Pickling line monitoring system

Abstract

The invention provides a pickling line monitoring system, which comprises a sensor, a control module and an actuator, the sensor monitors the acid concentration, temperature, liquid level and pickling line transmission speed of a pickling tank, and the actuator is used for controlling the technological actions of acid supplement, acid dilution, acid discharge, heating and circulation of the pickling tank. The control module controls the actuator in real time according to data of the sensor so as to maintain the concentration of acid liquor in the pickling tank to be close to the optimal value of the pickling process; the real-time control strategy of the control module comprises the steps that output parameters of an actuator are adjusted in real time through a feed-forward control and PID feedback control integrated composite control strategy, feed-forward compensation is improved for the change of the transmission speed of the pickling line through feed-forward control, and disturbance of acid concentration, temperature and liquid level data to output is reduced through PID feedback control setting dead zones. According to the invention, the acid concentration adjusting precision and the automation degree of the pickling line are improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of metal processing, and particularly relates to an acid pickling line monitoring system. BACKGROUND

[0002] In the steel and metal product processing industry, the acid pickling line is a crucial surface treatment process, which removes the oxide layer on the surface of the steel through acid liquor, directly affecting the final quality of the product. At present, most acid pickling lines still use a control system based on traditional PID feedback, which adjusts according to sensor data such as acid concentration and temperature. However, such systems have obvious limitations: on the one hand, they are difficult to respond to the severe disturbance caused by changes in the driving speed of the acid pickling line, resulting in a lag in concentration control; on the other hand, sensor measurement noise and small fluctuations easily cause the actuator to act frequently, not only accelerating equipment wear and tear, but also reducing the stability and control accuracy of the system. In addition, the existing system still has a lot of room for improvement in terms of anti-interference ability and set value tracking performance under dynamic conditions. SUMMARY

[0003] Therefore, the present application aims to provide an acid pickling line monitoring system to improve the acid concentration adjustment accuracy and automation of the acid pickling line.

[0004] To achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0005] An acid pickling line monitoring system.

[0006] Further, the system comprises a sensor, a control module, and an actuator. The sensor monitors the acid concentration, temperature, liquid level, and driving speed of the acid pickling line. The actuator is used to control the acid pickling pool's acid supplement, acid dilution, acid discharge, heating, and circulation process actions. The control module controls the actuator in real time based on sensor data to maintain the acid concentration in the acid pickling pool near the optimal value of the pickling process.

[0007] The real-time control strategy of the control module includes using a feedforward control and PID feedback control integrated control strategy to adjust the output parameters of the actuator in real time. The feedforward control improves the feedforward compensation for changes in the driving speed of the acid pickling line, and the PID feedback control sets a dead zone to reduce the disturbance of acid concentration, temperature, and liquid level data on the output.

[0008] Further, the sensor comprises an acid concentration sensor for monitoring the acid concentration value of the acid pickling pool and transmitting it to the control module through a 4-20mA analog signal.

[0009] A temperature sensor for monitoring the real-time temperature of the acid liquor in the acid pickling pool and transmitting it to the control module through a signal conversion module.

[0010] A liquid level sensor for monitoring the liquid level and total acid amount of the acid pickling pool and transmitting it to the control module through a 4-20mA analog signal.

[0011] Encoder, for measuring the speed of the pickling line drive, transmitting the real-time speed to the control module through high-speed pulse signal or fieldbus protocol.

[0012] Further, the actuators include several regulating valves for supplying acid and dilute acid to the pickling tank, which are controlled by the control module through analog output signals to control the opening of the valves.

[0013] On-off valves for draining the acid in the pickling tank, which are controlled by the control module through on-off signals to control the opening and closing of the valves.

[0014] Heaters for heating the temperature of the acid in the pickling tank, which are controlled by the control module through analog output signals to control the heating power of the heaters in real time.

[0015] Circulating pumps for circulating the acid in the pickling tank, which are controlled by the control module through on-off signals to control the start and stop of the pumps.

[0016] Further, the composite control strategy of the control module includes:

[0017] When the liquid level of the pickling tank is below a threshold value, the processor module starts a safety interlock to stop all outputs to the actuators and close all valves.

[0018] When the monitoring system is in manual mode, all outputs of the control module to the actuators are directly set by the staff.

[0019] When the monitoring system is in automatic mode, the control module determines whether the last program polling mode was manual mode. If so, it retains the PID feedback control parameters in the last manual mode and enables feedforward control. If not, it adjusts the PID feedback control parameters in real time according to the sensor data and enables feedforward control.

