Pneumatic pressure control system and control method

Abstract

The present invention discloses a pneumatic pressure control system and a control method, which are characterized by comprising a pressure sensor, a PLC control module with a preset target deviation calculation module, a PID control module, a PWM control module with a preset switch valve control rule and a switch valve group module, wherein the switch valve group module comprises a valve group base, a total air inlet pipe and a total air outlet pipe arranged in the valve group base, the total air inlet pipe is provided with a total air inlet connected to the air supply port of an external air supply device and an exhaust port provided with an exhaust switch valve, the total air outlet pipe is provided with a total air outlet connected to the air inlet port of the air-using device, the total air inlet pipe and the total air outlet pipe are connected through at least seven air inlet branches which are not connected to each other, and each air inlet branch pipe is provided with an air inlet switch valve, which has the advantage of effectively solving the problem that the switch valve cannot be opened when the duty cycle of the PWM control signal is low, and is fully opened early when the duty cycle is high, and the accuracy and stability of controlling the air pressure are improved, and the adjustment is fast.

Description

Technical Field

[0001] The present invention relates to a pressure control system and a control method, in particular to a pneumatic pressure control system and a control method. Background Art

[0002] At present, in pneumatic pressure control, proportional valves or high-speed switching valves are generally used to form a system to achieve continuous pressure regulation. Since proportional valves are expensive and large in size, more and more high-speed switching valves are used to form a pressure regulation system. However, the effect is not ideal in actual fine-tuning control. Due to the response ability of the solenoid valve and the movement time of the valve core, the PWM signal sent by the controller to the switching valve actually has a certain lag. The switching valve cannot be opened when the controller sets a low PWM duty cycle, and it fully opens early at a higher duty cycle. In addition, the adjustment accuracy is not high. When closed-loop adjustment is performed by receiving pressure feedback, multiple rounds of adjustment are required to reach the required pressure value, which takes a long time. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a pneumatic pressure control system and a control method with high air pressure control accuracy and relatively stable control.

[0004] The technical solution adopted by the present invention to solve the above technical problems is: a pneumatic pressure control system, including a pressure sensor, a PLC control module with a preset target deviation calculation module, a PID control module, a PWM control module with a preset switch valve control rule and a switch valve group module, the pressure sensor is used to detect the air pressure of the air inlet port of the air-using equipment to obtain the current air pressure feedback value and send it to the target deviation calculation module preset in the PLC control module, the target deviation calculation module obtains the corresponding current target deviation value according to the given pressure value input externally and the current air pressure feedback value and inputs it into the PID control module, the PID control module obtains the corresponding current control amount according to the current target deviation value and sends it to the PLC control module WM control module, the switch valve group module includes a valve group base, a main air inlet pipe and a main air outlet pipe arranged in the valve group base, the main air inlet pipe is provided with a main air inlet connected to the air supply port of an external air supply device and an exhaust port provided with an exhaust switch valve, the main air outlet pipe is provided with a main air outlet connected to the air inlet port of the air-using device, the main air inlet pipe and the main air outlet pipe are connected through at least seven air inlet branches that are not connected to each other, each of the air inlet branches is provided with an air inlet switch valve, the PWM control module outputs corresponding PWM control signals according to the current control amount and the preset switch valve control rules to individually control the ventilation volume of each of the air inlet switch valve and the exhaust switch valve.

[0005] There are 11 intake branches, which further improves the accuracy and makes it more convenient to set the numerical value in the preset switch valve control rule.

