Patent Description:
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 <CIT>.

An antiskid brake control system is provided as defined by claim <NUM>.

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.

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:.

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.

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.

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.

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.

In various embodiments, the disclosed systems and methods may be particularly useful for aircraft braking as the aircraft reaches slower speeds-e.g., <NUM> 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.

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.

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

In various embodiments, the aircraft <NUM> further includes an avionics unit <NUM>, 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 <NUM> controls, at least various parts of, the flight of, and operation of various components of, the aircraft <NUM>. For example, the avionics unit <NUM> 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.

In various embodiments, the aircraft <NUM> further includes a BCU <NUM>. The BCU <NUM> 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 <NUM> controls, at least various parts of, the braking of the aircraft <NUM>. For example, the BCU <NUM> 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 <NUM> may further include hardware capable of performing various logic using discreet power signals received from various aircraft systems.

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.

Referring again more particularly to <FIG>, the aircraft <NUM> further includes one or more brakes coupled to each wheel assembly. For example, a brake <NUM> is coupled to the outer wheel assembly <NUM> of the third landing gear <NUM> of the aircraft <NUM>. In operation, the brake <NUM> applies a braking force to the outer wheel assembly <NUM> upon receiving a brake command, such as from the BCU <NUM>. In various embodiments, the outer wheel assembly <NUM> of the third landing gear <NUM> of the aircraft <NUM> comprises any number of wheels.

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

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

In various embodiments, the braking system <NUM> further includes an output device and/or output display <NUM> coupled to the BCU <NUM>. The output device and/or output display <NUM> 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 <NUM> 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 <NUM> controls the output device and/or output display <NUM> to output the health status of the braking system <NUM>, including the various components thereof. The BCU <NUM> may also receive a series of discrete control signals associated with the aircraft <NUM>, generally represented as aircraft discretes <NUM>, for providing braking control thereof.

In various embodiments of the braking system, the BCU <NUM> receives brake command signals from a left pilot brake pedal <NUM> and a right pilot brake pedal 14r and/or a left co-pilot brake pedal <NUM> and a right co-pilot brake pedal 16r. The brake command signals from the left pilot brake pedal <NUM> and the right pilot brake pedal 14r and/or the left co-pilot brake pedal <NUM> 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 <NUM> may receive control signals from an auto-brake interface <NUM> for performing auto-brake and RTO braking functions.

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

In various embodiments, BCU <NUM> 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 <NUM> during a braking operation. In the illustrated embodiment, BCU <NUM> sends i) a left brake command signal <NUM> to a brake control component <NUM> to apply a braking force to a brake stack <NUM> via actuators <NUM> of a left wheel/brake assembly <NUM>; and ii) a right brake command signal 44r to a brake control component <NUM> to apply a braking force to a brake stack <NUM> via actuators <NUM> of a right wheel/brake assembly 22r. In various embodiments, the braking system <NUM> includes pressure sensors <NUM> for monitoring the pressure applied by actuators <NUM> and to provide such information back to the BCU <NUM>.

In various embodiments, the braking system <NUM> is a hydraulic braking system, wherein the brake control component <NUM> comprises one or more valves for controlling hydraulic pressure to actuators <NUM>. For example, brake control component <NUM> 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 <NUM> is an electric braking system, wherein the brake control component <NUM> 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 <NUM>. However, the brake control component <NUM> 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.

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

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

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

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

With additional reference to <FIG>, a plot is provided illustrating a coefficient of friction curve <NUM> of a coefficient of friction for a brake stack (e.g., brake stack <NUM>) versus aircraft kinetic energy (e.g., aircraft kinetic energy <NUM>). The coefficient curve <NUM> 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.

In various embodiments, BCU <NUM> may be programmed to perform brake control using default antiskid parameters (i.e., antiskid deceleration target <NUM>, 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.

