Method and process system for operating a process system for pressure pad control or fill level control in a tank

Abstract

A method for operating a process system for pressure pad control or fill level control in a tank containing a fluid, in particular a liquid and / or a gas, and a process system are disclosed, the method comprising a controller for setting a reference variable, in particular a pressure of a pressure pad in the tank or a fill level of the fluid contained in the tank, wherein the controller comprises at least a proportional element and an integral element, a proportional component of a control variable of the controller being set via the proportional element, an integral component of the control variable of the controller being set via the integral element. The process system is selectively operated in a first proportional operating mode or in a second integral operating mode. When the process system is operated in the second integral operating mode, the integral element of the controller does not contribute to the control variable of the controller, whereas when the process system is operated in the first proportional operating mode, the integral element of the controller contributes to the control variable of the controller.

Description

Technical Field

[0001] This invention relates to a method for controlling pressure pads or filling level in a process system operating a tank containing a fluid, such as a liquid and / or gas. Furthermore, this invention relates to process systems. Background Technology

[0002] When pressure pad control or fill level control is used to control industrial processes, different operating modes may occur. For example, pressure pad control or fill level control can be performed with continuous fluid extraction, which corresponds to a proportional process type. Alternatively, pressure pad control or fill level control can be performed without continuous extraction, which corresponds to an integral process type.

[0003] In proportional processes, the best control performance can be achieved using a PID controller, while in integral processes, the best control performance can be achieved using a PD controller.

[0004] In process systems that offer two operating modes (i.e., pressure pad control or fill level control with continuous withdrawal and pressure pad control or fill level control without continuous withdrawal), a controller compatible with the operating mode that is most frequently used or for which better control performance is desired is typically used. For the other operating mode, reduced control performance is acceptable. Summary of the Invention

[0005] However, it is desirable to achieve optimal control performance in both operating modes. In this regard, the object of the present invention is to provide an optimized method for operating a process system for pressure pad control or fill level control, as well as an optimized process system.

[0006] According to the invention, this objective is achieved by a method for controlling a pressure pad or filling level in a process system containing a fluid (e.g., liquid and / or gas) in a tank. The method includes a controller for setting a reference variable, specifically the pressure of the pressure pad in the tank or the filling level of the fluid (e.g., liquid or gas) contained in the tank. The controller includes at least a proportional element and an integral element, with the proportional element setting the proportional component of the controller's control variable and the integral element setting the integral component of the controller's control variable. The process system operates selectively in a first proportional operating mode or a second integral operating mode. When the process system operates in the second integral operating mode, the integral element of the controller does not contribute to the controller's control variable, while when the process system operates in the first proportional operating mode, the integral element of the controller contributes to the controller's control variable.

[0007] For example, the integral element of a controller can be selectively turned on or off, allowing it to contribute to or not contribute to the controller's controlled variable. Therefore, when the integral element is on, the controller functions similarly to a PID controller, while when it is off, it functions similarly to a PD controller. The proportional component (proportional element) ensures the system can quickly respond to deviations from the setpoint variable, while the integral component (integral element) contributes to eliminating persistent deviations (permanent control errors).

[0008] The method according to the invention offers the advantage of optimizing control behavior by always setting a control structure best suited to the corresponding operating mode, thereby achieving the best possible control performance. In other words, it allows for flexible response to changing process conditions.

[0009] Specifically, it avoids overshoot of the control signal during regulation, and the desired liquid level can be corrected without any control deviation when fluid is drawn from or supplied to the tank.

[0010] For example, the integrating element automatically turns on or off.

[0011] When the integrator is turned on, the controller responds not only to the current deviation but also to the deviation accumulated over time in order to correct the ongoing control deviation.

[0012] Applications of the invention include, for example, so-called tank covering, in which a gas covering (typically nitrogen) is maintained above a (different) fluid (e.g., liquid) in a closed tank, or for controlling the filling level in a closed or open tank, such as in watering cans in a large nursery. However, other applications are also conceivable, such as applications where the tank contains only gas and the gas pressure within the tank is controlled.

