Abstract:
Vehicles commonly include control-surfaces and other components that are selectively moved during operation among a plurality of positions. Movement of aircraft control-surface components is crucial in flight, and an actuating assembly must consistently and dependably perform during normal operation and be prepared to survive situations outside normal operation and/or to compensate for circumstances causing loss of actuator control. Jam tolerant electromechanically operated actuation systems, of both the rotary and linear types, together with their methods of operation are described herein. Specifically, electrical jam-detection and control systems and associated locking and damping devices can be electrically and mechanically engaged and disengaged, are automatically reversible, and are testable.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/315,242 filed Mar. 18, 2010, which is hereby incorporated herein by reference. 
    
    
     The present invention pertains to jam tolerant electromechanically operated actuation systems, of both the rotary and linear types, together with their methods of operation that can be utilized wherever such actuation systems are required, e.g., in vehicles, etc. Specifically, this invention pertains to electrical jam-detection and control systems and associated locking and damping devices that can be electrically and mechanically engaged and disengaged, that are reversible, and that are testable. 
     BACKGROUND 
     Vehicles such as manned and unmanned aircraft, marine, submarine, spacecraft, and ground vehicles commonly include control-surfaces and other components (e.g., stabilizers, rudders, elevators, flaps, ailerons, spoilers, slats, arms, etc.) that are selectively moved during operation among a plurality of positions. Selective movement can be achieved by an actuating assembly comprising an actuator, to which the control-surface component is attached, and means for providing actuator-moving power to the actuator. Specifically, movement of aircraft control-surface components is crucial in flight, whereby an actuating assembly must consistently and dependably perform during normal operation. Moreover, the actuating assembly must be prepared to survive situations outside normal operation and/or to compensate for circumstances causing loss of actuator control. 
     SUMMARY 
     The jam-tolerant electromechanical assembly described herein will make electromechanical actuators safer for primary flight control. The elimination of a mechanical jam potential in electromechanical actuators removes the last remaining technical obstacle that prevents electromechanical actuators from being used in primary flight control applications. 
     According to one aspect, a Damper System within a Simplex Jam-Tolerant Electromechanical Actuator (JTEMA) enables a passive, controlled (damped) rate of return of the JTEMA output and movable surface to a fail-safe position, plus a latching feature that captures and holds the output and movable surface when it reaches the fail-safe position. This damper system is activated whenever electrical power to the JTEMA is lost, or after an internal jam of the JTEMA requires decoupling of the ball nut from the output and movable surface. Furthermore, the damper system is ground testable and self-resettable. 
     According to another aspect, a Ball Nut Disconnect System (BNDS) for the Simplex Jam-Tolerant Electromechanical Actuator relies upon stored energy to provide a means to decouple the Ball Nut from the output and moveable surface upon loss of electrical power to the EMA even if the actuator is loaded up to the stall load. Furthermore this feature is ground testable and self-resettable. 
     According to another aspect, a Dual Ball Nut Disconnect System (DBNDS) for a Dual Jam-Tolerant Electromechanical Actuator combines the functions of two separate Ball Nut Disconnect Systems into one dual-purpose system in order to allow sharing of components, a reduced envelope, and reduced weight. Additionally, for actuators requiring ballistic tolerance, because the DBNDS co-locates the disconnect mechanisms for both ball nuts, it minimizes the amount of armored shielding needed for protection and provides for additional weight savings by enabling an EMA architecture that is partially sacrificial and thus does not require ballistic shielding. 
     According to one aspect of the present invention, an electromechanical actuator, includes a motor having a motor drive train that drives a screw, the screw coupled to a nut that is axially movable relative to the screw to control movement of an output rod connected to a movable surface; a damper assembly coupled to the output rod and including a damper and a damper drive train, wherein, in a normal motor operating state, the output rod is coupled to the nut to thereby control movement of the movable surface with the motor; and in a motor malfunction mode, the damper assembly is engaged to the output rod to provide a controlled rate of return of the movable surface to a fail-safe position. 
     According to another aspect, the damper assembly further includes a damper detent mechanism which couples the output rod to the damper in a normal damper operating state and which decouples the output rod from the damper in a damper malfunction state. 
