The invention relates to the field of control systems for turbomachines, in particular turboprop engines or turbomachines with a non-ducted fan, also known in English under the name “Unducted Single Fan” or USF.

Prior art

FIG. 1 represents a turbomachine with an unfaired fan according to the state of the art, or an unfaired fan. As illustrated in FIG. 1, a non-faired fan 1, also called “open rotor” in English, is an aircraft turbojet whose fan 2 is attached directly to the power turbine and outside a nacelle 3, which makes it possible to increase the dilution rate of the engine compared to a ducted turbojet, and thus to reduce fuel consumption.

An open rotor is generally equipped with a gas generator 4 and a free turbine 5 driving, via a reduction box 6, two contra-rotating variable-pitch propellers 7 and 8.

As illustrated in FIG. 2 which schematically represents a control system of an open rotor 1, an open rotor 1 can be considered from a control point of view as a multivariable system comprising three control quantities and three quantities output which must be regulated. The three open rotor 1 control quantities are the fuel flow, denoted WF, the upstream propeller pitch, also called the upstream pitch angle and noted bi, and the downstream propeller pitch, also called the pitch angle. downstream and noted b 2. The three output quantities of open rotor 1 are the low pressure compressor rotation speed, denoted XNP, the upstream propeller rotation speed, denoted XN1, and the downstream propeller rotation speed, denoted XN2 . The speed of rotation of the upstream propeller and that of the downstream propeller XN1 and X7V2 are controlled around several speed stages defined by the operating conditions.

Such a system comprises significant couplings between the various control and output quantities.

As illustrated in FIG. 2, the control system 9 generally comprises a multivariable regulator 90 with three inputs and three outputs, also denoted 3x3 multivariable regulator, which intrinsically takes into account the couplings between the various control and output quantities. The multivariable regulator 90 makes it possible to ensure satisfactory decoupling in most cases, in order to be able to vary the output quantities XNP, XN1 and XN2 of the open rotor 1 independently of one another.

The multivariable regulator 90 receives as input the values ​​of the three output variables XNP, XN1 and XN2 of the open rotor 1 as well as three corresponding output variable setpoints XNP dmd , XN1 dmd and XN2 dmd .

However, to comply with the operational constraints of the turbomachine, the calculated fuel flow control WF may be saturated or else not taken into account in certain cases. There are in fact minimum and maximum stops calculated in real time to protect the motor from pumping during transient phases. This saturation can be achieved by a limiter 95 independently of the other controls.

Likewise, the upstream and downstream setting angles can also be saturated using other limiters independently of the fuel flow control. As each limiter acts on a command independently of the other command, the commands applied are no longer consistent with each other.

In addition, various protection loops against overspeeds, over temperatures, overpressures, etc. are also put in competition at the level of the development of the setpoint of the fuel flow.

These cases pose problems for decoupling. Indeed, the commands resulting from the 3x3 multivariable corrector are calculated in such a way as to be coherent with each other in order to counteract the interactions and ensure the decoupling of the outputs.

If the value of a command is modified, decoupling is no longer ensured, which generally results in overshoots on the regulated outputs.

For example, if we take, to simplify, a 2x2 multivariable regulator, that is to say with 2 control inputs and two output variables to be regulated, if we do not modify the second control input when the first input is saturated, the direction of the resulting control vector formed from the two initial control vectors, each corresponding to one of the control inputs, is directly affected and erroneous.

Solutions have been proposed to remedy the desynchronization of the commands saturated by the limiters. One solution consists in adding additional states, such as temperature, pressure or altitude, in order to take into account the operating constraints when developing the control laws. This first solution is complex to implement.

Another solution consists in recomputing the command not affected by the saturation in order to make it compatible with the saturated command. This second solution is complex to implement and its complexity increases with the number of inputs / outputs.

