CN115291649B - Temperature control method of oven, temperature control method of film wrapping machine, oven and film wrapping machine - Google Patents
Temperature control method of oven, temperature control method of film wrapping machine, oven and film wrapping machine Download PDFInfo
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Abstract
The application provides a temperature control method of an oven, a temperature control method of a film wrapping machine, the oven and the film wrapping machine. Wherein the oven includes a plurality of heating units, and the temperature control method of oven includes: acquiring the current temperature of the oven and the target temperature of the oven; calculating a difference between the current temperature of the oven and the target temperature of the oven; comparing the difference between the current temperature of the oven and the target temperature of the oven with the preset temperature difference; when the difference value between the current temperature of the oven and the target temperature of the oven is greater than or equal to a preset temperature difference, starting a first heating mode to constantly heat the heating unit; and when the difference between the current temperature of the oven and the target temperature of the oven is smaller than the preset temperature difference, starting a second heating mode to constantly heat the partial heating unit and intermittently heat the partial heating unit. The film wrapping machine comprises a first oven and a second oven which are communicated, wherein the second oven is positioned at the downstream of the first oven, and the target temperature of the second oven is greater than that of the first oven.
Description
Technical Field
The embodiment of the application relates to the field of temperature control, in particular to a temperature control method of an oven, a temperature control method of a film wrapping machine, the oven and the film wrapping machine.
Background
The film packing machine is a machine which takes a film as a packing material, wraps and seals a packing material in a fixed specification form, and is mainly applied to the food and beverage industry. The film is a heat shrinkage film, when the temperature is different, the shrinkage effect is different, the key point for improving the heat shrinkage effect is to control the stability of the temperature, and once the heat shrinkage effect does not meet the requirement, the production efficiency is reduced, and certain economic loss is caused.
At present, most manufacturers adopt an electric heating mode, and the heating of a heating pipe is controlled by the difference between the set temperature and the actual temperature. The specific control mode is as follows: when the set temperature is higher than the actual temperature, the heating pipe is heated, and when the actual temperature is lower than the set temperature, the heating pipe is stopped. However, in the temperature control mode, the temperature fluctuation in the oven is large, the heat dissipation is uneven, and the heat shrinkage effect is poor.
Disclosure of Invention
The invention aims to overcome the defect of large temperature fluctuation of an oven in the prior art, and provides a temperature control method of the oven, a temperature control method of a film wrapping machine, the oven and the film wrapping machine.
The invention solves the technical problems by the following technical scheme:
in a first aspect, an embodiment of the present application provides a method for controlling a temperature of an oven, the oven including a plurality of heating units, the method including the steps of:
Acquiring the current temperature of the oven and the target temperature of the oven;
calculating a difference e (t) between the current temperature of the oven and the target temperature of the oven;
comparing the difference e (t) between the current temperature of the oven and the target temperature of the oven with a preset temperature difference A;
When the difference e (t) between the current temperature of the oven and the target temperature of the oven is greater than or equal to the preset temperature difference A, starting a first heating mode, wherein the first heating mode is that the heating unit constantly heats;
and when the difference e (t) between the current temperature of the oven and the target temperature of the oven is smaller than the preset temperature difference A, starting a second heating mode, wherein the second heating mode is that part of the heating units are constantly heated and part of the heating units are intermittently heated.
In the first heating mode, all heating units are constantly heated at the same time, so that the heat in the oven is rapidly improved, the heating time is saved, and the production efficiency is improved; the heating unit for constant heating in the second heating mode can ensure the basic heat required by the oven to reach the target temperature, and the heating unit for intermittent heating ensures the balance between the oven and the external heat exchange, so that the temperature of the oven is stabilized within the accuracy range of the target temperature.
In one possible implementation, the intermittent heating is to regulate and control the heating quantity of the heating unit by using PID control logic according to a difference e (t) between the current temperature of the oven and the target temperature of the oven.
The PID control can realize accurate control of temperature, so that temperature fluctuation is small.
In one possible implementation manner, the intermittent heating is to adjust and control the on-off time of the heating unit by adjusting the duty ratio of PWM by using PID control logic according to the difference e (t) between the current temperature of the oven and the target temperature of the oven.
In one possible implementation, the period of the PWM is greater than or equal to 2s.
