SYSTEMS AND METHODS FOR ANTI-SLIP BRAKING OF AIRCRAFT

Description

FIELD

[0001] In general, the arrangements disclosed herein relate to braking systems. More specifically, they relate to systems for antiskid brake control suitable for use in aircraft.BACKGROUND

[0002] Aircraft typically include a braking system operatively coupled to the wheels of the aircraft and configured to slow the wheels, and the aircraft, during, for example, landing or a rejected takeoff. Aircraft braking systems tend to utilize aircraft brake controllers, to control various aspects of the braking system. In this regard, as a pilot applies force to the brake pedals, the pressure or force applied at the brake is increased to decelerate the wheel and aircraft. As the pressure / force exceeds the braking condition supported by the tire / runway friction, antiskid control may become dominant to adjust brake pressure / braking force to prevent or reduce skidding. An antiskid braking system is disclosed in EP 3 556 619 A1.SUMMARY

[0003] An antiskid brake control system is provided as defined by claim 1.

[0004] In various embodiments, the antiskid parameter comprises at least one of a proportional gain value, a derivative gain value, and a deceleration target value, and the antiskid brake command signal is generated using the adjusted antiskid parameter.

[0005] The foregoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated otherwise. These features and elements as well as the operation thereof will become more apparent in light of the following description and the accompanying drawings. It should be understood, however, the following description and drawings are intended to be exemplary in nature and nonlimiting.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The accompanying drawings illustrate various embodiments employing the principles described herein and are a part of this specification. The illustrated embodiments are meant for description only, and they do not limit the scope of the claims, and in which: FIG. 1 illustrates an aircraft having multiple landing gear and brakes, in accordance with various embodiments; FIG. 2 illustrates a functional diagram of a braking system of the aircraft of FIG. 1, in accordance with various embodiments; FIG. 3 illustrates a schematic diagram of an antiskid brake control logic for the brake control unit, in accordance with various embodiments; FIG. 4 illustrates a flowchart of a method of antiskid brake control, in accordance with various embodiments; and FIG. 5 illustrates a plot of a coefficient of friction curve, in accordance with various embodiments. DETAILED DESCRIPTION

[0007] The detailed description of exemplary embodiments herein makes reference to the accompanying drawings, which show exemplary embodiments by way of illustration. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be realized and that logical changes and adaptations in design and construction may be made without departing from the scope of the invention as defined by the claims. Thus, the detailed description herein is presented for purposes of illustration only and not of limitation.

[0008] As used herein, the term "weight-on-wheels (WOW) condition" means that at least a portion of the aircraft is supported on the ground via the landing gear with the associated tire in contact with a ground surface.

[0009] Provided herein, according to various embodiments, are systems, methods, and devices for brake control, such as within a braking system of an aircraft. While numerous details are included herein pertaining to aircraft components, such as brake components, the systems and methods disclosed herein can be applied to other systems with antiskid brake control and the like.

[0010] A brake control system of the present invention includes a brake control unit (BCU) configured to generate a brake command signal that is optimal over a wide range of aircraft landing energies. The BCU calculates an aircraft kinetic energy based upon a wheel speed signal and an aircraft mass received by the BCU. The BCU then adjusts one or more antiskid parameters to optimize the brake command signal for the real-time, calculated aircraft energy.

[0011] In various embodiments, the disclosed systems and methods may be particularly useful for aircraft braking as the aircraft reaches slower speeds-e.g., 40 knots and slower-when it may be more difficult to control wheel speed deceleration. For example, brake coefficient of friction (µ) values may be higher for braking maneuvers of lower aircraft energy, which means that as the aircraft slows down, it may become more difficult to control the wheel speed deceleration due to the higher brake coefficient of friction (µ). Everything else being equal, a small change in pressure command creates a higher change in brake torque, which may tend to cause the wheel to skid or lock up faster.

