A short automatic yarn laying system dynamic process tension control method and device

Abstract

The application discloses a short yarn conveying automatic yarn laying system dynamic process tension control method and device, belongs to the technical field of automatic prepreg tow laying, and comprises the following steps: a mechanical equilibrium equation group considering the gravity of a floating part, friction between the floating part and a guide rail and an 'inertia force' caused by acceleration is established, real-time yarn tension is solved, and equivalent deformation of a tension spring is calculated based on the yarn tension. The torque of a hysteresis device is adjusted and the tow tension is controlled by comparing the equivalent deformation of the tension spring and the deformation of the tension spring at a balanced position. The tow tension calculated by the scheme has high precision, and the tension control precision of the short yarn conveying automatic yarn laying system dynamic process is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of automatic tow placement, and particularly relates to a dynamic process tension control method and device for short tow automatic placement system. BACKGROUND

[0002] Automatic tow placement technology is an automatic composite manufacturing technology in which a tow from a creel is independently transported and cut by a tow head, and then gathered into a pre-impregnated tape with adjustable width under a laying roller, and then placed on a mold surface heated by a heating system according to a predetermined laying track and compacted and shaped. According to the relative position of the creel and the tow head, the automatic tow placement equipment can be divided into a long-tow type tow placement equipment in which the creel and the tow head are separate, and a short-tow type tow placement equipment in which the creel and the tow head are integrated. The short-tow type tow placement equipment has been widely applied due to its short tow transmission distance and low probability of broken tow in the transmission process. In the laying process, the creel and the tow head of the short-tow type tow placement equipment move, rotate, pitch and deflect according to the predetermined laying track.

[0003] When laying a complex surface with variable curvature, improper selection of tow laying tension or poor control precision of the tow laying tension will cause laying defects such as tow deviation and bridging. Feedback and control of the pre-impregnated tow laying tension is one of the key technologies of the composite tow placement equipment. In the laying process, the tow head needs to constantly accelerate and decelerate according to the laying process requirements, especially for the short-tow type tow placement equipment, the creel structure is compact and always in dynamic motion, which brings great challenges to the control of the tow tension.

[0004] In existing filament laying equipment, a floating device connected to a tension spring or a cylinder at one end is arranged on a creel. The floating device not only can absorb the inertial overshoot of the creel during acceleration and deceleration to keep the filament bundle in a suspended state, but also can feedback the tension of the filament bundle in the creel in real time through a displacement sensor on the floating device. The slider in the floating device is connected to the tension spring or the cylinder. The tension value of the filament bundle can be solved by establishing a mathematical relationship between the position of the slider and the change amount of the elastic element. Then, the speed or torque of the creel is adjusted according to the feedback of the filament tension to control the tension in the filament bundle. For example, a Chinese invention patent application with the publication number CN115583539A, the publication date of January 10, 2023, and the name of "a filament tension control device and method for composite material filament laying" discloses a filament tension control device for composite material filament laying, which includes a tension control mechanism and a tension reduction mechanism. The tension control mechanism is used to strip the backing paper of the filament bundle, adjust the filament tension, and then transmit the filament bundle to the tension reduction mechanism for tension reduction processing. The floating roller reciprocates along the guide rail slider through the elastic element. The magnetic powder brake is used for control through analog input. The position sensor is used to output the detected position analog signal of the floating roller on the guide rail slider to the controller. The driving motor drives the transmission shaft to drive the friction wheel to move. The cylinder is used to drive the feed wheel mechanism to press or leave the friction wheel.

[0005] The above-mentioned patent uses an active adaptive method to reduce the tension of the filament before entering the filament laying head. However, since the gravity of the floating part of the floating device, the "inertial force" of the floating part during acceleration and deceleration, and the friction between the floating part and the guide rail are not considered, the feedback of the filament tension deviates greatly from the actual value, resulting in low tension control precision. SUMMARY

[0006] The present application aims to solve the technical problem of low tension control precision in the short transfer yarn automatic filament laying acceleration and deceleration process due to the lack of consideration of the gravity of the floating part, the "inertial force" of the floating part, and the friction between the floating part and the guide rail in the prior art. A short transfer yarn automatic filament laying system dynamic process tension control method and device are provided to improve the end effector tension dynamic control precision and the laying quality of the composite material part.

