Apparatus and method for controlling a control surface of a vehicle based on a load identified on the control surface

A method, apparatus, and computer program product are present for controlling a control surface. A load is identified on the control surface to form an identified load. A direction of movement of the control surface is identified from the identified load to form an identified movement. A brake associated with the control surface is engaged if the identified movement is away from a desired position for the control surface.

BACKGROUND INFORMATION

The present disclosure relates generally to aircraft and, in particular, to control systems for aircraft. Still more particularly, the present disclosure relates to a method and apparatus for controlling a control surface of an aircraft.

Flight control surfaces on an aircraft may be used to control the flight of an aircraft. Flight control surfaces may be used to adjust and control movement of an aircraft, such as flight attitude. With fixed-wing aircraft, control surfaces may be attached to an airframe on hinges and/or tracks. These control surfaces may move in a manner that deflects an airstream passing over the control surfaces. This redirection of the airstream may generate an unbalanced force to rotate the aircraft about an axis. This axis may be a vertical axis, a longitudinal axis, or a lateral axis. Movement around the vertical axis is referred to as yaw, movement around the longitudinal axis is referred to as bank or roll, and movement about the lateral axis is referred to as pitch.

In some situations, an actuator may not perform correctly to provide the desired movement. With this type of situation, redundant actuators may be present to provide movement of the control surface when the original actuator is unable to provide the desired movement.

This type of redundancy, however, may add to the weight of an aircraft. Further, by having additional redundant actuators for control surfaces, the expense to manufacture an aircraft also increases.

In these situations, the control surface may be moved to a predefined position. This operation is commonly implemented in hydraulic control actuators by means of a hydro-mechanical design commonly referred to as neutral lock or hole in the wall reversion mode.

Therefore, it would be desirable to have a system that possibly takes into account one or more of these issues as well as possibly other issues.

SUMMARY

In one advantageous embodiment, a method is present for controlling a control surface. A load is identified on the control surface to form an identified load. A direction of movement of the control surface is identified from the identified load to form an identified movement. A brake associated with the control surface is engaged if the identified movement is away from a desired position for the control surface.

In another advantageous embodiment, an apparatus comprises a control process and a data processing system capable of executing the control process. The control process is capable of identifying a load on the control surface to form an identified load. The control process is also capable of identifying a direction of movement of the control surface from the identified load to form an identified movement. Further, the control process is capable of engaging a brake associated with the control surface if the identified movement is away from a desired position for the control surface.

In yet another advantageous embodiment, a computer program product is present for controlling a control surface. The computer program product comprises a computer recordable storage medium and program code stored on the computer recordable storage medium. Program code is present for identifying a load on the control surface to form an identified load. Program code is also present for identifying a direction of movement of the control surface from the identified load to form an identified movement. Further, program code is present for engaging a brake associated with the control surface if the identified movement is away from a desired position for the control surface.

DETAILED DESCRIPTION

With reference now to the figures and, in particular, with reference now toFIG. 1, a diagram of a control surface control environment is depicted in accordance with an advantageous embodiment. Control surface control environment100may be implemented using vehicle102. In these examples, vehicle102may take various forms. For example, without limitation, vehicle102may be an aircraft, a surface ship, a train, a spacecraft, a submarine, an aircraft carrier, a pleasure boat, a bus, an automobile, or some other suitable vehicle.

Control surface system104is present within vehicle102and may be controlled to change the flow of air and/or liquid over different surfaces of vehicle102. Control surface system104may be controlled by actuator system106. Actuator system106may change the position of control surface system104in response to commands received from vehicle management system computer108.

In these examples, control surface system104contains control surface110. Actuator system106may include controller112and actuator114. Controller112may receive commands from vehicle management system computer108. In response to these commands, controller112may send signals to actuator114to move actuator114.

