Method of compensating for the hysteresis of an electrically operable actuator and piezoelectric valve implementing such method

Abstract

A method of compensating for the hysteresis of an electrically operable actuator, for example a piezoelectric valve, and controllable by applying a variable input driving voltage (Vin), comprises the steps of : - defining a first threshold value (β); if the over-time variation rate of the input driving voltage is lower than or equal to said first threshold value, calculating a compensated driving voltage value (Vcom) proportional to the value of the input driving voltage according to a proportionality coefficient dependent on the sign of the variation of the input driving voltage with respect to the last set value of the input driving voltage; if the over-time variation rate of the input driving voltage is greater than said first threshold value, said compensated driving voltage value (Vcom) corresponds to the value of the input driving voltage (Vin).

Description

"METHOD OF COMPENSATING FOR THE HYSTERESIS OF ANELECTRICALLY OPERABLE ACTUATOR AND PIEZOELECTRIC VALVE IMPLEMENTING SUCH METHOD" DESCRIPTION

[0001] The present invention relates to electrically operable actuators and particularly refers to a method of compensating for the hysteresis of such actuators.

[0002] A specific object of the present invention is also a fluid shut-off valve, for example compressed air, which employs a piezoelectric actuator to regulate the fluid flow in the valve.

[0003] As known, an unfavourable feature of some electrically driven actuators, such as piezoelectric actuators, is their hysteresis. This phenomenon results in that, when the supply voltage of the actuator is varied from a first value to a second value, and subsequently the supply voltage is brought back from the second value to the first value, the final excitation magnitude of the actuator, for example of the piezoelectric plate, does not correspond to the initial one obtained by nominally applying the same first voltage value.

[0004] Several methods have been proposed to compensate for the hysteresis phenomenon. Such methods, althoughtheoretically effective, nevertheless entail a use of computational resources such that they are not acceptable in certain application fields, particularly for reasons related to the space and / or costs required by such computational resources.

[0005] A typical example of application which would require containment of the space and production costs of the electronics necessary to implement a hysteresis compensation algorithm is fluid shut-off valves, for example compressed air, with piezoelectric actuator, in particular for the industrial automation sector. Indeed, the valves used in automation fields are increasingly miniaturised and, given their ever-wider use, must be robust, reliable and must not exceed a certain threshold cost of an automation plant.

[0006] An object of the present invention is to propose a method of compensating for the hysteresis of an electrically driven actuator which, while being able to significantly reduce the hysteresis phenomenon, requires a more limited use of computational resources compared to known algorithms.

[0007] Another object of the present invention is to propose a fluid shut-off valve provided with a piezoelectricactuator and electronic devices which allow the hysteresis of the piezoelectric actuator to be reduced without significantly affecting the dimensions and the production costs of the valve.

[0008] These objects are achieved with a method according to claim 1, with a piezoelectric actuator according to claim 8, and with a fluid shut-off valve according to claim 9. The dependent claims describe preferred or advantageous embodiments of the invention.

[0009] The features and advantages of the method, actuator, and valve according to the invention will however be evident from the following description of its preferred embodiments, given by way of illustration and not limitation, with reference to the accompanying figures, in which:

[0010] - Figure 1 is a flow diagram of method of compensating for the hysteresis according to the invention;

[0011] - Figure 2 is a flow diagram of the method of compensating, in a variant embodiment;

[0012] - Figure 3 is a block diagram of a piezoelectric actuator according to the invention;

[0013] - Figure 4 is an exploded perspective view of an example of a piezoelectric actuator according to the invention;

[0014] - Figure 5 is an exploded perspective view of an example of a fluid shut-off valve according to the invention;

[0015] - Figure 6 is a perspective view of the assembled valve;

[0016] - Figure 7 is an axial section of the valve of figure 6;

[0017] - Figures 8, 8a, 8b and 8c show respective flow rate diagrams of the valve as a function of the voltage applied to the piezoelectric actuator, in the absence of hysteresis compensation; and

[0018] - Figures 9, 9a, 9b and 9c are the same diagrams as figures 8-8c, but wherein the curves represented by solid lines represent hysteresis cycles in the case of a valve provided with a control unit configured to implement the hysteresis compensation method according to the invention.

