Pressure-compensating braking system and aircraft equipped with it

Abstract

Braking system comprising at least one brake (1A, 1B) provided with a fluidic actuator (2A, 2B) and a fluid circuit connected to the actuator (2A, 2B), the fluid circuit comprising a pressurized fluid source (12, 13) and a pilot distributor (3) which is placed between the actuator (2A, 2B) and the fluid source (12, 13) to pilot the actuator (2A, 2B) and which is controlled by pulse width modulation (PWM) by an electronic control unit (5) arranged to determine, as a function of a braking setpoint, a duty cycle for controlling the distributor (3). The system includes a pressure sensor (14) placed in the fluid circuit upstream of the distributor (3) and connected to the control unit (5) to provide it with a pressure signal, and the control unit (5) is arranged to correct the duty cycle as a function of the pressure signal to compensate at least partially for a pressure drop.Lander and aircraft comprising such a system. FIGURE IN ABRIDGED DIAGRAM: Fig. 2.

Description

Title of the invention: Pressure drop compensation braking system and aircraft equipped therewith

[0001] The invention relates to the field of braking of vehicles and in particular aircraft.

[0002] BACKGROUND OF THE INVENTION

[0003] In the aeronautical field, braking systems are known comprising brakes, each equipped with a hydraulic actuator, and a hydraulic circuit connected to the hydraulic actuator of each brake. The hydraulic circuit includes a pressurized hydraulic fluid source and a two-state pilot valve located between the actuator and the hydraulic fluid source to control the actuator and which is controlled by an electronic control unit (see, for example, document EP-A-3581446).

[0004] The pilot valve is generally a 3-way / 2-position solenoid valve (Pilot Solenoid Valve), controlled by a pulsed electrical signal supplied by the control unit. The pilot valve has only two positions, namely a closed position (actuator at exhaust) and an open position (actuator subjected to upstream pressure), and, depending on the type of valve, the rest position (valve not electrically controlled) can be either the closed or open position.

[0005] The pressure level in the brakes can then be controlled by modulating the pulse width (PWM) of the electrical signal supplied by the control unit. The general principle of pulse width modulation consists of applying a succession of discrete ON / OFF states for predetermined durations and at a fixed frequency, thus making it possible to obtain, on average over a certain period, any intermediate pressure value. The modulation is defined by the ratio of the duration in the ON state to the total duration of a cycle (signal period). Thus, a ratio of 0% corresponds to a permanently closed state, a ratio of 100% corresponds to a permanently open state, and a ratio of 50% corresponds to the distributor being open 50% of the time during a cycle. This ratio is called the duty cycle or PWM ratio.The PWM control allows the two-state pilot valve to be transformed into a proportional valve by implementing electrical control.

[0006] To implement this piloting mode, the control unit is therefore arranged to determine, according to a braking instruction issued by the aircraft pilot, the control duty cycle of the piloting distributor.

[0007] This piloting method is particularly effective when the pressure supplied by the hydraulic pressure source is constant, which is the case when the pressure source is a hydraulic pump. However, it is common to combine the hydraulic pump with a pressure accumulator to compensate for a pump failure. The pressure supplied by such an accumulator tends to decrease as the actuator empties, and aircraft pilots have become accustomed to partially compensating for this pressure drop by increasing the command sent to the control unit. Nevertheless, braking distances increase when the pressure source is the accumulator, and this increase depends on the pilot's experience and reaction time, especially since a partial failure of the braking system, resulting in the use of the accumulator as a pressure source, causes stress for the pilot.

[0008] SUBJECT OF THE INVENTION

[0009] The invention aims to provide a more efficient braking system. PRESENTATION OF THE INVENTION

[0010] To this end, the invention proposes a braking system comprising at least one brake equipped with a fluidic actuator and a fluid circuit connected to the actuator. The fluid circuit includes a pressurized fluid source and a pilot valve located between the actuator and the fluid source to control the actuator. This pilot valve is controlled by pulse-width modulation by an electronic control unit arranged to determine, based on a braking setpoint, a duty cycle for controlling the valve. The system includes a pressure sensor located in the fluid circuit upstream of the valve and connected to the control unit to provide it with a pressure signal. The control unit is arranged to correct the duty cycle based on the pressure signal to at least partially compensate for a pressure drop.

[0011] Thus, the control unit is designed to compensate for a pressure drop in the pressurized fluid circuit upstream of the servovalve's supply port, regardless of the cause, without pilot intervention. This results in improved braking efficiency in the event of a pressure drop in the pressurized fluid circuit, while also reducing the pilot's mental workload.