The period of PWM is more than or equal to 2s, so that the heating stability of the whole oven is ensured.
In a second aspect, an embodiment of the present application provides a method for controlling a temperature of a film wrapping machine, where the film wrapping machine includes a first oven and a second oven that are connected to each other, and the second oven is located downstream of the first oven, and the method includes:
setting a target temperature SV1 of a first oven and a target temperature SV2 of a second oven, wherein the target temperature SV1 of the first oven is smaller than the target temperature SV2 of the second oven;
acquiring the current temperature PV1 of the first oven, and calculating a difference e (t) 1 between the current temperature PV1 of the first oven and the target temperature SV1 of the first oven; comparing the difference e (t) 1 between the current temperature PV1 of the first oven and the target temperature SV1 of the first oven with the preset temperature difference A1 of the first oven;
When a difference e (t) 1 between the current temperature PV1 of the first oven and the target temperature SV1 of the first oven is greater than or equal to a preset temperature difference A1 of the first oven, starting a first heating mode of the first oven, wherein the first heating mode of the first oven is that a heating unit of the first oven is constantly heated;
When the difference e (t) 1 between the current temperature PV1 of the first oven and the target temperature SV1 of the first oven is smaller than the preset temperature difference A1 of the first oven, starting a second heating mode of the first oven, wherein the second heating mode of the first oven is that a part of heating units of the first oven are constantly heated and a part of heating units of the first oven are intermittently heated;
Acquiring the current temperature PV2 of the second oven, and calculating a difference e (t) 2 between the current temperature PV2 of the second oven and the target temperature SV2 of the second oven; comparing the difference e (t) 2 between the current temperature PV2 of the second oven and the target temperature SV2 of the second oven with the preset temperature difference A2 of the second oven;
When a difference e (t) 2 between the current temperature PV2 of the second oven and the target temperature SV2 of the second oven is greater than or equal to a preset temperature difference A2 of the second oven, starting a first heating mode of the second oven, wherein the first heating mode of the second oven is constant heating of a heating unit of the second oven;
And when the difference e (t) 2 between the current temperature PV2 of the second oven and the target temperature SV2 of the second oven is smaller than the preset temperature difference A2 of the second oven, starting a second heating mode of the second oven, wherein the second heating mode of the second oven is that a part of heating units of the second oven are constantly heated and a part of heating units of the second oven are intermittently heated.
The product is subjected to final heat shrinkage by using a relatively low temperature in the first oven, so that the product is slightly wrapped by the shrink film, and then the product is subjected to final heat shrinkage by using a relatively high temperature in the second oven, thereby effectively avoiding excessive heat shrinkage caused by high initial temperature, improving the aesthetic property and realizing good heat shrinkage effect; different heating modes are adopted according to the difference value between the current temperature and the target temperature, so that the temperature of the first oven and the temperature of the second oven are accurately controlled, the heat shrinkage effect of the product is improved, and the qualification rate of the product is ensured.
In one possible implementation manner, the intermittent heating is to adjust and control the on-off time of the heating unit by adjusting the duty ratio of PWM by using PID control logic according to the difference e (t) between the current temperature of the oven and the target temperature of the oven.
The PID control can realize accurate control of temperature, so that temperature fluctuation is small.
In a third aspect, embodiments of the present application provide an oven, the oven comprising:
a first heating device;
a second heating device;
The temperature detection device is used for detecting the temperature in the oven in real time;
a control system in signal connection with the first heating device, the second heating device and the temperature detection device, the control system being configured to control heating modes of the first heating device and the second heating device according to a relation between a difference e (t) between a current temperature of the oven and a target temperature of the oven and a preset temperature difference A,
When the difference e (t) between the current temperature of the oven and the target temperature of the oven is greater than or equal to the preset temperature difference A, a first heating mode is started, wherein the first heating mode is that the first heating device and the second heating device are constantly heated;
And when the difference e (t) between the current temperature of the oven and the target temperature of the oven is smaller than the preset temperature difference A, starting a second heating mode, wherein the second heating mode is that the first heating device is constantly heated and the second heating device is intermittently heated.
In one possible implementation, the control system includes a PID control module configured to regulate, in the second heating mode, the on-off time of the second heating device according to a difference e (t) between the current temperature of the oven and the target temperature of the oven, by adjusting a duty cycle of PWM using PID control logic.