[0012] The disclosed methods may adjust an "aggressiveness" of antiskid braking tuning to improve antiskid activity, particularly at lower aircraft speeds. The disclosed methods may be based on initial landing / rejected take-off ("RTO") energy conditions. The disclosed methods may reduce deep skid activity during a braking maneuver and improve comfort while reducing tire wear. At higher energy stops, the disclosed methods also allow the antiskid tuning to be more aggressive and therefore improve overall braking efficiency performance when there is elevated energy to dissipate, without compromising the braking response at lower energy braking.

[0013] Referring now to FIG. 1, an aircraft 100 includes multiple landing gear systems, including a first landing gear 110, second landing gear 120, and third landing gear 130. The first landing gear 110, second landing gear 120, and third landing gear 130 each include one or more wheel assemblies. For example, the third landing gear 130 includes an inner wheel assembly 132 and an outer wheel assembly 134. The first landing gear 110, second landing gear 120, and third landing gear 130 support the aircraft 100 when the aircraft 100 is not flying, thereby allowing the aircraft 100 to take off, land, and taxi without damaging the aircraft 100. In various embodiments, the second landing gear 120 is also a nose landing gear for the aircraft 100, and oftentimes, one or more of the first landing gear 110, second landing gear 120, and third landing gear 130 are operationally retractable into the aircraft 100 when the aircraft 100 is in flight and / or airborne.

[0014] In various embodiments, the aircraft 100 further includes an avionics unit 140, which includes one or more controllers (e.g., processors) and one or more tangible, non-transitory memories capable of implementing digital or programmatic logic. In various embodiments, for example, the one or more controllers are one or more of a general purpose processor, digital signal processor (DSP), application specific integrated circuit (ASIC), field programmable gate array (FPGA), or other programmable logic device, discrete gate, transistor logic, or discrete hardware components, or any various combinations thereof or the like. In various embodiments, the avionics unit 140 controls, at least various parts of, the flight of, and operation of various components of, the aircraft 100. For example, the avionics unit 140 controls various parameters of flight, such as an air traffic management systems, auto-pilot systems, auto-thrust systems, crew alerting systems, electrical systems, electronic checklist systems, electronic flight bag systems, engine systems flight control systems, environmental systems, hydraulics systems, lighting systems, pneumatics systems, traffic avoidance systems, trim systems, and the like.

[0015] In various embodiments, the aircraft 100 further includes a BCU 150. The BCU 150 includes one or more controllers (e.g., processors) and one or more tangible, non-transitory memories capable of implementing digital or programmatic logic. In various embodiments, for example, the one or more controllers are one or more of a general purpose processor, DSP, ASIC, FPGA, or other programmable logic device, discrete gate, transistor logic, or discrete hardware components, or any various combinations thereof or the like, and the one or more memories store instructions that are implemented by the one or more controllers for performing various functions, such as antiskid brake control, as will be discussed herein. In various embodiments, the BCU 150 controls, at least various parts of, the braking of the aircraft 100. For example, the BCU 150 controls various parameters of braking, such as manual brake control, automatic brake control, antiskid control, locked wheel protection, touchdown protection, park capability, gear retraction braking, and the like. The BCU 150 may further include hardware capable of performing various logic using discreet power signals received from various aircraft systems.

[0016] System program instructions and / or controller instructions may be loaded onto a non-transitory, tangible computer-readable medium having instructions stored thereon that, in response to execution by a controller, cause the controller to perform various operations. The term "non-transitory" is to be understood to remove only propagating transitory signals per se from the claim scope and does not relinquish rights to all standard computer-readable media that are not only propagating transitory signals per se.

[0017] Referring again more particularly to FIG. 1, the aircraft 100 further includes one or more brakes coupled to each wheel assembly. For example, a brake 160 is coupled to the outer wheel assembly 134 of the third landing gear 130 of the aircraft 100. In operation, the brake 160 applies a braking force to the outer wheel assembly 134 upon receiving a brake command, such as from the BCU 150. In various embodiments, the outer wheel assembly 134 of the third landing gear 130 of the aircraft 100 comprises any number of wheels.

