Patent Description:
<CIT> relates to a slide valve comprising a bushing in which fluid openings are provided which extend through the wall of bushing, a slide which is arranged adjustably in the bushing and is provided with at least one fluid duct, and an electroactive polymer actuator which can adjust the slide in the bushing. <CIT> relates to a fluidic actuator having at least one membrane consisting of an electroactive polymer or a dielectric elastomer, such as a valve, having an actuator device, having means for adjusting and detecting an elongation of the membrane and to a method for operating such a fluidic actuator. <CIT> relates to a fluid control systems employing compliant electroactive materials. It relates to valves constructed of transducers made of compliant electroactive materials.

A pneumatic positioner, respectively a system including valve positioners with pneumatic output, faces two contrary business demands. On the one hand, there is a demand for high pneumatic pressure to operate the actuator; on the other hand, there are stringent requirements for a low power consumption of the overall system. For this, a conventional positioner includes several submodules. These submodules can be seen as force amplifiers. However, this state-of-the-art arrangement leads to a complex and bulky setup. In order to operate high pneumatic pressures with low, particularly electrical, power, a close to equilibrium topology is applied, in which the forces by the pneumatic pressure are balanced by e.g. compensation springs. Thus, only a small force, and correspondingly energy, is sufficient to control a position of the process valve.

This small amount of "controlled force" is conventionally also based on pneumatic pressure. Therefore, a "pressure reducer" is used, which reduces the total pneumatic pressure partly to provide low-pressure to a subsystem, which is configured to be controlled with low electrical power. This "low-pressure-subsystem", is the "pilot stage". Using other words, the pilot stage acts as a force amplifier, controlling a larger force of a pneumatic pressure by a smaller controlled force. The usage of pilot stages in general is inefficient and cost intensive. Former power requirements have led to the design of a balanced main stage and a controllable sub-unit (pilot stage) that is to control a fraction of the pneumatic pressure.

State of the art valve positioner with pneumatic output systems are operated using such a pilot stage, which can be configured in different ways and are based on different technologies, as e.g. based on a piezo-nozzle or a flapper-nozzle. The usage of pilot stages in general leads to a bulky design and is cost intensive. A further problem using pilot stage designs for positioners is a constant blow-off of the pneumatic medium, which results in inefficiency.

Aspects of the present invention are related to a system of valve positioners with pneumatic output and a use of a system of valve positioners with pneumatic output as described in the independent claims.

Advantageous modifications of the invention are stated in the dependent claims. A dielectric elastomer actuator in membrane topology can be named "membrane actuator".

To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, there is provided a system of valve positioners with pneumatic output according to claim <NUM>.

A system of valve positioners with pneumatic output can be a device which is configured to control a pneumatic actuator.

The plurality of valve positioners with pneumatic output of the system of valve positioners with pneumatic output is configured to control a pneumatic actuator.

The pneumatic actuator can be mechanically coupled to a process valve to control the process valve.

Aspects of the present invention are related to a dielectric elastomer actuator in membrane topology, in the following named "membrane actuator" for controlling a valve positioner with pneumatic output a system of valve positioners with pneumatic output, and a use of a positioner drive.

The membrane actuator is configured to be mechanically coupled to a valve of the valve positioner with pneumatic output for controlling the pneumatic positioner.

The membrane actuator is configured to be controlled by electrical voltages and/or the membrane actuator is can be configured to be coupled to the valve of the pneumatic positioner by a central part of the membrane actuator.

Using other words, by using such a positioner drive units of a main stage of the system of valve positioners with pneumatic output, are driven and operated directly by the positioner drive to make a pilot stage and/or a pressure reducer obsolete to save energy and/or to have a less bulky system of valve positioners with pneumatic output. That means the system of valve positioners can be designed to have a reduced design space, as compared to systems of valve positioners with pneumatic output as is state-of-the-art.

This direct actuation by a positioner drive, not using pneumatic pressure to operate units of the main stage, can be controlled by electrical signals and/or electrical power provided to the positioner drive.

Advantageously the pneumatic positioner, which is mechanically coupled to a positioner drive can provide a robust system, because it can be built by a less complex mechanical construction. In addition, such pneumatic positioners can be configured to be more robust towards temperature changes and external vibrations than a pneumatic pilot stage and by this they can be adapted to a plurality of production environments. To drive the pneumatic positioners directly reduces the requirements in respect to a quality of the air of the overall pneumatic system, because they are less sensitive to particles distributed by the air, which may get stuck within, e.g., a pneumatic pilot stage.

