EP2088329A2 - Controller for a double-acting, pneumatic actuator, double-acting, pneumatic actuator, and method of operating same - Google Patents

Abstract

The position regulator has two pneumatically impinged working chambers (15,17) and a mobile working part. The working part is displaceable for a position movement with a difference of pressure in the working chambers. A device is provided for adjusting a pneumatic control signal (S-1) for the former working chamber. The device is performed such that the adjustment of the control signal is not influenced according to the controlled another pneumatic control signal (S-2). Independent claims are included for the following: (1) a double-acting pneumatic actuating drive with a pressurizing medium value; and (2) a method for operating a double-acting pneumatic actuating drive.

Description

The invention relates to a positioner for a double-acting pneumatic actuator.

Double-acting pneumatic actuators are widely used in the process industry. Typical applications of double-acting pneumatic actuators are, for example, directed to control tasks in which valve flaps are to be actuated in pipelines. A double-acting pneumatic drive can be formed, for example, by an actuating cylinder which is used in particular in power plant technology and can produce a defined differential pressure in an air duct by actuation of flaps.

Double-acting actuators have the general advantage of being particularly robust and durable, at the same time a structurally simple and cost-effective design is guaranteed.

Typically, the double-acting pneumatic actuator is position-controlled by a so-called electropneumatic positioner which converts electrical control signals into a pneumatic control signal which is supplied to the working chambers of the double-acting pneumatic actuator. The pneumatic working chambers of the double-acting pneumatic actuator are acted upon in opposite directions and are driven accordingly in opposite directions.

Typically, a double-acting actuator has a movable working part, such as a piston guided in a cylinder or a membrane wall, which is then displaced when a pressure difference between the first and second pneumatic working chamber of the double-acting pneumatic actuator is established.

It is known that the positioner for operating the pneumatic, double-acting actuator outputs two pneumatic control signals and directs them to the respective working chamber. Typically, a positioner with a supply pressure source of typically 6 bar is connected, wherein in the regulated state of the actuator, the average value of the pressure of both working chambers is usually 3 bar. 0

An example of a double-acting, pneumatic actuator in DE 100 21 744 A1 specified, in which the pressure difference between the two working chambers of the actuator is defined as a controlled variable. To adjust the pressure difference, a proportional valve arrangement is used, by which the pressure conditions in the working chambers are controlled in opposite directions.

Known positioners for controlling a double-acting pneumatic actuator may be provided with a port for applying a supply pressure of about 6 bar and two outputs via which two pneumatic control signals are delivered to the working chambers of the double-acting actuator. Via a translationally displaceable piston valve, the pneumatic size of the control signal is set in opposite directions at both outputs, whereby a decrease of the first pneumatic control signal leads to an increase of the second pneumatic control signal. In this respect, the regulation of the actuator is realized by generating a pressure difference.

Usually operate double-acting pneumatic actuators, which are connected to a supply pressure of about 6 bar, at a constant pressure mean value of 3 bar concerning the first and second working chamber. These known double-acting pneumatic actuators can realize fast control cycles, but have the disadvantage of not being sufficiently load-resistant due to the compressibility of the operating medium air. If the field of application of the drive requires a high load rigidity, hydraulic actuators are known to be used which are costly and costly to purchase especially for lack of environmental compatibility of the hydraulic oil not come into consideration for all applications.

It is an object of the invention to overcome the disadvantages of the prior art, in particular to provide a positioner which is to control a double-acting, pneumatic universally applicable actuator and is also operational when control cycles combined with a high and especially selectable load stiffness required by the actuator become.

This object is solved by the features of claim 1.