In particular, document FR 3 055 029 discloses a control system for a turboprop engine with control overload management which calculates the maximum admissible servo errors in order to avoid overloading of the controls. The method implemented by the system is based on the reversal of the transfer of the corrector which cannot be used on all turbomachines.

The solutions of the prior art for remedying the desynchronization of the commands saturated by the limiters are therefore not satisfactory.

Disclosure of the invention

The object of the invention is to propose a method and a system for controlling a turbomachine making it possible to synthesize coherent commands and respecting the operating constraints of the turboprop engine in a simple manner.

According to a first aspect of the invention, there is provided a method for controlling a first, a second and a third variable of a turbomachine as a function of a first, a second and a third control quantities of a turbomachine which can each be saturated as a function of the operating parameters of the turbomachine, the control method comprising:

- a measurement of the values ​​of the three variables of the turbomachine,

- reception, for each of said three variables received, of a corresponding setpoint,

a first determination in which the first values ​​of the three control quantities of the turbomachine are determined from the values ​​of the three variables and from said three corresponding setpoints,

a selection of the value of the first control quantity to be delivered to the turbomachine from among a maximum value of the first control quantity, a minimum value of the first control quantity and the value of the first control quantity resulting from said first determination, the first selection depending on the operating parameters of the turbomachine,

a second determination in which are determined second values ​​of the second and third control quantities of the turbomachine from the values ​​of the three variables, of the second and third corresponding setpoints, and of the value of the first control quantity selected during the first selection,

a choice of the pair of values ​​of the second and third control quantities to be delivered to the turbomachine between the torque of the second and third control quantities determined by the first corrector and the torque of the second and third control quantities determined by the second corrector, the choice of the pair of values ​​of the second and third control quantities to be delivered depending on the value of the selected first control quantity to be delivered, and

a transmission to the turbomachine of the value of the first selected control quantity and of the values ​​of the second and third selected control quantities.

The control method according to the invention thus makes it possible to guarantee in a simple and efficient manner the decoupling of the output quantities, that is to say of the three variables of the turbomachine, despite the complex management of one of the quantities of control such as fuel flow.

In a first aspect of the control method, the method can further comprise an integration of the value of the first control quantity selected and the values ​​of the second and third control quantities chosen before their transmission to the turbomachine.

The integration of the values ​​makes it possible to manage smooth transitions between the loops, whether at the level of a first control quantity such as the fuel flow or of the second and third control quantities such as blades.

In a second aspect of the control method, the first variable corresponds to the speed of rotation of a low pressure compressor of the turbomachine, the second variable corresponds to the speed of rotation of a propeller upstream of the turbomachine, and the third variable corresponds to the speed of rotation of a downstream propeller of the turbomachine, the first control quantity corresponds to the fuel flow of the turbomachine, the second control quantity corresponds to the pitch of the upstream propeller of the turbomachine and the third quantity of command corresponds to the pitch of the downstream propeller of the turbomachine.

In another object of the invention there is provided a system for controlling a first, a second and a third variable of a turbomachine as a function of a first, a second and a third control quantities of a turbomachine which can each be saturated as a function of the operating parameters of the turbomachine, the control system comprising:

a first corrector with three outputs receiving as input the values ​​of the three variables of the turbomachine as well as, for each of said three variables received, a corresponding setpoint, the three outputs of the first corrector corresponding to the three control quantities of the turbomachine,

a first selection unit configured to select, as a function of the operating parameters of the turbomachine, the value of the first control quantity to be delivered to the turbomachine from among a maximum value of the first control quantity, a minimum value of the first control quantity and the value of the first control quantity resulting from said first determination,

a second corrector with two outputs receiving as input the values ​​of the three variables of the turbomachine as well as the setpoint of the second variable and the setpoint of the third variable and the value of the first control quantity delivered by the first saturation unit, the two outputs of the second corrector corresponding to the second and third control quantities of the turbomachine, and

- a second selection unit configured to deliver as an output, depending on the selection of the first selection unit, either the pair of second and third control quantities determined by the first corrector, or the pair of second and third control quantities determined by the second corrector,

the control system delivering, in order to control the turbomachine, the value of the first control quantity delivered by the first saturation unit and the values ​​of the second and third control quantities delivered by the second saturation unit.