[0007] In order to achieve the above-mentioned application purpose, the technical scheme of the present application is as follows:

[0008] The short tows automatic fiber placement system dynamic process tension control device comprises a creel, a yarn roller, a film collecting roller, a floating device and an ultrasonic distance sensor, the yarn roller is provided with a hysteresis motor for real-time adjustment and control of the yarn roller damping, the film collecting roller is used for winding the tow backing on the roller shaft, and the ultrasonic distance sensor is used for detecting the radius of the yarn roll as an input parameter of the hysteresis motor torque control; after the tow with backing paper is drawn out from the yarn roller, the tow and the backing paper are separated at the film collecting roller, the backing paper is wound on the film collecting roller, and the tow is guided to the floating device after passing through the film collecting roller and enters the fiber placement head under the guidance of the tow turning device for subsequent laying operation.

[0009] Further, in an embodiment, the floating device comprises a shell, a tension spring, a guide rail, a floating part and a linear displacement sensor; the shell is mounted on the creel, the guide rail is mounted on the shell in parallel with the linear displacement sensor; one end of the tension spring is connected with the floating part, and the other end is fixed on the side of the shell; the floating part slides along the guide rail under the action of the tow tension during laying, and the linear displacement sensor is used for real-time recording of the position of the floating part.

[0010] Further, in an embodiment, the floating part comprises a sliding block, a screw rod and a sleeve; the sliding block is matched with the guide rail, and the screw rod is fixed on the sliding block; the sleeve is mounted on the screw rod through a flange bearing.

[0011] Further, in an embodiment, the screw rod is provided with end caps for limiting the ends, and the gap between the tapered boss at the connecting part of the sleeve and the outer diameter of the sleeve is 0.2-0.3 mm.

[0012] Further, in an embodiment, the sleeve is made of smooth carbon fiber.

[0013] According to the above device, the application further provides a short tows automatic fiber placement system dynamic process tension control method, which comprises the following steps:

[0014] A mechanical equilibrium equation group considering the gravity of the floating part, the friction between the floating part and the guide rail and the “inertial force” caused by acceleration is established, and the real-time tow tension is solved; the equivalent deformation amount of the tension spring is converted from the real-time tow tension; the torque of the hysteresis motor is adjusted by comparing the equivalent deformation amount of the tension spring and the deformation amount of the tension spring at the balance position, so as to control the tow tension.

[0015] Further, the mechanical equilibrium equation group of the floating part during laying is:

[0016]

[0017] Wherein, F1 is the incoming tow tension, F2 is the outgoing tow tension, α1 is the included angle between the incoming tow direction and the guide rail direction, α2 is the included angle between the outgoing tow direction and the guide rail direction, FN F is the tension of the tension spring G1 F is the component of the gravity of the floating part along the guide rail direction G2 F is the component of the gravity of the floating part along the vertical direction of the guide rail, μ is the friction coefficient between the floating part and the guide rail, η is the direction coefficient, m is the mass of the floating part, a1 is the acceleration of the floating part, J is the rotational inertia of the sleeve, a2 is the acceleration of the yarn at the sleeve, r is the radius of the sleeve, k is the elastic coefficient of the tension spring, and △x is the elongation of the tension spring.

[0018] Further, the optimal yarn delivery tension F 2-OPT is obtained by calculation or experience, and the elongation △x of the tension spring at the equilibrium position is obtained by the following formula OPT :

[0019] △x OPT = F 2-OPT / k;

[0020] According to the real-time yarn delivery tension F2, the equivalent elongation △x' of the tension spring is obtained by the following formula:

[0021] △x' = F2 / k;

[0022] When △x' > △x OPT , the hysteresis torque T is reduced, and the yarn roll unwinding speed is increased; when △x' < △x OPT , the hysteresis torque T is increased, and the yarn roll unwinding speed is reduced, so that the floating device is stabilized at the equilibrium position.

