Needling force reduction method and needling device for carbon fiber brake disc preform

Abstract

The invention discloses a needling force reducing method and a needling device for a carbon fiber brake disc preform, a needle plate device is divided into different units, and the needling force is reduced by dynamically adjusting the needling depth, density and frequency and the needling force borne by each layer. And it is ensured that each needling unit can achieve accurate force reduction control according to the thickness and density of the carbon fiber preform. According to the device, through the design of the composite gradual change needle plate, the unit dividing technology and the batch needling mode are utilized, the overall stress is reduced, the motor power in the needling process is optimized and adjusted through the composite needling algorithm, and it is ensured that the needling output power of a motor system is smooth, and the system runs stably. The stability of the device can be improved, meanwhile, fluctuation of motor power output is remarkably reduced, the needling operation efficiency of the carbon fiber brake disc prefabricated body is further improved, the device can adapt to the structural design requirements of various different products, and the needling processing refinement level of the prefabricated body is improved.

Description

Technical Field

[0001] The invention relates to the technical field of carbon fiber brake disc manufacturing, and in particular to a needling force reduction method and a needling device for a carbon fiber brake disc preform. Background Art

[0002] Carbon fiber materials are widely used in aerospace, automobile and high-performance brake disc manufacturing due to their light weight, high strength and excellent heat resistance. The superior properties of this material enable it to perform well under high load and high temperature environments. However, during the production process, stress concentration often occurs inside the material, which seriously affects the overall mechanical properties and service life of the brake disc. Stress concentration not only reduces the strength of the material, but may also cause cracks and fatigue failure, thereby shortening the product's service life.

[0003] The manufacturing of carbon fiber preforms now mainly relies on semi-manual and semi-mechanical needling manufacturing and molding. Needling technology performs well in improving material properties and can reduce stress concentration and optimize fiber arrangement through mechanical stimulation. However, the needling operation either relies on manual operation or traditional needling equipment usually uses a fixed mode needling operation, which cannot apply appropriate needling force and depth according to different areas of the preform, resulting in uneven fiber arrangement, which in turn affects the consistency and strength of the final product. Therefore, there is an urgent need for a method and device that can adjust the force reduction according to actual conditions during the needling operation, further refine the manufacturing and processing of the preform, and thus improve the quality of the product. Summary of the invention

[0004] Purpose of the invention: To solve the problems mentioned in the background technology, the present invention discloses a needling force reduction method and a needling device for a carbon fiber brake disc preform. By combining the preform preparation and positioning module with the needling pattern algorithm, the gradient needling algorithm and the dynamic adjustment needling algorithm, the parameters such as the needling force and frequency in the needling operation can be further accurately controlled, the influence of objective factors such as the preform thickness on the final product can be reduced, the needling process can be optimized, and the overall performance and durability of the carbon fiber brake disc can be improved.

[0005] Technical solution:

[0006] The present invention discloses a method for reducing stress by needling a carbon fiber brake disc preform, the method comprising the following steps:

[0007] S1 constructs a preform preparation and positioning module and a control module to position the carbon fiber preform, wherein the preform preparation and positioning module dynamically adjusts the clamping force and provides real-time feedback of position information to control subsequent needling work;

[0008] S2 analyzes the thickness and density of the positioned carbon fiber preform, collects the thickness and density data of each layer and divides the thickness of each layer into layers for accurate calculation of the needle punching force;

[0009] S3 sets the acupuncture pattern for each layer based on the data analyzed by S2, and defines the acupuncture pattern algorithm according to the thickness and density of different layers;

[0010] S4 performs acupuncture operations of different strengths, frequencies, and depths on carbon fiber preforms of different layers. When the thickness of the preform increases, the acupuncture strength is dynamically adjusted based on the composite gradient acupuncture algorithm.