[0020] Further, the composite control strategy of the control module is formulated as:

[0021] ;

[0022] ;

[0023] ;

[0024] wherein, is the target opening of the acid supply regulating valve, is the feedforward control output, is the PID feedback control output, is the gain coefficient, is the real-time linear speed of the pickling line drive, is the reference linear speed of the pickling line drive, is the reference opening of the acid supply regulating valve. is a proportional term, is an integral term, is a differential term, is an acid concentration target value after dead zone processing, is an effective error integral, is an acid concentration change rate for suppressing overshoot.

[0025] Further, the control module realizes logical calculation and control through an MCU, and the MCU control content includes:

[0026] The composite control strategy calculation is based on the acid concentration value, the acid liquid temperature value, the liquid level height value, and the transmission speed value fed back by the system, and combines the acid concentration set value, the temperature set value, and the liquid level upper and lower limits set by the human being to calculate and output the acid supplementing regulating valve opening degree, the acid dilution regulating valve opening degree, the heater regulating power, and the acid discharge switch valve off state in real time;

[0027] The automatic mode switching judgment is that when the system switches from automatic to manual, the integral term of the PID controller is initialized according to the current PID feedback control parameter and the last polling PID feedback control parameter to conform to the actual valve position of the current manual operation, so that the controller output is continuously smooth before and after the switching, and vice versa, when the system switches from manual to automatic, the integral term of the PID controller is initialized according to the actual valve position of the current manual operation to conform to the current automatic mode PID feedback control parameter and the last polling PID feedback control parameter, so that the controller output is continuously smooth before and after the switching, and the last polling hand-automatic control state is stored to respond to the next hand-automatic switching action.

[0028] Further, the control module MCU packs the input variables, the output variables, the set values, and the parameter values into a structure according to the order address, and the main function analyzes and reads and writes the structure to realize high real-time and high refresh rate response to the composite control strategy;

[0029] The control module MCU executes the composite control strategy calculation and the automatic mode switching judgment by using an interrupt service function, and switches the working state by using the main function, including updating the set value, recording the data, state monitoring, and low power consumption management state.

[0030] Further, the control module MCU establishes input buffers for each sensor and output buffers for each actuator, the sensor raw data is stored in the sensor input buffer, the actuator output parameter is calculated in the interrupt service function and stored in the actuator output buffer, and the buffer is called in the main function to output to the actuator control parameter, so as to eliminate the race condition of the interrupt service function and the main function.

[0031] Compared with the prior art, the pickling line monitoring system has the following beneficial effects:

[0032] (1) The monitoring system comprises a sensor, a control module and an actuator to form a closed-loop control system, wherein the sensor monitors multiple parameters such as acid liquid concentration, temperature, liquid level and steel belt transmission speed in real time, the control module adopts a composite strategy combining feedforward control and PID feedback control, the feedforward control pre-compensates for acid liquid consumption according to transmission speed changes, the PID control suppresses measurement fluctuation interference through a dead zone algorithm, and finally the acid liquid concentration is dynamically stabilized in an optimal process interval through precise adjustment of the acid supplement valve, the dilution valve, the acid discharge valve and other actuators, so that the pickling process quality and the degree of automation are improved;

[0033] (2) The monitoring system encapsulates all input, output and set value data into a structure, and only needs to pass a structure pointer when passing parameters to a function, thereby reducing the use of stack space and time overhead of parameter passing, and when modifying the code related to the sensor, the actuator or other parts are not accidentally affected;

[0034] (3) The monitoring system establishes an input buffer and an output buffer double buffering mechanism to eliminate the race condition between the interrupt service function and the main function, the interrupt service function only writes sampling data, and the main function only reads current data, so that data damage or inconsistency caused by simultaneous reading and writing of a variable is avoided;

[0035] (4) The monitoring system can perform a disturbance-free switching from a manual mode to an automatic mode, and at the moment of switching from the manual mode to the automatic mode, the actual valve position of the current manual operation is used to initialize the integral term of the PID controller, so that the output values of the controller before and after switching are consistent, and a sudden control signal is avoided, thereby avoiding the impact on the pickling line. BRIEF DESCRIPTION OF DRAWINGS

[0036] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the present application, and the illustrative embodiments of the present application and their description serve the purpose of explaining the present application, and do not constitute improper limitations on the present application. In the drawings:

[0037] Figure 1 The monitoring system electrical topology schematic diagram described in the embodiments of the present application;

[0038] Figure 2 The monitoring process schematic diagram described in the embodiments of the present application;

[0039] Figure 3 The monitoring principle schematic diagram described in the embodiments of the present application.

