DE102015103604B4 - Method for determining the control range of a valve actuator - Google Patents

Abstract

Method for determining a control range (9) of a valve actuator, the valve actuator having an electric motor for opening and closing a valve (1) and the control range (9) being given by an engagement point (20) and a closing point (24) of the valve, wherein Starting from a fully open valve (1), the valve (1) is closed by the electric motor, the current curve (15) of the current required to drive the electric motor is recorded in relation to the travel of the valve (1) and from the current curve ( 15) the engagement point (20) and the closing point (24) of the valve are determined, characterized in that to determine the control range, the detected current profile (15) is derived to obtain a current gradient profile (17), a gradient threshold value (18) being determined and the engagement point (20) of the valve (1) is defined by the first local maximum (21) of the current gradient (17), which is above the gradient threshold (18), and with the current profile values between the intervention point (20) and the Intersection (25) at which the current gradient curve (17) intersects the gradient threshold value (18), a first compensation straight line (26) is formed and a second compensation straight line (27) is formed with the current curve values from this intersection point (25), whereby the Closing point (24) is defined by the intersection of the two compensation lines (26, 27).

Description

The invention relates to determining the control range of a valve actuator, in particular a valve actuator for controlling a radiator valve. A radiator valve is usually located in the inflow or outflow connection of a radiator. The radiator valve has a valve plate that can be moved between two valve seats. If the valve pin rests on a first valve seat, the valve is completely open. To close the valve and thus the flow, the valve pin must be moved towards the second valve seat. If the valve plate rests all around, i.e. completely on a second valve seat, the valve is completely closed.

The invention is described below using a radiator valve, although it should not be limited to this application. Rather, the invention can in principle be used with any valve to regulate a gas or liquid flow.

To regulate the flow, an actuator that can move the valve plate is required. Such an actuator is, for example, a valve actuator that is placed on the radiator valve. The valve actuator also has an actuator that acts on the valve pin. The valve actuator can, for example, be part of a radiator thermostat, the radiator thermostat having a means for determining the ambient temperature and a temperature preselection. The position of the actuator then results from the difference between the preselected and the current ambient temperature.

To date, mechanical valve actuators, or radiator thermostats, have been common and widespread. Due to rising energy prices, the urge to save energy is also increasing. For this reason, electrically or electronically controlled radiator thermostats are becoming increasingly popular. These have an electronic temperature sensor to determine the ambient temperature. The temperature preselection is carried out, for example, with the help of a digital display and input buttons. The actuator for moving the valve pin is an electric motor. The advantage of these electronic radiator thermostats is that they have extended control functions, such as night reduction, weekly programs or window open detection.

There are now many different types of radiator valves from different manufacturers. Each of these radiator valves has a different characteristic. This means that the control range of the valve pin is different. The control range is defined by the distance the valve pin must be moved between fully closed and fully open valve.

Furthermore, it may be that the valve pin has an offset, which means that when the valve pin is moved, the valve does not begin to close immediately, but only after an offset distance.

So that an electronic radiator thermostat can be used as universally as possible on all radiator valves, it must be designed for the largest known control range between closed and open states. If a radiator valve has a short control range, it can happen that the radiator thermostat tries to move the valve pin further even when the valve is already fully open, because it cannot recognize that the control range has already been completely passed through. This puts further strain on the electric motor, which increases power consumption unnecessarily. Likewise, the control or regulation cannot be carried out effectively because the travel distance required for a certain temperature difference is longer for valves with a long control range than for valves with a short control range. This means that the adjustment path for readjusting a determined temperature difference cannot be determined exactly. The electric motor must therefore be activated practically on suspicion and readjusted more frequently.

This makes controlling the electric motor complex and ineffective. In the end, this increases the power consumption of the radiator thermostat, which means that the battery has to be changed more frequently. This is complex and cannot be carried out in large residential units without increasing costs.

To solve this problem, some prior art electronic radiator thermostats have a table in which the control ranges of some radiator valves are stored. During installation, the correct valve type only needs to be selected once for configuration. However, this method has the disadvantage that, due to the large number of different valve types, in principle all valve types can never be recorded in the table. Likewise, if the selection is too large, the wrong valve can easily be selected, which is why such principles are prone to errors. There is also the problem that even the same valve types can have larger tolerances among each other, which in turn has a negative impact on the efficiency of the control.