[0012] According to optional features, used individually or in whole or in combination: - the control unit is arranged to determine a correction factor based on the pressure signal and also the duty cycle; - The correction uses the following formula: r, = Mir^ K (Ps, ts) xr, ; 1)

[0013] with

[0014] Min the minimum function,

[0015] K the correction factor,

[0016] Ps the pressure obtained from the pressure signal,

[0017] The duty cycle calculated from the setpoint,

[0018] t's the corrected cyclic ratio; - the control unit has a memory containing a table relating reference values ​​of correction factor, duty cycle and pressure; - the control unit is arranged to determine the value of the correction factor to be applied by interpolation from the reference values ​​contained in the table; - the control unit is arranged to apply the correction in the form of a stored mathematical equation; - the mathematical equation is of the type gç p ~ A^P^Xr* with ^.(p^ — g.. x PPFL m and n are positive integers, B;j is a real number; - the mathematical equation is of the type K — Ax Ps + B with K the correction value, Ps the pressure from the pressure signal, A and B constants.

[0019] The invention also relates to an aircraft equipped with such a braking system.

[0020] The invention will be better understood in the light of the following description of a particular embodiment of the invention, DESCRIPTION OF FIGURES

[0021] Reference will be made to the figures in the attached drawings, among which:

[0022] [Fig. 1] is a schematic front view of an aircraft equipped with a system of braking according to the invention;

[0023] [Fig.2] is a diagram of the hydraulic system according to the invention;

[0024] [Fig.3] is a diagram showing the operation of the electronic control of the pulse width modulation braking system;

[0025] [Fig.4] is a diagram showing the pressure in the brakes as a function of the command and in the absence of duty cycle correction;

[0026] [Fig.5] is a diagram showing theoretical values ​​of the compensator according to the invention for different pressures of the hydraulic circuit of the braking system;

[0027] [Fig.6] is a diagram showing the pressure in the brakes as a function of the control and with correction of the duty cycle according to a particular embodiment of the invention;

[0028] [Fig.7] is a diagram showing the pressure in the brakes as a function of the control and with correction of the duty cycle according to another particular embodiment;

[0029] [Fig. 8] is a diagram showing the distance traveled by the aircraft as a function of time during braking, with and without duty cycle correction. DETAILED DESCRIPTION OF THE INVENTION

[0030] With reference to [Fig. 1], the invention is herein described in application to an aircraft 100 comprising main landing gear 101 having ends provided with an axle 102 on which are mounted wheels 103 pivoting about a central axis X of the axle 102.

[0031] Figure [Fig. 2] illustrates a hydraulic diagram of the braking system according to the invention. The braking system comprises two brakes IA and IB associated with braked wheels 103A and 103B of each landing gear 101. The brakes IA and IB are known in themselves and each comprise a stack of brake discs comprising alternately stator discs rotationally linked to the axle 102 and rotor discs rotationally linked to a rim of the wheel 103A, 103B, and a hydraulic actuator 2A, 2B of the cylinder type arranged to press the discs against each other so as to generate by friction a braking torque.

[0032] The hydraulic actuators 2A, 2B are connected to the service port 3.1 of a two-state distributor 3 which is connected to an electronic control unit itself connected to a control instrument 4.

[0033] The distributor 3 has a movable spool in two positions, one corresponding to a stable rest state (illustrated in [Fig. 1]) in which the spool of the distributor 3 connects the service port 3.1 to a return port 3.2, and, for the other position, to an unstable active state in which the spool of the distributor 3 connects the service port 3.1 to a supply port 3.3. An electromagnetic actuator 7 forces the spool of the distributor 3 to move into the active state when the coil 7 is energized by a control voltage, and a spring 8 returns the spool of the distributor 3 to the rest state when the coil 7 is no longer energized. The return port 3.2 is connected to a fluid reservoir 9 via a non-return valve 10. The supply port 3.3 is connected on the one hand, via a non-return valve 11, to a discharge port of a pump 12 whose suction port is connected to the fluid reservoir 9 and, on the other hand, to a fluid accumulator 13.

[0034] In operation, the control unit 5 supplies the coil 7 so that the pressure Pc delivered to the brakes IA, IB via the service port 3.1 is a function of the position of the instrument (which can be a pedal or a lever) operated by the aircraft pilot. For this purpose, the position of the instrument 4, which is representative The braking command is measured here by means of a potentiometer whose output is transmitted to the electronic control unit 5, which includes signal processing means adapted to generate a command for a first selector switch that selectively connects a first terminal of the coil 7 either to ground or to a DC voltage source (here, 28VDC). This is known in itself.