[0023] Further, the component F G1 of the gravity of the floating part along the guide rail direction is:

[0024]

[0025] In the formula, is the rotation factor when the yarn laying device rotates;

[0026] is the unit vector of the i-th floating roller guide rail,

[0027] is the gravity vector of the floating roller,

[0028] θ i is the included angle with the X-axis.

[0029] Further, the component F G2 of the gravity of the floating part along the vertical direction of the guide rail is:

[0030]

[0031] wherein,​ The rotation factor is the rotational factor when the wire-laying equipment rotates. It is the unit vector of gravity.

[0032] In summary, the present invention has the following advantages:

[0033] This invention provides a dynamic tension control method and device for an automatic yarn placement system for short yarn feeders, establishing a set of mechanical equilibrium equations considering the gravity of the floating part, friction between the floating part and the guide rail, and the "inertial force" caused by acceleration. The rotation factor is obtained by collecting coordinate data and rotation information from the A, B, and C axes. Solve for the component of gravity F of the floating part along the guide rail. G1 The component of gravity of the floating part along the direction perpendicular to the yarn frame, F G2 Furthermore, by introducing the direction coefficient η, the real-time wire tension F2 is calculated. The equivalent deformation Δx′ of the tension spring and the deformation Δx at the equilibrium position are compared. OPT The torque T of the hysteresis coil is adjusted to control the yarn tension. This method calculates the yarn tension with high accuracy, improving the tension control accuracy of the dynamic process of the short yarn automatic yarn placement system. Attached Figure Description

[0034] Figure 1 For short-yarn automatic yarn placement system yarn frame;

[0035] Figure 2 This is a schematic diagram of a floating device;

[0036] Figure 3 This is a cross-sectional view of the floating portion;

[0037] Figure 4 This is a force analysis diagram of the floating part;

[0038] Figure 5 Flowchart of dynamic process tension control method;

[0039] In the picture:

[0040] 1. Yarn frame, 2. Yarn roller, 3. Take-up roller, 4. Floating device, 5. Ultrasonic distance sensor, 6. Housing, 7. Cover plate, 8. Tension spring, 9. Guide rail, 10. Linear displacement sensor, 11. Slider, 12. Screw, 13. End cap, 14. Sleeve, 15. Flange bearing, 16. Tapered boss, 17. Yarn bundle. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0042] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0043] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0044] In the description of this invention, it should be noted that the terms "upper," "vertical," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0045] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," and "connect" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0046] Example 1

[0047] This invention provides a dynamic process tension control device for an automatic yarn placement system for short yarns, such as... Figure 1 As shown, the system includes a yarn frame 1, a yarn roller 2, a take-up roller 3, a floating device 4, and an ultrasonic distance sensor 5. These components constitute a constant tension unwinding system. In actual operation, multiple unwinding systems can be arranged as follows: Figure 1As shown in the disc shape, the tension of the yarn bundle in each unwinding system is independently controlled.

[0048] A hysteresis device is installed on the top of the yarn roller 2 to control the damping of the yarn roller 2, and the torque can be adjusted in real time.

[0049] The take-up roller 3 is used to wind the backing of the filament bundle 17 onto the roller shaft. It is controlled by a torque motor, and the take-up torque is stable and adjustable.

[0050] As the yarn roll is laid out, its diameter changes continuously. The ultrasonic distance sensor 5 is used to detect the yarn roll radius, which serves as an important input parameter for hysteresis torque control.

[0051] like Figure 2 As shown, the floating device 4 mainly includes a housing 6, a cover plate 7, a tension spring 8, a guide rail 9, a linear displacement sensor 10, and a floating part. The housing 6 is connected to the cover plate 7 and is mounted on the yarn frame 1 via the cover plate 7. The guide rail 9 and the linear displacement sensor 10 are mounted parallel to each other inside the housing 6. The cover plate 7 is provided with a clearance hole for the floating part. One end of the tension spring 8 is connected to the floating part, and the other end is fixed to the side of the housing 6. During laying, the floating part slides along the guide rail 9 under the tension of the yarn bundle 17, and the linear displacement sensor 10 can record the position of the floating part in real time.

