Patent Description:
Vehicles, such as aircrafts, may use a wheel brake assembly that includes a multi-disc brake assembly. For example, the multi-disc brake assembly may include a disc stack comprising plurality of rotor discs engaged with a wheel and a plurality of stator discs interleaved with the rotor discs. The rotor discs and wheel are configured to rotate around an axle, while the stator discs remain stationary. To decelerate rotational motion of a rotating wheel, the brake assembly may displace pistons against a pressure plate to compress the rotating rotor discs engaged with the wheel against the stationary stator discs, therefore producing torque that decelerates the rotational motion of the wheel. Document <CIT> discloses an aircraft brake actuation system including an actuator for selectively supplying a commanded brake force to one or more aircraft wheels. Document <CIT> discloses a disc brake with high reliability. Document <CIT> discloses an actuator comprising: two motors; an output member; and a harmonic gear comprising: an elliptical wave generator component; a flexible spline component which is coupled to the wave generator by a bearing and flexes to conform to the elliptical shape of the wave generator; and a circular spline component which surrounds and meshes with the flexible spline component.

The invention relates to a brake assembly of a vehicle. There is provided a brake assembly having the features of claim <NUM> and a system having the features of claim <NUM> below. Further optional features of the brake assembly and system are set out in dependent claims <NUM> to <NUM> below.

There is also provided a method having the features of claim <NUM> below. Further optional features of the method are set out in dependent claim <NUM> below.

The invention relates to a brake assembly of a vehicle that includes a motor and a harmonic drive configured to transfer a torque generated by the motor to a brake disc stack. The brake assembly includes a disc stack which includes one or more rotor discs and one or more stator discs. For example, the disc stack may include a plurality of rotor discs interleaved with a plurality of stator discs. The rotor discs are rotationally coupled with a wheel of the vehicle, such that a rotation of the wheel around a wheel axis causes rotation of the rotor discs around the wheel axis. The stator discs are configured to remain substantially stationary relative to the wheel and the rotor discs. The brake assembly is configured to compress the disc stack to cause engagement of friction surfaces on the rotating rotor discs and the stationary stator discs, reducing a rotational speed of the rotor discs around the wheel axis. The rotor discs are configured to engage the wheel, such that the reduction in the rotational speed of the rotor discs causes a reduction in the speed of the wheel.

The brake assembly includes an actuator assembly configured to cause compression of the disc stack when braking is desired, e.g., in response to user input or more automatic control. According to the invention, the actuator assembly is configured to cause a translation of a piston configured to exert a compression force on the disc stack. The compression force exerted by the actuator assembly causes the rotor discs and the stator discs to slidably translate (e.g., in an axial direction of the wheel) to cause engagement between the rotating rotor discs and the stationary stator discs to generate and/or increase braking forces on the wheel. The actuator assembly is also configured to reduce and/or eliminate the compression force on the disc stack, in order to reduce an engagement between the rotating rotor discs and the stationary stator discs to reduce braking forces on the wheel. For example, the actuator assembly may be configured to exert the compression force on the disc stack to reduce and/or decrease a rotation of the wheel, and may be configured to reduce and/or eliminate the compression force to allow and/or increase a rotation of the wheel.

The brake assembly may include control circuitry configured to cause the actuator assembly to compress the disc stack based on a braking signal. For example, the control circuitry may be configured to transmit the braking signal in response to the actuation of a user input device (e.g., a foot pedal) located remotely from the brake assembly (e.g., in the cockpit of an aircraft). In examples described herein, the actuator assembly includes an motor (e.g., an electric motor) configured to generate a rotary motion in response to the braking signal and convert the rotary motion of the motor into a linear translation in order to cause the compression of the disc stack.

In examples, the motor is configured to cause the rotary motion in a first rotary direction of a motor shaft ("first shaft direction") and in a second rotary direction of the motor shaft ("second shaft direction") opposite the first shaft direction based, for example, on the braking signal. The actuator assembly is configured to convert the rotary motion in the first shaft direction into a linear translation in a first direction to, for example, increase and/or initiate a compression force exerted on the disc stack. The actuator assembly may be configured to convert the rotary motion in the second shaft direction into a linear translation in a second direction opposite the first direction to, for example, reduce and/or eliminate a compression force exerted on the disc stack. In examples, the motor defines a housing and is configured to generate the rotary motion of the motor shaft relative to the housing. The housing may be substantially stationary with respect to some portion of the brake assembly, such as a torque tube.

In examples, the actuator assembly is configured to generate a first rotary torque at a first rotational speed using the motor, generate a second rotary torque at a second rotational speed less than the first rotational speed using a harmonic drive, and convert the second rotary torque to linear motion using a linear actuator to translate a piston. The piston may be configured to cause the compression force on the disc stack. According to the invention, the motor is configured to generate the first rotary torque around a motor axis and the linear actuator is configured to produce the linear motion along a compression axis different from the motor axis. The harmonic drive is configured to receive the first rotary torque and provide the second rotary torque to a gear set. The gear set is configured to receive the second rotary torque and cause an output gear to transfer at least some portion of the second rotary torque to the linear actuator, such that the linear actuator causes the linear motion along the compression axis. The linear actuator is configured to displace the piston substantially along the compression axis.

Hence, in the invention, the actuator assembly is configured such that the motor generates the first rotary torque around a motor axis and the linear actuator causes compression of the disc stack by displacing the piston along a compression axis different from the motor axis. The arrangement whereby the motor generates the first torque around a motor axis and the linear actuator translates the piston over a separate compression axis may allow for a more compact actuator assembly configuration as compared to in-line actuators where a single axis serves as both the motor axis and the compression axis.

The actuator assembly may be configured to substantially step-down a rotary speed generated by the motor during braking operations, in order to allow a finer control of the linear motion acting to increase or decrease the compression force on the disc stack. The finer control of the linear motion may enable increased control of the compression force applied to the disc stack, potentially improving the responsiveness and sensitivity of the braking system. In some examples, the actuator assembly steps-down the rotary speed generated by the motor using the harmonic drive. Use of the harmonic drive may reduce and/or eliminate gear backlash during alterations in motor speed that may occur in brake assemblies primarily using a meshed gearbox for speed step-down. The relatively smooth operation of the harmonic drive may allow increased braking operations-per-second compared to braking systems using a gearbox having an input gear configured to synchronously rotate with the motor for speed step-down.

In the invention, the actuator assembly is configured to translate the piston when the linear actuator converts the rotary motion produced by the motor into a linear translation. For example, the actuator assembly may be configured to cause the translation of the piston in a direction substantially parallel to the axis of the wheel. The piston is configured to translate to cause the compression force (or to eliminate a previously applied compressive force) on the disc stack. In some examples, the actuator assembly includes an actuator body configured to be substantially stationary with respect to a portion of the brake assembly (e.g., a torque tube), and the actuator assembly is configured to translate the piston relative to the actuator body using the linear translation. In some examples, the actuator assembly is configured to cause the piston to translate in the first direction (e.g., to increase and/or initiate the compression force on the disc stack) when the motor generates the rotary motion in the first shaft direction, and is configured to cause the piston to translate in the second direction opposite the first direction (e.g., to reduce and/or eliminate the compression force on the disc stack) when the motor generates the rotary motion in the second shaft direction.

The harmonic drive of the actuator assembly is configured to receive the first rotary torque in the first rotational direction and the first rotational speed from the motor and produce a second rotary torque using the first rotary torque. The harmonic drive is configured to produce the second rotary torque in a second rotational direction opposite the first rotational direction, and at a second rotational speed less than the first rotational speed. In some examples, the harmonic drive includes a harmonic wave generator configured to receive the first rotary torque from the motor (e.g., the motor shaft) and rotate relative to the motor housing in the same rotational direction as the motor shaft rotates relative to the motor housing. For example, the harmonic drive may include a flexible spline configured such that, as the harmonic wave generator rotates in the first rotational direction (e.g., under the influence of the first rotary torque), the flexible spline produces the second rotary torque in the second rotational direction. Hence, the direction of rotation of the motor shaft (e.g., in the first shaft direction or the second shaft direction) may determine the first rotational direction of the first rotary torque, and may thereby determine the second rotational direction of the second rotary torque.

The motor may impart the first rotary torque in the first rotational direction to the harmonic drive by at least causing the motor shaft to rotate in either the first shaft direction or the second shaft direction. Thus, as used herein, the first rotational direction refers to a rotational direction of the first rotary torque imparted to the harmonic drive by the motor, rather than a direction of shaft rotation employed by the motor to impart the first rotary torque. The second rotational direction refers to a rotational direction of the second rotary torque produced by the harmonic drive using the first rotary torque, rather than a direction of shaft rotation employed by the motor when the harmonic drive generates the second rotary torque.

Similarly, the flexible spline of the harmonic drive may rotate in a first spline direction or a second spline direction opposite the first spline direction to produce a second rotary torque in the second rotary direction opposite the first rotary direction. In some examples, the motor shaft and the flexible spline rotate around a common axis (e.g., a motor axis), and the motor shaft and flexible spline are configured to rotate around the common axis in opposite rotational directions.

The harmonic drive, which may be referred to as a harmonic reducer in some examples, has any suitable configuration. In some examples, the harmonic drive includes a fixed spline configured to remain substantially stationary with respect to the motor housing, and a flexible spline. The flexible spline defines external gear teeth configured to mesh with internal gear teeth defined by the fixed spline to generate the second rotary torque in the second rotational direction and the second speed. In some examples, the fixed spline defines a substantially circular (e.g., circular or nearly circular to the extent permitted by manufacturing tolerances) pitch circle and the harmonic wave generator is configured to cause the flexible spline to define a substantially elliptical pitch circle. In some of these examples, the harmonic drive is configured to cause the external teeth of the flexible spline to mesh with the internal teeth of the circular spline at points substantially along a major axis of the substantially elliptical pitch circle to generate the second rotary torque. The harmonic drive is configured to cause a speed reduction from the first rotary torque to the second rotary torque based on a reduction ratio dependent on the tooth number (e.g., the number of teeth) of the flexible spline and the tooth number of the fixed spline. In examples, the tooth number of the fixed spline is greater than the tooth number of the flexible spline.

The harmonic drive (e.g., the flexible spline of the harmonic drive) may be configured to impart the second rotary torque to an input gear of a gear set to cause a rotation of the input gear. For example, the harmonic drive can be configured to cause a rotation of the input gear based on the second rotational direction of the second rotary torque. In some examples, the gear set includes an output gear, and the input gear is configured to cause a rotation of the output gear when the harmonic drive causes the rotation of the input gear. The gear set may be configured such that a direction of rotation of the input gear (e.g., by the harmonic drive) substantially determines a direction of rotation of the output gear ("output gear direction"). Hence, the actuator assembly may be configured such that when the motor shaft imparts the first rotary torque in the first rotational direction to the harmonic drive, and the harmonic drive uses the first rotary torque to impart the second rotary torque in the second rotational direction to the input gear, the output gear direction is determined by the direction of rotation of the motor shaft.

In some examples, the actuator assembly is configured such that rotation of the motor shaft in the first shaft direction causes the output gear to rotate in a first output gear direction, and such that rotation of the motor shaft in the second shaft direction causes the output gear to rotate in a second output gear direction opposite the first output gear direction.

