Method and system for dynamically adjusting punch pressure of tablet press

Abstract

The invention discloses a method and system for dynamically adjusting punch pressure of a tablet press, and belongs to the field of tablet presses. In order to solve the problems that existing pressure adjustment depends on manpower, consumed time is long, and the pressing effect is poor, the method for dynamically adjusting the punch pressure of the tablet press comprises the steps that a dynamic response model of the punch pressure in the tablet press is established, and a closed-loop period parameter, a proportion parameter, an integral parameter and a differential parameter are determined; punch pressure data are obtained in real time, the error between the actual pressure and the target pressure of the impulsive force pressure head is calculated, and the error is input into a PID algorithm to obtain a control signal; and adjusting the punch according to the control signal. According to the method, the basis is provided for the subsequent PID algorithm by constructing the dynamic response model of the punch pressure, the P, I and D parameters are dynamically adjusted through the PID algorithm so that precise control over the punch pressure can be achieved, operation is easy, high-efficiency and high-precision dynamic adjustment of the punch pressure can be achieved without tedious programs, and the stability and the consistency of the tablet quality are guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of tablet presses, and more specifically, relates to a method and system for dynamically adjusting punch pressure of a tablet press. Background Art

[0002] Tablet press is a machine that places granular or powdered materials in a die hole and presses them into tablets by a punch. The application scope of tablet press is very wide. It is not only limited to the tablet process research in the pharmaceutical industry, but also can be used to press health food, veterinary tablets, chemical tablets and food tablets. The high-speed rotary tablet press is mainly composed of three parts: upper punch, middle die and lower punch. These parts are connected as a whole, and 40 to 70 pairs of dies are evenly arranged around them. These dies are distributed on the edge of the turntable. The tails of the upper and lower punches are embedded in the fixed curved guide rails. When the turntable rotates, the upper and lower punches move up and down along the curved guide rails to achieve the purpose of tableting. In the prior art, tablet presses usually need to perform pre-compression tests before producing tablets to determine the appropriate pressure parameters before starting formal production. The adjustment of the punch pressure usually depends on manually setting fixed parameters. However, during the production process, if the pressure exceeds the preset range, it is necessary to stop the machine for manual intervention. This method is difficult to cope with changes in production conditions, resulting in time-consuming and labor-intensive pre-compression adjustments. When the tablet quality is unstable during the compression process, it is necessary to stop the process and readjust the height of each punch to adjust the pressure.

[0003] Corresponding improvements have also been made to the above problems, such as Chinese patent application number CN202010785028.6, which was published on November 6, 2020. The patent discloses a method, device, storage medium and electronic device for controlling the punch pressure of a tablet press. Among them, the method for controlling the punch pressure of a tablet press includes: obtaining the punch pressure signal of each punch position of the tablet press, and detecting whether the tablet press has completed the action of kicking out the waste tablets at each punch position; if the valid data of the punch pressure signal of a punch position is within a preset reasonable range, and the action of kicking out the waste tablets is completed at the punch position, it is considered that the tablet press has an error at the punch position; real-time statistics of the errors of the tablet press at each punch position, if the number of consecutive errors at the punch position reaches a preset number value, the punch pressure of the tablet press is adjusted to adjust the punch pressure back to the preset punch pressure value. The disadvantage of this patent is that although it can automatically correct the punch pressure of the tablet press, the procedure is complicated and time-consuming.

[0004] Another example is Chinese patent application number CN202410872948.X, published on July 26, 2024. The patent discloses a load correction method for a multi-point eccentric drive mechanism of a press. The load correction method can detect the load of each stamping point in the multi-point eccentric drive mechanism in real time when the high-speed press is in use. When the load of a certain stamping point exceeds the limit, it can automatically stop and remind the staff, and each stamping point can be adjusted separately. The load of all stamping points of the multi-point eccentric drive mechanism remains consistent, ensuring that the high-speed press is always in reasonable and safe conditions of use. The shortcomings of this patent are: the detection process is cumbersome and the cost is high. Summary of the invention

[0005] 1. Problems to be solved

[0006] In view of the problem that the existing pressure regulation relies on manual labor, is time-consuming and has poor pressing effect, the present invention provides a method and system for dynamically adjusting the punch pressure of a tablet press. The method of the present invention provides a basis for the subsequent PID algorithm by constructing a dynamic response model of the punch pressure, and dynamically adjusts the P, I, and D parameters using the PID algorithm to achieve precise control of the punch pressure. The operation is simple, and high-efficiency and high-precision dynamic regulation of the punch pressure can be achieved without cumbersome procedures, and stability and consistency of tablet quality are guaranteed; the system structure of the present invention is simple, and can realize automatic adjustment of the punch pressure so that it can be stably maintained within a preset pressure value.