Thereafter, a positioner for a double-acting pneumatic actuator with a first and a second pneumatically actuated working chamber and a movable working part, such as a piston, is provided. The working part may be displaced at a difference of pressure in the first and second working chambers. The positioner supplies a first and second pneumatic control signal to the first and second working chamber, respectively. According to the invention, the positioner has at least one device for setting the first pneumatic control signal for the first working chamber, wherein the device is designed such that the setting of the first pneumatic control signal can regulate the second control signal is unaffected. According to the invention, therefore, the adjustability of the first control signal is to be accompanied independently of the second pneumatic control signal, in particular independent of the pneumatic size of the second pneumatic control signal. With the measure according to the invention, it is possible to increase the load rigidity of an actuator by the pressures within the working chamber of the actuator individually and independently are increased simultaneously, ie without necessarily inherent pressure change in the pneumatic working chambers is accompanied by design. Due to increased pressure in the working chamber, the overall system of the actuator becomes stiffer. Due to the individual adjustability of the pressure in at least one of the working chambers, pressure ratios of, for example, 5.8 bar in the first working chamber and 5.4 bar in the second working chamber can be generated, wherein the generated differential pressure of 0.4 bar the desired displacement of the working part of the Actuator causes. Due to the high pressure of more than 5 bar, the actuator is given a higher rigidity.

In a preferred embodiment of the invention, the second pneumatic control signal is formed by a constant pressure of a pneumatic supply source, in particular in the amount of 6 bar. In order to adjust the pressure difference between the first and the second working chamber, the first pneumatic control signal can be modified accordingly to produce pressure differences in the range of 6 bar. In this case, the device for adjusting the first pneumatic control signal having a control electronics connected to the flow pressure transducer and optionally have a pneumatic amplifier which is connected to the pneumatic supply source. The constant supply pressure according to the second pneumatic control signal remains unchanged when setting the first pneumatic control signal by means of the current pressure transducer, for example at 6 bar.

In a further development of the invention, the positioner comprises, in addition to a first device for setting the first pneumatic control signal for the first working chamber, a second device for setting the second pneumatic control signal for the second working chamber. In this case, the first and second devices are operated independently of each other, i.e., independently of each other. the positioner generated by its two devices individually evoked pneumatic control signals that are to be supplied to the respective working chamber.

In a preferred embodiment of the invention, the first and second devices each have a current pressure transducer, such as a solenoid valve. The current pressure transducer can receive electrical control signals from a particular common control electronics. The control electronics for this purpose has two separate outputs for connection to the respective current and pressure transducer. The control electronics emit the first and the second electrical control signal via the outputs.

Preferably, each current pressure transducer downstream of a pneumatic amplifier, which is connected via lines to the respective chamber of the pneumatic actuator.

In a preferred embodiment of the invention, a control electronics of the positioner is connected to a respective sensor for detecting the pressure of the first and second chambers. The pressure sensors may be arranged in a connecting line from the positioner to the respective working chamber of the actuator. Alternatively, the pressure sensors may be located within the working chamber of the actuator.

In a further development of the invention, a control electronics of the positioner is connected to a position sensor for detecting the position of an actuator to be provided by the actuator, such as a valve member.

Furthermore, the invention relates to a positioner arrangement for a double-acting pneumatic actuator with a first and a second pneumatically actuated working chamber and a movable working part which is accelerated for an actuating movement at a pressure difference in the first and second working chamber. According to the invention, the first working chamber is assigned a first positioner and the second working chamber is assigned a second positioner, which is independent of the first positioner, in order to supply pneumatic control signals which are independent of each other to the working chambers. According to the invention, the positioner arrangement has two positioners, which can be operated independently of one another and can supply corresponding, independently calculated pneumatic control signals to the respective working chamber.

Furthermore, the invention relates to a double-acting pneumatic actuator, in particular with an above-mentioned positioner according to the invention. The double-acting pneumatic actuator has a first and a second pneumatic working chamber and a movable working part, such as a piston. The working part may be displaced at a difference of pressure in a first and a second working chamber. In addition, the positioner outputs the first or second pneumatic control signal to the first and the second working chamber. The actuator is connected to a pneumatic supply source via the positioner.

In a regulated state of the actuator, a (theoretical) pressure average with respect to the pressures in the first and second working chamber can be determined. This is half the supply pressure in a conventional double acting pneumatic actuator the pneumatic supply source. According to the invention, to increase the rigidity of the actuator, the at least one positioner will be designed to vary the mean pressure of the working chambers, in particular to increase beyond half the supply pressure of the pneumatic supply source.

