Aircraft braking

Abstract

The invention relates to aircraft braking. A brake system and a method of applying one or more aircraft wheel brakes according to at least one of a plurality of wheel brake control functions are disclosed. The method comprises receiving an indication of an aircraft speed from an aircraft speed indicator; controlling wheel brake operation of the aircraft according to at least a first wheel brake control function if the aircraft speed indicated by the aircraft speed indicator exceeds a speed threshold; and controlling wheel brake operation of the aircraft according to at least a second wheel brake control function if the aircraft speed does not exceed the speed threshold. An aircraft comprising one or more aircraft wheel brakes and the disclosed brake system is also disclosed.

Description

Technical Field

[0001] This invention relates to aircraft braking. Specifically, but not exclusively, this invention relates to controlling aircraft braking based on at least one of a plurality of wheel brake control functions. Background Technology

[0002] Aircraft wheel brakes can be controlled by a braking system. The way the braking system applies the aircraft wheel brakes can affect the aircraft's behavior during braking and its operational efficiency. It may be desirable to provide a braking system for aircraft that controls the aircraft wheel brakes in a safe and efficient manner. Summary of the Invention

[0003] A first aspect of the invention provides a braking system for an aircraft, operable to apply one or more aircraft wheel brakes according to at least one wheel actuator control function of a plurality of wheel brake control functions. The braking system includes an aircraft speed indicator and a controller, the controller being configured to: control the aircraft wheel braking operation at least according to a first wheel brake control function when the aircraft speed indicated by the aircraft speed indicator exceeds a speed threshold; and control the aircraft wheel braking operation at least according to a second wheel brake control function when the aircraft speed does not exceed the speed threshold.

[0004] Optionally, the braking system includes a brake status indicator, wherein the controller is configured to select a second wheel brake control function from the plurality of wheel brake control functions based on the status of the one or more aircraft wheel brakes.

[0005] Optionally, the brake condition indicator includes a brake temperature characteristic indicator; and the brake condition includes the temperature characteristics of the one or more aircraft wheel brakes.

[0006] Optionally, the controller is configured to select a second wheel brake control function based on the temperature characteristics of the one or more aircraft wheel brakes.

[0007] Optionally, the temperature characteristics include the temperature of the one or more aircraft wheel brakes; and the controller is configured to select the brake cooling time coordination function as a second wheel brake control function if the temperature of at least one aircraft wheel brake is higher than the scheduling temperature threshold.

[0008] Optionally, the brake cooling time coordination function controls the amount of braking provided by each of the aircraft wheel brakes such that the predicted time for all the aircraft wheel brakes in the one or more aircraft wheel brakes to cool to the scheduled temperature threshold is approximately the same.

[0009] Optionally, the controller is configured to select the thermal oxidation limiting function as the second wheel brake control function if the temperature characteristics of at least one aircraft wheel brake meet the thermal oxidation limiting criterion.

[0010] Optionally, the thermal oxidation limiting function disables the brakes of at least one aircraft wheel.

[0011] Optionally, the controller is configured to select the brake wear reduction function as the second wheel brake control function if the temperature of at least one aircraft wheel brake is not higher than the dispatch temperature threshold.

[0012] Optionally, the brake wear reduction function controls the number of times the brakes of the one or more aircraft wheels are applied.

[0013] Optionally, the brake condition indicator also includes a brake wear indicator and a brake thermal oxidation condition indicator, and the brake condition also includes the amount of brake wear of the one or more aircraft wheel brakes and the thermal oxidation condition of the one or more aircraft wheel brakes.

[0014] Optionally, the controller is configured to select either a brake wear reduction function or a thermal oxidation coordination function as a second-wheel brake control function based on the amount of brake wear and thermal oxidation state of the one or more aircraft wheel brakes when the temperature of at least one aircraft wheel brake is below a scheduling temperature threshold.

[0015] Optionally, the controller is configured to control wheel braking operation based on the first wheel brake control function and the brake wear reduction function when the brake wear reduction function is selected as the second wheel brake control function.

[0016] Optionally, the first-wheel brake control function is a torque equalization function.

[0017] Optionally, the torque equalization function controls the wheel braking operation so that the distribution of torque reacted by the applied one or more aircraft wheel brakes is symmetrical about the direction of travel of the aircraft and / or a portion of the aircraft.

[0018] Optionally, the controller can be configured to select either brake wear reduction or thermal oxidation coordination as a secondary control function.

[0019] A second aspect of the invention provides an aircraft including one or more aircraft wheel brakes and a braking system according to the first aspect, the braking system being configured to apply the one or more aircraft wheel brakes.

[0020] A third aspect of the invention provides a method for applying one or more aircraft wheel brakes according to at least one of a plurality of wheel brake control functions, the method comprising: receiving an indication of aircraft speed from an aircraft speed indicator; controlling the wheel braking operation of the aircraft at least according to a first wheel brake control function if the aircraft speed indicated by the aircraft speed indicator exceeds a speed threshold; and controlling the wheel braking operation of the aircraft at least according to a second wheel brake control function if the aircraft speed does not exceed the speed threshold.

[0021] Optionally, the method according to the third aspect includes: receiving an indication of the status of the one or more aircraft wheel brakes from a brake status indicator; and selecting a second wheel brake control function from the plurality of wheel brake control functions based on the status of the one or more aircraft wheel brakes.

[0022] Optionally, in the method according to the third aspect, the brake condition indicator includes a brake temperature characteristic indicator; and the brake condition includes the temperature characteristics of the one or more aircraft wheel brakes.

[0023] Optionally, the method according to the third aspect includes: selecting a second wheel brake control function based on the temperature characteristics of the one or more aircraft wheel brakes.

[0024] Optionally, in the method according to the third aspect, the temperature characteristics include the temperatures of the one or more aircraft wheel brakes; and the method includes: selecting a brake cooling time coordination function as a second wheel brake control function when the temperature of at least one aircraft wheel brake is higher than a scheduling temperature threshold.

[0025] Optionally, in the method according to the third aspect, the brake cooling time coordination function controls the amount of braking provided by each of the aircraft wheel brakes such that the predicted time for cooling all of the one or more aircraft wheel brakes to the scheduled temperature threshold is approximately the same.

[0026] Optionally, in the method according to the third aspect, the method includes: selecting a thermal oxidation limiting function as a second wheel brake control function if the temperature characteristics of at least one aircraft wheel brake meet the thermal oxidation limiting criterion.

[0027] Optionally, the thermal oxidation limiting function disables the brakes of at least one aircraft wheel.

[0028] Optionally, in the method according to the third aspect, the method includes: selecting a brake wear reduction function as a second wheel brake control function when the temperature of at least one aircraft wheel brake is not higher than a scheduling temperature threshold.

[0029] Optionally, the brake wear reduction function controls the number of times the brakes of the one or more aircraft wheels are applied.

[0030] Optionally, in the method according to the third aspect, the brake condition indicator further includes a brake wear indicator and a brake thermal oxidation condition indicator, and the brake condition also includes the amount of brake wear of the one or more aircraft wheel brakes and the thermal oxidation condition of the one or more aircraft wheel brakes.

[0031] Optionally, the method includes: selecting a brake wear reduction function or a thermal oxidation coordination function as a second wheel brake control function based on the amount of brake wear and thermal oxidation state of the one or more aircraft wheel brakes, provided that the temperature of at least one aircraft wheel brake is not higher than a scheduling temperature threshold.

[0032] Optionally, the method according to the third aspect includes: when the brake wear reduction function is selected as the second wheel brake control function, controlling the wheel braking operation according to the first wheel brake control function and the brake wear reduction function.

[0033] Optionally, in the method according to the third aspect, the first wheel brake control function is a torque equalization function.

[0034] Optionally, in the method according to the third aspect, the torque balancing function controls the wheel braking operation so that the distribution of torque reacted by one or more applied aircraft wheel brakes is symmetrical about the direction of travel of the aircraft and / or a portion of the aircraft.

[0035] Optionally, the method according to the third aspect includes: selecting a brake wear reduction function or a thermal oxidation coordination function as a second control function.

[0036] A fourth aspect of the invention provides a braking system for an aircraft, operable to apply a plurality of aircraft wheel brakes, the braking system including a controller configured to control the application of the brakes based on the corresponding thermal oxidation state of one of the plurality of brakes relative to the corresponding thermal oxidation state of the other brakes.

[0037] Optionally, in the braking system according to the fourth aspect, the controller is configured to control each of the plurality of brakes such that each brake reaches its respective thermal oxidation threshold approximately simultaneously.

[0038] A fifth aspect of the invention provides a braking system for an aircraft, operable to apply a plurality of aircraft wheel brakes, the braking system including a controller configured to control the application of the brakes based on a corresponding predicted time for one of the brakes to cool to a scheduled temperature threshold compared to a corresponding predicted time for the other brakes to cool to a scheduled temperature threshold.

[0039] Optionally, in the braking system according to the fifth aspect, the controller is configured to control each of the plurality of brakes such that the predicted time for cooling all of the plurality of brakes to the scheduled temperature threshold is approximately the same. Attached Figure Description

[0040] Various embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which:

[0041] Figure 1 This is a schematic diagram showing the various example aircraft that can be deployed on it;

[0042] Figure 2 This is a schematic diagram of the brake assembly and wheels of an example aircraft landing gear assembly;

[0043] Figure 3 This is a schematic diagram of the braking system of an example aircraft;

[0044] Figure 4a This is a first flowchart of a method for applying one or more aircraft wheel brakes according to an example; and

[0045] Figure 4b This is a second flowchart of a method for applying one or more aircraft wheel brakes according to an example.

[0046] Figure 5 This is a flowchart of an exemplary method for determining the thermal oxidation state of the brakes of an aircraft landing gear;

[0047] Figure 6 This is a flowchart of an exemplary method for determining the thermal oxidation state of the brakes of an aircraft landing gear;

[0048] Figure 7 This is an exemplary graph illustrating the temperature of the brake relative to time;

[0049] Figure 8 This is an exemplary graph illustrating the thermal oxidation state of a brake at a specific temperature versus time.

[0050] Figure 9 This is an exemplary flowchart of a method for determining the amount of brake wear based on an example; and

[0051] Figure 10 This is an exemplary flowchart of a method for predicting the number of good future service cycles related to aircraft brakes, based on an example. Detailed Implementation

[0052] Figure 1 This is a simplified schematic diagram of an aircraft 100. The aircraft 100 includes multiple landing gear assemblies 102. Each landing gear assembly 102 may include a main landing gear and a nose landing gear that can extend during takeoff and landing and retract during flight. Each landing gear assembly 102 includes wheels, such as wheels 104. The aircraft 100 includes a computing system 106, which may include, for example, one or more processors and one or more computer-readable storage media. The aircraft 100 may also include instruments 108, such as instruments or sensors for measuring characteristics or parameters related to the aircraft, and instruments or sensors for measuring environmental characteristics. It should be understood that in some examples, instruments 108 may be distributed at various different locations within the aircraft 100. The aircraft 100 also includes one or more aircraft wheel brake assemblies (not shown in the diagram). Figure 1 As shown in the figure, the one or more aircraft wheel brake assemblies are used to provide braking to suppress the rotational movement of wheels such as wheel 104.

[0053] Figure 2 This is a simplified schematic diagram of an aircraft wheel brake assembly 200 associated with the wheels 104 of aircraft 100. The aircraft wheel brake assembly is referred to below as a "brake assembly". Each wheel of aircraft 100 may have its own associated brake assembly 200. Therefore, aircraft 100 may include one or more brake assemblies 200. The brake assembly 200 applies braking force to suppress rotation of the wheels 104. In this example, the brake assembly 200 includes multiple brake discs 202, each including a pressure plate 204, a reaction plate 206, and multiple rotors and multiple stators such as rotors 208 and stators 210. In this example, the brake discs 202 include multiple rotors and multiple stators, and therefore, the brake assembly 200 is a multi-disc brake. In other examples, the brake assembly 200 may not be a multi-disc brake. It will be understood that the type of brakes used in aircraft landing gear depends on the characteristics of the aircraft in question, such as size and load capacity.