In some examples, the linear actuator is configured to produce the linear motion using the rotation of the output gear directly or indirectly. For example, the actuator assembly can be configured such that rotation of the output gear in the first output gear direction causes the linear actuator to generate the linear motion in the first direction, and rotation of the output gear in the second output gear direction causes the linear actuator to generate the linear motion in the second direction. Hence, the actuator assembly may be configured such that when the motor shaft rotates in the first shaft direction to cause the output gear to rotate in the first output gear direction, the linear actuator displaces the piston in the first direction to increase and/or initiate the compression force on the disc stack and when the motor shaft rotates in the second shaft direction to cause the output gear to rotate in the second output gear direction, the linear actuator displaces the piston in the second direction to reduce and/or eliminate the compression force on the disc stack.

According to the invention, the linear actuator includes a driver configured to cause a screw to linearly translate when the driver rotates relative to the screw. The output gear is configured to cause the rotation of the driver when the motor (e.g., via the harmonic drive) causes the rotation of the output gear. The linear actuator may be configured such that a direction of rotation of the driver around the screw determines a direction of the linear translation of the screw (e.g., the first direction or the second direction). Hence, the linear actuator may be configured to generate the linear motion based on a direction of the rotary motion received from the gear set. In some examples, the driver is a ball nut and a screw is a ball screw. The linear actuator may be configured to cause a plurality of ball bearings between the ball nut and the ball screw to transmit a force to the ball screw when the ball nut rotates relative to the ball screw.

Hence, the brake assemblies described herein are configured to exert a compression force on a disc stack using an actuator assembly to control braking forces applied to a wheel. The actuator assembly is configured to generate a first rotary torque (e.g., around a motor axis defined by the motor) at a first rotational speed using a motor and generate a second rotary torque at a second rotational speed using a harmonic drive. The actuator assembly is configured to use the second rotary torque to translate a piston along a compression axis different than the motor axis. The arrangement whereby the motor generates the first torque around a motor axis and the linear actuator translates the piston over a separate compression axis may allow for a more compact actuator assembly as compared to in-line actuators where a single axis serves as both the motor axis and the compression axis. The use of the harmonic drive may reduce and/or eliminate gear backlash during alterations in motor speed and may allow increased braking operations-per-second compared to braking systems that primarily use a meshed gearbox for speed step-down.

<FIG> is a perspective view illustrating an example wheel <NUM>. In some examples, wheel <NUM> is a part of an aircraft vehicle. In other examples, wheel <NUM> may be a part of any other vehicle, such as, for example, any land vehicle or other vehicle. In the example shown in <FIG>, wheel <NUM> includes a wheel rim <NUM> defining an exterior surface <NUM> and interior surface <NUM>. Wheel rim <NUM> includes tubewell <NUM> and wheel hub <NUM>. In some examples, interior surface <NUM> may include an inner diameter of tubewell <NUM> of wheel <NUM>. For example, in some cases, interior surface <NUM> may be referred to as an inner diameter surface of wheel <NUM>. Interior surface <NUM> and wheel hub <NUM> may define a wheel cavity <NUM> (e.g., a volume) between interior surface <NUM> and wheel hub <NUM>. In some examples, a tire (not shown) may be mounted on exterior surface <NUM> of rim <NUM>. Wheel <NUM> may include an inboard bead seat <NUM> and an outboard bead seat <NUM> configured to retain a tire on exterior surface <NUM> of rim <NUM>. In examples, wheel <NUM> may comprise an inboard section <NUM> (e.g., including inboard bead seat <NUM>) and an outboard section <NUM> (e.g., including outboard bead seat <NUM>). Wheel <NUM> is configured to rotate around the axis of rotation A. An axial direction A1 of wheel <NUM> is parallel to the axis of rotation A. An axial direction A2 of wheel <NUM> is parallel to the axis of rotation A and opposite the direction A1.

Wheel <NUM> includes a plurality of rotor drive keys <NUM> on interior surface <NUM> of wheel <NUM>, such as rotor drive key <NUM> and rotor drive key <NUM>. In some examples, each rotor drive key of the plurality of rotor drive keys <NUM> extends in the axial direction A1 of wheel <NUM> (e.g., in a direction parallel to the axis of rotation A). The plurality of rotor drive keys <NUM> ("rotor drive keys <NUM>") and interior surface <NUM> are configured to be substantially stationary with respect to each other, such that when wheel <NUM> (and interior surface <NUM>) rotates around axis of rotation A, each of the rotor drive keys (e.g., rotor drive keys <NUM>, <NUM>) translates over a closed path around axis A. Consequently, when wheel <NUM>, interior surface <NUM>, and rotor drive keys <NUM> are rotating around axis of rotation A, a force on one or more of rotor drive keys <NUM> opposing the direction of rotation acts to slow or cease the rotation. Rotor drive keys <NUM> may be configured to receive a torque from a brake assembly (e.g., brake assembly <NUM> shown in <FIG> or other brake assemblies) configured to reduce and/or cease a rotation of wheel <NUM>. Rotor drive keys <NUM> may be integrally formed with interior surface <NUM>, or may be separate from and mechanically affixed to interior surface <NUM>.

<FIG> is a schematic cross-sectional view illustrating wheel <NUM> and an example brake assembly <NUM>. Wheel <NUM> includes wheel rim <NUM>, exterior surface <NUM>, interior surface <NUM>, wheel cavity <NUM>, wheel hub <NUM>, inboard bead seat <NUM>, outboard bead seat <NUM>, inboard section <NUM>, outboard section <NUM>, and rotor drive key <NUM>. <FIG> illustrates wheel rim <NUM> as a split rim wheel with lug bolt <NUM> and lug nut <NUM> connecting inboard section <NUM> and outboard section <NUM>, however wheel rim <NUM> may utilize other configurations (e.g., a unified wheel rim) in other examples. Wheel <NUM> and brake assembly <NUM> is shown and described to provide context to the example drive inserts described here. The drive inserts described herein, however, may be used with any suitable wheel and brake assembly in other examples.

Wheel <NUM> is configured to rotate about wheel axis A extending through axial assembly <NUM>. Axial assembly <NUM> is figured to support wheel <NUM> while allowing wheel <NUM> to rotate around wheel axis A using bearing <NUM> and bearing <NUM>. For example, bearings <NUM>, <NUM> may define a substantially circular track around axial assembly <NUM>. A torque tube <NUM> is coupled to axial assembly <NUM> (e.g., via bolts <NUM>, <NUM>), such that torque tube <NUM> remains substantially stationary when wheel <NUM> rotates around axial assembly <NUM> and wheel axis A. Torque tube <NUM> may at least partially surround an exterior of axial assembly <NUM>. Axial assembly <NUM> may be mechanically coupled to a structure (e.g., a strut) attached to a vehicle.

In the example shown in <FIG>, the portion of brake assembly <NUM> depicted is shown as being positioned within wheel <NUM> and is configured to engage torque tube <NUM> and rotor drive key <NUM>. Brake assembly <NUM> is configured to generate a torque to oppose a rotation of wheel <NUM> around wheel axis A and transfer the torque to rotor drive key <NUM>, reducing and/or eliminating the rotation of wheel <NUM> around wheel axis A. Brake assembly <NUM> includes a disc stack <NUM> which includes one or more rotor discs (e.g., rotor discs <NUM>, <NUM>, <NUM>, <NUM>) and one or more stator discs (e.g., stator discs <NUM>, <NUM>, <NUM>). Rotor discs <NUM>, <NUM>, <NUM>, <NUM>, and/or stator discs <NUM>, <NUM>, <NUM>, may have any suitable configuration. For example, rotor discs <NUM>, <NUM>, <NUM>, <NUM> and/or stator discs <NUM>, <NUM>, <NUM> can each be substantially annular discs surrounding axial assembly <NUM>. Stator discs <NUM>, <NUM>, <NUM> are coupled to torque tube <NUM> via spline <NUM> and remain rotationally stationary with respect to torque tube <NUM> (and axial assembly <NUM>) as wheel <NUM> rotates. Rotor discs <NUM>, <NUM>, <NUM>, <NUM> are rotationally coupled to rotor drive key <NUM> and interior surface <NUM> and rotate substantially synchronously with wheel <NUM> around axis A. For example, rotor drive key <NUM> may be configured to extend through a drive slot on a perimeter of one or more of rotor discs <NUM>, <NUM>, <NUM>, <NUM> to cause rotor discs <NUM>, <NUM>, <NUM>, <NUM> to rotate substantially synchronously with wheel <NUM>. Disc stack <NUM> may include any number of rotor discs and stator discs.

Rotor discs <NUM>, <NUM>, <NUM>, <NUM>, and/or stator discs <NUM>, <NUM>, <NUM>, may be configured to provide opposing friction surfaces for braking a vehicle, such as an aircraft. Compression of disc stack <NUM> (e.g., between pressure plate <NUM> and backing plate <NUM>) may bring the opposing friction surfaces into contact, generating shearing forces between the rotor discs rotating substantially synchronously with wheel <NUM> and the stator discs remaining substantially stationary with respect to torque tube <NUM>. The shearing forces may cause a rotor disc (e.g., rotor discs <NUM>, <NUM>, <NUM>, <NUM>) engaged with rotor drive key <NUM> to impart a torque on rotor drive key <NUM> opposing the rotation of wheel <NUM>. The rotor disc may impart the opposing torque to rotor drive key <NUM> using the drive slot through which rotor drive key <NUM> extends.

An actuator assembly <NUM> including actuator body <NUM> is configured to cause a piston <NUM> to translate relative to actuator body <NUM> to cause the compression of disc stack <NUM>. Actuator assembly <NUM> may be configured to cause piston <NUM> to translate in the direction A1 and in the direction A2. For example, actuator assembly <NUM> can be configured to cause piston <NUM> to compress disc stack <NUM> when piston <NUM> translates substantially in the direction A1, and configured to cause piston <NUM> to relieve (e.g., reduce and/or eliminate) the compression when piston <NUM> translate in the direction substantially in the direction A2. Brake assembly <NUM> may be configured such that the compression of disc stack <NUM> (e.g., by translating piston <NUM> substantially in the direction A1) causes engagement between the friction surfaces of rotor discs <NUM>, <NUM>, <NUM>, <NUM> and stator discs <NUM>, <NUM>, <NUM>, generating braking forces to reduce and/or substantially prevent a rotation of wheel <NUM>. Brake assembly <NUM> may be configured such that reducing and/or eliminating the compression of disc stack <NUM> (e.g., by translating piston <NUM> substantially in the direction A2) reduces and/or eliminates the engagement of rotor discs <NUM>, <NUM>, <NUM>, <NUM> and stator discs <NUM>, <NUM>, <NUM>, reducing and/or eliminating the braking forces on wheel <NUM>.

In the example shown in <FIG>, piston <NUM> defines a piston face <NUM> configured to establish a contract pressure on pressure plate <NUM> when actuator assembly <NUM> translates piston <NUM> in the direction A1. Actuator assembly <NUM> is configured to increase the contact pressure by causing piston <NUM> to translate in the direction A1, in order to increase the braking force on wheel <NUM> generated by the friction surfaces of rotor discs <NUM>, <NUM>, <NUM>, <NUM> and stator discs <NUM>, <NUM>, <NUM>. Actuator assembly <NUM> is configured to decrease the contact pressure by causing piston <NUM> to translate in the direction A2, in order to decrease the braking force on wheel <NUM> generated by the friction surfaces of rotor discs <NUM>, <NUM>, <NUM>, <NUM> and stator discs <NUM>, <NUM>, <NUM>.