[0013] According to one aspect, in the first proportional operating mode, fluid is drawn from or supplied to the tank while a reference variable is kept constant through control, whereas in the second integral operating mode, no fluid is drawn from the tank. Control of the reference variable in the proportional operating mode ensures the stability of control parameters, particularly the pressure level or fill level, during the drawing process. This ensures that the process is not affected by fluctuations in pressure level or fill level.

[0014] In the first operating mode, for example, the pressure of the pressure pad in the tank is kept constant by control during fluid extraction, and in the second operating mode, the pressure of the pressure pad in the tank is controlled while maintaining a constant fill level, particularly in the second operating mode where the pressure level is varied. A constant pressure of the pressure pad during fluid extraction is essential to ensure a controlled extraction process. Maintaining a constant pressure ensures the process remains stable and predictable despite fluid discharge. In the second operating mode, the variation in pressure level at a constant fill level allows the conditions within the tank to be optimally adapted to subsequent processes.

[0015] The pressure level changes in the second operating mode occur when adjusting the pressure level for different batches, for example, during tank covering.

[0016] In pure fill level control for water tanks, the tank is open, so that only the fill level is controlled and not the pressure inside the tank.

[0017] The tank may be equipped with an inlet valve and a drain valve, or a combination of inlet and drain valves may be present to remove fluid, particularly liquid, from the tank, or to supply fluid, particularly liquid, to the tank. The current operating mode may be determined based on the switching and / or opening state of at least one valve, i.e., whether fluid is being extracted or supplied, and the integral element of the controller may be driven based on the determined operating mode.

[0018] The combined inlet and outlet valve is a valve that functions as both an inlet and outlet valve.

[0019] In the case of a combined inlet and outlet valve, the valve is, for example, a 3 / 3-way valve that operates against hydrostatic pressure during filling. In the case of separate inlet and outlet valves, these valves are, for example, designed as 2 / 2-way valves.

[0020] By reading the switching or open state of at least one valve, it is particularly easy to determine whether fluid extraction or supply, such as liquid extraction or supply, is currently in progress. More specifically, direct and reliable detection of the current operating mode is possible without additional sensors. Therefore, the probability of false positives or delays in detecting operating modes is low. The absence of additional sensors also reduces the complexity of the system architecture.

[0021] With at least one inlet valve and / or drain valve open, the controller detects that a first operating mode is active, and the integral element provides an integral component to the control variable. If at least one inlet valve and / or drain valve is closed, the controller detects that a second operating mode is active, and the integral element does not provide an integral component to the control variable. Therefore, the control structure dynamically, particularly in real-time, adapts to the current process conditions, thereby optimizing control performance.

[0022] In one respect, the controller receives the switching and / or opening states of inlet and drain valves, or a combination of inlet and drain valves, as input variables. By receiving real-time information about the valve states, the controller can react to changes in the system particularly quickly. This improves the dynamic performance of the system and ensures efficient attainment and maintenance of setpoints. This reduces the risk of control errors due to erroneous data.

[0023] Based on the detected operating mode, a binary signal is generated representing the corresponding current operating mode, and the integrator of the controller is controlled based on this binary signal. Directly controlling the integrator of the controller using a simple binary signal simplifies the control technique. Furthermore, binary signals present only a very low risk of interpretation errors.

[0024] The tank can be a closed tank, and the pressure of the pressure buffer pad inside the tank can be set by means of at least one control valve. The current operating mode of the process system can be automatically detected based on the controller's control variables (including the opening state of at least one control valve) and additionally based on control deviation, and the integral element of the controller can be controlled according to the detected operating mode. The controller's control variables correspond to the controller's output signal.

[0025] Automated detection of the current operating mode based on the opening state and control deviation of at least one control valve enables continuous monitoring of the process system, thereby allowing for optimal response to changes. By determining the operating mode based on the controller's control variables and, additionally, on the control deviation of at least one control valve, the separate switching inputs on the controller for detecting the state of the inlet and / or drain valves can be eliminated. This also means that signal lines from the inlet and drain valves to the controller are unnecessary. Therefore, the process system can be manufactured particularly easily and cost-effectively.

