Method, measuring arrangement and computer program product for controlling a valve

Abstract

The invention relates to a method for controlling a valve (1) which is arranged in a line (6) for conducting a gas, in particular a gas mixture, comprising the method steps: - determining a current measured value of a gas property of the guided gas, in particular a density measured value, preferably by means of a density sensor (2); - Determining a current flow measurement value by means of a flow sensor (3); - determining at least one control parameter of a controller (4), in particular a continuously linear controller (4), as a function of the current measured value, in particular the density measured value, by means of a measuring and operating circuit (5); - generating an operating signal for operating the valve (1) for a set target flow value, taking into account the at least one control parameter and the current flow measurement value by means of the controller (4); and - Operating the valve (1) using the operating signal.

Description

The invention relates to a method for regulating a valve, which is arranged in a line for conducting a gas, in particular a gas mixture, to a measuring arrangement for regulating a flow rate of a gas, in particular of a gas mixture, in a line, and to a computer program product for regulating a valve.Known mass flow meters, such as thermal flow meters, and mass flow controllers, must be calibrated to the medium to be monitored in order to be able to measure correctly. Gas mixtures can likewise only be measured if the composition of the mixture is known, it does not change and the mass flowmeter and mass flow controller have been calibrated therewith. However, this is not always the case. Furthermore, especially on account of these requirements, commissioning and use by laymen is not possible at all.The object of the invention is to provide a remedy for the problem.The object is achieved by the method according to claim 1, the measuring arrangement according to claim 9 and the computer program product according to claim 14.The method according to the invention for regulating a valve, which is arranged in a line for conducting a gas, in particular a gas mixture, comprises the method steps:determining a current measured value of a gas property of the guided gas, in particular a density measured value, preferably by means of a density sensor;determining a current flow measurement value by means of a flow sensor;determining at least one control parameter of a controller, in particular of a continuously linear controller, as a function of the current measured value, in particular of the density measured value, by means of a measurement and operating circuit;generating an operating signal for operating the valve for a set setpoint flow value by means of the controller taking into account the at least one control parameter and the current flow value; andoperating the valve by means of the operating signal.This solution has the advantage that precise regulation of the valve is possible even in the case of gas mixtures and likewise when the precise gas properties are not known to the user. In addition, the method according to the invention is also automatically responsive to changes in the gas properties, such as a change in the gas composition or a change in the density, without the need to reparametrize manually.Advantageous embodiments of the invention are the subject matter of the dependent claims.One configuration provides that the at least one control parameter comprises a first control parameter, wherein the first control parameter is a zero-point offset Koff of the operating signal.The valve only opens starting from a certain valve current or coil current or already closes at a certain valve current or coil current. Therefore, a zero point offset is provided which offsets the zero point of the manipulated variable in percent by a defined number of percentage points (relative to the maximum coil current). This improves the time required for the valve to rise from about 0 sccm to the desired flow rate, since the controller does not first need to control the current from 0 mA to the actual zero point of the valve.From measurements with different gases it can be established that the parameters of the controller and the zero point offset Koffare gas dependent. After manually adjusting the parameters for the various gases, it can be determined that the parameters are proportional to the density of the gases. Thus, a multiplication factor (the slope) and a zero crossing of the Y axis can be calculated, whereby, based on the density of the current gas, the at least one control parameter for the offset can be calculated. This has the consequence that any gas or binary gas mixture can be regulated within the density range of the already measured gases without having to manually adapt any parameters.One embodiment provides that the first control parameter is determined from a provided first linear function.In one embodiment, the controller comprises a P element and an I element, the at least one control parameter comprising a second and a third control parameter, the second control parameter being a controlled variable Kp of the P element, the third control parameter being a controlled variable Ki of the I element.It has proven advantageous to choose the second control parameter of the P element and the third control parameter of the I element additionally or alternatively to the first control parameter as a function of the currently measured measurement variable of the gas property, in particular of the density of the gas, and not fixedly during startup. This prevents an overregulation of the valve in the case of changing gases or in the case of incorrectly