[0040] Explanation of reference signs: DETAILED DESCRIPTION

[0041] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0042] In the description of the present application, it needs to be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application. In addition, the terms "first", "second" and the like are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first", "second" and the like can explicitly or implicitly include one or more features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0043] In the description of the present application, it needs to be understood that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral connection; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium, or the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood through specific circumstances.

[0044] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0045] An acid pickling line monitoring system, as shown in Figure 1 includes sensors, control modules, actuators, sensors monitor the acid concentration, temperature, liquid level, driving speed of the acid pickling line (i.e. the moving speed of the steel belt) of the acid pickling tank, the actuators are used to control the acid pickling tank to add acid, dilute acid, discharge acid, heating, circulating process action, the control module controls the actuators in real time according to the sensor data to maintain the acid concentration in the acid pickling tank near the optimal value of the acid pickling process; the real-time control strategy of the control module includes using the integrated control strategy of feedforward control and PID feedback control to adjust the output parameters of the actuators in real time, the feedforward control improves the feedforward compensation for the change of the driving speed of the acid pickling line, and the PID feedback control sets the dead zone to reduce the disturbance of the acid concentration, temperature and liquid level data on the output.

[0046] Specifically, the sensors include: an acid concentration sensor for monitoring the acid concentration value of the pickling tank and transmitting to the control module through a 4-20 mA analog signal; a temperature sensor for monitoring the real-time temperature of the pickling tank acid liquid and transmitting to the control module through a signal conversion module; a liquid level sensor for monitoring the pickling tank liquid level and total acid amount, transmitting to the control module through a 4-20 mA analog signal; an encoder for measuring the pickling line driving speed, transmitting the real-time transmission speed to the control module through a high-speed pulse signal or a field bus protocol. The actuators include: several regulating valves for acid supplement and dilute acid for the pickling tank, which are controlled by the control module to control the opening degree of the valve through an analog output signal; a switch valve for removing the acid liquid in the pickling tank, which is controlled by the control module through a switch signal; a heater for heating the temperature of the pickling tank acid liquid, which is controlled by the control module in real time to control the heating power of the heater through an analog output signal; a circulating pump for circulating the acid liquid in the pickling tank, which is controlled by the control module through a switch signal to start and stop.

[0047] Further, as shown in the control module Figure 2 The composite control strategy of the control module includes:

[0048] When the pickling tank liquid level is lower than the threshold value, the processor module starts the safety interlock to stop all outputs to the actuators, and closes all valves; when the monitoring system is in manual mode, the control module directly sets all outputs to the actuators by the staff; when the monitoring system is in automatic mode, the control module judges whether the last program polling working mode is manual mode, if yes, the PID feedback control parameters in the last manual mode are retained, and the feedforward control is enabled, if not, the PID feedback control parameters are adjusted in real time according to the sensor data, and the feedforward control is enabled.

[0049] The formula of the composite control strategy of the control module is:

[0050] ;

[0051] ;

[0052] ;

[0053] In the formula, is the target opening degree of the acid supplement regulating valve, is the feedforward control output, is the PID feedback control output, is the gain coefficient, is the real-time line speed of the pickling line driving, is the reference line speed of the pickling line driving, is the reference opening degree of the acid supplement regulating valve; is the proportional term, is the integral term, is the differential term, is the acid concentration target value after dead zone processing, is the effective error integral; is the acid concentration change rate for suppressing overshoot, only the change rate of the feedback value is concerned when the measured value is differentiated, the mutation of the set value will not affect the instantaneous change rate of the feedback value, so the output change is smooth, which improves the stability and operation experience of the system.

[0054] wherein, needs to be processed by dead zone:

[0055] ;

[0056] ;

[0057] ;

[0058] is the acid concentration set value, is the actual acid concentration value fed back by the concentration sensor, is the dead zone range, the advantage of introducing dead zone for PID input is to avoid the valve to make high-frequency and abrasive small actions for a trivial error which may be caused by noise, which improves the stability and service life of the system.