[0026] For example, a single control valve in the form of a 3 / 3-way valve can be provided, or two 2 / 2-way valves can be provided.

[0027] According to another embodiment, the filling level in the tank can be set, wherein the current operating mode of the process system is automatically detected based on the controller's control variables (including the opening states of the inlet valve and the outlet valve, or a combination of the inlet valve and the outlet valve), in other words, based on the controller's output signal and additionally based on the control deviation, and the integral element of the controller is controlled according to the detected operating mode. This embodiment is also applicable to pure filling level control without pressure buffer control, particularly for open tanks.

[0028] For example, the controller switches, more precisely, the controller activates the integral component, when the controller's control variable remains constant for a defined time period, and additionally, when there is a persistent control deviation for, for example, at least one second, and particularly at least ten seconds. In this case, the control deviation is particularly low and non-zero. In an exemplary embodiment, the switching occurs when the control deviation is non-zero and remains constant for at least ten seconds.

[0029] Continuous control deviation over a defined time period indicates that the system may be permanently controlling incorrectly. By automatically activating the integral component, the controller can correct such deviations. As previously explained, this improves control performance.

[0030] In one aspect, the actual pressure in the tank is detected by a pressure sensor, and the control deviation is calculated based on the difference between the actual pressure and the setpoint. Calculating the control deviation based on the difference between the actual and setpoints allows the controller to respond immediately to the deviation. This contributes to the system's ability to respond quickly and effectively to changes or disturbances during the process. By continuously monitoring the control deviation, the controller can dynamically adjust its strategy to maximize the efficiency of pressure control.

[0031] For example, the controller executes an algorithm to determine the current operating mode based on the controller's control variables and control deviations. The use of algorithms enables the automatic and accurate determination of the current operating mode in real time. This reduces the need for human intervention and minimizes human error by controlling the process in a data-driven manner. Therefore, the use of algorithms improves the overall performance of the system.

[0032] For example, when the controller switches from a first proportional operation mode to a second integral operation mode or from a second integral operation mode to a first proportional operation mode, at least one parameter of the integral element is changed.

[0033] Specifically, the settling time is changed to set the integral component of the controller. The settling time determines the strength of the controller's integral component's response to control deviation. The shorter the settling time, the stronger the effect of the integral element.

[0034] If the controller's integral element is not intended to contribute to the controller's control variables, the settling time is set to infinity. The integral element is therefore effectively turned off and thus inactive.

[0035] If the settling time is less than infinity, the integral element is activated and thus contributes to the control variable.

[0036] When the integral element is activated, the corresponding specific value of the adjustment time depends on the desired process dynamics and is determined and set by the user.

[0037] The integral element described above, depending on the process of being turned on or off, specifically means switching between an infinite settling time and a settling time value specified by the user.

[0038] According to the invention, this objective is also achieved through a process system specifically designed for performing the method according to the invention, the process system comprising a tank containing a fluid, such as a liquid and / or gas, and for setting a reference variable, in particular the pressure of a pressure buffer in the tank or the filling level of the fluid contained in the tank, wherein the controller comprises at least: a proportional element, via which a proportional component of the controller's control variable is set; and an integral element, via which an integral component of the controller's control variable is set. The process system is adapted to operate selectively in a first proportional operating mode or a second integral operating mode. The controller is configured to detect whether the process system is operating in a proportional operating mode or an integral operating mode, and, when the process system is operating in an integral operating mode, to control the integral element such that the integral element does not contribute to the controller's control variable, and, when the process system is operating in a proportional operating mode, to control the integral element such that the integral element contributes to the controller's control variable.

[0039] As already described in conjunction with the method according to the invention, the advantage provided by the process system according to the invention is that control behavior can be optimized by always setting the control structure most suitable for the corresponding operating mode, so that the best possible control performance can be achieved. Attached Figure Description

[0040] Other advantages and features of the invention will become apparent from the following description and from the accompanying drawings, with reference to the drawings and in which:

[0041] - Figure 1 The process system according to the present invention is illustrated schematically.