[0035] Here, the control unit 5 is adapted to implement a pulse-width modulation (PWM) process illustrated in [Fig. 3]. When the instrument 4 is moved by the pilot from an initial position, referred to as 0%, the selector energizes the coil 7 for a predetermined initial time, which promotes the filling of the actuators 2B, 2A of the brakes IA, IB with hydraulic fluid. Then, for each successive period, the control unit 5 determines: - an opening time which here is a function of the position of instrument 4 between the 0% position and the 100% position which corresponds to the maximum stroke of instrument 4, for example according to a proportional law, - a free escape time complementary to the opening time, - an electrical impulse control C presenting a duty cycle rs representative of the ratio of opening time to total time.

[0036] The distributor 3 then connects the service port 3.1 to the supply port 3.3 during the opening time, and connects the service port 3.1 to the return port 3.2 during the exhaust time, which is complementary to the opening time. The average pressure Pc seen by the actuators 2A, 2B of the brakes IA, IB is a function of the duty cycle rs and increases with this duty cycle rs between the return pressure and the supply pressure. The pulse width modulation frequency naturally depends on the bandwidth of the aircraft's hydraulic circuit, and therefore on the length of the hydraulic circuit, the volume of the cavities of the actuators 2A, 2B of the brakes IA, IB, etc. Typically, a frequency of a few hertz is sufficient to ensure proportional control, taking into account the natural filtering induced by the hydraulic circuit.Thus, thanks to a simple two-state distributor, we obtain a control proportional to the position of the control instrument 4.

[0037] The pressure Pc in actuators 2A, 2B is calculated as follows: 100381

[0039] With:

[0040] Bm the bulk modulus of the fluid, which depends in particular on the fluid pressure,

[0041] V the volume of all the pressurized cavities of the actuators 2A, 2B downstream of the distributor 3,

[0042] Q the average flow rate in all these cavities

[0043] The average flow rate Qp in the cavities relates to the average flow rates entering and exiting through the service port 3.1 of the distributor 3, and their relationship is defined as:

[0044] Q P = Q s - Q r PI

[0045] Qs and Qr respectively denote the inflow and outflow of distributor 3 and are defined by the following mathematical relationships (assuming that the flow is constantly turbulent through the service port 3.1 of distributor 3):

[0046]

[0047] Q R — 1 T S) x Cq x S x [4]

[0048] With:

[0049] Q the pressure loss coefficient through distributor 3,

[0050] $ the passage section in the distributor 3,

[0051] the density of the fluid flowing through the distributor 3,

[0052] Ps the supply pressure at the supply port 3.3 of the distributor 3,

[0053] For the pressure at the return port 3.2 of the distributor 3,

[0054] rs the duty cycle of the control signal emitted by the control unit 5, between 0 and 1.

[0055] Figure 4 illustrates the pressure curve Pc that can be obtained in actuators 2A, 2B as a function of the pressure at the supply port 3.3 and the duty cycle: The Pc2Oo curve represents the pressure curve Pc that can be obtained in actuators 2A, 2B for a pressure of 200 bars at the supply port 3.3; The Pc i60 curve represents the pressure curve Pc that can be obtained in actuators 2A, 2B for a pressure of 160 bars at the supply port 3.3; The Pc n 0 curve represents the pressure curve Pc that can be obtained in actuators 2A, 2B for a pressure of 120 bars at the supply port 3.3; The PCs curve represents the pressure curve Pc that can be obtained in actuators 2A, 2B for a pressure of 80 bars at the supply port 3.3; The Pc 6 0 curve represents the pressure curve Pc that can be obtained in actuators 2A, 2B for a pressure of 60 bars at the supply port 3.3; - the Pc 4 0 curve represents the pressure curve Pc that can be obtained in actuators 2A, 2B for a pressure of 40 bars at the supply port 3.3.

[0056] The pressure that can be obtained in the actuators 2A, 2B, and therefore the maximum braking torque that can be obtained, is obviously highly dependent on the pressure at the supply port 3.3. In nominal operating mode, the supply port 3.3 of the distributor 3 is supplied by the pump 12 at a constant pressure of 200 bar. Conversely, when the pump 12 fails, the supply port 3.3 of the distributor 3 is supplied by the accumulator 13, the pressure of which decreases as it empties.

