Patent Description:
The present invention relates to aircraft wheel and brake systems and, more particularly, to systems and methods for enhancing redundancy in aircraft wheel and brake systems via hybrid brake systems having both hydraulic and electric braking subsystems.

Aircraft typically utilize brake systems on wheels to slow or stop the aircraft during landings, taxiing and emergency situations, such as, for example, a rejected takeoff (RTO), which generally refers to engagement of a brake system during an aborted takeoff and involves high braking loads over a short time period, resulting in a rapid increase in the brake temperature. The brake systems generally employ a heat sink comprising a series of friction disks, sandwiched between a pressure plate and an end plate, that may be forced into sliding contact with one another during a brake application to slow or stop the aircraft.

A typical hydraulic brake system may include, without limitation, a source of pressurized hydraulic fluid, a hydraulic actuator for exerting a force across the heat sink (e.g., across the pressure plate, the series of friction disks and the end plate), a valve for controlling a pressure level provided to the hydraulic actuator and a brake control unit for receiving inputs from a pilot and from various feedback mechanisms and for producing responsive outputs to the valve. Upon activation of the brake system (e.g., by depressing a brake pedal), a pressurized fluid is applied to the hydraulic actuator, which may comprise a piston configured to translate the pressure plate toward the end plate. A typical electric brake system includes various electromechanical counterparts to a hydraulic brake system, such as, for example, an electromechanical actuator in place of the hydraulic actuator and a source of electric power in place of the source of pressurized hydraulic fluid. Brake systems are disclosed in <CIT>, <CIT> and <CIT>.

A braking system is provided as defined by claim <NUM>.

In various embodiments, the brake assembly includes a pressure plate and an end plate and both the hydraulic brake actuator and the electric brake actuator are configured to translate the pressure plate toward the end plate. In various embodiments, the hydraulic brake actuator is one of a plurality of hydraulic brake actuators configured to translate the pressure plate toward the end plate. In various embodiments, the electric brake actuator is one of a plurality of electric brake actuators configured to translate the pressure plate toward the end plate. In various embodiments, the plurality of hydraulic brake actuators comprises four hydraulic brake actuators spaced at ninety degree intervals about the pressure plate. In various embodiments, the plurality of electric brake actuators comprises four electric brake actuators spaced at ninety degree intervals about the pressure plate.

In various embodiments, the hydraulic braking subsystem includes a hydraulic brake control unit configured to control operation of the hydraulic brake actuator. In various embodiments, the electric braking subsystem includes an electric brake control unit configured to control operation of the electric brake actuator. In various embodiments, the braking system includes an intercommunication bus between the hydraulic brake control unit and the electric brake control unit.

In various embodiments, the hydraulic brake control unit is configured to transfer operation of the braking system to the electric brake control unit following a failure occurring within the hydraulic braking subsystem. In various embodiments, a pressure transducer is configured to sense the failure, via a loss or a reduction of fluid pressure, occurring within the hydraulic braking subsystem. In various embodiments, the electric brake control unit is configured to transfer operation of the braking system to the hydraulic brake control unit following a failure occurring within the electric braking subsystem. In various embodiments, a hydraulic brake position sensor is coupled to the hydraulic brake control unit and configured to sense a brake pedal position. In various embodiments, an electric brake position sensor is coupled to the electric brake control unit and configured to sense the brake pedal position.

A redundant braking system for an aircraft is provided as defined by claim <NUM>.

In various embodiments, the hydraulic brake actuator is one of a plurality of hydraulic brake actuators spaced at equal degree intervals about the pressure plate. In various embodiments, the electric brake actuator is one of a plurality of electric brake actuators spaced at equal degree intervals about the pressure plate.

In various embodiments, the hydraulic braking subsystem includes a hydraulic brake control unit configured to control operation of the hydraulic brake actuator and the electric braking subsystem includes an electric brake control unit configured to control operation of the electric brake actuator. In various embodiments, the hydraulic brake control unit is configured to transfer operation of the redundant braking system to the electric brake control unit following a failure occurring within the hydraulic braking subsystem. In various embodiments, the electric brake control unit is configured to transfer operation of the redundant braking system to the hydraulic brake control unit following a failure occurring within the electric braking subsystem.

The subject matter of the present invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. A more complete understanding of the present invention, however, may best be obtained by referring to the following detailed description and claims in connection with the following drawings.