The valve actuator is also used in other applications than in a radiator thermostat Electrically or electronically controlled valve position is desirable, for example for electrically or electronically controlling a flow rate of a pipe system.

The DE 41 07 860 A1 discloses a method for detecting a relative opening position of an electrically actuated cold and hot water valve of a sanitary mixer tap with an electric motor drive unit which can be plugged onto the valve shaft of the respective valve and fastened to the valve housing and which has a potentiometer. Using the potentiometer, the relative opening or closing position can be electronically recorded and evaluated via a voltage measurement value corresponding to this position. The electromotive drive unit is coupled to the valve shaft and connected to the power supply. An electronic control is then switched on and the valve is moved into the closed position using the drive unit. To detect the closing position, the current increase is then measured and compared with a specified threshold value. When the current rises above the threshold value, the potentiometer voltage is recorded and read into a loadable counter via an analog/digital converter. This digital measured value is stored as a zero point definition in a non-volatile memory, and then the electronic control for zero point determination is switched off.

The DE 40 01 801 A1 describes an arrangement for controlling a heating or cooling medium with a temperature control device and a valve that has a valve housing, a valve seat, a valve body and a valve spindle, the valve spindle having a device for converting the stroke of the rotary valve spindle into a rotary movement and a gear is connected to a servomotor and is connected to a position detection device for detecting the position of the valve spindle relative to the valve housing. The position detection device has a device for detecting the zero position and/or the fully open position of the valve spindle, wherein the device for detecting the zero position and/or the fully open position responds to a slowdown in the rotational speed of the servomotor. In addition, a device for measuring and evaluating the motor current of the servomotor is provided, which compares the motor current measured in a feed line of the servomotor between the output stage circuit and the servomotor with a current threshold value of a current threshold value transmitter. If the measured motor current exceeds the current threshold value, the device switches off the servomotor by acting on the output stage circuit.

In the DE 197 42 098 A1 A method for determining the closing point of a valve is described, in which a closing body is moved against a valve seat via a motor, a gear and a spindle and the closing point is detected and stored for further control of the valve. The valve is closed from an initial position, with the motor being controlled to a constant speed and the closing point being derived from a drop in the motor's speed by a predetermined percentage.

The object of the invention is to create a valve actuator that can be used on a variety of valves and can be operated effectively and energy-savingly.

This object is achieved according to the invention by the method with the features described in the main claim.

According to the invention, a method for determining the control range of a valve using a valve actuator is provided. The valve actuator has an electric motor to open and close the valve. The control range is now given by an intervention point and a closing point of the valve. To determine this, starting from a fully open valve, the valve is closed without interruption. The current curve of the current required to drive the electric motor is recorded in relation to the valve travel and, if necessary, recorded. The current curve is recorded, for example, continuously or at intervals. The engagement point and the closing point of the valve are finally determined from the current curve.

The valve is preferably provided by a radiator valve. It is also preferred that the valve actuator is part of a radiator thermostat. Such a radiator thermostat can then be used on a variety of radiator valves and can always be equally effective and energy-saving. This makes it possible to keep the energy consumption of the radiator thermostat low, so that in particular energy-autonomous operation of the radiator thermostat is also possible. This can be achieved, for example, by supplying the valve actuator with energy from the ambient energy. Likewise, the lifespan of a battery used to operate the valve actuator can be extended by such an energy-efficient radiator thermostat. This means that the radiator thermostat can be operated virtually maintenance-free, as changing the battery is only necessary very rarely or not at all.

According to the invention, the detected and possibly recorded current profile is obtained derived from a current gradient. The current gradient curve can then be used to determine or define the engagement point and/or the closing point of the valve. For example, the intersection of the current gradient with a predetermined curve or the achievement of a predetermined current gradient value can be used to determine the closing point.

In some preferred embodiments, the detected or recorded current waveform is smoothed and the smoothed current waveform is derived to obtain a current slope waveform. Equivalent to this, the current curve can of course also be derived first and the current gradient curve obtained can be smoothed. In addition, the curve obtained can also be further scaled or transformed, which means that a wide variety of properties of the valve actuator can be taken into account.