In examples, actuator assembly <NUM> is configured to cause piston <NUM> to translate using motion (e.g., a rotary motion) generated by an electric motor. Actuator assembly <NUM> may be configured to convert the rotary motion of the electric motor to linear motion to cause the translation of piston <NUM> in the direction A1 and/or the direction A2. In some examples, actuator assembly <NUM> is configured to generate a first rotary torque at a first speed using the electric motor and convert the first rotary torque to a second rotary torque at a second speed less than the first speed. Actuator assembly <NUM> may be configured to rotate some portion of a linear actuator using the second rotary torque in order to cause the translation of piston <NUM> in the direction A1 and the direction A2.

In examples, actuator assembly <NUM> also includes a harmonic reducer configured to receive the first rotary torque at the first speed and generate the second rotary torque at the second speed. In some examples, actuator assembly <NUM> further includes a gear set configured such that the electric motor generates the first rotary torque around a motor axis and piston <NUM> compresses disc stack <NUM> along a compression axis, where the motor axis is different (e.g., displaced from) the compression axis.

Wheel <NUM> and brake assembly <NUM> may be used with any variety of private, commercial, or military aircraft or other type of vehicle. Wheel <NUM> may be mounted to a vehicle via, for example, axial assembly <NUM>, or some other appropriate arrangement to allow wheel <NUM> to rotate around wheel axis A. Axial assembly <NUM> may be mounted on a strut of a landing gear (not shown) or other suitable component of a vehicle to connect wheel <NUM> to the vehicle. Wheel <NUM> may rotate around wheel axis A and axial assembly <NUM> to impart motion to the vehicle. Wheel <NUM> is shown and described to provide context to the brake assembly described herein, however the brake assembly described herein may be used with any suitable wheel assembly in other examples.

<FIG> is a conceptual illustration of an example actuator assembly <NUM>, which is useful for understanding the present invention, and illustrates part of actuator assembly <NUM> in cross-section and parts as functional block diagram, with reference to the x-y-z axes shown. Actuator assembly <NUM> includes actuator body <NUM>. Actuator assembly <NUM> is an example of actuator assembly <NUM> and actuator body <NUM> is an example of actuator body <NUM> (<FIG>). <FIG> illustrates another view of actuator assembly <NUM> and includes the x-y-z axes of <FIG> for reference. Actuator assembly <NUM> includes motor <NUM>, harmonic drive <NUM>, gear set <NUM>, and linear actuator <NUM>. Portions of harmonic drive <NUM> are shown in dashed lines in <FIG>. Axial direction A1 and A2 are illustrated in <FIG> and <FIG>, with axial direction A1 proceeding out of the page and axial direction A2 proceeding into the page in <FIG>.

Actuator assembly <NUM> is configured to cause compression of disc stack <NUM> using piston <NUM> when braking is desired. Actuator assembly <NUM> is configured to translate piston <NUM> in a first direction (e.g., in the axial direction A1) to cause a compression force on disc stack <NUM> (e.g., via pressure plate <NUM>) to generate and/or increase braking forces on wheel <NUM> (<FIG>). Actuator assembly <NUM> is configured to translate piston <NUM> in a second direction substantially opposite the first direction (e.g., the axial direction A2) to reduce and/or eliminate the compression force on disc stack <NUM>, in order to reduce and/or substantially eliminate braking forces on wheel <NUM>. In the example shown in <FIG> and <FIG>, actuator body <NUM> is configured to be substantially stationary with respect to a portion of brake assembly <NUM> (e.g., torque tube <NUM>, or some other portion). In some examples, actuator assembly <NUM> is configured to translate piston <NUM> relative to actuator body <NUM>.

Actuator assembly <NUM> is configured to convert a rotary motion produced by motor <NUM> into a linear translation of piston <NUM> to control the braking forces on wheel <NUM> generated by brake assembly <NUM> (<FIG>). In the example shown in <FIG> and <FIG>, motor <NUM> includes a motor housing <NUM> and a motor shaft <NUM>, and motor <NUM> is configured to generate the rotary motion by at least causing a rotation of motor shaft <NUM> relative to motor housing <NUM>. Motor housing <NUM> may be configured to be substantially stationary with respect to actuator body <NUM>. Motor <NUM> may be configured cause the rotation of motor shaft <NUM> around a motor axis MA defined by motor shaft <NUM>. In examples, motor <NUM> is configured to cause a rotation of motor shaft <NUM> in a first shaft direction R1 (e.g., clockwise around motor axis MA) and in a second shaft direction R2 substantially opposite the first shaft direction R1 (e.g., counter-clockwise around motor axis MA). Motor housing <NUM> may be configured to be substantially stationary with respect to actuator body <NUM>. Further, the first shaft direction R1 and second shaft direction R2 are illustrated as examples only. In other examples, the first shaft direction R1 may be counter-clockwise and the second shaft direction R2 clockwise around motor axis MA, or first shaft direction R1 and first shaft direction R2 may have some other arrangement with respect to actuator assembly <NUM>.

In some examples, actuator assembly <NUM> is configured such that a rotary motion of motor shaft <NUM> in the first shaft direction R1 causes piston <NUM> to increase and/or initiate a compression force on disc stack <NUM>, increasing the braking forces transmitted from brake assembly <NUM> to wheel <NUM> (e.g., via rotor drive keys <NUM>, <NUM>, <NUM> (<FIG> and <FIG>)). In addition, actuator assembly <NUM> may be configured such that a rotary motion of motor shaft <NUM> in the second shaft direction R2 causes piston <NUM> to decrease and/or substantially eliminate a compression force on disc stack <NUM>, decreasing the braking forces transmitted from brake assembly <NUM> to wheel <NUM>. In examples, actuator assembly <NUM> is configured to convert a rotary motion of motor shaft <NUM> in the first shaft direction R1 into a linear translation of piston <NUM> in the first direction (e.g., the axial direction A1), and to convert a rotary motion of motor shaft <NUM> in the second shaft direction R2 into a linear translation of piston <NUM> in the second direction (e.g., the axial direction A2).

Control circuitry <NUM> is configured to control actuator assembly <NUM>. For example, control circuitry <NUM> may be configured to transmit a braking signal to actuator assembly <NUM> to cause actuator assembly <NUM> to translate piston <NUM>. In examples, control circuitry <NUM> is configured to transmit the braking signal using communication link <NUM>. Motor <NUM> may be configured to generate rotary motion in response to the braking signal. In some examples, control circuitry <NUM> is configured to receive a user input from an input device <NUM> (e.g., a foot pedal in a cockpit and/or an Anti-lock Braking System (ABS)) and transmit the braking signal to actuator assembly <NUM> based on the user input. Input device <NUM> may transmit the braking signal to control circuitry <NUM> using communication link <NUM>. In examples, control circuitry <NUM> is configured receive a first user input (e.g., indicative of a desire for increased braking) and transmit the braking signal to actuator assembly <NUM> causing motor <NUM> to generate a rotary motion in the first shaft direction R1, and is further configured receive a second user input (e.g., indicative of a desire for reduced braking) and transmit the braking signal to actuator assembly <NUM> causing motor <NUM> to generate a rotary motion in the second shaft direction R2.

Actuator assembly <NUM> is configured to produce a first rotary torque at a first rotational speed using motor <NUM>. In examples, actuator assembly <NUM> produces the first rotary torque using the rotation of motor shaft <NUM>. Actuator assembly <NUM> may produce the first rotary torque in a first rotational direction. In examples, the first rotational direction of the first rotary torque is determined by a direction of rotation of motor shaft <NUM>. Motor shaft <NUM> may generate the first rotary torque having the first rotational direction when motor shaft <NUM> rotates in either the first shaft direction R1 or the second shaft direction R2. Hence, in some examples, the first rotary direction of the first rotary torque has the same rotational direction as the first shaft direction R1 (as illustrated by T1-A (<FIG>), and in other examples, the first rotary direction of the first rotary torque has the same rotational direction as the second shaft direction R2 (as illustrated by T1-B (<FIG>)). In some examples, actuator assembly <NUM> is configured such that the first rotary torque acts around motor axis MA. In addition or instead, in some examples, actuator assembly <NUM> is configured such that the first rotary torque acts around motor shaft <NUM>.

Actuator assembly <NUM> is configured to step-down the first rotational speed by at least using the first rotary torque to produce a second rotary torque having a second rotational speed less than the first rotational speed. In examples, the first rotational speed is dependent on or substantially equal to a rotational speed of motor shaft <NUM>. Stepping down the first rotational speed may allow motor <NUM> to be a relatively high-speed motor configured to generate rotation at higher shaft speeds that may be desired for other components (e.g., gear set <NUM> and/or linear actuator <NUM>) of actuator assembly <NUM>. Further, the first rotary torque produced by motor <NUM> may be lower than what might be desired for operation of actuator assembly <NUM>. Stepping down the first rotational speed to the second rotational speed may cause the second rotary torque produced to exceed the first rotary torque, such that the remainder of actuator assembly <NUM> (e.g., gear set <NUM> and/or linear actuator <NUM>) may be acted on by a torque exceeding that produced by motor <NUM>. Thus, in examples, actuator assembly <NUM> is configured to use the first rotary torque at the first rotational speed produced by motor <NUM> to produce a second rotary torque at a second rotational speed, wherein the second rotary torque is greater than the first rotary torque and the second rotational speed is less than the first rotational speed.

Harmonic drive <NUM> is configured to receive the first rotary torque (e.g., T1-A or T1-B) from motor <NUM> and produce the second rotary torque at the second rotational speed in response to the first rotary torque. The second rotary speed is less than the first rotary speed in some examples. The second rotary torque is greater than the first rotary torque in some examples. In some examples, the first rotary torque has a first rotational direction, and harmonic drive <NUM> is configured to produce the second rotary torque in a second rotational direction opposite the first rotational direction. For example, harmonic drive <NUM> may be configured to receive the first rotary torque T1-A (<FIG>) having the first rotational direction clockwise around motor axis MA (or some other axis) and generate a second rotary torque T2-A having the second rotational direction counter-clockwise around motor axis MA (or the other axis). Harmonic drive <NUM> may be configured to receive the first rotary torque T1-B having the first rotational direction counter-clockwise around motor axis MA (or some other axis) and generate a second rotary torque T2-B having the second rotational direction clockwise around motor axis MA (or the other axis).

Hence, harmonic drive <NUM> is configured to produce the second rotary torque having the second rotational direction opposite the first rotational direction when motor shaft <NUM> rotates in either the first shaft direction R1 or the second shaft direction R2. In examples, when motor shaft <NUM> rotates in the first shaft direction R1 around motor axis MA, the first rotational direction of the first rotary torque (e.g., T1-A) is substantially the same as the first shaft direction R1, and the second rotational direction of the second rotary torque (e.g., T2-A) is substantially the same as the second shaft direction R2. In examples, when motor shaft <NUM> rotates in the second shaft direction R2 around motor axis MA, the first rotational direction of the first rotary torque (e.g., T1-B) is substantially the same as the second shaft direction R2 and the second rotational direction of the second rotary torque (e.g., T2-B) is substantially the same as the first shaft direction R1.