While these various 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 changes may be made without departing from the scope of the invention as defined by the claims.

Referring now to <FIG>, an aircraft <NUM> includes multiple landing gear systems, including a first landing gear <NUM> (or a port-side landing gear), a second landing gear <NUM> (or a nose landing gear) and a third landing gear <NUM> (or a starboard-side landing gear). The first landing gear <NUM>, the second landing gear <NUM> and the 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>, the second landing gear <NUM> and the third landing gear <NUM> support the aircraft <NUM> when the aircraft <NUM> is not flying, thereby enabling the aircraft <NUM> to take off, land and taxi without incurring damage. In various embodiments, one or more of the first landing gear <NUM>, the second landing gear <NUM> and the third landing gear <NUM> is operationally retractable into the aircraft <NUM> while the aircraft <NUM> is in flight.

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 component, or any of various combinations thereof or the like. In various embodiments, the avionics unit <NUM> controls 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, brake systems and the like.

In various embodiments, the aircraft <NUM> further includes a brake control unit (BCU) <NUM>. With brief reference now to <FIG>, the BCU <NUM> includes one or more controllers <NUM> (e.g., processors) and one or more memories <NUM> (e.g., tangible, non-transitory memories) capable of implementing digital or programable logic. In various embodiments, for example, the one or more controllers <NUM> is one or more of a general purpose processor, DSP, ASIC, FPGA, or other programmable logic device, discrete gate, transistor logic, or discrete hardware component, or any of various combinations thereof or the like, and the one or more memories <NUM> is configured to store instructions that are implemented by the one or more controllers <NUM> for performing various functions, such as adjusting the hydraulic pressure or electric power provided to a brake actuator depending on the degree of braking desired. In various embodiments, the BCU <NUM> controls 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 braking, locked wheel protection, touchdown protection, emergency/parking brake monitoring or gear retraction braking. The BCU <NUM> may further include hardware <NUM> capable of performing various logic using discreet power signals received from various aircraft systems. Referring again to <FIG>, the aircraft <NUM> further includes one or more brake assemblies coupled to each wheel assembly. For example, a brake assembly <NUM> is coupled to the outer wheel assembly <NUM> of the third landing gear <NUM> of the aircraft <NUM>. During operation, the brake assembly <NUM> applies a braking force to the outer wheel assembly <NUM> upon receiving a brake command from the BCU <NUM>. In various embodiments, the outer wheel assembly <NUM> of the third landing gear <NUM> of the aircraft <NUM> (or of any of the other landing gear described above and herein) comprises any number of wheels or brake assemblies.

Referring now to <FIG>, schematic details of the brake assembly <NUM> illustrated in <FIG> are provided. In various embodiments, the brake assembly <NUM> is mounted on an axle <NUM> for use with a wheel <NUM> disposed on and configured to rotate about the axle <NUM> via one or more bearing assemblies <NUM>. A central axis <NUM> extends through the axle <NUM> and defines a center of rotation of the wheel <NUM>. A torque plate barrel <NUM> (sometimes referred to as a torque tube or barrel or a torque plate) is aligned concentrically with the central axis <NUM>, and the wheel <NUM> is rotatable relative to the torque plate barrel <NUM>. The brake assembly <NUM> includes an actuator ram assembly <NUM>, a pressure plate <NUM> disposed adjacent the actuator ram assembly <NUM>, an end plate <NUM> positioned a distal location from the actuator ram assembly <NUM>, and a plurality of rotor disks <NUM> interleaved with a plurality of stator disks <NUM> positioned intermediate the pressure plate <NUM> and the end plate <NUM>. The pressure plate <NUM>, the plurality of rotor disks <NUM>, the plurality of stator disks <NUM> and the end plate <NUM> together form a brake heat sink or brake stack <NUM>. The pressure plate <NUM>, the end plate <NUM> and the plurality of stator disks <NUM> are mounted to the torque plate barrel <NUM> and remain rotationally stationary relative to the axle <NUM>. The plurality of rotor disks <NUM> is mounted to the wheel <NUM> and rotate with respect to each of the pressure plate <NUM>, the end plate <NUM> and the plurality of stator disks <NUM>.