[0011] During the acupuncture operation, S5 uses real-time monitoring feedback from the preform preparation and positioning module, and builds a dynamic adjustment acupuncture algorithm to further adjust the acupuncture intensity and frequency according to the actual effect of acupuncture.

[0012] Furthermore, the preform preparation and positioning module includes a high-precision clamp and a sensing system, which can accurately fix the carbon fiber preform in the needling device through precise multi-point clamping and real-time monitoring and positioning. The preform preparation and positioning module can dynamically adjust the clamping force and provide real-time feedback of position information to ensure the position stability and needling position accuracy of the preform during the needling process. When the sensing system detects that the preform position deviation exceeds the set threshold, the control module can automatically adjust or suspend the needling operation to achieve precise regulation of the needling force distribution.

[0013] Furthermore, the specific steps of position deviation detection are as follows:

[0014] The algorithm for calculating the deviation between the current prefab position and the target position is:

[0015] ΔP=P current -P garget

[0016] If the deviation exceeds the set threshold, i.e., |ΔP>∈|, enter S2; otherwise, continue the acupuncture operation;

[0017] Where ΔP is the position deviation; P current The current position information of the prefabricated body fed back by the sensor system; garget is the preset ideal position;∈ is the preset deviation threshold;

[0018] Adjust the clamping force by proportional control or PID control:

[0019] F adjusted＝ F target +K P .ΔP

[0020] In the formula, F adjusted is the clamping force after adjustment; F target is the preset clamping force range; K Pis the proportional gain; if the position deviation is too large, consider suspending the acupuncture operation until the clamping force is adjusted and recalibrating the position: if the position deviation is within the acceptable range, continue the acupuncture; if the position deviation or clamping force fluctuates unexpectedly, make dynamic adjustments:

[0021] If |ΔP|>∈or|F current -F target |>δ→Adjustparameters

[0022] Where δ is the tolerance threshold of the clamping force, which is used to determine whether the current clamping force deviates significantly from the target clamping force. If the difference in the clamping force is greater than δ, it is considered that the clamping force is not within an acceptable range and needs to be adjusted.

[0023] Furthermore, S2 performs thickness and density analysis on the carbon fiber preform through the sensing system after S1 positioning is completed, accurately collects thickness and density data of each layer of the preform, divides the thickness of each layer into layers according to the collected data, and automatically determines the actual thickness of each layer for accurate calculation of the needling force, thereby ensuring that the needling process achieves a uniformly distributed force reduction effect for different thickness areas.

[0024] Further, the algorithm definition of the needle punching mode with different layer thicknesses in S3 is implemented as follows: the total thickness of the carbon fiber preform is set to H, which is divided into n layers, each layer thickness is hi (i = 1, 2, ..., n), and the needle punching force Fi can be calculated according to the following formula:

[0025] F i = k·E i ·A i

[0026] The sum of the needling forces of all layers is expressed as follows:

[0027]

[0028] Then calculate the acupuncture intensity of each layer

[0029]

[0030] Where Ei is the elastic modulus of the i-th layer, taking into account that different layers may have different material properties; Ai is the effective contact area of ​​the needle head on the i-th layer; k is a coefficient related to the material properties; the total thickness H is divided into n layers, and hi is the layer thickness.

[0031] Furthermore, the implementation process of the composite gradient acupuncture algorithm in S4 is as follows:

[0032] The carbon fiber brake disc preforms with different layers are subjected to acupuncture operations of different strengths, frequencies, and depths. When the thickness H of the preform increases, the acupuncture strength needs to be dynamically adjusted to maintain effectiveness. The following formula is used for calculation:

[0033]

[0034] In the formula, F adjusted is the adjusted acupuncture intensity; F base The initial acupuncture force set when the system is started;

[0035] The acupuncture process is divided into three stages: the initial insertion stage is superficial insertion, the acupuncture is shallow, and the acupuncture force increases rapidly; the middle stage is the acupuncture depth increases, the force gradually stabilizes, the force is moderate, and remains constant; the final stage is the depth close to the maximum, the force decreases: the acupuncture force gradually decreases, and the piecewise function is given:

