1-th discrete point in the tool coordinate system; the axial vector in the tool coordinate system is transformed into the second axial vector in the base coordinate system, and the second axial vector satisfies the following formula:

[0012]

[0013] in, Represents the second axial vector, Rot(z,a i-1 ) represents the counterclockwise rotation angle a around the z-axis of the base coordinate system i-1 ,Rot(y,b i-1 ) represents the counterclockwise rotation angle b around the y-axis of the base coordinate system i-1 ,Rot(x,c i-1 ) represents the counterclockwise rotation angle c around the x-axis of the base coordinate system i-1 , represents the first axial vector; the angle is obtained according to the second axial vector combined with the normal vector of the braiding point section, and the angle satisfies the following formula:

[0014]

[0015] in, represents the angle, represents the cross-section normal vector of the braiding point, Represents the second axial vector.

[0016] Optionally, the method of obtaining the length of a braided fabric woven by the braiding machine on the equivalent core mold when adjusting the posture of the equivalent core mold comprises the following steps: obtaining a functional relationship of a convergence length change at any time within the adjustment of the posture of the equivalent core mold; obtaining a braiding point moving speed by differentiating the functional relationship of the convergence length change with respect to time; obtaining a braiding speed by using the braiding point moving speed; and obtaining the length of the braided fabric by combining the braiding speed with the length of time spent in adjusting the posture of the equivalent core mold.

[0017] Optionally, the braid length satisfies the following formula:

[0018]

[0019] Where L(i) represents the length of the braid, V represents the pulling speed, and r i represents the approximate radius of the equivalent core mold of the i-th segment, ω represents the knitting circumferential speed of the knitting machine, R represents the guide wheel radius of the knitting machine, and h i represents the convergence length of the equivalent core mode of the i-th segment, h i-1 Represents the convergence length of the i-1th equivalent core mode.

[0020] Optionally, the traction speed satisfies the following constraints:

[0021]

[0022] Among them, V(t i / 2) represents the knitting speed corresponding to the midpoint of the time taken by the robot to adjust the equivalent core mold posture, V S represents the desired weaving speed; V represents the traction speed, r irepresents the approximate radius of the equivalent core mode of the i-th segment, r i-1 Represents the approximate radius of the i-1th equivalent core mode.

[0023] Optionally, the method of advancing the equivalent core mold after adjusting the posture by controlling the traction trajectory and traction speed of the traction robot until the weaving operation on the equivalent core mold is completed includes the following steps: obtaining the feed length of the equivalent core mold by utilizing the relative structural characteristics of the weaving machine and the equivalent core mold; obtaining the coordinates of the second target traction point after the traction robot advances the equivalent core mold through the feed length; and advancing the movement from the first target traction point coordinates to the second target traction point coordinates by controlling the traction trajectory and traction speed of the traction robot.

[0024] Optionally, the first target traction point coordinates and the second target traction point coordinates respectively satisfy the following formulas:

[0025]

[0026]

[0027] Wherein, T1(i) represents the coordinate of the first target traction point, T2(i) represents the coordinate of the second target traction point, h0(i) represents the initial convergence length of the i-th section of equivalent core mold weaving, L(i) represents the unstable weaving length of the i-th section of equivalent core mold weaving, d(i) represents the feed length of the i-th section of equivalent core mold weaving, Represents the direction vector from the origin of the tool coordinate system to the discrete point O(i-1), Representation vector The projected length on the x-axis of the base coordinate system, Representation vector The projected length on the y-axis of the base coordinate system, Representation vector The projected length on the z-axis of the base coordinate system.

