Tension control system based on Siemens S7-1215C

Abstract

The invention discloses a tension control system based on Siemens S7-1215C, solves the problem of poor dynamic performance of an existing tension control technology, and belongs to the technical field of composite material equipment development. The control system comprises a main control unit, a tension detection unit, a data acquisition unit and a speed feedback and execution unit, the data acquisition unit is used for connecting the main control unit with the tension detection unit and the speed feedback and execution unit, the main control unit is realized by adopting a Siemens S7-1215C programmable logic controller, and the main control unit controls the speed feedback and execution unit according to a tension value detected by the tension detection unit in real time and in combination with a target tension value. On the basis of the received current rotating speed of the unwinding unit motor, feedforward rotating speed searching is carried out, then self-adaptive PID fine adjustment is carried out, or the self-adaptive PID fine adjustment is directly carried out, a control signal for driving the unwinding unit motor is obtained and output to the data acquisition unit, and the speed feedback and execution unit is further driven to control the rotating speed of the motor. Therefore, high-response, high-precision and high-robustness tension control is realized.

Description

Technical Field

[0001] This application relates to a tension control system based on Siemens S7-1215C, belonging to the field of composite material equipment development technology. Background Technology

[0002] In modern roll-to-roll processing fields such as papermaking, printing, film production, and lithium electrode sheet manufacturing, high-precision tension control is a core technology for ensuring product quality and production efficiency. While existing tension control systems are widely used, they still face significant challenges in handling high-speed, high-precision, and variable operating conditions. First, traditional PID controllers, using fixed parameters, struggle to adapt to time-varying nonlinear characteristics caused by changes in roll diameter and system start-up / shutdown, often leading to tension overshoot and oscillations, affecting product consistency. Second, closed-loop control relying solely on sensor feedback has inherent response lag, failing to proactively and quickly suppress disturbances such as sudden speed changes, making it difficult to meet the dynamic performance requirements of high-speed production lines.

[0003] To compensate for the shortcomings of feedback control, feedforward control schemes based on convolution diameter estimation have been introduced. However, due to the complexity of model establishment and susceptibility to accumulated errors, their compensation accuracy is limited, making it difficult to achieve ideal results. While advanced algorithms such as fuzzy control and neural networks have superior theoretical performance, they often rely on expensive dedicated controllers or industrial PCs, making integration with widely used PLC platforms difficult, resulting in high implementation costs, long development cycles, and complex maintenance.

[0004] The following are the core problems existing in current tension control technology:

[0005] 1. Response lag versus accuracy contradiction: Traditional PID feedback control suffers from poor dynamic performance due to response lag, while feedforward control based on ideal mathematical models is difficult to achieve high-precision compensation due to the inaccuracy of the model.

[0006] 2. Poor adaptability to working conditions: The PID controller with fixed parameters cannot adapt to changes in working conditions such as roll diameter and speed, resulting in unstable control effect of the system throughout the process, especially tension fluctuations during start-up, shutdown and speed change.

[0007] 3. Complex implementation and high cost: Advanced intelligent algorithms usually rely on dedicated controllers, which are difficult to integrate with standard PLC platforms, resulting in high engineering implementation costs and inconvenient maintenance. Summary of the Invention

[0008] To address the issue of poor dynamic performance in existing tension control technologies, this application provides a tension control system based on Siemens S7-1215C.

[0009] This application discloses a tension control system based on Siemens S7-1215C, comprising:

[0010] The main control unit is implemented using a Siemens S7-1215C programmable logic controller. The main control unit is connected to the data acquisition unit through a switch. It is used to perform feedforward speed search based on the tension value detected in real time by the tension detection unit and the target tension value, and the current speed of the unwinding unit motor. Then, it performs adaptive PID fine-tuning or direct adaptive PID fine-tuning to obtain the control signal to drive the unwinding unit motor and output it to the data acquisition unit.

[0011] The tension detection unit, connected to the data acquisition unit, is used to detect the tension of the roll material in real time and send the data to the data acquisition unit.

