Actuation system comprising stable equilibrium positioning device and method for positioning system in stable equilibrium state

Abstract

The invention relates to an actuation system (2) comprising an actuator comprising a servo cylinder (4) having a rod (10) provided with a piston (12), the actuator having a device (14) for positioning the piston (12) of the servo cylinder (4) in a predetermined stable equilibrium position, the device (14) having a cylinder (16) provided with a rod (18) mechanically fixed to the rod (10) of the servo cylinder (4), the cylinder (16) comprises a piston (20) mounted on a rod (18) of the cylinder (16) such that a first chamber subject to a first pressure and a second chamber subject to a second pressure are defined on either side of the piston (20) in the cylinder (16), the first chamber and the second chamber being configured to contain a fluid, and a piston (12) of the servo cylinder (4) is configured to be positioned in a predetermined stable equilibrium position when the first pressure is equal to the second pressure.

Description

Technical Field

[0001] The invention relates to an actuation system comprising an actuator comprising a servo cylinder and a device for setting a stable equilibrium position of a piston of the servo cylinder.

[0002] In particular, the invention enables the piston to be arranged in a stable equilibrium position, for example a position corresponding to a safe state of the actuating system and a safe state of the actuated system, in particular in the event of a loss of control of the servo cylinder.

[0003] In general, the invention is applicable to any actuation system comprising a cylinder provided with a piston. Background Art

[0004] In order to be able to position the piston of a hydraulic cylinder of an actuation system in a stable equilibrium position during an accident, the actuation system usually comprises means for bringing the piston of the cylinder into abutment against, for example, one end of the cylinder. The abutment means usually comprises a spring acting on a rod of the cylinder to place the piston into abutment against the cylinder when control of the cylinder is lost. In particular, the spring exerts a continuous force on the piston, in particular against the movement of the piston. The actuation system has to compensate for the spring force, which deteriorates the efficiency of the actuation system.

[0005] Another solution for positioning the piston of the cylinder in a stable equilibrium position is to modify the regulation of the device for supplying fluid to the cylinder. For example, the fluid supply to the cylinder can be modified so that more fluid is supplied to the chamber of the cylinder. Thus, the piston is set in an abutment position.

[0006] Another disadvantage of the abutment device as described above is that it is not possible to arrange the cylinder in an intermediate position which lies on the piston travel between the abutment positions of the cylinder.

[0007] Known solutions for setting intermediate stable equilibrium positions include providing complex arrangements that are harmful to the actuation system. In addition, these solutions do not allow the cylinder to be in a stable equilibrium position in all intermediate positions. Summary of the invention

[0008] Therefore, the object of the present invention is to overcome all or part of the above-mentioned disadvantages and to provide an actuation system comprising a servo cylinder and a device for setting a predetermined stable equilibrium position of a piston of the servo cylinder.

[0009] One object of the present invention is an actuation system including an actuator, the actuator including a servo cylinder, the servo cylinder including a rod provided with a piston, the actuator including a device for setting a predetermined stable equilibrium position of the piston of the servo cylinder, the device including a cylinder provided with a rod, the rod being mechanically fixed to the rod of the servo cylinder, the cylinder including a piston mounted to the rod of the cylinder, so that a first chamber subjected to a first pressure and a second chamber subjected to a second pressure are defined on either side of the piston in the cylinder, the first chamber and the second chamber being configured to contain a fluid, the piston of the servo cylinder being configured so that when the first pressure is equal to the second pressure, the piston of the servo cylinder is positioned in a predetermined stable equilibrium position.

[0010] The invention thus enables the piston of the servo cylinder to be set at any predetermined position of the piston's travel. When designing an apparatus for setting a stable equilibrium position, the invention enables the piston of the servo cylinder to be set at a predetermined stable equilibrium position by returning the piston to a defined position. The invention also allows the fault tolerance of the actuation system to be improved.

[0011] Advantageously, the actuation system comprises a fluid supply arrangement configured to supply fluid to the actuator.

[0012] Preferably, the servo cylinder comprises a servo valve and the actuator comprises an electro-hydraulic selector configured to interrupt the supply of fluid to the servo valve when the undesired behavior occurs.

[0013] Advantageously, the cylinder comprises a first inlet for fluid in the first chamber and a second inlet for fluid in the second chamber.