[0028] In the second aspect, the present invention also provides a large curvature core mold weaving traction trajectory optimization control system, the large curvature core mold weaving traction trajectory optimization control system includes: a coordinate setting module, the coordinate setting module is used to establish a coordinate system according to the relative position of the traction robot and the braiding machine; a core mold discrete module, the core mold discrete module is used to convert the large curvature core mold into multiple equivalent core molds in the coordinate system; a first adjustment module, the first adjustment module is used to adjust the posture of the equivalent core mold by controlling the traction trajectory and traction speed of the traction robot, so that the feeding direction of the equivalent core mold is perpendicular to the braiding point section; a second adjustment module, the second adjustment module is used to advance the equivalent core mold after the posture adjustment by controlling the traction trajectory and traction speed of the traction robot until the braiding operation on the equivalent core mold is completed; a braiding cycle module, the braiding cycle module is used to control the braiding cycle process according to the discrete result of the core mold discrete module. The large curvature core mold weaving traction trajectory optimization control system stably implements the large curvature core mold weaving traction trajectory optimization control method through the coordinated work of multiple modules. At the same time, the system has a compact structure, stable operation, and is easy to install, which improves the practical applicability of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a flow chart of the large curvature core mold weaving traction trajectory optimization control method of the present invention;

[0030] Figure 2 A coordinate system established for the application of the present invention in actual weaving operations;

[0031] Figure 3 It is a schematic diagram of the core mode discretization of the present invention;

[0032] Figure 4 It is a schematic diagram of the relative structural features of the braiding machine and the equivalent core mold of the present invention;

[0033] Figure 5 A schematic diagram of the process of the traction robot designed for the present invention to traction an equivalent core mold;

[0034] Figure 6 A method flow chart of an optional embodiment of the present invention;

[0035] Figure 7 It is a schematic diagram of a module of a large curvature core mold weaving traction trajectory optimization control system of the present invention;

[0036] Figure 8 A comparison diagram of preforms obtained by the method of the present invention and a conventional weaving method;

[0037] Fig. 9 The figure is a comparison diagram of the braiding angles of the preform obtained by the method of the present invention and the traditional braiding method. DETAILED DESCRIPTION

[0038] The specific embodiments of the present invention will be described in detail below. It should be noted that the embodiments described herein are only for illustration and are not intended to limit the present invention. In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is obvious to those of ordinary skill in the art that these specific details do not need to be adopted to implement the present invention. In other examples, in order to avoid confusing the present invention, known circuits, software or methods are not specifically described.

[0039] Throughout the specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "in one embodiment," "in an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily all refer to the same embodiment or example. In addition, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any suitable combination and / or subcombination. In addition, it should be understood by those of ordinary skill in the art that the figures provided herein are for illustrative purposes and that the figures are not necessarily drawn to scale.

[0040] In one embodiment, see Figure 1 The present invention provides a method for optimizing and controlling a traction trajectory of a large curvature core mold weaving, comprising the following steps:

[0041] S1. Establish a coordinate system according to the relative positions of the traction robot and the knitting machine.

[0042] In an alternative embodiment, see Figure 2 The coordinate system is established according to the relative position of the traction robot and the braiding machine, and the coordinate system includes a basic coordinate system and a tool coordinate system, including the following steps: taking the traction robot on the ground as the origin o, the ground as the xoy plane, and the z axis perpendicular to the xoy plane to construct a basic coordinate system o-xyz; taking the traction robot traction core mold contact point as the origin o T , the flange surface of the traction robot is x T o T y T plane, perpendicular to x T o T y T The plane is z T Axis, build tool coordinate system o T -x T y T z T . Figure 2 The present invention shows the basic coordinate system o-xyz and tool coordinate system o established in actual weaving operation.T -x T y T z T , where a represents the braiding machine, b represents the core mold, c represents the robot, d represents the guide ring of the braiding machine, and e represents the flange of the traction robot.

[0043] S2. In the coordinate system, the large curvature core mode is equivalent to multiple sections of equivalent core modes.

[0044] In an alternative embodiment, see Figure 3 , the large curvature mandrel is equivalent to a multi-segment equivalent mandrel in the coordinate system, comprising the following steps: in the tool coordinate system, O(i) is used to represent the coordinates of discrete points on the central axis of the large curvature mandrel, where i=0,1,2…,n-1, |O(i)-O(i-1)|=d; the large curvature mandrel is divided into a multi-segment cylinder using the discrete points; the cylinder is equivalent to a cylinder, and the cylinder is defined as an equivalent mandrel, and the approximate radius of the equivalent mandrel satisfies the following formula:

[0045]

[0046] Among them, r i represents the approximate radius of the equivalent core mode of the i-th segment, r O(i-1) represents the radius of the large curvature core mold section corresponding to the i-1th discrete point, r O(i) Represents the large curvature core mold cross-section radius corresponding to the i-th discrete point. Figure 3 It is a discretized schematic diagram of the large curvature core mold involved in the present invention, wherein H represents the cross section where the braiding point is located.