The mean pressure of the working chambers is preferably adjustable, preferably between a minimum and an approximately full supply pressure, in particular between 3 and up to 5 and 6 bar.

Finally, the invention relates to a method for operating a particular invention, double-acting pneumatic actuator with a first and a second working chamber. According to the method, the working chambers are supplied with separate pneumatic control signals. In a regulated state of the actuator, the mean pressure value between the pressures prevailing in the first and the second working chamber can be determined. According to the invention, the pressure mean value of the working chambers is increased or decreased to increase or reduce the rigidity of the actuator.

According to the invention, it is proposed that the controlling controller determines which operating state it should assume. This can e.g. the state "high load stiffness - low dynamics" or the state "low load stiffness - high dynamics". The determination of the operating state can e.g. by observing the dynamics of the setpoint input. While a regulator according to known prior art thus only sets the output variable "pressure difference", the regulator proposed according to the invention additionally regulates the output variable "pressure level".

In a controlled state without acting on the actuator disturbance d the first and the second working chamber are subjected to the same pressure from the same supply source. According to the invention, to increase the rigidity of the actuator, pressures in the chamber are increased beyond half the supply pressure of the pneumatic supply source.

The method according to the invention can optionally be implemented in a positioner. Then, in the case of a necessary high rigidity, the positioner can have a high pressure in the chambers, while for a good dynamic behavior it is advantageous to reduce the static pressure of the chambers, for example back to half the supply pressure, for example back to half supply pressure.

Preferably, the two working chambers with approximately the full supply pressure of the pneumatic supply source, in particular up to 5 or 6 bar, applied when an increased load rigidity for the pneumatic, double-acting actuator is required.

Figur 1

eine schematische Prinzipskizze eines erfindungsgemäßen, pneumatischen Stellantriebssystem mit einem pneumatischen, doppeltwirkenden Stellantrieb und einem elektropneumatischen Stellungsregler;

Figur 2a

eine graphische Darstellung einer Druckbestandsaufnahme bei Einstatz des erfindungsgemäßen Verfahrens für eine erhöhte Steifigkeit des pneumatischen Stellantriebs; und

Figur 2b

eine graphische Darstellung der Druckverhältnisse für ein dynamisch gutes Verhalten des pneumatischen Stellantriebs.

Further features, advantages and features of the invention will become apparent from the following description of a preferred embodiment with reference to the accompanying drawings, in which:

FIG. 1

a schematic diagram of a pneumatic actuator system according to the invention with a pneumatic, double-acting actuator and an electropneumatic positioner;

FIG. 2a

a graphical representation of a pressure inventory when the method of the invention for increased rigidity of the pneumatic actuator; and

FIG. 2b

a graphical representation of the pressure conditions for a dynamic good behavior of the pneumatic actuator.

In FIG. 1 an actuator system according to the invention is generally provided with the reference numeral 1. The pneumatic actuator system 1 comprises a pneumatic, double-acting actuator 3, an electropneumatic positioner 5, which acts on the actuator 3 with pneumatic control signals s ₁ and s ₂ of about 1 to 6 bar. The pneumatic actuator 3 provides a control valve. 7

The pneumatic actuator 3 has an actuating rod 9, the drive side opens into a piston 11, which divides an outer cylinder 13 of the pneumatic actuator 3 into two working chambers 15, 17.

Depending on which pneumatic values the control signals s ₁ , s ₂ should have, the working chambers 15, 17 are acted upon by pressures p ₁ , p ₂ . At a pressure difference between p ₁ and p ₂ , a displacement of the rod 9 is set.

The positioner 5 has an input 21 for connection to a pneumatic supply source 23, which provides a constant supply pressure P _v of 6 bar.

Furthermore, the positioner 5 has an input for supplying desired data w to perform the control by means of a microprocessor 25. The microprocessor 25 is connected to a position sensor 27 which accesses the latter for detecting the position of the control rod 9 and a position signal x to the Microprocessor 25 outputs.