[0042] - Figure 2 Another process system according to the present invention is illustrated schematically.

[0043] - Figure 3 The pressure and fill level curves in the tank of the process system according to the invention are shown during control in integral operation mode using the PD control structure.

[0044] - Figure 4 The pressure and fill level curves in the tank of the process system according to the invention are shown during control in integral operation mode using a PID control structure.

[0045] - Figure 5The pressure and fill level curves in the tank of the process system according to the invention are shown during control using a PID control structure in proportional operation mode.

[0046] - Figure 6 The pressure and fill level curves in the tank of the process system according to the invention are shown during control in proportional operation mode using the PD control structure. Detailed Implementation

[0047] Figure 1 The process system 10 is shown schematically.

[0048] Process system 10 includes a tank 12 in which fluids are contained. For example, liquids and gases are contained in tank 12. Figure 1 In the example embodiment shown, can 12 is a sealed can.

[0049] In addition, the process system 10 includes a controller 14, which is used to set control variables, particularly the pressure of the pressure buffer pad in the tank 12 or the filling level of the fluid contained in the tank 12.

[0050] Tank 12 is provided with an inlet valve 16 and a drain valve 18, which enable the extraction of fluid from or supply of fluid to tank 12. The inlet valve 16 and the drain valve 18 can be designed as on / off valves or proportional valves.

[0051] Inlet valve 16 and outlet valve 18 are driven by signal 17, signal 17 in Figure 1 and Figure 2 The diagram schematically illustrates, in particular, that the control unit is not shown in the figures for simplicity, and is driven by signal 17.

[0052] Instead of two separate valves, a combined inlet and outlet valve can also be provided.

[0053] Additionally, a control valve 20 is provided for setting the pressure of the pressure buffer pad in tank 12. The control valve 20 is driven, for example, by a motor pneumatically or hydraulically.

[0054] The pressure in tank 12 is detected by pressure sensor 22. If tank 12 contains liquid, the pressure is determined above the fill level. Pressure sensor 22 is connected to controller 14 via signal transmission.

[0055] According to Figure 1 In process system 10, controller 14 is configured to drive control valve 20 to control the pressure in tank 12. Therefore, the open state of control valve 20 represents the control variable of controller 14.

[0056] The pressure of the pressure pad located in tank 12 represents the reference variable of controller 14.

[0057] Pressure sensor 22 supplies the actual pressure in tank 12 as a feedback variable to controller 14, so that controller 14 can calculate the control deviation between the reference variable and the feedback variable, especially the difference between the actual value and the set value of the pressure in tank 12.

[0058] The controller 14 includes a proportional element (I element) 24, a derivative element (D element) 26 and an integral element (I element) 28, wherein, as described in detail below, the controller 14 is configured to control the integral element such that the integral element does not contribute to the control variable of the controller 14.

[0059] The process system 10 can selectively operate in two different operating modes, namely, in a first proportional operating mode or in a second integral operating mode.

[0060] In the first proportional operation mode, fluid (especially liquid) is drawn from tank 12 during fluid extraction while a reference variable (i.e., the pressure of the pressure pad) is kept constant through control. The same applies when fluid is supplied.

[0061] In the second integral operating mode, no fluid, especially liquid, is drawn from tank 12. Therefore, while maintaining a constant fill level, the pressure of the pressure pad in tank 12 is controlled; the pressure level in the second operating mode is altered, specifically increased or decreased.

[0062] Such operating conditions occur, for example, in a so-called tank cover. In a tank cover, for example, tank 12 contains liquid and a pressure pad located above the liquid.

[0063] When process system 10 operates in the first proportional operation mode, it is expected that integral element 28 will contribute to the control variables of controller 14.

[0064] However, when the process system 10 is operating in the second integral operation mode, the integral element 28 has a negative impact on the control performance.