A discret operation of the individual valves of the pneumatic positioners by the corresponding positioner drives can improve the performance of the valve positioner with pneumatic output system. Because there is no steady state air flow necessary for a pilot stage this steady-state air consumption is eliminated.

Advantageously only minor changes have to be designed to modify existing positioner drives to include the membrane actuator, thereby existing designs, which can be configured for high flow rates and high pressures with a customer proven technology, can be used, as key valve components, for the proposed positioner drives, which include the membrane actuator.

According to an aspect, the membrane actuator can be configured to be mechanically coupled directly to a plunger of the valve of the pneumatic positioner.

This direct mechanically coupling with the plunger of the valve enables to set up a simple system using such valve positioner with pneumatic output including a positioner drive, which can be driven directly by electrical signals provided to the membrane actuator.

According to the invention, the membrane actuator is configured to seal a pneumatic compartment of the pneumatic positioner.

Advantageously the membrane actuator includes the functionality of controlling the respective pneumatic positioner as well as sealing the pneumatic positioner.

That means pneumatic positioners or valve positioner with pneumatic output units of a main stage can be operated directly by the membrane actuator by having a functional integration of a sealing and actuation.

According to the invention, the membrane actuator comprises a dielectric-elastomer membrane; and at least one electrical electrode adjacent to the dielectric-elastomer membrane to control the membrane actuator based on an electrical voltage provided to the electrical electrode.

Dielectric Elastomer Actuators (DEA) are members of the group of "nonconventional actuators", which are based on smart materials. Advantageously dielectric elastomer actuators have a proven track record in various applications and can be adapted for the described purpose as described. The anticipated solution is to use a DEA in membrane topology, which allows for a functional integration of both pressure sealing, mechanical guiding and actuation.

DEAs include elastic membranes, as e.g. silicon, with an electrode on each side for providing an electrical field. The topology can be seen analogue to a conventional capacitor, but with an elastic dielectric material in between the electrodes. When the electrical field is activated, electric forces compress the elastic dielectric material and thereby stretches the membrane actuator. Using the membrane actuator topology the membrane can be elongate as a result of the electric field and allow for an out of plane motion of the membrane actuator, which can drive the direct operation of a main stage valve, which is included within the pneumatic positioner.

That means pneumatic positioners or valve positioner with pneumatic output units of a main stage can be operated directly by Dielectric Elastomer Actuators (DEA) in "membrane topology", ideally by having a functional integration of sealing and actuation by DEAs.

According to an aspect, the membrane actuator comprises an electrical counter electrode adjacent to the dielectric-elastomer membrane at the opposite side of the dielectric-elastomer membrane as the electrical electrode for generating an electrical field between the electrodes if an electrical voltage is provided to the electrodes.

According to an aspect, the membrane actuator includes: a first electrical contact electrically coupled to the electrical electrode; and a second electrical electrode with a second electrical contact; for provision of electrical voltages to operate the membrane actuator.

According to an aspect, the membrane actuator is configured to be arranged within a housing of the pneumatic positioner.

Building of a pneumatic positioner, wherein the positioner drive is inside of the housing of the valve positioner with pneumatic output enables a compact design of the pneumatic positioner.

According to an aspect, the membrane actuator is configured to be mechanically coupled to a housing of the pneumatic positioner for controlling the pneumatic positioner.

A peripheral part of the membrane actuator can be coupled to the housing of the pneumatic positioner for enabling the out of the plane movement of the membrane actuator to move the valve of the pneumatic positioner.

According to the invention, the dielectric-elastomer membrane is configured to seal an inner pneumatic compartment of the pneumatic positioners against an outer environment of the pneumatic positioner in respect to a pneumatic fluid within the pneumatic compartment.

According to an aspect, the positioner drive includes a compensation element for compensation of forces originated from pneumatic pressure within the respective pneumatic positioner, wherein the compensation element is configured to provide a negative rate force-displacement relationship.

A negative rate force-displacement relationship means that, if the compensation element provides a force to balance forces originated from pneumatic pressure acting on the valve at a balanced and/or rest position of the valve, as for instance a closed position, and the valve has to be opened, then the additional displacement of the valve or the mechanically coupled compensation element will not further increase the necessary force for the displacement of the compensation element, but the force to further displace the compensation element will be reduced. That means the compensation element can be configured such that a forced displacement gradient is negative.

