Control algorithm for realizing feedback dynamic uniform dropwise adding of liquid through delivery pump

Abstract

The invention discloses a control algorithm for realizing feedback of dynamic uniform dropwise adding of liquid through a delivery pump, which comprises an HMI (Human Machine Interface), a PLC (Programmable Logic Controller), a weighing system, a speed regulation metering pump and a reaction kettle in parts by weight, and specifically comprises the following steps of: transmitting real-time weighing mass data of the weighing system to the PLC as real-time original weighing data; the method comprises the following steps: discretizing an input set value of a client into per second, then taking the discretized set value as a current set value input by a PID control algorithm, and calculating the mass (weight reduction method) leaving the weighing system according to the variable quantity of real-time mass data of the weighing system as an input actual quantity of the PID control algorithm. The invention belongs to the technical field of articles of daily use, and particularly relates to a control algorithm for realizing feedback dynamic uniform dropwise adding of liquid through a delivery pump.

Description

Technical Field

[0001] The present invention belongs to the technical field of daily necessities, and specifically refers to a control algorithm for uniformly dripping liquid using feedback dynamics achieved through a delivery pump. Background Art

[0002] Generally, the method used by PLC (Programmable Logic Controller) systems, DCS (Distributed Control System) systems, or customer-defined modeling is to calculate the real-time flow rate per unit time, i.e., the flow rate, by using the accumulated pump running time as the denominator and the real-time weight feedback from the weighing system as the numerator. The flow rate feedback is then used as the PV of the PID (proportional-integral-derivative control) and the calculated result of the set addition amount and addition time as the SV flow rate. The output of the feedback calculation is applied to the delivery pump to achieve automatic feedback flow control of the pump.

[0003] The limitation of this method is that the customer is very objective and simply inputs the process requirements into the system, obtains the SV (setpoint), and then calculates the PV (present value) based on the accumulated time to calculate the PID output. Therefore, if there is a slight mismatch in the PID parameters, the set flow rate cannot be compensated within a period of time. PID adjustment is then performed, and then the reverse adjustment is made again in the next cycle. This repeated process results in a fluctuating addition amount, which ultimately leads to inconsistent addition amount within the customer's time period, which will inevitably affect the process test conditions and ultimately lead to experimental failure. Summary of the Invention

[0004] The present invention does not rely on a linear metering pump. It only requires an on-site weighing system with data transmission, an ordinary speed-regulating metering pump, a PLC or a controller with programming function to achieve the purpose of uniformly adding liquid phase materials, and solves various process problems caused by the long nonlinear adjustment time of flow rate and pump.

[0005] In order to achieve the above functions, the technical solution adopted by the present invention is as follows: a control algorithm for dynamic and uniform dropwise addition of liquid by feedback implemented by a delivery pump, including an HMI human-machine interface, a PLC controller, a weighing system, a speed-regulating metering pump, and a reactor, specifically comprising the following steps:

[0006] S1: The PLC controller transmits the real-time weighing quality data of the on-site weighing system to the PLC controller through the communication bus as the real-time original weighing data;

[0007] S2: The PLC controller receives the data input signal from the HMI human-machine interface, takes the data input by the customer as the set value (g / m) grams per minute, and then discretizes it into per second or within each set acquisition period, converts it into the mass grams (g) of the material to be fed, and then uses it as the current set value input to the PID control algorithm;

[0008] S3: After the PID control algorithm acquires the set value, it calculates the mass that has left the weighing system (by the weight-loss method) based on the change in the real-time mass data of the feedback weighing system, uses it as the actual input quantity of the PID control algorithm, and then calculates the pump speed of the speed-regulating metering pump to be corrected in the next cycle, predicting whether to increase or decrease the speed in the next cycle to correct the mass deviation of the previous time, rather than directly participating in the calculation of the flow rate, so as to dynamically control the liquid to be evenly dropped into the reaction kettle.

[0009] Preferably, in the PID control algorithm in step S2 and step S3, the real-time changing mass weighing data is used as the input port of the actual data control end, which is the control object of the PID control algorithm. The theoretically planned increased mass within the discretized unit time is used as the set value as the control target. By outputting and adjusting the speed to the speed-regulating metering pump, adjusting the speed to make the amount of liquid fed reach the mass to be added within the discretized unit time. If there is a deviation, the pump speed will be adjusted in the next cycle.

[0010] Preferably, the discretization calculation is: Sv(g) = [Sv(g / m) / 60]*CP, where Sv(g / m) is the data input by the customer as the set value grams per minute, CP is the control period (S), and Sv(g) is the mass grams (g) of the material to be fed converted within the acquisition period after discretization.

