A method and system for dynamically adjusting punch pressure of a tablet press

Abstract

The application discloses a tablet press dynamic adjustment punch pressure method and system, and belongs to the tablet press field. In view of the problem that the existing pressure regulation relies on manual operation, is time-consuming and has poor pressing effect, the application provides a tablet press dynamic adjustment punch pressure method, which comprises the following steps: a dynamic response model of punch pressure in a tablet press is established, and closed loop period parameters, proportional parameters, integral parameters and differential parameters are determined; punch pressure data are acquired in real time, an error between actual punch pressure and target punch pressure is calculated, the error is input into a PID algorithm to obtain a control signal; and the punch is adjusted according to the control signal. The application provides a basis for subsequent PID algorithm by constructing the dynamic response model of punch pressure, and the PID algorithm is used to dynamically adjust P, I and D parameters to realize accurate control of punch pressure, so that high-efficiency and high-precision dynamic adjustment of punch pressure can be realized without complicated procedures, and the stability and consistency of tablet quality are ensured.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of tablet press, more particularly, relates to a method and system for dynamically adjusting punch pressure of a tablet press. BACKGROUND

[0002] A tablet press is a machine that places granular or powdery material into a die and presses it into a tablet by a punch. The tablet press has a very wide range of applications, not limited to tablet process research in the pharmaceutical industry, but also used for pressing health food tablets, veterinary medicine tablets, chemical tablets and food tablets. A high-speed rotary tablet press mainly consists of an upper punch, a middle die and a lower punch, which are connected as a whole and surrounded by 40 to 70 punches evenly arranged at the edge of the rotating disc. The tail of the upper and lower punch bars is embedded in a fixed curved guide rail, and when the rotating disc rotates, the upper and lower punch bars move up and down along the curved guide rail, thereby achieving the purpose of tablet pressing. In the prior art, the tablet press usually needs to be pre-pressed before producing tablets to determine the appropriate pressure parameters, and then start formal production. The adjustment of punch pressure usually relies on manual setting of fixed parameters. However, if the pressure exceeds the preset range during production, manual intervention is required to stop the machine. This method is difficult to cope with changes in production conditions, resulting in time-consuming and labor-intensive pre-pressing adjustment. When the quality of the tablets is unstable during the pressing process, the machine needs to be stopped and the height of each punch needs to be adjusted to adjust the pressure.

[0003] Corresponding improvements have also been made for the above problems, such as Chinese patent application No. CN202010785028.6, published on November 6, 2020, which discloses a control method and device for punch pressure of a tablet press, a storage medium and electronic equipment. The control method for punch pressure of a tablet press includes: obtaining punch pressure signals of each punch position of the tablet press, and detecting whether the tablet press has completed the action of kicking out 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 waste tablets at the punch position is completed, it is considered that an error has occurred in the punch position of the tablet press; real-time statistics of the error occurrence of the tablet press at each punch position, if the number of continuous error occurrence of the punch position reaches a preset number of times, the punch pressure of the tablet press is adjusted to adjust the punch pressure back to the preset punch pressure value. The deficiency of this patent is that although it can automatically correct the punch pressure of the tablet press, the program is complex and time-consuming.

[0004] Another example is Chinese patent application number CN202410872948.X, published on July 26, 2024. This patent discloses a load correction method for a multi-point eccentric drive mechanism of a press. This 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 alert the staff, and can adjust the load of each stamping point separately, so that 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 that the detection process is cumbersome and costly. Summary of the Invention

[0005] 1. Problems to be solved

[0006] To address the problem that existing pressure regulation relies on manual labor, is time-consuming, and has poor compression effects, the present invention provides a method and system for dynamically adjusting the punch pressure of a tablet press. The method of the present invention constructs a dynamic response model of the punch pressure to provide a basis for a subsequent PID algorithm. The PID algorithm is used to dynamically adjust the P, I, and D parameters to achieve precise control of the punch pressure. The method is simple to operate and can achieve highly efficient and precise dynamic regulation of the punch pressure without requiring complex procedures, while ensuring stability and consistency in tablet quality. The system of the present invention has a simple structural composition and can automatically adjust the punch pressure to maintain it 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 the 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] Further, the step S1 of establishing the dynamic response model comprises the following steps:

[0016] S11: data acquisition and preprocessing: real-time acquisition of punch pressure data and denoising and removal of outliers of 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 the specific values of the parameters in the dynamic response model through parameter identification;

[0019] S14: determining the closed loop period parameter, the proportional parameter, the integral parameter and the differential parameter according to the dynamic response model, and constructing the PID algorithm.

[0020] Further, the step S13 further comprises simulation verification of the dynamic response model: inputting the dynamic response model into a simulation environment, using data not participating 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 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.

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

[0022] Further, the excitation signal in the step S12 is the pressure target value of the punch; and the set time is 4-6s.

[0023] A system adopting the method of dynamically adjusting the punch pressure of the tablet press according to any one of the above, comprising:

[0024] A pressure sensor for collecting punch pressure data;

[0025] A PID controller for calculating the error between the actual pressure of the punch and the target pressure, and outputting a control signal;

[0026] An actuator for adjusting the height and / or pressure of the punch according to the control signal output by the PID controller.

[0027] 3. Advantageous effects

[0028] Compared with the prior art, the advantageous effects of the present application are:

[0029] (1) The present application establishes a dynamic response model of punch pressure, reflects the change rule of pressure with time and the relationship between pressure and PID algorithm in real time through the dynamic response model, provides basis for the initial parameters in the PID algorithm, enables more accurate and efficient prediction and response to the change of punch pressure, thereby realizing accurate adjustment of punch pressure, ensuring the stability and consistency of punch pressure in the machining process, and ultimately improving the machining precision and surface quality of products; and the adaptability of the whole method is increased by adjusting and optimizing according to different control requirements; the whole method is simple to operate, and high-efficiency and high-precision dynamic adjustment of punch pressure can be realized without complicated procedures;

[0030] (2) In the establishment process of the dynamic response model, different excitation signals are set to excite the dynamic characteristics of the system, so that the dynamic response process can be more accurately described; different excitation signals can simulate different working conditions, so that the dynamic response model constructed 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, the parameter identification can determine the parameter values of the model based on experimental data and theoretical model, so that the numerical results calculated by the model can best fit the test data, effectively guaranteeing the accuracy of model establishment and the precision of the whole process;

[0031] (3) After the dynamic response model is constructed, the dynamic response model is simulated and verified, the simulation verification can verify the dynamic response model for multiple times in a short time, thereby improving the work efficiency; and the simulation verification can be visualized, which is convenient for the staff to intuitively understand and analyze the characteristics of the dynamic response model; the whole verification method has multiple advantages such as high efficiency, safety, flexibility, repeatability and visualization;

[0032] (4) The system for dynamically adjusting punch pressure of the present application has simple composition, real-time acquisition of pressure data in the production process, comparison with the preset value, automatic adjustment of punch height when the pressure value deviates from the preset range, dynamic adjustment of punch pressure during equipment operation, effectively reducing the situation of stopping for manual adjustment of punch pressure, ensuring that the pressure always maintains at the preset target value, thereby improving the stability and consistency of tablet production. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The flowchart of the present application. DETAILED DESCRIPTION

[0034] The present application will be further described below in combination with specific embodiments and drawings.

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

[0036] S1: a dynamic response model of the punch pressure in the tablet press is established, and closed loop period parameters, proportional parameters, integral parameters and differential parameters are determined 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 a complex frequency variable in Laplace transform; it is explained that s is a complex frequency variable for describing the frequency domain characteristics of the system, and through which, the transfer function G(s) can fully reflect the dynamic characteristics of the system; and in the mathematical model of the control system and signal processing, that is, in the present application, s represents a complex frequency variable in Laplace transform, which is usually used to describe the dynamic characteristics of the system; s 2 And s are both for describing the dynamic characteristics of the system, indicating that the system contains a second-order and first-order dynamic process, and are used to describe the inertia and oscillation characteristics of the tablet press system; and the highest order of the transfer function s 2 Indicates that the dynamic behavior of the system contains acceleration and speed response, which is a second-order system;

[0039] S2: real-time acquisition of punch pressure data, calculation of the error between the actual pressure of the punch and the target pressure, input of 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, the adjustment including adjusting the height of the punch and / or the pressure of the punch.