The proposed solution thus consists in implementing, in addition to the first multivariable corrector with three outputs, a second multivariable corrector to calculate two control quantities such as setting angles which make it possible to preserve directionality, using the information of the first quantity selected control such as the selected fuel flow.

The second corrector makes it possible to manage two variables via two control quantities, the second and the third, as a function of the value of another control quantity, the first in this case. In other words, in a specific case, the second corrector makes it possible to manage the speeds of the propellers by acting on the setting angles, taking into account the information on the fuel flow rate and the speed of the low pressure body.

The two correctors run in parallel and a selection logic makes it possible to use one or the other of the setting setpoints, depending on the selection logic applied to the first control quantity which can be indicated for example via an indicator calculated by the first selection unit.

This architecture can be used for any application requiring multivariable control with the management of saturation on a control quantity such as the fuel flow, in particular turboprop engines, turbomachines with a non-faired fan.

In a first aspect of the control system, the control system may further comprise an integrator receiving as input the value of the first control quantity supplied by the first saturation unit and the values ​​of the second and third control quantities supplied by the second saturation unit, and delivering the processed values ​​of the first, second and third control quantities to the turbomachine.

The common and unique integrator is placed downstream of the first and second selection units. The first and second correctors thus calculate control increments, which can be limited to take account of the different constraints (for example, the C / P stop). The fuel increment value finally retained is added to the current fuel command by this integrator.

In another object of the invention, an aircraft is provided comprising at least one turbomachine and at least one control system as defined above controlling at least one of said at least one turbomachine.

According to one aspect of the aircraft, at least one of said at least one turbomachine controlled by said at least one control system may be a turbomachine with an unfit fan.

Brief description of the drawings

[Fig. 1] FIG. 1, already described, represents a turbomachine with a non-faired fan according to the state of the art.

[Fig. 2] FIG. 2, already described, diagrammatically represents a control system according to the state of the art for the non-ducted fan of FIG. 1.

[Fig. 3] FIG. 3 diagrammatically represents a control system of a turbomachine according to one embodiment of the invention.

[Fig. 4] FIG. 4 shows a flowchart of a method for controlling a turbomachine according to an embodiment of the invention.

Description of the embodiments

In FIG. 3 is schematically represented a control system 10 of a turbomachine according to one embodiment of the invention. The turbomachine controlled by the control system 10 according to the invention may be a turbomachine 1 with an uncured fan such as that described in FIG. 2.

The control system 10 comprises a first corrector 11, a second corrector 12, a first selection unit 13, a second selection unit 14 and an integrator 15.

The first corrector 1 1 comprises three outputs delivering a first value for each of the three control quantities. The first control variable corresponds to the fuel flow WF of the open rotor 1, the second control variable corresponds to the pitch bi of the upstream propeller of the open rotor 1 and the third control variable corresponds to the pitch b 2 of the downstream propeller of the open rotor 1.

The first corrector 1 1 receives as input the values ​​of three variables of the open rotor 1, the first variable corresponding to the speed of rotation XNP of a low pressure compressor of the open rotor 1, the second variable corresponding to the speed of rotation XN1 of a propeller upstream of the open rotor 1, and the third variable corresponding to the speed of rotation XN2 of a propeller downstream of the open rotor 1. The first corrector 11 also receives a speed instruction as input of rotation XNP dmd of the low pressure compressor, a setpoint of rotation speed XN1 dmd of the upstream propeller, and a setpoint of rotation speed XN2 dmd of the downstream propeller.