[0012] The data acquisition unit, connected to the speed feedback and execution unit, is used to process the tension detected by the tension detection unit and the speed of the unwinding unit motor, and then send them to the main control unit through the switch. It is also used to process the control signals of the main control unit and then send them to the speed feedback and execution unit.

[0013] The speed feedback and execution unit is used to control the speed of the unwinding unit motor according to the control signal of the main control unit, and also to detect the speed of the unwinding unit motor and send it to the data acquisition unit.

[0014] Preferably, the main control unit, based on the tension value detected in real time by the tension detection unit and combined with the target tension value, performs a feedforward speed search based on the current speed of the unwinding unit motor, and then performs adaptive PID fine-tuning, or directly performs adaptive PID fine-tuning, to obtain the control signal for driving the unwinding unit motor. This method includes:

[0015] Obtain the target tension With real-time detected tension value absolute error Obtain percentage error :

[0016]

[0017] If percentage error If the speed is less than the mode selection threshold, the system enters the adaptive PID fine-tuning mode; otherwise, it enters the feedforward speed search mode.

[0018] Feedforward speed search mode:

[0019] Disable the output of the PID feedback control loop, set the search range with the current speed as the center, and set the base speed for the first search. As the current rotational speed;

[0020] The main control unit starts from the lower limit of the set search range, and based on the current speed, adjusts the search based on the speed step size. The control signal for gradually increasing or decreasing the rotational speed is output.

[0021] After outputting the control signal for each rotational speed, a delay is made until the system stabilizes. Then, the tension detected by the tension detection unit is read through the data acquisition unit. ;

[0022] Real-time comparison The size, when When the speed is at its minimum, record the corresponding rotational speed as the optimal feedforward speed. Then it switches to adaptive PID fine-tuning mode;

[0023] After entering adaptive PID fine-tuning mode, the output of the PID controller is: The control signal output by the main control unit is the speed command for driving the unwinding unit motor. .

[0024] As a preferred option, the adaptive PID fine-tuning mode is:

[0025] Start the PID controller; the input is the tension error. To the PID controller;

[0026] PID controller parameter adaptation:

[0027] When the absolute value of tension error Exceeding the threshold At this time, the proportional gain of the PID controller is amplified;

[0028] When the rate of change of tension error Exceeding the threshold At that time, the differential gain is used for amplification;

[0029] Calculate the integral gain based on the cumulative value of the integral term and the tension error during the previous PID control.

[0030] Based on the proportional gain, derivative gain, and integral gain, the output of the PID controller before limiting is obtained. For output After limiting, the output is obtained. .

[0031] Preferably, when the absolute value of the tension error exceeds the integral action threshold, the integral accumulation is temporarily disabled and the integral term is cleared. Simultaneously, after the PID controller outputs, the integral gain is updated through feedback compensation. This will be used as the cumulative integral term for the next PID calculation.

[0032] .

[0033] Preferably, the data acquisition unit reads the tension detected by the tension detection unit. Method:

[0034] The tension detected by the tension detection unit is Converted to engineering values ​​in Newtons. :

[0035]

[0036]

[0037] in, This indicates that an integer type has been converted to a real number type. This represents the tension value after filtering.

[0038] Preferably, the speed step size in the feedforward speed search mode For adaptive values:

[0039]

[0040] in, , k is the proportionality coefficient, when As the speed increases, the speed step size increases; when When the speed is reduced, the speed step size becomes smaller.

[0041] Preferably, the system also includes a human-machine interface unit for setting target tension, start / stop control, and online monitoring of actual tension, motor speed, and current control mode.

[0042] The beneficial effects of this application are that it provides a tension control system based on a Siemens S7-1215C PLC, which integrates feedforward speed search and parameter adaptive PID fine-tuning tension control to achieve high-response, high-precision and robust tension control. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the principle of the object controlled by this application;

[0044] Figure 2 This is a schematic diagram of the tension control system of this application;

[0045] Figure 3 This is a flowchart of the control method of this application;

[0046] Figure 4 This is a flowchart of the feedforward velocity search mode of this application;

[0047] Figure 5 A flowchart for the adaptive PID fine-tuning mode;

[0048] Figure 6 This is a tension control effect diagram of an embodiment of this application, where the horizontal axis represents the period and the vertical axis represents the detected tension;

[0049] Figure 7 This is a tension control error diagram of an embodiment of this application, with the horizontal axis representing the period and the vertical axis representing the tension control error;

[0050] Figure 8 This is a motor speed diagram according to an embodiment of this application, with the horizontal axis representing the period and the vertical axis representing the motor speed. Detailed Implementation

[0051] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0052] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0053] The present application will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the application.