According to the invention, a slope threshold is set. The action point of the valve is then defined by the first local maximum of the current gradient, which is above the threshold value. This local maximum of the current gradient curve can, on the one hand, be the maximum of the raw data and, on the other hand, also be determined by the smoothed current gradient curve.

As a rule, after this local maximum, the slope drops back below the slope threshold value. The closing point of the valve can then be defined by the intersection of the current gradient curve with the gradient threshold value, at which the current gradient curve increases again above the gradient threshold value after the intervention point. Depending on how the slope threshold value is calculated, it can happen that fluctuations in the current slope curve exceed the slope threshold value even before the closing point is reached. However, these fall relatively quickly again below the gradient threshold and can therefore be distinguished from reaching the closing point. However, after reaching the closing point, the current gradient will remain above the gradient threshold value.

The increase in gradient observed to determine the closing point occurs because the seal of the valve pin is pressed against the valve seat and thereby compressed. However, the actual closing point is a little earlier.

In order to approximate the real closing point, in a further development of the invention the closing point is shifted by a predetermined offset.

In some embodiments of the method according to the invention, it is preferred if the slope threshold value is determined such that when the valve is closed, the current slope curve is always below the slope threshold value after reaching its first local maximum. In the access area, all fluctuations in the current gradient should be below the gradient threshold. The first local maximum of the current gradient curve should be cut as low as possible from the gradient threshold value. At the same time, the largest possible area, limited by the current gradient, should lie above the curve of the gradient threshold value. The first local maximum marks the beginning of the control range, from which the valve begins to close. In the case of a typical valve in a radiator thermostat, the slope threshold is, for example, in the range of 0.005 A/s to 0.04 A/s, in particular in the range of 0.1 A/s to 0.2 A/s.

The method according to the invention now has the advantage that the control range can be determined very quickly and very precisely for each radiator valve. The process is designed so that it can be carried out completely automatically. It is therefore possible to implement the method according to the invention in a radiator thermostat, so that the radiator thermostat can automatically calibrate itself to the radiator valve used.

In addition, the method according to the invention enables a very precise determination of the control range, that is to say the intervention point and the closing point. In the case of a typical radiator thermostat, the determined closing point only deviates by up to +/- 0.1 mm from the actual closing position of the valve. The determined engagement point can be determined with similar precision and in such applications deviates up to a maximum of +/- 0.2 mm from the actual engagement point. The closing point is particularly crucial for regulating the flow rate. Overall, the control range can therefore be determined very precisely and the flow rate of a valve actuator that is operated with the method according to the invention can be regulated very precisely. For example, a control and/or regulation in a radiator thermostat can carry out the valve position very precisely and precisely via the electric motor. This eliminates the need for lengthy readjustments, which increases the control speed and significantly reduces power consumption.

In an advantageous embodiment of the invention, the point of intervention is the apex of the local maximum.

In a further, preferred embodiment of the invention, the intervention point is the average of the two intersection points of the current gradient curve with the threshold value before and after the local maximum.

In principle, the intervention point can be placed anywhere in the area of the first local maximum using an arbitrary offset. The actual intervention point can therefore be shifted by an offset in the direction of a smaller travel path or in the direction of a larger travel path, as viewed from the apex of the first local maximum.

Preferably, the actual closing point is shifted away from the previously determined closing point by a predetermined offset in the direction of a smaller travel distance.

In the method according to the invention, the closing point is determined as follows: A first compensation line is formed with the current curve values between the intervention point and the position at which the current gradient curve intersects the threshold value. A second straight line is formed with the current curve values from this intersection point. The closing point is now defined by the intersection of the two compensation lines. The method according to the invention therefore corresponds to a dynamic determination of the offset by further adapting the previously determined closing point using the compensation straight line. Instead of compensation straight lines, other compensation curves can of course also be used to adjust the closing point. It can also be provided that an additional constant offset is offset against the dynamic offset and the closing point is thereby further adjusted.

