WO2024100481A1

WO2024100481A1 - Actuator comprising an actuating means made of shape memory alloy material and a feedback control unit

Info

Publication number: WO2024100481A1
Application number: PCT/IB2023/060561
Authority: WO
Inventors: Vincenzo MARCANTONIO
Original assignee: Ceme S.P.A.
Priority date: 2022-11-09
Filing date: 2023-10-19
Publication date: 2024-05-16

Abstract

An actuator (1) comprises an actuating means (2) made of shape memory material adapted to move a movable body (5) relative to a stationary body (4) by means of a feedback control unit (3) using state parameters of the actuator as input.

Description

ACTUATOR COMPRISING AN ACTUATING MEANS MADE OF SHAPE MEMORY ALLOY MATERIAL AND A FEEDBACK CONTROL UNIT

DESCRIPTION

The present invention relates to an actuator comprising an actuating means composed of shape memory alloy (or SMA) material for moving a movable body relative to a stationary body for driving pumping systems or servo commander valves or the like, and comprising a feedback control unit configured to measure or receive measurements of actuator status parameters in order to calibrate the displacement of the movable body relative to the stationary body under various operating conditions of the working environment.

In the prior art, the most commonly used apparatus for actuator-induced movement is a solenoid, which is a device for converting electrical energy into a displacement of a movable element, such as a piston or a mechanical arm or the like for driving pumping systems or servo-command and direct-acting valves or the like.

For example, known from US6494225 is a proportional flow control valve having at least one gripping jaw that is movable between the open and closed positions to engage a fluid flow line passing through the valve. The valve includes a valve actuator generally formed by a shape memory alloy that engages and moves at least one movable gripper jaw. When an electric current is applied to the shape memory alloy, the shape memory alloy exerts a moving force on the gripping jaw to move the gripping jaw in or out of engagement with a flow tube to control the opening and closing of the valve.

A solenoid typically comprises electrically conductive windings wrapped around a magnetic core in such a way that the windings produce a magnetic field when an electric current is passed through them, thus causing the magnetic core to move axially. The movable element is coupled to the magnetic core in such a way that it can be actuated to achieve linear displacement.

Typically, these solenoid valves have an actuator able to move a movable element between two ON/OFF positions, which for example may correspond to the opening/closing of a passage for a working fluid within a hydraulic circuit.

A common limitation of solenoids, particularly when used in small consumer applications, is that they have high electric power requirements. In fact, solenoids require an expensive and complex power source for operation, as they must be equipped with AC to DC power converters or expensive battery varieties in a “series” configuration. In addition, precision control may be difficult or have a longer response time than desired.

In recent decades, actuators have been replacing solenoids with components comprising shape memory alloy (SMA) materials. In the scientific literature, the phenomenon of shape memory is quite well-known and common. In particular, the phenomenon consists of the fact that a mechanical part, generally composed of specific metal-based alloys, is able to transition, in the presence of a change in its temperature, between two forms or, more specifically, between two different crystalline structures by means of a change of state. In other words, an SMA material has two physical phases, a first phase corresponding to a first crystalline structure stable at a lower temperature and a second phase corresponding to a second crystalline structure stable at a higher temperature. An SMA material is able to make phase transitions with structural changes to its crystal structure by varying its physical and mechanical properties.

In most common SMA materials, the transition between the two above- mentioned phases involves controlled shortening. For example, a first possible shape memory alloy wire can be used to move one or more movable elements within an actuator. Typically, such a wire is heated through the passage of an electric current by the Joule effect. Such a wire can change from form A to form B by heating, but then return reversibly from form B to form A exclusively by cooling.

Advantageously, the use of SMA elements includes a very low energy expenditure in comparison to conventional solenoid-based actuators, which can be achieved by means of rather low electric current applications.

Additionally, some specific shape memory alloy materials are able to exhibit dimensional variations, e.g. length, proportional to the specific temperatures of the transient phases between the two states, where the two crystalline structures corresponding to both phases of the material coexist in the material.

Consequently, a further advantage of using SMA-type elements results in the possibility of exploiting not only actuators comprising two moving positions of the movable body, i.e. ON/OFF operating configurations, corresponding for example to the opening or closing of a valve, but rather, the moving position can be one from a finite but continuous set of possible moving positions. This use is particularly advantageous for obtaining partial openings of a solenoid valve, for example, to allow a predetermined flow rate of a fluid to pass through a circuit.

A further advantage of using SMA-type elements compared to conventional actuators results in high durability and a high number of working cycles, provided that the deformation of the SMA mechanical element has a short stroke length, given the deformation capacity of the SMA material. If the stroke does not exceed 3% of the significant size, the material is able to maintain its physical-mechanical characteristics for a large number of cycles. This characteristic is also advantageous in cases where small actuators need to be used, as these wires are discreetly miniaturised due to the modification of the material at molecular level.

