Patent Description:
Systems are known for controlling an electromechanical actuator (EMA) of an aircraft. Often these may include a locking device that is configured to mechanically lock the actuator in a first fixed position and to mechanically unlock the actuator from the first fixed position. A controller may be configured to be in communication with both the locking device and the actuator. The controller may monitor a position of the actuator during flight and react when it is detected that the actuator has not moved for a set amount of time.

Some known systems may be operable in fault-tolerant mode to accommodate usual fault situations. In some flight control surface actuation systems, a plurality of actuators may be attached to one or more summing levers, each having an actuator output point that is attached to the flight control surface. <CIT> describes EMA thermal management optimization, wherein a system for controlling an electromechanical actuator of an aircraft includes a locking device configured to mechanically lock said actuator in a first fixed position and to mechanically unlock said actuator from said first fixed position and a controller configured to be in bi-directional communication with both said locking device and said actuator. The controller is configured to monitor a position of said actuator during flight and to detect when said actuator has not moved for a set amount of time, said controller further being configured to instruct said locking device to lock said actuator in said first, locked position when said set time has been reached. In addition, there is provided a method for controlling the thermal properties of an electromechanical actuator of an aircraft.

<CIT> describes trailing edge wing flap systems. <CIT> describes a method and device for controlling an aircraft maneuvering component. <CIT> describes the autonomous reconfiguration of a multi-redundant actuator control system.

A system for controlling a flight control surface is described herein and defined in claim <NUM>.

In some examples, in normal operation, both of the first and second EMAs are operating in said active mode.

In some examples, said first and second EMAs are connected to the flight control surface that is being controlled.

In some examples, the first and second EMAs are each connected to a flight control computer (FCC).

In some examples, said first and second EMAs are provided in a housing and wherein, in the event that a temperature of said housing reaches an upper threshold, the system is configured to operate with both the first and the second EMAs in said blocked/blocked mode.

In some examples, in the event that either one or both the first and second EMAs fail, the system is configured to switch the first and second EMAs into said blocked/blocked mode.

A method for controlling a flight control surface is also described herein, and defined in claim <NUM>.

In some examples, the method comprises in normal operation, controlling said flight control surface by operating both of the first and second EMAs in said active mode.

In some examples, said first and second EMAs are provided in a housing and in the event that a temperature of said housing reaches an upper threshold, the flight surface is controlled with both the first and the second EMAs in said blocked/blocked mode.

In some examples, in the event that either or both the first and second EMAs fail, the flight surface is controlled with the first and second EMAs being held in said blocked/blocked mode.

The examples described herein relate to electromechanical actuators (EMAs) and, in particular, their use in aileron, elevator or rudder flight control surfaces.

In known systems, such flight control surfaces are driven by two electro hydraulic servo actuators (EHSAs) or by one EHSA in parallel with one electro hydraulic actuator (EHA) that is in an active or damped arrangement. These actuators have two modes, which are active or damped.

The new examples described herein involve using EMA technology to drive flight control surfaces. Due to this, air framers may be forced to switch to an active/active arrangement in order to reduce the actuator size, due to envelope constraints found in thin wing designs.

<FIG> depicts a known design <NUM> for the movement of a flight control surface. The known design comprises a first EHSA <NUM> and associated Remote Electronic Unit (REU) <NUM> and a second EHSA <NUM> and associated REU <NUM>. Each of these REUs <NUM>, <NUM> are connected to the flight control computers (FCCs) <NUM> and each of the EHSAs <NUM>, <NUM> are connected to the flight control surface <NUM>.

As mentioned above, these known systems have EHSs that act in two modes - Active or Damped. In normal operation, one, e.g. the first EHSA <NUM> is active, controlling the position of the flight control surface <NUM> and reacting to the full surface hinge moment, while the adjacent, i.e. second EHSA <NUM> remains in damped mode. In the event of failure of the first EHSA <NUM>, the system switches the first EHSA <NUM> into the damped mode and the adjacent, or second EHSA <NUM>, switches into active mode. The system then operates as previously.

In the event that both EHSAs <NUM>, <NUM>, fail, the two actuators switch into the damped mode. This means that the surface <NUM> is no longer controlled in position and this in turn generates aerodynamic drag.

In addition to this, this electric system architecture (which is replicating the conventional hydraulic system architecture) leads to a very bulky EMA system which is sized to react to the full surface hinge moment and the drag generated by the motion of the adjacent actuator in damped mode. Such systems are twice as large as their equivalent EHSA and need to dissipate locally the heat generated (copper losses) by reacting external loads.

The new examples described herein and with reference to <FIG> allow the EMAs to introduce a third mode, which is an anti-extension or blocked mode into the EMA design. This third, anti-extension or blocked mode is controlled in use by the adjacent actuator.