[0018] Referring now also to FIG. 2, including with continued reference to FIG. 1, a braking system 10 is shown in accordance with various embodiments. The braking system 10 includes the brake control unit (BCU) 150 of FIG. 1, which is programmed to control the various braking functions described herein. In various embodiments, the braking system 10 enables the aircraft 100 to brake, thereby slowing aircraft 100 when on the ground. However, it will be appreciated that the braking system 10 may also be used in connection with other types of vehicles without departing from the scope of the inventive arrangements.

[0019] As described herein, the braking system generally includes, inter alia, the brake control unit 150, a wheel / brake assembly including one or more wheels and brake stacks (e.g., wheel / brake assembly 221 includes one or more wheels 24 and brake stacks 26), and one or more wheel speed sensors 27 that provide wheel speed information to the BCU 150 for carrying out brake control operations. In addition, power to the BCU 150 may be provided from an aircraft power source 72, such as a DC power source within the aircraft 100. In various embodiments, power is transmitted from the aircraft power source 72 to the BCU 150.

[0020] In various embodiments, the braking system 10 further includes an output device and / or output display 74 coupled to the BCU 150. The output device and / or output display 74 is configured to communicate information to the pilot, co-pilot, and / or maintenance crew relating to the braking operations. For example, in various embodiments, the output device and / or output display 74 includes a display, a speaker, a network access device, and / or the like that sends a message to a remote terminal, or the like. In various embodiments, the BCU 150 controls the output device and / or output display 74 to output the health status of the braking system 10, including the various components thereof. The BCU 150 may also receive a series of discrete control signals associated with the aircraft 100, generally represented as aircraft discretes 20, for providing braking control thereof.

[0021] In various embodiments of the braking system, the BCU 150 receives brake command signals from a left pilot brake pedal 141 and a right pilot brake pedal 14r and / or a left co-pilot brake pedal 161 and a right co-pilot brake pedal 16r. The brake command signals from the left pilot brake pedal 14l and the right pilot brake pedal 14r and / or the left co-pilot brake pedal 16l and the right co-pilot brake pedal 16r are indicative of a desired amount of braking. However, any suitable brake pedal configuration is within the scope of the present invention as defined by the claims. Furthermore, the BCU 150 may receive control signals from an auto-brake interface 18 for performing auto-brake and RTO braking functions.

[0022] In various embodiments, the BCU 150 controls braking of the left wheel / brake assembly 22l and the right wheel / brake assembly 22r. The left wheel / brake assembly 22l includes one or more wheels 24 and brake stacks 26. A plurality of actuators 28 may be provided for exerting braking forces on the brake stacks 26 in order to brake the wheels 24. The right wheel / brake assembly 22r has a similar, mirrored configuration. Both the left wheel / brake assembly 221 and the right wheel / brake assembly 22r also include, in various embodiments, wheel speed sensors 27 that provide wheel speed information to the BCU 150 for carrying out brake control operations.

[0023] In various embodiments, BCU 150 sends brake command signals (also referred to herein as antiskid brake command signals) to a brake control component to apply a braking force to the wheels 24 during a braking operation. In the illustrated embodiment, BCU 150 sends i) a left brake command signal 44l to a brake control component 70 to apply a braking force to a brake stack 26 via actuators 28 of a left wheel / brake assembly 22l; and ii) a right brake command signal 44r to a brake control component 70 to apply a braking force to a brake stack 26 via actuators 28 of a right wheel / brake assembly 22r. In various embodiments, the braking system 10 includes pressure sensors 48 for monitoring the pressure applied by actuators 28 and to provide such information back to the BCU 150.