Disadvantageously, both traditional type actuators and actuators using SMA mechanical elements can have defects at structural level, which are difficult to detect, and which can affect the effective stroke of the actuator's movable element. In SMA-based actuators, this issue results from deformations or imperfections in the crystal structure of the actuating means, as well as possibly in other motion-transmitting components.

The problem of adjusting the displacement of the movable element and correcting any unintentional displacement is quite common in all actuators. In particular, this issue is further impacted when precise partial displacements of the movable element are required.

Additionally, when operating in high-pressure or high-temperature environments, reaction forces driven by the working fluid on the movable element may be present, e.g. from the pressure of the fluid itself, which can contribute to the above-mentioned phenomenon.

In order to guarantee precise displacement of the movable element, these actuators must be calibrated to the specific operating parameters within a given working system, which can necessarily be obtained by means of appropriate detecting means or sensors.

In the prior art, detecting means arranged externally to the actuator are generally used to obtain measurements on certain parameters of the working environment, e.g. temperature, pressure, volume or similar sensors. Disadvantageously, such sensors often require high power consumption for their activation.

However, these detecting means may have different accuracy values depending on the environmental conditions of the system where they operate. For example, some of the above-mentioned sensors may perform differently when operating in low-temperature environments than in higher- temperature environments.

Additionally, such actuators connected to the aforementioned detecting members are often not easily miniaturised overall, thus penalising the overall footprint within such systems employing such actuators.

The object of the present invention is to provide an actuator for an electromechanical valve for managing a flow of a working fluid comprising an actuating means made of shape memory alloy material able to overcome the problems arising in the prior art.

In particular, the object of the present invention results in an actuator able to control the displacement of a movable body, being able to measure or receive measurements of state parameters of the actuator itself, and acting in feedback to calibrate and/or correct the actual displacement of the movable body under different operating conditions of the working environment.

It is a further object of the present invention to provide an actuator for an electromechanical valve comprising detecting means arranged on the actuator itself, in conjunction with or in the absence of detecting means external to said actuator, so as to accurately detect the displacement made by the movable body of the actuator.

A further object of the present invention is to provide detecting means comprised in the above-mentioned actuator such that they are miniaturised, immune to the conditions of the working environment and have low power consumption.

A further object of the present invention is to provide a system for managing a flow of a working fluid employing the aforementioned actuator comprising an actuating means made of shape memory alloy material and a feedback control unit employing as input state parameters of said actuator, derived or derivable by means of the aforementioned detecting means.

The specified technical task and purposes are substantially achieved by an actuator for an electromechanical valve or the like for managing a flow of a working fluid comprising an actuating means made of shape memory alloy material and a feedback control unit, comprising the technical features set forth in one or more of the appended claims.

In particular, this technical task and the specified purposes are basically achieved by an actuator for an electromechanical valve for managing a flow of a working fluid. The actuator comprises a stationary body and a movable body, the movable body being movable relative to the stationary body. The actuator comprises at least one actuating means, made of shape memory alloy material, interposed and/or connected or connectable, preferably in a fixed manner, between the stationary body and the movable body. The actuating means is deformable so as to realise a relative displacement of said movable body relative to said stationary body. The actuator performs the deformation of the actuating means by means of at least one current generator, adapted to generate an electric current submitted or submittable to the actuating means and to modify the intensity of said electric current applied so as to obtain specific reference deformations of the actuating means. The actuator controls the relative displacement of the stationary body with respect to the movable body by means of a feedback control unit able to send command signals to the generator in order to generate specific electric current intensities corresponding to the specific deformations of the actuating means. The feedback control unit is configured to measure or receive measurements of state parameters of the actuator and to compare them with reference state parameters of the actuating means itself. If the comparison shows that the measured state parameter differs from the reference state parameter, the feedback control unit changes the electric current intensity to make the necessary corrections and obtain the required reference state parameter.

The actuating means is able to detecting state parameters of the actuator itself by appropriate detecting means.

In particular, a first type results in displacement detecting means, capable of taking measurements of the displacement of the movable body relative to the stationary body and communicating these displacement measurements to the feedback control unit. In particular, such means are implemented in the form of an inductive circuit arranged on the stationary body to create a magnetic field by self-induction. The movable body, on the other hand, is magnetically permeable. The relative displacement of the movable body relative to the stationary body causes a variation of the intensity of the magnetic field within the inductive circuit.

A second type results in detecting means of the resistance of the electric current passing through the actuating means. It comprises at least two electrical resistance detecting means arranged along the actuating means, adapted to measure the value of the electrical resistance of said actuating means as a function of the specific deformations assumed and to communicate this measurement to the feedback control unit.

