JP4936717B2 - Electric linear actuator - Google Patents

Description

The present invention relates to actuators. An “actuator” is defined in the 10th edition of Merriam-Webster's Collegiate Dictionary as a mechanical device for moving or controlling something. Actuators perform a myriad of functions and make many modern instruments available.

  For example, an aircraft needs an actuator to fly. Each wing flap, spoiler and aileron each require an actuator. The tail actuator controls the rudder and elevator. The fuselage actuator opens and closes the door that covers the landing gear housing. The actuator raises and lowers the landing gear. Each engine actuator controls a thrust reverser, which causes the aircraft to decelerate.

  In addition to aircraft applications, actuators are used in computer disk drives to control the location of read / write heads, whereby data is stored on and read from the disk. Actuators are used to assemble products in robots, ie in automated factories. Actuators operate vehicle brakes, open and close doors, raise and lower railroad gates, and perform a myriad of other daily tasks.

  Prior art actuators fall into two general categories. That is, there is a hydraulic type and an electric type, and the difference between these two categories is in the power to be moved or controlled. Hydraulic actuators require a pressurized, incompressible working fluid, usually oil. The electric actuator uses an electric motor, and the rotation of its shaft causes a linear displacement using some kind of transmission device.

  The problem with hydraulic actuators is the piping needed to distribute and control the pressurized working fluid. In aircraft, the pumps that provide the high pressure working fluid and the piping to route the working fluid add weight and increase design complexity because the hydraulic lines must be carefully routed.

  Electric actuators powered and controlled by electrical energy require only wires for operation and control, but the problem with prior art electric actuators is their reliability. Electric motor windings are susceptible to damage from heat and water. Motor shaft bearings wear out. Transmissions that are between the motor and the load and are inherently more complex than the pistons and cylinders used in hydraulic actuators are also prone to failure. Although electric actuators have advantages over hydraulic actuators, electric actuators that provide increased reliability would be an improvement over the prior art. Fault tolerance, ie the ability to continue to work while suffering a failure or failure of one or more components, will provide an improvement over prior art electric actuators.

SUMMARY OF THE INVENTION A fault tolerant electric actuator uses two or more independent integrated motor modules in the same housing to drive an output ram that can be pulled out and retracted into the housing, the housing comprising the ram Encloses an electric motor module that is driven into and out of the housing. The integrated motor module (FIG. 2) is defined as a unit consisting of one or more electric motor armature / field units that provide drive functions for engaged or active roller, screw and nut assemblies. The roller / screw / nut assembly (FIG. 2A) consists of a helically threaded roller, and the nut assembly is directly coupled to a common screw shaft. The outer surface of the ram is threaded. Since the output ram is threaded, the ram can be moved into and out of the housing by rotation of one or more “drive nuts” that engage its threads, Rotating but fixed laterally so that the output ram moves laterally as the drive nut rotates.

  The “drive nut” is provided by a roller screw that forms part of the motor armature and engages the threads of the output ram. As this "drive nut" rotates, the rotation translates the output ram, i.e., moves into or out of the housing. Reliability and fault tolerance are provided by a large number of motors and a drive nut armature in each motor that allows each motor to be disengaged and / or engageable separately.

Detailed Description of the Preferred Embodiment FIG. 1 is a cross-sectional view of a preferred embodiment of an electric actuator 10 having electrical fault tolerance.

  Briefly, the actuator 10 comprises a cylindrical housing 20, which encloses two or more (three are shown) integrated electric motor modules 24, 30 and 34 that can drive the output ram 12. The outer surface 16 of the output ram 12 is threaded in a spiral. Spiral threads 18 (also referred to as “threads”) on the surface of the output ram 12 are passed through one or more complementary “drive nuts” in the housing, which drive nuts are threaded output rams 12. And is rotatable about the output ram 12 but is fixed laterally within the housing, i.e., they cannot move along the length of the output ram 12. When the end of the output ram (not shown in FIG. 1) is connected to a machine such as an aircraft control surface, the lateral movement of the ram 12 operates or controls the coupled machine of the output ram 12. To do.

  The output ram 12 can be withdrawn from and retracted into the housing simply by controlling at least one direction of rotation of the “drive nut” that engages the threaded surface 16. The direction of rotation of the drive nut is easily changed by the power applied to the field windings 26 of the motors 24, 30 and 34 that drive the output ram 12.