[0036]

[0037] Where, t is the acupuncture time; d is the acupuncture depth; ρ is the acupuncture density; F 0· is the initial acupuncture force; d max is the maximum acupuncture depth; α is the time increment coefficient, indicating that the force increases slightly with time in the initial stage; Fmid is the intermediate constant value of the acupuncture force; d1 and d2 are the critical depth values ​​of the segment, indicating the beginning and end of the intermediate stage; β is the attenuation coefficient that controls the reduction of force, which determines the speed of force reduction in the final stage.

[0038] Furthermore, in order to ensure that the force meets the needs of actual operation during the dynamic adjustment process, avoid excessive or insufficient force, and meet the constraints of depth, time and density to ensure the rationality and adaptability of acupuncture force, the following function is given:

[0039]

[0040] Where, the force must be a non-negative value, that is, F(t, d, ρ) ≥ 0; when t exceeds the maximum allowable time tmax, the force returns to zero or remains constant; when the depth d exceeds the maximum allowable depth d max When the force stops or remains constant, the density ρ should be within a reasonable range: ρ min ≤ρ≤ρ max .

[0041] Furthermore, the implementation process of the method for dynamically adjusting acupuncture in S5 is as follows:

[0042] Adjust the acupuncture frequency to achieve stable motor power output:

[0043]

[0044] In the formula, f(t) is the dynamic function of acupuncture frequency changing with time. The initial acupuncture frequency flow increases with time to reduce the instantaneous impact of the motor; the medium-term frequency f is kept constant. mid , suitable for most acupuncture work; in the later stage when approaching the bottom layer, the frequency f high Gradually decreasing, power fluctuations;

[0045] To ensure a reasonable load distribution, the number of needles N can be set as follows:

[0046]

[0047] In the formula, the number of acupuncture points N0 in the initial stage increases with time; the maximum number of acupuncture points N0 in the intermediate stage is maintained. mid ; The number of acupuncture points gradually decreased in the later period max , adapt to the underlying needs;

[0048] By dynamically adjusting the acupuncture unit, the load and frequency of each group of acupuncture can be controlled. The needle plate is divided into groups, and the needles are punctured in batches. The needle frequency fi and the number Ni of each group of needles are controlled to avoid instantaneous high load. The acupuncture time of each group is staggered to ensure the stable power output of the motor. The expression of the number of acupuncture units is as follows:

[0049]

[0050] The time interval Δt between each group of acupuncture is set according to the motor response speed to ensure that the puncture action of each group of needles is carried out in an orderly manner. The gradual acupuncture mode is set in a three-stage time division method: in the initial stage, the puncture frequency and number of acupuncture units gradually increase; in the middle stage, the number and frequency of needles per unit time are kept stable; in the later stage, the number of acupuncture units gradually decreases to avoid excessive impact.

[0051] Furthermore, the present invention discloses a needling device for a carbon fiber brake disc preform, the device comprising a composite gradient needle plate and a distributed control and feedback system, the surface of the needle plate is divided according to different functional areas, each cell corresponds to a specific needling mode and intensity, and the needling intensity and frequency of each cell are dynamically adjusted through a control module to ensure that different needling processes are performed in different areas according to the thickness, density and number of layers of the preform;

[0052] Each cell performs fine regulation of the acupuncture process through the distributed control system, and adjusts the acupuncture parameters in real time in combination with feedback data from the sensor system to maintain device operation and reduce power fluctuations.

[0053] Beneficial effects:

[0054] 1. The present invention adopts a dynamically adjusted needling force calculation method, combined with segmented control of depth, time and density, so that the needling force of each layer can accurately match the thickness requirements of different layers of the preform, thereby avoiding the occurrence of excessive force peaks and improving the stability of the needling process.

