METHOD FOR CONTROLLING AN ELECTROMAGNETIC ACTUATOR OF AN EXPANSION VALVE AND ACTUATOR AND EXPANSION VALVE CONFIGURED TO IMPLEMENT SUCH A METHOD

Description

[0001] The present invention relates to the field of electromagnetic actuators, configured in particular to actuate an electronically controlled pressure reducer, more particularly such a pressure reducer adapted to regulate the pressure of a fluid downstream of the pressure reducer.

[0002] It is known to use an electromagnetic actuator to actuate a pressure reducer. In particular, it is known to control the actuator according to a determined voltage to produce a given electromagnetic force and thus obtain precise positioning of a valve flap of a pressure reducer, for example, or of a pump piston, or for other applications of the electromagnetic actuator, for example for active anti-vibration control of a structure (see FR 3 007 855 A1).

[0003] The control law for known electromagnetic actuators, however, does not allow a precise flow rate to be obtained from a given valve position. The invention therefore aims to propose a solution to all or part of these problems.

[0004] To this end, the present invention relates to an electronically controlled pressure reducer, of the type comprising a controlled valve inserted between a fluid source at a first pressure and a fluid outlet at a second pressure, the second pressure being lower than the first pressure, a pressure sensor adapted to measure the second pressure and a control computer adapted to control the valve in such a way that the valve generates a pressure drop between the fluid source and the outlet making it possible to control the second pressure at a set pressure; the controlled valve comprising an actuator adapted to restrict a fluid passage section, between the source and the fluid outlet, so as to vary said passage section, the restriction being carried out by means of a fluid passage orifice and a shutter member placed in the axis of the orifice and arranged so that an axial movement of the shutter member causes a variation in the fluid passage section, the shutter member being driven by the actuator, the regulator comprising a position sensor of the shutter member, characterized in that the control computer is adapted to converge, according to a first control law, the position of the shutter member towards a set position, the set position being determined by a second control law to converge the second pressure towards the set pressure, on the basis of a model of a flow rate of the regulator,the flow rate of the regulator being the flow rate of the fluid flowing through the passage section between the regulator and the fluid outlet, said model of the flow rate of the regulator being defined as a function of the position of the shutter member, said second control law being further determined on the basis of a model of the second pressure as a function of the flow rate of the regulator and a consumption flow rate downstream of the fluid outlet.

[0005] According to one embodiment, the invention comprises one or more of the following features, alone or in a technically acceptable combination.

[0006] According to one embodiment, the dynamics of the shutter member is not taken into account, in other words in which the first control law is such that the position of the shutter member is equal to the set position, and in which the model of the second pressure is a linear model, without saturation of the flow rate.

[0007] According to one embodiment, the linear model without flow saturation is defined by the equation: P ˙ 2 = K s D col − D s

[0008] According to one embodiment, the dynamics of the shutter member is not taken into account, in other words in which the first control law is such that the position of the shutter member is equal to the set position, and in which the model of the second pressure is a linear model, with saturation of the flow rate.

[0009] According to one embodiment, the linear model with flow saturation is defined by the equations: P ˙ 2 = K s sat 1 D col − D s with : sat 1 D col = D max si D col > D max , D col si D min ≤ D col ≤ D max D min si D col < D min .

[0010] According to one embodiment, the second control law is a saturated proportional integral type law, and in which the model of the second pressure is a linear model with saturation of the flow rate.

[0011] According to one embodiment, the second control law, of the saturated integral proportional type, according to the linear model determines the set position according to the equation:

[0012] According to one embodiment, the second control law is a saturated proportional integral type law, and in which the model of the second pressure is a non-linear model with saturation of the flow rate.

[0013] According to one embodiment, the second control law, of the saturated integral proportional type according to the non-linear model of the second pressure, determines the set position according to the equation:

[0014] According to one embodiment, the actuator is a variable reluctance electromagnetic actuator comprising a fixed ferromagnetic armature, a magnetization coil secured to this armature and a moving assembly in alternative translations, secured to the shutter member, the actuator being arranged so that a movement of the moving assembly causes an axial movement of the shutter member relative to the fluid passage orifice, the first control law being determined to converge the position towards the set position by applying a voltage to the terminals of the coil to produce a desired magnetic force applied to the moving assembly so as to cause the axial movement of the shutter member towards the set position.

