Automatic control method and system for a four-roll roll coater

Abstract

The application discloses an automatic control method and system of a four-roller roller coater, and the method comprises the following steps: when a welding seam detection signal is received when no coating is performed, the coating roller and the strip roller of the upper and lower coating heads are controlled to move to a specified position and rotate at a linear velocity setting value; the inter-roller pressure is obtained, the step motor of the strip roller is adjusted to control the inter-roller pressure to a setting value and keep, then the down action of the hydraulic cylinder of the upper and lower coating heads is delayed to start coating the strip steel; when a welding seam detection signal is received during the coating process, if the coating needs to be continued, the quick opening and down action of the hydraulic cylinder of the upper and lower coating heads is performed, so that the corresponding coating head hydraulic cylinder is in an open state when the welding seam passes through the upper and lower coating heads; if the coating does not need to be continued, the hydraulic cylinder of the upper and lower coating heads is opened to wait for the next coating instruction. The application adopts a quick opening hydraulic cylinder to solve the problem that the roller coater equipment may be damaged when the welding seam passes through the roller coater, and adopts an inter-roller pressure closed-loop control method to solve the control precision problem of the inter-roller pressure.

Description

Technical Field

[0001] This invention belongs to the field of roller coating machine control technology, specifically relating to an automatic control method and system for a four-roller roller coating machine. Background Technology

[0002] Roller coaters are used to coat the upper and lower surfaces of strip steel with a coating liquid. If multiple strip steels are to be coated continuously, the weld seam needs to be treated when it passes through the roller coater. Otherwise, the weld seam may scratch the coating roller and damage the roller coater equipment. In addition, when the specifications of two strip steels are significantly different, the process parameters of the roller coater also need to be switched quickly near the weld seam.

[0003] The primary indicator for judging the coating quality of a roller coater is the thickness of the coating film. Strip steel has very strict requirements regarding the thickness of the coating film; if the thickness is too thin or uneven, the strip steel will oxidize and corrode too quickly due to insufficient protection. Conversely, if the thickness is too thick, it also fails to meet quality requirements and results in wasted coating material. Furthermore, the precision of the inter-roller pressure—the pressure between the coating roller and the strip roller—directly affects the coating thickness accuracy and has a significant impact on the coating quality. Summary of the Invention

[0004] The purpose of this invention is to provide an automatic control method and system for a four-roller coating machine. It uses a quick-opening hydraulic cylinder to solve the problem of potential damage to the coating machine equipment when the weld seam passes through the machine, and uses a closed-loop control method for inter-roller pressure to solve the problem of control accuracy of inter-roller pressure.

[0005] The technical solution adopted in this invention is as follows:

[0006] An automatic control method for a four-roller coating machine includes the following steps:

[0007] When a weld detection signal is received before coating, the coating rollers and material rollers of the upper and lower coating heads are controlled to move to the designated position and rotate at the set linear speed value.

[0008] Obtain the inter-roller pressure, adjust the stepper motor of the strip roller to control the inter-roller pressure to the set value and maintain it, and then delay the pressing action of the upper and lower coating head hydraulic cylinders to start coating the strip.

[0009] The start-up delay time is calculated based on the weld distance and coating distance.

[0010] T Start，UR =(D gap，UR +D Coate ) / V Line -T SDown，UR

[0011] T Start，DR =(D gap，UR +D Coate ) / V Line -TSDown，DR

[0012] In the formula, T Start，UR and T Start，DR These are the start-up delay times for the upper and lower coating heads, respectively. The timing begins upon receiving the weld detection signal. If the timing reaches the start-up delay time for the upper and lower coating heads, the corresponding coating head hydraulic cylinder will press down. gap，UR D is the distance between the weld seam and the center point of the coating roller on the top coating head. Coate V is the coating distance. Line T is the linear velocity of the generator unit. SDown，UR and T SDown，DR These represent the time required for the upper and lower coating head hydraulic cylinders to perform the pressing action;

[0013] When a weld detection signal is received during the coating process, if coating needs to continue, the upper and lower coating head hydraulic cylinders are quickly opened and pressed down, so that the corresponding coating head hydraulic cylinder is in the open state when the weld passes through the upper and lower coating heads, and in the closed state after passing through the upper and lower coating heads; if coating does not need to continue, the upper and lower coating head hydraulic cylinders are opened to wait for the next coating command.

[0014] The quick-opening delay time of the hydraulic cylinders for the upper and lower coating heads is calculated based on the weld distance and quick-opening distance:

[0015] T QOpen，UR =(D gap，UR -D QOpen ) / V Line

[0016] T QOpen，DR =(D gap，UR -D QOpen -D UR，DR ) / V Line

[0017] In the formula, T QOpen，UR and T QOpen，DR These are the quick-opening delay times for the hydraulic cylinders of the upper and lower coating heads, respectively. The timing begins when the weld inspection signal is most recently received. If the timing reaches the quick-opening delay time for the hydraulic cylinders of the upper and lower coating heads, the corresponding coating head hydraulic cylinder will open. QOpen To increase the opening distance, D UR，DR This refers to the distance between the coating rollers of the upper and lower coating heads;

[0018] Calculate the hydraulic cylinder pressing delay time of the upper and lower coating heads based on the action time of the upper and lower coating heads hydraulic cylinders:

[0019] T QClose，UR =(D gap，UR -D QOpen ) / V Line +T SDown，DR +TOpen，DR -T SDown，UR

[0020] T QClose，DR =(D gap，UR -D QOpen -D UR，DR ) / V Line +T Open，DR

[0021] In the formula, T QClose，UR and T QClose，DR These are the hydraulic cylinder pressing delay times for the upper and lower coating heads, respectively. The timing starts from the last received weld inspection signal. If the timing reaches the hydraulic cylinder pressing delay time for both the upper and lower coating heads, the corresponding coating head hydraulic cylinder will press down. T Open，DR The time required for the quick-opening action of the hydraulic cylinder of the coating head.

[0022] Furthermore, the linear velocity setting value is calculated based on the speed ratio setting value:

[0023] V CR，Line =V Line ×R CR

[0024] V PR，Line =V Line ×R PR

[0025] In the formula, V CR，Line and V PR，Line These are the linear speed settings for the coating roller and the conveyor roller, R. CR and R PR These are the set speed ratios of the coating roller and the conveyor roller, V. Line This refers to the unit's linear velocity.

