Mutually redundant, fully electrically redundant, lockable retractable electromechanical actuators

Abstract

This invention proposes a fully redundant, lockable retractable electromechanical actuator with mutual backup, offering reliable safety margins. This can be achieved through the following technical solution: An auxiliary motor, corresponding to the main motor, is located at the output end of the piston cylinder assembly. The auxiliary motor meshes with a lead screw sleeve end gear mounted on the output end of the piston cylinder assembly via a secondary transmission gear. The axially necked cylinder is constrained within the annular groove on the inner wall of the piston cylinder assembly by bearings on its stepped end faces. A locking device is located on the free end to control the linear displacement of the piston cylinder assembly. This locking device follows the lead screw nut fitted onto the lead screw sleeve, moving linearly along the guide rail output from the bottom end of the EMA outer cylinder, forming two relatively independent redundant transmission chains integrated together by the piston cylinder assembly. The main motor drives the main lead screw and lead screw nut to rotate, moving along the guide rail to the limit position at the bottom end of the lead screw sleeve, thus pushing the piston cylinder assembly to retract, achieving mechanical locking; conversely, retraction achieves mechanical unlocking.

Description

Technical Field

[0001] This invention relates to an electric actuator cylinder positioning locking and unlocking mechanism, specifically a dual-redundant emergency unlocking, retraction, and retraction locking structure applied to all-electric actuators. More specifically, this invention relates to an innovative structure that improves the safety and reliability of all-electric actuators, enabling the other motor and transmission components to complete the unlocking, piston rod retraction, and locking actions in the event of a motor failure or transmission chain jamming. Background Technology

[0002] With the continuous improvement of motor technology and power electronics technology, electromechanical actuators (EMAs) are playing an increasingly important role. EMAs also offer higher reliability, flexibility, and greater survivability. An EMA is a type of actuator that controls the movement of a load by controlling an electric motor. The landing gear retraction EMA for small aircraft is designed to meet the need for fully electronic control, replacing the traditional hydraulic control system. The technical specifications of the landing gear retraction EMA for small aircraft are no less than those of hydraulic control systems under the same conditions. Its main function is to achieve landing gear retraction and locking in the lowered position, with a non-electrical locking mechanism in the lowered position. The EMA control system controls the aircraft landing gear retraction and extension by controlling the mechanical transmission of the EMA, including the landing gear retraction and extension process, position detection, and locking of the landing gear in the retracted and lowered positions. Typically, an Electromechanical Actuator (EMA) control system needs to simultaneously control multiple landing gears (e.g., one nose landing gear and two main landing gears). An EMA consists of a control circuit and a mechanical actuator. The control circuit mainly comprises a main control module and a motor drive control module; the mechanical actuator is a linear motion actuator used to achieve linear reciprocating motion or oscillating motion less than 360° of the working mechanism. Common mechanical actuators mainly consist of a piston cylinder, a motor, a gearbox transmission component connected to the motor output shaft, a linear displacement output device and a linear displacement locking device installed inside the piston cylinder and connected to the output end of the gearbox, and a piston assembly connected to the linear displacement output device. The basic components mainly include: a ball screw pair, an outer cylinder assembly, a piston rod assembly, and a self-locking assembly. The disadvantages of conventional locking devices are high energy consumption; in emergency deployment, they can only rotate the screw to pull out the piston, making it difficult to withstand the huge impact load when the aircraft lands. Faults are not easily detected, and the landing gear may not lock smoothly in the deployed position, or even jam during emergency deployment. This fails to meet the high reliability requirements of aircraft. Electromechanical actuators with self-locking devices prevent erratic movement caused by external forces when stopped at a defined position. These devices are typically locked by a mechanical lock within the actuator cylinder. Common types of mechanical locks include ball locks, locking grooves, conical pistons, and springs. In fault-tolerant conditions, the power output from the faulty channel in an EMA system must be shared by other normal channels, requiring power redistribution. This increases power losses in the motor and inverter and can also affect mechanical components. When the landing gear control system malfunctions, the landing gear cannot retract or extend normally; therefore, an emergency system is essential.