[0054] When the aircraft 100, supported by landing gear 102, travels along the ground, the rotor rotates with wheel 104, while the stator, pressure plate 204, and reaction plate 206 do not rotate with wheel 104. When braking is applied, pressure plate 204 is pushed toward reaction plate 206, causing brake discs 202 to contact each other (as in...). Figure 2 (As shown in box 212) and friction is used to suppress the rotational motion of the rotor, thereby generating braking force.

[0055] Figure 3 This is a simplified schematic diagram of a braking system 300 for an aircraft, such as aircraft 100, operable to apply one or more aircraft wheel brakes, such as brake assemblies 200. The braking system 300 applies brake assemblies 200 in response to a braking request (e.g., when the pilot of aircraft 100 presses the brake pedal). For example, one or more brake assemblies 200 may be hydraulically or electrically actuated, and the braking system 300 may control a brake actuation system (not shown) to apply brake assemblies 200. The braking system 300 may communicate with the brake actuation system via a wireless or wired communication link.

[0056] Braking system 300 is operable to apply one or more aircraft wheel brakes, such as brake assembly 200, according to at least one of a plurality of wheel brake control functions (which may be referred to hereinafter as "control functions"). In this example, braking system 300 includes aircraft speed indicator 302 and controller 304. The aircraft speed indicator provides an indication of the speed of aircraft 100. The aircraft speed indicator provides the controller 304 with an indication of the aircraft speed.

[0057] In addition to the aircraft speed indicator 302, the braking system 300 may also include one or more other indicators as described below. Each indicator may provide an indication of a corresponding parameter relating to the aircraft 100 or the braking assembly 200. Each indicator may include a corresponding sensor for measuring the corresponding parameter. For example, the aircraft speed indicator 302 may include the aircraft speed sensor included in instrument 108.

[0058] In some examples, the corresponding sensors may provide indications of corresponding parameters to controller 304 via wired or wireless communication links. In some examples, one or more indicators included in braking system 300—such as aircraft speed indicator 302—may include a processor that receives indications of corresponding parameters from the corresponding sensors via wired or wireless communication links. The processor of said one or more indicators may then transmit the corresponding parameters to controller 304 via wired or wireless communication links. The processor of said one or more indicators may be a processor included in computing system 106.

[0059] In some examples, instead of a processor or in addition to a processor, the one or more indicators include a computer-readable storage medium in which information relating to the corresponding parameters is stored. For example, the corresponding sensor or processor of the one or more indicators can write information relating to the corresponding parameters to the computer-readable storage medium. The controller 304 can read temperature information from the storage medium. The computer-readable storage medium of the one or more indicators may be a computer-readable storage medium included in the computing system 106.

[0060] Controller 304 may receive indications from one or more corresponding parameters of the one or more indicators in real time. Controller 304 may receive indications from one or more corresponding parameters continuously, or alternatively, controller 304 may periodically receive discrete information items related to the one or more corresponding parameters. In some examples, controller 304 may request indications from one or more parameters of the corresponding indicators and receive the requested indications in response.

[0061] Controller 304 is configured to control the wheel braking operation of aircraft 100 at least according to a first control function if the aircraft speed indicated by the aircraft speed indicator exceeds a speed threshold. Conversely, controller 304 is configured to control the wheel braking operation of aircraft 100 at least according to a second control function if the aircraft speed does not exceed the speed threshold. The wheel braking operation (hereinafter referred to as "braking operation") involves applying one or more of the brake components 200 in response to a braking request. For example, a braking request may include information related to the requested braking intensity. The braking operation may involve applying one or more of the brake components 200 to provide the requested braking intensity.

[0062] The control function determines which brake assembly 200 is applied and determines the order, duration, braking pressure, etc., of application for each brake assembly 200 in order to provide the requested braking intensity. For example, the control function may determine these aspects of wheel braking operation to prioritize the braking characteristics or conditions of the brake assembly 200 used in wheel braking operation. Further details and examples of the control function are described below.

[0063] Figure 4aThis is a flowchart illustrating a method 400 performed by controller 304 to apply one or more brake components 200 according to at least one of a plurality of control functions. At block 402, an indication of aircraft speed is received from aircraft speed indicator 302. For example, controller 304 receives an indication of aircraft speed from aircraft speed indicator 302 as described above.

[0064] As indicated by box 404, if the aircraft speed indicated by aircraft speed indicator 302 exceeds a speed threshold, method 400 proceeds to box 406. At box 406, the wheel braking operation of aircraft 100 is controlled at least according to a first control function. On the other hand, as indicated by box 404, if the aircraft speed does not exceed the speed threshold, method 400 proceeds to box 408. At box 408, the wheel braking operation of aircraft 100 is controlled at least according to a second control function.

[0065] The first control function can be a torque balancing function. When the aircraft speed exceeds a speed threshold, the controller 304 can control the braking operation according to the torque balancing function. The torque balancing function can control the wheel braking operation such that the distribution of torque reacted by the applied one or more aircraft wheel brakes is symmetrical about the direction of travel on the aircraft and / or a portion of the aircraft. For example, the amount of torque reacted by the brake assembly can be symmetrically distributed about the direction of travel on the aircraft 100. For example, if the aircraft 100 is traveling in a forward direction without turning, the torque balancing function can control the braking operation such that the total amount of torque reacted by the applied brake assembly 200 on the left side of the aircraft 100 is approximately the same as the total amount of torque reacted by the applied brake assembly 200 on the right side of the aircraft 100. In some such examples, the torque balancing function can cause each of the applied brake assemblies 200 to react with approximately the same amount of torque. This could be, for example, when the aircraft 100 is traveling in a forward direction and the symmetrical distribution of the brake assemblies 200 is applied relative to the direction of travel.

[0066] As needed, the torque equalization function can control braking operation to provide a symmetrical distribution of the responsive torque when an asymmetrical distribution of brake assemblies is employed with respect to the direction of travel, by causing different brake assemblies to respond with correspondingly different amounts of torque. In some examples, the distribution of the responsive torque can be symmetrical about the direction of travel on a single landing gear. For example, the torque equalization function can control the applied brake assemblies 200 of a given landing gear such that the torque responded by these brake assemblies 200 is symmetrically distributed about the direction of travel. This avoids asymmetrical loading of the given landing gear. In some examples of applying a symmetrical distribution of the brake assemblies 200 of a given landing gear, the torque equalization function causes the brake assemblies of that given landing gear to respond with approximately the same amount of torque. The torque equalization function can control braking operation when the aircraft 100 is turning. In some such examples, the torque equalization function may not provide a symmetrical distribution of the responsive torque about the forward direction on the aircraft 100. However, in these examples, the torque equalization function can control the distribution of torque on the individual landing gears as described.

[0067] To control the torque responded to by a given brake assembly 200, the braking pressure applied to that given brake assembly 200 can be adjusted based on the amount of torque responded to by that given brake assembly 200. For example, instrument 108 may include a torque sensor associated with each brake assembly 200. The torque sensor may include any suitable torque sensing device or system. The torque sensor may be configured to directly measure torque, or alternatively, the torque sensor may be configured to measure parameters (such as force) from which torque can be derived. For example, the torque sensor may include fiber-optic sensors such as fiber Bragg grating (BFG) sensors, strain gauges, force sensors, or any other sensor suitable for measuring torque or parameters from which torque can be derived. On aircraft where brake torque is responded to via a torque pin and / or torque rod (e.g., an aircraft with a conventional bogie arrangement), the torque sensor may include an instrumented torque pin positioned at the interface between the brake lug and the brake torque rod to sense shear force. Alternatively, an optical torque sensor can be used to measure the torque in the corresponding shaft on which the brake assembly 200 is mounted.

[0068] When controller 304 controls the braking operation according to the torque balancing function, controller 304 can receive torque measurements from the corresponding torque sensor of each brake assembly in the applied brake assembly 200 during the braking operation. As described, the torque sensor can measure parameters from which torque can be derived. In this example, controller 304 can derive the amount of torque reacted by the corresponding brake assembly 200. Controller 304 can receive torque measurements as described above.

[0069] Based on the received torque measurements, controller 304 can adjust the braking pressure of the applied brake assembly 200 to obtain the desired distribution of the responsive torque. It may be necessary to control the distribution of the responsive torque so that the flight direction and / or orientation of the aircraft 100 is unaffected by the braking operation. It may also be necessary to control the distribution of the responsive torque to avoid asymmetrical loading of certain components of the aircraft 100. Controller 304 can implement a control loop to adjust the braking pressure based on the corresponding torque measurements. For example, controller 304 can implement a proportional-integral-derivative (PID) loop or any other suitable loop to control the braking pressure to control the distribution of torque in the applied brake assembly 200. Controller 304 can operate at, for example, between 10 [units per second]. 2 Next to 10 3 The controller 304 can adjust the braking pressure at a similar rate by receiving torque measurements at high speeds between cycles.

[0070] The speed threshold can be set at a level where controlling the torque distribution is a priority over other braking characteristics or the condition of the brake assembly 200. For example, at relatively high speeds, ensuring the orientation or direction of the aircraft 100 is unaffected and / or avoiding asymmetrical loading of aircraft components may be a priority. In some examples, the speed threshold can be set to a speed associated with taxiing operations; for example, the speed threshold can be between 10 knots and 50 knots. In a particular example, the speed threshold could be 30 knots. The speed threshold can be set, for example, based on the mass or weight distribution of the aircraft 100. The speed threshold can also be set based on the expected taxiing path of the aircraft 100.

[0071] If the aircraft speed is below a speed threshold, the controller 304 can select a different control function to control the braking operation. The second control function can be any of the following: brake cooling time coordination function, thermal oxidation limitation function, brake wear reduction function, or thermal oxidation coordination function. For example, the controller 304 can select one of these functions as the second control function to control the braking operation. These control functions will be described in more detail below. In one example, the controller 304 selects the brake wear reduction function when the aircraft speed is below a speed threshold.

[0072] Refer again Figure 3 The braking system 300 may include a brake condition indicator 306. The controller 304 may be configured to select a second control function from the plurality of wheel brake control functions based on the condition of the brake assembly 200. For example, the controller 304 may receive an indication of the condition of the brake assembly 200 from the brake condition indicator 306, and the controller 304 may select the second control function based on the condition of the brake assembly 200. The brake condition indicator 306 may include a brake temperature characteristic indicator 308. In this example, the brake condition may include the temperature characteristics of the brake assembly 200. The controller 304 may be configured to select the second control function based on the temperature characteristics of the brake assembly 200.

[0073] Temperature characteristics may include the temperature of brake assembly 200. The temperature of brake assembly 200 may specifically be the temperature of the corresponding brake disc 202. A brake temperature characteristic indicator may include a temperature sensor 216 associated with each brake assembly 200 (see [link to relevant documentation]). Figure 2 Temperature sensor 216 may be part of instrument 108. Temperature sensor 216 may be configured to make thermal contact with one brake disc in each brake disc of brake assembly 200. Figure 2In this example, temperature sensor 216 is disposed on stator 210. In this example, stator 210 is the brake disc most likely to reach the highest temperature. Temperature sensor 216 can be any type of temperature sensor suitable for use in an aircraft brake assembly. For example, temperature sensor 216 can function appropriately within the temperature range most likely to be reached by brake disc 202. For example, temperature sensor 216 can be a thermocouple, surface acoustic wave (SAW) sensor, eddy current sensor, resistance temperature detector (RTD) sensor, strain gauge, or similar sensor. If the temperature sensor is disposed on a portion of a given brake assembly 200 other than on one of the brake discs 202, the temperature of brake disc 202 can be determined using an indication of the relationship between the temperature measured by the temperature sensor and the temperature of brake disc 202. In some examples, the indication of this relationship can be determined experimentally. In some examples, the indication of this relationship can be determined using a brake thermal model. In some examples, the temperature characteristics may also include the rate of increase of the temperature of brake assembly 200.

[0074] In some examples, the brake temperature characteristic indicator 308 may include a brake temperature prediction function (e.g., implemented by a processor of the brake temperature characteristic indicator 308). The brake temperature prediction function can predict the temperature of the brake assembly 200 based on the energy input to the brake assembly 200 during braking operation. Using the energy input to a given brake assembly 200, the mass of the given brake assembly 200, and the specific heat capacity of the given brake assembly 200, the temperature change of the given brake assembly 200 caused by the input energy can be determined. The temperature of the given brake assembly 200 can then be determined using the temperature change, i.e., by adding the temperature change to the initial temperature. The initial temperature before braking operation can be obtained from the results of previous iterations of this calculation. On the other hand, if the energy input is exactly the first brake application of the day (i.e., the given brake assembly 200 has not been applied for a considerable period of time), the initial temperature can be considered the ambient temperature.