The actuating means uses the state parameters detected by the above- mentioned detecting means as input signals to the feedback control unit. The output feedback control unit is able to command the current generator the intensity of the current to be submitted to the actuating means by employing a proportional-integral-derivative control process as feedback. According to a preferred but not exclusive embodiment, the actuating means is characterised by comprising the movable body relative to the stationary body by means of a linear translation.

This displacement is achieved by means of an actuating means implemented in the form of at least one linear or threadlike element mechanically connected or connectable between the movable body and the stationary body and electrically connected or connectable to the generator. This implementation means is deformable by longitudinal contraction and/or by longitudinal expansion. Further, this displacement of the movable body relative to the stationary body is assisted by connecting means, interposed between or connecting the movable body and the stationary body.

Further, the specified technical task and purposes are substantially achieved by a flow of a working fluid management system comprising a shape memory system actuator, an inlet channel, an outlet channel and an electromechanical valve adapted to manage a flow of a working fluid between the inlet channel and the outlet channel, actuated or actuatable by the actuator. This system takes a configuration comprised between a blocking configuration, wherein the system prevents the passage of a flow of said working fluid, and at least one flow configuration wherein the system allows the passage of a corresponding flow of said working fluid.

This system manages this flow by means of a shutter linearly movable and mechanically connected to the movable actuator body. This system is able to remain in the blocking configuration in the event of an unintentional interruption of the power supply to said actuator.

Additionally, such a system is able to manage a flow of fluid in both directions relative to the inlet channel and the outlet channel.

Further features and advantages of the present invention will become clearer from the indicative, and therefore non-limiting, description of a preferred, but not exclusive, embodiment of an actuator for an electromechanical valve for managing a flow of a working fluid and a system for managing a flow of a working fluid employing such an actuator. Such description will be set forth herein below with reference to the accompanying drawings, provided for merely indicative and therefore nonlimiting purposes, wherein:

- figure 1 is a representation of a top view of an embodiment of a linear actuator comprising a wire actuation means made of shape memory alloy material;

- figure 2 is a representation of a side view of an “S” section of the actuating means depicted in figure 1 ;

- figure 3 is an exploded view of the actuator shown in figure 1 ;

- figure 4 is a representation of a top view of an embodiment of a system for managing a flow of a working fluid comprising an actuator depicted in figure 1 in conjunction with a solenoid valve, comprising a partial section representing the inside of the solenoid valve;

- figure 5 is a representation of a side view of an “S” section of the system for managing a flow of a working fluid depicted in figure 4. With reference to the appended figures, (1) indicates an actuator for an electromechanical valve (130) for managing a flow of a working fluid comprising an actuating means (2) made of shape memory alloy material and a feedback control unit (3).

The actuator comprises a stationary body (4) and a movable body (5), preferably arranged adjacent to each other, connected or connectable to each other. In particular, the movable body (5) is movable relative to the stationary body (4). The stationary body (4) is preferably anchored securely to the working environment.

Preferably, the stationary body (4) and the movable body (5) are mutually engaged by means of connecting means (6), interposed between or connecting said movable body (5) and said stationary body (4). These connecting means (6) are adapted to assist the relative displacement of the movable body (5) relative to the stationary body (4).

In Figures 1 , 2 and 3, a preferred but not exclusive embodiment of the actuator (1 ) is illustrated: in particular, the actuator (1 ) has a movable body (5) which can be moved relative to the stationary body (4) by means of a linear translation.

In particular, the movable body (5) is essentially implemented in the form of a rectangular parallelepiped. The stationary body (4) is also implemented in the form of a parallelepiped, but with larger plan dimensions than the movable body (5).

The movable body (5) is aligned longitudinally relative to the stationary body (4), preferably arranged in an overlapping manner. With reference to figure 3, in the current embodiment, the stationary body (4) has connecting members (6) with the movable body (5), consisting of at least one sliding channel (7) accommodating at least one extension (8) of the movable body (5), compatible in shape with said sliding channel (7) and allowing the movable body (5) to slide longitudinally in a linear manner relative to the stationary body (4). Generally, a movable body (5) of an actuator can itself be the active component of an actuator in order to perform certain mechanical tasks, e.g. opening or closing the passage of a flow of fluid within a valve, or as an intermediary on a third element acting as a movable core, e.g. a piston, a shutter of a solenoid valve and the like.

For illustrative purposes only, in the present preferred embodiment, the movable body (5) acts as an intermediary on a third acting element.

In various embodiments not depicted in these figures, the displacement of the movable body (5) relative to the stationary body (4) may present a different trajectory than the trajectory described above, for example, it may present a rotational or roto-translational trajectory. For example, a movable body (5) and a stationary body (4) may have a cylindrical geometry, arranged on the same axis, wherein the movable body (5) is displaced by axial rotation or axial roto-translation relative to the stationary body (4).