[0024] In various embodiments, the braking system 10 is a hydraulic braking system, wherein the brake control component 70 comprises one or more valves for controlling hydraulic pressure to actuators 28. For example, brake control component 70 may comprise one or more shutoff valves and / or one or more servo valves, such as a coil valve for example. In various embodiments, the braking system 10 is an electric braking system, wherein the brake control component 70 comprises an electromechanical actuator controller (EMAC). An EMAC may receive and interpret a brake force command and receives electrical power to then provide power to drive electromechanical actuators 28. However, the brake control component 70 may comprise any type of brake component (i.e., hydraulic, electromechanical, etc.) without departing from the scope of the present invention and is not intended to be limited by the illustrated embodiment.

[0025] In various embodiments, the braking system 10 may be activated by the left pilot brake pedal 14l, the right pilot brake pedal 14r, the left co-pilot brake pedal 16l, and the right co-pilot brake pedal 16r respectively acting through the left brake command signal 44l, and the right brake command signal 44r. The braking system 10 may also be activated in an autobraking mode.

[0026] With reference to FIG. 3, a schematic view of a portion of the braking system 10 with additional detail of a brake control logic of BCU 150 is illustrated, in accordance with various embodiments. The illustrated embodiments depicts BCU 150 in electronic communication with brake control component 70 of wheel / brake assembly 22 comprising the brake control component 70, brake stack 26, and wheel 24. The BCU 150 may be configured to output brake command signal 44 (e.g., a current signal or a voltage signal) to the brake control component 70 for controlling the braking force applied to brake stack 26 via actuator 28. A wheel speed sensor 27 is provided for detecting wheel speed data, including wheel speed 218 of wheel 24 which is received by BCU 150. The wheel speed 218 (e.g., in units of revolutions per second) is used by BCU 150 for calculating an antiskid brake command signal 44 adjusted for aircraft kinetic energy, as provided herein.

[0027] In various embodiments, the BCU 150 may utilize the wheel speed 218 to estimate an aircraft speed 204. BCU 150 may utilize a plurality of wheel speeds 218, for example an average based upon each monitored wheel of the aircraft, to estimate aircraft speed 204. In various embodiments, aircraft speed 204 may be received from avionics unit 140 (see FIG. 1). The aircraft speed 204 may correspond to an estimated linear velocity (e.g., in units of meters per second (m / s)) of the aircraft. The BCU 150 may further receive aircraft mass data 202 comprising the present (i.e., real-time) total mass (e.g., in units of kilograms (kg)) of the aircraft. The BCU 150 may receive the aircraft mass data 202 from an external control unit, such as avionics unit 140 (see FIG. 1). The BCU 150 may use the aircraft mass data 202 and the aircraft speed 204 to calculate an aircraft kinetic energy 206 which corresponds to a total kinetic energy of the aircraft. In various embodiments, the BCU 150 calculates the aircraft kinetic energy 206 using the equation KE = 1 2 mV 2 , where KE is the aircraft kinetic energy 206, m is the aircraft mass data 202, and V is the aircraft speed 204.

[0028] Wheel reference speed 210 may comprise a value corresponding to the rotational speed of wheel 24 as if wheel 24 were free rolling (i.e., no braking being applied). In this regard, the difference between WRS 210 and wheel speed 218 may be proportional to the difference between the linear speed of the aircraft (i.e., aircraft speed 204) and a speed of the wheel 24 of the aircraft, also referred to as wheel slip 212. Wheel slip 212 may be sent to antiskid proportional-integral-derivative (PID) controller 214 for generating antiskid brake command signal 44. BCU 150 may use wheel speed 218 to calculate wheel reference speed 210. During braking, wheel reference speed 210 may be adjusted to be equal to the wheel speed 218 in response to wheel 24 decelerating at a rate that is not greater than antiskid deceleration target 208, in which case wheel slip 212 is zero. In response to wheel 24 decelerating at a rate greater than antiskid deceleration target 208, the wheel slip 212 is monitored and antiskid PID controller 214 may adjust brake command signal 44 to maintain a deceleration of wheel speed 218 to be not greater than the antiskid deceleration target 208. In response to the wheel speed 218 changing at a rate which is greater than antiskid deceleration target 208, the wheel slip 212 comprises a negative value and the antiskid PID controller 214 acts in response to this error by adjusting brake command signal 44 to allow the wheel speed 218 to recover to an acceptable deceleration. In this regard, antiskid deceleration target 208 may be a maximum allowable deceleration of a wheel.