  More specifically, the ram 12 has a central axis 14 because it is formed in a cylindrical shape. Its outer surface 16 has a helical thread or thread 18 on its outer surface 16 so that the ram 12 can be considered “threaded” like a bolt or screw. The helical “thread” 18 on the outer surface 16 of the ram 12 allows the ram 12 to move axially by engaging the thread 18 of the output ram 12 with the rotating “drive nut” in the housing 20. The drive nut is constructed and arranged to rotate about the shaft 14 and engage the thread 18 but is laterally fixed in the housing 20, that is, moves along the shaft 14 of the output ram 12. Can not. The pitch of the thread 18 affects the speed of the ram (ie the speed at which it moves axially) and the load that the drive motors 24, 30 and 34 are "seen".

As shown in FIG. 1, the housing 20 has at least one opening 22 at one end of the housing, through which the output ram 12 can be withdrawn or retracted as shown in FIG. (Not shown) can be controlled or moved. In at least one alternative embodiment shown in FIG. 7, the embodiment requires a double-acting output ram 12, but the housing 20 has a second opening opposite the first opening 22. The second opening required to implement the embodiment of FIG. 7 is not shown in FIG. 1 for simplicity.

  Each motor 24, 30 and 34 has a stator 26, also known as a "field" or "field winding" as shown in cross section in FIG. As is well known, the application of current to the field winding 26 induces one or more magnetic fields that extend into the motor's armature and rotate the armature. Each field winding 26 leans against the inner wall of the cylindrical housing 20 which also serves as a heat sink for the motor windings.

  The structure and operation of the electric element 28 of each motor 24, 30 and 34 is the above “drive nut” that rotates about the ram 12 and is fixed in the axial direction. The threaded roller screw in the armature 28 engages the thread 18 and is rotatable about the output ram 12, but is fixed in the lateral direction. Thereby, the motor element 28 of each motor acts as a “drive nut” that also provides the ability to drive the output ram 12 but be released from (or coupled to) the threads 18 of the output ram 12. .

  The armature 28 has two or more helically threaded roller screws 44-1 and 44-2 that are equally spaced around the output ram 12 and are thread 18 of the output ram 12. Engage with. Roller screws 44-1 and 44-2 are fixed in the lateral direction, but are not shown in the figure but are caged 50 (shown in FIG. 2) which is laterally restrained by axial thrust bearings well known to those skilled in the art. Is freely rotatable around the center.

  When the field 26 is energized, it rotates the armature structure 28 about the output ram 12 and forces the ram 12 to a roller screw 44 within the cage 50 that engages the threaded output ram 12. Rotate as a center and apply a lateral force to the thread 18. The lateral force of the thread 18 moves the ram 12 in the lateral direction.

  For the purposes of this disclosure and claims interpretation, the term “electron” is interchangeable with “rotor” and is considered synonymous. In other words, “rotor” is synonymous with “electron” and vice versa. Similarly, the term “stator” is considered synonymous with “field” winding.

  FIG. 2 shows the cage 50 and the included roller screw 44 in more detail. The cage 50 radially separates two or more helically threaded roller screws 44-1 and 44-2 that mate with the threads 18 of the output ram 12. The thread of the roller screw 44 is sized and formed to mate with the thread 18 on the surface 16 of the output ram 12 so that the roller screw 44 can rotate smoothly about the output ram 12. Those skilled in the art will appreciate that the thread pitch of the roller screw should match the thread pitch of the output ram 12.

It can be seen from the electrical representation of one of the motors shown in FIG. 3 that the cage 50 with the included roller screw 44 functions as an electric element. In FIG. 3, the electric element 28 has six poles 29 centered on the shaft 14, and each pole 29 is formed by one of the band portions 51 extending between the bearing caps 55-1 and 55-2. Formed and corresponding to this. Each pole 29 serves to enclose the roller screw 44 and to provide a field line path. The armature structure 28 rotates in response to a magnetic field generated around the armature 28 by the stator 26. The rotation of the armature structure 28 causes the roller screw 44 to rotate. (Those skilled in the art will recognize that the roller screws 44 rotate about their axis of rotation even in the opposite direction to the rotation 28 of the armature).

  Referring to FIG. 2 again, the metal band 51 extending in parallel with the roller screw 44 carries a magnetic field line. They also provide strengthening of the cage 50, thereby helping to maintain radial separation between the separate roller screws 44-1 and 44-2. The journal 45 (shown in FIG. 2B) at the end of the roller screw 44 is hooked into a small bearing hole 53 in the opposing bearing cap bearing caps 55-1 and 55-2.