[0003] In applications with high safety and mission reliability requirements, such as aerospace, single-motor systems often cannot meet the demands. For example, electromechanical actuators used in aircraft landing gear retraction and extension require a safety margin for landing gear deployment. To improve reliability, redundancy design is generally employed. Redundancy technology refers to a design method that improves the overall system reliability by adding multiple resources to the system and managing these resources effectively. Currently, there are two redundancy methods: parallel dual-redundant motors and two motors in series. Schemes using electromechanical actuators for landing gear retraction and extension include both piston rod extension and retraction to lower the landing gear. A common multi-redundant design for electromechanical actuators uses a backup motor. When the main motor fails, the backup motor operates to provide emergency piston rod deployment. However, this cannot solve the single-point failure problem of lead screw jamming, resulting in low mission reliability and poor practicality. The existing technology employs a dual-machine coaxial redundant service system, which is a permanent magnet synchronous motor redundant system. Structurally, it uses a series structure, with two identical motors mounted symmetrically on the same shaft and in the same housing. The core components of this redundant system are two isolated permanent magnet synchronous motors. Two sets of inverters are electrically independent, each controlling one motor, thus forming a dual-redundant permanent magnet synchronous motor system. Although in cold backup operation mode, only one redundancy is normally in operation, and only when this redundancy fails is the faulty redundancy disconnected, and the other redundancy begins operation. When a driver or motor winding in one of the redundancy systems fails, the controller immediately blocks the three-phase drive signals of the inverter circuit and cuts off the path between the inverter and the motor. At this time, the three-phase current of the faulty redundancy decreases to zero within a short period of time, while the other redundancy begins operation, bearing the full load. During the redundancy switching, the speed and torque fluctuate to some extent. In this single-machine operation mode, only one motor in the redundant system is outputting power, resulting in low system efficiency. Although in hot backup redundancy mode, both redundancies operate simultaneously, and the system can disconnect the faulty redundancy and start single redundancy mode when one redundancy fails, differences in power devices and motor winding inductive reactance can cause torque pulsation in the redundant motor system during operation. Furthermore, the windings of the two motors may heat up differently, leading to excessive temperature rise in one motor winding, thus shortening the lifespan of the redundancy system and reducing its reliability. Summary of the Invention

[0004] This invention provides a technical solution for a compact, reliable safety margin electromechanical actuator that enables emergency unlocking, retraction, and locking of the piston rod retraction under power-only conditions. This fully electric redundant emergency locking electromechanical actuator effectively solves the problem of single-point failure of lead screw pair jamming that conventional dual-redundant electromechanical actuators cannot solve, and achieves fully electric redundant emergency response.

[0005] The technical solution adopted by this invention to solve its technical problem is: a fully electric redundant lockable retractable electromechanical actuator with mutual backup, comprising: a gear transmission assembly encapsulated on one side of the outer cylinder transmission box of the electromechanical actuator and connected to the output shaft of the main motor 1; a main lead screw 3 connected to the gear transmission assembly; a piston cylinder assembly 8 that performs telescopic linear motion in the moving cavity of the outer cylinder 4 of the electromechanical actuator; and a lead screw nut 6 installed in the piston cylinder assembly 8 and connected to the output end of the main lead screw 3. The characteristic feature is that: an auxiliary motor 9 with an output gear is provided at the output end of the piston cylinder assembly 8, facing the main motor 1; the shaft-coupled gear of the auxiliary motor 9 meshes with the cylinder end gear of the lead screw sleeve 7 assembled in the output direction of the piston cylinder assembly 8 through an auxiliary transmission gear 10; the axial necking cylinder of the cylinder end gear is constrained by bearings on the stepped end faces at both ends. The piston cylinder assembly 8 is provided with a locking device in the inner wall annular groove and on the free end to control the linear displacement of the piston cylinder assembly 8. The locking device follows the lead screw sleeve 7 and the piston cylinder assembly 8 and moves along the axial direction of the outer cylinder 4 of the electromechanical actuator. The lead screw sleeve 7 and the lead screw nut 6 are designed with independent inner and outer ring helical raceways. The lead screw nut 6 is engaged with the main lead screw 3, the outer ring helical raceway is engaged with the lead screw sleeve 7, and the inner ring helical raceway of the lead screw sleeve 7 is engaged with the outer ring helical raceway of the lead screw nut 6. The linear displacement locking device is rolled in the generatrix locking groove in the inner wall of the piston cylinder assembly 8. The lead screw nut 6 is engaged by the inner helical raceway of the lead screw sleeve 7, which drives the lead screw nut 6 to perform linear displacement along the guide rail 5 output from the bottom end of the outer cylinder 4 of the electromechanical actuator, forming two relatively independent redundant transmission chains integrated together by the piston cylinder assembly 8.