[0029] With additional reference to FIG. 5, a plot is provided illustrating a coefficient of friction curve 501 of a coefficient of friction for a brake stack (e.g., brake stack 26) versus aircraft kinetic energy (e.g., aircraft kinetic energy 206). The coefficient curve 501 shows that the coefficient of friction of the brake stack decreases as the landing / RTO aircraft kinetic energy increases. In this regard, an aircraft braking system may be more responsive for aircraft having lower energies (i.e., due to reduced speed, mass, or both) than for aircraft having higher energies (i.e., due to increased speed, mass, or both). Stated differently, an aircraft braking system may tend to become less responsive as aircraft landing energy increases. In this regard, it may be desirable to adjust a brake command based upon the landing / RTO aircraft kinetic energy in order to tune brake control for a wide range of aircraft landing energies.

[0030] In various embodiments, BCU 150 may be programmed to perform brake control using default antiskid parameters (i.e., antiskid deceleration target 208, proportional gain (P), and derivative gain (D)). Based upon the measured aircraft kinetic energy, these default antiskid parameters may be scaled proportionate to the difference between the coefficient of friction value associated with the default antiskid parameters and the coefficient of friction value associated with the landing / RTO aircraft kinetic energy that is measured when the braking operation is initiated.

[0031] In various embodiments, BCU 150 comprises an antiskid PID controller 214. The antiskid PID controller 214 may apply a correction to the brake command signal based on proportional, integral, and derivative terms, denoted P, I, and D, respectively. In accordance with the present invention, the proportional gain (P) and / or the derivative gain (D) may be scaled or adjusted based upon the landing / RTO aircraft kinetic energy 206. In various embodiments, the proportional gain (P) and / or the derivative gain (D) may be scaled or adjusted based upon the landing / RTO aircraft kinetic energy 206, in accordance with coefficient curve 501 of FIG. 5. For example, with combined reference to FIG. 3 and FIG. 5, BCU 150 may operate using default antiskid parameters associated with a coefficient of friction 530 (also referred to herein as a first coefficient of friction) which corresponds to a landing / RTO kinetic energy 510 (also referred to herein as a default kinetic energy or a first kinetic energy). It should be noted that the BCU may default to any coefficient of friction, be it relatively high or relatively low with respect to coefficient curve 501. The BCU 150 may determine that an aircraft comprises a landing / RTO kinetic energy 520 (also referred to herein as a second kinetic energy) during a braking maneuver (such as during landing or RTO) which corresponds to a coefficient of friction 540 (also referred to herein as a second coefficient of friction). In response to detecting the landing / RTO kinetic energy 520, BCU 150 may adjust the proportional gain (P) and / or the derivative gain (D) to scale the brake command signal 44 proportional to the percent difference 550 between the coefficient of friction 530 and the coefficient of friction 540, which in this example would proportionally increase a commanded braking force due to the estimated reduced coefficient of friction of the brake stack with respect to the coefficient of friction 530.

