Title of the invention: Method of controlling a cylinder

Technical area

The present invention relates to the field of controlling jacks, and in particular jacks making it possible to actuate moving parts of a variable-geometry turbomachine.

In the field of aeronautics, aircraft turbomachines include components called “variable geometries”. A variable geometry of a turbomachine such as a turbojet is a movable member whose position can be controlled to act on the circulation of a fluid in the turbojet, for example on the gas flow in the primary flow stream of a bypass turbojet, in order to control the behavior of the turbojet. The variable geometries can be, for example, valves or moving vanes, such as air relief valves also commonly referred to as VBV (for Variable Bleed Valve) or vanes of a variable-pitch stator vane. The valves can also be valves for regulating the flow of cooling air for turbine housings,

Prior art

The cylinders traditionally comprise a piston movable in translation in a cylinder body. There are known cylinders provided with position sensors and controlled by servovalves, in order to control the position of the piston in the body of said cylinder. Such an assembly formed by a jack, a servovalve and a plurality of position sensors is also called a servo jack. The servovalve forms a control member of the jack, for example configured to regulate the pressure or the flow of fluid supplying said jack, in order to regulate the position of the piston in the body of the jack.

It is known to use measuring devices in order to measure the position of the piston in the body of the jack. Said measuring devices traditionally comprise, and for safety reasons, two redundant position sensors configured to measure simultaneously and independently of one another the position of said piston. The position of the piston in the cylinder body is then generally regulated from a

average of the piston position measurements provided by the two position sensors.

A drawback of this type of process is that in the event of a breakdown or malfunction of one of the two position sensors resulting in drifts or amplitude bias, the servo-control of the position of the piston in the cylinder body is disturbed. , this even in cases where said average is only slightly affected. As a result, the position of the piston in the cylinder body is not precisely regulated. Thus, when the cylinder is used to actuate variable geometries of a turbomachine such as, for example, VSVs (for Variable Stator Valve) which are variable-pitch vanes in a stator vane (called a rectifier) ​​of a high pressure compressor, this causes disturbances in the control of said blades which have the shape of fins, risking damage to them, in particular because the compressor risks initiating pumping. The control of the turbomachine itself is also disturbed by the lack of control of the VSVs or even of the LSVs, risking loss of power control (Loss of Thrust Control), which is not desirable. .

Disclosure of the invention

An aim of the present invention is to provide a method for controlling a jack overcoming the aforementioned problems.

To do this, the invention relates to a method for controlling a jack, comprising steps according to which:

a jack is provided comprising a jack body and a piston movable in translation inside the jack body;

providing a servovalve configured to regulate the energy supplied to said cylinder, so as to control the position of the piston in the body of the cylinder;

providing a measuring device having at least a first position sensor and a second position sensor;

measurements of the position of the piston in the cylinder body are carried out simultaneously with the first position sensor and the second position sensor;

at least a first displacement speed of the piston is determined from the piston position measurements obtained with the first position sensor;

at least a second displacement speed of the piston is determined from the piston position measurements obtained with the second position sensor; and each of the first and second determined piston displacement speeds is compared with a modeled or predetermined displacement speed of the piston, so as to identify the most reliable position sensor.

In a non-limiting manner, the jack can be a pneumatic or hydraulic jack and is preferably a double-acting jack. Still without limitation, the jack can be used to actuate variable-pitch vanes in a stator blading of a high-pressure compressor of a turbomachine.

The servovalve controls the supply of the cylinder, for example with fluid, from an electronic control signal that it receives as input, in order to control the movement of the piston in the body of the cylinder and to regulate the position of said piston.

Each of the position sensors forms a separate measuring device. In a nonlimiting manner, they may be inductive or magnetic position sensors. These position sensors can be passive electronic linear displacement sensors (or LVDT, for Linear Variable Differential Transformer in English).

The assembly formed by the actuator, the servovable and the measuring device forms a servo-actuator making it possible to control the position of the actuator in the actuator body. In other words, the position of the jack is corrected from the position measurements supplied by the sensors and from a position setpoint for the piston.

The first and second position sensors are identical and placed under similar measurement conditions in order to perform piston position measurements. These measurements are taken at the same time. Also, in normal operation of the two position sensors, the position measurements they provide are substantially identical.

The modeled or predetermined speed serves as a reference and is considered to be the actual and exact speed of the piston, which would be measured by a perfect position sensor.