[0014] Preferably, the cylinder comprises an outlet for fluid, the outlet being arranged between the first inlet and the second inlet and the outlet being dimensioned to allow fluid from the first inlet and the second inlet to pass through the outlet when the piston of the servo valve is in a predetermined stable equilibrium position.

[0015] In one embodiment, the cylinder includes a first outlet for fluid and a second outlet for fluid, the first outlet and the second outlet being longitudinally disposed at different positions between the first inlet and the second inlet and being sized such that when the piston of the servo cylinder is in a predetermined stable equilibrium position, the first outlet allows the fluid from the first inlet to pass through, and the second outlet allows the fluid from the second inlet to pass through.

[0016] Advantageously, the actuator comprises a position sensor for the piston of the servo cylinder.

[0017] Preferably, the actuation system comprises a computer configured to detect a failure of the servo cylinder.

[0018] In one embodiment, the cross-sectional area of ​​the piston of the cylinder is smaller than the cross-sectional area of ​​the piston of the servo cylinder.

[0019] An object of the present invention is also a method for setting a predetermined stable equilibrium position of a servo cylinder of an actuation system, the method comprising the following steps:

[0020] - interrupting the fluid supply to the servo valve of the servo cylinder in the event of an undesired behavior;

[0021] - supplying fluid to the cylinder of the device for setting a predetermined stable equilibrium position of the piston of the servo cylinder;

[0022] - translating the servo cylinder to a predetermined stable equilibrium position; and

[0023] -Maintaining the piston of the servo cylinder at a predetermined stable equilibrium position, the first pressure is equal to the second pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Other objects, features and advantages of the present invention will become apparent from a reading of the following description given by way of non-limiting example only and with reference to the accompanying drawings, in which:

[0025] [ Figure 1 ] schematically shows an actuation system according to the present invention;

[0026] [ Figure 2 ] schematically shows a device for setting a predetermined stable equilibrium position of an actuation system according to the invention to a stable equilibrium position;

[0027] [ Figure 3 ] schematically shows a device for setting a stable equilibrium position of an actuation system according to the invention, the piston of which leaves the first outlet and the second outlet free;

[0028] [ Figure 4 ] schematically shows a device for setting a stable equilibrium position of an actuation system according to the present invention, the piston of which blocks a first outlet and a second outlet; and

[0029] [ Figure 5 ] schematically illustrates a method for setting a servo cylinder of an actuation system according to the present invention to a predetermined stable equilibrium position. DETAILED DESCRIPTION

[0030] Figure 1 Schematically shown is an actuation system 2 comprising an actuator comprising a servo cylinder 4 comprising, for example, a servo-controlled cylinder 6 equipped with a servo valve 8. Alternatively, the servo-controlled cylinder 6 comprises, for example, a proportional control distributor.

[0031] The servo control cylinder 6 comprises a rod 10 provided with a piston 12 moving between two abutment positions. The piston 12 of the servo cylinder 4 defines two chambers, each chamber being supplied by a servo valve 8. The servo cylinder 4 advantageously comprises a low friction seal to provide sealing of the two chambers when the piston 12 of the servo cylinder 4 moves.

[0032] The servo cylinder 4 of the actuation system 2 enables, for example, an aerospace system or an automotive system to be actuated. The actuation system 2 described herein is particularly useful for single-engine aircraft architectures.

[0033] The actuator further comprises a device 14 for setting a predetermined stable equilibrium position. The device 14 comprises a cylinder 16 provided with a rod 18, which is mechanically fixed to the rod 10 of the servo cylinder 4. For example, the rod 18 of the cylinder 16 and the rod 10 of the servo cylinder 4 are welded to each other at their ends or are manufactured as a single unit. Alternatively, the rod 18 of the cylinder 16 is coupled to the rod 10 of the servo cylinder 4, for example by a detachable coupling element. The coupling element makes it possible, for example, to correct position errors between the cylinder 16 and the servo cylinder 4. Furthermore, when the rod 18 of the cylinder 16 moves, the rod 10 of the servo cylinder 4 also moves, and vice versa.