[0057] It follows that for the same displacement of instrument 4, the pressure that can be obtained in actuators 2A, 2B, and therefore the resulting braking force, depends on the pressure at the supply port 3.3. Figure 6 illustrates the pressure curve Pc that can be obtained in actuators 2A, 2B as a function of the pressure at the supply port 3.3 and the displacement of instrument 4: - the Pc2Oo curve represents the pressure curve Pc that can be obtained in actuators 2A, 2B for a pressure of 200 bars at the supply port 3.3; - the Pc i80 curve represents the pressure curve Pc that can be obtained in actuators 2A, 2B for a pressure of 180 bars at the supply port 3.3; - the Pc i60 curve represents the pressure curve Pc that can be obtained in actuators 2A, 2B for a pressure of 160 bars at the supply port 3.3; - the Pc M0 curve represents the pressure curve Pc that can be obtained in actuators 2A, 2B for a pressure of 140 bars at the supply port 3.3; - the Pc i2 o curve represents the pressure curve Pc that can be obtained in actuators 2A, 2B for a pressure of 120 bars at the supply port 3.3; - the curve Pc i0 o represents the pressure curve Pc that can be obtained in actuators 2A, 2B for a pressure of 100 bars at the supply port 3.3; - the PC8 curve represents the pressure curve Pc that can be obtained in actuators 2A, 2B for a pressure of 80 bars at the supply port 3.3; - the Pc 6 0 curve represents the pressure curve Pc that can be obtained in actuators 2A, 2B for a pressure of 60 bars at the supply port 3.3; - the Pc 4 0 curve represents the pressure curve Pc that can be obtained in actuators 2A, 2B for a pressure of 40 bars at the supply port 3.3.

[0058] It is therefore understood that the response of the braking system to the movement of the instrument 4 is completely different between a supply by the pump 12 and a supply by the accumulator 13, and is completely different between the moment when the accumulator 13 at the beginning of use provides a pressure of 200 bars and the moment when the accumulator 13 at the end of use provides a pressure of 20 bars.

[0059] According to the invention, a pressure sensor 14 is mounted between the accumulator 13 and the supply port 3.3 of the distributor 3 (i.e., upstream of the distributor 3 with reference to fluid circulation during the supply of the distributor 3). The pressure sensor 14 is mounted here just downstream of the accumulator 13, but it could be mounted elsewhere upstream of the supply port 3.3 and, for example, immediately downstream of the check valve 11.

[0060] According to the invention, the pressure sensor 14 is connected to the control unit 5 to provide it with a pressure signal representative of the supply pressure Ps and the control unit 5 is arranged to correct the duty cycle as a function of the pressure signal to compensate at least partially for a pressure drop.

[0061] More specifically, the control unit 5 is arranged to determine a correction factor based on the pressure signal and also on the duty cycle, and the correction implements the following formula:

[0062] Ts = Mwk. K(PSy rs) xr^l)

[0063] With

[0064] Min the minimum function,

[0065] K the correction factor,

[0066] Ps the pressure obtained from the pressure signal,

[0067] The duty cycle is calculated from the setpoint and a theoretical pressure value of 200 bar,

[0068] A the corrected cyclic ratio.

[0069] The minimum function prevents the corrected duty cycle from taking a value greater than 1.

[0070] Figure 5 gives examples of values ​​of the correction factor K as a function of the initial duty cycle Ts, corresponding to the full supply pressure here 200 bar, and as a function of the supply pressure Ps: - the r'18O curve represents the corrected duty cycle curve, for a pressure of 180 bars at the supply port 3.3; - the curve r^i60 represents the corrected duty cycle curve, for a pressure of 160 bars at the supply port 3.3; - the t^140 curve represents the corrected duty cycle curve, for a pressure of 140 bars at the supply port 3.3; - the r^120 curve represents the corrected duty cycle curve, for a pressure of 120 bars at the supply port 3.3; - the t's 100 curve represents the corrected duty cycle curve, for a pressure of 100 bars at the supply port 3.3; - curve 7"'g0 represents the corrected duty cycle curve for a pressure of 80 bars at the supply port 3.3; - the curve represents the corrected duty cycle curve, for a pressure of 60 bars at the supply port 3.3; - the t$40 curve represents the corrected duty cycle curve, for a pressure of 40 bars at the supply port 3.3.