An actuating mechanism for the brake assembly <NUM> includes a plurality of actuator ram assemblies, including the actuator ram assembly <NUM>, circumferentially spaced around a piston housing <NUM> (only one actuator ram assembly is illustrated in <FIG>). Upon actuation, the plurality of actuator ram assemblies affects a braking action by urging the pressure plate <NUM> and the plurality of stator disks <NUM> into frictional engagement with the plurality of rotor disks <NUM> and against the end plate <NUM>. Through compression of the plurality of rotor disks <NUM> and the plurality of stator disks <NUM> between the pressure plate <NUM> and the end plate <NUM>, the resulting frictional contact slows or stops or otherwise prevents rotation of the wheel <NUM>. In various embodiments, the plurality of rotor disks <NUM> and the plurality of stator disks <NUM> are fabricated from various materials, such as, for example, ceramic matrix composite materials, that enable the brake disks to withstand and dissipate the heat generated during and following a braking action. As discussed in further detail below, in various embodiments, the actuator ram assemblies comprise a combination of electrically operated actuator rams (or electric brake actuators) and hydraulically operated (or pneumatically operated) actuator rams (or hydraulic brake actuators or pneumatic brake actuators).

Referring now to <FIG>, a braking system <NUM> (or a redundant braking system or a hybrid braking system) is illustrated, in accordance with various embodiments. Generally, the braking system <NUM> may be separated into a hydraulic braking subsystem <NUM> and an electric braking subsystem <NUM>. Referring first to the hydraulic braking subsystem <NUM>, the braking system <NUM> includes a hydraulic brake control unit <NUM>, which is programmed to control the various braking functions performed by the hydraulic braking subsystem <NUM>. The hydraulic braking subsystem <NUM> includes a hydraulic power source <NUM> configured to provide a hydraulic fluid to a primary brake control module <NUM> via a primary hydraulic line <NUM>. A primary pressure transducer <NUM> senses the pressure of the hydraulic fluid and provides a signal reflective of the pressure to the hydraulic brake control unit <NUM> via a data circuit <NUM>. In various embodiments, the hydraulic braking subsystem <NUM> includes a hydraulic fluid return <NUM> that is configured to return hydraulic fluid from the primary brake control module <NUM> to the hydraulic power source <NUM> via a return hydraulic line <NUM>.

A secondary hydraulic line <NUM> fluidly couples the primary brake control module <NUM> to a brake assembly <NUM>, similar to the brake assembly <NUM> described above with reference to <FIG>. More particularly, the secondary hydraulic line <NUM> is fluidly coupled to a hydraulic brake actuator <NUM> (or a plurality of hydraulic brake actuators) housed within the brake assembly <NUM>. In various embodiments, a fuse <NUM> is fluidly coupled to the secondary hydraulic line <NUM> downstream of the primary brake control module <NUM>. The fuse <NUM> acts as a shut-off valve or switch in the event the secondary hydraulic line <NUM> experiences a loss of pressure - e.g., in the event of a leak in the secondary hydraulic line <NUM> or the brake assembly <NUM> - thereby preventing hydraulic fluid from continuing to flow to the secondary hydraulic line <NUM> and leaking out of the hydraulic system. A secondary pressure transducer <NUM> is fluidly coupled to the secondary hydraulic line <NUM> and electrically coupled to the hydraulic brake control unit <NUM> via the data circuit <NUM>. In the event the secondary pressure transducer <NUM> senses a loss of pressure within the secondary hydraulic line <NUM>, the hydraulic brake control unit <NUM> may, in redundant fashion, pass control of the braking system <NUM> to the electric braking subsystem <NUM>. As illustrated, the secondary hydraulic line <NUM>, the fuse <NUM>, the secondary pressure transducer <NUM> and the brake assembly <NUM> are replicated for each of a plurality of outer wheel assemblies <NUM> and for each of a plurality of inner wheel assemblies <NUM> comprised within the braking system <NUM>. Without loss of generality, in various embodiments, the hydraulic braking subsystem <NUM> also includes wheel speed transducers and brake temperature sensors, such as, for example, an inboard wheel speed transducer <NUM> and an outboard wheel speed transducer <NUM>, and an inboard brake temperature sensor <NUM> and an outboard brake temperature sensor <NUM>.