[0006] The locking device includes: an upper locking ball 15 that is locked in the front and rear locking ring groove 16 of the piston head outer ring and closely attached to the inner wall of the electromechanical actuator outer cylinder 4; a lower locking ball 12 that is rolled and locked in the locking ball ring groove of the inner ring surface of the electromechanical actuator outer cylinder 4; an upper locking bushing 14 that is closely attached to the inner ring surface of the piston head and constrains the locking spring 13 between the end ring locking groove and the retaining ring of the lead screw sleeve 7; and a lower upper locking bushing 11. The upper locking bushing 14 and the lower upper locking bushing 11 are symmetrically facing each other. The rolling direction of the upper locking ball 15 and the lower locking ball 12 and the extension and retraction direction of the piston cylinder assembly 8 are controlled by the chamfered surfaces at both ends to lock them in place.

[0007] After receiving the landing gear retraction or extension command from the aircraft's main control system, the main motor 1 control module sends a command to the motor drive module through the corresponding path according to the predetermined program. This drives the main motor 1 to rotate, which in turn drives the main lead screw 3 to rotate through the main transmission gear 2 and the lead screw nut 6. The lead screw nut 6 moves along the guide rail 5 to the bottom limit position of the lead screw sleeve 7, pushing the piston cylinder assembly 8 to retract. The lower locking ball 12 on the locking device disengages from the lower locking groove of the electromechanical actuator outer cylinder 4, thus unlocking the mechanical lock. The lead screw nut 6 pushes the lead screw sleeve 7 to retract the piston cylinder assembly 8 back to the bottom of the electromechanical actuator outer cylinder 4. The upper locking ball 15 is pushed at an angle into the locking ring groove 16 at the bottom of the electromechanical actuator outer cylinder 4 by the upper locking bushing 14, which is provided with elastic force by the locking spring 13 in the locking device. This achieves mechanical locking, and vice versa.

[0008] Compared with the prior art, the present invention has the following advantages:

[0009] This invention employs a gear transmission assembly encapsulated on one side of the transmission box of the electromechanical actuator's outer cylinder and connected to the output shaft of the main motor 1. A main lead screw 3 is connected to the gear transmission assembly. A piston cylinder assembly 8 performs telescopic linear motion within the moving cavity of the electromechanical actuator's outer cylinder 4. A lead screw nut is installed inside the piston cylinder assembly 8 and connected to the output end of the main lead screw 3. A corresponding main motor 1 is positioned at the output end of the piston cylinder assembly 8. Compared to existing series or parallel motor combinations, this design is more compact and occupies less space.

[0010] This invention designs independent inner and outer ring helical raceways on the lead screw sleeve 7 and lead screw nut 6. The lead screw nut 6 engages with the main lead screw 3, the outer ring helical raceway engages with the lead screw sleeve 7, and the inner ring helical raceway of the lead screw sleeve 7 engages with the outer ring helical raceway of the lead screw nut 6. This forms two relatively independent redundant transmission chains integrated together by the piston cylinder assembly 8, enabling the main lead screw 3 to be driven by the main motor 1 and the lead screw sleeve 7 to be driven by the auxiliary motor 9. This design is not only compact and reliable with a high safety margin, but also allows for emergency unlocking, piston rod retraction, and locking even with only electrical power supply. The redundancy management technology using a work / backup mode maximizes the reliability and safety of task completion, ensuring high efficiency during normal operation and timely isolation of the fault source to minimize performance degradation in the event of a failure.

[0011] This invention employs a linear displacement locking device that rolls within the inner wall of the piston cylinder assembly 8. The screw nut 6 is engaged with the spiral raceway within the screw sleeve 7, causing it to move linearly along the guide rail 5 output from the bottom of the outer cylinder 4 of the electromechanical actuator. This forms two relatively independent redundant transmission chains integrated together by the piston cylinder assembly 8. This dual-machine hot backup system, utilizing two identical channels, ensures high system reliability. When the main motor 1 and auxiliary motor 9 operate simultaneously, the piston rod extends and retracts at twice the speed of a single motor. If either motor fails or its corresponding transmission chain jams, the other motor can independently unlock, retract the piston rod, and lock, enabling unobstructed landing gear release. In emergency deployment, energy is not dissipated due to the rotation of the piston-driven screw, and there is no risk of jamming or inability to lock. This eliminates the need for a dedicated control system and an additional emergency deployment mechanism, thus solving the single-point failure problem of screw pair jamming that conventional electromechanical actuators cannot address.