[0015] According to one embodiment, the first control law is based on a first unsaturated model for calculating the desired magnetic force, the first unsaturated model not taking into account magnetic saturation of the ferromagnetic armature.

[0016] According to one embodiment, the first control law is based on a second unsaturated model for calculating the desired magnetic force, the second unsaturated model taking into account a spreading of the field lines in a space between the ferromagnetic armature and the moving assembly.

[0017] According to one embodiment, the first control law is based on a saturated model for calculating the magnetic force, the saturated model taking into account the magnetic saturation of the ferromagnetic armature, and a spreading of the field lines in a space between the ferromagnetic armature and the moving assembly.

[0018] According to one embodiment, the saturated model for calculating the desired magnetic force comprises a first part of the model applicable when a current flowing in the magnetization coil is less than a saturation current, and a second part of the model applicable when the current is greater than the saturation current, the second part of the model being identified from measurements of the desired magnetic force carried out, for different values ​​of the current greater than the saturation current, during a phase of identification of the second part of the model.

[0019] According to one embodiment, the first control law further comprises an integral effect for limiting noise due to a reconstruction of a speed of the shutter member estimated from the measured position of the shutter member.

[0020] According to one embodiment, the first control law further comprises an integral effect to compensate for a modeling error.

[0021] According to one embodiment, the regulator further comprises an elastic device adapted to return the shutter member to a position such that the moving assembly is distant from the fixed ferromagnetic armature.

[0022] According to one embodiment, the regulator comprises a device for at least partial compensation of the forces exerted by the pressure of the fluid on the shutter member.

[0023] For a better understanding, an embodiment and / or implementation of the invention is described with reference to the attached drawings representing, by way of non-limiting example, an embodiment or implementation respectively of a device and / or a method according to the invention. The same references in the drawings designate similar elements or elements whose functions are similar. [ Fig.1 ] is a schematic representation of a regulator according to the invention. [ Fig.2 ] is a more detailed schematic representation of a regulator according to the invention. [ Fig.3 ] is a schematic representation of a mode of operation of a control law of the expander according to the invention. [ Fig.4 ] is a schematic representation of a first simplified mode of operation of the control law of the regulator according to the invention, in which the positioning model of the actuator is neglected. [ Fig.5 ] is a schematic representation of a second simplified mode of operation of the control law of the regulator according to the invention. [ Fig.6 ] is a schematic representation of a third mode of operation of the control law of the regulator according to the invention. [ Fig.7 ] is a schematic representation of the magnetic circuit of the actuator of the regulator according to the invention.

[0024] As illustrated in the figure 1 , a pressure regulator 1 is a device 1 used to expand a fluid contained in a reservoir or a source 2 to a first pressure P1, typically very high, towards an outlet 3 configured to open downstream of the device 1 into another reservoir 4 at a lower pressure P2, for example a few bars or tens of bars, depending on the uses. For example, in the propulsion system of a space launcher, the fluid could be helium contained in the source 2 at a pressure P1 of 400 bars, the regulator 1 being configured to expand the helium from the source 2 towards the outlet 3 pouring into a cavity 4 of a fuel tank 5 so as to maintain said fuel 5 at a pressure P2 of a few bars, upstream of a combustion chamber 6.

[0025] As illustrated in detail on the figure 2 , a regulator 1 according to an operating mode of the invention comprises a controlled valve 10, inserted between the source 2 of fluid at a first pressure P1 and the outlet 3 of fluid at a second pressure P2; the regulator 1 further comprises a pressure sensor 9 adapted to measure the second pressure P2 and a control computer 7 adapted to control the valve 10 so that the valve generates a pressure drop between the source of fluid and the outlet making it possible to control the second pressure P2 at a set pressure P ref; the controlled valve 10 comprises an actuator 14 adapted to restrict a passage section 11 of the fluid, between the regulator 1 and the outlet 3 of fluid, so as to vary said passage section;the restriction being made by means of an orifice 12 for the passage of the fluid and a shutter member 13 placed in the axis of the orifice and arranged so that an axial displacement of the shutter member 13 causes a variation in the fluid passage section; the shutter member 13 being driven by the actuator (14); the regulator 1 also comprises a position sensor 19 configured to measure a position X1 of the shutter member 13 along the direction of displacement of the shutter member 13.;