  As shown in FIG. 2A, the roller screw 44 has a central threaded portion 49. The taper 43 is just inside the journal bearing portion 45. The journal portion 45 is hung on bearing caps 55-1 and 55-2 at each end of the roller screw 44, freely rotating around the output ram 12, and not engaging with the thread of the output ram 12. .

  The taper 43 in the roller screw 44 provides a structure by which the roller screw 44 can be disengaged from the helical thread of the output ram 12. The roller screws 44 are disengaged using complementary tapers in the bearing caps 55-1 and 55-2, which slide "below" the taper 43 to lift the roller screw 44 upwards, The roller screw 44 can be disengaged from the output ram 12. The bearing caps 55-1 and 55-2 are directed toward each other to disengage the roller screw 44 if the motor fails.

  During operation, a fault tolerant electromechanical actuator or “EMA” generates signals such as voltage, current, speed, and position. A microprocessor, not shown, monitors voltage, current, speed, and position, and detects when excessive torque is generated by one or more drive motors, typically due to the unusually high current drawn by the motor To do.

  Referring to FIG. 4, if it is determined that excessive torque is about to occur, the microprocessor or other controller fully engages the problematic motor roller (44) from the screw (12). The lamp to be released and the lock mechanism (57) are operated. The ramp and locking mechanism (57) provides lateral movement of the ramp and locking mechanism (57) to lift the roller (44) from the screw (12) and segment itself into the roller cage / nut (5). Requires an electromagnetic actuation device (59) to lock onto.

  If the lamp and locking mechanism (57) is required, i.e. there is an excessive amount of drawn current, the microprocessor or other controller provides voltage / current to the coil (90). The coil (90) becomes an electromagnet and generates magnetic field lines. This flux is transferred from the coil (90) through the small air gap of the thrust bearing (91) to the opposite magnetic field on the ramp and locking mechanism (57). As the current increases, the magnetic flux increases, causing the ramp and locking mechanism (57) to move, thereby raising the roller (44) away from contact with the thread of the screw. Once engaged, the ramp and locking mechanism (57) is fixed in place on the segmented roller cage / nut (50) to completely eliminate any further movement of the motor module or contact with the screw (12). . In normal operation, the ramp and locking mechanism (57) does not have any magnetic contact with the electrical coil and the roller (44) is fully engaged with the screw (12) and the motor module is fully functional.

In the preferred embodiment, motors 24, 30 and 34 in the housing engage the threads 18 of the output ram 12. All motors are powered and assist in driving the output ram 12. In such an embodiment, the motor shares the load due to the output ram 12. When the motor fails, the structure within the electric element 28 disconnects the electric element 28 from the thread 18 of the output ram 12 and loads the ram 12 without interference from the motor where the other motor has failed. Make it available.

  In an alternative embodiment, all motors engage threads 18 in the output ram 12, but one motor is powered to drive the load provided by the output ram 12. The other motors 20 in the housing 20 are only “go along for the ride” and do not provide power support. When the drive motor fails, the failed motor's electrical element 28 disconnects the electrical element 28 from the thread 18 in the output ram 12, and one or more other motors interfere with the failed motor. So that the load from the ram 12 can be received.

  In yet another alternative embodiment, two or more motors are engaged to engage the threads 18 in the output ram 12 and are driven to drive the load provided by the output ram 12, thereby between them. Share the load. A single additional motor is also engaged but not powered so that it can be used as a “backup” or extra motor. If the drive motor fails, the structure within the failed motor's electrical element 28 disconnects the failed motor's electrical element 28 from the thread 18 in the output ram 12 to one or more other motors. Can receive the load from the ram 12 without interference from the failed motor.

  In yet another alternative embodiment, only one of the many motors engages the threads 18 of the output ram 12 to handle the load of the output ram 12. The other motor in the housing 20 is a “backup” or extra motor. When the drive motor fails, the structure within the failed motor's electrical element 28 disconnects the failed motor's electrical element 28 from the thread 18 in the output ram 12. In this embodiment, the structure in the other motor's armature engages one or more of the other motor's armatures so that this (or these) rams are not interfered with by the failed motor. The load from 12 is received.