The most reliable position sensor is understood to mean the position sensor whose position measurements are the most precise and the most consistent with the actual position of the piston in the cylinder body. The most reliable position sensor is the one providing position measurements making it possible to determine a displacement speed of the piston closest to the modeled or predetermined displacement speed.

In order to compare them, the first and second displacement speeds and the modeled or predetermined displacement speed of the piston are advantageously considered under similar operating conditions, for example in response to a given servovalve control signal.

The method according to the invention makes it possible to identify the most reliable position sensor quickly, precisely and with a minimum of measurements to be carried out. It is then possible to regulate the position of the piston from the position measurements supplied by said position sensor identified as being the most reliable. The servo-control of the position of the piston is therefore improved compared to the methods of the prior art in which the position of the piston is regulated on the basis of an average of the position measurements of the two position sensors.

The position of the piston is controlled more precisely so that the method according to the invention reduces the risk of damage to at least one variable geometry actuated by the jack in the turbomachine. The method according to the invention also makes it possible to overcome losses of power control.

An advantage of the method according to the invention is also to target a defective position sensor from among the two position sensors, so as not to regulate the position of the piston from the position measurements supplied by this defective sensor and possibly to replace it.

The identification of the defective position sensor also makes it possible to aid maintenance and thus brings a substantial saving of time, since there is no longer any need to find the fault by other means.

In the variant where the first and second displacement speeds of the piston are compared with a modeled displacement speed of the piston, said modeled displacement speed of the piston is preferably determined from a pre-established model of operation of the assembly formed by the servovalve and the cylinder. This model is considered to reflect the normal operation, without incident, of this assembly. This piston speed model has the particular advantage of being very precise and easy to implement, and in particular much more precise and easy to implement than the cylinder piston position models.

Indeed, the assembly formed by the servovalve and the cylinder behaves like an integrator. Also, it is difficult to estimate the position of the piston from a position model and to compare positions measured with such a modeled position. The comparison of the displacement speeds of the piston, obtained from position measurements, with a modeled displacement speed is easier.

Using a modeled speed therefore makes it possible to identify the most reliable position sensor more quickly and efficiently.

In the variant where the first and second displacement speeds of the piston are compared with a predetermined displacement speed of the piston, said predetermined displacement speed can be extracted from a table of characteristic values ​​of the displacement speeds of the piston, for example in normal operating conditions. This predetermined displacement speed can be stored in an internal memory of the measuring device.

Preferably, the steps of determining the first and second displacement speeds of the piston are repeated over a period chosen so as to determine a plurality of first and second displacement speeds of the piston. The set of first and second speeds thus determined of displacement of the piston is then compared with a plurality of modeled or predetermined displacement speeds of the piston.

Preferably, the comparison of said first and second determined piston displacement speeds with said predetermined or modeled displacement speed of the piston comprises a step of calculating a comparison factor R and determining the sign of said comparison factor. Without limitation, a positive comparison factor indicates that the first position sensor is the most reliable and a negative comparison factor indicates that the second position sensor is the most reliable or vice versa.

Preferably, the comparison factor R is calculated from the following equation:

[Math. 1]

Where Vi and v 2 are the first and second determined displacement speeds of the piston in the cylinder body and v m0 d is the predetermined or modeled displacement speed of the piston.

The integration is preferably carried out over a chosen period of time, so that the comparison factor reflects a comparison of the first and second displacement speeds of the piston with the modeled displacement speed of the piston over said chosen period of time. The use of the integral makes it possible to overcome the measurement aberrations and the noise which may appear during the determination of said first and second displacement speeds of the piston. The accuracy of the comparison and therefore the identification of the most reliable position sensor is therefore improved.

The comparison factor is preferably kept in memory.

Advantageously, the piston is configured to delimit a first chamber and a second chamber inside the piston body and the modeled displacement speed of the piston is a function of a modeled pressure difference between said first and second chambers.

In the case where the cylinder is used as an actuator within a turbomachine comprising an injection chamber, the modeled pressure difference may be a function of a modeled flow rate of fuel injected into the combustion chamber of the turbomachine as well as of the pressure upstream of the combustion chamber.

Preferably, the modeled displacement speed of the piston is a function of a supply current to the servovalve. This current is also called the wrap current.