[0055] 2. The present invention divides the needling into multiple independent units through a composite gradient needling algorithm, and designs a personalized needling pattern according to the thickness and density parameters of different areas, so that the device can accurately control the strength and density of each area, thereby enhancing the overall mechanical properties and product consistency of the carbon fiber brake disc preform.

[0056] 3. The present invention reduces the operation of the motor under unnecessary power through reasonably set piecewise functions and compound gradient strategies, optimizes the efficiency and energy consumption of the acupuncture process, reduces the overall energy consumption, and shows good energy-saving and low-carbon effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It is a flow chart of the steps of the present invention;

[0058] Figure 2 It is a schematic diagram of the algorithm of the present invention;

[0059] Figure 3 It is a schematic diagram of the composite gradient needle plate unit of the present invention;

[0060] Figure 4 Schematic diagram of the composite gradient needle plate. DETAILED DESCRIPTION

[0061] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0062] During the needling process, due to the change in thickness and density of the preform, the needling device is subjected to uneven load, resulting in device instability and motor power fluctuations. In addition, it is also necessary to solve how to accurately control the needling force and frequency according to the different layers and regions of the preform, reduce stress concentration, extend the service life of the preform, and improve production efficiency. To achieve the above objectives, according to Figure 1-Figure 2 As shown, this embodiment provides a method for reducing stress by needling a carbon fiber brake disc preform, and the steps are as follows:

[0063] Step 1: Use high-precision fixtures and sensor systems to position the carbon fiber preform to form a preform preparation and positioning module to ensure the stability and accuracy of its needle punching position. Through precise multi-point clamping and real-time monitoring and positioning, the carbon fiber preform is accurately fixed in the needle punching device.

[0064] The preform preparation and positioning module can dynamically adjust the clamping force and provide real-time feedback of position information to ensure the position stability and accuracy of the preform during the needling process. When the sensing system detects that the preform position deviation exceeds the set threshold, the control module can automatically adjust or suspend the needling operation, thereby achieving precise control of the needling force distribution, significantly improving the uniformity of the needling process and the mechanical properties of the carbon fiber brake disc.

[0065] (11) Position deviation detection: the algorithm for calculating the deviation between the current preform position and the target position is:

[0066] ΔP=P current -P garget

[0067] If the deviation exceeds the set threshold (i.e. |ΔP>∈|), proceed to step 2; otherwise, continue the acupuncture operation.

[0068] Where ΔP is the position deviation; P current The current position information of the prefabricated body fed back by the sensor system; garget is the preset ideal position; ∈ is the preset deviation threshold.

[0069] (12) Adjust the clamping force according to the position deviation to compensate for the preform position deviation:

[0070] Here simple proportional control or PID control can be used to adjust the clamping force

[0071] F adjusted＝ F target +K P .ΔP

[0072] In the formula, F adjusted is the clamping force after adjustment; F target is the preset clamping force range; K P is the proportional gain.

[0073] If the adjusted clamping force exceeds the preset range, an upper or lower limit can be set to ensure that the clamping force is not too large or too small:

[0074] F adjusted =min(max(F adjusted , F min ), F max )

[0075] In the formula, F min The minimum clamping force limit; F max This is the maximum limit of the clamping force.

[0076] (13) The algorithm for position recovery and feedback is:

[0077] If the position deviation is too large, consider suspending the needling operation until the clamping force is adjusted and recalibrating the position:

[0078] Operation status =Pause

[0079] If the position deviation is within the acceptable range, continue with acupuncture:

[0080] Operation status =Continue

[0081] In the formula, Operation status This is the acupuncture operation state after adjustment.

[0082] Step 2: Perform thickness and density analysis on the carbon fiber preform located in step 1 according to the sensing system, accurately collect thickness and density data of each layer of the carbon fiber preform, and then divide the thickness of each layer into layers to determine the thickness of each layer for accurate calculation of the needle punching force.

