Patent Publication Number: US-10323999-B2

Title: Variable load and load vector application system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of, and claims priority under 35 U.S.C. § 119(e) to, previously filed application U.S. Ser. No. 15/073,260, filed Mar. 17, 2016. 
    
    
     FIELD 
     This disclosure relates generally to structural testing and more particularly to load testing in aircraft components. 
     BACKGROUND 
     Components used in transportation vehicles must be tested to ensure that their design and construction are safe for operation in their expected operating environment. This often involves applying physical loads to structures that are well above the expected loads in actual use. During testing of structures that have limited movement, a load can be applied at a desired angle, such as normal to a surface. Even if the surface angle changes slightly during testing, the change in angle of the load may be ignored. Some larger changes in position of the article under test may be handled by moving the load source farther from the unit under test to minimize the angular change of the point load. However, testing structural components that are actively moved during operation, such as wing flaps and spoilers, present a problem for maintaining a correct load angle during testing. 
     SUMMARY 
     In an aspect of the disclosure, a method of providing a load to an article under test, the article under test having a surface movable about an axis of rotation, comprises: determining a change in attitude of the article under test about the axis of rotation; and responsive to the change in the attitude of the article under test, adjusting in real time a position of a load mechanism that provides the load to the surface of the article under test. In some such embodiments, adjusting in real time the position of the load mechanism comprises moving the load mechanism along a track that partially surrounds the article under test. The shape of the track is an arc of a circle, in some embodiments. 
     In some such embodiments, the method further comprises adjusting in real time a magnitude of the load provided by the load mechanism; and at least one of predicting the attitude of the article under test or sensing the attitude of the article under test. In some embodiments, the load mechanism is coupled to a cart that is movable along a track that partially surrounds the article under test; the cart is movable in a plane perpendicular to the axis of rotation of the surface of the article under test; the cart includes a linear table that moves the load mechanism perpendicular to a longitudinal direction of the track responsive to instructions from a controller; a controller dynamically adjusts the load via the load mechanism as the cart is moved in relation to the article under test; the load mechanism is a cable and an adjustable tensioner is coupled to the cable; and the load mechanism is a rod and a compression device, wherein the compression device is at least one of a hydraulic cylinder or a motor. 
     In another aspect of the disclosure, the method comprises: moving a cart in relation to the surface of the article under test; providing an adjustable load, via a load mechanism coupled to the cart, to the surface of the article under test; maintaining, via a controller configured to coordinate in real time motion of the cart with movement of the surface of the article under test, a desired load angle between the load mechanism and the surface of the article under test; and receiving, from a sensor, a measurement corresponding to an actual angle between the load mechanism and the article under test. 
     In some such embodiments, the measurement is at least one of an angle of the surface of the article under test or an attitude of the surface of the article under test; the cart moves along a track that guides the motion of the cart; and a shape of the track is an arc of a circle. 
     In yet another aspect of the disclosure, the method comprises: moving a cart, via a drive mechanism configured, along a track, the track comprising a longitudinal direction perpendicular to the axis of rotation of the surface of the article under test; providing a load, via a load mechanism coupled to the cart, to the surface of the article under test; determining an attitude of the surface of the article under test as the surface moves about the axis of rotation; and sending instructions, via a controller, to one or both of the drive mechanism and the load mechanism to move the cart and adjust the load, respectively, based at least in part on the determined attitude of the surface of the article under test. 
     In some such embodiments, the track translates parallel to the axis of rotation to set a first angle between the load mechanism and the surface of the article under test; a shape of the track is determined by a path of motion of the surface of the article under test; the load mechanism is a cable and an adjustable tensioner coupled to the cable; and the load mechanism is a rod and a compression device. 
     The features, functions, and advantages that have been discussed can be achieved independently in various embodiments or may be combined in yet other embodiments further details of which can be seen with reference to the following description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the disclosed methods and apparatuses, reference should be made to the embodiment illustrated in greater detail on the accompanying drawings, wherein: 
         FIG. 1  is a perspective view illustrating a test rig in accordance with the current disclosure; 
         FIG. 2  is another perspective view of the test rig of  FIG. 1  with some elements removed for better visibility; 
         FIG. 3  is a side view of the test rig of  FIG. 1 ; 
         FIG. 4  is a perspective view of a track and carts of the test rig; 
         FIG. 5  is a perspective view detail of the track and cart; 
         FIG. 6  is an illustration of an alternate embodiment of a drive mechanism for the cart; 
         FIG. 7  is an illustration of an alternate embodiment of a load mechanism; 
         FIG. 8  is an illustration of an alternate embodiment of a track; 
         FIG. 9  is an illustration of an alternate device for determining an attitude of an article under test; 
         FIG. 10  is a perspective view of an article under test showing load angles; 
         FIG. 11  is a block diagram of a control system for the test rig of  FIG. 1 ; and 
         FIG. 12  is an illustration of operations performed by one embodiment a test rig operating to perform a test in accordance with the current disclosure. 