[0012] This invention employs a lead screw nut 6 that moves along the guide rail 5 to the bottom limit position of the lead screw sleeve 7, pushing the piston cylinder assembly 8 to retract. This causes the lower locking ball 12 in the linear displacement positioning locking device to disengage from the lower locking groove of the electromechanical actuator outer cylinder 4, thus unlocking the mechanical lock. The lead screw nut 6 then pushes the lead screw sleeve 7 to retract the piston cylinder assembly 8 back to the bottom of the electromechanical actuator outer cylinder 4. The upper locking ball 15, with the elastic force provided by the locking spring 13, is pushed at an angle into the locking ring groove at the bottom of the electromechanical actuator outer cylinder 4, thus locking the upper locking ball 15 mechanically. Conversely, the upper locking ball 15 is mechanically unlocked. This mechanism provides both mechanical locking and unlocking. The resulting actuator positioning locking and unlocking mechanism is highly reliable. Even if one motor fails or the transmission chain is jammed, the other motor and transmission components can still complete the unlocking, piston rod retraction, and locking actions, thereby improving the safety and reliability of the entire electromechanical actuator. This invention effectively solves the problem of low reliability in emergency unlocking and piston rod retraction tasks caused by the unreliability of conventional dual-redundant electromechanical actuator lead screw pairs with locking functions, which cannot address the issue of lead screw pair jamming. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the piston cylinder extension state of the interlocking, fully redundant, lockable retractable electromechanical actuator of the present invention.

[0014] Figure 2 yes Figure 1 Schematic diagram of the piston cylinder in retracted state;

[0015] In the diagram: 1. Main motor, 2. Main transmission gear, 3. Main lead screw, 4. Electromechanical actuator outer cylinder, 5. Guide rail, 6. Lead screw nut, 7. Lead screw sleeve, 8. Piston cylinder assembly, 9. Auxiliary motor, 10. Auxiliary transmission gear, 11. Lower locking bushing, 12. Lower locking ball, 13. Locking spring, 14. Upper locking bushing, 15. Upper locking ball, 16. Locking ring groove.

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this does not limit the invention to the scope of the described embodiments. All these concepts should be considered as the content disclosed in this technology and the scope of protection of this invention. Detailed Implementation

[0017] See Figure 1 , Figure 2 In the preferred embodiment described below, a fully electrically redundant lockable retractable electromechanical actuator with backups includes: a gear transmission assembly encapsulated on one side of the actuator's outer cylinder transmission box and connected to the output shaft of the main motor 1; a main lead screw 3 connected to the gear transmission assembly; a piston cylinder assembly 8 that performs telescopic linear motion in the moving cavity of the actuator's outer cylinder 4; and a lead screw nut 6 installed in the piston cylinder assembly 8 and connected to the output end of the main lead screw 3. At the output end of the piston cylinder assembly 8, there is an auxiliary motor 9 facing the main motor 1 and equipped with an output gear. The shaft gear of the auxiliary motor 9 meshes with the cylinder end gear of the lead screw sleeve 7 mounted in the output direction of the piston cylinder assembly 8 through the auxiliary transmission gear 10. The cylinder end gear is axially necked and constrained in the annular groove of the inner wall of the piston cylinder assembly 8 by bearings on the stepped end faces at both ends. A locking device is provided on the free end to control the linear displacement of the piston cylinder assembly 8. The locking device follows the lead screw nut 6 fitted with the lead screw sleeve 7 and moves linearly along the guide rail 5 output from the bottom end of the electromechanical actuator outer cylinder 4, forming two relatively independent redundant transmission chains integrated together by the piston cylinder assembly 8. The main motor 1 control module receives the landing gear retraction or extension command sent by the aircraft main control system. After the command is given, the command is sent to the motor drive module through the corresponding channel according to the established procedure, driving the main motor 1 to run. The main drive gear 2 drives the main lead screw 3 to rotate with the lead screw nut 6. The lead screw nut 6 moves along the guide rail 5 to the bottom limit position of the lead screw sleeve 7, pushing the piston cylinder assembly 8 to retract. The lower locking ball 12 on the locking device disengages from the lower locking groove of the electromechanical actuator outer cylinder 4, realizing the mechanical lock unlocking. The lead screw nut 6 pushes the lead screw sleeve 7 to drive the piston cylinder assembly 8 to retract back to the bottom of the electromechanical actuator outer cylinder 4. The upper locking ball 15 is pushed into the locking ring groove 16 at the bottom direction of the electromechanical actuator outer cylinder 4 by the upper locking bushing 14 end face angled by the locking spring 13 in the locking device, realizing the mechanical lock locking. Conversely, the mechanical unlocking is realized.