[0052] like Figure 3 As shown, the floating part mainly consists of a slider 11, a screw 12, an end cap 13, and a sleeve 14. The slider 11 is mated with the guide rail 9, and the screw 12 is fixed to the slider 11 by threads. The sleeve 14 is mounted on the screw 12 via a flanged bearing 15, allowing it to rotate around the screw 12 with low resistance. End caps 13 are installed at both ends of the screw 12 to limit the bearing. The tapered boss 16 at the connection between the end cap 13 and the sleeve 14 has a gap of 0.2-0.3mm with the outer diameter of the sleeve 14, which prevents the sleeve 14 from coming off in extreme cases and avoids friction between the end cap 13 and the sleeve 14 that would hinder the rotation of the sleeve 14. In addition, the sleeve 14 is made of smooth carbon fiber, which reduces the adhesion between the pre-impregnated fiber bundle 17 and the sleeve 14.

[0053] The movement of the filament bundle 17 in the yarn frame 1 is as follows: After the filament bundle 17 covered with backing paper is drawn out from the yarn roller 2, under the action of the torque motor, the filament bundle 17 separates from the backing paper at the take-up roller 3. The backing paper is wound around the take-up roller 3. After the filament bundle 17 has wrapped around the take-up roller 3 for about half a turn, it is guided to the floating device 4. Then, under the guidance of the filament bundle 17 turning device, it enters the yarn laying head for subsequent laying operations. In this process, each filament bundle 17 is independently controlled.

[0054] Regarding the calculation of filament tension, such as Figure 4 As shown, taking a certain filament bundle as an example, the mechanical equilibrium equations for the floating part during the laying process are as follows:

[0055]

[0056] In equation (1), F1 is the wire feeding tension, F2 is the wire exiting tension, α1 is the angle between the wire feeding direction and the guide rail direction, α2 is the angle between the wire exiting direction and the guide rail direction, and F N F is the tension force of the tension spring. G1 F represents the component of gravity of the floating part along the guide rail direction. G2 Let α1, α2, μ, m, J, a2, r, and k be the component of the gravity of the floating part along the direction perpendicular to the yarn frame, μ be the coefficient of friction between the floating part and the guide rail, η be the direction coefficient (η = 1 when the floating part moves along the guide rail towards the center of the yarn tray; η = -1 when the floating part moves away from the center of the yarn tray along the guide rail), m be the mass of the floating part, a1 be the acceleration of the floating part (positive direction is along the guide rail towards the center of the yarn tray), J be the moment of inertia of the sleeve, a2 be the acceleration of the yarn bundle at the sleeve, r be the radius of the sleeve, k be the elastic coefficient of the tension spring, and Δx be the elongation of the tension spring. α1, α2, μ, m, J, a2, r, and k can be obtained directly, while η, a1, and Δx can be obtained through a linear displacement sensor.

[0057] Therefore, we only need to solve for F. G1 F G2 The real-time yarn tension F2 can be obtained by solving the above system of equations.

[0058] Example 2

[0059] Based on the dynamic process tension control device of the automatic short yarn placement system described in Embodiment 1, this embodiment provides a dynamic process tension control method for the automatic short yarn placement system, including the following steps:

[0060] S1. First, obtain the optimal yarn tension F through calculation or experience. 2-OPT The spring deformation Δx at the equilibrium position is obtained by the following formula. OPT :

[0061] △x OPT =F 2-OPT / k

[0062] S2. Obtain the angle α1 between the wire feeding direction and the guide rail direction, the angle α2 between the wire exit direction and the guide rail direction, the mass m of the floating part in the floating device, the moment of inertia J of the sleeve, the radius r of the sleeve, and the elastic coefficient k of the tension spring through the end effector design drawings and digital models.

[0063] S3. The coefficient of friction μ between the floating device and the guide rail was measured by experiment;

[0064] S4. Obtain the filament bundle acceleration a2 at the sleeve by collecting the laying acceleration of the end effector;

[0065] S5. The displacement / time curve of the floating part can be obtained from the linear displacement sensor. After processing, the velocity / time curve and acceleration / time curve of the floating part can be obtained, and then the spring elongation Δx, the acceleration a1 of the floating part, and the direction coefficient η can be obtained.