[0026] As shown in the figure 3 , the control computer 7 of the regulator 1 is adapted to converge, according to a first control law LC1, the position X 1 of the shutter member 13 towards a set position Y r , the set position Y r being determined by a second control law LC2 to converge the second pressure P2 towards the set pressure P ref , on the basis of an MD model of a flow rate D neck of the regulator 1, the flow rate D neck of the regulator 1 being the flow rate of the fluid flowing through the passage section between the regulator 1 and the fluid outlet 3; said MD model of the flow rate D neck of the regulator 1 is defined as a function of the position X 1 of the shutter member 13; furthermore, said second control law LC2 is determined on the basis of an MP model of the second pressure P2, said MP model of the second pressure P2 being a function of the flow rate D neck of the regulator 1 and of a consumption flow rate D s downstream of the fluid outlet 3;the consumption flow rate D s downstream of the fluid outlet 3 is, for example, determined by the fuel consumption 5 in the combustion chamber downstream of the tank 4.;

[0027] According to an exemplary embodiment, the actuator (14) is a variable reluctance electromagnetic actuator comprising a fixed ferromagnetic armature (15), a magnetization winding (16) secured to this armature and a moving assembly (17) in alternative translations, secured to the shutter member (13), the actuator being arranged so that a movement of the moving assembly causes an axial movement of the shutter member relative to the orifice (12) for the passage of the fluid, the first control law (LC1) being determined to converge the position (X 1 ) towards the set position (Y r ) by applying a voltage (U) to the terminals of the winding (16) to produce a desired magnetic force (F d ) applied to the moving assembly so as to cause the axial movement of the shutter member (13) towards the set position (Y r ).

[0028] In particular, when the dynamics of the shutter member is not taken into account, in other words the position X 1 of the shutter member 13 is equal to the set position Y r , as illustrated in the figure 4 , the MP model of the second pressure P2 is for example a linear model, without saturation of the flow.

[0029] More specifically, the linear model without flow saturation is defined by the equation: P ˙ 2 = K s D col − D s ∈ in which Ṗ 2 is the time derivative of the second pressure P2, and in which K s is a constant.

[0030] For example, under certain assumptions of flow of a gaseous fluid, in adiabatic compression and expansion regime, with a constant temperature T 2 of the fluid in cavity 5 of reservoir 4, it can be established that: K s = rT 2 V 2 where V 2 is the volume of the fluid in cavity 5 of reservoir 4, and r is the ideal gas constant divided by the molar mass of the gaseous fluid.

[0031] According to another example of embodiment, illustrated on the figure 5 , the dynamics of the shutter member 13 still not being taken into account, in other words the position X 1 of the shutter member 13 still being assumed to be equal to the set position Y r , the MP model of the second pressure P2 is for example a linear model, with saturation of the flow rate.

[0032] More specifically, the linear model with flow saturation is defined by the equations: P ˙ 2 = K s sat 1 D col − D s And:

[0033] According to this model, the flow rate D through the neck of the regulator 1 is limited within an interval between D min and D max.

[0034] According to another example of embodiment, illustrated in the figure 6 , the second control law LC2 is a saturated proportional-integral type law, and the MP model of the second pressure P2 is a linear model with flow saturation.

[0035] More specifically, the second control law LC2, of the saturated integral proportional type, determines the set position Y r according to the equation: in which K p and K i are constant gains, and in which d is a parameter of an MD model of the flow rate D through the neck of the regulator 1; according to an example of said MD model of the flow rate D through the neck of the regulator 1, said flow rate D through the neck of the regulator 1 is a linear function of the position X 1 of the shutter member 13, defined by the equation: D col X 1 = c X 1 + d where c is another parameter of this linear function.

[0036] Advantageously, for the parameter c, a value equal to the product of a first coefficient cs, and a density and a speed of the fluid at the neck of the regulator will be chosen, i.e. where the passage section of the regulator is the smallest for the determined position X 1 of the shutter member 13; for the parameter d, a value equal to the product of a second coefficient ds and the density and the speed of the fluid at the neck of the regulator will be chosen; the first coefficient cs and the second coefficient ds are the two parameters of an affine linear function which represents the passage section S neck of the regulator 1 as a function of a distance e, or air gap, separating the ferromagnetic armature 15 and the moving assembly 17 in alternating translations, integral with the shutter member 13, so that: S col e = c s e + d s

[0037] According to another exemplary embodiment, the second control law LC2 is a saturated proportional-integral type law, and the MP model of the second pressure P2 is a non-linear model with flow saturation.

