Patent Publication Number: US-2018029701-A1

Title: Jam-Tolerant Rotary Control Motor for Hydraulic Actuator Valve

Description:
TECHNICAL FIELD 
     This invention relates generally to rotorcraft flight control systems, and more particularly, to a jam-tolerant linear control motor for a hydraulic actuator valve. 
     BACKGROUND 
     A rotorcraft may include one or more rotor systems. One example of a rotorcraft rotor system is a main rotor system. A main rotor system may generate aerodynamic lift to support the weight of the rotorcraft in flight and thrust to counteract aerodynamic drag and move the rotorcraft in forward flight. Another example of a rotorcraft rotor system is a tail rotor system. A tail rotor system may generate thrust in the same direction as the main rotor system&#39;s rotation to counter the torque effect created by the main rotor system. A rotor system may include one or more devices to rotate, deflect, and/or adjust rotor blades. 
     SUMMARY 
     Particular embodiments of the present disclosure may provide one or more technical advantages. A technical advantage of one embodiment may include the capability to reduce magnetic seizing in a control motor for a rotorcraft blade actuator. A technical advantage of one embodiment may include the capability to detect bearing failures in a control motor prior to catastrophic failure. A technical advantage of one embodiment may include the capability to reduce failures in joints that convert rotary motion into linear motion. 
     Certain embodiments of the present disclosure may include some, all, or none of the above advantages. One or more other technical advantages may be readily apparent to those skilled in the art from the figures, descriptions, and claims included herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       To provide a more complete understanding of the present invention and the features and advantages thereof, reference is made to the following description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1A  shows a rotorcraft according to one example configuration; 
         FIG. 1B  shows the rotor system and blades of  FIG. 1A  according to one example configuration; 
         FIG. 2A  shows an example redundant control system for a fixed-wing aircraft; 
         FIG. 2B  shows an example redundant control system for a rotorcraft such as the rotorcraft of  FIG. 1A ; 
         FIG. 3  shows a cross-section view of a linear control motor according to one example embodiment; 
         FIG. 4  shows a cross-section view of a linear control motor according to another example embodiment; 
         FIG. 5  shows a cross-section view of a linear control motor according to yet another example embodiment; 
         FIG. 6  shows a cross-section view of a linear control motor according to yet another example embodiment; 
         FIG. 7A  shows a control system featuring a rotary control motor, a hydraulic system, and an actuator according to one example embodiment; 
         FIG. 7B  shows side view of a joint associated with the control system of  FIG. 7A ; 
         FIGS. 7C-7F  shows a cross-section views of the joint of  FIG. 7B ; 
         FIGS. 8A and 8B  show cross-section views of a rotary control motor according to one example embodiment; 
         FIGS. 9A and 9B  show cross-section views of a rotary control motor according to another example embodiment; 
         FIGS. 10A and 10B  show cross-section views of a rotary control motor according to yet another example embodiment; 
         FIGS. 11A and 11B  show cross-section views of a rotary control motor according to yet another example embodiment; and 
         FIGS. 12A, 12B, and 12C  show cross-section views of a rotary control motor according to yet another example embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  shows a rotorcraft  100  according to one example configuration. Rotorcraft  100  features a rotor system  110 , blades  120 , a fuselage  130 , a landing gear  140 , and an empennage  150 . Rotor system  110  may rotate blades  120 . Rotor system  110  may include a control system for selectively controlling the pitch of each blade  120  in order to selectively control direction, thrust, and lift of rotorcraft  100 . Fuselage  130  represents the body of rotorcraft  100  and may be coupled to rotor system  110  such that rotor system  110  and blades  120  may move fuselage  130  through the air. Landing gear  140  supports rotorcraft  100  when rotorcraft  100  is landing and/or when rotorcraft  100  is at rest on the ground. Empennage  150  represents the tail section of the aircraft and features components of a rotor system  110  and blades  120 ′. Blades  120 ′ may provide thrust in the same direction as the rotation of blades  120  so as to counter the torque effect created by rotor system  110  and blades  120 . Teachings of certain embodiments relating to rotor systems described herein may apply to rotor system  110  and/or other rotor systems, such as other tilt rotor and helicopter rotor systems. It should also be appreciated that teachings from rotorcraft  100  may apply to aircraft other than rotorcraft, such as airplanes and unmanned aircraft, to name a few examples. 