[0041] The present application provides a basis for the initial parameters in the PID algorithm by establishing a dynamic response model of the punch pressure, reflecting the change rule of the pressure with time and the relationship between the pressure and the PID algorithm in real time through the dynamic response model, enabling more accurate and efficient prediction and response of the change of the punch pressure, thereby realizing accurate adjustment of the punch pressure, ensuring the stability and consistency of the punch pressure in the processing process, and ultimately improving the processing precision and surface quality of the product; and the adaptability of the whole method is increased by adjusting and optimizing according to different control requirements; the whole method is simple to operate, and high-efficiency and high-precision dynamic adjustment of the punch pressure can be realized without complicated procedures.

[0042] The existing punch pressure is basically relied on manual adjustment, but such adjustment mode needs to stop work and cannot realize a dynamic adjustment process. Therefore, the application combines a dynamic response model and a PID algorithm to automatically adjust the punch pressure, so as to meet the pressure requirement and ensure the stability and consistency of tablet production; and the dynamic response model is used to determine the appropriate closed loop period, proportion (P), integral (I) and differential (D) parameters in sequence; the closed loop period refers to the time interval of one complete control cycle of the PID control to the system, which directly affects the stability of the PID control, and too short cannot guarantee the stability and too long increases the consumption of resources; the proportion (P), integral (I) and differential (D) parameters make the constructed PID algorithm have good performance and control effect, so as to realize the accurate control and stability of the whole system.

[0043] The construction of the PID algorithm depends on the dynamic response model, the dynamic response model can more accurately describe the dynamic behavior of the punch of the press, can more accurately determine the proportional coefficient (Kp), integral coefficient (Ki) and differential coefficient (Kd) in the PID algorithm, so as to realize more accurate control; and the dynamic response model can consider various uncertain factors of the system, so the PID parameters constructed based on the dynamic response model can better adapt to the uncertain factors, so as to guarantee the stability and reliability of the whole process. Although the prior art uses the PID algorithm for control, the parameters in the PID algorithm often depend on the experience and trial-and-error process of the operator, cannot well adapt to various uncertain factors and change conditions of the system, and it is difficult to guarantee the accuracy and stability of the whole process.

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

[0045] S11: data acquisition and preprocessing: real-time acquisition of punch pressure data and denoising and removal of abnormal values of the punch pressure data;

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

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

[0048] S14: determining the closed loop period parameter, proportion parameter, integral parameter and differential parameter according to the dynamic response model, and constructing the PID algorithm;

[0049] In the process of establishing the dynamic response model, different excitation signals can be set to stimulate the dynamic characteristics of the system, so that the dynamic response process can be more accurately described. Different excitation signals can simulate different working conditions, so that the dynamic response model constructed 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 the model establishment and the accuracy of the entire process.

[0050] In one specific embodiment, the step S13 further includes simulation verification of the dynamic response model: inputting the dynamic response model into a simulation environment, using data not participating 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 the difference is less than or equal to a threshold, the dynamic response model is not adjusted; if the difference is greater than the threshold, the dynamic response model is adjusted.

[0051] After the dynamic response model is constructed, simulation verification of the constructed dynamic response model is further included. Simulation verification can verify the dynamic response model multiple times in a short period of time, thereby improving work efficiency. Simulation verification can be intuitive and visual, making it easy for workers 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 one specific embodiment, the step S13 uses the least squares method to obtain the values of the parameters K, τ, and ζ in the dynamic response model. The least squares method is simple in principle, easy to calculate, widely applicable, and can be used for model verification and optimization of parameter estimation. In the step S12, the excitation signal is the target value of the punch pressure, and the set time is 4-6s. Avoiding setting the time too short to reflect the changes, and setting the time too long to increase resource consumption, so as to meet the consideration of precision and efficiency.