[0018] The gear transmission assembly includes: a main transmission gear 2 disposed on one side of the outer cylinder transmission box and meshing with the gear at the output shaft end of the main motor 1, and a main lead screw 3 end gear transmission system meshing with the main transmission gear 2.

[0019] The gear transmission assembly also includes: a cylinder end gear mounted on the radial end of the piston cylinder assembly 8, which meshes with the lead screw sleeve 7 via the secondary transmission gear 10, and meshes with the output shaft gear of the secondary motor 9 via the secondary transmission gear 10.

[0020] The main lead screw 3, which meshes with the main drive gear 2, is limited by the thrust angular contact ball bearing in the hollow stepped hole at the bottom of the outer cylinder of the electromechanical actuator 4 to the end face of its necked shaft ring groove. Then, it is fitted with the lead screw nut 6 through the transmission cavity of the outer cylinder of the electromechanical actuator 4 and the lead screw sleeve 7 assembled on the piston cylinder assembly 8. Finally, it is fitted with the guide rail 5 through the rod end sleeve, which limits the axial movement freedom of the lead screw nut 6 on the guide rail 5.

[0021] The locking device includes: an upper locking ball 15 that is locked in the front-back direction locking ring groove 16 of the piston head outer ring and closely attached to the inner wall of the electromechanical actuator outer cylinder 4; a lower locking ball 12 that is rolled and locked in the locking ball ring groove of the inner ring surface of the electromechanical actuator outer cylinder 4; an upper locking bushing 14 that is closely attached to the inner ring surface of the piston head and constrains the locking spring 13 between the end ring locking groove and the retaining ring of the lead screw sleeve 7; and a lower upper locking bushing 11. The upper locking bushing 14 and the lower upper locking bushing 11 are symmetrically facing each other. The rolling direction of the upper locking ball 15 and the lower locking ball 12 and the extension and retraction direction of the piston cylinder assembly 8 are controlled by the chamfered surfaces at both ends to lock them in place.

[0022] The lead screw sleeve 7 is installed in the stepped hole of the hollow piston head in the piston cylinder assembly 8. The lead screw sleeve 7 has an annular groove for constraining the upper locking bushing 14 and the lower locking bushing 11. The upper locking bushing 14 and the lower locking bushing 11 are symmetrically facing each other and constrain the locking spring 13 in the annular groove. The upper locking bushing 14 and the lower locking bushing 11 are close to the inner wall of the annular groove of the inner stepped piston head. The upper locking ball 15 and the lower locking ball 12 are constrained by the chamfered surfaces at both ends. At the same time, the lower locking ball 12 is locked in the locking ball annular groove on the inner annular surface of the outer cylinder 4 of the electromechanical actuator.

[0023] The thrust angular contact ball bearing inner ring end face axially limits the screw sleeve 7, which is installed in the stepped hole at the port of piston cylinder assembly 8, and bears the load of the screw nut 6 that is matched with the inner helical raceway.

[0024] The lead screw sleeve 7, which is assembled in the transmission cavity of the piston cylinder assembly 8, transmits the piston rod load sequentially to the lead screw nut 6, the main lead screw 3, and finally to the outer cylinder 4 of the electromechanical actuator.

[0025] In optional embodiments, the main motor 1 and auxiliary motor 9 can operate in two modes depending on their normal operating status: cold backup single-channel operation and hot backup dual-channel simultaneous operation. In cold backup, only one channel operates during normal operation, with the other serving as a backup. When the operating channel fails, it is disconnected from the system, and the backup channel is activated. Under cold backup, the system uses only one channel to handle the load at any given time, with the other channel serving as a backup. When the operating channel fails, it automatically switches according to the control signal to ensure uninterrupted system operation. If the redundant main motor 1 fails, it automatically switches to the redundant auxiliary motor 9.