[0075] The energy input to a given brake assembly 200 can be determined using measurements from instruments included in instrument 108. Instrument 108 may include a torque sensor as described above. Instrument 108 may also include a tachometer for measuring the rotational speed of the wheel 104 associated with the given brake assembly 200. In this example, the energy input to the given brake assembly 200 is calculated by integrating the product of the wheel speed and the torque over time.

[0076] In some examples, taking into account the amount of energy input to a given brake assembly 200, a brake thermal model (e.g., a computational fluid dynamics model) can be used to predict the temperature of the given brake assembly 200. For example, the physical properties of the given brake assembly 200 (e.g., mass, heat capacity, etc.), environmental characteristics, and the energy input to the given brake assembly 200 can be input into the brake thermal model, and the brake thermal model can output a predicted temperature of the given brake assembly 200. Environmental characteristics may include ambient temperature (e.g., the ambient temperature near the given brake assembly 200), wind conditions, or other characteristics that may affect the temperature of the given brake assembly 200. Environmental characteristics can be measured, for example, by instruments included in instrument 108.

[0077] In some examples, the rate of increase in temperature of brake assembly 200 can be predicted using a brake temperature prediction function based on the energy input to brake assembly 200. For example, this rate of increase can be predicted using a brake thermal model based on the energy input to a given brake assembly 200 and the physical properties of that given brake assembly 200.

[0078] Figure 4b This is a flowchart illustrating other boxes that can be executed as part of method 400. Figure 4b The box shown may be part of box 408, where wheel braking operation is controlled at least according to a second control function. At box 410, an indication of the condition of the brake assembly 200 is received from brake condition indicator 306. For example, controller 304 receives the indication of the condition from brake condition indicator 306. For example, at box 410, controller 304 receives the temperature characteristics of brake assembly 200.

[0079] As indicated by block 412, if the temperature characteristics of at least one brake assembly 200 meet the thermal oxidation limit criterion, method 400 can proceed to block 414. At block 414, the thermal oxidation limit function is selected as a second control function. For example, controller 304 is configured to select the thermal oxidation limit function as the second control function. The thermal oxidation limit function disables the at least one brake assembly 200 (which meets the thermal oxidation limit criterion).

[0080] Each brake assembly 200 may have its own thermal oxidation limit standard. If the temperature of a given brake assembly 200 exceeds a temperature trigger point, the temperature characteristics of that given brake assembly 200 meet the corresponding thermal oxidation limit standard. Any or more of the rotor, stator, pressure plate 204, and reaction plate 206 may be made of carbon-carbon (CC) composite material. A brake including a brake disc made of CC composite material may be referred to as a carbon brake. For example, brake disc 202 may be made of a graphite matrix reinforced with carbon fibers. During use, brake disc 202 may reach high temperatures. Thermal oxidation of brake disc 202 may occur at high temperatures. During the thermal oxidation reaction, oxygen reacts with the carbon in brake disc 202, resulting in the removal of carbon atoms from brake disc 202 due to the generation of carbon dioxide and / or carbon monoxide, thus leading to a loss of mass.

[0081] The temperature trigger point for a given brake assembly 200 can be a temperature value at which thermal oxidation of the given brake assembly 200 (specifically, thermal oxidation of the CC composite component) is expected to occur. In some examples, the temperature trigger point may be between 400°C and 750°C. In some examples, the thermal oxidation limitation criterion may alternatively or additionally include a temperature increase rate threshold. In such examples where the temperature characteristic includes the temperature increase rate of the given brake assembly 200, the thermal oxidation limitation criterion can be met if the temperature increase rate exceeds the temperature increase rate threshold.

[0082] For example, if a given brake assembly 200 is disabled, the controller 304 may assign a "disabled" state to that brake assembly 200. Disabling a given brake assembly 200 means that when the braking system 300 receives a braking request, the braking system 300 will not apply the given brake assembly 200. The requested braking may instead be provided by other brake assemblies associated with other wheels of the corresponding landing gear 102. In cases where, for example, it is necessary to use the given brake assembly 200 to provide the requested amount of braking in a safe manner, the given brake assembly 200 may not be disabled, regardless of whether thermal oxidation limit standards are met. In some examples, if it is necessary for the aircraft 100 to rapidly reduce its speed (e.g., if the pilot of the aircraft 100 requests a high braking intensity), the given brake assembly 200 may not be disabled.

[0083] If a given brake component 200 has been disabled and its temperature characteristics no longer meet the thermal oxidation limit criterion, the controller 304 can change the state of the given brake component 200 from "disabled" to "enabled". When enabled, the given brake component 200 can be used again by the braking system 300 to provide braking in response to a braking request. The thermal oxidation limit function restricts the use of brake components that meet specific temperature conditions (i.e., the thermal oxidation limit criterion), thereby reducing or suppressing further thermal oxidation of these brake components.

[0084] The thermal oxidation limiting function enables controller 304 to determine whether the temperature of any brake component in brake assembly 200 meets the corresponding thermal oxidation limiting criterion. For example, controller 304 can determine whether the thermal oxidation limiting criterion is met in real time during aircraft operation. The thermal oxidation limiting function can control the braking in real time as described, based on whether the thermal oxidation limiting criterion is met. For example, controller 304 can rapidly and repeatedly determine whether the thermal oxidation limiting criterion is met by sampling the temperature of brake assembly 200 multiple times per second—determined by the sampling rate of the corresponding temperature sensor 216. In some examples, controller 304 can receive such indication of whether the corresponding thermal oxidation limiting criterion is met from a device configured to provide an indication of whether the corresponding thermal oxidation limiting criterion is met.

[0085] The thermal oxidation limit criterion can depend on the thermal oxidation state of the corresponding brake assembly 200. The following describes how the thermal oxidation state of the brake assembly 200 can be determined. For example, if the thermal oxidation state of the corresponding brake assembly 200 is reached more advanced, the temperature trigger point can be a relatively low temperature value. In this way, if a given brake assembly 200 meets a specific temperature condition depending on the thermal oxidation state of that given brake assembly 200, then the given brake assembly 200 can be disabled.

[0086] As indicated by box 412, if the temperature characteristics of at least one brake assembly 200 do not meet the corresponding thermal oxidation limit criterion, then method 400 may proceed to box 416. As indicated by box 416, if the temperature of at least one brake assembly 200 is higher than the dispatch temperature threshold, then method 400 may proceed to box 418. At box 418, a brake cooling time coordination function is selected as the second control function. For example, at box 418, controller 304 is configured to select the brake cooling time coordination function as the second control function.

[0087] The cooling time coordination function enables controller 304 to control the application of a given brake assembly 200 based on the predicted time for that brake assembly 200 to cool to a scheduled temperature threshold compared to the predicted times for other brake assemblies 200 to cool to the scheduled temperature threshold. For example, the given brake assembly 200 can be applied based on the predicted time it takes for that given brake assembly 200 to reach the scheduled temperature threshold compared to the predicted time it takes for other brake assemblies 200 to reach the scheduled temperature threshold. More specifically, the brake cooling time coordination function can control the braking amount provided by each brake assembly in the brake assemblies 200 so that the predicted times for all brake assemblies to cool to the scheduled temperature threshold are approximately the same. The scheduled temperature threshold can be set as a safe scheduled temperature. The safe scheduled temperature can be used to ensure that the brake assembly 200 is adequately cooled for use in the next flight cycle. For example, once the temperature of the brake assembly is at or below the safe scheduled temperature, the aircraft 100 can be allowed to begin flight. In some examples, the scheduled temperature threshold can be a temperature value close to the safe scheduled temperature. The safe scheduling temperature (and therefore the scheduling temperature threshold) can be varied depending on the characteristics of the airport where the aircraft 100 will be flying. For example, the safe scheduling temperature can depend on the taxiway path, runway length, etc. In some examples, the safe scheduling temperature can be in the range of 200°C to 600°C and the scheduling temperature threshold can be set to a temperature in the range of 200°C to 600°C. In some examples, the scheduling temperature threshold can be 300°C.

[0088] The cooling time coordination function determines the predicted time for each brake assembly 200 to cool to a scheduled temperature threshold. For example, the cooling time coordination function receives the temperature of each brake assembly 200 from the brake temperature characteristic indicator 308 and predicts the amount of time required for each brake assembly 200 to cool to the scheduled temperature threshold. It will be understood that the cooling time may depend on local environmental conditions.

[0089] Given the temperature of a given brake assembly 200 and a scheduling temperature threshold, the cooling time coordination function can predict the corresponding cooling time based on the physical properties of the given brake assembly 200 and the ambient temperature. Physical properties may include the mass, specific heat capacity, and heat transfer coefficient of the given brake assembly 200. In some examples, the heat transfer coefficient of the given brake assembly 200 can be determined experimentally (or obtained from the manufacturer of the given brake assembly 200) and can be verified using simulations of the given brake assembly 200. For example, simulations can be performed using the brake thermal model described earlier. In some examples, the cooling time can be predicted directly from the brake thermal model.

[0090] The physical properties (e.g., heat transfer coefficient) of the brake assembly 200 can be stored in a computer-readable storage medium of the computing system 106, and the physical properties (e.g., heat transfer coefficient) of the brake assembly 200 can be retrieved by the controller 304 as needed when the controller 304 is controlling the braking operation according to the cooling time coordination function.

[0091] The cooling time coordination function distributes braking across the brake assemblies so that each brake assembly 200 reaches its scheduled temperature threshold approximately simultaneously. For example, during braking operations controlled according to the cooling time coordination function, the brake assembly 200 with the shortest predicted cooling time can be used first. The cooling time coordination function can adjust the braking distribution in real time during braking operations. It rapidly and repeatedly determines the time required for each brake assembly 200 to cool to the scheduled temperature threshold and adjusts the braking distribution by sampling the temperature of the brake assembly 200 multiple times per second—determined by the sampling rate of the corresponding temperature sensor (up to). In a simple example, a first given brake assembly 200 (along with the other brake assemblies 200) can be used first because it has the shortest predicted cooling time. However, during braking operations, the predicted cooling time of the brake assembly being used can be changed, and the cooling time coordination function can switch from the first brake assembly 200 to a second brake assembly 200 that now has a shorter predicted cooling time.

[0092] Coordinating cooling times in this way allows for the prediction of waiting times (i.e., port dwell times) between flights and can reduce total waiting times.

[0093] It should be understood that, Figure 4b A specific example is illustrated. In other examples, blocks 412 through 418 may be executed in a different order. For example, after receiving an indication of the condition of brake assembly 200, it can be determined whether the temperature of at least one brake component in brake assembly 200 is higher than a scheduled temperature threshold (i.e., block 416 can be executed directly after block 410), and if so, the method can proceed to block 418, where the cooling time coordination function is selected as a second control function. If the scheduled temperature threshold is not exceeded, the method can proceed to block 412, and if the thermal oxidation limit criterion is met, proceed to block 414. In some examples, blocks 412 and 414 may be omitted. In some examples, blocks 416 through 418 may be omitted.

[0094] Brake condition indicator 306 may also include brake wear indicator 310, and brake condition may further include the amount of brake wear on brake assembly 200. Alternatively or additionally, brake condition indicator 306 may also include brake thermal oxidation state indicator 312, and brake condition may further include the thermal oxidation state of brake assembly 200. In the following example, brake condition indicator 306 includes brake wear indicator 310 and thermal oxidation state indicator 312. Brake wear indicator 310 may be configured in a manner similar to any of the other indicators included in braking system 300 as described above. Controller 304 may receive the amount of brake wear from each brake assembly 200 of brake wear indicator 310.