[0026] Furthermore, a proportional controller is used to control the movement of the coating roller to the coating work position:

[0027] S UCRDS，SP =K UCR，Pos ×(L UCR，Work -L UCRDS，Act )

[0028] In the formula, S UCRDS，SP K is the speed setting value for the stepper motor of the coating roller. UCR，Pos L is the proportional parameter of the coating roller proportional controller. UCR，Work L is the working position setting value for the stepper motor of the coating roller. UCRDS，Act This represents the actual position of the stepper motor for the coating roller.

[0029] Use a proportional controller to move the feed roller to the position where it will contact the coating roller:

[0030] S UPRDS，SP =K UPR，Pos ×(L UPR，Touch -L UPRDS，Act )

[0031] In the formula, S UPRDS，SP K is the speed setpoint for the stepper motor of the conveyor roller. UPR，Pos L is the proportional parameter of the belt roller proportional controller. UPR，Touch The value L is set to the position where the feed roller is about to contact the coating roller. UPRDS，Act This represents the actual position of the stepper motor for the conveyor roller.

[0032] Furthermore, the process of obtaining the inter-roller pressure, adjusting the stepper motor of the conveyor roller to control the inter-roller pressure to a set value and maintaining it includes:

[0033] Obtain the actual value of the inter-roller pressure and calculate the pressure difference, which is the inter-roller pressure setpoint minus the actual inter-roller pressure. Use a proportional-integral controller to calculate the stepper motor speed control amount of the conveyor roller based on the pressure difference, and limit the stepper motor speed control amount, as shown in the following formula:

[0034]

[0035] In the formula, S UPRDS，SP (N) represents the current speed control value of the stepper motor for the conveyor roller, S UPRDS，SP (N-1) represents the speed control value of the stepper motor of the conveyor roller at the previous moment; LIM represents the limiting circuit, which controls the calculated speed control value within a reasonable range; K UPR，Press and T I，Press These are the proportional parameter and the integral time parameter, respectively, which are the PI control parameter values ​​of the proportional-integral controller; T S P represents the sampling time interval. UR，Act (N) represents the actual value of the roller pressure at the current moment, P UR，Act (N-1) represents the actual value of the roller pressure at the previous moment; P UR，SP This is the set value for the inter-roller pressure.

[0036] Furthermore, the stepper motor of the conveyor roller is adjusted to move the conveyor roller to a position where it is about to contact the coating roller. Once in position, the pressure sensor between the coating roller and the conveyor roller is zeroed and filtered to obtain the actual value of the inter-roller pressure, including:

[0037] There are four pressure sensors between the coating roller and the conveyor roller, located on the upper coating head drive side, the upper coating head operation side, the lower coating head drive side, and the lower coating head operation side, respectively.

[0038] After the feed roller moves to the position where it is about to contact the coating roller, record the pressure measurement values ​​of the pressure sensors on the upper coating head drive side, upper coating head operating side, lower coating head drive side, and lower coating head operating side as the pressure zeroing values, and denote them as P. 0，URDS P 0，UROS P 0，DRDS and P 0，DROS ;

[0039] The measured values ​​from each pressure sensor need to be smoothed and filtered by a first-order hysteresis circuit PT1. The average of the filtered pressure values ​​from both sides of the coating head then yields the actual inter-roll pressure value between the upper and lower coating heads.

[0040] P UR，Act =0.5×[PT1(P UR，DS -P 0，URDS )+PT1(P UR，OS -P 0，UROS )]

[0041] P DR，Act =0.5×[PT1(P DR，DS -P 0，DRDS )+PT1(P DR，OS -P 0，DROS )]

[0042] In the formula, P UR，Act and P DR，Act These are the actual values ​​of the roller pressure between the upper and lower coating heads, P. UR，DS P UR，OS P DR，DS and P DR，OS These are the measured values ​​from the pressure sensors on the upper coating head drive side, upper coating head operation side, lower coating head drive side, and lower coating head operation side, respectively. PT1 represents the first-order hysteresis element, and the algorithm for the discrete PT1 element is as follows:

[0043]

[0044] In the formula, Y PT1 (N) represents the current output value of the PT1 circuit; Y PT1 (N-1) represents the output value of the PT1 circuit at the previous time step; T S T is the sampling time interval; PT1 X(N) is the time constant of the PT1 stage; X(N) is the pressure measurement value of the pressure sensor at the current moment.

[0045] Furthermore, the position where the gap between the conveyor roller and the coating roller is 1.0 mm is the position where the conveyor roller and the coating roller are about to make contact.

[0046] Furthermore, the PI control parameter values ​​for the roller pressure are initially calculated based on experience, and then the PI control parameter values ​​are adaptively adjusted according to the pressure difference and unit speed to obtain the final PI control parameter values:

[0047] The PI control parameter value for the roller pressure is initially calculated using an empirical formula, namely:

[0048]

[0049]

[0050] In the formula, K P，PressIni and T I，PressIni These are the initial proportional parameter and the initial integral time parameter, T. S T is the sampling time interval. C K is the time constant of the stepper motor. C This represents the gain coefficient of the stepper motor;

[0051] The proportional parameter is adaptively adjusted based on the pressure difference:

[0052] K P，Press =K P，PressIni ×G a

[0053] In the formula, K P，Press For the final scaling parameter; G a The adaptive factor is determined based on the absolute value of the pressure difference; the larger the absolute value of the pressure difference, the larger the adaptive factor.

[0054] The integral time parameter is adaptively adjusted based on the unit's linear velocity.

[0055]

[0056] In the formula, T I，Press For the final integration time parameter, V Line V is the linear velocity of the generator unit. Mid This is the median value of the unit's linear velocity.

[0057] Furthermore, if further coating is not required, the stop delay time is calculated based on the stop distance:

[0058] T Stop，UR =(D gap，UR -D Stop ) / V Line -T Open，UR

[0059] T Stop，DR =(D gap，DR -D Stop ) / V Line -T Open，DR

[0060] In the formula, T Stop，UR and T Stop，DR These are the stop delay times for the upper and lower coating heads, respectively, D. gap，UR and D gap，DR D represents the distance from the weld seam to the center point of the coating rollers at the upper and lower coating heads, respectively. Stop Stop distance D Stop T Open，UR and T Open，DR These represent the time required for the upper and lower coating head hydraulic cylinders to perform the quick-opening action, respectively.

[0061] Furthermore, the stopping distance D Stop =0.6m.

[0062] An automatic control system for a four-roller coating machine for implementing the automatic control method of any one of the above-described methods, comprising:

[0063] Four pressure sensors, located on the drive side of the upper coating head, the operating side of the upper coating head, the drive side of the lower coating head, and the operating side of the lower coating head, are used to measure the pressure between the coating roller and the conveyor roller of the upper and lower coating heads.

