Patent Publication Number: US-10780977-B2

Title: Aerodynamic control surface movement monitoring system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of an earlier filing date from U.S. Provisional Application Ser. No. 62/296,459 filed Feb. 17, 2016, the entire disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Modern aircraft often use a variety of high lift leading and trailing edge devices to improve high angle of attack performance during various phases of flight, for example, takeoff and landing. One such device is a trailing edge flap. Current trailing edge flaps generally have a stowed position in which the flap forms a portion of a trailing edge of a wing, and one or more deployed positions in which the flap extends forward and down to increase the camber and/or plan form area of the wing. The stowed position is generally associated with low drag at low angles of attack and can be suitable for cruise and other low angle of attack operations. The extended position(s) is/are generally associated with improved air flow characteristics over the aircraft&#39;s wing at higher angles of attack. 
     Proper extension and retraction of such flaps is important for control of the aircraft during different maneuvers. As such, it is conventional to include multiple feedback systems to monitor flap deployment and retraction. For example, sensor systems may monitor absolute flap position, flap skew position and detection of a jam or disconnected actuator. 
     In general, such systems can include a control unit that causes a main drive unit to produce rotation of a shaft. This rotation can then be converted to flap extension in known manners such as by use of a ball screw. In such systems, each flap typically includes two actuators, one for each side of the flap. If the two actuators do not extend two sides of the flap the same amount, the flap experiences skew. Further, in some cases, the actuator may not be working effectively and determination of such, as well as skew, may be beneficial. 
     BRIEF DESCRIPTION 
     According to an embodiment, an actuator system for controlling a flight surface of an aircraft is disclosed. The system includes a first actuator having a first actuator input and a first linear translation element that moves based on rotational motion received at the first actuator input and a first sensor coupled to the first linear translation element that generates a first output based on a displacement of the first linear translation element. The system also includes a second actuator having a second actuator input and a second linear translation element that moves based on rotational motion received at the second actuator input and a second sensor coupled to the second linear translation element that generates a second output based on a displacement of the second linear translation element. The system further includes a control unit that receives the first and second outputs and determines if an error condition exists for the system based on first and second output. 
     In the actuator system of any prior embodiment the flight surface can be a flap. 
     In the actuator system of any prior embodiment the error condition is a flap skew condition and is determined when the signals from the first and second sensors do not match. 
     In the actuator system of any prior embodiment, the system can further include: a drive shaft coupled to the first input and the second input; a drive unit that causes the drive shaft to rotate based on signals received from the control unit. 
     In the actuator system of any prior embodiment, the error can be an actuator malfunction and is determined when a drive shaft&#39;s rotation is not proportional to one of the first or second outputs. 
     In the actuator system of any prior embodiment, the first sensor can be is one of: a rotatory variable transformer, a liner variable transformer, a synchro/resolver or an encoder. 
     In the actuator system of any prior embodiment, the first linear translation element can be a ball screw. 
     In the actuator system of any prior embodiment, the first linear translation element can be a hydraulic actuator. 
     According to one embodiment, a method of controlling and monitoring an aircraft control surface is disclosed. The method includes: sending a control signal from a control unit to a drive to cause a drive shaft to rotate; generating a first output with a first sensor coupled to a first linear translation element of a first actuator, the first output being based an amount of linear motion of the first linear translation element; generating a second output with a second sensor coupled to a second linear translation element of a second actuator, the second output being based an amount of linear motion of the first linear translation element; comparing an expected sensor outputs to the first and second outputs with the control to determine if an error condition exists; and generating an error indication when the error condition exists. 
     In the method of any prior embodiment, the flight surface can be a flap. 
     In the method of any prior embodiment, the error condition can be a flap skew condition and is determined when the signals from the first and second sensors do not match. 
     In the method of any prior embodiment, the error can be an actuator malfunction and is determined when a drive shaft rotations is not proportion to one of the first or second outputs. 
     In the method of any prior embodiment, wherein the first sensor can be one of: a rotatory variable transformer, a liner variable transformer, a synchro/resolver or an encoder. 
     In the method of any prior embodiment, the first linear translation element can be a ball screw. 
     In the method of any prior embodiment, the first linear translation element can be a hydraulic actuator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter which is regarded as the present disclosure is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the present disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a perspective view of an aircraft that includes moveable control surfaces; 
         FIG. 2  is schematic of an actuator control system that includes one or more actuators having a positional sensor attached thereto; and 
         FIG. 3  shows a simplified example of an actuator according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
     Disclosed herein is an aerodynamic control surface movement monitoring system (also referred to as an actuator system herein) that provides feedback for an aircraft flap or slat or other movable aerodynamic control surface. The disclosed system provides a single solution for: a) positional location (i.e. feedback of the control surface position), b) skew position feedback of the control surface, and c) failure detection for a jam or failure of a portion of an actuation system configured to move the aerodynamic control surface. The system disclosed, by combining multiple functions, allows part count reduction, weight reduction and reliability improvement compared to conventional systems. 
     In one embodiment, a single or dual channel synchro/resolver or rotary variable differential transformer (RVDT) may be utilized as the sensor. Of course, other types of sensors such as a linear variable transformer (LVT) may also be used. The sensor is mechanically linked to an output portion of the actuator. A ball nut is an example of such an output portion. As the actuator delivers mechanical motion to the aerodynamic control surface (e.g., slat), the sensor provides a change in its electrical output that is proportional to distance moved by the output of the actuator and, consequently, the controlled surface. Detection of a jam or disconnected actuator is established when the sensor output is not proportional to the actuators input. As will be understood, the input can be determined by a control system that drives an input shaft as more fully described below. 