specified mixing ratios.One configuration provides that the second control parameter is determined from a provided second linear function, and / or wherein the third control parameter is determined from a provided third linear function.One configuration provides that the controller further comprises a D element, wherein the at least one control parameter comprises a fourth control parameter, wherein the fourth control parameter is a controlled variable Kd of the D element.It has been found that a regulator without a D-element tends to settle slowly, especially at a low reference variable. In order to improve the settling time and to achieve a more rapid adjustment of the setpoint value, it is advantageous to implement a PID controller instead of a PI controller.One configuration provides that the fourth control parameter is determined from a provided fourth linear function.One embodiment provides that the first, second, third and / or fourth linear functions are determined for a fixed pressure.A measuring arrangement according to the invention for regulating a flow of a gas, in particular of a gas mixture, in a line comprises:a valve for controlling the flow;a sensor for ascertaining a current measured value of a gas property, in particular a density sensor for ascertaining a current density measured value of the gas;a flow sensor for determining a current flow measurement value;a measuring and operating circuit for operating the valve by means of an operating signal,wherein the measuring and operating circuit comprises a controller, in particular a continuously linear controller, wherein the controller is configured to generate the operating signal for a set setpoint flow value as a function of the current flow measurement value and at least one control parameter, wherein the measuring and operating circuit is configured to determine the at least one control parameter as a function of the current measurement value, in particular the current density measurement value.One configuration provides that the at least one control parameter comprises a first control parameter, wherein the first control parameter is a zero-point offset Koffof the operating signal, wherein the measurement and operating circuit is configured to determine the first control parameter as a function of the current measured value, in particular the density measured value.In one embodiment, the controller comprises a P element and an I element, the at least one control parameter comprising a second and a third control parameter, the second control parameter being a controlled variable Kp of the P element, the third control parameter being a controlled variable Ki of the I element, the measurement and operating circuit being configured to determine the second and third control parameters as a function of the current density measured value.In one embodiment, the controller further comprises a D element, wherein the at least one control parameter comprises a fourth control parameter, wherein the fourth control parameter is a controlled variable Kd of the D element, wherein the measurement and operating circuit is configured to determine the fourth control parameter as a function of the current density measured value.One configuration provides that the first control parameter is determined from a provided first linear function, and / or wherein the second control parameter is determined from a provided second linear function, and / or wherein the third control parameter is determined from a provided third linear function, and / or wherein the fourth control parameter is determined from a provided fourth linear function.A computer program product according to the invention for controlling a valve, configured to execute the following method steps when executed on a computer:receiving a current measured value of a gas property, in particular a current measured density value, preferably determined by means of a density sensor;receiving a current flow measurement value, in particular determined by means of a flow sensor;determining at least one control parameter as a function of the current measured value, in particular the current density measured value;generating an operating signal for operating the valve for a set setpoint flow value taking into account the at least one control parameter and the current flow value; andproviding the operating signal.One configuration provides that the at least one control parameter comprises a first control parameter, wherein the first control parameter is a zero-point offset Koff of the operating signal.One embodiment provides that the at least one control parameter comprises a second and a third control parameter, wherein the second control parameter is a controlled variable Kp which comprises a proportional portion of the control, wherein the third control parameter is a controlled variable Ki which comprises an integral portion of the control.One embodiment provides that the at least one control parameter comprises a fourth control parameter, wherein the fourth control parameter is a controlled variable Kd, which comprises a differential portion of the control.One configuration provides that the first control parameter is determined from a provided first linear function, and / or wherein the second control parameter is determined from a provided second linear function, and / or wherein the third control parameter is determined from a provided third linear function, and / or wherein the fourth control parameter is determined from a provided fourth linear function.The invention is explained in more detail with reference to the following figures. It shows: FIG. 1 : shows a perspective view of an embodiment of the measuring arrangement according to the invention; FIG. 2 : shows a flow diagram of an embodiment of the method according to the invention; FIG. 3 : a graph which depicts the density dependence of the zero-point offset (in %) of the coil current; and FIG. 4 : a graph which depicts the density dependence of the control parameters of the coil current.FIG. 1 shows a perspective view of an embodiment of the measuring arrangement according to the invention. The measuring arrangement is configured to regulate a flow of a gas, in particular of a gas mixture, in a line 6. The line 6 can be, for example, a hose or a pipeline.In order to be able to regulate the flow rate of the gas, the measuring arrangement comprises a valve 1 for regulating the flow rate. The valve 1 is configured to shut off the flow of the gas through the line 6 or to control it in response to a reference variable. The valve 1 may be a proportional solenoid valve. Proportional valves allow a sensitive control of the flow in comparison with shut-off valves which can only be opened or closed completely. The opening rate is controlled in proportion to the current intensity, whereby a higher current intensity leads to a higher flow rate. These valve types are based on electromagnetic switching valves in which a spring presses the stroke armature onto the valve seat and thus keeps the valve closed in the normally closed (normally closed) state. A seal at the base of the valve ensures that no medium flows out. The current flow through the coil produces a magnetic field which raises the lifting armature and opens the valve. By changing the switching solenoid valves, a balance between spring force and magnetic force can be achieved for each desired flow. The valve 1 can specifically be a stroke anchor valve. The flow rate can comprise a flow-speed-dependent measurement variable, such as e.g. the flow rate, the volume flow or the mass flow. The valve 1 is connected to the line 6.A further component which is necessary for regulating the flow rate is a flow sensor 3 for determining a current flow rate measurement value. With the aid of the current flow measurement value, a comparison with the reference variable-in the case of the desired flow measurement value-can be carried out in order, in the event of a deviation, to actuate the valve 1 such that a future flow measurement value is closer to the value of the reference variable. The flow sensor has two connections via which it is connected to the line 6. The flow sensor 3 can be a thermal flow measuring device. This functions according to the calorimetric principle and can therefore detect not only the flow speed but also the flow direction.According to the invention, the measuring arrangement has a further component which is necessary for regulating the flow. This is a sensor for ascertaining a current measured value of a gas property. The gas property may be the thermal conductivity, viscosity, pressure, temperature or density of the gas. The sensor is in particular a density sensor 2 for ascertaining a current density measurement value of the gas. The density sensor 2 can likewise have two connections, like the flow sensor, and can be integrated in the line 6. Alternatively, the density sensor 2 can also be arranged in a lateral opening in the lateral surface of the line 6.The sensor for ascertaining the current measured value of the gas property of the gas around a density sensor 2 can be arranged together with the flow sensor 3 in a common housing 8. An example thereof is taught in DE 202022107233 U1, which teaches a density sensor in combination with a flow sensor. Reference is made in its entirety to DE 202022107233 U1. The flow sensor disclosed therein is a thermal flow measuring device. Thermal flow meters are usually adjusted for a particular gas, since the measured value determined is influenced by the thermal conductivity and heat capacity of the gas. Thus, a specifically calibrated thermal flowmeter is required for each gas, or correction factors are stored specifically in the thermal flowmeter by the manufacturer for different gases. Consequently, it is always necessary to communicate to the thermal flowmeter first which gas is being measured. However, if the gas composition changes during measurement, the existing thermal flow meters are unable to properly determine the flow rate. The density sensor taught in DE 202022107233 U1 comprises an oscillator (e.g. a quartz tuning fork or a cantilever oscillator) and is designed as a MEMS sensor element. However, the density sensor does not have to be integrated in the line 6. Alternatively, the density sensor can also be connected to a gas tank, from which the gas is conducted into the line 6.In addition, a measuring and operating circuit 5 for operating the valve 1 by means of an operating signal (e.g. a current or voltage signal or a digital signal) with a microcontroller is provided. The measuring and operating circuit 5 can be arranged at, on or in the flow sensor, sensor, in particular density sensor 2, valve 1 or remote from the sensors and from the valve. Moreover, the measuring and operating circuit 5 is in communication with the valve 1, the flow sensor and the sensor, in particular the density sensor. Furthermore, the measuring and operating circuit 5 has a regulator 4, in particular a continuously linear regulator. The controller 4 can be, for example, a PI controller having a P element and an I element or a PID controller having a P element, I element and D element. The PID controller is a widely used control algorithm that combines proportional, integral, and differential control actions to enable rapid, accurate, and stable control of a process variable. The proportional part adjusts the control output on the basis of the current deviation between the desired