[0064] Four stepper motors for the conveyor rollers are connected to each conveyor roller in pairs, and are used to move the conveyor rollers.

[0065] Four coating roller stepper motors are used to move the coating rollers, with each pair of coating roller stepper motors connected to one coating roller.

[0066] The weld inspection instrument is located at the feed end of the four-roller coater and is used to inspect welds and send weld inspection signals.

[0067] The frequency converter is connected to the drive motor of the coating roller and the conveyor roller of the upper coating head and the lower coating head, and is used to control the speed of the coating roller and the conveyor roller.

[0068] A stepper motor amplifier, connected to eight stepper motors, is used to control the eight stepper motors, and in turn control the position of the coating roller and the conveyor roller;

[0069] The upper and lower coating head hydraulic cylinders are connected to the upper and lower coating heads respectively, and are used to perform the quick opening and pressing actions of the upper and lower coating head hydraulic cylinders;

[0070] The PLC controller, connected to a weld inspection instrument, frequency converter, stepper motor amplifier, and four pressure sensors, is used to control the coating rollers and strip rollers of the upper and lower coating heads to move to a designated position and rotate at a set linear speed after receiving a weld inspection signal when no coating is applied. It is also used to acquire the inter-roller pressure, adjust the stepper motor of the strip roller to control the inter-roller pressure to the set value and maintain it, and then, after a delay, perform the pressing action of the hydraulic cylinders of the upper and lower coating heads to begin coating the strip. Furthermore, when a weld inspection signal is received during the coating process, if continued coating is required, it performs a quick opening and pressing action of the hydraulic cylinders of the upper and lower coating heads, so that the corresponding hydraulic cylinder is open when the weld passes through the upper and lower coating heads and closed after passing through them; if continued coating is not required, it opens the hydraulic cylinders of the upper and lower coating heads to await the next coating command.

[0071] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0072] The automatic control method and system for the four-roller coating machine provided by this invention realizes the function of automatically coating the upper and lower surfaces of the strip steel. By using the quick opening and pressing action of the hydraulic cylinders of the upper and lower coating heads, the problem of potential equipment damage when the weld seam passes through the coating machine is solved. Furthermore, by using the inter-roller pressure signal fed back by the pressure sensor and using a PI controller to adjust the speed of the stepper motor, the closed-loop control function of the inter-roller pressure is completed, which improves the control accuracy of the inter-roller pressure and reduces the labor intensity of the workers. Attached Figure Description

[0073] Figure 1 This is a flowchart illustrating the automatic control method for a four-roller coating machine according to an embodiment of the present invention.

[0074] Figure 2 This is a schematic diagram of the automatic control system of a four-roller coating machine according to an embodiment of the present invention.

[0075] In the diagram: 1-Strip steel, 2-Stepper motor driven by the upper coating head conveyor roller, 3-Driver motor of the upper conveyor roller, 4-Upper conveyor roller, 5-Pressure sensor of the upper coating head, 6-Hydraulic cylinder of the upper coating head, 7-Stepper motor driven by the upper coating head coating roller, 8-Driver motor of the upper coating roller, 9-Upper coating roller, 10-Frequency converter, 11-Stepper motor amplifier, 12-PLC controller, 13-Driver motor of the lower coating roller, 14-Lower coating roller, 15-Hydraulic cylinder of the lower coating head, 16-Stepper motor driven by the lower coating head coating roller, 17-Driver motor of the lower conveyor roller, 18-Lower conveyor roller, 19-Pressure sensor of the lower coating head, 20-Stepper motor driven by the lower coating head conveyor roller, 21-Weld inspection instrument. Detailed Implementation

[0076] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0077] This invention provides an automatic control method and system for a four-roller coater. The method includes: upon receiving a weld detection signal before coating, adjusting the drive motor to rotate to a set speed, and adjusting the stepper motor to move the coating roller and the strip roller to a designated position; adjusting the stepper motor of the strip roller to control the inter-roller pressure to a set value and maintaining it, then delaying the closing action of the upper and lower coating head hydraulic cylinders to begin coating the strip; if a weld detection signal is received during coating, and coating needs to continue, the hydraulic cylinders are quickly opened and closed; otherwise, coating is not needed, the hydraulic cylinders are opened to await the next coating command. This automatic control method and system for a four-roller coater solves the problem of potential equipment damage when welds pass through the coater. It utilizes the inter-roller pressure signal fed back by a pressure sensor and employs a proportional-integral controller to achieve closed-loop control of the inter-roller pressure, improving the control accuracy of the inter-roller pressure.

[0078] like Figure 1 As shown, this embodiment of the invention provides an automatic control method for a four-roller coating machine, comprising the following steps:

[0079] S10. When a weld detection signal is received before coating, adjust the drive motor to rotate to the set speed, and adjust the stepper motor to move the coating roller and the material roller to the designated position.

[0080] S20. Adjust the stepper motor of the strip roller to control the pressure between the rollers to the set value and maintain it. Then, after a delay, perform the closing action of the upper and lower coating head hydraulic cylinders to start coating the strip.

[0081] S30. If a weld detection signal is received during the coating process, and coating needs to continue, the hydraulic cylinder will quickly open and close; if coating does not need to continue, the hydraulic cylinder will open and wait for the next coating command.

[0082] Step S10 specifically includes:

[0083] S101. When the weld detection signal rises before coating, a start-up preparation signal is issued, and the coating roller and the conveyor roller rotate to the specified linear speed.

[0084] When the weld detection signal shows a rising edge before coating, it indicates that a strip of steel is approaching the roll coater. At this time, the PLC immediately sends a roll coater start-up preparation signal C. PrepSimultaneously, a command is sent to the frequency converter to control the coating rollers and conveyor rollers of the upper and lower coating heads to start rotating. After rotating to the specified linear speed, they are maintained. The linear speed setpoint is calculated based on the speed ratio setpoint, i.e.:

[0085] V CR，Line =V Line ×R CR

[0086] V PR，Line =V Line ×R PR

[0087] In the formula, V CR，Line and V PR，Line These are the linear speed settings for the coating roller and the conveyor roller, R. CR and R PR These are the set speed ratios of the coating roller and the conveyor roller, V. Line This refers to the unit's linear velocity.

[0088] S102. Adjust the stepper motor of the coating roller and use a proportional controller to control the coating roller to move to the coating work position.