       FIG. 1B  shows rotor system  110  and blades  120  of  FIG. 1A  according to one example configuration. In the example configuration of  FIG. 1B , rotor system  110  features a power train  112 , a hub  114 , a swashplate  116 , and pitch links  118 . In some examples, rotor system  110  may include more or fewer components. For example, FIG.  1 B does not show components such as a gearbox, a swash plate, drive links, drive levers, and other components that may be incorporated. 
     Power train  112  features a power source  112   a  and a drive shaft  112   b . Power source  112   a , drive shaft  112   b , and hub  114  are mechanical components for transmitting torque and/or rotation. Power train  112  may include a variety of components, including an engine, a transmission, and differentials. In operation, drive shaft  112   b  receives torque or rotational energy from power source  112   a  and rotates hub  114 . Rotation of rotor hub  114  causes blades  120  to rotate about drive shaft  112   b.    
     Swashplate  116  translates rotorcraft flight control input into motion of blades  120 . Because blades  120  are typically spinning when the rotorcraft is in flight, swashplate  116  may transmit flight control input from the non-rotating fuselage to the hub  114 , blades  120 , and/or components coupling hub  114  to blades  120  (e.g., grips and pitch horns). References in this description to coupling between a pitch link and a hub may also include, but are not limited to, coupling between a pitch link and a blade or components coupling a hub to a blade. 
     In some examples, swashplate  116  may include a non-rotating swashplate ring  116   a  and a rotating swashplate ring  116   b . Non-rotating swashplate ring  116   a  does not rotate with drive shaft  112   b , whereas rotating swashplate ring  116   b  does rotate with drive shaft  112   b . In the example of  FIG. 1B , pitch links  118  connect rotating swashplate ring  116   b  to blades  120 . 
     In operation, according to one example embodiment, translating the non-rotating swashplate ring  116   a  along the axis of drive shaft  112   b  causes the pitch links  118  to move up or down. This changes the pitch angle of all blades  120  equally, increasing or decreasing the thrust of the rotor and causing the aircraft to ascend or descend. Tilting the non-rotating swashplate ring  116   a  causes the rotating swashplate  116   b  to tilt, moving the pitch links  118  up and down cyclically as they rotate with the drive shaft. This tilts the thrust vector of the rotor, causing rotorcraft  100  to translate horizontally following the direction the swashplate is tilted. 
     Redundant flight control components may be provided to improve safety of rotorcraft  100 . For example, the rotor system  110  of  FIG. 1B  may include redundant components for controlling deflection and position of blades  120 . However, providing flight control redundancy in a rotorcraft, such as the example rotorcraft  100 , may be somewhat more difficult than providing flight control redundancy in a fixed-wing aircraft. 
       FIGS. 2A and 2B  show example redundant control systems for a fixed-wing aircraft and for a rotorcraft. The example of  FIG. 2A  represents a redundant control system for a fixed-wing aircraft. In the example of  FIG. 2A , two redundant flight control devices  210 ′ and  210 ″ are provided. Each flight control device is controlled by two redundant actuators  220  (for a total of four actuators). The four actuators  220  are controlled by three redundant hydraulic systems  230 . 
     The example of  FIG. 2B , on the other hand, represents a redundant control system for a rotorcraft. Unlike the example of  FIG. 2A , the system of  FIG. 2B  includes a single flight control device  210 . In this example embodiment, flight control device  210  may represent a rotorcraft flight control component, such as swashplate  116 , that does not have a redundant counterpart installed on rotorcraft  100 . 
     Teachings of certain embodiments recognize that providing redundancy in the system of  FIG. 2B  is therefore more important when only a single flight control device  210  is provided. In the example of  FIG. 2B , two redundant actuators  220  are provided to position flight control device  210 . The two redundant actuators  220  are controlled by hydraulic systems  230 , hydraulic systems  232 , and a switching valve  234 . 
     In one example embodiment, actuators  220  and hydraulic systems  230  may represent the dual motor dual concentric valve actuator  101  described and/or suggested by U.S. Pat. No. 7,828,245, issued on Nov. 9, 2010. For example, actuator  220  may represent the parallel dual piston actuator  111  of U.S. Pat. No. 7,828,245, and hydraulic system  230  may represent dual concentric valve  202 , which is controlled by motor  119 . U.S. Pat. No. 7,828,245 is hereby incorporated by reference in its entirety. 