The new examples described herein improve the remaining thermal management in case of an adjacent EMA failure, which will react to a surface full hinge moment. They also reduce aerodynamic drag in case of a dual EMA failure (such that there is no free float).

In contrast to this known arrangement, a new example of a new type of system <NUM> for controlling a flight surface <NUM> is shown in <FIG>. As can be seen in this figure, a first EMA <NUM> is provided which comprises an associated first Motor Drive Electronics (MDE) <NUM> and a first solenoid <NUM>. The system further comprises a second EMA <NUM> which comprises an associated second MDE <NUM> and a second solenoid <NUM>.

As can be seen in <FIG>, each of the first and second EMAs <NUM>, <NUM> are connected to the flight control surface <NUM>. The first and second EMAs <NUM>, <NUM> as well as their associated MDEs <NUM>, <NUM> are each connected to the flight control computers (FCCs) <NUM>. Usually there are several FCCs <NUM> in a primary control system and two adjacent actuators are controlled by a different FCC to avoid common mode failures. The FCCs may be considered to correspond to the "brain" of the system (i.e., the master), whereas the MDEs/actuators (EMAs) are the slaves in that they respond to the orders sent from the FCCs and report the EMA health status.

The first solenoid <NUM> of the first EMA <NUM> is further connected to the second MDE <NUM> of the second EMA <NUM> and the second solenoid <NUM> of the second EMA <NUM> is connected to the first MDE <NUM> of the first EMA <NUM>. Due to this arrangement the solenoid <NUM>, <NUM> of each EMA <NUM>, <NUM> can be activated by the adjacent EMA <NUM>, <NUM> (in this example, via the MDE of the adjacent EMA).

This new system is able to work in three modes, i.e. in <NUM>) an active/active mode, wherein both the EMAs <NUM>, <NUM> are in the active mode, <NUM>) an active/stand-by mode, wherein one of the EMAs <NUM>, <NUM> is in the active mode and the other is in the stand-by mode, or <NUM>) a blocked/blocked mode, wherein both the EMAs <NUM>, <NUM> are in the blocked mode. In some examples, the blocked mode can be replaced with an anti-extension mode if required (e.g. for an aileron application).

In the Active/Active mode, both EMAs <NUM>, <NUM> are electrically supplied by aircraft high and low power networks. Both EMAs <NUM>, <NUM> receive a signal from the FCCs to switch into the active mode (each MDE activates its own EMA solenoid and adjacent EMA solenoid). Both EMAs <NUM>, <NUM> receive the same position order from the FCCs to control the flight control surface position. The EMAs may exchange information in order to alleviate the force flight generated between the two actuators connected to the same surface (the force fight is usually generated by the control loop difference/error between the two channels through surface structural stiffness).

In the Active/Stand-by mode, at least one EMA <NUM>, <NUM> is electrically supplied by aircraft high and low power networks. The adjacent EMA <NUM>, <NUM> may or may not be electrically supplied by aircraft high and low power networks, that is, it can be alive and functioning normally, or failed, the same goes for its FCC. The EMA <NUM>, <NUM> which is electrically supplied also receives a signal from its FCC to switch into the active mode (the MDE activates its own EMA solenoid and adjacent EMA solenoid). The EMA <NUM>, <NUM> which is electrically supplied also receives a position order from its FCC to control the flight control surface position. The Adjacent EMA <NUM>, <NUM> which is still connected to the flight control surface is back driven by the active EMA <NUM>, <NUM>.

In the blocked/blocked mode, both EMAs may be, or may not be, electrically supplied by aircraft high and low power networks. Both EMAs may or may not receive a signal from FCCs to switch into the blocked mode (when not electrically energized, the solenoids switch naturally into the blocked mode). The flight control surface is blocked in a given position.

The functioning of this <NUM> mode EMA will now be described in detail. As mentioned above, the three modes in which each of the individual EMAs operate are Active, Stand-by or Blocked. In normal system operation, both of the first and second EMAs <NUM>, <NUM> are operating in the active mode, controlling the position of the flight control surface <NUM> and reacting to each half of the surface hinge moment (i.e. the system is in the active/active mode).

In the event of failure, for example, of the first EMA <NUM>, the adjacent, second EMA <NUM> (which is still operating normally in the active mode) is configured to unlock the failed, first EMA <NUM> by energizing the solenoid <NUM> of the first EMA <NUM>. The system is therefore now in an active/stand-by configuration. The remaining active EMA, i.e. the second EMA <NUM>, then controls the surface position and reacts electromechanically to the full surface hinge moment.

Both EMAs <NUM>, <NUM> may be positioned within a housing (not shown). In the event that the housing temperature reaches a specified upper limit, both the first and the second EMAs <NUM>, <NUM> can be switched into blocking mode (i.e. the blocked/blocked mode). The flight control surface <NUM> is then in a blocked position and the surface hinge moment is reacted mechanically by the first and second EMAs <NUM>, <NUM>.