  With reference to FIGS. 1, 2, 2A and 4, when the roller screw 44 is lifted away from the thread 18, the motor is disengaged from the thread 18 of the output ram 12, and the cage 50 is The output ram 12 can be freely rotated about the center. The roller screw 44 can be lifted away from the thread 18 using a tapered portion 43 (shown in FIG. 2) between the straight journal portion 45 and the threaded portion 49. The taper that slides under the taper 43 when the complementary taper is pressed against the taper 43 in the bearing caps 55-1 and 55-2 or in the clutch mechanism is a roller screw. 44 is disengaged from the thread 18.

  Many of the embodiments described above are configured such that all motor armatures engage the threads 18 of the output ram 12. In these embodiments, in the event of a motor failure, the failed motor is removed from the output ram 12 using the taper 43 and the bearing caps 55-1 and 55-2 or the complementary taper in the clutch. The engagement is released. The roller screw 44 initially disengaged with the taper can then be engaged with the thread 18 by retracting the complementary taper away from the taper 43 in the roller screw 44. In an alternative embodiment where not all motors are initially engaged, the failed motor is disengaged as described above, and the roller is lowered so that the backup motor engages the output ram 12. As a result, the backup motor operates the actuator 10.

FIG. 4 better shows the ramp and locking mechanism 57 at both ends of the cage 50 that prevents lateral movement of the cage 50. As shown in FIG. 4, the complementary taper 58 in the ramp and locking mechanism 57 lifts and disengages the roller screw 44 when the ramp and locking mechanism 57 is directed toward the roller screw 44. The displacement of the lamp and locking mechanism is controlled by an electromagnetic actuator and a microprocessor.

  Whether the ram 12 is pulled out of or into the housing 20 is determined by the direction of rotation of the electric element. The direction of rotation of the electron element is determined electrically. Therefore, the output ram 12 of the actuator 10 can be moved in different directions only by changing the power source.

  In addition to electrically changing the direction of the output ram, the speed of the output ram 12 can also be determined electrically. In the case of a DC motor, the rotation speed is determined by the amplitude of the applied voltage. In the case of a synchronous AC motor, the rotation speed is determined by the frequency of the applied AC voltage. As is well known, the speed of an AC induction motor can be varied somewhat by changing the voltage amplitude, but can also be varied by changing the AC duty cycle.

  For a given motor speed, the thread pitch of the ram 12 affects the displacement speed of the output ram 12. A relatively large number of threads per inch requires a lot of motor rotation per unit of linear displacement, but increasing the threads per inch causes the drive motor to “receive” from the output ram 12 ( see) ”also reduces the amount of force.

  The simplicity with which the direction and speed of the output ram 12 can be changed is two significant advantages that the actuator 10 has over prior art hydraulic actuators. Fault tolerance, and thus reliability, of the actuator 10 is achieved by driving the output ram 12 with multiple motors so that if the motor fails, it can be disengaged.

  Referring again to FIG. 1, a second motor 30 is shown in the housing 20 just to the right of the first motor 24. The structure and operation of the second motor 32 are preferably the same as the first motor 24. An alternative embodiment also has a third motor 34. Like the electric motor of the first motor 24, the electric motor of the second motor 30 is provided with two or more roller screws 44-1 and 44-2 by a cage 50.

  As noted above, fault tolerance is obtained by the ability to isolate one motor if it fails and allow other motors to continue to operate and receive a load. As shown in FIG. 4, the output ram 12 includes a rotor 28 depending on whether the roller screw 44 in the armature cage was initially engaged or disengaged from the threads of the output ram 12. And can be engaged or disengaged from the rotor 28. The roller screw 44 can be disengaged from the output ram, so that the motor 24 is engaged from the output ram 12 by sliding the roller engaging thrust bearing 47 against the tapered portion 43 of the roller screw 44. Can be released. By doing so, the roller screw 44 is lifted from engagement with the output ram 12 and physically separates the motor and the output ram 12.

  The ramp and lock mechanism 57 is pressed along the axis of the roller screw and against the roller screw 44 by either a mechanical or electrical clutch (not shown), which causes the motor to output ram 12. Depending on whether to engage or disengage, the thrust bearing 47 is pressed against the roller screw taper 43 or the thrust bearing is pulled away from the taper 43. By lifting the roller screw 44 of one motor from the thread of the output ram 12, the motor armature 28 of that motor can be disengaged from the ram 12. Other motors can be engaged with the output ram 12 by lowering different motor roller screws into the threads of the output ram 12.