Referring now to the electric braking subsystem <NUM>, the braking system <NUM> includes an electric brake control unit <NUM>, which is programmed to control the various braking functions performed by the electric braking subsystem <NUM>. The electric braking subsystem <NUM> includes an electric power source <NUM> configured to provide electric power to an electric brake actuator controller <NUM>, which, for example, may be an inboard electric brake actuator controller or an outboard electric brake actuator controller. The electric power is provided to the electric brake actuator controller <NUM> via an electric power circuit <NUM>. The electric brake actuator controller <NUM> is electrically coupled to an electric brake actuator <NUM> (or a plurality of electric brake actuators) that is housed within the brake assembly <NUM>. In various embodiments, the electric brake actuator <NUM> includes or is connected to a control circuitry <NUM> configured to monitor various aspects of a braking operation. The control circuitry <NUM> may include, for example, a load cell configured to monitor the load applied via the electric brake actuator <NUM>. In various embodiments, the electric brake actuator controller <NUM> provides force commands to the electric brake actuator <NUM>, directing the electric brake actuator <NUM> to cause the brake assembly <NUM> to mechanically operate, thereby driving the brake assembly <NUM> to provide braking power. In various embodiments, the electric brake actuator controller <NUM> is coupled to the electric brake control unit <NUM> via a communication link <NUM>. The communication link <NUM> may comprise, for example, a controller area network bus <NUM>. Similar to the hydraulic braking subsystem <NUM>, and without loss of generality, the electric braking subsystem <NUM> also includes wheel speed transducers, such as, for example, an inboard wheel speed transducer <NUM> and an outboard wheel speed transducer <NUM>, or brake temperature sensors.

Referring now to <FIG>, the brake assembly <NUM> is described with further detail. As illustrated, the brake assembly <NUM> includes a pressure plate <NUM> configured to apply a compressive load against a brake stack or heat sink, which includes a plurality of brake rotors and a plurality of brake stators sandwiched between the pressure plate and an end plate. As described above, the brake assembly <NUM> includes the hydraulic brake actuator <NUM> (or a plurality of such hydraulic brake actuators) and the electric brake actuator <NUM> (or a plurality of such electric brake actuators). In various embodiments, the brake assembly <NUM> includes four electric brake actuators spaced at ninety degree (<NUM>°) intervals about the pressure plate <NUM> and four hydraulic brake actuators spaced at ninety degree (<NUM>°) intervals about the pressure plate <NUM>, with each electric brake actuator and each hydraulic brake actuator spaced at forty-five degree (<NUM>°) intervals. Fewer or greater numbers of actuators, both electric and hydraulic, are contemplated within the scope of the invention.

During operation, a pilot or a co-pilot depresses a pilot brake pedal <NUM> or a co-pilot brake pedal <NUM>, each of which is connected to a hydraulic brake position sensor <NUM> and to an electric brake position sensor <NUM>. The hydraulic brake position sensor <NUM> generates a signal reflective of the pedal position that is transmitted to the hydraulic brake control unit <NUM> via a hydraulic brake sensor bus <NUM>. The hydraulic brake control unit <NUM>, if employed, then activates the hydraulic brake actuator <NUM> based on a current signal that is transmitted to the primary brake control module <NUM> via a primary brake control bus <NUM>. Similarly, the electric brake position sensor <NUM> generates a signal reflective of the pedal position that is transmitted to the electric brake control unit <NUM> via an electric brake sensor bus <NUM>. The electric brake control unit <NUM>, if employed, then activates the electric brake actuator <NUM> based on a force request that is transmitted to the electric brake actuator controller <NUM> via the communication link <NUM>. In various embodiments, an avionics system <NUM> is configured to employ one or both of the hydraulic braking subsystem <NUM> and the electric braking subsystem <NUM> via signals transmitted over a respective data bus <NUM>. In various embodiments, an autobrake selector <NUM> is configured to employ one or both of the hydraulic braking subsystem <NUM> and the electric braking subsystem <NUM> via signals transmitted over an autobrake data bus <NUM>.