[0026] During operation, the hot backup system operates with both channels running simultaneously. If one channel fails, the system automatically disconnects the faulty channel and switches to single-channel operation mode, degrading to a lower performance level. In hot backup mode, both channels of the redundant motor operate simultaneously in normal mode. If the redundant auxiliary motor 9 fails, the faulty channel is disconnected based on the fault signal to ensure uninterrupted system operation; the operating state at this time is the same as during a cold backup failure. Under normal operating conditions, during hot backup, both the redundant main motor 1 and auxiliary motor 9 simultaneously provide power to the load.

[0027] During normal operation, the main motor 1 and the auxiliary motor 9 serve as backups for each other. They can work simultaneously or either one motor can work while the other motor is in cold standby mode. When the main motor 1 and the auxiliary motor 9 work simultaneously, the main motor 1 drives the main lead screw 3 to rotate through the gear transmission assembly, which drives the lead screw nut 6 to retract. The auxiliary motor 9 drives the lead screw sleeve 7 to rotate through the auxiliary transmission gear 10. The lead screw nut 6 moves to the left along the guide rail 5, which drives the lead screw sleeve 7, which meshes with the spur teeth of the auxiliary transmission gear 10, to move to the left. This pushes the lower upper locking bushing 11 to disengage from the lower edge of the lower locking ball 12. The lower locking ball 12 disengages from the lower locking groove of the outer cylinder 4 of the electromechanical actuator, thus unlocking the mechanical lock. The lead screw sleeve 7 pushes the right-end thrust angular contact ball bearing, which drives the piston cylinder assembly 8 to move and causes the lower locking ball 12 to retract into the piston cylinder assembly 8.

[0028] If the main motor 1 is working, the auxiliary motor 9 fails, or the transmission chain is jammed, the main motor 1 drives the main lead screw 3 to rotate through the main transmission gear 2, drives the lead screw nut 6 to retract along the guide rail 5 and drives the lead screw sleeve 7 to retract, pushes the lower locking bushing 11, and the lower locking ball 12 disengages from the lower locking groove of the electromechanical actuator outer cylinder 4. The lower locking ball 12 is mechanically unlocked, and the lead screw sleeve 7 pushes the right end thrust angular contact ball bearing, driving the piston rod to retract.

[0029] If the main motor 1 fails or the transmission chain is jammed, the auxiliary motor 9 will work. The auxiliary motor 9 will drive the lead screw sleeve 7 to rotate through the auxiliary transmission gear 10, drive the lead screw sleeve 7 to rotate and move to the left, push the lower locking bushing 11, and the lower locking ball 12 will disengage from the lower locking groove of the outer cylinder 4 of the electromechanical actuator, thereby unlocking the mechanical lock.

[0030] The auxiliary motor 9 drives the lead screw sleeve 7 to rotate through the auxiliary transmission gear 10. The lead screw sleeve 7 pushes the right-end thrust angular contact ball bearing, causing the piston rod of the piston cylinder assembly 8 to retract. The piston cylinder assembly 8 retracts towards the bottom of the electromechanical actuator outer cylinder 4 in the locking ring groove 16. Under the action of the locking spring 13, the upper locking bushing 14 is inserted into the lower edge of the upper locking ball 15 through the end-facing chamfered bevel. The upper locking ball 15 is moved to the upper locking groove of the electromechanical actuator outer cylinder 4 and then inserted into the locking ring groove, realizing the upper mechanical locking of the piston cylinder assembly 8.

[0031] Although the present invention has been described in conjunction with some preferred embodiments, the invention is not limited to these embodiments. Rather, the invention is intended to encompass all alternatives, modifications, and equivalents, provided that such alternatives are included within the core spirit and scope of the invention as defined by the appended claims.

