High-temperature semi-puffing control system and control method based on PLC (Programmable Logic Controller)

Abstract

The invention discloses a high-temperature semi-puffing control system based on a PLC (Programmable Logic Controller), which comprises a PLC element, a relay module, a heater, a hydraulic motor, a data acquisition module, a puffing extruder frequency converter, a feeding machine frequency converter, a transmitter module and a temperature sensor, the bulking extruder frequency converter and the feeding machine frequency converter are connected with the data acquisition module, and the temperature sensor is connected with the transmitter module; the PLC element comprises a communication module, a man-machine interface module, a switching value input module and a switching value output module, and the communication module, the man-machine interface module, the switching value input module and the switching value output module are connected in sequence; the data acquisition module, the bulking extruder frequency converter and the feeding machine frequency converter are connected with the communication module, the interaction device is connected with the man-machine interface module, the hydraulic motor, the bulking extruder frequency converter and the feeding machine frequency converter are connected with the switching value input module, and the relay module is connected with the switching value output module.

Description

Technical Field

[0001] The present invention relates to the technical field of high-temperature puffing extrusion molding, and in particular to a PLC-based high-temperature semi-puffing control system and a control method for producing puffed food. Background Art

[0002] my country has not been using modern extrusion puffing technology to produce puffed food for a long time. In the late 1970s, the research on puffing technology and puffed food began. As a multi-step, multi-functional and thermal and mechanical processing method, extrusion puffing technology has been widely used in food processing and is an ideal method for large-scale production of various foods. Since extrusion puffing technology is very suitable for industrial production of products, the research on this technology is becoming increasingly diverse and in-depth.

[0003] Although temperature control has been widely used in various industries in China, the overall development level of temperature controllers produced in China is still not high, and there is still a big gap compared with advanced countries such as Japan, the United States, and Germany. At present, my country's overall technical level in this regard is at the level of the late 1980s. Mature temperature control products are mainly based on "point" control and conventional PID controllers, which can only adapt to general temperature system control and are difficult to control lagging, complex, and time-varying temperature system control. Although there are many mature products abroad for intelligent and adaptive temperature control instruments suitable for higher control requirements, domestic technology is not yet very mature due to the confidentiality of foreign technology and the lag in my country's development work.

[0004] The temperature control parts of the extruder are generally divided into two parts: barrel temperature control and die temperature control. The die temperature directly affects the surface brightness of the product, and the barrel temperature affects the internal expansion effect of the product. The two have the same principle, and the barrel temperature control plays a major role. The extruder temperature control system generally adopts the control method of "temperature control instrument + contactor + electric heater". The early extruder temperature control system used a two-position regulating instrument to control the heating coil on and off by simply turning on the relay switch to achieve the purpose of controlling the barrel temperature. The temperature control effect of this scheme is not ideal, with large overshoot, long response time, and large steady-state error, reaching ±10°C. Later, a three-position regulating instrument was used, and its temperature control accuracy was ±5°C.

[0005] Since the temperature control meter is the main control system of the separated components, it is difficult to maintain and repair, and it is also inconvenient to operate. The programmable controller has the characteristics of high reliability, easy use and wide application range. The solution of using PLC as a high-temperature semi-expansion control system has been recognized by the market. The existing high-temperature semi-expansion control system uses a relay control system. For complex system control, the design and installation of the entire relay control system is particularly large and sometimes impossible to complete. The physical contact of the mechanical contacts is prone to damage; the wiring is also susceptible to vibration and other effects, and the reliability will deteriorate. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art, provide a high-temperature semi-expanding control system and control method based on PLC, use PLC components for optimization design, simplify the start-up and shutdown procedures of high-temperature semi-expanding operation, save time, reduce material and energy losses, realize full-process control and monitoring of processing temperature and feeding speed, and improve equipment production efficiency and stability.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A high-temperature semi-expanding control system based on PLC, comprising a PLC element, a relay module, a heater, a hydraulic motor, a data acquisition module, an extruder frequency converter, a feeder frequency converter, a transmitter module and a temperature sensor, wherein the heater and the hydraulic motor are respectively connected to the relay module, the transmitter module, the extruder frequency converter and the feeder frequency converter are respectively connected to the data acquisition module, and the temperature sensor is connected to the transmitter module;

[0009] The PLC components include a power supply module, a central processing module, a communication module, a human-machine interface module, a switch quantity input module and a switch quantity output module, wherein the power supply module and the central processing module are respectively connected with the communication module, the human-machine interface module, the switch quantity input module and the switch quantity output module;

[0010] The communication module, the human-machine interface module, the switch input module, and the switch output module are connected in sequence, the data acquisition module, the extruder frequency converter and the feeder frequency converter are connected to the communication module respectively, the interactive device is connected to the human-machine interface module, the hydraulic motor, the extruder frequency converter and the feeder frequency converter are connected to the switch input module respectively, and the relay module is connected to the switch output module.