Harmonic drive <NUM> has any suitable configuration. In some examples, as shown in <FIG>, harmonic drive <NUM> includes a harmonic wave generator <NUM>, a flexible spline <NUM>, and a fixed spline <NUM> (<FIG>). Harmonic wave generator <NUM> is configured to rotate around an axis (e.g., motor axis MA) when harmonic wave generator <NUM> receives the first rotary torque from motor <NUM>. Fixed spline <NUM> is configured to be substantially stationary with respect to actuator body <NUM> and/or motor housing <NUM>. Flexible spline <NUM> engages both harmonic wave generator <NUM> and fixed spline <NUM>. In examples, flexible spline <NUM> is positioned between harmonic wave generator <NUM> and fixed spline <NUM>. Harmonic drive <NUM> is configured to cause flexible spline <NUM> to produce the second rotary torque in the second rotational direction when harmonic wave generator <NUM> receives the first rotary torque in the first rotational direction (e.g., from motor <NUM>).

Actuator assembly <NUM> may be configured to cause gear set <NUM> to rotate in response to the second rotary torque. For example, harmonic drive <NUM> (e.g., flexible spline <NUM>) can be configured to impart the second rotary torque to gear set <NUM> to cause the rotation. Gear set <NUM> may include one or more gears (e.g., input gear <NUM> and output gear <NUM>) configured to transfer the rotary motion to linear actuator <NUM>, to cause linear actuator <NUM> to translate piston <NUM> in the axial direction A1 (e.g., to increase and/or initiate a compression force on disc stack <NUM>) or the axial direction A2 (e.g., to reduce and/or substantially eliminate the compression force on disc stack <NUM>).

Gear set <NUM> is configured such that a direction of rotation of the rotary motion transferred to linear actuator <NUM> is dependent on the second rotational direction of the second rotary torque imparted by harmonic drive <NUM>. Linear actuator <NUM> may be configured such that the direction of rotation of the rotary motion transferred from gear set <NUM> substantially determines the linear direction (e.g., axial direction A1 or axial direction A2) which linear actuator <NUM> translates piston <NUM>. Hence, actuator assembly <NUM> may be configured such that the direction of linear translation generated by linear actuator <NUM> is dependent on the direction of rotation of motor shaft <NUM>. For example, when motor shaft <NUM> rotates in one direction (e.g., the first shaft direction R1 or second shaft direction R2), actuator assembly <NUM> may be configured such that linear actuator <NUM> translates piston <NUM> to increase and/or initiate the compression force on disc stack <NUM>; and when motor shaft <NUM> rotates in another direction (e.g., the other of first shaft direction R1 or second shaft direction R2), actuator assembly <NUM> may be configured such that linear actuator <NUM> translates piston <NUM> to decrease and/or substantially eliminate the compression force on disc stack <NUM>.

In some examples, harmonic drive <NUM> (e.g., flexible spline <NUM>) is configured to impart the second rotary torque to an input gear <NUM> of gear set <NUM> to cause a rotation of input gear <NUM>. In examples, actuator assembly <NUM> is configured to cause a rotation of input gear <NUM> based on the second rotational direction of the second rotary torque. For example, when harmonic drive <NUM> produces the second rotary torque T2-A, actuator assembly <NUM> may be configured to cause a rotation of input gear <NUM> in substantially the same direction as the second rotary torque T2-A. When harmonic drive <NUM> produces the second rotary torque T2-B, actuator assembly <NUM> may be configured to cause a rotation of input gear <NUM> in substantially the same direction as the second rotary torque T2-B. In some examples, actuator assembly <NUM> is configured to cause a rotation of input gear <NUM> in a direction opposite the rotation of motor shaft <NUM>.

In some examples, input gear <NUM> defines gear teeth <NUM> ("input gear teeth <NUM>") around an outer perimeter <NUM> of input gear <NUM>. For example, input gear <NUM> may define input gear teeth <NUM> around a pitch circle surrounding a gear axis of input gear <NUM>. In some examples, input gear <NUM> is configured such that input gear teeth <NUM> substantially rotate around motor axis MA when the second rotary torque is imparted to input gear <NUM>. For example, the gear axis of input gear <NUM> may be substantially parallel to or substantially coincident with motor axis MA defined by motor <NUM>.

Gear set <NUM> further includes an output gear <NUM>. Gear set <NUM> is configured such that the rotation of input gear <NUM> causes a corresponding rotation of output gear <NUM>. In examples, gear set <NUM> is configured such that a direction of rotation of input gear <NUM> substantially determines the output gear direction of output gear <NUM>. Hence, when motor shaft <NUM> imparts the first rotary torque (e.g., T1-A or T1-B) in the first rotational direction to harmonic drive <NUM>, and harmonic drive <NUM> uses the first rotary torque to impart the second rotary torque (e.g., T2-A or T2-B) in the second rotational direction to input gear <NUM>, actuator assembly <NUM> may be configured such that the output gear direction of output gear <NUM> is dependent on the direction of rotation of motor shaft <NUM>. In examples, actuator assembly <NUM> is configured such that rotation of motor shaft <NUM> in first shaft direction R1 causes output gear <NUM> to rotate in a first output gear direction (e.g., output gear direction R3 (<FIG>)), and rotation of motor shaft <NUM> in second shaft direction R2 causes output gear <NUM> to rotate in a second output gear direction opposite the first output gear direction (e.g., output gear direction R4 (<FIG>)). Output gear <NUM> may be configured to transfer rotary motion to linear actuator <NUM> in either the first output gear direction or the second output gear direction.

In some examples, output gear <NUM> defines gear teeth <NUM> ("output gear teeth <NUM>") around an outer perimeter <NUM> of output gear <NUM>, e.g., around a pitch circle surrounding a gear axis of output gear <NUM>. In examples, and as depicted at <FIG> and <FIG>, output gear teeth <NUM> are configured to mesh with input gear teeth <NUM>, such that input gear teeth <NUM> exert a torque on output gear teeth <NUM> causing the rotation of output gear <NUM> around the axis of output gear <NUM>. In examples, actuator assembly <NUM> is configured such that the gear axis of output gear <NUM> is displaced from the gear axis of input gear <NUM>. In examples, actuator assembly <NUM> is configured such that the gear axis of output gear <NUM> is substantially parallel to the gear axis of input gear <NUM>. Actuator assembly <NUM> may be configured such that the gear axis of output gear <NUM> is substantially parallel (e.g., parallel or nearly parallel to the extent permitted by manufacturing tolerances) to motor axis MA defined by motor <NUM>.

Linear actuator <NUM> is configured to cause piston <NUM> to linearly translate substantially along a compression axis CA. As shown in <FIG>, in some examples, compression axis CA is displaced from motor axis MA, e.g., in the y-axis direction as shown or one or more other or additional axes. In examples, as shown in <FIG>, gear set <NUM> is configured to convert a rotary motion around motor axis MA (e.g., from flexible spline <NUM>) to a rotary motion around compression axis CA. In examples, actuator assembly <NUM> is configured such that input gear <NUM> rotates around motor axis MA and output gear <NUM> rotates around compression axis CA. In some examples, actuator assembly <NUM> is configured such that motor <NUM> and/or harmonic drive <NUM> is displaced from compression axis CA in one or more of the x-y-z axes (e.g., the y-axis as shown in <FIG>). Actuator assembly <NUM> may be configured such that linear actuator <NUM> is displaced from motor axis MA in one or more of the x-y-z axes (e.g., the y-axis as shown in <FIG>). Thus, actuator assembly <NUM> allows flexibility in the relative positioning of motor <NUM>, harmonic drive <NUM>, and/or linear actuator <NUM> as compared to in-line actuators which may be configured to rotate a motor shaft around a motor axis and cause a piston to translate over a compression axis substantially coincident with the motor axis.

Linear actuator <NUM> is configured to receive the rotary motion from gear set <NUM> and convert the rotary motion into a linear translation substantially along compression axis CA. In examples, linear actuator <NUM> includes a driver <NUM> configured to receive the rotary motion from gear set <NUM>. Driver <NUM> may be configured to rotate (e.g., around compression axis CA) when driver <NUM> receives the rotary motion from gear set <NUM>. Linear actuator <NUM> may be configured to produce the linear translation substantially along compression axis CA when driver <NUM> rotates. In examples, output gear <NUM> is configured to transfer the rotary motion to driver <NUM>. Driver <NUM> may be configured to rotate in a first direction ("first driver direction") when output gear <NUM> transfers rotary motion to driver <NUM> in the first output gear direction, and configured to rotate in a second direction ("second driver direction") opposite the first driver direction when output gear <NUM> transfers rotary motion to driver <NUM> in the second output gear direction.

In some examples, output gear <NUM> and driver <NUM> form a substantially rigid body (e.g., form a substantially unitary component), such that driver <NUM> and output gear <NUM> rotate in the same rotational direction. For example, actuator assembly <NUM> may be configured such that, when output gear <NUM> rotates in the direction R3 around compression axis CA, driver <NUM> rotates in the direction R3 around compression axis CA. Actuator assembly <NUM> may be configured such that, when output gear <NUM> rotates in the direction R4 around compression axis CA, driver <NUM> rotates in the direction R4 around compression axis CA.

Actuator assembly <NUM> has any suitable configuration that is configured to cause piston <NUM> to translate in the axial direction A1 or A2. In some examples, actuator assembly <NUM> includes a screw <NUM> configured to linearly translate along compression axis CA when driver <NUM> rotates, where screw <NUM> is configured to cause piston <NUM> to translate in the axial direction A1 or the axial direction A2 when screw <NUM> linearly translates. In examples, screw <NUM> is configured to linearly translate in the first axial direction A1 when driver <NUM> rotates in the first driver direction (e.g., the direction R3). Screw <NUM> may be configured to linearly translate in the second axial direction A2 when driver <NUM> rotates in the second driver direction (e.g., the direction R4).

Screw <NUM> may be configured to cause piston <NUM> to increase and/or initiate a compression force on disc stack <NUM> when screw <NUM> linearly displaces piston <NUM> in the axial direction A1. Screw <NUM> may be configured to cause piston <NUM> to decrease and/or eliminate the compression force on disc stack <NUM> when screw <NUM> linearly displaces piston <NUM> in the axial direction A2. The direction of linear translation of screw <NUM> is dependent on the driver direction of driver <NUM> and output gear direction of output gear <NUM>, which is dependent on the second rotational direction of the second rotary torque (T2-A or T2-B) determined by motor shaft <NUM>. Thus, the direction of linear translation produced by screw <NUM> may be dependent on the direction of rotation of motor shaft <NUM>.