Claims

1. A fully redundant, lockable retractable electromechanical actuator with mutual backup, comprising: The gear transmission assembly encapsulated on one side of the transmission box of the electromechanical actuator outer cylinder and connected to the output shaft of the main motor (1), the main lead screw (3) connected to the gear transmission assembly, the piston cylinder assembly (8) that performs telescopic linear motion in the moving cavity of the electromechanical actuator outer cylinder (4), and the lead screw nut (6) installed in the piston cylinder assembly (8) and connected to the output end of the main lead screw (3) are characterized in that: an auxiliary motor (9) with an output gear is provided at the output end of the piston cylinder assembly (8) and facing the main motor (1). The shaft gear of the auxiliary motor (9) meshes with the cylinder end gear of the lead screw sleeve (7) assembled in the direction of the output end of the piston cylinder assembly (8) through the auxiliary transmission gear (10). The cylinder end gear is axially necked in the annular groove of the inner wall of the piston cylinder assembly (8) by bearings on the stepped end faces at both ends. A control piston cylinder is provided on the free end. The locking device for linear displacement of component (8) follows the lead screw sleeve (7) and piston cylinder assembly (8) and moves along the axial direction of the outer cylinder (4) of the electromechanical actuator. Independent inner and outer ring spiral raceways are designed on the lead screw sleeve (7) and lead screw nut (6). The lead screw nut (6) is engaged with the main lead screw (3), the outer ring spiral raceway is engaged with the lead screw sleeve (7), and the inner ring spiral raceway of the lead screw sleeve (7) is engaged with the outer ring spiral raceway of the lead screw nut (6). The linear displacement locking device that rolls in the generatrix locking groove on the inner wall of piston cylinder assembly (8) is adopted. The lead screw nut (6) is engaged through the inner spiral raceway of the lead screw sleeve (7), which drives the lead screw nut (6) to perform linear displacement along the guide rail (5) output from the bottom end of the outer cylinder (4) of the electromechanical actuator, forming two relatively independent redundant transmission chains integrated together by piston cylinder assembly (8). The locking device includes: an upper locking ball (15) that is locked in the front and rear direction locking ring groove (16) of the piston head outer ring and closely attached to the inner wall of the electromechanical actuator outer cylinder (4); a lower locking ball (12) that is rolled and locked in the locking ball ring groove of the inner ring surface of the electromechanical actuator outer cylinder (4) and closely attached to the inner ring surface of the piston head, which constrains the locking spring (13) between the end ring locking groove and the retaining ring of the lead screw sleeve (7); a lower upper locking bushing (11); the upper locking bushing (14) and the lower upper locking bushing (11) are symmetrically facing each other, and the rolling direction of the upper locking ball (15) and the lower locking ball (12) and the extension and retraction movement direction of the piston cylinder assembly (8) are controlled by the chamfered surfaces at both ends to lock them in place; After receiving the landing gear retraction or extension command from the aircraft's main control system, the main motor (1) control module sends a command to the motor drive module through the corresponding path according to the predetermined program, driving the main motor (1) to run. Through the main transmission gear (2), the main lead screw (3) rotates in conjunction with the lead screw nut (6). The lead screw nut (6) moves along the guide rail (5) to the bottom limit position of the lead screw sleeve (7), pushing the piston cylinder assembly (8) to retract. The lower locking device... The locking ball (12) disengages from the lower locking groove of the outer cylinder (4) of the electromechanical actuator, thereby unlocking the mechanical lock. The screw nut (6) pushes the screw sleeve (7) to drive the piston cylinder assembly (8) back to the bottom of the outer cylinder (4) of the electromechanical actuator. The upper locking ball (15) is pushed into the locking ring groove (16) at the bottom direction of the EMA outer cylinder (4) by the upper locking bushing (14) with the elastic force provided by the locking spring (13) in the locking device, thereby locking the mechanical lock. Conversely, the mechanical unlocking is achieved.

2. The mutually redundant, fully electrically redundant, lockable retractable electromechanical actuator as described in claim 1, characterized in that: Also includes: It is installed at the radial end of the piston cylinder assembly (8), and the cylinder end gear of the lead screw sleeve (7) is engaged by the auxiliary transmission gear (10), and the output shaft gear of the auxiliary motor (9) is engaged by the auxiliary transmission gear (10).