Advantageously, the modeled displacement speed of the piston is a function of an equilibrium current determined by applying a first order filtering function to said supply current of the servovalve. The use of said equilibrium current makes it possible to obtain a particularly precise model of the displacement speed of the piston.

The modeled displacement speed of the piston is preferably determined from the following relationship:

[Math. 2]

where i
ve, i eq is the equilibrium current, DR is the modeled pressure difference between said first and second chambers. K is a gain that can be determined by linear regression from the modeled displacement speed of the piston, the servovalve feed current and said pressure difference.

Preferably, a preliminary step of detecting the presence of at least one defective position sensor is carried out and the step of comparing the first and second determined speeds of displacement of the piston with the modeled or predetermined displacement speed of the piston is carried out when the presence of a defective position sensor is detected.

The term "defective" is understood to mean a position sensor in which the position measurements of the piston of the jack are particularly aberrant with respect to the actual position of the piston in the body of the jack and are therefore not satisfactory. It may in particular be a faulty, improperly adjusted or poorly calibrated position sensor. The failure of a position sensor generally leads to a drift in the position measurements it provides.

The comparison step makes it possible to identify the position sensor providing the most accurate piston position measurements and the most consistent with the actual position of the piston in the cylinder body, among the two position sensors. If one position sensor is faulty while the other is functioning properly, the properly functioning position sensor will be identified as the most reliable. In the event that both position sensors are faulty, the less faulty position sensor will be identified as the most reliable.

The detection step makes it possible to carry out the comparison step only when a failure of one of the position sensors is detected. This makes it possible not to carry out the comparison step permanently and to identify the most reliable position sensor only when necessary. One advantage is to save computing resources. In addition, the comparison step is carried out only over a limited time interval, facilitating the identification of the fault, from a reduced number of piston position measurements. The identification of the most reliable position sensor is improved.

In a nonlimiting manner, the presence of a defective position sensor can be detected by the observation of particularly aberrant position measurements provided by one of the position sensors or even by the observation of a failure or a fault. incident in checking the position of the cylinder piston. The detection step advantageously makes it possible to detect a failure or a very slight disturbance of one of the sensors, for example low amplitude biases or slow drifts.

Preferably, the presence of a defective position sensor is detected from the piston position measurements obtained respectively with the first position sensor and with the second position sensor. The presence of a defective position sensor is advantageously detected by observing a divergence between said piston position measurements supplied by the two position sensors.

Even more preferably, the step of detecting the presence of a defective position sensor comprises a step according to which the difference between the piston position measurements obtained with the first position sensor and the piston position measurements is determined. obtained with the second position sensor.

Advantageously, the step of detecting the presence of a defective position sensor further comprises steps according to which the variance of said difference is calculated and said variance is compared with a predetermined detection threshold. In the presence of a defective position sensor, for example broken down, the position measurements that it provides drift just like said difference, more or less strongly. The variance of said difference evolves much more quickly and strongly and therefore makes it possible to more quickly detect a defective position sensor and therefore even a slight failure of the sensor.

The predetermined detection threshold is preferably chosen very low, so as to very quickly detect the presence of a defective position sensor. This also makes it possible to detect even a slight failure of a position sensor, for example the presence of a slightly misaligned position sensor. One advantage is to allow the identification of the most reliable position sensor as soon as one of the position sensors is slightly defective. The detection is therefore precise, thanks to which the control of the cylinder is improved.

Preferably, a counter is triggered from the detection of the presence of a defective position sensor and the step of comparing the first and second determined speeds of displacement of the piston with a modeled or predetermined displacement speed of the piston is interrupted. when the counter value is greater than a counter threshold. The value of the counter increments periodically from its initial value, for example every second. The counter threshold is set arbitrarily, for example at 30 seconds.

The use of the counter makes it possible to carry out the comparison step over a limited period of time, from the detection of a defective position sensor. This further facilitates the identification of the most reliable position sensor and reduces the resources mobilized to perform the step of comparing the first and second determined speeds of movement of the piston with the modeled or predetermined speed of movement of the piston.

Advantageously, the position sensor identified as being the most reliable is selected and the position of the piston is regulated using the piston position measurements supplied by said selected position sensor. One advantage is to control the position of the piston with precision, from the most precise measurements of the position of the piston in the cylinder body and in accordance with the actual position of the piston. The regulation of the position of the piston is improved compared to the methods of the prior art providing for regulation from the average of the position measurements supplied by all of the position sensors. The regulation of the piston position is not affected in the event of failure of one of the position sensors.