Position115of control surface110may be changed by actuator114under the control of controller112. In these examples, control surface110may take various forms. For example, when vehicle102takes the form of a fixed wing aircraft, control surface110may be, for example, without limitation, an aileron, an elevator, a rudder, an elevator trim, a rudder trim, a flap, a flaperon, and/or some other suitable control surface. Actuator114may be an electromechanical actuator, a hydraulic actuator, or some other suitable type of actuator capable of changing position115of control surface110.

Processes116may execute on vehicle management system computer108to control various systems, including actuator system106. Control laws118in processes116may be used to control actuator system106to provide appropriate commands to actuator114to change position115of control surface110. Position sensor120in actuator114may provide information to control laws118to identify position115of control surface110. Alternatively, position115may be measured directly from control surface110and/or by any means that provides an accurate identification of the true surface position of control surface110.

In the event that a failure occurs within actuator system106or somewhere between actuator system106and vehicle management system computer108, control process122in control laws118may be used to control position115of control surface110. For example, a failure may occur in actuator114. In some instances, commands sent by control laws118to actuator114may fail to reach actuator114.

The different advantageous embodiments recognize and take into account that redundant actuator control processes and actuators may be present to control control surface110. However, the different advantageous embodiments recognize and take into account that these additional components may add to the weight and expense of an aircraft.

Control process122, in these examples, may provide a coarser control for control surface110. Control process122may send commands123to control brake124. Brake124may be controlled in a manner that allows control surface110to be selectively moved based on load126applied to control surface110.

In some advantageous embodiments, instead of using control process122in control laws118, control process128in controller112may be used to control brake124.

In response to detecting a failure of actuator114to change position115to desired position138for control surface110, control process122may identify load126on control surface110. Load126may be identified using load sensor132, which is associated with control surface110.

In other advantageous embodiments, load126may be identified using surface load model134. Surface load model134may be a table, a database, and/or some other suitable data structure that is capable of identifying load126on control surface110based on inputs. These inputs may include, for example, without limitation, at least one of an angle of attack, a mach number, a surface position of the control surface, and/or some other suitable input. The output is an estimated load, which is load126in these examples.

Based on identifying load126, control process122is capable of identifying direction of movement136for control surface110. Direction of movement136may be the actual direction that control surface110moves and/or may be the possible direction that control surface110may move in response to load126. In other words, direction of movement136may not be the actual movement of the control surface, but the movement that load126can cause for control surface110.

Based on direction of movement136and desired position138for control surface110, brake124may be changed between engaged state140and disengaged state142. If control surface110has direction of movement136away from desired position138, control process122sends commands123to change brake124to engaged state140.

By engaging brake124and placing brake124in engaged state140, movement of control surface110away from desired position138may be halted. When in engaged state140, if control process122identifies load126as being capable of causing direction of movement136towards desired position138, control process122sends commands123to release brake124placing brake124in disengaged state142.

In disengaged state142, brake124remains in this state as long as direction of movement136is towards desired position138and/or in desired position138. In some advantageous embodiments, brake124may be engaged once control surface110reaches desired position138.

In these illustrative examples, brake124may be implemented in a number of different ways. For example, brake124may be implemented as part of actuator114. With this type of implementation, brake124may be a spring biased disc brake that may be electromagnetically energized and de-energized.

Further, brake124may be implemented as a separate device that may be located in a location in which brake124is capable of holding control surface110in position115and/or desired position138. Brake124may be a friction brake or any other suitable brake that is capable of stopping movement of control surface110in position115and/or desired position138. Brake124may be attached to the same component as actuator114to control movement if actuator114is incapable of moving control surface110.

In this manner, one or more of the different advantageous embodiments may be capable of positioning a control surface, such as control surface110, if actuator114is unable to move control surface110to desired position138. This capability may be provided to provide a backup that may require less complexity, expense, and/or weight as compared to current redundancy systems in place. Additionally, the different advantageous embodiments may prevent movement of control surface110away from and/or farther away from desired position138. Further, as desired position138changes, the different advantageous embodiments may be capable of achieving desired position138.