The PID control can realize accurate control of temperature, so that temperature fluctuation is small.
In one possible implementation, the period of the PWM is greater than or equal to 2s.
The period of PWM is more than or equal to 2s, so that the heating stability of the oven is ensured.
In one possible implementation, the first heating device and the second heating device provide heat by constant heating greater than or equal to 20% of the maximum heat required by the product, and the first heating device provides heat by constant heating greater than or equal to 20% of the minimum heat required by the product.
In a fourth aspect, an embodiment of the present application provides a film wrapping machine, where the film wrapping machine includes a first oven and a second oven as described above, where the first oven is in communication with the second oven and the second oven is located downstream of the first oven, and a target temperature of the second oven is greater than a target temperature of the first oven.
In the oven and the temperature control method of the oven provided by the embodiment of the application, different heating modes are adopted according to the relation between the difference e (t) between the current temperature of the oven and the target temperature of the oven and the preset temperature difference A: when the difference e (t) between the current temperature of the oven and the target temperature of the oven is greater than or equal to the preset temperature difference A, a first heating mode is adopted, and in the first heating mode, all heating units are heated constantly at the same time, so that the heat in the oven is improved rapidly, the heating time is saved, and the production efficiency is improved; when the difference e (t) between the current temperature of the oven and the target temperature of the oven is smaller than the preset temperature difference, a second heating mode is adopted, in the second heating mode, the heating unit with constant heating can ensure the basic heat required by the oven to reach the target temperature, and meanwhile, the heating unit with intermittent heating ensures the balance when the oven exchanges heat with the outside, so that the temperature of the oven is stabilized within the precision range of the target temperature.
In the film wrapping machine and the temperature control method of the film wrapping machine provided by the embodiment of the application, the target temperature SV1 of the first oven is set to be smaller than the target temperature SV2 of the second oven, the first oven uses the relatively lower temperature SV1 for pre-heat shrinkage, so that the shrink film slightly wraps the product, and then the second oven uses the relatively higher temperature SV2 for final heat shrinkage, thereby effectively avoiding excessive heat shrinkage caused by higher initial temperature, improving the aesthetic property and realizing good heat shrinkage effect; different heating modes are adopted according to the difference value between the current temperature and the target temperature, so that the temperature of the first oven and the temperature of the second oven are accurately controlled, the heat shrinkage effect of the product is improved, and the qualification rate of the product is ensured.
Drawings
The following drawings are only for purposes of illustration and explanation of the present application and are not intended to limit the scope of the application. Wherein,
Fig. 1 shows a schematic structure of an oven according to embodiment 1 of the present application;
fig. 2 shows a flowchart of a temperature control method of an oven according to embodiment 1 of the present application;
FIG. 3 shows a schematic diagram of a temperature control process according to an embodiment of the application;
FIG. 4 shows a schematic diagram of PID output control PWM pulse width according to an embodiment of the application;
FIG. 5 shows a PID output map according to an embodiment of the application;
Fig. 6 shows temperature control graphs of a first oven and a second oven of the film wrapping machine according to embodiment 2 of the present application, wherein fig. 6A is a temperature control curve of the first oven and fig. 6B is a temperature control curve of the second oven;
fig. 7 shows temperature control graphs of a first oven and a second oven of the film wrapping machine according to embodiment 2 of the present application, wherein fig. 7A is a temperature control curve of the first oven and fig. 7B is a temperature control curve of the second oven;
Fig. 8 shows temperature control graphs of a first oven and a second oven of the film wrapping machine according to embodiment 2 of the present application, wherein fig. 8A is a temperature control curve of the first oven and fig. 8B is a temperature control curve of the second oven;
Fig. 9 shows temperature control graphs of a first oven and a second oven of the film wrapping machine according to embodiment 2 of the present application, wherein fig. 9A is a temperature control curve of the first oven and fig. 9B is a temperature control curve of the second oven;
Reference numerals illustrate:
first heating device 100
Second heating device 200
Temperature detection device 300
Control system 400
Current temperature 10
Target temperature 20
Actuator 30
PID regulator 40
PWM output 50
Energizing 60
Detailed Description
The present application will be described in further detail below with reference to the drawings and examples in order to make the objects, technical solutions, and advantages of the present application more apparent. It will be apparent that the described embodiments are only some, but not all, embodiments of the application. All other technical solutions obtained by a person skilled in the art based on the embodiments of the present application fall within the scope of protection of the present application.