[0038] More specifically, the second control law LC2, of the saturated integral proportional type, determines the set position Y r according to the equation: y r = − d 1 sat 1 K p P ref − P 2 + K i ∫ 0 t P ref − P 2 θ dθ + d 2 + c 2 . in which K p and K i are the constant gains, and in which d 2 and c 2 are in particular determined by the equations below: c 1 = d − b 2 c 2 = − c / 2 b d 2 = − c 1 / b d 1 = 1 / bρ col C col with ρ col = a density of the fluid at the neck of the regulator, i.e. where the passage section of the regulator is the smallest for the determined position X 1 of the obturator member 13, and C col = a velocity of the fluid at the neck of the regulator, and where the parameters b, c, and d are the coefficients of a second degree MD model of the flow rate D neck of the regulator 1; as a function of the position X 1 of the obturator member 13, said model being defined by the equation: D col X 1 = b X 1 2 + c X 1 + d

[0039] Advantageously, for the parameter c, a value equal to the product of a first coefficient cs, and the density ρ col and the speed C col of the fluid at the neck of the expander will be chosen; even more advantageously, for the parameter d, a value equal to the product of a second coefficient ds and the density ρ col and the speed C col of the fluid at the neck of the expander will be chosen; even more advantageously, for the parameter b, a value equal to the product of a third coefficient bs, and the density ρ col and the speed C col of the fluid at the neck of the expander will be chosen; the first coefficient cs, the second coefficient ds, the third coefficient bs, being the coefficients of a second degree function, which represents the passage section S neck of the regulator 1 as a function of the air gap e, separating the ferromagnetic armature 15 and the mobile assembly 17 in alternative translations, integral with the shutter member 13, so that: S col e = b s e 2 + c s e + d s

[0040] The air gap e is determined, to within a constant, by the position X 1 of the shutter member 13.

[0041] The first control law LC1 is determined to converge the position X, towards the set position Y r by applying a voltage U to the terminals of the winding 16 to produce a desired magnetic force F d applied to the moving assembly so as to cause the axial displacement of the shutter member 13 towards the set position Y r .

[0042] The magnetic force is a function of a current i which flows in the magnetization coil 16, integral with the ferromagnetic armature 15, and depends on an inductance L of a magnetic circuit formed by the coil 16, the ferromagnetic armature 15 and the moving element 17. This inductance L depends on the air gap e which separates the ferromagnetic armature 15 and the moving element 17. According to a formula known to those skilled in the art, the magnetic force F mag created by the magnetic circuit on the moving element 17 can be written:

[0043] A model of the desired magnetic force is therefore determined by a corresponding model of the inductance of the magnetic circuit formed by the winding 16 of the ferromagnetic armature 15 and the moving assembly 17.

[0044] In particular, according to a first example, the first control law LC1 is based on a first unsaturated model for calculating the desired magnetic force F d , said first unsaturated model not taking into account magnetic saturation of the ferromagnetic armature 15.

[0045] To be representative of the complexity of the magnetic phenomena to be taken into account, this unsaturated model, more particularly according to a second example, can take into account a spreading of the field lines in a space between the ferromagnetic armature 15 and the mobile assembly 17.

[0046] On the figure 7 representing an exemplary embodiment of a magnetic circuit formed by the winding 16 of the ferromagnetic armature 15 and the moving assembly 17, an average field line 30 of the magnetic field created in the magnetic circuit by the circulation of the current in the winding 16 not shown in the figure. The sections S 1 and S 3 shown in the figure 7 , are the sections of a magnetic flux tube in air, in the space of the air gap which separates the ferromagnetic armature 15 and the moving assembly 17. Said sections S 1 and S 3 depend on the air gap to take into account a spreading effect of the field lines.

[0047] Under the assumption of an absence of leakage inductance, an example of an unsaturated model not taking into account a magnetic saturation of the ferromagnetic armature 15, but taking into account a spreading effect of the field lines will be based on an inductance L modeled according to the formula:

[0048] In which N is a number of turns of the winding 16.

