A thermal control system and method with mobile dead zone function

Abstract

The present invention discloses a thermal control system and method with a mobile dead zone function, including an analog input module, which converts a standard 4-20mA DC signal received from a field transmitter into a digital signal that can be recognized by a control module; a control module, which receives the digital signal of the analog input module, and sends it to an analog output module after discretization processing through the calculation loop of the present invention; an analog output module, which receives the digital signal sent by the control module, and converts it into a standard 4-20mA DC signal and outputs it to an actuator; an actuator, which receives the standard 4-20mA DC signal of the analog output module to control the operation of a motor and drive a valve switch. The present invention is aimed at an analog control system with low requirements for adjustment accuracy, reduces unnecessary adjustment actions, and can transform a system that continuously controls the valve opening into a control system for multi-gear valve opening, reduce the scouring and wear of the valve by the process medium, and eliminate the phenomenon of repeated oscillation of the actuator caused by input signal fluctuations.

Description

Technical Field

[0001] The invention relates to the field of thermal control, and in particular to a thermal control system and method with a mobile dead zone function. Background Art

[0002] In thermal control strategies, the broken line function is a very commonly used functional block. It is a convenient and quick approximate fit to achieve y=f(x). However, in some control loops that do not require high regulation accuracy, if the process system is controlled classically and continuously, it will not only increase the number of adjustments unnecessarily, increase the loss of the actuator and valve, but also cause harmful disturbances to the process system. At this time, a discontinuous discrete correspondence is required. However, in the process of discrete conversion, in order to avoid the swing of the regulated quantity near the critical point causing the actuator to oscillate repeatedly, it is necessary to have asymmetric processing of the rising and falling processes, that is, to realize the function of moving the dead zone. The moving dead zone is a dead zone designed to prevent the input signal from fluctuating near the critical value of the step function and causing the output value to oscillate repeatedly. The dead zone follows the input signal instead of being fixed at a certain threshold.

[0003] For example, the control of the minimum flow regulating valve of the water pump is to control the water flow of the water pump recirculation, and the accuracy requirement is not high. In the current control system, whether it is PID closed-loop control or broken line function open-loop control, the valve is continuously controlled, which makes the valve often suffer severe erosion and the flow fluctuation is also frequent. For this reason, the process system requires the minimum flow regulating valve to stay at only a few fixed openings, while the ordinary step broken line function will cause the valve to oscillate repeatedly when the flow fluctuates at the step. Summary of the invention

[0004] The purpose of the present invention is to provide a thermal control system and method with a moving dead zone function in order to solve the above problems.

[0005] The invention objective of the present invention is achieved through the following technical solutions: A thermal control system with a mobile dead zone function, comprising: an analog input module, which converts a standard DC signal received from the field into a digital signal that can be recognized by a control module; a control module, which receives the digital signal of the analog input module, and sends it to the analog output module after discretization through an asymmetric discrete broken line function calculation loop; an analog output module, which receives the digital signal sent by the control module, and converts it into a standard 4~20mA DC signal and outputs it to an actuator; an actuator, which receives the standard 4~20mA DC signal of the analog output module to control the operation of the motor and drive the valve switch. ;

[0006] Wherein, the control module includes an asymmetric discrete broken line function calculation loop with a moving dead zone function.

[0007] The analog input module can receive the standard DC signal sent by the pressure transmitter, temperature transmitter, water level transmitter and displacement transmitter and convert it into a digital signal that can be recognized by the control module.

[0008] The control module receives the digital signal from the analog input module, performs discretization processing through an asymmetric discrete broken line function calculation loop, and then sends it to the analog output module.

[0009] The analog output module receives the digital signal sent by the control module and converts it into a standard DC signal and outputs it to the actuator.

[0010] The actuator includes a control unit, which controls the valve opening by receiving a standard DC signal.