Preferably, an additional step of detecting the presence of a defective position sensor is carried out and the step of selecting the most reliable position sensor is carried out if a defective position sensor has been detected during the detection step. additional. One advantage is to ensure the presence of a defective position sensor and not to select a position sensor if all the position sensors are functioning correctly. If no faulty position sensor is detected during the additional detection step, the position of the piston in the cylinder body will be regulated from the position measurements provided by all of the position sensors.

In the embodiment where the method comprises a preliminary detection step, prior to the comparison step and conditioning the triggering of said comparison step, the additional detection step makes it possible to confirm the presence of a defective position sensor. . Indeed, the preliminary detection step, conditioning the triggering of the comparison step, is preferably strict and may lead to the detection by error of a defective position sensor. The additional detection step is preferably less strict and makes it possible to detect only a significant failure of the position sensors and therefore to take into account only the truly defective position sensors. One advantage is to ensure the presence of a

faulty position and to proceed to the step of selecting the most reliable position sensor only when necessary.

Preferably, the additional step of detecting the presence of a defective position sensor comprises a step of calculating the difference between the piston position measurements obtained respectively with the first position sensor and with the second position sensor. and the step of selecting the most reliable position sensor is carried out if the absolute value of said difference is greater than a predetermined additional detection threshold. The presence of a defective position sensor is therefore detected when the piston position measurements provided by the two position sensors diverge sharply.

The predetermined additional detection threshold is preferably set at a value large enough for the selection step to be carried out only when the difference between the position measurements obtained with the two position sensors is particularly large, indicating a failure or a significant measurement inaccuracy of one of the position sensors. Below the predetermined additional detection threshold, it is considered that no position sensor is defective and the step of selecting the most reliable position sensor is not carried out.

The invention also relates to a device for controlling a jack comprising a jack body and a piston movable in translation inside the jack body, the control device comprising:

a servovalve configured to regulate the energy supplied to the cylinder, so as to control the position of the piston in the body of the cylinder;

a measuring device comprising at least a first position sensor and a second position sensor, the position sensor being configured to simultaneously perform position measurements of the piston in the body of the cylinder; and a processing module configured to determine at least a first speed of movement of the piston from the measurements of piston position obtained with the first position sensor and configured to determine at least a second speed of movement of the piston from the measurements of piston position obtained with the second position sensor, the processing module being configured to compare said first and second determined piston displacement speeds with a modeled or predetermined displacement speed of the piston.

The processing module advantageously comprises a module for determining the speed of the piston configured to determine said first and second speeds of movement of the piston and a comparison module configured to compare said first and second determined speeds of movement of the piston with the speed of movement. modeled or predetermined of the piston.

Brief description of the drawings

The invention will be better understood on reading the following description of an embodiment of the invention given by way of non-limiting example, with reference to the appended drawings, in which:

[Fig. Figure 1 illustrates a control device according to the invention;

[Fig. 2] FIG. 2 illustrates a processing module of the control device of FIG. 1;

[Fig. 3] FIG. 3 is a detailed view of the processing module of FIG. 2; and

[Fig. 4] FIG. 4 illustrates the steps of the method for checking a jack according to the invention.

Description of embodiments

The invention relates to a method for controlling a jack as well as to a device for controlling a jack, making it possible to implement the method. This control method makes it possible to identify the most reliable position sensor among a set of position sensors and to control the position of the cylinder piston using the piston position measurements provided by this position sensor.

With the aid of FIGS. 1 to 3, a device for controlling a jack according to the present invention will be described, making it possible to implement a method for controlling a jack according to the invention.

In this non-limiting example, the jack makes it possible to actuate variable-pitch vanes in a compressor, forming moving parts of a turbomachine. The turbomachine conventionally comprises a combustion chamber.

FIG. 1 illustrates a control device 10 of a jack 12 in accordance with the present invention. The control device 10 comprises a servovalve 14, a measuring device 16 and a processing module 18.

The jack 12 comprises a jack body 20 and a piston 22 movable in translation in the body of the jack. The piston defines a first chamber 24 and a second chamber 26 inside the cylinder body 20. In a non-limiting manner, the cylinder is a double-acting cylinder, so that it moves in the body of the cylinder 20 as a function of of the fluid pressure present in the first and second chambers 24,26.