The illustration inFIG. 1is not meant to imply physical or architectural limitations to the manner in which control surface control environment100may be implemented. Other components in addition to, or in place of, the ones illustrated may be used in some advantageous embodiments. Further, in yet other advantageous embodiments, some components may be unnecessary.

For example, in some advantageous embodiments, other control surfaces, in addition to control surface110, may be controlled using brakes in addition to brake124. In still other advantageous embodiments, load sensor132may be unnecessary. In still other advantageous embodiments, control process128in controller112may be used to generate commands123to control brake124.

The illustration of control surface control environment100is not meant to imply physical or architectural limitations to the manner in which different advantageous embodiments may be implemented. Other components in addition to, or in place of, the ones illustrated may be implemented depending on the particular embodiment. Further, in some advantageous embodiments, some components may be unnecessary.

As another example, although control surface control environment100is implemented in vehicle102, some advantageous embodiments may be implemented in objects other than a vehicle. For example, control surface control environment100may be implemented in an air conditioning system to control various control surfaces such as, for example, louvers, valves, and/or other suitable control surfaces to control airflow.

In yet other advantageous embodiments, control surface control environment100may be implemented in a hydraulic system and/or refining plant to control the flow of liquids. As yet another example, control process122may be implemented as an application specific integrated circuit or as a combination of hardware and software.

With reference now toFIG. 2, a diagram of an aircraft is depicted in accordance with an advantageous embodiment. Aircraft200is an example of one environment in which control surface control environment100may be implemented. Aircraft200is only one example of an implementation for vehicle102inFIG. 1. In this illustrative example, aircraft200has wings202and204attached to body206. Aircraft200includes wing-mounted engine208, wing-mounted engine210, and tail212. Tail212has horizontal stabilizer214, horizontal stabilizer216, and vertical stabilizer218.

The advantageous embodiments may be implemented in one or more of the different control surfaces for aircraft200. In particular, these control surfaces may be trailing edge control surfaces. For example, the different advantageous embodiments may be implemented to control flap220on wing202and/or to control flap222on wing204. Further, aileron224on wing202and aileron226on wing204are examples of other trailing edge control surfaces that may be controlled using different advantageous embodiments. As yet additional examples, elevator228on horizontal stabilizer214, elevator230on horizontal stabilizer216, and rudder232on vertical stabilizer218are additional examples of trailing edge control surfaces that may be controlled using different advantageous embodiments.

Turning now toFIG. 3, a diagram of a data processing system is depicted in accordance with an illustrative embodiment. In this illustrative example, data processing system300may be used to implement a computer, a controller, and/or some other suitable device. Data processing system300includes communications fabric302, which provides communications between processor unit304, memory306, persistent storage308, communications unit310, and input/output (I/O) unit312. Data processing system300may be used to implement devices in control surface control environment100inFIG. 1and in aircraft200inFIG. 2. For example, data processing system300may be used to implement vehicle management system computer108and/or controller112inFIG. 1.

Memory306and persistent storage308are examples of storage devices. A storage device is any piece of hardware that is capable of storing information either on a temporary basis and/or a permanent basis. Memory306, in these examples, may be, for example, a random access memory or any other suitable volatile or non-volatile storage device. Persistent storage308may take various forms, depending on the particular implementation. For example, persistent storage308may contain one or more components or devices. For example, persistent storage308may be a hard drive, a flash memory, a rewritable optical disk, a rewritable magnetic tape, or some combination of the above. The media used by persistent storage308also may be removable. For example, a removable hard drive may be used for persistent storage308.

Communications unit310, in these examples, provides for communications with other data processing systems or devices. In these examples, communications unit310is a network interface card. Communications unit310may provide communications through the use of either or both physical and wireless communications links.

Input/output unit312allows for input and output of data with other devices that may be connected to data processing system300. For example, input/output unit312may provide a connection for user input through a keyboard, a mouse, and/or some other suitable input device. Input/output unit312also may include one or more of these devices. Further, input/output unit312may send output to a printer. When data processing system300takes the form of a controller, input/output unit312may receive information from and/or send commands to a device, such as a sensor, an actuator, and/or some other suitable device.

