Composite part winding pressure control method and system based on high-gain observer

Abstract

This invention provides a method and system for controlling the winding pressure of composite material parts based on a high-gain observer. The method includes: determining a four-bar linkage as the pressure transmission mechanism for applying positive pressure along the mandrel radially; performing static and dynamic analyses on the pressure transmission mechanism; optimizing the deformation and dynamic load of the four-bar linkage using a three-dimensional simulation platform to obtain an optimized four-bar linkage; establishing a dynamic model of the pressure control system; comparing the detected value of the winding pressure signal with the set value using an industrial control computer; determining the control input value using a high-gain observer-based model control method; and sending the control input value to a proportional valve to control the valve opening until the detected value of the winding pressure signal matches the set value. The control method and system proposed in this invention ensure stable control of the pressure roller applying positive pressure along the mandrel radially to the prepreg tape, improving the accuracy and stability of the winding pressure transmission in composite prepreg tape winding machines, and mitigating pressure transmission hysteresis and fluctuation problems.

Description

Technical Field

[0001] This invention relates to the field of winding pressure control technology for composite material winding products, and specifically to a method for controlling the winding pressure of composite material parts based on a high-gain observer sliding mode control strategy. Background Technology

[0002] Composite materials are multiphase materials, generally composed of two or more components with different properties and forms, combined through a composite process. This not only retains the important characteristics of the original constituent materials but also achieves superior properties not possessed by the original components through the composite process effect. The preparation process of composite material winding generally includes a winding process and a curing process.

[0003] The prepreg winding process for composite materials involves heating the resin matrix on the prepreg tape to a molten state under winding temperature. Then, under the combined action of positive pressure from hot rollers and tension applied by a torque motor, the prepreg tape is wound onto a mandrel, ensuring tight adhesion between each layer. During winding, the prepreg tape enters the contact area between the hot rollers and the mandrel, where the hot rollers apply radial positive pressure to the prepreg tape. This process removes air bubbles, applies pressure for bonding, and maintains the smoothness of the prepreg tape, preventing slippage caused by wrinkles on the inner edges due to deformation.

[0004] Therefore, the stability of pressure control is extremely important. The pressure control system is a nonlinear system that is easily disturbed. Excessive pressure fluctuations can lead to overpressure or voids between the prepreg layers, resulting in uneven stress distribution in composite material components, which in turn reduces their mechanical properties. Summary of the Invention

[0005] To address the issue of pressure fluctuations during composite prepreg winding, ensure stable control of the radial positive pressure applied by the hot press roller to the prepreg along the mandrel, improve the accuracy and stability of pressure transmission in composite prepreg winding machines, and mitigate pressure transmission hysteresis and fluctuations, this invention proposes a composite part winding pressure control method and control system based on a high-gain observer.

[0006] To achieve the above objectives, the present invention provides the following technical solution.

[0007] A composite material part winding pressure control system, comprising:

[0008] Four-bar linkage;

[0009] Cylinder; the cylinder applies a positive pressure along the radial direction of the mandrel to the prepreg tape via a four-bar linkage mechanism;

[0010] A proportional valve, connected to the cylinder, is used to control the gas flow rate in the cylinder.

[0011] Pressure sensor, used to acquire the winding pressure signal of prepreg tape;

[0012] Using an industrial control computer, analyze the statics and dynamics of a four-bar linkage to determine the quantitative relationship between the error and hysteresis effects of friction between the mechanisms on pressure output;

[0013] A three-dimensional simulation platform is used to optimize the deformation and dynamic load of a four-bar linkage based on the quantitative relationship between the error and hysteresis effect of friction between mechanisms on pressure output.

[0014] The industrial control computer is used to derive the dynamic model of the pressure control system based on the cylinder piston pressure balance and the ideal gas law using the Laplace transform, and establish the dynamic model of the pressure control system. The industrial control computer is also used to compare the detected value of the winding pressure signal with the set value, determine the control input value through the sliding mode control method based on the high-gain observer, and send it to the proportional valve to control the valve port until the detected value of the winding pressure signal is consistent with the set value.

[0015] Preferably, the four-bar linkage includes:

[0016] The four-bar linkage includes a drive shaft, two rotating connecting plates, and four connecting rods; the drive shaft passes through one of the rotating connecting plates and is connected to the push rod end of the cylinder via a coupling; the rotating connecting plate is fixedly connected to the drive shaft; the outer end face of the other rotating connecting plate is fixedly connected to one end of the hot press roller bracket.