     
    
    
     It should be understood that the drawings are not necessarily to scale and that the disclosed embodiments are sometimes illustrated diagrammatically and in partial views. In certain instances, details which are not necessary for an understanding of the disclosed methods and apparatuses or which render other details difficult to perceive may have been omitted. It should be understood, of course, that this disclosure is not limited to the particular embodiments illustrated herein. 
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a test rig  100  that, in an embodiment is used to provide a load to an article under test  110 . Test rig includes a frame  102  and a support stand  104  that is either rigidly attached to the frame  102  or, in an embodiment, may be translatable in a direction  111  along a width of the frame  102 . Attached to the support stand  104  is a track  106  that supports a cart  108 . The cart  108  is movable along the track  106 . The support stand  104  and track  106  must be capable of supporting the load forces applied during testing. The article under test  110  may be an entire component to be tested or may be a portion of a larger assembly.  FIG. 1  depicts the article under test  110  to be a flap of an airplane wing. An axis of rotation  112  of the article under test  110  will be discussed in more detail below. In various embodiments, the test rig  100  may include multiple support stands and tracks, limited in number only by the amount of space between ends of the frame  102 . 
     In actual use on an airplane in flight, the illustrated article under test  110 , that is, the flap, may be deployed relatively quickly from a retracted position generally on-plane with the rest of the wing to fully deployed at an angle of 45° or more. Other components that may be tested include, for example, a spoiler that may be deployed very rapidly. A spoiler may be deployed just after landing when it is desirable to rapidly reduce the lift capacity of the wing. During such operations, wing flaps and spoilers may be subjected to rapidly changing loads as each travels from retracted to fully deployed. 
     Static testing of such a component at discrete angles provides some useful data about expected performance and safety margins. However, the ability to continuously apply a load to the article under test at an appropriate angle over its full range of motion in real time and to also vary the load in real time during a simulated deployment provides a more real-world test of the structure including surfaces, actuators, and hinges. 
     Other components that move during operation can also benefit from the ability to change in real time both load magnitude and load angle during testing. The components include, but are not limited to trim tabs, ailerons, and landing gears. However, many other components that are more or less static, such as wings, may benefit from testing using varying load angles and magnitudes to simulate various conditions during flight. Even though static testing may achieve acceptable test results in these latter case, the dramatic improvement in speed provided by the test rig  100  over one-at-a-time load positioning represents a significant benefit to developers and test operators. 
     Turning to  FIG. 2 , the test rig  100  of  FIG. 1  is illustrated with the support stand  104  partially removed for better visualization of the track  106 . In the illustrated embodiment, the track  106  is an arc of a circle. In some embodiments, the center of the circle is located at the axis of rotation  112  of the article under test  110 . Generally, the track  106  in this shape allows the cart  108  to maintain a position that is generally normal to the article under test  110  as it moves about the axis of rotation  112  and minimizes distance changes between the cart  108  and the article under test  110 . The term generally normal, or simply, normal, is understood to be perpendicular to the axis of rotation  112  and/or perpendicular to a surface to which the load is attached, within the tolerances of the test rig  100  and such that the needs of the test protocol for application of the load are met. In some circumstances, the application may require that the load angle remain within a few degrees of perpendicular, whereas in other applications, a variation of ten degrees or more may be sufficient. In other embodiments, the track  106  can be a more complex curve in order to more closely match components whose movement is not simply rotational but includes both translation as well as rotation. An example is the course of an aft wing flap or leading edge flap which both translate and rotate relative to a main wing body. This alternative is discussed more below with respect to  FIG. 8 . A longitudinal direction  109  of the track  106  is generally perpendicular to the axis of rotation  112  of the article under test. As above, the term generally perpendicular, or simply, perpendicular, in this respect is understood to be within the tolerances of the test rig  100  and track  106  and such that the needs of the test protocol for a particular article under test are met. 