[0011] Furthermore, the power module is externally connected to a DC power supply or is powered by an AC 220V power supply, or the power module has a built-in UPS battery pack.

[0012] Furthermore, the communication module uses the MODBUS-RTU communication protocol for communication connection, and the communication module and the data acquisition module, the extruder inverter and the feeder inverter communicate in a master-slave communication mode, with the PLC element as the master station and the data acquisition module, the extruder inverter and the feeder inverter as the slave stations.

[0013] Furthermore, the transmitter module includes a voltage transmitter, a current transmitter, a temperature transmitter and a pressure transmitter, and the temperature sensor is connected to the temperature transmitter.

[0014] Furthermore, the data acquisition module uses a 4-20mA signal to RS-485MODBUS data acquisition module. The data acquisition module:

[0015] Channel 1 uses a voltage transmitter to collect phase voltage signals, channel 2 uses a voltage transmitter to collect line voltage signals, channels 3, 4, and 5 use current transmitters to collect electromagnetic heater load current signals, channels 7, 8, 9, and 11 use temperature transmitters to collect barrel and die temperature signals through temperature sensors, and channel 12 uses a pressure transmitter to collect die pressure signals.

[0016] A high temperature semi-expansion control method based on PLC, applied to any of the above-mentioned high temperature semi-expansion control systems based on PLC, comprises the following steps:

[0017] S1: inputting the preset temperature of each temperature zone of the extruder, starting the heater of each temperature zone of the extruder, and heating each temperature zone of the extruder;

[0018] S2: The temperature sensor detects the temperature of each temperature zone of the extruder and transmits the detected temperature to the data acquisition module through the temperature transmitter;

[0019] S3: The data acquisition module transmits the temperature to the PLC component, and the PLC component adjusts the heating temperature of each temperature zone through PID control according to the temperature of each temperature zone;

[0020] S4: When each temperature zone reaches the preset temperature, the extruder and feeder are started, and the PLC component adjusts the feeding amount of the feeder according to the current value of the extruder.

[0021] Furthermore, in step S1, the preset temperature range is 0°C-180°C; in step S2, a barrel of the extruder with three-point temperature measurement and a die head of the extruder with one-point temperature measurement are used.

[0022] Furthermore, in step S3, the mathematical model of PID control is expressed as

[0023]

[0024] In the formula, u(t) represents the control quantity, e(t) represents the control deviation of the control system, and K p represents the proportionality coefficient, T I represents the integration time constant, T D represents the differential time constant;

[0025] Because it is discrete time control, the control quantity can only be calculated based on the deviation value at the sampling time. The continuous PID control needs to be discretized. If the sampling period is T, the differential equation of PID control is expressed as:

[0026]

[0027] In the formula, u(k) represents the output at k sampling period, and e(k) represents the deviation at k sampling period;

[0028] Let △e(k)=e(k)-e(k-1), but

[0029]

[0030] The incremental PID control is expressed as:

[0031] △u(k)=u(k)-u(k-1)

[0032] =K p [e(k)-e(k-1)]+K I e(k)+K D [e(k)-2e(k-1)+e(k-2)].

[0033] Furthermore, during the sampling period, the temperature sensor transmits the detected barrel and die temperatures to the data acquisition module through the temperature transmitter, and the data acquisition module is connected to the PLC component MODBUS-RTU communication, and the PLC component reads the barrel and die temperatures, and the PLC component compares the read value with the set value to obtain the deviation between the predetermined temperature and the actual temperature;

[0034] The PLC element calculates according to the size of the deviation and the temperature control strategy to obtain the control output, that is, the conduction ratio of the relay in the sampling period. After pulse width modulation, the conduction time of the relay in the sampling period is obtained. By controlling the conduction time of the relay in the sampling period, the heating time of the heater is controlled to achieve the purpose of controlling the heating temperature, so that each temperature zone of the extruder reaches the preset temperature.