[0017] Sleeves are fixedly provided on the two opposite end faces of the two rotating connecting plates, and the drive shaft passes through the two sleeves in sequence and slides with the sleeves through linear bearings;

[0018] The two connecting rods are hinged together at their midpoints to form an X-shape; wherein, one end of the two non-hinged connecting rods is hinged together, and the other end is respectively hinged to two rotating connecting plates.

[0019] A method for controlling winding pressure in a composite material part winding pressure control system includes the following steps:

[0020] The four-bar linkage was determined as the pressure transmission mechanism for applying positive pressure along the radial direction of the mandrel. Static and dynamic analyses were performed on the pressure transmission mechanism to determine the quantitative relationship between the error and hysteresis effects of friction between the mechanisms on the pressure output.

[0021] Based on the quantitative relationship between the error and hysteresis effect of inter-mechanism friction on pressure output, a three-dimensional simulation platform is used to optimize the deformation and dynamic load of the four-bar linkage, and the optimized four-bar linkage is obtained.

[0022] Based on the cylinder piston pressure balance and the ideal gas law, the dynamic model of the pressure control system was derived using the Laplace transform, and the dynamic model of the pressure control system was established.

[0023] The industrial control computer compares the detected value of the winding pressure signal with the set value, determines the control input value using a sliding mode control method based on a high-gain observer, and sends it to the proportional valve to control the valve port until the detected value of the winding pressure signal matches the set value.

[0024] Preferably, the static and dynamic analysis of the pressure transmission mechanism to determine the quantitative relationship between the error and hysteresis effects of inter-mechanical friction on pressure output includes the following steps:

[0025] A static analysis of the pressure transmission mechanism was performed, and the equilibrium equations were established as follows:

[0026]

[0027] In the formula, Fz It is the supporting force of the linear bearing. It is the tangential force between the core mold and the hot press roller. The drive shaft is subjected to torque. It is the weight of the hot press roller itself. It is the weight of the linear bearing itself. It is the weight of the coupling itself. L This is the distance from the center of the coupling to the center of the hot press roller. L 1 represents the distance from the linear bearing to the center of the hot press roller. L 2 represents the distance from the linear bearing to the coupling. r The radius of the hot press roller;

[0028] Therefore, the winding normal force and frictional force are obtained from the following formula:

[0029]

[0030] In the formula, It is the entanglement positive pressure. It is friction. It is the coefficient of friction. The winding pressure will cause hysteresis and fluctuation as the coefficient of friction and tangential force change. Due to the existence of friction between the linear bearing and the push rod, there will be a certain error and hysteresis between the pressure output value and the set value.

[0031] Preferably, the optimization of the deformation and dynamic load of the four-bar linkage using a three-dimensional simulation platform includes the following steps:

[0032] Static and modal harmonic response analyses were performed on the 3D model using a simulation platform; a hexahedral free mesh generation method was adopted to control the global dimensions, and the mesh was refined in local contact areas;

[0033] Modal analysis is performed by constraining the degrees of freedom of the three-dimensional structural components and applying boundary conditions.

[0034] A variable frequency load is applied radially to the hot press roller, and the weakest link of the mechanism is selected as the harmonic response test point. The harmonic response is analyzed by modal superposition method.

[0035] Through simulation analysis of the four-bar linkage, the stress-strain values, overall deformation, and dynamic load-bearing capacity of the mechanism are obtained.

[0036] Preferably, the construction of the dynamic model of the pressure control system includes the following steps:

[0037] The theoretical output thrust of the cylinder piston is calculated by the following formula:

[0038]

[0039] in, It is piston thrust. It is the area of ​​the right chamber of the cylinder. It is the pressure in the right chamber of the cylinder. It is the area of ​​the left chamber of the cylinder. It is the pressure in the left chamber of the cylinder;

[0040] Considering the inertial forces of the moving parts of the cylinder and the mechanical friction between the cylinder wall and the piston sealing ring, the cylinder mechanical equilibrium equations are established according to Newton's second law:

[0041]

[0042] In the formula, This represents the total frictional force inside the cylinder. For the total mass of the moving parts, For piston displacement, The viscous damping coefficients of the load and piston;

[0043] The nonlinear equation for the flow rate of an ideal gas through a valve port is derived as follows:

[0044]

[0045] in, and The proportional valve provides input and output air pressure. This refers to the proportional valve core displacement. The proportional valve orifice area gradient, R Let be the ideal gas constant. TAbsolute temperature;

[0046] The transfer function of the winding pressure control system is obtained through Laplace transform and corresponding equation derivation, thus completing the construction of the system dynamic model:

[0047]

[0048] In the formula, m 1 represents the mass of the gas in the right chamber. k The adiabatic index of the gas. m For the total mass of the moving parts, V 1 represents the gas volume in the right chamber. s This is the argument of the transfer function.