[0034] The cylinder 16 includes a piston 20 mounted to the rod 18 of the cylinder 16 so that a first chamber 22 subjected to a first pressure P1 and a second chamber 24 subjected to a second pressure P2 are defined on either side of the piston 20 in the cylinder 16. Advantageously, the stroke that the piston 20 moves in the cylinder 16 is substantially equal to the stroke of the piston 12 in the servo-control cylinder 6, within the range of mechanical tolerances allowed between the cylinder 16 and the servo cylinder 4. In addition, when the piston 20 of the cylinder 16 moves, the piston 12 of the servo cylinder 4 moves in the same manner, and vice versa.

[0035] The first chamber 22 and the second chamber 24 are configured to contain a fluid, such as oil.

[0036] Advantageously, the actuation system 2 comprises a computer 26 electrically connected to the servo valve 8. The computer 26 controls the servo valve 8, for example, to supply a fluid (e.g., oil) to the servo control cylinder 6 to control the position of the piston 12 of the servo cylinder 4. For example, the computer 26 sends a command in the form of an electrical signal to the servo valve 8, and the servo valve 8 supplies fluid to the servo control cylinder 6 according to the command from the computer to position the cylinder at a desired position.

[0037] Advantageously, the servo-control cylinder 6 , the first chamber 22 and the second chamber 24 are supplied with the same fluid. Advantageously, in order to improve the responsiveness of the servo-control cylinder 4 , the servo-valve 8 is mounted directly to the servo-control cylinder 6 .

[0038] Optionally, the actuator includes a position sensor 28 for electrically connecting the piston 12 of the servo cylinder 4 to the computer 26. The computer 26 analyzes the position of the piston 12 of the servo cylinder 4 measured by the position sensor 28, and detects whether the position of the piston 12 of the servo cylinder 4 is the position controlled by the computer 26. In one embodiment, the position sensor 28 is coupled to the rod 10 of the servo cylinder 4. In another embodiment, the position sensor 28 is coupled to the rod 18 of the cylinder 16.

[0039] In one embodiment, the servo valve 8 includes a flow rate sensor (not shown) that enables checking the flow rate of the fluid supplied by the servo valve 8 to the servo control cylinder 6. The flow rate sensor is electrically connected to the calculator 26. The calculator 26 analyzes the flow rate of the fluid measured by the flow rate sensor, and detects whether the flow rate of the fluid supplied by the servo valve 8 is the flow rate controlled by the calculator 26.

[0040] Computer 26 is therefore configured to detect a malfunction of actuation system 2 corresponding, for example, to an active malfunction, ie an abnormal supply to servo valve 8 , or to a passive malfunction, ie a lack of fluid distribution by servo valve 8 .

[0041] Advantageously, the actuator comprises an electrohydraulic selector 30 electrically connected to the computer 26 and fluidically connected to the servo valve 8 and to the cylinder 16 of the device 14 for setting a predetermined stable equilibrium position.

[0042] Advantageously, the actuation system 2 comprises high-pressure and low-pressure fluid supplies 31, which are fluidically connected to the electrohydraulic selector 30, the servo-valve 8 and the device 14 for setting the equilibrium position. Advantageously, the electrohydraulic selector 30 is connected to a hydraulic circuit connecting the supply 31 to the servo-valve 8, such that the fluid circulating between the supply 31 and the servo-valve 8 passes through the electrohydraulic selector 30. Advantageously, the electrohydraulic selector 30 is connected to a hydraulic circuit connecting the supply 31 to the cylinder 16 of the device 14, such that the fluid circulating between the supply 31 and the cylinder 16 of the device 14 passes through the electrohydraulic selector 30. Preferably, the servo-valve 8 is permanently connected to the low-pressure fluid supply 31 by a hydraulic line. Preferably, the cylinder 16 of the device 14 is permanently connected to the low-pressure fluid supply 31 by a hydraulic line.

[0043] Supplying high-pressure fluid comprises, for example, injecting fluid at a pressure close to 10 bar or at a pressure between 10 bar and 350 bar, for example at a pressure of 210 bar, into the pipes of the actuation system 2. Supplying low-pressure fluid comprises, for example, exhausting fluid circulating in the actuation system 2.

[0044] The electro-hydraulic selector 30 includes, for example, a distributor having four circulation ports and two possible distributor positions. The four circulation ports include, for example, a high-pressure fluid inlet port, a discharge outlet port, a first circulation port, and a second circulation port. The first position of the distributor corresponds to, for example, the circulation of high-pressure fluid from the high-pressure fluid inlet port to the first circulation port, and the discharge of fluid from the second circulation port to the discharge outlet port. The second position of the distributor corresponds to, for example, the circulation of high-pressure fluid from the high-pressure fluid inlet port to the second circulation port, and the discharge of fluid from the first circulation port to the discharge outlet port.