[0011] Preferably, the dynamic calculation of the feeding amount is: W2 = W0 - W1, where W0(g): calculates the actual value by the weight-loss method of the weighing system; W1(g): the weight value measured by the weighing system in real time; W2(g): the weight of the liquid that has been added to the reaction kettle.

[0012] Preferably, the PID data input is: ysp(t) = Sv(g); e(t) = Sv(g) - W2; d(t) = 0, without considering the differential term; the error e(t) is the difference between the set value and the actual value. Here, the actual value is the negative value of the added weight (because it is the weight-loss method, and the decrease in weight indicates feeding).

[0013] Preferably, the output y(t): frequency change amount = y(t) * calibrated initial frequency, where the output y(t) represents the frequency change amount of the speed-regulating metering pump, and the calibrated initial frequency is the initial operating frequency of the metering pump, which is input by the user according to the inherent parameters of the pump. By changing the frequency of the pump, the rotational speed of the pump can be adjusted, thereby controlling the flow rate of the liquid and achieving dynamic adjustment of the liquid dropping amount.

[0014] The present invention adopts the above structure to achieve the following beneficial effects: Through this control algorithm, combined with devices such as the HMI human-machine interface, PLC controller, weighing system, and speed-regulating metering pump, high-precision control of the liquid addition amount can be achieved. Discretization processing is performed on the input value set by the customer, and the feeding mass in each acquisition period is accurately calculated to ensure that the liquid is evenly dropped into the reaction kettle. It does not rely on a linear metering pump, solving various process problems caused by the too long non-linear adjustment time of the flow rate and the pump. Brief Description of the Drawings

[0015] Figure 1 It is the system control flow block diagram of the specific embodiment of the present invention. Specific Embodiments

[0016] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0017] A control algorithm for realizing feedback dynamic uniform liquid dropping through a delivery pump according to the present invention includes, by weight parts, an HMI human-machine interface, a PLC controller, a weighing system, a speed-regulating metering pump, and a reaction kettle. The steps are as follows:

[0018] S1: Install the HMI human-machine interface to facilitate the user to input set values and monitor the system operation status. Connect the PLC controller to the weighing system to ensure accurate transmission of real-time weighing quality data through the communication bus. Connect the speed-regulating metering pump to the reaction kettle and perform signal connection with the PLC controller to achieve adjustment control of the pump speed;

[0019] S2: The user inputs a set value through the HMI human-machine interface. For example, the set value is 500 g / m (grams per minute). The PLC controller performs discretization calculation according to the set value. Assuming the control period CP is 15 s, then the feeding mass per unit time after discretization The weighing system measures the weight of the reaction kettle and the internal substances in real time. The initial weight W0 (g) = 10000 g. As the liquid is added, the current actual weight W1 continuously changes. The PLC controller performs data acquisition and processing according to the set control period (15 seconds).

[0020] S3: At the beginning of the first control cycle, the weighing system measures the current actual weight W1 in real time. Assuming it is 9980g, the added weight W2 = W0 - W1 = 20g;

[0021] PID data input: set value ysp(t) = Sv(g), e(t) = Sv(g)-W2; where e(t) = 125-20 = 105g, d(t) = 0; differential term is not considered;

[0022] The PID control algorithm calculates the frequency change y(t) of the speed-regulating metering pump based on the error. Assuming that the algorithm calculates y(t) = 0.25, if the initial frequency is calibrated to 40 Hz, the actual frequency of the speed-regulating metering pump becomes: 0.25 × 40 = 10 Hz;

[0023] S4: At the beginning of the second control cycle, the current actual weight W1 is measured again. Assuming it is 9960g, then W2=40g, the set value ysp(t) and the error e(t) are recalculated, and the speed of the speed-regulating metering pump is further adjusted;

[0024] S5: This cycle repeats, and each control cycle is adjusted according to the real-time weighing data and the set value to correct the mass deviation of the previous cycle;

[0025] S6: The operator can monitor the weight change, set value, actual addition amount, speed of the speed regulating metering pump and other parameters of the reactor in real time through the HMI human-machine interface;

[0026] S7: If any abnormality is found in the system operation, such as abnormal weight change, unstable pump speed, etc., adjustments can be made in time or the system can be stopped for troubleshooting.