     Although the example of  FIG. 2B  features redundant actuators  220 ,  FIG. 2B  shows the redundant actuators  220  coupled together in series. Thus, in this example, failure by one actuator  220  could cause the redundant actuator  220  to fail. For example, if one actuator  220  locks in a fixed position, the locked actuator  220  could prevent the redundant  220  from moving. 
     Accordingly, teachings of certain embodiments recognize that performance of actuator  220  may be critical to flight safety. As will be explained in greater detail below, teachings of certain embodiments recognize the capability to prevent failures of actuator  220 . In particular, teachings of certain embodiments recognize the capability to prevent failures of actuator  220  by preventing failures of the control motor that controls hydraulic fluid flow to actuator  220 . 
       FIG. 3  shows a cross-section view of a control motor  300  according to one example embodiment. In the example of  FIG. 3 , control motor  300  is coupled to hydraulic system  230 . In some embodiments, hydraulic system  230  may represent dual concentric valve  202  of U.S. Pat. No. 7,828,245, and control motor  300  may represent an example configuration of the motor  119  of U.S. Pat. No. 7,828,245. In the example of  FIG. 3 , hydraulic system  230  is shown as a simplified hydraulic valve featuring a servo valve and a spool extending through the servo valve. 
     In the example of  FIG. 3 , control motor  300  features a magnet  310 , a coil  320 , magnetic material  330 , non-magnetic material  340 , and a shaft  350 . In this example, magnet  310  and magnetic material  330  may be considered static components, and coil  320  may be considered a movable component. A movable component may represent any component that moves relative to a static component. A static component may be considered fixed relative to movable components, although in reality static components themselves may be subject to some movement. 
     In operation, magnet  310  generates magnetic flux along magnetic flux path  315 . Magnetic material  330  is disposed at least partially in magnetic flux path  315  and may reduce loss of flux along magnetic flux path  315 . Coil  320  selectively adds magnetic flux to and/or subtracts magnetic flux from magnetic flux path  315 . Adding or subtracting magnetic flux may cause coil  320  to move linearly within control motor  300 . Non-magnetic material  340  and shaft  350  couple coil  320  to the spool of hydraulic system  230  such that the spool of hydraulic system  230  moves in response variations in magnetic flux in magnetic flux path  315 . 
     Magnet  310  may represent any material or object that is operable to produce a magnetic field and/or generate a magnetic flux path. Examples of magnet  310  may include a permanent magnet or an electromagnetic. Coil  320  may represent any material or object that is operable to add or remove flux to or from a magnetic flux path. In some embodiments, coil  320  resembles a series of loops of conductive material, such as solid copper wire. Magnetic material  330  may represent any material or object that is attracted to (or repulsed by) a magnet. In some embodiments, magnetic material  330  may include ferromagnetic materials, such as iron, nickel, cobalt, rare earth magnets, and some alloys. Non-magnetic material  340  may represent material is not attracted to (or repulsed by) a magnet. Examples of non-magnetic material  340  may include some rubbers, plastics, and wood. 
     In the example of  FIG. 3 , coil  320  is disposed within control motor  300  adjacent to magnetic material  330 . During normal operation, coil  320  may be free to move linearly within control motor  300  adjacent to magnetic material  330 . A failure can occur, however, if coil  320  magnetically seizes to magnetic material  330 . In this failure mode, coil  320  becomes fixed and prevents shaft  350  from moving the spool of hydraulic system  230 , which may result in a failure of the actuator  220  coupled to hydraulic system  230 . Accordingly, as will be explained in greater detail below, teachings of certain embodiments recognize the capability to prevent failures of actuator  220  and hydraulic system  230  by preventing magnetic seizing of the control motor. 
       FIG. 4  shows a cross-section view of a control motor  400  according to one example embodiment. In the example of  FIG. 4 , control motor  400  is coupled to hydraulic system  230 . In some embodiments, hydraulic system  230  may represent dual concentric valve  202  of U.S. Pat. No. 7,828,245, and control motor  400  may represent an example configuration of the motor  119  of U.S. Pat. No. 7,828,245. In the example of  FIG. 4 , hydraulic system  230  is shown as a simplified hydraulic valve featuring a servo valve and a spool extending through the servo valve. 
