Control method for reducing brake fill time in a hydraulic braking system of an aircraft landing gear

Abstract

The invention relates to a method for controlling a hydraulic braking system (10) of an aircraft landing gear, which comprises at least one control member (12) generating an initial command, a servo valve (16) and a hydraulic brake (14). After an initial command has been generated, the control method determines an actual command that is to be transmitted to the hydraulic brake. Such an actual command makes it possible to ensure satisfactory responsiveness of the hydraulic braking system. The step of determining the actual command may, for example, comprise applying to the initial command a predetermined constant additional command that represents a predetermined braking pressure value, for example. The actual command can also be determined, for example, on the basis of the result of a comparison between the initial command and a predetermined threshold value representing a braking pressure.

Description

Description Title of the invention: Control method for reducing the filling time of a brake on a hydraulic braking system of an aircraft landing gear Technical Field

[0001] This presentation relates to a control method for controlling a hydraulic braking system of an aircraft landing gear, a computer program corresponding to this method, and a medium on which the computer program is recorded. Previous technique

[0002] As is well known, aircraft landing gear, particularly that of airplanes, is equipped with hydraulic brakes comprising a plurality of hydraulically actuated pistons and a plurality of brake discs pressed by the pistons. Some of the discs, called "rotor discs," are coupled to the wheel (for example, the rim) of the landing gear and rotate with it; the other part, called "stator discs," is coupled to a fixed part relative to the wheel. The rotor discs are mounted alternately with the stator discs. The aircraft's braking is achieved by the friction of the discs against each other when the pistons are actuated.

[0003] In this type of brake, there is a constant need to ensure a certain responsiveness of the braking while avoiding excessively abrupt braking in order to preserve a certain comfort for the aircraft passengers as well as the integrity of the various systems involved in the aircraft. Description of the invention

[0004] One embodiment relates to a method for controlling a hydraulic braking system of an aircraft landing gear, the hydraulic braking system comprising at least one control element, a servovalve, and a hydraulic brake, the hydraulic brake comprising a plurality of brake discs and pistons configured to press the discs of the plurality of discs, the control method comprising the implementation by computer or electronic equipment of: - detecting an initial command from the control element, - determine an effective order greater than or equal to the initial order, and - transmit the effective command to the hydraulic brake.

[0005] Hereafter and unless otherwise indicated, "braking system" means "hydraulic braking system".

[0006] The control device may be a brake pedal installed in the cockpit and / or an automatic braking system (or "autobrake") that can be activated during takeoff, landing, taxiing, etc. The braking system may include a hydraulic circuit, which includes at least one servovalve (defined later in this document) for activating the pistons based on the pressure of a fluid, such as brake fluid, within the hydraulic circuit. The braking system may also include computer or electronic equipment, which may be dedicated to it or shared with other aircraft equipment.

[0007] The command from the control element can be a control signal, for example, an electrical signal such as a change in voltage or current. The initial command can be, for example, in the form of a step function with a step value and a step duration; or in the form of a variable curve, representing the variations and adjustments of the command from the control element.

[0008] In some embodiments, the initial command, following its generation, can be converted into an initial current command, or into an initial pressure command.

[0009] Computer or electronic equipment can perform all or part of the operations of the control process described in this presentation. For example, computer or electronic equipment can detect the initial command from the control element, determine the actual command and / or transmit the actual command to the brake, either directly or via other elements, such as sensors, actuators, converters, the servo valve, etc.

[0010] For example, the initial command and the effective command can be pressure commands.

[0011] In another example, the initial command and the effective command can both be current commands. For instance, the effective command can then be converted into a pressure command within the hydraulic circuit by a current-to-pressure converter.

[0012] The latency, or response time, between the initial command and the actual braking within the brake depends on the value of the initial command. Specifically, depending on the strength of the initial command, the pressurization time within the hydraulic circuit, which may also be called "filling time" by those in the trade, and which corresponds to the free stroke time of the pistons before they press against the multiple brake discs, varies.

[0013] In the case of a relatively weak initial command, for example resulting from a light pressure on the brake pedal, the reaction time of the braking system can be relatively long.