Hence, actuator assembly <NUM> is configured to generate a first rotary torque (T1-A or T2-B) at a first rotational speed using motor <NUM>, generate a second rotary torque (T2-A or T2-B) at a second rotational speed less than the first rotational speed using harmonic drive <NUM>, and convert the second rotary torque to linear motion using linear actuator <NUM>. Linear actuator <NUM> may translate piston <NUM> in a direction dependent on the direction of rotation of motor shaft <NUM>. In examples, motor <NUM> is configured to generate the first rotary torque around motor axis MA and linear actuator <NUM> is configured to produce the linear motion along compression axis CA different from motor axis MA. Thus, actuator assembly <NUM> allows flexibility in the relative positioning of motor <NUM>, harmonic drive <NUM>, and/or linear actuator <NUM> as compared to in-line actuators which may be configured to rotate a motor shaft around a motor axis and cause a piston to translate over a compression axis substantially coincident with the motor axis.

Motor <NUM> is configured to receive electrical power (e.g., from an on-board power generation system) and convert the electrical power into a rotation of motor shaft <NUM> relative to motor housing <NUM>. Motor <NUM> may be configured to receive AC (Alternating Current) or DC (Direct Current) electrical power. Motor <NUM> may comprises a rotor and a stator, and may be configured to produce a rotating field on the stator to generate a torque on the rotor. In some examples, motor <NUM> is a brushless DC (BLDC) motor configured to accept a DC power input and generate the rotating field on the stator through electronic commutation. Motor <NUM> may utilize a plurality of permanent magnets on the rotor in order to prompt rotor torque in response to the rotating stator field. Motor shaft <NUM> may be coupled to the rotor, such that rotation of the rotor in response to the rotor torque causes rotation of motor shaft <NUM> around motor axis MA. In examples, motor <NUM> is a configured to provide a rotating or commutated field on the rotor in order to generate the torque.

Control circuitry <NUM> is configured to control the direction of rotation of motor shaft <NUM> based on, for example, an input from input device <NUM>. Control circuitry <NUM> may be configured to cause motor <NUM> to rotate motor shaft <NUM> in the first shaft direction R1 or the second shaft direction R2. In examples, control circuitry <NUM> is configured to control a speed of rotation of motor shaft <NUM> around motor axis MA. Control circuitry <NUM> may be configured to, for example, increase or decrease a speed of rotation of motor shaft <NUM> based on an input from input device <NUM> to increase or decrease a speed of the linear translation of piston <NUM> over the compression axis CA. In some examples, control circuitry <NUM> is configured to receive a signal from a sensor <NUM> configured to sense an operating parameter of motor shaft <NUM> such as a speed, position, and/or rotational direction. Control circuitry <NUM> may be configured to use the sensed operating parameter in order to maintain or determine a needed alteration in the operation of motor <NUM> to achieve a desired braking operation. Control circuitry <NUM> may be configured to communicate with other control systems on a vehicle, such as an anti-lock braking system (ABS), a brake control unit (BCU), or other systems.

<FIG> schematically depicts harmonic drive <NUM> including harmonic wave generator <NUM>, flexible spline <NUM>, and fixed spline <NUM>. <FIG> depict harmonic drive <NUM> receiving a first rotary torque T1 on harmonic wave generator <NUM> and producing a second rotary torque T2 on flexible spline <NUM> using first rotary torque T1. In <FIG>, the first rotary torque T1 may be torque T1-A (<FIG>) when the second rotary torque T2 is torque T2-A, or the first rotary torque T1 may be torque T1-B when the second rotary torque T2 is torque T2-B.

Motor shaft <NUM> is attached to harmonic wave generator <NUM>, such that rotation of motor shaft <NUM> around motor axis MA causes rotation of harmonic wave generator <NUM> around motor axis MA. Harmonic wave generator <NUM> defines a substantially elliptical (e.g., elliptical or nearly elliptical to the extent permitted by manufacturing tolerances) perimeter P around motor axis MA. Fixed spline <NUM> is configured to remain substantially stationary with respect to actuator body <NUM> and includes internal teeth <NUM> around a substantially circular pitch circle. In examples, harmonic wave generator <NUM> includes a plurality of ball bearings <NUM> including ball bearing <NUM> and ball bearing <NUM>. Flexible spline <NUM> is positioned between harmonic wave generator <NUM> and fixed spline <NUM> and includes external teeth <NUM> configured to mesh with internal teeth <NUM>.

Harmonic drive <NUM> is configured such that harmonic wave generator <NUM> and flexible spline <NUM> may rotate asynchronously. For example, when motor shaft <NUM> causes rotation of harmonic wave generator <NUM> around motor axis MA, harmonic drive <NUM> may be configured such that ball bearings <NUM> enable harmonic wave generator <NUM> (and perimeter P) to substantially slip underneath flexible spline <NUM> as harmonic wave generator <NUM> rotates around motor axis MA. Flexible spline <NUM> is configured to flex to substantially conform to perimeter P as harmonic wave generator <NUM> rotates asynchronously with respect to flexible spline <NUM>. Perimeter P of harmonic wave generator <NUM> causes flexible spline <NUM> to define an elliptical pitch circle having a major axis AX1 and a minor axis AX2, with minor axis AX2 defining a length less than major axis AX1.

Harmonic drive <NUM> is configured such that, as the perimeter P of harmonic wave generator <NUM> rotates around motor axis MA, flexible spline <NUM> flexes (e.g., elastically deforms) such that major axis AX1 and minor axis AX2 rotate at the same rotation speed as harmonic wave generator <NUM>. As harmonic wave generator <NUM> slips underneath flexible spline <NUM>, flexible spline <NUM> deforms into the elliptical shape and defines the elliptical pitch circle, causing external teeth <NUM> to mesh with internal teeth <NUM> substantially along major axis AX1. Further, the elliptical pitch circle causes external teeth <NUM> to disengage from internal teeth <NUM> substantially along minor axis AX2. Hence, rotation of motor shaft <NUM> around motor axis MA causes harmonic wave generator <NUM> to rotate around motor axis MA, and harmonic wave generator <NUM> causes flexible spline <NUM> to flex such that major axis AX1 and minor axis AX2 rotate synchronously with motor shaft <NUM> and harmonic wave generator <NUM>. Flexible spline <NUM> flexes (e.g., elastically deforms) to cause external teeth <NUM> to mesh with internal teeth <NUM> along major axis AX1, and to cause external teeth <NUM> to disengage from internal teeth <NUM> along minor axis AX2 as major axis AX1 and minor axis AX2 rotate.

Flexible spline <NUM> is configured to rotate around motor axis MA in a rotational direction opposite that of harmonic wave generator <NUM>. In examples, flexible spline <NUM> defines a number of external teeth <NUM> which is fewer than the number of internal teeth <NUM> defined by fixed spline <NUM>. In examples, flexible spline <NUM> defines a number of external teeth <NUM> with at least two teeth (e.g., two, three, four or more) fewer than the number of internal teeth <NUM>. The elliptical pitch circle of fixed spline <NUM> combined with the reduced number of external teeth <NUM> causes flexible spline <NUM> rotate in an opposite direction around motor axis MA compared to harmonic wave generator <NUM>. In examples, as harmonic wave generator <NUM> (and major axis AX1) rotates <NUM> degrees clockwise, flexible spline <NUM> rotates counter-clockwise by one tooth of internal teeth <NUM> relative to fixed spline <NUM>. For every one full rotation clockwise (<NUM> degrees) of harmonic wave generator <NUM>, the flexible spline <NUM> may move counter-clockwise by two teeth of internal teeth <NUM> relative to fixed spline <NUM>. Hence, when motor shaft <NUM> imparts a first torque (T1-A or T1-B) on harmonic wave generator <NUM> in a first rotational direction, harmonic drive <NUM> is configured to cause flexible spline <NUM> to produce a second torque (T2-A or T2-B) in a second rotational direction opposite the first rotational direction.

As an example, <FIG> depict harmonic drive <NUM> with motor shaft <NUM> exerting the first torque T1 on harmonic wave generator <NUM>. In the example of <FIG>, first torque T1 causes a rotation of harmonic wave generator <NUM> in the counter-clockwise direction. Relative to <FIG>, first torque T1 has caused harmonic wave generator <NUM> to rotate <NUM> degrees counter-clockwise in <FIG>, <NUM> degrees counter-clockwise in <FIG>, and <NUM> degrees counter-clockwise in <FIG>.

A fixed point M is depicted on flexible spline <NUM>. Harmonic drive <NUM> is configured such that, as harmonic wave generator <NUM> rotates counter-clockwise, fixed point M on flexible spline <NUM> rotates clockwise. For example, in <FIG>, the <NUM> degree counter-clockwise rotation of harmonic wave generator <NUM> has caused fixed point M to rotate clockwise over an angular displacement indicated by angle G1. In <FIG>, the <NUM> degree counter-clockwise rotation of harmonic wave generator <NUM> has caused fixed point M to rotate clockwise over an angular displacement indicated by angle G2, with angle G2 greater than angle G1. In <FIG>, the <NUM> degree counter-clockwise rotation of harmonic wave generator <NUM> has caused fixed point M to rotate clockwise over an angular displacement indicated by angle G3, with angle G3 greater than angle G2. The rotation of flexible spline <NUM> (causing rotation of fixed point M) causes flexible spline <NUM> to produce a second torque T2 having a rotational direction opposite that of first torque T1.

Further, as illustrated at <FIG>, harmonic drive <NUM> provides a speed reduction from a first rotational speed of first torque T1 to a second rotational speed of second torque T2. In examples, harmonic drive <NUM> produces a speed reduction from the first rotational speed to the second rotational speed based on the number of external teeth <NUM> and the number of internal teeth <NUM>. In examples, the speed reduction is substantially equal to the number of external teeth <NUM> divided by the difference between the number of internal teeth <NUM> and the number of external teeth <NUM>. Stated similarly, the speed reduction may be substantially equal to N1 / (N2 - N1), where N1 is the number of external teeth <NUM> and N1 is the number of internal teeth <NUM>.

In some examples, flexible spline <NUM> is configured substantially as a thin-walled steel cup with external teeth <NUM> machined into an outer surface near and/or adjacent to an open end of the cup (e.g., at the "top" of the cup). Flexible spline <NUM> may include a diaphragm at an end of the cup opposite the open end (e.g., at the "bottom" of the cup). Flexible spline <NUM> is configured to transmit the second rotary torque generated by the engagement of external teeth <NUM> and internal teeth <NUM> to the diaphragm. In examples, harmonic drive <NUM> is configured to impart the second rotary torque on gear set <NUM> (<FIG>, <FIG>) using the diaphragm. In examples, harmonic drive <NUM> is configured to impart the second rotary torque around the motor axis MA.

Input gear <NUM> (<FIG>) may be configured to receive the second rotary torque from the diaphragm of harmonic drive <NUM>. Input gear <NUM> may define input gear teeth <NUM> around a pitch circle surrounding an input gear axis, such that a torque on input gear <NUM> around the input gear axis causes input gear teeth <NUM> to rotate around the input gear axis. In examples, the input gear axis is substantially parallel to or substantially coaxial with motor axis MA. In examples, input gear <NUM> is configured to receive the second rotary torque from harmonic drive <NUM> and rotate around the input gear axis in the second rotational direction of the second rotary torque. Input gear <NUM> may be configured to rotate in the second rotational direction when motor shaft <NUM> rotates in the first rotational direction. In examples, actuator assembly <NUM> is configured such that rotation of motor shaft <NUM> in the first shaft direction around motor axis MA causes a rotation of input gear <NUM> in the second shaft direction opposite the first shaft direction, and such that rotation of shaft <NUM> in the second shaft direction around motor axis MA causes a rotation of input gear <NUM> in the first shaft direction.