     According to another aspect the damper assembly further including a latch that restricts movement of the output rod in a fail-safe mode and thereby restricts movement of the movable surface. 
     According to another aspect, the damper assembly includes a damper screw coupled to the damper drive train, a damper nut coupled to and axially movable relative to the damper screw, and wherein the latch engages the damper nut in the fail-safe mode to thereby limit movement of the damper nut relative to the damper screw. 
     According to another aspect, the damper nut is coupled to the output rod. 
     According to another aspect of the present invention, an electromechanical actuating assembly includes a motor having a motor drive train that drives a screw, the screw coupled to a nut that is axially movable relative to the screw to control movement of an output rod; a nut disconnect system including at least one coupler key movable between a locked position in which the key maintains coupling between the output rod and the nut to thereby control movement of the output rod with the motor and an unlocked position in which the key decouples the output rod from the nut to thereby remove control of the output rod from the motor. 
     According to another aspect, the nut disconnect system includes a release mechanism operable to decouple the nut from the output rod by moving the key to the unlocked position. 
     According to another aspect, the release mechanism is a solenoid-operated release mechanism. 
     According to another aspect, the release mechanism is powered by stored energy electronics that automatically release stored energy to activate the release mechanism upon a loss of power to the electromechanical actuating assembly. 
     According to another aspect, the nut disconnect system includes a drive mechanism coupled to the stored energy electronics and the nut coupler, the drive mechanism transmitting the stored energy from the stored energy electronics to the nut coupler to move the coupler key to the unlocked position. 
     According to another aspect, the electromechanical actuating assembly further includes a damper assembly coupled to the nut and including a damper that provides a controlled rate of return of the output rod upon decoupling of the output rod from the motor. 
     According to another aspect, the damper assembly further includes a damper detent mechanism between the nut and the damper, the damper detent mechanism movable from an unlocked position in which the damper is uncoupled from the nut and a locked position in which the damper is coupled to the nut. 
     According to another aspect, the damper assembly further includes a latch mechanism that restricts movement of the nut in a fail-safe mode. 
     According to another aspect, the drive mechanism is configured to provide the following operations in sequence: (i) lock the damper detent mechanism; (ii) trigger an electrical switch to enable the damper; (iii) enable the latch mechanism that restricts movement of the nut in fail-safe mode; and (iv) decouple the nut from the output rod. 
     According to another aspect, the stored-energy electronics include a reset mechanism including a motor and a drive that reverses the sequence of operations of the drive mechanism. 
     According to another aspect of the present invention, an electromechanical actuating assembly includes a front screw coupled to a front nut that is axially movable relative to the front screw to control movement of an output rod, the front screw coupled to a motor through a motor drive train; a front nut coupler that selectively couples the front nut to the output rod to thereby control movement of the output rod with a motor and decouples the front nut from the output rod to thereby remove control of the output rod from the motor; a back screw coupled to a back nut that is axially movable relative to the back screw to control movement of the output rod, the back screw coupled to a motor though a motor drive train; a back nut coupler that selectively couples the back nut to the output rod to thereby control movement of the output rod with a motor and decouples the back nut from the output rod to thereby remove control of the output rod from the motor. 
     According to another aspect, the electromechanical actuating assembly further includes a motor for commonly driving the front screw and the back screw. 
     According to another aspect, the electromechanical actuating assembly further includes a first motor for driving the front screw and a second motor for driving the back screw. 
     According to another aspect, the front nut coupler and the back nut coupler are coupled to one another and to the output rod. 
     According to another aspect, the electromechanical actuating assembly further includes at least one extension arm connecting the back nut to the back nut coupler. 
     According to another aspect, the front nut coupler and the back nut coupler are contained within a housing. 
     According to another aspect, the front nut coupler includes one or more rollers for engaging one or more corresponding keys, the keys movable between a first position and a second position, wherein in the first position the rollers are disengaged from the keys to thereby disengage the front nut coupler from the front nut, and in the second position the rollers are engaged to the keys to thereby engage the front nut coupler with the front nut. 