reference variable and the measured volume flow. The differential portion peaks the control value based on the change in the control deviation to improve the settling time, and the integral part accumulates the deviation with time to reduce the deviation. The controller is configured to generate the operating signal for a set setpoint flow value (=control variable) as a function of the current flow measurement value and at least one control parameter. In this case, the measurement and operating circuit 5 is likewise configured to determine the at least one control parameter as a function of the current measured value, in particular the current density measured value.The at least one control parameter may comprise a first control parameter which is a zero-point offset Koff of the operating signal. The zero offset Koff is the minimum value of the operation signal that must be adjusted for the valve 1 to open. Thus, when using a lift armature valve, the operating signal can be a coil current and the zero-point offset Koff can be the minimum coil current which has to be applied in order for the lift armature to be lifted and the gas can thus be passed through. The zero-point offset Koffcan describe an absolute current or a relative current (for example with respect to the maximum possible coil current). The measuring and operating circuit 5 is configured to determine the first control parameter as a function of the current measured value, in particular the density measured value. The zero-point offset Koff is thus dependent on the density of the gas. The coil current required for the valve 1 to open decreases with increasing density of the gas. This can be explained by the fact that the denser gas displaces the stroke armature of the valve 1 to a greater extent and thus acts to a greater degree of assistance than the less dense gas. Therefore, with denser gas, less minimum coil current is required to displace the lift armature of the valve.The at least one control parameter can further or alternatively comprise a second and a third control parameter. If the controller is at least one PI controller, then the second control parameter can be a controlled variable Kp of the P element and the third control parameter can be a controlled variable Ki of the I element. Both control parameters have a dependence on the density of the gas. Therefore, the measuring and operating circuit 5 can be configured to determine the second and third control parameters depending on the current density measurement value.The at least one control parameter can furthermore comprise a fourth control parameter. In this context, controller 4 may be a PID controller having a D element and the fourth control parameter may be a controlled variable Kd of the D element. The fourth control parameter set for optimum control of the valve is likewise dependent on the current density measurement value of the gas. The measuring and operating circuit 5 is therefore configured to determine the fourth control parameter as a function of the current density measurement value.The at least one control parameter, in particular the four control parameters, can always be stored in the measurement and operating circuit 5 in conjunction with a density measurement value in a look-up table. The at least one control parameter, in particular the four control parameters, can each be determined from a provided polynomial function, in particular from a provided polynomial function of third, second or first degree. Furthermore, the second control parameter can be determined from a provided second linear function. Furthermore, the third control parameter can be determined from a provided third linear function. Furthermore, the fourth control parameter can be determined from a provided fourth linear function. The four linear functions differ from one another. The individual linear functions each have a slope and can each have an offset. The linear functions can each be stored as an equation in an electronic memory in the measuring and operating circuit 5.FIG. 2 shows a flow diagram of an embodiment of the method according to the invention for regulating a valve, which is arranged in a line for conducting a gas, in particular a gas mixture. The embodiment has the following five method steps, which can be carried out with the measuring arrangement shown in FIG. 1. The order of the five method steps may deviate from the order used. I. Determining a current measured value of a gas property of the guided gas, in particular a density measured value or a measured variable dependent on the density, preferably by means of a density sensor. The gas property may be the thermal conductivity, viscosity, pressure, temperature or density of the gas. The ascertained current measured value is provided to a measuring and operating circuit and serves as a basis for the determination of at least one control parameter. Determination is understood to mean measurement by means of a sensor. Determining a current flow measurement value by means of a flow sensor. The flow sensor can be, for example, a thermal flow meter, a magnetoinductive flow meter, an ultrasonic flow meter, a vortex flow meter or a Coriolis flow meter. Alternatively, a mechanical-volumetric flowmeter can be used to determine the current flowmeter value. Determining at least one control parameter of a controller, in particular of a continuously linear controller, as a function of the current measured value, in particular of the density measured value, by means of a measurement and operating circuit. The at least one control parameter can be a zero-point offset Koff (= first control parameters) of the operating signal. Alternatively or additionally, the at least one control parameter comprises