3. The mutually redundant, fully electrically redundant, lockable retractable electromechanical actuator as described in claim 1, characterized in that: The main lead screw (3) meshing with the main drive gear (2) is limited to the end face of the necked shaft ring groove by the thrust angular contact ball bearing in the hollow stepped hole of the bottom cylinder of the electromechanical actuator outer cylinder (4). Then, the lead screw nut (6) is fitted by the lead screw sleeve (7) assembled on the piston cylinder assembly (8) through the transmission cavity of the electromechanical actuator outer cylinder (4) and the lead screw nut (6). The lead screw nut (6) is fitted by the guide rail (5) through the rod end sleeve, which limits the axial movement stroke freedom of the lead screw nut (6) on the guide rail (5).

4. The mutually redundant, fully electrically redundant, lockable retractable electromechanical actuator as described in claim 1, characterized in that: The thrust angular contact ball bearing inner ring end face axially limiting screw sleeve (7) installed in the stepped hole of the piston cylinder assembly (8) bears the load of the screw nut (6) that is matched with the inner helical raceway.

5. The mutually redundant, fully electrically redundant, lockable retractable electromechanical actuator as described in claim 1, characterized in that: The lead screw sleeve (7) assembled in the transmission cavity of the piston cylinder assembly (8) transmits the piston rod load sequentially to the lead screw nut (6), the main lead screw (3), and finally to the outer cylinder (4) of the electromechanical actuator.

6. The mutually redundant, fully electrically redundant, lockable retractable electromechanical actuator as described in claim 1, characterized in that: During normal operation, the main motor (1) and the auxiliary motor (9) serve as backups for each other and can work simultaneously or either motor can work while the other motor is a cold backup. When the main motor (1) and the auxiliary motor (9) work simultaneously, the main motor (1) drives the main screw (3) to rotate through the gear transmission assembly, which drives the screw nut (6) to retract. The auxiliary motor (9) drives the screw sleeve (7) to rotate through the auxiliary transmission gear (10). The screw nut (6) moves to the left along the guide rail (5), which drives the screw sleeve (7) that meshes with the spur teeth of the auxiliary transmission gear (10) to move to the left, pushing the lower upper locking bushing (11) to disengage from the lower locking ball (12). The lower locking ball (12) disengages from the lower locking groove of the EMA outer cylinder (4), thus unlocking the mechanical lock. The screw sleeve (7) pushes the right-end thrust angular contact ball bearing, which drives the piston cylinder assembly (8) to move and causes the lower locking ball (12) to retract into the piston cylinder assembly (8).

7. The mutually redundant, fully electrically redundant, lockable retractable electromechanical actuator as described in claim 1, characterized in that: If the main motor (1) is working, the auxiliary motor (9) fails or the transmission chain is jammed, the main motor (1) drives the main screw (3) to rotate through the main transmission gear (2), drives the screw nut (6) to retract along the guide rail (5) and drives the screw sleeve (7) to retract, pushes the lower locking bushing (11), and the lower locking ball (12) disengages from the lower locking groove of the electromechanical actuator outer cylinder (4), the lower locking ball (12) mechanically unlocks, and the screw sleeve (7) pushes the right end thrust angular contact ball bearing, driving the piston rod to retract.

8. The mutually redundant, fully electrically redundant, lockable retractable electromechanical actuator as described in claim 1, characterized in that: If the main motor (1) fails or the transmission chain is jammed, the auxiliary motor (9) will work. The auxiliary motor (9) will drive the lead screw sleeve (7) to rotate through the auxiliary transmission gear (10), drive the lead screw sleeve (7) to rotate and move to the left, push the lower upper locking bushing (11), and the lower locking ball (12) will disengage from the lower locking groove of the outer cylinder (4) of the electromechanical actuator, thereby unlocking the mechanical lock.

9. The mutually redundant, fully electrically redundant, lockable retractable electromechanical actuator as described in claim 1, characterized in that: The auxiliary motor (9) drives the lead screw sleeve (7) to rotate through the auxiliary transmission gear (10). The lead screw sleeve (7) pushes the right end thrust angular contact ball bearing, causing the piston rod of the piston cylinder assembly (8) to retract. The piston cylinder assembly (8) retracts towards the bottom of the locking ring groove (16) of the electromechanical actuator outer cylinder (4). Under the elastic force of the locking spring (13), the upper locking bushing (14) is inserted into the lower edge of the upper locking ball (15) through the end-to-end chamfered bevel. The upper locking ball (15) moves to the upper locking groove of the EMA outer cylinder (4) and is then inserted into the locking ring groove, thus realizing the upper mechanical locking of the piston cylinder assembly (8).

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