[0049] Preferably, the high-gain observer-based sliding mode control method includes the following steps:

[0050] The high-gain observer asymptotically estimates the state based on the measurement results and is designed separately from the state feedback controller; the state feedback controller is shown in the following equation:

[0051]

[0052] in, To output winding pressure, The rate of change of force is The first derivative of cannot be measured directly; This refers to the second derivative of force; a and b are positive real coefficients. To control the input gain coefficient; For system control input; Digital-to-analog signal conversion gain; Analog-to-digital signal conversion gain; Friction gain; The system's inherent gain coefficient; The system's natural vibration frequency; The system's inherent frequency; Damping coefficient;

[0053] The above equations are transformed into the following state-space equations:

[0054]

[0055] Where y is the dependent variable in the state-space equation; for a second-order system, only the output... Designing a controller is very complex, therefore, we added... ,because Since it cannot be measured, the controller is designed using the following observer estimation:

[0056]

[0057] in, and It is a positive real number; It is a coefficient, and ; for Observed values; for The first derivative of the observed value; for Observed values; for The first derivative of the observed value;

[0058] assumed The equation is then transformed into:

[0059]

[0060] Define the observation error matrix as , This is the actual value. For the observed values, Based on the above equation, we obtain:

[0061]

[0062] in for The observation error value; for The first derivative of the observation error value; rate of change of force The observation error;

[0063] Further deduction:

[0064]

[0065] Where s are Laplace complex parameters; I is the identity matrix; A is the state-space matrix; p are the poles of the system transfer function; and the following settings are applied. and The value of makes the matrix It satisfies the Hurwitz stability criterion; the characteristic equation of the matrix is ​​denoted as:

[0066]

[0067] in, Solving the above equations simultaneously, we can deduce:

[0068]

[0069] For this equation, the sliding mode function is designed as follows:

[0070]

[0071] Where: s is the sliding mode function; This is an estimate of the sliding mode function; The coefficient of performance is the synovial membrane. It is the generalized error vector; The derivative value of the generalized error vector; This is an estimate of the generalized error vector; Let be the estimated value of the derivative of the generalized error vector; adding the equivalent and robust terms of the sliding mode control law, and substituting the system observation data and derivative observations, we obtain the sliding mode control law based on the high-gain observer as follows:

[0072]

[0073] in, The ideal position signal function; The first derivative of the ideal position signal function; The second derivative of the ideal position signal function; It is the first derivative of the estimate of the generalized error vector; Here are the coefficients for the approach law;

[0074] Design a Lyapunov function for sliding mode control to prove the stability of the closed-loop function; the basic formula of the Lyapunov function is shown below:

[0075]

[0076] Let s represent the Lyapunov candidate function; s is a complex parameter variable; The first derivative of the complex parameter variable; The second derivative of the error vector;

[0077] According to the sliding mode function, since

[0078]

[0079] get:

[0080]

[0081]

[0082]

[0083]

[0084] in, 、 、 、 、 The relationship is given by the following formula:

[0085]

[0086] and, The calculation formula is obtained from the sliding mode function and the above relationship:

[0087]

[0088] in, ;

[0089] because:

[0090]

[0091] Based on the above inequality, we can obtain:

[0092]

[0093] Therefore, the Lyapunov function of the closed-loop system is as follows:

[0094]

[0095] in, It is a transpose operator; The value of the open-loop Lyapunov function; The first derivative of the open-loop Lyapunov function value;

[0096]

[0097] Determine convergence and divergence to verify the rationality of the design; obtain exponential convergence based on the equations:

[0098]

[0099] in, and For positive constants; t is the time variable; This is the initial time; It is a constant; as verified, It converges exponentially; since the observer converges exponentially, then:

[0100]

[0101] in, , , yes K types of functions; according to the theorem, for ， ,inequality The simplified formula is as follows:

[0102]

[0103] in, It is an arbitrary constant, and according to the equation:

[0104]

[0105] in, , The coefficients are intermediate variables. ,because When t approaches infinity, ,therefore, It is exponentially convergent, and the convergence accuracy depends on The controller is reasonably designed.

[0106] The beneficial effects of this invention are:

[0107] (1) The present invention mainly improves the existing pressure transmission mechanism in the composite material winding molding process, designs a new control system, and establishes a composite material part winding pressure control method based on a high-gain observer sliding mode control strategy. This control method can provide appropriate positive pressure during the prepreg winding process, reduce adverse effects such as friction and vibration, and improve pressure transmission hysteresis and fluctuation problems.