     According to another aspect, the back nut coupler includes one or more rollers for engaging one or more corresponding keys, the keys movable between a first position and a second position, wherein in the first position the rollers are disengaged from the keys to thereby disengage the back nut coupler from the back nut, and in the second position the rollers are engaged to the keys to thereby engage the back nut coupler with the back nut. 
     According to another aspect the electromechanical actuating assembly further includes a dual stored energy device system including a first solenoid coupled to the front nut coupler and a second solenoid coupled to the back nut coupler, the dual stored energy device storing mechanical energy to decouple the front nut coupler and the front nut or to decouple the back nut coupler and the back nut, thereby to selectively control the output rod by only the front nut or by only the back nut. 
     The jam-tolerant electromechanical actuator can be used in aircraft (manned and unmanned), missiles, spacecraft, ships, submarines, unmanned underwater vehicles, military ground vehicles, and the like. 
     Further features of the invention will become apparent from the following detailed description when considered in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustrating an exemplary Jam Tolerant Electromagnetic Actuator System. 
         FIG. 2  is a block diagram illustrating an exemplary Jam Tolerant Electromagnetic Actuator System. 
         FIG. 3  is a diagram illustrating an exemplary Jam Tolerant Electromagnetic Actuator System. 
         FIG. 4  is a schematic illustrating an exemplary Jam Tolerant Electromagnetic Actuator System during normal operation. 
         FIG. 5  is a schematic illustrating an exemplary Jam Tolerant Electromagnetic Actuator System during jammed operation. 
         FIG. 6  is a diagram illustrating an exemplary damper drive detent mechanism during normal operation. 
         FIG. 7  is a diagram illustrating an exemplary damper drive detent mechanism during jammed operation. 
         FIG. 8  is a diagram illustrating an exemplary damper drive detent mechanism during damper-jammed operation. 
         FIG. 9  is a diagram illustrating an exemplary stored energy device. 
         FIG. 10  is a diagram illustrating an exemplary Jam Tolerant Electromagnetic Actuator ball nut coupler during normal operation. 
         FIG. 11  is a diagram illustrating an exemplary Jam Tolerant Electromagnetic Actuator ball nut coupler during jammed operation. 
         FIG. 12A  is a diagram illustrating an exemplary Jam Tolerant Electromagnetic Actuator ball nut coupler during jammed operation. 
         FIG. 12B  is a diagram illustrating an exemplary Jam Tolerant Electromagnetic Actuator ball nut coupler during normal operation. 
         FIG. 13  is a diagram illustrating an exemplary Jam Tolerant Electromagnetic Actuator ball nut and corresponding keys and rollers. 
         FIG. 14  is a diagram illustrating an exemplary ball nut disconnect system. 
         FIG. 15  is a diagram illustrating an exemplary ball nut disconnect system. 
         FIG. 16  is a schematic illustrating an exemplary dual stored energy device. 
         FIG. 17  is a diagram illustrating an exemplary dual ball nut disconnect system. 
         FIG. 18  is a diagram illustrating an exemplary dual ball nut disconnect system. 
         FIG. 19  is a diagram illustrating an exemplary dual ball nut disconnect system. 
         FIG. 20  is a diagram illustrating an exemplary back ball nut coupler mechanism. 
     
    
    
     DETAILED DESCRIPTION 
     When used herein, “normal operation” or like phrases denote operation of the system during times generally excluding jam situations and testing situations. Testing situations may simulate both normal operation and jammed-mode operation. Further, “fail-safe” positions are positions taken by various elements when a jam of some sort is detected. 