The servovalve 14 is a distributor making it possible to regulate the flow of fluid supplying the first and second chambers of the jack, as a function of an electronic control signal that it receives as an input. The servovalve 14 therefore makes it possible to adjust the position of the piston 22 in the body of the jack 20, as a function of a setpoint position.

The measuring device 16 includes a first position sensor 28 and a second position sensor 30, each configured to measure the position and provide position measurements of the piston in the cylinder body.

As illustrated in Figure 2, the processing device 18 comprises a detection module 32 configured to detect the presence of a faulty position sensor, an identification module 34 configured to identify the most reliable position sensor, and a module selection 36 configured to select the most reliable position sensor and control the regulation of the position of the piston from the position measurements obtained by said selected position sensor. The processing device also includes a reset module 37.

It can be seen that the processing device 18 further comprises a module for determining a modeled speed 38 configured to determine a modeled displacement speed v m0 d of the piston in the body 20 of the jack 12. The module for determining a speed model 38 comprises a module for estimating a pressure difference 40, a module for determining an equilibrium current 42 and a computer 44. The module for estimating a pressure difference 40 is configured to determine a pressure difference DR between the first and second chambers 24,26 of the cylinder 20.

As illustrated in FIG. 3, the detection module 32 comprises an alert module 46, configured to generate a detection signal Y 0 , as well as a counter 48.

The identification module 34 comprises a comparison module 50 and a module for determining the speed of the piston 52 configured to determine a first displacement speed Vi of the piston from the position measurements provided by the first position sensor 28 and a second displacement speed v 2 of the piston in the cylinder body from the position measurements provided by the second position sensor 30.

The most reliable position sensor selection module 36 includes an additional detection module 54 and a control module 56.

We will now describe the steps of the control method, in accordance with the present invention, implemented by the control device

10.

The control device 10 of the jack 12 makes it possible to control in real time the position of the piston 22 in the body of the jack 20. In particular, the first and second position sensors 28,30 are configured to each provide measurements of the position. piston. The servovalve 14 then controls the supply of fluid making it possible to bring the piston to a setpoint position, as a function of the position measured by the position sensors.

In normal operation, the first and second position sensors continuously and simultaneously measure the position of the piston in the cylinder body. The first position sensor 28 makes it possible to obtain a plurality of first measurements Xi of the position of the piston and the second position sensor 30 makes it possible to obtain second measurements X 2 of the position of the piston. The position measurements Xi, X 2 obtained by each of the first and second position sensors 28,30 are supplied to the detection module 32 and more precisely to the alert module 46 of the detection module.

The alert module 46 is configured to determine in real time the difference between the first Xi and second X 2 position measurements obtained simultaneously by the first and second position sensors and to calculate the variance of said difference. The alert module 46 then compares said variance with a predetermined detection threshold.

As long as said variance remains below said predetermined detection threshold, which reflects the absence of a defective position sensor, the alert module 46 does not transmit any detection signal and the control of the jack is not affected.

We will now consider that the first position sensor 28 is faulty and therefore defective, so that the first position measurements Xi that it provides are imprecise and diverge and are therefore far from the real position of the piston and from the second measurements of position X 2

provided by the second position sensor 30. Also, the difference between the first and second position measurements Ci, C ΐ varies rapidly and with a high amplitude.

The variance of said deviation, calculated by the alert module 46, then exceeds the predetermined detection threshold. This reflects the presence of a defective position sensor and the alert module then transmits a detection signal Y 0 to the counter 48 placed at an initial value.

The detection threshold is advantageously chosen low, in order to rapidly detect a failure, even a slight one, of one of the position sensors. For example, a slight divergence of the position measurements Ci, C ΐ obtained by one of the position sensors 28,30 will be detected.

On receipt of the detection signal Y 0 , the counter 48 triggers a counting, during which the value of the counter is periodically incremented, and transmits a trigger signal Yi to the identification module 34 and more precisely to the comparison module 50.

In parallel, the module for determining a modeled speed 38 determines in real time a modeled speed v m0 d of the piston 22 in the body of the jack 20, which it supplies to the comparison module 50.

To do this, the module for estimating a pressure difference 40 calculates a pressure difference DR between the first chamber 24 and the second chamber 26 of the piston. This pressure difference is, without limitation, determined from the fuel injection flow rate D in the combustion chamber of the turbomachine, the pressure P 0 upstream of said combustion chamber and the speed of rotation a of the turbomachine. high pressure body of the turbomachine.