[0095] The brake wear indicator 310 may include a wear sensor for measuring parameters related to the wear condition of each brake assembly in the brake assembly 200. The wear sensor may measure the length L of the brake disc 202, the mass of the brake disc 202, or any other parameter from which the wear condition can be derived. The wear sensor may have any suitable design. For example, in the case where the brake assembly 200 is hydraulically actuated, the wear sensor may include a linear variable differential converter (LVDT) type sensor or a Hall effect sensor configured to measure the linear displacement (wear) of the components of the brake assembly 200. Such a linear displacement sensor may, for example, be positioned on the rear of the brake piston housing. In an example where the brake assembly 200 is an electrically actuated brake including an electric brake controller, brake wear may be measured as part of the electric brake controller.

[0096] The brake thermal oxidation state indicator 312 can be configured in a manner similar to any of the other indicators included in the braking system 300 as described above. The controller 304 can receive the thermal oxidation state of each brake assembly 200 from the brake thermal oxidation state indicator 312. In some examples, the brake thermal oxidation state indicator 312 can determine the thermal oxidation state of each brake assembly 200 using the methods and systems described in an earlier, unpublished application appended to this application—GB patent application number 1803203.7. For example, the thermal oxidation state of a given brake assembly 200 after a braking operation can be determined using a thermal oxidation model based on the initial thermal oxidation state of the given brake assembly 200 before the braking operation and the temperature profile of the given brake assembly 200 over time. The brake thermal oxidation state indicator 312 can store the latest thermal oxidation state of a given brake assembly 200 in a computer-readable storage medium (e.g., a computer-readable storage medium as part of computing system 106), and the controller 304 can retrieve the thermal oxidation state of a given brake assembly 200 from the computer-readable storage medium.

[0097] The controller 304 can be configured to select either a brake wear reduction function or a thermal oxidation coordination function as a second-wheel brake control function based on the amount of brake wear and thermal oxidation state of the brake assembly 200, provided that the temperature of at least one aircraft wheel brake is not higher than the scheduling temperature threshold.

[0098] As indicated by box 416, if the temperature of at least one brake assembly in brake assembly 200 is not higher than a dispatch temperature threshold, method 400 may proceed to box 420. As indicated by box 420, based on the amount of brake wear and the thermal oxidation state of brake assembly 200, method 400 may proceed to box 422 or box 424. For example, if the amount of brake wear of brake assembly 200 is reached earlier than the thermal oxidation state of brake assembly 200, method 400 proceeds to box 422. To determine whether the amount of brake wear or the thermal oxidation state of a given brake assembly 200 is reached earlier, the amount of brake wear may be compared to a brake wear threshold of the given brake assembly 200, and the thermal oxidation state may be compared to the thermal oxidation threshold of the given brake assembly 200.

[0099] The brake wear threshold can be related to the amount of reduction in the length L of the brake disc 202 compared to its original length. In this example, the amount of brake wear can be expressed as the reduction in the length of the brake disc 202, which is already presented as a percentage of the original length. The percentage of the amount of brake wear for a given brake assembly 200 and the percentage of the brake wear threshold can be determined. For example, if the brake wear threshold is 22.6% and the amount of brake wear is 11.3%, then the amount of brake wear is 50% of the brake wear threshold. This percentage can be used as a measure of how much the brake wear of a given brake assembly 200 has been advanced.

[0100] The thermal oxidation threshold can be related to the amount of mass lost from a given brake assembly 200 due to thermal oxidation (as a percentage of the original mass). In this example, the thermal oxidation state of a given brake assembly 200 can be expressed as the amount of mass lost from that given brake assembly 200 due to thermal oxidation (as a percentage of the original mass). A percentage of the thermal oxidation threshold and a percentage of the thermal oxidation state of a given brake assembly 200 can be determined. For example, if the thermal oxidation threshold is 5% and the thermal oxidation state of a given brake assembly 200 is 2%, then the thermal oxidation state is 40% of the thermal oxidation threshold. This percentage can be used as a measure of how far the thermal oxidation state of the given brake assembly 200 has been advanced.

[0101] Brake wear thresholds and thermal oxidation thresholds can be set at levels at which repair or replacement of a given brake assembly 200 (or a component of a given brake assembly 200) may be necessary. Depending on the physical characteristics of the brake assembly 200, the thermal oxidation threshold can range from 4% to 6.5% of the original brake mass loss. In some examples, the thermal oxidation threshold can be 5.7% of the original brake mass loss. Furthermore, depending on the characteristics of a given brake assembly 200, the brake wear threshold can be 22% to 24% of the original length. The length reduction that triggers repair or replacement may depend on the type of brake. In some examples, a reduction of 35 mm to 65 mm in the length L of the brake disc may trigger repair or replacement. For an exemplary disc with an original length L of approximately 221 mm, a length reduction of approximately 50 mm may trigger repair or replacement.

[0102] In other examples, the thermal oxidation state can be expressed as a percentage of the original mass loss due to thermal oxidation (as described above), and the amount of brake wear can be expressed as a percentage of the original mass loss due to brake wear. In this example, the amount of brake wear and the thermal oxidation state can be directly compared to determine which of the two was reached earlier to a greater extent.

[0103] In the specific example described, the degree of brake wear on a given brake assembly is greater (at 50% of the corresponding threshold). To determine whether the thermal oxidation state of brake assembly 200 or the amount of brake wear is reached more prematurely overall, the average brake wear value on all brake assemblies 200 can be compared with the average thermal oxidation state of all brake assemblies 200 in any of the ways described above. Controller 304 can select either a brake wear reduction function or a thermal oxidation coordination function based on the overall comparison result of all brake assemblies 200.

[0104] If the amount of brake wear on brake assembly 200 is reached earlier and to a greater extent overall, the method can proceed to block 422. At block 422, controller 304 selects a brake wear reduction function as a second control function. The brake wear reduction function controls the number of times brake assembly 200 is applied. In this example, aircraft 100 includes multiple brake assemblies 200. The brake wear reduction function can define at least two brake groups, each defined brake group being a different subgroup of the multiple brake assemblies 200. Each defined brake group can be positioned on aircraft 100 such that each defined brake group includes a symmetrical arrangement of brake assemblies. This symmetrical arrangement prevents aircraft 100 from deviating from its flight path when the brake group is applied.

[0105] The brake wear reduction function can be applied to a subgroup of a defined brake assembly to provide braking during braking operations. The brake wear reduction function can alternate between different subgroups of the defined brake assembly to reduce the total number of times each brake assembly in brake assembly 200 is used for braking applications.

[0106] It should be understood that the amount of brake wear on carbon brakes may be significantly related to the number of braking applications. Therefore, reducing the total number of times a given brake assembly 200 is used for braking applications can reduce the amount of brake wear over time compared to using all brake assemblies 200 in every braking application.

[0107] In some examples, if the temperature of at least one brake component in brake assembly 200 is not higher than a scheduling temperature threshold (as determined at block 416), method 400 can proceed directly to block 422 to select the brake wear reduction function as the second control function. In this example, blocks 420 and 424 can be omitted.

[0108] If the thermal oxidation state of the brake assembly is reached earlier than expected at block 420, method 400 can proceed to block 424, and controller 304 can select the thermal oxidation coordination function as a second control function to control the braking operation.

[0109] The thermal oxidation coordination function enables the controller 304 to control the application of a given brake assembly 200 based on its corresponding thermal oxidation state compared to the corresponding thermal oxidation states of other brake assemblies 200. For example, a given brake assembly 200 may be applied based on the degree to which its oxidation state is advanced compared to the corresponding thermal oxidation states of other brake assemblies 200. In some examples, all brake assemblies 200 may have the same thermal oxidation threshold. In such examples, the corresponding oxidation states of different brake assemblies can be directly compared. In examples where the thermal oxidation thresholds differ among the brake assemblies, the degree to which the thermal oxidation state of a particular brake assembly is advanced can be determined relative to that particular brake assembly's thermal oxidation threshold.

[0110] The thermal oxidation coordination function enables the controller 304 to control each brake assembly in the brake assembly 200 so that each brake assembly 200 reaches the corresponding oxidation threshold approximately simultaneously.

[0111] For example, the thermal oxidation coordination function distributes braking across brake assemblies 200 based on their respective thermal oxidation states, such that each brake assembly 200 reaches its corresponding thermal oxidation value approximately simultaneously. Brake assemblies that reach their thermal oxidation states less prematurely may be applied preferentially over those that reach their thermal oxidation states more prematurely. For instance, the oxidation state of a given brake assembly 200 can be compared to the corresponding oxidation states of other brake assemblies 200. If the thermal oxidation state of a given brake assembly is reached less prematurely than that of other brake assemblies, then that given brake assembly 200 may be applied preferentially over the other brake assemblies 200.

[0112] This control over the application of brake assembly 200 may result in brake assemblies 200 that have reached their thermal oxidation state with a smaller degree of premature activation being used and further oxidized (if these brake assemblies reach sufficiently high temperatures), while unused brake assemblies (due to reaching their thermal oxidation state with a larger degree of premature activation) will not oxidize further. Therefore, the thermal oxidation coordination function can cause all brake assemblies 200 to reach their respective thermal oxidation thresholds approximately simultaneously, and require repair or replacement of all or some of the brake assemblies 200 approximately simultaneously. This can advantageously allow for improved maintenance schedules and, for example, allow for fewer maintenance requirements.

[0113] The thermal oxidation coordination function enables the controller 304 to control braking based on the thermal oxidation state of each brake assembly in the brake assembly 200, as indicated by the brake thermal oxidation state indicator 312. In an example where the braking system 300 does not include the brake thermal oxidation state indicator 312, the controller 304 may receive the thermal oxidation state of each brake assembly in the brake assembly 200 from a device separate from the braking system 300 in order to control braking according to the thermal oxidation coordination function.

[0114] In some examples, boxes 410 to 420 can be omitted, and controller 304 can be... Figure 4a The braking operation is simply controlled at box 408 as shown, based on the brake wear reduction function. In some examples, boxes 410 to 422 can be omitted, and controller 304 can be... Figure 4a The braking operation is simply controlled at box 408 according to the thermal oxidation coordination function. Controller 304 can be configured to select either the brake wear reduction function or the thermal oxidation coordination function as a second control function. In some examples, boxes 412 to 418 can be omitted, and the method can proceed directly from box 410 to box 420. In some examples, box 420 can be omitted, and only one of boxes 422 and 424 may be included.

[0115] In some examples, Figure 4b The blocks shown can be executed in different orders, such that block 420 is executed directly after block 410. In this example, if the amount of brake wear is reached earlier to a greater extent, the method can proceed to block 422, and a brake wear reduction function can be selected. In some such examples, if the thermal oxidation state of brake assembly 200 is reached earlier to a greater extent, the method can proceed to block 412, and then proceed to block 414 or block 416 depending on whether the thermal oxidation limit criterion is met. Alternatively, in this example, the method can proceed from block 420 to block 416, and then proceed to block 418 if a scheduling temperature threshold is exceeded, and to block 412 if the scheduling temperature threshold is not exceeded.

[0116] Any of the described brake control functions can be implemented independently without performing the described methods. For example, the braking system 300 may not compare the speed of the aircraft 100 with a speed threshold and may not select a brake control function based on the condition of the brake assembly 200. In such an example, the braking system 300 may simply utilize one of the described brake control functions to control the braking operation without selection based on any criteria. For example, the braking system 300 may control the braking based on a thermal oxidation coordination function. In some examples, the braking system 300 may control the braking based on a cooling time coordination function or any other described function.

[0117] Any given brake control function described can be implemented by a braking system that includes at least the necessary features for implementing the given brake control function. For example, a braking system for an aircraft can be provided, operable to apply multiple aircraft wheel brakes according to corresponding thermal oxidation states. Such a braking system may include a controller configured to control the application of the brakes based on the corresponding thermal oxidation state of one of the brakes relative to the corresponding thermal oxidation states of other brakes. Such a braking system may include a thermal oxidation state indicator 312, or the controller of such a braking system may receive the thermal oxidation states of the multiple brakes from elsewhere. In this example, the controller may be configured to control each of the multiple brakes such that each brake reaches its corresponding thermal oxidation threshold approximately simultaneously. This example illustrates the implementation of a thermal oxidation coordination function by the braking system.

[0118] In some examples, a braking system for an aircraft may be provided, operable to apply multiple aircraft wheel brakes based on corresponding times it takes for them to cool to a scheduled temperature threshold. Such a braking system may include a controller configured to control the application of the brakes based on a predicted time for each brake to cool to a scheduled temperature threshold compared to predicted times for other brakes. In this example, the controller may be configured to control each of the multiple brakes such that the predicted times for cooling to the scheduled temperature threshold for all brakes are substantially the same. This example illustrates a braking system implementing a brake cooling time coordination function.