[0059] Optionally, as shown in the control module is realized by MCU logic calculation and control, in this embodiment, the control module is preferably developed in C language as the development environment, and the MCU control content includes: Figure 3

[0060] ​The composite control strategy calculates and outputs the opening of the acid replenishment valve, the opening of the acid dilution valve, the heater adjustment power, and the closed status of the acid discharge valve in real time, based on the acid concentration, acid temperature, liquid level, and transmission speed values ​​fed back by the system, combined with the manually set acid concentration setpoint, temperature setpoint, and upper and lower liquid level limits. For automatic mode switching, when the system switches from automatic to manual, the integral term of the PID controller is initialized according to the current PID feedback control parameters, the previously polled PID feedback control parameters, and the actual valve position of the previous manual operation, ensuring a continuous and smooth output value before and after the switch. Conversely, when the system switches from manual to automatic, the integral term of the PID controller is initialized according to the current manual operation's actual valve position, the current automatic mode PID feedback control parameters, and the previously polled PID feedback control parameters, ensuring a continuous and smooth output value before and after the switch. The previously polled manual / automatic control status is also stored to prepare for the next manual / automatic switching action. The specific implementation includes: declaring input variable structures, output variable structures, setpoint structures, control function parameter structures, and interrupt service functions in the header file; input variable structure elements include acid concentration value, acid temperature value, liquid level height value, transmission speed value, and manual / automatic switching signal; output variable structure elements include acid replenishment valve opening degree, acid dilution valve opening degree, heater adjustment power, and acid discharge switch valve closing status; setpoint structure elements include acid concentration setpoint, temperature setpoint, and upper and lower liquid level limits; control function parameter structure elements include current PID feedback control parameters, last polled PID feedback control parameters, and last polled manual / automatic control status; all input variable structures, output variable structures, setpoint structures, and control function parameter structures pass parameters in pointer form; the main program imports the header file and defines the corresponding global variables and constants for its structures, updates the output variable structure through function calculations, and outputs it to the corresponding actuator. The advantage is that the system encapsulates all input, output, and setpoint data into a structure. When passing parameters to a function, only a structure pointer needs to be passed, which reduces the use of stack space and the time overhead of parameter passing. Furthermore, when modifying sensor-related code, it will not accidentally affect the actuator or other parts.

[0061] Specifically, the control module (MCU) packages input variables, output variables, setpoints, and parameter values ​​into a structure according to their sequential addresses. The main function parses and reads / writes this structure to achieve high real-time performance and high refresh rate response to the composite control strategy. The MCU utilizes interrupt service functions to perform composite control strategy calculations and automatic mode switching judgments, and uses the main function to switch operating states, including updating setpoints, recording data, status monitoring, and low-power management. The main program places manual / automatic mode switching judgments, safety interlock checks, and composite control strategy calculations within interrupt service functions, which are then placed within the main function. The main function uses a while loop to switch operating states, including updating setpoints, recording data, status monitoring, and low-power management. An inline feedforward control calculation function is provided for use in composite control strategy calculations. It also includes an output limiting function to prevent integral term saturation in PID feedback control; the interrupt service function calls the output limiting function to limit the final output value to the actuator. The control module (MCU) establishes input buffers for each sensor and output buffers for each actuator. Raw sensor data is stored in the sensor input buffer. The interrupt service routine (ISR) calculates the actuator output parameters and stores them in the actuator output buffer. The main function then calls the buffer to output the control parameters to the actuator, eliminating race conditions between the ISR and the main function. The ISR only writes the sampled data, while the main function only reads the current data, avoiding data corruption or inconsistency caused by simultaneous reading and writing of the same variable. Furthermore, the ISR can perform a seamless switch between manual and automatic modes. At the instant of switching from manual to automatic mode, the integral term of the PID controller is initialized with the actual valve position currently operated manually, ensuring that the controller output value is consistent before and after the switch, preventing a sudden change in the control signal and thus avoiding impact on the pickling line.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A pickling line monitoring system, characterized in that: It includes sensors, a control module, and actuators. The sensors monitor the acid concentration, temperature, liquid level, and pickling line speed of the pickling tank. The actuators are used to control the acid replenishment, acid dilution, acid discharge, heating, and circulation processes of the pickling tank. The control module controls the actuators in real time based on the sensor data to maintain the acid concentration in the pickling tank near the optimal value of the pickling process. The real-time control strategy of the control module includes adjusting the output parameters of the actuator in real time using a composite control strategy that integrates feedforward control and PID feedback control. Feedforward control improves feedforward compensation for changes in the speed of the pickling line drive, and PID feedback control sets a dead zone to reduce the disturbance of acid concentration, temperature and liquid level data on the output.