[0047] S3. Adjust the posture of the equivalent core mold by controlling the traction trajectory and traction speed of the traction robot so that the feeding direction of the equivalent core mold is perpendicular to the cross section of the weaving point.

[0048] In an optional embodiment, the posture of the equivalent core mold is adjusted by controlling the traction trajectory and traction speed of the traction robot so that the feeding direction of the equivalent core mold is perpendicular to the weaving point section, including the following steps: obtaining the starting traction point coordinates of the traction trajectory in the current weaving stage; obtaining the angle between the axial vector of the equivalent core mold and the normal vector of the weaving point section; obtaining the length of the braided fabric weaved by the braiding machine on the equivalent core mold when adjusting the posture of the equivalent core mold; using the angle in combination with the length of the braided fabric to obtain the first target traction point coordinates after the traction robot adjusts the posture of the equivalent core mold; by controlling the traction trajectory and traction speed of the traction robot, the feeding direction of the equivalent core mold is perpendicular to the weaving point section, and the equivalent core mold is moved from the starting traction point coordinates to the first target traction point coordinates.

[0049] In an optional embodiment, the step of obtaining the angle between the axial vector of the equivalent mandrel and the normal vector of the braiding point cross section comprises the following steps: obtaining a first axial vector of the equivalent mandrel, wherein the first axial vector satisfies the following equation:

[0050]

[0051] in, represents the first axial vector, O(i) represents the coordinates of the i-th discrete point in the tool coordinate system, and O(i-1) represents the coordinates of the i-1-th discrete point in the tool coordinate system; the axial vector in the tool coordinate system is transformed into the second axial vector in the base coordinate system, and the second axial vector satisfies the following formula:

[0052]

[0053] in, Represents the second axial vector, Rot(z,a i-1 ) represents the counterclockwise rotation angle a around the z-axis of the base coordinate system i-1 ,Rot(y,b i-1 ) represents the counterclockwise rotation angle b around the y-axis of the base coordinate system i-1 ,Rot(x,c i-1 ) represents the counterclockwise rotation angle c around the x-axis of the base coordinate system i-1 , represents the first axial vector; the angle is obtained according to the second axial vector combined with the normal vector of the braiding point section, and the angle satisfies the following formula:

[0054]

[0055] in, represents the angle, represents the cross-section normal vector of the braiding point, Represents the second axial vector.

[0056] In an optional embodiment, since the angle of the equivalent core mold needs to be adjusted during the adjustment of the posture of the equivalent core mold, the braiding machine is in an unstable braiding state during this period. At this time, the traction speed of the braiding point can be decomposed into the braiding speed and the moving speed of the braiding point; since the braiding point changes with time in the unstable stage, the convergence length in this stage also changes with time until the posture adjustment is completed. Therefore, the functional relationship between the braiding point speed and time during this period can be obtained by the functional relationship between the convergence length and time, and then the synthesis of the braiding point traction speed can be used to obtain the functional relationship between the braiding speed and time during this period. By integrating the functional relationship between the braiding speed and time over time, the braiding length of the braiding machine during the unstable weaving period can be obtained.

[0057] In this embodiment, the step of obtaining the length of the braided fabric woven by the braiding machine on the equivalent core mold when adjusting the equivalent core mold posture comprises the following steps: obtaining a functional relationship of the convergence length change at any time within the adjustment of the equivalent core mold posture, and the functional relationship of the convergence length change satisfies the following formula:

[0058]

[0059] Among them, h i-1 represents the convergence length of the i-1th section of the core mold during stable weaving, V represents the pulling speed, r i represents the approximate radius of the equivalent core mold of the i-th section, ω represents the knitting circumferential speed of the knitting machine, and R represents the guide wheel radius of the knitting machine. The knitting point moving speed is obtained by taking the derivative of the functional relationship of the convergence length change with respect to time, and the knitting point moving speed satisfies the following relationship:

[0060]

[0061] Among them, V r (t) represents the moving speed of the knitting point. The knitting speed is obtained by using the moving speed of the knitting point. The knitting speed satisfies the following relationship:

[0062]

[0063] Among them, V r Indicates the moving speed of the knitting point, V a Represents the braiding speed. The braid length is obtained by combining the braiding speed with the time length of the equivalent core mold posture adjustment. Specifically, the time length and the braid length satisfy the following relationship:

[0064]

[0065]

[0066] Among them, t i represents the time length, L(i) represents the braid length, V represents the pulling speed, r i represents the approximate radius of the equivalent core mold of the i-th segment, ω represents the knitting circumferential speed of the knitting machine, R represents the guide wheel radius of the knitting machine, and h i represents the convergence length of the equivalent core mode of the i-th segment, h i-1 Represents the convergence length of the i-1th equivalent core mode.

[0067] In an optional embodiment, when the pulling speed is V, the synthesized braiding speed at the braiding point satisfies the following formula:

[0068] V(t)=Vcosφ+ωR T(t)cosδ(t),

[0069] Among them, φ represents the angle between the normal vector of the braiding point section and the straight line trajectory of the traction point coordinates, ω represents the braiding circumferential speed of the braiding machine, and R T (t) represents the real-time length from the traction point coordinate to the center point coordinate of the braiding point section, and δ(t) represents the real-time angle between the traction point coordinate to the braiding point coordinate vector and the braiding point section normal vector. By using the synthesized braiding speed combined with the relationship between the braiding point speed and time, the constraint conditions of the traction speed can be obtained, and the traction speed satisfies the following constraints:

[0070]

[0071] Among them, V(t i / 2) represents the corresponding weaving at the midpoint of the time the robot adjusts the equivalent core model posture, V S represents the desired weaving speed; V represents the traction speed, r i represents the approximate radius of the equivalent core mode of the i-th segment, r i-1 Represents the approximate radius of the i-1th equivalent core mode.

[0072] S4, advancing the equivalent core mold after the posture adjustment by controlling the traction trajectory and traction speed of the traction robot until the weaving operation on the equivalent core mold is completed.

[0073] In an optional embodiment, the equivalent core mold after the posture adjustment is advanced by controlling the traction trajectory and traction speed of the traction robot until the weaving operation on the equivalent core mold is completed, comprising the following steps: obtaining the feed length of the equivalent core mold by utilizing the relative structural characteristics of the weaving machine and the equivalent core mold; obtaining the coordinates of the second target traction point after the traction robot advances the equivalent core mold through the feed length; and advancing the movement from the first target traction point coordinates to the second target traction point coordinates by controlling the traction trajectory and traction speed of the traction robot.

[0074] In an alternative embodiment, see Figure 4 , Figure 4 The relative structural characteristics of the braiding machine and the equivalent core mold are shown. Figure 4 In the figure, A represents the guide ring of the braiding machine, B represents the braid outside the special-shaped structure core mold, C represents the propulsion direction, D represents the rotation direction of the guide ring, and θ represents the braiding angle. The braiding angle θ satisfies the following formula:

[0075]

[0076] Where θ represents the braiding angle, R represents the radius of the guide ring, and r irepresents the approximate radius of the i-th equivalent core mold; h(i) represents the convergence length of the i-th equivalent core mold. The feed length of the equivalent core mold is obtained by using the relative structural characteristics of the braiding machine and the equivalent core mold, and the feed length satisfies the following formula:

[0077]

[0078] Where d is the equivalent length of the core mode.

[0079] In an optional embodiment, the first target traction point coordinates and the second target traction point coordinates respectively satisfy the following formulas:

[0080]

[0081]

[0082] Wherein, T1(i) represents the coordinate of the first target traction point, T2(i) represents the coordinate of the second target traction point, h0(i) represents the initial convergence length of the i-th section of equivalent core mold weaving, L(i) represents the unstable weaving length of the i-th section of equivalent core mold weaving, d(i) represents the feed length of the i-th section of equivalent core mold weaving, Represents the direction vector from the origin of the tool coordinate system to the discrete point O(i-1), Representation vector The projected length on the x-axis of the base coordinate system, Representation vector The projected length on the y-axis of the base coordinate system, Representation vector The projected length on the z-axis of the base coordinate system.