Displacement of the movable body (5) relative to the stationary body (4) takes place via the actuating means (2) made of shape memory alloy material. Generally, the actuating means (2), depending on the arrangement between the stationary body (4) and the movable body (5), its geometry and the intensity of the applied current (which causes an increase in temperature by means of the Joule effect) can undergo various deformations, preferably a contraction and/or expansion in a privileged direction, moving the movable body (5) along a specific trajectory. By means of appropriate empirical tests, a proportionality relationship can be obtained between the applied current intensity and the amount of deformation of the actuating means (2) employed.

The actuating means (2) may be interposed between the stationary body (4) and the movable body (5) and/or connected or connectable to the stationary body (4) and the movable body (5).

In the present embodiment illustrated in the appended figures, the actuator (1 ) comprises a linear or threadlike actuating means (2) connected or connectable to the movable body (5) and the stationary body (4), so that it contracts and/or expands longitudinally, permitting a linear translation of the movable body (5) relative to the stationary body (4). In particular, the actuating means (2) is a wire, bent into a “U” shape.

The actuating means (2) has a first end (9a) and a second end (9b) fixed integrally to the stationary body (4) by means of at least a first set of fastening means (10). In the portion (11 ) bent into a “U” shape, the wire is arranged around a transmission element (12) which is attached to the movable body (5) by means of a second set of fastening means (13) and, preferably, as round as possible to avoid bending the actuating means (2) at excessively acute angles.

Preferably, the connecting members 6 comprise at least one compensating member (14) connecting the stationary body (4) and the movable body (5). Preferably, this compensating member (14) is arranged at one end pair of the stationary body (4) and the movable body (5) correspondingly.

The compensating member (14) provides additional support in the mutual connection between the stationary body (4) and the movable body (5). More precisely, the compensating member (14) has a first component (15) fastened integrally to the stationary body (4) by means of a first set of fastening elements (16) and a second component (17) fastened integrally to the movable body (5) by means of a corresponding fastening element (not shown in the figures).

The first component (15) and the second component (17) are engaged by means of the intermediation of at least one flexible element (18), preferably elastic, even more preferably a set of helical springs. The presence of this flexible member (18) allows elastic interaction between the first component (15) and the second component (17) and, consequently, between the stationary body (4) and the movable body (5).

In particular, in the present embodiment, this compensating member (14) is able to mediate the relative displacement between the movable body (5) relative to the stationary body (4), caused by the deformation of the actuating means (2), in order to make the aforementioned relative displacement more precise.

In particular, the wire constituting the actuating means (2) is tensioned by a first group of fastening members (10) integral with the stationary body (4) and between the transmission member (12) attached to the movable body (5) by means of the second group of fastening members (13) and can undergo two types of deformation. The type of deformation is chosen appropriately depending on the desired type of displacement of the movable body (5) relative to the stationary body (4).

In the first case, the wire corresponding to the actuating means (2) undergoes contraction when subjected to an electric current. This contraction is able to transmit a tensile force on the movable body (5) relative to the stationary body (4). This contraction causes a displacement of the movable body (5) in the direction of the arrangement of the first set of fastening members (10) of the actuating means (2). The newly achieved balance position is mediated by the compensating member (14), pushing with elastic force in the opposite direction to the direction of contraction of the wire corresponding to the actuating means (2).

Alternatively, the wire corresponding to the actuating means (2) undergoes expansion when subjected to an electric current. In such circumstances, the compensating member (14) causes a thrust by means of elastic force on the movable body (5) in the opposite direction to the constraining reaction exerted by the first set of fastening members (10), as permitted by the expansion of the wire corresponding to the actuating means (2), until a new balance position is reached.

In the present embodiment, advantageously, the first set of fastening elements (16) comprises a sub-set (16a) such that this sub-set fastens the first set of fastening members (10) of the ends (9a) and (9b) of the actuating means (2) by means of the first component (15) of the compensating member (14). For illustrative purposes only and not depicted in these figures, a different embodiment may be envisaged, which may include an actuating means

(2) having a different geometry from the linear shape mentioned above. For example, such a geometry can result in a helical arrangement of a wire made of shape memory alloy material. This actuating means (2) may be interposed between a stationary body (4) and a movable body (5), both of which have a cylindrical geometry and are arranged in such a way that they are arranged on the same axis and each attached to a corresponding end of the actuating means (2). Thus, a deformation of the actuating means (2) would correspond to a rotation or roto-translation of the movable body (5) relative to the stationary body (4) about the common axis on which they are arranged.

The electric current applied to the transmission means is transmitted at appropriate transmission points arranged along the body of the transmission means itself.

In the embodiment illustrated in the appended figures, these transmission points correspond to the first group of fastening members (10).