     Further, a profile of the track  106  does not need to be limited to an arc. The profile can be adjusted to match the path of motion of the component being tested. There are advantages to having a track profile that matches the path of the component being tested. Briefly, by minimizing the distance variations between cart  108  and the article under test  110 , the weight of the cart  108  can be kept low and the cart  108  can be moved faster, improving testing capabilities. More specifically, by keeping the variation in distance between the article under test  110  and the cart  108  to a minimum, the change in length of the cable  118  or rod  136  is also minimized. This allows the amount of adjustment required by the tensioner  120  to be minimized, thereby reducing the size and weight of the tensioner  120 . When the size and weight of the tensioner  120  are kept low, the size and weight of the drive mechanism  125  can also be kept low. When the overall momentum of the cart  108  is minimized, the cart  108  may be driven at a higher speed, which increases the versatility of the test rig  100 . 
     In some embodiments, a second cart  114  or even a third cart  115  is used on the same track  106  in order to provide additional loads to the article under test  110 , or to other components mounted in the test rig  100 . 
     A side view of the test rig  100  is illustrated in  FIG. 3 . As seen in this view, an angle  116  is formed between the article under test  110  and a cable  118  attached between the cart  108  and the article under test  110 . A benefit of a cable  118  for load application is that the force applied is always collinear with the cable  118 , and in that respect is easy to predict when a position of the cart  108  is known. In an alternate embodiment discussed below, the cable  118  providing a tension load may be replaced by a rod providing a compression load. 
       FIG. 4  shows the track  106 , cart  108 , and cart  114  in more detail. In an embodiment, the cart  108  includes a pulley  117  over which the cable  118  runs with a load on the cable  118  provided by a tensioner  120 . The tensioner  120  may be an adjustable tensioner comprising any of a number of devices that can produce a variable force including, but not limited to, a winch, a ball screw and jack, or a hydraulic cylinder. The tensioner  120 , cable  118 , pulley  117  may be referred to as a load mechanism  158 . 
     Additional details of one embodiment of a cart  108  are shown in  FIG. 5 . In the illustrated embodiment, the cart  108  rides on rails  122  using rollers  124  for support. A drive mechanism  125  may include a motor  126  coupled to pinion gears  128  that drive the cart  108  along a rack  129 . The rack and pinion drive provides positive traction and allows accurate positioning of the cart  108  because there is no slip during drive operations. In an embodiment, it is expected that the cart may move at speeds of 60 inches per second or more. For those components that include more complex motion, the cart  108 , the load mechanism, or both may be moved laterally, for example, using a linear table  121 . The linear table  121  allows the cart  108  and/or the load mechanism  158  to be moved so that the load angle can to be adjusted laterally, that is, perpendicular to the longitudinal direction  109  of the track, providing two directions of motion, or degrees of freedom to adjust the angle of the load. That is, while the cart  108  may be moved along the track  106 , the cart  108  or the load mechanism  158  can be moved independently orthogonal to the track  106 . Alternatively, or in addition to this lateral translation, the entire support stand  104  and track  106  can be oriented to match a complex path of motion of an article under test  110 . As discussed above, in some embodiments, the entire support stand  104  can be moved laterally, in direction  111 , that is, along the direction of the axis of rotation  112  relative to the frame  102 . 
     Other forms of moving the cart  108  are discussed with respect to  FIG. 6 . Turning to  FIG. 6 , the track  106  is shown in side view. In this embodiment, the cart  108  is moved by an alternate drive mechanism. The drive mechanism  130  uses a wire  131  or chain  132  and one or more motors  133 . In an embodiment using a wire  131 , the cart  108  is attached at a bracket  134  and moved by winding and unwinding the wire  131 , respectively, at opposite motors  133 . In one embodiment using a chain, the chain  132  is placed in a loop that starts and ends at the bracket  134 . The drive motors  133  turn in the same way in one direction or the other to move the cart  108  along the track  106 . Similar to the rack and pinion drive shown in  FIG. 5 , either the wire drive or chain drive alternatives provide a positive response when a change in position of the cart  108  is required. 