[0035] Furthermore, in step S4, the extruder inverter and the feeder inverter are connected to the PLC component MODBUS-RTU communication. After the data acquisition module obtains the real-time current signal of the extruder inverter, the current signal is transmitted to the PLC component. The PLC component compares the collected current value with the set current value, adjusts the frequency of the feeding inverter, and adjusts the speed of the feeding motor, so as to achieve the purpose of controlling the feeding amount of the feeder.

[0036] Compared with the prior art, the present invention utilizes PLC components for optimized design to realize intelligent and unified control of the equipment. Automatic control can be realized according to the logic of the PLC control program without human intervention, thus saving labor costs. The high-temperature semi-expansion operation procedure is simplified, time is saved, and the loss of materials and energy is reduced. The whole-process control and monitoring of the processing temperature and feeding speed are realized, thereby improving the production efficiency and stability of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a partial structural diagram of the high-temperature semi-expansion control system based on PLC.

[0038] Figure 2 This is a schematic diagram of the temperature measurement points in each temperature zone of the expansion extruder.

[0039] Figure 3 This is the temperature control principle diagram of the control system.

[0040] Figure 4 This is the block diagram of PID control principle.

[0041] Figure 5 This is the block diagram of the automatic feeding principle.

[0042] Figure 6 This is the automatic feeding control flow chart. DETAILED DESCRIPTION

[0043] The high temperature semi-expansion control system and control method based on PLC of the present invention will be specifically described below in conjunction with the accompanying drawings and specific embodiments.

[0044] See also Figure 1 The present invention discloses a high-temperature semi-expanding control system based on PLC, comprising a PLC element, a relay module, a heater, a hydraulic motor, a data acquisition module, an extruder frequency converter, a feeder frequency converter, a transmitter module and a temperature sensor. The heater and the hydraulic motor are respectively connected to the relay module, the transmitter module, the extruder frequency converter and the feeder frequency converter are respectively connected to the data acquisition module, and the temperature sensor is connected to the transmitter module.

[0045] The PLC components include a power supply module, a central processing module, a communication module, a human-machine interface module, a switch input module and a switch output module. The power supply module and the central processing module are respectively connected to the communication module, the human-machine interface module, the switch input module and the switch output module.

[0046] The communication module, the human-machine interface module, the switch input module, and the switch output module are connected in sequence, the data acquisition module, the extruder frequency converter and the feeder frequency converter are connected to the communication module respectively, the interactive device is connected to the human-machine interface module, the hydraulic motor, the extruder frequency converter and the feeder frequency converter are connected to the switch input module respectively, and the relay module is connected to the switch output module.

[0047] The power module is powered by an external DC power supply or an AC 220V power supply, or the power module has its own UPS battery pack.

[0048] The communication module uses the MODBUS-RTU communication protocol for communication connection. The communication module and the data acquisition module, the extruder inverter and the feeder inverter use a master-slave communication method. The PLC element is the master station, and the data acquisition module, the extruder inverter and the feeder inverter are the slave stations.

[0049] The PLC component periodically sends instruction frames (the COM indicator light of the PLC component flashes periodically, indicating that the PLC component periodically sends instruction frames). After receiving the instruction frames from the PLC component, the data acquisition module, the extruder inverter, and the feeder inverter perform verification and make corresponding responses.

[0050] The relay module includes: a relay for controlling the heating operation of the barrel of the extruder, a relay for controlling the heating operation of the die head of the extruder, a relay for controlling the operation of the hydraulic station, and a relay for controlling the hydraulic advance and retreat. The heater includes an electromagnetic heater and an electric heater. The electromagnetic heater uses the principle of electromagnetic induction to heat the workpiece.

[0051] The relay that controls the heating operation of the barrel of the extruder is connected to the electromagnetic heater, the relay that controls the heating operation of the die head of the extruder is connected to the electric heater, the relay that controls the operation of the hydraulic station is connected to the hydraulic motor, and the relay that controls the advance and retreat of the hydraulic cylinder is connected to the electromagnetic valve. The switch output module also has an alarm output function, and the alarm output is connected to the buzzer.