Advantageously, the first group of fastening members (10) also acts as electrodes through which the transmission of the electric current takes place. In alternative embodiment, different modes and points of electric current transmission can be envisaged.

The electric current can have different values of current intensity, generated and controlled by a current generator (not shown in these figures). This current generator is controlled by the feedback control unit

(3). The proportional deformation of the actuating means (2) is driven by the feedback control unit (3), which sends command signals to the generator to generate a specific current intensity for a specific time interval, in order to achieve a specific temperature of the actuating means (2) due to the Joule effect and consequently a specific deformation of the actuating means (2) itself. In this way, the feedback control unit (3) is able to drive the displacement of the movable body (5) relative to the stationary body (4). depending on the type of drive required by the movable body (5). For example, the movable body (5) is able to perform a simple actuation such as managing the opening or closing of a valve (130) or a complex actuation such as linear volume regulation of a flow through a calibrated hole.

In the present embodiment illustrated in the appended figures, this generator and feedback control unit (3) are advantageously arranged on a single printed circuit board or PCB (19). This PCB (19) can be single-layer or multi-layer, wherein he various layers are arranged in an overlapping manner so as to recover space and reduce the overall longitudinal footprint of the actuator (1 ), depending on the arrangement of the feedback control unit (3) and the generator but also on the type number of additional circuits to be utilised.

In particular, in the present embodiment, the PCB (19) is secured to the stationary body (4) by means of appropriate fastening means (20).

The feedback control unit (3) is able to perform specific internal processing in order to derive the required deformation of the actuating means (2) and consequently the overall displacement of the movable body (5). The feedback control unit (3) is able to operate both autonomously from the outside and receive feedback of state parameters that can be obtained detected from the outside. In particular, these state parameters can be entered either by means of a command from a human operator or by means of other systems. In particular, the PCB (19) is equipped with appropriate connections, by means of which the actuator (1) can in fact be placed in communication with the outside world via WIFI, Bluetooth, Nb- loT and the like. In particular, in the present embodiment, appropriate peripheral ports (21 ) may be present on the PCB (19) to transmit the information communicated from outside via appropriate circuited paths to the feedback control unit (3) in order to obtain the aforementioned parameters. Advantageously, the feedback control unit (3) is configured to measure or receive measurements of state parameters not only from outside, but also from within the working environment and to compare them with reference state parameters. If from said comparison shows that said measured state parameter differs from said reference state parameter, the feedback control unit (3) calculates the appropriate corrections to be made and sends feedback command signals to the generator to control the actual electric current intensity to be applied to the actuating means (2) in order to achieve an alignment of the actuator's (1 ) behaviour to the correct reference state parameter under analysis.

State parameters that can be obtained internally from the working environment can include measurements of the temperature of a fluid, the pressure of a working fluid, the flow rate of a working fluid or the like.

These parameters can be obtained by means of corresponding detecting means (not shown), generally corresponding to sensors known in the state of the art.

A subset of the peripheral ports (21 ) can also be used to connect such detecting means to the feedback control unit (3).

Advantageously, the actuator (1 ) is also able to operate independently of the above-mentioned external acquisition peripherals, i.e., of state parameters such as temperature, pressure or flow rate of a working fluid and the like.

In particular, this useful effect is achieved by exploiting displacement detecting means (22) to directly measure the extent of the translation of the movable body (5) with respect to the stationary body (4).

This displacement detecting means (22) uses an inductive displacement transducer sensor, more precisely, a linear variable differential transformer or LVDT. Although this technology is known in the state of the art, it has no use in displacement measurements of movable bodies within actuators, and in particular, actuators employing SMA actuating means. Advantageously, an LVDT sensor has several positive aspects, including high accuracy and high detection speed, micrometric resolution, high tolerance to use in very high temperature environments, and has a much lower power consumption required for operation than other types of sensors.

The use of an LVDT sensor is particularly effective when measurements are required in actuators with a range of working positions, such as in the case of volumetric solenoid valves with partial openings, able to detect openings of a few micrometres in order to ensure a specific flow rate.

This LVDT sensor is preferably placed or available out of contact with the working environment in order to be further shielded from the environmental conditions. This LVDT sensor is particularly suitable for use in actuators using SMA actuating means as, unlike a solenoid actuator, it is sensitive to external magnetic fields. In particular, an SMA actuating means (2) also produces a magnetic field due to the current flowing through it, however, this magnetic field is modest given the low current intensities used and can be neglected if the actuating means (2) is positioned carefully at a certain distance from the LVDT sensor itself.

An LVDT sensor measures the variation in inductive coupling between two groups of coils, the first group comprising at least one coil, known as the primary winding, and the second group comprising linear differential transformers, consisting of a transformer with two equal and symmetrical secondary windings connected in “push-pull” mode. The primary winding is inductively coupled with the secondary windings. In particular, the primary winding is connected to a source of electric current and enables the creation of a magnetic field.