  The thrust bearing tapered surface 43, or any other structure that lifts the roller screw 44 from the output ram or lowers the roller screw 44 to engage the output ram 12, includes the motor armature / rotor and helical threads and output. It should be considered as a roller engagement / roller disengagement mechanism that operably couples or disconnects from the ram. By doing so, the thrust bearing and / or its tapered surface acts as a mechanism to engage or disengage the motor and output ram 12 in combination with the tapered portion of the roller screw.

  As described above in the background of the invention, hydraulic and electric actuators perform a myriad of tasks. The applications of the electric linear actuator described above and shown in FIGS.

  As is well known, a “journal” is a spindle or shaft that rotates within a bearing. In its most common application, the output or distal end 62 of the electric linear actuator 10 is mounted on the journal 60 of the crank arm 68 as shown in FIG. The journal 60 is housed in the opening of the ram 12 at its distal end 62 where the journal 60 pivots with the reciprocation of the output ram 12 indicated by reference numeral 60.

  As shown, the displacement of the journal 60 at the end of the crank arm 68 causes the drive shaft 70 to vary about its rotational axis, as indicated by reference numeral 72. In the rotating machine, the actuator 10 can reach rotation by reciprocating displacement using the structure shown in FIG.

  It is well known that aircraft have wings attached to the fuselage. The control surface on the wing controls, among other things, the speed of ascent and descent. A tail mounted on the rear of the fuselage provides steering and maneuverability. The engine provides thrust and can be mounted against the wing vane, at the tail, or against the fuselage. Since the structure of the aircraft is well known, its illustration is omitted here for the sake of brevity.

  As described above, prior art actuators controlled the wing, tail, landing gear, landing gear housing, control surface, and engine thrust reverser motion. In yet another embodiment of the present invention shown in FIG. 6, the output end 62 of the output ram 12 is pivoted on the control surface 76 of an aircraft (not shown for clarity but is well known in the art). Coupled to point 74. Translation (movement) in the direction indicated by the arrow 64 of the output ram 12 allows the actuator 10 to move a control surface, such as a spoiler, flap, elevator, rudder or aileron, thereby controlling the aircraft. Is one embodiment. Similar translations may control other control surfaces, fuselage doors, landing gear and / or thrust reversal.

  Those skilled in the art will recognize that the aircraft has the well-known prior art structure described above, but also includes a fault tolerant electric actuator 10 described herein and shown in FIG. Accordingly, aircraft safety and reliability can be improved by manipulating the flight control surface, landing gear, landing gear door and engine thrust reverser using actuators 10 in the wing, fuselage or tail as required. I will.

  In yet another embodiment shown in FIG. 7, the output ram 12 may extend through both ends of the actuator housing 20. One side or end 12-1 of the output ram is connected to the first steerable wheel 80 of the vehicle. The other side or end 12-2 is connected to a steering link for another steerable wheel 82. As output ram 12 translates in the direction indicated by reference numeral 64, steerable wheels 80 and 82 rotate on pivot points or axes 86, 88, thereby controlling steerable wheels 80 and 82.

Automobiles and trucks are all well known and need no explanation, at least one steerable wheel (in the case of a tricycle), a chassis or frame to which the wheel is rotatably coupled, a body with a door, an engine and a transmission Although it is well known to have a brake, significant weight loss may be possible by replacing the hydraulic actuators used to control steering with the above-described highly reliable fault tolerant actuators.

  Other embodiments of the electric linear actuator may include use as a power source for a lift for the door by appropriately coupling the output ram to a mechanism where the load is lifted and the door is opened.

  The preferred embodiment of the electric linear actuators disclosed and claimed herein used DC motors because they are easily reversible and their output speed is easily controllable. However, alternative embodiments may include reversible AC motors and stepper motors. However, those skilled in the art will appreciate that stepper motors require more complex electronic devices than DC or AC motors.

  Realizes linear actuators with fault tolerance that are electrically powered by providing two or more motors that are fixed in the housing, each of which can be independently coupled to or released from the helical threaded output shaft Can do.

It is sectional drawing of the electric actuator which has failure tolerance. It is a perspective view of the roller screw nut used as an electric element of the electric motor used in the electric actuator which has failure tolerance, and shows the clutch to release. FIG. 6 is a view showing a roller screw nut assembly. It is a figure which shows a helical thread cutting roller. It is a figure which shows the electric pole of the stator and electric element of an electric motor, and the electric element engages with the electric element of an electric actuator. FIG. 3 is a single view of a motor and a portion of an output ram within a housing of an electric actuator. It is a figure which shows the crank arm which drives the actuator which has failure tolerance, and a drive shaft. It is a figure which shows the flight control surface of an actuator which has fault tolerance, and an aircraft. It is a figure which shows the actuator which has fault tolerance, and the steering system of a vehicle.

