Patent Description:
Actuators in aircraft secondary control mechanisms have conventionally been hydraulic/mechanical system. However, recent advances have resulted in the use of electro-mechanical actuators (EMA) instead of hydraulic-based systems. In many instances the operation of the electro-mechanical actuators should be synchronized such that common control surfaces operated by a plurality of EMA's are not subjected to uneven loading, and such that corresponding control surfaces on each wing are operated at the same time and rate so as to not adversely affect the operation of the aircraft. Although synchronization approaches have been developed, improvements are desired.

In <CIT> there is disclosed an actuator control system as it is defined in the pre-characterizing portion of claim <NUM>. A system for controlling one or more flaps on an aircraft also is described in <CIT>.

The present invention is an actuator control system as it is defined in claim <NUM> and a method for synchronizing a plurality of electro-mechanical actuators as it is defined in claim <NUM>. The actuator control system includes a plurality of electro-mechanical actuators for operating one or more end effectors, and a plurality of position sensors associated with the plurality of electro-mechanical actuators, each of the plurality of positions sensors providing an output indicating an actual position value, and a control system. The control system is configured to receive an activation command signal and the position sensor outputs, and send a speed command for each of the plurality of electro-mechanical actuators. In accordance with the present invention the control system further is configured to adjust the speed command of each of the plurality of electro-mechanical actuators using a common reference parameter to synchronize movement of the plurality of electro-mechanical actuators together, wherein the common reference parameter is a virtual position value generated from a virtual actuator system.

In some examples, the virtual actuator controller utilizes a nominal actuator load value to generate the virtual position value over time.

In some examples, the common reference parameter is independent from the outputs of the plurality of position sensors.

In some examples, the plurality of electro-mechanical actuators are linear acting actuators.

In some examples, the control system includes an EMA controller for each electro-mechanical actuator that receives the position sensor output and sends the speed command.

In some examples, the control system includes a virtual EMA controller that calculates the common reference parameter.

In some examples, the control system includes a synchronization controller for each electro-mechanical actuator, the synchronization controller referencing the virtual EMA controller and sending a speed command adjustment parameter to the to the EMA controller.

In some examples, the synchronization controllers are identically configured and have adjustable control parameters.

The method for synchronizing a plurality of electro-mechanical actuators comprises the steps of receiving an actuator position demand, sending a speed command to each of the plurality of electro-mechanical actuators, receiving outputs from positions sensors associated with the plurality of electro-mechanical actuators, and adjusting the speed command of each of the plurality of electro-mechanical actuators using a common reference parameter to synchronize movement of the plurality of electro-mechanical actuators together, wherein the common reference parameter is a virtual position value generated from a virtual actuator controller.

In some examples, the sending and receiving steps are performed at an EMA controller provided for each electro-mechanical actuator.

In some examples, a virtual EMA controller calculates the common reference parameter , wherein a synchronization controller is provided for each electro-mechanical actuator and references the virtual EMA controller and sends a speed command adjustment parameter to the to the EMA controller, wherein the synchronization controllers are identical to each other.

Non-limiting and non-exhaustive embodiments are described with reference to the following figures, which are not necessarily drawn to scale, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified.

Referring to <FIG>, a schematic representation of an example aircraft <NUM> is presented. In general terms, the aircraft <NUM> includes a fuselage <NUM>, left and right wings <NUM>, <NUM>, a vertical stabilizer <NUM>, and left and right horizontal stabilizers <NUM>, <NUM>. The aircraft <NUM> is also provided with a number of primary flight control surfaces for operating the aircraft <NUM> during flight. Examples of such primary flight control surfaces are ailerons 14a, 16a and spoilers 14b, 16b associated with the left and right wings <NUM>, <NUM>, a rudder 18a associated with the vertical stabilizer <NUM>, and elevators 20a, 22a associated with the left and right horizontal stabilizers <NUM>, <NUM>. The aircraft <NUM> is also shown as being provided with jet engines <NUM>, <NUM> respectively associated with the left and right wings <NUM>, <NUM>. The aircraft <NUM> is also provided with a number of secondary control surfaces <NUM> which are generally used during take-off and landing procedures. Examples of such secondary control surfaces <NUM> are slats <NUM> (102a - 102d) and flaps <NUM> (106a - 106c) associated with the left wing <NUM>, slats <NUM> (104a - 104d) and flaps <NUM> (108a - 108c) associated with the right wing <NUM>, and thrust reversers <NUM> (110a, 110b), <NUM> (112a, 112b) respectively associated with the left and right engines <NUM>, <NUM>.