The module for estimating a pressure difference 40 supplies said determined pressure difference DR to the computer 44.

The module for determining an equilibrium current 42 is configured to determine an equilibrium current i eq from a current i supplying the servovalve 14, also called the “wrap” current. When the position of the jack is constant or varies slightly, the equilibrium current i eq is determined by applying a first order filter to said current i for supplying the servovalve

In a nonlimiting manner, the module for determining an equilibrium current 42 is configured to determine the sliding variance of the position of the piston of the jack measured by one of the two position sensors. The module for determining an equilibrium current 42 is configured to keep the value of the equilibrium current i eq constant when said sliding variance is greater than a sliding variance threshold, which reflects a sudden variation in the position of the jack. .

The supply current of the servovalve i and the equilibrium current i eq are transmitted to the computer 44. The computer is configured to calculate the modeled displacement speed v m0 d of the piston in the body 20 of the jack 12. In such a way, no limiting, this modeled displacement speed is calculated according to the following equation:

[Math. 3]

K is a gain which can be determined by linear regression on the basis of said modeled speed v m0 d, of the supply current of the servovalve i and of the pressure difference DR between the first chamber 24 and the second chamber 26 of the piston. Said modeled speed v m0 d is transmitted to the comparison module 50.

In parallel, the module for determining the speed of the piston 52 of the identification module 34 determines a first displacement speed vi of the piston from the first position measurements Xi supplied by the first position sensor 28. It is understood that said first displacement speed vi of the piston is determined from a plurality of first position measurements Xi of the piston 22 supplied by the first position sensor 28. The module for determining the speed of the piston 52 also determines a second displacement speed v 2 of the piston from the second position measurements X 2 supplied by the second position sensor 30.

The values ​​of the first and second displacement speeds vi, v 2 of the piston are transmitted to the comparison module 50 of the identification module 34.

In the absence of a trigger signal Yi received by the comparison module 50, the latter remains inactive.

On the other hand, as soon as a trigger signal Yi is received by the comparison module 50, the latter performs a comparison of the first and second displacement speeds vi, v 2 of the piston with the modeled speed v m0 d used as the value of reference. To do this, the comparison module 50 calculates a comparison factor R and determines the sign of said comparison factor R. The comparison factor R is calculated according to the following equation:

[Math.

R =

The integrations are carried out over a chosen period of time, for example 0.3 seconds, in order to reduce the measurement noise. When the comparison factor R is positive, the first displacement speed Vi of the piston, determined from the first position measurements Xi obtained with the first position sensor 28, is further from the modeled speed v m0d than the second speed of displacement v 2 of the piston, determined from the second position measurements obtained with the second position sensor 30, over the chosen period of time. This reflects the fact that the first displacement speed of the piston is less satisfactory than the second displacement speed of the piston, and that the second position measurements X 2 of the piston obtained with the second position sensor 30 are more precise than the first position measurements Xi of the piston obtained with the first position sensor 28.

A positive comparison factor R therefore indicates that the second position sensor 30 is more reliable than the first position sensor 28. Conversely, a negative comparison factor R reflects the fact that the position measurements obtained with the first sensor position are more precise than those obtained with the second position sensor. The first position sensor is then considered to be the most reliable.

In this example, it is considered that the first sensor is defective, and that the calculated comparison factor R is therefore positive.

The comparison module 50 calculates, updates in real time and stores the comparison factor R, as long as the value of the counter remains below a predetermined counter threshold, for example 30 seconds. The comparison module transmits the comparison factor R, positive in this example, to the selection module 36 and more precisely to the control module 56.

When the value of the counter 48 reaches the predetermined counter threshold, the counter transmits an end of comparison signal Y 2 to the comparison module 50 and to the reset module 37. On receipt of the end of comparison signal Y 2 , the module comparison 50 interrupts the calculation of the comparison factor R.

The comparison module 50 is therefore only active after receiving the trigger signal Yi and before receiving the end of comparison signal Y 2 .

In parallel with the detection of the presence of at least one defective position sensor carried out by the detection module 32, and the identification of the most reliable position sensor carried out by the identification module 34, the module of Additional identification 54 of the selection module 36 is configured to verify and confirm the presence of a faulty position sensor. To do this, the additional detection module 54 calculates in real time the absolute value of the difference between the first position measurements of the piston Xi obtained with the first position sensor 28 and the second position measurements X 2 obtained with the second. position sensor 30 and compares this absolute value with an additional detection threshold.