[0089] like Figure 2 As shown, adjust the four stepper motors on both sides of the upper and lower coating rollers. Figure 2 The above only shows two stepper motors on the drive side: stepper motor 7 on the upper coating head coating roller drive side and stepper motor 16 on the lower coating head coating roller drive side (there are two more stepper motors on the operating side). A proportional controller is used to calculate the stepper motor speed control value to move the coating roller to the coating working position. Taking stepper motor 7 on the upper coating head coating roller drive side as an example, the calculation method for the other three stepper motors is similar, that is:

[0090] S UCRDS，SP =K UCR，Pos ×(L UCR，Work -L UCRDS，Act )

[0091] In the formula, S UCRDS，SP K is the speed setting value for the stepper motor on the drive side of the coating head coating roller. UCR，Pos L is the proportional parameter of the proportional controller in the position control mode of the stepper motor of the coating head coating roller. UCR，Work L is the working position setting value for the stepper motor of the coating head coating roller. UCRDS，Act The actual position value of the stepper motor on the drive side of the coating roller of the top coating head is provided by the absolute pulse encoder built into the stepper motor.

[0092] S103. Adjust the stepper motor of the conveyor roller and use a proportional controller to control the conveyor roller to move to the position where it will contact the coating roller.

[0093] like Figure 2As shown, adjust the four stepper motors on both sides of the upper and lower conveyor rollers. Figure 2 Only two stepper motors on the drive side are shown: stepper motor 2 on the upper coating head conveyor roller drive side and stepper motor 20 on the lower coating head conveyor roller drive side (there are two more stepper motors on the operation side). A proportional controller is used to calculate the stepper motor speed control amount, moving the conveyor roller to the position where it will almost contact the coating roller. In this embodiment, this position is defined as the distance between the surface of the conveyor roller and the coating roller being 1.0 mm. Taking stepper motor 2 on the upper coating head conveyor roller drive side as an example, the calculation method for the other three stepper motors is similar, that is:

[0094] S UPRDS，SP =K UPR，Pos ×(L UPR，Touch -L UPRDS，Act )

[0095] In the formula, S UPRDS，SP K is the speed setting value for the stepper motor on the drive side of the coating head conveyor roller. UPR，Pos L is the proportional parameter of the proportional controller in the position control mode of the stepper motor of the coating head conveyor roller. UPR，Touch L is the set value for the position where the top coating head conveyor roller is about to contact the coating roller. UPRDS，Act The actual position value of the stepper motor on the drive side of the coating head conveyor roller is provided by the absolute pulse encoder built into the stepper motor.

[0096] Step S20 specifically includes:

[0097] S201. Adjust the stepper motor of the conveyor roller and use a proportional-integral controller to control the inter-roller pressure to reach and maintain the set value.

[0098] Once the conveyor roller is about to contact the coating roller, the system switches to pressure control mode. A proportional-integral (PI) controller calculates the speed control value of the stepper motor, and a limiting circuit restricts the speed control value within a certain range. This controls the inter-roller pressure to the set value and maintains it. Using the stepper motor on the conveyor roller drive side of the coating head as an example, the calculation method for the other three stepper motors is similar:

[0099]

[0100]

[0101] In the formula, S UPRDS，SP (N) represents the speed control value of the stepper motor on the drive side of the coating head conveyor roller at the current moment, S UPRDS，SP(N-1) represents the stepper motor speed control value at the previous moment. Note that the calculated stepper motor speed control value is simultaneously applied to the stepper motors on both sides of the conveyor roller to maintain synchronization. LIM represents the limiting stage, which requires controlling the calculated speed control value within a reasonable range. P UR，SP P is the set value for the inter-roller pressure. UR，Act (N) and P UR，Act (N-1) represents the actual values ​​of the roller pressure of the coating head at the current time and the previous time, respectively, which are obtained by averaging the measured values ​​of the pressure sensors on both sides of the coating head.

[0102] Furthermore, the stepper motor of the conveyor roller is adjusted to move the conveyor roller to a position where it is about to contact the coating roller. Once in position, the pressure sensor between the coating roller and the conveyor roller is zeroed and filtered to obtain the actual value of the inter-roller pressure, including:

[0103] There are four pressure sensors between the coating roller and the conveyor roller, located on the upper coating head drive side, the upper coating head operation side, the lower coating head drive side, and the lower coating head operation side, respectively.

[0104] After the feed roller moves to the position where it is about to contact the coating roller, record the pressure measurement values ​​of the pressure sensors on the upper coating head drive side, upper coating head operating side, lower coating head drive side, and lower coating head operating side as the pressure zeroing values, and denote them as P. 0，URDS P 0，UROS P 0，DRDS and P 0，DROS ;

[0105] The measured values ​​from each pressure sensor need to be smoothed and filtered by a first-order hysteresis circuit PT1. The average of the filtered pressure values ​​from both sides of the coating head then yields the actual inter-roll pressure value between the upper and lower coating heads.

[0106] P UR，Act =0.5×[PT1(P UR，DS -P 0，URDS )+PT1(P UR，OS -P 0，UROS )]

[0107] P DR，Act =0.5×[PT1(P DR，DS -P 0，DRDS )+PT1(P DR，OS -P 0，DROS )]

[0108] In the formula, P UR，Act and P DR，Act These are the actual values ​​of the roller pressure between the upper and lower coating heads, P. UR，DS P UR，OS P DR，DS and PDR，OS These are the measured values ​​from the pressure sensors on the upper coating head drive side, upper coating head operation side, lower coating head drive side, and lower coating head operation side, respectively. PT1 represents the first-order hysteresis element, and the algorithm for the discrete PT1 element is as follows:

[0109]

[0110] In the formula, Y PT1 (N) represents the current output value of the PT1 circuit; Y PT1 (N-1) represents the output value of the PT1 circuit at the previous time step; T S T is the sampling time interval; PT1 X(N) is the time constant of the PT1 stage; X(N) is the pressure measurement value of the pressure sensor at the current moment.

[0111] Furthermore, the PI control parameter values ​​for the roller pressure are initially calculated based on experience, and then the PI control parameter values ​​are adaptively adjusted according to the pressure difference and unit speed to obtain the final PI control parameter values:

[0112] The PI control parameter value for the roller pressure is initially calculated using an empirical formula, namely:

[0113]

[0114]

[0115] In the formula, K P，PressIni and T I，PressIni These are the initial proportional parameter and the initial integral time parameter, T. S T is the sampling time interval. C K is the time constant of the stepper motor. C This represents the gain coefficient of the stepper motor;

[0116] The proportional parameter is adaptively adjusted based on the pressure difference:

[0117] K P，Press =K P，PressIni ×G a

[0118] In the formula, K P，Press For the final scaling parameter; G a The adaptive factor is determined based on the absolute value of the pressure difference; the larger the absolute value of the pressure difference, the larger the adaptive factor.