     In the example of  FIG. 4 , control motor  400  features a magnet  410 , a coil  420 , magnetic material  430 , non-magnetic material  440 , and a shaft  450 . In some embodiments, some of these components may resemble the magnet  310 , coil  320 , magnetic material  330 , non-magnetic material  340 , and shaft  350  of control motor  300 . Unlike control motor  300 , however, control motor  400  features additional non-magnetic material  440  separating coil  420  from magnetic material  430 . Teachings of certain embodiments recognize that the non-magnetic material  440  may prevent coil  420  from seizing to magnetic material  430  by preventing physical contact between coil  420  and the magnetic material  430 . 
     In the example of  FIG. 4 , control motor  400  also features springs  445  that may allow the non-magnetic material  440  to move somewhat relative to coil  420  and/or magnetic material  430 . Teachings of certain embodiments recognize that allowing some movement by the non-magnetic material  440  separating coil  420  from magnetic material  430  may further reduce seizing by control motor  400 . 
       FIG. 5  shows a cross-section view of a control motor  500  according to one example embodiment. Control motor  500  may represent an alternative configuration of the control motor  300  of  FIG. 3 . In the example of  FIG. 5 , control motor  500  is coupled to hydraulic system  230 . In some embodiments, hydraulic system  230  may represent dual concentric valve  202  of U.S. Pat. No. 7,828,245, and control motor  500  may represent an example configuration of the motor  119  of U.S. Pat. No. 7,828,245. In the example of  FIG. 5 , hydraulic system  230  is shown as a simplified hydraulic valve featuring a servo valve and a spool extending through the servo valve. 
     In the example of  FIG. 5 , control motor  500  features magnets  510 , a coil  520 , magnetic material  530 , a magnetic armature  535 , non-magnetic material  540 , and a shaft  550 . In this example, magnets  510 , coil  520 , and magnetic material  530  may be considered static components, and armature  535  may be considered a movable component. 
     In operation, magnets  510  generate magnetic flux along magnetic flux paths  515 . Magnetic material  530  is disposed at least partially in a magnetic flux path  515  and may reduce loss of flux along magnetic flux path  515 . Coil  520  selectively adds magnetic flux to and/or subtracts magnetic flux from magnetic flux paths  515 . Magnetic armature  535  is also at least partially disposed in the magnetic flux paths  515 . Adding or subtracting magnetic flux may cause magnetic armature  535  to move linearly within control motor  500 . Non-magnetic material  540  and shaft  550  couple magnetic armature  535  to the spool of hydraulic system  230  such that the spool of hydraulic system  230  moves in response variations in magnetic flux in magnetic flux paths  515 . 
     In the example of  FIG. 5 , magnets  510  generate two magnetic flux paths  515 . In this example, magnetic flux paths  515  flow in opposite directions such that the first magnetic flux path  515  is operable to move magnetic armature  535  in a first direction and the second magnetic flux path  515  is operable to move magnetic armature  535  in an opposite second direction. If the magnitude of the two magnetic flux paths  515  is equal, the two magnetic flux paths may substantially maintain magnetic armature  535  in equilibrium. If the magnitude of the two magnetic flux paths  515  is not equal, then equilibrium is not maintained, and magnetic armature  535  may move linearly as a result of the difference in flux in the two magnetic flux paths. 
     Magnet  510  may represent any material or object that is operable to produce a magnetic field and/or generate a magnetic flux path. Examples of magnet  510  may include a permanent magnet or an electromagnetic. Coil  520  may represent any material or object that is operable to add or remove flux to or from a magnetic flux path. In some embodiments, coil  520  resembles a series of loops of conductive material, such as solid copper wire. Magnetic material  530  and magnetic armature  535  may represent any material or object that is attracted to (or repulsed by) a magnet. In some embodiments, magnetic material  530  and magnetic armature  535  may include ferromagnetic materials, such as iron, nickel, cobalt, rare earth magnets, and some alloys. Non-magnetic material  540  may represent material is not attracted to (or repulsed by) a magnet. Examples of non-magnetic material  540  may include some rubbers, plastics, and wood. 