[0006] The preset switch valve control rules are as follows:

[0007] The current control quantity output by the PID control module is recorded as Q%, -Q m %≤Q%≤Q m %,Q m % represents the control amount corresponding to the ventilation volume when the 10 intake switch valves are fully opened. Let Q m %=100%, define the dead zone duty ratio range corresponding to the PWM control signal failing to open the intake switch valve and the exhaust switch valve as 0~(10S1)%, define the duty ratio range corresponding to the PWM control signal fully opening the intake switch valve and the exhaust switch valve as (10S2)%~100%, set S1 to S1=2.0, and set S2 to S2=8.0;

[0008] Judge Q. If Q>0, divide Q by 10 to get the quotient N and remainder R. 0≤N≤10, 0≤R<10. When 2.0≤R<8.0, execute rule 1. When R<2.0, execute rule 2. When 8.0≤R<10.0, execute rule 3.

[0009] Rule 1 is as follows: set the duty ratio of the PWM control signal corresponding to the N intake switch valves to a fixed value greater than 80%, set the duty ratio of the PWM control signal corresponding to one of the other intake switch valves to (10R)%, and set the duty ratio of the PWM control signal corresponding to the remaining intake switch valves to 0%;

[0010] Rule 2 is as follows: set the duty cycle of the PWM control signal corresponding to the N intake switch valves to a fixed value greater than 80%, set the duty cycle of the PWM control signal corresponding to one of the other intake switch valves to (10A)%, set the duty cycle of the PWM control signal corresponding to the exhaust switch valve to (10B)%, where A is a preset fixed value, 5<A<8, A-B=R, and set the duty cycle of the PWM control signal corresponding to the remaining intake switch valves to 0%;

[0011] Rule three is as follows: the duty ratio of the PWM control signals corresponding to the N intake switch valves is set to a fixed value greater than 80%, the duty ratio of the PWM control signals corresponding to two of the other intake switch valves is set to (10C)%, where C=R / 2, and the duty ratio of the PWM control signals corresponding to the remaining intake switch valves is set to 0%;

[0012] If Q=0, rule 4 is executed as follows: the PWM control signal output by the PWM control module remains unchanged;

[0013] If -2.0≤Q<0, execute rule 5 as follows: set the duty cycle of the PWM control signal corresponding to one of the intake switch valves to (10D)%, and set the duty cycle of the PWM control signal corresponding to the exhaust switch valve to (10E)%, where E is a preset fixed value, 5<E<8, D-E=Q;

[0014] If -10.0<Q<-2.0, execute rule six as follows: set the duty cycle of the PWM control signal corresponding to the exhaust switch valve to (-10Q)%;

[0015] If Q≤-10.0, execute rule seven as follows: set the duty cycle of the PWM control signal corresponding to the exhaust switch valve to a fixed value greater than 80%.

[0016] At least one spare air intake pipe is arranged between the main air intake pipe and the main air outlet pipe, and a spare switch valve for controlling the on / off state of the spare air intake pipe is arranged in the spare air intake pipe. When one of the air intake switch valves fails, the PWM control module switches the PWM control signal originally sent to the failed air intake switch valve to one of the spare switch valves according to a preset switch valve control rule.

[0017] The air intake switch valve and the spare switch valve are staggered and arranged in two rows on the valve group base. The structure is compact and the volume of the valve group base is effectively reduced.

[0018] The control method using the above-mentioned pneumatic pressure control system comprises the following steps:

[0019] The PLC control module initially sends the externally given pressure value directly to the PID control module. The PID control module obtains the current control amount according to the externally given pressure value and sends it to the PWM control module. The PWM control module outputs corresponding PWM control signals according to the current control amount and the preset switch valve control rules to individually control the ventilation volume of each of the intake switch valve and the exhaust switch valve. The air supply port of the external air supply device starts to supply air to the total air inlet port of the total air inlet pipe, and sends the supplied gas to the air inlet port of the air-consuming device through the total air outlet.

[0020] The pressure sensor detects the air pressure of the air inlet port of the air-using equipment to obtain the current air pressure feedback value and sends it to the target deviation calculation module preset in the PLC control module;

[0021] The target deviation calculation module obtains the corresponding current target deviation value according to the given pressure value input externally and the current air pressure feedback value and inputs it into the PID control module;

[0022] The PID control module obtains the corresponding current control quantity according to the current target deviation value and sends it to the PWM control module;

[0023] The PWM control module outputs corresponding PWM control signals according to the current control amount and the preset switch valve control rules to individually control the ventilation volume of each of the intake switch valve and the exhaust switch valve;

[0024] Repeat steps , until the current target deviation value is 0, the control process of the pneumatic pressure control system is completed.