In one example use of the secondary control surfaces, the slats <NUM>, <NUM> and flaps <NUM>, <NUM> can be extended during takeoff to increase the overall size and lift of the wings <NUM>, <NUM>. In the extended position, the slats <NUM>, <NUM> and flaps <NUM>, <NUM> greatly increase the lift generated by the wings <NUM>, <NUM> which in turn enables the aircraft <NUM> to take off more capably and under heavier loads. When takeoff is complete and the aircraft <NUM> enters a cruising phase, the slats <NUM>, <NUM> and flaps <NUM>, <NUM> can be retracted to reduce drag on the wings <NUM>, <NUM> and therefore allow for more efficient operation. The slats <NUM>, <NUM> and/or flaps <NUM>, <NUM> can also be used during the landing procedure to reduce the required distance and speed to safely land the aircraft <NUM>. In one aspect, the slats <NUM>, <NUM> and flaps <NUM>, <NUM> can be characterized as being high-lift devices.

In another example use of the secondary control surfaces, the thrust reversers <NUM>, <NUM> can be activated into an extended position to temporarily divert the thrust of the engines <NUM>, <NUM>. By activating the thrust reversers <NUM>, <NUM>, the diverted thrust acts against the forward direction of the aircraft <NUM> to provide deceleration just after touch-down such that the diverted thrust acts against the forward travel of the aircraft. The incorporation of thrust reversers <NUM>, <NUM> therefore enables the aircraft <NUM> to land over a shorter distance and reduces the wear on the brakes of the aircraft <NUM>. In one aspect, the thrust reversers <NUM>, <NUM> can be characterized as forming part of a thrust reverser actuation system (TRAS).

With operations of the type described above involving secondary control surfaces, for safe operation of the aircraft <NUM>, it is necessary for the actuators controlling the secondary control surfaces associated with the left wing <NUM> to operate simultaneously with the actuators controlling the counterpart secondary control surfaces associated with the right wing <NUM> such that undesired forces are not generated on the aircraft <NUM> which may cause the aircraft to roll and/or yaw in an unexpected and potentially unsafe manner. Additionally, where multiple actuators are used to operate a single secondary control surface, it is also necessary for the actuators to operate simultaneously to avoid imparting unnecessary stresses onto the component defining the secondary control surface.

Although one example of an aircraft <NUM> is presented with three examples of secondary control surfaces <NUM> (e.g., slats <NUM>/<NUM>, flaps <NUM>/<NUM>, thrust reversers <NUM>/<NUM>), many other configurations of the aircraft <NUM> and secondary control surfaces <NUM> are possible without departing from the concepts presented herein.

Referring to <FIG> and <FIG>, schematics are presented showing a control surface actuation system usable to operate control surfaces <NUM> of the aircraft <NUM>, including but not limited to, the above-described secondary control surfaces <NUM>. As shown at <FIG>, a plurality of control surfaces <NUM> (100a - 100d) are presented, wherein each of the control surfaces <NUM> is driven by a single actuator <NUM>. As shown at <FIG>, a plurality of control surfaces <NUM> (100a - 100b) are presented, wherein each of the control surfaces <NUM> is driven by a plurality of actuators <NUM>. As shown at <FIG>, a plurality of control surfaces <NUM> (100a - 100d) are presented, wherein some of the control surfaces <NUM> (100a, 100b) are driven by a single actuator <NUM> and some of the control surfaces <NUM> (100c, 100d) are driven by a plurality of actuators <NUM>. Although <FIG> and <FIG> shows two actuators <NUM> driving some of the control surfaces <NUM>, more actuators <NUM> can be provided, for example, three, four, six, eight, or more actuators <NUM>.