[0083] In an optional embodiment, the traction trajectory and traction speed are controlled by the first target traction point coordinates, the second target traction point coordinates and constraint conditions, so that the feeding direction of the equivalent core mold is perpendicular to the weaving point plane until the current weaving stage ends. In this embodiment, the selected traction robot is a KUKA robot. After obtaining the first target traction point coordinates and the second target traction point coordinates, the LIN instructions of the KUKA robot are used to adjust the posture, that is, the traction speed is controlled within the constraint range, and the first target traction point coordinates and the second target traction point coordinates are reached successively, and the feeding direction of the core mold is ensured to be perpendicular to the weaving point plane in multiple traction cycles until the current weaving stage ends. Please refer to Figure 5 , Figure 5 (1) It shows that the core mold reaches the coordinates of the first target traction point after posture adjustment under the traction of the traction robot so that the feeding direction of the core mold is perpendicular to the weaving point plane. Figure 5 (2) It shows Figure 5(1) The basic traction robot makes the core mold reach the coordinates of the second target traction point through feed length compensation.

[0084] In an optional embodiment, the posture of the equivalent core mold is adjusted by controlling the traction trajectory and traction speed of the traction robot in step S3, and the equivalent core mold after the posture is adjusted is advanced by controlling the traction trajectory and traction speed of the traction robot in step S4. The operation can be completed by the machine language of the traction robot in combination with the coordinates of the first target traction point and the coordinates of the second target traction point. The traction robot is selected as a KUKA robot, and its traction trajectory is determined by the data contained in the coordinates of the first target traction point and the second target traction point. The large curvature core mold of the present invention is divided into multiple sections of equivalent core molds, and two transformations are set between the weaving operations of each section of the equivalent core mold: T1(i) (at this time i is 1, 2, ..., n-1) is the robot following the LIN instruction, so that the target traction point runs a straight trajectory at a constant traction speed V1 relative to the base coordinate system, and at the same time at a constant angular velocity ω T After adjusting the core mold position around the work center so that it is perpendicular to the weaving point plane, the position represented by T1(i) reached by the end of the traction robot. T Limited by the robot motor speed, angular velocity ω T Satisfies the following formula:

[0085] ω T =qV1,

[0086] Where q represents the adjustment coefficient determined by the traction robot's own parameters. i The starting point of the instruction is T2(i-1) and the end point is T1(i). When there is a radius change between each discrete core mold and the next core mold connected, an unstable weaving length Li will inevitably appear due to the adjustment of the weaving point. Since the unstable weaving stage is inevitable, the present invention uses this weaving length to adjust the core mold posture to reduce the yarn accumulation condition, that is, to supplement the second adjustment step, and translate d(i)-L(i) at a speed V2 on the basis of T1(i) to reach the position represented by T2(i) (at this time i is 0, 1,..., n-1). In this embodiment, obtaining the target traction point coordinates T1(i) and the target traction point coordinates T2(i) includes the following steps:

[0087] Using T2(i-1)=(x i-1 ,y i-1 ,z i-1 ; a i-1 ,b i-1 ,c i-1 );The axial vector of the current weaving stage Convert to vector in base coordinate system Using Vectors Combine the normal vector to get the angle Through the angle Define the rotation operation Rot i ,Rot i satisfy Rotation operation i After the traction center is rotated, since the equivalent core mold of the discrete segment only meets the requirement of being perpendicular to the weaving point plane, the traction center coordinate tool coordinate system is also translated along the z-axis and x-axis directions. Specifically, the z-axis and x-axis directions are direction, so that the traction center coordinates coincide with the center coordinates of the knitting point plane H, and then the target point P(i) = [x s +h(i)+L(i),y s ,z s ]; According to the coordinates of point O(i-1), the target point P(i) and the vector Get the step vector Trans from the coordinates of point O(i-1) to the target point P(i) i , the step vector Using this step vector Trans i Combined with Rotation i The transformation matrix T can be obtained i , the transformation matrix T i =Trans i ·Rot i ; The transformation matrix T i After homogenization, the position information and angle information of the target traction point coordinates T1(i) and the target traction point coordinates T2(i) can be obtained respectively.