[0119] The integral time parameter is adaptively adjusted based on the unit's linear velocity.

[0120]

[0121] In the formula, T I，PressFor the final integration time parameter, V Line V is the linear velocity of the generator unit. Mid This is the median value of the unit's linear velocity.

[0122] Furthermore, if further coating is not required, the stop delay time is calculated based on the stop distance:

[0123] T Stop，UR =(D gap，UR -D Stop ) / V Line -T Open，UR

[0124] T Stop，DR =(D gap，DR -D Stop ) / V Line -T Open，DR

[0125] In the formula, T Stop，UR and T Stop，DR These are the stop delay times for the upper and lower coating heads, respectively, D. gap，UR and D gap，DR D represents the distance from the weld seam to the center point of the coating rollers at the upper and lower coating heads, respectively. Stop Stop distance D Stop T Open，UR and T Open，DR These represent the time required for the upper and lower coating head hydraulic cylinders to perform the quick-opening action, respectively.

[0126] S202. Calculate the start-up delay time based on the weld distance and coating distance.

[0127] Startup delay time T Start Calculated based on weld spacing and coating distance, i.e.:

[0128] T Start，UR =(D gap，UR +D Coate ) / V Line -T SDown，UR

[0129] T Start，DR =(D gap，UR +D Coate ) / V Line -T SDown，DR

[0130] In the formula, T Start，UR and T Start，DR D represents the start-up delay time for the upper coating head and the lower coating head, respectively. gap，UR The distance between the weld inspection instrument and the center point of the upper coating head's coating roller is used; the start-up delay time of the lower coating head also uses D. gap，URThis is to ensure that the upper and lower coating heads begin coating at exactly the same position (there is a small distance between the center points of the coating rollers of the upper and lower coating heads). Generally, coating begins a short distance after the weld seam has passed the center point of the coating roller; this distance is called the coating distance D. Coate For example, in this embodiment, D is set Coate =0.5m. T SDown，UR and T SDown，DR These are the times required for the upper and lower coating head hydraulic cylinders to perform the pressing action, respectively. Since the stroke of the lower coating head hydraulic cylinder is longer, the pressing action time of the lower coating head hydraulic cylinder is slightly longer.

[0131] S203. After the timer reaches the start delay time, the upper and lower coating head hydraulic cylinders close to start coating.

[0132] Two timers, Timer1 and Timer2, are used to record the delay time of the upper and lower coating heads, respectively. Timing begins when the weld detection signal shows a rising edge. The delay time of Timer1 equals the upper coating head start delay time T. Start，UR At this time, the hydraulic cylinder of the top coating head begins to close, and the top coating roller gradually contacts the strip and creates a small wrap angle, initiating the coating process on the upper surface. Similarly, when the delay time of Timer2 equals the start-up delay time T of the top coating head... Start，DR At this time, the hydraulic cylinder of the lower coating head begins to close, and the lower coating roller gradually contacts the strip steel and creates a small wrap angle, thus beginning the coating process on the lower surface.

[0133] Step S30 specifically includes:

[0134] S301. During the coating process, a weld detection signal is received, and the hydraulic cylinder quick-opening delay time of the upper and lower coating heads is calculated based on the weld distance and quick-opening distance.

[0135] During the coating process, the rising edge of the weld detection signal indicates that the coating of this strip steel coil is about to be completed. The quick-opening delay time of the hydraulic cylinders of the upper and lower coating heads is calculated based on the weld distance and quick-opening distance.

[0136] T QOpen，UR =(D gap，UR -D QOpen ) / V Line

[0137] T QOpen，DR =(D gap，UR -D QOpen -D UR，DR ) / V Line

[0138] In the formula, T QOpen，UR and T QOpen，DRThese are the quick-opening delay times for the hydraulic cylinders of the upper and lower coating heads, respectively. Generally, the hydraulic cylinders need to open when the weld seam is still a short distance from the center of the coating roller to prevent the weld seam from scratching the coating roller. This distance is called the quick-opening distance D. QOpen For example, in this embodiment, D is set. QOpen =0.5m. D UR，DR The distance between the center lines of the coating rollers of the upper and lower coating heads is such that, in order to perform a quick-opening operation at the same distance between the weld seam and the upper and lower surfaces of the strip, the quick-opening delay time of the hydraulic cylinder of the lower coating head is slightly shorter.

[0139] S302. If coating is required to continue, calculate the hydraulic cylinder pressing delay time of the upper and lower coating heads based on the hydraulic cylinder action time.

[0140] If another strip needs coating immediately after the current strip is coated, the hydraulic cylinder pressing delay time needs to be calculated. Because the hydraulic cylinder stroke of the lower coating head is longer, both the quick-opening and pressing actions of the lower coating head's hydraulic cylinder are slightly longer. To save time as much as possible, it is stipulated that the pressing action should be performed immediately after the lower coating head's quick-opening is completed, so as to resume the coating process as quickly as possible. Therefore, the hydraulic cylinder pressing delay time T of the lower coating head is... QClose，DR for:

[0141] T QClose，DR =(D gap，UR -D QOpen -D UR，DR ) / V Line +T Open，DR

[0142] In the formula, T Open，DR The time required for the quick-opening action of the hydraulic cylinder of the coating head.

[0143] To ensure that the upper and lower coating heads restart coating at the same position on the strip, the hydraulic cylinder of the upper coating head needs to wait a short period after completing the quick-opening action before performing the pressing action. Therefore, the pressing delay time T of the hydraulic cylinder of the upper coating head is... QClose，UR for:

[0144] T QClose，UR =(D gap，UR -D QOpen ) / V Line +T SDown，DR +T Open，DR -T SDown，UR

[0145] S303. If no further coating is required, calculate the stop delay time based on the stop distance.

[0146] If no further coating is required after the coating of this strip is completed, the stop delay time shall be calculated based on the stop distance:

[0147] T Stop，UR =(D gap，UR -D Stop ) / V Line -T Open，UR

[0148] T Stop，DR =(D gap，DR -D Stop ) / V Line -T Open，DR

[0149] In the formula, T Stop，UR and T Stop，DR These are the stop delay times for the upper and lower coating heads, respectively, D. gap，UR and D gap，DR These are the distances from the weld inspection instrument to the center points of the coating rollers at the upper and lower coating heads, respectively. Generally, the operation should be stopped when the weld is still a short distance from the center point of the coating roller; this distance is called the stop distance D. Stop In this embodiment, D is set Stop =0.6m. T Open，UR and T Open，DR These represent the time required for the upper and lower coating head hydraulic cylinders to perform the quick-opening action, respectively.