2. The pickling line monitoring system according to claim 1, characterized in that: The sensor includes an acid concentration sensor, used to monitor the acid concentration value of the pickling tank and transmit it to the control module via a 4-20mA analog signal; A temperature sensor is used to monitor the real-time temperature of the acid solution in the pickling tank and transmit it to the control module through a signal conversion module; The level sensor is used to monitor the level and total acid volume in the pickling tank, and transmits the signal to the control module via a 4-20mA analog signal. The encoder is used to measure the speed of the pickling line drive and transmits the real-time speed to the control module via high-speed pulse signals or fieldbus protocols.

3. The pickling line monitoring system according to claim 2, characterized in that: The actuator includes: several regulating valves for replenishing acid to the pickling tank and diluting acid, and the opening degree of the valves is controlled by the control module with analog output signals; The on / off valve is used to drain acid from the pickling tank, and its opening and closing are controlled by the control module through a switching signal. The heater is used to heat the acid solution in the pickling tank. The heating power of the heater is controlled in real time by the control module using an analog output signal. The circulating pump is used to circulate the acid solution in the pickling tank, and its start and stop are controlled by the control module through a switch signal.

4. The pickling line monitoring system according to claim 3, characterized in that: The composite control strategy of the control module includes: When the pickling tank level falls below the threshold, the processor module activates a safety interlock to stop all outputs to the actuators and close all valves. When the monitoring system is in manual mode, all outputs of the control module to the actuator are directly set by the operator. When the monitoring system is in automatic mode, the control module determines whether the last program polling mode was manual mode. If so, it retains the PID feedback control parameters from the last manual mode and enables feedforward control. Otherwise, it adjusts the PID feedback control parameters in real time based on sensor data and enables feedforward control.

5. The pickling line monitoring system according to claim 3, characterized in that: The formula for the composite control strategy of the control module is as follows: ； ； ； In the formula, To adjust the target opening of the acid replenishment regulating valve, For feedforward control output, For PID feedback control output, This is the gain coefficient. This refers to the real-time linear speed of the pickling line drive. This is the baseline speed for the pickling line drive. The reference opening degree for adjusting the acid replenishment valve; For the proportion term, For integration, For differential terms, This represents the target acid concentration after dead zone treatment. For the effective error integral, To suppress the overshoot rate of change in acid concentration.

6. The pickling line monitoring system according to claim 4, characterized in that: The control module performs logic calculations and control through an MCU. The MCU control functions include: The composite control strategy calculation is based on the acid concentration value, acid temperature value, liquid level height value, and transmission speed value fed back by the system, combined with the manually set acid concentration set value, temperature set value, and upper and lower limits of liquid level. It calculates and outputs in real time the opening degree of the acid replenishment regulating valve, the opening degree of the acid dilution regulating valve, the regulating power of the heater, and the closed state of the acid discharge switch valve. Automatic mode switching judgment: When the system switches from automatic to manual, the integral term of the PID controller is initialized according to the current PID feedback control parameters, the PID feedback control parameters of the last polled mode, and the actual valve position of the previous manual operation, so that the controller outputs a continuous and smooth value before and after the switch. Conversely, when the system switches from manual to automatic, the integral term of the PID controller is initialized according to the actual valve position of the current manual operation, the PID feedback control parameters of the current automatic mode, and the PID feedback control parameters of the last polled mode, so that the controller outputs a continuous and smooth value before and after the switch. The last polled manual / automatic control state is stored to prepare for the next manual / automatic switching action.

7. The pickling line monitoring system according to claim 6, characterized in that: The control module MCU packages input variables, output variables, set values, and parameter values ​​into a structure according to their sequential addresses. The main function parses and reads / writes the structure to achieve high real-time performance and high refresh rate response to the composite control strategy. The control module MCU uses interrupt service functions to perform composite control strategy calculations and automatic mode switching judgments, and uses the main function to switch working states including updating set values, recording data, status monitoring, and low power management.

8. The pickling line monitoring system according to claim 7, characterized in that: The control module MCU establishes input buffers for each sensor and output buffers for each actuator. The raw sensor data is stored in the sensor input buffer. The interrupt service function calculates the actuator output parameters and stores them in the actuator output buffer. The buffer is called in the main function to output the control parameters to the actuator, thereby eliminating the race condition between the interrupt service function and the main function.

Images