[0032] In various embodiments, BCU may further comprise an antiskid deceleration target 208. The antiskid deceleration target 208 may be programmed into the BCU 150. For example, the antiskid deceleration target 208 may comprise a value such as negative six meters per second squared (-6 m / s 2< ), negative four and a half meters per second squared (-4.5 m / s 2< ), negative three meters per second squared (-3 m / s 2< ), or any other suitable deceleration target value for an aircraft. The present invention is not intended to be limited by the particular value of the antiskid deceleration target 208. In addition to, or as an alternative to, adjusting the proportional gain (P) and / or the derivative gain (D) of the antiskid PID controller 214, BCU may adjust the antiskid deceleration target 208 to compensate for a detected aircraft kinetic energy 206. Continuing with the above example, BCU 150 may adjust the antiskid deceleration target 208 to scale the brake command signal 44 proportional to the percent difference 550 between the coefficient of friction 530 and the coefficient of friction 540, which in this example the BCU may increase the absolute value of the antiskid deceleration target 208 to proportionally increase a commanded braking force due to the reduction in the estimated coefficient of friction of the brake stack with respect to the coefficient of friction 530.

[0033] With reference to FIG. 4, a method 400 for antiskid brake control is provided, in accordance with various embodiments. Method 400 may be initiated in response to the BCU detecting a landing or RTO event (step 402). Method 400 includes receiving, by a BCU, an aircraft weight (step 404). Method 400 includes receiving, by the BCU, a wheel speed (step 406). Method 400 includes calculating, by the BCU, an aircraft speed (step 408). Method 400 includes calculating an aircraft energy (step 410). Method 400 includes adjusting, by the BCU, an antiskid parameter(s) (step 412). Method 400 includes generating, by the BCU, an adjusted antiskid brake command signal based upon the adjusted antiskid parameter(s) (step 414). Method 400 includes sending, by the BCU, the adjusted antiskid brake command signal to a brake system component (step 416).

[0034] With combined reference to FIG. 3 and FIG. 4, step 402 may comprise detecting, by BCU 150, a landing event or an RTO event. Step 402 may comprise detecting, by BCU 150, a weight-on-wheels condition of the aircraft. Step 402 may comprise detecting, by BCU 150, an RTO based upon a brake signal received from a cockpit of the aircraft. Step 404 may comprise receiving, by BCU 150, aircraft mass data 202 from avionics unit 140 (see FIG. 1). Step 406 may comprise receiving, by BCU 150, wheel speed 218. Step 408 may comprise calculating, by BCU 150, aircraft speed 204. Step 410 may comprise calculating, by BCU 150, aircraft kinetic energy 206. Step 412 may comprise adjusting, by BCU 150, an antiskid parameter(s), such as proportional gain (P), derivative gain (D), and / or antiskid deceleration target 208, as described herein. Step 414 may comprise generating, by BCU 150, brake command signal 44 based upon the adjusted antiskid parameter(s). Step 416 may comprise sending, by BCU 150, the adjusted antiskid brake command signal (i.e., brake command signal 44) to brake control component 70 to apply a stopping force to wheel 24 (e.g., via actuator 28).

[0035] Benefits, other advantages, and solutions to problems have been described herein with regard to specific embodiments. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent exemplary functional relationships and / or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in a practical system.

[0036] The scope of the invention is accordingly to be limited by nothing other than the appended claims.

Claims

1. An antiskid brake control system, comprising: a brake control unit, BCU (150); a wheel / brake assembly (132,134) comprising a wheel (24), a brake stack (26), and an actuator (28) configured to apply a braking force onto the brake stack; and a wheel speed sensor (27) in electronic communication with the BCU, the wheel speed sensor configured to detect a wheel speed corresponding to the wheel; wherein the BCU is configured to: receive an aircraft mass from an avionics unit; calculate an aircraft kinetic energy; generate an antiskid brake command signal based upon the aircraft kinetic energy; and send the antiskid brake command signal to a brake control component for controlling the braking force; and characterised in that the BCU is further configured to calculate an aircraft speed based upon the wheel speed, and the BCU calculates the aircraft kinetic energy using the aircraft speed and the aircraft mass, and wherein the BCU is further configured to adjust an antiskid parameter based upon the aircraft kinetic energy.

2. The antiskid brake control system of claim 1, wherein the antiskid parameter comprises at least one of a proportional gain value, a derivative gain value, and a deceleration target value, and the antiskid brake command signal is generated using the adjusted antiskid parameter.