[0150] S304. Use a timer to wait for the delay of each action to arrive, and then execute the corresponding action.

[0151] If another strip needs coating immediately after the current strip is coated, four timers (Timer3, Timer4, Timer5, and Timer6) are used to record the quick-opening delay time and pressing delay time of the upper and lower coating heads, respectively, starting from the moment the weld detection signal shows a rising edge during the coating process. The delay time of Timer3 is equal to the quick-opening delay time T of the upper coating head hydraulic cylinder. QOpen，UR When the delay time of Timer4 equals the delay time T of the quick-opening hydraulic cylinder of the lower coating head, the upper coating head hydraulic cylinder will perform a quick-opening action. QOpen，DR When the timer5 delay is equal to the upper coating head hydraulic cylinder's downward delay time T, the lower coating head hydraulic cylinder will quickly open; when the delay time of Timer5 is equal to the delay time T of the upper coating head hydraulic cylinder, the lower coating head hydraulic cylinder will quickly open. QClose，UR When the upper coating head hydraulic cylinder presses down, the coating can continue to coat the upper surface of the next strip of steel. When the delay time of Timer6 is equal to the lower coating head hydraulic cylinder pressing down delay time T... QClose，DR At that time, the hydraulic cylinder of the lower coating head is pressed down, and after the action is completed, the coating can continue to the lower surface of the next strip of steel.

[0152] If no next strip needs coating after the current strip coating is completed, two timers, Timer7 and Timer8, are used to record the stop delay time of the upper and lower coating heads, respectively, starting from the rising edge of the weld detection signal received during the coating process. The delay time of Timer7 equals the stop delay time T of the upper coating head. Stop，UR When the upper coating head hydraulic cylinder quickly opens, it waits for the next coating command; when the delay time of Timer8 equals the lower coating head stop delay time T... Stop，DR At this time, the hydraulic cylinder of the coating head is quickly opened, and then it waits for the next coating command.

[0153] By following the steps above, all the processes for coating one strip of steel can be completed, and then the corresponding operation will be automatically performed depending on whether the next strip of steel needs to be coated.

[0154] This invention also provides an automatic control system for a four-roller coating machine, used to implement the above-described method embodiments, such as... Figure 2 As shown, the system includes a PLC controller 12, a frequency converter 10, a stepper motor amplifier 11, an upper coating roller 9, an upper conveyor roller 4, a lower coating roller 14, a lower conveyor roller 18, an upper coating head hydraulic cylinder 6, a lower coating head hydraulic cylinder 15, an upper conveyor roller drive motor 3, an upper coating roller drive motor 8, a lower coating roller drive motor 13 and a lower conveyor roller drive motor 17, an upper coating head conveyor roller drive-side stepper motor 2, an upper coating head coating roller drive-side stepper motor 7, a lower coating head coating roller drive-side stepper motor 16 and a lower coating head conveyor roller drive-side stepper motor 20, an upper coating head pressure sensor 5 and a lower coating head pressure sensor 19, and a weld inspection instrument 21. The upper coating roller 9 and the lower coating roller 14 are used to coat the upper and lower surfaces of the strip steel 1 with coating material. The upper conveyor roller 4 and the lower conveyor roller 18 are used to convey the coating material to the coating rollers. The frequency converter 10 controls the drive motors of the four rollers: the upper conveyor roller drive motor 3, the upper coating roller drive motor 8, the lower coating roller drive motor 13, and the lower conveyor roller drive motor 17, causing the four rollers to rotate at a set speed. The stepper motor amplifier 11 controls eight stepper motors: the upper coating head conveyor roller drive side stepper motor 2, the upper coating head coating roller drive side stepper motor 7, the lower coating head coating roller drive side stepper motor 16, and the lower coating head conveyor roller drive side stepper motor 20 (the roller coater has four stepper motors on both the drive side and the operating side). Figure 2Only four stepper motors on the drive side are shown above. Stepper motor 2 on the upper coating head conveyor roller drive side and stepper motor 20 on the lower coating head conveyor roller drive side are used to move the conveyor roller. The conveyor roller moves towards the coating roller in the positive direction. After the conveyor roller contacts the coating roller, continued positive movement will generate pressure between the two rollers. Stepper motor 7 on the upper coating head coating roller drive side and stepper motor 16 on the lower coating head coating roller drive side are used to move the coating roller. The coating roller moves towards the strip in the positive direction. During coating, the stepper motor moves in the positive direction, so that the coating roller contacts the strip 1 and generates a certain wrap angle. Hydraulic cylinder 6 on the upper coating head and hydraulic cylinder 15 on the lower coating head are used to control the upper and lower coating heads to open quickly when the weld passes through the roller coater. After the weld passes, the upper and lower coating heads are closed to continue coating. Pressure sensor 5 on the upper coating head and pressure sensor 19 on the lower coating head (there are a total of 4 pressure sensors, one on the drive side and one on the operation side of the upper and lower coating heads). Figure 2 The pressure sensor (showing only one side) is used to measure the pressure between the upper and lower coating heads. The weld seam detector 21 is used to detect weld seams in the strip steel. When a weld seam is detected, it sends a signal to the PLC controller 12. The PLC controller 12 communicates with the frequency converter 10 and the stepper motor amplifier 11. The PLC issues control commands to the drive motor and stepper motor. The frequency converter and stepper motor amplifier execute the PLC commands and return the actual values ​​to the PLC. The PLC controller also reads and processes the inter-roller pressure from the pressure sensor. Furthermore, the PLC controller sends open and close commands to the upper coating head hydraulic cylinder 6 and the lower coating head hydraulic cylinder 15 when the roller coater passes through the weld seam. The automatic inter-roller control method of the roller coater described in this invention is entirely programmed and implemented in the PLC controller 12.