[0025] Compared with the prior art, the advantage of the present invention is that it adopts a closed-loop PID control system, including a pressure sensor, a PLC control module with a preset target deviation calculation module, a PID control module, a PWM control module with a preset switch valve control rule and a switch valve group module, wherein the switch valve group module includes a valve group base, a total air inlet pipe and a total air outlet pipe arranged in the valve group base, the total air inlet pipe is provided with a total air inlet connected to the air supply port of an external air supply device and an exhaust port provided with an exhaust switch valve, the total air outlet pipe is provided with a total air outlet connected to the air inlet port of an air-using device, the total air inlet pipe and the total air outlet pipe are connected through at least seven air inlet branches that are not connected to each other, each air inlet branch is provided with an air inlet switch valve, wherein the pressure sensor detects the air pressure of the air inlet port of the air-using device to obtain the current air pressure feedback value and sends it to the target deviation calculation module preset in the PLC control module, the target The deviation calculation module obtains the corresponding current target deviation value according to the given pressure value input externally and the current air pressure feedback value and inputs it into the PID control module. The PID control module obtains the corresponding current control amount according to the current target deviation value and sends it to the PWM control module. The PWM control module outputs corresponding PWM control signals according to the current control amount and the preset switch valve control rules to individually control the ventilation volume of each intake switch valve and exhaust switch valve to control multiple switch valves to follow the given pressure; wherein the number of intake branches is at least seven, and the current control amount can be realized as a whole by setting a separate control amount for each intake switch valve and exhaust switch valve according to the preset switch valve control rules, effectively solving the problem that the switch valve cannot be opened when the PWM control signal duty cycle is low and fully opened early at a higher duty cycle, and improves the accuracy of controlling air pressure, increases stability, and adjusts faster. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1is a system block diagram of Embodiment 1;

[0027] Figure 2 This is a structural schematic diagram of the switch valve group module in Example 2;

[0028] Figure 3 This is a pressure feedback curve collected by the PLC control module when the method of Example 3 is actually working. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below with reference to the accompanying drawings.

[0030] Embodiment 1: A pneumatic pressure control system, comprising a pressure sensor 1, a PLC control module 2 with a preset target deviation calculation module, a PID control module 3, a PWM control module 4 with a preset switch valve control rule, and a switch valve group module 5, wherein the pressure sensor 1 is used to detect the air pressure of the air inlet port of the gas-using equipment 6 to obtain the current air pressure feedback value and send it to the target deviation calculation module preset in the PLC control module 2, the target deviation calculation module obtains the corresponding current target deviation value according to the given pressure value input externally and the current air pressure feedback value and inputs it to the PID control module 3, the PID control module 3 obtains the corresponding current control amount according to the current target deviation value and sends it to the PWM control module 4, the switch valve group module 5 includes a valve group base 51, which is arranged at The main air inlet pipe (not shown) and the main air outlet pipe (not shown) in the valve group base 51 are provided with a main air inlet port 52 connected to the air supply port of the external air supply device 7 and an exhaust port (not shown) provided with an exhaust switch valve (not shown). The main air outlet pipe is provided with a main air outlet port 53 connected to the air inlet port of the air-using device 6. The main air inlet pipe and the main air outlet pipe are connected through 11 air inlet branches (not shown) that are not connected to each other. Each air inlet branch is provided with an air inlet switch valve 54. The PWM control module 4 outputs corresponding PWM control signals according to the current control amount and the preset switch valve control rules to individually control the ventilation volume of each air inlet switch valve 54 and the exhaust switch valve. The preset switch valve control rules are as follows:

[0031] The current control quantity output by PID control module 3 is recorded as Q%, -Q m %≤Q%≤Q m %,Q m % represents the control amount corresponding to the ventilation volume when the 10 intake switch valves 54 are fully opened. Let Q m%=100%, the duty cycle range corresponding to the PWM control signal failing to open the intake switch valve 54 and the exhaust switch valve is defined as 0~(10S1)%, the duty cycle range corresponding to the PWM control signal fully opening the intake switch valve 54 and the exhaust switch valve is defined as (10S2)%~100%, S1 is set to S1=2.0, and S2 is set to S2=8.0; at this time, the opening time of the intake switch valve 54 is 10ms, the closing time is 10ms, the operating frequency is 10Hz, and the parameters of the exhaust switch valve and the intake switch valve 54 are the same;

[0032] Judge Q. If Q>0, divide Q by 10 to get the quotient N and remainder R. 0≤N≤10, 0≤R<10. When 2.0≤R<8.0, execute rule 1. When R<2.0, execute rule 2. When 8.0≤R<10.0, execute rule 3.

[0033] Rule 1 is as follows: the duty ratio of the PWM control signals corresponding to the N intake switch valves 54 is set to 90%, the duty ratio of the PWM control signals corresponding to one of the other intake switch valves 54 is set to (10R)%, and the duty ratio of the PWM control signals corresponding to the remaining intake switch valves 54 is set to 0%;

[0034] Rule 2 is as follows: set the duty ratio of the PWM control signal corresponding to the N intake switch valves 54 to 90%, set the duty ratio of the PWM control signal corresponding to one of the other intake switch valves 54 to (10A)%, set the duty ratio of the PWM control signal corresponding to the exhaust switch valve to (10B)%, where A is a preset constant, 5<A<8, A-B=R, and set the duty ratio of the PWM control signal corresponding to the remaining intake switch valves 54 to 0%; for example, R=1.2, A=6.0, B=4.8;

[0035] Rule three is as follows: the duty ratios of the PWM control signals corresponding to the N intake switch valves 54 are set to 90%, the duty ratios of the PWM control signals corresponding to two of the other intake switch valves 54 are set to (10C)%, where C=R / 2, and the duty ratios of the PWM control signals corresponding to the remaining intake switch valves 54 are set to 0%; for example, R=9.2, C=4.6;

[0036] If Q=0, rule 4 is executed as follows: the PWM control signal output by the PWM control module 4 remains unchanged;

[0037] If -2.0≤Q<0, rule five is executed as follows: the duty ratio of the PWM control signal corresponding to one of the intake switch valves 54 is set to (10D)%, and the duty ratio of the PWM control signal corresponding to the exhaust switch valve is set to (10E)%, where E is a preset constant value, 5<E<8, D-E=Q; for example, Q=-1.3, D=4.8, E=6.1;

[0038] If -10.0<Q<-2.0, execute rule six as follows: set the duty cycle of the PWM control signal corresponding to the exhaust switch valve to (-10Q)%;

[0039] If Q≤-10.0, execute rule seven as follows: set the duty cycle of the PWM control signal corresponding to the exhaust switch valve to 90%. The duty cycle of the PWM control signal is set to 90%, and can also be set to any value greater than 80%.

[0040] Embodiment 2: The rest of the embodiment is the same as that of Embodiment 1, except that two spare intake pipes (not shown) are arranged between the main intake pipe and the main outlet pipe, and a spare switch valve 55 for controlling the on / off state of the spare intake pipe is arranged in the spare intake pipe. When one of the intake switch valves 54 fails, the PWM control module 4 switches the PWM control signal originally sent to the failed intake switch valve 54 to a spare switch valve 55 according to a preset switch valve control rule. The intake switch valves 54 and the spare switch valves 55 are staggered and arranged in two rows on the valve group base 51.