[0119] During aircraft operation, all or part of the described methods can be executed in real time. For example, the described methods can be executed in real time when the aircraft 100 is in a taxiing phase and / or when a braking operation occurs. For example, the aircraft speed can be repeatedly compared with an aircraft speed threshold, and the condition of the brake assembly 200 can be repeatedly compared with relevant standards and thresholds (e.g., thermal oxidation limit standards, scheduling temperature thresholds, etc.). For example, all or part of the described methods can be executed live, such that during braking operation—according to which the braking operation is controlled—a control function is switched from one to another. For example, during a single braking operation, the aircraft speed can change from above the aircraft speed threshold to below the aircraft speed threshold. In this example, when the described methods are executed in real time, the controller 304 can switch from using a torque equalization function to a second control function. It should be understood that the controller 304 can also switch from one second control function to another second control function in real time during braking operation (e.g., from a cooling time coordination function to a brake wear reduction function, etc.).

[0120] For example, all or part of the described method can be performed rapidly and repeatedly, wherein aircraft speed, temperature and / or other brake condition parameters are sampled multiple times per second—determined by the sampling rate of the corresponding sensors and detectors.

[0121] It should be understood that, Figure 4b The method boxes illustrate specific examples of the method boxes that can be executed as part of box 408. However, Figure 4b The method boxes can be executed in any other order. Additionally, the following can be omitted: Figure 4b One or more method boxes in the various method boxes.

[0122] In some examples, when the brake wear reduction function is selected as the second wheel brake control function, the controller 304 controls the wheel braking operation based on the first wheel brake control function (i.e., the torque equalization function) and the brake wear reduction function. For example, when the method proceeds to block 422 and brake wear reduction is selected, the controller 304 can control the braking operation simultaneously based on the torque equalization function and brake wear reduction (even if the aircraft speed is below the previously described speed threshold). For example, during braking operation, the controller 304 can select a given brake group to provide braking. The controller can then control the brake assembly 200 within that brake group such that the torque reacted by the applied brake assembly 200 is controlled according to any of the foregoing examples.

[0123] As described, a braking request may include information related to the requested braking intensity. In some scenarios, it may be desirable to apply some or all of the brake components 200 without controlling braking operation according to a second control function. For example, if the pilot wants the aircraft 100 to stop immediately or wants the speed of the aircraft 100 to decrease for a short period of time, the requested braking intensity may be higher than a braking intensity threshold. If the requested braking intensity is higher than the braking intensity threshold, the controller 304 may deactivate the second control function that is currently in use and enable some or all of the brake components 200 to provide the required braking (as needed). For example, one or more disabled brake components may be enabled to provide the required braking. In this example, the controller 304 may control the braking operation according to a torque equalization function. Alternatively, the controller 304 may not use any of the described control functions.

[0124] Figure 5 An exemplary method 500 for determining the thermal oxidation state of a brake, such as a flight brake assembly 200, of an aircraft landing gear assembly 102 is summarized. Method 500 includes using a thermal oxidation model to determine the thermal oxidation state of the brake assembly 200 after a braking event, based on an initial thermal oxidation state prior to a braking event (also referred to as the initial thermal oxidation level) and a temperature profile of the brake over time. The determined thermal oxidation state of the brake assembly 200 after the braking event is also referred to as the updated thermal oxidation state. This is because the thermal oxidation state of the brake assembly 200 after the braking event takes into account the change in the initial thermal oxidation state caused by the braking event.

[0125] A braking event is an event related to the application of brake assembly 200. For example, a braking event may include one or more applications of brake assembly 200 to slow or stop aircraft 100. In some examples, a braking event may be a portion of a period during which brake assembly 200 is continuously applied. Whenever brake assembly 200 is applied, the temperature of brake assembly 200 may rise. This is because when brake assembly 200 is applied to reduce the speed of aircraft 100, some of the kinetic energy of aircraft 100 is absorbed as heat into brake assembly 200, causing its temperature to rise. Therefore, the temperature change of brake assembly 200 can be used to determine whether brake assembly 200 has been applied.

[0126] At block 502 of method 500, a temperature profile and initial thermal oxidation state of the brake assembly 200 are input. As explained above, the temperature profile indicates the temperature change over time. The input temperature profile may, for example, be related to the service life of the aircraft 100. For example, the temperature profile may be for the entire service life of the aircraft 100, such as from the time the aircraft 100 is at the departure point before flight to the time the aircraft 100 is at the arrival point after flight. In particular, the temperature profile may indicate the temperature change over time for all braking events that occur during a cycle. In other examples, the temperature profile may not be for the entire service life of the aircraft 100. For example, the temperature profile may be for a single braking event or a portion of a cycle with many braking events. In some examples, multiple temperature profiles belonging to a particular service life may be used to determine the thermal oxidation state of the brake assembly 200 after that service life.

[0127] For example, the temperature profile can be related to a usage cycle that has already occurred. In other words, the temperature profile can include actual data from the temperature sensor 216 of the aircraft 100 during a previous usage cycle. In such an example, the temperature profile is related to real data. On the other hand, in some examples, the temperature profile can be a predicted temperature profile for a predicted future usage cycle of the aircraft 100. In this context, the braking event can be a predicted future braking event.

[0128] The initial thermal oxidation state of brake assembly 200 is the thermal oxidation state of brake assembly 200 prior to a braking event, and the updated thermal oxidation state is determined with respect to that oxidation state. For example, for a new brake assembly 200 installed in aircraft 100, the initial oxidation state may indicate no oxidation. In some examples, the initial oxidation state for a newly installed brake assembly 200 may be set by aircraft maintenance personnel at the time of installation and may indicate no oxidation or some degree of oxidation as assessed by the personnel performing the installation. In examples where brake assembly 200 is not a new brake assembly, the initial oxidation state may be the oxidation state calculated at a previous moment in the execution of method 500. In some examples, a non-new brake or brake component may be installed on aircraft 100. If temperature profile information for all previous braking events involving the brake or brake component is available, the available temperature profile information may be used to determine the thermal oxidation state at the time of installation using method 500 or other methods disclosed herein.

[0129] At block 504 of method 500, a thermal oxidation model is used to determine the thermal oxidation state (updated thermal oxidation state) following the braking event. For example, a thermal oxidation model is applied based on the input temperature profile and the initial thermal oxidation state of the brake assembly 200. For example, the thermal oxidation state indicates how the expected thermal oxidation state changes over time for various temperatures, starting from the initial thermal oxidation state. The thermal oxidation model is a model of the thermal oxidation evolution of the brake. For example, which thermal oxidation state is used may depend on the initial thermal oxidation state. Details and selection of appropriate thermal oxidation models are further described below. In some examples, method 500 may be performed in the field during the service life of aircraft 100. In the case of performing method 500 in the field (i.e., in real-time or near real-time), for example, the temperature profile used may be derived from temperature data acquired so far by temperature sensor 216. Therefore, at block 504, it is determined how the oxidation state changes from the initial oxidation state due to the increased temperature associated with the braking event in question.

[0130] After determining the updated thermal oxidation state, the initial thermal oxidation state can be set to the updated thermal oxidation state. In this way, the initial thermal oxidation state always follows all previous braking events. In examples where the temperature profile involves more than one braking event, method 500 can be executed again to determine the updated thermal oxidation state after subsequent braking events. Updating the initial thermal oxidation state in this way ensures that the initial thermal oxidation state used for subsequent braking events takes into account all previous braking events.

[0131] In an example of a temperature profile for the entire service life of the aircraft 100, method 500 can be performed to determine the corresponding updated thermal oxidation state after each braking event within that service life. It should be understood that this process can be performed sequentially relative to the chronological order of the braking events. This allows the determination of the updated thermal oxidation state for each braking event to be performed from the starting point (initial thermal oxidation state) considering all previous braking events.

[0132] In method 500, for example, an appropriate thermal oxidation model can be used to determine the updated thermal oxidation state after the braking event based on the high temperature interval, the initial thermal oxidation state, and the thermal oxidation rate parameter.

[0133] Figure 6This is a flowchart illustrating a method 600 that can be performed as part of method 500. For example, method 600 relates to a more specific example of block 504 of method 500. Block 602 is identical to block 502 of method 500, where a temperature profile of the brake relative to time and the initial thermal oxidation state of the brake assembly 200 are input. At block 604, the temperature profile is compared to a set of temperature standards. This set of temperature standards includes a set of temperature thresholds. For example, the set of temperature standards may include a first temperature threshold of 400°C and a second temperature threshold of 750°C. In other examples, different temperature thresholds may be used depending on the physical properties of the brake assembly 200. For example, the comparison of the temperature profiles may be performed sequentially according to the chronological order of the temperature data contained in the temperature profiles. For example, temperature values ​​may be compared to the set of temperature thresholds, and subsequently, the next temperature value may be compared to the set of temperature thresholds.

[0134] In box 606, it is determined whether one or more temperature criteria are met. For example, if no temperature threshold is exceeded, method 600 ends. It should be understood that thermal oxidation of the CC compound of the brake disc 202 is the most significant process at high temperatures. Therefore, comparison of temperature profiles with a set of temperature thresholds identifies high-temperature events corresponding to braking events that may lead to thermal oxidation. As mentioned above, for example, a braking event is the application of brake assembly 200. However, a high-temperature event is an event in which the temperature of the brake assembly exceeds at least one of the temperature thresholds due to the braking event. For example, if the temperature of brake assembly 200 remains below all temperature thresholds during a braking event (i.e., brake application), then no high-temperature event occurs during that braking event. On the other hand, if the temperature of the brake assembly exceeds a temperature threshold during a braking event, the portion of the braking event exceeding the temperature threshold can be referred to as a high-temperature event. If more than one temperature threshold is exceeded, then a high-temperature event is the portion of the braking event exceeding the highest temperature threshold.

[0135] A temperature threshold can be set based on the following temperature: above which a significant amount of thermal oxidation is expected. Therefore, if no temperature threshold is exceeded, method 600 terminates. This is because, in this example, no braking event occurs that would cause a sufficiently high temperature for thermal oxidation. In such an example, the updated thermal oxidation state after the braking event can simply be set to the initial thermal oxidation state prior to the braking event in question.

[0136] On the other hand, if at least one of the temperature thresholds is exceeded, a high-temperature event corresponding to the braking event in question is identified at block 608 of method 600. A high-temperature event corresponds to the portion of the temperature curve that exceeds the highest temperature threshold among the exceeded temperature thresholds. This is because the portion of the temperature curve that exceeds the highest threshold among the exceeded thresholds corresponds to the portion of the braking event that exceeds the highest temperature threshold. (See also...) Figure 7 The identification of high-temperature events is described. Figure 7 This is a graph illustrating a portion of an example temperature curve. Figure 7 In the graph, the vertical axis represents the temperature of the brake assembly 200, and the horizontal axis represents time. In this example, the curve portion 702 indicates that the temperature of the brake assembly 200 exceeds a first temperature threshold 704 and a second temperature threshold 706. In this example, a high-temperature event is identified as the portion of curve 702 above the second temperature threshold 706, because the second temperature threshold 706 is the highest temperature threshold exceeded.

[0137] Compared to thermal oxidation occurring above the first temperature threshold 704 but below the second temperature threshold 706, the amount of thermal oxidation occurring above the second temperature threshold 706 can be significantly greater over a given interval. Therefore, in this example, the portion of the temperature curve below the second temperature threshold 706 is not considered. In other examples, for example, when method 600 is used for on-site oxidation state monitoring as further described below, the portion of the temperature curve between the two temperature thresholds can be considered. It should be understood that... Figure 7 The curve is merely an illustrative example for purposes of explanation.

[0138] At box 610, the time interval occupied by the high-temperature event is defined as the high-temperature interval. As mentioned above, the updated thermal oxidation state can be determined based on the high-temperature interval (among other factors). Figure 7 In the example, the high-temperature interval was determined to be time interval 708.