[0019] In the following description, all directional references (for example, upper, lower, upward, downwardleft, right, leftward, rightward, top, bottom, above, below, vertical, horizontal, clockwise, and counterclockwise) are used solely for identification purposes to assist the reader in understanding the described embodiments and do not create limitations, particularly with regard to the position, orientation or use of the described embodiments.

[0020] Connection references (for example, fixed, coupled, connected and the like) must be interpreted broadly and may include intermediate elements between a connection of elements and relative movement between elements. Therefore, connection references do not necessarily imply that two elements are directly connected and in a fixed relationship to each other.

[0021] Figure 1 is a flow diagram of a method of compensating for the hysteresis 500 for a piezoelectric actuator, in an embodiment. The piezoelectric actuator is controllable by applying an input driving voltage (Vin). The input driving voltage is variable, for example continuously, within a range of input driving voltages.

[0022] The method provides (step 502) for defining a first threshold value (p) related to the over-time variation rate of the input driving voltage (Vin).

[0023] A variation rate (Vin) of the input driving voltage (Vin) is calculated (step 504) with respect to the last set value of the input driving voltage.

[0024] The method therefore comprises a comparison step 506 between the over-time variation rate (V±n) of the input driving voltage (V±n) and the first threshold value (p).

[0025] If the over-time variation rate (V±n) of the input driving voltage (V±n) is lower than or equal to the first threshold value (p), a compensated driving voltage value (Vcom) is calculated (step 508), which is proportional to the value of the input driving voltage (V±n) according to a proportionality coefficient dependent on the sign of the variation of the input driving voltage with respect to the last set value of the input driving voltage.

[0026] If, on the other hand, the over-time variation rate of the input driving voltage is greater than the first threshold value, a compensated driving voltage value (Vcom) equal to the value of the input driving voltage (V±n) is assumed (step 510).

[0027] The actuator is supplied (step 512) with an actuator driving voltage value (Vout) calculated on the basis of said compensated driving voltage value (Vcom).

[0028] Therefore, the method of compensating considers both the speed at which the input driving voltage varies and the direction of the variation, that is, whether the input driving voltage is increasing or decreasing.

[0029] In particular, the first threshold value (p) can be determined to identify a very sudden variation, as in the case of a driving voltage having the form of a square wave. In this case, hysteresis compensation is not performed and the compensated driving voltage corresponds in fact to the input driving voltage.

[0030] If instead the variation rate of the input driving voltage is equal to or lower than the preset threshold value, hysteresis compensation is actually applied and the compensated driving voltage corresponds to the input driving voltage multiplied by a proportionality factor whose value depends on the sign of the variation of the input driving voltage, that is, whether such voltage is increasing or decreasing.

[0031] In particular, the inventors have experienced that good hysteresis compensation is also obtained using a constant proportionality factor.

[0032] Therefore, the proportionality coefficient may take a constant value greater than 1 (1+a), in the case of anincrease in the input driving voltage with respect to the last set input driving voltage value, or a constant value lower than 1 (1-a), in the case of a decrease in the input driving voltage with respect to the last set input driving voltage value.

[0033] Figure 2 is a flow diagram of an embodiment 600 of the hysteresis compensation method which also considers the maximum width of the hysteresis loop of the actuator.

[0034] In particular, the method provides for defining, in addition to the first threshold value (p) (step 602), a second threshold value (A) (step 604) dependent on the maximum width of the hysteresis loop.

[0035] As with the embodiment of the hysteresis method 500 previously described, a variation rate (Vin) of the input driving voltage (Vin) with respect to the last set value of the input driving voltage is calculated (step 606).

[0036] The method comprises a comparison step 608 between the over-time variation rate (Vin) of the input driving voltage (Vin) and the first threshold value (p).

[0037] If the over-time variation rate of the input driving voltage is greater than the first threshold value, a compensated driving voltage value (Vcom) equal to the valueof the input driving voltage (Vin) is assumed (step 610).

[0038] If the over-time variation rate (Vjn) of the input driving voltage (Vin) is lower than or equal to the first threshold value (p), the method comprises a comparison step 612 between the maximum width (A) of the hysteresis loop and the second threshold value (A).