[0054] The tension control system based on Siemens S7-1215C in this embodiment includes:

[0055] The main control unit is implemented using a Siemens S7-1215C programmable logic controller (PLC). The main control unit is connected to the data acquisition unit through a switch. It is used to perform feedforward speed search based on the tension value detected in real time by the tension detection unit and the target tension value, and the current speed of the unwinding unit motor. Then, it performs adaptive PID fine-tuning or direct adaptive PID fine-tuning to obtain the control signal to drive the unwinding unit motor and output it to the data acquisition unit.

[0056] In this implementation, the main control unit is a Siemens S7-1215C DC / DC / RLY type PLC. This PLC serves as the control core of the system, and its internal programming implements the control logic, including a feedforward speed search algorithm, an adaptive PID fine-tuning algorithm, and communication management with external devices.

[0057] The tension detection unit, connected to the data acquisition unit, is used to detect the tension of the roll material in real time and send the data to the data acquisition unit.

[0058] The tension detection unit in this embodiment consists of a Winding Electric LN500 tension sensor and a Winding Electric TN500 tension amplifier. The Winding Electric LN500 tension sensor converts the detected physical tension (0-500N) into a weak voltage signal of 0-20mV, which is then linearly amplified by the Winding Electric TN500 tension amplifier into a standard 0-10V (e.g., 0-500N corresponds to 0-10V) analog voltage signal, and supplied to the data acquisition unit.

[0059] The data acquisition unit, connected to the speed feedback and execution unit, is used to process the tension detected by the tension detection unit and the speed of the unwinding unit motor, and then send them to the main control unit through the switch. It is also used to process the control signals of the main control unit and then send them to the speed feedback and execution unit.

[0060] The data acquisition unit employs an ETH-MODBUS-IO8R-A data acquisition module. This module receives the 0-10V tension signal from the tension amplifier and the rotational speed signal output from the servo driver, converts these analog signals into digital signals, and exchanges data at high speed with the PLC via an Ethernet interface using the Modbus TCP protocol. The data acquisition unit also receives the control digital signals from the PLC for driving the unwinding unit motor, converts them into 0-10V analog voltage signals, and outputs them to the speed feedback and execution unit.

[0061] The speed feedback and execution unit is used to control the speed of the unwinding unit motor according to the control signal of the main control unit, and also to detect the speed of the unwinding unit motor and send it to the data acquisition unit.

[0062] Speed ​​detection: The motor speed analog signal is output from the X4 interface of a Panasonic MINAS A6 servo drive.

[0063] Speed ​​feedback: The analog output port (pin 43 of the X4 interface) of the servo driver is configured to output a voltage signal that is proportional to the actual speed of the unwinding unit motor. This signal is used by the PLC as the initial speed reference value `Voltage43Pin` of the system.

[0064] Execution: The servo driver receives a 0-10V speed command voltage from the data acquisition unit and precisely controls the speed of the unwinding unit motor.

[0065] The control system in this embodiment also includes a human-computer interaction unit and a network unit:

[0066] The human-machine interface unit is implemented using a Siemens SIMATIC HMI KTP700 basic touch screen, which is used by the operator to set the target tension, start and stop control, and monitor the actual tension, motor speed and current control mode online.

[0067] The network unit is implemented through an industrial Ethernet switch, connecting the PLC, human-machine interface unit and data acquisition module in the same local area network to achieve efficient and reliable transmission of control commands and status data.