[0108] (2) The control method in this invention is based on the dynamic and static analysis of the novel winding pressure control system. It mainly determines the quantitative relationship between the error and hysteresis effect of inter-mechanical friction on pressure output. Based on the cylinder piston pressure balance and the ideal gas state equation, the dynamic model of the pressure control system is derived by using the Laplace transform. This method has universality for similar problems.

[0109] (3) Based on the state feedback of the high-gain observer, the present invention builds a closed-loop control system and adds a disturbance element to improve the spatial state equation of the system and obtain a state feedback controller. On this basis, sliding mode control is added to the controller and observation compensation is introduced to obtain the feedback controller gain, which greatly reduces the influence of external disturbance factors and improves the control performance. Attached Figure Description

[0110] Figure 1 This is a structural diagram of a new type of linkage mechanism pressure control system.

[0111] Figure 2 Optimization design diagram for the winding pressure control method system;

[0112] Figure 3 This is a detailed structural diagram of a four-bar linkage. Detailed Implementation

[0113] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0114] Example 1

[0115] This invention proposes a pressure control system based on a novel linkage mechanism, such as... Figure 1-3 As shown.

[0116] This invention relates to a method for controlling the winding pressure of composite material parts based on a high-gain observer sliding mode control strategy. It involves a novel linkage mechanism pressure transmission structure, mainly comprising: an industrial control computer, a pressure gauge, a cylinder, a four-bar linkage, a proportional valve, a solenoid directional valve, and a pressure sensor. The industrial control computer, acting as the controller of the pressure control system, processes the collected winding pressure feedback signal and sends a control signal to the proportional valve. The proportional valve monitors the winding pressure in real time by controlling the gas flow into the cylinder. The proportional valve collects the power signal of the hot-pressing roller pressure. The gauge compares the detected value with the set value using a built-in algorithm, outputs a control signal, and adjusts the proportional valve orifice to ensure consistency between the detected and set values ​​of the hot-pressing roller pressure. The pressure controller portion of the industrial control computer is based on a high-gain observer sliding mode control strategy, combined with observation compensation. Based on the designed controller gain and operational formula, the system is input into the industrial control computer according to the industrial control computer's language to perform closed-loop control, thereby suppressing friction and other external interference factors, effectively reducing system chattering, and improving the speed, accuracy, stability, and sensitivity of pressure control.

[0117] A method for controlling the winding pressure of composite material parts using a pressure control system, such as Figure 2 As shown, it includes the following steps:

[0118] The four-bar linkage 4 is determined as the pressure transmission mechanism that applies positive pressure along the radial direction of the mandrel. Static and dynamic analyses are performed on the pressure transmission mechanism to determine the quantitative relationship between the error and hysteresis effects of friction between the mechanisms on the pressure output.

[0119] Based on the quantitative relationship between the error and hysteresis effect of inter-mechanism friction on pressure output, a three-dimensional simulation platform is used to optimize the deformation and dynamic load of the four-bar linkage, and the optimized four-bar linkage is obtained.

[0120] Based on the cylinder piston pressure balance and the ideal gas law, the dynamic model of the pressure control system was derived using the Laplace transform, and the dynamic model of the pressure control system was established.

[0121] The industrial control computer compares the detected value of the winding pressure signal with the set value, determines the control input value using a sliding mode control method based on a high-gain observer, and sends it to the proportional valve to control the valve port until the detected value of the winding pressure signal matches the set value.

[0122] Specifically:

[0123] (1) Four-bar linkage pressure transmission system

[0124] like Figure 3 As shown, cylinder 2 is supported by cylinder bracket 1, hot press roller 6 is mounted by rotating hot press roller bracket, and scraper 5 is mounted on hot press roller bracket.

[0125] The four-bar linkage includes a drive shaft, two rotating connecting plates 401 and four connecting rods 402; the drive shaft passes through one rotating connecting plate 401 and is connected to the push rod end of the cylinder 2 via a coupling 3, and the rotating connecting plate 401 is fixedly connected to the drive shaft; the outer end face of the other rotating connecting plate 401 is fixedly connected to one end of the hot press roller bracket.

[0126] Sleeves are fixedly installed on the two opposite end faces of the two rotating connecting plates 401. The drive shaft passes through the two sleeves in sequence and slides with the sleeves through linear bearings.