[0039] If the maximum width of the hysteresis loop (A) is lower than said second threshold value (A), the hysteresis compensation method 600 proceeds similarly to the method previously described. A compensated driving voltage value (Vcom) is therefore calculated (step 614), which is proportional to the value of the input driving voltage (Vin) according to a proportionality coefficient dependent on the sign of the variation of the input driving voltage with respect to the last set value of the input driving voltage.

[0040] If instead the maximum hysteresis width is greater than said second threshold value (A), then the compensated driving voltage value (Vcom) corresponds to the value of the input driving voltage (V±n) to which the second threshold value (A) is added or subtracted, depending on the sign of the variation of the input driving voltage with respect to the last set input driving voltage value(step 616).

[0041] The actuator is supplied (step 618) with an actuator driving voltage value (Vout) calculated on the basis of the compensated driving voltage value (Vcom).

[0042] Therefore, the second condition based on the maximum width of the hysteresis loop allows avoiding algorithm saturation situations, by setting a maximum cap to the compensation.

[0043] For example, the second threshold value may be chosen as the average of the hysteresis loop width values, which, with good approximation, can be defined as half the maximum width value (A= 4max / 2).

[0044] In one embodiment, the compensated driving voltage value (Vcom) is mathematically calculated as: )and with (sgn(Vin), if |7in|< / ? lo, if\vin\>p<z, / ?,A are constant parameters, and wherein the function sgn (x) assumes the value 1 or -1 depending on the sign of its argument (x).

[0045] In this embodiment, the variation rate of the input driving voltage corresponds to the first derivative of the over-time variation of the input driving voltage.

[0046] In one embodiment, the actuator driving voltage value (Vout) corresponds to the compensated driving voltage value (VCOmp), compared to a wider range of actuator driving voltages than the range of input driving voltages. Such range of actuator driving voltages may, for example, correspond to the range of driving voltages compatible with the electrical characteristics of the piezoelectric actuator.

[0047] For example, the range of input driving voltages may be between 0V and 10V. The actuator driving voltage may, for example, vary between 0V and 260V.

[0048] Therefore, in one embodiment the method of compensating for the hysteresis provides, once the compensated driving voltage has been calculated, to convert such voltage into an actuator driving voltage (Vout) compared to a range of actuator driving voltages, for example the range 0-260V.

[0049] The method of compensating for hysteresis described above may be advantageously adopted in all those applications which require limited dimensions and / or costsof the control electronics implementing the compensation method.

[0050] For example, in the industrial automation sector, the proposed compensation method may be used to compensate for the hysteresis of a solenoid of an electropneumatic valve or of a piezoelectric actuator of a fluid shut-off valve.

[0051] In the following description, by way of example, reference will be made to a piezoelectric actuator and to a fluid shut-off valve employing the piezoelectric actuator.

[0052] Figure 3 shows a block diagram of a piezoelectric actuator 200 according to the invention.

[0053] Figure 4 shows, in an exploded perspective view, an example of a practical embodiment of a piezoelectric actuator 200 according to the invention, particularly adapted to be integrated into a fluid shut-off valve.

[0054] The piezoelectric actuator 200 comprises a piezoelectric plate 202 adapted to deform when activated by the application of an electric driving voltage.

[0055] The piezoelectric plate 202 is driven by an electronic processing unit 204. The electronic processing unit 204 is adapted to drive the piezoelectric plate 202 by means ofa variable driving voltage within a range of driving voltages, for example from 0 to 260V.

[0056] The piezoelectric actuator 200 comprises actuator control means operable to set an input driving voltage readable by the electronic processing unit 204. For example, the actuator control means comprise a voltage selector 206, for example of the analog type, operable by a user to set a desired input driving voltage.

[0057] The electronic processing unit 204 is programmed to implement the method of compensating for the hysteresis described above, so as to drive the piezoelectric plate 202 with a compensated driving voltage Vcombased on the input driving voltage Vin.

[0058] In the embodiment illustrated in the block diagram of figure 3 and in the example of figure 4, the processing unit 202 is based on a microcontroller, for example a microcontroller operating in 32-bit and with integers.

[0059] Moreover, the processing unit comprises an amplifier stage 208 which, as explained above, is responsible for converting, more precisely amplifying, for example with a step-up converter circuit, the value of the input driving voltage, after compensation, into an actuator driving voltage value Vout compatible with the electricalcharacteristics of the piezoelectric plate 202.