[0071] It can be seen that the minimum function saturates the value of the correction factor so that the result of the multiplication of this factor and the initial duty cycle does not exceed 100%.

[0072] According to a first, digital embodiment, the control unit 5 has a memory containing a table relating reference values: the correction factor, the duty cycle, and the pressure. The control unit 5 is configured to determine the value of the correction factor to be applied by interpolation from the reference values ​​contained in the table. A drawback of this embodiment is that a large number of reference values ​​are required in the table to avoid non-linearities in the correction function. Therefore, the memory must be relatively large.

[0073] According to a second embodiment using a microcontroller, the control unit 5 is arranged to determine the correction to be applied in the form of a stored mathematical equation established from basic mathematical, trigonometric and / or logarithmic functions.

[0074] More precisely, the mathematical equation is non-linear and has a polynomial form of the type:

[0075] j = ^A^P,} xTj

[0076] With: [°° 77 1 P*'

[0078] i is a positive integer,

[0079] j is a positive integer,

[0080] m is a positive integer,

[0081] n is a positive integer,

[0082] Bÿ is a real number.

[0083] The coefficients Bÿ define each polynomial function A;(PS) of degree m.

[0084] The function A;(PS) determines the value of the coefficients that define the polynomial function K(PS) of degree n.

[0085] The values ​​i and j are the indices which define the mathematical expression of the sum and designate the coefficients which allow to encompass the terms which must be considered in the sum, this mathematical expression is an international representation.

[0086] On the other hand, m and n (positive integers) respectively define the degree of the polynomial functions A;(PS) and K. These values ​​m and n are chosen so as to obtain the best representation of the correction coefficient K. Generally a degree 2 is sufficient to obtain a sufficient representation.

[0087] It is possible to define distinct polynomial degrees for each function A;.

[0088] For example, with m=2, we will have:

[0089] K(P* rs) = A2(Ps)x + Ax (Ps) x rs + Aq

[0090] With:

[0091] A(PS) = BQ2x Pj + B0]x Ps + Bm with n=2

[0092] A^Ps) = B13x Pg + B12x Pi + Bux Ps + B10 with n=3

[0093] A2(PA=B22x P] + B2ix Ps + B20 with n=2

[0094] This implementation method requires computing resources such as requiring the use of a microcontroller or microprocessor with the associated computer program.

[0095] A purely analog solution can also be considered. It is difficult to use the equation of the second implementation mode for this purpose because it would require the use of specific analog components of the multiplier type, which would complicate the control unit 5, resulting in a higher cost and a greater mass.

[0096] On the other hand, it is possible to opt for a simpler analog solution based on a linear correction function implemented using simple electronic components.

[0097] According to a third, analogous embodiment, the mathematical equation is simpler and the correction coefficient depends only on the pressure Ps.

[0098] The equation used to determine the value of the correction coefficient is then linear of the type

[0099] K = AxPs + B

[0100] In this equation, K is the correction factor and Ps the pressure from the pressure signal, A and B are constants.

[0101] Figures 7 and 8 show the pressure curve Pc that can be obtained in actuators 2A, 2B as a function of the pressure at the supply port 3.3 and the displacement of the instrument 4, after correction of the duty cycle by the second implementation mode ([Fig.7]) and by the third implementation mode ([Fig.8]): - the Pc2Oo curve represents the pressure curve Pc that can be obtained in actuators 2A, 2B for a pressure of 200 bars at the supply port 3.3; - the Pc i80 curve represents the pressure curve Pc that can be obtained in actuators 2A, 2B for a pressure of 180 bars at the supply port 3.3; - the Pc i60 curve represents the pressure curve Pc that can be obtained in actuators 2A, 2B for a pressure of 160 bars at the supply port 3.3; - the Pc i40 curve represents the pressure curve Pc that can be obtained in actuators 2A, 2B for a pressure of 140 bars at the supply port 3.3; - the Pc n 0 curve represents the pressure curve Pc that can be obtained in actuators 2A, 2B for a pressure of 120 bars at the supply port 3.3; - the curve Pc i0 o represents the pressure curve Pc that can be obtained in actuators 2A, 2B for a pressure of 100 bars at the supply port 3.3; - the PC8 curve represents the pressure curve Pc that can be obtained in actuators 2A, 2B for a pressure of 80 bars at the supply port 3.3; - the Pc 6 0 curve represents the pressure curve Pc that can be obtained in actuators 2A, 2B for a pressure of 60 bars at the supply port 3.3; - the Pc 4 0 curve represents the pressure curve Pc that can be obtained in actuators 2A, 2B for a pressure of 40 bars at the supply port 3.3.