In various embodiments, BCU <NUM> comprises an antiskid PID controller <NUM>. The antiskid PID controller <NUM> 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 <NUM>. 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 <NUM>, in accordance with coefficient curve <NUM> of <FIG>. For example, with combined reference to <FIG> and <FIG>, BCU <NUM> may operate using default antiskid parameters associated with a coefficient of friction <NUM> (also referred to herein as a first coefficient of friction) which corresponds to a landing/RTO kinetic energy <NUM> (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 <NUM>. The BCU <NUM> may determine that an aircraft comprises a landing/RTO kinetic energy <NUM> (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 <NUM> (also referred to herein as a second coefficient of friction). In response to detecting the landing/RTO kinetic energy <NUM>, BCU <NUM> may adjust the proportional gain (P) and/or the derivative gain (D) to scale the brake command signal <NUM> proportional to the percent difference <NUM> between the coefficient of friction <NUM> and the coefficient of friction <NUM>, 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 <NUM>.

In various embodiments, BCU may further comprise an antiskid deceleration target <NUM>. The antiskid deceleration target <NUM> may be programmed into the BCU <NUM>. For example, the antiskid deceleration target <NUM> may comprise a value such as negative six meters per second squared (-<NUM>/s<NUM>), negative four and a half meters per second squared (-<NUM>/s<NUM>), negative three meters per second squared (-<NUM>/s<NUM>), 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 <NUM>. In addition to, or as an alternative to, adjusting the proportional gain (P) and/or the derivative gain (D) of the antiskid PID controller <NUM>, BCU may adjust the antiskid deceleration target <NUM> to compensate for a detected aircraft kinetic energy <NUM>. Continuing with the above example, BCU <NUM> may adjust the antiskid deceleration target <NUM> to scale the brake command signal <NUM> proportional to the percent difference <NUM> between the coefficient of friction <NUM> and the coefficient of friction <NUM>, which in this example the BCU may increase the absolute value of the antiskid deceleration target <NUM> 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 <NUM>.

With reference to <FIG>, a method <NUM> for antiskid brake control is provided, in accordance with various embodiments. Method <NUM> may be initiated in response to the BCU detecting a landing or RTO event (step <NUM>). Method <NUM> includes receiving, by a BCU, an aircraft weight (step <NUM>). Method <NUM> includes receiving, by the BCU, a wheel speed (step <NUM>). Method <NUM> includes calculating, by the BCU, an aircraft speed (step <NUM>). Method <NUM> includes calculating an aircraft energy (step <NUM>). Method <NUM> includes adjusting, by the BCU, an antiskid parameter(s) (step <NUM>). Method <NUM> includes generating, by the BCU, an adjusted antiskid brake command signal based upon the adjusted antiskid parameter(s) (step <NUM>). Method <NUM> includes sending, by the BCU, the adjusted antiskid brake command signal to a brake system component (step <NUM>).

With combined reference to <FIG> and <FIG>, step <NUM> may comprise detecting, by BCU <NUM>, a landing event or an RTO event. Step <NUM> may comprise detecting, by BCU <NUM>, a weight-on-wheels condition of the aircraft. Step <NUM> may comprise detecting, by BCU <NUM>, an RTO based upon a brake signal received from a cockpit of the aircraft. Step <NUM> may comprise receiving, by BCU <NUM>, aircraft mass data <NUM> from avionics unit <NUM> (see <FIG>). Step <NUM> may comprise receiving, by BCU <NUM>, wheel speed <NUM>. Step <NUM> may comprise calculating, by BCU <NUM>, aircraft speed <NUM>. Step <NUM> may comprise calculating, by BCU <NUM>, aircraft kinetic energy <NUM>. Step <NUM> may comprise adjusting, by BCU <NUM>, an antiskid parameter(s), such as proportional gain (P), derivative gain (D), and/or antiskid deceleration target <NUM>, as described herein. Step <NUM> may comprise generating, by BCU <NUM>, brake command signal <NUM> based upon the adjusted antiskid parameter(s). Step <NUM> may comprise sending, by BCU <NUM>, the adjusted antiskid brake command signal (i.e., brake command signal <NUM>) to brake control component <NUM> to apply a stopping force to wheel <NUM> (e.g., via actuator <NUM>).

Claim 1:
An antiskid brake control system, comprising:
a brake control unit, BCU (<NUM>);
a wheel/brake assembly (<NUM>,<NUM>) comprising a wheel (<NUM>), a brake stack (<NUM>), and an actuator (<NUM>) configured to apply a braking force onto the brake stack; and
a wheel speed sensor (<NUM>) 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.