[0052] The transmitter module includes a voltage transmitter, a current transmitter, a temperature transmitter and a pressure transmitter, and the temperature sensor is connected to the temperature transmitter. In this embodiment, the temperature sensor adopts a thermal resistor, and the interactive device adopts a 12-inch touch screen. The 12-inch color touch screen can conveniently and flexibly set control parameters and monitor the system operation status in real time, and effectively manage the control system.

[0053] The data acquisition module uses a 4-20mA signal to RS-485MODBUS data acquisition module. The data acquisition module:

[0054] Channel 1 uses a voltage transmitter to collect phase voltage signals, channel 2 uses a voltage transmitter to collect line voltage signals, channels 3, 4, and 5 use current transmitters to collect electromagnetic heater load current signals, channels 7, 8, 9, and 11 use temperature transmitters to collect barrel and die temperature signals through temperature sensors, and channel 12 uses a pressure transmitter to collect die pressure signals.

[0055] The present invention also discloses a PLC-based high-temperature semi-expansion control method, which is applied to any of the above-mentioned PLC-based high-temperature semi-expansion control systems, and comprises the following steps:

[0056] S1: inputting the preset temperature of each temperature zone of the extruder, starting the heater of each temperature zone of the extruder, and heating each temperature zone of the extruder;

[0057] S2: The temperature sensor detects the temperature of each temperature zone of the extruder and transmits the detected temperature to the data acquisition module through the temperature transmitter;

[0058] S3: The data acquisition module transmits the temperature to the PLC component, and the PLC component adjusts the heating temperature of each temperature zone through PID control according to the temperature of each temperature zone;

[0059] S4: When each temperature zone reaches the preset temperature, the extruder and feeder are started, and the PLC component adjusts the feeding amount of the feeder according to the current value of the extruder.

[0060] In step S1, the preset temperature of each temperature zone of the extruder is input on the touch screen, and the preset temperature range is 0° C.-180° C. The electromagnetic heater heats the barrel of the extruder, and the electric heater heats the die head of the extruder.

[0061] In step S2, the control system is responsible for controlling the barrel temperature. Considering that the barrel is relatively long and is affected by many factors such as the barrel's own thermal inertia, ambient temperature, and the different entry times of materials in the barrel, a three-point temperature measurement is used for the barrel of the extruder, and a one-point temperature measurement is used for the die head of the extruder. The schematic diagram of the temperature measurement points in each temperature zone of the extruder is shown in FIG. Figure 2 shown.

[0062] In step S3, the electromagnetic heater adopts a non-contact heating method. Since the energy is transferred in the form of electromagnetic waves during the induction heating process, it is less affected by external interference and less energy diffusion, which greatly improves the energy utilization and the heating efficiency. The temperature control principle of the control system is as follows: Figure 3 shown.

[0063] During the heating process of each temperature zone, the heating temperature is adjusted by proportional-integral-differential PID control. PID control is the abbreviation of Proportional, Integral, and Differential control. PID control controls the control object by linearly combining the proportional, integral, and differential of the deviation to form a control quantity based on the control deviation e(t) formed by the given value r(t) and the actual output value c(t). The block diagram of the PID control principle is shown in the figure below. Figure 4 shown.

[0064] The deviation of PID control is expressed as

[0065] e(t)=r(t)-c(t)

[0066] The mathematical model of PID control is expressed as

[0067]

[0068] In the formula, u(t) represents the control quantity, e(t) represents the control deviation of the control system, and K p Represents the proportionality coefficient, T I represents the integration time constant, T D Represents the differential time constant.

[0069] The proportional part of PID control K p e(t) responds to the deviation signal e(t) of the control system in real time and proportionally. Once the deviation occurs, it is immediately adjusted in the direction of reducing the deviation.

[0070] The integral part of PID control The integral accumulation of e can eliminate static error in the control system and improve the error-free degree of the control system. The strength of the integral effect depends on the integral time constant T. I . T I The larger it is, the weaker the integral effect is, and vice versa.

[0071] The differential part of PID control Respond to the change of e, control according to the trend of deviation change, and introduce an effective early correction signal into the control system before the value of the deviation signal becomes too large, so as to eliminate the deviation in the bud.