[0068] This implementation method achieves decoupling of control logic and physical signals through Ethernet communication between the PLC, human-machine interface unit, and data acquisition module, resulting in a clear structure. Through the PLC's built-in algorithm, it achieves an innovative combination of feedforward and feedback, significantly improving the overall performance of the tension control system. The core control logic of this implementation method is implemented within the PLC by a function block named "core_cal". Specifically, the PLC, based on the tension value received in real-time from the tension detection unit and combined with the target tension value, performs a feedforward speed search based on the current speed of the unwinding unit motor, and then performs adaptive PID fine-tuning, or directly performs adaptive PID fine-tuning, to obtain the control signal driving the unwinding unit motor. The method includes:

[0069] PLC initialization and signal preprocessing:

[0070] Start-up Reset: When the start signal on the HMI is triggered, the system initializes. The PID integral term and historical error are reset, and the initial state of the system is determined according to the main switch setting: if search is enabled, it enters the feedforward speed search mode; otherwise, it directly enters the adaptive PID fine-tuning mode. Simultaneously, the initial motor speed is converted into a base speed as the starting point for subsequent calculations.

[0071] Signal Conversion and Filtering: In each scan cycle, the function block reads the raw digital value of tension from the data acquisition unit. Through the formula:

[0072] Convert to the engineering value ActualTension in Newtons (N). A first-order low-pass filtering algorithm is used to eliminate signal noise.

[0073]

[0074] The actual tension value is smoothed.

[0075] Set target tension value and the basic speed of the motor The base rotational speed serves as the initial feedforward speed reference, and can be specifically set through the human-machine interface unit.

[0076] Calculate target tension With real-time detected tension value absolute error Obtain percentage error :

[0077]

[0078] If percentage error If the speed is less than the mode selection threshold, the system enters the adaptive PID fine-tuning mode; otherwise, it enters the feedforward speed search mode.

[0079] The feedforward speed search mode is the system's open-loop pre-tuning process, aiming to actively find an optimal open-loop speed compensation amount. The feedforward speed search modes include:

[0080] Pause feedback regulation: Temporarily disable the output of the PID feedback control loop, so that the system is in an open-loop or pure feedforward state.

[0081] Iterative search: using the current speed or the base speed Centered on a search range and a fine-grained velocity step size, a search range is set. ).

[0082] The PLC starts from the lower limit of the set search range and, based on the current speed, adjusts the search based on the speed step size. The control signal for gradually increasing or decreasing the rotational speed is output.

[0083] Optimization record: At each speed step, after a short delay to wait for the system to stabilize, the tension detected by the tension detection unit is read through the data acquisition unit. .

[0084] Real-time comparison The size, when When the speed is at its minimum, record the corresponding rotational speed as the optimal feedforward speed. This value is the speed reference closest to the target tension under the current operating conditions.

[0085] The feedforward speed search mode aims to quickly find a base speed that roughly stabilizes the tension. A timer periodically coarsely adjusts the base speed. When the timer expires, the current tension error is considered. The symbol indicates that the base velocity is increased by a step size of 15.0. (negative) or decrease ( (Positive). This is an open-loop, large-step climbing search that can quickly pull the system back from a large deviation state to the vicinity of the target area.

[0086] Search step size of the feedforward speed search mode It is not a fixed value. Its magnitude can be related to tension error. Proportional, that is

[0087]

[0088] in, k is the proportionality coefficient;

[0089] Thus, when When the step size increases, the search step size increases, and the convergence speed increases; when When the step size is reduced, the search step size automatically decreases, the search process becomes smoother, and the optimal speed can be located more accurately.

[0090] Exit condition: When the percentage error When the absolute value of the error decreases below the preset threshold for entering the PID control, the system considers a suitable operating point to have been found and automatically switches to PID fine-tuning mode. Before switching, the integral term is cleared to zero, and the current error is stored as a historical error to prepare for PID calculation.

[0091] The adaptive PID fine-tuning mode performs closed-loop fine-tuning based on the optimal feedforward determined by the feedforward speed search. The adaptive PID fine-tuning modes include:

[0092] Enable feedback control: Start the PID controller, whose input is the tension error. To the PID controller.