In one aspect, the actuators <NUM> drive the control surfaces <NUM> by operating a member <NUM> operably connected to the control surfaces <NUM>. Each actuator <NUM> is shown as being an electro-mechanical actuator <NUM> driven by a motor <NUM>. The actuator <NUM> can be, for example, a linear acting actuator with a linear screw driven by the motor <NUM>. In some examples, the member <NUM> is operably connected to the actuator <NUM> via a gear set, such as a planetary gear set. In some examples, the member <NUM> is a part of the actuator <NUM>, such as a shaft of the actuator <NUM>. The control surfaces 100a - 100d of <FIG> and the control surfaces 100a - 100b of <FIG> can correspond to any of the control surfaces <NUM>, <NUM>, <NUM>, <NUM> shown in <FIG>. Although four control surfaces <NUM> are shown at <FIG> and two control surfaces <NUM> are shown at <FIG>, the actuation systems of <FIG> and <FIG> can include any number of control surfaces <NUM> and corresponding actuators <NUM>. For example, an actuation system associated with the aircraft slats <NUM>, <NUM> would include eight control surfaces (102a - 102d, 104a - 104d) and at least eight actuators <NUM>. Where each of the control surfaces in such an arrangement are driven by a single actuator <NUM>, the arrangement of <FIG> would be applicable. Where multiple actuators <NUM> are used to drive each control surface, the arrangement of <FIG> would be applicable. As mentioned above, an arrangement wherein some of the control surfaces <NUM> are driven by different numbers of actuators <NUM> is also possible. For example, an arrangement could exist where the flaps 106a, 106c, 108a, 108c could be driven by a single actuator <NUM> and the flaps 106b, 108b are driven by multiple actuators <NUM>.

With continued reference to <FIG>, <FIG>, and <FIG>, the actuation system can further include control system <NUM> including one or more programmable controllers, e.g. processor, microprocessor, field programmable gate array (FPGA) typical of an avionics control system. In one aspect, the control system <NUM> includes an EMA controller <NUM> for controlling each actuator <NUM>. Multiple actuation systems and control systems <NUM> can be provided in a system. For example, for the example disclosed aircraft <NUM>, an actuation and control system <NUM> could be provided to operate the slats <NUM> (102a - 102d), <NUM> (104a - 104d), an actuation and control system <NUM> could be provided to operate the flaps <NUM> (106a - 106c), <NUM> (108a - 108c), and an actuation and control system <NUM> could be provided to operate the thrust reversers <NUM> (110a - 110b), <NUM> (112a - 112b). In one aspect, each control system <NUM> is configured to receive a user command signal to position the associated control surfaces <NUM>. The user command signal can be received centrally and distributed to the EMA controllers of the control system <NUM> or can be received directly at each EMA controller. In some examples, the user command signal can be a signal activated by a pilot of the aircraft <NUM> via a user interface (e.g., selector knob, switch, GUI, etc.). An automatic command signal can also be provided where the command signal is generated automatically by another part of the control system. A user command signal and an automatic command signal can be generically referred to as an activation command signal.

Each EMA controller <NUM> is configured to send a speed command signal to the motor <NUM> and to receive an output from a position sensor <NUM> associated with the actuator <NUM>. As the actuator <NUM> is mechanically coupled to the control surface <NUM>, a simple calculation can be used to translate the output of each of the position sensors <NUM> to the angular position of the control surface <NUM>. This position can be used as a reference point for further action, for example, deactivating the actuator <NUM> once a predetermined angle or position has been reached. Other reference points based on the position sensor outputs can be used as well for certain calculations, for example the position of the actuator <NUM>.

As mentioned previously, it is advantageous to synchronize the movement of control surfaces <NUM> to every extent possible. Thus, the outputs of the EMA controllers <NUM> should be coordinated to accomplish this objective. In one aspect, even after receiving the same speed command signal, actuators <NUM> can move more quickly or slowly relative to each other, either due to uneven external forces on the control surfaces <NUM>, or other internal or external forces. Accordingly, the output of one EMA controller <NUM> may need to be different from another EMA controller <NUM> in order to achieve the desired end result of the corresponding control surfaces moving simultaneously in a synchronized fashion. To accomplish this synchronization objective, a synchronization controller <NUM> is provided for each EMA controller <NUM> where each of the synchronization controllers <NUM> reference a common virtual EMA controller <NUM>. In some examples, the synchronization controllers <NUM> are identically configured but have individually adjustable control parameters (e.g., controller gains) that can be set as required by the associated actuator <NUM> and EMA controller <NUM>.