The microcomputer 25 is also connected to a first pressure sensor 31 and a second pressure sensor 33, which is intended to determine the pressures prevailing in the working chambers 15, 17. In the in FIG. 1 In the embodiment shown, the pressure sensors 31, 33 are arranged in the respective connection line 35, 37, which connect the respective working chamber 15, 17 to a respective pneumatic amplifier 41, 43.

The pneumatic boosters 41, 43, which are responsible for generating the pressure for the respective pneumatic control signals s ₁ , s ₂ , are both connected to the pneumatic supply source 23. Both pneumatic amplifiers 41, 43 can be vented via appropriately controlled outputs 47.

The positioner according to the invention comprises two current pressure transducers 51, 53 to which an electrical control signal e ₁ , e _{2 is} supplied from the microcomputer 25 via lines.

Based on the electrical control signal e ₁ , e ₂ , the current pressure converter 51, 53 outputs a corresponding pneumatic pilot signal to the pneumatic amplifier 41, 43 from.

In this way, the positioner 5 according to the invention can generate pneumatic control signals s ₁ , s ₂ , which are completely independent of each other. In this respect, individual pressures at specified pressure differences within the working chambers 15, 17 can be adjusted to adjust the stiffness or softness of the actuator 3.

In the event that the actuator is to provide a high rigidity, the working chambers 15, 17 are supplied with approximately the complete supply pressure P _v , so that prevail about 6 bar in both chambers. In order to be able to carry out the desired control, the current pressure transducers 51, 53 can generate a pressure difference in the range of 6 bar within the working chambers 15, 17 by appropriate control.

In FIG. 2a is such a case indicated in which approximately the supply pressure P _v in working chambers 15, 17 prevails. For both pressures p ₁ , p ₂ more than 50% of the supply pressure P _v in the working chambers 15, 17 are passed.

In this case, either a pressure difference to the maximum supply pressure (.DELTA.P _V ), the pressure difference in the working chambers (.DELTA.P) or pressure difference for venting (.DELTA.P ₀ ) can be determined and used accordingly for control. A pressure average P _M can be in both cases ( Figure 2a, 2b ) easily determine. In both cases $${\mathrm{P}}_{\mathrm{M}}\mathrm{=}{\mathrm{.DELTA.P}}_{\mathrm{0}}\mathrm{+}\mathrm{½\Delta P}\mathrm{,}$$

In order to vary the stiffness of the actuator, the position control system according to the invention is adapted to change the rigidity of the actuator by either the pressure average value P _M is increased to increase the rigidity or lowered to reduce the rigidity.

In FIG. 2b is the pneumatic actuator 3 is placed in an operating state in which he has a good dynamic behavior in which the static pressure in the chambers 15, 17 is set to half supply pressure P _V again. Accordingly, the pressure difference .DELTA.P _V have changed .DELTA.P ₀ (the maximum of the supply pressure, to vent pressure), without that the pressure difference AP in the chambers 15, would have changed 17th In both operating states according to FIGS. 2a and 2b is the same adjustment of the piston 11 guarantee, once with a rigid actuator system according to FIG. 2a and once in a soft actuator system according to FIG. 1a.

The features disclosed in the foregoing description, the figures and the claims may be of importance both individually and in any combination for the realization of the invention in the various embodiments.

LIST OF REFERENCE NUMBERS

1

Actuator system

3

double, acting actuator

5

Electropneumatic positioner

7

Control valve

9

control rod

11

piston

13

outer cylinder

15, 17

working chamber

21

entrance

23

source

25

microprocessor

27

position sensor

31, 33

pressure sensor

35.37

interconnectors

41.43

pneumatic amplifier

47

outputs

51, 53

Current pressure transducer

C _z

supply pressure

e ₁ , e ₂

control signal

P _V

supply pressure

p ₁ , p ₂

pressures

s ₁ , s ₂

pneumatic control signals

x

position signal

ΔP _V

maximum supply pressure

.DELTA.P

Pressure difference in working chambers

ΔP ₀

Pressure difference for venting

P _M

Pressure value

w

nominal data

Claims (13)