The first selection unit 13 receives as input the value determined by the first corrector 11 for the fuel flow rate WF, a maximum value of the first control quantity WFmax, and a minimum value of the first control quantity WFmin.

The first selection unit 13 is configured to output one of the three previous values ​​WF, WFmax or WFmin depending on the operating parameters of the open rotor 1. The value outputted from the first selection unit 13 corresponds to the value of the first actuating variable, WF, to be delivered to open rotor 1.

Le second correcteur 12 comprend deux sorties délivrant une seconde valeur pour la deuxième et la troisième grandeurs de commande b1 et b2. Comme le premier correcteur 1 1 , le second correcteur 12 reçoit en entrée les valeurs de trois variables de sortie de l’open rotor 1 mesurées par les capteurs correspondants, c’est-à-dire la vitesse de rotation XNP du compresseur basse pression, la vitesse de rotation XN1 de l’hélice amont et la vitesse de rotation XN2 de l’hélice aval. Le second correcteur 12 reçoit également en entrée la consigne de vitesse de rotation XN1dmd de l’hélice amont et la consigne de vitesse de rotation XN2dmd de l’hélice aval, mais pas la consigne de vitesse de rotation XNPdmd du compresseur basse pression. Le second correcteur 12 reçoit en outre en entrée, la valeur du débit de carburant délivrée en sortie de la première unité de sélection 13.

Le second correcteur 12 est configuré pour déterminer une seconde valeur pour chacune des deuxième et troisième grandeurs de commande b1 et b2de l’open rotor 1 en fonction notamment de la valeur sélectionnée pour la première grandeur de commande, c’est-à-dire ici le débit de carburant WF.

La seconde unité de sélection 14 reçoit en entrée deux couples de valeurs et un indicateur. Le premier couple de valeurs reçu correspond au couple comprenant la première valeur de la deuxième grandeur de commande b1 et la première valeur de la troisième grandeur de commande b2, et le second couple de valeurs reçu comprend la seconde valeur de la deuxième grandeur de commande b1 et la seconde valeur de la troisième grandeur de commande b2. L’indicateur reçu par l’unité de sélection 14 correspond à une indication délivrée par la première unité de sélection 13 et permettant d’indiquer laquelle des trois valeurs de la première grandeur de commande WF a été sélectionnée.

La seconde unité de sélection 14 est configurée pour délivrer en sortie le couple de valeurs des deuxième et troisième grandeurs de commande sélectionné en fonction de l’indicateur délivré par la première unité de sélection. La seconde unité de

selection 14 thus delivers at output either the pair of first values ​​of second and third control quantities determined by the first corrector 1 1, or the pair of second values ​​of second and third control quantities determined by the second corrector 12, the selection depending on the value of the first control quantity selected by the first selection unit 13. The values ​​delivered at the output of the second selection unit 14 correspond to the values ​​of the second and third control quantities, b 1 and b 2 , to be delivered to l 'open rotor 1.

Before being transmitted to the open rotor 1, the value of the first control quantity WF selected by the first selection unit 13 and the values ​​of the second and third control quantities bi and b 2 selected by the second selection unit 14 are delivered to an integrator 15 to avoid jerks in the control of the open rotor 1. The integrator 15 then delivers to the open rotor 1 the values ​​of the first, second and third control quantities as well processed.

In FIG. 4 is illustrated a flowchart of a control method implemented by the control system 10.

According to the mode of implementation presented in FIG. 4, the control method comprises a first step 100 in which the values ​​of the three variables XNP, XN1 and XN2 of the open rotor 1 are measured from different dedicated sensors and one transmits them to the first corrector 1 1 and to the second corrector 12.

In a following step 1 10, we receive instructions for each of the three variables of the open rotor 1. More particularly, in this step 1 10, the first corrector 1 1 receives the rotation speed instruction XNP dmd of the low pressure compressor. , the rotation speed reference XN1 dmd of the upstream propeller, and the rotation speed reference XN2 dmd of the downstream propeller, and the second corrector 12 receives the rotation speed reference XN1 dmd of the upstream propeller and the rotation speed setpoint XN2 dmd ûe the downstream propeller.