In one aspect, the virtual EMA controller <NUM> includes the same logic as the EMA controllers <NUM>, but incorporates a model function using a virtual actuator working against a nominal load. Using such an approach, the virtual EMA controller <NUM> is able to continuously calculate a virtual position value over the time period beginning from when the virtual actuator is activated to when the virtual actuator reaches its final position. In one aspect, each synchronization controller <NUM> receives the virtual position value from the virtual EMA controller <NUM> and also receives an actual position value from the associated EMA controller <NUM>. The synchronization controller <NUM> can then perform a comparison between the two values such that an angle error value can be calculated. Based on this comparison, each synchronization controller <NUM> provides an output to the associated EMA controller <NUM> to adjust the speed command to the actuator <NUM> to match the virtual position value, thereby minimizing the angle error value to the extent possible. In an illustrative example, an actuation and control system can include three EMA controllers <NUM>, wherein the initial speed command signal is <NUM>,<NUM> rpm, wherein the synchronization controllers <NUM> increase the speed command signal for one EMA controller <NUM> to <NUM>,<NUM>, decrease the speed command signal for another EMA controller <NUM> to <NUM>,<NUM>, and does not change the speed command signal for the third EMA controller in order to achieve synchronized movement of the associated control surfaces <NUM>.

In one example, the speed command signal is adjusted to ensure that a maximum angle error value is not exceed. By synchronizing each of the EMA controllers <NUM> to the virtual EMA controllers <NUM>, the EMA controllers <NUM> are synchronized together as a result. Where the control surface <NUM> is used as the common reference component for the virtual and actual position values, a maximum angle error value can be chosen that is equal to one half of the acceptable angle error between any two control surfaces controlled by the EMA controllers <NUM>. Using such an approach, the maximum angle error between any two control surfaces will necessarily fall within the acceptable angle error as two values less than or equal to one half will always sum to be one or less.

Referring to <FIG>, an example operation <NUM> of the control system <NUM>, including the EMA controllers <NUM>, the synchronization controller <NUM>, and the virtual EMA controller <NUM>, is presented. In an initial step <NUM>, the control system <NUM> receives a user command signal relating to a group of end effectors, for example secondary control surfaces <NUM>. Other types of end effectors are also possible, for example, primary flight control surfaces or any other type of mechanical components for which synchronized movement is desired. As related above, the user command signal can be generated by the pilot of the aircraft. However, step <NUM> can alternatively include an automatically generated command signal received from another control system of the aircraft <NUM>. In response to the user command signal, each of the EMA controllers <NUM> sends a speed command signal to the associated actuator <NUM> to move the control surface <NUM> to a desired position at a step <NUM>. The EMA controllers <NUM> receive outputs from the position sensors <NUM> associated with the actuators <NUM> at a step <NUM> and, based on the position sensor outputs, determine an actual position value at a step <NUM>. In a step <NUM>, a virtual position value is calculated at the virtual EMA controller <NUM>. In a step <NUM>, the speed command for each of the actuators <NUM> is adjusted such that the actual position value is synchronized to match the virtual position value, for example such that the difference between the actual and virtual position values to within a predefined maximum angle error value.

Claim 1:
An actuator control system comprising:
(a) a plurality of electro-mechanical actuators (<NUM>) for operating one or more end effectors;
(b) a plurality of position sensors (<NUM>) associated with the plurality of electro-mechanical actuators (<NUM>), each of the plurality of position sensors providing an output indicating an actual position value; and
(c) a control system (<NUM>) configured to receive an activation command signal and the position sensor outputs, and send a speed command for each of the plurality of electro-mechanical actuators (<NUM>);
characterized in that the control system (<NUM>) further is configured to:
adjust the speed command of each of the plurality of electro-mechanical actuators (<NUM>) using a common reference parameter to synchronize movement of the plurality of electro-mechanical actuators together, wherein the common reference parameter is a virtual position value generated from a virtual actuator controller.