     Illustrated schematically in  FIG. 1 , operationally in  FIG. 2  as a block diagram, and physically in  FIG. 3  is a Jam-Tolerant Electromechanical Actuator (JTEMA) system  5  including a primary drive system  8  which may include a main drive motor  10 , a clutch  12  (which may, e.g., be a skewed roller clutch), a drive gear train  14  rotationally coupling the drive motor  10  to the ball screw drive gear  16 , which transfers power to a ball screw  18 , that moves a ball nut  20 , which effectuates the actuation of the output rod  22 . The output rod  22  has a rod end  24  which is connected to the control surface (not shown) to be controlled by the JTEMA system  5 . The rod end  24  may be connected to a measuring device, for example to one end of a linear variable differential transformer (LVDT)  26 , which can measure the displacement of the rod end  24  with respect to a fixed location on the vehicle employing the JTEMA system  5  (e.g., on a fixed tailstock  28  that may also support the ball screw  18 , or other elements of the JTEMA system  5 ). The movement of the output rod may be limited, for example, by physical stops. At full retraction, for instance, the output rod  22  may be limited by the ball nut  20  coming into contact with the retract stop  30 . Conversely, at full extension, for instance, the output rod  22  may be limited by the ball nut  20  coming into contact with the extend stop  32 . 
     The JTEMA system  5  may also contain a damper system  40  consisting of subsystems described in more detail below in the “Damper System” section. Further, the JTEMA system  5  may also be equipped with a Ball nut Disconnect System (BNDS)  80  and/or a dual ball nut disconnect system (DBNDS)  130 , both of which are described in more detail below in their own respective sections. 
     Damper System 
     Referring now to  FIGS. 1-5 , the Damper System  40  consists of the following components which are described in detail in the following subsections: a Jam Tolerant Damper Drive (JTDD)  42 , an Electro-Dynamic Damper (EDD)  43 , a JTDD Detent Mechanism  44 , and JTEMA Electronics  70 . 
     Jam Tolerant Damper Drive (JTDD). 
     In flight, for example, great force may be exerted on a control surface due to aerodynamic drag. A jam in the primary drive system  8  may necessitate that the output rod  22  be decoupled from the primary drive system  8 . In order to prevent fast and powerful movements and vibrations in the control surface after it is decoupled from the primary drive system  8 , a damper  43  may be used to damp this movement. The JTDD  42  is used to couple the output rod  22  to this damper  43 . 
     The JTDD  42  may consist of a JTDD detent mechanism  44  (described in more detail below), a fail-safe position latch  46 , a damper-drive ball screw  48 , a damper-drive ball nut  50 , and a damper-drive gear train  52  connecting the output rod  22  to a damper  43  that can be, for example, the Electro-Dynamic Damper (EDD)  43 . 
     Movement of the output rod  22  is transferred to the damper-drive ball nut  50  by, for example, direct coupling. The damper-drive ball nut  50  transfers this linear displacement into a rotational movement of the damper-drive ball screw  48 . The damper-drive ball screw  48  is coupled (e.g., is fixedly attached) to the first gear in the damper-drive gear train  52 , which transfers the rotational movement to the damper  43 . The number of gears and the gear ratios in the damper-drive gear train  52  may be selected to best fit the particular installation and purpose of the JTEMA system  5 , and may be chosen by one of ordinary skill in the art after reading and understanding this disclosure. 
     Although the damping helps to mitigate dangerous movements, it may be advantageous to completely halt the movement of a control surface in a particularly advantageous position. For example, it might be advantageous in some situations to lock an aileron in a position to provide maximum flight time or maximum flight distance, or minimum flight speed without stalling. In such cases, the fail-safe position latch  46  may be used to halt the movement of a control surface once the surface has been pushed to this position by external forces (for example, aerodynamic drag). The fail-safe position latch  46  is normally deactivated by being held in place in a disabled position by a latch disabler  54 . When the latch disabler  54  is removed, the fail-safe position latch  46  is moved to an active position (by, e.g., a spring  47 ). Once in the active position, shown, for example, in  FIGS. 5 and 7 , the fail-safe position latch  46  passively latches and locks the control surface in the fail-safe position when it is driven there by aerodynamic forces acting on the surface. More specifically, the fail-safe position latch  46  may engage a depression  56  in the damper-drive ball nut  50  once the damper-drive ball nut  50  reaches a fail-safe position after being driven there by the output rod  22 . 
     Electro-Dynamic Damper (EDD). 