[0045] In addition, the electro-hydraulic selector 30 is configured to switch between several operating modes. For example, in a first operating mode, the electro-hydraulic selector 30 supplies the servo-valve 8 with high-pressure fluid from the supply device 31, and supplies the cylinder 16 of the device 14 with low-pressure fluid from the supply device 31. For example, in a second operating mode, the electro-hydraulic selector 30 supplies the servo-valve 8 with low-pressure fluid from the supply device 31, and supplies the cylinder 16 of the device 14 with high-pressure fluid from the supply device 31.

[0046] During normal operation of the actuation system 2, for example when the calculator 26 detects no fault, the electrohydraulic selector 30 connects the servo valve 8 to the supply device 31 to supply high-pressure fluid to the servo valve 8, and connects the cylinder 16 of the device 14 to the supply device 31 to discharge low-pressure fluid from the cylinder 16 of the device 14.

[0047] During abnormal operation of the actuation system 2, for example, when the computer 26 detects a fault (including an erroneous position of the cylinder 6) due to an unexpected fluid supply provided by the servo valve 8, or when the computer 26 detects an unexpected behavior of the servo valve 8, the electrohydraulic selector 30 connects the servo valve 8 to the supply device 31 to discharge low-pressure fluid from the servo valve 8, and connects the cylinder 16 of the device 14 to the supply device 31 to supply high-pressure fluid to the cylinder 16 of the device 14. This interrupts the unexpected fluid supply from the servo valve 8 and enables the servo-controlled cylinder 6 to be set in a stable equilibrium position.

[0048] The stable equilibrium position corresponds, for example, to a rest position of the actuation system 2 which makes it available for new uses, to a collection position of the actuation system 2 , or to a maintenance position which allows simplified access to the actuation system 2 , in particular for servicing the actuation system 2 .

[0049] Figure 2 A device 14 for setting a stable equilibrium position according to the invention is schematically shown. The device 14 is shown in a predetermined stable equilibrium position.

[0050] Cylinder 16 of device 14 includes a first inlet 32 ​​for high pressure fluid in first chamber 22 and a second inlet 34 for high pressure fluid in second chamber 24. After a fault is detected, first inlet 32 ​​and second inlet 34 are supplied with high pressure fluid by electrohydraulic selector 30.

[0051] The cylinder 16 of the device 14 further comprises a first outlet 36 for low-pressure fluid and a second outlet 38 for low-pressure fluid, which are longitudinally arranged at different positions between the first inlet 32 ​​and the second inlet 34. The first outlet 36 and the second outlet 38 are arranged in an element 39 constituting a wall of the cylinder 16 of the device 14. When designing the device 14, the longitudinal position of the element 39 is advantageously chosen so as to be able to construct an actuation system 2 whose predetermined stable equilibrium position can be adjusted from one manufacture to another. Preferably, the first outlet 36 and the second outlet 38 are connected to the low-pressure fluid supply 31.

[0052] When the first inlet 32 ​​and the second inlet 34 are supplied with high-pressure fluid, and the first outlet 36 and the second outlet 38 are connected to the low-pressure fluid supply device 31, the piston 20 of the cylinder 16 moves through the difference between the first pressure P1 and the second pressure P2 to place itself in a stable equilibrium position. In addition, the first pressure P1 and the second pressure P2 apply a force to the piston 20 of the cylinder 16. This force moves the rod 10 of the servo cylinder 4 that is mechanically fixed to the rod 18 of the cylinder 16. More specifically, when the piston 20 of the cylinder 16 moves, the first pressure P1 and the second pressure P2 change until they are both equal, so when the servo cylinder 4 is set in its stable equilibrium position, the first pressure P1 and the second pressure P2 apply equal forces to the piston 20 of the cylinder 16.

[0053] The cross section of the cylinder 16 of the device 14 is advantageously configured to provide a force sufficient to place the servo-controlled cylinder 6 in a stable equilibrium position. The larger cross section of the cylinder 16 of the device 14 enables greater opposing forces, in particular from the servo-controlled cylinder 6, to be overcome.