[0093] PID controller parameter adaptation: the proportional coefficient of the PID controller ( The system performs online adaptive adjustment based on the magnitude of the error. The adjustment strategy is as follows:

[0094] When the absolute value of tension error Exceeding the threshold At this time, the proportional gain of the PID controller is amplified, which can be multiplied by an amplification factor to achieve large error and strong response:

[0095]

[0096] in, Based on the proportional gain, This is the adaptive gain coefficient. This strategy enables a rapid response when the error is large, suppresses overshoot when the error is small, and improves system stability.

[0097] When the rate of change of tension error Exceeding the threshold At this time, the differential gain is amplified and can be multiplied by an amplification factor to achieve strong suppression of rapid disturbances;

[0098] Calculate the integral gain based on the cumulative value of the integral term and the tension error during the previous PID control.

[0099] Based on the proportional gain, derivative gain, and integral gain, the output of the PID controller before limiting is obtained. To protect the mechanical and electrical systems, the final calculated motor speed was strictly limited to a safe operating range, and the output speed was also strictly controlled. After limiting, the output is obtained. .

[0100] Control output: Output of the PID controller As a fine compensation for the optimal feedforward speed, the final speed command drives the motor. .

[0101] In a preferred embodiment, this implementation further includes integral separation and anti-saturation steps:

[0102] When the absolute value of the tension error exceeds the integral action threshold, integral accumulation is temporarily disabled and the integral term is cleared to prevent integral oversaturation during significant system fluctuations. Simultaneously, the integral gain is updated via feedback compensation after the PID controller output. This will be used as the cumulative integral term for the next PID calculation.

[0103] .

[0104] Achieve standard anti-integral saturation and ensure stable PID output.

[0105] During normal production, the system continuously executes closed-loop control in adaptive PID fine-tuning mode. Simultaneously, by setting trigger conditions (such as roll diameter changes exceeding a preset threshold, production batch switching, operator manual triggering, or percentage error exceeding a threshold again due to a large external disturbance), the system automatically or manually returns to feedforward speed search mode. Dynamic updates are performed to ensure that the feedforward reference can always adapt to changing operating conditions.

[0106] At the end of each cycle, the current error is stored for use in the differential calculation of the next cycle.

[0107] Through the above implementation methods, this application seamlessly integrates open-loop fast search and closed-loop adaptive fine-tuning through a clever state machine. Relying on a standard industrial hardware platform, it achieves high-performance and highly adaptable control of the tension system. To verify the actual effect of the control method and system described in this application, experimental tests were conducted. Figures 6 to 8The figures show the actual operating data curves of the control system described in this application during a typical operating condition test cycle. During the test, multiple time points simulated step-like changes in production speed. As can be seen from the figures, even when the motor speed experienced drastic and large-amplitude step changes, the tension only fluctuated briefly and slightly (<5%) before quickly returning to a stable state, with almost no overshoot or prolonged oscillations. In summary, the experimental results strongly demonstrate that the tension control method and system based on dual-modal adaptive switching proposed in this application successfully overcomes the shortcomings of traditional control methods in terms of dynamic response, disturbance rejection capability, and operating condition adaptability. It can achieve high-precision, high-stability, and high-robust tension control under varying production conditions, and has significant industrial application value.

[0108] While this application has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of this application. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of this application as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A tension control system based on Siemens S7-1215C, characterized in that, include: The main control unit, implemented using a Siemens S7-1215C programmable logic controller, connects to the data acquisition unit via a switch. It uses the tension value received from the tension detection unit in real-time, combined with the target tension value, and based on the current speed of the unwinding unit motor, to perform a feedforward speed search. Then, it performs adaptive PID fine-tuning, or directly performs adaptive PID fine-tuning, to obtain the control signal driving the unwinding unit motor, and outputs it to the data acquisition unit. The tension detection unit, connected to the data acquisition unit, detects the tension of the roll material in real-time and sends the data to the data acquisition unit. The data acquisition unit, connected to the speed feedback and execution unit, processes the tension detected by the tension detection unit and the speed of the unwinding unit motor, and then sends them to the main control unit through the switch. It also processes the control signals from the main control unit and sends them to the speed feedback and execution unit. The speed feedback and execution unit is used to control the speed of the unwinding unit motor according to the control signal of the main control unit, and also to detect the speed of the unwinding unit motor and send it to the data acquisition unit.