[0155] In summary, this invention provides an automatic control method and system for a four-roller coating machine. The method includes: if a weld detection signal is received before coating, adjusting the drive motor to rotate the four rollers to a specified speed and maintaining it; then adjusting the stepper motor to move the coating roller to the working position, while simultaneously moving the material roller to a position about to contact the coating roller; then continuing to adjust the stepper motor of the material roller so that the pressure between the material roller and the coating roller reaches a set value; delaying until the weld has passed a short distance after the upper and lower coating rollers, and then starting the coating process; if a weld detection signal is received during the coating process, and coating needs to continue, the hydraulic cylinder is quickly opened and closed; if coating does not need to continue, the hydraulic cylinder is opened to wait for the next coating command. This automatic control method and system for a four-roller coating machine provides the function of automatically coating the upper and lower surfaces of the strip steel. Through the quick opening and closing action of the hydraulic cylinders of the upper and lower coating heads, the problem of potential equipment damage when the weld passes through the coating machine is solved. By using the pressure signal fed back from the pressure sensor between the rollers, and adjusting the speed of the stepper motor with a PI controller, the closed-loop control function of the roller pressure is completed, which improves the control accuracy of the roller pressure and reduces the labor intensity of workers.

[0156] It should be noted that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0157] It should be noted that, depending on the implementation needs, the various steps / components described in this application can be broken down into more steps / components, or two or more steps / components or parts of the operation of steps / components can be combined into new steps / components to achieve the purpose of this invention.

[0158] Those skilled in the art will readily understand that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An automatic control method for a four-roller coating machine, characterized in that, Includes the following steps: When a weld detection signal is received before coating, the coating rollers and material rollers of the upper and lower coating heads are controlled to move to the designated position and rotate at the set linear speed value. Obtain the inter-roller pressure, adjust the stepper motor of the strip roller to control the inter-roller pressure to the set value and maintain it, and then delay the pressing action of the upper and lower coating head hydraulic cylinders to start coating the strip. The start-up delay time is calculated based on the weld distance and coating distance. T Start,UR =(D gap,UR +D Coate ) / V Line -T SDown,UR T Start,DR =(D gap,UR +D Coate ) / V Line -T SDown,DR In the formula, T Start,UR and T Start,DR These are the start-up delay times for the upper and lower coating heads, respectively. The timing begins upon receiving the weld detection signal. If the timing reaches the start-up delay time for the upper and lower coating heads, the corresponding coating head hydraulic cylinder will press down. gap,UR D is the distance between the weld seam and the center point of the coating roller on the top coating head. Coate V is the coating distance. Line T is the linear velocity of the generator unit. SDown,UR and T SDown,DR These represent the time required for the upper and lower coating head hydraulic cylinders to perform the pressing action; When a weld detection signal is received during the coating process, if coating needs to continue, the upper and lower coating head hydraulic cylinders are quickly opened and pressed down, so that the corresponding coating head hydraulic cylinder is in the open state when the weld passes through the upper and lower coating heads, and in the closed state after passing through the upper and lower coating heads; if coating does not need to continue, the upper and lower coating head hydraulic cylinders are opened to wait for the next coating command. The quick-opening delay time of the hydraulic cylinders for the upper and lower coating heads is calculated based on the weld distance and quick-opening distance: T QOpen,UR =(D gap,UR -D QOpen ) / V Line T QOpen,DR =(D gap,UR -D QOpen -D UR,DR ) / V Line In the formula, T QOpen,UR and T QOpen,DR These are the quick-opening delay times for the hydraulic cylinders of the upper and lower coating heads, respectively. The timing begins when the weld inspection signal is most recently received. If the timing reaches the quick-opening delay time for the hydraulic cylinders of the upper and lower coating heads, the corresponding coating head hydraulic cylinder will open. QOpen To increase the opening distance, D UR,DR This refers to the distance between the coating rollers of the upper and lower coating heads; Calculate the hydraulic cylinder pressing delay time of the upper and lower coating heads based on the action time of the upper and lower coating heads hydraulic cylinders: T QClose,UR =(D gap,UR -D Qopen ) / V Line +T SDown,DR +T Open,DR -T SDown,UR T QClose,DR =(D gap,UR -D QOpen -D UR,DR ) / V Line +T Open,DR In the formula, T QClose,UR and T QClose,DR These are the hydraulic cylinder pressing delay times for the upper and lower coating heads, respectively. The timing starts from the last received weld inspection signal. If the timing reaches the hydraulic cylinder pressing delay time for both the upper and lower coating heads, the corresponding coating head hydraulic cylinder will press down. T Open,DR The time required for the quick-opening action of the hydraulic cylinder of the coating head.

2. The automatic control method for a four-roller coating machine according to claim 1, characterized in that, The linear velocity setting value is calculated based on the speed ratio setting value: V CR,Line =V Line ×R CR V PR,line =V Line ×R PR In the formula, V CR,Line and V PR,Line These are the linear speed settings for the coating roller and the conveyor roller, R. CR and R PR These are the set speed ratios of the coating roller and the conveyor roller, V. Line This refers to the unit's linear velocity.

3. The automatic control method for a four-roller coating machine according to claim 1, characterized in that, Use a proportional controller to control the movement of the coating roller to the coating work position: S UCRDS,SP =K UCR,Pos ×(L UCR,Work -L UCRDS,ACt ) In the formula, S UCRDS,SP K is the speed setting value for the stepper motor of the coating roller. UCR,Pos L is the proportional parameter of the coating roller proportional controller. UCR,Work L is the working position setting value for the stepper motor of the coating roller. UCRDS,Act This represents the actual position of the stepper motor for the coating roller. Use a proportional controller to move the feed roller to the position where it will contact the coating roller: S UPRDS,SP =K UPR,Pos ×(L UPR,Touch -L UPRDS,Act ) In the formula, S UPRDS,SP K is the speed setpoint for the stepper motor of the conveyor roller. UPR,Pos L is the proportional parameter of the belt roller proportional controller. UPR,Touch The value L is set to the position where the feed roller is about to contact the coating roller. UPRDS,Act This represents the actual position of the stepper motor for the conveyor roller.

4. The automatic control method for a four-roller coating machine according to claim 1, characterized in that, Obtaining the inter-roller pressure, adjusting the stepper motor of the conveyor roller to control the inter-roller pressure to a set value and maintaining it, including: Obtain the actual value of the inter-roller pressure and calculate the pressure difference, which is the inter-roller pressure setpoint minus the actual inter-roller pressure. Use a proportional-integral controller to calculate the stepper motor speed control amount of the conveyor roller based on the pressure difference, and limit the stepper motor speed control amount, as shown in the following formula: In the formula, S UPRDS,SP (N) represents the current speed control value of the stepper motor for the conveyor roller, S UPRDS,SP (N-1) represents the speed control value of the stepper motor of the conveyor roller at the previous moment; LIM represents the limiting circuit, which controls the calculated speed control value within a reasonable range; K UPR,Press and T I,Press These are the proportional parameter and the integral time parameter, respectively, which are the PI control parameter values ​​of the proportional-integral controller; T S P represents the sampling time interval. UR,Act (N) represents the actual value of the roller pressure at the current moment, P UR,Act (N-1) represents the actual value of the roller pressure at the previous moment; P UR,SP This is the set value for the inter-roller pressure.