[0054] The present invention also enables the application of mechanical force through hydraulic adjustment.

[0055] In another embodiment, the actuation system 2 does not include the electrohydraulic selector 30. Then, both the cylinder 16 of the device 14 and the servo-control cylinder 6 are connected to the high-pressure fluid supply 31, and the cylinder 16 of the device 14 continuously applies a force to the servo-control cylinder 6 to return it to its stable equilibrium position. Advantageously, the cross-sectional area of ​​the piston 20 of the cylinder 16 is smaller than the cross-sectional area of ​​the piston 12 of the servo cylinder 4, so that the cylinder 16 of the device 14 exerts less parasitic forces on the servo-control cylinder 6 during its normal operation. During a passive fault of the servo cylinder 4, the cylinder 16 of the device 14 places the servo-control cylinder 6 in its stable equilibrium position. Advantageously, during an active fault, for example, the supply to the servo cylinder 4 is manually cut off, and the device 14 places the servo-control cylinder 6 in its stable equilibrium position.

[0056] The piston 20 of the device 14 includes a portion 40 of generally cylindrical shape having a diameter substantially equal to the diameter of the inner cross-section of the piston 20 of the device 14 and a height substantially equal to the longitudinal distance between the first outlet 36 and the second outlet 38. In the stable equilibrium position, the first outlet 36 and the second outlet 38 are partially located on either side of the piston 20 of the device 14. Advantageously, the angle of the portion 40 of the piston 20 is inclined so that when the cylinder 16 of the device 14 is in the stable equilibrium position, the fluid circulates from the first inlet 32 ​​to the first outlet 36 and from the second inlet 34 to the second outlet 38. In another embodiment, the angle of the portion 40 of the piston 20 has a sharp edge or any other transition shape.

[0057] The piston 20 of the device 14 advantageously includes a low friction seal to provide sealing of the first chamber 22 and the second chamber 24 as the piston 20 of the device 14 moves.

[0058] The piston 20 of the device 14 comprises two stops 42 on either side of the portion 40. Advantageously, the first inlet 32 ​​is as close as possible to the resting position of the piston 20 on the side of the first chamber 22, the corresponding stop 42 being dimensioned so that when the piston 20 of the device 14 is in the resting position, a high-pressure fluid can enter the first chamber 22 through the first inlet 32. Advantageously, the second inlet 34 is as close as possible to the resting position of the piston 20 on the side of the second chamber 24, the corresponding stop 42 being dimensioned so that when the piston 20 of the device 14 is in the resting position, a high-pressure fluid can enter the second chamber 24 through the second inlet 34.

[0059] In one embodiment, the first inlet 32 ​​and the second inlet 34 are provided with an adjustable restriction 44, which is arranged in the discharge line of the first inlet 32 ​​and the second inlet 34. When the actuation system 2 is in a stable equilibrium position, the forces exerted on the piston 20 of the device 14 are balanced. The adjustable restriction 44 can be used to modify, for example, the speed to set the stable equilibrium position of the actuation system 2. The value of the first pressure P1 and the second pressure P2 and / or the value of the repositioning speed and / or the value of the fluid circulation from the first inlet 32 ​​and the second inlet 34 to the first outlet 36 and the second outlet 38 is determined, for example, by the size of the restriction 44 and the overlap of the portion 40 of the piston 20 with the first outlet 36 and the second outlet 38. The repositioning speed also depends on the device implemented by the use of connecting the servo valve 8 in the event of a fault, which device is not described because it is known in the prior art.

[0060] Figure 3 The device 14 for setting a stable equilibrium position according to the present invention is schematically shown. The device 14 is shown in a position such that the volume of the first chamber 22 is smaller than the volume of the second chamber 24. When a failure of the servo cylinder 4 is detected, the electrohydraulic selector 30 switches to change the supply mode and cuts off the high-pressure fluid supply to the servo valve 8, thereby cutting off the high-pressure fluid supply to the servo control cylinder 6. The electrohydraulic selector 30 then supplies the high-pressure fluid to the first inlet 32 ​​and the second inlet 34 at the same time, for example.