[0007] 2. Technical solution

[0008] To solve the above problems, the present invention adopts the following technical solutions.

[0009] A method for dynamically adjusting punch pressure of a tablet press comprises the following steps:

[0010] S1: Establish a dynamic response model of the punch pressure in the tablet press, and determine the closed-loop cycle parameter, proportional parameter, integral parameter and differential parameter according to the dynamic response model; the dynamic response model is:

[0011]

[0012] Where K is the system gain, τ is the time constant, ζ is the damping ratio, and s is the complex frequency variable in the Laplace transform;

[0013] S2: Obtain punch pressure data in real time, calculate the error between the actual pressure of the punch and the target pressure, and input the error into the PID algorithm to obtain a control signal;

[0014] S3: adjusting the punch according to the control signal output by the PID algorithm, wherein the adjustment includes adjusting the height of the punch and / or the pressure of the punch.

[0015] Furthermore, the establishment of the dynamic response model in step S1 includes the following steps:

[0016] S11: Data collection and preprocessing: real-time collection of punch pressure data and denoising and removal of outliers on the punch pressure data;

[0017] S12: Obtaining pressure response data: by setting different excitation signals, obtaining the pressure change data of each excitation signal within a set time;

[0018] S13: obtaining a dynamic response model according to the pressure change data, and obtaining specific values ​​of parameters in the dynamic response model through parameter identification;

[0019] S14: Determine closed-loop cycle parameters, proportional parameters, integral parameters and differential parameters according to the dynamic response model, and construct a PID algorithm.

[0020] Furthermore, after step S13, the step also includes simulating and verifying the dynamic response model: inputting the dynamic response model into a simulation environment, using data that does not participate in the construction of the dynamic response model to verify the dynamic response model, comparing the difference between the output of the dynamic response model and the actual output, if it is lower than or equal to a threshold, the dynamic response model is not adjusted; if it is higher than the threshold, the dynamic response model is adjusted.

[0021] Furthermore, in step S13, the least square method is used to obtain the values ​​of the parameters K, τ, and ζ in the dynamic response model.

[0022] Furthermore, in step S12, the excitation signal is the target pressure value of the punch; and the setting time is 4 to 6 seconds.

[0023] A system adopting the method for dynamically adjusting punch pressure of a tablet press as described in any one of the above items, comprising:

[0024] Pressure sensor: used to collect punch pressure data;

[0025] PID controller: used to calculate the error between the actual pressure of the punch head and the target pressure, and output the control signal;

[0026] Actuator: used to adjust the height and / or pressure of the punch according to the control signal output by the PID controller.

[0027] 3. Beneficial effects

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The present invention establishes a dynamic response model of punch pressure, and uses the dynamic response model to reflect the change law of pressure over time and the relationship between pressure and PID algorithm in real time, so as to provide a basis for the initial parameters in the PID algorithm, so that it can more accurately and efficiently predict and respond to the change of punch pressure, thereby realizing precise adjustment of punch pressure, ensuring the stability and consistency of punch pressure during the processing, and ultimately improving the processing accuracy and surface quality of the product; and it can also be adjusted and optimized according to different control requirements, thereby increasing the adaptability of the whole method; the whole method is simple to operate, and can realize high-efficiency and high-precision dynamic adjustment of punch pressure without complicated procedures;

[0030] (2) In the process of establishing the dynamic response model, the present invention can stimulate the dynamic characteristics of the system by setting different excitation signals, and can more accurately describe the dynamic response process; and different excitation signals can simulate different working conditions, so that the constructed dynamic response model can adapt to different application scenarios and improve its generalization ability; at the same time, the parameter values ​​in the dynamic response model are obtained by parameter identification, and the parameter identification can determine the parameter values ​​of the model based on experimental data and theoretical models, so that the numerical results calculated by the model can best fit the test data, effectively ensuring the accuracy of the model establishment, thereby ensuring the accuracy of the entire process;

[0031] (3) After constructing the dynamic response model, the present invention also includes simulation verification of the constructed dynamic response model. The simulation verification can realize multiple verifications of the dynamic response model in a short time, thereby improving work efficiency; and the simulation verification can be intuitively visualized, which is convenient for the staff to intuitively understand and analyze the characteristics of the dynamic response model; the entire verification method has multiple advantages such as high efficiency, safety, flexibility, repeatability and visualization;

[0032] (4) The system for dynamically adjusting the punch pressure of the present invention is simple in composition. It collects pressure data in real time during the production process and compares it with the preset value. Once it is found that the pressure value deviates from the preset range, the system will automatically adjust the punch height. The punch pressure is dynamically adjusted during the operation of the equipment, which effectively reduces the need to stop the equipment for manual adjustment of the punch pressure, thereby ensuring that the pressure is always maintained at the preset target value, thereby improving the stability and consistency of tablet production. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with specific embodiments and drawings.