[0088] In yet another alternative embodiment, see Figure 6 , Figure 6 is a flow chart of the method of this embodiment. When , it means that the equivalent core mode does not need to adjust the angle, so let T2(i-1) = (x i-1 ,y i-1 ,z i-1 ; a i-1 ,b i-1 ,c i-1 )=T1(i), that is, the traction coordinates at the end of the previous weaving stage are used as the starting point of the current stage T2(i) for feed compensation, thereby completing the weaving operation of the current stage.

[0089] In an optional embodiment, the equivalent core mold axis is discretized into n segments of equivalent core molds and is defined in the tool coordinate system o T -x T yT z T O(i) is used to represent the coordinates of n discrete points, where i = 0, 1, 2…, n, and |O(i)-O(i-1)| = d. Therefore, when i≤n-1 is set during the loop, the traction action continues; when i>n-1, the traction action ends and the compilation operation is completed.

[0090] The optimization control method of the present invention takes into account the change of convergence length when the traction robot adjusts the traction trajectory, adopts a dynamic weaving point plane, takes the axis of each discrete core mold perpendicular to the weaving point plane during steady-state weaving as a spatial constraint, and uses the transition weaving length from the initial weaving point to the stable weaving point during the weaving process to adjust the posture of the core mold, so that the core mold can perform weaving feed movement under the premise of achieving the spatial constraint, thereby avoiding large coverage fluctuations in the bending section of the preform, and controlling the traction speed to make the weaving enter the stable stage as soon as possible. The optimization control method of the present invention can effectively reduce the error in the weaving process of the core mold with large curvature and complex structure, and improve the mechanical properties of the preform; at the same time, it solves the process defects such as local yarn accumulation and unsmooth traction trajectory in the process of using industrial robots to pull the core mold with variable cross-section, large curvature and other characteristics for weaving, and ensures stable weaving angle and coverage.

[0091] See also Figure 7 The present invention also provides a large curvature core mold weaving traction trajectory optimization control system, the large curvature core mold weaving traction trajectory optimization control system includes: a coordinate setting module, the coordinate setting module is used to establish a coordinate system according to the relative position of the traction robot and the braiding machine; a core mold discrete module, the core mold discrete module is used to convert the large curvature core mold into multiple equivalent core molds in the coordinate system; a first adjustment module, the first adjustment module is used to adjust the posture of the equivalent core mold by controlling the traction trajectory and traction speed of the traction robot, so that the feeding direction of the equivalent core mold is perpendicular to the braiding point section; a second adjustment module, the second adjustment module is used to advance the equivalent core mold after the posture adjustment by controlling the traction trajectory and traction speed of the traction robot until the braiding operation on the equivalent core mold is completed; a braiding cycle module, the braiding cycle module is used to control the braiding cycle process according to the discrete result of the core mold discrete module. The large curvature core mold weaving traction trajectory optimization control system stably implements the large curvature core mold weaving traction trajectory optimization control method through the coordinated work of multiple modules. At the same time, the system has a compact structure, stable operation, and is easy to install, which improves the practical applicability of the present invention.