[0014] The control method described herein improves the responsiveness of the braking system by determining, following the detection of an initial command, an effective command that is greater than or equal to the initial command. By delivering this effective command to the brake, satisfactory responsiveness of the braking system is ensured, for example, when a procedure such as aircraft taxiing is implemented, regardless of the initial command (i.e., regardless of its value).

[0015] In some embodiments, the determination of the effective control includes the implementation of applying to the initial control an additional control, for example a predetermined constant additional control, for example representative of a predetermined value of braking pressure which is between 0.5 MPa (megapascal) and 5 MPa.

[0016] Applying the additional command to the initial command to determine the effective command can, for example, correspond to a sum of the two commands. The additional command is therefore of the same maturity as the initial command.

[0017] The inventors have established that the invention has a greater effect on the filling time when the initial command from the control element is low, due to the asymptotic behavior of the filling time as the piston / disc contact pressure is approached (zero torque pressure due to the braking system's regulating element). A command lower than the piston / disc contact pressure does not generate any braking torque. The piston / disc contact pressure can, for example, correspond to a pressure between 1 MPa and 2 MPa.

[0018] As mentioned above, the predetermined constant additional control can, for example, represent a predetermined braking pressure value. It can also correspond, for example, to a current value representing this predetermined braking pressure value. The determined braking pressure value can, for example, be between 0.5 MPa and 5 In one particular embodiment, this predetermined braking pressure value is equal to 1.2 MPa. This range of values ​​allows the control method described in the presentation to be applied to different types of aircraft, with the aim of ensuring satisfactory responsiveness of their braking system.

[0019] In some embodiments, determining the effective command involves comparing the initial command to a predetermined threshold value, and: - when the initial order is less than the predetermined threshold value, the effective order is equal to the sum of the initial order plus an additional order, and - when the initial order is greater than or equal to the predetermined threshold value, the effective order is equal to the initial order.

[0020] Hereafter, and unless otherwise indicated, "threshold value" means "predetermined threshold value".

[0021] The threshold value can, for example, correspond to a predetermined pressure threshold within the hydraulic circuit when both the initial and effective commands are pressure commands. It can also correspond to a predetermined current threshold when both the initial and effective commands are current commands.

[0022] When the initial command is below the threshold value, the braking system's response time can be relatively long. Conversely, the braking system's response time is satisfactory when the initial command is equal to or greater than the threshold value.

[0023] Thus, when an initial command is issued by the control unit, the initial command (i.e., the initial command value) is compared, for example using computer or electronic equipment, with the threshold value to determine whether the initial command needs to be adjusted so that the effective command, which is ultimately transmitted to the brake, is greater than or equal to the threshold value. For example, if the initial command is a step, then the effective command can be derived from comparing the step value with the threshold value.

[0024] When the initial command is greater than or equal to the threshold value, the effective command determined and transmitted to the brake corresponds to the initial command itself.

[0025] When the initial command is less than the threshold value, the effective command is determined by applying an additional command, called A variable whose value depends on that of the initial command. Applying the additional command to the initial command results in the sum of the two commands. The sum of the values ​​of the variable additional command and the initial command is such that it equals the threshold value.

[0026] By comparing the initial command to the threshold value, and then determining, based on the result of this comparison, an effective command to be transmitted to the brake which is equal to or greater than the threshold value, the control method ensures, for a plurality of aircraft types, a satisfactory responsiveness of their braking system.

[0027] In some embodiments, the predetermined threshold value is representative of a braking pressure, for example between 3 MPa and 10 MPa.

[0028] The threshold value can, for example, correspond to a current threshold value representing a braking threshold pressure, or it can directly correspond to a braking threshold pressure value.

[0029] The braking threshold pressure corresponds to the minimum pressure that must be applied within the hydraulic circuit and ultimately to the brakes. Such ranges of values ​​can achieve a certain balance between the responsiveness of the braking system and the abruptness of the braking action. This helps ensure responsive braking while preventing excessively abrupt braking, thus preserving passenger comfort and the integrity of the aircraft's various systems.

[0030] According to a characteristic of the control process, the additional control is applied for a predetermined duration.