[0035] like Figure 1As shown, a method for dynamically adjusting the punch pressure of a tablet press comprises the following steps:

[0036] S1: Establish a dynamic response model of the punch pressure in the tablet press, and determine the closed-loop cycle parameter, proportional parameter, integral parameter and differential parameter according to the dynamic response model; the dynamic response model is:

[0037]

[0038] Wherein, K is the system gain, τ is the time constant, ζ is the damping ratio, and s is the complex frequency variable in Laplace transform; it is explained here that s is a complex frequency variable used to describe the frequency domain characteristics of the system, through which the transfer function G(s) can fully reflect the dynamic characteristics of the system; and in the mathematical model of control systems and signal processing, that is, in this application, s represents the complex frequency variable in Laplace transform, which is usually used to describe the dynamic characteristics of the system; s 2 and s are used to describe the dynamic characteristics of the system, indicating that the system contains second-order and first-order dynamic processes, which are used to describe the inertia and oscillation characteristics of the tablet press system; and the highest order of the transfer function is s 2 It shows that the dynamic behavior of the system includes the response of acceleration and velocity, and it is a second-order system;

[0039] S2: Obtain punch pressure data in real time, calculate the error between the actual pressure of the punch and the target pressure, and input the error into the PID algorithm to obtain a control signal;

[0040] S3: adjusting the punch according to the control signal output by the PID algorithm, wherein the adjustment includes adjusting the height of the punch and / or the pressure of the punch.

[0041] The present invention establishes a dynamic response model of the punch pressure, and uses the dynamic response model to reflect in real time the change pattern of pressure over time and the relationship between the pressure and the PID algorithm, so as to provide a basis for the initial parameters in the PID algorithm, so that it can more accurately and efficiently predict and respond to the change of the punch pressure, thereby realizing precise adjustment of the punch pressure, ensuring the stability and consistency of the punch pressure during the processing, and ultimately improving the processing accuracy and surface quality of the product; and it can also be adjusted and optimized according to different control requirements, thereby increasing the adaptability of the whole method; the whole method is simple to operate, and high-efficiency and high-precision dynamic adjustment of the punch pressure can be achieved without complicated procedures.

[0042] It is explained here that the existing punch pressure basically relies on manual labor, but this adjustment method requires shutdown and cannot achieve a dynamic adjustment process. Therefore, this application combines the dynamic response model with the PID algorithm to automatically adjust the punch pressure so that it can meet the pressure requirements, thereby ensuring the stability and consistency of tablet production; and according to the dynamic response model, the appropriate closed-loop cycle, proportion (P), integral (I), and differential (D) parameters are determined in turn; the closed-loop cycle refers to the time interval for PID control to perform a complete control cycle on the system. This parameter directly affects the stability of PID control. If it is too short, its stability cannot be guaranteed, and if it is too long, resource consumption will be increased; the three parameters of proportion (P), integral (I), and differential (D) enable the constructed PID algorithm to have good performance and control effect, thereby achieving precise control and stability of the entire system.

[0043] And the construction of PID algorithm depends on the dynamic response model, which can more accurately describe the dynamic behavior of the punch of the press, and can more accurately determine the proportional coefficient (Kp), integral coefficient (Ki) and differential coefficient (Kd) in the PID algorithm, so as to achieve more precise control; and the dynamic response model can take into account various uncertainties of the system, so the PID parameters constructed based on the dynamic response model can better adapt to the uncertainties, thereby ensuring the stability and reliability of the whole process. Although the PID algorithm is used for control in the prior art, the parameters in the PID algorithm often depend on the operator's experience and trial and error process, and cannot adapt well to various uncertainties and changing conditions of the system, and it is difficult to ensure the accuracy and stability of the whole process.