     In the example of  FIG. 5 , magnetic armature  535  is disposed within control motor  500  adjacent to magnets  510  and/or magnetic material  530 . During normal operation, magnetic armature  535  may be free to move linearly within control motor  500  adjacent to magnets  510  and/or magnetic material  530 . A failure can occur, however, if magnetic armature  535  magnetically seizes to magnets  510  and/or magnetic material  530 . In this failure mode, magnetic armature  535  becomes fixed and prevents shaft  550  from moving the spool of hydraulic system  230 , which may result in a failure of the actuator  220  coupled to hydraulic system  230 . Accordingly, as will be explained in greater detail below, teachings of certain embodiments recognize the capability to prevent failures of actuator  220  and hydraulic system  230  by preventing magnetic seizing of the control motor. 
       FIG. 6  shows a cross-section view of a control motor  600  according to one example embodiment. In the example of  FIG. 6 , control motor  600  is coupled to hydraulic system  230 . In some embodiments, hydraulic system  230  may represent dual concentric valve  202  of U.S. Pat. No. 7,828,245, and control motor  600  may represent an example configuration of the motor  119  of U.S. Pat. No. 7,828,245. In the example of  FIG. 6 , hydraulic system  230  is shown as a simplified hydraulic valve featuring a servo valve and a spool extending through the servo valve. 
     In the example of  FIG. 6 , control motor  600  features a magnet  610 , a coil  620 , magnetic material  630 , magnetic armature  635 , non-magnetic material  640 , and a shaft  650 . In some embodiments, some of these components may resemble the magnet  510 , coil  520 , magnetic material  530 , magnetic armature  535 , non-magnetic material  540 , and shaft  550  of control motor  500 . Unlike control motor  500 , however, control motor  600  features additional non-magnetic material  640  separating magnetic armature  635  from magnets  610  and magnetic material  630 . Teachings of certain embodiments recognize that the non-magnetic material  640  may prevent magnetic armature  635  from seizing to magnets  610  and/or magnetic material  630  by preventing physical contact between magnetic armature  635  and the magnets  610  and/or magnetic material  630 . 
     In the example of  FIG. 6 , control motor  600  also features springs  645  that may allow the non-magnetic material  640  to move somewhat relative to magnetic armature  635 , magnets  610 , and/or magnetic material  630 . Teachings of certain embodiments recognize that allowing some movement by the non-magnetic material  640  separating magnetic armature  635  from magnets  610  and/or magnetic material  630  may further reduce seizing by control motor  600 . 
     In the examples of  FIGS. 3-6 , the control motor includes a shaft that moves linearly in an effort to adjust the spool of a hydraulic system  230 . Teachings of certain embodiments recognize, however, the ability to provide a rotary control motor that adjusts the spool of a hydraulic system  230 . 
       FIG. 7A  shows a control system  700  featuring a control motor  710 , a hydraulic system  230 , and an actuator  220 . In the example of  FIG. 7 , control motor  710 , hydraulic system  230 , and actuator  220  may resemble the motor  119 , the dual concentric valve  202 , and the parallel dual piston actuator  111  of U.S. Pat. No. 7,828,245. 
     As seen in the example of  FIG. 7 , control motor  710  is a rotary control motor that adjusts the spool of hydraulic system  230  by rotating its output shaft  715 . A joint  720  converts rotation of the output shaft  715  into linear movements of the spool of hydraulic system  230 . Measurement devices  730  measure rotation of the output shaft  715  and linear movement of the spool of hydraulic system  230 . In one example embodiment, measurement devices  730  are differential transformers (e.g., linear variable differential transformers). 
       FIG. 7B  shows side view of joint  720 , and  FIG. 7C  shows a cross-section end view of joint  720  according to one example embodiment. In the example of  FIGS. 7B and 7C , the spool of hydraulic system  230  features two disks forming a trough  722  between them. A spherical member  724  resides at least partially in trough  722 . Output shaft  715  features a disk  725  that includes a recess sized to receive at least part of spherical member  724 . In operation, according to one example embodiment, rotation of output shaft  715  causes disk  725  to reposition spherical member  724 . Repositioning spherical member  724  causes spherical member  724  to apply force against one of the disks forming trough  722 . This force results in linear movement of the spool of hydraulic system  230 . 
     In the example of  FIGS. 7A-7C , however, control system  700  may fail if joint  720  jams. For example, jamming of joint  720  may lock the position of the spool of hydraulic system  230  and thus prevent both control motors  710  from operating. Accordingly, teachings of certain embodiments recognize the capability to reduce failures of joint  720 . 