In simple radiator thermostats, absolute position information about the travel is not always available. In order to simplify the recording of the current curve, in a particularly expedient embodiment of the invention the radiator valve is closed at a constant speed. The current curve is then recorded in time intervals, whereby the time is directly proportional to the positioning path due to the constant speed.

The invention is explained in more detail below using preferred exemplary embodiments with reference to the accompanying drawings.

• 1: Einen ausschnittsweisen Querschnitt eines Heizkörperventils,
• 2: Einen Querschnitt eines beispielhaften Heizkörperthermostats,
• 3: Ein Diagramm mit einem Strom-Weg-Verlauf eines ersten erfindungsgemäßen Verfahrens,
• 4: Ein Diagramm mit dem Steigungsverlauf des Strom-Weg-Verlaufs der 3
• 5: Ein Diagramm mit einem Strom-Weg-Verlauf eines zweiten erfindungsgemäßen Verfahrens und
• 6: Ein Diagramm mit dem Steigungsverlauf des Strom-Weg-Verlaufs der 5

It shows:

• 1 : A partial cross section of a radiator valve,
• 2 : A cross section of an exemplary radiator thermostat,
• 3 : A diagram with a current-path curve of a first method according to the invention,
• 4 : A diagram with the gradient of the current-path curve of the 3
• 5 : A diagram with a current-path curve of a second method according to the invention and
• 6 : A diagram with the gradient of the current-path curve of the 5

The 1 shows the cross section of a radiator valve 1. The radiator valve 1 has a valve plate 2, which is pressed against a first valve seat 4 by a compression spring 3. In this example the valve is shown in a fully open state.

To close the valve 1, the valve plate 2 must be pressed in the axial direction against a second valve seat 5 in order to close the flow. So that the valve plate 2 closes the flow properly, it has a seal 6 which comes to rest on the second valve seat 5.

The valve plate 2 is connected to a valve pin 7, via which the valve plate 2 can be moved from the outside. The radiator valve 1 also has a valve flange 8 onto which a radiator thermostat can be placed.

The distance that the valve plate 2 has to cover between the first valve seat 4 and the second valve seat 5 corresponds to the control range 9 of the radiator valve 1. Depending on the design of the compression spring 3 and the connection between the valve pin 7 and the valve plate 2, it may well be that with one Movement of the valve pin 7 initially only compresses the compression spring 3 before the valve plate begins to move. In such a case, the radiator valve 1 also has a movement offset that must be taken into account.

A radiator thermostat 10 with a valve actuator, which is operated according to the method according to the invention, is exemplified in 2 shown. The invention is designed for the use of electrical or electronic valve actuators, which is why the radiator thermostat 10 shown is an electronically controlled radiator thermostat 10. The exact design of the radiator thermostat 10, however, does not play a significant role, which is why non-essential features of the radiator thermostat 10 will not be discussed in more detail.

The radiator thermostat 10 has a counter flange 11 which can be placed on the valve flange 8 of the radiator valve 1. To fix it on the radiator valve 1, the radiator thermostat 10 has a threaded ring 12 with an internal thread, which can be screwed onto an external thread of the valve flange 8.

The radiator thermostat 10 has an actuator 13 which is in operative connection with the valve pin 7. It may well be that when the radiator thermostat 10 is placed on the radiator valve 1 there is still no contact between the actuator 13 and the valve pin 7.

The actuator 13 is driven by an electric motor 14. The rotary movement of the electric motor 14 must be transferred into a linear movement of the actuator 13. This can be done in many different ways, which is why this is not the subject of the invention.

Different radiator valves 1 can have very different control ranges 9, which is why a radiator thermostat 10 usually has to be adapted to the radiator valve 1 used.

The invention now describes a method for determining the control range 9 of a radiator valve 1. Preferably, the method can be implemented in a radiator thermostat 10, so that the radiator thermostat 10 can automatically adapt to the radiator valve 1 used.

In a first embodiment of the method according to the invention, starting from a completely open radiator valve 1, the radiator valve 1 is closed continuously and at a constant speed without interruption.