[0041] Embodiment 3: A control method using the pneumatic pressure control system of embodiment 1 comprises the following steps:

[0042] The PLC control module 2 initially sends the externally given pressure value directly to the PID control module 3. The PID control module 3 obtains the current control amount according to the externally given pressure value and sends it to the PWM control module 4. The PWM control module 4 outputs corresponding PWM control signals according to the current control amount and the preset switch valve control rules to individually control the ventilation volume of each intake switch valve 54 and the exhaust switch valve. The air supply port of the external air supply device 7 starts to supply air to the total air inlet port 52 of the total air inlet pipe, and sends the supplied gas to the air inlet port of the gas-using device 6 through the total air outlet port 53.

[0043] The pressure sensor 1 detects the air pressure of the air inlet port of the air-using device 6 to obtain the current air pressure feedback value and sends it to the target deviation calculation module preset in the PLC control module 2;

[0044] The target deviation calculation module obtains the corresponding current target deviation value according to the given pressure value input externally and the current air pressure feedback value and inputs it into the PID control module 3;

[0045] The PID control module 3 obtains the corresponding current control amount according to the current target deviation value and sends it to the PWM control module 4;

[0046] The PWM control module 4 outputs corresponding PWM control signals according to the current control amount and the preset switch valve control rules to individually control the ventilation volume of each intake switch valve 54 and the exhaust switch valve;

[0047] Repeat steps , until the current target deviation value is 0, the control process of the pneumatic pressure control system is completed. When the pressure is initially supplied, the feedback value is 0, so the current control amount Q%=100%, and all 10 intake switch valves 54 are opened.

[0048] like Figure 3 As shown, I is the PID control stage, II is the waveform of the pressure stabilization stage, and III is the system response when a negative step pressure is given after the pressure output is stabilized. It can be seen that the system responds quickly, has no obvious overshoot, and has good control stability.

Claims

1. A pneumatic pressure control system, comprising a pressure sensor, a PLC control module with a preset target deviation calculation module, a PID control module, a PWM control module with a preset switch valve control rule, and a switch valve group module, wherein the pressure sensor is used to detect the air pressure of the air inlet port of the air-using equipment to obtain the current air pressure feedback value and send it to the target deviation calculation module preset in the PLC control module, the target deviation calculation module obtains the corresponding current target deviation value according to the given pressure value input from the outside and the current air pressure feedback value and inputs it into the PID control module, the PID control module obtains the corresponding current control amount according to the current target deviation value and sends it to the PWM control module, characterized in that The switch valve group module includes a valve group base, a main air inlet pipe and a main air outlet pipe arranged in the valve group base, the main air inlet pipe is provided with a main air inlet connected to the air supply port of the external air supply device and an exhaust port provided with an exhaust switch valve, the main air outlet pipe is provided with a main air outlet connected to the air inlet port of the air-using device, the main air inlet pipe is connected to the main air outlet pipe through at least seven air inlet branches that are not connected to each other, each of the air inlet branches is provided with an air inlet switch valve, and the PWM control module outputs corresponding PWM control signals according to the current control amount and the preset switch valve control rules to individually control the ventilation volume of each of the air inlet switch valve and the exhaust switch valve; The preset switch valve control rules are as follows: The current control quantity output by the PID control module is recorded as Q%, -Q m %≤Q%≤Q m %,Q m % represents the control amount corresponding to the ventilation volume when the 10 intake switch valves are fully opened. Let Q m %=100%, defines the dead zone duty ratio range corresponding to the PWM control signal failing to open the intake switch valve and the exhaust switch valve as 0~(10S1)%, defines the duty ratio range corresponding to the PWM control signal fully opening the intake switch valve and the exhaust switch valve as (10S2)%~100%, where 10S1+10S2=100, sets S1 to S1=2.0, and sets S2 to S2=8.0; Judge Q. If Q>0, divide Q by 10 to get the quotient N and remainder R. 0≤N≤10, 0≤R<10. When 2.0≤R<8.0, execute rule 1. When R<2.0, execute rule 2. When 8.0≤R<10.0, execute rule 3. Rule 1 is as follows: set the duty ratio of the PWM control signal corresponding to the N intake switch valves to a fixed value greater than 80%, set the duty ratio of the PWM control signal corresponding to one of the other intake switch valves to (10R)%, and set the duty ratio of the PWM control signal corresponding to the remaining intake switch valves to 0%; Rule 2 is as follows: set the duty cycle of the PWM control signal corresponding to the N intake switch valves to a fixed value greater than 80%, set the duty cycle of the PWM control signal corresponding to one of the other intake switch valves to (10A)%, set the duty cycle of the PWM control signal corresponding to the exhaust switch valve to (10B)%, where A is a preset fixed value, 5<A<8, A-B=R, and set the duty cycle of the PWM control signal corresponding to the remaining intake switch valves to 0%; Rule three is as follows: the duty ratio of the PWM control signals corresponding to the N intake switch valves is set to a fixed value greater than 80%, the duty ratio of the PWM control signals corresponding to two of the other intake switch valves is set to (10C)%, where C=R / 2, and the duty ratio of the PWM control signals corresponding to the remaining intake switch valves is set to 0%; If Q=0, rule 4 is executed as follows: the PWM control signal output by the PWM control module remains unchanged; If -2.0≤Q<0, execute rule 5 as follows: set the duty cycle of the PWM control signal corresponding to one of the intake switch valves to (10D)%, and set the duty cycle of the PWM control signal corresponding to the exhaust switch valve to (10E)%, where E is a preset fixed value, 5<E<8, D-E=Q; If -10.0<Q<-2.0, execute rule six as follows: set the duty cycle of the PWM control signal corresponding to the exhaust switch valve to (-10Q)%; If Q≤-10.0, execute rule seven as follows: set the duty cycle of the PWM control signal corresponding to the exhaust switch valve to a fixed value greater than 80%.