Specific implementations of embodiments of the application are described in detail below with reference to the accompanying drawings.
Example 1
For ease of understanding, the structure and operation of the oven will be described with reference to fig. 1. Fig. 1 is a schematic structural diagram of an oven according to embodiment 1 of the present application.
As shown in fig. 1, the oven of embodiment 1 includes a first heating device 100, a second heating device 200, a temperature detecting device 300, and a control system 400. Wherein the first heating device 100 and the second heating device 200 are used for heating the oven, the temperature detection device 300 is used for detecting the temperature in the oven in real time, the control system 400 is in signal connection with the first heating device 100, the second heating device 200 and the temperature detection device 300, the control system 400 is configured to control the heating mode of the first heating device 100 and the second heating device 200 according to the relation between the difference e (t) between the current temperature of the oven and the target temperature of the oven and the preset temperature difference A, in particular, when the difference e (t) between the current temperature of the oven and the target temperature of the oven is larger than or equal to the preset temperature difference A, the first heating mode is started; and when the difference e (t) between the current temperature of the oven and the target temperature of the oven is smaller than the preset temperature difference A, starting a second heating mode. In the first heating mode, the first heating device 100 and the second heating device 200 are constantly heated at the same time, so that the heat in the oven is rapidly increased, the heating time is saved, and the efficiency is improved; in the second heating mode, the first heating device 100 is constantly heated, the second heating device 200 is intermittently heated, the first heating device 100 for constant heating ensures the basic heat required by the oven to reach the target temperature, and the second heating device 200 for intermittent heating ensures the balance of the oven during heat exchange with the outside, so that the temperature of the oven is stabilized within the accuracy range of the target temperature.
The power levels of the first heating device 100 and the second heating device 200 are different according to the heat required by the products. Specifically, in one possible implementation, the first heating device 100 and the second heating device 200 simultaneously provide heat that is 20% higher than the maximum heat required for the product by constant heating, and the heat that the first heating device 100 provides when it alone is 20% higher than the minimum heat required for the product.
In one possible implementation manner, the intermittent heating is controlled by adopting a mode of controlling the PWM output through PID adjustment according to a difference value e (t) between a current temperature of the oven and a target temperature of the oven and a preset temperature difference a, and the executing mechanism is a relay and an ac contactor, and the on-off time of the second heating device 200 is controlled, so as to further control the heat provided by the second heating device 200 to the oven in the second heating mode, as shown in fig. 3.
As shown in fig. 5, when the heating adjustment is completed, the PID output is gradually reduced by the oscillation and finally reaches a constant state without adjusting the external factor, and the temperature in the oven is also stabilized within the tolerance range of the target temperature. The packaging heat shrinkage effect of the product should reach the best state at this time.
Wherein the formula of PID control is as follows:
wherein Y (t) is the output; e (t) is the temperature difference; kp is the proportional gain; ti is the integration time constant; td is the differential time.
Based on the above-mentioned oven, fig. 2 is a flowchart of a temperature control method according to an embodiment of the present application. As shown in fig. 2, the method includes:
s102: acquiring the current temperature of the oven and the target temperature of the oven;
S104: calculating a difference e (t) between the current temperature of the oven and the target temperature of the oven;
s106: comparing the difference e (t) between the current temperature of the oven and the target temperature of the oven with the preset temperature difference A;
S108: when the difference e (t) between the current temperature of the oven and the target temperature of the oven is greater than or equal to a preset temperature difference, starting a first heating mode, wherein the first heating mode is constant heating of the heating unit;
S110: and when the difference e (t) between the current temperature of the oven and the target temperature of the oven is smaller than the preset temperature difference, starting a second heating mode, wherein the second heating mode is that the partial heating unit is constantly heated and the partial heating unit is intermittently heated.