[0083] After positioning is completed, the thickness and density of the carbon fiber preform are analyzed, and the thickness and density data of each layer of the preform are accurately collected. The system divides the thickness of each layer according to the collected data, automatically determines the actual thickness of each layer, and then uses it to accurately calculate the needle punching force, thereby ensuring that the needle punching process achieves a uniformly distributed force reduction effect for different thickness areas, thereby improving the overall mechanical properties and durability of the carbon fiber brake disc.

[0084] Step 3: Analyze the material data in step 2, set the needling pattern for each layer, and design the needling pattern calculation method for different layer thicknesses according to the thickness and density of different layers. The implementation process of the needling pattern calculation method for different layer thicknesses is as follows:

[0085] Layer Thickness and Needle Puncture The total thickness of the carbon fiber preform is set to H, which is divided into n layers, each layer thickness is hi (i = 1, 2, ..., n), and the needle punching force Fi can be calculated according to the following formula:

[0086] F i = k·E i ·A i

[0087] The sum of the needling forces of all layers is expressed as follows:

[0088]

[0089] Then calculate the acupuncture intensity of each layer

[0090]

[0091] Where Ei is the elastic modulus of the i-th layer, taking into account that different layers may have different material properties; Ai is the effective contact area of ​​the needle head on the i-th layer; k is a coefficient related to the material properties (which can be determined experimentally); the total thickness H is divided into n layers, and hi is the layer thickness.

[0092] Step 4: According to the calculation method of the needling pattern of different layer thicknesses in step 3, the carbon fiber brake disc preforms of different layers are subjected to needling operations of different strengths, frequencies, and depths to form a calculation method of composite gradient needling, so that the overall needling process of the preform is optimized. Further, the implementation process of the calculation method of composite gradient needling in step (4) is as follows:

[0093] The carbon fiber brake disc preforms with different layers are subjected to acupuncture operations of different strengths, frequencies, and depths. When the thickness H of the preform increases, the acupuncture strength needs to be dynamically adjusted to maintain effectiveness. The following formula is used for calculation:

[0094]

[0095] In the formula, F adjusted is the adjusted acupuncture intensity; F base It is the initial acupuncture force set when the system is started.

[0096] Assume that the acupuncture process is divided into three stages: in the initial penetration stage (surface penetration, shallow acupuncture), the acupuncture force increases rapidly; in the middle stage (the acupuncture depth increases and the force gradually stabilizes), the force is moderate and remains constant; in the final stage (the depth is close to the maximum and the force decreases): the acupuncture force gradually decreases to avoid excessive penetration and material damage. According to these three stages, a piecewise function is given:

[0097]

[0098] Where, t is the acupuncture time; d is the acupuncture depth; ρ is the acupuncture density (the number of acupunctures per unit area); F 0· is the initial acupuncture force; d max is the maximum acupuncture depth; α is the time increment coefficient, indicating that the force increases slightly with time in the initial stage; Fmid is the intermediate constant value of the acupuncture force; d1 and d2 are the critical depth values ​​of the segment, indicating the beginning and end of the intermediate stage; β is the attenuation coefficient that controls the reduction of force, which determines the speed of force reduction in the final stage.

[0099] The significance of the piecewise function design is that it meets the needs of carbon fiber preform structures at different depths through partitioning and increasing, constant, and decreasing segmented control, optimizes the force distribution during the needling process, thereby improving the overall needling effect and ensuring the structural uniformity and strength of the material. This design can effectively improve the quality of the finished product of the preform and extend its service life.

[0100] In order to ensure that the force meets the needs of actual operation during the dynamic adjustment process, avoid excessive or insufficient force, and meet the constraints of depth, time and density to ensure the rationality and adaptability of acupuncture force, the following function is given:

[0101]

[0102] In the formula, the force must be a non-negative value, that is, F(t,d,ρ)≥0; when t exceeds the maximum allowable time tmax, the force returns to zero or remains constant; when the depth d exceeds the maximum allowable depth dmax, the force stops or remains constant; the density ρ should be within a reasonable range: ρmin≤ρ≤ρmax.