[0139] At box 612, a high-temperature event value for brake assembly 200 is determined for a high-temperature interval. The high-temperature event value is the temperature attributed to a high-temperature event. In some examples, the high-temperature event value is the average temperature during the high-temperature interval. An alternative to the high-temperature event value as an average temperature is described below in the context of field oxidation monitoring.

[0140] At box 614, the oxidation rate parameter is calculated based on the high-temperature event value and physical property information of the brake. For example, the oxidation rate parameter for the thermal oxidation reaction can be determined based on the Arrhenius formula as shown in Equation 1 below:

[0141]

[0142] In Formula 1, k(T) is the thermal oxidation rate, A is the pre-constant, and E... A R is the activation energy of the carbon atoms in the CC composite component of brake 200, R is the universal gas constant, and T is the temperature. In this example, for a specific high-temperature event, the temperature T in Formula 1 is set to the high-temperature event value for the purposes of box 614. In this example, the thermal oxidation rate k(T) is the oxidation parameter determined at box 614. Activation energy E A The values ​​of the pre-exponential constant A depend on the physical properties of the CC compound of the brake assembly 200 (in this example, brake disc 202). For example, the values ​​of these parameters can depend on density, porosity, manufacturing process, contaminants present in the CC compound structure, surface finish of the component, and surface coatings of the brake assembly 200. Activation energy E A Furthermore, the value of the pre-exponential constant A can also change based on the high-temperature event value and the initial thermal oxidation state. Therefore, to determine the oxidation parameters, the activation energy E can be selected based on the physical properties of the brake assembly 200, the high-temperature event value, and the initial thermal oxidation state prior to the braking event under discussion. A And a suitable value for the pre-exponential constant A.

[0143] For example, activation energy E A It can be inversely proportional to temperature. Activation energy E A The activation energy E may decrease at temperatures where oxygen molecules can penetrate the surface of the brake disc 202 and deeper carbon within the brake disc 202 can undergo oxidation. For example, the activation energy E can be experimentally determined for different initial thermal oxidation levels, temperatures, and physical characteristics of the brake considered prior to implementing method 600. A The appropriate value for the pre-exponential factor A.

[0144] Figure 8 This is a graph illustrating an example of the evolution of the thermal oxidation state of the brake disc of brake assembly 200 at a specific temperature over time. Figure 8 The vertical axis of the graph represents a measurement of thermal oxidation, expressed as the thermal oxidation state Ox. For example, the thermal oxidation state Ox can be proportional to the mass loss of brake assembly 200 due to thermal oxidation of brake disc 202. Evolution curve 802 shows how the proportion of mass loss due to thermal oxidation at a specific temperature increases over time. It should be noted that different evolution curves will represent the change of the thermal oxidation rate Ox over time for different temperature values.

[0145] In this example, the thermal oxidation state Ox changes over time in a different manner below thermal oxidation state level 804 than it does above thermal oxidation state level 804. In this example, the thermal oxidation state Ox (i.e., the mass loss due to thermal oxidation) is shown to increase non-linearly over time below oxidation state level 804 and to change approximately linearly over time above oxidation state level 804. In this example, the thermal oxidation state increases at an accelerating rate over time until it reaches thermal oxidation state level 804. After reaching thermal oxidation state level 804, the rate of change of the thermal oxidation state Ox over time remains approximately constant. Figure 8 The portion of the curve below the thermal oxidation state level 804 can be considered, for example, as the first thermal oxidation region, i.e., region 1, and Figure 8 The portion of the curve above the thermal oxidation state level 804 can be considered, for example, as a second thermal oxidation region, i.e., region 2.

[0146] In some examples, different activation energies E can be used depending on which thermal oxidation region the brake assembly 200 is in, as indicated by its initial thermal oxidation state. A Value and pre-exponential factor A value.

[0147] At box 616, a thermal oxidation model is selected based on the initial thermal oxidation state prior to the braking event. The thermal oxidation model describes the evolution of the thermal oxidation state Ox of the brake assembly 200 for different temperature values. When the initial thermal oxidation state is in region 1, a thermal oxidation model describing the evolution of the thermal oxidation state Ox in region 1 can be selected. When the initial thermal oxidation state is in region 2, a thermal oxidation model describing the evolution of the thermal oxidation state Ox in region 2 can be selected. For example, a first thermal oxidation model, i.e., Model 1, can be selected for region 1, and a second thermal oxidation model, i.e., Model 2, can be selected for region 2. Model 1, describing the nonlinear change of the thermal oxidation state Ox over time for region 1, can be represented by Equation 2. Model 2, describing the linear change of the thermal oxidation state Ox over time for region 2, can be represented by Equation 3 below.

[0148]

[0149] OX = k(T)Xt eq (3)

[0150] In Equations 2 and 3 above, k(T) is the thermal oxidation rate defined by Equation 1. The parameter t... eqThis is the equivalent time, which is the time it would take to reach the thermal oxidative state Ox at temperature T. The parameter n refers to the order of the formula and depends on the properties of the CC composite material used in the brake assembly 200. The parameter n can be determined experimentally, for example, for a brake using a specific CC composite material.

[0151] In some examples, a different thermal oxidation model than the thermal oxidation models described in Equations 2 and 3 may be used. In some examples, a single thermal oxidation model may be used, which describes the evolution of thermal oxidation states Ox for all thermal oxidation states Ox associated with brake assembly 200. In some examples, more than two thermal oxidation models may be used for a given range of thermal oxidation states Ox. Method 600 may be appropriately modified to use such alternative thermal oxidation models. For example, a different set of inputs than those described in this particular example of method 600 may be applied to the thermal oxidation model, depending on the circumstances.

[0152] It will be understood that once box 602 has been executed, box 616 can be executed at any stage of method 600, because box 616 requires an initial thermal oxidation state.

[0153] At box 618, the updated thermal oxidation state for the high-temperature event is determined using the selected thermal oxidation model based on the high-temperature interval, the initial thermal oxidation state, and the determined thermal oxidation rate parameter. For example, the time taken to reach the initial thermal oxidation state from zero at the high-temperature value is determined, and the high-temperature interval is added to this time to determine the t to be used in the selected thermal oxidation model. eq The value of t will be determined from this. eq The values ​​and thermal oxidation parameters are input into the formula selected from Formulas 2 and 3 above, resulting in an updated thermal oxidation state of the brake assembly 200 after a high-temperature event as the output.

[0154] The updated thermal oxidation state can be set as the new initial thermal oxidation state for subsequent use of method 600 in response to subsequent high-temperature events in the temperature profile.

[0155] In some examples, methods 500 and / or 600 can be performed on-site during the usage cycle in which the braking event is occurring. In such examples, for example, a portion of method 600 can be modified to allow on-site brake oxidation monitoring, and the temperature profile can correspond to the temperature values ​​measured on-site. For example, the temperature information provided by temperature sensor 216 can be continuously compared with the set of temperature standards according to block 604 of method 600, and the high-temperature time can be identified substantially when a high-temperature event occurs. It will be understood that even though this type of oxidation state monitoring is described as on-site, the extent to which this type of oxidation state monitoring is performed in real time will depend on the limitations of various hardware and software (e.g., processing speed). For example, there may be a time delay between the temperature value corresponding to the high-temperature event measured by temperature sensor 216 and those values ​​that lead to an update of the thermal oxidation state of brake assembly 200.

[0156] For example, a high-temperature event can be identified as a smaller portion of the temperature curve than the example described above. See again... Figure 7 The portion of curve 702 occurring within the time interval represented by 710 can be considered a high-temperature event, and interval 710 is considered a high-temperature interval of the high-temperature event. In this example, the high-temperature event value can be considered, for example, the temperature value measured at the beginning or end of the high-temperature interval 710, or the average of the two temperature values. Unlike the example above, in the case of field monitoring, even when the temperature exceeds the second temperature threshold 706, the portion of the temperature curve between the first and second temperature thresholds can be considered. In the case of field monitoring, any portion of the temperature curve above at least one temperature threshold, such as the portion represented by interval 710, can be identified as a high-temperature event. It will be understood that this modification allows the thermal oxidation state of the brake assembly 200 to be updated when a high-temperature event corresponding to a braking event is occurring. In some examples, a high-temperature event can be identified based on the time between subsequent temperature measurements obtained by temperature sensor 216. For example, interval 710 can be the time between subsequent temperature measurements obtained by temperature sensor 216.

[0157] Methods 500 and 600 can be used to determine the thermal oxidation state of the brake assembly 200 in a field manner, either after or during an actual service life of the aircraft 100. In this example, this can be based on one or more temperature profiles covering braking events within the service life. As mentioned above, in some examples, the thermal oxidation state of the brake assembly 200 is determined using temperature profile information collected by temperature sensor 216 with respect to a service life that has actually occurred.

[0158] On the other hand, in some examples, method 500 or method 600 can be used to predict the future thermal oxidation state of the brake assembly 200 after a first plurality of predicted future use cycles of the aircraft 100. The first plurality of future use cycles can be cycles after which a thermal oxidation threshold is reached. Each predicted future use cycle can include a corresponding plurality of braking events. For each predicted future use cycle, the prediction can be based on a corresponding predicted temperature profile of the actuator assembly 200 and the current thermal oxidation state. The current thermal oxidation state is, for example, taking into account the oxidation state of all previous braking events experienced by the brake assembly 200.

[0159] For example, the predicted temperature profile can be input into method 500 or method 600, for instance, in chronological order, to determine the future thermal oxidation state of the brake assembly 200. This predicted temperature profile for the predicted future service life can be based on a previous temperature profile for a previous actual service life of the aircraft 100. For example, the landing phase portion of the previous temperature profile can be used to predict the landing phase portion of the temperature profile for the future service life. For the purpose of predicting the future thermal oxidation state, when method 500 or method 600 is executed for an actual service life of the aircraft 100, high-temperature events, high-temperature event values, etc., can be stored in a computer-readable storage medium.

[0160] In some examples, data from previous cycles may be unavailable, for example, because the brake assembly 200 may be new. In some examples, there may not be enough available data to reliably predict the temperature profile for the predicted future usage cycles. In such examples, a predetermined temperature profile can be used. The predetermined temperature profile may be a profile typically expected for the future usage cycles of the aircraft 100.

[0161] The predicted temperature profile can, for example, take into account the future flight schedule of aircraft 100. For instance, aircraft 100 may be anticipated to land at an airfield with a short runway, thus requiring high-energy (i.e., high-temperature) braking upon landing for some of the predicted future service cycles of the aircraft. For those predicted future service cycles, the predicted temperature profile indicates high-energy braking upon landing. It will be understood that when predicting the temperature profile, various other factors can be taken into account, such as taxiing time at various stages of the predicted future service cycle, and waiting time between the taxiing stage and the previous landing stage.

[0162] As mentioned above, the first plurality of predicted future use cycles can be a plurality of predicted future use cycles after which the predicted future thermal oxidation state reaches a thermal oxidation threshold. For example, prediction of the future thermal oxidation state can be stopped after a cycle in which the thermal oxidation threshold is reached. In some examples, prediction of the future thermal oxidation state can be stopped as soon as the thermal oxidation threshold is reached. The thermal oxidation threshold can be an oxidation state in which brake assembly 200 or a component of brake assembly 200 requires repair or replacement. For example, brake assembly 200 may require repair if the mass of brake assembly is reduced by between 4% and 6.5%, for example, by 5.7%, where the selected percentage threshold can vary, for example, based on the original manufactured disc density. In this example, the first plurality of predicted future use cycles are the plurality of cycles in which the mass loss due to thermal oxidation reaches or exceeds, for example, 5.7% (i.e., in the range between 4% and 6.5%).

[0163] On the other hand, in some examples, the prediction of future thermal oxidation state can cease at the end of one of the predicted future use cycles: during said predicted future use cycle, the future thermal oxidation state is almost close to the thermal oxidation threshold, such that the future thermal oxidation state can be expected to reach the thermal oxidation threshold during the next predicted future use cycle. In such examples, the thermal oxidation threshold can be considered to have been reached within the first plurality of predicted future use cycles. This is because, in practice, an aircraft 100 having a brake assembly 200 that is expected to reach the thermal oxidation threshold in a strict sense exactly in the next cycle will not be permitted to fly, and at this time, maintenance or replacement related to the brake assembly 200 can be performed.