When said absolute value of the difference between the first and second position measurements is greater than said additional detection threshold, the additional detection module 54 transmits an additional detection signal Y 3 to the control module 56 as well as to the reset module 37. The additional detection threshold is preferably set at a value high enough so that the transmission of the additional detection signal Y 3 takes place only when the position measurements obtained with the two position sensors are particularly different and inconsistent, reflecting a significant measurement inaccuracy of one of the position sensors.

The transmission of the additional detection signal Y 3 makes it possible to confirm the presence of a defective position sensor and to ensure that the presence of a defective position sensor has not been detected by error by the detection module 32 .

In the absence of an additional detection signal Y 3 received by the control module 56, the presence of a defective position sensor is not confirmed and the control module 56 remains inactive.

On the other hand, when the control module 56 receives an additional detection signal Y 3 , the presence of a defective position sensor is confirmed.

In this example, the first position measurements Xi supplied by the first sensor 28 are particularly aberrant and far from the second position measurements X 2 supplied by the second position sensor 30. Also, the additional detection module 54 transmits the detection signal. additional Y 3 .

The control module 56 then selects the most reliable position sensor among the first and second position sensor 28,30, from the comparison factor R. In this example, the comparison factor R is positive so that the second sensor 30 is selected as being the most reliable. The control module 56 then transmits a control signal Z, in particular to the servovalve, in order to select the most reliable position sensor, in this case the second sensor 30, and to control the regulation of the position of the piston 22 in the body 20 of the jack 12 only from the position measurements obtained with the selected position sensor.

The step of selecting the most reliable position sensor is therefore carried out only when the presence of a defective position sensor is confirmed by the additional detection module 54.

If an end of comparison signal Y 2 is transmitted to the reset module 37 but no additional detection signal Y3 is transmitted to it, the reset module 37 transmits a reset signal Y 4 to the comparison module 50. This translates into the detection by error of a defective position sensor by the detection module 32. On receipt of the reset signal Y 4 The comparison module 50 places the value of the comparison factor R at a chosen initial value, for example 0. On the other hand, if it receives an additional detection signal Y3, the reset module 37 remains inactive.

FIG. 4 illustrates the steps of an embodiment of the method for controlling a jack according to the invention. This method can be implemented by the control device illustrated in FIGS. 1 to 3. First of all, in a first step S1, measurements of the position of the piston in the cylinder body are carried out simultaneously with the first position sensor. and the second position sensor. In a second step S2, a first displacement speed of the piston is determined from the piston position measurements obtained with the first position sensor and a second piston displacement speed is determined from the piston position measurements obtained with the second position sensor.

A third step S3 of detecting the presence of at least one defective position sensor is then carried out on the basis of the piston position measurements obtained respectively with the first position sensor and with the second position sensor. In a nonlimiting manner, this third detection step S3 comprises the steps according to which the difference between the piston position measurements obtained with the first position sensor and the piston position measurements obtained with the second position sensor is determined, the variance of said difference is calculated and said variance is compared with a predetermined detection threshold.

If a defective position sensor is detected, a fourth step S4 is carried out for comparing each of the first and second determined speeds of displacement of the piston with a modeled or predetermined displacement speed of the piston, so as to identify the most position sensor. reliable.

In parallel with the fourth comparison step S4, a fifth step S5 for triggering a counter is carried out. The fourth step S4 of comparison is carried out until the value of the counter exceeds a counter threshold.

A sixth step S6 of additional detection of the presence of a defective position sensor is then carried out. This step comprises a step of calculating the difference between the piston position measurements obtained respectively with the first position sensor and with the second position sensor and the absolute value of said difference is compared with a predetermined additional detection threshold.

If the absolute value of said difference is greater than the predetermined additional detection threshold, the presence of a defective position sensor is confirmed and a seventh step S7 is then carried out for selecting the position sensor identified as being the most reliable.

An eighth step S8 of regulating the position of the piston is then carried out using the piston position measurements supplied by said selected position sensor.