[0072] Because computer control is discrete time control, the control quantity can only be calculated based on the deviation value at the sampling time. The continuous PID control needs to be discretized. If the sampling period is T, the differential equation of PID control is expressed as:

[0073]

[0074] In the formula, u(k) represents the output at k sampling period, and e(k) represents the deviation at k sampling period;

[0075] Let △e(k)=e(k)-e(k-1), but

[0076]

[0077] As can be seen from the above formula, the integral term of PID control is the accumulation of previous successive deviations e(j), which occupies more storage units and is not convenient for programming. Therefore, the incremental PID control is expressed as:

[0078] △u(k)=u(k)-u(k-1)

[0079] =K p [e(k)-e(k-1)]+K I e(k)+K D [e(k)-2e(k-1)+e(k-2)].

[0080] PID control is a control strategy based on classical control theory. Since the design algorithm and control structure of PID control are very simple and it is easy to compensate for the requirements of most characteristic parameters of the control system, it has simple principles, is easy to use, and has strong practicality. It can achieve satisfactory results for most control objects.

[0081] During the sampling period, the temperature sensor transmits the detected barrel and die temperatures to the data acquisition module through the temperature transmitter. The data acquisition module is connected to the PLC component MODBUS-RTU communication. The PLC component reads the barrel and die temperatures. The central processing module (CPU) of the PLC component compares the read value with the set value to obtain the deviation between the predetermined temperature and the actual temperature.

[0082] The PLC element calculates according to the size of the deviation and the temperature control strategy to obtain the control output, that is, the conduction ratio of the relay in the sampling period. After pulse width modulation, the conduction time of the relay in the sampling period is obtained. By controlling the conduction time of the relay in the sampling period, the heating time of the heater is controlled to achieve the purpose of controlling the heating temperature, so that each temperature zone of the extruder reaches the preset temperature.

[0083] In step S4, the extruder inverter and the feeder inverter are connected to the PLC element MODBUS-RTU communication. After the data acquisition module obtains the real-time current signal of the extruder inverter, the current signal is transmitted to the PLC element. The PLC element compares the collected current value with the set current value, adjusts the frequency of the feeder inverter to adjust the speed of the feeder motor, and achieves the purpose of controlling the feeding amount of the feeder. The automatic feeding principle block diagram is shown as follows: Figure 5 shown.

[0084] The software flow of the control system is as follows Figure 6 As shown, it mainly includes initialization, motor forward and reverse control, light load adjustment, overload adjustment, alarm processing, normal working state calibration and shutdown control.

[0085] In summary, the present invention uses PLC components for optimization design to achieve intelligent and unified control of the equipment. Automatic control can be achieved according to the logic of the PLC control program without human intervention, saving labor costs; simplifying the high-temperature semi-expansion operation procedure, saving time, reducing the loss of materials and energy, achieving full control and monitoring of processing temperature and feeding speed, and improving equipment production efficiency and stability.

[0086] The above description is a detailed description of the preferred feasible embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modified changes completed under the technical spirit disclosed by the present invention should fall within the patent scope covered by the present invention.

Claims

1. A high temperature semi-expansion control system based on PLC, characterized in that: It includes a PLC component, a relay module, a heater, a hydraulic motor, a data acquisition module, an extruder frequency converter, a feeder frequency converter, a transmitter module and a temperature sensor. The heater and the hydraulic motor are respectively connected to the relay module, the transmitter module, the extruder frequency converter and the feeder frequency converter are respectively connected to the data acquisition module, and the temperature sensor is connected to the transmitter module; The PLC components include a power supply module, a central processing module, a communication module, a human-machine interface module, a switch quantity input module and a switch quantity output module, wherein the power supply module and the central processing module are respectively connected with the communication module, the human-machine interface module, the switch quantity input module and the switch quantity output module; The communication module, the human-machine interface module, the switch input module, and the switch output module are connected in sequence, the data acquisition module, the extruder frequency converter and the feeder frequency converter are connected to the communication module respectively, the interactive device is connected to the human-machine interface module, the hydraulic motor, the extruder frequency converter and the feeder frequency converter are connected to the switch input module respectively, and the relay module is connected to the switch output module.

2. The high temperature semi-expansion control system based on PLC according to claim 1 is characterized in that: The power module is powered by an external DC power supply or an AC 220V power supply, or the power module has its own UPS battery pack.