[0060] In the block diagram of figure 3 there are also shown an electrical connector 210, for connecting the piezoelectric actuator to a power supply source and to a possible remote control interface, a power supply unit 212 for powering the amplification stage 208, a power control device 214 of the processing unit 204, and a diagnostic interface 216, for example with LEDs.

[0061] Figure 4 illustrates a practical example of implementation of the piezoelectric actuator 200, designed in particular to be used in the fluid shut-off valve described further below.

[0062] The piezoelectric plate 202 is connected, through electrical contacts 218, to an electronic board 220 on which the microcontroller-based processing unit 204, the amplification stage 208, and the circuit components necessary for the operation of the piezoelectric actuator are mounted.

[0063] The electronic board 220 is made in two overlapping parts in order to contain the dimensions of the actuator.

[0064] An elastic pusher element 30 may be associated with the piezoelectric plate 202, adapted to return thepiezoelectric plate 202 to an inactive position upon cessation of the electrical signal causing its deformation.

[0065] Figures 5-7 illustrate an example of a fluid shut-off valve 1, such as compressed air, which employs the piezoelectric actuator of figure 4.

[0066] In one embodiment, the shut-off valve 1 comprises a valve body 10 having an inlet duct 12 for a pressurised fluid, an outlet duct 14 for the fluid, and a valve seat 16 which puts the inlet duct 12 and the outlet duct 14 in fluid communication.

[0067] The piezoelectric plate 202 of the piezoelectric actuator 200 is housed in the valve body 10 and is adapted to deform when activated by a variable driving voltage within a range of driving voltages to adjust the fluid passage port through the valve seat 16 according to the value of the driving voltage.

[0068] In or on the valve body 10, the electronic circuitry 220 is housed, comprising the electronic processing unit 204 adapted to drive the piezoelectric plate 202 by means of the driving voltage.

[0069] The actuator control means operable to set an input driving voltage readable by the electronic processing unitare connected to the electronic processing unit 204.

[0070] The electronic processing unit 204 is programmed to implement the hysteresis compensation method described above, so as to drive the piezoelectric plate 202 with a compensated driving voltage based on the input driving voltage.

[0071] In one embodiment, the electronic circuitry 220 is housed in a respective circuit seat 230 formed in, or positioned on, the valve body 10.

[0072] In particular, the electronic circuitry 220 is designed in such a way as not to significantly affect the transverse dimension of the valve body 10.

[0073] As previously mentioned, in one embodiment, the electronic processing unit 204 is based on a microcontroller, for example a 32-bit controller operating with integers, in order to contain the dimensions and cost of the piezoelectric actuator 200, while still allowing for effective compensation of the hysteresis phenomenon.

[0074] In one embodiment, the valve body 10 has a prismatic shape and extends mainly along a main body axis X which, in the represented example, is a vertical axis.

[0075] Therefore, in the continuation of the presentdescription, terms such as "upper", "lower", or synonyms, shall be used with reference to the example shown in the drawings, wherein the piezoelectric valve 1 is arranged with a mainly vertical extension.

[0076] In one embodiment, the valve body 10 can be assembled on a base 2 in which at least two ducts 2a, 2b are formed, for example supply and exhaust ducts, adapted to be placed in fluid communication with the inlet duct 12 and the outlet duct 14.

[0077] In one embodiment, the piezoelectric plate 202 extends mainly along a plate axis Y, parallel to or coinciding with the main body axis X.

[0078] The piezoelectric plate 202 ends with a distal portion 202'. As a result of the electric activation of the piezoelectric plate 202, this distal portion 202' moves along a direction substantially orthogonal to the plate axis Y.

[0079] An internal chamber 22 is also formed in the valve body 10. This internal chamber 22 communicates with the valve seat 16 and with the outlet duct 14. Therefore, the internal chamber 22 is adapted to be filled with the fluid when the valve seat 16 is (at least partially) open.

[0080] A sealing membrane 24 is housed in the internal chamber 22, serving both as a separation means between the fluid flowing in the valve and the piezoelectric plate 202, and as a shut-off element of the valve seat 16.