[0044] In a specific implementation, the establishment of the dynamic response model in step S1 includes the following steps:

[0045] S11: Data collection and preprocessing: real-time collection of punch pressure data and denoising and removal of outliers on the punch pressure data;

[0046] S12: Obtaining pressure response data: by setting different excitation signals, obtaining the pressure change data of each excitation signal within a set time;

[0047] S13: obtaining a dynamic response model according to the pressure change data, and obtaining specific values ​​of parameters in the dynamic response model through parameter identification;

[0048] S14: Determine closed-loop cycle parameters, proportional parameters, integral parameters and differential parameters according to the dynamic response model, and construct a PID algorithm;

[0049] In the process of establishing the dynamic response model, by setting different excitation signals, the dynamic characteristics of the system can be stimulated, and the dynamic response process can be described more accurately; and different excitation signals can simulate different working conditions, so that the constructed dynamic response model can adapt to different application scenarios and improve its generalization ability; at the same time, the parameter values ​​in the dynamic response model are obtained through parameter identification. Parameter identification can determine the parameter values ​​of the model based on experimental data and theoretical models, so that the numerical results calculated by the model can best fit the test data, effectively ensuring the accuracy of model establishment, thereby ensuring the accuracy of the entire process.

[0050] In a specific embodiment, step S13 further includes simulating and verifying the dynamic response model: inputting the dynamic response model into a simulation environment, using data that does not participate in the construction of the dynamic response model to verify the dynamic response model, comparing the difference between the output of the dynamic response model and the actual output, and if it is lower than or equal to a threshold, not adjusting the dynamic response model; if it is higher than the threshold, adjusting the dynamic response model.

[0051] After constructing the dynamic response model, it also includes simulation verification of the constructed dynamic response model. Simulation verification can realize multiple verifications of the dynamic response model in a short period of time, thereby improving work efficiency; and the simulation verification can be intuitive and visual, which is convenient for staff to intuitively understand and analyze the characteristics of the dynamic response model; the entire verification method has multiple advantages such as high efficiency, safety, flexibility, repeatability and visualization.

[0052] In a specific embodiment, the least square method is used in step S13 to obtain the values ​​of parameters K, τ, and ζ in the dynamic response model; the least square method has a simple principle, simple calculation, and wide applicability, and can perform model verification and optimize parameter estimation. The excitation signal in step S12 is the target pressure value of the punch; and the setting time is 4 to 6s; avoid setting the time too short to reflect the change, and too long to increase resource consumption, so as to meet the balance of accuracy and efficiency.

[0053] A system adopting the method for dynamically adjusting punch pressure of a tablet press as described in any one of the above items, comprising:

[0054] Pressure sensor: used to collect punch pressure data;

[0055] PID controller: used to calculate the error between the actual pressure of the punch and the target pressure, and output a control signal; it is explained here that the construction process of the PID controller is as follows: establish a dynamic response model, and determine the parameters in the dynamic response model, determine the IPD initial parameters according to the determined dynamic response model, apply the PID initial parameters to the PID controller, and then tune and verify it; the tuning verification includes: the PID controller adjusts the initial P, I, D parameters according to the error between the actual pressure and the target pressure through manual tuning or self-tuning function, so as to achieve precise control of the upper and lower limits of the punch pressure value, and determine the final closed-loop cycle parameters, proportional parameters, integral parameters and differential parameters;

[0056] Actuator: used to adjust the height and / or pressure of the punch according to the control signal output by the PID controller; it is explained here that the composition of the actuator can adopt the existing structural composition, and only requires components that can change the height and / or pressure of the punch. This application does not elaborate on the composition and working principle of the actuator.

[0057] The system structure of the present invention is simple. The punch pressure data is collected in real time during the press production process by a pressure sensor and compared with the target pressure value. Once it is found that the actual pressure value deviates from the target pressure value, the PID controller controls the actuator to automatically adjust the punch height and / or pressure so that the punch pressure is always maintained at the target pressure value. At the same time, the system can automatically adapt to changes in production conditions and accurately control the punch pressure, thereby improving the stability and consistency of tablet production.