       FIGS. 7D-7F  show cross-section views of joint  720  according to one example embodiment. As seen in  FIGS. 7D-7F , disk  725  features a pin  726 , a detent member  727 , and a spring  728 . In this example, detent member  727  is positioned between pin  726  and spring  728 , and spring  728  applies a force against detent member  727  towards pin  726 . Pin  726  features a detent portion that is sized to receive at least a portion of detent member  727  when the detent portion is facing detent member  727 . 
     Spherical member  724  is positioned between trough  722  and pin  726 . During normal operation, according to one example embodiment, disk  725  repositions spherical member  724  without substantially moving pin  726 . For example, spring  728  may apply sufficient force against pin  726  to prevent pin  726  from rotating during normal operation. 
     As friction increases in joint  720 , however, spherical member  724  may cause pin  726  to rotate within disk  725 . If the increased friction persists, pin  726  may continue to rotate until its detent portion faces detent member  727 . At this point, spring  728  may force detent member  727  at least partially into the detent portion of pin  726 , thus preventing pin  726  from rotating further. 
     In this example, joint  720  may continue to operate for some time with detent member  727  forced into the detent portion of pin  726 . Forcing detent member  727  at least partially into the detent portion of pin  726 , however, may represent visual evidence of increased friction in joint  720 . This visual evidence may be apparent, for example, during a preflight check of joint  720 . Evidence of increased friction in joint  720  may indicate that joint  720  is close to failing. Accordingly, teachings of certain embodiments recognize that providing visual evidence of increased friction may allow joint  720  to be repaired and/or replaced prior to failure. 
     Thus, teachings of certain embodiments recognize the capability to reduce failures of joint  720 . In addition, teachings of certain embodiments recognize the capability to reduce failures in control motors such as control motor  710 . 
       FIGS. 8A and 8B  show cross-section views of a control motor  800  according to one example embodiment. In the example of  FIGS. 8A and 8B , control motor  800  features magnets  810 , coils  820 , magnetic material  830 , non-magnetic material  840 , and a shaft  850 . In this example, coils  820  may be considered static components, and magnet  810 , magnetic material  830 , and shaft  850  may be considered movable components. 
     In operation, magnets  810  generate magnetic flux along a magnetic flux path. Magnetic material  830  may reduce loss of flux along the magnetic flux path. Coil  820  selectively adds magnetic flux to and/or subtracts magnetic flux from the magnetic flux path. Adding or subtracting magnetic flux may cause magnets  810  and magnetic material  830  to rotate within control motor  800 . Shaft  850  is coupled to magnetic material  830  and is configured to rotate with magnetic material  830 . 
     Magnet  810  may represent any material or object that is operable to produce a magnetic field and/or generate a magnetic flux path. Examples of magnet  810  may include a permanent magnet or an electromagnetic. Coil  820  may represent any material or object that is operable to add or remove flux to or from a magnetic flux path. In some embodiments, coil  820  resembles a series of loops of conductive material, such as solid copper wire. Magnetic material  830  may represent any material or object that is attracted to (or repulsed by) a magnet. In some embodiments, magnetic material  830  may include ferromagnetic materials, such as iron, nickel, cobalt, rare earth magnets, and some alloys. Non-magnetic material  840  may represent material is not attracted to (or repulsed by) a magnet. Examples of non-magnetic material  840  may include some rubbers, plastics, and wood. In the example of  FIGS. 8A and 8B , non-magnetic material may hold magnets  810  against magnetic material  930 . 
     In the example of  FIG. 8A , shaft  850  rotates within control motor  800 . In some embodiments, bearings  860  may be provided to separate shaft  850  from static components of control motor  800  and allow for rotation of shaft  850  within control motor  800 . Bearings  860  may fail during operation, however, and restrict rotation of shaft  850 . Accordingly, teachings of certain embodiments recognize the capability to provide break wires  865  proximate to bearings  860 . Break wires  865  may detect failure of a bearing  860  by severing in response to a failure of the bearing  860 . Teachings of certain embodiments recognize that detecting failure of bearing  860  may allow maintenance workers to replace the bearing  860  so as to prevent further damage and/or more catastrophic failures. 