When the production preparation is performed, the temperature in the oven needs to be raised, firstly, the fan of the oven needs to be started, at the moment, the target temperature of the oven is set, and because the oven just enters a heating state, the difference e (t) between the current temperature of the oven and the target temperature of the oven is larger than the preset temperature difference A, at the moment, the first heating mode is used, that is, all the heating units (the first heating device 100 and the second heating device 200) are constantly heated at the same time, so that the heat in the oven is rapidly raised, and the heating time of the oven is saved. As the temperature of the oven increases, the difference e (t) between the current temperature of the oven and the target temperature of the oven gradually decreases, and when the difference e (t) between the current temperature of the oven and the target temperature of the oven decreases to less than the preset temperature difference a, the oven is already full of heat, and if the first heating mode is continuously maintained, the temperature in the oven quickly exceeds the target temperature, resulting in more overshoot. Therefore, when the difference e (t) between the current temperature of the oven and the target temperature of the oven is reduced to be smaller than the preset temperature difference a, the second heating mode is started, at which time the partial heating unit (the first heating device 100) is constantly heated and the partial heating unit (the second heating device 200) is intermittently heated. The heating unit with constant heating can ensure the basic heat required by the oven to reach the target temperature, and the heating unit with intermittent heating ensures the balance between the oven and the outside heat exchange, so that the temperature of the oven is stabilized within the precision range of the target temperature.
In one possible implementation manner, the on-off time of the heating unit is regulated and controlled by adjusting the duty ratio of the PWM through PID control logic according to the difference e (t) between the current temperature of the oven and the target temperature of the oven.
In one possible implementation, the PWM minimum period is 2s in order to guarantee the stability of the system. The pulse width of the PWM is regulated by the PID output, for example, when the PID output is 20%, the single heating period is 2/0.2=10s, i.e., the current state is on for 2s, off for 8s, as shown in fig. 4.
Example 2
Embodiment 2 is a film wrapping machine, and the detailed implementation of embodiment 3 is described below with reference to the accompanying drawings.
The film wrapping machine of this embodiment includes first oven and second oven that communicate with each other, and wherein the second oven is located the low reaches of first oven, and first oven and second oven have independent heating system respectively, and first oven includes the first heating device of first oven, the second heating device of first oven, the temperature detection device of first oven and the control system of first oven, and the second oven includes the first heating device of second oven, the second heating device of second oven, the temperature detection device of second oven and the control system of second oven. The method for controlling the temperature of the film wrapping machine in this embodiment is as follows:
Setting a target temperature SV1 of the first oven and a target temperature SV2 of the second oven, wherein the target temperature SV1 of the first oven is smaller than the target temperature SV2 of the second oven;
Acquiring the current temperature PV1 of the first oven, and calculating a difference e (t) 1 between the current temperature PV1 of the first oven and the target temperature SV1 of the first oven; comparing the difference e (t) 1 between the current temperature PV1 of the first oven and the target temperature SV1 of the first oven with the preset temperature difference A1 of the first oven;
When the difference e (t) 1 between the current temperature PV1 of the first oven and the target temperature SV1 of the first oven is greater than or equal to the preset temperature difference A1 of the first oven, starting a first heating mode of the first oven, wherein the first heating mode of the first oven is that the first heating unit is constantly heated;
When the difference e (t) 1 between the current temperature PV1 of the first oven and the target temperature SV1 of the first oven is smaller than the preset temperature difference A1 of the first oven, starting a second heating mode of the first oven, wherein the second heating mode of the first oven is that part of the first heating units are constantly heated and part of the first heating units are intermittently heated;
Acquiring the current temperature PV2 of the second oven, and calculating a difference e (t) 2 between the current temperature PV2 of the second oven and the target temperature SV2 of the second oven; comparing the difference e (t) 2 between the current temperature PV2 of the second oven and the target temperature SV2 of the second oven with the preset temperature difference A2 of the second oven;
when the difference e (t) 2 between the current temperature PV2 of the second oven and the target temperature SV2 of the second oven is greater than or equal to the preset temperature difference A2 of the second oven, starting a first heating mode of the second oven, wherein the first heating mode of the second oven is that the second heating unit is constantly heated;
when the difference e (t) 2 between the current temperature PV2 of the second oven and the target temperature SV2 of the second oven is smaller than the preset temperature difference A2 of the second oven, a second heating mode of the second oven is started, wherein the second heating mode of the second oven is that part of the second heating units are constantly heated and part of the second heating units are intermittently heated.