[0031] For example, the predetermined duration can be defined as being less than or equal to the brake filling time, so as not to ultimately apply a command to the brake greater than the initial command. In other words, the additional command can be applied for the entire time required for the pistons to leave their rest position, press the plurality of brake discs, and generate the braking torque required by the initial command; thus ensuring that the braking system's response time is sufficient to provide a certain degree of braking responsiveness while avoiding excessively abrupt braking, thereby preserving passenger comfort and the integrity of the aircraft's various systems.

[0032] In one variant, this predetermined duration may correspond to the duration for which the predetermined constant additional command is applied to the initial command to determine the effective command.

[0033] In another variant, following the result of the comparison between the initial command and the threshold value, and when the initial command is less than the threshold value, this predetermined duration can correspond to the duration for which the additional variable command is applied to the initial command to determine the effective command.

[0034] In some embodiments, the predetermined duration of the additional command is greater than or equal to 50 ms (milliseconds).

[0035] Such a range of values ​​can, on a wide range of landing gear, ensure a certain responsiveness of braking, and allow the pilot, even following for example a light pressure on the brake pedal, to feel the braking of the aircraft quickly.

[0036] The predetermined duration of the additional command is intended to be less than or equal to the brake filling time to ensure that no effective braking is obtained that exceeds the initial command.

[0037] In some embodiments, the effective control is a current or pressure control configured to control the servovalve.

[0038] A servovalve is a hydraulic distributor controlled by an electrical signal (current or voltage), which converts this electrical signal into a proportional hydraulic signal (flow rate or pressure). Thus, the servovalve in a braking system can, for example, be configured to convert the actual signal, which is a current signal, into a pressure signal that corresponds to the pressure at which fluid is delivered to the hydraulic brake.

[0039] One type of servovalve technology is the mechanical feedback servovalve, where the servovalve is controlled by an external control system positioned upstream of the servovalve in the hydraulic circuit. The purpose of the mechanical feedback servovalve is to deliver fluid to the brake and requires measuring the fluid pressure and transmitting it to the external control system. Based on the pressure measurement received, the external control system adjusts the electrical signal sent to the servovalve, ensuring that it delivers fluid to the brake at the required pressure.

[0040] Comparatively, the direct-drive servovalve is not controlled by an external control system, and is configured to autonomously correct the pressure of the fluid delivered to the brake through internal regulation.

[0041] One embodiment may relate to an aircraft landing gear hydraulic braking system comprising a primary system and a backup system. The main system and the backup system can share the same control unit and the same hydraulic brake(s). The control method described can therefore be implemented in the operation of both a main system and a backup braking system to ensure satisfactory responsiveness.

[0042] An embodiment relates to a computer program comprising instructions which, when said program is executed by a computer, cause the computer to implement the control method according to any one of the embodiments described in this exposition.

[0043] An embodiment relates to a computer-readable data carrier on which the computer program is recorded according to the embodiment described in this presentation.

[0044] An embodiment relates to an integrated circuit or an electronic board configured to perform the control process according to any one of the embodiments described in this exposition.

[0045] The control method can correspond, for example, to a function implemented in a computer comprising only electronic components and no embedded software. The control method is implemented by the computer when it executes said function. Brief description of the drawings

[0046] The control method described in this presentation and its advantages will be better understood upon reading the detailed description below of various embodiments given as non-limiting examples. This description refers to the attached figure pages, on which:

[0047] [Fig. 1] Figure 1 is a schematic representation of a hydraulic braking system for the landing gear of an aircraft.

[0048] [Fig. 2] Figure 2 is a flowchart of the control process.

[0049] [Fig. 3] Figure 3 illustrates examples of pressure response of a braking system as a function of an initial command and an effective command as defined in the control method; for which characteristics relating to the two said commands are indicated and represented.

[0050] [Fig. 4] Figure 4, which is similar to Figure 3, illustrates temporally a decomposition into several phases of the pressure responses of the braking system following the receipt by the brake of the initial command or the effective command, as well as the influence of the two types of command on these different phases. Description of the implementation methods

[0051] An architecture of a hydraulic braking system 10 of an aircraft landing gear for which the control method 100 subject of the presentation is implemented is illustrated in Figure 1. This architecture is given in an illustrative and non-restrictive manner.