[0127] The two connecting rods 402 are hinged to each other at the middle to form an X state; among them, the two connecting rods 402 that are not hinged to each other have one end hinged to each other, and the other end is respectively hinged to two rotating connecting plates 401.

[0128] Four connecting rods 402 are connected in pairs at their midpoints to form an X-shape; among them, the two non-connected connecting rods 402 are connected at one end to each other, and the other end is connected to two rotating connecting plates 401 respectively. All hinge points are connected by hinge bolts 403.

[0129] A static analysis of the pressure transmission mechanism was performed, and the equilibrium equations were established as follows:

[0130]

[0131] In the formula, Fz It is the supporting force of the linear bearing. It is the tangential force between the core mold and the hot press roller. The drive shaft is subjected to torque. It is the weight of the hot press roller itself. It is the weight of the linear bearing itself. It is the weight of the coupling itself. L This is the distance from the center of the coupling to the center of the hot press roller. L 1 represents the distance from the linear bearing to the center of the hot press roller. L 2 represents the distance from the linear bearing to the coupling. r The radius of the hot press roller;

[0132] Therefore, the winding normal force and frictional force are obtained from the following formula:

[0133]

[0134] In the formula, It is the entanglement positive pressure. It is friction. It is the coefficient of friction. The winding pressure will cause hysteresis and fluctuation as the coefficient of friction and tangential force change. Due to the existence of friction between the linear bearing and the push rod, there will be a certain error and hysteresis between the pressure output value and the set value.

[0135] A novel four-bar linkage mechanism was used as the pressure transmission unit to reduce the impact of friction on pressure control accuracy and stability. Static and modal harmonic response analyses were performed on the 3D model using a simulation platform. A hexahedral free mesh generation method was employed to control the global dimensions, while the mesh was refined in local contact areas. Degrees of freedom constraints were imposed on the 3D structural components, and boundary conditions were applied for modal analysis. A variable-frequency load was applied radially to the hot-pressing roller, and the weakest link in the mechanism was selected as a harmonic response test point for harmonic response analysis using the modal superposition method. Through simulation analysis of the novel linkage mechanism, the stress-strain values, overall deformation, and dynamic load-bearing capacity of the mechanism were obtained.

[0136] (2) Establish a dynamic model of the winding pressure control system.

[0137] The theoretical output thrust of the cylinder piston is calculated by the following formula:

[0138]

[0139] in, It is piston thrust. It is the area of ​​the right chamber of the cylinder. It is the pressure in the right chamber of the cylinder. It is the area of ​​the left chamber of the cylinder. It is the pressure in the left chamber of the cylinder;

[0140] Considering the inertial forces of the moving parts of the cylinder and the mechanical friction between the cylinder wall and the piston sealing ring, the cylinder mechanical equilibrium equations are established according to Newton's second law:

[0141]

[0142] In the formula, This represents the total frictional force inside the cylinder. For the total mass of the moving parts, For piston displacement, The viscous damping coefficients of the load and piston;

[0143] The nonlinear equation for the flow rate of an ideal gas through a valve port is derived as follows:

[0144]

[0145] in, and The proportional valve provides input and output air pressure. This refers to the proportional valve core displacement. The proportional valve orifice area gradient, R Let be the ideal gas constant. T Absolute temperature;

[0146] The transfer function of the winding pressure control system is obtained through Laplace transform and corresponding equation derivation, thus completing the construction of the system dynamic model:

[0147]

[0148] In the formula, m 1 represents the mass of the gas in the right chamber. k The adiabatic index of the gas. m For the total mass of the moving parts, V 1 represents the gas volume in the right chamber. s This is the argument of the transfer function.

[0149] (3) Design of a high-gain observer-based mode control strategy

[0150] The high-gain observer asymptotically estimates the state based on the measurement results and is designed separately from the state feedback controller; the state feedback controller is shown in the following equation:

[0151]

[0152] in, To output winding pressure, The rate of change of force is The first derivative of cannot be measured directly; This refers to the second derivative of force; a and b are positive real coefficients. To control the input gain coefficient; For system control input; Digital-to-analog signal conversion gain; Analog-to-digital signal conversion gain; Friction gain; The system's inherent gain coefficient; The system's natural vibration frequency; The system's inherent frequency; Damping coefficient;

[0153] The above equations are transformed into the following state-space equations:

[0154]

[0155] Where y is the dependent variable in the state-space equation; for a second-order system, only the output... Designing a controller is very complex, therefore, we added... ,because Since it cannot be measured, the controller is designed using the following observer estimation:

[0156]