[0081] More in detail, the sealing membrane 24 has a shutoff portion 242 facing the valve seat 16. The sealing membrane 24 is also arranged at least partially around the piezoelectric plate 202 so as to prevent contact between the piezoelectric plate 202 and the fluid flowing in the valve.

[0082] The distal portion 202' of the piezoelectric plate 202 is operatively connected to the sealing membrane 24 through at least one rigid force transfer element 26.

[0083] Therefore, the distal plate portion 202' is movable between a first position, in which it causes, through the at least one rigid element 26, a deformation of at least the shut-off portion 242 of the sealing membrane 24 to close the valve seat 16, and a second position, in which it allows at least the shut-off portion 242 to remain in an undeformed state in which it is detached from the valve seat 16. In this second position, therefore, the valve seat 16 is open.

[0084] It should be noted that the piezoelectric valve 1 canoperate both as an on-off valve to allow or block the passage of fluid through the valve seat 16, and as a proportional valve to regulate the fluid flow rate. In this second case, in fact, by modulating the intensity of the electric voltage difference applied to the piezoelectric plate 202 it is possible to accordingly regulate the excursion of the distal plate portion 202' and therefore the deformation of the shut-off portion 242 of the sealing membrane 24. In other words, the shut-off portion 242 can assume a fully deformed configuration, in which it sealingly closes the valve seat 16, an undeformed configuration, in which it fully opens the valve seat 16, and intermediate deformed configurations, in which it regulates the flow rate of the fluid passing through the valve seat 16.

[0085] In one embodiment, the piezoelectric valve 1 further comprises an elastic pusher element 30 cooperating with the piezoelectric plate 202.

[0086] In detail, when the piezoelectric plate 202 is not electrically activated, the distal plate portion 202' is influenced by the elastic pusher element 30 to remain in the first position, in which the valve seat 16 is completely sealingly closed by the shut-off portion 242 of the sealing membrane 24.

[0087] When the piezoelectric plate 202 is electrically activated, the distal plate portion 202' switches from the first position to the second position (or to an intermediate position in the case of a proportional valve) overcoming the force of the elastic pusher element 30.

[0088] In an embodiment, the operation of the piezoelectric valve may be the opposite. In fact, when the piezoelectric plate 202 is not electrically activated, the distal plate portion 202' may be influenced by the elastic pusher element 30 to remain in the second position, in which the valve seat 16 is completely open; conversely, when the piezoelectric plate 202 is electrically activated, the distal plate portion 202' switches from the second position to the first position (or to an intermediate position in the case of a proportional valve) overcoming the force of the elastic pusher element 30.

[0089] In one embodiment, the distal plate portion 202' is positioned between two rigid force transfer elements 26 identical to one another and engaging two respective opposite portions of the sealing membrane 24, namely the shut-off portion 242 and an opposite portion 244. In this way, when the distal plate portion 202' is in the second position, the resultant of the forces exerted by the pressurised fluid present in the internal chamber 22 onthe distal plate portion 202' is substantially zero. In this situation, therefore, the piezoelectric plate 202 only needs to be electrically driven to overcome the force of the elastic pusher element 30, and not also the pressure exerted by the fluid.

[0090] In one embodiment, the at least one rigid force transfer element 26 is a sphere positioned with the ability to translate between the distal plate portion 202' and the shut-off portion 242 of the sealing membrane 24.

[0091] In one embodiment, the rigid force transfer element 26 is housed in a guide seat 262 formed or inserted in the valve body 10.

[0092] In the illustrated embodiment, the distal plate portion 202' is inserted between two spheres 26, each engaging a respective portion 242, 244 of the sealing membrane. The spheres 26 and the portions 242, 244 of the sealing membrane 24 are positioned substantially symmetrically with respect to the plate axis Y.

[0093] In one embodiment, the inlet and outlet ducts 12 and 14 and the valve seat 16 are formed or included in an outer portion 102 of the valve body 10, for example an outer portion which also forms the base of the valve body 10.

[0094] The distal plate portion 202' is housed in an inner portion 104 of the valve body 10 which forms, with the outer portion 102, the internal chamber 22. The distal plate portion 202', and the elastic pusher element 30 if present, extend axially in a plate chamber 106 formed in the inner portion 104.