In a following step 120, first values ​​are determined for the three control quantities of the open rotor 1 from the values ​​of the three variables XNP, XN1 and XN2 and from the three corresponding setpoints XNP dmd , XN1 dmd and XN2 dmd .

In a following step 130, the value of the first control quantity to be delivered to the open rotor 1 is selected from among a maximum value of the first control quantity, a minimum value of the first control quantity and the value of the first control quantity resulting from the determination in the previous step 120, the selection depending on the operating parameters of the open rotor 1.

In a following step 140, second values ​​are determined for the second and third control quantities of the open rotor 1 from the values ​​of the three variables XNP, XN1 and XN2, of the second and third corresponding setpoints XN1 dmd and XN2 dmd , and the value of the first control quantity WF selected during the first selection in the preceding step 130.

In a following step 150, a choice is made of the pair of values ​​of the second and third control quantities to be delivered to the open rotor 1 between the torque of the second and third control quantities determined in step 120 and the torque of the second and third control quantities determined in step 140, the choice of the pair of values ​​of the second and third control quantities to be delivered depending on the value of the first control quantity to be delivered selected in step 130.

In a following step 160, each of the values ​​selected in step 130 and in step 150 is integrated using an integrator, then in a following step 170, the integrated values ​​are transmitted to the open rotor 1. of the first, second and third control variables.

The control method according to the invention thus makes it possible to guarantee in a simple and efficient manner the decoupling of the output quantities, that is to say of the three variables of the turbomachine, despite the complex management of one of the quantities of control such as fuel flow.

WE CLAIMS

Claim 1] Method for controlling a first, a second and a third variable (XNP, XNi, XN 2 ) of a turbomachine (1) as a function of a first, a second and a 'a third control quantities (WF, bi, b 2 ) of a turbomachine (1) which can each be saturated as a function of the operating parameters of the turbomachine (1), the control method comprising:

- a measurement (100) of the values ​​of the three variables (XNP, XNi, XN 2 ) of the turbomachine (1),

- a reception (110), for each of said three variables received (XNP, XNi, XN 2 ), of a corresponding setpoint ( XNP m , XNi d m d , XN 2dmd ),

- a first determination (120) in which the first values ​​of the three control quantities (WF, bi, b 2 ) of the turbomachine (1) are determined from the values ​​of the three variables (XNP, XNi, XN 2 ) and of said three corresponding setpoints ( XNP dmd , XNi m , XN 2 m ),

- a selection (130) of the value of the first control quantity (WF) to be delivered to the turbomachine (1) from a maximum value of the first control quantity, a minimum value of the first control quantity and the value of the first control variable resulting from said first determination, the first selection depending on the operating parameters of the turbomachine (1),

- a second determination (140) in which are determined second values ​​of the second and third control quantities (bi, b 2 ) of the turbomachine (1) from the values ​​of the three variables (XNP, XNi, XN 2 ), second and third corresponding setpoints (XNi m , XN 2 m ), and the value of the first command quantity selected during selection (130),

- a choice (150) of the pair of values ​​of the second and third control quantities to be delivered to the turbomachine between the torque of the second and third control quantities (bi, b 2 ) determined during the first determination (120) and the torque of the second and third control quantities (bi, b 2 ) determined during the second determination (140), the choice of the pair of values ​​of the second and third control quantities (bi, b 2 ) to be delivered depending on the value of the first control variable (WF) to be delivered selected during the selection (130), and - a transmission (170) to the turbomachine (1) of the value of the first selected control variable (WF) and of the values ​​of the second and third control quantities (bi, b2 ) chosen.

[Claim 2] A control method according to claim 1, further comprising an integration (160) of the value of the first selected control quantity (WF) and the values ​​of the second and third control quantities (bi, b 2 ) chosen before. their transmission to the turbomachine (1).