[0061] After the fault is detected, the first chamber 22 is supplied with a high-pressure fluid that cannot be discharged through the first outlet 36 and the second outlet 38 located in the second chamber 24. Then, the pressure P1 in the first chamber 22 increases and is greater than the pressure P2 in the second chamber 24. The pressure in the first chamber 22 is, for example, equal to the pressure of the fluid injected under high pressure. The pressure in the second chamber 24 is, for example, equal to the pressure of the fluid in the low-pressure circuit of the supply device 31. In one embodiment, the fluid in the first chamber 22 flows between the element 39 and the portion 40 of the piston 20 of the device 14 at a very low flow rate to control the repositioning speed, and the pressure in the first chamber 22 does not increase too quickly. The forces exerted on the piston 20 of the device 14 by the first pressure P1 and the second pressure P2 tend to move it toward its stable equilibrium position.

[0062] Preferably, this very low flow rate between the element 39 and the portion 40 of the piston 20 of the device is taken into account when designing the actuation system 2. The values ​​of the first pressure P1 and the second pressure P2 and / or the value of the repositioning speed and / or the value of the circulation of the fluid from the first inlet 32 ​​and the second inlet 34 to the first outlet 36 and the second outlet 38 are advantageously determined by the size of the restriction 44, the overlap of the portion 40 of the piston 20 with the first outlet 36 and the second outlet 38, and the value of this flow rate.

[0063] Figure 4 A device 14 for setting a stable equilibrium position according to the invention is schematically shown. The device 14 is shown located Figure 2 and Figure 3 Since the fluid in the first chamber 22 still cannot reach the fluid outlets 36, 38, the piston 20 of the device 14 overlaps the first outlet 36. The pressure P1 in the first chamber 22 is still higher than the pressure P2 in the second chamber 24. Therefore, the piston 20 of the device 14 continues to move toward Figure 2 The stable equilibrium position shown shifts.

[0064] When the device 14 is in a position such that the volume of the first chamber 22 is greater than the volume of the second chamber 24, the opposite situation is understood symmetrically in a similar manner.

[0065] Figure 2 The device 14 shown in FIG. 1 has a transverse axis of symmetry, however other configurations of the cylinder 16 of the device 14 are possible. For example, when the piston 20 of the device 14 is at the center of its stroke, the volume of the first chamber 22 may be different from the volume of the second chamber 24.

[0066] The first outlet 36 and the second outlet 38 are, for example, located on either side of the piston 20 of the device 14, which is positioned in a non-central position of its stroke to define a stable equilibrium position of the servo-control cylinder 6 that is different from the central position of the piston stroke. The choice of the intermediate stable equilibrium position is free in design and is in particular predefined by modifying the overlap of the piston 20 of the device 14 with the first outlet 36 and the second outlet 38.

[0067] In another embodiment, the first outlet 36 and the second outlet 38 are fluidly connected, such as by a slot provided in the wall of the piston 20 of the device 14, so that the first outlet 36 and the second outlet 38 are in fluid communication and form a single outlet.

[0068] Figure 5 Also shown are the steps of a method 46 for setting a predetermined stable equilibrium position of a servo cylinder 4 of an actuation system 2 .

[0069] First, a step 48 is performed: interrupting the undesired fluid supply provided by the servo valve 8 of the servo cylinder 4. The interruption step 48 occurs, for example, after the computer 26 has detected a fault. Before the fault, the electrohydraulic selector 30, for example, connects the means 31 for supplying high-pressure fluid to the servo valve 8 and, for example, connects the device 14 to the low-pressure fluid supply means 31.

[0070] Then, a step 50 is performed of supplying fluid to the cylinder 16 of the device 14 for setting a predetermined stable equilibrium position of the piston 12 of the servo cylinder 4. During the supply step 50, the electrohydraulic selector 30 connects the servo valve 8, for example, to the low-pressure fluid supply 31 and connects the device 14, for example, to the high-pressure fluid supply 31. Advantageously, steps 48 and 50 are carried out simultaneously, in particular by switching the electrohydraulic selector 30 between two operating modes.

[0071] Next, step 52 is performed: translating the servo cylinder 4 to a predetermined stable equilibrium position. Advantageously, step 52 is performed simultaneously with step 50. By simultaneous action of step 50 and step 52, it is meant that steps 50 and 52 occur simultaneously, or are offset in time by a negligible amount.