In one possible implementation manner, the intermittent heating is controlled by adopting a mode of PID regulation and PWM output, the actuating mechanism is a relay and an alternating current contactor, and the on-off time of the second heating device of the first oven is controlled so as to control the heat provided by the second heating device of the first oven to the first oven in the second heating mode of the first oven; and the on-off time of the second heating device of the second oven is controlled, so that the heat provided by the second heating device of the second oven to the second oven is controlled in the second heating mode of the second oven.
In one possible implementation, the PWM minimum period is 2s. The pulse width of the PWM is regulated by the PID output, for example, when the PID output is 20%, the single heating period is 2/0.2=10s, i.e., the current state is on for 2s, off for 8s, as shown in fig. 4.
In this embodiment, since the first oven and the second oven are mutually communicated and the target temperature SV1 of the first oven is smaller than the target temperature SV2 of the second oven, the temperature control process of the film wrapping machine of this embodiment is more complicated than that of a single oven. In order to facilitate a clearer understanding of the technical solution of the present embodiment, the following description is made in detail with reference to fig. 6 to 9.
Fig. 6 to 9 are temperature control graphs of the first oven and the second oven arranged in time sequence, wherein pid_temp_i is a temperature control curve of the first oven, pid_temp_ii is a temperature control curve of the second oven, a solid line represents a PID output-time curve, and a dotted line represents a temperature-time curve.
In this example, the target temperature SV1 of the first oven was set to 160 ℃, and the target temperature SV2 of the second oven was set to 170 ℃.
As shown in fig. 6, the first and second ovens are started at point 0, and since the first and second ovens just enter the heating state, the difference e (t) 1 between the current temperature PV1 of the first oven and the target temperature SV1 of the first oven is greater than the preset temperature difference A1 of the first oven, and the difference e (t) 2 between the current temperature PV2 of the second oven and the target temperature SV2 of the second oven is greater than the preset temperature difference A2 of the second oven, both the first and second ovens are in the first heating mode. As shown in fig. 6A, the first heating device and the second heating device of the first oven are constantly heated at the same time, the pid=100% of the first oven, and the temperature of the first oven is in a rapid rising stage; as shown in fig. 6B, the first heating device and the second heating device of the second oven are constantly heated at the same time, pid=100% of the second oven, and the temperature of the second oven rapidly rises. Since the target temperature SV1 set by the first oven is lower than the target temperature SV2 of the second oven, compared with the second oven, at point M1, the first oven first enters the critical temperature of e1=a1 as shown in fig. 6A, and at this time, the difference e (t) 2 between the current temperature PV2 of the second oven and the target temperature SV2 of the second oven is still greater than the preset temperature difference A2 of the second oven as shown in fig. 6B.
As the temperature continues to rise, the difference e (t) 1 between the current temperature PV1 of the first oven and the target temperature SV1 of the first oven is smaller than the preset temperature difference A1 of the first oven, and at this time, the first oven enters a second heating mode first, that is, the first heating device of the first oven is constantly heated, and the second heating device of the first oven is intermittently heated under the control of the PID algorithm, and in the second heating mode, the PID output continuously changes along with the change of the difference e (t) 1 between the current temperature PV1 of the first oven and the target temperature SV1 of the first oven, as shown in fig. 6A. In this process, the second oven also enters the critical temperature of e2=a2 at point M2, as the temperature of the second oven continues to rise, the difference e (t) 2 between the current temperature PV2 of the second oven and the target temperature SV2 of the second oven is smaller than the preset temperature difference A2 of the second oven, i.e. e (t) 2< A2, and the second oven also enters the second heating mode, i.e. the first heating device of the second oven is constantly heated, and the second heating device of the second oven is intermittently heated under the control of the PID algorithm, and in the second heating mode, the PID output of the second oven continuously fluctuates as the difference e (t) 2 between the current temperature PV2 of the second oven and the target temperature SV2 of the second oven changes, as shown in fig. 6B.
Because the target temperature set by the first oven is lower than the target temperature of the second oven, compared with the second oven, the temperature of the first oven firstly enters a steady state at the point N1, namely the current temperature PV1 of the first oven is relatively stable within the precision range of the target temperature SV1 of the first oven, and the PID output of the first oven is relatively constant as shown in FIG. 6A; at this point, the second oven is also in the second heating mode, i.e., the PID output of the second oven and the temperature of the second oven are also continuously fluctuating, as shown in fig. 6B.