[0157] in, and It is a positive real number; It is a coefficient, and ; for Observed values; for The first derivative of the observed value; for Observed values; for The first derivative of the observed value;

[0158] assumed The equation is then transformed into:

[0159]

[0160] Define the observation error matrix as , This is the actual value. For the observed values, Based on the above equation, we obtain:

[0161]

[0162] in for The observation error value; for The first derivative of the observation error value; rate of change of force The observation error;

[0163] Further deduction:

[0164]

[0165] Where s are Laplace complex parameters; I is the identity matrix; A is the state-space matrix; p are the poles of the system transfer function; and the following settings are applied. and The value of makes the matrix It satisfies the Hurwitz stability criterion; the characteristic equation of the matrix is ​​denoted as:

[0166]

[0167] in, Solving the above equations simultaneously, we can deduce:

[0168]

[0169] For this equation, the sliding mode function is designed as follows:

[0170]

[0171] Where: s is the sliding mode function; This is an estimate of the sliding mode function; The coefficient of performance is the synovial membrane. It is the generalized error vector; The derivative value of the generalized error vector; This is an estimate of the generalized error vector; Let be the estimated value of the derivative of the generalized error vector; adding the equivalent and robust terms of the sliding mode control law, and substituting the system observation data and derivative observations, we obtain the sliding mode control law based on the high-gain observer as follows:

[0172]

[0173] in, The ideal position signal function; The first derivative of the ideal position signal function; The second derivative of the ideal position signal function; It is the first derivative of the estimate of the generalized error vector; Here are the coefficients for the approach law;

[0174] Design a Lyapunov function for sliding mode control to prove the stability of the closed-loop function; the basic formula of the Lyapunov function is shown below:

[0175]

[0176] Let s represent the Lyapunov candidate function; s is a complex parameter variable; The first derivative of the complex parameter variable; The second derivative of the error vector;

[0177] According to the sliding mode function, since

[0178]

[0179] get:

[0180]

[0181]

[0182]

[0183]

[0184] in, 、 、 、 、 The relationship is given by the following formula:

[0185]

[0186] and, The calculation formula is obtained from the sliding mode function and the above relationship:

[0187]

[0188] in, ;

[0189] because:

[0190]

[0191] Based on the above inequality, we can obtain:

[0192]

[0193] Therefore, the Lyapunov function of the closed-loop system is as follows:

[0194]

[0195] in, It is a transpose operator; The value of the open-loop Lyapunov function; The first derivative of the open-loop Lyapunov function value;

[0196]

[0197] Determine convergence and divergence to verify the rationality of the design; obtain exponential convergence based on the equations:

[0198]

[0199] in, and For positive constants; t is the time variable; This is the initial time; It is a constant; as verified, It converges exponentially; since the observer converges exponentially, then:

[0200]

[0201] in, , , yes K types of functions; according to the theorem, for ， ,inequality The simplified formula is as follows:

[0202]

[0203] in, It is an arbitrary constant, and according to the equation:

[0204]

[0205] in, , The coefficients are intermediate variables. ,because ,when t When it approaches infinity, ,therefore, It is exponentially convergent, and the convergence accuracy depends on The controller is reasonably designed.

[0206] In this embodiment, as Figure 2As shown, a simulation experiment analysis of the pressure control system is presented. To verify the effectiveness of the algorithm, a hardware-in-the-loop (HIL) simulation experiment was conducted using the mathematical model of the winding pressure control system as the controlled object, employing a square wave signal with an amplitude of 500N for positioning control. From the simulation and experimental results of the traditional winding pressure control system, it can be seen that the pressure exhibits significant time delay and fluctuation.

[0207] For a novel linkage mechanism pressure transmission system, a sliding mode control strategy based on a high-gain observer is presented. Simulation results of the square wave response of the system's PID algorithm and the high-gain observer sliding mode control strategy are analyzed, yielding control errors of 18.58 N and 9.56 N, respectively. Clearly, the high-gain observer sliding mode control strategy exhibits strong robustness and effectively reduces control error. The algorithm meets the requirements of low control input chattering and low control error in tension control systems.