The EMA that has not failed can then cool down and when the EMA housing temperature reaches a given lower value or threshold, the system can be reconfigured into the Active/stand-by arrangement.

In the event that either or both of the first and second EMAs <NUM>, <NUM> fail, the first and second actuators are switched into blocked mode, thereby avoiding surface free float and associated drag penalty.

The architecture of the new systems described herein and depicted in <FIG> reduces the size of the EMA for thin wing applications. The EMA system can be sized for only a percentage of the full hinge moment (higher than <NUM>%) and does not generate any damping in case of failure.

<FIG> shows the components of a current EMA design. The current EMA design comprises an actuator body <NUM>, having an attachment bearing <NUM> at a first longitudinal end and a roller bearing <NUM> at the opposite longitudinal end. The roller bearing <NUM> is connected to the actuator rod <NUM>, which in turn is connected to a linear position transducer <NUM>. A sealing system <NUM> is provided between the actuator rod <NUM> and the actuator body <NUM>. A motor stator <NUM> internal to the actuator body <NUM> and a motor rotor <NUM> provide torque to a ball or a roller screw nut <NUM> which interacts with balls or rollers <NUM> which are positioned externally to the actuator rod <NUM>. A linear position transducer <NUM> provides actuator rod <NUM> position to the actuator control electronic. A trust bearing <NUM> is provided externally to the ball or roller screw nut <NUM>. An angular position sensor <NUM> is provided to measure the angle of the rotor of the electric motor. An end stop <NUM> is provided to limit the movement of the actuator rod <NUM>, as well as an anti-rotation device <NUM> which prevents rotation of the actuator rod <NUM>. A ball bearing <NUM> is also provided around the actuator rod <NUM> to guide the motor rotor <NUM>.

<FIG> shows the inner workings of new EMA design that can be used in the system <NUM> shown in <FIG>, which has many of the same features as that shown in <FIG>, but additionally has a pawl <NUM>, a solenoid <NUM> and a ratchet wheel <NUM>. This allows the EMA to work in three modes with an anti-extension device as described above with reference to <FIG>. When the solenoid <NUM> is energized, it disengages the pawl <NUM> from the ratchet wheel <NUM> and thus enabling the ball screw or roller screw nut <NUM> to rotate and the actuator rod <NUM> to translate in both directions under external load application. When the solenoid <NUM> is de-energized, the pawl <NUM> engages into a teeth of the ratchet wheel <NUM> and prevents the rotation of the ball or roller screw nut <NUM> and the translation of the actuator rod in the extension direction.

Although the example shown here in <FIG> has a direct drive EMA architecture (i.e. there is no gearbox), this could be replaced by a geared drive EMA architecture, with a gearbox being positioned between the electric motor and the hall/roller screw.

The linear EMA could also/alternatively be replaced by a rotary EMA using a gearbox and an output lever connected to the rotary output of the gearbox.

Claim 1:
A system for controlling a flight control surface (<NUM>), wherein said system comprises:
a first electromechanical actuator "EMA" (<NUM>) and characterized by further comprising a second EMA (<NUM>), each of which are connected to said flight control surface (<NUM>);
and wherein each EMA (<NUM>, <NUM>) is configured to be arranged in, and switched between, three modes;
said three modes comprising:
an active mode, a stand-by mode and a blocked or anti-extension mode and
wherein said first EMA (<NUM>) comprises a first Motor Drive Electronics "MDE" (<NUM>) and a first solenoid (<NUM>), and wherein said second EMA (<NUM>) comprises a second MDE (<NUM>) and a second solenoid (<NUM>); T
wherein said second MDE (<NUM>) of said second EMA (<NUM>) is connected to said first solenoid (<NUM>) of said first EMA (<NUM>);
wherein said first MDE (<NUM>) of said first EMA (<NUM>) is connected to said second solenoid (<NUM>) of said second EMA (<NUM>);
and wherein the system is configured to be operable in and switchable between:
an active/active mode, wherein both said first and second EMAs (<NUM>, (<NUM>) are in the active mode;
an active/stand-by mode wherein the first EMA (<NUM>) is in the active mode and the second EMA (<NUM>) is in the stand-by mode; and
a blocked/blocked mode or anti-extension/anti-extension mode, wherein both EMAs (<NUM>, <NUM>) are in a blocked or anti-extension mode, and further wherein, in the event of failure of the first EMA (<NUM>), the second EMA (<NUM>) is configured to unlock the first EMA (<NUM>) by energizing the solenoid (<NUM>) of the first EMA (<NUM>), thereby switching said system into said active/standby mode.