Instructions for the operating system and applications or programs are located on persistent storage308. These instructions may be loaded into memory306for execution by processor unit304. The processes of the different embodiments may be performed by processor unit304using computer implemented instructions, which may be located in a memory, such as memory306. These instructions are referred to as program code, computer usable program code, or computer readable program code that may be read and executed by a processor in processor unit304. The program code in the different embodiments may be embodied on different physical or tangible computer readable media, such as memory306or persistent storage308.

Program code316is located in a functional form on computer readable media318that is selectively removable and may be loaded onto or transferred to data processing system300for execution by processor unit304. In these examples, program code316may be program code for control process122and/or control process128inFIG. 1. Program code316and computer readable media318form computer program product320in these examples.

In one example, computer readable media318may be in a tangible form such as, for example, an optical or magnetic disc that is inserted or placed into a drive or other device that is part of persistent storage308for transfer onto a storage device, such as a hard drive that is part of persistent storage308. In a tangible form, computer readable media318also may take the form of a persistent storage, such as a hard drive, a thumb drive, or a flash memory that is connected to data processing system300. The tangible form of computer readable media318is also referred to as computer recordable storage media. In some instances, computer readable media318may not be removable.

Alternatively, program code316may be transferred to data processing system300from computer readable media318through a communications link to communications unit310and/or through a connection to input/output unit312. The communications link and/or the connection may be physical or wireless in the illustrative examples. The computer readable media also may take the form of non-tangible media, such as communications links or wireless transmissions containing the program code.

In some illustrative embodiments, program code316may be downloaded over a network to persistent storage308from another device or data processing system for use within data processing system300. For instance, program code stored in a computer readable storage medium in a server data processing system may be downloaded over a network from the server to data processing system300. The data processing system providing program code316may be a server computer, a client computer, or some other device capable of storing and transmitting program code316.

The different embodiments may be implemented using any hardware device or system capable of executing program code. As one example, the data processing system may include organic components integrated with inorganic components and/or may be comprised entirely of organic components excluding a human being. For example, a storage device may be comprised of an organic semiconductor.

As another example, a storage device in data processing system300is any hardware apparatus that may store data. Memory306, persistent storage308, and computer readable media318are examples of storage devices in a tangible form.

With reference now toFIG. 4, a logic diagram for a control process is depicted in accordance with an advantageous embodiment. In this example, logic400is an example of logic that may be implemented in a software and/or hardware component. Logic400may be implemented as program code316inFIG. 3in these illustrative examples. For example, logic400may be implemented in control process122executing as part of control laws118inFIG. 1.

As illustrated, logic400comprises dead zone unit402, subtractor404, product unit406, gain unit408, transfer function410, saturation unit412, and sign unit414. Input into logic400includes load416, desired position418, and actual position420. The output of logic400is brake command422. Brake command422is an example of a command within commands123inFIG. 1. Brake command422may be a command to either engage or disengage a brake, such as brake124inFIG. 1.

The brake command can come from a single data processing system, multiple data processing systems, or vehicle management system computer108inFIG. 1as redundancy requirements of the controlled vehicle dictate. The choice to engage or disengage the brake by default in loss of power to multiple computers may be determined by the air vehicle designers based on the severity of failure modes that may occur in the brake system.

Load416may be an estimated load generated from a load sensor and/or a surface load model. Desired position418is the desired position for the control surface. Actual position420is the actual position of the control surface.

In this illustrative example, dead zone unit402produces a non-zero output when load416is greater than a minimum load needed to back drive an actuator associated with the control surface. In other words, dead zone unit402only generates a value when load416is greater than the force needed to overcome the friction to move the actuator. When the actuator is not powered, friction is present, which may prevent the actuator from moving unless a sufficient amount of load is present on the control surface. In other words, the control surface will not move unless load416is greater than the force needed to move the actuator.