The inductive coupling between the primary winding and the secondary windings is influenced by the position of a body made of magnetically permeable material called the “target”, which is formed in such a way as to make relative displacements of the aforementioned primary winding and secondary windings. Using this magnetic field produced by the primary winding, an induced current proportional to the position of the core is produced in the secondary windings. This causes the target position information to be transformed into an electrical signal. When the target is in the rest position, generally arranged in a central position relative to the two secondary windings, the difference between the two mutual inductances of the two secondary windings is null. The ratio of the energy transmitted by induction on each of the secondary windings, on the other hand, varies in the case of relative displacement of the target, and in particular depending on the direction, it being possible to discriminate a more intense inductive coupling with one rather than the other secondary winding. As a result, the signal output by each secondary winding and detectable by the control unit will also vary proportionally to the displacement of the target. By exploiting phase discriminating demodulators, it is subsequently possible to translate the signal output by the secondary windings into a signal representative of the displacement of the “target” such that it can be interpreted by the control unit.

In the present embodiment, this displacement detecting means (22) is arranged or available directly on the actuator (1 ) itself, so that it detects the actual relative displacement of the movable body (5) relative to the stationary body (4). In particular, displacement detecting means (22) of the LVDT type implemented in the form of an inductive circuit placed on the stationary body (4) is used. The movable body (5), on the other hand, is equipped with a magnetically permeable body or “target” arranged integrally with the movable body (5) itself in a dedicated housing (23). In more detail, this inductive circuit corresponds to the primary winding and, more precisely, results in a circuit path arranged on the PCB (19) (not shown in these figures), specifically on a portion with two fully laminated faces. The PCB (19) also has a first linear differential transformer (24) and a second linear differential transformer (25) corresponding to the two secondary windings. The target moves linearly with the movable body (5) relative to the primary winding and the secondary windings arranged on the PCB (19).

Consequently, the relative displacement of the movable body (5) relative to the stationary body (4) is detectable by the displacement detecting means (22) due to the variation of the intensity of the magnetic field detected by the secondary windings, which communicate this variation as a state parameter to the feedback control unit (3) by means of a dedicated circuit printed directly on the PCB (19).

Advantageously, the displacement detecting means (22) communicates directly with the feedback control unit (3) about the relative linear displacement of the movable body (5) relative to the stationary body (4), being able to detect and compensate for any unforeseen variations in this displacement caused by structural defects of the actuating means (2) or by the connecting members (6).

Advantageously, an LVDT sensor constructed as described above is compatible with being miniaturised for use in small actuators, limited only by the size of the PCB (19) and the target used.

In various embodiments not illustrated in these figures, displacement detecting means based on LVDT sensors can be applied to actuators with kinematics of any kind. For example, in the case of a movable body (5) and a stationary body (4) characterised by bodies with circular geometry and relative rotational or roto-translational displacement, the arrangement of the displacement detecting means based on LVDT sensors can be used in such an arrangement as to control the measurement of the angular displacement of the movable body (5) relative to the stationary body (4).

In a joint or alternative manner, the actuator according to the present invention may also provide for the exploitation of an electrical resistance detecting means (not shown in the present figures) arranged on the wire corresponding to the actuating means (2), adapted to measure the value of the electrical resistance of said actuating means (2) as a function of the specific deformations assumed and to communicate this measurement to the feedback control unit (3). Depending on the different crystal structure assumed by the actuating means (2), a specific resistance to the passage of electric current within the wire can be associated with a specific stage of the state of the SMA material or any transient states. In particular, such a measurement can be achieved by employing at least two electrical resistance detecting means arranged along said actuating means (2) at appropriate measuring points, adapted to measure the value of the electrical resistance and communicate this measured value as a state parameter of the actuator 1 to the feedback control unit (3). The feedback control unit (3), by processing this information, is able to compare this parameter with reference state parameters and drive any necessary corrective actions.

The feedback control unit (3) is able to communicate to the current generator the intensity of said current to be submitted to said actuating means (2) using a proportional-integral-derivative or PID control process as feedback. The exploitation of PID processes is known in the prior art relating to actuators comprising control units. In the present invention, the PID process is specifically exploited to dynamically drive the deformation of the actuating means (2) by dynamically varying the gains during the operating steps of the actuator (1 ).

In particular, a generic command signal comprises a sum of gains given by a proportional gain, an integral gain and a derivative gain. The PID control is comprised within the actuator preferably as a permanent logic component. In this preferred embodiment, the PID control is implemented as a permanent logic component arranged on the PCB (19) or within one of its layers.