a second and a third control parameter, wherein the second control parameter is a controlled variable Kp of the P element and the third control parameter is a controlled variable Ki of the I element. The P element multiplies the control deviation by its controlled variable Kp and outputs this value. The I element sums or integrates the control deviation over time and multiplies the sum or the integral by the controlled variable Ki. Alternatively or additionally, the at least one control parameter comprises a fourth control parameter, wherein the fourth control parameter is a controlled variable Kd of the D-gate. The D element adds the output of the P element with a D component which results from the change in the control deviation. The change in the control deviation (difference or time derivative) is multiplied by the controlled variable Kd and the calculated value is added to the output of the P element. All four control parameters are determined from a provided first linear function which was previously determined in an adjustment method. IV. generating an operating signal for operating the valve for a set setpoint flow value by means of the controller taking into account the at least one control parameter and the current flow value; and V. operating the valve by means of the operating signal.FIG. 3 shows a graph depicting the density dependence of the zero-point offset of the minimum coil current (in % of the maximum coil current) for a density measurement value between 0.15 and 2 kg / m 3. FIG. 4 shows a graph which depicts the density dependence of the control parameters of the coil current for a density measurement value between 0.15 and 2 kg / m 3. The measurements were all carried out under the same conditions. For the determination of the control parameters, the valve was flushed with helium (He), air, nitrogen (N2), argon (Ar) and carbon dioxide (CO2) in succession at a pressure of 4 bar. For the determination of the zero point offset (see FIG. 3 ), the minimum coil current necessary to open and close the valve was determined in each case for the different gases. It can be seen that the measurement data can be written with a straight line function with a negative gradient. For the determination of the density-dependent controlled variables, the value of the controlled variable Kp was varied, while the remaining controlled variables were set to zero. Iterative tests have determined the Kp values of the controller for the different gases. With these values, the regulator has a good settling time, without or with only very little overshoot. Next, in order to reduce the residual error, the values of the controlled variable Ki and the controlled variable Kd were adjusted. It has been found that there is a linear relationship between the controlled variables and the density. This relationship can be described by a straight line with a constant slope (multiplication factor) and an offset (Y-axis shift). The dependence of the controlled variable on the density can be explained by the fact that the gas is heavier, the denser it is, as a result of which the valve becomes sluggish. At the zero offset Koff, the zero point, i.e., the coil current, that it needs to keep the valve closed is lower as the density of the gas is higher. This could in turn be due to a heavier gas pressing the valve more firmly in the closed state than a light gas. With the determined and stored multiplication factor and Y-axis shift of the straight line, the controlled variables can be automatically adapted to the current gas property. The depicted measurement results were all determined at the same pressure. For the determination of the ideal controlled variables, the current pressure in the line can also be taken into account. For this purpose, a further sensor, namely a pressure sensor, can preferably be installed in the line, which is in communication with the measurement and operating circuit and is configured to provide a current measurement value of the pressure in the line. The measuring and operating circuit can be configured accordingly to determine the controlled variables as a function of the density and the pressure.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 202022107233 U1

[0034]

Claims

Method for regulating a valve (1) which is arranged in a line (6) for conducting a gas, in particular a gas mixture, comprising the method steps: - determining a current measured value of a gas property of the conducted gas, in particular a density measured value, preferably by means of a density sensor (2); - determining a current flow measurement value by means of a flow sensor (3); - determining at least one regulating parameter of a regulator (4), in particular of a continuously linear regulator (4), as a function of the current measured value, in particular of the density measured value, by means of a measurement and operating circuit (5); - generating an operating signal for operating the valve (1) for a set setpoint flow value, taking into account the at least one regulating parameter and the current flow measurement value by means of the regulator (4); and - operating the valve (1) by means of the operating signal.Method according to claim 1, wherein the at least one control parameter comprises a first control parameter, wherein the first control parameter is a zero-point offset Koff of the operating signal.Method according to Claim 2, wherein the first control parameter is determined from a provided first linear function.Method according to one of Claims 1 to 3, wherein the controller comprises a P element and an I element, wherein the at least one control parameter comprises a second and a third control parameter, wherein the second control parameter is a controlled variable