     The EDD  43  may operate as a generator to convert the aerodynamic energy load of the disconnected flight surface into waste heat inside the damper windings  58  or electrical energy that may be stored in a suitable electrical storage device such as batteries (not shown) or capacitors  74 ,  76 . The EDD  43  passively controls (damps) the rate of motion of the control surface as the surface returns to the fail-safe position when acted upon by, for example, aerodynamic forces. The EDD  43  may include, for example, damper windings  58 , a simplex damper electronics (SDE)  60 , a damper switch  62 , and a damper relay  63 . 
     The damper windings  58  may be, for example, a resisting wire used to convert mechanical movement into electrical current when used with one or more magnets  64  coupled to the last gear in the damper-drive gear train  52 . These windings may also then dissipate electrical current energy into heat energy through inherent resistivity or external electrical resistors (not shown). The windings and/or resistors may be cooled by some sort of cooling system (not shown) known to one of ordinary skill in the art, may be exposed to ambient air or water flow, or may be contained in a closed housing (not shown). 
     The SDE  60  may be used to, for example, control the amount of damping, and may monitor, for example, the current and the heat generated in the damper  43 . The SDE  60  may also control the flow of electrical current to various storage devices if these are being utilized. 
     The damper switch  62  is open during normal operation in order to prevent damping of the movement of the output rod  22  and control surface. If a jam of the primary drive system  8  is detected, the damper switch  62  is closed by the damper relay  63 , completing the circuits in the EDD  43 , which may now damp the movements of the output rod  22 . 
     The Jam-Tolerant Damper Drive (JTDD) Detent Mechanism. 
     Referring now to  FIGS. 6-8 , the detent mechanism  44  provides jam tolerance for the JTDD  42 . 
     The detent mechanism  44  may be attached to one or more detent springs  66  to effectuate the movement of the detent mechanism  44  into one or more detent recesses  68  in the damper-drive ball nut  50 . During normal operation the only forces the JTDD  42  is required to carry are the loads required to accelerate the inertia of the JTDD  42 , because the damping system  43  has not been engaged (e.g., the damper switch  62  has not been closed). The spring(s)  66  may be preloaded with enough stored energy to provide enough force to carry the inertial loads of the JTDD  42 , thus ensuring that the damper  43  always remains indirectly coupled to the output rod  22 . This connection enables the JTDD  42  to be quickly activated in the event that damping is required. 
     During jammed-mode operation—and as part of the ball nut disconnect sequence described further below—the first action that the Damper System  40  makes is to lock the detent mechanism  44  in the “drive” or “engaged” position using the detent uplock switch  69 . The detent uplock switch  69  may be inserted into a notch or recess  45  in the detent mechanism  44 . Locking the detent mechanism  44  in this position enables the JTDD  42  to carry the high damping loads associated with returning the control surface to the fail-safe position. 
     In addition to the possibility of a jam in the primary drive system  8 , it is also possible for the JTDD  42  to jam. The JTDD  42  is jam tolerant, however, because the detent mechanism  44  passively disengages the Damper System  40  in the event of a jam in the Damper System  40 , allowing the primary drive system  8  to continue its normal operation control functions. Disengagement occurs whenever the driving forces on the JTDD  42  are high enough to overcome the detent mechanism  44  spring  66  preload. This situation should only occur if there is a malfunction (such as a jam or excessive friction drag) within the JTDD  42 . The disengagement of the Damper System  40  is detected by a continuous monitor in the JTEMA electronics  70  which will create a Damper INOP fault message. 
     The JTEMA system  5  can automatically test and reset these jam-tolerant features of the Damper System  40  during an on-the-ground test. 
     JTEMA Electronics. 
     Referring back to  FIG. 2 , the EMAS  5  may be equipped with JTEMA electronics  70  configured to, for example, control and monitor the Damper System  40 . 
     During normal operation the JTEMA electronics  70  provide continuous monitoring of the damper resolver  72 . This monitoring enables continuous detection of a damper-drive jam that causes the Damper System  40  to detent free of the primary drive system  8 . The damper resolver  72  may be any type of sensor, but is preferably a rotational sensor. In a preferred embodiment the damper resolver  72  is an analog resolver. In another preferred embodiment, the damper resolver is a digital encoder. Under normal conditions, there should be a constant gear ratio between the damper resolver  72  and the LVDT  26 , within a tolerance band dependent on the specific configuration of the JTEMA system  5  and the vehicle or device the JTEMA system  5  is installed in. If this gear ratio tolerance band is exceeded, the JTEMA electronics  70  may create a fault message. 