The current generator is preferably a DC generator and includes a system able to manage the intensity of the output current by means of pulse or PWM signal modulation, with frequencies and “duty cycles” that can be dynamically modified during use and repeated over time. The “duty cycle” is the ratio between the time the square wave takes a “high” value and the period T, where “T” is the inverse of frequency: T=1/f. Preferably, the current produced and relative current intensity is fedback by the control unit and monitored by an additional dedicated microprocessor.

Advantageously, the above-mentioned features enable the actuator control unit to manage displacements of the movable body (5) with high speed and accuracy, with response times of the actuating means (2) of up to 10 microseconds. Further, the control unit is able to control and modulate the opening and/or closing speed in a deferred manner.

The shape memory system actuator can be comprised in a multitude of fluid flow management systems. In particular, such an actuator can be used in conjunction with a plurality of flow control devices, such as valves of various geometries, both linear and rotary.

Next, we present a preferred embodiment for a system (100) for managing a flow of a working fluid, respectively comprising a shape memory system actuator (1) according to the present preferred embodiment illustrated in the appended figures. In particular, this system (100) further comprises an inlet conduit (110) of a fluid flow, an outlet conduit (120) of the flow of the aforementioned fluid and an electromechanical valve (130) for managing the flow of the aforementioned fluid, between the inlet conduit (110) and the outlet conduit (120), actuated or actuatable by said actuator (1 ).

In particular, it is observed that said system (100) is able to assume a configuration comprised between a blocking configuration, wherein said system (100) by means of the closing of valve (130) prevents the passage of a flow of a working fluid, and at least one flow configuration wherein said system (100) allows the passage of a corresponding flow of a working fluid.

In the present embodiment, the valve (130) comprises: a valve body (131 ) having a main channel (132) arranged internally and passing through the entire valve body (131), and a secondary channel (133) communicating with said main channel (132) and arranged transversely to said main channel (132). The inlet conduit (110) comprises an inner channel (1 1 1 ) aligned and communicating with a first end (134) of the main channel (132). The outlet conduit (120) comprises an outlet channel (121 ), aligned and communicating with the secondary channel (133). The outlet conduit (120) is therefore arranged transversely to the main channel (132). At a second end (135) of the main channel (132) there is an opening, communicating with the outside of said valve body (131 ). A shutter (137) is arranged inside the main channel (132), sliding linearly along the main channel (132). The shutter (137) has a first portion (138) protruding from said valve body (131 ), which is mechanically connected or connectable to the movable body (5) of the actuator (1 ).

This connection is made by means of inserting and securing, preferably by interlocking, the first portion (138) of the shutter (137) within a dedicated housing (26) arranged on the movable body (5). A second portion (139) of the shutter (137), arranged in an opposite manner to said first portion (138), is arranged internally to said main channel (132) and has a preferably truncated cone geometry with the lower section oriented in the direction of the inlet conduit (1 10). The inner surface of said first end (134) of the main channel (132) communicating with the inlet conduit (1 10) is made compatible in shape with said second portion (139) of the shutter (137). This geometry allows both the total blockage of fluid flow and the passage of fluid in the event of total or partial opening of the valve (130).

The shutter (137) appears to have a central portion (140) comprised between the first portion (138) and the second portion (139).

The central portion (140) appropriately has at least one flange (141 ) and/or at least one recess (142) provided with a suitable gasket (143), altogether adapted to improve the blocking of the fluid flow when the valve

(130) is closed and to allow the fluid to flow when the valve (130) is open, but without allowing unwanted leakage of the fluid from the valve body

(131 ). In particular, the flange (141 ) appears to extend along the surface of a section (144), which is comprised in the main channel (132). This section (144) has a cross-sectional dimension compatible with the length of the flange (141 ) itself. This section (144) allows the flange (141 ) to slide along its inner surface.

Further, this section (144) has a first lateral end (145) aligned and communicating with the first inlet section (134) and a second lateral end (146) arranged adjacent to and communicating with the secondary channel (133). The total length between the first lateral end (145) and the second lateral end (146) of this section (144) corresponds to the length of the stroke of the shutter (137).

The flange (141 ) is fully adhered to the first lateral end (145), blocking the passage of the flow, when the system (100) is in the blocking configuration.

As this widening moves towards the second lateral end (146), it allows a progressive opening to the passage of the flow of a working fluid, when the system (100) is in one of the possible flow configurations.

In the blocking configuration this system (100) has the actuating means (2) of the actuator at rest and the shutter (137) closes the passage to the flow of fluid between the inlet conduit (110) and the outlet conduit (120). Additionally, the system (100) provides for the valve (130) to remain in this blocking configuration or to spontaneously return to this configuration in the event of an unintentional interruption of the power supply to the actuator (1) itself.