[0052] The braking system 10 includes a hydraulic brake 14, which hydraulic brake 14 includes a plurality of brake discs (not shown) and pistons (not shown) configured to squeeze the discs of the plurality of discs and generate braking torque for deceleration and / or stopping of the aircraft.

[0053] The braking system 10 includes a hydraulic circuit 15, which comprises at least one servovalve 16, described in more detail later, for activating the brake 14 according to the pressure of a fluid, for example, brake fluid. The fluid pressure is a function of a command, called the initial command Ci, issued by a control element 12 included in the braking system 10. The control element 12 may be a brake pedal installed in the cockpit and / or an automatic braking system (or "autobrake").

[0054] The initial command Ci from the control element can be a control signal, for example, an electrical signal, such as a change in voltage or current. The initial command Ci can be, for example, a step input with a step value and a step duration; or a variable curve representing the changes and adjustments of the command from the control element. In the described embodiments, the initial command Ci is a current step. In other, undescribed embodiments, the initial command Ci can be a voltage step, a pressure step, etc.

[0055] The braking system 10 includes computer or electronic equipment 18 connected and / or in communication with the control unit 12, as well as with a number of hydraulic circuit components 15, including the servovalve 16.

[0056] In this example, the computer or electronic equipment 18 includes a current generator 20.

[0057] In one variant, the computer or electronic equipment 18 can communicate with the servovalve 16.

[0058] When the control unit 12 is activated, the command from the control unit 12 passes through the computer or electronic equipment 18, which in turn transmits it to the servovalve 16, the latter controlling the pressure within the hydraulic circuit 15 according to the command transmitted by the computer or electronic equipment 18 in order to activate the brake 14.

[0059] Figure 2 represents, in an illustrative and non-restrictive manner, a flowchart of one embodiment of the control process 100 according to the present exposition, implemented for example within the braking system 10 of Figure 1.

[0060] The control method 100 includes a detection step E1, implemented by the computer or electronic equipment 18, of the initial command Ci from the control element 12 when the latter is actuated. When the control element 12 corresponds to a brake pedal, step E1 occurs at the moment the aircraft pilot presses the brake pedal.

[0061] Following step E1, the control process 100 includes a determination step E2, implemented by the computer or electronic equipment 18, during which a Ceff control is determined, which in this example is a current control.

[0062] In a first embodiment, step E2 involves applying an additional current control signal Ca to the initial control signal Ci. This additional control signal Ca is generated and then supplied by the current generator 20. The additional control signal Ca corresponds to a predetermined constant additional control signal, defined such that its application to the initial control signal Ci allows the determination of an effective control signal Ceff. For example, the predetermined constant additional control signal represents a predetermined braking pressure value between 0.5 MPa and 5 MPa, for instance, being equal to 1.2 MPa.

[0063] In a second embodiment of the invention, step E2 comprises the implementation by the computer or electronic equipment 18 of a comparison between the initial command Ci and the predetermined threshold value val1. Based on the result of the comparison, the effective command Ceff is determined: - when the initial command Ci is greater than or equal to the predetermined threshold value val1, as corresponding to the initial command Ci; and - when the initial command Ci is less than the predetermined threshold value val1, as being equal to the predetermined threshold value val1.

[0064] The predetermined threshold value val1 is a current value representative of a braking threshold pressure, which is for example between 3 MPa and 10 MPa.

[0065] In the second case, the effective command Ceff is obtained by summing the initial command Ci to an additional command Ca, which corresponds to a variable additional command whose value depends on that of the initial command Ci. In other words, by summing the initial command Ci with the additional command Ca, we obtain an effective command Ceff whose value is equal to the predetermined threshold value val1.

[0066] At the end of step E2, the effective command Ceff is transmitted to the brake 14 during a transmission step E3.

[0067] Before proceeding to step E3, the control method 100 may include, as in this example where the braking device 10 includes a servovalve 16, a transmission by the computer or electronic equipment 18 of the effective command Ceff, which is as indicated above a current command, to the servovalve 16. Once the effective command Ceff is received, the servovalve 16 converts, during a conversion step Econv, the effective command Ceff into a pressure variation proportional to the current variation.