[0065] According to the method used for operating process system 10, the integral element 28 can be turned off so that the integral element 28 does not contribute to the control variables of controller 14.

[0066] Figure 1 This explains that the switching is performed by switch 19, which can switch between a first state and a second state of controller 14. In the first state, the integrator 28 is active, and in the second state, the integrator 28 is inactive.

[0067] The following section describes in detail how to implement this method.

[0068] First, it must be determined in which operating mode the process system 10 is currently operating.

[0069] exist Figure 1 In the example embodiment shown, this is achieved by first determining the switching state of the inlet valve 16 and the outlet valve 18, specifically by the controller 14. For this purpose, the controller 14 includes a switching input 32 that is connected to the inlet valve 16 and the outlet valve 18 in a signal transmission manner.

[0070] Therefore, the controller 14 receives the switching state and / or opening state of the inlet valve 16 and the outlet valve 18 as input variables.

[0071] If inlet valve 16 and / or outlet valve 18 are open, controller 14 detects that process system 10 is currently operating in the first proportional operation mode.

[0072] If inlet valve 16 and outlet valve 18 are closed, controller 14 detects that process system 10 is currently operating in the second integral operation mode.

[0073] Therefore, the operating mode is automatically detected by the controller 14.

[0074] If there is a change from the first proportional operation mode to the second integral operation mode, the controller 14 shuts down the integral element 28 so that it no longer contributes to the control variable.

[0075] Conversely, when changing from the second integral operating mode to the first proportional operating mode, the controller 14 turns on the integral element 28, causing the integral element 28 to contribute to the control variable again.

[0076] Based on the detected operating mode, a binary signal representing the corresponding current operating mode is generated, and the integrator element 28 of the controller 14 is controlled based on this signal. Specifically, the controller 14 generates the binary signal.

[0077] When the controller 14 switches from a first proportional operation mode to a second integral operation mode, or from a second integral operation mode to a first proportional operation mode, at least one parameter of the integral element 28 is changed. According to... Figure 1 In an example implementation, this is achieved using binary signals.

[0078] Specifically, the adjustment time is changed to turn the integral element of controller 14 on or off.

[0079] When switching from the first proportional operating mode to the second integral operating mode, the settling time is set to infinity. Therefore, the integral element 28 is effectively turned off and thus ineffective, meaning it contributes nothing to the control variable.

[0080] When switching from the second integral operating mode to the first proportional operating mode, the integral element 28 is reactivated, which is achieved by setting the settling time to a predetermined value less than infinity. For example, a value between 0.1 and 100 can be envisioned.

[0081] Figure 2 Another process system 10 is schematically illustrated. According to... Figure 2 The processing system and Figure 1 The difference in the processing system 10 shown is that there is no signal transmission connection between the inlet valve 16 and the outlet valve 18 and the controller 14, and therefore the controller 14 does not receive the switching state and / or opening state of the inlet valve 16 and the outlet valve 18 as input variables.

[0082] Therefore, it is impossible to determine the corresponding current operating mode based on the switching and / or opening states of the inlet valve 16 and the outlet valve 18.

[0083] Alternatively, the current operating mode is determined based on the control variables of controller 14, which include the opening state of at least one control valve 20, in other words, based on the output signal of controller 14, and additionally based on the control deviation, i.e., the difference between the actual value and the set value of the pressure existing in tank 12.

[0084] The operating status is also automatically detected here.

[0085] For example, controller 14 executes an algorithm, which may be stored on processor 33, to detect the current operating mode based on the controller's control variables and control deviations.

[0086] For example, if the controller's control variable remains constant within a specified time period and there is a continuous control deviation, then controller 14 switches.

[0087] Reference Figures 3 to 6 The process is described in detail.

[0088] Figures 3 to 6 The actual pressure in tank 12 based on curve 34, the expected pressure based on curve 36, and the filling level curve in tank 12 based on curve 38 are shown respectively.

[0089] Pressure is plotted in bars, and liquid level is plotted in percentage.