[0053] A system for dynamically adjusting the punch pressure of a tablet press using the method described in any of the above embodiments, comprising:

[0054] Pressure sensor: for collecting punch pressure data;

[0055] PID controller: for calculating the error between the actual pressure of the punch force head and the target pressure, and outputting a control signal; what is described here is that the construction process of the PID controller is as follows: a dynamic response model is established, and the parameters in the dynamic response model are determined, the IPD initial parameters are determined according to the determined dynamic response model, the PID initial parameters are applied to the PID controller, and then the PID initial parameters are optimized and verified; the optimization and verification include: the PID controller adjusts the initial P, I and D parameters according to the error between the actual pressure and the target pressure through manual setting or self-setting function, realizes accurate control within the upper and lower limit range of the punch pressure value, and determines the final closed loop period parameter, proportional parameter, integral parameter and differential parameter;

[0056] Actuator: for adjusting the height and / or pressure of the punch according to the control signal output by the PID controller; what is described here is that the composition of the actuator can adopt the existing structure composition, only the components that can change the height and / or pressure of the punch are needed, and the composition and working principle of the actuator are not described in detail.

[0057] The system structure of the present application is simple, the punch pressure data is collected in real time by the pressure sensor during the production process of the press, and is compared with the target pressure value, once the actual pressure value deviates from the target pressure value, the height or / and pressure of the punch is automatically adjusted by the PID controller to control the actuator, so that the punch pressure is always kept at the target pressure value; at the same time, the system can automatically adapt to the change of production conditions, accurately control the punch pressure, and thus improve the stability and consistency of tablet production.

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

[0059] Embodiment 1

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

[0061] S11: data acquisition and pretreatment: the pressure sensor installed on the punch collects pressure data, and records the pressure data within 5 minutes under the condition that the constant pressure target value is 70 kN; here, the pressure sensor can be installed above or below the punch according to the structure of the tablet press;

[0062] S12: obtain pressure response data: excitation signal: set different pressure target values, such as 60 kN, 65 kN, 70 kN and 75 kN, and observe the pressure response of the system under each target value;

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

[0064] S13: Obtain the dynamic response model by comparing the response data; after obtaining the dynamic response model, select recursive least squares (RLS) for parameter identification, input the excitation signal and the response data, and 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: use the data not involved in modeling for simulation verification. In the case of target pressure of 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 the empirical formula or standard tuning rule (such as 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 for subsequent PID algorithm parameter setting.

[0069] The examples described in the present application are only used to describe the preferred embodiments of the present application, and do not limit the concept and scope of the present application. Without departing from the design idea of the present application, various modifications and improvements of the technical solutions of the present application made by the engineering and technical personnel in the field shall fall within the protection scope of the present application.

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 the 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; The establishment of the dynamic response model in step S1 includes the following steps: S11: Data acquisition and preprocessing: real-time acquisition 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; After step S13, the method further includes performing simulation verification on 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 output of the dynamic response model with the actual output, and if the difference is lower than or equal to a threshold, not adjusting the dynamic response model; if the difference is higher than the threshold, adjusting the dynamic response model.

2. The method for dynamically adjusting punch pressure of a tablet press according to claim 1, wherein: 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.

3. The method for dynamically adjusting punch pressure of a tablet press according to claim 1, wherein: In step S12, the excitation signal is the target pressure value of the punch; and the set time is 4 to 6 seconds.

4. A system using the method for dynamically adjusting punch pressure of a tablet press according to any one of claims 1 to 3, 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 and the target pressure, and output a control signal; Actuator: used to adjust the height and / or pressure of the punch according to the control signal output by the PID controller.

Images