     In addition to bearing failure, control motor  800  may also be prone to failure due to magnetic seizing. In the example of  FIGS. 8A and 8B , magnets  810  and magnetic material  830  are disposed within control motor  800  adjacent to coil  820 . During normal operation, magnets  810  and magnetic material  830  may be free to rotate within control motor  800  adjacent to coil  820 . A failure can occur, however, if magnets  810  or magnetic material  830  seizes to coil  820 . In this failure mode, magnets  810  and magnetic material  830  become fixed and prevent shaft  850  from rotating. Preventing shaft  850  from rotating may, in turn, prevent shaft  850  from moving the spool of hydraulic system  230 , which may result in a failure of the actuator  220  coupled to hydraulic system  230 . Accordingly, as will be explained in greater detail below, teachings of certain embodiments recognize the capability to prevent failures of actuator  220  and hydraulic system  230  by preventing magnetic seizing of the control motor. 
       FIGS. 9A and 9B  show cross-section views of a control motor  900  according to one example embodiment. In the example of  FIGS. 9A and 9B , control motor  900  features magnets  910 , coils  920 , magnetic material  930 , non-magnetic material  940 , and a shaft  950 . In some embodiments, some of these components may resemble the magnets  810 , coils  820 , magnetic material  830 , non-magnetic material  840 , and shaft  850  of control motor  800 . Unlike control motor  800 , however, control motor  900  features additional non-magnetic material  940  adjacent to coil  920  and separating coil  920  from magnets  910  and magnetic material  930 . Teachings of certain embodiments recognize that the additional non-magnetic material  940  may prevent coil  920  from seizing to magnets  910  and/or magnetic material  930  by preventing physical contact between coil  920  and the magnets  910  and/or magnetic material  930 . 
       FIGS. 10A and 10B  show cross-section views of a control motor  900  according to another example embodiment. In the example of  FIGS. 10A and 10B , control motor  1000  features magnets  1010 , coils  1020 , magnetic material  1030 , non-magnetic material  1040 , and a shaft  1050 . In some embodiments, some of these components may resemble the magnets  810 , coils  820 , magnetic material  830 , non-magnetic material  840 , and shaft  850  of control motor  800 . 
     Unlike control motor  800 , however, control motor  1000  features additional non-magnetic material  1045  separating coil  1020  from magnets  1010  and magnetic material  1030 . In the example of  FIGS. 10A and 10B , the additional non-magnetic material  1045  is at least partially movable relative to both coil  1020  and the moving components of magnets  1010 , magnetic material  1030 , and shaft  1050 . For example, in  FIG. 10A , bearings  1046  allow the additional non-magnetic material  1045  to rotate relative to shaft  1050  (i.e., shaft  1050  is free to rotate inside non-magnetic material  1045  and/or non-magnetic material  1045  is free to rotate about shaft  1050 ). 
     In addition, a spring  1047  couples the additional non-magnetic material  1045  to the static portion of control motor  1000 . In this example, spring  1047  allows the additional non-magnetic material  1045  to at least partially move relative to the static portion of control motor  1000 . In addition, spring  1047  restricts (but does not completely prevent) rotation of non-magnetic material  1045  relative to shaft  1050 . 
     Teachings of certain embodiments recognize that the additional non-magnetic material  1045  may prevent coil  1020  from seizing to magnets  1010  and/or magnetic material  1030  by preventing physical contact between coil  1020  and the magnets  1010  and/or magnetic material  1030 . In addition, allowing the additional non-magnetic material  1045  to move relative to both the movable and static components of control motor  1000  may further reduce seizing by control motor  1000  and may reduce friction and wear within control motor  1000   
     In each of the example control motors  800 ,  900 , and  1000 , break wires are provided to detect bearing failures. 
     In each of these examples, break wires may detect failure of a bearing by severing in response to a failure of the bearing. Teachings of certain embodiments recognize, however, other mechanisms for detecting failure of a bearing. 
       FIGS. 11A and 11B  show cross-section views of a control motor  1100  according to one example embodiment. In the example of  FIGS. 11A and 11B , control motor  1100  features magnets  1110 , coils  1120 , magnetic material  1130 , non-magnetic material  1140 , and a shaft  1150 . In some embodiments, some of these components may resemble the magnets  810 , coils  820 , magnetic material  830 , non-magnetic material  840 , and shaft  850  of control motor  800 . 