The braking system <NUM> may operate in a fully hydraulic mode, employing only the hydraulic braking subsystem <NUM>, or in a fully electric mode, employing only the electric braking subsystem <NUM>. In addition, the invention contemplates, in various embodiments, the hydraulic braking subsystem <NUM> being employed as the principal braking system, while the electric braking subsystem <NUM> is employed as a backup braking system in the event a failure occurs with the hydraulic braking subsystem <NUM>. The invention also contemplates, in various embodiments, the electric braking subsystem <NUM> being employed as a parking brake when the aircraft is at rest. In various embodiments, the hydraulic brake control unit <NUM> and the electric brake control unit <NUM> are configured to communicate with one another via an intercommunication bus <NUM>. Such communication enables, for example, transfer of control from the hydraulic brake control unit <NUM> to the electric brake control unit <NUM> following a failure of the hydraulic braking subsystem <NUM>. For example, in the event the hydraulic brake control unit <NUM> detects a leak of hydraulic fluid within the hydraulic braking subsystem <NUM>, the hydraulic brake control unit <NUM> may communicate with the electric brake control unit <NUM> and transfer control of the brake system <NUM> to the electric brake control unit <NUM>. Similarly, in the event the electric brake control unit <NUM> detects a failure within the electric braking subsystem <NUM>, the electric brake control unit <NUM> may communicate with the hydraulic brake control unit <NUM> and transfer control of the brake system <NUM> to the hydraulic brake control unit <NUM>.

The above invention provides for a hybrid braking architecture. In various embodiments, the architecture employs hydraulic power for normal braking and electric power for an alternate braking system or a parking brake system. The architecture provides a fully redundant braking system for normal pedal operated braking and for emergency braking. In various embodiments, the piston housing (e.g., the piston housing <NUM> referred to in <FIG>) is modified to accept four hydraulic actuators and four electric actuators, spaced equally and alternating between one hydraulic actuator and one electric actuator; though any number of actuators is contemplated by the invention. The equal spacing of forty-five degrees (<NUM>°) between alternating hydraulic and electric brake actuators allows for uniform force application on the brake stack when the hydraulic system is active or the electric system is active.

In various embodiments, the architecture is operated using pedals in the cockpit. This allows seamless activity and minimum pilot effort when, for example, the emergency system is engaged. The architecture is transparent for actuation (e.g., automated), although crew-alerting system (CAS) messages may be employed to inform the pilot that the emergency system (e.g., the electric braking subsystem) has become active. The hydraulic and electric brake control units are in constant communication using, for example, controller area network (CAN) communication links, such that when the primary brake control unit (either the hydraulic or the electric brake control unit) detects a loss of braking or other fault, the alternate brake control unit (either the hydraulic or the electric brake control unit) may take over control and operate the braking. In various embodiments, a switch may also be provided in the cockpit to allow the pilot to manually switch from the one braking subsystem to the other - e.g., the hydraulic subsystem to the electric sub system - depending on the failure and any other issues or faults occurring with the power supplies or other aircraft system degradations.

However, the benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of the invention. The scope of the invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more.

After reading the description, it will be apparent to one skilled in the relevant art(s) how to implement the invention in alternative embodiments.

Numbers, percentages, or other values stated herein are intended to include that value, and also other values that are about or approximately equal to the stated value, as would be appreciated by one of ordinary skill in the art encompassed by various embodiments of the present invention. A stated value should therefore be interpreted broadly enough to encompass values that are at least close enough to the stated value to perform a desired function or achieve a desired result. The stated values include at least the variation to be expected in a suitable industrial process, and may include values that are within <NUM>%, within <NUM>%, within <NUM>%, within <NUM>%, or within <NUM>% of a stated value. Additionally, the terms "substantially," "about" or "approximately" as used herein represent an amount close to the stated amount that still performs a desired function or achieves a desired result. For example, the term "substantially," "about" or "approximately" may refer to an amount that is within <NUM>% of, within <NUM>% of, within <NUM>% of, within <NUM>% of, and within <NUM>% of a stated amount or value.

Claim 1:
A braking system, comprising:
a brake assembly (<NUM>) including a pressure plate (<NUM>);
a hydraulic braking subsystem (<NUM>) having a hydraulic brake actuator (<NUM>) disposed adjacent to the pressure plate and configured to operate the brake assembly; and
an electric braking subsystem (<NUM>) having an electric brake actuator (<NUM>) disposed adjacent to the pressure plate and configured to operate the brake assembly separate from the hydraulic braking subsystem, characterised in that the electric brake actuator being spaced about the pressure plate at an interval from the hydraulic brake actuator.