[0058] In order to further understand how the dynamic response model is constructed in this application, the following example is given:

[0059] Example 1

[0060] The background of this embodiment is: when a tablet press is pressing a specific tablet, the target pressure is 70 kN. Punch pressure data under different conditions are collected, and a dynamic response model of the tablet press under this target pressure needs to be established. The construction of the dynamic response model includes the following steps:

[0061] S11: Data acquisition and preprocessing: The pressure sensor installed on the punch collects pressure data, and records the pressure data within 5 minutes when the constant pressure target value is 70 kN. The pressure sensor here can be installed above or below the punch according to the different structures of the tablet press;

[0062] S12: Obtaining pressure response data: Excitation signal: Setting different pressure target values, such as 60 kN, 65 kN, 70 kN, and 75 kN, and observing the pressure response of the system at each target value;

[0063] Response data: record the pressure change data of the system within 5 seconds at each target value, and summarize and analyze it;

[0064] S13: By comparing the response data, a dynamic response model is obtained; after the dynamic response model is obtained, the recursive least squares method (RLS) is selected for parameter identification, and the excitation signal and the response data are input to obtain the parameter values ​​in the dynamic response model: gain K = 1.05 (system gain); time constant τ = 0.4 seconds; damping ratio ζ = 0.7;

[0065] S15: Model verification: Simulation verification is performed using data that is not involved in modeling. When the target pressure is 72 kN, the comparison curve between the actual system and the model output is as follows: Actual system response: the maximum deviation value is ±0.3 kN; Model output: the maximum deviation value is ±0.2 kN; Conclusion: The model can better reflect the dynamic response of the actual system;

[0066] S14: Determine the dynamic response model as:

[0067]

[0068] Then use empirical formulas or standard tuning rules (such as the Ziegler-Nichols method) to calculate the appropriate closed-loop period Ts, proportional parameter P, integral parameter I and differential parameter D, and use the closed-loop period Ts, proportional parameter P, integral parameter I and differential parameter D to set the parameters of the subsequent PID algorithm.

[0069] The examples described in the present invention are merely descriptions of the preferred implementation modes of the present invention, and are not intended to limit the concept and scope of the present invention. Without departing from the design concept of the present invention, various modifications and improvements made to the technical solutions of the present invention by engineers and technicians in this field should all fall within the protection scope of the present invention.

Claims

1. A method for dynamically adjusting punch pressure of a tablet press, characterized in that: The steps include: S1: Establish a dynamic response model of the punch pressure in the tablet press, and determine the closed-loop cycle parameter, proportional parameter, integral parameter and differential parameter according to the dynamic response model; the dynamic response model is: Where K is the system gain, τ is the time constant, ζ is the damping ratio; s is the complex frequency variable in the Laplace transform; S2: Obtain punch pressure data in real time, calculate the error between the actual pressure of the punch and the target pressure, and input the error into the PID algorithm to obtain a control signal; S3: adjusting the punch according to the control signal output by the PID algorithm, wherein the adjustment includes adjusting the height of the punch and / or the pressure of the punch.

2. A method for dynamically adjusting punch pressure of a tablet press according to claim 1, characterized in that: The establishment of the dynamic response model in step S1 includes the following steps: S11: Data collection and preprocessing: real-time collection of punch pressure data and denoising and removal of outliers on the punch pressure data; S12: Obtaining pressure response data: by setting different excitation signals, obtaining the pressure change data of each excitation signal within a set time; S13: obtaining a dynamic response model according to the pressure change data, and obtaining specific values ​​of parameters in the dynamic response model through parameter identification; S14: Determine closed-loop cycle parameters, proportional parameters, integral parameters and differential parameters according to the dynamic response model, and construct a PID algorithm.

3. A method for dynamically adjusting punch pressure of a tablet press according to claim 2, characterized in that: After step S13, the method further includes simulating and verifying the dynamic response model: inputting the dynamic response model into a simulation environment, using data that does not participate in the construction of the dynamic response model to verify the dynamic response model, and comparing the difference between the output of the dynamic response model and the actual output. If the difference is lower than or equal to a threshold, the dynamic response model is not adjusted; if the difference is higher than the threshold, the dynamic response model is adjusted.

4. A method for dynamically adjusting punch pressure of a tablet press according to claim 2 or 3, characterized in that: In step S13, the least square method is used to obtain the values ​​of the parameters K, τ, and ζ in the dynamic response model.

5. The method for dynamically adjusting punch pressure of a tablet press according to claim 2, characterized in that: In step S12, the excitation signal is the target pressure value of the punch; and the setting time is 4 to 6 seconds.

6. A system using the method for dynamically adjusting punch pressure of a tablet press according to any one of claims 1 to 5, characterized in that: include: Pressure sensor: used to collect punch pressure data; PID controller: used to calculate the error between the actual pressure of the punch head and the target pressure, and output the control signal; Actuator: used to adjust the height and / or pressure of the punch according to the control signal output by the PID controller.

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