[0164] Using the first plurality of predicted future usage cycles, an indication can be given regarding how many usage cycles can occur before the brake assembly 200 or a component of the brake assembly 200 requires repair or replacement due to thermal oxidation. In an example where the thermal oxidation threshold is strictly reached or exceeded during the last future cycle of the first plurality of future cycles, the number of cycles before requiring repair or replacement due to thermal oxidation can be predicted as one less than the number of cycles in the first plurality. In an example where the prediction of future thermal oxidation states ceases when the thermal oxidation threshold is expected to be reached in the next cycle after the first plurality, the first plurality is considered to be the number of cycles before requiring repair and replacement due to thermal oxidation.

[0165] Figure 9This is a flowchart of method 900, which uses a brake wear model to determine the amount of brake wear caused by a braking event based on the amount of energy absorbed by the brake assembly 200 due to a braking event and the density parameters of the brake assembly 200. The amount of brake wear can be determined for all braking events in which energy is input into the brake assembly 200 during friction processes that will lead to wear on the surface of the brake disc. For example, wear of the brake disc due to friction can cause the length of the brake disc 202 to decrease as the brake disc material is lost under friction.

[0166] For example, brake wear can be determined for braking events that do not involve any high-temperature events. For method 900, a braking event can be identified, for example, based on a temperature profile, as an event indicating an increase in the temperature of the brake assembly 200. In some examples, a braking event can be simply identified based on an indication that the brake assembly 200 has been applied. For example, the computing system 106 of the aircraft 100 can detect when the brake assembly 200 is applied and when it is released.

[0167] At block 902 of method 900, the energy input to brake assembly 200 during a braking event is determined. The energy input to brake assembly 200 can be determined, for example, based on characteristics of aircraft 100 during the braking event—such as the mass of aircraft 100, the speed of aircraft 100 during the braking event, etc. The energy absorbed by brake assembly 200 can be calculated based on these characteristics of aircraft 100 by determining the kinetic energy of aircraft 100. For example, a given proportion of the kinetic energy of aircraft 100 can be absorbed by brake assembly 200 to reduce the kinetic energy of aircraft 100. In some examples, the energy input to brake assembly 200 can be determined based on measurements obtained by instrument 108 of aircraft 100. For example, instrument 108 may include a tachometer associated with wheel 104, which is associated with brake assembly 200. In this example, the tachometer measures the rotational speed of wheel 104, and the energy absorbed by brake assembly 200 can be determined using the change in rotational speed relative to time.

[0168] In other examples, if the mass of brake assembly 200 is known, the absorbed energy can be determined based on the increase in temperature of brake assembly 200, taking into account the specific heat of brake assembly 200. In some examples, the mass of brake assembly 200 can be determined based on the thermal oxidation state of brake assembly 200 as determined by the method described above, because: as described above, the thermal oxidation state can be expressed as the amount of mass loss of brake assembly 200 due to thermal oxidation.

[0169] At block 904 of method 900, the density parameter of brake assembly 200 is determined. Taking into account mass loss, the density parameter is, for example, a parameter indicating the reduction in the density of brake assembly 200 compared to its original density. The density of brake assembly 200 may decrease, for example, due to thermal oxidation. It will be understood that thermal oxidation leads to a decrease in mass because carbon atoms react with oxygen to form carbon dioxide or carbon monoxide, and thus carbon atoms are removed from brake disc 202. However, thermal oxidation may not necessarily change the volume of brake disc 202. This is because thermal oxidation may not act uniformly on a particular surface of the brake disc but may occur at a certain depth within the brake disc.

[0170] The density parameter can be expressed as (1-Ox), where the thermal oxidation state Ox is represented as a number between 0 and 1. For example, the density of brake assembly 200 is reduced by a factor (1-Ox) compared to its initial density before any thermal oxidation occurs (i.e., when brake assembly 200 is new). Therefore, the density parameter can be determined based on the initial oxidation state before the braking event.

[0171] In some examples, the reduced density of brake assembly 200 can be determined based on measurements performed by instruments included in instrument 108. For example, the mass of brake assembly 200 can be calculated based on the amount of energy absorbed by brake assembly 200 (e.g., based on measurements from a tachometer) and the subsequent temperature rise of brake assembly 200 (e.g., based on measurements from temperature sensor 216). The reduced density of brake assembly 200 can be determined based on the calculated mass of brake assembly 200. Aircraft 100 may include a wear pin associated with brake assembly 200. Typically, the wear pin provides an indication of the reduction in the length L of the brake, and thus an indication of brake wear. For example, the wear pin can be checked by ground personnel between cycles, and updated volume values ​​of brake assembly 200 can be obtained. In some examples, other methods of measuring changes in the length L of brake assembly 200 may exist. For example, a length sensor can be provided for brake assembly 200, and / or an electrically actuated brake can be used. Updated volume values ​​can be determined based on the reduced length L and used to determine the reduced density based on the mass. During a single cycle, the volume change of the brake assembly 200 may be negligible for the purpose of calculating density parameters, and updated volumes can be obtained after multiple cycles. Based on the reduced density, the density parameters can be determined.

[0172] At block 906 of method 900, the amount of brake wear caused by a braking event is determined using a brake wear model based on the energy absorbed by brake assembly 200 and the density parameter from block 904. For example, the mass lost by brake assembly 200 due to wear during a wear event is determined using the brake wear model of Equation 4 below.

[0173]

[0174] In formula 4 above, m 磨损 E is the mass lost due to wear during a braking event. 制动器 The energy absorbed by the brake assembly 200 is W, X, Y, and Z, which are constants. These constants W, X, Y, and Z can be determined in advance, for example, through experimentation, and can vary depending on the characteristics of the brake assembly 200. The amount of brake wear during a braking event can be determined based on the reduction in mass of the brake assembly 200 during the braking event due to the decrease in brake wear, as a reduction in the length L of the brake assembly 200.

[0175] As mentioned above, in some examples, the initial thermal oxidation rate is used to determine the density parameter. In these examples, the initial thermal oxidation state can be used to determine block 906 when a braking event occurs—which also occurs during the braking event. This is because brake wear occurs in a shorter time period than thermal oxidation.

[0176] The amount of brake wear determined for a braking event can be added to the amount of brake wear for all previous braking events of the brake assembly 200 to determine the total amount of brake wear.

[0177] For example, method 900 can be performed in the field during a braking event, or in the field within the already occurred usage cycle using relevant data from the usage cycle. Method 900 can also be used to predict future brake wear of the brake assembly 200 after a second plurality of predicted future usage cycles of the aircraft 100. The second plurality of predicted future usage cycles can be a plurality of cycles after which a thermal oxidation threshold is reached. Each predicted future usage cycle can include a corresponding plurality of braking events. For example, method 900 can be performed for each braking event in the second plurality of predicted future usage cycles. The wear amounts from each of these braking events can be summed to predict the future brake wear amount for the second plurality of predicted future usage cycles. For each predicted future usage cycle, the prediction can be based on the predicted amount of energy absorbed by the brake during the corresponding braking event and a corresponding predicted density parameter of the brake for the corresponding braking event. For example, braking events can be identified and the energy absorbed by the brake assembly 200 for these braking events can be determined based on a predicted temperature profile. In other examples, the predicted amount of absorbed energy can be based on data from previous cycles. If the brake assembly 200 is new, or if sufficient prior data is not available, the amount of energy to be predicted can be determined in advance.

[0178] To predict future brake wear, method 900 can be used in conjunction with method 500 or 600. In these examples, the latest initial thermal oxidation state is known exactly before each predicted braking event (e.g., a predicted future braking event). In this way, the mass of brake assembly 200, and therefore its density parameter, can be determined using the initial thermal oxidation prior to the future braking event in question.

[0179] As described above, the second plurality of predicted future use cycles can be multiple predicted future cycles after which the predicted future brake wear amount reaches the brake wear threshold. For example, the prediction of future brake wear amount can be stopped after the cycle that reaches the brake wear threshold. In some examples, the prediction of future brake wear amount can be stopped once the total brake wear amount reaches the brake wear threshold. The brake wear threshold can be the total amount of brake wear at which the brake assembly 200 or a component of the brake assembly 200 needs to be repaired or replaced. For example, in the brake assembly, such as... Figure 2If the length L of the brake assembly 200 is reduced by, for example, 22% to 24% depending on the type of disc and its initial manufacturing density, the brake assembly may require repair. For an exemplary disc with an initial length L of approximately 221 mm, a length reduction of approximately 50 mm may necessitate repair or replacement. In this example, the second plurality of predicted future service cycles is the number of cycles required for the total brake wear to reach or exceed, for example, 50 mm (again, for an initial disc with a length L of approximately 221 mm).

[0180] On the other hand, in some examples, the prediction of future brake wear can cease at the end of a predicted future service period during which the total brake wear is close to the brake wear threshold, such that the total brake wear can be expected to reach the brake wear threshold in the next predicted future service period. In this example, it can be assumed that the brake wear threshold is reached within a second or more predicted future service periods. This is because, in practice, the aircraft 100 with brake assembly 200, which is strictly expected to reach the brake wear threshold in the next period, will not be permitted to fly, and maintenance or replacement related to brake assembly 200 may occur at that point.

[0181] By using a second plurality of predicted future use cycles, an indication can be given of how many use cycles can occur before brake assembly 200 or a component of brake assembly 200 requires repair or replacement due to brake wear. In an example where the brake wear threshold is strictly reached or exceeded during the last cycle of the second plurality of predicted future use cycles, the number of cycles before repair or replacement due to brake wear can be predicted as one less than the number of cycles in the second plurality of predicted future use cycles. In an example where the prediction of future brake wear is stopped when the brake wear threshold is expected to be reached in the next cycle following the second plurality of predicted future use cycles, the second plurality of predicted future use cycles are considered as the number of cycles before repair or replacement is required.

[0182] Figure 10This is a flowchart of a method 1000 for determining the number of favorable future service cycles before reaching either a thermal oxidation threshold or a brake wear threshold. The number of favorable future service cycles is the number of remaining service cycles before reaching either the thermal oxidation threshold or the brake wear threshold. Method 1000 can be performed for several predicted future service cycles until a first threshold is reached. Method 1000 includes predicting the future thermal oxidation state and future brake wear amount after the predicted future service cycle, and, if either the thermal oxidation threshold or the brake wear threshold is reached, determining the number of favorable future service cycles before reaching either threshold. If one of the thresholds is not reached, a prediction is performed for the next predicted future service cycle. As in the example above, each predicted future service cycle includes multiple braking events. For each predicted future service cycle, the prediction is based on the corresponding predicted temperature profile of the brake, the current thermal oxidation state, the predicted amount of energy absorbed by the brake during the corresponding braking event, and the corresponding predicted density parameter of the brake for the corresponding braking event.

[0183] The number of good future service cycles is the number of cycles after which brake assembly 200 or components of brake assembly 200 will require maintenance or replacement. It should be understood that maintenance or replacement of brake assembly 200 may be performed when either the thermal oxidation threshold or the brake wear threshold is first reached. The first threshold reached may depend, for example, on the handling of aircraft 100 during its service and its flight schedule. For example, if aircraft 100's schedule involves flights to most airports with long runways, short taxiways, etc., the brake wear threshold may be reached first. This is because, in this example, the temperature of brake assembly 200 may not frequently exceed any temperature threshold associated with thermal oxidation. On the other hand, aircraft 100 may frequently experience high-energy braking (e.g., due to short runways), resulting in temperatures exceeding the threshold associated with thermal oxidation. In this example, the thermal oxidation threshold may be reached first.

[0184] At block 1002 of method 1000, the future thermal oxidation state after the predicted future service life is predicted. The prediction of the future thermal oxidation state is performed as described above, for example, using an appropriate thermal oxidation model based on the predicted temperature profile of the predicted future service life discussed. At block 1004 of method 1000, the future brake wear amount after the same predicted future service life is predicted. The prediction is performed in the context of method 900 as described above.

[0185] At block 1006 of method 1000, it is determined whether a thermal oxidation threshold and / or a brake wear threshold has been reached. For example, if the thermal oxidation threshold is reached, method 1000 proceeds to block 1008, where a number of good future service cycles is determined before either the thermal oxidation threshold or the brake wear threshold is reached, and method 1000 ends. For example, if the thermal oxidation threshold is strictly reached or exceeded after a given number of predicted future service cycles, the number of good future service cycles is one less than the given number. For example, if the thermal oxidation threshold is expected to be reached in the next predicted future service cycle, the number of good future service cycles is determined to be the number of predicted future service cycles for which method 1000 has been executed so far.