2. The tension control system based on Siemens S7-1215C according to claim 1, characterized in that, The main control unit obtains the control signal to drive the unwinding unit motor by performing a feedforward speed search based on the tension value detected in real time by the tension detection unit and the target tension value, combined with the current speed of the unwinding unit motor, and then performing adaptive PID fine-tuning, or by directly performing adaptive PID fine-tuning. This method includes: Obtain the target tension With real-time detected tension value absolute error Obtain percentage error : If percentage error If the speed is less than the mode selection threshold, the system enters the adaptive PID fine-tuning mode; otherwise, it enters the feedforward speed search mode. Feedforward speed search mode: Disable the output of the PID feedback control loop, set the search range with the current speed as the center, and set the base speed for the first search. As the current rotational speed; The main control unit starts from the lower limit of the set search range, and based on the current speed, adjusts the search based on the speed step size. The control signal for gradually increasing or decreasing the speed is output. After outputting the control signal for each rotational speed, a delay is made until the system stabilizes. Then, the tension detected by the tension detection unit is read through the data acquisition unit. ; Real-time comparison The size, when When the speed is at its minimum, record the corresponding rotational speed as the optimal feedforward speed. Then it switches to adaptive PID fine-tuning mode; After entering adaptive PID fine-tuning mode, the output of the PID controller is: The control signal output by the main control unit is the speed command for driving the unwinding unit motor. .

3. The tension control system based on Siemens S7-1215C according to claim 2, characterized in that, Adaptive PID fine-tuning mode: Start the PID controller; the input is the tension error. To the PID controller; PID controller parameter adaptation: When the absolute value of tension error Exceeding the threshold At this time, the proportional gain of the PID controller is amplified; When the rate of change of tension error Exceeding the threshold At that time, the differential gain is used for amplification; Calculate the integral gain based on the cumulative value of the integral term and the tension error during the previous PID control. Based on the proportional gain, derivative gain, and integral gain, the output of the PID controller before limiting is obtained. For output After limiting, the output is obtained. .

4. The tension control system based on Siemens S7-1215C according to claim 3, characterized in that, When the absolute value of the tension error exceeds the integral action threshold, integral accumulation is temporarily disabled and the integral term is cleared to zero. Simultaneously, after the PID controller output, the integral gain is updated through feedback compensation. This will be used as the cumulative integral term for the next PID calculation. 。 5. The tension control system based on Siemens S7-1215C according to claim 2, characterized in that, The data acquisition unit reads the tension detected by the tension detection unit. Method: The tension detected by the tension detection unit is Converted to engineering values ​​in Newtons. : in, This indicates that an integer type has been converted to a real number type. This represents the tension value after filtering.

6. The tension control system based on Siemens S7-1215C according to claim 2, characterized in that, Speed ​​step size in feedforward speed search mode For adaptive values: in, , k is the proportionality coefficient, when As the speed increases, the speed step size increases; when When the speed is reduced, the speed step size becomes smaller.

7. The tension control system based on Siemens S7-1215C according to claim 1, characterized in that, The system also includes a human-machine interface unit for setting target tension, start / stop control, and online monitoring of actual tension, motor speed, and current control mode.

8. The tension control system based on Siemens S7-1215C according to claim 1, characterized in that, The data acquisition unit is implemented using the ETH-MODBUS-IO8R-A data acquisition device.

9. The tension control system based on Siemens S7-1215C according to claim 1, characterized in that, The tension detection unit includes a winding electric LN500 tension sensor and a winding electric TN500 tension amplifier. The voltage signal collected by the winding electric LN500 tension sensor is linearly amplified by the winding electric TN500 tension amplifier into a standard 0-10V analog voltage signal, which is then sent to the data acquisition unit.

10. The tension control system based on Siemens S7-1215C according to claim 1, characterized in that, The speed feedback and execution unit is implemented using the Panasonic MINAS A6 servo drive and its matching servo motor.

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