[0027] Effect verification: The PID control input and output here are no longer flow rates, but weighing (mass g). That is to say, the system collects the real-time weighing data inside the barrel as the PV value, and then substitutes this value into the system for flow discretization calculation. The theoretical added weighing weight is calculated every moment, and then calculated with the real-time weighing of the current measurement sample, and the adjustment speed of the next control cycle is output; thereby quickly correcting the error value of the previous cycle, and the speed can be kept constant within a range, and ultimately a uniform addition of liquid materials within a time period of 10 seconds or 20 seconds can be achieved. This effect has been continuously run on site for one month by the user. With a 50L reactor body and a set amount of 500g / m3 added, the average accuracy can be within the error range of plus or minus 0.5g, which has effectively solved the problem of uniformity of liquid-phase added materials that has been plaguing users.

[0028] The above describes the present invention and its implementation manners, and such description is not restrictive. Generally speaking, if those of ordinary skill in the art are inspired by it and, without departing from the gist of the present invention, design similar structural manners and embodiments to this technical solution without creative efforts, they shall fall within the protection scope of the present invention.

Claims

1. A control algorithm for realizing feedback dynamic uniform liquid dropping through a delivery pump, characterized in that, It includes an HMI (Human Machine Interface), a PLC (Programmable Logic Controller) controller, a weighing system, a speed-regulating metering pump, and a reaction kettle by weight parts, and specifically includes the following steps. S1: The PLC controller transmits the real-time weighing quality data of the on-site weighing system to the PLC controller through the communication bus as the real-time original weighing data. S2: The PLC controller receives the data input signal from the HMI. The data input by the customer is used as the set value (g / m) grams per minute. Then, it is discretized into per second or within each set acquisition period to convert it into the mass in grams (g) of the material to be fed, and then used as the current set value input to the PID control algorithm. After the PID control algorithm acquires the set value, according to the change amount of the real-time quality data of the feedback weighing system, it calculates the mass that has left the weighing system (subtraction method) as the actual input quantity of the PID control algorithm. Then, it calculates the pump speed of the speed-regulating metering pump to be corrected in the next cycle, predicting whether to increase or decrease the speed in the next cycle to correct the mass deviation of the previous time, rather than directly participating in the calculation of the flow rate, so as to dynamically control the liquid to be evenly dropped into the reaction kettle.

2. The control algorithm for realizing feedback dynamic uniform liquid dropping by means of a delivery pump according to claim 1, wherein In the PID control algorithm in steps S2 and S3, the real-time changing mass weighing data is used as the input port of the actual data control end, which is the control object of the PID control algorithm. The theoretically planned increased mass within the unit time after discretization is used as the set value as the control target. By adjusting the speed to the speed-regulating metering pump through the output, the speed is adjusted to make the amount of liquid entering reach the mass to be added within the unit time after discretization. If there is a deviation, the pump speed will be adjusted in the next cycle.

3. The control algorithm for realizing the feedback dynamic uniform dripping of liquid through a delivery pump according to claim 1, characterized in that: The discretization calculation: Sv(g) = [Sv(g / m) / 60] * CP, where Sv(g / m) is the data input by the customer as the set value grams per minute, CP is the control period (S), and Sv(g) is the mass in grams (g) of the material to be fed converted within the acquisition period after discretization.

4. The control algorithm for realizing the feedback dynamic uniform dripping of liquid by means of a delivery pump according to claim 3, wherein: The dynamic calculation of the feeding amount: W2 = W0 - W1, where W0(g) is calculated by the subtraction method of the weighing system as the actual value; W1(g) is the weight value measured by the weighing system in real time; W2(g) is the weight of the liquid that has been added to the reaction kettle.

5. A control algorithm for realizing feedback dynamic uniform liquid dropping by a delivery pump according to claim 3, characterized in that: The PID data input: ysp(t) = Sv(g); e(t) = Sv(g) - W2; d(t) = 0, without considering the differential term; the error e(t) is the difference between the set value and the actual value. Here, the actual value is the negative value of the added weight.

6. The control algorithm for realizing feedback dynamic uniform liquid dropping through a delivery pump according to claim 5, characterized in that: The output y(t): The frequency change amount = y(t) * calibrated initial frequency, where y(t) output represents the frequency change amount of the speed-regulating metering pump, and the calibrated initial frequency is the initial operating frequency of the metering pump initialization. This value is input by the user according to the inherent parameters of the pump. By changing the frequency of the pump, the rotation speed of the pump can be adjusted, and then the flow rate of the liquid can be controlled to achieve the dynamic adjustment of the liquid dropping amount.

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