Gear set <NUM> is configured such that a rotation of input gear <NUM> causes a rotation of output gear <NUM>. In examples, output gear <NUM> defines output gear teeth <NUM> around a pitch circle surrounding an output gear axis, such that a rotation of output gear <NUM> around the output gear axis causes output gear teeth <NUM> to rotate around the output gear axis. In examples, the output gear axis of output gear <NUM> is displaced (e.g., different ) from the input gear axis of input gear <NUM>. Hence, gear set <NUM> may be configured to receive the second rotary torque to cause a rotation of input gear <NUM> around the input gear axis, and transfer at least some portion of the second rotary torque to output gear <NUM> to cause a rotation of output gear <NUM> around an output gear axis different from the input gear axis. In examples, the input gear axis is substantially aligned (e.g., substantially coaxial with) motor axis MA. In examples, the output gear axis is substantially aligned (e.g., substantially coincident with) compression axis CA. Hence, gear set <NUM> may be configured to substantially transfer torque from the motor axis MA to compression axis CA, to allow for a more compact actuator assembly as compared to in-line actuators where a single axis is substantially coincident with both the motor axis MA and the compression axis CA.

In examples, gear set <NUM> is configured such that input gear teeth <NUM> mesh with output gear teeth <NUM> to cause the rotation of output gear <NUM>. In some examples, gear set <NUM> is configured such that input gear <NUM> drives the rotation of output gear <NUM> without the use of one or more idler gears between input gear <NUM> and output gear <NUM>. Gear set <NUM> may be configured such that a rotational speed of input gear <NUM> is greater than a rotational speed of output gear <NUM>. In examples, input gear <NUM> defines a number of input gear teeth <NUM> and output gear <NUM> defines a number of output gear teeth <NUM>, and the number of input gear teeth <NUM> is less than the number of output gear teeth <NUM>. Gear set <NUM> may be configured such that a rotational speed of output gear <NUM> is reduced from a rotational speed of input gear <NUM> by a factor substantially equal to the number of input gear teeth <NUM> divided by the number of output gear teeth <NUM>. Stated similarly, the speed reduction from input gear <NUM> to output gear <NUM> may be substantially equal to N3 / N4, where N3 is the number of input gear teeth <NUM> and N4 is the number of output gear teeth <NUM>.

Hence, actuator assembly <NUM> may be configured such that, when motor <NUM> generates the first torque (e.g., T1-A or T1-B) at the first rotational speed, harmonic drive <NUM> may cause a first speed reduction by using the first torque to produce the second torque at the second rotational speed less than the first rotational speed. The first speed reduction may be substantially equal to N1 / (N2 - N1), where N1 is the number of external teeth <NUM> and N1 is the number of internal teeth <NUM>. Actuator assembly <NUM> may be configured such that, when gear set <NUM> receives the second rotary torque at the second rotational speed, gear set <NUM> causes a second speed reduction when gear set <NUM> uses the second rotary torque to produce a rotation of output gear <NUM>. The second speed reduction may be substantially equal to N3 / N4, where N3 is the number of input gear teeth <NUM> and N4 is the number of output gear teeth <NUM>.

In examples, actuator assembly <NUM> may be configured such that the first speed reduction and the second speed reduction cause an overall speed reduction of at least <NUM>:<NUM>, and in some examples at least <NUM>:<NUM>. Further, actuator assembly <NUM> may be configured to cause the overall speed reduction without the use of one or more idler gears between input gear <NUM> and output gear <NUM>, reducing and/or eliminating gear backlash during alterations in the speed and/or rotational direction of motor shaft <NUM>. In addition, accomplishing the speed reduction using harmonic drive <NUM> and gear set <NUM> without the use of idler gears may allow for a more compact actuator assembly as compared to actuators configured to primarily use only a meshed gearbox for speed step-down.

Gear set <NUM> is configured such that the rotational direction of input gear <NUM> substantially determines the output gear direction of output gear <NUM>. Actuator assembly <NUM> is configured such that the rotational direction of motor shaft <NUM> (e.g., the first shaft direction R1 or the second shaft direction R2) substantially determines the rotational direction of input gear <NUM>. Hence, actuator assembly <NUM> is configured such that the rotational direction of motor shaft <NUM> determines the output gear direction of output gear <NUM>. In examples, rotation of motor shaft <NUM> in first shaft direction R1 causes output gear <NUM> to rotate in a first output gear direction (e.g., output gear direction R3 (<FIG>)), and rotation of motor shaft <NUM> in second shaft direction R2 causes output gear <NUM> to rotate in a second output gear direction opposite the first output gear direction (e.g., output gear direction R4 (<FIG>)).

Output gear <NUM> is configured to transfer rotary motion to linear actuator <NUM> in either the first output gear direction or the second output gear direction. In examples, output gear <NUM> is configured to cause a portion of linear actuator <NUM> (e.g., driver <NUM>) to rotate around compression axis CA. Linear actuator <NUM> is configured to receive the rotary motion from output gear <NUM> (in the first output gear direction or second output gear direction) and convert the rotary motion into a linear translation substantially along compression axis CA. In examples, linear actuator <NUM> is configured to produce the linear translation substantially along compression axis CA when driver <NUM> rotates substantially around the compression axis CA. In examples, driver <NUM> is configured to rotate in a first driver direction when output gear <NUM> transfers rotary motion to driver <NUM> in the first output gear direction, and configured to rotate in a second driver direction opposite the first driver direction when output gear <NUM> transfers rotary motion to driver <NUM> in the second output gear direction.

In examples, screw <NUM> is configured to linearly translate along compression axis CA when driver <NUM> rotates around compression axis CA. Linear actuator may be configured such that screw <NUM> translates in the axial direction A1 when driver <NUM> rotates in the first driver direction, and such that screw <NUM> translates in the axial direction A2 when driver <NUM> rotates in the second driver direction. Hence, actuator assembly <NUM> may be configured such that the rotational direction of motor shaft <NUM> determines the rotational direction of driver <NUM> around compression axis CA, and thereby determines the direction of translation of screw <NUM>. For example, in some examples, when motor <NUM> causes motor shaft <NUM> to rotate in the first shaft direction R1, driver <NUM> causes screw <NUM> to linearly translate in the direction A1 to increase and/or initiate a compression force on disc stack <NUM>, and when motor <NUM> causes motor shaft <NUM> to rotate in the second shaft direction R2, driver <NUM> causes screw <NUM> to linearly translate in the direction A2 to decrease and/or substantially eliminate a compression force on disc stack <NUM>. In other examples, when motor <NUM> causes motor shaft <NUM> to rotate in the second shaft direction R2, driver <NUM> causes screw <NUM> to linearly translate in the direction A1 to increase and/or initiate a compression force on disc stack <NUM>, and when motor <NUM> causes motor shaft <NUM> to rotate in the first shaft direction R1, driver <NUM> causes screw <NUM> to linearly translate in the direction A2 to decrease and/or substantially eliminate a compression force on disc stack <NUM>.

In examples, the driver <NUM> is a ball nut and screw <NUM> is a ball screw. Linear actuator <NUM> may include a plurality of ball bearings <NUM> ("actuator ball bearings <NUM>") such as ball bearing <NUM> and ball bearing <NUM> (<FIG>). In some of these examples, linear actuator <NUM> is configured such that a rotation of driver <NUM> around compression axis CA exerts a force in the direction A1 or the direction A2 on actuator ball bearings <NUM>, and actuator ball bearings <NUM> transmit the force to screw <NUM> causing screw <NUM> to translate in the direction A1 or A2 respectively. In examples, as shown in <FIG>, driver <NUM> defines a helical track <NUM> ("driver helical track <NUM>") surrounding compression axis CA and screw <NUM> defines a helical track <NUM> ("screw helical track <NUM>") surrounding compression axis CA, and linear actuator <NUM> is configured to confine at least a portion or all of actuator ball bearings <NUM> within the driver helical track <NUM> and screw helical track <NUM>. In examples, driver <NUM> is configured to exert the force on actuator ball bearings <NUM> using driver helical track <NUM>, and actuator ball bearings <NUM> are configured to transmit the force to screw <NUM> using screw helical track <NUM>. In examples, linear actuator <NUM> includes a ball return <NUM> configured to allow actuator ball bearings <NUM> to exit from and return to driver helical track <NUM> and screw helical track <NUM> as screw <NUM> translates in the direction A1 or the direction A2.

Actuator assembly <NUM> may include an anti-rotation member <NUM> (<FIG>) configured to limit rotational movement of screw <NUM> with respect to actuator body <NUM>, motor housing <NUM>, or some other portion of brake assembly <NUM> (e.g., torque tube <NUM>). Anti-rotation member <NUM> may be configured to allow screw <NUM> to translate in a linear direction (e.g., the direction A1 or the direction A2) while limiting the rotational movement of screw <NUM>. In examples, anti-rotation member <NUM> is configured to cause screw <NUM> to substantially resist torques which may be imparted to screw <NUM> during the rotation of driver <NUM> by output gear <NUM>. In examples, anti-rotation member <NUM> is configured to remain substantially stationary with respect to actuator body <NUM>. Actuator body <NUM> may mechanically support anti-rotation member <NUM>, such that anti-rotation member <NUM> causes screw <NUM> to resist torques imparted by driver <NUM>.

Anti-rotation member <NUM> may include a linear bearing <NUM> configured to engage screw <NUM> to substantially maintain screw <NUM> rotationally stationary with respect to driver <NUM>. Linear bearing <NUM> may be configured such that, when screw <NUM> exerts a torque around compression axis CA on linear bearing <NUM>, linear bearing <NUM> exerts a substantially equal and opposite reaction torque on screw <NUM> to prevent rotation of screw <NUM> around compression axis CA. Linear bearing <NUM> may be configured to translate in a linear direction (e.g., the direction A1 or the direction A2) while limiting the rotational movement of screw <NUM>. In examples, linear bearing <NUM> includes a plurality of ball bearings <NUM> ("linear ball bearings <NUM>") such as ball bearing <NUM> and ball bearing <NUM>. In examples, linear bearing <NUM> is configured such that, if rotation of driver <NUM> around compression axis CA imparts a torque to screw <NUM>, linear ball bearings <NUM> transmit the torque to anti-rotation member <NUM>, causing linear bearing <NUM> to exert the substantially equal and opposite reaction torque on screw <NUM>.

Linear bearing <NUM> is configured to allow screw <NUM> to translate in a linear direction (e.g., the direction A1 or the direction A2) relative to anti-rotation member <NUM>. For example, when driver <NUM> rotates relative to screw <NUM> to cause linear motion of screw <NUM>, linear bearing <NUM> may be configured to offer limited or substantially no resistance to the linear motion while substantially resisting any rotational motion of screw <NUM> that might be caused by torques imparted to screw <NUM> by driver <NUM>. In examples, anti-rotation member <NUM> defines a linear track <NUM> and screw <NUM> defines a linear track <NUM> ("screw linear track <NUM>"), and anti-rotation member <NUM> is configured to confine linear ball bearings <NUM> within linear track <NUM> and screw linear track <NUM>. In examples, linear track <NUM> and screw linear track <NUM> are configured to define a path for linear ball bearings <NUM> substantially parallel to compression axis CA. In examples, actuator assembly <NUM> is configured such that, when driver <NUM> exerts a torque around compression axis CA on screw <NUM>, screw linear track <NUM> transmits the torque to anti-rotation member <NUM> via linear ball bearings <NUM> and linear track <NUM>, and anti-rotation member <NUM> exerts a substantially equal and opposite reaction to screw <NUM> via linear track <NUM> and linear ball bearings <NUM> to substantially limit rotational motion of screw <NUM>.