3. The high temperature semi-expansion control system based on PLC according to claim 1 is characterized in that: The communication module uses the MODBUS-RTU communication protocol for communication connection. The communication module and the data acquisition module, the extruder inverter and the feeder inverter use a master-slave communication method. The PLC element is the master station, and the data acquisition module, the extruder inverter and the feeder inverter are the slave stations.

4. The high temperature semi-expansion control system based on PLC according to claim 1 is characterized in that: The transmitter module comprises a voltage transmitter, a current transmitter, a temperature transmitter and a pressure transmitter, and the temperature sensor is connected to the temperature transmitter.

5. The high temperature semi-expansion control system based on PLC according to claim 1 is characterized in that: The data acquisition module uses a 4-20mA signal to RS-485MODBUS data acquisition module. The data acquisition module: Channel 1 uses a voltage transmitter to collect phase voltage signals, channel 2 uses a voltage transmitter to collect line voltage signals, channels 3, 4, and 5 use current transmitters to collect electromagnetic heater load current signals, channels 7, 8, 9, and 11 use temperature transmitters to collect barrel and die temperature signals through temperature sensors, and channel 12 uses a pressure transmitter to collect die pressure signals.

6. A PLC-based high-temperature semi-expansion control method, applied to the PLC-based high-temperature semi-expansion control system according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1: inputting the preset temperature of each temperature zone of the extruder, starting the heater of each temperature zone of the extruder, and heating each temperature zone of the extruder; S2: The temperature sensor detects the temperature of each temperature zone of the extruder and transmits the detected temperature to the data acquisition module through the temperature transmitter; S3: The data acquisition module transmits the temperature to the PLC component, and the PLC component adjusts the heating temperature of each temperature zone through PID control according to the temperature of each temperature zone; S4: When each temperature zone reaches the preset temperature, the extruder and feeder are started, and the PLC component adjusts the feeding amount of the feeder according to the current value of the extruder.

7. The high temperature semi-expansion control method based on PLC according to claim 6, characterized in that: In step S1, the preset temperature range is 0°C-180°C; in step S2, a barrel of the extruder is subjected to three-point temperature measurement, and a die head of the extruder is subjected to one-point temperature measurement.

8. The high temperature semi-expansion control method based on PLC according to claim 7, characterized in that: In step S3, the mathematical model of PID control is expressed as In the formula, u(t) represents the control quantity, e(t) represents the control deviation of the control system, and K p Represents the proportionality coefficient, T I represents the integration time constant, T D represents the differential time constant; Because it is discrete time control, the control quantity can only be calculated based on the deviation value at the sampling time. The continuous PID control needs to be discretized. If the sampling period is T, the differential equation of PID control is expressed as: In the formula, u(k) represents the output at k sampling period, and e(k) represents the deviation at k sampling period; Let △e(k)=e(k)-e(k-1), but The incremental PID control is expressed as: △u(k)=u(k)-u(k-1) =K p [e(k)-e(k-1)]+K I e(k)+K D [e(k)-2e(k-1)+e(k-2)]。 9. The high temperature semi-expansion control method based on PLC according to claim 8, characterized in that: During the sampling period, the temperature sensor transmits the detected barrel and die temperature to the data acquisition module through the temperature transmitter. The data acquisition module is connected to the PLC component MODBUS-RTU communication. The PLC component reads the barrel and die temperature. The PLC component compares the read value with the set value to obtain the deviation between the preset temperature and the actual temperature. The PLC element calculates according to the size of the deviation and the temperature control strategy to obtain the control output, that is, the conduction ratio of the relay in the sampling period. After pulse width modulation, the conduction time of the relay in the sampling period is obtained. By controlling the conduction time of the relay in the sampling period, the heating time of the heater is controlled to achieve the purpose of controlling the heating temperature, so that each temperature zone of the extruder reaches the preset temperature.

10. The high temperature semi-expansion control method based on PLC according to claim 1, characterized in that: In step S4, the extruder inverter and the feeder inverter are connected to the PLC component MODBUS-RTU communication. After the data acquisition module obtains the real-time current signal of the extruder inverter, the current signal is transmitted to the PLC component. The PLC component compares the collected current value with the set current value, adjusts the frequency of the feeding inverter, and adjusts the speed of the feeding motor to achieve the purpose of controlling the feeding amount of the feeder.

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