When the system (100) needs to assume a flow configuration, the feedback control unit (3) drives a certain current intensity to the actuating means (2). In the present embodiment of the system (100), this current leads to deformation by contraction of this actuating means (2). This contraction is accompanied by a translation of the movable body (5), which in turn causes the linear translation of the shutter (137), loosening the flange (141 ) from the first lateral end (145). This translation corresponds to a response to the traction action of the shutter (137) itself, causing it to open to the passage of the flow of working fluid between the inlet conduit (110) and the outlet conduit (120).

The shutter (137) is in a blocking configuration when the actuating means (2) of the actuator (1 ) is at rest. In specific cases, this management system (100) may provide for managing a flow of working fluid in both directions between said inlet channel (110) and said outlet channel (120). Since this shutter (137) is in a blocking configuration when the actuating means (2) of the actuator (1 ) is at rest, the use of an inverted flow from the outlet conduit (120) to the inlet conduit (110) is preferable in circumstances where fluid flow management is required using a more facilitated closure of fluid passage, such as, for example, when managing turbulent working fluids or pressure surges.

Claims

1. Actuator (1 ) for an electromechanical valve (130) for managing a flow of a working fluid, wherein said actuator comprises:

- a stationary body (4);

- a movable body (5);

- at least one actuating means (2), made of a shape memory alloy material, interposed between and/or connected or connectable to said stationary body (4) and said movable body (5) and deformable so as to perform said relative displacement of said movable body (5) relative to said stationary body (4);

- at least one electric current generator adapted to generate an electric current to be submitted to said actuating means (2) and to modify an intensity of said electric current applied to said actuating means (2) so as to obtain specific reference deformations of said actuating means (2); and

- a feedback control unit (3) adapted to control said relative displacement of said movable body (5) with respect to said stationary body (4), by sending control signals to said electric current generator in such a way as to obtain specific electric current intensities corresponding to said specific reference deformations, said feedback control unit (3) being configured to measure or receive measurements of state parameters of said actuation means (2) and to compare them with reference state parameters of said actuating means (2) in such a way that if from said comparison it appears that said measured state parameter differs from said reference state parameter, said feedback control unit (3) modifies said intensity of the electric current to obtain said reference state parameter, characterised in that it further comprises:

- displacement detecting means (22) adapted to measure the displacement of said movable body (5) relative to said stationary body (4) and communicating said displacement measurements to said feedback control unit (3), said displacement detecting means (22) being implemented in the form of an inductive circuit arranged on said stationary body (4) adapted to create a magnetic field by self-induction, wherein:

- said movable body (5) is provided with a magnetically permeable body and wherein said relative displacement of said movable body (5) relative to said stationary body (4) causes a variation of the intensity of said magnetic field within said inductive circuit; and wherein

- said feedback control unit (3) commands, to said electric current generator, the intensity of said current to be submitted to said actuating means (2) by employing a proportional-integral-derivative control process.

2. Actuator, according to claim 1 , comprising at least two electrical resistance detecting means arranged along said actuating means (2), adapted to measure the value of the electrical resistance of said actuating means (2) based on the specific deformations taken and to communicate said electrical resistance value to said feedback control unit (3).

3. Actuator, according to one or more of the preceding claims, wherein said movable body (5) is movable relative to said stationary body (4) by means of a linear translation.

4. Actuator according to claim 1 wherein said actuating means (2) is implemented in the form of at least one linear or threadlike element mechanically connected or connectable between said movable body (5) and said stationary body (4) and electrically connected or connectable to said generator.

5. Actuator according to claim 4, wherein said linear or threadlike element is deformable by longitudinal contraction and/or by longitudinal expansion.

6. Actuator, according to one or more of the preceding claims, wherein said actuator comprises connecting means (6), interposed between or connecting said movable body (5) and said stationary body (4), adapted to assist the relative displacement of said movable body (5) relative to said stationary body (4).

7. System (100) for managing a flow of a working fluid comprising:

- a shape memory system actuator (1) according to one or more of the preceding claims;

- an inlet channel (110);

- an outlet channel (120);

- an electromechanical valve (130) for managing a flow of a working fluid between said inlet channel (110) and said outlet channel (120), actuated or actuatable by said actuator (1 ); wherein said system (100) takes a configuration comprised between a blocking configuration, wherein said system (100) prevents the passage of a flow of said working fluid, and at least one flow configuration wherein said system (100) allows the passage of a corresponding flow of said working fluid.

8. System (100) for managing a flow of a working fluid according to claim 7, wherein said valve (130) comprises a shutter (137) linearly sliding and mechanically connected to said movable body (5) of the actuator (1 ).

9. System (100) for managing a flow of a working fluid according to claim 7 or 8, wherein said valve (130) remains in said blocking configuration in the event of accidental interruption of the power supply to said actuator (1 )-

10. System (100) for managing a flow of a working fluid according to claim 7 or 8 or 9, wherein said management system (100) is capable of managing a flow of a working fluid in both directions between said inlet channel (110) and said outlet channel (120).