Claims

1. A method of controlling a jack (12), comprising steps according to which:

- A jack is provided comprising a jack body (20) and a piston (22) movable in translation inside the jack body;

- Providing a servovalve (14) configured to regulate the energy supplied to said cylinder, so as to control the position of the piston in the body of the cylinder;

- Providing a measuring device (16) comprising at least a first position sensor (28) and a second position sensor (30);

- Position measurements (Xi, X2) of the piston in the cylinder body are carried out simultaneously with the first position sensor and the second position sensor;

- At least a first displacement speed (vi) of the piston is determined from the piston position measurements obtained with the first position sensor;

- At least one second displacement speed (v 2 ) of the piston is determined from the piston position measurements obtained with the second position sensor;

- The presence of at least one defective position sensor is detected; then

- when the presence of a defective position sensor is detected, each of the first and second determined speeds of displacement of the piston is compared with a modeled (v m0d ) or predetermined displacement speed of the piston, so as to identify the position sensor the most reliable.

2. The control method according to claim 1, wherein the comparison of said first and second determined displacement speeds (vi, v 2 ) of the piston with said modeled displacement speed (v m0d ) of the piston comprises a step of calculating a comparison factor R and determining the sign of said comparison factor.

3. Control method according to claim 2, wherein the comparison factor R is calculated from the following equation:

where Vi and v 2 are the first and second determined piston displacement speeds and v m0d is the modeled piston displacement speed.

4. Control method according to any one of claims 1 to 3, wherein the piston is configured to define a first chamber (24) and a second chamber (26) inside the piston body (20) and in wherein the modeled displacement speed (v m0d ) of the piston is a function of a modeled pressure difference between said first and second chambers.

5. Control method according to any one of claims 1 to 4, wherein the modeled displacement speed of the piston is a function of a supply current (i) of the servovalve (14).

6. The control method according to claim 5, wherein the modeled displacement speed (v m0d ) of the piston is a function of an equilibrium current (i eq ) determined by applying a first order filtering function to said current. supply (i) to the servovalve (14).

7. Control method according to any one of claims 1 to 6, wherein the presence of a defective position sensor is detected from the measurements (Xi, X2) of the piston position obtained respectively with the first position sensor. (28) and with the second position sensor (30).

8. The control method according to claim 7, wherein the step of detecting the presence of a defective position sensor comprises a step according to which the difference between the piston position measurements obtained with the first sensor is determined. position and piston position measurements obtained with the second position sensor.

9. The control method according to claim 8, characterized in that the step of detecting the presence of a defective position sensor further comprises steps according to which the variance of said deviation is calculated and said variance is compared with a threshold. predetermined detection.

10. Control method according to any one of claims 1 to 9, in which a counter is triggered from the detection of the presence of a defective position sensor and in which the step of comparing the first and second is interrupted. second determined displacement speeds (vi, v 2 ) of the piston with a modeled displacement speed (v m0d ) or predetermined displacement of the piston when the value of the counter is greater than a counter threshold.

11. Control method according to any one of claims 1 to

10, in which the position sensor identified as being the most reliable is selected and in which the piston position is regulated using the piston position measurements provided by said selected position sensor.

12. The control method as claimed in claim 11, in which an additional step of detecting the presence of a defective position sensor is carried out and the step of selecting the most reliable position sensor is carried out if a defective position sensor is carried out. was detected during the additional detection step.

13. The control method according to claim 12, wherein the additional step of detecting the presence of a defective position sensor comprises a step of calculating the difference between the position measurements of the piston (Xi, X 2 ). obtained respectively with the first position sensor (28) and with the second position sensor (30) and in which the step of selecting the most reliable position sensor is carried out if the absolute value of said difference is greater than a threshold of predetermined additional detection.

14. Control device (10) of a jack (12) comprising a jack body (20) and a piston (22) movable in translation inside the jack body, the control device comprising:

a servovalve (14) configured to regulate the energy supplied to the cylinder, so as to control the position of the piston in the body of the cylinder;

a measuring device (16) comprising at least a first position sensor (28) and a second position sensor

(30), the position sensor being configured to simultaneously perform position measurements of the piston in the cylinder body; and a processing module (18) configured to determine at least a first displacement speed (vi) of the piston from the piston position measurements obtained with the first position sensor and configured to determine at least a second displacement speed ( v 2 ) of the piston from the piston position measurements obtained with the second position sensor, the processing module being configured to detect the presence of a defective position sensor and to compare said first and second determined speeds of movement of the piston. piston with a modeled displacement speed (v m0d) or predetermined of the piston, when the presence of a defective position sensor is detected.