[0103] Step 5: Based on the calculation method of acupuncture patterns of different layer thicknesses in step 3, the system adjusts the acupuncture intensity and frequency according to the actual effect of acupuncture through real-time monitoring feedback from sensors to ensure that the acupuncture needs at different levels are met, thus forming a calculation method for dynamically adjusting acupuncture. The algorithm for adjusting the acupuncture frequency to achieve stable motor power output is:

[0104]

[0105] Where, the initial acupuncture frequency f low Increases with time to reduce instantaneous impact on the motor; maintains a constant frequency f in the medium term mid , suitable for most acupuncture work; in the later stage when approaching the bottom layer, the frequency f high Gradually decreasing, power fluctuations.

[0106] To ensure a reasonable load distribution, the number of needles N can be set as follows:

[0107]

[0108] In the formula, the number of acupuncture points N0 in the initial stage increases with time; the maximum number of acupuncture points N0 in the intermediate stage is maintained. mid ; The number of acupuncture points gradually decreased in the later period max , adapted to the underlying needs.

[0109] The acupuncture unit indicates how the needles on the needle board are grouped and how each group of needles is inserted in sequence. By dynamically adjusting the acupuncture unit, the load and frequency of each group of needles can be controlled. The needle board is divided into m groups, and the needles are inserted in batches. The needle insertion frequency fi and the number Ni of each group of needles are controlled to avoid instantaneous high load. The acupuncture time of each group is staggered to ensure stable motor power output. The expression of the number of acupuncture units is as follows:

[0110]

[0111] The time interval Δt of each group of acupuncture is set according to the motor response speed to ensure that the puncture action of each group of needles is carried out in an orderly manner. The gradual acupuncture mode is set in three time divisions: the frequency and number of acupuncture units gradually increase in the early stage; the number and frequency of needles per unit time are kept stable in the middle stage; and the number of acupuncture units gradually decreases in the late stage to avoid excessive impact.

[0112] This embodiment also provides a carbon fiber brake disc preform needle punching device, such as Figure 3-4 As shown, the device includes a composite gradient needle plate and a distributed control and feedback system. The surface of the needle plate is divided according to different functional areas. Each cell corresponds to a specific needling mode and intensity. The needling intensity and frequency of each cell are dynamically adjusted through the control module to ensure that different needling processes are performed in different areas according to the thickness, density and number of layers of the preform.

[0113] Each cell uses a distributed control system to fine-tune the acupuncture process, and adjusts the acupuncture parameters in real time based on feedback data from the sensor system to maintain device operation and reduce power fluctuations.

[0114] The above description of the embodiments enables professionals and technicians in the field to implement or use the present invention. Various modifications to the embodiments will be apparent to professionals and technicians. The general principles of the present invention can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention should not be limited to the embodiments shown herein, but should cover the widest range consistent with the principles and novel features disclosed in the present invention.

Claims

1. A method for reducing the force of a carbon fiber brake disc preform by needling, characterized in that: The method comprises the following steps: S1 constructs a preform preparation and positioning module and a control module to position the carbon fiber preform, wherein the preform preparation and positioning module dynamically adjusts the clamping force and provides real-time feedback of position information to control subsequent needling work; S2 analyzes the thickness and density of the positioned carbon fiber preform, collects the thickness and density data of each layer and divides the thickness of each layer into layers for accurate calculation of the needle punching force; S3 sets the acupuncture pattern for each layer based on the data analyzed by S2, and defines the acupuncture pattern algorithm according to the thickness and density of different layers; S4 performs acupuncture operations of different strengths, frequencies, and depths on carbon fiber preforms of different layers. When the thickness of the preform increases, the acupuncture strength is dynamically adjusted based on the composite gradient acupuncture algorithm. During the acupuncture operation, S5 uses real-time monitoring feedback from the preform preparation and positioning module, and builds a dynamic adjustment acupuncture algorithm to further adjust the acupuncture intensity and frequency according to the actual effect of acupuncture.