According to an aspect, the compensation element comprises a system of compression springs, which is configured to provide the negative rate force-displacement relationship and/or a convex disc spring, which is configured to provide the negative rate force-displacement relationship and/or a permanent magnet system, which is configured to provide the negative rate force-displacement relationship.

The compensation element based on a system of compression springs can include two compression springs, which are mechanically coupled with each other at one site of each spring at a coupling point and wherein each other end of each spring can be mechanically coupled to a rigid means, as for instance a housing of the pneumatic positioner. Based on the described mechanically coupling of the two springs the compensation element is configured to provide the negative rate force-displacement relationship. The coupling point of the system of compression springs can be mechanically coupled, e.g., to a valve of the pneumatic positioner to compensate forces originated from pneumatic pressure within the pneumatic positioner acting on the valve.

According to the invention, the plurality of pneumatic positioners and the plurality of membrane positioner drives of the valve positioner with pneumatic output system are configured to provide the functionality of a <NUM>/<NUM> positioner valve system.

Pneumatic positioners, respectively systems of valve positioners with pneumatic output, including "<NUM>/<NUM> valve functionality" are a demand from the industry. This term means a system of valve positioners with pneumatic output including "<NUM>" pneumatic ports: a pressure inlet; a first and a second output port; and a ventilation port including "<NUM>" possible operation modes: forward; backward; and blocked movement of the pneumatic actuator. In general, different main stage topologies for the system of valve positioners with pneumatic output exist to allow for a <NUM>/<NUM> valve functionality, e.g. four parallel on/off valves, spool valves, etc. That means using the pneumatic positioner as described for building the system of valve positioners with pneumatic output with <NUM>/<NUM> functionality provides advantagesly a modular setup for a required functionality and an assembly of the system of valve positioner with pneumatic output.

Each of the pneumatic positioners of the system of valve positioners with pneumatic output is operated directly by a positioner drive as described.

An actuation of the positioner drive can additionally be based on different physical principals like pneumatics, hydraulics, electricity, etc., what is not claimed.

A use of a system of valve positioners with pneumatic output as described above is proposed, for controlling a process valve.

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention and together with the description serve to explain the principle of the invention. The drawings display:.

<FIG> sketches schematically an overall topology of a system to control a process valve <NUM> according to the state of the art, which is operated by a pneumatic actuator <NUM> to control a position of the pneumatic actuator <NUM>, and wherein the pneumatic actuator <NUM> is controlled by a system including valve positioners with pneumatic output <NUM>. For operation of such a system of valve positioners with pneumatic output <NUM> it includes a "main stage" <NUM> and a "pilot stage" <NUM>.

The main stage <NUM> is configured to operate the pneumatic actuator <NUM>, which is coupled to the process valve <NUM> at a required pneumatic operation pressure, as e.g. <NUM> bars. The main stage <NUM> can be configured to have one operating point close to a force balance, such that only small changes using a control pressure can lead to the desired tripping of the process valve <NUM>. The main stage <NUM>, respectively valve positioners of the main stage <NUM>, can include components to provide the close-to-force-balance operation to enable the force balance.

This small amount of "controlled force" is conventionally as well based on pneumatic pressure. Therefore, a "pressure reducer" <NUM> is used, which reduces the total pneumatic pressure partly to a low-pressure subsystem, which can then be controlled with low electrical power. The reduced pressure for operating the pilot stage <NUM> is a fraction of the pneumatic operation pressure and adjusted by the pressure reducer <NUM>.

The pilot stage <NUM> represents a "low-pressure-subsystem" of the system including valve positioners with pneumatic output <NUM> and is configured to control the control pressure, which can be controlled by electrical signals generated by electronics <NUM>. Using other words, the pilot stage <NUM> acts as a force amplifier, controlling a larger force of a pneumatic pressure by a smaller controlled force. Typically, systems of valve positioners with pneumatic output <NUM> are operated via a pilot stage <NUM>, which can be realized in different ways and by using different technologies, as e.g. using a piezo- or a flapper-nozzle.