     During all operations, the JTEMA electronics  70  may provide continuous monitoring of the main drive motor  10  via a main drive resolver  78 . The main drive resolver  78  may monitor the motor current, speed, torque, position, and the like. The main drive resolver  78  may be an analog resolver or any other individual sensor or suite of sensors known in the art to monitor the main drive motor  10 . 
     During normal operation the JTEMA electronics  70  also provide continuous monitoring of the energy storage capacitors used to provide energy during an electrical failure. Both the Stored Energy Device (SED)  91  activation capacitors  74  and the damper switch  62  trigger capacitors  76  should be kept charged at all times to ensure immediate energy availability upon loss of system electrical power. A fault message is created by the JTEMA electronics  70  any time these capacitor sets lose their charge during operation. 
     Upon loss of system power, the JTEMA electronics  70  uses stored electrical energy in the activation capacitors  74  to activate the SED  91  which enables the Damper System  40  prior to disconnecting the ball nut  20 . The JTEMA electronics  70  uses stored electrical energy from the trigger capacitors  76  to close the damper switch  62  with the damper relay  63 , thus closing the damper  43  circuits after the SED  91  triggers the damper detent uplock switch  69 . 
     During ground tests, the JTEMA electronics  70  automatically run the Damper System  40  performance tests. These tests may include, for example driving and stopping the SED reset motor  92  at the position where the main drive motor  10  can be run while the Damper System  40  is activated. The Damper System  40  performance may be verified by measuring the main drive motor  10  current at a given main drive motor  10  speed. If the main drive motor  10  current is below an allowable threshold a Damper System  40  performance fault message will be created. The current falling below a certain value would indicate that the activated Damper System  40  is not sufficiently restricting the movement of the output rod  22  (moving under the power of the main drive motor  10  in this testing mode). 
     During ground tests, the JTEMA electronics  70  may measure the time from SED solenoid  94  command until the damper switch  62  is closed. If this time is longer than the allowable time, the JTEMA electronics creates a SED  91  performance fault message. 
     During ground tests, the JTEMA electronics  70  may automatically run the damper detent mechanism  44  performance test by driving the main drive motor  10  while the Damper System  40  is activated but the detent mechanism  44  is not locked up by the detent uplock switch  69  to verify that the detent mechanism  44  will disconnect from the damper-drive ball nut  50  at loads above the normal operating loads. These loads may be verified by main drive motor  10  current draw at a speed which would create a Damper System  40  load above a threshold value, or by a separate sensor known in the art that may measure the force directly or indirectly. If the detent mechanism  44  fails to disconnect the Damper System  40  from the primary drive system  8 , a damper detent mechanism  44  performance fault message will be created. Following a successful completion of this test, the JTEMA Electronics  70  may automatically run the damper detent mechanism  44  reset sequence described more fully below. 
     Ball Nut Disconnect System (BNDS) 
     Referring now to  FIGS. 9-15 , the BNDS  80  consists of the following principal components which are described in detail in the following sections: Stored Energy Device System (SEDS)  90 , and Stored Energy Electronics  110 . 
     Stored Energy Device System (SEDS). 
     The SEDS  90  consists of the Stored Energy Device (SED)  91  (a preferred embodiment is shown in detail in  FIG. 9 ), the SED drive mechanism  95 , and the SED reset mechanism  96  which are described herein. 
     Upon loss of electrical power, the JTEMA electronics  70  automatically provides stored electrical energy to the SED solenoid  94  which releases stored energy (e.g., mechanical spring energy) in the SED  91  to provide input motion and torque via the SED drive mechanism  95  to the BNC  120  to disconnect the ball nut  20  from the output rod  22 . The SED  91  may include a compressed mechanical or gas spring  98  and a solenoid-operated release mechanism  99 . 