[0011] A thermal control method with a moving dead zone function comprises the following steps:

[0012] S1. Convert the standard 4~20mA DC signal received from the transmitter into a digital signal that can be recognized by the control module;

[0013] S2. The control module receives the digital signal of the analog input module and sends it to the analog output module after discretization through the asymmetric discrete broken line function calculation loop;

[0014] S3. The analog output module receives the digital signal sent by the control module and converts it into a standard 4~20mA DC signal and outputs it to the actuator;

[0015] S4. The actuator receives the standard 4~20mA DC signal from the analog output module to control the motor operation and change the valve opening.

[0016] The beneficial effects of the present invention include reducing unnecessary adjustment actions of the analog quantity adjustment system, converting the system for continuously controlling the valve opening into a control system for multi-position valve opening, reducing the scouring and wear of the valve by the process medium, and eliminating the phenomenon of repeated oscillation of the actuator caused by fluctuations in the input signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a system structure diagram of the present invention;

[0018] Figure 2 It is a circuit principle diagram of the analog input module (A / D conversion) of the present invention;

[0019] Figure 3 The algorithm SAMA diagram of the control module of the present invention;

[0020] Figure 4 It is a circuit principle diagram of the analog output module (D / A conversion) of the present invention;

[0021] Figure 5 It is a step-line function diagram of flow rate and valve opening of a conventional control system;

[0022] Figure 6 It is a discrete broken line function diagram of flow rate and valve opening of the present invention. DETAILED DESCRIPTION

[0023] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation methods of the present invention are first described with reference to the accompanying drawings.

[0024] The specific method principle of this embodiment is as follows:

[0025] like Figure 1 As shown, a thermal control system with a mobile dead zone function includes: an analog input module, which converts a standard 4~20mA DC signal received from a field transmitter into a digital signal that can be recognized by a control module; a control module, which receives the digital signal of the analog input module, and sends it to the analog output module after discretization through an asymmetric discrete broken line function calculation loop; an analog output module, which receives the digital signal sent by the control module, and converts it into a standard 4~20mA DC signal and outputs it to an actuator; an actuator, which receives the standard 4~20mA DC signal of the analog output module to control the operation of the motor and drive the valve switch;

[0026] Wherein, the control module includes an asymmetric discrete broken line function calculation loop with a moving dead zone function.

[0027] The analog input module can receive the standard 4~20mA DC signal sent by the pressure transmitter, temperature transmitter, water level transmitter and displacement transmitter and convert it into a digital signal that can be recognized by the control module. Figure 2 As shown, signal conversion is performed and the converted digital signal is sent to the control module.

[0028] The control module receives the digital signal from the analog input module, performs discretization processing through an asymmetric discrete broken line function calculation loop, and then sends it to the analog output module.

[0029] The analog output module, through Figure 4 As shown, the digital signal sent by the receiving control module is converted into a standard 4~20mA DC signal and output to the actuator.

[0030] The actuator includes a control unit, which controls the valve opening by receiving a standard 4-20 mA DC signal.

[0031] A thermal control method with a moving dead zone function comprises the following steps:

[0032] S1. Convert the standard 4~20mA DC signal received from the transmitter into a digital signal that can be recognized by the control module;

[0033] S2. The control module receives the digital signal of the analog input module and sends it to the analog output module after discretization through the asymmetric discrete broken line function calculation loop;

[0034] S3. The analog output module receives the digital signal sent by the control module and converts it into a standard 4~20mA DC signal and outputs it to the actuator;

[0035] S4. The actuator receives the standard 4~20mA DC signal from the analog output module to control the motor operation and change the valve opening.

[0036] The traditional control of the minimum flow regulating valve of the water feed pump is to control the water flow of the water feed pump recirculation, and the precision requirement is not high. In the current control system, whether it is PID closed-loop control or broken line function open-loop control, the valve is continuously controlled, which often causes the valve to suffer severe scouring. At the same time, the flow fluctuation is also frequent. For this reason, the process system requires the minimum flow regulating valve to stay at only a few fixed openings. However, the ordinary step broken line function will cause the valve to oscillate repeatedly when the flow fluctuates at the step. Figure 5 shown.