2. A pneumatic pressure control system according to claim 1, characterized in that There are 11 air intake branch pipes.

3. A pneumatic pressure control system according to claim 1, characterized in that At least one spare air intake pipe is arranged between the main air intake pipe and the main air outlet pipe, and a spare switch valve for controlling the on / off state of the spare air intake pipe is arranged in the spare air intake pipe. When one of the air intake switch valves fails, the PWM control module switches the PWM control signal originally sent to the failed air intake switch valve to one of the spare switch valves according to a preset switch valve control rule.

4. A pneumatic pressure control system according to claim 3, characterized in that The air intake switch valve and the spare switch valve are staggered and arranged in two rows on the valve group base.

5. A control method using the pneumatic pressure control system according to claim 1, characterized in that The following steps are involved: The PLC control module initially sends the externally given pressure value directly to the PID control module. The PID control module obtains the current control amount according to the externally given pressure value and sends it to the PWM control module. The PWM control module outputs corresponding PWM control signals according to the current control amount and the preset switch valve control rules to individually control the ventilation volume of each of the intake switch valve and the exhaust switch valve. The air supply port of the external air supply device starts to supply air to the total air inlet port of the total air inlet pipe, and sends the supplied gas to the air inlet port of the air-consuming device through the total air outlet. The pressure sensor detects the air pressure of the air inlet port of the air-using equipment to obtain the current air pressure feedback value and sends it to the target deviation calculation module preset in the PLC control module; The target deviation calculation module obtains the corresponding current target deviation value according to the given pressure value input externally and the current air pressure feedback value and inputs it into the PID control module; The PID control module obtains the corresponding current control quantity according to the current target deviation value and sends it to the PWM control module; The PWM control module outputs corresponding PWM control signals according to the current control amount and the preset switch valve control rules to individually control the ventilation volume of each of the intake switch valve and the exhaust switch valve; Repeat steps , until the current target deviation value is 0, the control process of the pneumatic pressure control system is completed.

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