[0092] In an optional embodiment, a large curvature core mold weaving traction trajectory optimization control system is used to implement weaving control operations on a core mold with a head end section radius of 54.mm and a tail end section radius of 79.5mm. The weaving operation uses a Yunlu Composites 176-spindle radial braiding machine and a Kuka KR250 R2700-2 robot. During the weaving process, the yarn carrier angular velocity ω is 0.031rad / s, and the vibration motor frequency is 46Hz. Please refer to Figure 8 , Figure 8 Comparison diagram of preforms obtained by the method of the present invention and the conventional weaving method, Figure 8 The prefabricated body on the left is obtained by traditional weaving method. Figure 8 The prefabricated molded body on the right is obtained by the method of the present invention. Figure 8 It can be seen that in the weaving process of the traditional control method, the robot trajectory does not take into account the need for the core mold to feed at the weaving point during the core mold posture adjustment process, resulting in yarn accumulation at the starting weaving point of the core mold and excessive fluctuations in the weaving angle. At the same time, the robot traction speed of the traditional method does not take into account the changes in the cross section, resulting in the inability to keep the preform braiding angle constant. Using the traction trajectory optimization control method proposed by the present invention to weave the preform, the yarns are relatively tight and the braiding angle fluctuates less. Please refer to Fig. 9 , Fig. 9 The comparison diagram of the braiding angle of the preform obtained by the method of the present invention and the traditional braiding method is shown in FIG. Fig. 9 It can be seen that when the robot performs auxiliary weaving, the braiding angle obtained by the traditional method differs from the expected braiding angle by more than 7° at most, and a high-quality composite material preform cannot be obtained. After the robot position and posture and the traction speed are adjusted by the traction trajectory optimization control method proposed in the present invention, the large curvature curved variable cross-section core mold can be accurately woven. The braiding angle of this type of special-shaped structure core mold can float within 3.5° above and below the expected value, thereby improving the weaving efficiency and, under the same conditions, improving the mechanical properties of the composite material.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A method for optimizing the control of the traction trajectory of a large curvature core mold weaving, characterized in that: The steps include: A coordinate system is established according to the relative positions of the traction robot and the braiding machine, wherein the coordinate system includes a basic coordinate system and a tool coordinate system; In the coordinate system, the large curvature core mode is equivalent to multiple sections of equivalent core modes; The posture of the equivalent core mold is adjusted by controlling the traction trajectory and traction speed of the traction robot so that the feeding direction of the equivalent core mold is perpendicular to the cross section of the braiding point; The equivalent core mold after the posture adjustment is advanced by controlling the traction trajectory and traction speed of the traction robot until the weaving operation on the equivalent core mold is completed; The step of establishing a coordinate system according to the relative positions of the traction robot and the knitting machine comprises the following steps: The fulcrum of the traction robot on the ground is taken as the origin o, the ground is the xoy plane, and the z axis is perpendicular to the xoy plane to construct the basic coordinate system o-xyz; The contact point of the traction robot traction core mold is taken as the origin o T , the flange surface of the traction robot is x T o T y T plane, perpendicular to x T o T y T The plane is z T Axis, build tool coordinate system o T -x T y T z T ; The step of converting the large curvature core mode into multiple equivalent core modes in the coordinate system comprises the following steps: In the tool coordinate system, O(i) represents the coordinates of discrete points on the central axis of the large curvature mandrel, where i=0, 1, 2…, n-1, |O(i)-O(i-1)|=d; Using the discrete points to divide the large curvature core mold into multiple cylinder sections; The cylinder is equivalent to a cylinder, and the cylinder is defined as an equivalent mandrel. The approximate radius of the equivalent mandrel satisfies the following formula: Among them, r i represents the approximate radius of the equivalent core mode of the i-th segment, r O(i-1) represents the radius of the large curvature core mold section corresponding to the i-1th discrete point, r O(i) Represents the large curvature core mold cross-section radius corresponding to the i-th discrete point.

2. The large curvature core mold weaving traction trajectory optimization control method according to claim 1 is characterized in that: The step of adjusting the posture of the equivalent mandrel by controlling the traction trajectory and traction speed of the traction robot so that the feeding direction of the equivalent mandrel is perpendicular to the cross section of the braiding point comprises the following steps: Obtaining the coordinates of the starting traction point of the traction trajectory in the current weaving stage; Obtaining the angle between the axial vector of the equivalent core mold and the normal vector of the cross section of the braiding point; Obtaining the length of the braided fabric woven by the braiding machine on the equivalent mandrel when the posture of the equivalent mandrel is adjusted; The angle is combined with the length of the braided fabric to obtain the coordinates of the first target traction point after the traction robot adjusts the posture of the equivalent core mold; By controlling the traction trajectory and traction speed of the traction robot, the feeding direction of the equivalent core mold is perpendicular to the braiding point section, and the equivalent core mold is moved from the starting traction point coordinates to the first target traction point coordinates.