In general, a valve positioner with pneumatic output <NUM>, respectively a system of valve positioners with pneumatic output <NUM>, faces two contrary demands for industrial production:
On the one hand, there is a demand for high pneumatic pressure to operate; on the other hand, there are stringent requirements for a low power consumption.

To realize this, a conventional system of valve positioners with pneumatic output <NUM> as shown in <FIG> comprises several submodules, respectively valve positioners with pneumatic output. These submodules can be seen as force amplifiers. However, this state-of-the-art arrangement leads to a complex and bulky assembly.

As mentioned before, in order to operate high pneumatic pressures with low electrical power, a close to equilibrium topology of the submodules is typically designed, in which the forces originated by the pneumatic pressure are balanced by, e.g., counter springs. By this, only a small force and corresponding energy can be sufficient to change a position of the process valve <NUM>.

The usage of a pilot stage <NUM> in general leads to a bulky assembly of a system of valve positioners with pneumatic output <NUM> and is cost intensive. A further disadvantage of using a pilot stage116 is that a constant blow-off of the pneumatic medium is required, which makes the system inefficient.

<FIG> sketches a state-of-the-art valve positioner with pneumatic output of a main stage <NUM>, that means a part of the main stage <NUM>, including a valve <NUM> a plunger of the valve <NUM> mechanically coupled to the valve <NUM>, the first valve compartment <NUM> and a second valve compartment <NUM>, which can be pneumatically coupled by the valve <NUM> and a first sealing diaphragm <NUM>, which seals the first compartment <NUM> in respect to an outside of the valve positioner with pneumatic output as well as a second sealing diaphragm <NUM>, configured to seal the second compartment of the valve positioner with pneumatic output to the outside of the valve positioner with pneumatic output. The first and the second sealing diaphragms <NUM>, <NUM> are mounted in a housing of the valve positioner with pneumatic output and are coupled to the plunger <NUM> of the valve.

<FIG> sketches schematically the state of the art valve positioner with pneumatic output of the main stage <NUM> as described with <FIG>, where the reference signs are corresponding to the description of the <FIG>, to explain the functionality of a compensation element <NUM> of a state of the art balanced valve design, wherein the compensation element <NUM> is coupled to the plunger <NUM> of the valve to compensate forces acting on the valve <NUM> based on a pressure of the pneumatic fluid within the first chamber <NUM> of the valve positioner with pneumatic output unit and/or the second chamber <NUM>. Using other words, the compensation element <NUM> is configured and arranged to reduce the force necessary to open and/or close the valve <NUM>.

<FIG> sketches schematically a positioner drive <NUM> not according to the claimed invention for controlling a valve positioner with pneumatic output <NUM>, respectively a unit of a valve positioner with pneumatic output <NUM>, wherein the positioner drive <NUM> is configured to be mechanically coupled to a valve <NUM> of the valve positioner with pneumatic output <NUM> for controlling the valve positioner with pneumatic output <NUM>. The positioner drive <NUM> can be configured to be mechanically coupled directly to a plunger <NUM> of the valve <NUM> of the valve positioner with pneumatic output <NUM>. The positioner drive <NUM> as shown in <FIG> is configured to be arranged outside of a housing <NUM> of the valve positioner with pneumatic output <NUM>.

The valve positioner with pneumatic output <NUM> with the positioner drive <NUM> as shown in <FIG>, for use in the claimed invention corresponds to the valve positioner with pneumatic output <NUM> as shown in <FIG>, but this positioner drive <NUM> is configured and arranged inside of the housing <NUM> of the valve positioner with pneumatic output <NUM>.

<FIG> sketches a valve positioner with pneumatic output <NUM>, respectively a unit of a valve positioner with pneumatic output100, including a first positioner drive 200a, which is configured as a membrane positioner drive 200a, wherein the membrane positioner drive 200a includes a dielectric-elastomer membrane drive. The first positioner drive 200a is coupled to a plunger <NUM> of the valve of the valve positioner with pneumatic output <NUM> to control the valve <NUM> of the valve positioner with pneumatic output <NUM>.

The valve positioner with pneumatic output <NUM> can include a second positioner drive 200b, which is configured as a membrane positioner drive 200b, wherein the membrane positioner drive 200b can include a dielectric-elastomer membrane drive. The second positioner drive 200b is coupled to the plunger <NUM> of the valve of the valve positioner with pneumatic output <NUM> to control the valve <NUM> of the valve positioner with pneumatic output <NUM>.