[0037] For the present invention, Figure 6 As shown, by setting an asymmetric discrete broken line function calculation loop with a moving dead zone function, assuming that the input signal is flow, the output signal is valve opening, the current valve opening is P2, and the corresponding flow is F2. As long as the flow changes in the interval (F1, F3), the valve opening will not change and will remain at P2. Only when the flow = F3 will the valve opening be closed to P3. At this time, similar to the above process, as long as the flow changes in the interval (F2, F4), the valve opening will remain unchanged at P3. This prevents the valve opening from swinging when the flow oscillates near the critical point.

[0038] The asymmetric discrete broken line function calculation loop with moving dead zone function is as follows: Figure 3 As shown: the FT block outputs to the second input terminal of the T block, the first H / block, and the + input terminal of the △ block at the same time;

[0039] The output of the first H / block goes to the first input of the & block;

[0040] The T block outputs to its own first input terminal, the - input terminal of the △ block, and the f(x) block simultaneously;

[0041] The △ block outputs to the second H / block and the / L block simultaneously;

[0042] The second H / block and / L block output to the two input terminals of ≥1 block respectively;

[0043] ≥1 block output to the second input of the & block;

[0044] & block output to the third input terminal of T block;

[0045] The f(x) block outputs to the MO block.

[0046] It shows a control algorithm that starts to open the valve when the flow value reaches 100, and then switches the valve in steps of 50. The valve will only stay at the corresponding opening when the flow rate is 100, 150, 200, 250, ... The valve will not move when the flow fluctuation is less than ±50 on the above scale.

[0047] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A thermal control system with a mobile dead zone function, characterized in that: include: The analog input module converts the standard DC signal sent by the receiving transmitter into a digital signal that can be recognized by the control module; The control module receives the digital signal of the analog input module, and sends it to the analog output module after discretization through an asymmetric discrete broken line function calculation loop; The analog output module receives the digital signal sent by the control module after discretization processing, converts it into a standard DC signal and outputs it to the actuator; The actuator receives the standard DC signal from the analog output module to control the motor operation and drive the valve switch; Wherein, the control module includes an asymmetric discrete broken line function calculation loop with a moving dead zone function; The structure of the asymmetric discrete broken line function calculation loop is: The FT block outputs to the second input of the T block, the first H / block, and the + input of the △ block simultaneously; The output of the first H / block goes to the first input of the & block; The T block outputs to its own first input terminal, the - input terminal of the △ block, and the f(x) block simultaneously; The △ block outputs to the second H / block and the / L block simultaneously; The second H / block and / L block output to the two input terminals of ≥1 block respectively; ≥1 block output to the second input of the & block; & block output to the third input terminal of T block; The f(x) block outputs to the MO block; When the flow value reaches 100, the valve starts to open, and then opens and closes in steps of 50. When the flow fluctuates between ±50, the valve will not move.

2. According to the thermal control system with a mobile dead zone function described in claim 1, the analog input module can receive standard DC signals sent by a pressure transmitter, a temperature transmitter, a water level transmitter and a displacement transmitter.

3. A thermal control system with a moving dead zone function according to claim 1, characterized in that: The actuator includes a control unit, which controls the valve opening by receiving a standard DC signal.

4. A thermal control system with a moving dead zone function according to claim 1, characterized in that: The standard DC signal is a 4~20mA DC signal.

5. A thermal control method with a moving dead zone function, applied to a thermal control system with a moving dead zone function as claimed in any one of claims 1 to 4, characterized in that: The following steps are involved: S1. Convert the standard 4~20mA DC signal received from the transmitter into a digital signal that can be recognized by the control module; S2. The control module receives the digital signal of the analog input module and sends it to the analog output module after discretization through the asymmetric discrete broken line function calculation loop; S3. The analog output module receives the digital signal sent by the control module after discretization, and converts it into a standard 4~20mA DC signal and outputs it to the actuator; S4. The actuator receives the standard 4~20mA DC signal from the analog output module to control the motor operation and change the valve opening.

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