[0208] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A composite material part winding pressure control system, characterized in that, include: Four-bar linkage; Cylinder; the cylinder applies a positive pressure along the radial direction of the mandrel to the prepreg tape via a four-bar linkage mechanism; A proportional valve, connected to the cylinder, is used to control the gas flow rate in the cylinder. Pressure sensor, used to acquire the winding pressure signal of prepreg tape; Using an industrial control computer, analyze the statics and dynamics of a four-bar linkage to determine the quantitative relationship between the error and hysteresis effects of friction between the mechanisms on pressure output; A three-dimensional simulation platform is used to optimize the deformation and dynamic load of a four-bar linkage based on the quantitative relationship between the error and hysteresis effect of friction between mechanisms on pressure output. The industrial control computer is used to derive the dynamic model of the pressure control system based on the cylinder piston pressure balance and the ideal gas law using the Laplace transform, and establish the dynamic model of the pressure control system. The industrial control computer is also used to compare the detected value of the winding pressure signal with the set value, determine the control input value through the sliding mode control method based on the high-gain observer, and send it to the proportional valve to control the valve port until the detected value of the winding pressure signal is consistent with the set value.

2. The composite material part winding pressure control system according to claim 1, characterized in that, The four-bar linkage includes a drive shaft, two rotating connecting plates (401) and four connecting rods (402); the drive shaft passes through one of the rotating connecting plates (401) and is connected to the push rod end of the cylinder via a coupling; the rotating connecting plate (401) is fixedly connected to the drive shaft; the outer end face of the other rotating connecting plate (401) is fixedly connected to one end of the hot press roller bracket. Sleeves are fixedly provided on the two opposite end faces of the two rotating connecting plates (401), and the drive shaft passes through the two sleeves in sequence and slides with the sleeves through a linear bearing; The two connecting rods (402) are hinged to each other at the middle to form an X state; wherein, one end of the two connecting rods (402) that are not hinged to each other is hinged to each other, and the other end is respectively hinged to two rotating connecting plates (401).

3. A method for controlling winding pressure using the composite material part winding pressure control system as described in claim 2, characterized in that, Includes the following steps: The four-bar linkage was determined as the pressure transmission mechanism for applying positive pressure along the radial direction of the mandrel. Static and dynamic analyses were performed on the pressure transmission mechanism to determine the quantitative relationship between the error and hysteresis effects of friction between the mechanisms on the pressure output. Based on the quantitative relationship between the error and hysteresis effect of inter-mechanism friction on pressure output, a three-dimensional simulation platform is used to optimize the deformation and dynamic load of the four-bar linkage, and the optimized four-bar linkage is obtained. Based on the cylinder piston pressure balance and the ideal gas law, the dynamic model of the pressure control system was derived using the Laplace transform, and the dynamic model of the pressure control system was established. The industrial control computer compares the detected value of the winding pressure signal with the set value, determines the control input value using a sliding mode control method based on a high-gain observer, and sends it to the proportional valve to control the valve port until the detected value of the winding pressure signal matches the set value.

4. The method according to claim 3, characterized in that, The static and dynamic analysis of the pressure transmission mechanism to determine the quantitative relationship between the error and hysteresis effects of inter-mechanical friction on pressure output includes the following steps: A static analysis of the pressure transmission mechanism was performed, and the equilibrium equations were established as follows: In the formula, Fz It is the supporting force of the linear bearing. It is the tangential force between the core mold and the hot press roller. The drive shaft is subjected to torque. It is the weight of the hot press roller itself. It is the weight of the linear bearing itself. It is the weight of the coupling itself. L This is the distance from the center of the coupling to the center of the hot press roller. L 1 represents the distance from the linear bearing to the center of the hot press roller. L 2 represents the distance from the linear bearing to the coupling. r The radius of the hot press roller; Therefore, the winding normal force and frictional force are obtained from the following formula: In the formula, It is the entanglement positive pressure. It is friction. It is the coefficient of friction. The winding pressure will cause hysteresis and fluctuation as the coefficient of friction and tangential force change. Due to the existence of friction between the linear bearing and the push rod, there will be a certain error and hysteresis between the pressure output value and the set value.

5. The method according to claim 3, characterized in that, The optimization of the deformation and dynamic load of the four-bar linkage using a three-dimensional simulation platform includes the following steps: Static and modal harmonic response analyses were performed on the 3D model using a simulation platform; a hexahedral free mesh generation method was adopted to control the global dimensions, and the mesh was refined in local contact areas; Modal analysis is performed by constraining the degrees of freedom of the three-dimensional structural components and applying boundary conditions. A variable frequency load is applied radially to the hot press roller, and the weakest link of the mechanism is selected as the harmonic response test point. The harmonic response is analyzed by modal superposition method. Through simulation analysis of the four-bar linkage, the stress-strain values, overall deformation, and dynamic load-bearing capacity of the mechanism are obtained.