       FIG. 7  illustrates another embodiment of the test rig  100  that provides either a tension load or a compression load to the surface under test  110 . In this embodiment, a rod  136  is coupled to a compression device  137  that applies a selectable pressure or tension to the article under test  110 . The compression device  137  may be a ball and screw drive, a hydraulic cylinder or other similar device. Because the rod  136  and compression device  137  are more or less rigid, in order to accommodate changes in the angle of the cart  108  to the article under test  110 , the compression device  137  may be mounted to the cart  108  using a pivot  138 . That is, even though the rod  136  may be at a desired angle to the article under test  110 , the angle of the rod with respect to the cart  108  may change. Mounting the compression device  137  at the pivot  138  accommodates these angular variations. 
     Also illustrated in  FIG. 7  is a sensor  142  that determines a position of the article under test  110 . In embodiments incorporating this technology, the sensor  142  is attached at the axis of rotation  112  and either reports a position relative to the frame  102  or reports the position relative to a fixed structure  140  such as a wing. The sensor  142  may be a rotary sensor attached to either the article under test  110  or a shaft (not depicted) on which the article under test  110  rotates. Alternatively, the sensor  142  may be part of the equipment being tested, that is, the sensor  142  may be a sensor that would be deployed on a production aircraft. Because the sensor reports an angle, or alternatively, a position of an actuator, and not the actual attitude of the article under test  110 , an algorithm may be required to translate the sensor reading to an actual position or attitude of the article under test  110 . 
     As discussed above, in some embodiments, the track is a more a complex shape in both lateral and vertical directions. An alternate embodiment of a track  106  showing such complexity in the vertical direction is illustrated in  FIG. 8 . In this embodiment, the track  106  is not a smooth geometric shape, such as an arc illustrated in  FIG. 7  above but rather is shaped to follow the nonlinear path of the article under test  110 , or, in an embodiment, to keep the distance between the cart  108  and the article under test  110  relatively constant. Complex track shapes, as discussed above, can lead to reduced cart weight and better agility of the overall test rig  100 . 
       FIG. 9  is an illustration of an alternate embodiment of the test rig  100  that uses one or more optical sensors  144 , such as LIDAR sensors, to determine an attitude of the article under test  110  by measuring separate points on the article under test  110  with one or more laser beams  145 . This embodiment allows the cart  108  to operate independently of the article under test  110 , that is, there is no dependence on sensors  142  or equipment position sensors used in other embodiments to mechanically measure the attitude of the article under test  110 . 
     The load angle between the article under test  110  and the cable  118  (or rod  136 , in the case of the embodiment of  FIG. 7 ) is illustrated in  FIG. 10 . An angle  116  is measured in a plane perpendicular to the axis of rotation  112  and a lateral angle  148  is measured in a plane parallel to the axis of rotation  112 . As part of the feedback control of the cart  108 , discussed in more detail below, the measured or calculated angle  116  is used to determine when and how much to move the cart  108 . While it is anticipated that there is an ability to respond more rapidly to changes relative to angle  116 , there is also an ability to adjust or maintain angle  148  through lateral translation of the support stand  104 . 
     A block diagram of a control system  150  suitable for use with the test rig  100  is illustrated in  FIG. 11 . The ability to maintain the cable  118  or rod  136  at a desired angle is a direct function of the ability to move the cart  108  as the article under test  110  is moved. Similarly, the load profile, or desired load, may change as the article under test  110  moves, simulating actual use conditions. As well, it would be expected that the distance between the cart  108  and the article under test  110  may vary as the cart  108  moves. This requires further real time adjustments to the load to maintain the desired load profile, even if the desired load is constant over the range of motion of the article under test  110 . 
     The controller  151  may have a variety of inputs and outputs to receive information about the environment and maintain the desired angle and load. In various embodiments, sensor inputs  168  collect data from a variety of sensors, such as, but not limited to, a cart position sensor  174 , a load sensor  160  and either or both of an equipment position sensor  162  or an external sensor  152 . The external position sensor  152 , the same as or similar to sensor  142 , is used to report information relative to an attitude of the article under test  110 , such as an angle of a shaft at the axis of rotation  112 . Alternatively, or in addition to the previous information, the equipment position sensor  162 , provides the same information that would be provided in flight, such as a position of an actuator (not depicted). Data from these position sensors  152  and/or  162  is used by a position algorithm  172  to determine an attitude of the article under test  110  relative to either a fixed structure  140  or the frame  102  of the test rig  100 . 