2. The method for reducing stress by needling a carbon fiber brake disc preform according to claim 1, characterized in that: The preform preparation and positioning module includes a high-precision clamp and a sensing system. The carbon fiber preform is accurately fixed in the needling device through precise multi-point clamping and real-time monitoring and positioning. The preform preparation and positioning module can dynamically adjust the clamping force and provide real-time feedback of position information to ensure the position stability and needling position accuracy of the preform during the needling process. When the sensing system detects that the preform position deviation exceeds the set threshold, the control module can automatically adjust or suspend the needling operation to achieve precise regulation of the needling force distribution.

3. The method for reducing stress by needling a carbon fiber brake disc preform according to claim 2, characterized in that: The specific steps of position deviation detection are as follows: The algorithm for calculating the deviation between the current prefab position and the target position is: ΔP=P current -P garget If the deviation exceeds the set threshold, i.e., |ΔP>∈|, enter S2; otherwise, continue the acupuncture operation; Where ΔP is the position deviation; P current The current position information of the prefabricated body fed back by the sensor system; garget is the preset ideal position;∈ is the preset deviation threshold; Adjust the clamping force by proportional control or PID control: F adjusted＝ F target +K P .ΔP In the formula, F adjusted is the clamping force after adjustment; F target is the preset clamping force range; K P is the proportional gain; if the position deviation is too large, consider suspending the acupuncture operation until the clamping force is adjusted and recalibrating the position: if the position deviation is within the acceptable range, continue the acupuncture; if the position deviation or clamping force fluctuates unexpectedly, make dynamic adjustments: If|ΔP|>∈or|F current -F target |>δ→Adjustparameters Where δ is the tolerance threshold of the clamping force, which is used to determine whether the current clamping force deviates significantly from the target clamping force. If the difference in the clamping force is greater than δ, it is considered that the clamping force is not within an acceptable range and needs to be adjusted.

4. The method for reducing stress by needling a carbon fiber brake disc preform according to claim 2, characterized in that: S2 performs thickness and density analysis on the carbon fiber preform through the sensing system after S1 positioning is completed, accurately collects thickness and density data of each layer of the preform, divides the thickness of each layer into layers according to the collected data, and automatically determines the actual thickness of each layer for accurate calculation of the needling force, thereby ensuring that the needling process achieves a uniformly distributed force reduction effect for different thickness areas.

5. The method for reducing stress by needling a carbon fiber brake disc preform according to claim 1, characterized in that: The implementation process of the acupuncture pattern algorithm definition of different layer thicknesses described in S3 is as follows: Layer Thickness and Needle Puncture The total thickness of the carbon fiber preform is set to H, which is divided into n layers, each layer thickness is hi (i = 1, 2, ..., n), and the needle punching force Fi can be calculated according to the following formula: F i =k·E i ·A i The sum of the needling forces of all layers is expressed as follows: Then calculate the acupuncture intensity of each layer Where Ei is the elastic modulus of the i-th layer, taking into account that different layers may have different material properties; Ai is the effective contact area of ​​the needle head on the i-th layer; k is a coefficient related to the material properties; the total thickness H is divided into n layers, and hi is the layer thickness.