Kp of the P element, wherein the third control parameter is a controlled variable Ki of the I element.Method according to Claim 4, wherein the second control parameter is determined from a second linear function provided, and / or wherein the third control parameter is determined from a third linear function provided.Method according to Claim 4 or 5, wherein the controller further comprises a D-element, wherein the at least one control parameter comprises a fourth control parameter, wherein the fourth control parameter is a controlled variable Kd of the D-element.Method according to Claim 6, wherein the fourth control parameter is determined from a provided fourth linear function.Method according to one of Claims 2 to 7, wherein the first, second, third and / or fourth linear function is determined for a fixed pressure.Measuring arrangement for regulating a flow rate of a gas, in particular of a gas mixture, in a line, comprising: - a valve (1) for regulating the flow rate; - a sensor for determining a current measured value of a gas property, in particular a density sensor (2) for determining a current density measured value of the gas; - a flow sensor (3) for determining a current flow rate value; a measuring and operating circuit (5) for operating the valve (1) by means of an operating signal, wherein the measuring and operating circuit (5) comprises a regulator (4), in particular a continuously linear regulator, wherein the regulator (4) is configured to generate the operating signal for a set desired flow value as a function of the current flow measurement value and at least one regulating parameter, wherein the measuring and operating circuit (5) is configured to determine the at least one regulating parameter as a function of the current measurement value, in particular the current density measurement value.Measuring arrangement according to Claim 9, wherein the at least one control parameter comprises a first control parameter, wherein the first control parameter is a zero-point offset Koff of the operating signal, wherein the measuring and operating circuit (5) is configured to determine the first control parameter as a function of the current measured value, in particular the density measured value.Measuring arrangement according to Claim 9 or 10, wherein the controller (4) comprises a P element and an I element, wherein the at least one control parameter comprises a second and a third control parameter, wherein the second control parameter is a controlled variable Kp of the P element, wherein the third control parameter is a controlled variable Ki of the I element, wherein the measurement and operating circuit (5) is configured to determine the second and third control parameter as a function of the current density measured value.Measuring arrangement according to Claim 11, wherein the controller further comprises a D element, wherein the at least one control parameter comprises a fourth control parameter, wherein the fourth control parameter is a controlled variable Kd of the D element, wherein the measuring and operating circuit (5) is configured to determine the fourth control parameter as a function of the current density measured value.Measuring arrangement according to at least one of Claims 10 to 12, wherein the first control parameter is determined from a provided first linear function, and / or wherein the second control parameter is determined from a provided second linear function, and / or wherein the third control parameter is determined from a provided third linear function, and / or wherein the fourth control parameter is determined from a provided fourth linear function.Computer program product for controlling a valve (1), configured to carry out the following method steps when executed on a computer: - receiving a current measured value of a gas property, in particular a current density measured value, preferably determined by means of a density sensor (2); - receiving a current flow measurement value, in particular determined by means of a flow sensor (3); - determining at least one control parameter as a function of the current measured value, in particular the current density measured value; - generating an operating signal for operating the valve (1) for a set setpoint flow value taking into account the at least one control parameter and the current flow measurement value; and - providing the operating signal.The computer program product of claim 14, wherein the at least one control parameter comprises a first control parameter, wherein the first control parameter is a zero offset Koff of the operating signal.Computer program product according to one of Claims 14 to 15, wherein the at least one control parameter comprises a second and a third control parameter, wherein the second control parameter is a controlled variable Kp which comprises a proportional portion of the control, wherein the third control parameter is a controlled variable Ki which comprises an integral portion of the control.Computer program product according to Claim 16, wherein the at least one control parameter comprises a fourth control parameter, wherein the fourth control parameter is a controlled variable Kd which comprises a differential portion of the control.The computer program product according to at least one of claims 15 to 17, wherein the first control parameter is determined from a provided first linear function, and / or wherein the second control parameter is determined from a provided second linear function, and / or wherein the third control parameter is determined from a provided third linear function, and / or wherein the fourth control parameter is determined from a provided fourth linear function.

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