Each of the dielectric-elastomer membrane drives 200a, 200b can be electrically coupled by electrical coupling means for providing electrical signals to the dielectric-elastomer membrane drives 200a, 200b for operating, wherein the electrical coupling means are not shown in <FIG>.

The membrane positioner drives 200a, 200b as described above can be configured and arranged to integrate a functionality of a positioner drive as well as a sealing membrane.

<FIG>sketches schematic drawings of a membrane positioner drive 200a including a dielectric-elastomer membrane. <FIG> sketches a system <NUM> of a voltage source <NUM> which is configured using a switch <NUM> to be connected to the dielectric-elastomer membrane drive 200a, such that the dielectric elastomer membrane drive 200a will deflect upwards because of the electric field and by this can control, e.g., a valve <NUM> of a valve positioner with pneumatic output <NUM>.

<FIG> sketches a dielectric-elastomer membrane drive 200a coupled to a spring <NUM>, wherein the dielectric-elastomer membrane drive 200a is controlled by different voltages to move the spring <NUM>, which is coupled to the dielectric-elastomer membrane drive 200a because of the related forces the dielectric-elastomer membrane drive 200a applies to the spring <NUM>.

The dielectric-elastomer membrane drive 200a can be coupled at a perimeter of the dielectric-elastomer membrane drive to a housing of the valve positioner with pneumatic output <NUM> as indicated in <FIG>.

<FIG> sketches schematically different embodiments of compensation elements <NUM> of a valve positioner with pneumatic output <NUM> for compensation of forces originated from pneumatic pressure within the valve positioner with pneumatic output <NUM> acting on the valve <NUM>, wherein each of the compensation elements <NUM> is configured to provide a negative rate force-displacement relationship.

The compensation element <NUM> of <FIG> comprises a system of compression springs <NUM>, <NUM>, which are mechanically coupled with each other at one site of each spring <NUM>, <NUM> at a coupling point <NUM> and wherein each other end of each spring <NUM>, <NUM> can be mechanically coupled to a rigid means <NUM>, as for instance a housing of the valve positioner with pneumatic output <NUM>. Based on the described mechanically coupling of the two springs <NUM>, <NUM> the compensation element <NUM> of <FIG> is configured to provide the negative rate force-displacement relationship. The coupling point <NUM> can be mechanically coupled, e.g., to the valve <NUM> of the valve positioner <NUM> to compensate forces originated from pneumatic pressure within the valve positioner with pneumatic output <NUM> acting on the valve <NUM>.

The compensation element <NUM> as sketched within <FIG> comprises a convex disc spring <NUM>, wherein both end points, respectively parts or the whole perimeter, of the convex disc spring can be mechanically coupled to a rigid means <NUM>, as for instance a housing of the valve positioner with pneumatic output <NUM>. Based on the described mechanically coupling of the convex disc spring <NUM> the compensation element <NUM> of <FIG> is configured to provide the negative rate force-displacement relationship. A central coupling point <NUM> can be mechanically coupled, e.g., to the valve <NUM> of the valve positioner with pneumatic output <NUM> to compensate forces originated from pneumatic pressure within the valve positioner with pneumatic output <NUM> acting on the valve <NUM>.

A third embodiment of the compensation element <NUM> <FIG> includes a permanent magnet system <NUM>, which is configured to provide the negative rate force-displacement relationship. A permanent magnet of the permanent magnet system <NUM> can be mechanically coupled to a rigid means, as for instance the housing <NUM> of the valve positioner with pneumatic output <NUM> and this permanent magnet can be arranged and configured to couple to the valve <NUM> of the valve positioner with pneumatic output <NUM> by magnetic forces. For this, the valve <NUM> and/or the plunger <NUM> of the valve <NUM> can include a ferromagnetic part and/or another permanent magnet for the magnetic coupling. Because the magnetic coupling of permanent magnets and/or permanent magnets with ferromagnetic material decreases with a distance of the corresponding parts the permanent magnet system <NUM> can be configured to compensate forces originated from pneumatic pressure within the valve positioner with pneumatic output <NUM> acting on the valve <NUM> by providing a negative rate force-displacement relationship.