[0049] Even more particularly, according to a third example, the first control law is based on a saturated model for calculating the magnetic force, the saturated model takes into account the magnetic saturation of the ferromagnetic armature 15, and a spreading of the field lines in a space between the ferromagnetic armature 15 and the moving assembly 17. In this case, the expression of the magnetic force uses a knowledge model derived from the theory if the electric current is less than the saturation current and a behavior model if the current is greater than the saturation current, modeled according to the formula: in which is represents a saturation current, dependent on the air gap e, i.e. the space between the ferromagnetic armature 15 and the moving element 17.

[0050] An example of a saturated model taking into account a magnetic saturation of the ferromagnetic armature 15, and a blooming effect of the field lines will be based on an inductance L modeled according to the formula: In which: µ 0 = magnetic permeability of the vacuum; µ r = relative magnetic permeability of the material of the ferromagnetic armature and the moving part; I PM = thickness of the moving part in mm; S PM = Section of the moving part in mm 2<; I CM1 = thickness of the fixed part 1 in mm; S CM1 = Section of the fixed part 1 in mm 2<; I CM2 = thickness of the fixed part 2 in mm; S CM2 = Section of the fixed part 2 in mm 2<; I CM3 = thickness of the fixed part 3 in mm; S CM3 = Section of the fixed part 3 in mm 2<;

[0051] To be even more representative of reality, the saturated model for calculating the desired magnetic force (F d ) comprises a first part of the model applicable when the current i which circulates in the magnetization coil 16 is less than the saturation current is , and a second part of the model applicable when the current i is greater than the saturation current i s.

[0052] According to the first part of the saturated model, the desired magnetic force (F d ) is preferably described by the expression:

[0053] According to the second part of the saturated model, the desired magnetic force F d is preferably described by an expression identified on the basis of measurements made during an identification phase, for values ​​of the current i greater than the saturation current is . More particularly, the expression identified on the basis of the measurements consists of an interpolation between measured values ​​of the desired magnetic force F d , recorded in a table of measured values ​​corresponding to different values ​​of the current i, or the identified expression is a parametric formula whose parameters are determined from the measured values ​​of the desired magnetic force F d .

[0054] More specifically, the saturation current is is determined as a function of the air gap e according to another parametric formula identified on the basis of measurements.

[0055] All the control laws described above use a value of the speed of the moving assembly 17, that is to say of the shutter member 13. In the absence of a speed sensor, a value of the speed is estimated by a digital method from the position sensor signal. This introduces a reconstruction noise of the speed of the shutter member. To limit said reconstruction noise, the first control law further comprises a limitation of the noise by adding an integral effect to the first control law.

[0056] According to an exemplary embodiment, the regulator according to the invention further comprises an elastic device 18 adapted to return the shutter member 13 to a position such that the mobile assembly 17 is distant from the fixed ferromagnetic armature 15.

[0057] According to an exemplary embodiment, the regulator according to the invention comprises a device 20, 21, 22 for at least partial compensation of the forces exerted by the pressure of the fluid on the shutter member 13.

Claims

1. An electronically controlled expansion valve (1), of the type including a controlled valve (10) inserted between a source (2) of fluid at a first pressure (P1) and an outlet (3) of fluid at a second pressure (P2), the second pressure being lower than the first pressure, a pressure sensor (9) adapted to measure the second pressure and a control computer (7) adapted to control the valve (10) such that the valve generates a pressure drop between the fluid source and the outlet making it possible to slave the second pressure (P2) to a set pressure (Pref); - the controlled valve (10) comprising an actuator (14) adapted to restrict a fluid passage section (11), between the source (2) and the fluid outlet (3), so as to vary said passage section, - the restriction being carried out by means of a fluid passage orifice (12) and a shutter member (13) placed in the axis of the orifice and arranged so that an axial displacement of the shutter member (13) causes a variation in the fluid passage section, - the shutter member (31) being driven by the actuator (14), - the expansion valve (1) including a position sensor (19) of the shutter member (13), characterized in that the control computer (7) is adapted to converge, according to a first control law (LC1), the position (X1) of the shutter member (13) towards a set position (Yr), the set position (Yr) being determined by a second control law (LC2) to converge the second pressure (P2) towards the set pressure (Pref), on the basis of a model (MD) of a flow rate (Dcol) of the expansion valve (1), the flow rate (Dcol) of the expansion valve being the flow rate of the fluid flowing through the passage section between the expansion valve (1) and the fluid outlet (3), said model (MD) of the flow rate (Dcol) of the expansion valve being defined as a function of the position (X1) of the shutter member (13), said second control law (LC2) being further determined on the basis of a model (MP) of the second pressure (P2) as a function of the flow rate (Dcol) of the expansion valve and of a consumption flow rate (Ds) downstream of the fluid outlet (3).