In examples, screw <NUM> defines void <NUM> and may be configured such that anti-rotation member <NUM> is positioned within void <NUM>. In examples, one of driver <NUM> or anti-rotation member <NUM> is positioned within void <NUM> (e.g., substantially within screw <NUM>) and the other of driver <NUM> or anti-rotation member <NUM> is positioned outside of void <NUM> (e.g., substantially outside of screw <NUM>). For example, in the example of <FIG>, anti-rotation member <NUM> is positioned within void <NUM> and driver <NUM> is positioned outside of void <NUM>. Screw <NUM> may include a substantially tubular section defining void <NUM>. Piston <NUM> may be supported by screw <NUM> on an end of the substantially tubular section.

Screw <NUM> includes an inner surface <NUM> ("screw inner surface <NUM>") defining a boundary of void <NUM>. Anti-rotation member <NUM> includes an outer surface <NUM> ("anti-rotation outer surface <NUM>") configured to face screw inner surface <NUM> when anti-rotation member <NUM> positions in void <NUM>. In examples, anti-rotation outer surface <NUM> defines linear track <NUM> and screw inner surface <NUM> defines screw linear track <NUM>. In the example of <FIG> and in other examples, driver <NUM> may be configured to substantially surround a portion of screw <NUM>, such that driver <NUM> is positioned outside of void <NUM>. Driver <NUM> may include an inner surface <NUM> ("driver inner surface <NUM>") configured to face screw <NUM> when driver <NUM> substantially surrounds the portion of screw <NUM>. In examples, screw <NUM> includes an outer surface <NUM> ("screw outer surface <NUM>") configured to face driver inner surface <NUM> when driver <NUM> substantially surrounds the portion of screw <NUM>. In examples, driver inner surface <NUM> defines driver helical track <NUM> and screw outer surface <NUM> defines screw helical track <NUM>.

<FIG> is a conceptual illustration of another example actuator assembly <NUM> according to the present invention, the actuator assembly <NUM> includes actuator body <NUM>, linear actuator <NUM>, and anti-rotation member <NUM>. Linear actuator <NUM> includes driver <NUM> and screw <NUM> and defines a void <NUM>. Linear actuator <NUM> is configured such that driver <NUM> is positioned within void <NUM> and anti-rotation member <NUM> is positioned outside of void <NUM> (e.g., partially and/or substantially surrounding screw <NUM>). <FIG> illustrates part of actuator assembly <NUM> in cross-section and parts as functional block diagram, with reference to the x-y-z axes shown. Actuator assembly <NUM> may be an example of actuator assembly <NUM>, <NUM>, actuator body <NUM> may be an example of actuator body <NUM>, <NUM>, linear actuator <NUM> may be an example of linear actuator <NUM>, driver <NUM> may be an example of driver <NUM>, screw <NUM> may be an example of screw <NUM>, and anti-rotation member <NUM> may be an example of anti-rotation member <NUM> (<FIG>). Actuator assembly <NUM> further includes motor <NUM>, motor shaft <NUM>, harmonic drive <NUM>, input gear <NUM>, output gear <NUM>, control circuitry <NUM>, and input device <NUM>.

Output gear <NUM> is configured to rotate driver <NUM> within void <NUM> when output gear <NUM> rotates. Driver <NUM> is configured to rotate substantially within a void <NUM> defined by screw <NUM> to cause a linear translation of screw <NUM> in the axial direction A1 or the axial direction A2. Linear actuator <NUM> includes an anti-rotation member <NUM> surrounding screw <NUM> and configured to limit rotational movement of screw <NUM> as driver <NUM> rotates around screw <NUM>. In examples, output gear <NUM> is configured to cause driver <NUM> to rotate within void <NUM> around compression axis CA. Screw <NUM> may include a substantially tubular section defining void <NUM>. Piston <NUM> may be supported by screw <NUM> on an end of the substantially tubular section. In examples, output gear <NUM> is configured to cause driver <NUM> to rotate in the first driver direction when output gear <NUM> rotates in the first output gear direction, and configured to cause driver <NUM> to rotate in the second driver direction when output gear <NUM> rotates in the second output gear direction.

Screw <NUM> is configured to linearly translate along compression axis CA when driver <NUM> rotates around compression axis CA. Linear actuator <NUM> may be configured such that screw <NUM> translates in the axial direction A1 when driver <NUM> rotates in the first driver direction, and such that screw <NUM> translates in the axial direction A2 when driver <NUM> rotates in the second driver direction. Hence, actuator assembly <NUM> may be configured such that the rotational direction of motor shaft <NUM> determines the rotational direction of driver <NUM> around compression axis CA, and thereby determines the direction of translation of screw <NUM>.

In some examples, driver <NUM> is a ball nut and screw <NUM> is a ball screw. Linear actuator <NUM> may be configured such that a rotation of driver <NUM> around compression axis CA exerts a force in the direction A1 or the direction A2 on actuator ball bearings <NUM>, and actuator ball bearings <NUM> transmit the force to screw <NUM> causing screw <NUM> to translate in the direction A1 or A2 respectively. In examples, as shown in <FIG>, driver <NUM> defines a helical track <NUM> ("driver helical track <NUM>") surrounding compression axis CA and screw <NUM> defines a helical track <NUM> ("screw helical track <NUM>") surrounding compression axis CA, and linear actuator <NUM> is configured to confine at least a portion or all of actuator ball bearings <NUM> within the driver helical track <NUM> and screw helical track <NUM>. Driver <NUM> can be configured to exert the force on actuator ball bearings <NUM> using driver helical track <NUM>, and actuator ball bearings <NUM> are configured to transmit the force to screw <NUM> using screw helical track <NUM>. In examples, linear actuator <NUM> includes a ball return <NUM> configured to allow actuator ball bearings <NUM> to exit from and return to driver helical track <NUM> and screw helical track <NUM> as screw <NUM> translates in the direction A1 or the direction A2.

Screw <NUM> includes an inner surface <NUM> ("screw inner surface <NUM>") defining a boundary of void <NUM>. In examples, screw inner surface <NUM> defines screw helical track <NUM>. Driver <NUM> may include an outer surface <NUM> ("driver outer surface <NUM>") configured to face screw <NUM> when screw <NUM> substantially driver <NUM>. In examples, driver outer surface <NUM> defines driver helical track <NUM>.

Anti-rotation member <NUM> is configured to limit rotational movement of screw <NUM> with respect to actuator body <NUM>, motor housing <NUM>, or some other portion of brake assembly <NUM> (e.g., torque tube <NUM>). Anti-rotation member <NUM> may be configured to allow screw <NUM> to translate in a linear direction (e.g., the direction A1 or the direction A2) while limiting the rotational movement of screw <NUM>. Anti-rotation member <NUM> may be configured to cause screw <NUM> to substantially resist torques which may be imparted to screw <NUM> during the rotation of driver <NUM> by output gear <NUM>. In examples, anti-rotation member <NUM> is configured to remain substantially stationary with respect to actuator body <NUM>. Actuator body <NUM> may mechanically support anti-rotation member <NUM>, such that anti-rotation member <NUM> causes screw <NUM> to resist torques imparted by driver <NUM>.

Anti-rotation member <NUM> may include a linear bearing <NUM> configured to engage screw <NUM> to substantially maintain screw <NUM> rotationally stationary with respect to driver <NUM>. Linear bearing <NUM> may be configured such that, when screw <NUM> exerts a torque around compression axis CA on linear bearing <NUM>, linear bearing <NUM> exerts a substantially equal and opposite reaction torque on screw <NUM> to prevent rotation of screw <NUM> around compression axis CA. Linear bearing <NUM> may be configured to translate in a linear direction (e.g., the direction A1 or the direction A2) while limiting the rotational movement of screw <NUM>. Linear bearing <NUM> may include linear ball bearings <NUM> with linear bearing <NUM> is configured such that, if rotation of driver <NUM> around compression axis CA imparts a torque to screw <NUM>, linear ball bearings <NUM> transmit the torque to anti-rotation member <NUM>, causing linear bearing <NUM> to exert the substantially equal and opposite reaction torque on screw <NUM>.

Linear bearing <NUM> is configured to allow screw <NUM> to translate in a linear direction (e.g., the direction A1 or the direction A2) relative to anti-rotation member <NUM>. For example, when driver <NUM> rotates relative to screw <NUM> to cause linear motion of screw <NUM>, linear bearing <NUM> may be configured to offer limited or substantially no resistance to the linear motion while substantially resisting any rotational motion of screw <NUM> that might be caused by torques imparted to screw <NUM> by driver <NUM>. In examples, anti-rotation member <NUM> defines a linear track <NUM> and screw <NUM> defines a linear track <NUM> ("screw linear track <NUM>"), and anti-rotation member <NUM> is configured to confine linear ball bearings <NUM> within linear track <NUM> and screw linear track <NUM>. In examples, linear track <NUM> and screw linear track <NUM> are configured to define a path for linear ball bearings <NUM> substantially parallel to compression axis CA. In examples, actuator assembly <NUM> is configured such that, when driver <NUM> exerts a torque around compression axis CA on screw <NUM>, screw linear track <NUM> transmits the torque to anti-rotation member <NUM> via linear ball bearings <NUM> and linear track <NUM>, and anti-rotation member <NUM> exerts a substantially equal and opposite reaction torque to screw <NUM> via linear track <NUM> and linear ball bearings <NUM> to substantially limit rotational motion of screw <NUM>.

Anti-rotation member <NUM> may include an inner surface <NUM> ("anti-rotation inner surface <NUM>") configured to face an outer surface <NUM> of screw <NUM> ("screw outer surface <NUM>") when anti-rotation member <NUM> positions in void <NUM>. In examples, anti-rotation inner surface <NUM> defines linear track <NUM> and screw outer surface <NUM> defines screw linear track <NUM>.

Brake assembly <NUM> may include any suitable number of actuators such as actuator assembly <NUM>, <NUM>, and/or <NUM> configured to exert and/or increase a compression force on disc stack <NUM>, and/or configured to reduce and/or eliminate the compression force on disc stack <NUM>. The actuators may be arranged within brake assembly <NUM> in any suitable arrangement. In examples, brake assembly <NUM> includes a plurality of actuators arranged around a perimeter surrounding wheel axis A. Two or more actuators may be configured to translate a respective piston substantially simultaneously based on a command issued by control circuitry <NUM> to the two or more actuators, and/or may be configured to translate the respective pistons substantially individually based on individual command issued by control circuitry <NUM> to an individual actuator.