5. The automatic control method for a four-roller coating machine according to claim 4, characterized in that, The stepper motor of the conveyor belt roller is adjusted to move the conveyor belt roller to a position where it is about to contact the coating roller. After it reaches the position, the pressure sensor between the coating roller and the conveyor belt roller is zeroed and filtered to obtain the actual value of the inter-roller pressure, including: There are four pressure sensors between the coating roller and the conveyor roller, located on the upper coating head drive side, the upper coating head operation side, the lower coating head drive side, and the lower coating head operation side, respectively. After the feed roller moves to the position where it is about to contact the coating roller, record the pressure measurement values ​​of the pressure sensors on the upper coating head drive side, upper coating head operating side, lower coating head drive side, and lower coating head operating side as the pressure zeroing values, and denote them as P. 0,URDS P 0,UROS P 0,DRDS and P 0,DROS ; The measured values ​​from each pressure sensor need to be smoothed and filtered by a first-order hysteresis circuit PT1. The average of the filtered pressure values ​​from both sides of the coating head then yields the actual inter-roll pressure value between the upper and lower coating heads. P UR,Act =0.5×[PT1(P UR,DS -P 0,URDS )+PT1(P UR,OS -P 0,UROS )] P DR,Act =0.5×[PT1(P DR,DS -P 0,DRDS )+PT1(P DR,OS -P 0,DROS )] In the formula, P UR,Act and P DR,Act These are the actual values ​​of the roller pressure between the upper and lower coating heads, P. UR,DS P UR,OS P DR,DS and P DR,OS These are the measured values ​​from the pressure sensors on the upper coating head drive side, upper coating head operation side, lower coating head drive side, and lower coating head operation side, respectively. PT1 represents the first-order hysteresis element, and the algorithm for the discrete PT1 element is as follows: In the formula, Y PT1 (N) represents the current output value of the PT1 circuit; Y PT1 (N-1) represents the output value of the PT1 circuit at the previous time step; T S T is the sampling time interval; PT1 X(N) is the time constant of the PT1 stage; X(N) is the pressure measurement value of the pressure sensor at the current moment.

6. The automatic control method for a four-roller coating machine according to claim 5, characterized in that, The position where the gap between the conveyor roller and the coating roller is 1.0 mm is the position where the conveyor roller and the coating roller are about to make contact.

7. The automatic control method for a four-roller coating machine according to claim 4, characterized in that, The PI control parameter values ​​for the roller pressure are initially calculated based on experience. Then, the PI control parameter values ​​are adaptively adjusted according to the pressure difference and unit speed to obtain the final PI control parameter values. The PI control parameter value for the roller pressure is initially calculated using an empirical formula, namely: In the formula, K P,PressIni and T I,PressIni These are the initial proportional parameter and the initial integral time parameter, T. S T is the sampling time interval. C K is the time constant of the stepper motor. C This represents the gain coefficient of the stepper motor; The proportional parameter is adaptively adjusted based on the pressure difference: K P,Press =K P,PressIni ×G a In the formula, K P,Press For the final scaling parameter; G a The adaptive factor is determined based on the absolute value of the pressure difference; the larger the absolute value of the pressure difference, the larger the adaptive factor. The integral time parameter is adaptively adjusted based on the unit's linear velocity. In the formula, T I,Press For the final integration time parameter, V Line V is the linear velocity of the generator unit. Mid This is the median value of the unit's linear velocity.

8. The automatic control method for a four-roller coating machine according to claim 1, characterized in that, If no further coating is required, calculate the stop delay time based on the stop distance: T Stop,UR =(D gap,UR -D Stop ) / V Line -T Open,UR T Stop,DR =(D gap,DR -D Stop ) / V Line -T Open,DR In the formula, T Stop,UR and T Stop,DR These are the stop delay times for the upper and lower coating heads, respectively, D. gap,UR and D gap,DR D represents the distance from the weld seam to the center point of the coating rollers at the upper and lower coating heads, respectively. Stop Stop distance D Stop T Open,UR and T Open,DR These represent the time required for the upper and lower coating head hydraulic cylinders to perform the quick-opening action, respectively.

9. The automatic control method for a four-roller coating machine according to claim 8, characterized in that, Stop distance D Stop =0.6m.

10. An automatic control system for a four-roller coating machine for implementing the automatic control method of any one of claims 1 to 9, characterized in that, include: Four pressure sensors, located on the drive side of the upper coating head, the operating side of the upper coating head, the drive side of the lower coating head, and the operating side of the lower coating head, are used to measure the pressure between the coating roller and the conveyor roller of the upper and lower coating heads. Four stepper motors for the conveyor rollers are connected to each conveyor roller in pairs, and are used to move the conveyor rollers. Four coating roller stepper motors are used to move the coating rollers, with each pair of coating roller stepper motors connected to one coating roller. The weld inspection instrument is located at the feed end of the four-roller coater and is used to inspect welds and send weld inspection signals. The frequency converter is connected to the drive motor of the coating roller and the conveyor roller of the upper coating head and the lower coating head, and is used to control the speed of the coating roller and the conveyor roller. A stepper motor amplifier, connected to eight stepper motors, is used to control the eight stepper motors, and in turn control the position of the coating roller and the conveyor roller; The upper and lower coating head hydraulic cylinders are connected to the upper and lower coating heads respectively, and are used to perform the quick opening and pressing actions of the upper and lower coating head hydraulic cylinders; The PLC controller, connected to a weld inspection instrument, frequency converter, stepper motor amplifier, and four pressure sensors, is used to control the coating rollers and strip rollers of the upper and lower coating heads to move to a designated position and rotate at a set linear speed after receiving a weld inspection signal when no coating is applied. It is also used to acquire the inter-roller pressure, adjust the stepper motor of the strip roller to control the inter-roller pressure to the set value and maintain it, and then, after a delay, perform the pressing action of the hydraulic cylinders of the upper and lower coating heads to begin coating the strip. Furthermore, when a weld inspection signal is received during the coating process, if continued coating is required, it performs a quick opening and pressing action of the hydraulic cylinders of the upper and lower coating heads, so that the corresponding hydraulic cylinder is open when the weld passes through the upper and lower coating heads and closed after passing through them; if continued coating is not required, it opens the hydraulic cylinders of the upper and lower coating heads to await the next coating command.

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