2. The expansion valve (1) according to claim 1, wherein the dynamics of the shutter member are not taken into account, in other words wherein the first control law (LC1) is such that the position (X1) of the shutter member (13) is equal to the set position (Yr), and wherein the model (MP) of the second pressure (P2) is a linear model, without saturation of the flow rate.

3. The expansion valve (1) according to claim 1, wherein the dynamics of the shutter member are not taken into account, in other words wherein the first control law (LC1) is such that the position (X1) of the shutter member (13) is equal to the set position (Yr), and wherein the model (MP) of the second pressure (P2) is a linear model, with saturation of the flow rate.

4. The expansion valve (1) according to claim 1, wherein the second control law is a saturated proportional-integral type law, and wherein the model (MP) of the second pressure (P2) is a linear model with saturation of the flow rate.

5. The expansion valve (1) according to claim 1, wherein the second control law is a saturated proportional-integral type law, and wherein the model (MP) of the second pressure (P2) is a non-linear model with saturation of the flow rate.

6. The expansion valve (1) according to any of claims 1 to 4, wherein the actuator (14) is a variable-reluctance electromagnetic actuator comprising a fixed ferromagnetic armature (15), a magnetization winding (16) secured to this armature and a mobile assembly (17) in alternative translations, secured to the shutter member (13), the actuator being arranged so that a displacement of the mobile assembly causes an axial displacement of the shutter member relative to the fluid passage orifice (12), the first control law (LC1) being determined to converge the position (X1) towards the set position (Yr) by applying a voltage (U) to the terminals of the winding (16) to produce a desired magnetic force (Fd) applied to the mobile assembly so as to cause the axial displacement of the shutter member (13) towards the set position (Yr).

7. The expansion valve (1) according to claim 4, wherein the first control law (LC1) is based on a first unsaturated model for calculating the desired magnetic force (Fd), the first unsaturated model not taking into account a magnetic saturation of the ferromagnetic armature (15).

8. The expansion valve (1) according to claim 4, wherein the first control law is based on a second unsaturated model for calculating the desired magnetic force (Fd), the second unsaturated model taking into account a spreading of the field lines in a space comprised between the ferromagnetic armature (15) and the mobile assembly (17).

9. The expansion valve (1) according to claim 4, wherein the first control law is based on a saturated model for calculating the desired magnetic force (Fd), the saturated model taking into account the magnetic saturation of the ferromagnetic armature (15), and a spreading of the field lines in a space comprised between the ferromagnetic armature (15) and the mobile assembly (17).

10. The expansion valve (1) according to claim 9, wherein the saturated model for calculating the desired magnetic force (Fd) comprises a first part of the model applicable when a current flowing in the magnetization winding 16 is less than a saturation current, and a second part of the model applicable when the current is greater than the saturation current, the second part of the model being identified from measurements of the desired magnetic force (Fd) carried out, for different values of the current greater than the saturation current, during a phase of identifying the second part of the model.

11. The expansion valve (1) according to any of claims 1 to 9, wherein the first control law further comprises an integral effect for limiting noise due to a reconstruction of a speed of the shutter member estimated from the measured position of the shutter member (13).

12. The expansion valve (1) according to any of claims 1 to 10, wherein the first control law further comprises an integral effect for compensating for a modeling error.

13. The expansion valve according to any of claims 6 to 11, characterized in that it further includes an elastic device (18) adapted to return the shutter member (13) to a position such that the mobile assembly (17) is distant from the fixed ferromagnetic armature (15).

14. The expansion valve according to any of claims 1 to 12, characterized in that it includes a device (20, 21, 22) for at least partially compensating the forces exerted by the pressure of the fluid on the shutter member (13).