[0068] Figures 3 and 4 illustrate a comparison of the time response in pressure within the hydraulic circuit 15, and therefore the actuation pressure of the brake 14, in response to a command from the control member 12, when the control method 100 is implemented (see solid line curve / response R2) and when the control method 100 is not implemented (see solid line curve / response R1).

[0069] The dashed curves illustrated in these two figures correspond to pressure commands C1, C2 representing the servovalve control current, such as: - the pressure command C1 is representative of an initial command Ci generated by the control element 12, and for which the control process 100 is not implemented; and - the pressure control C2 is representative of an effective control Ceff when the control process 100 is implemented (i.e. at the end of step E2).

[0070] Thus, the response R1 (respectively the response R2) is obtained following the reception by the brake 14 of the pressure command C1 (respectively of the pressure command C2).

[0071] In this example, the initial command Ci corresponds to a step with a step duration dCi and a step value ACi. The step value ACi can, for example, result from the aircraft pilot pressing the brake pedal and represent an associated control pressure required within the braking system 10. The step duration dCi can, in turn, correspond to the time the aircraft pilot presses the brake pedal.

[0072] In the first embodiment presented above, during step E2, the additional command Ca, which is a constant additional command, is applied to the initial command Ci for a predetermined duration dCa to determine an effective command Ceff having a value ACeff.

[0073] In the second embodiment presented above, during step E2, the step value ACi of the initial command Ci is compared to the predetermined threshold value val 1, then: - when the step value ACi of the initial command Ci is greater than or equal to the predetermined threshold value val1, the amplitude Ceff of the effective command Ceff corresponds to the step amplitude ACi of the initial command; or - when the step value ACi of the initial command Ci is less than the predetermined threshold value val1, the additional command Ca is applied to the initial command Ci during the predetermined duration dCa; with the effective command Ceff then having an amplitude ACeff such that it is equal to the predetermined threshold value val1 during the predetermined duration dCa; and equal to the step amplitude ACi of the initial command Ci otherwise.

[0074] The first phase of the responses R1, R2 corresponds to a preload phase PP corresponding to the pressurization of the hydraulic circuit 15, and to the preload of the brake pistons 14 when it receives the pressure command C1, C2.

[0075] The pistons are preloaded very rapidly following the receipt by brake 14 of the initial pressure command Ci, or the effective pressure command Ceff, during the step rise time. The times t1 R1 and t1 R2 at which the pistons are preloaded coincide for both responses R1 and R2. In other words, adjusting an initial command Ci during the determination step E2 to obtain an effective command Ceff, for example by applying an additional command Ca, has no effect on the piston preload.

[0076] The second phase of responses R1, R2 corresponds to a filling phase FP which begins at time t1 R1, t1 R2 for each of responses R1, R2, once the brake pistons 14 are pre-charged. During this filling phase FP, the pistons leave their rest position to press the brake discs. The filling phase FP ends at a time t2R1, t2R2 for each of the responses R1, R2, when the pistons press the brake discs.

[0077] The filling phase FP of the response R1 is defined by a duration FPR1 equal to time t2R1 minus time t1R1. The filling phase FP of the response R2 is defined by a duration FPR2 equal to time t2R2 minus time t1R2, with time t2R2 less than time t2R1.

[0078] The predetermined duration dCa during which the additional command Ca is applied to the initial command Ci is defined as being less than or equal to the duration FPR2 of the filling phase FP, to ensure that the effective braking does not exceed the initial command. In other words, it can be applied to the initial command Ci for a maximum of until braking BP begins, to ensure a certain responsiveness of the latter, such that it is felt, for example, by the aircraft pilot as soon as they press the brake pedal. The predetermined duration dCa is defined as being greater than or equal to 50 ms. It can, for example, be equal to 270 ms.

[0079] The duration FPR2 of the FP filling phase of response R2 is less than the duration FPR1 of the FP filling phase of response R1. Thus, adjusting an initial command Ci during the determination step E2 to obtain an effective command Ceff, for example by applying an additional command Ca, ultimately improves / accelerates the pressurization of brake 14, i.e., reduces the duration of the FP filling phase. As illustrated in the figures, the time saved on the FP filling phase, and therefore on the response time of the braking system 10, by implementing the control method 100, is equal to t2R1 - t2R2.