[0090] Figure 3 and Figure 4The first proportional operation mode is shown, in which, as can be seen from the changing fill level, fluid, particularly liquid, is drawn from the tank while the reference variable, namely the pressure present in tank 12, is kept constant through control.

[0091] In this state, regardless of changes in the filling liquid level, control valve 20 opens to maintain a constant pressure on the pressure pad.

[0092] Since the control valve 20 is driven by the controller 14 itself, the controller 14 can obtain information about the opening state, especially the degree of opening, i.e., the degree to which the control valve 20 is open.

[0093] In addition, the controller 14 continuously calculates the control deviation, which is the difference between the actual pressure value detected by the pressure sensor 22 and the pressure set value.

[0094] The current operating mode of the process system 10 is automatically detected based on the opening state of the control valve 20 and, additionally, based on the control deviation.

[0095] exist Figure 3 In the state shown, the integrator 28 of the controller 14 is disabled, which results in a non-zero continuous control deviation.

[0096] When the first operating mode has been determined and the optimal control structure has not been set, the controller 14 switches, that is, it controls the integral element 28 of the controller 14 according to the detected operating mode.

[0097] exist Figure 3 In the scenario shown, the control deviation remains constant over a relatively long period of time, especially over a period of more than one minute.

[0098] If it appears Figure 3 In the scenario shown, controller 14 activates integral element 28.

[0099] exist Figure 4 The first operating mode also appears in the scenario shown. However, in Figure 4 In the curve shown, the integral element 28 has been activated, so there is no sustained control deviation. In this case, when switching between filling and extraction modes, the control deviation only appears briefly as a slight overshoot.

[0100] Figure 5 and Figure 6 The second integral operating mode is shown. In this operating mode, no fluid, specifically no liquid, is drawn from tank 12; that is, the liquid level remains constant as the pressure changes.

[0101] exist Figure 5In the scenario shown, the integrator 28 of the controller 14 is activated. This results in a significant overshoot of the pressure level during pressure regulation.

[0102] Similarly, in this case, the controller 14 determines the current operating mode based on the opening state of the control valve 20 and the control deviation, and then... Figure 5 In an example implementation, this operating mode lasts for approximately 10 to 15 seconds.

[0103] In order to adjust the pressure level without overshoot, the controller 14 shuts down the integral element 28 once the second operating mode is detected.

[0104] The method and process system have been described above in the context of tank covering applications.

[0105] However, other applications can also be envisioned.

[0106] For example, this method can also be used in conjunction with filling level control in open tanks.

[0107] In this case, the fill level is used as a reference variable for controller 14.

[0108] In this case, the control variables of controller 14 include the open state of inlet valve 16 and outlet valve 18, or the combination of inlet and outlet valves.

[0109] Based on the control variables of controller 14, and additionally based on the control deviation, i.e. the difference between the actual filling level and the desired filling level, the current operating mode of process system 10 can also be automatically detected, and the integrator element 28 of controller 14 can be controlled according to the detected operating mode.

[0110] The first operating mode is, for example, a proportional operating mode, in which the filling level in tank 12 remains constant during fluid extraction and / or fluid supply.

[0111] The second operating mode is, for example, the integral operating mode, in which the filling liquid level remains constant and no fluid is extracted.

Claims

1. A method for operating a process system (10) for pressure pad control or fill level control in a tank (12) containing a fluid, such as a liquid and / or gas, the process system (10) including a controller (14) for setting reference variables, particularly the pressure of the pressure pad in the tank (12) or the fill level of the fluid contained in the tank (12), wherein, The controller includes at least a proportional element (24) and an integral element (28). The proportional element (24) sets the proportional component of the control variable of the controller (14), and the integral element (28) sets the integral component of the control variable of the controller (14). The process system (10) operates selectively in either a first proportional operation mode or a second integral operation mode. Specifically, when the process system (10) operates in the second integral operation mode, the integral element (28) of the controller (14) does not contribute to the control variable of the controller (14), and when the process system (10) operates in the first proportional operation mode, the integral element (28) of the controller (14) contributes to the control variable of the controller (14).