     The system may include two or more of the actuator/sensor combinations for each control surface. In one embodiment, a measurement of travel distance of the output of an actuator is used to measure control surface position and/or skew. 
       FIG. 1  illustrates an example of a commercial aircraft  10  having aircraft engines  20  that may embody aspects of the teachings of this disclosure. The aircraft  10  includes two wings  22  that each includes one or more slats  24  and one or more flaps  26 . The term “control surface” used herein can refer to either a slat or a flap. 
       FIG. 2  illustrates, generally, a system  100  that can control and monitor the location of one or more control surfaces of aircraft. As illustrated, the control surfaces are flaps  26 . In particular, 2 flaps  26   a ,  26   n  are illustrated but any number of flaps could be controlled and monitored by the system  100 . Further, while flaps  26  are illustrated, the same teachings herein can also applied to slats  24  shown in  FIG. 1 . 
     The system includes a controller  102 . The controller  102  is configured to issue control commands to a drive unit  104 . The commands can include commands to cause the drive unit  104  to rotate a drive shaft  105  in order to move one or more of the flaps  26  in either direction in or out as generally indicated by arrow A. To convert the rotary motion of the drive shaft  105  into linear motion to move the flaps  26   s , one or more actuator units  106   a  . . .  106   n  are provided, with each flap or other control surface having its own actuator unit  106 . 
     Each actuator unit  106  includes two actuators. For example, a first actuator unit  106   a  includes first and second actuators  200 ,  202 . The first actuator  200  includes an actuator drive unit  204  and a linear translation element  208 . The actuator drive unit  204  receives rotatory motion from the drive shaft  105  and causes the linear translation element  208  to move linearly in the direction shown generally by arrow A. Similarly, the second actuator  202  includes an actuator drive unit  206  and a linear translation element  210 . The actuator drive unit  206  also receives rotatory motion from the drive shaft  105  and causes the linear translation element  210  to move linearly in the direction shown generally by arrow A. In one embodiment, the linear translation units  208 ,  210  are ball screws. In another, they may be hydraulic drive shafts. 
     Each actuator  202 ,  202  includes a sensor  212 ,  214  coupled thereto. The sensors measure a linear displacement of the linear translation elements  208 ,  210 , respectively. The sensors could be any type of suitable sensor including a resolver, an LVT or an RVDT. 
       FIG. 3  illustrates a simplified version of actuator  300  that may be any actuator shown in  FIG. 2 . The actuator  300  can be connected to a drive shaft  105 . The drive shaft can be controlled as described above. Rotation of the drive shaft causes the linear translator  304  to move in the direction shown by arrow B in a known manner. The linear translator  304  is illustrated as a ball screw but that is not required. 
     The actuator  300  includes a sensor  308 . The illustrated sensor  308  is an RVDT that includes a rotational input  310  that contacts and rotates with gear  306  or other connection mechanism that rotates as the linear translator  304  rotates. In this manner, the linear motion of the linear translator can be measured. As illustrated, the sensor  308  includes two sensor units but only one is required. The second unit can be provided for redundancy. 
     Referring back now to  FIG. 2 , it shall be understood that each of the actuators  200 ,  202  could be the same or similar to that shown in  FIG. 3  and, as such, the sensors  212 ,  214  or each actuator  200 ,  202  can measure the linear translation of the translating elements  208 ,  210 . The output of the sensors is a voltage or other electrical measurement (e.g. current) and can be provided to the controller. 
     As stated above, the controller  102  issues commands to cause the drive unit  104  to rotate shaft  105 . The rotation causes linear motion of the linear translating elements  208 ,  210 . The amount of translation (e.g., the voltage output by the sensors) should be proportion to the amount of rotation of the shaft  105  in a properly operating actuator. Thus, the controller need only compare the amount of expected sensor output for a given drive unit  104  command signal to determine if either of the actuators  200 ,  202  is not operating properly. 
     If the outputs of both sensors  204 ,  206  fail to match the expected positions based on the actuator inputs then the system  100  (e.g., controller  102 ) determines that a jam or other actuator malfunction has occurred If the output of the two sensors does not match each other, then the controller attributes it to a skew condition. Additionally, the output of the two sensors provides a positional location information of the control surface  26 . 
     Skew and actuator malfunction can generally be referred to as “error conditions” herein. These error conditions can be determined by comparisons to the sensor outputs and what is expected based on what the control unit instructs to the drive unit. For instance, the control unit  102  can instruct the drive unit  104  move the flaps to a fully extended position. This could mean that the drive unit  104  is to rotate the drive shaft  105   10  rotations. These to rotations should cause a proportional linear translation element ( 208 ,  210 ) motion which is measured by the sensors  212 ,  214 . If they do not, an actuator jam or other failure could be determined to have existed. In such a case, the control unit  102  may generate an alarm that could be provided on a screen or other output device to an operator of the aircraft. Further, when the signals received from the sensors do not match, a flap  26  or other control surface skew condition may be determined and an alert as described above generated. 
     While the present disclosure has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the present disclosure is not limited to such disclosed embodiments. Rather, the present disclosure can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the present disclosure. Additionally, while various embodiments of the present disclosure have been described, it is to be understood that aspects of the present disclosure may include only some of the described embodiments. Accordingly, the present disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.