Subtractor404subtracts desired position418from actual position420. Dead zone unit402generates signal424, which may be, for example, a monotonically increasing positive number or monotonically decreasing negative number. Alternatively, the output of dead zone unit402may be zero or a fixed positive or negative value. A non-zero value is present when load416is greater than the force needed to move the actuator. Subtractor404generates error426. Optionally, dead zone unit402may be applied to error426if it is desired or acceptable to the vehicle control laws to allow a small amount of error to be considered equivalent to zero error. In this manner, the brake may be engaged from a disengaged state when the position is within an acceptable error of the desired surface position.

Error426is multiplied by signal424at product unit406. Error428is generated by product unit406. Error428is zero if signal424or error426is zero. Otherwise, the sign of error428provides the direction the surface is expected to move based on the applied load and the actual surface position versus the desired surface position. In these illustrative examples, the output of product unit406is a positive value if the load is expected to push or move the surface away from the desired position.

Different sign conventions may be used, in the different advantageous embodiments, so long as the logic is configured to produce a signal to engage the brake when the load is expected to push or move the surface away from the desired position and release the brake when the surface is to be moved towards the desired position.

Error428is multiplied by gain unit408to generate modified error430. Gain unit408may be used to set the sensitivity of logic400to the inputs. Modified error430is sent into transfer function410to generate filtered error432.

Transfer function410eliminates unwanted noise in the input signals in this example. Transfer function410may be implemented using any type of mathematical filter that eliminates real or mathematical noise from the various signals and does not introduce unacceptable time delay and/or reduced sensitivity to the control signals. Saturation unit412receives filtered error432and limits filtered error432to range from zero to one. The output of saturation unit412is limited signal434.

Limited signal434is sent to sign unit414, which generates a logic zero or a logic one for brake command422. In these examples, a logic one for brake command422engages the brake, while a logic zero for brake command422disengages the brake. In other advantageous embodiments, it may be desirable to engage the brake with a logic zero or logic one and disengage the brake on negative value.

To implement this feature, saturation unit412may be changed to limit range from negative to positive one. In another embodiment, a zero output may be considered the same as logic one and a negative output considered logic zero if it is desired to use a logic one to engage the brake, and logic zero to disengage the brake.

With reference now toFIG. 5, a flowchart of a process for controlling a control surface is depicted in accordance with an advantageous embodiment. The process illustrated inFIG. 5may be implemented in a control surface control environment such as, for example, control surface control environment100inFIG. 1. The process illustrated in this example may be implemented as a software component and/or hardware component. As a software component, the process may be implemented in a component such as, for example, control process122inFIG. 1.

The process begins by determining whether an actuator failure is present (operation500). If an actuator failure is not present, the process continues to return to operation500. If an actuator failure is present preventing proper control of the actuator, the process identifies a load on the control surface (operation502). The process identifies a direction of movement of the control surface from the load (operation504).

The load identified in operation502may be a load as measured from a load sensor associated with the control surface. Alternatively, the load identified in operation502may be an estimated load using a surface load model for the control surface.

A determination is then made as to whether the direction of movement is away from a desired position (operation506). If the direction of movement is away from the desired position, the brake is engaged (operation508), with the process then returning to operation502as described above. If the direction of movement is not away from the desired position in operation506, the brake is disengaged (operation510), with the process then returning to operation502.

Thus, the different advantageous embodiments provide a method for controlling a control surface. The different advantageous embodiments may be used in situations in which a primary control for an actuator fails to control the control surface as desired. The different advantageous embodiments selectively engage and disengage a brake associated with the control surface based on the direction of movement of the control surface. If the direction of movement of the control surface caused by the load is towards the desired position, the brake remains in a disengaged position. If the direction of movement of the control surface is away from the desired position, the brake is engaged.

Thus, at least some of the different advantageous embodiments may provide additional redundancy for actuator control systems. Further, when weight and cost is a factor, this type of system may be used in place of additional actuator redundancies. This type of redundancy system may be desirable for unmanned vehicles and/or as additional redundancies for actuator control systems.