[0095] In the inner portion 104 of the valve body 10, the guide seat 262 for the at least one rigid force transfer element 26 is formed or housed. The sealing membrane 24 is fitted in a sealed manner and with shape coupling on the inner portion 104 of the valve body 10.

[0096] In one embodiment, the inner portion 104 forms at least one flat wall 112 (two opposite parallel flat walls in the illustrated example). The at least one flat wall 112 faces the valve seat 16. In the at least one flat wall 112, preferably in the pair of opposite flat walls 112, there is an opening that forms or in which the guide seat 262 is housed, which places the internal chamber 22 in communication with the plate chamber 106. From the opening facing the valve seat 16, the rigid force transfer element 26 may protrude to deform the shut-off portion 242 of the sealing membrane 24.

[0097] The sealing membrane 24, in one embodiment, has a cupshape. The sealing membrane 24 can also be locked in position through a thickened upper edge 146 retained between the lateral wall of the inner portion 104 and the facing lateral wall of the outer portion 102 which delimits the internal cavity 108.

[0098] In one embodiment, the valve seat 16 is formed at the end of a nozzle 120 inserted in a sealed manner into a nozzle seat 122 formed in the valve body 10, for example in the outer portion 102 of the valve body 10. Said nozzle seat 122 communicates fluidically with the inlet duct 12 and with the internal chamber 22.

[0099] In one embodiment, the nozzle 120 and the valve seat 16 extend around a nozzle axis Z perpendicular to the plate axis Y.

[0100] In one embodiment, the nozzle seat 122 is also open to the outside and allows adjustment of the insertion depth of the nozzle 120 into the nozzle seat 122, thus adjusting the distance between the valve seat 16 and the shut-off portion 242 of the sealing membrane 24, and therefore the flow rate of the fluid exiting the valve seat when the shut-off portion 242 is in the undeformed position.

[0101] Returning now to the elastic pusher element 30in one embodiment it is made of a flexural spring extending alongside the piezoelectric plate 202 and whose distal end 302, for example provided with a spherical protrusion, engages the distal plate portion 202'.

[0102] In one embodiment, the elastic pusher element 30 is made of electrically conductive material and is electrically connected to the piezoelectric plate 202, for example via an electrical connection tab 304.

[0103] In one embodiment, the piezoelectric plate 202 actually has a first pole electrically connected to a first power supply terminal 203, which is for example made from an electrical contact having at least one lamella 203' in contact with said first pole, and a second pole electrically connected, for example through the electrical connection tab 304, to the elastic pusher element 30, which thus also acts as the second power supply terminal.

[0104] For example, the first power supply terminal 203 and the elastic pusher element 30 have respective projections 203", 306 protruding, for example upwardly, from the valve body 10.

[0105] In one embodiment, the circuit seat 230 is formed by a casing 231, provided with a cover 232, which closes the valve body 10 from above and may integrate anelectrical connector for the electrical connection of the electronic circuitry 220.

[0106] Figures 8-8c show respective flow rate diagrams of the piezoelectric valve 1 described above as a function of the driving voltage of the piezoelectric plate, in the absence of the hysteresis compensation method. The diagrams vary based on the inlet pressure and the diameter of the valve seat. The maximum hysteresis is between approximately 18% and 38%.

[0107] Figures 9-9c show the same diagrams, but with the electronic processing unit programmed to implement the method of compensating for the hysteresis according to the invention. The hysteresis was reduced to 3.6%-5.5%, i.e., it is about 15%-20% of the hysteresis without compensation.

[0108] Therefore, thanks to the proposed method, the objective of significantly reducing the hysteresis phenomenon has been achieved, while employing limited computational resources, and consequently with modest manufacturing costs and without significantly increasing the overall dimensions of the electrically driven device.

[0109] To the embodiments of the hysteresis compensation method, the electrically operable actuator, and the piezoelectric valve according to the invention, aperson skilled in the art may apply modifications, adaptations and replacements of elements with others functionally equivalent, without departing from the scope of the following claims. Each of the features described as belonging to a possible embodiment may be implemented independently of the other described embodiments.