[Claim 3] A control method according to one of claims 1 or 2, in which the first variable (XNP) corresponds to the speed of rotation of a low pressure compressor of the turbomachine (1), the second variable (XNi) corresponds to the speed of rotation of a propeller upstream of the turbomachine (1), and the third variable (XN 2 ) corresponds to the speed of rotation of a propeller downstream of the turbomachine (1), the first control variable corresponds at the fuel flow rate of the turbomachine (1), the second control variable (bi) corresponds to the pitch of the upstream propeller of the turbomachine (1) and the third control variable (b 2 ) corresponds to the pitch of the propeller downstream of the turbomachine (1).

[Claim 4] System for controlling (10) a first, a second and a third variable (XNP, XNi, XN 2 ) of a turbomachine (1) as a function of a first, a second and third control quantities (WF, bi, b 2 ) of a turbomachine (1) which can each be saturated as a function of the operating parameters of the turbomachine (1), the control system (10) comprising:

- a first corrector (11) with three outputs receiving as input the values ​​of the three variables (XNP, XNi, XN 2 ) of the turbomachine (1) as well as, for each of said three variables received (XNP, XNi, XN 2 ), a corresponding setpoint ( XNP m , XNi d m d , XN 2dmd ), the three outputs of the first corrector corresponding to the three control quantities (WF, bi, b 2 ) of the turbomachine (1),

- a first selection unit (13) configured to select, as a function of the operating parameters of the turbomachine (1), the value of the first control variable (WF) to be delivered to the turbomachine (1) from a maximum value of the first control quantity, a minimum value of the first control quantity and the value of the first control quantity resulting from said first determination,

- a second corrector (12) with two outputs receiving as input the values ​​of the three variables (XNP, XNi, XN 2 ) of the turbomachine (1) as well as the setpoint of the second variable (XNi dmd ) and the setpoint of the third variable (XN 2 m ) and the value of the first control quantity (WF) delivered by the first saturation unit, the two outputs of the second corrector corresponding to the second and third control quantities (bi, b 2 ) of the turbomachine ( 1), and

- a second selection unit (14) configured to deliver as an output, depending on the selection of the first selection unit, either the couple of second and third control quantities determined by the first corrector, or the couple of second and third control quantities determined by the second corrector,

the control system (10) delivering at output, to control the turbomachine (1), the value of the first control quantity (WF) delivered by the first saturation unit and the values ​​of the second and third control quantities (bi, b 2 ) delivered by the second saturation unit.

[Claim 5] A control system (10) according to claim 4, further comprising an integrator (15) receiving as input the value of the first control quantity (WF) delivered by the first saturation unit and the values ​​of the second and third control quantities (bi, b 2 ) delivered by the second saturation unit, and delivering the processed values ​​of the first, second and third control quantities to the turbomachine (1).

[Claim 6] A control system (10) according to one of claims 4 or 5, in which the first variable (XNP) corresponds to the speed of rotation of a low pressure compressor of the turbomachine (1), the second variable (XNi) corresponds to the speed of rotation of an upstream propeller of the turbomachine (1), and the third variable (XN2) corresponds to the speed of rotation of a downstream propeller of the turbomachine (1), the first magnitude of control corresponds to the fuel flow of the turbomachine (1), the second control variable (bi) corresponds to the pitch of the upstream propeller of the turbomachine (1) and the third control variable (b2) corresponds to the pitch of the downstream propeller of the turbomachine (1).

[Claim 7] An aircraft comprising at least one turbomachine (1) and at least one control system (10) according to one of claims 1 to 6 controlling at least one of said at least one turbomachine (1).

[Claim 8] An aircraft according to claim 7, wherein at least one of said at least one turbomachine (1) controlled by said at least one control system (10) is a non-ducted fan turbomachine.