The current curve is preferably recorded continuously at narrow time intervals in relation to time. The time intervals are, for example, in the range between 0.01 s and 0.1 s. Due to the approximately constant speed, each time interval corresponds directly to a distance interval, that is, the time is approximately directly proportional to the travel distance traveled. However, in order to accurately determine the distance traveled, it is advantageous if the travel distance traveled is recorded, for example via a sensor. In particular, the electric motor of the valve actuator can have a speed detection. This can be done via a capacitive or an inductive sensor. For example, a Hall sensor can be used to detect the rotor position of the electric motor or to detect the number of rotor revolutions of the electric motor. Sensorless position detection of the electric motor can also be used. The determined number of revolutions of the rotor can then be used to determine the travel distance traveled by the valve pin 7. Alternatively, the travel distance traveled can be approximately determined via the travel time. As a rough approximation, a constant speed and thus a linear relationship between the positioning time and the positioning path can be assumed. To increase the accuracy, however, a different relationship can also be assumed or determined, so that, for example, the decrease in speed when the closing point is reached is taken into account.

Recording the current results in a current curve 15 as shown in 3 is shown as an example in the form of a diagram.

The current curve I(t) of an electric motor corresponds to an alternating current curve. Furthermore, the current has noise, which can be partially reduced using appropriate filters. For example, a low-pass filter can be provided for attenuation. In order to be able to use the method better, the current curve is smoothed in this exemplary embodiment. For this purpose, for example, an RMS value or a simple average is calculated. If the current curve is very smooth, additional smoothing can in principle be dispensed with.

The smoothed current curve 16 is derived to obtain a current gradient curve 17, which is in 4 is shown in diagram form. In addition to the current gradient curve 17 (the derivative dI/dt of the current curve I(t) over time), a smoothed current gradient curve 19 is also shown.

Furthermore, a slope threshold value 18 is set, which is usually slightly above 0. In the example, the slope threshold is approximately 0.015 A/s. Typically, the slope threshold value for a valve actuator in a radiator thermostat will be in the range of 0.005 A/s to 0.04 A/s. However, for other applications the value can deviate significantly from the values mentioned.

To simplify the process, the current gradient curve can also be smoothed 19, although this is not absolutely necessary. Alternatively, for example, the current curve can be smoothed directly so that the current gradient curve derived from it has a sufficiently smooth course.

The intervention point 20 of the radiator valve is now through the first local maximum 21 of the current gradient curve 17, which is above the slope threshold value 18 is defined. The first local maximum 21 of the current gradient curve 17 is determined via the first local maximum 21 of the smoothed current gradient curve. For very smooth and low-noise signals, the maximum can also be determined directly from the derivation of the recorded current curve.

The maximum 21 arises from the fact that the actuator 13 of the radiator thermostat 10 does not yet touch the valve pin 7. Therefore, the load on the electric motor 14 is still low. As soon as the actuator 13 touches the valve pin 7, a force begins to build up and the power consumption increases. Until this moment, the radiator valve 1 is completely open. As soon as the valve pin 7 has broken loose and started to move, the power consumption drops again and the valve begins to close. This relatively large mechanical resistance at the beginning of the closing process results from the static friction of the moving parts, any tension that may occur in the gear and a variety of other reasons. If the radiator valve has a movement offset, for example due to gear backlash, this can also be determined, since the current gradient is still below the gradient threshold value 18.

In the example, the intervention point 20 is not located directly in the vertex 22 of the local maximum 21 but in the middle between the two intersection points 23 of the current gradient curve 17 with the gradient threshold value 18 to the right and left of the vertex 22. Of course, the intervention point 20 can also go directly through the vertex 22 be set. It can also be provided that the engagement point 20 is pushed to the desired location by specifying any offset. In general, the intervention point 20 lies in the area of the local maximum 21 or in the current gradient curve 17 plotted over time before the local maximum 21. The intervention point 20 could, for example, also be defined at the first intersection 23 of the rising current gradient curve 17 with the gradient threshold value 18.

Since the load on the electric motor 14 is constant again from then on, the current gradient curve 17 drops again towards 0, that is to say below the gradient threshold value 18.

If the valve plate 2 now hits the second valve seat 5, the radiator valve 1 is completely closed. If the electric motor 14 moves further, the seal 6 is compressed against the valve seat 5. As a result, the load on the electric motor 14 increases sharply, which is why the current gradient 17 also increases again.