Since the first and second ovens are in communication with each other, the steady state of the first oven is then broken at point O1, and the PID output and temperature of the first oven begin to fluctuate again, as shown in fig. 7A, under the influence of the changing temperature of the second oven. While the second oven gradually reaches steady state at point N2 as shown in fig. 7B.
Since the first oven and the second oven are in communication with each other, the steady state of the second oven is broken at the O2 point, and the temperature and PID output of the second oven begin to fluctuate, as shown in fig. 7B, under the influence of the constantly changing temperature of the first oven. Starting from the O2 point, the temperatures of the first oven and the second oven are continuously fluctuating, wherein the temperature of the first oven fluctuates around the target temperature of the first oven, the temperature of the second oven fluctuates around the target temperature of the second oven, but the amplitude of fluctuation is reduced, and the PID output of the first oven and the PID output of the second oven vibrate to be reduced and gradually tend to be constant, as shown in fig. 7 and 8, wherein fig. 7A and 8A are temperature control curves of the first oven, and fig. 7B and 8B are temperature control curves of the second oven.
As the temperature fluctuation amplitude of the first oven and the second oven decreases and the PID output tends to be constant, the final first oven reaches a final steady state at point P1, the second oven reaches a final steady state at point P2, i.e., the current temperature PV1 of the first oven stabilizes within the tolerance range of the target temperature SV1 of the first oven, the current temperature PV2 of the second oven stabilizes within the tolerance range of the target temperature SV2 of the second oven, and the PID output of the first oven and the second oven is constant, as shown in fig. 9, where fig. 9A is a temperature control curve of the first oven, and fig. 9B is a temperature control curve of the second oven. At this time, the film wrapping machine is used for carrying out heat shrinkage on the product to achieve the best heat shrinkage state.
In this embodiment, since the first oven and the second oven are connected to each other, there is a temperature interaction, and since a certain time is required for heating to dissipate the heat, a hysteresis phenomenon exists in the whole system, so that a differentiation effect is added to the PID parameters. The PWM shortest on period is 2s. Wherein the formula of PID control is as follows:
wherein Y (t) is the output; e (t) is the temperature difference; kp is the proportional gain; ti is the integration time constant; td is the differential time.
While specific embodiments of the invention have been described above, it will be appreciated by those skilled in the art that this is by way of example only, and the scope of the invention is defined by the appended claims. Various changes and modifications to these embodiments may be made by those skilled in the art without departing from the principles and spirit of the invention, but such changes and modifications fall within the scope of the invention.
Claims (6)
1. A method of controlling the temperature of a film wrapping machine, the film wrapping machine comprising a first oven and a second oven in communication with each other, wherein the second oven is downstream of the first oven, the method comprising:
setting a target temperature SV1 of a first oven and a target temperature SV2 of a second oven, wherein the target temperature SV1 of the first oven is smaller than the target temperature SV2 of the second oven;
Acquiring the current temperature PV1 of the first oven, and calculating a difference e (t) 1 between the current temperature PV1 of the first oven and the target temperature SV1 of the first oven; comparing the difference e (t) 1 between the current temperature PV1 of the first oven and the target temperature SV1 of the first oven with the preset temperature difference A1 of the first oven;
When a difference e (t) 1 between the current temperature PV1 of the first oven and the target temperature SV1 of the first oven is greater than or equal to a preset temperature difference A1 of the first oven, starting a first heating mode of the first oven, wherein the first heating mode of the first oven is that a heating unit of the first oven is constantly heated;
When the difference e (t) 1 between the current temperature PV1 of the first oven and the target temperature SV1 of the first oven is smaller than the preset temperature difference A1 of the first oven, starting a second heating mode of the first oven, wherein the second heating mode of the first oven is that a part of heating units of the first oven are constantly heated and a part of heating units of the first oven are intermittently heated;
acquiring the current temperature PV2 of the second oven, and calculating a difference e (t) 2 between the current temperature PV2 of the second oven and the target temperature SV2 of the second oven; comparing the difference e (t) 2 between the current temperature PV2 of the second oven and the target temperature SV2 of the second oven with the preset temperature difference A2 of the second oven;
When a difference e (t) 2 between the current temperature PV2 of the second oven and the target temperature SV2 of the second oven is greater than or equal to a preset temperature difference A2 of the second oven, starting a first heating mode of the second oven, wherein the first heating mode of the second oven is constant heating of a heating unit of the second oven;
when the difference e (t) 2 between the current temperature PV2 of the second oven and the target temperature SV2 of the second oven is smaller than the preset temperature difference A2 of the second oven, starting a second heating mode of the second oven, wherein the second heating mode of the second oven is that a part of heating units of the second oven are constantly heated and a part of heating units of the second oven are intermittently heated;
Wherein in the second heating mode, the constant heating unit provides basic heat required by the oven to reach the target temperature, and the intermittent heating unit provides balance when the oven exchanges heat with the outside.