[0102] By comparing the curves of figures 7 and 8 with those of [Fig.6] (in which the duty cycle is not corrected to compensate for a drop in pressure), it can be seen that the pressure in actuators 2A, 2B increases much more rapidly with the correction of the duty cycle so that, for the same braking setpoint, the pressure in actuators 2A, 2B with the correction of the duty cycle is greater than the pressure in actuators 2A, 2B without correction of the duty cycle.

[0103] Figure 8 shows the distance travelled by aircraft 100 as a function of time during braking: - the dl curve corresponds to the nominal braking in which the distributor 3 is supplied by the pump 12, - Curve d2 corresponds to degraded braking in which distributor 3 is supplied by accumulator 13 with duty cycle correction, - curve d3 corresponds to degraded braking in which distributor 3 is supplied by accumulator 13 without correction of the duty cycle.

[0104] It is observed that the correction of the duty cycle in degraded braking makes it possible to keep the performance of the braking system close to that obtained in nominal braking, without corrective action by the pilot (the pilot's command remains the same).

[0105] The invention is not limited to what has just been described but on the contrary encompasses any variant falling within the scope defined by the claims.

[0106] In particular, although here the distributor 3 is actuated by means of a coil, any other actuator may be used, such as for example an electric motor.

[0107] Although the sensor of the instrument is here a potentiometer, any other type of sensor may be used, such as for example an RVDT type inductive sensor.

[0108] The electronic unit may be analog or digital; it may include a microprocessor, a microcontroller and / or a programmable logic circuit, for example of the FPGA type.

[0109] The hydraulic circuit may have a different structure from that described and include, for example, flow reducers, flow sensors, filters, valves, and others.

[0110] The actuator of the distributor 3 can be a monostable actuator as shown here or bistable (without spring 8: the transition from active state to inactive state is carried out via a control of the actuator 7).

[0111] The number of wheels and the number of brakes may be different (for example two, four, eight or other...).

[0112] The invention is applicable to any type of vehicle equipped with wheels, and in particular to aircraft, land vehicles...

Claims

Demands

1. Braking system comprising at least one brake (IA, IB) provided with a fluidic actuator (2A, 2B) and a fluid circuit connected to the actuator (2A, 2B), the fluid circuit comprising a pressurized fluid source (12, 13) and a pilot valve (3) which is placed between the actuator (2A, 2B) and the fluid source (12, 13) to pilot the actuator (2A, 2B) and which is controlled by pulse width modulation (PWM) by an electronic control unit (5) arranged to determine, as a function of a braking setpoint, a duty cycle for controlling the valve (3),characterized in that the system comprises a pressure sensor (14) placed in the fluid circuit upstream of the distributor (3) and connected to the control unit (5) to provide it with a pressure signal, and in that the control unit (5) is arranged to correct the duty cycle according to the pressure signal to compensate at least partially for a pressure drop.

2. System according to claim 1, wherein the control unit (5) is arranged to determine a correction factor as a function of the pressure signal and also of the duty cycle.

3. System according to claim 2, wherein the correction implements the following formula: t's = Min( K( ts ) x ts ; 1) With Min the minimum function, K the correction factor, Ps the pressure obtained from the pressure signal, 's the duty cycle calculated from the setpoint, ts the corrected duty cycle.

4. System according to any one of claims 2 and 3, wherein the control unit (5) has a memory containing a table relating reference values ​​of correction factor, duty cycle and pressure.

5. System according to claim 4, wherein the control unit (5) is arranged to determine the value of the correction factor to be applied by interpolation from the reference values ​​contained in the table.

6. System according to any one of claims 2 to 5, wherein the control unit (5) is arranged to apply the correction in the form of a stored mathematical equation.

7. System according to claim 6, wherein the mathematical equation is of the type K ( p} = A(p\ x : with K the correction factor, Ps the pressure obtained from the pressure signal, Ts the duty cycle calculated from the setpoint, i, j, m and n are positive integers, Bÿ is a real number.

8. System according to claim 6, wherein the mathematical equation is of the type K — A x Ps + B with K the correction value, Ps the pressure from the pressure signal, A and B constants.

9. Landing gear (101) having at least one wheel (103) equipped with a brake (IA, IB) belonging to a braking system according to any one of the preceding claims.

10. Aircraft (100) comprising at least one landing gear (101) according to claim 9.

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