The closing point 24 of the radiator valve 1 is now defined by the intersection of the current gradient curve 17 with the gradient threshold value 18, at which the current gradient profile 17 rises again above the gradient threshold value 18 after the maximum 21.

Since the seal 6 is already compressed here, the actual closing point is slightly earlier, which is why the final closing point is corrected by an offset 28.

This easy-to-implement procedure allows the control range of each radiator valve to be determined quickly, precisely and repeatably.

The method according to the invention is used to determine the closing point, as described in 5 current course shown and in 6 The current gradient curve shown is explained below.

The intervention point 20 is determined as described above. To determine the closing point, a first compensation straight line 26 is formed using the current curve values between the intervention point 20 and the intersection point 25 at which the current gradient curve 17 intersects the gradient threshold value 18. A second straight line 27 is formed with the current curve values from this intersection point 25. The closing point is now determined using an intersection point 29 of the two compensation lines 26, 27. This therefore corresponds to a dynamic determination of an offset 30 of the closing point 24 relative to the intersection of the current gradient curve with the curve of the gradient threshold value 18. In this embodiment of the method according to the invention, the now dynamically determined offset 30 can additionally be offset against a predefined or previously determined or fixed offset 28 .

Reference symbol list

1

Radiator valve

2

valve plate

3

Compression spring

4

first valve seat

5

second valve seat

6

poetry

7

Valve pin

8th

Valve flange

9

Control range

10

Radiator thermostat

11

flange

12

Threaded ring

13

Actor

14

Electric motor

15

Current flow

16

smoothed current curve

17

Current gradient curve

18

Slope threshold

19

smoothed current gradient curve

20

point of intervention

21

local maximum

22

vertex

23

Intersection points

24

Closing point

25

intersection

26

Equilibrium line 1

27

Equilibrium line 2

28

offset

29

intersection

30

Dynamic offset

Claims (9)

Method for determining a control range (9) of a valve actuator, the valve actuator having an electric motor for opening and closing a valve (1) and the control range (9) being given by an engagement point (20) and a closing point (24) of the valve, starting from a fully open valve (1), the valve (1) is closed by the electric motor, the current curve (15) of the current required to drive the electric motor being recorded in relation to the travel of the valve (1) and from the current curve (15) the engagement point (20) and the closing point (24) of the valve are determined, characterized in that in order to determine the control range, the detected current profile (15) is derived to obtain a current gradient profile (17), a gradient threshold value (18) being defined and the engagement point (20) of the valve (1) is defined by the first local maximum (21) of the current gradient (17), which is above the gradient threshold (18), and with the current profile values between the intervention point (20) and the intersection point (25) at which the current gradient curve (17) intersects the gradient threshold value (18), a first compensation straight line (26) is formed and a second compensation straight line (27) is formed with the current curve values from this intersection point (25), wherein the closing point (24) is defined by the intersection of the two compensation lines (26, 27). Procedure according to Claim 1 , characterized in that the detected current is recorded. Procedure according to one of the Claims 1 or 2 , characterized in that the detected current curve (15) is smoothed before it is derived to obtain the current gradient curve (17). Procedure according to Claim 1 , characterized in that the intervention point (20) is the mean value of the two intersection points (23) of the current gradient curve (17) with the gradient threshold value (18) immediately before and after the local maximum (21). Method according to one of the preceding claims, characterized in that the actual closing point (24) is shifted by a predetermined offset (28) in the direction of a smaller travel distance from the previously determined closing point (24). Method according to one of the preceding claims, characterized in that the valve (1) is closed at a constant speed. Method according to one of the preceding claims, characterized in that the slope threshold value (18) is selected such that the current slope curve (17) or the smoothed current slope curve (17) as a function of time in a range between the first local maximum (25) and the The increase in the current gradient (17) when reaching the closing point (24) is completely below the gradient threshold (18). Method according to one of the preceding claims, characterized in that the valve (1) is a radiator valve. Method according to one of the preceding claims, characterized in that the valve actuator is part of a radiator thermostat.

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