     The load sensor  160  provides data to the load algorithm  170  that is used to adjust in real time a magnitude of the force applied to the article under test  110 . The load sensor  160  provides information corresponding to the amount of force applied to the article under test  110  by the cable  118  or rod  136 . The load sensor  160  may be a strain gauge mounted to the tensioner  120  or compression device  137 . In other embodiments, the load sensor  160  is part of the load mechanism  158 , for example, a torque sensor when the tensioner  120  is a motor that tensions the cable  118 . 
     Similarly, a location sensor  159  or the drive mechanism  125 ,  130  itself may provide information to the controller  151  relative to the location of the cart  108  using, for example, optical marks or Hall effect sensors. Alternatively, the controller  151  may maintain the location of the cart  108  by accounting for commands used to move the cart  108  during the course of a test. For example, when the drive mechanism  125 ,  130  uses a stepper motor, the controller  151  can simply translate the motion commands sent to the drive mechanism  125  into a position of the cart  108 . 
     The position algorithm  172  may also be used to determine a position of the cart  108  based on information from the drive mechanism  125  or other sensors as discussed above. Because the position algorithm  172  has knowledge of both the position of the article under test  110  and the cart  108 , and, in some embodiments, a priori information from a test sequence  166 , the position algorithm  172  can adjust the location of the cart  108  and the load provided to the article under test  110 . The adjustments in load may result from known changes in the distance between the cart  108  and the article under test  110  as well as changes required by the test sequence that simulate operating conditions. 
     In some embodiments, the controller  151  also includes the test sequence  166  that either manages or can be synchronized to other physical elements of the test so that the cart movement does not necessarily have to be reactive to movement of the article under test  110  but can be moved in a coordinated fashion as the test sequence is carried out. For example, the controller  151  may also be in control of movement of the article under test  110 , so that the cart movement can be synchronized to the movement of the article under test  110 . 
     A method  200  of providing a load to an article under test  110  is illustrated in the flowchart of  FIG. 12 . At block  202 , a moveable cart  108  is used to apply a load at a desired angle. In different embodiments, an actual angle  116  is determined by comparing a location of the cart  108  with the article under test  110 , while in other embodiments, the actual angle  116  is determined by a measurement, such as an optical measurement. 
     At block  204 , a change in an attitude of the article under test may be determined. The change in angle  116  can be calculated using knowledge of an updated attitude of the article under test  110  from sensor data and knowledge of location of the cart  108 . Alternatively, the change in angle  116  can be determined programmatically based on knowledge of the test sequence  166 , as discussed above. When no movement has occurred, the ‘no’ branch is be taken to block  210 . When movement has occurred, the ‘yes’ branch is be taken to block  206 . 
     Optionally, at block  206  a decision may be made as to whether the change causes angle  116  to exceed a threshold value for deviation from a desired angle. For example, in one embodiment, the desired angle is 105 degrees, plus or minus 5 degrees. If the change in attitude of the article under test  110  causes the angle  116  to fall outside that range, the ‘yes’ branch is be taken to block  208 . In other embodiments, the check for a threshold value may not be performed and measurable movement of the article under test  110  may prompt a change in location of the cart  108 . 
     At block  208 , the cart  108  may be moved to a new location, responsive to instructions from the controller  151  in order to maintain the angle  116  of the load within the desired range. Execution, in this embodiment, continues at block  210 , which may also be accessed by the ‘no’ branch from block  206 . At block  210 , a determination is made if a change in load is required. In an embodiment, the test sequence may call for a change in a magnitude of the load even if the article under test  110  has not moved. Additionally, as discussed above, even if the desired load is unchanged, a change in location of the cart  108  may affect the load being delivered and an adjustment may be required. If a load change is required, the change is be made at block  212  and execution continued at the top of the loop, block  202 . 
     The ability to maintain a vector load, that is both a desired angle and a desired magnitude of a load relative to a moving structure is a benefit to designers, testers, and regulators. Testing structures, particularly airframe components, in real time as the structures move following actual use patterns provides more accurate data about predicted operation and represents a significant reduction in test time over manually placed loads at discrete attitudes of structures being tested. Because the test is performed in real time over the continuous range of motion of the article under test  110 , the need to interpolate data between discrete test points is eliminated. Further, the support structures and actuators coupled to the article under test  110  are also tested under more realistic operating conditions compared to a series of static tests. 
     While only certain embodiments have been set forth, alternatives and modifications will be apparent from the above description to those skilled in the art. In particular, aspects of the different embodiments can be combined with or substituted by one another. These and other alternatives are considered equivalents and within the spirit and scope of this disclosure and the appended claims.