[0186] On the other hand, if it is determined that the brake wear threshold has been reached, the method proceeds to block 1008, where the number of good future use cycles is determined, and method 1000 ends. For example, if the brake wear threshold is strictly reached or exceeded after a given number of predicted future use cycles, the number of good future use cycles is one less than the given number. For example, if the brake wear threshold is expected to be reached in the next predicted future use cycle, the number of good future use cycles is determined to be the number of predicted future use cycles for which method 1000 has been executed so far.

[0187] For example, if both thresholds are reached, method 1000 proceeds to box 1008, where the number of remaining good future use cycles is determined before either the thermal oxidation threshold or the brake wear threshold is reached, and method 1000 terminates. In this example, if at least one of the thresholds is strictly reached or exceeded after a given number of predicted future use cycles, the number of good future use cycles is one less than the given number. Otherwise, the number of good future use cycles is determined to be the number of predicted future use cycles for which method 1000 has been executed so far.

[0188] If the brake wear threshold is not reached, method 1000 proceeds to box 1010, and boxes 1002 to 1010 are repeated for the next predicted future usage cycle.

[0189] In this way, the number of good future service cycles can be predicted based on whether the thermal oxidation threshold or the brake wear threshold is reached first. This is because once the first of these thresholds is reached, brake assembly 200 may require repair or replacement, or a component of brake assembly 200 may require repair or replacement. It should be understood that, for example, brake assembly 200 will not continue to be used if, instead of the brake wear threshold, it is reached. It should also be understood that block 1004 of method 1000 can be performed in any suitable order. For example, block 1004 may be performed before block 1002, and / or block 1010 may be performed before block 1006.

[0190] One or more of the methods described above, namely methods 500, 600, 900, 1000, or any variations thereof (e.g., on-site determination of oxidation or brake wear, or prediction of future thermal oxidation state or future brake wear, etc.), can be executed by the processor of the computing system 106 of the aircraft 100, for example, based on instructions stored in a computer-readable storage medium of the computing system 106. For example, monitoring the thermal oxidation state (after a period of use or on-site) can be performed by the processor of the computing system 106. Alternatively or additionally, monitoring brake wear (after a period of use or on-site) can be performed by the processor of the computing system. Alternatively or in addition to any of these examples, predictions relating to future thermal oxidation state and / or future brake wear state can be performed by the processor of the computing system 106. These methods can be performed, for example, using data from instrument 108. For example, temperature data measured by temperature sensor 216 can be used. In the case of prediction, future temperature profiles and / or other predicted data can be predicted by the processor of the computing system 106. Alternatively, the data for prediction can be determined on a computing system not on the aircraft 100, and the data can be stored in a computer-readable storage medium of the computing system 106.

[0191] All or part of the instructions for performing the above procedures can be generated, and / or any suitable software or combination of software can be used to execute the procedures. In one example, "MATLAB" and / or "SCADE" can be used to generate all or part of the instructions for various processors to execute any of the above procedures. In other examples, other software packages can be used. For example, any suitable programming language, development environment, software package, etc., can be used. Other examples of programming languages ​​include PYTHON, C++, C, JAVASCRIPT, FORTRAN, etc.

[0192] It should be noted that, unless otherwise expressly stated, the term "or" as used herein should be interpreted as meaning "and / or". Although the invention has been described above with reference to one or more preferred examples, it should be understood that various changes or modifications may be made without departing from the scope of the invention as defined by the appended claims.

Claims

1. A brake system for an aircraft, the brake system operable to apply one or more aircraft wheel brakes in accordance with at least one of a plurality of wheel brake control functions, the brake system comprising: an aircraft speed indicator; and a controller configured to: control wheel brake operation of the aircraft in accordance with at least a first wheel brake control function if an aircraft speed indicated by the aircraft speed indicator exceeds a speed threshold, wherein the first wheel brake control function is a torque equalization function that causes the wheel brake operation to be controlled such that a distribution of torque reacted by the applied aircraft wheel brakes is symmetrical about a direction of travel of the aircraft over the aircraft and / or a portion of the aircraft; control the wheel brake operation of the aircraft in accordance with at least a second wheel brake control function if the aircraft speed does not exceed the speed threshold; select a wheel brake cooling time coordination function, a wheel brake thermal oxidation limiting function, a wheel brake wear reduction function, or a wheel brake thermal oxidation coordination function as the second wheel brake control function: the wheel brake cooling time coordination function causes an amount of braking provided by each of the aircraft wheel brakes to be controlled such that a predicted time for cooling of all of the aircraft wheel brakes to a scheduled temperature threshold is approximately the same; the wheel brake thermal oxidation limiting function causes at least one of the aircraft wheel brakes to be disabled or enabled based on a thermal oxidation limiting condition; the wheel brake wear reduction function defines at least two brake groups, each defined brake group of the at least two brake groups being a different subset of the aircraft wheel brakes; the wheel brake wear reduction function applies a subset of the defined at least two brake groups to provide braking during a braking operation; and the wheel brake wear reduction function alternates between different subsets of the defined at least two brake groups to reduce a total number of times each of the aircraft wheel brakes is used to make a braking application; the wheel brake thermal oxidation coordination function distributes an amount of braking provided by each of the aircraft wheel brakes among the aircraft wheel brakes based on a respective thermal oxidation state of each of the aircraft wheel brakes such that each of the aircraft wheel brakes reaches a respective oxidation threshold at approximately the same time; and apply the aircraft wheel brakes in accordance with the aircraft speed and the respective selected wheel brake control function.

2. The brake system of claim 1, further comprising a brake condition indicator, wherein, the controller is configured to select the second wheel brake control function in accordance with a condition of the one or more aircraft wheel brakes.

3. The brake system of claim 2, wherein: the brake condition indicator comprises a brake temperature characteristic indicator; and the brake condition comprises a temperature characteristic of the one or more aircraft wheel brakes.

4. The brake system of claim 3, wherein: the brake temperature characteristic indicator comprises a brake temperature sensor; and the temperature characteristic of the one or more aircraft wheel brakes comprises a temperature of the one or more aircraft wheel brakes. the controller is configured to select the second wheel brake control function based on the temperature characteristic of the one or more aircraft wheel brakes.

5. The brake system of claim 4, wherein, the temperature characteristic comprises a temperature of the one or more aircraft wheel brakes; and the controller is configured to select the wheel brake cooling time coordination function as the second wheel brake control function in the event that the temperature of at least one aircraft wheel brake is above the dispatch temperature threshold.

6. The brake system of claim 4 or 5, wherein, the controller is configured to select the wheel brake thermal oxidation limiting function as the second wheel brake control function in the event that the temperature characteristic of at least one aircraft wheel brake meets a thermal oxidation limiting criterion.

7. The brake system of claim 5, wherein, the controller is configured to select the wheel brake wear reduction function as the second wheel brake control function in the event that the temperature of at least one aircraft wheel brake is not above the dispatch temperature threshold.

8. The brake system of claim 7, wherein, the brake condition indicator further comprises a brake wear indicator and a brake thermal oxidation status indicator; and the brake condition further comprises an amount of brake wear of the one or more aircraft wheel brakes and a thermal oxidation status of the one or more aircraft wheel brakes.

9. The brake system of claim 8, wherein, the controller is configured to select the wheel brake wear reduction function or the wheel brake thermal oxidation coordination function as the second wheel brake control function based on the amount of brake wear and the thermal oxidation status of the one or more aircraft wheel brakes in the event that the temperature of at least one aircraft wheel brake is below the dispatch temperature threshold.

10. The brake system according to any one of claims 7 to 9, wherein, the controller is configured to control the wheel brake operation according to the first wheel brake control function and the wheel brake wear reduction function when the wheel brake wear reduction function is selected as the second wheel brake control function.

11. An aircraft comprising: one or more aircraft wheel brakes; and the brake system of any one of claims 1 to 10, the brake system being arranged to apply the one or more aircraft wheel brakes.

12. A method of applying one or more aircraft wheel brakes according to at least one of a plurality of wheel brake control functions, the method comprising: receiving an indication of an aircraft speed from an aircraft speed indicator; controlling a wheel brake operation of an aircraft according to at least a first wheel brake control function in the event that the aircraft speed indicated by the aircraft speed indicator exceeds a speed threshold, wherein the first wheel brake control function is a torque equalization function that causes the wheel brake operation to be controlled such that a distribution of torque reacted by the applied aircraft wheel brakes is symmetrical about a direction of travel of the aircraft over the aircraft and / or a portion of the aircraft; controlling the wheel brake operation of the aircraft according to a second wheel brake control function in the event that the speed of the aircraft does not exceed the speed threshold; and selecting a wheel brake cooling time coordination function, a wheel brake thermal oxidation limiting function, a wheel brake wear reduction function, or a wheel brake thermal oxidation coordination function as the second wheel brake control function: the wheel brake cooling time coordination function causes the amount of braking provided by each of the aircraft wheel brakes to be controlled such that the predicted time for cooling of all of the aircraft wheel brakes to a scheduled temperature threshold is approximately the same; the wheel brake thermal oxidation limiting function causes at least one of the aircraft wheel brakes to be disabled or enabled based on a thermal oxidation limiting condition; the wheel brake wear reduction function defines at least two brake groups, each defined brake group of the at least two brake groups being a different subset of the aircraft wheel brakes; the wheel brake wear reduction function applies a subset of the at least two defined brake groups to provide braking during a braking operation; the wheel brake wear reduction function alternates between different subsets of the at least two defined brake groups to reduce the total number of times each of the aircraft wheel brakes is used to apply braking; the wheel brake thermal oxidation coordination function distributes the amount of braking provided by each of the aircraft wheel brakes among the aircraft wheel brakes based on the respective thermal oxidation state of each of the aircraft wheel brakes such that each of the aircraft wheel brakes reaches a respective oxidation threshold at approximately the same time; and applying the aircraft wheel brakes according to the speed of the aircraft and the respective selected wheel brake control function.

13. The method of claim 12, comprising: receiving an indication of a condition of the one or more aircraft wheel brakes from a brake condition indicator; and selecting the second wheel brake control function according to the condition of the one or more aircraft wheel brakes.

14. The method of claim 13, wherein: the brake condition indicator comprises a brake temperature characteristic indicator; and a brake condition comprises a temperature characteristic of the one or more aircraft wheel brakes.

15. The method of claim 14, comprising: selecting the second wheel brake control function based on the temperature characteristic of the one or more aircraft wheel brakes.

16. The method of claim 15, wherein: the temperature characteristic comprises a temperature of the one or more aircraft wheel brakes; the method comprises selecting the wheel brake cooling time coordination function as the second wheel brake control function in the event that a temperature of at least one of the aircraft wheel brakes is above the scheduled temperature threshold.

17. The method of claim 15 or 16, wherein: The method includes selecting the wheel brake wear reduction function as the second wheel brake control function if a temperature of at least one of the aircraft wheel brakes is not higher than the dispatch temperature threshold.

18. The method of claim 16, wherein, The method includes selecting the wheel brake wear reduction function as the second wheel brake control function if a temperature of at least one of the aircraft wheel brakes is not higher than the dispatch temperature threshold.

19. The method of claim 18, wherein, The brake condition indicator further includes a brake wear indicator and a brake thermal oxidation status indicator; and The brake condition further includes an amount of brake wear of the one or more aircraft wheel brakes and a thermal oxidation status of the one or more aircraft wheel brakes.

20. The method of claim 19, wherein, The method includes selecting the wheel brake wear reduction function or the wheel brake thermal oxidation coordination function as the second wheel brake control function based on the amount of brake wear and the thermal oxidation status of the one or more aircraft wheel brakes if a temperature of at least one of the aircraft wheel brakes is not higher than the dispatch temperature threshold.

21. The method of any of claims 18-20, comprising: The wheel brake operation is controlled according to the first wheel brake control function and the wheel brake wear reduction function when the wheel brake wear reduction function is selected as the second wheel brake control function.

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