Claims

CLAIMS1. A method of compensating for the hysteresis of an electrically operable actuator, wherein the actuator is controllable by applying an input driving voltage (Vin) varying within a range of input driving voltages, the method comprising the steps of:- defining a first threshold value (p) related to the over-time variation rate of the input driving voltage (V^) ;- calculating a compensated driving voltage value (Vcom);- supplying the actuator with an actuator driving voltage value (Vout) calculated based on said compensated driving voltage value (Vcom); wherein:- if the over-time variation rate of the input driving voltage is lower than or equal to said first threshold value, said compensated driving voltage value (Vcom) is proportional to the input driving voltage value according to a proportionality coefficient dependent on the sign of the variation of the input driving voltage with respect to the last set input driving voltage value;- if the over-time variation rate of the input drivingvoltage is greater than said first threshold value, said compensated driving voltage value (Vcom) corresponds to the input driving voltage value (Vin).

2. The method according to claim 1, wherein said proportionality coefficient takes:- a constant value greater than 1, in case of an increase in the input driving voltage with respect to the last set input driving voltage value;- a constant value smaller than 1, in case of a decrease in the input driving voltage with respect to the last set input driving voltage value.

3. The method according to claim 1 or 2, further comprising the step of:- defining a second threshold value (A) dependent on the maximum width of the hysteresis loop, wherein, if the over-time variation rate of the input driving voltage is lower than or equal to the first threshold value (p), and if the width of the hysteresis is greater than said second threshold value (A), said compensated driving voltage value (Vcom) corresponds to the input driving voltage value (Vin) to which said second threshold value (A) is added or subtracted, depending onthe sign of the variation of the input driving voltage with respect to the last set input driving voltage value.

4. The method according to claim 3, wherein the compensated driving voltage value (Vcom) is calculated as:and with (sgn(Vin), if |7in|< / ?lo, if\vin\>p where a,p,A are constant parameters.

5. The method according to any one of the preceding claims, wherein said actuator driving voltage value (Vout) corresponds to the compensated driving voltage value (Vcom) compared to a wider range of actuator driving voltages than the range of input driving voltages.

6. The method according to any one of the preceding claims, wherein the electrically operable actuator is a solenoid valve.

7. The method according to any one of the preceding claims, wherein the electrically operable actuator is a piezoelectric actuator (200).

8. A piezoelectric actuator (200), comprising:- a piezoelectric plate (202);- an electronic processing unit (220) adapted to drive the piezoelectric plate (202) by means of a variable driving voltage within a range of driving voltages;- actuator control means (206) operable to set an input driving voltage (Vin) readable by the electronic processing unit (220), wherein the electronic processing unit (220) is programmed to implement the hysteresis compensation method according to any one of claims 1-5, so as to drive the piezoelectric plate (202) with a compensated driving voltage (Vcom) based on the input driving voltage.

9. A fluid flow regulating valve (1), comprising:- a valve body (10) having an inlet duct (12) for a pressurized fluid, a fluid outlet duct (14), and a valve seat (16) which puts the inlet duct and the outlet duct in fluid communication;- a piezoelectric plate (202) housed in the valve body and adapted to deform when activated by a variable driving voltage within a range of driving voltages to adjust the fluid passage port through said valve seat according to the value of said driving voltage;- an electronic processing unit (220) housed in the valve31 body and adapted to drive the piezoelectric plate by means of said driving voltage;- actuator control means operable to set an input driving voltage readable by the electronic processing unit, wherein the electronic processing unit is programmed to implement the hysteresis compensation method according to any one of claims 1-5, so as to drive the piezoelectric plate with a compensated driving voltage based on the input driving voltage.

10. The valve according to claim 9, wherein the electronic processing unit (220) is housed in a circuit seat obtained in, or positioned on, the valve body.

11. The valve according to claim 9 or 10, wherein the electronic processing unit (220) is based on a microcontroller (204).

12. The valve according to claim 11, wherein the microcontroller operates in 32-bit and with integers.

13. The valve according to any one of claims 9-12, wherein the actuator control means comprise an analog selector (206) adapted to allow a selection of the input driving voltage within the range of input driving voltages, and wherein the electronic processing unit comprises an amplifier stage (208) adapted to amplify the compensated driving voltage so as to compare it to a wider range ofactuator driving voltages than the range of input driving voltages.

Images