Actuator assembly <NUM>, wheel <NUM>, brake assembly <NUM>, and the components thereof can be formed using any suitable technique. Actuator assembly <NUM>, wheel <NUM>, brake assembly <NUM>, and the components thereof may be forged, casted, made from bar stock, additive manufactured (e.g., three-dimensionally (3D) printed), extruded, drawn, or be produced using other suitable methods. In some examples, actuator assembly <NUM>, wheel <NUM>, brake assembly <NUM>, and the components thereof may be machined to define the configurations described herein. In other examples, actuator assembly <NUM>, wheel <NUM>, brake assembly <NUM>, and the components thereof may be formed without having to be substantially machined.

In some examples, wheel <NUM> may be finish machined from a near-net-shaped aluminum forging and contain an axial assembly and/or wheel rim for assembly of brake assembly <NUM> and/or actuator assembly <NUM> onto wheel <NUM>. In other examples, wheel <NUM> may be manufactured in a different manner. In yet other examples, wheel <NUM> may be obtained rather than manufactured. Wheel <NUM> may be made of any suitable material. In some examples, wheel <NUM> includes a metal or a metal alloy. For example, wheel <NUM> may include aluminum, a nickel alloy, a steel alloy (e.g., stainless steel), titanium, a carbon-composite material, or magnesium.

Control circuitry <NUM> may comprise a processor, memory, and, in some examples, input/output (I/O) peripherals. In examples, control circuitry <NUM> may include any one or more of a microcontroller (MCU), e.g., a computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals, a microcontroller (µP), e.g., a central processing unit (CPU) on a single integrated circuit (IC), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a system on chip (SoC) or equivalent discrete or integrated logic circuitry. Control circuitry <NUM> may include integrated circuitry, i.e., integrated control circuitry, and the integrated control circuitry may be realized as fixed hardware processing circuitry, programmable processing circuitry and/or a combination of both fixed and programmable processing circuitry. The memory may include any volatile or non-volatile media, such as a random access memory (RAM), read only memory (ROM), non-volatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), flash memory, and the like. In addition, in some examples, the memory or another memory may also store executable instructions for causing the one or more controllers described herein to perform the actions attributed to them.

Input device <NUM> may have any suitable configuration. For example, input device <NUM> may include a foot pedal, a button or keypad, a speaker configured to receive voice commands from a user, a display, such as a liquid crystal (LCD), light-emitting diode (LED), or organic light-emitting diode (OLED). In some examples, input device <NUM> may include a touch screen. Input device <NUM> is configured to receive user input, e.g., in the form of placing a foot pedal in a specific position and/or pressing one or more buttons on a keypad or via a touch screen, which may be a user input selecting one or more actuators for actuation. In some examples, input device <NUM> is also configured to display information, such as one or more indications providing information on the actuation of brake assembly <NUM>.

Communication links <NUM>, <NUM> may be hard-line and/or wireless communications links. In some examples, communication links <NUM>, <NUM> may comprise some portion of control circuitry <NUM>. In some examples, communication links <NUM>, <NUM> comprise a wired connection, a wireless Internet connection, a direct wireless connection such as wireless LAN, Bluetooth™ Wi-Fi™, and/or an infrared connection. Communication links <NUM>, <NUM> may utilize any wireless or remote communication protocol.

Brake discs described herein, including rotor discs <NUM>, <NUM>, <NUM>, <NUM> and stator discs <NUM>, <NUM>, <NUM>, may be manufactured from any suitable material. In some examples, the brake discs described herein may be manufactured from a metal or a metal alloy, such as a steel alloy. In some examples, the brake discs may be manufactured using a ceramic material, such as a ceramic composite. In some examples, the brake discs may be manufactured from a carbon-carbon composite material. In some examples, the brake discs may be manufactured using a carbon-carbon composite material having a high thermal stability, a high wear resistance, and/or stable friction properties. The brake discs may include a carbon material with a plurality of carbon fibers and densifying material. The carbon fibers may be arranged in a woven or non-woven as either a single layer or multilayer structure.

<FIG> is a flow diagram illustrating an example technique for compressing a disc stack in a brake assembly. While the technique is described with reference to brake assembly <NUM> and wheel <NUM> described herein, the technique may be used with other examples components described herein.

The technique includes generating a first rotary torque (e.g., T1-A, T1-B) using motor <NUM> of actuator assembly <NUM>, <NUM>, <NUM> (<NUM>). Actuator assembly <NUM>, <NUM>, <NUM> may include actuator body <NUM>, <NUM>, <NUM> configured to remain substantially stationary with respect to some portion of brake assembly <NUM>, such as torque tube <NUM>. Motor <NUM> may include motor housing <NUM> configured to remain substantially stationary with respect to actuator body <NUM>, <NUM>, <NUM>. Motor <NUM> may be configured to generate the first rotary torque by rotating motor shaft <NUM> relative to motor housing <NUM>. In examples, actuator assembly <NUM>, <NUM>, <NUM> is configured to generate the first rotary torque in response to a braking signal received from control circuitry <NUM>. Control circuitry <NUM> may be configured to receive a user input from input device <NUM> and transmit the braking signal to actuator assembly <NUM>, <NUM>, <NUM> based on the user input.

The technique may include generating the first rotary torque at a first rotational speed and in a first rotational direction. In examples, motor housing <NUM> defines a motor axis MA, and motor <NUM> is configured to generate the first rotary torque around the motor axis MA. Motor housing <NUM> may be configured to rotate motor shaft <NUM> around motor axis MA to generate the first rotary torque. Motor <NUM> may be configured to rotate motor shaft <NUM> around motor axis MA in a first shaft direction R1 or in a second shaft direction R2 opposite first shaft direction R1 to generate the first rotary torque.

The technique includes generating a second rotary torque using harmonic drive <NUM> (<NUM>). Harmonic drive <NUM> may be configured to generate the second rotary torque using the first rotary torque produced by motor <NUM>. Harmonic drive <NUM> may generate the second rotary torque at a second rotational speed less than the first rotational speed and in a second rotational direction opposite the first rotation direction.

In examples, harmonic drive <NUM> includes harmonic wave generator <NUM>, flexible spline <NUM> defining external teeth <NUM> , and fixed spline <NUM> defining internal teeth <NUM>. Fixed spline <NUM> may define a substantially circular pitch circle and be configured to remain substantially stationary with respect to actuator body <NUM>, motor housing <NUM>, and/or another portion of brake assembly <NUM> such as torque tube <NUM>. Harmonic wave generator <NUM> may be configured to cause flexible spline <NUM> to define an elliptical pitch circle. The technique may include using the first rotary torque to cause a rotation of harmonic wave generator <NUM>. The technique may include causing external teeth <NUM> to mesh with internal teeth <NUM> substantially at a major axis of the elliptical pitch circle as harmonic wave generator <NUM> rotates. The technique may include generating the second rotary torque using flexible spline <NUM>. Flexible spline <NUM> may be configured to generate the second rotary torque around the motor axis MA. In examples, the technique includes using the harmonic drive to generate the second rotary torque at a second rotational speed using the first rotary torque at a first rotational speed, where the second rotational speed is less than the first rotational speed.

The technique may include rotating output gear <NUM> of gear set <NUM> using the second rotary torque. In examples, harmonic drive <NUM> is configured to cause the rotation of input gear <NUM> to cause the rotation of output gear <NUM>. Input gear <NUM> may define input gear teeth <NUM> and output gear <NUM> may define output gear teeth <NUM>. In examples, input gear <NUM> is configured to mesh input gear teeth <NUM> with output gear teeth <NUM>. In examples, gear set <NUM> is configured to rotate input gear <NUM> around an input gear axis and rotate output gear <NUM> around an output gear axis displaced (e.g., different) from the input gear axis.

The technique includes translating piston <NUM> using the second rotary torque (<NUM>). The technique may include causing linear actuator <NUM>, <NUM> to generate a linear motion to translate piston <NUM> using the second rotary torque. In examples, output gear <NUM> is configured to cause a rotation of driver <NUM> when the second rotary torque causes a rotation of output gear <NUM>. Linear actuator <NUM>, <NUM> may include screw <NUM>, <NUM> configured to linearly translate when driver <NUM>, <NUM> rotates. In examples, screw <NUM>, <NUM> is configured to linearly translate along compression axis CA. Compression axis CA may be substantially coincident with the output gear axis of output gear <NUM>. In some examples, driver <NUM> is configured to rotate substantially around a portion of screw <NUM> to cause the linear translation. In some examples, driver <NUM> may be configured to rotate within void <NUM> defined by screw <NUM> to cause the linear translation.

In examples, the technique includes causing screw <NUM>, <NUM> to initiate and/or increase a compression force on disc stack <NUM> when motor <NUM> rotates motor shaft <NUM> in the first shaft direction R1. Actuator assembly <NUM>, <NUM>, <NUM> may be configured to cause output gear <NUM> to rotate in a first output gear direction around the output gear axis when motor <NUM> rotates motor shaft <NUM> in the first shaft direction R1. Actuator may be configured to cause driver <NUM>, <NUM> to rotate in a first driver direction when output gear <NUM> rotates in the first output gear direction. Driver <NUM>, <NUM> may be configured to cause screw <NUM> to translate in a first axial direction A1 to initiate and/or increase the compression on disc stack <NUM> when driver <NUM>,<NUM> rotates in the first driver direction. In examples, the technique includes causing screw <NUM>, <NUM> to decrease and/or substantially eliminate a compression force on disc stack <NUM> when motor <NUM> rotates motor shaft <NUM> in the second shaft direction R2. Actuator assembly <NUM>, <NUM>, <NUM> may be configured to cause output gear <NUM> to rotate in a second output gear direction opposite the first output gear direction when motor <NUM> rotates motor shaft <NUM> in the second shaft direction R2. Actuator may be configured to cause driver <NUM>, <NUM> to rotate in a second driver direction opposite the first driver direction when output gear <NUM> rotates in the second output gear direction. Driver <NUM>, <NUM> may be configured to cause screw <NUM>, <NUM> to translate in a second axial direction A2 to decrease and/or substantially eliminate the compression on disc stack <NUM> when driver <NUM>, <NUM> rotates in the second driver direction.

Claim 1:
A brake assembly (<NUM>) comprising:
a brake disc stack;
an actuator assembly (<NUM>, <NUM>, <NUM>) comprising:
an electric motor (<NUM>) configured to generate a first rotary torque around a motor axis;
a harmonic drive (<NUM>) configured to generate a second rotary torque in response to the first rotary torque;
a gear set (<NUM>) comprising an output gear (<NUM>) configured to rotate in response to the second rotary torque; and
a linear actuator (<NUM>, <NUM>) mechanically coupled with the gear set (<NUM>),
wherein the linear actuator is configured to generate linear motion along a compression axis and cause a piston (<NUM>) to compress the brake disc stack when the output gear rotates, wherein the compression axis is different than the motor axis, wherein the linear actuator includes a driver (<NUM>, <NUM>) and a screw (<NUM>, <NUM>) and defines a void (<NUM>, <NUM>), wherein the output gear is configured to rotate the driver within the void when the output gear rotates to cause a linear translation of screw, wherein the driver is positioned within void, wherein the linear actuator further comprises an anti-rotation member (<NUM>, <NUM>) positioned outside the void and at least partially surrounding the screw, wherein the anti-rotation member is configured to limit rotational movement of the screw as the driver rotates around the screw.