[0066] S6. Collect coordinate data and rotation information for the A, B, and C axes, and obtain the rotation factor. And calculate the component of gravity F of the floating part along the guide rail. G1 The component of gravity of the floating part along the direction perpendicular to the yarn frame, F G2 ;

[0067] S7. Substitute the above parameters into the mechanical equilibrium equations of the floating part to solve for the real-time yarn tension F2.

[0068] S8. Substitute F2 into the following formula to obtain the equivalent deformation of the tension spring △x′;

[0069] △x′=F2 / k

[0070] S9. When △x′>△x OPT When the hysteresis torque T is reduced, the unwinding speed of the yarn roller is increased; when Δx′ < Δx OPT At this time, increase the hysteresis torque T and decrease the unwinding speed of the yarn roller to stabilize the floating device in the equilibrium position.

[0071] The component of gravity of the floating part along the guide rail direction, F G1 Calculate as follows:

[0072] The motion of the fiber placement equipment can be decomposed into translational motion followed by rotational motion. During the translational motion, the unit vector of the floating roller guide rail... With the gravity vector of the floating roller Always vertical, F G1 =0N. Taking a six-axis machine with an end effector mounted on a structure of XYZABC as an example, the rotation factor is denoted as when the machine rotates. The rotation process of the end effector can be decomposed into three parts: first, rotation γ around the X-axis; then, rotation β around the Y-axis; and finally, rotation α around the Z-axis. This can be expressed as:

[0073]

[0074] The vector of the floating roller guide groove at position i is The angle between the X-axis and the X-axis is θ i The component of gravity along the guide rail direction F G1 for:

[0075]

[0076] In the formula,

[0077] The component of gravity of the floating part along the guide rail direction, F, can be obtained. G1 for:

[0078]

[0079] The component of gravity of the floating part along the guide rail direction, F G2 Calculate as follows:

[0080] The unit vector of gravity is The component of gravity along the guide rail direction F G2 for:

[0081]

[0082] In the formula,

[0083] The component of gravity of the floating part along the direction perpendicular to the yarn frame, F, can be obtained. G2 for:

[0084]

[0085] The above control method establishes a set of mechanical equilibrium equations considering the gravity of the floating part, the friction between the floating part and the guide rail, and the "inertial force" caused by acceleration. The rotation factor is obtained by collecting coordinate data and rotation information along the A, B, and C axes. Solve for the component of gravity F of the floating part along the guide rail. G1 The component of gravity of the floating part along the direction perpendicular to the yarn frame, F G2 Furthermore, by introducing the direction coefficient η, the real-time wire tension F2 is calculated. The equivalent deformation Δx′ of the tension spring and the deformation Δx at the equilibrium position are compared. OPT This is used to adjust the torque T of the hysteresis coil, thereby controlling the tension of the wire bundle.

[0086] In this scheme, the optimal yarn tension is related to the laying process conditions (part surface shape, raw material properties, laying speed, laying acceleration, etc.), which can be obtained through calculation or experience. The mechanical equilibrium equation established by this scheme can calculate the real-time yarn tension. By comparing the real-time yarn tension with the required optimal yarn tension, the torque of the unwinding mechanism is adjusted to change the yarn tension, striving to match it as closely as possible to the required optimal yarn tension. The yarn bundle tension calculated by this scheme has high accuracy, improving the tension control accuracy of the dynamic process of the short yarn automatic yarn laying system.

[0087] Although specific embodiments of the present invention have been described in detail with reference to the accompanying drawings, this should not be construed as limiting the scope of protection of this patent. Various modifications and variations that can be made by those skilled in the art without inventive effort within the scope described in the claims still fall within the scope of protection of this patent.