2. The method of claim 1, wherein the intermittent heating is to adjust the on-off time of the heating unit by adjusting the duty ratio of the PWM by PID control logic according to the difference e (t) between the current temperature of the oven and the target temperature of the oven.
3. A film wrapping machine, characterized in that the film wrapping machine comprises a first oven and a second oven, wherein the first oven is communicated with the second oven and the second oven is positioned at the downstream of the first oven, and the target temperature of the second oven is greater than the target temperature of the first oven; wherein each of the ovens comprises:
a first heating device;
a second heating device;
The temperature detection device is used for detecting the temperature in the oven in real time;
a control system in signal connection with the first heating device, the second heating device and the temperature detection device, the control system being configured to control heating modes of the first heating device and the second heating device according to a relation between a difference e (t) between a current temperature of the oven and a target temperature of the oven and a preset temperature difference A,
When the difference e (t) between the current temperature of the oven and the target temperature of the oven is greater than or equal to the preset temperature difference A, a first heating mode is started, wherein the first heating mode is that the first heating device and the second heating device are constantly heated;
And when the difference e (t) between the current temperature of the oven and the target temperature of the oven is smaller than the preset temperature difference A, starting a second heating mode, wherein the second heating mode is that the first heating device is constantly heated and the second heating device is intermittently heated, a heating unit for constantly heating provides basic heat required by the oven to reach the target temperature, and a heating unit for intermittently heating provides balance when the oven exchanges heat with the outside.
4. A film wrapping machine as recited in claim 3, wherein the control system includes a PID control module configured to regulate the on-off time of the second heating device in the second heating mode by adjusting the duty cycle of the PWM using PID control logic based on a difference e (t) between the current temperature of the oven and a target temperature of the oven.
5. The film wrapping machine of claim 4 wherein the period of PWM is greater than or equal to 2s.
6. The film wrapping machine of claim 5 wherein said first heating means and said second heating means provide heat at a constant level greater than or equal to 20% of the maximum heat required by the product and said first heating means provide heat at a constant level greater than or equal to 20% of the minimum heat required by the product.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210948280.3A CN115291649B (en) | 2022-08-09 | Temperature control method of oven, temperature control method of film wrapping machine, oven and film wrapping machine |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210948280.3A CN115291649B (en) | 2022-08-09 | Temperature control method of oven, temperature control method of film wrapping machine, oven and film wrapping machine |
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| Publication Number | Publication Date |
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| CN115291649A CN115291649A (en) | 2022-11-04 |
| CN115291649B true CN115291649B (en) | 2024-07-05 |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106060975A (en) * | 2016-05-31 | 2016-10-26 | 郑州治世长云科技有限公司 | Electric heating/drying oven heating control system and control method |
| CN208530972U (en) * | 2018-05-28 | 2019-02-22 | 嘉兴雁荡包装有限公司 | A kind of thermal-shrinkage furnace that can be improved set mark film and shrink efficiency |
| CN112426056A (en) * | 2020-11-13 | 2021-03-02 | 珠海格力电器股份有限公司 | Heating control method and device for steaming and baking oven and steaming and baking oven |
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106060975A (en) * | 2016-05-31 | 2016-10-26 | 郑州治世长云科技有限公司 | Electric heating/drying oven heating control system and control method |
| CN208530972U (en) * | 2018-05-28 | 2019-02-22 | 嘉兴雁荡包装有限公司 | A kind of thermal-shrinkage furnace that can be improved set mark film and shrink efficiency |
| CN112426056A (en) * | 2020-11-13 | 2021-03-02 | 珠海格力电器股份有限公司 | Heating control method and device for steaming and baking oven and steaming and baking oven |
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