[0072] Step 52 consists in translating the piston 20 of the cylinder 16 to a predetermined stable equilibrium position. During step 52, the rod 10 of the servo cylinder 4, which is mechanically fixed to the rod 18 of the cylinder 16, also translates to a stable equilibrium position, thereby positioning the servo cylinder 4 in the predetermined stable equilibrium position. Finally, step 54 is performed: the piston 12 of the servo cylinder 4 is kept in the predetermined stable equilibrium position. During step 54, the first pressure P1 is equal to the second pressure P2. When the piston 12 of the servo cylinder 4 moves away from the stable equilibrium position, the capping of the first outlet 36 and the second outlet 38 is modified. Thus, the first pressure P1 and the second pressure P2 are modified and tend to return the piston 12 of the servo cylinder 4 to the stable equilibrium position. The pressure of the chamber whose volume is reduced increases and exerts on the piston 12 of the servo cylinder 4 a force greater than the force exerted on the piston 12 of the servo cylinder 4 by the pressure of the other chamber, which greater force returns the piston 12 of the servo cylinder 4 to the stable equilibrium position where the first pressure P1 is equal to the second pressure P2.

Claims

1. An actuation system (2), the actuation system comprising an actuator, the actuator comprising a servo cylinder (4), the servo cylinder (4) comprising a rod (10) provided with a piston (12), the actuator comprising a device (14) for setting a predetermined stable equilibrium position of the piston (12) of the servo cylinder (4), the device (14) comprising a cylinder (16) provided with a rod (18), the rod of the cylinder being mechanically fixed to the rod (10) of the servo cylinder (4), the cylinder (16) comprising a cylinder (16) mounted to the cylinder (18) 16), so that a first chamber (22) subjected to a first pressure (P1) and a second chamber (24) subjected to a second pressure (P2) are defined on either side of the piston (20) in the cylinder (16), the first and second chambers (22, 24) being configured to contain a fluid, the piston (12) of the servo cylinder (4) being configured such that when the first and second pressures (P1, P2) are equal, the piston of the servo cylinder is positioned at the predetermined stable equilibrium position, characterized in that The cylinder (16) includes a first inlet (32) for fluid in the first chamber (22) and a second inlet (34) for fluid in the second chamber (24), the cylinder (16) including a first outlet (36) for fluid and a second outlet (38) for fluid, the first outlet and the second outlet being longitudinally disposed at different positions between the first and second inlets (32, 34) and sized such that when the piston (12) of the servo cylinder (4) is in the predetermined stable equilibrium position, the first outlet (36) allows fluid from the first inlet (32) to pass and the second outlet (38) allows fluid from the second inlet (34) to pass.

2. The system (2) according to claim 1, comprising a fluid supply device (31) configured to supply fluid to the actuator.

3. The system (2) according to any one of claims 1 and 2, wherein: The servo cylinder (4) comprises a servo valve (8), and the actuator comprises an electrohydraulic selector (30) configured to interrupt the fluid supply to the servo valve (8) in the event of an undesired behavior.

4. The system (2) according to any one of claims 1 to 3, wherein: The first and second outlets (36, 38) are fluidly connected, and a slot is provided in the wall of the piston (20) of the device (14) so ​​that the first and second outlets (36, 38) are in fluid communication and form a single outlet.

5. The system (2) according to any one of claims 1 to 4, wherein: The actuator comprises a position sensor (28) for the piston (12) of the servo cylinder (4).

6. The system (2) according to any one of claims 1 to 5, comprising a computer (26) configured to detect a malfunction of the servo cylinder (4).

7. The system (2) according to any one of claims 1 to 6, wherein: The cross-sectional area of ​​the piston (20) of the cylinder (16) is smaller than the cross-sectional area of ​​the piston (12) of the servo cylinder (4).

8. A method (46) for setting a predetermined stable equilibrium position of a servo cylinder (4) of an actuation system (2) according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: - interrupting the fluid supply to the servo valve (8) of the servo cylinder (4) in the event of an undesired behavior; - supplying fluid to the cylinder (16) of the device (14) for setting a predetermined stable equilibrium position of the piston (12) of the servo cylinder (4); - translating the servo cylinder (4) to the predetermined stable equilibrium position; and - Maintaining the piston (12) of the servo cylinder (4) in the predetermined stable equilibrium position, the first and second pressures (P1, P2) being equal.

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