[0088] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A dynamic process tension control method of a short tows automated fiber placement system, the method is based on a dynamic process tension control device of a short tows automated fiber placement system, the device specifically comprises a creel (1) and a yarn roll (2), a film take-up roll (3), a floating device (4) and an ultrasonic distance sensor (5) arranged on the creel (1), characterized in that, The yarn roller (2) is provided with a hysteresis damper for real-time adjustment of the yarn roller (2) damping, and the film collecting roller (3) is used for winding the tows (17) backing to the roller shaft; the ultrasonic distance sensor (5) is used for detecting the radius of the thread roll, as an input parameter for the hysteresis damper torque control; after the tows (17) covered with backing paper are drawn out from the yarn roller (2), the tows (17) are separated from the backing paper at the film collecting roller (3), the backing paper is wound on the film collecting roller (3), and the tows (17) are guided to the floating device (4) after passing through the film collecting roller (3), and are guided into the tows laying head under the guidance of the tows (17) turning device for subsequent laying operation; the floating device (4) comprises a housing (6), a tension spring (8), a guide rail (9), a floating part and a linear displacement sensor (10); the housing (6) is installed on the creel (1), the guide rail (9) and the linear displacement sensor (10) are installed on the housing (6) in parallel, one end of the tension spring (8) is connected with the floating part, and the other end is fixed on the side surface of the housing (6); the floating part slides along the guide rail (9) under the action of the tows (17) tension during laying, and the linear displacement sensor (10) is used for real-time recording of the position of the floating part; the tension control method based on the foregoing device comprises: A mechanical equilibrium equation set considering the gravity of the floating part, the friction between the floating part and the guide rail and the "inertial force" caused by acceleration is established, and the real-time tows tension is solved; the equivalent deformation amount of the tension spring is converted according to the real-time tows tension; the torque of the hysteresis damper is adjusted by comparing the equivalent deformation amount of the tension spring and the deformation amount of the tension spring at the balance position, so as to control the tows tension; the mechanical equilibrium equation set of the floating part during laying is: ； wherein, is the infeed tension, is the outfeed tension, is the included angle between the infeed direction and the guide direction, is the included angle between the outfeed direction and the guide direction, is the tension of the tension spring, is the component of the gravity of the floating part along the guide direction, is the component of the gravity of the floating part along the vertical creel direction, is the friction coefficient between the floating part and the guide, is the direction coefficient, is the mass of the floating part, is the acceleration of the floating part, is the moment of inertia of the sleeve, is the acceleration of the tows at the sleeve, is the radius of the sleeve, is the spring constant of the tension spring, is the elongation of the tension spring.

2. The dynamic tension control method of a short tows automated fiber placement system according to claim 1, wherein, The floating part comprises a sliding block (11), a screw rod (12) and a sleeve (14); the sliding block (11) is matched with the cooperation surface of the guide rail (9), and the screw rod (12) is fixed on the sliding block (11); the sleeve (14) is installed on the screw rod (12) through a flange bearing (15).

3. The dynamic tension control method of a short tows automated fiber placement system according to claim 2, wherein, The screw rod (12) is provided with end covers (13) for limiting the ends, and the gap between the tapered boss (16) at the matching connection part of the end cover (13) and the outer diameter of the sleeve (14) is 0.2-0.3mm.

4. The dynamic tension control method of a short tows automated fiber placement system according to claim 2 or 3, characterized in that, The sleeve (14) is made of smooth carbon fiber.

5. The method of claim 1, wherein the dynamic tension control method of the short tows automated fiber placement system is characterized by, Optimum wire feed tension is obtained by calculation or empirically and the equilibrium position spring deflection is obtained from : ； According to real-time wire tension The equivalent deformation of the tension spring is obtained by the following formula ; ； When the hysteresis torque is reduced , the yarn roll unwinding speed is increased; when the hysteresis torque is increased , the yarn roll unwinding speed is reduced, and the floating device is stabilized at the equilibrium position.

6. The method of claim 1, wherein, Floating part gravity along guide rail direction component Is: ； In the formula, is a rotation factor for the rotation of the filament-laying device; for the first i where the floating roller guide rail unit vector, ; for the gravity vector of the floatation roller, ; For With Axial angle.

7. The method of claim 1, wherein the dynamic tension control method is used in an automatic fiber placement system. Floating partial gravity component in vertical creel direction Is: ； wherein, is a rotation factor for the rotation of the filament laying device; is a unit vector of gravity.

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