     The SED drive mechanism  95  may be a mechanical drive train between the SED  91  and the Ball Nut Coupler  120  (BNC). In addition to transmitting the stored energy from the SED  91  to the BNC  120 , the SED drive mechanism  95  performs the following operations in sequence: 
     Step  1 : Disable (lock) the damper detent mechanism  44  (Refer to the detent uplock switch  69  in  FIGS. 4 and 13 ). 
     Step  2 : Trigger the damper switch  62  to enable the damper  43  (Refer to the damper switch  62  in  FIG. 4 ). 
     Step  3 : Enable the fail-safe latch  46  (Refer to the latch disabler  54  feature in  FIGS. 4 and 13 ). 
     Step  4 : Decouple (disconnect) the ball nut  20  from the output rod  22  and control surface (Refer to  FIGS. 4 ,  6  and  7 ). 
     These operations may be reset by the SED reset mechanism  96 . The SED reset mechanism  96  may include a SED reset motor  92  (which may include, e.g., some type of electric motor and a mechanical drive) which provides the motion and force required to reverse the sequence of operations described above by rotating the SED rotor  100  back to the normal operating position while the vehicle or device is not in full operation (e.g., the aircraft is on the ground). The JTEMA electronics  70  may drive the primary drive system  8  to align the ball nut  20  with the BNC  120  in the output rod  22 . The SED reset motor  92  may compress the linear SED springs  98  (or, if the SED  91  is a rotary mechanism, rewinds the SED torsion spring  98 ) to reset the SED  91 . The SED reset mechanism  96  may reset and disable (lock) the fail-safe latch  46  by, for example, covering it with the latch disabler  54 . The damper switch  62  may be released to disable the damper  43 . The SED reset mechanism may withdraw the detent uplock switch  69  to enable (unlock) the damper detent mechanism  44 . Finally, the ball nut  20  may be reconnected to the output rod  22  with the following part motions: the SED motor reset cam  102  rotates the SED rotor  100  via the cam follower  104  (See  FIG. 11 ), rotation of the SED rotor  100  rotates the BNC roller cage  122  (See  FIG. 11 ), rotation of the BNC roller cage  122  drives the rollers  124  on top of the outside surface  125  of BNC keys  126  which force the keys  126  radially inward to engage the slots  128  in the ball nut  20  (See  FIGS. 12A and 12B ). The keys  126  may be any appropriate shape including substantially square, rectangular, or trapezoidal, for example. Preferably, the keys have rounded or angled edges to ease and smooth the path of the rollers  124  when rolling onto the surface  125  of the keys  126 . 
     Stored Energy Electronics. 
     A portion of the JTEMA electronics  70  may be dedicated to providing sequenced operations in controlling the Ball Nut Disconnect System  80  (BNDS): 
     During a system power up time, the JTEMA electronics  70  may automatically align the ball nut  20  with the output rod  22  by driving the primary drive system  8 . Then, the JTEMA electronics  70  may drive the SED reset motor  92  to engage (mechanically connect) the ball nut  20  with the output rod  22  and to reset the Stored Energy Device (SED)  91 . Also during system power up, the JTMEA electronics  70  may store electrical energy in the SED activation capacitors  74 . 
     During system power down (e.g., when power is disconnected from the JTEMA system  5 ), the JTEMA electronics  70  automatically releases stored electrical energy to activate the SED solenoid  94  in the SED  91 . (Refer to the schematic portion of  FIG. 2 ). 
     Dual Ball Nut Disconnect System (DBNDS): 
     Referring now to  FIGS. 16-20 , the DBNDS  130  consists of the following principal components which are described in detail in the following sections: Dual Jam Tolerant Electronics (DJTE)  140 , Dual Stored Energy Device System (DSEDS)  160 , and Dual Ball Nut Coupler (DBNC)  180 . In these sections a “prime” notation is used to denote features associated with a first or a front element while a “double prime” notation is used to denote features associated with a second or a back element. Where a feature or element is identical to a feature or element already described, sometimes the “prime” notation is omitted for clarity. 
     Dual Jam Tolerant Electronics (DJTE). 