6. The method for reducing stress by needling a carbon fiber brake disc preform according to claim 1, characterized in that: The implementation process of the composite gradient acupuncture algorithm described in S4 is as follows: The carbon fiber brake disc preforms with different layers are subjected to acupuncture operations of different strengths, frequencies, and depths. When the thickness H of the preform increases, the acupuncture strength needs to be dynamically adjusted to maintain effectiveness. The following formula is used for calculation: In the formula, F adjusted is the adjusted acupuncture intensity; F base The initial acupuncture force set when the system is started; The acupuncture process is divided into three stages: the initial insertion stage is superficial insertion, the acupuncture is shallow, and the acupuncture force increases rapidly; the middle stage is the acupuncture depth increases, the force gradually stabilizes, the force is moderate, and remains constant; the final stage is the depth close to the maximum, the force decreases: the acupuncture force gradually decreases, and the piecewise function is given: Where, t is the acupuncture time; d is the acupuncture depth; ρ is the acupuncture density; F 0· is the initial acupuncture force; d max is the maximum acupuncture depth; α is the time increment coefficient, indicating that the force increases slightly with time in the initial stage; Fmid is the intermediate constant value of the acupuncture force; d1 and d2 are the critical depth values ​​of the segment, indicating the beginning and end of the intermediate stage; β is the attenuation coefficient that controls the reduction of force, which determines the speed of force reduction in the final stage.

7. The method for reducing stress by needling a carbon fiber brake disc preform according to claim 5, characterized in that: In order to ensure that the force meets the needs of actual operation during the dynamic adjustment process, avoid excessive or insufficient force, and meet the constraints of depth, time and density to ensure the rationality and adaptability of acupuncture force, the following function is given: Where, the force must be a non-negative value, that is, F(t, d, ρ) ≥ 0; when t exceeds the maximum allowable time tmax, the force returns to zero or remains constant; when the depth d exceeds the maximum allowable depth d max When the force stops or remains constant, the density ρ should be within a reasonable range: ρ min ≤ρ≤ρ max .

8. The method for reducing stress by needling a carbon fiber brake disc preform according to claim 1, characterized in that: The implementation process of the method for dynamically adjusting acupuncture in S5 is as follows: Adjust the acupuncture frequency to achieve stable motor power output: In the formula, f(t) is the dynamic function of acupuncture frequency changing with time. The initial acupuncture frequency flow increases with time to reduce the instantaneous impact of the motor; the medium-term frequency f is kept constant. mid , suitable for most acupuncture work; in the later stage when approaching the bottom layer, the frequency f high Gradually decreasing, power fluctuations; To ensure a reasonable load distribution, the number of needles N can be set as follows: In the formula, the number of acupuncture points N0 in the initial stage increases with time; the maximum number of acupuncture points N0 in the intermediate stage is maintained. mid ; The number of acupuncture points gradually decreased in the later period max , adapt to the underlying needs; By dynamically adjusting the acupuncture unit, the load and frequency of each group of acupuncture can be controlled. The needle plate can be divided into multiple groups, and the needles can be inserted in batches. The needle insertion frequency fi and the number Ni of each group of needles can be controlled to avoid instantaneous high load. The acupuncture time of each group can be staggered to ensure the stable power output of the motor. The expression of the number of acupuncture units is as follows: The time interval Δt between each group of acupuncture is set according to the motor response speed to ensure that the puncture action of each group of needles is carried out in an orderly manner. The gradual acupuncture mode is set in a three-stage time division method: in the initial stage, the puncture frequency and number of acupuncture units gradually increase; in the middle stage, the number and frequency of needles per unit time are kept stable; in the later stage, the number of acupuncture units gradually decreases to avoid excessive impact.

9. The needling device for a carbon fiber brake disc preform according to any one of claims 1 to 8, characterized in that: The device includes a composite gradient needle plate and a distributed control and feedback system. The surface of the needle plate is divided according to different functional areas. Each cell corresponds to a specific needling mode and intensity. The needling intensity and frequency of each cell are dynamically adjusted through a control module to ensure that different needling processes are performed in different areas according to the thickness, density and number of layers of the preform. Each cell performs fine regulation of the acupuncture process through the distributed control system, and adjusts the acupuncture parameters in real time in combination with feedback data from the sensor system to maintain device operation and reduce power fluctuations.

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