3. The large curvature core mold weaving traction trajectory optimization control method according to claim 2 is characterized in that: The step of obtaining the angle between the axial vector of the equivalent core mold and the normal vector of the braiding point cross section comprises the following steps: The first axial vector of the equivalent core mode is obtained, and the first axial vector satisfies the following equation: in, represents the first axial vector, O(i) represents the coordinates of the i-th discrete point in the tool coordinate system, and O(i-1) represents the coordinates of the i-1th discrete point in the tool coordinate system; The axial vector in the tool coordinate system is transformed into a second axial vector in the base coordinate system, and the second axial vector satisfies the following formula: in, Represents the second axial vector, Rot(z,a i-1 ) represents the counterclockwise rotation angle a around the z-axis of the base coordinate system i-1 ,Rot(y,b i-1 ) represents the counterclockwise rotation angle b around the y-axis of the base coordinate system i-1 ,Rot(x,c i-1 ) represents the counterclockwise rotation angle c around the x-axis of the base coordinate system i-1 , represents the first axial vector; According to the second axial vector combined with the cross-section normal vector of the braiding point, an angle is obtained, and the angle satisfies the following formula: in, represents the angle, represents the cross-section normal vector of the braiding point, Represents the second axial vector.

4. The large curvature core mold weaving traction trajectory optimization control method according to claim 2 is characterized in that: The method of obtaining the length of the braided fabric woven by the braiding machine on the equivalent mandrel when adjusting the posture of the equivalent mandrel comprises the following steps: Obtaining the functional relationship of the change of the convergence length at any time within the adjustment of the equivalent core mode posture; The moving speed of the braiding point is obtained by taking the derivative of the functional relationship of the convergence length change with respect to time; Using the braiding point moving speed, obtaining the braiding speed; The braid length is obtained by adjusting the braiding speed in combination with the time length of the equivalent core mold posture.

5. The large curvature core mold weaving traction trajectory optimization control method according to claim 4 is characterized in that: The braid length satisfies the following formula: Where L(i) represents the length of the braid, V represents the pulling speed, and r i represents the approximate radius of the equivalent core mold of the i-th segment, ω represents the knitting circumferential speed of the knitting machine, R represents the guide wheel radius of the knitting machine, and h i represents the convergence length of the equivalent core mode of the i-th segment, h i-1 Represents the convergence length of the i-1th equivalent core mode.

6. The large curvature core mold weaving traction trajectory optimization control method according to claim 2 is characterized in that: The traction speed meets the following constraints: Among them, V(t i / 2) represents the knitting speed corresponding to the midpoint of the time taken by the robot to adjust the equivalent core mold posture, V S represents the desired weaving speed; V represents the traction speed, r i represents the approximate radius of the equivalent core mode of the i-th segment, r i-1 Represents the approximate radius of the i-1th equivalent core mode.

7. The large curvature core mold weaving traction trajectory optimization control method according to claim 2 is characterized in that: The method of advancing the equivalent core mold after adjusting the posture by controlling the traction trajectory and traction speed of the traction robot until the weaving operation on the equivalent core mold is completed includes the following steps: Using the relative structural characteristics of the braiding machine and the equivalent core mold, the feed length of the equivalent core mold is obtained; Obtaining the coordinates of the second target traction point after the traction robot pushes the equivalent core mold through the feeding length; By controlling the traction trajectory and traction speed of the traction robot, the robot is advanced to move from the first target traction point coordinates to the second target traction point coordinates.

8. The large curvature core mold weaving traction trajectory optimization control method according to claim 7 is characterized in that: The coordinates of the first target traction point and the coordinates of the second target traction point satisfy the following formulas respectively: Wherein, T1(i) represents the coordinate of the first target traction point, T2(i) represents the coordinate of the second target traction point, h0(i) represents the initial convergence length of the i-th section of equivalent core mold weaving, L(i) represents the unstable weaving length of the i-th section of equivalent core mold weaving, d(i) represents the feed length of the i-th section of equivalent core mold weaving, Represents the direction vector from the origin of the tool coordinate system to the discrete point O(i-1), Representation vector The projected length on the x-axis of the base coordinate system, Representation vector The projected length on the y-axis of the base coordinate system, Representation vector The projected length on the z-axis of the base coordinate system.

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