     In operation (e.g., in flight), the DJTE  140  evaluates load sensor data (which may come, e.g., from the LVDT  26 ) and main drive motor data (which may come, e.g., from the main drive resolver  78 ) to detect and then isolate a jam in a first primary drive system  8 . The DJTE  140  may then command the appropriate dual stored energy device solenoid  162  to disconnect the jammed primary drive system from the output rod  22 , and control the first or a second primary drive system  8  in order to facilitate jam recovery and maintain command of the control surface. 
     After operations of the vehicle are completed (e.g., the aircraft is on the ground), the DJTE  140  commands the SED reset motor  92  (which may be, for example, a servo motor, a stepper motor, or the like) to re-energize the SED  91  and functions as a component of the JTEMA electronics&#39;  70  automatic self-test system as described above in regards to the BNDS  80 . 
     The DJTE  140  may be a part of JTEMA electronics  70 , or may be a separate system. 
     Dual Stored Energy Device System (DSEDS). 
     Referring now to  FIG. 16 , shown is a diagram of a DSEDS  160 . The DSEDS  160  is similar to the SEDS  90  (described above) except that it uses two solenoids  94 ′,  94 ″ (one for each BNC  120  system), a single output rod  22  either extends or retracts from a neutral position depending upon which ball nut  20 ′,  20 ″ is to be disconnected from the output rod  22 . Further, the DSEDS  160  also uses an energy absorbing device  98 ′,  98 ″ (such as a stack of ringfeder springs) at each end of the SED output  162  stroke. 
     The DSEDS  160  stores sufficient mechanical energy to drive and decouple either of the ball nuts  20 ′,  20 ″ while the JTEMA system  5  is loaded up to stall load, and releases the stored mechanical energy (spring energy) and transmits the energy to one side of the Dual Ball Nut Coupler (DBNC)  180  to rotate the roller cage  122 . 
     Dual Ball Nut Coupler (DBNC). 
     Referring now to  FIGS. 17 ,  18  and  19 , shown is a Dual Ball Nut Coupler (DBNC)  180 . The DBNC  180  disconnects one or the other of the ball nuts  20 ′,  20 ″ (but not both) from the output rod  22 , and reconnects the disconnected ball nut  20 ′  20 ″ to the output rod  22  during on-the-ground automatic self-testing/reset procedures. The DBNC  180  enables a minimally-armored but fully protected architecture of a dual ballistic tolerant JTEMA by, for example, requiring only one armored housing unit to protect only one actuator system that provides similar redundancy to a system having two separate JTEMAs. Note in  FIG. 17  that the stationary housing  164  protects the ball nut couplers  120 ′,  120 ″ for both the front ball nut  20 ′ and the back ball nut  20 ″. 
     The DBNC  180  may include a front ball nut coupler  120 ′. The front BNC  120 ′ is identical to the JTLEMA Simplex BNC  120  shown in  FIGS. 10 ,  11 ,  12 A and  12 B. To engage the front BNC  120 ′, the roller cage  122  and rollers  124  are rotated to the outside surfaces  125  of the BNC keys  126  in order to drive the keys inward into the slots  128  of the front ball nut  20 ′. During normal operation the front BNC keys  126  are held inward to keep the front ball nut  20 ′ connected to the output rod  22 . When the front ball nut  20 ′ is to be disconnected, the BNC keys  126  are driven out when the roller cage  122  and rollers  124  are rotated off the outside surfaces  125  of the keys  126 . 
     The DBNC  180  also includes a back ball nut coupler  120 ″. The back BNC  120 ″ works in an opposite manner from the front BNC (See  FIG. 19 )  120 ′. Accordingly, to engage the back BNC  120 ″, the roller cage  122 ″ and rollers  124 ″ are rotated to the inside surfaces  125 ″ of the back BNC keys  126 ″ in order to drive the keys  126 ″ outward. 
     Referring now to  FIGS. 18 ,  19  and  20 , during normal operation, the back BNC keys  126 ″ are held outward to keep the extension arms  182  from the back ball nut  20 ″ connected to the output rod  22 . When the back ball nut  20 ″ is to be disconnected, the BNC keys  126 ″ are driven inward when the roller cage  122 ″ and rollers  124 ″ are rotated off the inside surfaces  125 ″ of the keys  126 ″.