     Unlike control motor  800 , however, control motor  1100  features a metal tube  1152  positioned around shaft  1150 . In one example embodiment, metal tube  1152  is aluminum or an aluminum alloy. Control motor  1100  also features electrical transmission lines  1154  and  1154 . In the example of  FIGS. 11A and 11B , electrical transmission line  1154  is associated with shaft  1150 , and electrical transmission line  1156  is associated with tube  1152 . In one example embodiment, electrical transmission lines  1154  and  1156  are electrically coupled to shaft  1150  and tube  1152 . In another example embodiment, electrical transmission lines  1154  and  1156  are located adjacent to shaft  1150  and tube  1152 . 
     Control motor  1100  also features jam members  1162  and  1172 . Jam member  1162  is located proximate to spherical member  1160 . In one example embodiment, spherical member  1162  may resemble and/or operate similarly to spherical member  724 . Jam members  1172  are located proximate to bearings  1170  and secondary bearings  1171 . In one example embodiment, bearings  1170  may resemble and/or operate similarly to bearings  860 . Secondary bearings  1171  may act as backup bearings and engage in response to a failure by bearings  1170 . 
     In operation, according to one example embodiment, elements such as spherical member  1160  and bearings  1170  may jam or otherwise fail.  FIG. 11A  shows the position of jam members  1162  and  1172  prior to failure by spherical member  1160  and bearings  1170 . As seen in  FIG. 11B , failure by spherical member  1160  or a bearing  1170  may cause jam members  1162  and  1172  to deform part of tube  1152 . For example, a failure by one of the bearings  1170  may cause secondary bearings  1171  to engage, which causes secondary bearings  1171  to displace jam members  1172 . 
     In the example of  FIG. 11B , deforming tube  1152  relieves the jam and causes tube  1152  to contact shaft  1150 , thus completing an electrical circuit between electrical transmission line  1154  and electrical transmission line  1156 . Completing the electrical circuit may alert maintenance workers to a failure within control motor  1100  and may allow maintenance workers to perform repairs so as to prevent further damage and/or more catastrophic failures. In addition, deforming tube  1152  may relieve the jam by spherical member  1160  and/or bearings  1170  and therefore allow control motor  1100  to continue operating until repairs can be made. 
       FIGS. 12A-12C  show cross-section views of a control motor  1200  according to another example embodiment. In the example of  FIGS. 12A and 12B , control motor  1200  features magnets  1210 , coils  1220 , magnetic material  1230 , non-magnetic material  1240 , a shaft  1250 , a spherical member  1260 , bearings  1270 , and secondary bearings  1271 . In some embodiments, some of these components may resemble the magnets  1110 , coils  1120 , magnetic material  1130 , non-magnetic material  1140 , shaft  1150 , spherical member  1160 , bearings  1170 , and secondary bearings  1171  of control motor  1100 . 
     Unlike control motor  1100 , however, control motor  1200  features resettable ball detents  1172  and springs  1274 .  FIG. 12A  shows the positions of ball detents  1272  prior to failure by bearings  1270 . As seen in  FIG. 12A , spring  1274  forces ball detents  1172  against secondary bearings  1271 . 
       FIGS. 12B and 12C  show the positions of ball detents  1272  after failure by bearings  1270 . In these examples, failure of bearings  1270  causes secondary bearings  1271  to force ball detents  1272  back against spring  1274 . Forcing ball detents  1272  back against spring  1274  pulls detent pin  1252  downwards and closes the electrical circuit between electrical transmission line  1254  and electrical transmission line  1256 . 
     In some embodiments, ball detents  1272  may be reset after the bearing jam is repaired. For example, after bearings  1270  and/or secondary bearings  1271  are reset/repaired/replaced, detent pin  1252  may be pulled upwards, and spring  1274  may force ball detents  1272  into the original position. Teachings of certain embodiments recognize that providing resettable ball detents may reduce the time and expense necessary to repair a bearing jam. 
     Modifications, additions, or omissions may be made to the systems and apparatuses described herein without departing from the scope of the invention. The components of the systems and apparatuses may be integrated or separated. Moreover, the operations of the systems and apparatuses may be performed by more, fewer, or other components. The methods may include more, fewer, or other steps. Additionally, steps may be performed in any suitable order. 
     Although several embodiments have been illustrated and described in detail, it will be recognized that substitutions and alterations are possible without departing from the spirit and scope of the present invention, as defined by the appended claims. 
     To aid the Patent Office, and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants wish to note that they do not intend any of the appended claims to invoke paragraph  6  of 35 U.S.C. §112 as it exists on the date of filing hereof unless the words “means for” or “step for” are explicitly used in the particular claim.