Positioner for a double-acting pneumatic actuator (3) having a first and a second pneumatically actuable working chamber (15, 17) and a movable working part (9) suitable for an actuating movement with a difference of pressure in the first and second working chamber (15, 17 ) is displaceable, wherein the positioner of the first and second working chamber, a first and second pneumatic control signal (s ₁ , s ₂ ) supplies, characterized in that it comprises at least one means for setting the first pneumatic control signal (s ₁ ) for the first Working chamber, wherein the device is designed such that the setting of the first control signal according to regulations leaves the second pneumatic control signal unaffected. Positioner according to Claim 1, characterized in that the second pneumatic control signal is formed by a constant supply pressure (P _v ) of a pneumatic supply source, in particular in the amount of 6 bar, which remains invariable when adjusting the first pneumatic control signal (s ₁ ), wherein in particular the Device having an associated with a control electronics current pressure transducer (51) and optionally a pneumatic amplifier (41) which is connected to the pneumatic supply source. Positioner according to Claim 1 or 2, characterized in that, in addition to a first device for setting the first pneumatic control signal (s ₁ ) for the first working chamber (15), a second device for setting the second pneumatic control signal (s ₂ ) for the second working chamber (17), wherein the first and the second device are operated independently of each other according to regulations. Positioner according to claim 3, characterized in that both devices are connected to a common pneumatic supply source or in each case to its own pneumatic supply source. Positioner according to claim 3 or 4, characterized in that the first and second means each comprise a flow pressure transducer (51, 53) or a solenoid valve receiving in particular electrical control signals from a common control electronics (25) having a first and a second control signal (s ₁ , s ₂ ) generates and outputs. Positioner according to Claim 5, characterized in that a pneumatic amplifier (41, 43) is connected downstream of each current pressure converter (51, 53). Positioner according to one of claims 1 to 6, characterized in that a control electronics (25) of the positioner (5) with a sensor (31), (33) for detecting pressure in the first and second working chamber is connected. Positioner according to claim 7, characterized in that a pressure sensor is arranged in a connecting line from the positioner (5) to the respective working chamber of the actuator. Positioner according to one of claims 1 to 8, characterized in that a control electronics (25) of the positioner (5) is connected to a position sensor (27) for detecting the position of an actuator to be provided by the actuator. Positioner arrangement for a double-acting pneumatic actuator (3) having a first and a second pneumatically actuated working chamber (15, 17) and a movable working part which is displaceable for an actuating movement at a difference of pressure in the first and second working chamber (15, 17) , characterized in that the first working chamber, a first positioner and the second working chamber, a second, independent of the first positioner Positioner is assigned to supply the working chambers regulationally independent pneumatic control signals. Double-acting pneumatic actuator with at least one positioner (5), in particular according to one of claims 1 to 9, a first and a second pneumatic working chamber (15, 17) and a movable working part (9), which at a difference of pressure in the first and second working chamber (15, 17) is displaceable, wherein the positioner (5) the first and second pneumatic control signal (s ₁ , s ₂ ) to the first and second working chamber (15, 17) emits, wherein the actuator to a pneumatic Supply source is connected and in a controlled state of the actuator in the first and second working chamber (15, 17) a pressure average (P _M ) with respect to the pressures in the first and second working chamber can be determined, characterized in that to increase the rigidity of the actuator at least one positioner (5) is adapted to vary the pressure mean value (P _M ) of the working chambers (15, 17), ins to increase more than half the supply pressure (P _V ) of the pneumatic supply source. Actuator according to claim 11, characterized in that the pressure mean value (P _M ) of the working chambers between a minimum and an approximately full supply pressure (P _V ), in particular between 3 and up to 5 or 6 bar, is adjustable. Method for operating a double-acting, pneumatic actuator with a first and a second pneumatic working chamber (15, 17), wherein the working chambers (15, 17) are acted upon with separate pneumatic control signals and in a regulated state of the actuator, a pressure average value (P _M ) of the first and second working chamber is determined, characterized in that to increase or reduce the rigidity of the actuator, the pressure medium value (P _M ) of the working chambers (15, 17) is increased or decreased.

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