<FIG> sketches schematically a <NUM>/<NUM> direction positioner valve <NUM> not according to the claimed invention, respectively a system of valve positioners with pneumatic output <NUM>, including a twin on/off valve topology. The functionality of the <NUM>/<NUM> direction positioner valve <NUM> is schematically indicated by a de-aerate position 500a, a block position 500b and an aerate position 500c as indicated in <FIG>. Such a <NUM>/<NUM> direction positioner valve can include an inlet port <NUM>, an outlet port <NUM> and a ventilation port <NUM> to provide the mentioned functionality.

<FIG> sketches schematically a block diagram of the <NUM>/<NUM> direction positioner valve <NUM> not according to the claimed invention including a twin on/off valve topology, including two valve positioner with pneumatic output <NUM>, <NUM>, which are pneumatically coupled at an outlet side of the valve positioner with pneumatic output <NUM>, <NUM>, which is pneumatically coupled to the outlet port <NUM> of the system of valve positioners with pneumatic output <NUM>. An inlet port of the first positioner <NUM> is pneumatically connected to the inlet <NUM> of the system of valve positioners with pneumatic output <NUM> and an inlet port of the second positioner <NUM> is pneumatically connected to a ventilation port <NUM> of the system of valve positioners with pneumatic output <NUM>.

The following operation matrix indicate a position of the first positioner unit V1 <NUM> and the second positioner unit V2 <NUM> to provide the functionality as described above:.

<FIG> sketches schematically a <NUM>/<NUM> direction positioner valve <NUM> according to the claimed invention, respectively a system of valve positioners with pneumatic output <NUM>, including a quattro on/off valve topology. The functionality of the <NUM>/<NUM> direction positioner valve <NUM> is schematically indicated by an open position 600a, a block position 600b and a closed position 600c as indicated in <FIG>. Such a <NUM>/<NUM> direction positioner valve <NUM> can include an inlet port <NUM>, a first outlet port <NUM>, a second outlet port <NUM> and a ventilation port <NUM> to provide the described functionality.

<FIG> sketches schematically a block diagram of the <NUM>/<NUM> direction positioner valve <NUM> including a quattro on/off valve topology, having four valve positioners with pneumatic output <NUM>, <NUM>, <NUM>, <NUM>, wherein the first valve positioner with pneumatic output <NUM> and the second positioner <NUM> are pneumatically coupled at an outlet side of the first and the second valve positioner with pneumatic output <NUM>, <NUM>, which is pneumatically coupled to the second outlet port <NUM> of the system of valve positioner with pneumatic output <NUM>. An inlet port of the first positioner <NUM> is pneumatically connected to the inlet port of a third valve positioner with pneumatic output <NUM>, such that both are pneumatically connected to a first inlet port <NUM> of the valve positioner with pneumatic output <NUM>. An inlet port of a second positioner unit <NUM> is pneumatically connected to an inlet port of a fourth valve positioner with pneumatic output unit <NUM>, such that both are pneumatically connected to a second inlet port <NUM> of the system of valve positioner with pneumatic output <NUM>.

The following operation matrix indicate a position of the first positioner unit V1 <NUM>, the second positioner unit V2 <NUM>, the third positioner unit V3 <NUM> and the fourth positioner unit V4 <NUM> to provide the functionality as described above:.

Claim 1:
A system of valve positioners with pneumatic output, comprising
a plurality of pneumatic positioners (<NUM>); and
a plurality of positioner drives (<NUM>), which are configured to control the plurality of pneumatic positioners (<NUM>) respectively,
wherein the plurality of pneumatic positioners (<NUM>) and the plurality of positioner drives (<NUM>), are configured to provide the functionality of a <NUM>/<NUM> positioner valve system,
wherein the plurality of positioner drives (<NUM>) comprises a membrane actuator (200a, 200b) respectively, wherein the membrane actuator is configured to be mechanically coupled to a valve (<NUM>) of the plurality of pneumatic positioners (<NUM>) respectively for controlling of the respective pneumatic positioner (<NUM>),
wherein the membrane actuator (200a, 200b) comprises a dielectric-elastomer membrane; and at least one electrical electrode adjacent to the dielectric-elastomer membrane to control the membrane actuator (200a, 200b) based on an electrical voltage provided to the electrical electrode, wherein the membrane actuator (200a, 200b) is configured to seal an inner pneumatic compartment (<NUM>, <NUM>) of the pneumatic positioners (<NUM>) against an outer environment of the pneumatic positioners (<NUM>) in respect to a pneumatic fluid within the inner pneumatic compartment.