Explanation of symbols

  12 output rams, 18 threads, 28 electrons, 44-1, 44-2 roller screws.

Claims (9)

An electric linear actuator,
An output ram having a central axis and an outer threaded surface (hereinafter "output ram");
A housing having a first opening through which the output ram is withdrawn and retracted;
A first electric motor (hereinafter referred to as “first motor”) fixed in the housing, wherein the first motor includes a first stator and the output in the first stator. A first electric element that rotates about the axis of the ram, wherein the first electric element is rotated about the output ram axis while preventing axial movement along the output ram axis. Supported in an enabled manner, rotation of the first electric element retracts the output ram into or out of the housing when the first electric element engages a threaded surface of the output ram. Drawer, the linear actuator further
A second electric motor (hereinafter referred to as a “second motor”) fixed in the housing and adjacent to the electric motor, the second motor having a second stator centered on the output ram; A second electric element rotating about an axis of the output ram in the second stator, the second electric element being prevented from moving in the axial direction along the output ram axis. While being supported in a manner that allows its rotation about an output ram axis, the rotation of the second electric element is when the second electric element engages a threaded surface of the output ram. Pulling the output ram into or out of the housing, the linear actuator further comprising:
It said first electrical terminal and said second at least one operatively coupled out of the armature, viewed including the armature release mechanism for disconnecting the corresponding armature from the output ram if there is a failure,
The first electric element and the second electric element have an axis substantially parallel to the output ram axis, and are prevented from moving in the axial direction along the output ram axis while being centered on the output ram axis. A roller screw carried to enable its rotation, wherein the roller screw causes the output so that rotation of at least one roller screw pulls the output ram into or out of the actuator housing. A helical thread that fits and releasably engages the threaded surface of the ram;
The electric linear actuator , wherein the armature release mechanism disconnects the corresponding armature from the output ram by disengaging the threaded surface of the output ram and the helical screw . Both the first and second electric elements are initially engaged with the threaded surface of the output ram;
The electric linear actuator according to claim 1, wherein the armature releasing mechanism disconnects the corresponding armature when the corresponding motor fails. One of the first electric element and the second electric element is initially engaged with a threaded surface of the output ram;
The armature release mechanism disconnects the engaged armature in the event of a failure of the corresponding motor,
The electric linear actuator of claim 1, wherein after the other armature is engaged with the threaded surface of the output ram, at least one electron release mechanism separates the previously engaged armature.   The armature release mechanism is replaced with at least one armature engagement mechanism, and the armature engagement mechanism is operatively coupled to at least one of the first armature and the second armature. The electric linear actuator of claim 1, wherein the electric linear actuator is engaged with a threaded surface of the output ram. The apparatus further includes a third electric motor (hereinafter, “third motor”) fixed in the housing, wherein the third motor has a third stator centered on the output ram, and the third motor. A third electric element rotating about the axis of the output ram in the stator, wherein the third electric element is prevented from moving in the axial direction along the output ram axis while the output ram axis The rotation of the third electric element causes the output ram to move when the third electric element engages a threaded surface of the output ram. Retracting into or withdrawing from the housing, the linear actuator further comprising:
At least one electron release mechanism operably coupled to at least one of the first, second and third electron elements to disconnect a corresponding one from the output ram only including, the third armature, the rotary movement of the axial direction has a substantially axis parallel to the output ram shaft along the output ram shaft around the output ram shaft while being prevented A roller screw carried to enable the threading of the output ram so that rotation of at least one roller screw pulls the output ram into or out of the actuator housing. The electric linear actuator of claim 1, comprising a helical screw that mates and releasably engages a surface . The cylindrical output ram has an output end that is distal to the housing, and the electric linear actuator further includes:
Coupled to the output end of the output ram,
A journal whose linear displacement causes rotation of machine parts,
The control surface of the airplane,
A steerable wheel for the vehicle;
Lift,
Door,
The electric linear actuator according to claim 1, comprising at least one of the following.   The electric linear actuator according to claim 1, wherein the first motor and the second motor are DC motors.   The electric linear actuator according to claim 1, wherein the first motor and the second motor are reversible AC motors.   The electric linear actuator according to claim 1, wherein the first motor and the second motor are stepper motors.

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