6. The method according to claim 3, characterized in that, The construction of the dynamic model of the pressure control system includes the following steps: The theoretical output thrust of the cylinder piston is calculated by the following formula: in, It is piston thrust. It is the area of ​​the right chamber of the cylinder. It is the pressure in the right chamber of the cylinder. It is the area of ​​the left chamber of the cylinder. It is the pressure in the left chamber of the cylinder; Considering the inertial forces of the moving parts of the cylinder and the mechanical friction between the cylinder wall and the piston sealing ring, the cylinder mechanical equilibrium equations are established according to Newton's second law: In the formula, This represents the total frictional force inside the cylinder. For the total mass of the moving parts, For piston displacement, The viscous damping coefficients of the load and piston; The nonlinear equation for the flow rate of an ideal gas through a valve port is derived as follows: in, and The proportional valve provides input and output air pressure. This refers to the proportional valve core displacement. The proportional valve orifice area gradient, R Let be the ideal gas constant. T Absolute temperature; The transfer function of the winding pressure control system is obtained through Laplace transform and corresponding equation derivation, thus completing the construction of the system dynamic model: In the formula, m 1 represents the mass of the gas in the right chamber. k The adiabatic index of the gas. m For the total mass of the moving parts, V 1 represents the gas volume in the right chamber. s This is the argument of the transfer function.

7. The method according to claim 3, characterized in that, The high-gain observer-based sliding mode control method includes the following steps: The high-gain observer asymptotically estimates the state based on the measurement results and is designed separately from the state feedback controller; the state feedback controller is shown in the following equation: in, To output winding pressure, The rate of change of force is The first derivative of cannot be measured directly; This refers to the second derivative of force; a and b are positive real coefficients. To control the input gain coefficient; For system control input; Digital-to-analog signal conversion gain; Analog-to-digital signal conversion gain; Friction gain; The system's inherent gain coefficient; The system's natural vibration frequency; The system's inherent frequency; Damping coefficient; The above equations are transformed into the following state-space equations: Where y is the dependent variable in the state-space equation; for a second-order system, only the output... Designing a controller is very complex, therefore, we added... ,because Since it cannot be measured, the controller is designed using the following observer estimation: in, and It is a positive real number; It is a coefficient, and ; for Observed values; for The first derivative of the observed value; for Observed values; for The first derivative of the observed value; assumed The equation is then transformed into: Define the observation error matrix as , This is the actual value. For the observed values, Based on the above equation, we obtain: in for The observation error value; for The first derivative of the observation error value; rate of change of force The observation error; Further deduction: Where s are Laplace complex parameters; I is the identity matrix; A is the state-space matrix; p are the poles of the system transfer function; and the following settings are applied. and The value of makes the matrix It satisfies the Hurwitz stability criterion; the characteristic equation of the matrix is ​​denoted as: in, Solving the above equations simultaneously, we can deduce: For this equation, the sliding mode function is designed as follows: Where: s is the sliding mode function; This is an estimate of the sliding mode function; The sliding mode coefficient; It is the generalized error vector; The derivative value of the generalized error vector; This is an estimate of the generalized error vector; Let be the estimated value of the derivative of the generalized error vector; adding the equivalent and robust terms of the sliding mode control law, and substituting the system observation data and derivative observations, we obtain the sliding mode control law based on the high-gain observer as follows: in, The ideal position signal function; The first derivative of the ideal position signal function; The second derivative of the ideal position signal function; It is the first derivative of the estimate of the generalized error vector; Here are the coefficients for the approach law; Design a Lyapunov function for sliding mode control to prove the stability of the closed-loop function; the basic formula of the Lyapunov function is shown below: Let s represent the Lyapunov candidate function; s is a complex parameter variable; The first derivative of the complex parameter variable; The second derivative of the error vector; According to the sliding mode function, since get: in, 、 、 、 、 The relationship is given by the following formula: and, The calculation formula is obtained from the sliding mode function and the above relationship: in, ; because: Based on the above inequality, we can obtain: Therefore, the Lyapunov function of the closed-loop system is as follows: in, It is a transpose operator; The value of the open-loop Lyapunov function; The first derivative of the open-loop Lyapunov function value; Determine convergence and divergence to verify the rationality of the design; obtain exponential convergence based on the equations: in, and For positive constants; t is the time variable; This is the initial time; It is a constant; as verified, It converges exponentially; since the observer converges exponentially, then: in, , , yes K types of functions; according to the theorem, for ， ,inequality The simplified formula is as follows: in, It is an arbitrary constant, and according to the equation: in, , The coefficients are intermediate variables. ,because ,when t When it approaches infinity, ,therefore, It is exponentially convergent, and the convergence accuracy depends on The controller is reasonably designed.

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