2. The method according to claim 1, characterized in that, In the first proportional operation mode, fluid, particularly liquid, is drawn from or supplied to the tank (12) while the reference variable is kept constant by control, whereas in the second integral operation mode, no drawing from the tank (12) occurs.

3. The method according to any one of the preceding claims, characterized in that, In the first operating mode, the pressure of the pressure pad in the tank (12) is kept constant during fluid extraction, particularly during liquid extraction, and in the second operating mode, the pressure of the pressure pad in the tank (12) is controlled at a constant fill level, wherein, in particular, the pressure level is changed in the second operating mode.

4. The method according to any one of the preceding claims, characterized in that, An inlet valve (16) and a drain valve (18), or a combination of inlet and drain valves, are provided on the tank (12) for drawing fluid from or supplying fluid to the tank (12), wherein the current operating mode is determined based on the switching and / or opening state of the at least one valve (16, 18), and the integral element (28) of the controller (14) is driven based on the determined operating mode.

5. The method according to claim 4, characterized in that, The controller (14) receives the switching state and / or open state of the inlet valve (16) and the drain valve (18), or the combination of the inlet valve and drain valve, as input variables.

6. The method according to claim 4 or 5, characterized in that, Based on the detected operating mode, a binary signal is generated, which represents the corresponding current operating mode, and the integrator (28) of the controller (14) is controlled based on the binary signal.

7. The method according to any one of the preceding claims, characterized in that, The tank (12) is a closed tank (12), and the pressure of the pressure pad in the tank (12) is set by means of at least one control valve (20), wherein the current operating mode of the process system (10) is automatically detected based on the control variables of the controller (14) and additionally based on the control deviation, the control variables including the open state of the at least one control valve (20), and the integral element (28) of the controller (14) is controlled according to the detected operating mode.

8. The method according to any one of claims 4 to 6, characterized in that, The filling level in the tank (12) is set, wherein the current operating mode of the process system (10) is automatically detected based on the control variables of the controller (14) and additionally based on the control deviation, the control variables including the opening state of the inlet valve (16) and the drain valve (18) or the combination of the inlet valve and drain valve, and the integral element (28) of the controller (14) is controlled according to the detected operating mode.

9. The method according to claim 7 or 8, characterized in that, When the control variable of the controller (14) remains constant within a limited time period and there is a continuous control deviation, the controller (14) switches.

10. The method according to any one of the preceding claims, characterized in that, The actual value of the pressure in the tank (12) is detected by means of a pressure sensor (22), and the control deviation is calculated based on the difference between the actual value of the pressure and the set value.

11. The method according to any one of the preceding claims, characterized in that, The controller (14) executes an algorithm based on the control variables and control deviations of the controller (14) to detect the current operating mode.

12. The method according to any one of the preceding claims, characterized in that, When the controller (14) switches from the first proportional operation mode to the second integral operation mode or from the second integral operation mode to the first proportional operation mode, it changes at least one parameter of the integral element (28).

13. A process system (10), particularly for performing the method according to any one of the preceding claims, said process system (10) comprising: A tank (12) containing a fluid, such as a liquid and / or a gas, and a controller (14) for setting a reference variable, particularly the pressure of a pressure pad in the tank (12) or the filling level of the fluid contained in the tank, wherein the controller (14) includes at least a proportional element (24) and an integral element (28), the proportional component of the control variable of the controller (14) being set via the proportional element (24) and the integral component of the control variable of the controller (14) being set via the integral element (28). The process system (10) is adapted to operate selectively in a first proportional operation mode or a second integral operation mode. The controller (14) is configured to detect whether the process system (10) is operating in the proportional operation mode or the integral operation mode, and when the process system (10) is operating in the integral operation mode, to control the integral element (28) such that the integral element (28) does not contribute to the control variable of the controller (14), and when the process system (10) is operating in the proportional operation mode, to control the integral element (28) such that the integral element (28) contributes to the control variable of the controller (14).

Images