[0080] The third and final phase of responses R1 and R2 corresponds to a BP braking phase beginning at time t2R1 and t2R2, once the FP filling phase is complete. This BP braking phase corresponds to the actual braking of the aircraft, when the brake pistons 14 effectively press the brake discs. This response is similar for both responses R1 and R2.

[0081] Since the FP filling phase of response R2 is shorter (i.e. lasts less time) than that of response R1, the BP braking phase of response R2 starts earlier than that of response R1.

[0082] Thus, the reception by the brake 14 of a pressure representative of the effective command Ceff, and not a pressure command representative of the initial command Ci, makes it possible to reduce the response time of the braking system 10, and therefore to initiate the braking of the aircraft earlier.

[0083] This demonstrates that implementing the 100 command procedure saves time during the refueling phase, significantly improving the responsiveness of the braking system. For example, this time saving exceeds 100 milliseconds for certain aircraft types by adjusting initial commands Ci, giving the pilot greater braking control.

[0084] Although the present invention has been described with reference to specific embodiments, it is evident that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various embodiments illustrated / mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

[0085] It is also evident that all the characteristics described with reference to a process are transposable, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device are transposable, alone or in combination, to a process.

Claims

Demands

1. A method for controlling (100) a hydraulic braking system (10) of an aircraft landing gear, the hydraulic braking system (10) comprising at least one control element (12), a servovalve (16), and a hydraulic brake (14), the hydraulic brake (14) comprising a plurality of brake discs and pistons configured to press the discs of the plurality of discs, the control method (100) comprising the implementation by computer or electronic equipment (18) of: - detect (E1) an initial command (Ci) from the control unit (12), - determine (E2) an effective control (Ceff) greater than or equal to the initial control (Ci), and - transmit (E3) the effective command (Ceff) to the hydraulic brake (14); in which the determination (E2) of the effective command (Ceff) includes the implementation of applying to the initial command (Ci) an additional command (Ca), for example a predetermined constant additional command, for example representative of a predetermined value of braking pressure which is between 0.5 MPa and 5 MPa.

2. A method for controlling (100) a hydraulic braking system (10) of an aircraft landing gear, the hydraulic braking system (10) comprising at least one control element (12), a servovalve (16), and a hydraulic brake (14), the hydraulic brake (14) comprising a plurality of brake discs and pistons configured to press the discs of the plurality of discs, the control method (100) comprising the implementation by computer or electronic equipment (18) of: - detect (E1) an initial command (Ci) from the control unit (12), - determine (E2) an effective control (Ceff) greater than or equal to the initial control (Ci), and - transmit (E3) the effective command (Ceff) to the hydraulic brake (14); wherein the determination (E2) of the effective command (Ceff) includes the implementation of comparing the initial command (Ci) to a predetermined threshold value (val1), and: - when the initial command (Ci) is less than the predetermined threshold value (val1), the effective command (Ceff) is equal to the sum of the initial command (Ci) with an additional command (Ca), and - when the initial command (Ci) is greater than or equal to the threshold value predetermined (val1), the effective command (Ceff) is equal to the initial command (Ci).

3. Control method (100) according to claim 1 or 2, wherein the predetermined threshold value (val1) is representative of a braking threshold pressure, for example between 3 MPa and 10 MPa.

4. Control method (100) according to any one of claims 1 to 3, wherein the additional control (Ca) is applied for a predetermined duration (dCa).

5. Control method (100) according to claim 4, wherein the predetermined time (dCa) is greater than or equal to 50 ms.

6. Control method (100) according to any one of claims 1 to 5, wherein the effective control (Ceff) is a current or pressure control configured to control the servovalve (16).

7. A computer program comprising instructions which, when said program is executed by a computer, cause the computer to implement the control method (100) according to any one of claims 1 to 6.

8. A computer-readable data carrier on which the computer program according to claim 7 is recorded.

9. Integrated circuit or electronic board configured to perform the control method (100) according to any one of claims 1 to 6.

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